Fatty acids activate a chimera of the clofibric acid-activated receptor and the glucocorticoid receptor.

PubMed Central

Göttlicher, M; Widmark, E; Li, Q; Gustafsson, J A

1992-01-01

Peroxisome proliferators such as clofibric acid, nafenopin, and WY-14,643 have been shown to activate PPAR (peroxisome proliferator-activated receptor), a member of the steroid nuclear receptor superfamily. We have cloned the cDNA from the rat that is homologous to that from the mouse [Issemann, I. & Green, S. (1990) Nature (London) 347, 645-650], which encodes a 97% similar protein with a particularly well-conserved putative ligand-binding domain. To search for physiologically occurring activators, we established a transcriptional transactivation assay by stably expressing in CHO cells a chimera of rat PPAR and the human glucocorticoid receptor that activates expression of the placental alkaline phosphatase reporter gene under the control of the mouse mammary tumor virus promoter. Testing of compounds related to lipid metabolism or peroxisomal proliferation revealed that 150 microM concentrations of arachidonic or linoleic acid but not of dehydroepiandrosterone, cholesterol, or 25-hydroxy-cholesterol, activate the receptor chimera. In addition, saturated fatty acids induce the reporter gene. Shortening the chain length to n = 6 or introduction of an omega-terminal carboxylic group abolished the activation potential of the fatty acid. In conclusion, the present results indicate that fatty acids can regulate gene expression mediated by a member of the steroid nuclear receptor superfamily. Images PMID:1316614

High Concentrations of Tranexamic Acid Inhibit Ionotropic Glutamate Receptors.

PubMed

Lecker, Irene; Wang, Dian-Shi; Kaneshwaran, Kirusanthy; Mazer, C David; Orser, Beverley A

2017-07-01

The antifibrinolytic drug tranexamic acid is structurally similar to the amino acid glycine and may cause seizures and myoclonus by acting as a competitive antagonist of glycine receptors. Glycine is an obligatory co-agonist of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors. Thus, it is plausible that tranexamic acid inhibits NMDA receptors by acting as a competitive antagonist at the glycine binding site. The aim of this study was to determine whether tranexamic acid inhibits NMDA receptors, as well as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and kainate subtypes of ionotropic glutamate receptors. Tranexamic acid modulation of NMDA, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, and kainate receptors was studied using whole cell voltage-clamp recordings of current from cultured mouse hippocampal neurons. Tranexamic acid rapidly and reversibly inhibited NMDA receptors (half maximal inhibitory concentration = 241 ± 45 mM, mean ± SD; 95% CI, 200 to 281; n = 5) and shifted the glycine concentration-response curve for NMDA-evoked current to the right. Tranexamic acid also inhibited α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (half maximal inhibitory concentration = 231 ± 91 mM; 95% CI, 148 to 314; n = 5 to 6) and kainate receptors (half maximal inhibitory concentration = 90 ± 24 mM; 95% CI, 68 to 112; n = 5). Tranexamic acid inhibits NMDA receptors likely by reducing the binding of the co-agonist glycine and also inhibits α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and kainate receptors. Receptor blockade occurs at high millimolar concentrations of tranexamic acid, similar to the concentrations that occur after topical application to peripheral tissues. Glutamate receptors in tissues including bone, heart, and nerves play various physiologic roles, and tranexamic acid inhibition of these receptors may contribute to adverse drug effects.

Tracing the biosynthetic source of essential amino acids in marine turtles using delta13C fingerprints.

PubMed

Arthur, Karen E; Kelez, Shaleyla; Larsen, Thomas; Choy, C Anela; Popp, Brian N

2014-05-01

Plants, bacteria, and fungi produce essential amino acids (EAAs) with distinctive patterns of delta13C values that can be used as naturally occurring fingerprints of biosynthetic origin of EAAs in a food web. Because animals cannot synthesize EAAs and must obtain them from food, their tissues reflect delta13C(EAA) patterns found in diet, but it is not known how microbes responsible for hindgut fermentation in some herbivores influence the delta13C values of EAAs in their hosts' tissues. We examined whether distinctive delta13C fingerprints of hindgut flora are evident in the tissues of green turtles (Chelonia mydas), which are known to be facultative hindgut fermenters. We determined delta13C(EAA) values in tissues of green turtles foraging herbivorously in neritic habitats of Hawaii and compared them with those from green, olive ridley, and loggerhead turtles foraging carnivorously in oceanic environments of the central and southeast Pacific Ocean. Results of multivariate statistical analysis revealed two distinct groups that could be distinguished based on unique delta13C(EAA) patterns. A three-end-member predictive linear discriminant model indicated that delta13C(EAA) fingerprints existed in the tissues of carnivorous turtles that resembled patterns found in microalgae, which form the base of an oceanic food web, whereas herbivorous turtles derive EAAs from a bacterial or seagrass source. This study demonstrates the capacity for delta13C fingerprinting to establish the biosynthetic origin of EAAs in higher consumers, and that marine turtles foraging on macroalgal diets appear to receive nutritional supplementation from bacterial symbionts in their digestive system.

Presynaptic Inhibition of Diverse Afferents to the Locus Coeruleus by Kappa Opiate Receptors: a Novel Mechanism for Regulating the Central Norepinephrine System

PubMed Central

Kreibich, Arati S.; Reyes, Beverly A. S.; Curtis, Andre L.; Ecke, Laurel; Chavkin, Charles; Van Bockstaele, Elisabeth J.; Valentino, Rita J.

2008-01-01

The norepinephrine nucleus, locus coeruleus (LC), is activated by diverse stimuli and modulates arousal and behavioral strategies in response to these stimuli through its divergent efferent system. Afferents communicating information to the LC include excitatory amino acids (EAA), corticotropin-releasing factor (CRF) and endogenous opioids acting at μ-opiate receptors. As the LC is also innervated by the endogenous κ-opiate receptor (κ-OR) ligand, dynorphin, and expresses κ-ORs, this study investigated κ-OR regulation of LC neuronal activity in rat. Immunoelectron microscopy revealed a prominent localization of κ-ORs in axon terminals in the LC that also contained either the vesicular glutamate transporter or CRF. Microinfusion of the κ-OR agonist, U50488, into the LC did not alter LC spontaneous discharge but attenuated phasic discharge evoked by stimuli that engage EAA afferents to the LC, including sciatic nerve stimulation and auditory stimuli and the tonic activation associated with opiate withdrawal. Inhibitory effects of the κ-OR agonist were not restricted to EAA afferents, as U50488 also attenuated tonic LC activation by hypotensive stress, an effect mediated by CRF afferents. Together, these results indicate that κ-ORs are poised to presynaptically inhibit diverse afferent signaling to the LC. This is a novel and potentially powerful means of regulating the LC-NE system that can impact on forebrain processing of stimuli and the organization of behavioral strategies in response to environmental stimuli. The results implicate κ-ORs as a novel target for alleviating symptoms of opiate withdrawal, stress-related disorders or disorders characterized by abnormal sensory responses, such as autism. PMID:18562623

Presynaptic inhibition of diverse afferents to the locus ceruleus by kappa-opiate receptors: a novel mechanism for regulating the central norepinephrine system.

PubMed

Kreibich, Arati; Reyes, Beverly A S; Curtis, Andre L; Ecke, Laurel; Chavkin, Charles; Van Bockstaele, Elisabeth J; Valentino, Rita J

2008-06-18

The norepinephrine nucleus, locus ceruleus (LC), is activated by diverse stimuli and modulates arousal and behavioral strategies in response to these stimuli through its divergent efferent system. Afferents communicating information to the LC include excitatory amino acids (EAAs), corticotropin-releasing factor (CRF), and endogenous opioids acting at mu-opiate receptors. Because the LC is also innervated by the endogenous kappa-opiate receptor (kappa-OR) ligand dynorphin and expresses kappa-ORs, this study investigated kappa-OR regulation of LC neuronal activity in rat. Immunoelectron microscopy revealed a prominent localization of kappa-ORs in axon terminals in the LC that also contained either the vesicular glutamate transporter or CRF. Microinfusion of the kappa-OR agonist (trans)-3,4-dichloro-N-methyl-N-[2-1-pyrrolidinyl)-cyclo-hexyl] benzeneacetamide (U50488) into the LC did not alter LC spontaneous discharge but attenuated phasic discharge evoked by stimuli that engage EAA afferents to the LC, including sciatic nerve stimulation and auditory stimuli and the tonic activation associated with opiate withdrawal. Inhibitory effects of the kappa-OR agonist were not restricted to EAA afferents, as U50488 also attenuated tonic LC activation by hypotensive stress, an effect mediated by CRF afferents. Together, these results indicate that kappa-ORs are poised to presynaptically inhibit diverse afferent signaling to the LC. This is a novel and potentially powerful means of regulating the LC-norepinephrine system that can impact on forebrain processing of stimuli and the organization of behavioral strategies in response to environmental stimuli. The results implicate kappa-ORs as a novel target for alleviating symptoms of opiate withdrawal, stress-related disorders, or disorders characterized by abnormal sensory responses, such as autism.

Whey protein ingestion in elderly persons results in greater muscle protein accrual than ingestion of its constituent essential amino acid content.

PubMed

Katsanos, Christos S; Chinkes, David L; Paddon-Jones, Douglas; Zhang, Xiao-jun; Aarsland, Asle; Wolfe, Robert R

2008-10-01

It is recognized that both whey protein (WY) and essential amino acids (EAA) are stimuli for muscle protein anabolism. The aim of the present study was to determine if the effects of WY ingestion on muscle protein accrual in elderly persons are due solely to its constituent EAA content. Fifteen elderly persons were randomly assigned to ingest a bolus of either 15 g of WY, 6.72 g of EAA, or 7.57 g of nonessential amino acids (NEAA). We used the leg arteriovenous model to measure the leg phenylalanine balance, which is an index of muscle protein accrual. Phenylalanine balance (nmol x min(-1) kg lean leg mass(-1)) during the 3.5 hours after the bolus ingestion improved in the WY (-216 +/- 14 vs -105 +/- 19; P < .05) but not in the EAA (-203 +/- 21 vs -172 +/- 38; P > .05) or NEAA groups (-203 +/- 19 vs -204 +/- 21; P > .05). The insulin response (uIU x mL(-1) 210 min(-1)) during the same period was lower in both the NEAA (48 +/- 40) and EAA (213 +/- 127) when compared to the WY (1073 +/- 229; P < .05). In conclusion, WY ingestion improves skeletal muscle protein accrual through mechanisms that are beyond those attributed to its EAA content. This finding may have practical implications for the formulation of nutritional supplements to enhance muscle anabolism in older individuals.

Effect of probiotics and thyme essential oil on the essential amino acid content of the broiler chicken meat.

PubMed

Alfaig, Ebrahim; Angelovičova, Maria; Kral, Martin; Bučko, Ondrej

2014-01-01

Differences in the types and percentages of essential amino acids (EAAs) in food could influence the value of protein consumed and proteins with a high content of EAAs are the most important components of poultry meat. The use of probiotics for meat and carcass quality improvement has been questioned, while feed supplementation with thyme essential oil (TEO) could be considered as useful natural supplement to be applied in the poultry industry to improve meat quality. Day-old broilers Ross 308 (n = 400) were randomly divided into four groups based on the feed supplement as follows: control, probiotics 0.05%, TEO 0.05% and combination of probiotics and TEO, while the fattening period was 42 days. Six birds of both sexes from each group were selected as a sample, slaughtered and then stored (-18°C) for 6 months till the analysis. The muscular homogeneous sample (50 g) from the breast and thigh of each sample bird was analysed by the Fourier Transform Infrared Spectroscopy method using the device Nicolet 6700. The essential amino acids content was determined and the quality indicators include chemical score, amino acid score, EAA index and biological value were calculated. The obtained results show that for all the tested EAAs of the breast and thigh muscles, the content numerically increased gradually and progressively within the groups as the control scored the minimum followed by the probiotics group, then the combination group and finally the TEO group which scored the highest results. It can be concluded that the TEO promoted the increase of all the EAAs and consequently the quality indicators with significant different compared with the control group and significantly different for some EAAs and quality indicators compared with the probiotics group and the combination group.

Nutrient balancing of the adult worker bumblebee (Bombus terrestris) depends on the dietary source of essential amino acids.

PubMed

Stabler, Daniel; Paoli, Pier P; Nicolson, Susan W; Wright, Geraldine A

2015-03-01

Animals carefully regulate the amount of protein that they consume. The quantity of individual essential amino acids (EAAs) obtained from dietary protein depends on the protein source, but how the proportion of EAAs in the diet affects nutrient balancing has rarely been studied. Recent research using the Geometric Framework for Nutrition has revealed that forager honeybees who receive much of their dietary EAAs from floral nectar and not from solid protein have relatively low requirements for dietary EAAs. Here, we examined the nutritional requirements for protein and carbohydrates of foragers of the buff-tailed bumblebee Bombus terrestris. By using protein (sodium caseinate) or an equimolar mixture of the 10 EAAs, we found that the intake target (nutritional optimum) of adult workers depended on the source and proportion of dietary EAAs. When bees consumed caseinate-containing diets in a range of ratios between 1:250 and 1:25 (protein to carbohydrate), they achieved an intake target (IT) of 1:149 (w/w). In contrast to those fed protein, bees fed the EAA diets had an IT more biased towards carbohydrates (1:560 w/w) but also had a greater risk of death than those fed caseinate. We also tested how the dietary source of EAAs affected free AAs in bee haemolymph. Bees fed diets near their IT had similar haemolymph AA profiles, whereas bees fed diets high in caseinate had elevated levels of leucine, threonine, valine and alanine in the haemolymph. We found that like honeybees, bumblebee workers prioritize carbohydrate intake and have a relatively low requirement for protein. The dietary source of EAAs influenced both the ratio of protein/EAA to carbohydrate and the overall amount of carbohydrate eaten. Our data support the idea that EAAs and carbohydrates in haemolymph are important determinants of nutritional state in insects. © 2015. Published by The Company of Biologists Ltd.

Nutrient balancing of the adult worker bumblebee (Bombus terrestris) depends on the dietary source of essential amino acids

PubMed Central

Stabler, Daniel; Paoli, Pier P.; Nicolson, Susan W.; Wright, Geraldine A.

2015-01-01

ABSTRACT Animals carefully regulate the amount of protein that they consume. The quantity of individual essential amino acids (EAAs) obtained from dietary protein depends on the protein source, but how the proportion of EAAs in the diet affects nutrient balancing has rarely been studied. Recent research using the Geometric Framework for Nutrition has revealed that forager honeybees who receive much of their dietary EAAs from floral nectar and not from solid protein have relatively low requirements for dietary EAAs. Here, we examined the nutritional requirements for protein and carbohydrates of foragers of the buff-tailed bumblebee Bombus terrestris. By using protein (sodium caseinate) or an equimolar mixture of the 10 EAAs, we found that the intake target (nutritional optimum) of adult workers depended on the source and proportion of dietary EAAs. When bees consumed caseinate-containing diets in a range of ratios between 1:250 and 1:25 (protein to carbohydrate), they achieved an intake target (IT) of 1:149 (w/w). In contrast to those fed protein, bees fed the EAA diets had an IT more biased towards carbohydrates (1:560 w/w) but also had a greater risk of death than those fed caseinate. We also tested how the dietary source of EAAs affected free AAs in bee haemolymph. Bees fed diets near their IT had similar haemolymph AA profiles, whereas bees fed diets high in caseinate had elevated levels of leucine, threonine, valine and alanine in the haemolymph. We found that like honeybees, bumblebee workers prioritize carbohydrate intake and have a relatively low requirement for protein. The dietary source of EAAs influenced both the ratio of protein/EAA to carbohydrate and the overall amount of carbohydrate eaten. Our data support the idea that EAAs and carbohydrates in haemolymph are important determinants of nutritional state in insects. PMID:25617453

A Combination of Amino Acids and Caffeine Enhances Sprint Running Capacity in a Hot, Hypoxic Environment.

PubMed

Eaton, Tom R; Potter, Aaron; Billaut, François; Panchuk, Derek; Pyne, David B; Gore, Christopher J; Chen, Ting-Ting; McQuade, Leon; Stepto, Nigel K

2016-02-01

Heat and hypoxia exacerbate central nervous system (CNS) fatigue. We therefore investigated whether essential amino acid (EAA) and caffeine ingestion attenuates CNS fatigue in a simulated team sport-specific running protocol in a hot, hypoxic environment. Subelite male team sport athletes (n = 8) performed a repeat sprint running protocol on a nonmotorized treadmill in an extreme environment on 4 separate occasions. Participants ingested one of four supplements: a double placebo, 3 mg.kg-1 body mass of caffeine + placebo, 2 x 7 g EAA (Musashi Create)+placebo, or caffeine + EAA before each exercise session using a randomized, double-blind crossover design. Electromyography (EMG) activity and quadriceps evoked responses to magnetic stimulation were assessed from the dominant leg at preexercise, halftime, and postexercise. Central activation ratio (CAR) was used to quantify completeness of quadriceps activation. Oxygenation of the prefrontal cortex was measured via near-infrared spectroscopy. Mean sprint work was higher (M = 174 J, 95% CI [23, 324], p < .05, d = 0.30; effect size, likely beneficial) in the caffeine + EAA condition versus EAAs alone. The decline in EMG activity was less (M = 13%, 95% CI [0, 26]; p < .01, d = 0.58, likely beneficial) in caffeine + EAA versus EAA alone. Similarly, the pre- to postexercise decrement in CAR was significantly less (M = -2.7%, 95% CI [0.4, 5.4]; p < .05, d = 0.50, likely beneficial) when caffeine + EAA were ingested compared with placebo. Cerebral oxygenation was lower (M = -5.6%, 95% CI [1.0, 10.1]; p < .01, d = 0.60, very likely beneficial) in the caffeine + EAA condition compared with LNAA alone. Co-ingestion of caffeine and EAA appears to maintain muscle activation and central drive, with a small improvement in running performance.

Hypercortisolemia alters muscle protein anabolism following ingestion of essential amino acids

NASA Technical Reports Server (NTRS)

Paddon-Jones, Douglas; Sheffield-Moore, Melinda; Creson, Daniel L.; Sanford, Arthur P.; Wolf, Steven E.; Wolfe, Robert R.; Ferrando, Arny A.

2003-01-01

Debilitating injury is accompanied by hypercortisolemia, muscle wasting, and disruption of the normal anabolic response to food. We sought to determine whether acute hypercortisolemia alters muscle protein metabolism following ingestion of a potent anabolic stimulus: essential amino acids (EAA). A 27-h infusion (80 microg. kg(-1). h(-1)) of hydrocortisone sodium succinate mimicked cortisol (C) levels accompanying severe injury (>30 microg/dl), (C + AA; n = 6). The control group (AA) received intravenous saline (n = 6). Femoral arteriovenous blood samples and muscle biopsies were obtained during a primed (2.0 micromol/kg) constant infusion (0.05 micromol. kg(-1). min(-1)) of l-[ring-(2)H(5)]phenylalanine before and after ingestion of 15 g of EAA. Hypercortisolemia [36.5 +/- 2.1 (C + AA) vs. 9.0 +/- 1.0 microg/dl (AA)] increased postabsorptive arterial, venous, and muscle intracellular phenylalanine concentrations. Hypercortisolemia also increased postabsorptive and post-EAA insulin concentrations. Net protein balance was blunted (40% lower) following EAA ingestion but remained positive for a greater period of time (60 vs. 180 min) in the C + AA group. Thus, although differences in protein metabolism were evident, EAA ingestion improved muscle protein anabolism during acute hypercortisolemia and may help minimize muscle loss following debilitating injury.

Hyodeoxycholic acid derivatives as liver X receptor α and G-protein-coupled bile acid receptor agonists

NASA Astrophysics Data System (ADS)

de Marino, Simona; Carino, Adriana; Masullo, Dario; Finamore, Claudia; Marchianò, Silvia; Cipriani, Sabrina; di Leva, Francesco Saverio; Catalanotti, Bruno; Novellino, Ettore; Limongelli, Vittorio; Fiorucci, Stefano; Zampella, Angela

2017-02-01

Bile acids are extensively investigated for their potential in the treatment of human disorders. The liver X receptors (LXRs), activated by oxysterols and by a secondary bile acid named hyodeoxycholic acid (HDCA), have been found essential in the regulation of lipid homeostasis in mammals. Unfortunately, LXRα activates lipogenic enzymes causing accumulation of lipid in the liver. In addition to LXRs, HDCA has been also shown to function as ligand for GPBAR1, a G protein coupled receptor for secondary bile acids whose activation represents a promising approach to liver steatosis. In the present study, we report a library of HDCA derivatives endowed with modulatory activity on the two receptors. The lead optimization of HDCA moiety was rationally driven by the structural information on the binding site of the two targets and results from pharmacological characterization allowed the identification of hyodeoxycholane derivatives with selective agonistic activity toward LXRα and GPBAR1 and notably to the identification of the first example of potent dual LXRα/GPBAR1 agonists. The new chemical entities might hold utility in the treatment of dyslipidemic disorders.

Epsilon Aminocaproic Acid Pretreatment Provides Neuroprotection Following Surgically Induced Brain Injury in a Rat Model.

PubMed

Komanapalli, Esther S; Sherchan, Prativa; Rolland, William; Khatibi, Nikan; Martin, Robert D; Applegate, Richard L; Tang, Jiping; Zhang, John H

2016-01-01

Neurosurgical procedures can damage viable brain tissue unintentionally by a wide range of mechanisms. This surgically induced brain injury (SBI) can be a result of direct incision, electrocauterization, or tissue retraction. Plasmin, a serine protease that dissolves fibrin blood clots, has been shown to enhance cerebral edema and hemorrhage accumulation in the brain through disruption of the blood brain barrier. Epsilon aminocaproic acid (EAA), a recognized antifibrinolytic lysine analogue, can reduce the levels of active plasmin and, in doing so, potentially can preserve the neurovascular unit of the brain. We investigated the role of EAA as a pretreatment neuroprotective modality in a SBI rat model, hypothesizing that EAA therapy would protect brain tissue integrity, translating into preserved neurobehavioral function. Male Sprague-Dawley rats were randomly assigned to one of four groups: sham (n = 7), SBI (n = 7), SBI with low-dose EAA, 150 mg/kg (n = 7), and SBI with high-dose EAA, 450 mg/kg (n = 7). SBI was induced by partial right frontal lobe resection through a frontal craniotomy. Postoperative assessment at 24 h included neurobehavioral testing and measurement of brain water content. Results at 24 h showed both low- and high-dose EAA reduced brain water content and improved neurobehavioral function compared with the SBI groups. This suggests that EAA may be a useful pretherapeutic modality for SBI. Further studies are needed to clarify optimal therapeutic dosing and to identify mechanisms of neuroprotection in rat SBI models.

Postexercise essential amino acid supplementation amplifies skeletal muscle satellite cell proliferation in older men 24 hours postexercise.

PubMed

Reidy, Paul T; Fry, Christopher S; Dickinson, Jared M; Drummond, Micah J; Rasmussen, Blake B

2017-06-01

Aged skeletal muscle has an attenuated and delayed ability to proliferate satellite cells in response to resistance exercise. The mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway is a focal point for cell growth, however, the effect of postexercise mTORC1 activation on human skeletal muscle satellite cell (SC) proliferation is unknown. To test the proliferative capacity of skeletal muscle SC in aging muscle to a potent mTORC1 activator (i.e., EAA; essential amino acids) we recruited older (~72y) men to conduct leg resistance exercise (8setsx10reps) without (-EAA; n  = 8) and with (+EAA: n  = 11) ingestion of 10 g of EAA 1 h postexercise. Muscle biopsies were taken before exercise (Pre) and 24 h postexercise (Post) for assessment of expression and fiber type-specific Pax7 + SC, Ki67 + Pax7 + SC and MyoD + SC -EAA did not show an increase in Pax7 + satellite cells at Post( P  > 0.82). Although statistical significance for an increase in Pax7 +  SC at 24 h post-RE was not observed in +EAA versus -EAA, we observed trends for a treatment difference ( P  < 0.1). When examining the change from Pre to Post trends were demonstrated (#/myofiber: P  = 0.076; and %/myonuclei: P  = 0.065) for a greater increase in +EAA versus -EAA Notably, we found an increase SC proliferation in +EAA, but not -EAA with increase in Ki67 + SC and MyoD + cells ( P  < 0.05). Ki67 + SC also exhibited a significant group difference Post ( P  < 0.010). Pax7 + SC in fast twitch myofibers did not change and were not different between groups ( P  > 0.10). CDK2, MEF2C, RB1 mRNA only increased in +EAA ( P  < 0.05). Acute muscle satellite cell proliferative capacity may be partially rescued with postexercise EAA ingestion in older men. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Incorporation of extra amino acids in peptide recognition probe to improve specificity and selectivity of an electrochemical peptide-based sensor.

PubMed

Zaitouna, Anita J; Maben, Alex J; Lai, Rebecca Y

2015-07-30

We investigated the effect of incorporating extra amino acids (AA) at the n-terminus of the thiolated and methylene blue-modified peptide probe on both specificity and selectivity of an electrochemical peptide-based (E-PB) HIV sensor. The addition of a flexible (SG)3 hexapeptide is, in particular, useful in improving sensor selectivity, whereas the addition of a highly hydrophilic (EK)3 hexapeptide has shown to be effective in enhancing sensor specificity. Overall, both E-PB sensors fabricated using peptide probes with the added AA (SG-EAA and EK-EAA) showed better specificity and selectivity, especially when compared to the sensor fabricated using a peptide probe without the extra AA (EAA). For example, the selectivity factor recorded in the 50% saliva was ∼2.5 for the EAA sensor, whereas the selectivity factor was 7.8 for both the SG-EAA and EK-EAA sensors. Other sensor properties such as the limit of detection and dynamic range were minimally affected by the addition of the six AA sequence. The limit of detection was 0.5 nM for the EAA sensor and 1 nM for both SG-EAA and EK-EAA sensors. The saturation target concentration was ∼200 nM for all three sensors. Unlike previously reported E-PB HIV sensors, the peptide probe functions as both the recognition element and antifouling passivating agent; this modification eliminates the need to include an additional antifouling diluent, which simplifies the sensor design and fabrication protocol. Copyright © 2015 Elsevier B.V. All rights reserved.

Growth and clinical variables in nitrogen-restricted piglets fed an adjusted essential amino acid mix: Effects using free amino acid-based diets

USDA-ARS?s Scientific Manuscript database

Excess protein intake in early life has been linked to obesity and metabolic syndrome in later life. Yet, protein, and in particular the essential amino acids (EAA), need to be present in adequate quantity to support growth. Using a piglet model restricted in dietary amino acids (AA), our objective...

Improved plasma amino acids pattern following 12 months of supplemented low-protein diet in peritoneal dialysis patients.

PubMed

Jiang, Na; Qian, Jiaqi; Lin, Aiwu; Fang, Wei; Cao, Liou; Wang, Qin; Ni, Zhaohui; Lindholm, Bengt; Axelsson, Jonas; Yao, Qiang

2010-07-01

Decreased plasma essential amino acid (EAA) levels, increased nonessential amino acid (NEAA) levels, and low EAA to NEAA ratio (E/NEAA) are common in peritoneal dialysis (PD) patients and may impact uremic complications. In the present study, we investigate the impact of keto acids-supplemented low-protein (sLP) diet on plasma amino acids (AAs) patterns in stable PD patients. This is a supplemental analysis of a previously published prospective and randomized trial. Thirty-nine PD patients selected from the original population were divided to receive either low (LP: 0.6-0.8 g/kg ideal body weight [IBW]/d, n = 13), keto acids-supplemented low- (sLP: 0.6-0.8 g/kg IBW/d + 0.12 g/kg IBW/d of keto acids, n = 12), or high- (HP: 1.0-1.2 g/kg IBW/d, n = 14) protein diets and followed for 1 year. Plasma AA patterns were assessed at baseline and 12 months using high-performance liquid chromatography. Whereas there were no significant differences between the three groups at baseline, following 12 months, the E/NEAA had increased significantly in group sLP (0.58 +/- 0.16 to 0.83 +/- 0.20, p < 0.05), but was not different in either LP (0.62 +/- 0.20 to 0.72 +/- 0.13, p = ns) or HP (0.66 +/- 0.14 to 0.74 +/- 0.12, p = ns) group. This change in E/NEAA in group sLP was due to a significant decrease in NEAA concomitantly with maintained EAA levels, whereas in the other two groups, neither EAA nor NEAA changed significantly. A low-protein diet supplemented with keto acids significantly improved the pattern of plasma AA in prevalent PD patients.

Free fatty acid (FFA) and hydroxy carboxylic acid (HCA) receptors.

PubMed

Offermanns, Stefan

2014-01-01

Saturated and unsaturated free fatty acids (FFAs), as well as hydroxy carboxylic acids (HCAs) such as lactate and ketone bodies, are carriers of metabolic energy, precursors of biological mediators, and components of biological structures. However, they are also able to exert cellular effects through G protein-coupled receptors named FFA1-FFA4 and HCA1-HCA3. Work during the past decade has shown that these receptors are widely expressed in the human body and regulate the metabolic, endocrine, immune and other systems to maintain homeostasis under changing dietary conditions. The development of genetic mouse models and the generation of synthetic ligands of individual FFA and HCA receptors have been instrumental in identifying cellular and biological functions of these receptors. These studies have produced strong evidence that several FFA and HCA receptors can be targets for the prevention and treatment of various diseases, including type 2 diabetes mellitus, obesity, and inflammation.

Functional cardiovascular action of L-cysteine microinjected into pressor sites of the rostral ventrolateral medulla of the rat.

PubMed

Takemoto, Yumi

2014-04-01

The endogenous sulfur-containing amino acid L-cysteine injected into the cerebrospinal fluid space of the cisterna magna increases arterial blood pressure (ABP) and heart rate (HR) in the freely moving rat. The present study examined (1) cardiovascular responses to L-cysteine microinjected into the rostral ventrolateral medulla (RVLM), where a group of neurons regulate activities of cardiovascular sympathetic neurons and (2) involvement of ionotropic excitatory amino acid (iEAA) receptors in response. In the RVLM of urethane-anesthetized rats accessed ventrally and identified with pressor responses to L-glutamate (10 mM, 34 nl), microinjections of L-cysteine increased ABP and HR dose dependently (3-100 mM, 34 nl). The cardiovascular responses to L-cysteine (30 mM) were not attenuated by a prior injection of either antagonist alone, MK801 (20 mM, 68 nl) for the NMDA type of iEAA receptors, or CNQX (2 mM) for the non-NMDA type. However, inhibition of both NMDA and non-NMDA receptors with additional prior injection of either antagonist completely blocked those responses to L-cysteine. The results indicate that L-cysteine has functional cardiovascular action in the RVLM of the anesthetized rat, and the responses to L-cysteine involve both NMDA and non-NMDA receptors albeit in a mutually exclusive parallel fashion. The findings may suggest endogenous roles of L-cysteine indirectly via iEAA receptors in the neuronal network of the RVLM for cardiovascular regulation in physiological and pathological situations.

Prediction of the amino acid digestibility of legume seeds in growing pigs: a meta-analysis approach.

PubMed

Messad, F; Létourneau-Montminy, M P; Charbonneau, E; Sauvant, D; Guay, F

2018-05-01

On pig farms, a high proportion of the cost of production comes from feed costs. However, the use of alternative ingredients such as legume seeds may help to reduce this cost. In fact, legume seeds are an important source of essential amino acids (EAA) and can therefore be an alternative to oilseed meals. However, the accurate use of these legume seeds requires a precise knowledge of the standardized ileal digestibility (SID) of EAA, which may vary depending on its botanical variety. A meta-analysis was performed on a database compiling data from 41 studies published between 1981 and 2013 and 178 dietary treatments. Models of prediction of the SID of EAA as well as the dietary concentration of digestible standardized EAA (dEAA) were obtained, based on the chemical composition of ingredients reported in the publications. The effect of the type of legume seeds (faba bean, lupin, pea and soya bean), surgical procedures (T-cannula, re-entrant cannulas, post valve T-cannulas and ileo-rectal anastomosis), and BW of pigs (BW⩽25 kg BW>25 kg) were also tested in each model. Results showed that dietary CP and crude fibre (CF) were, respectively, the best predictors of each EAA SID for faba bean, lupin and pea (R 2=0.42 to 0.89) and soya bean (R 2=0.32 to 0.77). For the dEAA content, the best prediction models included dietary CP and ADF for faba bean, lupin and pea and soya bean, respectively, with R 2 ranging from 0.66 to 0.98. Models developed in this study allow predicting the digestibility of EAA in these alternatives feedstuffs.

Proximate composition, amino acid and fatty acid profiles of marine snail Rapana venosa meat, visceral mass and operculum.

PubMed

Luo, Fenglei; Xing, Ronge; Wang, Xueqin; Peng, Quancai; Li, Pengcheng

2017-12-01

Rapana venosa (Rv), an important marine snail, demonstrates an increasing nutritional and economic importance. However, there is still limited information available on their nutritional composition. The present study highlights and provides new information on the proximate composition, amino acid and fatty acid profiles of different body parts of Rv, aiming for its better application and research. The operculum contained a high amount of protein and flavor amino acids. The edible tissues, including meat and visceral mass, were valuable sources of essential amino acids (EAA) apart from methionine and cysteine. In addition, the meat contained high amount of taurine. Fatty acid analysis indicated that the edible tissues contained high amounts of ω3 fatty acids, especially eicosapentaenoic acid (EPA) (C20:5ω3) and docosahexaenoic acid (DHA) (C22:6ω3), and had a low ω6/ω3 fatty acid ratio. Interestingly, significantly higher concentrations of most nutritional elements such as fat, EAA, EPA and DHA, were found in the visceral mass compared to those in the meat. The operculum of Rv may became a very interesting source for some protein and flavor peptide development, and the edible parts of Rv may be utilized for special dietary applications requiring high amounts of taurine, EPA, DHA and a lower ω6/ω3 fatty acid ratio. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Amino acid sequence of the human fibronectin receptor

PubMed Central

1987-01-01

The amino acid sequence deduced from cDNA of the human placental fibronectin receptor is reported. The receptor is composed of two subunits: an alpha subunit of 1,008 amino acids which is processed into two polypeptides disulfide bonded to one another, and a beta subunit of 778 amino acids. Each subunit has near its COOH terminus a hydrophobic segment. This and other sequence features suggest a structure for the receptor in which the hydrophobic segments serve as transmembrane domains anchoring each subunit to the membrane and dividing each into a large ectodomain and a short cytoplasmic domain. The alpha subunit ectodomain has five sequence elements homologous to consensus Ca2+- binding sites of several calcium-binding proteins, and the beta subunit contains a fourfold repeat strikingly rich in cysteine. The alpha subunit sequence is 46% homologous to the alpha subunit of the vitronectin receptor. The beta subunit is 44% homologous to the human platelet adhesion receptor subunit IIIa and 47% homologous to a leukocyte adhesion receptor beta subunit. The high degree of homology (85%) of the beta subunit with one of the polypeptides of a chicken adhesion receptor complex referred to as integrin complex strongly suggests that the latter polypeptide is the chicken homologue of the fibronectin receptor beta subunit. These receptor subunit homologies define a superfamily of adhesion receptors. The availability of the entire protein sequence for the fibronectin receptor will facilitate studies on the functions of these receptors. PMID:2958481

Comparison of Free Total Amino Acid Compositions and Their Functional Classifications in 13 Wild Edible Mushrooms.

PubMed

Sun, Liping; Liu, Qiuming; Bao, Changjun; Fan, Jian

2017-02-24

Thirteen popular wild edible mushroom species in Yunnan Province, Boletus bicolor , Boletus speciosus , Boletus sinicus , Boletus craspedius , Boletus griseus , Boletus ornatipes , Xerocomus , Suillus placidus , Boletinus pinetorus , Tricholoma terreum , Tricholomopsis lividipileata , Termitomyces microcarpus , and Amanita hemibapha , were analyzed for their free amino acid compositions by online pre-column derivazation reversed phase high-performance liquid chromatography (RP-HPLC) analysis. Twenty free amino acids, aspartic acid, glutamic acid, serine, glycine, alanine, praline, cysteine, valine, methionine, phenylalanine, isoleucine, leucine, lysine, histidine, threonine, asparagines, glutamine, arginine, tyrosine, and tryptophan, were determined. The total free amino acid (TAA) contents ranged from 1462.6 mg/100 g in B. craspedius to 13,106.2 mg/100 g in T. microcarpus . The different species showed distinct free amino acid profiles. The ratio of total essential amino acids (EAA) to TAA was 0.13-0.41. All of the analyzed species showed high contents of hydrophobic amino acids, at 33%-54% of TAA. Alanine, cysteine, glutamine, and glutamic acid were among the most abundant amino acids present in all species. The results showed that the analyzed mushrooms possessed significant free amino acid contents, which may be important compounds contributing to the typical mushroom taste, nutritional value, and potent antioxidant properties of these wild edible mushrooms. Furthermore, the principal component analysis (PCA) showed that the accumulative variance contribution rate of the first four principal components reached 94.39%. Cluster analysis revealed EAA composition and content might be an important parameter to separate the mushroom species, and T. microcarpus and A. hemibapha showed remarkable EAA content among the 13 species.

Cloning and characterization of the hamster and guinea pig nicotinic acid receptors.

PubMed

Torhan, April Smith; Cheewatrakoolpong, Boonlert; Kwee, Lia; Greenfeder, Scott

2007-09-01

In this study, we present the identification and characterization of hamster and guinea pig nicotinic acid receptors. The hamster receptor shares approximately 80-90% identity with the nucleotide and amino acid sequences of human, mouse, and rat receptors. The guinea pig receptor shares 76-80% identity with the nucleotide and amino acid sequences of these other species. [(3)H]nicotinic acid binding affinity at guinea pig and hamster receptors is similar to that in human (dissociation constant = 121 nM for guinea pig, 72 nM for hamster, and 74 nM for human), as are potencies of nicotinic acid analogs in competition binding studies. Inhibition of forskolin-stimulated cAMP production by nicotinic acid and related analogs is also similar to the activity in the human receptor. Analysis of mRNA tissue distribution for the hamster and guinea pig nicotinic acid receptors shows expression across a number of tissues, with higher expression in adipose, lung, skeletal muscle, spleen, testis, and ovary.

Essential amino acids: master regulators of nutrition and environmental footprint?

PubMed Central

Tessari, Paolo; Lante, Anna; Mosca, Giuliano

2016-01-01

The environmental footprint of animal food production is considered several-fold greater than that of crops cultivation. Therefore, the choice between animal and vegetarian diets may have a relevant environmental impact. In such comparisons however, an often neglected issue is the nutritional value of foods. Previous estimates of nutrients’ environmental footprint had predominantly been based on either food raw weight or caloric content, not in respect to human requirements. Essential amino acids (EAAs) are key parameters in food quality assessment. We re-evaluated here the environmental footprint (expressed both as land use for production and as Green House Gas Emission (GHGE), of some animal and vegetal foods, titrated to provide EAAs amounts in respect to human requirements. Production of high-quality animal proteins, in amounts sufficient to match the Recommended Daily Allowances of all the EAAs, would require a land use and a GHGE approximately equal, greater o smaller (by only ±1-fold), than that necessary to produce vegetal proteins, except for soybeans, that exhibited the smallest footprint. This new analysis downsizes the common concept of a large advantage, in respect to environmental footprint, of crops vs. animal foods production, when human requirements of EAAs are used for reference. PMID:27221394

Essential amino acids: master regulators of nutrition and environmental footprint?

PubMed

Tessari, Paolo; Lante, Anna; Mosca, Giuliano

2016-05-25

The environmental footprint of animal food production is considered several-fold greater than that of crops cultivation. Therefore, the choice between animal and vegetarian diets may have a relevant environmental impact. In such comparisons however, an often neglected issue is the nutritional value of foods. Previous estimates of nutrients' environmental footprint had predominantly been based on either food raw weight or caloric content, not in respect to human requirements. Essential amino acids (EAAs) are key parameters in food quality assessment. We re-evaluated here the environmental footprint (expressed both as land use for production and as Green House Gas Emission (GHGE), of some animal and vegetal foods, titrated to provide EAAs amounts in respect to human requirements. Production of high-quality animal proteins, in amounts sufficient to match the Recommended Daily Allowances of all the EAAs, would require a land use and a GHGE approximately equal, greater o smaller (by only ±1-fold), than that necessary to produce vegetal proteins, except for soybeans, that exhibited the smallest footprint. This new analysis downsizes the common concept of a large advantage, in respect to environmental footprint, of crops vs. animal foods production, when human requirements of EAAs are used for reference.

Excitatory amino acid receptors and disease.

PubMed

Meldrum, B S

1992-08-01

Recent advances in the molecular biology of excitatory amino acid receptors are reviewed. Evidence that drugs blocking the excitatory action of glutamate at the N-methyl-D-aspartate (NMDA) and non-NMDA receptors may be of clinical use in epilepsy, Parkinson's disease, cerebral ischaemia and trauma, acquired immune deficiency syndrome (AIDS) encephalopathy and neuropathic pain is summarized.

Growth and Clinical Variables in Nitrogen-Restricted Piglets Fed an Adjusted Essential Amino Acid Mix: Effects of Partially Intact Protein-Based Diets.

PubMed

Worsøe, Päivi S; Sangild, Per T; van Goudoever, Johannes B; Koletzko, Berthold; van der Beek, Eline M; Abrahamse-Berkeveld, Marieke; Burrin, Douglas G; van de Heijning, Bert J M; Thymann, Thomas

2018-06-13

Current recommendations for protein levels in infant formula are intended to ensure that growth matches or exceeds growth of breastfed infants, but may provide a surplus of amino acids (AAs). Recent infant studies with AA-based formulas support specific adjustment of the essential amino acid (EAA) composition allowing for potential lowering of total protein levels. With the use of a combination of intact protein and free EAAs, we designed a formula that meets these adjusted EAA requirements for infants. Our objective was to test whether this adjusted formula is safe and supports growth in a protein-restricted piglet model, and whether it shows better growth than an isonitrogenous formula based on free AAs. Term piglets (Landrace × Yorkshire × Duroc, n = 72) were fed 1 of 4 isoenergetic formulas containing 70% intact protein and 30% of an EAA mixture or a complete AA-based control for 20 d: standard formula (ST-100), ST-100 with 25% reduction in proteinaceous nitrogen (ST-75), ST-75 with an adjusted EAA composition (O-75), or a diet as O-75, given as a complete AA-based diet (O-75AA). After an initial adaptation period, ST-75 and O-75 pigs showed similar growth rates, both lower than ST-100 pigs (∼25 compared with 31 g · kg-1 · d-1, respectively). The O-75AA pigs showed further reduced growth rate (15 g · kg-1 · d-1) and fat proportion (both P < 0.05, relative to O-75). Formula based partly on intact protein is superior to AA-based formula in this experimental setting. The 25% lower, but EAA-adjusted, partially intact protein-based formula resulted in similar weight gain with a concomitant increased AA catabolism, compared with the standard 25% lower standard formula in artificially reared, protein-restricted piglets. Further studies should investigate if and how the specific EAA adjustments that allow for lowering of total protein levels will affect growth and body composition development in formula-fed infants.

Nutritional status of outpatients with chronic stable heart failure based on serum amino acid concentration.

PubMed

Tsuji, Shuhei; Koyama, Satoshi; Taniguchi, Ryoji; Fujiwara, Takako; Fujiwara, Hisayoshi; Sato, Yukihito

2018-06-06

Loss of skeletal muscle mass and low nutritional status are major complications of severe chronic heart failure (CHF) and have been associated with poor prognosis. This study aimed to identify the nutritional status of outpatients with CHF based on their body composition, such as skeletal muscle index (SMI) and serum amino acid concentration. We compared the body composition data and results of blood samples, including the serum amino acid concentration, of patients with CHF and those of controls. No significant difference was found in total amino acid concentration between 105 patients with CHF (62% men, mean age: 71.0±11.0 years) and 106 controls (67% men, mean age: 69.1±9.4 years) (CHF: 3459.1±504.9nmol/ml, control: 3575.8±513.1nmol/ml; p=0.072). However, the concentration of essential amino acids (EAA) (CHF: 949.5±197.9nmol/ml, control: 1034.1±207.3nmol/ml; p=0.002) and branched-chain amino acid (BCAA) (CHF: 449.3±114.3nmol/ml, control: 503.9±118.2nmol/ml; p<0.001) and Fischer's ratio (CHF: 2.86±0.62, control: 3.17±0.50; p<0.001) were significantly lower in patients with CHF. Integrated analysis of these data revealed that SMI was negatively correlated with age [correlation coefficient (R), -0.313; 95% confidence interval (CI), -0.514 to -0.079; p=0.010], but positively correlated with EAA concentration (R, 0.256; 95% CI, 0.017-0.467; p=0.037), BCAA concentration (R, 0.362; 95% CI, 0.134-0.554; p=0.003), and Fischer's ratio (R, 0.573; 95% CI, 0.386-0.715; p<0.001). Serum concentrations of EAA and BCAA and Fischer's ratio were lower in patients with CHF than in controls, while SMI correlated with EAA, BCAA, and Fischer's ratio. Copyright © 2018 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

Mammalian target of rapamycin complex 1 activation is required for the stimulation of human skeletal muscle protein synthesis by essential amino acids.

PubMed

Dickinson, Jared M; Fry, Christopher S; Drummond, Micah J; Gundermann, David M; Walker, Dillon K; Glynn, Erin L; Timmerman, Kyle L; Dhanani, Shaheen; Volpi, Elena; Rasmussen, Blake B

2011-05-01

The relationship between mammalian target of rapamycin complex 1 (mTORC1) signaling and muscle protein synthesis during instances of amino acid surplus in humans is based solely on correlational data. Therefore, the goal of this study was to use a mechanistic approach specifically designed to determine whether increased mTORC1 activation is requisite for the stimulation of muscle protein synthesis following L-essential amino acid (EAA) ingestion in humans. Examination of muscle protein synthesis and signaling were performed on vastus lateralis muscle biopsies obtained from 8 young (25 ± 2 y) individuals who were studied prior to and following ingestion of 10 g of EAA during 2 separate trials in a randomized, counterbalanced design. The trials were identical except during 1 trial, participants were administered a single oral dose of a potent mTORC1 inhibitor (rapamycin) prior to EAA ingestion. In response to EAA ingestion, an ~60% increase in muscle protein synthesis was observed during the control trial, concomitant with increased phosphorylation of mTOR (Ser(2448)), ribosomal S6 kinase 1 (Thr(389)), and eukaryotic initiation factor 4E binding protein 1 (Thr(37/46)). In contrast, prior administration of rapamycin completely blocked the increase in muscle protein synthesis and blocked or attenuated activation of mTORC1-signaling proteins. The inhibition of muscle protein synthesis and signaling was not due to differences in either extracellular or intracellular amino acid availability, because these variables were similar between trials. These data support a fundamental role for mTORC1 activation as a key regulator of human muscle protein synthesis in response to increased EAA availability. This information will be useful in the development of evidence-based nutritional therapies targeting mTORC1 to counteract muscle wasting associated with numerous clinical conditions.

Mechanisms for the activation of Toll-like receptor 2/4 by saturated fatty acids and inhibition by docosahexaenoic acid.

PubMed

Hwang, Daniel H; Kim, Jeong-A; Lee, Joo Young

2016-08-15

Saturated fatty acids can activate Toll-like receptor 2 (TLR2) and TLR4 but polyunsaturated fatty acids, particularly docosahexaenoic acid (DHA) inhibit the activation. Lipopolysaccharides (LPS) and lipopetides, ligands for TLR4 and TLR2, respectively, are acylated by saturated fatty acids. Removal of these fatty acids results in loss of their ligand activity suggesting that the saturated fatty acyl moieties are required for the receptor activation. X-ray crystallographic studies revealed that these saturated fatty acyl groups of the ligands directly occupy hydrophobic lipid binding domains of the receptors (or co-receptor) and induce the dimerization which is prerequisite for the receptor activation. Saturated fatty acids also induce the dimerization and translocation of TLR4 and TLR2 into lipid rafts in plasma membrane and this process is inhibited by DHA. Whether saturated fatty acids induce the dimerization of the receptors by interacting with these lipid binding domains is not known. Many experimental results suggest that saturated fatty acids promote the formation of lipid rafts and recruitment of TLRs into lipid rafts leading to ligand independent dimerization of the receptors. Such a mode of ligand independent receptor activation defies the conventional concept of ligand induced receptor activation; however, this may enable diverse non-microbial molecules with endogenous and dietary origins to modulate TLR-mediated immune responses. Emerging experimental evidence reveals that TLRs play a key role in bridging diet-induced endocrine and metabolic changes to immune responses. Published by Elsevier B.V.

Light-Induced Alterations in Basil Ganglia Kynurenic Acid Levels

NASA Technical Reports Server (NTRS)

Sroufe, Angela E.; Whittaker, J. A.; Patrickson, J. W.; Orr, M. C.

1997-01-01

The metabolic synthesis, release and breakdown of several known CNS neurotransmitters have been shown to follow a circadian pattern entrained to the environmental light/dark cycle. The levels of excitatory amino acid (EAA) transmitters such as glutamate, have been shown to vary with environmental lighting conditions. Kynurenic Acid (KA), an endogenous tryptophan metabolite and glutamate receptor antagonist, has been reported to have neuroprotective effects against EAA-induced excitotoxic cell damage. Changes in KA's activity within the mammalian basal ganglia has been proposed as being contributory to neurotoxicity in Huntington's Disease. It is not known whether CNS KA levels follow a circadian pattern or exhibit light-induced fluctuations. However, because the symptoms of certain degenerative motor disorders seem to fluctuate with daily 24 hour rhythm, we initiated studies to determine if basal ganglia KA were influenced by the daily light/dark cycle and could influence motor function. Therefore in this study, HPLC-EC was utilized to determine if basal ganglia KA levels in tissue extracts from adult male Long-Evans rats (200-250g) entrained to 24 and 48 hours constant light and dark conditions, respectively. Samples were taken one hour before the onset of the subjective day and one hour prior to the onset of the subjective night in order to detect possible phase differences in KA levels and to allow for accumulation of factors expressed in association with the light or dark phase. Data analysis revealed that KA levels in the basal ganglia vary with environmental lighting conditions; being elevated generally during the dark. Circadian phase differences in KA levels were also evident during the subjective night and subjective day, respectively. Results from these studies are discussed with respect to potential cyclic changes in neuronal susceptibility to excitotoxic damage during the daily 24 hour cycle and its possible relevance to future therapeutic approaches in

Prepuberal intranasal dopamine treatment in an animal model of ADHD ameliorates deficient spatial attention, working memory, amino acid transmitters and synaptic markers in prefrontal cortex, ventral and dorsal striatum.

PubMed

Ruocco, L A; Treno, C; Gironi Carnevale, U A; Arra, C; Mattern, C; Huston, J P; de Souza Silva, M A; Nikolaus, S; Scorziello, A; Nieddu, M; Boatto, G; Illiano, P; Pagano, C; Tino, A; Sadile, A G

2014-09-01

Intranasal application of dopamine (IN-DA) has been shown to increase motor activity and to release DA in the ventral (VS) and dorsal striatum (DS) of rats. The aim of the present study was to assess the effects of IN-DA treatment on parameters of DA and excitatory amino acid (EAA) function in prepuberal rats of the Naples high-excitability (NHE) line, an animal model for attention-deficit hyperactivity disorder (ADHD) and normal random bred (NRB) controls. NHE and NRB rats were daily administered IN-DA (0.075, 0.15, 0.30 mg/kg) or vehicle for 15 days from postnatal days 28-42 and subsequently tested in the Làt maze and in the Eight-arm radial Olton maze. Soluble and membrane-trapped L-glutamate (L-Glu) and L-aspartate (L-Asp) levels as well as NMDAR1 subunit protein levels were determined after sacrifice in IN-DA- and vehicle-treated NHE and NRB rats in prefrontal cortex (PFc), DS and VS. Moreover, DA transporter (DAT) protein and tyrosine hydroxylase (TH) levels were assessed in PFc, DS, VS and mesencephalon (MES) and in ventral tegmental area (VTA) and substantia nigra, respectively. In NHE rats, IN-DA (0.30 mg/kg) decreased horizontal activity and increased nonselective attention relative to vehicle, whereas the lower dose (0.15 mg/kg) increased selective spatial attention. In NHE rats, basal levels of soluble EAAs were reduced in PFc and DS relative to NRB controls, while membrane-trapped EAAs were elevated in VS. Moreover, basal NMDAR1 subunit protein levels were increased in PFc, DS and VS relative to NRB controls. In addition, DAT protein levels were elevated in PFc and VS relative to NRB controls. IN-DA led to a number of changes of EAA, NMDAR1 subunit protein, TH and DAT protein levels in PFc, DS, VS, MES and VTA, in both NHE and NRB rats with significant differences between lines. Our findings indicate that the NHE rat model of ADHD may be characterized by (1) prefrontal and striatal DAT hyperfunction, indicative of DA hyperactivty, and (2

Effects of the NMDA receptor antagonist, D-CPPene, on sensitization to the operant decrement produced by naloxone in morphine-treated rats.

PubMed

Bespalov, A Y; Medvedev, I O; Sukhotina, I A; Zvartau, E E

2001-04-01

Sensitization to the rate-decreasing effects of opioid antagonists induced by acute pretreatment with opioid agonists has been suggested to reflect initial changes in opioid systems that underlie physical dependence. Glutamate receptors are implicated in the development and expression of opioid dependence, and antagonists acting at the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors have been shown repeatedly to attenuate the severity of opioid withdrawal. The present study evaluated the ability of a competitive NMDA receptor antagonist, D-CPPene (SDZ EAA 494; 3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphonic acid), to affect morphine-induced sensitization to naloxone in rats trained to lever-press on a multiple-trial, fixed-ratio 10 schedule of food reinforcement. D-CPPene (0.3-3 mg/kg) was administered either 4 h or 30 min prior to the test session. Morphine (10 mg/kg) or its vehicle was administered 4 h before naloxone challenge (0.3-3 mg/kg). D-CPPene failed to prevent morphine-induced potentiation of the naloxone-produced decrement in operant performance. Thus, these results suggest that agonist-induced sensitization to behavioral effects of opioid antagonists may be insensitive to NMDA receptor blockade.

Application of GPCR Structures for Modelling of Free Fatty Acid Receptors.

PubMed

Tikhonova, Irina G

2017-01-01

Five G protein-coupled receptors (GPCRs) have been identified to be activated by free fatty acids (FFA). Among them, FFA1 (GPR40) and FFA4 (GPR120) bind long-chain fatty acids, FFA2 (GPR43) and FFA3 (GPR41) bind short-chain fatty acids and GPR84 binds medium-chain fatty acids. Free fatty acid receptors have now emerged as potential targets for the treatment of diabetes, obesity and immune diseases. The recent progress in crystallography of GPCRs has now enabled the elucidation of the structure of FFA1 and provided reliable templates for homology modelling of other FFA receptors. Analysis of the crystal structure and improved homology models, along with mutagenesis data and structure activity, highlighted an unusual arginine charge-pairing interaction in FFA1-3 for receptor modulation, distinct structural features for ligand binding to FFA1 and FFA4 and an arginine of the second extracellular loop as a possible anchoring point for FFA at GPR84. Structural data will be helpful for searching novel small-molecule modulators at the FFA receptors.

Bile acid receptors link nutrient sensing to metabolic regulation

PubMed Central

Li, Jibiao; Li, Tiangang

2017-01-01

Non-alcoholic fatty liver disease (NAFLD) is a common liver disease in Western populations. Non-alcoholic steatohepatitis (NASH) is a more debilitating form of NAFLD characterized by hepatocellular injury and inflammation, which significantly increase the risk of end-stage liver and cardiovascular diseases. Unfortunately, there are no available drug therapies for NASH. Bile acids are physiological detergent molecules that are synthesized from cholesterol exclusively in the hepatocytes. Bile acids circulate between the liver and intestine, where they are required for cholesterol solubilization in the bile and dietary fat emulsification in the gut. Bile acids also act as signaling molecules that regulate metabolic homeostasis and inflammatory processes. Many of these effects are mediated by the bile acid-activated nuclear receptor farnesoid X receptor (FXR) and the G protein-coupled receptor TGR5. Nutrient signaling regulates hepatic bile acid synthesis and circulating plasma bile acid concentrations, which in turn control metabolic homeostasis. The FXR agonist obeticholic acid has had beneficial effects on NASH in recent clinical trials. Preclinical studies have suggested that the TGR5 agonist and the FXR/TGR5 dual agonist are also potential therapies for metabolic liver diseases. Extensive studies in the past few decades have significantly improved our understanding of the metabolic regulatory function of bile acids, which has provided the molecular basis for developing promising bile acid-based therapeutic agents for NASH treatment. PMID:29098111

Environmentally Compliant Thermoplastic Powder Coating, Phase 1

DTIC Science & Technology

1992-10-07

TPC flame sprayed application equipment and ethylene acrylic acid (EAA) and ethylene methacrylic acid (EMAA) copolymers thermoplastic powder...have worked closely with Dow Chemical to develop and optimize their systems using Dow "Envelon" ethylene acrylic acid (EAA) thermoplastic copolymers...provide on/off control. CFS recommends the use of Dow "Envelon" ethylene acrylic acid (EAA) copolymer thermoplastic powder with this unit. The CFS system

PAR-2, IL-4R, TGF-β and TNF-α in bronchoalveolar lavage distinguishes extrinsic allergic alveolitis from sarcoidosis.

PubMed

Matěj, Radoslav; Smětáková, Magdalena; Vašáková, Martina; Nováková, Jana; Sterclová, Martina; Kukal, Jaromír; Olejár, Tomáš

2014-08-01

Sarcoidosis (SARC) and extrinsic allergic alveolitis (EAA) share certain markers, making a differential diagnosis difficult even with histopathological investigation. In lung tissue, proteinase-activated receptor-2 (PAR-2) is primarily investigated with regard to epithelial and inflammatory perspectives. Varying levels of certain chemokines can be a useful tool for distinguishing EAA and SARC. Thus, in the present study, differences in the levels of transforming growth factor (TGF)-β1, tumor necrosis factor (TNF)-α, interleukin-4 receptor (IL-4R) and PAR-2 in bronchoalveolar lavage fluid (BALF) were compared, using an ELISA method, between 14 patients with EAA and six patients with SARC. Statistically significant higher levels of IL-4R, PAR-2 and the PAR-2/TGF-β1 and PAR-2/TNF-α ratios were observed in EAA patients as compared with SARC patients. Furthermore, the ratios of TNF-α/total protein, TGF-β1/PAR-2 and TNF-α/PAR-2 were significantly lower in EAA patients than in SARC patients. The results indicated a higher detection of PAR-2 in EAA samples in association with TNF-α and TGF-β levels. As EAA and PAR-2 in parallel belong to the Th2-mediated pathway, the results significantly indicated an association between this receptor and etiology. In addition, the results indicated that SARC is predominantly a granulomatous inflammatory disease, thus, higher levels of TNF-α are observed. Therefore, the detection of PAR-2 and investigated chemokines in BALF may serve as a useful tool in the differential diagnosis between EAA and SARC.

A carnivore embryo's perspective on essential amino acids and ammonium in culture medium: effects on the development of feline embryos.

PubMed

Herrick, Jason R; Lyons, Sarah M; Greene-Ermisch, Alison F; Broeckling, Corey D; Schoolcraft, William B; Krisher, Rebecca L

2018-05-18

Carnivores are an interesting model for studies of embryonic amino acid metabolism and ammonium (NH4+) toxicity given the high protein content of their diets. Our objectives were to examine concentration- and stage-specific effects of essential amino acids (EAA; 0x, 0.125x, 0.25x, 0.5x, or 1.0x the concentrations in Minimum Essential Medium) and NH4+ (0, 300, or 600 μM) on the development and metabolism of feline embryos. The presence of EAA, regardless of concentration, during days 3 to 7 of culture increased (P < 0.01) the proportion of embryos that initiated hatching (>14.3%) and the total number of cells per blastocyst (>148.3 cells) compared to embryos cultured without EAA (0.0% and 113.2 ± 3.7 cells, respectively). The presence of EAA during days 1 to 3 (0.25x) and 3 to 7 (1.0x) of culture increased (P < 0.01) the proportions of embryos that formed blastocysts (82.9 ± 4.2%) and initiated hatching (32.9 ± 5.2%), and the number of cells per blastocyst (247.9 ± 12.1 cells), compared to control embryos (60.0 ± 5.3%, 0.0%, 123.2 ± 8.1 cells, respectively). The presence of NH4+ in the medium did not affect (P > 0.05) development of feline embryos. The addition of EAA or NH4+ during culture did not affect (P > 0.05) the production of Gln by feline embryos, but decreased (P < 0.05) production of Ala and increased (P < 0.05) production of urea. Additional work is needed to determine if our observations are unique to feline embryos or reflect an adaptation to a high protein diet that is conserved in other carnivores.

Azadirachtin Interacts with Retinoic Acid Receptors and Inhibits Retinoic Acid-mediated Biological Responses*

PubMed Central

Thoh, Maikho; Babajan, Banaganapalli; Raghavendra, Pongali B.; Sureshkumar, Chitta; Manna, Sunil K.

2011-01-01

Considering the role of retinoids in regulation of more than 500 genes involved in cell cycle and growth arrest, a detailed understanding of the mechanism and its regulation is useful for therapy. The extract of the medicinal plant Neem (Azadirachta indica) is used against several ailments especially for anti-inflammatory, anti-itching, spermicidal, anticancer, and insecticidal activities. In this report we prove the detailed mechanism on the regulation of retinoic acid-mediated cell signaling by azadirachtin, active components of neem extract. Azadirachtin repressed all trans-retinoic acid (ATRA)-mediated nuclear transcription factor κB (NF-κB) activation, not the DNA binding but the NF-κB-dependent gene expression. It did not inhibit IκBα degradation, IκBα kinase activity, or p65 phosphorylation and its nuclear translocation but inhibited NF-κB-dependent reporter gene expression. Azadirachtin inhibited TRAF6-mediated, but not TRAF2-mediated NF-κB activation. It inhibited ATRA-induced Sp1 and CREB (cAMP-response element-binding protein) DNA binding. Azadirachtin inhibited ATRA binding with retinoid receptors, which is supported by biochemical and in silico evidences. Azadirachtin showed strong interaction with retinoid receptors. It suppressed ATRA-mediated removal of retinoid receptors, bound with DNA by inhibiting ATRA binding to its receptors. Overall, our data suggest that azadirachtin interacts with retinoic acid receptors and suppresses ATRA binding, inhibits falling off the receptors, and activates transcription factors like CREB, Sp1, NF-κB, etc. Thus, azadirachtin exerts anti-inflammatory and anti-metastatic responses by a novel pathway that would be beneficial for further anti-inflammatory and anti-cancer therapies. PMID:21127062

Azadirachtin interacts with retinoic acid receptors and inhibits retinoic acid-mediated biological responses.

PubMed

Thoh, Maikho; Babajan, Banaganapalli; Raghavendra, Pongali B; Sureshkumar, Chitta; Manna, Sunil K

2011-02-11

Considering the role of retinoids in regulation of more than 500 genes involved in cell cycle and growth arrest, a detailed understanding of the mechanism and its regulation is useful for therapy. The extract of the medicinal plant Neem (Azadirachta indica) is used against several ailments especially for anti-inflammatory, anti-itching, spermicidal, anticancer, and insecticidal activities. In this report we prove the detailed mechanism on the regulation of retinoic acid-mediated cell signaling by azadirachtin, active components of neem extract. Azadirachtin repressed all trans-retinoic acid (ATRA)-mediated nuclear transcription factor κB (NF-κB) activation, not the DNA binding but the NF-κB-dependent gene expression. It did not inhibit IκBα degradation, IκBα kinase activity, or p65 phosphorylation and its nuclear translocation but inhibited NF-κB-dependent reporter gene expression. Azadirachtin inhibited TRAF6-mediated, but not TRAF2-mediated NF-κB activation. It inhibited ATRA-induced Sp1 and CREB (cAMP-response element-binding protein) DNA binding. Azadirachtin inhibited ATRA binding with retinoid receptors, which is supported by biochemical and in silico evidences. Azadirachtin showed strong interaction with retinoid receptors. It suppressed ATRA-mediated removal of retinoid receptors, bound with DNA by inhibiting ATRA binding to its receptors. Overall, our data suggest that azadirachtin interacts with retinoic acid receptors and suppresses ATRA binding, inhibits falling off the receptors, and activates transcription factors like CREB, Sp1, NF-κB, etc. Thus, azadirachtin exerts anti-inflammatory and anti-metastatic responses by a novel pathway that would be beneficial for further anti-inflammatory and anti-cancer therapies.

Unsaturated free fatty acids increase benzodiazepine receptor agonist binding depending on the subunit composition of the GABAA receptor complex.

PubMed

Witt, M R; Westh-Hansen, S E; Rasmussen, P B; Hastrup, S; Nielsen, M

1996-11-01

It has been shown previously that unsaturated free fatty acids (FFAs) strongly enhance the binding of agonist benzodiazepine receptor ligands and GABAA receptor ligands in the CNS in vitro. To investigate the selectivity of this effect, recombinant human GABAA/benzodiazepine receptor complexes formed by different subunit compositions (alpha x beta y gamma 2, x = 1, 2, 3, and 5; y = 1, 2, and 3) were expressed using the baculovirus-transfected Sf9 insect cell system. At 10(-4) M, unsaturated FFAs, particularly arachidonic (20:4) and docosahexaenoic (22:6) acids, strongly stimulated (> 200% of control values) the binding of [3H]flunitrazepam ([3H]FNM) to the alpha 3 beta 2 gamma 2 receptor combination in whole cell preparations. No effect or small increases in levels of unsaturated FFAs on [3H]FNM binding to alpha 1 beta x gamma 2 and alpha 2 beta x gamma 2 receptor combinations were observed, and weak effects (130% of control values) were detected using the alpha 5 beta 2 gamma 2 receptor combination. The saturated FFAs, stearic and palmitic acids, were without effect on [3H]FNM binding to any combination of receptor complexes. The hydroxylated unsaturated FFAs, ricinoleic and ricinelaidic acids, were shown to decrease the binding of [3H]FNM only if an alpha 1 beta 2 gamma 2 receptor combination was used. Given the heterogeneity of the GABAA/ benzodiazepine receptor subunit distribution in the CNS, the effects of FFAs on the benzodiazepine receptor can be assumed to vary at both cellular and regional levels.

Amino acid sensing in hypothalamic tanycytes via umami taste receptors.

PubMed

Lazutkaite, Greta; Soldà, Alice; Lossow, Kristina; Meyerhof, Wolfgang; Dale, Nicholas

2017-11-01

Hypothalamic tanycytes are glial cells that line the wall of the third ventricle and contact the cerebrospinal fluid (CSF). While they are known to detect glucose in the CSF we now show that tanycytes also detect amino acids, important nutrients that signal satiety. Ca 2+ imaging and ATP biosensing were used to detect tanycyte responses to l-amino acids. The downstream pathway of the responses was determined using ATP receptor antagonists and channel blockers. The receptors were characterized using mice lacking the Tas1r1 gene, as well as an mGluR4 receptor antagonist. Amino acids such as Arg, Lys, and Ala evoke Ca 2+ signals in tanycytes and evoke the release of ATP via pannexin 1 and CalHM1, which amplifies the signal via a P2 receptor dependent mechanism. Tanycytes from mice lacking the Tas1r1 gene had diminished responses to lysine and arginine but not alanine. Antagonists of mGluR4 greatly reduced the responses to alanine and lysine. Two receptors previously implicated in taste cells, the Tas1r1/Tas1r3 heterodimer and mGluR4, contribute to the detection of a range of amino acids by tanycytes in CSF. Copyright © 2017 The Authors. Published by Elsevier GmbH.. All rights reserved.

Identifying the receptor subtype selectivity of retinoid X and retinoic acid receptors via quantum mechanics.

PubMed

Tsuji, Motonori; Shudo, Koichi; Kagechika, Hiroyuki

2017-03-01

Understanding and identifying the receptor subtype selectivity of a ligand is an important issue in the field of drug discovery. Using a combination of classical molecular mechanics and quantum mechanical calculations, this report assesses the receptor subtype selectivity for the human retinoid X receptor (hRXR) and retinoic acid receptor (hRAR) ligand-binding domains (LBDs) complexed with retinoid ligands. The calculated energies show good correlation with the experimentally reported binding affinities. The technique proposed here is a promising method as it reveals the origin of the receptor subtype selectivity of selective ligands.

Dexmedetomidine Prevents Excessive γ-Aminobutyric Acid Type A Receptor Function after Anesthesia.

PubMed

Wang, Dian-Shi; Kaneshwaran, Kirusanthy; Lei, Gang; Mostafa, Fariya; Wang, Junhui; Lecker, Irene; Avramescu, Sinziana; Xie, Yu-Feng; Chan, Nathan K; Fernandez-Escobar, Alejandro; Woo, Junsung; Chan, Darren; Ramsey, Amy J; Sivak, Jeremy M; Lee, C Justin; Bonin, Robert P; Orser, Beverley A

2018-06-08

Postoperative delirium is associated with poor long-term outcomes and increased mortality. General anesthetic drugs may contribute to delirium because they increase cell-surface expression and function of α5 subunit-containing γ-aminobutyric acid type A receptors, an effect that persists long after the drugs have been eliminated. Dexmedetomidine, an α2 adrenergic receptor agonist, prevents delirium in patients and reduces cognitive deficits in animals. Thus, it was postulated that dexmedetomidine prevents excessive function of α5 γ-aminobutyric acid type A receptors. Injectable (etomidate) and inhaled (sevoflurane) anesthetic drugs were studied using cultured murine hippocampal neurons, cultured murine and human cortical astrocytes, and ex vivo murine hippocampal slices. γ-Aminobutyric acid type A receptor function and cell-signaling pathways were studied using electrophysiologic and biochemical methods. Memory and problem-solving behaviors were also studied. The etomidate-induced sustained increase in α5 γ-aminobutyric acid type A receptor cell-surface expression was reduced by dexmedetomidine (mean ± SD, etomidate: 146.4 ± 51.6% vs. etomidate + dexmedetomidine: 118.4 ± 39.1% of control, n = 8 each). Dexmedetomidine also reduced the persistent increase in tonic inhibitory current in hippocampal neurons (etomidate: 1.44 ± 0.33 pA/pF, n = 10; etomidate + dexmedetomidine: 1.01 ± 0.45 pA/pF, n = 9). Similarly, dexmedetomidine prevented a sevoflurane-induced increase in the tonic current. Dexmedetomidine stimulated astrocytes to release brain-derived neurotrophic factor, which acted as a paracrine factor to reduce excessive α5 γ-aminobutyric acid type A receptor function in neurons. Finally, dexmedetomidine attenuated memory and problem-solving deficits after anesthesia. Dexmedetomidine prevented excessive α5 γ-aminobutyric acid type A receptor function after anesthesia. This novel α2 adrenergic receptor- and brain-derived neurotrophic factor

Helminthosporic acid functions as an agonist for gibberellin receptor.

PubMed

Miyazaki, Sho; Jiang, Kai; Kobayashi, Masatomo; Asami, Tadao; Nakajima, Masatoshi

2017-11-01

Helminthosporol was isolated from a fungus, Helminthosporium sativum, as a natural plant growth regulator in 1963. It showed gibberellin-like bioactivity that stimulated the growth of the second leaf sheath of rice. After studying the structure-activity relationship between the compound and some synthesized analogs, it was found that helminthosporic acid (H-acid) has higher gibberellin-like activity and chemical stability than helminthosporol. In this study, we showed that (1) H-acid displays gibberellin-like activities not only in rice but also in Arabidopsis, (2) it regulates the expression of gibberellin-related genes, (3) it induces DELLA degradation through binding with a gibberellin receptor (GID1), and (4) it forms the GID1-(H-acid)-DELLA complex to transduce the gibberellin signal in the same manner as gibberellin. This work shows that the H-acid mode of action acts as an agonist for gibberellin receptor.

Identification of COUP-TFII Orphan Nuclear Receptor as a Retinoic Acid-Activated Receptor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruse, Schoen W; Suino-Powell, Kelly; Zhou, X Edward

2010-01-12

The chicken ovalbumin upstream promoter-transcription factors (COUP-TFI and II) make up the most conserved subfamily of nuclear receptors that play key roles in angiogenesis, neuronal development, organogenesis, cell fate determination, and metabolic homeostasis. Although the biological functions of COUP-TFs have been studied extensively, little is known of their structural features or aspects of ligand regulation. Here we report the ligand-free 1.48 {angstrom} crystal structure of the human COUP-TFII ligand-binding domain. The structure reveals an autorepressed conformation of the receptor, where helix {alpha}10 is bent into the ligand-binding pocket and the activation function-2 helix is folded into the cofactor binding site,more » thus preventing the recruitment of coactivators. In contrast, in multiple cell lines, COUP-TFII exhibits constitutive transcriptional activity, which can be further potentiated by nuclear receptor coactivators. Mutations designed to disrupt cofactor binding, dimerization, and ligand binding, substantially reduce the COUP-TFII transcriptional activity. Importantly, retinoid acids are able to promote COUP-TFII to recruit coactivators and activate a COUP-TF reporter construct. Although the concentration needed is higher than the physiological levels of retinoic acids, these findings demonstrate that COUP-TFII is a ligand-regulated nuclear receptor, in which ligands activate the receptor by releasing it from the autorepressed conformation.« less

Postprandial portal fluxes of essential amino acids, volatile fatty acids, and urea-nitrogen in growing pigs fed a high-fiber diet supplemented with a multi-enzyme cocktail.

PubMed

Agyekum, A K; Kiarie, E; Walsh, M C; Nyachoti, C M

2016-09-01

The present study investigated the effects of adding a multi-enzyme cocktail (MC) to a high-fiber diet on net portal-drained viscera (PDV) fluxes of essential AA (EAA), volatile fatty acids (VFA), and blood urea-N (BUN) in growing pigs. Five female pigs (22.8 ± 1.6 kg BW), with catheters in the portal vein, ileal vein, and carotid artery, were fed 3 isocaloric-nitrogenous diets at 4% of their BW once daily at 0900 h for 7 d in a replicated 3 × 3 Latin square design. The diets contained corn and soybean meal with 0% (control) or 30% distillers' dried grains with solubles (DDGS; HF) produced from a 1:1 mixture of wheat and corn. The third diet was supplemented with MC in addition to the 30% DDGS (HF + MC). The MC supplied (analyzed values) 5,397 U of xylanase, 162 U of β-glucanase, and 2,000 U of protease and guaranteed minimum activities of 1,000 U of α-amylase and 25 U of pectinase per kg of diet. On d 7, para-amino hippuric acid was infused into the ileal vein (to measure flow rate), and blood was sampled from the portal vein and carotid artery for 7 h after feeding to assay EAA, urea-N, and VFA. Portal absorption of nutrients was derived by multiplying the porto-arterial plasma concentration differences by portal vein blood flow. Diet had no effect on postprandial portal vein plasma flow rate and net BUN flux, but portal BUN tended to be lower ( = 0.070) and arterial BUN was lower ( 0.05) over the 7 h in pigs fed control. Postprandial portal Arg, Ile, Leu, Trp, and Val or net fluxes were lower ( 0.05) in HF-fed pigs from 30 to 240 min than control-fed pigs and MC supplementation tended (0.05 ≤ ≤ 0.10) to or improved ( 0.05) portal appearances of those AA, but not their fluxes. Control-fed pigs had higher ( 0.05) net portal fluxes of most EAA and pigs fed HF + MC had higher ( 0.05) Lys, and similar Met and Phe net portal fluxes were compared with control-fed pigs. Portal VFA was not affected by diet. However, total portal VFA flux was lower ( 0.05) in the

Modulation of GABAA receptors by valerian extracts is related to the content of valerenic acid.

PubMed

Trauner, Gabriele; Khom, Sophia; Baburin, Igor; Benedek, Birgit; Hering, Steffen; Kopp, Brigitte

2008-01-01

Valeriana Officinalis L . is a traditionally used sleep remedy, however, the mechanism of action and the substances responsible for its sedative and sleep-enhancing properties are not fully understood. As we previously identified valerenic acid as a subunit-specific allosteric modulator of GABAA receptors, we now investigated the relation between modulation of GABAA receptors by Valerian extracts of different polarity and the content of sesquiterpenic acids (valerenic acid, acetoxyvalerenic acid). All extracts were analysed by HPLC concerning the content of sesquiterpenic acids. GABAA receptors composed of alpha 1, beta 2 and gamma 2S subunits were expressed in Xenopus laevis oocytes and the modulation of chloride currents through GABAA receptors (IGABA) by Valerian extracts was investigated using the two-microelectrode voltage clamp technique. Apolar extracts induced a significant enhancement of IGABA, whereas polar extracts showed no effect. These results were confirmed by fractionating a highly active ethyl acetate extract: again fractions with high contents of valerenic acid exhibited strong receptor activation. In addition, removal of sesquiterpenic acids from the ethyl acetate extract led to a loss of I (GABA) enhancement. In conclusion, our data show that the extent of GABAA receptor modulation by Valerian extracts is related to the content of valerenic acid.

Liver X receptor alpha regulates fatty acid synthase expression in chicken.

PubMed

Demeure, O; Duby, C; Desert, C; Assaf, S; Hazard, D; Guillou, H; Lagarrigue, S

2009-12-01

Liver X receptor alpha (LXRalpha), also referred to as nuclear receptor subfamily 1, group H, member 3 is a member of the nuclear hormone receptor superfamily, and has recently been shown to act as a master transcription factor governing hepatic lipogenesis in mammals. Liver X receptor alpha directly regulates both the expression of other lipogenic transcription factors and the expression of lipogenic enzymes, thereby enhancing hepatic fatty acid synthesis (FASN). In birds, like in humans, fatty acid synthesis primarily occurs in the liver. Whether LXRalpha is involved in hepatic regulation of lipogenic genes remained to be investigated in this species. Here we show that fatty acid synthase and the expression of other lipogenic genes (sterol regulatory element binding protein 1 and steroyl coenzyme A desaturase 1) are induced in chicken hepatoma cells in response to a pharmacological liver X receptor agonist, T0901317. A detailed analysis of the chicken FASN promoter revealed a functional liver X response element. These data define the chicken FASN gene as a direct target of LXRalpha and further expand the role of LXRalpha as a regulator of lipid metabolism in this species.

Preparation and luminescent properties of the novel polymer-rare earth complexes composed of Poly(ethylene-co-acrylic acid) and Europium ions

NASA Astrophysics Data System (ADS)

Wu, Yuewen; Hao, Haixia; Wu, Qingyao; Gao, Zihan; Xie, Hongde

2018-06-01

A series of novel polymer-rare earth complexes with Eu3+ ions have been synthesized and investigated successfully, including the binary complexes containing the single ligand poly(ethylene-co-acrylic acid) (EAA) and the ternary complexes using 1,10-phenanthroline (phen), dibenzoylmethane (DBM) or thenoyltrifluoroacetone (TTA) as the second ligand. Their structures have been characterized by Fourier transform infrared spectroscopy (FT-IR), elemental analysis and X-ray diffraction (XRD), which confirm that both EAA and small molecules participate in the coordination reaction with rare earth ions, and they can disperse homogeneously in the polymer matrixes. Both ultraviolet-visible (UV-vis) absorption and photoluminescence tests for the complexes have been recorded. The relationship between fluorescence intensity of polymer-rare earth complexes and the quantity of ligand EAA has been studied and discussed. The films casted from the complexes solution can emit strong characteristic red light under UV light excitation. All these results suggest that the complexes possess potential application as luminescent materials.

Water-Soluble Nanoparticle Receptors Supramolecularly Coded for Acidic Peptides.

PubMed

Fa, Shixin; Zhao, Yan

2018-01-02

Sequence-specific recognition of peptides is of enormous importance to many chemical and biological applications, but has been difficult to achieve due to the minute differences in the side chains of amino acids. Acidic peptides are known to play important roles in cell growth and gene expression. In this work, we report molecularly imprinted micelles coded with molecular recognition information for the acidic and hydrophobic side chains of acidic peptides. The imprinted receptors could distinguish acidic amino acids from other polar and nonpolar amino acids, with dissociation constants of tens of nanomolar for biologically active peptides containing up to 18 amino acids. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Invited review: Current representation and future trends of predicting amino acid utilization in the lactating dairy cow.

PubMed

Arriola Apelo, S I; Knapp, J R; Hanigan, M D

2014-07-01

In current dairy production systems, an average of 25% of dietary N is captured in milk, with the remainder being excreted in urine and feces. About 60% of total N losses occur postabsorption. Splanchnic tissues extract a fixed proportion of total inflow of each essential AA (EAA). Those EAA removed by splanchnic tissues and not incorporated into protein are subjected to catabolism, with the resulting N converted to urea. Splanchnic affinity varies among individual EAA, from several fold lower than mammary glands' affinity for the branched-chain AA to similar or higher affinity for Phe, Met, His, and Arg. On average, 85% of absorbed EAA appear in peripheral circulation, indicating that first-pass removal is not the main source of loss. Essential AA in excess of the needs of the mammary glands return to general circulation. High splanchnic blood flow dictates that a large proportion of EAA that return to general circulation flow through splanchnic tissues. In association with this constant recycling, EAA are removed and catabolized by splanchnic tissues. This results in splanchnic catabolism equaling or surpassing the use of many EAA for milk protein synthesis. Recent studies have demonstrated that EAA, energy substrates, and hormones activate signaling pathways that in turn regulate local blood flow, tissue extraction of EAA, and rates of milk protein synthesis. These recent findings would allow manipulation of dairy diets to maximize mammary uptake of EAA and reduce catabolism by splanchnic tissues. Dairy cattle nutrient requirement systems consider EAA requirements in aggregate as metabolizable protein (MP) and assume a fixed efficiency of MP use for milk protein. Lysine and Met sufficiency is only considered after MP requirements have been met. By doing so, requirement systems limit the scope of diet manipulation to achieve improved gross N efficiency. Therefore, this review focuses on understanding the dynamics of EAA metabolism in mammary and splanchnic

Effect of abomasal glucose infusion on splanchnic amino acid metabolism in periparturient dairy cows.

PubMed

Larsen, M; Kristensen, N B

2009-07-01

Six Holstein cows fitted with ruminal cannulas and permanent indwelling catheters in the portal vein, hepatic vein, mesenteric vein, and an artery were used to study the effects of abomasal glucose infusion on splanchnic AA metabolism. The experimental design was a split plot, with cow as the whole plot, treatment as the whole-plot factor and days in milk (DIM) as the subplot factor. Cows were assigned to 1 of 2 treatments: control or infusion of 1,500 g/d of glucose into the abomasum from the day of calving to 29 DIM. Cows were sampled prepartum and at 4, 15, and 29 DIM. Postpartum dry matter intake increased at a lower rate with infusion compared with the control. Arterial concentrations of all essential AA (EAA) were lower with infusion compared with the control. Net portal fluxes of His, Ile, Leu, Lys, Met, Phe, Thr, Val, Ala, Pro, Ser, and Tyr were lower with infusion compared with the control and the net portal fluxes of these AA showed positive correlations with dry matter intake, whereas the net portal fluxes of Asp, Glu, and Gln were unaffected by treatment. Net hepatic fluxes of EAA were not affected by treatment but increased as lactation progressed with both treatments. On a net basis, all EAA were removed by the liver prepartum and at 4 DIM, whereas Met, Phe, and Thr were the only EAA being removed at 29 DIM. Except for Ala, AA removed by the liver might be used primarily for noncatabolic processes, as exemplified by the 16% of hepatic Gly uptake accounted for as urinary hippurate. The measured hepatic uptake of glucogenic precursors (glucogenic AA, volatile fatty acids, lactate, and glycerol) accounted for 50 to 90% of the hepatic release of glucose. The hepatic urea output accounted for more than 100% of the hepatic ureagenic precursor uptake, indicating that the glucogenic precursors unaccounted for are nonnitrogen-containing compounds. In conclusion, an increased exogenous glucose supply to the small intestine did not seem to affect the amount of

Glutamatergic modulation of separation distress: profound emotional effects of excitatory amino acids in chicks.

PubMed

Normansell, Larry; Panksepp, Jaak

2011-10-01

Pre-clinical models of brain affective circuits provide relevant evidence for understanding the brain systems that figure heavily in psychiatric disorders. Social isolation and the resulting separation distress contribute to the onset of depression. In this work, the effects of excitatory amino acids (EAA) on isolation-induced distress vocalization (DV) were assessed in young domestic chicks. Both glutamate and quisqualate (QA) produced dose-dependent reductions in DVs, while N-methyl-d-aspartate (NMDA) and kainate (KA) increased DVs. Such a differential pattern of responsiveness may indicate the presence of reciprocal or interacting EAA systems in the brain control of separation distress. Administration of either the NMDA receptor antagonist 2-amino-5-phosphonovalerate (APV) or the broad-spectrum antagonist gamma-d-glutamylglycine (DGG) greatly reduced DVs, as did the antagonist 2-amino-4-phosphonobutyrate (APB). APV did not attenuate the increase in vocalizations seen after NMDA or KA administration. DGG, however, was able to block the increase in calling produced by either of these agonists, suggesting a KA receptor mechanism. KA treatment inhibited the ability of other chicks, or auditory and somatosensory information, to suppress DVs. KA-treated animals exhibited a hyperemotional behavior pattern during which a variety of motivated behaviors were disrupted including reactions to novel objects, approaching the flock, and foraging. They could not sustain a coherent flock-like social cohesion, but exhibited strong fixed-action patterns of flight interspersed with hiding and crouching behaviors. The evident behavioral changes suggest that glutamatergic synapses directly influence sensory, motor and emotional processes in the brain and may be especially important in the integration of environmental stimuli with emotional central state processes of animals. Considering that unresolved social loss and grief have been deemed to be among the main precipitating causes

Heterodimers of Retinoic Acid Receptors and Thyroid Hormone Receptors Display Unique Combinatorial Regulatory Properties

PubMed Central

Lee, Sangho; Privalsky, Martin L.

2009-01-01

Nuclear receptors are ligand-regulated transcription factors that regulate key aspects of metazoan development, differentiation, and homeostasis. Nuclear receptors recognize target genes by binding to specific DNA recognition sequences, denoted hormone response elements (HREs). Many nuclear receptors can recognize HREs as either homodimers or heterodimers. Retinoid X receptors (RXRs), in particular, serve as important heterodimer partners for many other nuclear receptors, including thyroid hormone receptors (TRs), and RXR/TR heterodimers have been proposed to be the primary mediators of target gene regulation by T3 hormone. Here, we report that the retinoic acid receptors (RARs), a distinct class of nuclear receptors, are also efficient heterodimer partners for TRs. These RAR/TR heterodimers form with similar affinities as RXR/TR heterodimers on an assortment of consensus and natural HREs, and preferentially assemble with the RAR partner 5′ of the TR moiety. The corepressor and coactivator recruitment properties of these RAR/TR heterodimers and their transcriptional activities in vivo are distinct from those observed with the corresponding RXR heterodimers. Our studies indicate that RXRs are not unique in their ability to partner with TRs, and that RARs can also serve as robust heterodimer partners and combinatorial regulators of T3-modulated gene expression. PMID:15650024

Synthesis and biological evaluation of 2-heteroarylthioalkanoic acid analogues of clofibric acid as peroxisome proliferator-activated receptor alpha agonists.

PubMed

Giampietro, Letizia; Ammazzalorso, Alessandra; Giancristofaro, Antonella; Lannutti, Fabio; Bettoni, Giancarlo; De Filippis, Barbara; Fantacuzzi, Marialuigia; Maccallini, Cristina; Petruzzelli, Michele; Morgano, Annalisa; Moschetta, Antonio; Amoroso, Rosa

2009-10-22

A series of 2-heteroarylthioalkanoic acids were synthesized through systematic structural modifications of clofibric acid and evaluated for human peroxisome proliferator-activated receptor alpha (PPARalpha) transactivation activity, with the aim of obtaining new hypolipidemic compounds. Some thiophene and benzothiazole derivatives showing a good activation of the receptor alpha were screened for activity against the PPARgamma isoform. The gene induction of selected compounds was also investigated in the human hepatoma cell line.

Nicotinic Acid Receptor Abnormalities in Human Skin Cancer: Implications for a Role in Epidermal Differentiation

PubMed Central

Bermudez, Yira; Benavente, Claudia A.; Meyer, Ralph G.; Coyle, W. Russell; Jacobson, Myron K.; Jacobson, Elaine L.

2011-01-01

Background Chronic UV skin exposure leads to epidermal differentiation defects in humans that can be largely restored by pharmacological doses of nicotinic acid. Nicotinic acid has been identified as a ligand for the human G-protein-coupled receptors GPR109A and GPR109B that signal through Gi-mediated inhibition of adenylyl cyclase. We have examined the expression, cellular distribution, and functionality of GPR109A/B in human skin and skin derived epidermal cells. Results Nicotinic acid increases epidermal differentiation in photodamaged human skin as judged by the terminal differentiation markers caspase 14 and filaggrin. Both GPR109A and GPR109B genes are transcribed in human skin and in epidermal keratinocytes, but expression in dermal fibroblasts is below limits of detection. Receptor transcripts are greatly over-expressed in squamous cell cancers. Receptor protein in normal skin is prominent from the basal through granular layers of the epidermis, with cellular localization more dispersive in the basal layer but predominantly localized at the plasma membrane in more differentiated epidermal layers. In normal human primary and immortalized keratinocytes, nicotinic acid receptors show plasma membrane localization and functional Gi-mediated signaling. In contrast, in a squamous cell carcinoma derived cell line, receptor protein shows a more diffuse cellular localization and the receptors are nearly non-functional. Conclusions The results of these studies justify future genetic and pharmacological intervention studies to define possible specific role(s) of nicotinic acid receptors in human skin homeostasis. PMID:21655214

Endocytosis of lysosomal acid phosphatase; involvement of mannose receptor and effect of lectins.

PubMed

Imai, K; Yoshimura, T

1994-08-01

Acid phosphatase and beta-glucosidase are unique among lysosomal enzymes in that they have both high mannose and complex type sugasr chains, whereas oligosaccharide chains of lysosomal enzymes in matrix are of high mannose type. We have previously shown that beta-glucosidase was endocytosed into macrophages via an unidentified receptor different from a mannose/fucose receptor (K. Imai, Cell Struct. Funct. 13, 325-332, 1988). Here, we show that uptake of acid phosphatase purified from rat liver lysosomes into rat macrophages was inhibited by ligands for a mannose/fucose receptor and was mediated via an apparently single binding site with Kuptake of 24.7 nM. These results indicate that acid phosphatase and beta-glucosidase recognize different types of receptors even if they have similar sugar chains. Polyvalent concanavalin A which binds both to the enzyme and to macrophages specifically stimulated the uptake in a dose dependent manner, whereas wheat germ agglutinin and phytohaemagglutinin did not.

Proximate composition and nutritional quality of deep sea growth sea cucumbers (Stichopus japonicus) from different origins.

PubMed

Gao, Yue; Li, Zhibo; Qi, Yanxia; Guo, Zhenyu; Lin, Yantong; Li, Wei; Hu, Yucai; Zhao, Qiancheng

2016-05-01

Deep sea growth sea cucumber (Stichopus japonicus) (DSG-SC) is considered a most nutritious and luxurious seafood in Asia. This study compared the proximate composition and nutritional quality of collagen, polysaccharides, amino acids (AAs) and fatty acids (FAs) in DSG-SCs from different origins. The contents of protein, ash, carbohydrate, fat, collagen, saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), total amino acids (TAAs), essential amino acids (EAAs), fucose and uronic acid differed among the origins. DSG-SC of Dalian origin had lower contents of ash, fat, uronic acid, TAAs and EAAs but higher contents of protein, collagen, PUFAs, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and fucose compared with the other origins. DSG-SCs had a higher proportion of PUFAs and were richer in polysaccharides than other seafood. Glutamate and glycine were the dominant AAs, while leucine and threonine were the most abundant EAAs. DSG-SCs are a good source of collagen, polysaccharides (especially fucose), EAAs (especially leucine and threonine) and PUFAs (especially EPA and DHA). Dalian seems to be a promising origin to produce high-value sea cucumber with high PUFA, fucose, collagen and protein contents. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

Farnesoid X receptor induces Takeda G-protein receptor 5 cross-talk to regulate bile acid synthesis and hepatic metabolism.

PubMed

Pathak, Preeti; Liu, Hailiang; Boehme, Shannon; Xie, Cen; Krausz, Kristopher W; Gonzalez, Frank; Chiang, John Y L

2017-06-30

The bile acid-activated receptors, nuclear farnesoid X receptor (FXR) and the membrane Takeda G-protein receptor 5 (TGR5), are known to improve glucose and insulin sensitivity in obese and diabetic mice. However, the metabolic roles of these two receptors and the underlying mechanisms are incompletely understood. Here, we studied the effects of the dual FXR and TGR5 agonist INT-767 on hepatic bile acid synthesis and intestinal secretion of glucagon-like peptide-1 (GLP-1) in wild-type, Fxr -/- , and Tgr5 -/- mice. INT-767 efficaciously stimulated intracellular Ca 2+ levels, cAMP activity, and GLP-1 secretion and improved glucose and lipid metabolism more than did the FXR-selective obeticholic acid and TGR5-selective INT-777 agonists. Interestingly, INT-767 reduced expression of the genes in the classic bile acid synthesis pathway but induced those in the alternative pathway, which is consistent with decreased taurocholic acid and increased tauromuricholic acids in bile. Furthermore, FXR activation induced expression of FXR target genes, including fibroblast growth factor 15, and unexpectedly Tgr5 and prohormone convertase 1/3 gene expression in the ileum. We identified an FXR-responsive element on the Tgr5 gene promoter. Fxr -/- and Tgr5 -/- mice exhibited reduced GLP-1 secretion, which was stimulated by INT-767 in the Tgr5 -/- mice but not in the Fxr -/- mice. Our findings uncovered a novel mechanism in which INT-767 activation of FXR induces Tgr5 gene expression and increases Ca 2+ levels and cAMP activity to stimulate GLP-1 secretion and improve hepatic glucose and lipid metabolism in high-fat diet-induced obese mice. Activation of both FXR and TGR5 may therefore represent an effective therapy for managing hepatic steatosis, obesity, and diabetes. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Effect of ascorbic acid or increasing metabolizable energy level with or without supplementation of some essential amino acids on productive and physiological traits of slow-growing chicks exposed to chronic heat stress.

PubMed

Attia, Y A; Hassan, R A; Tag El-Din, A E; Abou-Shehema, B M

2011-12-01

Four hundred and twenty, 21-day-old slow-growing chicks were divided randomly into seven treatments, each containing five replicates. Each replicate was kept in a 1 × 1-m floor pen. One treatment was kept under thermo-neutral conditions in a semi-open house and fed a corn-soybean meal diet (positive control). The other six groups were kept under chronic heat stress (CHS) at 38 °C and 60% RH for 4 h from 12:00 to 16:00 pm for three successive days per week. Chicks in CHS treatments were fed a corn-soybean meal diet without (negative control) or with increasing metabolizable energy (ME) level by oil supplementation alone, or also with increasing some essential amino acids (EAA) such as methionine (Met), methionine and lysine (Met+Lys) or methionine, lysine and arginine (Met+Lys+Arg) or supplemented with 250 mg of ascorbic acid (AA)/kg. CHS impaired (p < 0.05) growth performance, increased plasma triglycerides and total serum Ca while decreasing (p < 0.05) plasma glucose and total serum protein. Meanwhile 250 mg AA/kg diet or an increasing ME without or with some EAA partially alleviated (p < 0.0001) the negative effect of CHS on growth while increasing (p < 0.05) feed intake and improving (p < 0.05) feed:gain ratio (F:G) and crude protein (CP) digestibility (p < 0.05). AA or increasing ME with or without EAA increased (p < 0.05) percentage dressing, liver and giblets to those of the positive control. AA or increasing ME with or without EAA partially alleviated the negative effect of CHS on blood pH, packed cell volume (PCV), haemoglobin (Hgb), total serum protein and total Ca, plasma glucose and triglyceride, rectal temperature and respiration rate. Increasing ME level improved chickens' tolerance to CHS without a significant difference from those supplemented with AA. However, increasing Met, Lys and Arg concentration did not improve performance over that recorded with increasing ME level alone. Under CHS, 250 mg AA/kg diet or increasing ME level by addition of 3

Growth and clinical variables in nitrogen-restricted piglets fed an adjusted essential amino acid mix: Effects using partially intact protein-based diets

USDA-ARS?s Scientific Manuscript database

Current recommendations for protein levels in infant formula ensure that growth matches or exceeds growth of breast-fed infants, but may provide a surplus of amino acids (AA). Recent studies in infants using AA-based formulas support specific adjustment of the essential AA (EAA) composition allowing...

Cell-type-specific regulation of the retinoic acid receptor mediated by the orphan nuclear receptor TLX.

PubMed

Kobayashi, M; Yu, R T; Yasuda, K; Umesono, K

2000-12-01

Malformations in the eye can be caused by either an excess or deficiency of retinoids. An early target gene of the retinoid metabolite, retinoic acid (RA), is that encoding one of its own receptors, the retinoic acid receptor beta (RARbeta). To better understand the mechanisms underlying this autologous regulation, we characterized the chick RARbeta2 promoter. The region surrounding the transcription start site of the avian RARbeta2 promoter is over 90% conserved with the corresponding region in mammals and confers strong RA-dependent transactivation in primary cultured embryonic retina cells. This response is selective for RAR but not retinoid X receptor-specific agonists, demonstrating a principal role for RAR(s) in retina cells. Retina cells exhibit a far higher sensitivity to RA than do fibroblasts or osteoblasts, a property we found likely due to expression of the orphan nuclear receptor TLX. Ectopic expression of TLX in fibroblasts resulted in increased sensitivity to RA induction, an effect that is conserved between chick and mammals. We have identified a cis element, the silencing element relieved by TLX (SET), within the RARbeta2 promoter region which confers TLX- and RA-dependent transactivation. These results indicate an important role for TLX in autologous regulation of the RARbeta gene in the eye.

Cell-Type-Specific Regulation of the Retinoic Acid Receptor Mediated by the Orphan Nuclear Receptor TLX†

PubMed Central

Kobayashi, Mime; Yu, Ruth T.; Yasuda, Kunio; Umesono, Kazuhiko

2000-01-01

Malformations in the eye can be caused by either an excess or deficiency of retinoids. An early target gene of the retinoid metabolite, retinoic acid (RA), is that encoding one of its own receptors, the retinoic acid receptor β (RARβ). To better understand the mechanisms underlying this autologous regulation, we characterized the chick RARβ2 promoter. The region surrounding the transcription start site of the avian RARβ2 promoter is over 90% conserved with the corresponding region in mammals and confers strong RA-dependent transactivation in primary cultured embryonic retina cells. This response is selective for RAR but not retinoid X receptor-specific agonists, demonstrating a principal role for RAR(s) in retina cells. Retina cells exhibit a far higher sensitivity to RA than do fibroblasts or osteoblasts, a property we found likely due to expression of the orphan nuclear receptor TLX. Ectopic expression of TLX in fibroblasts resulted in increased sensitivity to RA induction, an effect that is conserved between chick and mammals. We have identified a cis element, the silencing element relieved by TLX (SET), within the RARβ2 promoter region which confers TLX- and RA-dependent transactivation. These results indicate an important role for TLX in autologous regulation of the RARβ gene in the eye. PMID:11073974

Retinoic acid induces proteasome-dependent degradation of retinoic acid receptor α (RARα) and oncogenic RARα fusion proteins

PubMed Central

Zhu, Jun; Gianni, Maurizio; Kopf, Eliezer; Honoré, Nicole; Chelbi-Alix, Mounira; Koken, Marcel; Quignon, Frédérique; Rochette-Egly, Cécile; de Thé, Hugues

1999-01-01

Analyzing the pathways by which retinoic acid (RA) induces promyelocytic leukemia/retinoic acid receptor α (PML/RARα) catabolism in acute promyelocytic leukemia (APL), we found that, in addition to caspase-mediated PML/RARα cleavage, RA triggers degradation of both PML/RARα and RARα. Similarly, in non-APL cells, RA directly targeted RARα and RARα fusions to the proteasome degradation pathway. Activation of either RARα or RXRα by specific agonists induced degradation of both proteins. Conversely, a mutation in RARα that abolishes heterodimer formation and DNA binding, blocked both RARα and RXRα degradation. Mutations in the RARα DNA-binding domain or AF-2 transcriptional activation region also impaired RARα catabolism. Hence, our results link transcriptional activation to receptor catabolism and suggest that transcriptional up-regulation of nuclear receptors by their ligands may be a feedback mechanism allowing sustained target-gene activation. PMID:10611294

Concomitant Action of Structural Elements and Receptor Phosphorylation Determines Arrestin-3 Interaction with the Free Fatty Acid Receptor FFA4*

PubMed Central

Butcher, Adrian J.; Hudson, Brian D.; Shimpukade, Bharat; Alvarez-Curto, Elisa; Prihandoko, Rudi; Ulven, Trond; Milligan, Graeme; Tobin, Andrew B.

2014-01-01

In addition to being nutrients, free fatty acids act as signaling molecules by activating a family of G protein-coupled receptors. Among these is FFA4, previously called GPR120, which responds to medium and long chain fatty acids, including health-promoting ω-3 fatty acids, which have been implicated in the regulation of metabolic and inflammatory responses. Here we show, using mass spectrometry, mutagenesis, and phosphospecific antibodies, that agonist-regulated phosphorylation of the human FFA4 receptor occurred primarily at five residues (Thr347, Thr349, Ser350, Ser357, and Ser360) in the C-terminal tail. Mutation of these residues reduced both the efficacy and potency of ligand-mediated arrestin-3 recruitment as well as affecting recruitment kinetics. Combined mutagenesis of all five of these residues was insufficient to fully abrogate interaction with arrestin-3, but further mutagenesis of negatively charged residues revealed additional structural components for the interaction with arrestin-3 within the C-terminal tail of the receptor. These elements consist of the acidic residues Glu341, Asp348, and Asp355 located close to the phosphorylation sites. Receptor phosphorylation thus operates in concert with structural elements within the C-terminal tail of FFA4 to allow for the recruitment of arrestin-3. Importantly, these mechanisms of arrestin-3 recruitment operate independently from Gq/11 coupling, thereby offering the possibility that ligands showing stimulus bias could be developed that exploit these differential coupling mechanisms. Furthermore, this provides a strategy for the design of biased receptors to probe physiologically relevant signaling. PMID:24817122

Amino acid substitutions in the hormone-binding domain of the human androgen receptor alter the stability of the hormone receptor complex.

PubMed Central

Marcelli, M; Zoppi, S; Wilson, C M; Griffin, J E; McPhaul, M J

1994-01-01

We have investigated the basis of androgen resistance in seven unrelated individuals with complete testicular feminization or Reifenstein syndrome caused by single amino acid substitutions in the hormone-binding domain of the androgen receptor. Monolayer-binding assays of cultured genital skin fibroblasts demonstrated absent ligand binding, qualitative abnormalities of androgen binding, or a decreased amount of qualitatively normal receptor. The consequences of these mutations were examined by introducing the mutations by site-directed mutagenesis into the androgen receptor cDNA sequence and expressing the mutant cDNAs in mammalian cells. The effects of the amino acid substitutions on the binding of different androgens and on the capacity of the ligand-bound receptors to activate a reporter gene were investigated. Substantial differences were found in the responses of the mutant androgen receptors to incubation with testosterone, 5 alpha-dihydrotestosterone, and mibolerone. In several instances, increased doses of hormone or increased frequency of hormone addition to the incubation medium resulted in normal or near normal activation of a reporter gene by cells expressing the mutant androgen receptors. These studies suggest that the stability of the hormone receptor complex is a major determinant of receptor function in vivo. Images PMID:7929841

Modulation of Fc gamma receptors on I cells and monocytes by 15 hydroperoxyeicosatetranoic acid.

PubMed

Goodwin, J S; Gualde, N; Aldigier, J; Rigaud, M; Vanderhoek, J Y

1984-01-01

We investigated the effects of the 15-lipoxygenase products, 15 hydroperoxyeicosatetranoic acid (15 HPETE) and 15 hydroxyeicosatetranoic acid (15 HETE) on Fc gamma receptor expression on human T cells and monocytes. Incubation of these cells with 15 HPETE but not 15 HETE results in a shift to decreased density of Fc gamma receptors on the cell surface.

Modulation of GABA receptors expressed in Xenopus oocytes by 13-L-hydroxylinoleic acid and food additives.

PubMed

Aoshima, H; Tenpaku, Y

1997-12-01

To study the effects of 13-L-hydroxylinoleic acid (LOH) and food additives on gamma-aminobutyric acid (GABA) receptors, ionotropic GABA receptors were expressed in Xenopus oocytes by injecting mRNAs prepared from rat whole brain. LOH, which was prepared by reduction of 13-L-hydroperoxylinoleic acid (LOOH), inhibited the response of GABA receptors in the presence of high concentrations of GABA. LOH also inhibited nicotinic acetylcholine, glycine, and kainate receptors, while it had little effect on NMDA receptors expressed in Xenopus oocytes. However, LOH potentiated the response of GABA receptors as well as LOOH in the presence of low concentrations of GABA, possibly increasing the affinity of GABA for the receptors, while linoleic acid did not. Since some modification of the compounds seemed to change their effects on GABA receptors, the responses of GABA receptors elicited by 10 microM GABA were measured in the presence of compounds with various kinds of functional groups or the structural isomers of pentanol. Potentiation of GABA receptors depended strongly on the species of functional groups and also depended on the structure of the isomers. Then effects of various kinds of food additives on GABA receptors were also examined; perfumes such as alcohols or esters potentiated the responses strongly, while hexylamine, nicotinamide, or caffeine inhibited the responses, mainly in a competitive manner, and vanillin inhibited the responses noncompetitively. These results suggest the possibility that production of LOOH and LOH, or intake of much of some food additives, modulates the neural transmission in the brain, especially through ionotropic GABA receptors and changes the frame of the human mind, as alcohol or tobacco does.

Selective Cooperation between Fatty Acid Binding Proteins and Peroxisome Proliferator-Activated Receptors in Regulating Transcription

PubMed Central

Tan, Nguan-Soon; Shaw, Natacha S.; Vinckenbosch, Nicolas; Liu, Peng; Yasmin, Rubina; Desvergne, Béatrice; Wahli, Walter; Noy, Noa

2002-01-01

Lipophilic compounds such as retinoic acid and long-chain fatty acids regulate gene transcription by activating nuclear receptors such as retinoic acid receptors (RARs) and peroxisome proliferator-activated receptors (PPARs). These compounds also bind in cells to members of the family of intracellular lipid binding proteins, which includes cellular retinoic acid-binding proteins (CRABPs) and fatty acid binding proteins (FABPs). We previously reported that CRABP-II enhances the transcriptional activity of RAR by directly targeting retinoic acid to the receptor. Here, potential functional cooperation between FABPs and PPARs in regulating the transcriptional activities of their common ligands was investigated. We show that adipocyte FABP and keratinocyte FABP (A-FABP and K-FABP, respectively) selectively enhance the activities of PPARγ and PPARβ, respectively, and that these FABPs massively relocate to the nucleus in response to selective ligands for the PPAR isotype which they activate. We show further that A-FABP and K-FABP interact directly with PPARγ and PPARβ and that they do so in a receptor- and ligand-selective manner. Finally, the data demonstrate that the presence of high levels of K-FABP in keratinocytes is essential for PPARβ-mediated induction of differentiation of these cells. Taken together, the data establish that A-FABP and K-FABP govern the transcriptional activities of their ligands by targeting them to cognate PPARs in the nucleus, thereby enabling PPARs to exert their biological functions. PMID:12077340

Relation of soya bean meal level to the concentration of plasma free amino acids and body growth in white rats.

PubMed

Mandal, Tapas K; Parvin, Nargish; Mondal, Santanu; Saxena, Vijaylaxmi; Saxena, Ashok K; Sarkar, Sabyasachi; Saha, Mitali

2012-04-01

Amino acid (AA) levels in plasma and body growth were determined in rats (n20) fed diets with different soya bean meal levels. Free AA in plasma was determined by reversed-phase high-pressure liquid chromatography. We have used four levels of protein diets like 8%, 15%, 23% and 35% in this trial. Rats which were fed the low-protein (8%) diet with low percentage of soya bean meal were found to be growth-retarded. The body weight gain of high protein group (35%) was lower than that of the 23% groups. In the rats fed with the low-soya bean meal diet, some nonessential AA (NEAA) in plasma like asparagine, aspartic acid, cysteine, glutamic acid and serine increased, whereas the essential AA (EAA), with the exception of arginine, methionine and valine decreased. Here, plasma EAA-to-NEAA ratios were not correlated to growth and experimental diet. We hypothesize that AA metabolism is associated to changes in growth in rats on different protein intake. This study has showed the sensitivity of body mass gain, feed intake, feed conversion rate of rats to four levels of protein in the diet under controlled experimental conditions. © 2011 Blackwell Verlag GmbH.

Invited review: nutrient-sensing receptors for free fatty acids and hydroxycarboxylic acids in farm animals.

PubMed

Mielenz, M

2017-06-01

Data on nutrient sensing by free fatty acid receptors (FFAR1, FFAR2, FFAR3, FFAR4) and hydroxycarboxylic acid receptors (HCAR1, HCAR2) are increasing for human or rodent models. Both receptor families link intestinal fermentation by the microbiota and energy metabolism with cellular responses. Therefore, this finding provides a link that is independent of the only function of the fermentation products as energy substrates. For example, these reactions are associated with insulin secretion, regulation of lipolysis, adipose tissue differentiation and innate immune responses. In farm animals, the available data on both receptor families from the intestine and other tissues increase. However, currently, the data are primarily linked with the distribution of receptor messenger RNAs (mRNAs) and more rarely with proteins. Functional data on the importance of these receptors in farm animal species is not abundant and is often associated with the immune system. In certain farm animal species, the receptors were cloned and ligand binding was characterised. In chicken, only one FFAR2 was recently identified using genome analysis, which is contradictory to a study using an FFAR1 small interfering RNA. The chicken FFAR2 is composed of more than 20 paralogs. No data on HCAR1 or HCAR2 exist in this species. Currently, in pigs, most available data are on the mRNA distribution within intestine. However, no FFAR1 expression has been shown in this organ to date. In addition to FFAR2, an orthologue (FFAR2-like) with the highest abundance in intestine has been reported. The data on HCAR1 and HCAR2 in pigs is scarce. In ruminants, most of the currently available information on receptor distribution is linked to mRNA data and shows the expression, for example, in mammary gland and adipose tissue. However, some protein data on FFAR2 and FFAR1 protein has been reported and functional data availability is slowly increasing. The receptor mRNAs of HCAR1 and HCAR2 are expressed in bovine. The

Nutritional Signaling via Free Fatty Acid Receptors

PubMed Central

Miyamoto, Junki; Hasegawa, Sae; Kasubuchi, Mayu; Ichimura, Atsuhiko; Nakajima, Akira; Kimura, Ikuo

2016-01-01

Excess energy is stored primarily as triglycerides, which are mobilized when demand for energy arises. Dysfunction of energy balance by excess food intake leads to metabolic diseases, such as obesity and diabetes. Free fatty acids (FFAs) provided by dietary fat are not only important nutrients, but also contribute key physiological functions via FFA receptor (FFAR)-mediated signaling molecules, which depend on FFAs’ carbon chain length and the ligand specificity of the receptors. Functional analyses have revealed that FFARs are critical for metabolic functions, such as peptide hormone secretion and inflammation, and contribute to energy homeostasis. In particular, recent studies have shown that the administration of selective agonists of G protein-coupled receptor (GPR) 40 and GPR120 improved glucose metabolism and systemic metabolic disorders. Furthermore, the anti-inflammation and energy metabolism effects of short chain FAs have been linked to the activation of GPR41 and GPR43. In this review, we summarize recent progress in research on FFAs and their physiological roles in the regulation of energy metabolism. PMID:27023530

Concomitant action of structural elements and receptor phosphorylation determines arrestin-3 interaction with the free fatty acid receptor FFA4.

PubMed

Butcher, Adrian J; Hudson, Brian D; Shimpukade, Bharat; Alvarez-Curto, Elisa; Prihandoko, Rudi; Ulven, Trond; Milligan, Graeme; Tobin, Andrew B

2014-06-27

In addition to being nutrients, free fatty acids act as signaling molecules by activating a family of G protein-coupled receptors. Among these is FFA4, previously called GPR120, which responds to medium and long chain fatty acids, including health-promoting ω-3 fatty acids, which have been implicated in the regulation of metabolic and inflammatory responses. Here we show, using mass spectrometry, mutagenesis, and phosphospecific antibodies, that agonist-regulated phosphorylation of the human FFA4 receptor occurred primarily at five residues (Thr(347), Thr(349), Ser(350), Ser(357), and Ser(360)) in the C-terminal tail. Mutation of these residues reduced both the efficacy and potency of ligand-mediated arrestin-3 recruitment as well as affecting recruitment kinetics. Combined mutagenesis of all five of these residues was insufficient to fully abrogate interaction with arrestin-3, but further mutagenesis of negatively charged residues revealed additional structural components for the interaction with arrestin-3 within the C-terminal tail of the receptor. These elements consist of the acidic residues Glu(341), Asp(348), and Asp(355) located close to the phosphorylation sites. Receptor phosphorylation thus operates in concert with structural elements within the C-terminal tail of FFA4 to allow for the recruitment of arrestin-3. Importantly, these mechanisms of arrestin-3 recruitment operate independently from Gq/11 coupling, thereby offering the possibility that ligands showing stimulus bias could be developed that exploit these differential coupling mechanisms. Furthermore, this provides a strategy for the design of biased receptors to probe physiologically relevant signaling. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Short-chain fatty acid receptors inhibit invasive phenotypes in breast cancer cells

PubMed Central

Thirunavukkarasan, Madhumathi; Wang, Chao; Rao, Angad; Hind, Tatsuma; Teo, Yuan Ru; Siddiquee, Abrar Al-Mahmood; Goghari, Mohamed Ally Ibrahim; Kumar, Alan Prem

2017-01-01

Short chain fatty acids (2 to 6 carbons in length) are ubiquitous lipids that are present in human plasma at micromolar concentrations. In addition to serving as metabolic precursors for lipid and carbohydrate synthesis, they also act as cognate ligands for two known G protein-coupled receptors (GPCRs), FFAR2 and FFAR3. While there is evidence that these receptors may inhibit the progression of colorectal cancer, their roles in breast cancer cells are largely unknown. We evaluated the effects of enforced overexpression of these receptors in two phenotypically distinct breast cancer cell lines: MCF7 and MDA-MD-231. Our results demonstrate that both receptors inhibit cell invasiveness, but through different signaling processes. In invasive, mesenchymal-like MDA-MB-231 cells, FFAR2 inhibits the Hippo-Yap pathway and increases expression of adhesion protein E-cadherin, while FFAR3 inhibits MAPK signaling. Both receptors have the net effect of reducing actin polymerization and invasion of cells through a Matrigel matrix. These effects were absent in the less invasive, epithelial-like MCF7 cells. Correspondingly, there is reduced expression of both receptors in invasive breast carcinoma and in aggressive triple-negative breast tumors, relative to normal breast tissue. Cumulatively, our data suggest that the activation of cognate receptors by short chain fatty acids drives breast cancer cells toward a non-invasive phenotype and therefore may inhibit metastasis. PMID:29049318

Identification of a Novel Non-retinoid Pan Inverse Agonist of the Retinoic Acid Receptors

PubMed Central

Busby, Scott A.; Kumar, Naresh; Kuruvilla, Dana S.; Istrate, Monica A.; Conkright, Juliana J.; Wang, Yongjun; Kamenecka, Theodore M.; Cameron, Michael D.; Roush, William R.; Burris, Thomas P.; Griffin, Patrick R.

2011-01-01

Retinoids are potent forms of vitamin A and are involved in a broad range of physiological processes and the pharmacological effects of retinoids are primarily mediated by the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs). Several natural and synthetic RAR modulators have proven to be clinically useful for a number of therapeutic indications including cancer, psoriasis, and diabetes. Unfortunately, these agents lead to a number of significant side effects. Most synthetic retinoid ligands are based on the retinoid scaffold and thus have similarities to the natural ligand with all previously disclosed RAR ligands having a carboxylic acid that makes a critical ionic bridge within the ligand binding domain of the receptors. The potential therapeutic value offered from RAR modulation provides the impetus to identify novel ligands based on unique scaffolds that may offer improved toxicity and pharmacokinetic profiles. Here we describe the identification of an atypical RAR inverse agonist that represents the first non-acid, non-retinoid direct modulator of RAR receptor subfamily. SR-0065 functions as a pan-RAR inverse agonist suppressing the basal activity of RARα, RARβ, and RARγ as well as inhibiting agonist induced RAR activity. SR-0065 treatment enhanced receptor interaction with a peptide representative of the corepressor SMRT and in cells SR-0065 enhances recruitment of SMRT to RARγ. The acid form of SR-0065, SR-1758, was inactive in all assays. Thus, SR-0065 represents a new class of non-acid, non-retinoid RAR modulator that may be used as a point to initiate development of improved RAR-targeted drugs. PMID:21381756

Ursodeoxycholic Acid Suppresses Lipogenesis in Mouse Liver: Possible Role of the Decrease in β-Muricholic Acid, a Farnesoid X Receptor Antagonist.

PubMed

Fujita, Kyosuke; Iguchi, Yusuke; Une, Mizuho; Watanabe, Shiro

2017-04-01

The farnesoid X receptor (FXR) is a major nuclear receptor of bile acids; its activation suppresses sterol regulatory element-binding protein 1c (SREBP1c)-mediated lipogenesis and decreases the lipid contents in the liver. There are many reports showing that the administration of ursodeoxycholic acid (UDCA) suppresses lipogenesis and reduces the lipid contents in the liver of experimental animals. Since UDCA is not recognized as an FXR agonist, these effects of UDCA cannot be readily explained by its direct activation of FXR. We observed that the dietary administration of UDCA in mice decreased the expression levels of SREBP1c and its target lipogenic genes. Alpha- and β-muricholic acids (MCA) and cholic acid (CA) were the major bile acids in the mouse liver but their contents decreased upon UDCA administration. The hepatic contents of chenodeoxycholic acid and deoxycholic acid (DCA) were relatively low but were not changed by UDCA. UDCA did not show FXR agonistic or antagonistic potency in in vitro FXR transactivation assay. Taking these together, we deduced that the above-mentioned change in hepatic bile acid composition induced upon UDCA administration might cause the relative increase in the FXR activity in the liver, mainly by the reduction in the content of β-MCA, a farnesoid X receptor antagonist, which suggests a mechanism by which UDCA suppresses lipogenesis and decreases the lipid contents in the mouse liver.

Cyclic mu-opioid receptor ligands containing multiple N-methylated amino acid residues.

PubMed

Adamska-Bartłomiejczyk, Anna; Janecka, Anna; Szabó, Márton Richárd; Cerlesi, Maria Camilla; Calo, Girolamo; Kluczyk, Alicja; Tömböly, Csaba; Borics, Attila

2017-04-15

In this study we report the in vitro activities of four cyclic opioid peptides with various sequence length/macrocycle size and N-methylamino acid residue content. N-Methylated amino acids were incorporated and cyclization was employed to enhance conformational rigidity to various extent. The effect of such modifications on ligand structure and binding properties were studied. The pentapeptide containing one endocyclic and one exocyclic N-methylated amino acid displayed the highest affinity to the mu-opioid receptor. This peptide was also shown to be a full agonist, while the other analogs failed to activate the mu opioid receptor. Results of molecular docking studies provided rationale for the explanation of binding properties on a structural basis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Docking simulations suggest that all-trans retinoic acid could bind to retinoid X receptors.

PubMed

Tsuji, Motonori; Shudo, Koichi; Kagechika, Hiroyuki

2015-10-01

Retinoid X receptors (RXRs) are ligand-controlled transcription factors which heterodimerize with other nuclear receptors to regulate gene transcriptions associated with crucial biological events. 9-cis retinoic acid (9cRA), which transactivates RXRs, is believed to be an endogenous RXR ligand. All-trans retinoic acid (ATRA) is a natural ligand for retinoic acid receptors (RARs), which heterodimerize with RXRs. Although the concentration of 9cRA in tissues is very low, ATRA is relatively abundant and some reports show that ATRA activates RXRs. We computationally studied the possibility of ATRA binding to RXRs using two different docking methods with our developed programs to assess the binding affinities of naturally occurring retinoids. The simulations showed good correlations to the reported binding affinities of these molecules for RXRs and RARs.

Organoboron compounds as Lewis acid receptors of fluoride ions in polymeric membranes.

PubMed

Jańczyk, Martyna; Adamczyk-Woźniak, Agnieszka; Sporzyński, Andrzej; Wróblewski, Wojciech

2012-07-06

Newly synthesized organoboron compounds - 4-octyloxyphenylboronic acid (OPBA) and pinacol ester of 2,4,6-trifluorophenylboronic acid (PE-PBA) - were applied as Lewis acid receptors of fluoride anions. Despite enhanced selectivity, the polymer membrane electrodes containing the lipophilic receptor OPBA exhibited non-Nernstian slopes of the responses toward fluoride ions in acidic conditions. Such behavior was explained by the lability of the B-O bond in the boronic acids, and the OH(-)/F(-) exchange at higher fluoride content in the sample solution. In consequence, the stoichiometry of the OPBA-fluoride complexes in the membrane could vary during the calibration, changing the equilibrium concentration of the primary anion in membrane and providing super-Nernstian responses. The proposed mechanism was supported by (19)F NMR studies, which indicated that the fluoride complexation proceeds more effectively in acidic solution leading mainly to PhBF(3)(-) species. Finally, the performances of the membranes based on the phenylboronic acid pinacol ester, with a more stable B-O bond, were tested. As it was expected, Nernstian fluoride responses were recorded for such membranes with worsened fluoride selectivity. Copyright © 2012 Elsevier B.V. All rights reserved.

Enhancement of arachidonic acid signaling pathway by nicotinic acid receptor HM74A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Yuting; Zhou, Lubing; Gunnet, Joseph W.

2006-06-23

HM74A is a G protein-coupled receptor for nicotinic acid (niacin), which has been used clinically to treat dyslipidemia for decades. The molecular mechanisms whereby niacin exerts its pleiotropic effects on lipid metabolism remain largely unknown. In addition, the most common side effect in niacin therapy is skin flushing that is caused by prostaglandin release, suggesting that the phospholipase A{sub 2} (PLA{sub 2})/arachidonic acid (AA) pathway is involved. Various eicosanoids have been shown to activate peroxisome-proliferator activated receptors (PPAR) that play a diverse array of roles in lipid metabolism. To further elucidate the potential roles of HM74A in mediating the therapeuticmore » effects and/or side effects of niacin, we sought to explore the signaling events upon HM74A activation. Here we demonstrated that HM74A synergistically enhanced UTP- and bradykinin-mediated AA release in a pertussis toxin-sensitive manner in A431 cells. Activation of HM74A also led to Ca{sup 2+}-mobilization and enhanced bradykinin-promoted Ca{sup 2+}-mobilization through Gi protein. While HM74A increased ERK1/2 activation by the bradykinin receptor, it had no effects on UTP-promoted ERK1/2 activation.Furthermore, UTP- and bradykinin-mediated AA release was significantly decreased in the presence of both MAPK kinase inhibitor PD 098059 and PKC inhibitor GF 109203X. However, the synergistic effects of HM74A were not dramatically affected by co-treatment with both inhibitors, indicating the cross-talk occurred at the receptor level. Finally, stimulation of A431 cells transiently transfected with PPRE-luciferase with AA significantly induced luciferase activity, mimicking the effects of PPAR{gamma} agonist rosiglitazone, suggesting that alteration of AA signaling pathway can regulate gene expression via endogenous PPARs.« less

[Study of biological value of beef produced by interspecies hybrids of domestic cattle and wild yaks].

PubMed

Bagirov, V A; Chernukha, I M; Lisitsin, A V; Zinovieva, N A

2014-01-01

The comparative study of the chemical composition and biological values of beef produced by hybrids of Angus cattle with wild yaks (hybrid beef) and pure-bred Angus cattle (traditional beef) has been carried out. Longissimus muscle samples were used for analysis. It was observed, that the hybrid beef samples had the practically equal protein content comparing to traditional beef (21.1 vs. 21.6 per cent) but were characterized by the lower fat content (1.2 vs. 2.5 per cent). The higher biological value of hybrid beef comparing to traditional beef has been shown. The value of protein-quality index, calculated as the ratio of tryptophan amino acid to oxyprolin and characterizing the ratio of high biological value proteins to low biological value proteins was 8.1 vs. 5.7. The values of amino acid indexes [ratio of essential amino acids (EAA) to non-essential amino acids (NAA) and ratio of EAA to the total amount of amino acids (TAA)] were EAA/NAA = 0.77 vs. 0.65 and EAA/TAA = 0.43 vs. 0.39. The protein of hybrid beef was characterized by the higher content of a number of the essential amino acids: by a factor of 1, 77 for threonin, 1.23--for valin, 1.09--for lysin, 1.17--for leucine and 1.19--for tryptophan. The amount of the essential amino acids in 1 gram of protein of the hybrid beef was 434.7 mg against 393.1 mg for traditional beef It has been shown, that the protein of the hybrid beef comparing to traditional beef is characterized by the higher values of the amino acid scores calculated for EAA.

Decreased glucagon responsiveness by bile acids: a role for protein kinase Calpha and glucagon receptor phosphorylation.

PubMed

Ikegami, Tadashi; Krilov, Lada; Meng, Jianping; Patel, Bhumika; Chapin-Kennedy, Kelli; Bouscarel, Bernard

2006-11-01

Dihydroxy bile acids like chenodeoxycholic acid (CDCA) induce heterologous glucagon receptor desensitization. We previously demonstrated that protein kinase C (PKC) was activated by certain bile acids and mediated the CDCA-induced decrease in glucagon responsiveness. The aim of the present study was to explore the role of PKC in the phosphorylation and desensitization of the glucagon receptor by CDCA. Desensitization was evaluated by measuring adenylyl cyclase activity. Receptor phosphorylation was assayed by metabolic labeling with [gamma-(32)P] ATP. Protein kinase C (PKC) translocation and activation was visualized by fluorescence microscopy. CDCA decreased cAMP production induced by glucagon in a dose-dependent manner without affecting cAMP synthesis through stimulation of either stimulatory GTP-binding protein (Gs) by NaF or adenylyl cyclase by forskolin. The CDCA-induced inhibition of adenylyl cyclase activity was potentiated by the phosphatase inhibitor, okadaic acid. The desensitizing effect of CDCA was bile acid-specific and was significantly reduced in the presence of PKC inhibitors and after PKC down-regulation by phorbol 12-myristate 13-acetate. CDCA increased glucagon receptor phosphorylation more than 3-fold at concentrations as low as 25 mum. Furthermore, CDCA significantly stimulated human recombinant PKCalpha autophosphorylation in vitro, as well as PKCalpha translocation to the plasma membrane and phosphorylation in vivo at concentrations as low as 25 mum. CDCA also stimulated PKCdelta translocation to the perinuclear region. Activated PKCalpha, PKCzeta, and to a lesser extent, PKCdelta, phosphorylated the glucagon receptor in vitro. This study demonstrates that certain bile acids, such as CDCA, stimulate phosphorylation and heterologous desensitization of the glucagon receptor, involving at least PKCalpha activation.

Medium-chain fatty acid-sensing receptor, GPR84, is a proinflammatory receptor.

PubMed

Suzuki, Masakatsu; Takaishi, Sachiko; Nagasaki, Miyuki; Onozawa, Yoshiko; Iino, Ikue; Maeda, Hiroaki; Komai, Tomoaki; Oda, Tomiichiro

2013-04-12

G protein-coupled receptor 84 (GPR84) is a putative receptor for medium-chain fatty acids (MCFAs), whose pathophysiological roles have not yet been clarified. Here, we show that GPR84 was activated by MCFAs with the hydroxyl group at the 2- or 3-position more effectively than nonhydroxylated MCFAs. We also identified a surrogate agonist, 6-n-octylaminouracil (6-OAU), for GPR84. These potential ligands and the surrogate agonist, 6-OAU, stimulated [(35)S]GTP binding and accumulated phosphoinositides in a GPR84-dependent manner. The surrogate agonist, 6-OAU, internalized GPR84-EGFP from the cell surface. Both the potential ligands and 6-OAU elicited chemotaxis of human polymorphonuclear leukocytes (PMNs) and macrophages and amplified LPS-stimulated production of the proinflammatory cytokine IL-8 from PMNs and TNFα from macrophages. Furthermore, the intravenous injection of 6-OAU raised the blood CXCL1 level in rats, and the inoculation of 6-OAU into the rat air pouch accumulated PMNs and macrophages in the site. Our results indicate a proinflammatory role of GPR84, suggesting that the receptor may be a novel target to treat chronic low grade inflammation associated-disease.

Medium-chain Fatty Acid-sensing Receptor, GPR84, Is a Proinflammatory Receptor

PubMed Central

Suzuki, Masakatsu; Takaishi, Sachiko; Nagasaki, Miyuki; Onozawa, Yoshiko; Iino, Ikue; Maeda, Hiroaki; Komai, Tomoaki; Oda, Tomiichiro

2013-01-01

G protein-coupled receptor 84 (GPR84) is a putative receptor for medium-chain fatty acids (MCFAs), whose pathophysiological roles have not yet been clarified. Here, we show that GPR84 was activated by MCFAs with the hydroxyl group at the 2- or 3-position more effectively than nonhydroxylated MCFAs. We also identified a surrogate agonist, 6-n-octylaminouracil (6-OAU), for GPR84. These potential ligands and the surrogate agonist, 6-OAU, stimulated [35S]GTP binding and accumulated phosphoinositides in a GPR84-dependent manner. The surrogate agonist, 6-OAU, internalized GPR84-EGFP from the cell surface. Both the potential ligands and 6-OAU elicited chemotaxis of human polymorphonuclear leukocytes (PMNs) and macrophages and amplified LPS-stimulated production of the proinflammatory cytokine IL-8 from PMNs and TNFα from macrophages. Furthermore, the intravenous injection of 6-OAU raised the blood CXCL1 level in rats, and the inoculation of 6-OAU into the rat air pouch accumulated PMNs and macrophages in the site. Our results indicate a proinflammatory role of GPR84, suggesting that the receptor may be a novel target to treat chronic low grade inflammation associated-disease. PMID:23449982

Retinoic Acid Receptor-Related Orphan Receptors: Critical Roles in Tumorigenesis

PubMed Central

Fan, Jinshuo; Lv, Zhilei; Yang, Guanghai; Liao, Ting ting; Xu, Juanjuan; Wu, Feng; Huang, Qi; Guo, Mengfei; Hu, Guorong; Zhou, Mei; Duan, Limin; Liu, Shuqing; Jin, Yang

2018-01-01

Retinoic acid receptor-related orphan receptors (RORs) include RORα (NR1F1), RORβ (NR1F2), and RORγ (NR1F3). These receptors are reported to activate transcription through ligand-dependent interactions with co-regulators and are involved in the development of secondary lymphoid tissues, autoimmune diseases, inflammatory diseases, the circadian rhythm, and metabolism homeostasis. Researches on RORs contributing to cancer-related processes have been growing, and they provide evidence that RORs are likely to be considered as potential therapeutic targets in many cancers. RORα has been identified as a potential therapeutic target for breast cancer and has been investigated in melanoma, colorectal colon cancer, and gastric cancer. RORβ is mainly expressed in the central nervous system, but it has also been studied in pharyngeal cancer, uterine leiomyosarcoma, and colorectal cancer, in addition to neuroblastoma, and recent studies suggest that RORγ is involved in various cancers, including lymphoma, melanoma, and lung cancer. Some studies found RORγ to be upregulated in cancer tissues compared with normal tissues, while others indicated the opposite results. With respect to the mechanisms of RORs in cancer, previous studies on the regulatory mechanisms of RORs in cancer were mostly focused on immune cells and cytokines, but lately there have been investigations concentrating on RORs themselves. Thus, this review summarizes reports on the regulation of RORs in cancer and highlights potential therapeutic targets in cancer. PMID:29904382

Mapping General Anesthetic Sites in Heteromeric γ-Aminobutyric Acid Type A Receptors Reveals a Potential For Targeting Receptor Subtypes.

PubMed

Forman, Stuart A; Miller, Keith W

2016-11-01

IV general anesthetics, including propofol, etomidate, alphaxalone, and barbiturates, produce important actions by enhancing γ-aminobutyric acid type A (GABAA) receptor activation. In this article, we review scientific studies that have located and mapped IV anesthetic sites using photoaffinity labeling and substituted cysteine modification protection. These anesthetics bind in transmembrane pockets between subunits of typical synaptic GABAA receptors, and drugs that display stereoselectivity also show remarkably selective interactions with distinct interfacial sites. These results suggest strategies for developing new drugs that selectively modulate distinct GABAA receptor subtypes.

Characterization of cDNAs encoding the chick retinoic acid receptor gamma 2 and preferential distribution of retinoic acid receptor gamma transcripts during chick skin development.

PubMed

Michaille, J J; Blanchet, S; Kanzler, B; Garnier, J M; Dhouailly, D

1994-12-01

Retinoic acid receptors alpha, beta and gamma (RAR alpha, beta and gamma) are ligand-inductible transcriptional activators which belong to the steroid/thyroid hormone receptor superfamily. At least two major isoforms (1 and 2) of each RAR arise by differential use of two promoters and alternative splicing. In mouse, the three RAR genes are expressed in stage- and tissue-specific patterns during embryonic development. In order to understand the role of the different RARs in chick, RAR gamma 2 cDNAs were isolated from an 8.5-day (stage 35 of Hamburger and Hamilton) chick embryo skin library. The deduced chick RAR gamma 2 amino acid sequence displays uncommon features such as 21 specific amino acid replacements, 12 of them being clustered in the amino-terminal region (domains A2 and B), and a truncated acidic carboxy-terminal region (F domain). However, the pattern of RAR gamma expression in chick embryo resembles that reported in mouse, particularly in skin where RAR gamma expression occurs in both the dermal and epidermal layers at the beginning of feather formation, and is subsequently restricted to the differentiating epidermal cells. Northern blot analysis suggests that different RAR gamma isoforms could be successively required during chick development.

The nuclear receptor PPARγ individually responds to serotonin- and fatty acid-metabolites

PubMed Central

Waku, Tsuyoshi; Shiraki, Takuma; Oyama, Takuji; Maebara, Kanako; Nakamori, Rinna; Morikawa, Kosuke

2010-01-01

The nuclear receptor, peroxisome proliferator-activated receptor γ (PPARγ), recognizes various synthetic and endogenous ligands by the ligand-binding domain. Fatty-acid metabolites reportedly activate PPARγ through conformational changes of the Ω loop. Here, we report that serotonin metabolites act as endogenous agonists for PPARγ to regulate macrophage function and adipogenesis by directly binding to helix H12. A cyclooxygenase inhibitor, indomethacin, is a mimetic agonist of these metabolites. Crystallographic analyses revealed that an indole acetate functions as a common moiety for the recognition by the sub-pocket near helix H12. Intriguingly, a serotonin metabolite and a fatty-acid metabolite each bind to distinct sub-pockets, and the PPARγ antagonist, T0070907, blocked the fatty-acid agonism, but not that of the serotonin metabolites. Mutational analyses on receptor-mediated transcription and coactivator binding revealed that each metabolite individually uses coregulator and/or heterodimer interfaces in a ligand-type-specific manner. Furthermore, the inhibition of the serotonin metabolism reduced the expression of the endogenous PPARγ-target gene. Collectively, these results suggest a novel agonism, in which PPARγ functions as a multiple sensor in response to distinct metabolites. PMID:20717101

Influence of sialic acids on the galactose-recognizing receptor of rat peritoneal macrophages.

PubMed

Lee, H Y; Kelm, S; Michalski, J C; Schauer, R

1990-04-01

The interaction of the galactose-recognizing receptor from rat peritoneal macrophages with ligands containing terminal galactose residues, such as asialoorosomucoid, desialylated erythrocytes or lymphocytes, can be inhibited by free N-acetylneuraminic acid (Neu5Ac) and oligosaccharides or glycoproteins containing this sugar in terminal position. This effect of Neu5Ac on the receptor is specific. The other naturally occurring or most of synthetic neuraminic acid derivatives tested do not exhibit an equivalent inhibitory potency as Neu5Ac. Although free Neu5Ac inhibits 5-fold stronger (K50 = 0.2mM) than free galactose, clustering of Neu5Ac in oligosaccharides and glycoproteins does not lead to stronger inhibition, which is in contrast to galactose-containing ligands. A more branched (triantennary) sialooligosaccharide inhibits less than biantennary and unbranched sialooligosaccharides. This may be the reason, why complex sialic acid-containing ligands like native orosomucoid or blood cells are not bound and internalized by the macrophages. The dissociation of asialoorosomucoid from the receptor is slow under the influence of Neu5Ac and requires relatively high concentrations of this sugar, whereas the dissociation mediated by galactose is rapid and requires lower concentrations. An allosteric influence of Neu5Ac on the binding of galactose by the receptor is discussed.

Developmental toxicity of perfluorononanoic acid is dependent on peroxisome proliferator activated receptor-alpha.

EPA Science Inventory

Perfluorononanoic acid (PFNA) is one of the predominant perfluoroalkyl acids in the environment and in tissues of humans and wildlife. PFNA strongly activates the mouse and human peroxisome proliferator-activated receptor-alpha (PPARα) in vitro and negatively impacts development ...

Molecular receptive range variation among mouse odorant receptors for aliphatic carboxylic acids

PubMed Central

Repicky, Sarah E.; Luetje, Charles W.

2009-01-01

The ability of mammals to identify and distinguish among many thousands of different odorants suggests a combinatorial use of odorant receptors, with each receptor detecting multiple odorants and each odorant interacting with multiple receptors. Numerous receptors may be devoted to the sampling of particularly important regions of odor space. Here we explore the similarities and differences in the molecular receptive ranges of four mouse odorant receptors (MOR23-1, MOR31-4, MOR32-11 and MOR40-4), which have previously been identified as receptors for aliphatic carboxylic acids. Each receptor was expressed in Xenopus oocytes, along with Gαolf and the cystic fibrosis transmembrane regulator to allow electrophysiological assay of receptor responses. We find that even though these receptors are relatively unrelated, there is extensive overlap among their receptive ranges. That is, these receptors sample a similar region of odor space. However, the receptive range of each receptor is unique. Thus, these receptors contribute to the depth of coverage of this small region of odor space. Such a group of receptors with overlapping, but distinct receptive ranges, may participate in making fine distinctions among complex mixtures of closely related odorant compounds. PMID:19166503

L-Amino Acids Elicit Diverse Response Patterns in Taste Sensory Cells: A Role for Multiple Receptors

PubMed Central

Pal Choudhuri, Shreoshi; Delay, Rona J.; Delay, Eugene R.

2015-01-01

Umami, the fifth basic taste, is elicited by the L-amino acid, glutamate. A unique characteristic of umami taste is the response potentiation by 5’ ribonucleotide monophosphates, which are also capable of eliciting an umami taste. Initial reports using human embryonic kidney (HEK) cells suggested that there is one broadly tuned receptor heterodimer, T1r1+T1r3, which detects L-glutamate and all other L-amino acids. However, there is growing evidence that multiple receptors detect glutamate in the oral cavity. While much is understood about glutamate transduction, the mechanisms for detecting the tastes of other L-amino acids are less well understood. We used calcium imaging of isolated taste sensory cells and taste cell clusters from the circumvallate and foliate papillae of C57BL/6J and T1r3 knockout mice to determine if other receptors might also be involved in detection of L-amino acids. Ratiometric imaging with Fura-2 was used to study calcium responses to monopotassium L-glutamate, L-serine, L-arginine, and L-glutamine, with and without inosine 5’ monophosphate (IMP). The results of these experiments showed that the response patterns elicited by L-amino acids varied significantly across taste sensory cells. L-amino acids other than glutamate also elicited synergistic responses in a subset of taste sensory cells. Along with its role in synergism, IMP alone elicited a response in a large number of taste sensory cells. Our data indicate that synergistic and non-synergistic responses to L-amino acids and IMP are mediated by multiple receptors or possibly a receptor complex. PMID:26110622

Free fatty acid receptors: emerging targets for treatment of diabetes and its complications

PubMed Central

Vangaveti, Venkat; Shashidhar, Venkatesh; Jarrod, Ghassan; Baune, Bernhard T.; Kennedy, R. Lee

2010-01-01

Fatty acids (FAs) are important as metabolic substrates and as structural components of biological membranes. However, they also function as signalling molecules. Recently, a series of G protein-coupled receptors (GPRs) for FAs has been described and characterized. These receptors have differing specificities for FAs of differing chain length and degree of saturation, for FA derivatives such as oleoylethanolamide, and for oxidized FAs. They are a critical component of the body's nutrient sensing apparatus, and small molecule agonists and antagonists of these receptors show considerable promise in the management of diabetes and its complications. Agonists of the long-chain free fatty acid receptors FFAR1 and GPR119 act as insulin secretagogues, both directly and by increasing incretins. Although, drugs acting at short-chain FFA receptors (FFAR2 and FFAR3) have not yet been developed, they are attractive targets as they regulate nutrient balance through effects in the intestine and adipose tissue. These include regulation of the secretion of cholecystokinin, peptide YY and leptin. Finally, GPR132 is a receptor for oxidized FAs, which may be a sensor of lipid overload and oxidative stress, and which is involved in atherosclerosis. Regulation of its signalling pathways with drugs may decrease the macrovascular risk experienced by diabetic patients. In summary, FA receptors are emerging drug targets that are involved in the regulation of nutrient status and carbohydrate tolerance, and modulators of these receptors may well figure prominently in the next generation of antidiabetic drugs. PMID:23148161

REACTIVITY PROFILE OF LIGANDS OF MAMMALIAN RETINOIC ACID RECEPTORS: A PRELIMINARY COREPA ANALYSIS

EPA Science Inventory

Retinoic acid and associated derivatives comprise a class of endogenous hormones that bind to and activate different families of retinoic acid receptors (RARs, RXRs), and control many aspects of vertebrate development. Identification of potential RAR and RXR ligands is of interes...

The role of G-protein-coupled receptors in mediating the effect of fatty acids on inflammation and insulin sensitivity.

PubMed

Oh, Da Young; Lagakos, William S

2011-07-01

Chronic activation of inflammatory pathways mediates the pathogenesis of insulin resistance, and the macrophage/adipocyte nexus provides a key mechanism underlying decreased insulin sensitivity. Free fatty acids are important in the pathogenesis of insulin resistance, although their precise mechanisms of action have yet to be fully elucidated. Recently, a family of G-protein-coupled receptors has been identified that exhibits high affinity for fatty acids. This review summarizes recent findings on six of these receptors, their ligands, and their potential physiological functions in vivo. Upon activation, the free fatty acid receptors affect inflammation, glucose metabolism, and insulin sensitivity. Genetic deletion of GPR40 and GPR41, receptors for long-chain and short-chain fatty acids, respectively, results in resistance to diet-induced obesity. Deletion of GPR43 and GPR84 exacerbates inflammation, and deletion of the long-chain fatty acid receptors GPR119 and GPR120 reduces or is predicted to reduce glucose tolerance. These studies provide a new understanding of the general biology of gastric motility and also shed valuable insight into some potentially beneficial therapeutic targets. Furthermore, highly selective agonists or antagonists for the free fatty acid receptors have been developed and look promising for treating various metabolic diseases.

Correlation of deglutition in subacute ischemic stroke patients with peripheral blood adaptive immunity: Essential amino acid improvement.

PubMed

Aquilani, Roberto; Emilio, Benevolo; Dossena, Maurizia; Baiardi, Paola; Testa, Amidio; Boschi, Federica; Viglio, Simona; Iadarola, Paolo; Pasini, Evasio; Verri, Manuela

2015-12-01

We aimed to document in stroke patients peripheral blood immune cell profiles, their relations with neuro-functional tests, and any possible influence of supplemented essential amino acids (EAAs) may have on both the immune system and the relationship of the latter with neuro-function.Forty-two dysphagic stroke patients (27 men; 71±9 years) underwent bio-humoral measurements, neuro-functional tests, including Functional Independence Measure (FIM) and Dysphagia Outcome and Severity Scale (DOSS), and were randomized to receive EAAs 8 g/d (EAA group) or isocaloric maltodextrin (placebo group).At discharge all measurements were repeated 38±1 days after randomization.At admission, total white cell (TWC), neutrophil (N), and lymphocyte (Lymph) counts were normal and the N/Lymph ratio was higher than normal values (<3.0). At discharge, both TWC and N decreased while Lymph increased significantly. As a result, the N/Lymph ratio significantly decreased (P <0.001) returning to normal levels. Absolute Lymph counts and Lymph % TWC correlated positively with DOSS (r = +0.235, P = 0.04 and r = +0.224, P = 0.05, respectively), negatively with C-reactive protein natural logarithm (ln CRP) (P = 0.02 and P = 0.0001, respectively), which is an inflammation marker. N correlated positively with ln CRP (P = 0.001) and had a slight negative association with FIM (P = 0.07). The N/Lymph ratio was inversely related to FIM (r = -0.262, P = 0.02) and DOSS (r = -0.279, P = 0.01). Finally, FIM correlated with DOSS (r = +0.35, P = 0.05).For the regression analysis, the overtime changes of Lymph % TWC correlated significantly with DOSS (P = 0.01). There was a positive correlation between Lymph % TWC and DOSS for the entire stroke population (P = 0.015). While this correlation was not important for the placebo group (P = 0.27), it was significant in the EAA subgroup (P = 0.018).In the sub-acute stroke stage, there may be slight alterations of peripheral blood immune cells. Lymph cells are

Free fatty acid receptors act as nutrient sensors to regulate energy homeostasis.

PubMed

Ichimura, Atsuhiko; Hirasawa, Akira; Hara, Takafumi; Tsujimoto, Gozoh

2009-09-01

Free fatty acids (FFAs) have been demonstrated to act as ligands of several G-protein-coupled receptors (GPCRs) (FFAR1, FFAR2, FFAR3, GPR84, and GPR120). These fatty acid receptors are proposed to play critical roles in a variety of types of physiological homeostasis. FFAR1 and GPR120 are activated by medium- and long-chain FFAs. GPR84 is activated by medium-chain, but not long-chain, FFAs. In contrast, FFAR2 and FFAR3 are activated by short-chain FFAs. FFAR1 is expressed mainly in pancreatic beta-cells and mediates insulin secretion, whereas GPR120 is expressed abundantly in the intestine and promotes the secretion of glucagon-like peptide-1 (GLP-1). FFAR3 is expressed in enteroendocrine cells and regulates host energy balance through effects that are dependent upon the gut microbiota. In this review, we summarize the identification, structure, and pharmacology of these receptors and present an essential overview of the current understanding of their physiological roles.

Analysis of ileal sodium/bile acid cotransporter and related nuclear receptor genes in a family with multiple cases of idiopathic bile acid malabsorption

PubMed Central

Montagnani, Marco; Abrahamsson, Anna; Gälman, Cecilia; Eggertsen, Gösta; Marschall, Hanns-Ulrich; Ravaioli, Elisa; Einarsson, Curt; Dawson, Paul A

2006-01-01

The etiology of most cases of idiopathic bile acid malabsorption (IBAM) is unknown. In this study, a Swedish family with bile acid malabsorption in three consecutive generations was screened for mutations in the ileal apical sodium-bile acid cotransporter gene (ASBT; gene symbol, SLC10A2) and in the genes for several of the nuclear receptors known to be important for ASBT expression: the farnesoid X receptor (FXR) and peroxisome proliferator activated receptor alpha (PPARα). The patients presented with a clinical history of idiopathic chronic watery diarrhea, which was responsive to cholestyramine treatment and consistent with IBAM. Bile acid absorption was determined using 75Se-homocholic acid taurine (SeHCAT); bile acid synthesis was estimated by measuring the plasma levels of 7α-hydroxy-4-cholesten-3-one (C4). The ASBT, FXR, and PPARα genes in the affected and unaffected family members were analyzed using single stranded conformation polymorphism (SSCP), denaturing HPLC, and direct sequencing. No ASBT mutations were identified and the ASBT gene did not segregate with the bile acid malabsorption phenotype. Similarly, no mutations or polymorphisms were identified in the FXR or PPARα genes associated with the bile acid malabsorption phenotype. These studies indicate that the intestinal bile acid malabsorption in these patients cannot be attributed to defects in ASBT. In the absence of apparent ileal disease, alternative explanations such as accelerated transit through the small intestine may be responsible for the IBAM. PMID:17171805

Enhancement of gamma-aminobutyric acid receptor binding by protopine-type alkaloids.

PubMed

Kardos, J; Blaskó, G; Simonyi, M

1986-06-01

Protopine, cryptopine and allocryptopine were demonstrated to enhance 3H-gamma-aminobutyric acid (3H-GABA) binding to rat brain synaptic membrane receptors. The above finding might be indicative of benzodiazepine-like activity of these alkaloids.

Human Muscle Protein Synthetic Responses during Weight-Bearing and Non-Weight-Bearing Exercise: A Comparative Study of Exercise Modes and Recovery Nutrition.

PubMed

Pasiakos, Stefan M; McClung, Holly L; Margolis, Lee M; Murphy, Nancy E; Lin, Gregory G; Hydren, Jay R; Young, Andrew J

2015-01-01

Effects of conventional endurance (CE) exercise and essential amino acid (EAA) supplementation on protein turnover are well described. Protein turnover responses to weighted endurance exercise (i.e., load carriage, LC) and EAA may differ from CE, because the mechanical forces and contractile properties of LC and CE likely differ. This study examined muscle protein synthesis (MPS) and whole-body protein turnover in response to LC and CE, with and without EAA supplementation, using stable isotope amino acid tracer infusions. Forty adults (mean ± SD, 22 ± 4 y, 80 ± 10 kg, VO 2peak 4.0 ± 0.5 L ∙ min(-1)) were randomly assigned to perform 90 min, absolute intensity-matched (2.2 ± 0.1 VO2 L ∙ m(-1)) LC (performed on a treadmill wearing a vest equal to 30% of individual body mass, mean ± SD load carried 24 ± 3 kg) or CE (cycle ergometry performed at the same absolute VO2 as LC) exercise, during which EAA (10 g EAA, 3.6 g leucine) or control (CON, non-nutritive) drinks were consumed. Mixed-muscle and myofibrillar MPS were higher during exercise for LC than CE (mode main effect, P < 0.05), independent of dietary treatment. EAA enhanced mixed-muscle and sarcoplasmic MPS during exercise, regardless of mode (drink main effect, P < 0.05). Mixed-muscle and sarcoplasmic MPS were higher in recovery for LC than CE (mode main effect, P < 0.05). No other differences or interactions (mode x drink) were observed. However, EAA attenuated whole-body protein breakdown, increased amino acid oxidation, and enhanced net protein balance in recovery compared to CON, regardless of exercise mode (P < 0.05). These data show that, although whole-body protein turnover responses to absolute VO2-matched LC and CE are the same, LC elicited a greater muscle protein synthetic response than CE.

Prefrontal gamma-aminobutyric acid type A receptor insertion controls cue-induced relapse to nicotine seeking.

PubMed

Lubbers, Bart R; van Mourik, Yvar; Schetters, Dustin; Smit, August B; De Vries, Taco J; Spijker, Sabine

2014-11-01

Current smoking cessation therapies offer limited success, as relapse rates remain high. Nicotine, which is the major component of tobacco smoke, is thought to be primarily responsible for the addictive properties of tobacco. However, little is known about the molecular mechanisms underlying nicotine relapse, hampering development of more effective therapies. The objective of this study was to elucidate the role of medial prefrontal cortex (mPFC) glutamatergic and gamma-aminobutyric acid (GABA)ergic receptors in controlling relapse to nicotine seeking. Using an intravenous self-administration model, we studied glutamate and gamma-aminobutyric acid receptor regulation in the synaptic membrane fraction of the rat mPFC following extinction and cue-induced relapse to nicotine seeking. Subsequently, we locally intervened at the level of GABAergic signaling by using a mimetic peptide of the GABA receptor associated protein-interacting domain of GABA type A (GABAA) receptor subunit γ2 (TAT-GABAγ2) and muscimol, a GABAA receptor agonist. Alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid and N-methyl-D-aspartate receptors were not regulated after the 30-min relapse test. However, GABAA receptor subunits α1 and γ2 were upregulated, and interference with GABAA receptor insertion in the cell membrane using the TAT-GABAγ2 peptide in the dorsal mPFC, but not the ventral mPFC, significantly increased responding during relapse. Increasing GABAA transmission with muscimol in the dorsal and ventral mPFC attenuated relapse. These data indicate that cue-induced relapse entails a GABAergic plasticity mechanism that limits nicotine seeking by restoring inhibitory control in the dorsal mPFC. GABAA receptor-mediated neurotransmission in the dorsal mPFC constitutes a possible future therapeutic target for maintaining smoking abstinence. Copyright © 2014 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Bacterial D-Amino Acids Suppress Sinonasal Innate Immunity Through Sweet Taste Receptors in Solitary Chemosensory Cells

PubMed Central

Lee, Robert J.; Hariri, Benjamin M.; McMahon, Derek B.; Chen, Bei; Doghramjii, Laurel; Adappa, Nithin D.; Palmer, James N.; Kennedy, David W.; Jiang, Peihua; Margolskee, Robert F.; Cohen, Noam A.

2017-01-01

In the upper respiratory epithelium, bitter and sweet taste receptors present in solitary chemosensory cells influence antimicrobial innate immune defense responses. Whereas activation of the bitter taste receptor (T2R) stimulates surrounding epithelial cells to release antimicrobial peptides, activation of the sweet taste receptor (T1R) in the same cells inhibits this response. It is thought that this mechanism exists to control the magnitude of antimicrobial peptide release based upon the sugar content of airway surface liquid. We hypothesized that D-amino acids, which are produced by various bacteria and activate T1R in taste receptor cells in the mouth, may also activate T1R in the airway. Here, we show that both the T1R2 and T1R3 subunits of the sweet taste receptor (T1R2/3) are present in the same chemosensory cells of primary human sinonasal epithelial cultures. Respiratory isolates of Staphylococcus species, but not Pseudomonas aeruginosa, produced at least two D-amino acids that activate the sweet taste receptor. In addition to inhibiting P. aeruginosa biofilm formation, D-amino acids derived from Staphylococcus inhibited T2R-mediated signaling and defensin secretion in sinonasal cells by activating T1R2/3. D-amino acid–mediated activation of T1R2/3 also enhanced epithelial cell death during challenge with Staphylococcus aureus in the presence of the bitter-receptor–activating compound denatonium benzoate. These data establish a potential mechanism for interkingdom signaling in the airway mediated by bacterial D-amino acids and the mammalian sweet taste receptor in airway chemosensory cells. PMID:28874606

mRNA levels of enzymes and receptors implicated in arachidonic acid metabolism in gliomas.

PubMed

De Armas, Rafael; Durand, Karine; Guillaudeau, Angélique; Weinbreck, Nicolas; Robert, Sandrine; Moreau, Jean-Jacques; Caire, François; Acosta, Gisela; Pebet, Matias; Chaunavel, Alain; Marin, Benoît; Labrousse, François; Denizot, Yves

2010-07-01

Gliomas are tumors of the central nervous system derived from glial cells. They show cellular heterogeneity and lack specific diagnostic markers. Although a possible role for the eicosanoid cascade has been suggested in glioma tumorigenesis, the relationship between enzymes and receptors implicated in arachidonic acid metabolism, with histological tumor type has not yet been determined. Quantitative real-time reverse transcription-polymerase chain reaction was performed to measure and compare transcript levels of enzymes and receptors implicated in both lipoxygenase and cyclooxygenase pathways between oligodendrogliomas, astrocytomas, glioblastomas and mixed oligoastrocytomas. Arachidonic acid metabolism-related enzymes and receptor transcripts (i) were underexpressed in classical oligodendrogliomas compared to astrocytomas and/or glioblastomas, (ii) differed between astrocytomas and glioblastomas and (iii) had an intermediate expression in mixed oligoastrocytomas. mRNA levels of enzymes and receptors implicated both in lipoxygenase and cyclooxygenase pathways differed significantly in gliomas according to the histological type. Copyright 2010 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.

Metabolism meets immunity: The role of free fatty acid receptors in the immune system.

PubMed

Alvarez-Curto, Elisa; Milligan, Graeme

2016-08-15

There are significant numbers of nutrient sensing G protein-coupled receptors (GPCRs) that can be found in cells of the immune system and in tissues that are involved in metabolic function, such as the pancreas or the intestinal epithelium. The family of free fatty acid receptors (FFAR1-4, GPR84), plus a few other metabolite sensing receptors (GPR109A, GPR91, GPR35) have been for this reason the focus of studies linking the effects of nutrients with immunological responses. A number of the beneficial anti-inflammatory effects credited to dietary fats such as omega-3 fatty acids are attributed to their actions on FFAR4.This might play an important protective role in the development of obesity, insulin resistance or asthma. The role of the short-chain fatty acids resulting from fermentation of fibre by the intestinal microbiota in regulating acute inflammatory responses is also discussed. Finally we assess the therapeutic potential of this family of receptors to treat pathologies where inflammation is a major factor such as type 2 diabetes, whether by the use of novel synthetic molecules or by the modulation of the individual's diet. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Human sweet taste receptor mediates acid-induced sweetness of miraculin

PubMed Central

Koizumi, Ayako; Tsuchiya, Asami; Nakajima, Ken-ichiro; Ito, Keisuke; Terada, Tohru; Shimizu-Ibuka, Akiko; Briand, Loïc; Asakura, Tomiko; Misaka, Takumi; Abe, Keiko

2011-01-01

Miraculin (MCL) is a homodimeric protein isolated from the red berries of Richadella dulcifica. MCL, although flat in taste at neutral pH, has taste-modifying activity to convert sour stimuli to sweetness. Once MCL is held on the tongue, strong sweetness is sensed over 1 h each time we taste a sour solution. Nevertheless, no molecular mechanism underlying the taste-modifying activity has been clarified. In this study, we succeeded in quantitatively evaluating the acid-induced sweetness of MCL using a cell-based assay system and found that MCL activated hT1R2-hT1R3 pH-dependently as the pH decreased from 6.5 to 4.8, and that the receptor activation occurred every time an acid solution was applied. Although MCL per se is sensory-inactive at pH 6.7 or higher, it suppressed the response of hT1R2-hT1R3 to other sweeteners at neutral pH and enhanced the response at weakly acidic pH. Using human/mouse chimeric receptors and molecular modeling, we revealed that the amino-terminal domain of hT1R2 is required for the response to MCL. Our data suggest that MCL binds hT1R2-hT1R3 as an antagonist at neutral pH and functionally changes into an agonist at acidic pH, and we conclude this may cause its taste-modifying activity. PMID:21949380

Computational Analysis of the Interaction Energies between Amino Acid Residues of the Measles Virus Hemagglutinin and Its Receptors.

PubMed

Xu, Fengqi; Tanaka, Shigenori; Watanabe, Hirofumi; Shimane, Yasuhiro; Iwasawa, Misako; Ohishi, Kazue; Maruyama, Tadashi

2018-05-03

Measles virus (MV) causes an acute and highly devastating contagious disease in humans. Employing the crystal structures of three human receptors, signaling lymphocyte-activation molecule (SLAM), CD46, and Nectin-4, in complex with the measles virus hemagglutinin (MVH), we elucidated computationally the details of binding energies between the amino acid residues of MVH and those of the receptors with an ab initio fragment molecular orbital (FMO) method. The calculated inter-fragment interaction energies (IFIEs) revealed a number of significantly interacting amino acid residues of MVH that played essential roles in binding to the receptors. As predicted from previously reported experiments, some important amino-acid residues of MVH were shown to be common but others were specific to interactions with the three receptors. Particularly, some of the (non-polar) hydrophobic residues of MVH were found to be attractively interacting with multiple receptors, thus indicating the importance of the hydrophobic pocket for intermolecular interactions (especially in the case of Nectin-4). In contrast, the electrostatic interactions tended to be used for specific molecular recognition. Furthermore, we carried out FMO calculations for in silico experiments of amino acid mutations, finding reasonable agreements with virological experiments concerning the substitution effect of residues. Thus, the present study demonstrates that the electron-correlated FMO method is a powerful tool to search exhaustively for amino acid residues that contribute to interactions with receptor molecules. It is also applicable for designing inhibitors of MVH and engineered MVs for cancer therapy.

Effects of Alpha-Lipoic Acid on Oxidative Stress and Kinin Receptor Expression in Obese Zucker Diabetic Fatty Rats.

PubMed

Midaoui, Adil El; Talbot, Sébastien; Lahjouji, Karim; Dias, Jenny Pena; Fantus, I George; Couture, Réjean

2015-06-01

To investigate the impact of alpha-lipoic acid on superoxide anion production and NADPH oxidase activity as well as on the expression of kinin B1 and B2 receptors in key organs of obese Zucker Diabetic Fatty rats. Superoxide anion production was measured by lucigenin chemiluminescence. Kinin B1 and B2 receptors expression was measured at protein and mRNA levels by western blot and qRT-PCR in key organs of Zucker Diabetic Fatty and Zucker lean control rats treated for a period of 6 weeks with a standard diet or a diet containing the antioxidant α-lipoic acid (1 g/kg). Superoxide anion production and NADPH oxidase activity were significantly enhanced in aorta and adipose tissue of Zucker Diabetic Fatty rats. Kinin B1 and B2 receptors expression levels were also significantly increased in the liver and the gastrocnemius muscle of Zucker Diabetic Fatty rats. Expression of both receptors was not altered in the pancreas of Zucker Diabetic Fatty rats and was undetectable in white retroperitoneal adipose tissue. Alpha-lipoic acid prevented the rise in NADPH oxidase activity in aorta and epididymal adipose tissue of Zucker Diabetic Fatty rats and the upregulation of kinin B1 receptor in liver and gastrocnemius muscle and that of kinin B2 receptor in the liver. Alpha-lipoic acid treatment was found to prevent the final body weight increase without affecting significantly hyperglycemia, hyperinsulinemia and insulin resistance index in Zucker Diabetic Fatty rats. Findings support the hypothesis that oxidative stress is implicated in the induction of kinin B1 receptor in Zucker Diabetic Fatty rats. The ability of α-lipoic acid to blunt the body weight gain appears to be mediated in part by preventing NADPH oxidase activity rise in adipose tissue and reversing the hepatic upregulation of kinin B1 receptor in Zucker Diabetic Fatty rats.

Body Weight Loss and Tissue Wasting in Late Middle-Aged Mice on Slightly Imbalanced Essential/Non-essential Amino Acids Diet.

PubMed

Corsetti, Giovanni; Pasini, Evasio; Romano, Claudia; Calvani, Riccardo; Picca, Anna; Marzetti, Emanuele; Flati, Vincenzo; Dioguardi, Francesco S

2018-01-01

Objective: Inadequate protein intake can impair protein balance thus leading to skeletal muscle atrophy, impaired body growth, and functional decline. Foods provide both non-essential (NEAAs) and essential amino acids (EAAs) that may convey different metabolic stimuli to specific organs and tissues. In this study, we sought to evaluate the impact of six diets, with various EAA/NEAA blends, on body composition and the risk of developing tissue wasting in late middle-aged male mice. Methods: Six groups of late middle-aged male mice were fed for 35 days with iso-nutrients, iso-caloric, and iso-nitrogenous special diets containing different EAA/NEAA ratios ranging from 100/0% to 0/100%. One group fed with standard laboratory rodent diet (StD) served as control. Preliminarily, we verified the palatability of the diets by recording the mice preference, and by making accessible all diets simultaneously, in comparison to StD. Body weight, food and water consumption were measured every 3 days. Blood and urine samples, as well as heart, kidneys, liver, spleen, triceps surae, retroperitoneal WAT, and BAT were harvested and weighed. Results: Mice consuming NEAA-based diets, although showing increased food and calorie intake, suffered the most severe weight loss. Interestingly, the diet containing a EAA/NEAA-imbalance, with moderate NEAAs prevalence, was able to induce catabolic stimuli, generalized body wasting, and systemic metabolic alterations comparable to those observed with diet containing NEAA alone. In addition, complete depletion of retroperitoneal white adipose tissue and a severe loss (>75%) of brown adipose tissue were observed together with muscle wasting. Conversely, EAA-containing diets induced significant decreases in body weight by reducing primarily fat reserves, but at the same time they improved the clinical parameters. On these basis we can deduce that tissue wasting was caused by altered AA quality, independent of reduced nitrogen or caloric intake

Dietary fatty acids regulate hepatic low density lipoprotein (LDL) transport by altering LDL receptor protein and mRNA levels.

PubMed Central

Horton, J D; Cuthbert, J A; Spady, D K

1993-01-01

The concentration of LDL in plasma is strongly influenced by the amount and the type of lipid in the diet. Recent studies in the hamster have shown that dietary fatty acids differentially affect circulating LDL levels primarily by altering receptor-dependent LDL uptake in the liver. To investigate the mechanistic basis of this effect, rates of receptor-dependent LDL transport in the liver were correlated with LDL receptor protein and mRNA levels in hamsters fed safflower oil or coconut oil and varying amounts of cholesterol. Hepatic LDL receptor activity was significantly lower in animals fed coconut oil than in animals fed safflower oil at all levels of cholesterol intake (26, 53, and 61% lower at cholesterol intakes of 0, 0.06, and 0.12%, respectively). These fatty acid-induced changes in hepatic LDL receptor activity were accompanied by parallel changes in hepatic LDL receptor protein and mRNA levels, suggesting that dietary fatty acids regulate the LDL receptor pathway largely at the mRNA level. Images PMID:8349814

Receptor for protons: First observations on Acid Sensing Ion Channels.

PubMed

Krishtal, Oleg

2015-07-01

The history of ASICs began in 1980 with unexpected observation. The concept of highly selective Na(+) current gated by specific receptors for protons was not easily accepted. It took 16 years to get these receptor/channels cloned and start a new stage in their investigation. "The receptor for protons" became ASIC comprising under this name a family of receptor/channels ubiquitous for mammalian nervous system, both peripheral and central. The role of ASICs as putative nociceptors was suggested almost immediately after their discovery. This role subsequently was proven in many forms of pain-related phenomena. Many other functions of ASICs have been also found or primed for speculations both in physiology and in disease. Despite the width of field and strength of efforts, numerous basic questions are to be answered before we understand how the local changes in pH in the nervous tissue transform into electric and messenger signaling via ASICs as transducers. This article is part of the Special Issue entitled 'Acid-Sensing Ion Channels in the Nervous System'. Copyright © 2015. Published by Elsevier Ltd.

The Gamma-Aminobutyric Acid B Receptor in Depression and Reward.

PubMed

Jacobson, Laura H; Vlachou, Styliani; Slattery, David A; Li, Xia; Cryan, John F

2018-06-01

The metabotropic gamma-aminobutyric acid B (GABA B ) receptor was the first described obligate G protein-coupled receptor heterodimer and continues to set the stage for discoveries in G protein-coupled receptor signaling complexity. In this review, dedicated to the life and work of Athina Markou, we explore the role of GABA B receptors in depression, reward, and the convergence of these domains in anhedonia, a shared symptom of major depressive disorder and withdrawal from drugs of abuse. GABA B receptor expression and function are enhanced by antidepressants and reduced in animal models of depression. Generally, GABA B receptor antagonists are antidepressant-like and agonists are pro-depressive. Exceptions to this rule likely reflect the differential influence of GABA B1 isoforms in depression-related behavior and neurobiology, including the anhedonic effects of social stress. A wealth of data implicate GABA B receptors in the rewarding effects of drugs of abuse. We focus on nicotine as an example. GABA B receptor activation attenuates, and deactivation enhances, nicotine reward and associated neurobiological changes. In nicotine withdrawal, however, GABA B receptor agonists, antagonists, and positive allosteric modulators enhance anhedonia, perhaps owing to differential effects of GABA B1 isoforms on the dopaminergic system. Nicotine cue-induced reinstatement is more reliably attenuated by GABA B receptor activation. Separation of desirable and undesirable side effects of agonists is achievable with positive allosteric modulators, which are poised to enter clinical studies for drug abuse. GABA B1 isoforms are key to understanding the neurobiology of anhedonia, whereas allosteric modulators may offer a mechanism for targeting specific brain regions and processes associated with reward and depression. Copyright © 2018 Society of Biological Psychiatry. All rights reserved.

Nicotinic Acid Adenine Dinucleotide Phosphate Analogs Substituted on the Nicotinic Acid and Adenine Ribosides. Effects on Receptor-Mediated Ca2+ release

PubMed Central

Trabbic, Christopher J.; Zhang, Fan; Walseth, Timothy F.; Slama, James T.

2015-01-01

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a Ca2+ releasing intracellular second messenger in both mammals and echinoderms. We report that large functionalized substituents introduced at the nicotinic acid 5-position are recognized by the sea urchin receptor, albeit with a 20–500 fold loss in agonist potency. 5-(3-Azidopropyl)-NAADP was shown to release Ca2+ with an EC50 of 31 µM and to compete with NAADP for receptor binding with an IC50 of 56 nM. Attachment of charged groups to the nicotinic acid of NAADP is associated with loss of activity, suggesting that the nicotinate riboside moiety is recognized as a neutral zwitterion. Substituents (Br- and N3-) can be introduced at the 8-adenosyl position of NAADP while preserving high potency and agonist efficacy and an NAADP derivative substituted at both the 5-position of the nicotinic acid and at the 8-adenosyl position was also recognized although the agonist potency was significantly reduced. PMID:25826221

High Serum Essential Amino Acids as a Predictor of Skeletal Muscle Depletion in Patients With Cachexia and Advanced Gastrointestinal Cancers.

PubMed

Kitagawa, Moeko; Haji, Seiji; Amagai, Teruyoshi

2017-10-01

In recent years, the number of patients with cancer has increased. These patients are prone to sarcopenia as a result of the decrease in muscle mass and muscle weakness that occur in cancer cachexia. Amino Index Cancer Screening is carried out to evaluate cancer cachexia risk by examining amino acid concentration and analyzing amino acid balance. We conducted a retrospective chart review of consecutive patients with unresectable advanced gastrointestinal cancer (stage IV) receiving chemotherapy treatment (December 2012-September 2015) in an outpatient or in-hospital setting at our institution (N = 46). Data included characteristics, psoas muscle area per computed tomography, and biochemical blood test and serum amino acid profiles. Method 1: Comparison of biomarkers between 2 groups: psoas muscle index change rate (ΔPMI) decrease vs increase. Method 2.1: Correlation between ΔPMI and biomarkers. Method 2.2: Multiple regression of ΔPMI and biomarkers. EAA/TAA ratio (essential amino acids/total amino acids) in the decrease group was significantly higher than that in the increase group. Among all parameters, serum C-reactive protein (CRP), leucine, and isoleucine were negatively related to ΔPMI (correlation coefficients = -0.604, -0.540, -0.518; P = .004, .011, .016, respectively). On multiple regression analysis, serum CRP value was strongly related to ΔPMI ( r 2 = 0.452, β = -0.672, P = .001). Higher serum EAA/TAA ratio and CRP were associated with depletion in psoas muscle area, which led to a diagnosis of sarcopenia, in patients with advanced gastrointestinal cancers. These parameters at baseline could be predictors of cancer cachexia.

Phosphorylation and Internalization of Lysophosphatidic Acid Receptors LPA1, LPA2, and LPA3

PubMed Central

Alcántara-Hernández, Rocío; Hernández-Méndez, Aurelio; Campos-Martínez, Gisselle A.; Meizoso-Huesca, Aldo; García-Sáinz, J. Adolfo

2015-01-01

Results The lysophosphatidic acid receptors LPA1, LPA2, and LPA3 were individually expressed in C9 cells and their signaling and regulation were studied. Agonist-activation increases intracellular calcium concentration in a concentration-dependent fashion. Phorbol myristate acetate markedly inhibited LPA1- and LPA3-mediated effect, whereas that mediated by LPA2 was only partially diminished; the actions of the phorbol ester were inhibited by bisindolylmaleimide I and by overnight incubation with the protein kinase C activator, which leads to down regulation of this protein kinase. Homologous desensitization was also observed for the three LPA receptors studied, with that of LPA2 receptors being consistently of lesser magnitude; neither inhibition nor down-regulation of protein kinase C exerted any effect on homologous desensitization. Activation of LPA1–3 receptors induced ERK 1/2 phosphorylation; this effect was markedly attenuated by inhibition of epidermal growth factor receptor tyrosine kinase activity, suggesting growth factor receptor transactivation in this effect. Lysophosphatidic acid and phorbol myristate acetate were able to induce LPA1–3 phosphorylation, in time- and concentration-dependent fashions. It was also clearly observed that agonists and protein kinase C activation induced internalization of these receptors. Phosphorylation of the LPA2 subtype required larger concentrations of these agents and its internalization was less intense than that of the other subtypes. Conclusion Our data show that these three LPA receptors are phosphoproteins whose phosphorylation state is modulated by agonist-stimulation and protein kinase C-activation and that differences in regulation and cellular localization exist, among the subtypes. PMID:26473723

A New Pain Regulatory System via the Brain Long Chain Fatty Acid Receptor GPR40/FFA1 Signal.

PubMed

Nakamoto, Kazuo

2017-01-01

An increasingly large number of pharmacological and physiological works on fatty acids have shown that the functional properties of fatty acids are regulated by the amount of individual fatty acid intake and the distribution of fatty acids among organs. Recently, it has been determined that G-protein-coupled receptor 40/free fatty acid receptor 1 (GPR40/FFA1) is activated by long-chain fatty acids, such as docosahexaenoic acid (DHA). GPR40/FFA1 is mainly expressed in the β cell of the pancreas, spinal cord and brain. It is reported that this receptor has a functional role in controlling blood glucose levels via the modulation of insulin secretion. However, its physiological function in the brain remains unknown. Our previous studies have shown that GPR40/FFA1 is expressed in pro-opiomelanocortin (POMC)-positive neurons of the arcuate nucleus, serotonergic neurons in the nucleus raphe magnus, and in noradrenergic neurons in the locus coeruleus. Furthermore, the intracerebroventricular injection of DHA or GW9508, which is a selective GPR40/FFA1 agonist, attenuates formalin-induced inflammatory pain behavior through increasing β-endorphin release in the hypothalamus. It also suppresses complete Freund's adjuvant-induced mechanical allodynia and thermal hyperalgesia. Our findings suggest that brain free long-chain fatty acids-GPR40/FFA1 signaling might have an important role in the modulation of endogenous pain control systems. In this review, I discuss the current status and our recent study regarding a new pain regulatory system via the brain long chain fatty acid receptor GPR40/FFA1 signal.

Modification on ursodeoxycholic acid (UDCA) scaffold. discovery of bile acid derivatives as selective agonists of cell-surface G-protein coupled bile acid receptor 1 (GP-BAR1).

PubMed

Sepe, Valentina; Renga, Barbara; Festa, Carmen; D'Amore, Claudio; Masullo, Dario; Cipriani, Sabrina; Di Leva, Francesco Saverio; Monti, Maria Chiara; Novellino, Ettore; Limongelli, Vittorio; Zampella, Angela; Fiorucci, Stefano

2014-09-25

Bile acids are signaling molecules interacting with the nuclear receptor FXR and the G-protein coupled receptor 1 (GP-BAR1/TGR5). GP-BAR1 is a promising pharmacological target for the treatment of steatohepatitis, type 2 diabetes, and obesity. Endogenous bile acids and currently available semisynthetic bile acids are poorly selective toward GP-BAR1 and FXR. Thus, in the present study we have investigated around the structure of UDCA, a clinically used bile acid devoid of FXR agonist activity, to develop a large family of side chain modified 3α,7β-dihydroxyl cholanoids that selectively activate GP-BAR1. In vivo and in vitro pharmacological evaluation demonstrated that administration of compound 16 selectively increases the expression of pro-glucagon 1, a GP-BAR1 target, in the small intestine, while it had no effect on FXR target genes in the liver. Further, compound 16 results in a significant reshaping of bile acid pool in a rodent model of cholestasis. These data demonstrate that UDCA is a useful scaffold to generate novel and selective steroidal ligands for GP-BAR1.

Allspice and Clove As Source of Triterpene Acids Activating the G Protein-Coupled Bile Acid Receptor TGR5

PubMed Central

Ladurner, Angela; Zehl, Martin; Grienke, Ulrike; Hofstadler, Christoph; Faur, Nadina; Pereira, Fátima C.; Berry, David; Dirsch, Verena M.; Rollinger, Judith M.

2017-01-01

Worldwide, metabolic diseases such as obesity and type 2 diabetes have reached epidemic proportions. A major regulator of metabolic processes that gained interest in recent years is the bile acid receptor TGR5 (Takeda G protein-coupled receptor 5). This G protein-coupled membrane receptor can be found predominantly in the intestine, where it is mainly responsible for the secretion of the incretins glucagon-like peptide 1 (GLP-1) and peptide YY (PYY). The aim of this study was (i) to identify plant extracts with TGR5-activating potential, (ii) to narrow down their activity to the responsible constituents, and (iii) to assess whether the intestinal microbiota produces transformed metabolites with a different activity profile. Chenodeoxycholic acid (CDCA) served as positive control for both, the applied cell-based luciferase reporter gene assay for TGR5 activity and the biotransformation assay using mouse fecal slurry. The suitability of the workflow was demonstrated by the biotransformation of CDCA to lithocholic acid resulting in a distinct increase in TGR5 activity. Based on a traditional Tibetan formula, 19 plant extracts were selected and investigated for TGR5 activation. Extracts from the commonly used spices Syzygium aromaticum (SaroE, clove), Pimenta dioica (PdioE, allspice), and Kaempferia galanga (KgalE, aromatic ginger) significantly increased TGR5 activity. After biotransformation, only KgalE showed significant differences in its metabolite profile, which, however, did not alter its TGR5 activity compared to non-transformed KgalE. UHPLC-HRMS (high-resolution mass spectrometry) analysis revealed triterpene acids (TTAs) as the main constituents of the extracts SaroE and PdioE. Identification and quantification of TTAs in these two extracts as well as comparison of their TGR5 activity with reconstituted TTA mixtures allowed the attribution of the TGR5 activity to TTAs. EC50s were determined for the main TTAs, i.e., oleanolic acid (2.2 ± 1.6 μM), ursolic

Pharmacologically relevant receptor binding characteristics and 5alpha-reductase inhibitory activity of free Fatty acids contained in saw palmetto extract.

PubMed

Abe, Masayuki; Ito, Yoshihiko; Oyunzul, Luvsandorj; Oki-Fujino, Tomomi; Yamada, Shizuo

2009-04-01

Saw palmetto extract (SPE), used widely for the treatment of benign prostatic hyperplasia (BPH) has been shown to bind alpha(1)-adrenergic, muscarinic and 1,4-dihydropyridine (1,4-DHP) calcium channel antagonist receptors. Major constituents of SPE are lauric acid, oleic acid, myristic acid, palmitic acid and linoleic acid. The aim of this study was to investigate binding affinities of these fatty acids for pharmacologically relevant (alpha(1)-adrenergic, muscarinic and 1,4-DHP) receptors. The fatty acids inhibited specific [(3)H]prazosin binding in rat brain in a concentration-dependent manner with IC(50) values of 23.8 to 136 microg/ml, and specific (+)-[(3)H]PN 200-110 binding with IC(50) values of 24.5 to 79.5 microg/ml. Also, lauric acid, oleic acid, myristic acid and linoleic acid inhibited specific [(3)H]N-methylscopolamine ([(3)H]NMS) binding in rat brain with IC(50) values of 56.4 to 169 microg/ml. Palmitic acid had no effect on specific [(3)H]NMS binding. The affinity of oleic acid, myristic acid and linoleic acid for each receptor was greater than the affinity of SPE. Scatchard analysis revealed that oleic acid and lauric acid caused a significant decrease in the maximal number of binding sites (B(max)) for [(3)H]prazosin, [(3)H]NMS and (+)-[(3)H]PN 200-110. The results suggest that lauric acid and oleic acid bind noncompetitively to alpha(1)-adrenergic, muscarinic and 1,4-DHP calcium channel antagonist receptors. We developed a novel and convenient method of determining 5alpha-reductase activity using LC/MS. With this method, SPE was shown to inhibit 5alpha-reductase activity in rat liver with an IC(50) of 101 microg/ml. Similarly, all the fatty acids except palmitic acid inhibited 5alpha-reductase activity, with IC(50) values of 42.1 to 67.6 microg/ml. In conclusion, lauric acid, oleic acid, myristic acid, and linoleic acid, major constituents of SPE, exerted binding activities of alpha(1)-adrenergic, muscarinic and 1,4-DHP receptors and inhibited 5

Bile Acid Receptor Agonist GW4064 Regulates PPARγ Coactivator-1α Expression Through Estrogen Receptor-Related Receptor α

PubMed Central

Dwivedi, Shailendra Kumar Dhar; Singh, Nidhi; Kumari, Rashmi; Mishra, Jay Sharan; Tripathi, Sarita; Banerjee, Priyam; Shah, Priyanka; Kukshal, Vandana; Tyagi, Abdul Malik; Gaikwad, Anil Nilkanth; Chaturvedi, Rajnish Kumar; Mishra, Durga Prasad; Trivedi, Arun Kumar; Sanyal, Somali; Chattopadhyay, Naibedya; Ramachandran, Ravishankar; Siddiqi, Mohammad Imran; Bandyopadhyay, Arun; Arora, Ashish; Lundåsen, Thomas; Anakk, Sayee Priyadarshini; Moore, David D.

2011-01-01

Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) is induced in energy-starved conditions and is a key regulator of energy homeostasis. This makes PGC-1α an attractive therapeutic target for metabolic syndrome and diabetes. In our effort to identify new regulators of PGC-1α expression, we found that GW4064, a widely used synthetic agonist for the nuclear bile acid receptor [farnesoid X receptor (FXR)] strongly enhances PGC-1α promoter reporter activity, mRNA, and protein expression. This induction in PGC-1α concomitantly enhances mitochondrial mass and expression of several PGC-1α target genes involved in mitochondrial function. Using FXR-rich or FXR-nonexpressing cell lines and tissues, we found that this effect of GW4064 is not mediated directly by FXR but occurs via activation of estrogen receptor-related receptor α (ERRα). Cell-based, biochemical and biophysical assays indicate GW4064 as an agonist of ERR proteins. Interestingly, FXR disruption alters GW4064 induction of PGC-1α mRNA in a tissue-dependent manner. Using FXR-null [FXR knockout (FXRKO)] mice, we determined that GW4064 induction of PGC-1α expression is not affected in oxidative soleus muscles of FXRKO mice but is compromised in the FXRKO liver. Mechanistic studies to explain these differences revealed that FXR physically interacts with ERR and protects them from repression by the atypical corepressor, small heterodimer partner in liver. Together, this interplay between ERRα-FXR-PGC-1α and small heterodimer partner offers new insights into the biological functions of ERRα and FXR, thus providing a knowledge base for therapeutics in energy balance-related pathophysiology. PMID:21493670

p-Coumaric acid activates the GABA-A receptor in vitro and is orally anxiolytic in vivo.

PubMed

Scheepens, Arjan; Bisson, Jean-Francois; Skinner, Margot

2014-02-01

The increasing prevalence and social burden of subclinical anxiety in the western world represents a significant psychosocial and financial cost. Consumers are favouring a more natural and nonpharmacological approach for alleviating the effects of everyday stress and anxiety. The gamma-aminobutyric acid (GABA) receptor is the primary mediator of central inhibitory neurotransmission, and GABA-receptor agonists are well known to convey anxiolytic effects. Using an in vitro screening approach to identify naturally occurring phytochemical GABA agonists, we discovered the plant secondary metabolite p-coumaric acid to have significant GABAergic activity, an effect that could be blocked by co-administration of the specific GABA-receptor antagonist, picrotoxin. Oral administration of p-coumaric acid to rodents induced a significant anxiolytic effect in vivo as measured using the elevated plus paradigm, in line with the effects of oral diazepam. Given that p-coumaric acid is reasonably well absorbed following oral consumption in man and is relatively nontoxic, it may be suitable for the formulation of a safe and effective anxiolytic functional food. Copyright © 2013 John Wiley & Sons, Ltd.

Stimulation of acid secretion and phosphoinositol production by rat parietal cell muscarinic M sub 2 receptors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pfeiffer, A.; Rochlitz, H.; Herz, A.

The muscarinic receptor system involved in hydrogen production by enriched rat gastric parietal cells was investigated. Muscarinic receptor density determined by (N-methyl-{sup 3}H)scopolamine binding was 8,100/cell. The receptor appeared to be of the M{sub 2} muscarinic receptor subtype, since it had a low affinity (K{sub d} 189 nM) for the M{sub 1} receptor antagonist pirenzepine compared with atropine. Receptor activation by carbachol rapidly augmented levels of polyphosphoinositides, indicating an activation of phospholipase C. The dose-response relations for the increase in inositol phosphates closely paralleled the binding of carbachol to muscarinic receptors. The inositol phosphate response was antagonized by pirenzepine withmore » a K{sub i} of 177 nM. the stimulation of inositol phosphate levels by carbachol correlated well with the stimulation of ({sup 14}C)aminopyrine uptake, determine as an index of acid secretion. The muscarinic agonists oxotremorine, pilocarpine, and bethanechol elicited partial increases in inositol phosphates at maximal drug concentrations, and these partial increases correlated with their ability to stimulate ({sup 14}C)aminopyrine uptake. These data indicate that inositolpolyphosphates may be a second messenger of M{sub 2} receptors stimulating acid secretion.« less

The Barley Magnesium Chelatase 150-kD Subunit Is Not an Abscisic Acid Receptor1[OA

PubMed Central

Müller, André H.; Hansson, Mats

2009-01-01

Magnesium chelatase is the first unique enzyme of the chlorophyll biosynthetic pathway. It is composed of three gene products of which the largest is 150 kD. This protein was recently identified as an abscisic acid receptor in Arabidopsis (Arabidopsis thaliana). We have evaluated whether the barley (Hordeum vulgare) magnesium chelatase large subunit, XanF, could be a receptor for the phytohormone. The study involved analysis of recombinant magnesium chelatase protein as well as several induced chlorophyll-deficient magnesium chelatase mutants with defects identified at the gene and protein levels. Abscisic acid had no effect on magnesium chelatase activity and binding to the barley 150-kD protein could not be shown. Magnesium chelatase mutants showed a wild-type response in respect to postgermination growth and stomatal aperture. Our results question the function of the large magnesium chelatase subunit as an abscisic acid receptor. PMID:19176716

Pharmacological activation of lysophosphatidic acid receptors regulates erythropoiesis

PubMed Central

Lin, Kuan-Hung; Ho, Ya-Hsuan; Chiang, Jui-Chung; Li, Meng-Wei; Lin, Shi-Hung; Chen, Wei-Min; Chiang, Chi-Ling; Lin, Yu-Nung; Yang, Ya-Jan; Chen, Chiung-Nien; Lu, Jenher; Huang, Chang-Jen; Tigyi, Gabor; Yao, Chao-Ling; Lee, Hsinyu

2016-01-01

Lysophosphatidic acid (LPA), a growth factor-like phospholipid, regulates numerous physiological functions, including cell proliferation and differentiation. In a previous study, we have demonstrated that LPA activates erythropoiesis by activating the LPA 3 receptor subtype (LPA3) under erythropoietin (EPO) induction. In the present study, we applied a pharmacological approach to further elucidate the functions of LPA receptors during red blood cell (RBC) differentiation. In K562 human erythroleukemia cells, knockdown of LPA2 enhanced erythropoiesis, whereas knockdown of LPA3 inhibited RBC differentiation. In CD34+ human hematopoietic stem cells (hHSC) and K526 cells, the LPA3 agonist 1-oleoyl-2-methyl-sn-glycero-3-phosphothionate (2S-OMPT) promoted erythropoiesis, whereas the LPA2 agonist dodecyl monophosphate (DMP) and the nonlipid specific agonist GRI977143 (GRI) suppressed this process. In zebrafish embryos, hemoglobin expression was significantly increased by 2S-OMPT treatment but was inhibited by GRI. Furthermore, GRI treatment decreased, whereas 2S-OMPT treatment increased RBC counts and amount of hemoglobin level in adult BALB/c mice. These results indicate that LPA2 and LPA3 play opposing roles during RBC differentiation. The pharmacological activation of LPA receptor subtypes represent a novel strategies for augmenting or inhibiting erythropoiesis. PMID:27244685

Pharmacological activation of lysophosphatidic acid receptors regulates erythropoiesis.

PubMed

Lin, Kuan-Hung; Ho, Ya-Hsuan; Chiang, Jui-Chung; Li, Meng-Wei; Lin, Shi-Hung; Chen, Wei-Min; Chiang, Chi-Ling; Lin, Yu-Nung; Yang, Ya-Jan; Chen, Chiung-Nien; Lu, Jenher; Huang, Chang-Jen; Tigyi, Gabor; Yao, Chao-Ling; Lee, Hsinyu

2016-05-31

Lysophosphatidic acid (LPA), a growth factor-like phospholipid, regulates numerous physiological functions, including cell proliferation and differentiation. In a previous study, we have demonstrated that LPA activates erythropoiesis by activating the LPA 3 receptor subtype (LPA3) under erythropoietin (EPO) induction. In the present study, we applied a pharmacological approach to further elucidate the functions of LPA receptors during red blood cell (RBC) differentiation. In K562 human erythroleukemia cells, knockdown of LPA2 enhanced erythropoiesis, whereas knockdown of LPA3 inhibited RBC differentiation. In CD34(+) human hematopoietic stem cells (hHSC) and K526 cells, the LPA3 agonist 1-oleoyl-2-methyl-sn-glycero-3-phosphothionate (2S-OMPT) promoted erythropoiesis, whereas the LPA2 agonist dodecyl monophosphate (DMP) and the nonlipid specific agonist GRI977143 (GRI) suppressed this process. In zebrafish embryos, hemoglobin expression was significantly increased by 2S-OMPT treatment but was inhibited by GRI. Furthermore, GRI treatment decreased, whereas 2S-OMPT treatment increased RBC counts and amount of hemoglobin level in adult BALB/c mice. These results indicate that LPA2 and LPA3 play opposing roles during RBC differentiation. The pharmacological activation of LPA receptor subtypes represent a novel strategies for augmenting or inhibiting erythropoiesis.

Gamma-hydroxybutyric acid (GHB) and the mesoaccumbens reward circuit: evidence for GABA(B) receptor-mediated effects.

PubMed

Pistis, M; Muntoni, A L; Pillolla, G; Perra, S; Cignarella, G; Melis, M; Gessa, G L

2005-01-01

Gamma-hydroxybutyric acid (GHB) is a short-chain fatty acid naturally occurring in the mammalian brain, which recently emerged as a major recreational drug of abuse. GHB has multiple neuronal mechanisms including activation of both the GABA(B) receptor, and a distinct GHB-specific receptor. This complex GHB-GABA(B) receptor interaction is probably responsible for the multifaceted pharmacological, behavioral and toxicological profile of GHB. Drugs of abuse exert remarkably similar effects upon reward-related circuits, in particular the mesolimbic dopaminergic system and the nucleus accumbens (NAc). We used single unit recordings in vivo from urethane-anesthetized rats to characterize the effects of GHB on evoked firing in NAc "shell" neurons and on spontaneous activity of antidromically identified dopamine (DA) cells located in the ventral tegmental area. GHB was studied in comparison with the GABA(B) receptor agonist baclofen and antagonist (2S)(+)-5,5-dimethyl-2-morpholineacetic acid (SCH50911). Additionally, we utilized a GHB analog, gamma-(p-methoxybenzil)-gamma-hydroxybutyric acid (NCS-435), devoid of GABA(B) binding properties, but with high affinity for specific GHB binding sites. In common with other drugs of abuse, GHB depressed firing in NAc neurons evoked by the stimulation of the basolateral amygdala. On DA neurons, GHB exerted heterogeneous effects, which were correlated to the baseline firing rate of the cells but led to a moderate stimulation of the DA system. All GHB actions were mediated by GABA(B) receptors, since they were blocked by SCH50911 and were not mimicked by NCS-435. Our study indicates that the electrophysiological profile of GHB is close to typical drugs of abuse: both inhibition of NAc neurons and moderate to strong stimulation of DA transmission are distinctive features of diverse classes of abused drugs. Moreover, it is concluded that addictive and rewarding properties of GHB do not necessarily involve a putative high affinity GHB

Replacing dietary nonessential amino acids with ammonia nitrogen does not alter amino acid profile of deposited protein in the carcass of growing pigs fed a diet deficient in nonessential amino acid nitrogen.

PubMed

Mansilla, W D; Htoo, J K; de Lange, C F M

2017-10-01

Amino acid usage for protein retention, and, consequently, the AA profile of retained protein, is the main factor for determining AA requirements in growing animals. The objective of the present study was to determine the effect of supplementing ammonia N on whole-body N retention and the AA profile of retained protein in growing pigs fed a diet deficient in nonessential AA (NEAA) N. In total, 48 barrows with a mean initial BW of 13.6 kg (SD 0.7) were used. At the beginning of the study, 8 pigs were euthanized for determination of initial protein mass. The remaining animals were individually housed and fed 1 of 5 dietary treatments. A common basal diet (95% of experimental diets) was formulated to meet the requirements for all essential AA (EAA) but to be deficient in NEAA N (CP = 8.01%). The basal diet was supplemented (5%) with cornstarch (negative control) or 2 N sources (ammonia or NEAA) at 2 levels each to supply 1.35 or 2.70% extra CP. The final standardized ileal digestible (SID) NEAA content in the high-NEAA-supplemented diet (positive control) was based on the NEAA profile of whole-body protein of 20-kg pigs, and it was expected to reduce the endogenous synthesis of NEAA. Pigs were fed at 3.0 times maintenance energy requirements for ME in 3 equal meals daily. At the end of a 3-wk period, pigs were euthanized and the carcass and visceral organs were weighed, frozen, and ground for determination of protein mass. From pigs in the initial, negative control, high-ammonia, and high-NEAA groups, AA contents in the carcass and pooled visceral organs were analyzed to determine the total and deposited protein AA profile, dietary EAA efficiencies, and minimal de novo synthesis of NEAA. Carcass weight and whole-body N retention linearly increased ( < 0.05) with N supplementation. The AA profile of protein and deposited protein in the carcass was not different ( > 0.10) between N sources, but Cys content increased ( < 0.05) with NEAA compared with ammonia in visceral

Structure-based drug design targeting the cell membrane receptor GPBAR1: exploiting the bile acid scaffold towards selective agonism

NASA Astrophysics Data System (ADS)

di Leva, Francesco Saverio; Festa, Carmen; Renga, Barbara; Sepe, Valentina; Novellino, Ettore; Fiorucci, Stefano; Zampella, Angela; Limongelli, Vittorio

2015-11-01

Bile acids can regulate nutrient metabolism through the activation of the cell membrane receptor GPBAR1 and the nuclear receptor FXR. Developing an exogenous control over these receptors represents an attractive strategy for the treatment of enterohepatic and metabolic disorders. A number of dual GPBAR1/FXR agonists are known, however their therapeutic use is limited by multiple unwanted effects due to activation of the diverse downstream signals controlled by the two receptors. On the other hand, designing selective GPBAR1 and FXR agonists is challenging since the two proteins share similar structural requisites for ligand binding. Here, taking advantage of our knowledge of the two targets, we have identified through a rational drug design study a series of amine lithocholic acid derivatives as selective GPBAR1 agonists. The presence of the 3α-NH2 group on the steroidal scaffold is responsible for the selectivity over FXR unveiling unprecedented structural insights into bile acid receptors activity modulation.

Decrement in operant performance produced by NMDA receptor antagonists in the rat: tolerance and cross-tolerance.

PubMed

Dravolina, O A; Zvartau, E E; Bespalov, A Y

2000-04-01

Current perspectives on the clinical use of NMDA receptor antagonists infer repeated administration schedules for the management of different pathological states. The development of tolerance and cross-tolerance between different NMDA receptor antagonists may be an important factor contributing to the clinical efficacy of these drugs. The present study aimed to characterize the development of tolerance and cross-tolerance to the ability of various site-selective NMDA receptor antagonists to produce a decrement of operant responding (multiple extinction 9 s fixed-interval 1-s schedule of water reinforcement). Acute administration of D-CPPen (SDZ EAA 494; 1-5.6 mg/kg), dizocilpine (MK-801; 0.03-0.3 mg/kg), memantine (0.3-17 mg/kg), ACEA-1021 (10-56 mg/kg), and eliprodil (1-30 mg/kg) differentially affected operant responding. Both increases and decreases in response rates and accuracy of responding were observed. Repeated preexposure to D-CPPen (5.6 mg/kg, once a day for 7 days) attenuated a behavioral disruption produced by an acute challenge with D-CPPen or ACEA-1021, but potentiated the effects of dizocilpine, memantine, and eliprodil. Based on the present results, one can suggest that the repeated administration of a competitive NMDA receptor antagonist differentially affects the functional activity of various sites on NMDA receptor complex.

Discovery and Characterization of a Novel Small-Molecule Agonist for Medium-Chain Free Fatty Acid Receptor G Protein-Coupled Receptor 84.

PubMed

Zhang, Qing; Yang, Hui; Li, Jing; Xie, Xin

2016-05-01

G protein-coupled receptor 84 (GPR84) is a free fatty acid receptor activated by medium-chain free fatty acids with 9-14 carbons. It is expressed mainly in the immune-related tissues, such as spleen, bone marrow, and peripheral blood leukocytes. GPR84 plays significant roles in inflammatory processes and may represent a novel drug target for the treatment of immune-mediated diseases. However, the lack of potent and specific ligands for GPR84 hindered the study of its functions and the development of potential clinical applications. Here, we report the screen of 160,000 small-molecule compounds with a calcium mobilization assay using a human embryonic kidney 293 cell line stably expressing GPR84 and Gα16, and the identification of 2-(hexylthio)pyrimidine-4,6-diol (ZQ-16) as a potent and selective agonist of GPR84 with a novel structure. ZQ-16 activates several GPR84-mediated signaling pathways, including calcium mobilization, inhibition of cAMP accumulation, phosphorylation of extracellular signal-regulated protein kinase 1/2, receptor desensitization and internalization, and receptor-β-arrestin interaction. This compound may be a useful tool to study the functions of GPR84 and a potential candidate for further structural optimization. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

Agrochemical control of plant water use using engineered abscisic acid receptors.

PubMed

Park, Sang-Youl; Peterson, Francis C; Mosquna, Assaf; Yao, Jin; Volkman, Brian F; Cutler, Sean R

2015-04-23

Rising temperatures and lessening fresh water supplies are threatening agricultural productivity and have motivated efforts to improve plant water use and drought tolerance. During water deficit, plants produce elevated levels of abscisic acid (ABA), which improves water consumption and stress tolerance by controlling guard cell aperture and other protective responses. One attractive strategy for controlling water use is to develop compounds that activate ABA receptors, but agonists approved for use have yet to be developed. In principle, an engineered ABA receptor that can be activated by an existing agrochemical could achieve this goal. Here we describe a variant of the ABA receptor PYRABACTIN RESISTANCE 1 (PYR1) that possesses nanomolar sensitivity to the agrochemical mandipropamid and demonstrate its efficacy for controlling ABA responses and drought tolerance in transgenic plants. Furthermore, crystallographic studies provide a mechanistic basis for its activity and demonstrate the relative ease with which the PYR1 ligand-binding pocket can be altered to accommodate new ligands. Thus, we have successfully repurposed an agrochemical for a new application using receptor engineering. We anticipate that this strategy will be applied to other plant receptors and represents a new avenue for crop improvement.

Lipoic acid stimulates cAMP production via G protein coupled receptor dependent and independent mechanisms

PubMed Central

Salinthone, Sonemany; Schillace, Robynn V.; Tsang, Catherine; Regan, John W.; Bourdette, Dennis N.; Carr, Daniel W.

2010-01-01

Lipoic acid (LA) is a naturally occurring fatty acid that exhibits anti-oxidant and anti-inflammatory properties and is being pursued as a therapeutic for many diseases including multiple sclerosis, diabetic polyneuropathy and Alzheimer’s disease. We previously reported on the novel finding that racemic LA (50:50 mixture of R and S LA) stimulates cAMP production, activates prostanoid EP2 and EP4 receptors and adenylyl cyclases (AC), and suppresses activation and cytotoxicity in NK cells. In this study we present evidence that furthers our understanding of the mechanisms of action of LA. Using various LA derivatives, dihydrolipoic acid (DHLA), S,S-dimethyl lipoic acid (DMLA) and lipoamide (LPM), we discovered that only LA is capable of stimulating cAMP production in NK cells. Furthermore, there is no difference in cAMP production after stimulation with either R-LA, S-LA or racemic LA. Competition and synergistic studies indicate that LA may also activate AC independent of the EP2 and EP4 receptors. Pretreatment of PBMCc with KH7 (a specific peptide inhibitor of soluble AC) and the calcium inhibitor (Bapta) prior to LA treatment resulted in reduced cAMP levels, suggesting that soluble AC and calcium signaling mediate LA stimulation of cAMP production. In addition, pharmacological inhibitor studies demonstrate that LA also activates other G- protein coupled receptors, including histamine and adenosine, but not the beta adrenergic receptors. These novel findings provide information to better understand the mechanisms of action of LA, which can help facilitate the use of LA as a therapeutic for various diseases. PMID:21036588

Ursodeoxycholic Acid Induces Death Receptor-mediated Apoptosis in Prostate Cancer Cells

PubMed Central

Lee, Won Sup; Jung, Ji Hyun; Panchanathan, Radha; Yun, Jeong Won; Kim, Dong Hoon; Kim, Hye Jung; Kim, Gon Sup; Ryu, Chung Ho; Shin, Sung Chul; Hong, Soon Chan; Choi, Yung Hyun; Jung, Jin-Myung

2017-01-01

Background Bile acids have anti-cancer properties in a certain types of cancers. We determined anticancer activity and its underlying molecular mechanism of ursodeoxycholic acid (UDCA) in human DU145 prostate cancer cells. Methods Cell viability was measured with an MTT assay. UDCA-induced apoptosis was determined with flow cytometric analysis. The expression levels of apoptosis-related signaling proteins were examined with Western blotting. Results UDCA treatment significantly inhibited cell growth of DU145 in a dose-dependent manner. It induced cellular shrinkage and cytoplasmic blebs and accumulated the cells with sub-G1 DNA contents. Moreover, UDCA activated caspase 8, suggesting that UDCA-induced apoptosis is associated with extrinsic pathway. Consistent to this finding, UDCA increased the expressions of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor, death receptor 4 (DR4) and death receptor 5 (DR5), and TRAIL augmented the UDCA-induced cell death in DU145 cells. In addition, UDCA also increased the expressions of Bax and cytochrome c and decreased the expression of Bcl-xL in DU145 cells. This finding suggests that UDCA-induced apoptosis may be involved in intrinsic pathway. Conclusions UDCA induces apoptosis via extrinsic pathway as well as intrinsic pathway in DU145 prostate cancer cells. UDCA may be a promising anti-cancer agent against prostate cancer. PMID:28382282

Molecular determinants of the olfactory receptor Olfr544 activation by azelaic acid.

PubMed

Thach, Trung Thanh; Hong, Yu-Jung; Lee, Sangho; Lee, Sung-Joon

2017-04-01

The mouse olfactory receptor Olfr544 is expressed in several non-olfactory tissues and has been suggested as a functional receptor regulating different signaling pathways. However, the molecular interaction between Olfr544 and its natural ligand, azelaic acid (AzA), remains poorly characterized, primarily due to difficulties in the heterologous expression of the receptor protein on the cell membrane and lack of entire protein structure. In this report, we describe the molecular determinants of Olfr544 activation by AzA. N-terminal lucy-flag-rho tag ensured the heterologous expression of Olfr544 on the Hana3A cell surface. Molecular modeling and docking combined with mutational analysis identified amino acid residues in the Olfr544 for the interaction with AzA. Our data demonstrated that the Y109 residue in transmembrane helix 3 forms a hydrogen bond with AzA, which is crucial for the receptor-ligand interaction and activation. Y109 is required for the Olfr544 activation by AzA which, in turn, stimulates the Olfr544-dependent CREB-PGC-1α signaling axis and is followed by the induction of mitochondrial biogenesis in Olfr544 wild-type transfected Hana3A cells, but not in mock or Y109A mutant transfected cells. Collectively, these data indicated that a hydrogen bond between Y109 residue and AzA is a major determinant of the Olfr544-AzA interaction and activation. Copyright © 2017 Elsevier Inc. All rights reserved.

Unsurmountable antagonism of brain 5-hydroxytryptamine2 receptors by (+)-lysergic acid diethylamide and bromo-lysergic acid diethylamide.

PubMed

Burris, K D; Sanders-Bush, E

1992-11-01

Lysergic acid diethylamide (LSD) and its structural analogue 2-bromo-lysergic acid diethylamide (BOL) act as unsurmountable antagonists of serotonin-elicited contractions in smooth muscle preparations. Two different models, allosteric and kinetic, have been invoked to explain these findings. The present studies investigate the mechanism of antagonism of brain 5-hydroxytryptamine (5HT)2 receptors, utilizing cells transfected with 5HT2 receptor cDNA cloned from rat brain. A proximal cellular response, phosphoinositide hydrolysis, was examined in order to minimize possible postreceptor effects. Even though LSD behaved as a partial agonist and BOL as a pure antagonist, both drugs blocked the effect of serotonin in an unsurmountable manner, i.e., increasing concentrations of serotonin could not overcome the blocking effect of LSD or BOL. Radioligand binding studies showed that preincubation of membranes with either LSD or BOL reduced the density of [3H]ketanserin binding sites, suggesting that the drugs bind tightly to the 5HT2 receptor and are not displaced during the binding assay. Two additional experiments supported this hypothesis. First, the off-rate of [3H] LSD was slow (20 min), relative to that of [3H]ketanserin (approximately 4 min). Second, when the length of incubation with [3H]ketanserin was increased to 60 min, the LSD-induced decrease in Bmax was essentially eliminated. The possibility that LSD and BOL decrease [3H]ketanserin binding by interacting with an allosteric site was rejected, because neither drug altered the rate of dissociation of [3H]ketanserin. The most parsimonious interpretation of these results is that unsurmountable antagonism reflects prolonged occupancy of the receptor by slowly reversible antagonists.

Insulin receptor-related receptor as an extracellular pH sensor involved in the regulation of acid-base balance.

PubMed

Petrenko, Alexander G; Zozulya, Sergey A; Deyev, Igor E; Eladari, Dominique

2013-10-01

Recent studies of insulin receptor-related receptor (IRR) revealed its unusual property to activate upon extracellular application of mildly alkaline media, pH>7.9. The activation of IRR with hydroxyl anion has typical features of ligand-receptor interaction; it is specific, dose-dependent, involves the IRR extracellular domain and is accompanied by a major conformational change. IRR is a member of the insulin receptor minifamily and has been long viewed as an orphan receptor tyrosine kinase since no peptide or protein agonist of IRR was found. In the evolution, IRR is highly conserved since its divergence from the insulin and insulin-like growth factor receptors in amphibia. The latter two cannot be activated by alkali. Another major difference between them is that unlike ubiquitously expressed insulin and insulin-like growth factor receptors, IRR is found in specific sets of cells of only some tissues, most of them being exposed to extracorporeal liquids of extreme pH. In particular, largest concentrations of IRR are in beta-intercalated cells of the kidneys. The primary physiological function of these cells is to excrete excessive alkali as bicarbonate into urine. When IRR is removed genetically, animals loose the property to excrete bicarbonate upon experimentally induced alkalosis. In this review, we will discuss the available in vitro and in vivo data that support the hypothesis of IRR role as a physiological alkali sensor that regulates acid-base balance. This article is part of a Special Issue entitled: Emerging recognition and activation mechanisms of receptor tyrosine kinases. Copyright © 2012 Elsevier B.V. All rights reserved.

Role of amino acids in salivation and the localization of their receptors in the rat salivary gland.

PubMed

Shida, T; Kondo, E; Ueda, Y; Takai, N; Yoshida, Y; Araki, T; Kiyama, H; Tohyama, M

1995-11-01

The distribution of gamma-aminobutyric acid (GABA) receptor subunits such as GABAAR-gamma 1 and GABAAR-gamma 2, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) type receptor subunits such as GluR-1, GluR-2/3 and GluR-4, and N-methyl-D-aspartic acid (NMDA) type subunits such as NR1 were investigated by immunocytochemistry. Furthermore, the roles of these amino acids, GABA and glutamate, on salivation were analyzed in the rat submandibular and sublingual glands. Some similarities were observed in the distribution patterns of GABAA type receptors and AMPA receptors. In the submandibular ganglion cells, collecting ducts and striated ducts, these subunits were expressed strongly; however, there were some differences in their expression patterns between the submandibular and sublingual gland acinar cells. Since these receptor subunits were expressed in the acinar cell bodies of the submandibular gland, they were not expressed in the acinar cells but were expressed in the myoepithelial cells in the sublingual gland. On the other hand, no NR1 expression was observed. To examine the roles of GABA and glutamate in salivation, the submandibular and sublingual glands were perfused partially with Ringer's solution via a facial artery to avoid systemic influence, and substrates were infused into the perfusion solution. No salivary secretion was evoked by GABA or glutamate infusion in the absence of electrical stimulation (2-3 V, 5 ms, 20 Hz). Salivary flow evoked by electrical stimulation of the chorda-lingual nerve caused significant inhibition by GABA (10(-6), 10(-5), 10(-4) and 10(-3) M) and the GABAAR agonist muscimol 10(-3) and 10(-6) M) (n = 6, P < 0.05). Such GABA-induced inhibition was antagonized by the GABAAR antagonists bicuculline (BCC; 10(-6) and 10(-3) M) and picrotoxin (PTX; 10(-6) and 10(-3) M). On the other hand, salivary flow evoked by electrical stimulation (8-10 V, 5 ms, 20 Hz) of the superior cervical ganglion (SCG) was not affected by

Structure-activity relationships and mechanism of action of Eph-ephrin antagonists: interaction of cholanic acid with the EphA2 receptor

PubMed Central

Tognolini, Massimiliano; Incerti, Matteo; Mohamed, Iftiin Hassan; Giorgio, Carmine; Russo, Simonetta; Bruni, Renato; Lelli, Barbara; Bracci, Luisa; Noberini, Roberta; Pasquale, Elena B.; Barocelli, Elisabetta; Vicini, Paola; Mor, Marco

2012-01-01

The Eph–ephrin system, including the EphA2 receptor and the ephrin-A1 ligand, plays a critical role in tumor and vascular functions during carcinogenesis. We previously identified (3α,5β)-3-hydroxycholan-24-oic acid (lithocholic acid) as an Eph-ephrin antagonist able to inhibit EphA2 receptor activation and therefore potentially useful as a novel EphA2 receptor targeting agent. Here, we explore the structure-activity relationships of a focused set of lithocholic acid derivatives, based on molecular modelling investigation and displacement binding assays. Our exploration shows that while the 3-α-hydroxyl group of lithocholic acid has a negligible role in the recognition of the EphA2 receptor, its carboxylate group is critical for disrupting the binding of ephrin-A1 to the EphA2. As a result of our investigation, we identified (5β)-cholan-24-oic acid (cholanic acid) as a novel compound that competitively inhibits EphA2-ephrin-A1 interaction with higher potency than lithocholic acid. Surface plasmon resonance analysis indicates that cholanic acid binds specifically and reversibly to the ligand-binding domain of EphA2, with a steady-state dissociation constant (KD) in the low micromolar range. Furthermore, cholanic acid blocks the phosphorylation of EphA2 and cell retraction and rounding in PC3 prostate cancer cells, two effects that depend on EphA2 activation by the ephrin-A1 ligand. These findings suggest that cholanic acid can be used as a template structure to design effective EphA2 antagonists, with potential impact in the elucidation of the role played by this receptor in pathological conditions. PMID:22529030

Salicylic acid receptors activate jasmonic acid signalling through a non-canonical pathway to promote effector-triggered immunity.

PubMed

Liu, Lijing; Sonbol, Fathi-Mohamed; Huot, Bethany; Gu, Yangnan; Withers, John; Mwimba, Musoki; Yao, Jian; He, Sheng Yang; Dong, Xinnian

2016-10-11

It is an apparent conundrum how plants evolved effector-triggered immunity (ETI), involving programmed cell death (PCD), as a major defence mechanism against biotrophic pathogens, because ETI-associated PCD could leave them vulnerable to necrotrophic pathogens that thrive on dead host cells. Interestingly, during ETI, the normally antagonistic defence hormones, salicylic acid (SA) and jasmonic acid (JA) associated with defence against biotrophs and necrotrophs respectively, both accumulate to high levels. In this study, we made the surprising finding that JA is a positive regulator of RPS2-mediated ETI. Early induction of JA-responsive genes and de novo JA synthesis following SA accumulation is activated through the SA receptors NPR3 and NPR4, instead of the JA receptor COI1. We provide evidence that NPR3 and NPR4 may mediate this effect by promoting degradation of the JA transcriptional repressor JAZs. This unique interplay between SA and JA offers a possible explanation of how plants can mount defence against a biotrophic pathogen without becoming vulnerable to necrotrophic pathogens.

Channel opening of gamma-aminobutyric acid receptor from rat brain: molecular mechanisms of the receptor responses.

PubMed

Cash, D J; Subbarao, K

1987-12-01

The function of gamma-aminobutyric acid (GABA) receptors, which mediate transmembrane chloride flux, can be studied by use of 36Cl- isotope tracer with membrane from mammalian brain by quench-flow technique, with reaction times that allow resolution of the receptor desensitization rates from the ion flux rates. The rates of chloride exchange into the vesicles in the absence and presence of GABA were characterized with membrane from rat cerebral cortex. Unspecific 36Cl- influx was completed in three phases of ca. 3% (t 1/2 = 0.6 s), 56% (t 1/2 = 82 s), and 41% (t 1/2 = 23 min). GABA-mediated, specific chloride exchange occurred with 6.5% of the total vesicular internal volume. The GABA-dependent 36Cl- influx proceeded in two phases, each progressively slowed by desensitization. The measurements supported the presence of two distinguishable active GABA receptors on the same membrane mediating chloride exchange into the vesicles with initial first-order rate constants of 9.5 s-1 and 2.3 s-1 and desensitizing with first-order rate constants of 21 s-1 and 1.4 s-1, respectively, at saturation. The half-response concentrations were similar for both receptors, 150 microM and 114 microM GABA for desensitization and 105 microM and 82 microM for chloride exchange, for the faster and slower desensitizing receptors, respectively. The two receptors were present in the activity ratio of ca. 4/1, similar to the ratio of "low-affinity" to "high-affinity" GABA sites found in ligand binding experiments. The desensitization rates have a different dependence on GABA concentration than the channel-opening equilibria.(ABSTRACT TRUNCATED AT 250 WORDS)

Modafinil: A Molecule of Military Interest

DTIC Science & Technology

2001-06-01

noradrenalin LC: locus coeruleus iR-Glu: ionotropic MCn: magnocellular nucleus glutamate receptors (NMDA and non-NMDA) DR: dorsal raphe mR-Glu: metabotropic ...21 This metabotropic receptor agonist. However, the EAA- inhibition of cortical GABA outflow is antagonized release inhibitor propentofylline has...NMDA receptor antagonist and metabotropic psychostimulant, during a sixty-hour sleep receptor agonist. deprivation experiment. Fundam Clin Pharmacol

Postprandial fatty acid uptake and adipocyte remodeling in angiotensin type 2 receptor-deficient mice fed a high-fat/high-fructose diet

PubMed Central

Noll, Christophe; Labbé, Sébastien M.; Pinard, Sandra; Shum, Michael; Bilodeau, Lyne; Chouinard, Lucie; Phoenix, Serge; Lecomte, Roger; Carpentier, André C.; Gallo-Payet, Nicole

2016-01-01

ABSTRACT The role of the angiotensin type-2 receptor in adipose physiology remains controversial. The aim of the present study was to demonstrate whether genetic angiotensin type-2 receptor-deficiency prevents or worsens metabolic and adipose tissue morphometric changes observed following a 6-week high-fat/high-fructose diet with injection of a small dose of streptozotocin. We compared tissue uptake of nonesterified fatty acid and dietary fatty acid in wild-type and angiotensin type-2 receptor-deficient mice by using the radiotracer 14(R,S)-[18F]-fluoro-6-thia-heptadecanoic acid in mice fed a standard or high-fat diet. Postprandial fatty acid uptake in the heart, liver, skeletal muscle, kidney and adipose tissue was increased in wild-type mice after a high-fat diet and in angiotensin type-2 receptor-deficient mice on both standard and high-fat diets. Compared to the wild-type mice, angiotensin type-2 receptor-deficient mice had a lower body weight, an increase in fasting blood glucose and a decrease in plasma insulin and leptin levels. Mice fed a high-fat diet exhibited increased adipocyte size that was prevented by angiotensin type-2 receptor-deficiency. Angiotensin type-2 receptor-deficiency abolished the early hypertrophic adipocyte remodeling induced by a high-fat diet. The small size of adipocytes in the angiotensin type-2 receptor-deficient mice reflects their inability to store lipids and explains the increase in fatty acid uptake in non-adipose tissues. In conclusion, a genetic deletion of the angiotensin type-2 receptor is associated with metabolic dysfunction of white adipose depots, and indicates that adipocyte remodeling occurs before the onset of insulin resistance in the high-fat fed mouse model. PMID:27144096

Impact of supplementation with amino acids or their metabolites on muscle wasting in patients with critical illness or other muscle wasting illness: a systematic review.

PubMed

Wandrag, L; Brett, S J; Frost, G; Hickson, M

2015-08-01

Muscle wasting during critical illness impairs recovery. Dietary strategies to minimise wasting include nutritional supplements, particularly essential amino acids. We reviewed the evidence on enteral supplementation with amino acids or their metabolites in the critically ill and in muscle wasting illness with similarities to critical illness, aiming to assess whether this intervention could limit muscle wasting in vulnerable patient groups. Citation databases, including MEDLINE, Web of Knowledge, EMBASE, the meta-register of controlled trials and the Cochrane Collaboration library, were searched for articles from 1950 to 2013. Search terms included 'critical illness', 'muscle wasting', 'amino acid supplementation', 'chronic obstructive pulmonary disease', 'chronic heart failure', 'sarcopenia' and 'disuse atrophy'. Reviews, observational studies, sport nutrition, intravenous supplementation and studies in children were excluded. One hundred and eighty studies were assessed for eligibility and 158 were excluded. Twenty-two studies were graded according to standardised criteria using the GRADE methodology: four in critical care populations, and 18 from other clinically relevant areas. Methodologies, interventions and outcome measures used were highly heterogeneous and meta-analysis was not appropriate. Methodology and quality of studies were too varied to draw any firm conclusion. Dietary manipulation with leucine enriched essential amino acids (EAA), β-hydroxy-β-methylbutyrate and creatine warrant further investigation in critical care; EAA has demonstrated improvements in body composition and nutritional status in other groups with muscle wasting illness. High-quality research is required in critical care before treatment recommendations can be made. © 2014 The British Dietetic Association Ltd.

Mercaptoacetate and fatty acids exert direct and antagonistic effects on nodose neurons via GPR40 fatty acid receptors.

PubMed

Darling, Rebecca A; Zhao, Huan; Kinch, Dallas; Li, Ai-Jun; Simasko, Steven M; Ritter, Sue

2014-07-01

β-mercaptoacetate (MA) is a drug known to block mitochondrial oxidation of medium- and long-chain fatty acids (FAs) and to stimulate feeding. Because MA-induced feeding is vagally dependent, it has been assumed that the feeding response is mediated by MA's antimetabolic action at a peripheral, vagally innervated site. However, MA's site of action has not yet been identified. Therefore, we used fluorescent calcium measurements in isolated neurons from rat nodose ganglia to determine whether MA has direct effects on vagal sensory neurons. We found that MA alone did not alter cytosolic calcium concentrations in nodose neurons. However, MA (60 μM to 6 mM) significantly decreased calcium responses to both linoleic acid (LA; 10 μM) and caprylic acid (C8; 10 μM) in all neurons responsive to LA and C8. GW9508 (40 μM), an agonist of the FA receptor, G protein-coupled receptor 40 (GPR40), also increased calcium levels almost exclusively in FA-responsive neurons. MA significantly inhibited this response to GW9508. MA did not inhibit calcium responses to serotonin, high K(+), or capsaicin, which do not utilize GPRs, or to CCK, which acts on a different GPR. GPR40 was detected in nodose ganglia by RT-PCR. Results suggest that FAs directly activate vagal sensory neurons via GPR40 and that MA antagonizes this effect. Thus, we propose that MA's nonmetabolic actions on GPR40 membrane receptors, expressed by multiple peripheral tissues in addition to the vagus nerve, may contribute to or mediate MA-induced stimulation of feeding. Copyright © 2014 the American Physiological Society.

Fatty Acid Amide Hydrolase (FAAH) Inhibition Enhances Memory Acquisition through Activation of PPAR-alpha Nuclear Receptors

ERIC Educational Resources Information Center

Mazzola, Carmen; Medalie, Julie; Scherma, Maria; Panlilio, Leigh V.; Solinas, Marcello; Tanda, Gianluigi; Drago, Filippo; Cadet, Jean Lud; Goldberg, Steven R.; Yasar, Sevil

2009-01-01

Inhibitors of fatty acid amide hydrolase (FAAH) increase endogenous levels of anandamide (a cannabinoid CB[subscript 1]-receptor ligand) and oleoylethanolamide and palmitoylethanolamide (OEA and PEA, ligands for alpha-type peroxisome proliferator-activated nuclear receptors, PPAR-alpha) when and where they are naturally released in the brain.…

Identification of insulin as a novel retinoic acid receptor-related orphan receptor α target gene.

PubMed

Kuang, Jiangying; Hou, Xiaoming; Zhang, Jinlong; Chen, Yulong; Su, Zhiguang

2014-03-18

Insulin plays an important role in regulation of lipid and glucose metabolism. Retinoic acid receptor-related orphan receptor α (RORα) modulates physiopathological processes such as dyslipidemia and diabetes. In this study, we found overexpression of RORα in INS1 cells resulted in increased expression and secretion of insulin. Suppression of endogenous RORα caused a decrease of insulin expression. Luciferase and electrophoretic mobility shift assay (EMSA) assays demonstrated that RORα activated insulin transcription via direct binding to its promoter. RORα was also observed to regulate BETA2 expression, which is one of the insulin active transfactors. In vivo analyses showed that the insulin transcription is increased by the synthetic RORα agonist SR1078. These findings identify RORα as a transcriptional activator of insulin and suggest novel therapeutic opportunities for management of the disease. Copyright © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Expression of fatty acid sensing G-protein coupled receptors in peripartal Holstein cows.

PubMed

Agrawal, Alea; Alharthi, Abdulrahman; Vailati-Riboni, Mario; Zhou, Zheng; Loor, Juan J

2017-01-01

G-protein coupled receptors (GPCR), also referred as Free Fatty Acid Receptors (FFAR), are widely studied within human medicine as drug targets for metabolic disorders. To combat metabolic disorders prevalent in dairy cows during the transition period, which co-occur with negative energy balance and changes to lipid and glucose metabolism, it may be helpful to identify locations and roles of FFAR and other members of the GPCR family in bovine tissues. Quantitative RT-PCR (qPCR) of subcutaneous adipose, liver, and PMNL samples during the transition period (-10, +7, and +20 or +30 d) were used for expression profiling of medium- (MCFA) and long-chain fatty acid (LCFA) receptors GPR120 and GPR40 , MCFA receptor GPR84 , and niacin receptor HCAR2/3 . Adipose samples were obtained from cows with either high (HI; BCS ≥ 3.75) or low (LO; BCS ≤ 3.25) body condition score (BCS) to examine whether FFAR expression is correlated with this indicator of health and body reserves. Supplementation of rumen-protected methionine (MET), which may improve immune function and production postpartum, was also compared with unsupplemented control (CON) cows for liver and blood polymorphonuclear leukocytes (PMNL) samples. In adipose tissue, GPR84 and GPR120 were differentially expressed over time, while GPR40 was not expressed; in PMNL, GPR40 was differentially expressed over time and between MET vs. CON, GPR84 expression differed only between dietary groups, and GPR120 was not expressed; in liver, GPCR were either not expressed or barely detectable. The data indicate that there is likely not a direct role in liver for the selected GPCR during the transition period, but they do play variable roles in adipose and PMN. In future, these receptors may prove useful targets and/or markers for peripartal metabolism and immunity.

Expression of growth-related genes in young and older human skeletal muscle following an acute stimulation of protein synthesis.

PubMed

Drummond, Micah J; Miyazaki, Mitsunori; Dreyer, Hans C; Pennings, Bart; Dhanani, Shaheen; Volpi, Elena; Esser, Karyn A; Rasmussen, Blake B

2009-04-01

Muscle growth is associated with an activation of the mTOR signaling pathway and satellite cell regulators. The purpose of this study was to determine whether 17 selected genes associated with mTOR/muscle protein synthesis and the satellite cells/myogenic program are differentially expressed in young and older human skeletal muscle at rest and in response to a potent anabolic stimulus [resistance exercise + essential amino acid ingestion (RE+EAA)]. Twelve male subjects (6 young, 6 old) completed a bout of heavy resistance exercise. Muscle biopsies were obtained before and at 3 and 6 h post RE+EAA. Subjects ingested leucine-enriched essential amino acids at 1 h postexercise. mRNA expression was determined using qRT-PCR. At rest, hVps34 mRNA was elevated in the older subjects (P < 0.05) while there was a tendency for levels of myoD, myogenin, and TSC2 mRNA to be higher than young. The anabolic stimulus (RE+EAA) altered mRNAs associated with mTOR regulation. Notably, REDD2 decreased in both age groups (P < 0.05) but the expression of Rheb mRNA increased only in the young. Finally, cMyc mRNA was elevated (P < 0.05) in both young and old at 6 h post RE+EAA. Furthermore, RE+EAA also increased expression of several mRNAs associated with satellite function in the young (P < 0.05), while expression of these mRNAs did not change in the old. We conclude that several anabolic genes in muscle are more responsive in young men post RE+EAA. Our data provide new insights into the regulation of genes important for transcription and translation in young and old human skeletal muscle post RE+EAA.

Regulation of antibacterial defense in the small intestine by the nuclear bile acid receptor.

PubMed

Inagaki, Takeshi; Moschetta, Antonio; Lee, Youn-Kyoung; Peng, Li; Zhao, Guixiang; Downes, Michael; Yu, Ruth T; Shelton, John M; Richardson, James A; Repa, Joyce J; Mangelsdorf, David J; Kliewer, Steven A

2006-03-07

Obstruction of bile flow results in bacterial proliferation and mucosal injury in the small intestine that can lead to the translocation of bacteria across the epithelial barrier and systemic infection. These adverse effects of biliary obstruction can be inhibited by administration of bile acids. Here we show that the farnesoid X receptor (FXR), a nuclear receptor for bile acids, induces genes involved in enteroprotection and inhibits bacterial overgrowth and mucosal injury in ileum caused by bile duct ligation. Mice lacking FXR have increased ileal levels of bacteria and a compromised epithelial barrier. These findings reveal a central role for FXR in protecting the distal small intestine from bacterial invasion and suggest that FXR agonists may prevent epithelial deterioration and bacterial translocation in patients with impaired bile flow.

Periodic variation in bile acids controls circadian changes in uric acid via regulation of xanthine oxidase by the orphan nuclear receptor PPARα.

PubMed

Kanemitsu, Takumi; Tsurudome, Yuya; Kusunose, Naoki; Oda, Masayuki; Matsunaga, Naoya; Koyanagi, Satoru; Ohdo, Shigehiro

2017-12-29

Xanthine oxidase (XOD), also known as xanthine dehydrogenase, is a rate-limiting enzyme in purine nucleotide degradation, which produces uric acid. Uric acid concentrations in the blood and liver exhibit circadian oscillations in both humans and rodents; however, the underlying mechanisms remain unclear. Here, we demonstrate that XOD expression and enzymatic activity exhibit circadian oscillations in the mouse liver. We found that the orphan nuclear receptor peroxisome proliferator-activated receptor-α (PPARα) transcriptionally activated the mouse XOD gene and that bile acids suppressed XOD transactivation. The synthesis of bile acids is known to be under the control of the circadian clock, and we observed that the time-dependent accumulation of bile acids in hepatic cells interfered with the recruitment of the co-transcriptional activator p300 to PPARα, thereby repressing XOD expression. This time-dependent suppression of PPARα-mediated transactivation by bile acids caused an oscillation in the hepatic expression of XOD, which, in turn, led to circadian alterations in uric acid production. Finally, we also demonstrated that the anti-hyperuricemic effect of the XOD inhibitor febuxostat was enhanced by administering it at the time of day before hepatic XOD activity increased. These results suggest an underlying mechanism for the circadian alterations in uric acid production and also underscore the importance of selecting an appropriate time of day for administering XOD inhibitors. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

The distribution of excitatory amino acid receptors on acutely dissociated dorsal horn neurons from postnatal rats.

PubMed

Arancio, O; Yoshimura, M; Murase, K; MacDermott, A B

1993-01-01

Excitatory amino acid receptor distribution was mapped on acutely dissociated neurons from postnatal rat spinal cord dorsal horn. N-methyl D-aspartate, quisqualate and kainate were applied to multiple locations along the somal and dendritic surfaces of voltage-clamped neurons by means of a pressure application system. To partially compensate for the decrement of response amplitude due to current loss between the site of activation on the dendrite and the recording electrode at the soma, a solution containing 0.15 M KCl was applied on the cell bodies and dendrites of some cells to estimate an empirical length constant. In the majority of the cells tested, the dendritic membrane had regions of higher sensitivity to excitatory amino acid agonists than the somatic membrane, with dendritic response amplitudes reaching more than seven times those at the cell body. A comparison of the relative changes in sensitivity between each combination of two of the three excitatory amino acid agonists along the same dendrite showed different patterns of agonist sensitivity along the dendrite in the majority of the cells. These data were obtained from dorsal horn neurons that had developed and formed synaptic connections in vivo. They demonstrate that in contrast to observations made on ventral horn neurons, receptor density for all the excitatory amino acid receptors on dorsal horn neurons, including the N-methyl-D-aspartate receptor, are generally higher on the dendrites than on the soma. Further, these results are similar to those obtained from dorsal horn neurons grown in culture.

Nuclear hormone receptor NHR-49 controls fat consumption and fatty acid composition in C. elegans.

PubMed

Van Gilst, Marc R; Hadjivassiliou, Haralambos; Jolly, Amber; Yamamoto, Keith R

2005-02-01

Mammalian nuclear hormone receptors (NHRs), such as liver X receptor, farnesoid X receptor, and peroxisome proliferator-activated receptors (PPARs), precisely control energy metabolism. Consequently, these receptors are important targets for the treatment of metabolic diseases, including diabetes and obesity. A thorough understanding of NHR fat regulatory networks has been limited, however, by a lack of genetically tractable experimental systems. Here we show that deletion of the Caenorhabditis elegans NHR gene nhr-49 yielded worms with elevated fat content and shortened life span. Employing a quantitative RT-PCR screen, we found that nhr-49 influenced the expression of 13 genes involved in energy metabolism. Indeed, nhr-49 served as a key regulator of fat usage, modulating pathways that control the consumption of fat and maintain a normal balance of fatty acid saturation. We found that the two phenotypes of the nhr-49 knockout were linked to distinct pathways and were separable: The high-fat phenotype was due to reduced expression of enzymes in fatty acid beta-oxidation, and the shortened adult life span resulted from impaired expression of a stearoyl-CoA desaturase. Despite its sequence relationship with the mammalian hepatocyte nuclear factor 4 receptor, the biological activities of nhr-49 were most similar to those of the mammalian PPARs, implying an evolutionarily conserved role for NHRs in modulating fat consumption and composition. Our findings in C. elegans provide novel insights into how NHR regulatory networks are coordinated to govern fat metabolism.

Role of free fatty acid receptors in the regulation of energy metabolism.

PubMed

Hara, Takafumi; Kashihara, Daiji; Ichimura, Atsuhiko; Kimura, Ikuo; Tsujimoto, Gozoh; Hirasawa, Akira

2014-09-01

Free fatty acids (FFAs) are energy-generating nutrients that act as signaling molecules in various cellular processes. Several orphan G protein-coupled receptors (GPCRs) that act as FFA receptors (FFARs) have been identified and play important physiological roles in various diseases. FFA ligands are obtained from food sources and metabolites produced during digestion and lipase degradation of triglyceride stores. FFARs can be grouped according to ligand profiles, depending on the length of carbon chains of the FFAs. Medium- and long-chain FFAs activate FFA1/GPR40 and FFA4/GPR120. Short-chain FFAs activate FFA2/GPR43 and FFA3/GPR41. However, only medium-chain FFAs, and not long-chain FFAs, activate GPR84 receptor. A number of pharmacological and physiological studies have shown that these receptors are expressed in various tissues and are primarily involved in energy metabolism. Because an impairment of these processes is a part of the pathology of obesity and type 2 diabetes, FFARs are considered as key therapeutic targets. Here, we reviewed recently published studies on the physiological functions of these receptors, primarily focusing on energy homeostasis. Copyright © 2014 Elsevier B.V. All rights reserved.

A gate-latch-lock mechanism for hormone signalling by abscisic acid receptors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melcher, Karsten; Ng, Ley-Moy; Zhou, X Edward

2010-01-12

Abscisic acid (ABA) is a ubiquitous hormone that regulates plant growth, development and responses to environmental stresses. Its action is mediated by the PYR/PYL/RCAR family of START proteins, but it remains unclear how these receptors bind ABA and, in turn, how hormone binding leads to inhibition of the downstream type 2C protein phosphatase (PP2C) effectors. Here we report crystal structures of apo and ABA-bound receptors as well as a ternary PYL2-ABA-PP2C complex. The apo receptors contain an open ligand-binding pocket flanked by a gate that closes in response to ABA by way of conformational changes in two highly conserved β-loopsmore » that serve as a gate and latch. Moreover, ABA-induced closure of the gate creates a surface that enables the receptor to dock into and competitively inhibit the PP2C active site. A conserved tryptophan in the PP2C inserts directly between the gate and latch, which functions to further lock the receptor in a closed conformation. Together, our results identify a conserved gate-latch-lock mechanism underlying ABA signalling.« less

Efficient Receptor Mediated siRNA Delivery in Vitro by Folic Acid Targeted Pentablock Copolymer-Based Micelleplexes.

PubMed

Lehner, Roman; Liu, Kegang; Wang, Xueya; Hunziker, Patrick

2017-08-14

Novel, biocompatible polyplexes, based on the combination of cationic pentablock copolymers with folic acid functionalized copolymers, were designed and developed for target-specific siRNA delivery. The resulting micelleplexes spontaneously formed polymeric micelles with a hydrophobic core surrounded directly by a cationic poly-2-(4-aminobutyl)-oxazole (PABOXA) and subsequently shielded by hydrophilic poly-2-methyl-oxazole (PMOXA) layer. The described micelleplexes form highly stable particles even in complete serum after 24 h compared with the highly cationic polymer PEI, which show aggregate formation in serum containing buffer solution. Targeted siRNA delivery and gene knockdown could be shown using green fluorescent protein (GFP) expressing HeLa cells, resulting in ∼31% and ∼8% suppression of the expression of GFP for targeted and nontargeted micelleplexes, respectively. Comparison studies of folic-receptor positive HeLa cells with normal folic-receptor-negative HEK293 cells revealed involvement of receptor mediated cellular uptake of fluorescently labeled siRNA. The new designed nanocarrier showed no cytotoxicity, having a potential application. The presented concept of shielding a nucleic-acid complexing cationic chains with a stealth layer and combining it with receptor ligand overcomes typical problems with undesired protein and cell interactions in delivery of nucleic acids using polymeric systems, opening new doors for application if RNA inhibition in the organism.

Valerian extract and valerenic acid are partial agonists of the 5-HT5a receptor in vitro.

PubMed

Dietz, Birgit M; Mahady, Gail B; Pauli, Guido F; Farnsworth, Norman R

2005-08-18

Insomnia is the most frequently encountered sleep complaint worldwide. While many prescription drugs are used to treat insomnia, extracts of valerian (Valeriana officinalis L., Valerianaceae) are also used for the treatment of insomnia and restlessness. To determine novel mechanisms of action, radioligand binding studies were performed with valerian extracts (100% methanol, 50% methanol, dichloromethane [DCM], and petroleum ether [PE]) at the melatonin, glutamate, and GABA(A) receptors, and 8 serotonin receptor subtypes. Both DCM and PE extracts had strong binding affinity to the 5-HT(5a) receptor, but only weak binding affinity to the 5-HT(2b) and the serotonin transporter. Subsequent binding studies focused on the 5-HT(5a) receptor due to the distribution of this receptor in the suprachiasmatic nucleus of the brain, which is implicated in the sleep-wake cycle. The PE extract inhibited [(3)H]lysergic acid diethylamide (LSD) binding to the human 5-HT(5a) receptor (86% at 50 microg/ml) and the DCM extract inhibited LSD binding by 51%. Generation of an IC(50) curve for the PE extract produced a biphasic curve, thus GTP shift experiments were also performed. In the absence of GTP, the competition curve was biphasic (two affinity sites) with an IC(50) of 15.7 ng/ml for the high-affinity state and 27.7 microg/ml for the low-affinity state. The addition of GTP (100 microM) resulted in a right-hand shift of the binding curve with an IC(50) of 11.4 microg/ml. Valerenic acid, the active constituent of both extracts, had an IC(50) of 17.2 microM. These results indicate that valerian and valerenic acid are new partial agonists of the 5-HT(5a) receptor.

Valerian extract and valerenic acid are partial agonists of the 5-HT5a receptor in vitro

PubMed Central

Dietz, Birgit M.; Mahady, Gail B.; Pauli, Guido F.; Farnsworth, Norman R.

2018-01-01

Insomnia is the most frequently encountered sleep complaint worldwide. While many prescription drugs are used to treat insomnia, extracts of valerian (Valeriana officinalis L., Valerianaceae) are also used for the treatment of insomnia and restlessness. To determine novel mechanisms of action, radioligand binding studies were performed with valerian extracts (100% methanol, 50% methanol, dichloromethane [DCM], and petroleum ether [PE]) at the melatonin, glutamate, and GABAA receptors, and 8 serotonin receptor subtypes. Both DCM and PE extracts had strong binding affinity to the 5-HT5a receptor, but only weak binding affinity to the 5-HT2b and the serotonin transporter. Subsequent binding studies focused on the 5-HT5a receptor due to the distribution of this receptor in the suprachiasmatic nucleus of the brain, which is implicated in the sleep–wake cycle. The PE extract inhibited [3H]lysergic acid diethylamide (LSD) binding to the human 5-HT5a receptor (86% at 50 μg/ml) and the DCM extract inhibited LSD binding by 51%. Generation of an IC50 curve for the PE extract produced a biphasic curve, thus GTP shift experiments were also performed. In the absence of GTP, the competition curve was biphasic (two affinity sites) with an IC50 of 15.7 ng/ml for the high-affinity state and 27.7 μg/ml for the low-affinity state. The addition of GTP (100 AM) resulted in a right-hand shift of the binding curve with an IC50 of 11.4 μg/ml. Valerenic acid, the active constituent of both extracts, had an IC50 of 17.2 AM. These results indicate that valerian and valerenic acid are new partial agonists of the 5-HT5a receptor. PMID:15921820

LE135, a retinoid acid receptor antagonist, produces pain through direct activation of TRP channels.

PubMed

Yin, Shijin; Luo, Jialie; Qian, Aihua; Yu, Weihua; Hu, Hongzhen

2014-03-01

Retinoids, through their activation of retinoic acid receptors (RARs) and retinoid X receptors, regulate diverse cellular processes, and pharmacological intervention in their actions has been successful in the treatment of skin disorders and cancers. Despite the many beneficial effects, administration of retinoids causes irritating side effects with unknown mechanisms. Here, we demonstrate that LE135 [4-(7,8,9,10-tetrahydro-5,7,7,10,10-pentamethyl-5H-benzo[e]naphtho[2,3-b][1,4]diazepin-13-yl)benzoic acid], a selective antagonist of RARβ , is a potent activator of the capsaicin (TRPV1) and wasabi (TRPA1) receptors, two critical pain-initiating cation channels. We performed to investigate the excitatory effects of LE135 on TRPV1 and TRPA1 channels expressed in HEK293T cells and in dorsal root ganglia neurons with calcium imaging and patch-clamp recordings. We also used site-directed mutagenesis of the channels to determine the structural basis of LE135-induced activation of TRPV1 and TRPA1 channels and behavioural testing to examine if pharmacological inhibition and genetic deletion of the channels affected LE135-evoked pain-related behaviours. LE135 activated both the capsaicin receptor (TRPV1) and the allyl isothiocyanate receptor (TRPA1) heterologously expressed in HEK293T cells and endogenously expressed by sensory nociceptors. Mutations disrupting the capsaicin-binding site attenuated LE135 activation of TRPV1 channels and a single mutation (K170R) eliminated TRPA1 activity evoked by LE135. Intraplantar injection of LE135 evoked pain-related behaviours. Both TRPV1 and TRPA1 channels were involved in LE135-elicited pain-related responses, as shown by pharmacological and genetic ablation studies. This blocker of retinoid acid signalling also exerted non-genomic effects through activating the pain-initiating TRPV1 and TRPA1 channels. © 2013 The British Pharmacological Society.

Discovery of a Novel Series of CRTH2 (DP2) Receptor Antagonists Devoid of Carboxylic Acids

PubMed Central

2011-01-01

Antagonism of the CRTH2 receptor represents a very attractive target for a variety of allergic diseases. Most CRTH2 antagonists known to date possess a carboxylic acid moiety, which is essential for binding. However, potential acid metabolites O-acyl glucuronides might be linked to idiosynchratic toxicity in humans. In this communication, we describe a new series of compounds that lack the carboxylic acid moiety. Compounds with high affinity (Ki < 10 nM) for the receptor have been identified. Subsequent optimization succeeded in reducing the high metabolic clearance of the first compounds in human and rat liver microsomes. At the same time, inhibition of the CYP isoforms was optimized, giving rise to stable compounds with an acceptable CYP inhibition profile (IC50 CYP2C9 and 2C19 > 1 μM). Taken together, these data show that compounds devoid of carboxylic acid groups could represent an interesting alternative to current CRTH2 antagonists in development. PMID:24900284

Expression of functional receptors by the human γ-aminobutyric acid A γ2 subunit

PubMed Central

Martínez-Torres, Ataúlfo; Miledi, Ricardo

2004-01-01

γ-Aminobutyric acid A (GABAA) receptors are heteromeric membrane proteins formed mainly by various combinations of α, β, and γ subunits; and it is commonly thought that the γ2 subunit alone does not form functional receptors. In contrast, we found that cDNA encoding the γ2L subunit of the human GABAA receptor, injected alone into Xenopus oocytes, expressed functional GABA receptors whose properties were investigated by using the two-microelectrode voltage-clamp technique. GABA elicited desensitizing membrane currents that recovered after a few minutes' wash. Repetitive applications of GABA induced a “run-up” of GABA currents that nearly doubled the amplitude of the first response. The GABA currents inverted direction at about -30 mV, indicating that they are carried mainly by Cl- ions. The homomeric γ2L receptors were also activated by β-alanine > taurine > glycine, and, like some types of heteromeric GABAA receptors, the γ2L receptors were blocked by bicuculline and were potentiated by pentobarbital and flunitrazepam. These results indicate that the human γ2L subunit is capable of forming fully functional GABA receptors by itself in Xenopus oocytes and suggest that the roles proposed for the various subunits that make up the heteromeric GABAA receptors in situ require further clarification. PMID:14981251

The short-chain fatty acid receptor, FFA2, contributes to gestational glucose homeostasis.

PubMed

Fuller, Miles; Priyadarshini, Medha; Gibbons, Sean M; Angueira, Anthony R; Brodsky, Michael; Hayes, M Geoffrey; Kovatcheva-Datchary, Petia; Bäckhed, Fredrik; Gilbert, Jack A; Lowe, William L; Layden, Brian T

2015-11-15

The structure of the human gastrointestinal microbiota can change during pregnancy, which may influence gestational metabolism; however, a mechanism of action remains unclear. Here we observed that in wild-type (WT) mice the relative abundance of Actinobacteria and Bacteroidetes increased during pregnancy. Along with these changes, short-chain fatty acids (SCFAs), which are mainly produced through gut microbiota fermentation, significantly changed in both the cecum and peripheral blood throughout gestation in these mice. SCFAs are recognized by G protein-coupled receptors (GPCRs) such as free fatty acid receptor-2 (FFA2), and we have previously demonstrated that the fatty acid receptor-2 gene (Ffar2) expression is higher in pancreatic islets during pregnancy. Using female Ffar2-/- mice, we explored the physiological relevance of signaling through this GPCR and found that Ffar2-deficient female mice developed fasting hyperglycemia and impaired glucose tolerance in the setting of impaired insulin secretion compared with WT mice during, but not before, pregnancy. Insulin tolerance tests were similar in Ffar2-/- and WT mice before and during pregnancy. Next, we examined the role of FFA2 in gestational β-cell mass, observing that Ffar2-/- mice had diminished gestational expansion of β-cells during pregnancy. Interestingly, mouse genotype had no significant impact on the composition of the gut microbiome, but did affect the observed SCFA profiles, suggesting a functional difference in the microbiota. Together, these results suggest a potential link between increased Ffar2 expression in islets and the alteration of circulating SCFA levels, possibly explaining how changes in the gut microbiome contribute to gestational glucose homeostasis.

Optical control of trimeric P2X receptors and acid-sensing ion channels.

PubMed

Browne, Liam E; Nunes, João P M; Sim, Joan A; Chudasama, Vijay; Bragg, Laricia; Caddick, Stephen; North, R Alan

2014-01-07

P2X receptors are trimeric membrane proteins that function as ion channels gated by extracellular ATP. We have engineered a P2X2 receptor that opens within milliseconds by irradiation at 440 nm, and rapidly closes at 360 nm. This requires bridging receptor subunits via covalent attachment of 4,4'-bis(maleimido)azobenzene to a cysteine residue (P329C) introduced into each second transmembrane domain. The cis-trans isomerization of the azobenzene pushes apart the outer ends of the transmembrane helices and opens the channel in a light-dependent manner. Light-activated channels exhibited similar unitary currents, rectification, calcium permeability, and dye uptake as P2X2 receptors activated by ATP. P2X3 receptors with an equivalent mutation (P320C) were also light sensitive after chemical modification. They showed typical rapid desensitization, and they could coassemble with native P2X2 subunits in pheochromocytoma cells to form light-activated heteromeric P2X2/3 receptors. A similar approach was used to open and close human acid-sensing ion channels (ASICs), which are also trimers but are unrelated in sequence to P2X receptors. The experiments indicate that the opening of the permeation pathway requires similar and substantial movements of the transmembrane helices in both P2X receptors and ASICs, and the method will allow precise optical control of P2X receptors or ASICs in intact tissues.

Optical control of trimeric P2X receptors and acid-sensing ion channels

PubMed Central

Browne, Liam E.; Nunes, João P. M.; Sim, Joan A.; Chudasama, Vijay; Bragg, Laricia; Caddick, Stephen; Alan North, R.

2014-01-01

P2X receptors are trimeric membrane proteins that function as ion channels gated by extracellular ATP. We have engineered a P2X2 receptor that opens within milliseconds by irradiation at 440 nm, and rapidly closes at 360 nm. This requires bridging receptor subunits via covalent attachment of 4,4'-bis(maleimido)azobenzene to a cysteine residue (P329C) introduced into each second transmembrane domain. The cis–trans isomerization of the azobenzene pushes apart the outer ends of the transmembrane helices and opens the channel in a light-dependent manner. Light-activated channels exhibited similar unitary currents, rectification, calcium permeability, and dye uptake as P2X2 receptors activated by ATP. P2X3 receptors with an equivalent mutation (P320C) were also light sensitive after chemical modification. They showed typical rapid desensitization, and they could coassemble with native P2X2 subunits in pheochromocytoma cells to form light-activated heteromeric P2X2/3 receptors. A similar approach was used to open and close human acid-sensing ion channels (ASICs), which are also trimers but are unrelated in sequence to P2X receptors. The experiments indicate that the opening of the permeation pathway requires similar and substantial movements of the transmembrane helices in both P2X receptors and ASICs, and the method will allow precise optical control of P2X receptors or ASICs in intact tissues. PMID:24367083

Branched-Chain Amino Acids Are the Primary Limiting Amino Acids in the Diets of Endurance-Trained Men after a Bout of Prolonged Exercise.

PubMed

Kato, Hiroyuki; Suzuki, Katsuya; Bannai, Makoto; Moore, Daniel R

2018-05-09

The indicator amino acid oxidation (IAAO) method estimates the protein intake required to maximize whole-body protein synthesis and identify the daily protein requirement in a variety of populations. However, it is unclear whether the greater requirements for endurance athletes previously determined by the IAAO reflect an increased demand for all or only some amino acids. The aim of this study was to determine the primary rate-limiting amino acids in endurance-trained athletes after prolonged exercise, by measuring the oxidation of ingested [1-13C]phenylalanine in response to variable amino acid intake. Five endurance-trained men (means ± SDs: age, 26 ± 7 y; body weight, 66.9 ± 9.5 kg; maximal oxygen consumption, 63.3 ± 4.3 mL · kg-1 · min-1) performed 5 trials that involved 2 d of controlled diet (1.4 g protein · kg-1 · d-1) and running (10 km on day 1 and 5 km on day 2) prior to performing an acute bout of endurance exercise (20-km treadmill run) on day 3. During recovery on day 3, participants consumed test diets as 8 isocaloric hourly meals providing sufficient energy and carbohydrate but a variable amino acid intake. The test diets, consumed in random order, were deficient (BASE: 0.8 g · kg-1 · d-1) and sufficient (SUF; 1.75 g · kg-1 · d-1) amino acid diets modeled after egg protein, and BASE supplemented with branched-chain amino acids (BCAA diet; 1.03 g · kg-1 · d-1), essential amino acids (EAA diet; 1.23 g · kg-1 · d-1), or nonessential amino acids (NEAA diet; 1.75 g · kg-1 · d-1). Whole-body phenylalanine flux (Q), 13CO2 excretion (F13CO2), and phenylalanine oxidation (OX) were determined according to standard IAAO methodology. There was no effect of amino acid intake on Q (P = 0.43). F13CO2 was significantly (all P < 0.01) lower than BASE for the BCAA (∼32%), EAA (∼31%), and SUF (∼36%) diet treatments. F13CO2 for the NEAA diet was ∼18% lower than for BASE (P < 0.05) but ∼28% greater than for SUF (P < 0

Free fatty acids-sensing G protein-coupled receptors in drug targeting and therapeutics.

PubMed

Yonezawa, Tomo; Kurata, Riho; Yoshida, Kaori; Murayama, Masanori A; Cui, Xiaofeng; Hasegawa, Akihiko

2013-01-01

G protein-coupled receptor (GPCR) (also known as seven-transmembrane domain receptor) superfamily represents the largest protein family in the human genome. These receptors respond to various physiological ligands such as photons, odors, pheromones, hormones, ions, and small molecules including amines, amino acids to large peptides and steroids. Thus, GPCRs are involved in many diseases and the target of around half of all conventional drugs. The physiological roles of free fatty acids (FFAs), in particular, long-chain FFAs, are important for the development of many metabolic disease including obesity, diabetes, and atherosclerosis. In the past half decade, deorphanization of several GPCRs has revealed that GPR40, GPR41, GPR43, GPR84 and GPR120 sense concentration of extracellular FFAs with various carbon chain lengths. GPR40 and GPR120 are activated by medium- and long-chain FFAs. GPR84 is activated by medium- chain, but not long-chain, FFAs. GPR41 and GPR43 are activated by short-chain FFAs. GPR40 is highly expressed in pancreatic beta cells and plays a crucial role in FFAs-induced insulin secretion. GPR120 is mainly expressed in enteroendocrine cells and plays an important role for FFAs-induced glucagon-like peptide-1. GPR43 is abundant in leukocytes and adipose tissue, whilst GPR41 is highly expressed in adipose tissue, the pancreas and leukocytes. GPR84 is expressed in leukocytes and monocyte/macrophage. This review aims to shed light on the physiological roles and development of drugs targeting these receptors.

A single amino acid residue controls Ca2+ signaling by an octopamine receptor from Drosophila melanogaster

PubMed Central

Hoff, Max; Balfanz, Sabine; Ehling, Petra; Gensch, Thomas; Baumann, Arnd

2011-01-01

Rhythmic activity of cells and cellular networks plays an important role in physiology. In the nervous system oscillations of electrical activity and/or second messenger concentrations are important to synchronize neuronal activity. At the molecular level, rhythmic activity can be initiated by different routes. We have recently shown that an octopamine-activated G-protein-coupled receptor (GPCR; DmOctα1Rb, CG3856) from Drosophila initiates Ca2+ oscillations. Here, we have unraveled the molecular basis of cellular Ca2+ signaling controlled by the DmOctα1Rb receptor using a combination of pharmacological intervention, site-directed mutagenesis, and functional cellular Ca2+ imaging on heterologously expressed receptors. Phosphorylation of a single amino acid residue in the third intracellular loop of the GPCR by PKC is necessary and sufficient to desensitize the receptor. From its desensitized state, DmOctα1Rb is resensitized by dephosphorylation, and a new Ca2+ signal occurs on octopamine stimulation. Our findings show that transient changes of the receptor's surface profile have a strong effect on its physiological signaling properties. We expect that the detailed knowledge of DmOctα1Rb-dependent signal transduction fosters the identification of specific drugs that can be used for GPCR-mediated pest control, since octopamine serves important physiological and behavioral functions in arthropods.—Hoff M., Balfanz, S., Ehling, P., Gensch, T., Baumann, A. A single amino acid residue controls Ca2+ signaling by an octopamine receptor from Drosophila melanogaster. PMID:21478261

Glucocorticoid-dependent induction of interleukin-6 receptor expression in human hepatocytes facilitates interleukin-6 stimulation of amino acid transport.

PubMed

Fischer, C P; Bode, B P; Takahashi, K; Tanabe, K K; Souba, W W

1996-05-01

The authors studied the effects of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) on glutamine and alanine transport in isolated human hepatocytes. They also evaluated the role of dexamethasone in modulating this response and its effects on the expression of the plasma membrane high-affinity IL-6 receptor. Animal studies indicate that cytokines are important mediators of the increased hepatic amino acid uptake that occurs during cancer and sepsis, but studies in human tissues are lacking. The control of transport by cytokines and cytokine receptor expression in the liver may provide a mechanism by which hepatocytes can modulate amino acid availability during catabolic disease states. Human hepatocytes were isolated from wedge biopsy specimens and plated in 24-well trays. Interleukin-6 and TNF-alpha, in combination with the synthetic glucocorticoid dexamethasone, were added to hepatocytes in culture, and the transport of radiolabeled glutamine and alanine was measured. Fluorescent-activated cell sorter (FACS) analysis was used to study the effects of dexamethasone on IL-6 receptor number in the well-differentiated human hepatoma HepG2. Both IL-6 and TNF-alpha exerted a small stimulatory effect on alanine and glutamine transport. Dexamethasone alone did not alter transport rates, but pretreatment of cells augmented the effects of both cytokines on carrier-mediated amino acid uptake. Dexamethasone pretreatment and a combination of IL-6 and TNF-alpha resulted in a greater than twofold increase in transport activity. Fluorescent-activated cell sorter analysis demonstrated that dexamethasone induced a threefold increase in the expression of high-affinity IL-6 receptors. Interleukin-6 and TNF-alpha work coordinately with glucocorticoids to stimulate amino acid uptake in human hepatocytes. Dexamethasone exerts a permissive effect on cytokine-mediated increases in transport by increasing IL-6 receptor expression on the cell surface. It is likely that this

SIGNALLING THROUGH RETINOIC ACID RECEPTORS IN CARDIAC DEVELOPMENT: DOING THE RIGHT THINGS AT THE RIGHT TIMES

PubMed Central

Xavier-Neto, José; Costa, Ângela M. Sousa; Figueira, Ana Carolina M.; Caiaffa, Carlo Donato; do Amaral, Fabio Neves; Peres, Lara Maldanis Cerqueira; da Silva, Bárbara Santos Pires; Santos, Luana Nunes; Moise, Alexander R.; Castillo, Hozana Andrade

2015-01-01

Retinoic acid (RA) is a terpenoid that is synthesized from Vitamin A/retinol (ROL) and binds to the nuclear receptors retinoic acid receptor (RAR)/retinoid X receptor (RXR) to control multiple developmental processes in vertebrates. The available clinic and experimental data provide uncontested evidence for the pleiotropic roles of RA signalling in development of multiple embryonic structures and organs such eyes, central nervous system, gonads, lungs and heart. The development of any of these above-mentioned embryonic organ systems can be effectively utilized to showcase the many strategies utilized by RA signalling. However, it is very likely that the strategies employed to transfer RA signals during cardiac development comprise the majority of the relevant and sophisticated ways through which retinoid signals can be conveyed in a complex biological system. Here, we provide the reader with arguments indicating that RA signalling is exquisitely regulated according to specific phases of cardiac development and that RA signalling itself is one of the major regulators of the timing of cardiac morphogenesis and differentiation. We will focus on the role of signalling by RA receptors (RARs) in early phases of heart development. PMID:25134739

The short chain fatty acid receptor, FFA2, contributes to gestational glucose homeostasis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fuller, Miles; Priyadarshini, Medha; Gibbons, Sean M.

The structure of the human gastrointestinal microbiota can change during pregnancy, which may influence gestational metabolism; however, a mechanism of action remains unclear. Here we observed that in wild-type (WT) mice the relative abundance of Actinobacteria and Bacteroidetes increased during pregnancy. Along with these changes, short-chain fatty acids (SCFAs), which are mainly produced through gut microbiota fermentation, significantly changed in both the cecum and peripheral blood throughout gestation in these mice. SCFAs are recognized by G protein-coupled receptors (GPCRs) such as free fatty acid receptor-2 (FFA2), and we have previously demonstrated that the fatty acid receptor-2 gene ( Ffar2) expressionmore » is higher in pancreatic islets during pregnancy. Using female Ffar2-/- mice, we explored the physiological relevance of signaling through this GPCR and found that Ffar2-deficient female mice developed fasting hyperglycemia and impaired glucose tolerance in the setting of impaired insulin secretion compared with WT mice during, but not before, pregnancy. Insulin tolerance tests were similar in Ffar2-/- and WT mice before and during pregnancy. Next, we examined the role of FFA2 in gestational β-cell mass, observing that Ffar2-/- mice had diminished gestational expansion of β-cells during pregnancy. Interestingly, mouse genotype had no significant impact on the composition of the gut microbiome, but did affect the observed SCFA profiles, suggesting a functional difference in the microbiota. Altogether, these results suggest a potential link between increased Ffar2 expression in islets and the alteration of circulating SCFA levels, possibly explaining how changes in the gut microbiome contribute to gestational glucose homeostasis.« less

The short chain fatty acid receptor, FFA2, contributes to gestational glucose homeostasis

DOE PAGES

Fuller, Miles; Priyadarshini, Medha; Gibbons, Sean M.; ...

2015-09-22

The structure of the human gastrointestinal microbiota can change during pregnancy, which may influence gestational metabolism; however, a mechanism of action remains unclear. Here we observed that in wild-type (WT) mice the relative abundance of Actinobacteria and Bacteroidetes increased during pregnancy. Along with these changes, short-chain fatty acids (SCFAs), which are mainly produced through gut microbiota fermentation, significantly changed in both the cecum and peripheral blood throughout gestation in these mice. SCFAs are recognized by G protein-coupled receptors (GPCRs) such as free fatty acid receptor-2 (FFA2), and we have previously demonstrated that the fatty acid receptor-2 gene ( Ffar2) expressionmore » is higher in pancreatic islets during pregnancy. Using female Ffar2-/- mice, we explored the physiological relevance of signaling through this GPCR and found that Ffar2-deficient female mice developed fasting hyperglycemia and impaired glucose tolerance in the setting of impaired insulin secretion compared with WT mice during, but not before, pregnancy. Insulin tolerance tests were similar in Ffar2-/- and WT mice before and during pregnancy. Next, we examined the role of FFA2 in gestational β-cell mass, observing that Ffar2-/- mice had diminished gestational expansion of β-cells during pregnancy. Interestingly, mouse genotype had no significant impact on the composition of the gut microbiome, but did affect the observed SCFA profiles, suggesting a functional difference in the microbiota. Altogether, these results suggest a potential link between increased Ffar2 expression in islets and the alteration of circulating SCFA levels, possibly explaining how changes in the gut microbiome contribute to gestational glucose homeostasis.« less

Short-chain free fatty acid receptors FFA2/GPR43 and FFA3/GPR41 as new potential therapeutic targets

PubMed Central

Ulven, Trond

2012-01-01

The deorphanization of the free fatty acid (FFA) receptors FFA1 (GPR40), FFA2 (GPR43), FFA3 (GPR41), GPR84, and GPR120 has made clear that the body is capable of recognizing and responding directly to nonesterified fatty acid of virtually any chain length. Colonic fermentation of dietary fiber produces high concentrations of the short-chain fatty acids (SCFAs) acetate, propionate and butyrate, a process which is important to health. The phylogenetically related 7-transmembrane (7TM) receptors free fatty acid receptor 2 (FFA2) and FFA3 are activated by these SCFAs, and several lines of evidence indicate that FFA2 and FFA3 mediate beneficial effects associated with a fiber-rich diet, and that they may be of interest as targets for treatment of inflammatory and metabolic diseases. FFA2 is highly expressed on immune cells, in particular neutrophils, and several studies suggest that the receptor plays a role in diseases involving a dysfunctional neutrophil response, such as inflammatory bowel disease (IBD). Both FFA2 and FFA3 have been implicated in metabolic diseases such as type 2 diabetes and in regulation of appetite. More research is however required to clarify the potential of the receptors as drug targets and establish if activation or inhibition would be the preferred mode of action. The availability of potent and selective receptor modulators is a prerequisite for these studies. The few modulators of FFA2 or FFA3 that have been published hitherto in the peer-reviewed literature in general have properties that make them less than ideal as such tools, but published patent applications indicate that better tool compounds might soon become available which should enable studies critical to validate the receptors as new drug targets. PMID:23060857

Short-chain free fatty acid receptors FFA2/GPR43 and FFA3/GPR41 as new potential therapeutic targets.

PubMed

Ulven, Trond

2012-01-01

The deorphanization of the free fatty acid (FFA) receptors FFA1 (GPR40), FFA2 (GPR43), FFA3 (GPR41), GPR84, and GPR120 has made clear that the body is capable of recognizing and responding directly to nonesterified fatty acid of virtually any chain length. Colonic fermentation of dietary fiber produces high concentrations of the short-chain fatty acids (SCFAs) acetate, propionate and butyrate, a process which is important to health. The phylogenetically related 7-transmembrane (7TM) receptors free fatty acid receptor 2 (FFA2) and FFA3 are activated by these SCFAs, and several lines of evidence indicate that FFA2 and FFA3 mediate beneficial effects associated with a fiber-rich diet, and that they may be of interest as targets for treatment of inflammatory and metabolic diseases. FFA2 is highly expressed on immune cells, in particular neutrophils, and several studies suggest that the receptor plays a role in diseases involving a dysfunctional neutrophil response, such as inflammatory bowel disease (IBD). Both FFA2 and FFA3 have been implicated in metabolic diseases such as type 2 diabetes and in regulation of appetite. More research is however required to clarify the potential of the receptors as drug targets and establish if activation or inhibition would be the preferred mode of action. The availability of potent and selective receptor modulators is a prerequisite for these studies. The few modulators of FFA2 or FFA3 that have been published hitherto in the peer-reviewed literature in general have properties that make them less than ideal as such tools, but published patent applications indicate that better tool compounds might soon become available which should enable studies critical to validate the receptors as new drug targets.

Cholestenoic acids regulate motor neuron survival via liver X receptors

PubMed Central

Theofilopoulos, Spyridon; Griffiths, William J.; Crick, Peter J.; Yang, Shanzheng; Meljon, Anna; Ogundare, Michael; Kitambi, Satish Srinivas; Lockhart, Andrew; Tuschl, Karin; Clayton, Peter T.; Morris, Andrew A.; Martinez, Adelaida; Reddy, M. Ashwin; Martinuzzi, Andrea; Bassi, Maria T.; Honda, Akira; Mizuochi, Tatsuki; Kimura, Akihiko; Nittono, Hiroshi; De Michele, Giuseppe; Carbone, Rosa; Criscuolo, Chiara; Yau, Joyce L.; Seckl, Jonathan R.; Schüle, Rebecca; Schöls, Ludger; Sailer, Andreas W.; Kuhle, Jens; Fraidakis, Matthew J.; Gustafsson, Jan-Åke; Steffensen, Knut R.; Björkhem, Ingemar; Ernfors, Patrik; Sjövall, Jan; Arenas, Ernest; Wang, Yuqin

2014-01-01

Cholestenoic acids are formed as intermediates in metabolism of cholesterol to bile acids, and the biosynthetic enzymes that generate cholestenoic acids are expressed in the mammalian CNS. Here, we evaluated the cholestenoic acid profile of mammalian cerebrospinal fluid (CSF) and determined that specific cholestenoic acids activate the liver X receptors (LXRs), enhance islet-1 expression in zebrafish, and increase the number of oculomotor neurons in the developing mouse in vitro and in vivo. While 3β,7α-dihydroxycholest-5-en-26-oic acid (3β,7α-diHCA) promoted motor neuron survival in an LXR-dependent manner, 3β-hydroxy-7-oxocholest-5-en-26-oic acid (3βH,7O-CA) promoted maturation of precursors into islet-1+ cells. Unlike 3β,7α-diHCA and 3βH,7O-CA, 3β-hydroxycholest-5-en-26-oic acid (3β-HCA) caused motor neuron cell loss in mice. Mutations in CYP7B1 or CYP27A1, which encode enzymes involved in cholestenoic acid metabolism, result in different neurological diseases, hereditary spastic paresis type 5 (SPG5) and cerebrotendinous xanthomatosis (CTX), respectively. SPG5 is characterized by spastic paresis, and similar symptoms may occur in CTX. Analysis of CSF and plasma from patients with SPG5 revealed an excess of the toxic LXR ligand, 3β-HCA, while patients with CTX and SPG5 exhibited low levels of the survival-promoting LXR ligand 3β,7α-diHCA. Moreover, 3β,7α-diHCA prevented the loss of motor neurons induced by 3β-HCA in the developing mouse midbrain in vivo.Our results indicate that specific cholestenoic acids selectively work on motor neurons, via LXR, to regulate the balance between survival and death. PMID:25271621

Specificity of the Antibody Receptor Site to D-Lysergamide: Model of a Physiological Receptor for Lysergic Acid Diethylamide

PubMed Central

Vunakis, Helen Van; Farrow, John T.; Gjika, Hilda B.; Levine, Lawrence

1971-01-01

Antibodies to D-lysergic acid have been produced in rabbits and guinea pigs and a radioimmunoassay for the hapten was developed. The specificity of this lysergamide-antilysergamide reaction was determined by competitive binding with unlabeled lysergic acid diethylamide (LSD), psychotomimetic drugs, neurotransmitters, and other compounds with diverse structures. LSD and several related ergot alkaloids were potent competitors, three to seven times more potent than lysergic acid itself. The N,N-dimethyl derivatives of several compounds, including tryptamine, 5-hydroxytryptamine, 4-hydroxytryptamine, 5-methoxytryptamine, tyramine, and mescaline, were only about ten times less effective than lysergic acid, even though these compounds lack some of the ring systems of lysergic acid. The pattern of inhibition by related compounds with various substituents suggests that the antibody receptor site recognizes structural features resembling the LSD molecule. In particular, the aromatic nucleus and the dimethylated ethylamine side chain in phenylethylamine and tryptamine derivatives may assume in solution a conformation resembling ring A and the methylated nitrogen in ring C of LSD. Among the tryptamine derivatives, a large percentage of the most potent competitors are also psychotomimetic compounds. PMID:5283939

Functional screening for G protein-coupled receptor targets of 14,15-epoxyeicosatrienoic acid.

PubMed

Liu, Xuehong; Qian, Zu-Yuan; Xie, Fuchun; Fan, Wei; Nelson, Jonathan W; Xiao, Xiangshu; Kaul, Sanjiv; Barnes, Anthony P; Alkayed, Nabil J

2017-09-01

Epoxyeicosatrienoic acids (EETs) are potent vasodilators that play important roles in cardiovascular physiology and disease, yet the molecular mechanisms underlying the biological actions of EETs are not fully understood. Multiple lines of evidence suggest that the actions of EETs are in part mediated via G protein-coupled receptor (GPCR) signaling, but the identity of such a receptor has remained elusive. We sought to identify 14,15-EET-responsive GPCRs. A set of 105 clones were expressed in Xenopus oocyte and screened for their ability to activate cAMP-dependent chloride current. Several receptors responded to micromolar concentrations of 14,15-EET, with the top five being prostaglandin receptor subtypes (PTGER 2 , PTGER 4 , PTGFR, PTGDR, PTGER 3 IV). Overall, our results indicate that multiple low-affinity 14,15-EET GPCRs are capable of increasing cAMP levels following 14,15-EET stimulation, highlighting the potential for cross-talk between prostanoid and other ecosanoid GPCRs. Our data also indicate that none of the 105 GPCRs screened met our criteria for a high-affinity receptor for 14,15-EET. Copyright © 2016 Elsevier Inc. All rights reserved.

Retinoic acid receptor-related orphan receptor α-induced activation of adenosine monophosphate-activated protein kinase results in attenuation of hepatic steatosis.

PubMed

Kim, Eun-Jin; Yoon, Young-Sil; Hong, Suckchang; Son, Ho-Young; Na, Tae-Young; Lee, Min-Ho; Kang, Hyun-Jin; Park, Jinyoung; Cho, Won-Jea; Kim, Sang-Gun; Koo, Seung-Hoi; Park, Hyeung-geun; Lee, Mi-Ock

2012-05-01

There is increasing evidence that the retinoic acid receptor-related orphan receptor α (RORα) plays an important role in the regulation of metabolic pathways, particularly of fatty acid and cholesterol metabolism; however, the role of RORα in the regulation of hepatic lipogenesis has not been studied. Here, we report that RORα attenuates hepatic steatosis, probably via activation of the adenosine monophosphate (AMP)-activated protein kinase (AMPK) and repression of the liver X receptor α (LXRα). First, RORα and its activator, cholesterol sulfate (CS), induced phosphorylation of AMPK, which was accompanied by the activation of serine-threonine kinase liver kinase B1 (LKB1). Second, the activation of RORα, either by transient transfection or CS treatment, decreased the TO901317-induced transcriptional expression of LXRα and its downstream target genes, such as the sterol regulatory element binding protein-1 (SREBP-1) and fatty acid synthase. RORα interacted physically with LXRα and inhibited the LXRα response element in the promoter of LXRα, indicating that RORα interrupts the autoregulatory activation loop of LXRα. Third, infection with adenovirus encoding RORα suppressed the lipid accumulation that had been induced by a free-fatty-acid mixture in cultured cells. Furthermore, we observed that the level of expression of the RORα protein was decreased in the liver of mice that were fed a high-fat diet. Restoration of RORα via tail-vein injection of adenovirus (Ad)-RORα decreased the high-fat-diet-induced hepatic steatosis. Finally, we synthesized thiourea derivatives that activated RORα, thereby inducing activation of AMPK and repression of LXRα. These compounds decreased hepatic triglyceride levels and lipid droplets in the high-fat-diet-fed mice. We found that RORα induced activation of AMPK and inhibition of the lipogenic function of LXRα, which may be key phenomena that provide the beneficial effects of RORα against hepatic steatosis

Differential Effects of Military Training on Fat-Free Mass and Plasma Amino Acid Adaptations in Men and Women

PubMed Central

Margolis, Lee M.; Pasiakos, Stefan M.; Karl, J. Philip; Rood, Jennifer C.; Cable, Sonya J.; Williams, Kelly W.; Young, Andrew J.; McClung, James P.

2012-01-01

Fat-free mass (FFM) adaptations to physical training may differ between sexes based on disparities in fitness level, dietary intake, and levels of plasma amino acids (AA). This investigation aimed to determine FFM and plasma AA responses to military training, examine whether adaptations differ between male and female recruits, and explore potential associations between FFM and AA responses to training. Body composition and plasma AA levels were assessed in US Army recruits (n = 209, 118 males, 91 females) before (baseline) and every three weeks during basic combat training (BCT), a 10-week military training course. Body weight decreased in men but remained stable in women during BCT (sex-by-time interaction, P < 0.05). Fifty-eight percent of recruits gained FFM during BCT, with more (P < 0.05) females (88%) gaining FFM than males (36%). Total plasma AA increased (P < 0.05) during BCT, with greater (P < 0.05) increases observed in females (17%) then in males (4%). Essential amino acids (EAA) and branched-chain amino acids (BCAA) were increased (P < 0.05) in females but did not change in males (sex-by-time interaction, P < 0.05). Independent of sex, changes in EAA (r = 0.34) and BCAA (r = 0.27) from baseline were associated with changes in FFM (P < 0.05); greater (P < 0.05) increases in AA concentrations were observed for those who gained FFM. Increases in FFM and plasma AA suggest that BCT elicits a more pronounced anabolic response in women compared to men, which may reflect sex-specific differences in the relative intensity of the combined training and physiological stimulus associated with BCT. PMID:23250145

Differential effects of military training on fat-free mass and plasma amino acid adaptations in men and women.

PubMed

Margolis, Lee M; Pasiakos, Stefan M; Karl, J Philip; Rood, Jennifer C; Cable, Sonya J; Williams, Kelly W; Young, Andrew J; McClung, James P

2012-12-18

Fat-free mass (FFM) adaptations to physical training may differ between sexes based on disparities in fitness level, dietary intake, and levels of plasma amino acids (AA). This investigation aimed to determine FFM and plasma AA responses to military training, examine whether adaptations differ between male and female recruits, and explore potential associations between FFM and AA responses to training. Body composition and plasma AA levels were assessed in US Army recruits (n = 209, 118 males, 91 females) before (baseline) and every three weeks during basic combat training (BCT), a 10-week military training course. Body weight decreased in men but remained stable in women during BCT (sex-by-time interaction, P < 0.05). Fifty-eight percent of recruits gained FFM during BCT, with more (P < 0.05) females (88%) gaining FFM than males (36%). Total plasma AA increased (P < 0.05) during BCT, with greater (P < 0.05) increases observed in females (17%) then in males (4%). Essential amino acids (EAA) and branched-chain amino acids (BCAA) were increased (P < 0.05) in females but did not change in males (sex-by-time interaction, P < 0.05). Independent of sex, changes in EAA (r = 0.34) and BCAA (r = 0.27) from baseline were associated with changes in FFM (P < 0.05); greater (P < 0.05) increases in AA concentrations were observed for those who gained FFM. Increases in FFM and plasma AA suggest that BCT elicits a more pronounced anabolic response in women compared to men, which may reflect sex-specific differences in the relative intensity of the combined training and physiological stimulus associated with BCT.

Phosphatase inhibitors remove the run-down of γ-aminobutyric acid type A receptors in the human epileptic brain

PubMed Central

Palma, E.; Ragozzino, D. A.; Di Angelantonio, S.; Spinelli, G.; Trettel, F.; Martinez-Torres, A.; Torchia, G.; Arcella, A.; Di Gennaro, G.; Quarato, P. P.; Esposito, V.; Cantore, G.; Miledi, R.; Eusebi, F.

2004-01-01

The properties of γ-aminobutyric acid (GABA) type A receptors (GABAA receptors) microtransplanted from the human epileptic brain to the plasma membrane of Xenopus oocytes were compared with those recorded directly from neurons, or glial cells, in human brains slices. Cell membranes isolated from brain specimens, surgically obtained from six patients afflicted with drug-resistant temporal lobe epilepsy (TLE) were injected into frog oocytes. Within a few hours, these oocytes acquired GABAA receptors that generated GABA currents with an unusual run-down, which was inhibited by orthovanadate and okadaic acid. In contrast, receptors derived from membranes of a nonepileptic hippocampal uncus, membranes from mouse brain, or recombinant rat α1β2γ2-GABA receptors exhibited a much less pronounced GABA-current run-down. Moreover, the GABAA receptors of pyramidal neurons in temporal neocortex slices from the same six epileptic patients exhibited a stronger run-down than the receptors of rat pyramidal neurons. Interestingly, the GABAA receptors of neighboring glial cells remained substantially stable after repetitive activation. Therefore, the excessive GABA-current run-down observed in the membrane-injected oocytes recapitulates essentially what occurs in neurons, rather than in glial cells. Quantitative RT-PCR analyses from the same TLE neocortex specimens revealed that GABAA-receptor β1, β2, β3, and γ2 subunit mRNAs were significantly overexpressed (8- to 33-fold) compared with control autopsy tissues. Our results suggest that an abnormal GABA-receptor subunit transcription in the TLE brain leads to the expression of run-down-enhanced GABAA receptors. Blockage of phosphatases stabilizes the TLE GABAA receptors and strengthens GABAergic inhibition. It may be that this process can be targeted to develop new treatments for intractable epilepsy. PMID:15218107

Efficacy of the Essential Amino Acids and Keto-Analogues on the CKD progression rate in real practice in Russia - city nephrology registry data for outpatient clinic.

PubMed

Zemchenkov, Alexander; Konakova, Irina N

2016-07-07

Renal replacement therapy (RRT) is growing by 10 % per year in Russia, but pre-dialysis care which can retard CKD progression and delay the start of RRT remains limited. We evaluate the effect of Essential Amino Acids and Keto-analogues (EAA/KA) on CKD progression. The effect of low protein diet (LPD), supplemented by EAA/KA, on GFR slope changes between first and second treatment period (five sequential visits per period) in 96 patients withs CKD Stage 3B-5 was compared to GFR slope changes in the control group of 96 patients, randomly selected from matched (by gender, age, diagnosis and CKD Stage) cohort of 320 patients from the city Registry. The mean baseline eGFR was 23 ± 9 ml/min/1.73 m2; 29 % had CKD3B, 45 % - CKD4, 26 % - CKD5. The rate of eGFR decline changed from -2.71 ± 2.38 to -2.01 ± 2.26 ml/min/1.73 m2 per year in the treatment group and from -2.18 ± 2.01 to -2.04 ± 2.18 ml/min/1.73 m2 per year in the control group. Only in the treatment group the difference was significant (p = 0.04 and p = 0.6). Standardized effect size for intervention was significant in treatment group: -0.3 (of pooled SD), 95 % CI -0.58 ÷  -0.02 and non-significant in control group: -0.07 (-0.35 ÷ +0.22). The univariate and multivariate analysis of EAA/KA therapy effect demonstrated that it was probably more effective in patients of older age, with higher time-averaged proteinuria (PU), lower phosphate level, in patients with glomerular v. interstitial diseases, and in females. Only the latter factor was significant at pre-specified level (<0.05). LPD combined with EAA/KA supplementation lead to the decrease of the CKD progression both in well-designed clinical study and in real nephrology practice in wide variety diseases and settings. Registry data can be helpful to reveal patients with optimal chances for beneficial effect of LPD supplemented by EAA/KA. ISRCTN28190556 06/05/2016.

LE135, a retinoid acid receptor antagonist, produces pain through direct activation of TRP channels

PubMed Central

Yin, Shijin; Luo, Jialie; Qian, Aihua; Yu, Weihua; Hu, Hongzhen

2014-01-01

Background and PurposeRetinoids, through their activation of retinoic acid receptors (RARs) and retinoid X receptors, regulate diverse cellular processes, and pharmacological intervention in their actions has been successful in the treatment of skin disorders and cancers. Despite the many beneficial effects, administration of retinoids causes irritating side effects with unknown mechanisms. Here, we demonstrate that LE135 [4-(7,8,9,10-tetrahydro-5,7,7,10,10-pentamethyl-5H-benzo[e]naphtho[2,3-b][1,4]diazepin-13-yl)benzoic acid], a selective antagonist of RARβ, is a potent activator of the capsaicin (TRPV1) and wasabi (TRPA1) receptors, two critical pain-initiating cation channels. Experimental ApproachWe performed to investigate the excitatory effects of LE135 on TRPV1 and TRPA1 channels expressed in HEK293T cells and in dorsal root ganglia neurons with calcium imaging and patch-clamp recordings. We also used site-directed mutagenesis of the channels to determine the structural basis of LE135-induced activation of TRPV1 and TRPA1 channels and behavioural testing to examine if pharmacological inhibition and genetic deletion of the channels affected LE135-evoked pain-related behaviours. Key ResultsLE135 activated both the capsaicin receptor (TRPV1) and the allyl isothiocyanate receptor (TRPA1) heterologously expressed in HEK293T cells and endogenously expressed by sensory nociceptors. Mutations disrupting the capsaicin-binding site attenuated LE135 activation of TRPV1 channels and a single mutation (K170R) eliminated TRPA1 activity evoked by LE135. Intraplantar injection of LE135 evoked pain-related behaviours. Both TRPV1 and TRPA1 channels were involved in LE135-elicited pain-related responses, as shown by pharmacological and genetic ablation studies. Conclusions and ImplicationsThis blocker of retinoid acid signalling also exerted non-genomic effects through activating the pain-initiating TRPV1 and TRPA1 channels. PMID:24308840

Okadaic acid induces epileptic seizures and hyperphosphorylation of the NR2B subunit of the NMDA receptor in rat hippocampus in vivo.

PubMed

Arias, Clorinda; Montiel, Teresa; Peña, Fernando; Ferrera, Patricia; Tapia, Ricardo

2002-09-01

Overactivation of N-methyl-D-aspartate (NMDA) glutamate receptors is closely related to epilepsy and excitotoxicity, and the phosphorylation of these receptors may facilitate glutamate-mediated synaptic transmission. Here we show that in awake rats the microinjection into the hippocampus of okadaic acid, a potent inhibitor of protein phosphatases 1 and 2A, induces in about 20 min intense electroencephalographic and behavioral limbic-type seizures, which are suppressed by the systemic administration of the NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo-[a,d]cyclohepten-5,10-imine hydrogen maleate and by the intrahippocampal administration of 1-(5-isoquinolinesulfonyl)-2-methylpiperazine, an inhibitor of protein kinases. Two hours after okadaic acid, when the EEG seizures were intense, an increased serine phosphorylation of some hippocampal proteins, including an enhancement of the serine phosphorylation of the NMDA receptor subunit NR2B, was detected by immunoblotting. Twenty-four hours after okadaic acid a marked destruction of hippocampal CA1 region was observed, which was not prevented by the receptor antagonists. These findings suggest that hyperphosphorylation of glutamate receptors in vivo may result in an increased sensitivity to the endogenous transmitter and therefore induce neuronal hyperexcitability and epilepsy.

A novel polymorphism in the oxytocin receptor encoding gene (OXTR) affects milk fatty acid composition in Italian Mediterranean river buffalo.

PubMed

Cosenza, Gianfranco; Macciotta, Nicolò P P; Nudda, Anna; Coletta, Angelo; Ramunno, Luigi; Pauciullo, Alfredo

2017-05-01

The oxytocin receptor, also known as OXTR, is a protein which functions as receptor for the hormone and neurotransmitter oxytocin and the complex oxytocin-oxytocin receptor plays an important role in the uterus during calving. A characterisation of the river buffalo OXTR gene, amino acid sequences and phylogenetic analysis is presented. The DNA regions of the OXTR gene spanning exons 1, 2 and 3 of ten Mediterranean river buffalo DNA samples were analysed and 7 single nucleotide polymorphisms were found. We focused on the g.129C > T SNP detected in exon 3 and responsible for the amino acid replacement CGCArg > TGCCys in position 353. The relative frequency of T allele was of 0·257. An association study between this detected polymorphism and milk fatty acids composition in Italian Mediterranean river buffalo was carried out. The fatty acid composition traits, fatty acid classes and fat percentage of 306 individual milk samples were determined. Associations between OXTR g.129C > T genotype and milk fatty acids composition were tested using a mixed linear model. The OXTR CC genotype was found significantly associated with higher contents of odd branched-chain fatty acids (OBCFA) (P < 0·0006), polyunsaturated FA (PUFA n 3 and n 6) (P < 0·0032 and P < 0·0006, respectively), stearic acid (C18) (P < 0·02) and lower level of palmitic acid (C16) (P < 0·02). The results of this study suggest that the OXTR CC animals might be useful in selection toward the improvement of milk fatty acid composition.

Digestion and nutrient net fluxes across the rumen, and the mesenteric- and portal-drained viscera in sheep fed with fresh forage twice daily: net balance and dynamic aspects.

PubMed

Rémond, Didier; Bernard, Laurence; Chauveau, Béatrice; Nozière, Pierre; Poncet, Claude

2003-05-01

Digestion and portal net flux of nutrients were studied in sheep fed twice daily with fresh orchard-grass. Digestive flows were measured in six fistulated sheep using the double-marker technique. Three sheep were fitted with catheters and blood-flow probes, allowing nutrient net flux measurements across the portal-drained viscera (PDV), the mesenteric-drained viscera (MDV) and the rumen. Total tract apparent digestion of N was similar to portal net appearance of N, calculated as the sum of free amino acids (FAA), peptide amino acids (PAA), NH3, and urea net fluxes. PAA accounted for 25 % of non-protein amino acid net release across the PDV. With the exception of glycine and glutamate, the small intestine was the main contributor to this PAA net release. The essential amino acid (EAA) apparent disappearance between the duodenum and the ileum was lower than the net appearance of EAA (FAA + PAA) across the MDV. The value of PDV:MDV flux of free EAA was, on average, 78 %. The rumen accounted for 30 % of the net uptake of EAA by the PDV tissues not drained by the mesenteric vein. Rumen net release of acetate, propionate, butyrate, 3-hydroxybutyrate, and lactate accounted for 70, 55, 46, 77 and 52 %, respectively, of their portal net releases. Conversely, the small intestine was a net consumer of arterial acetate and 3-hydroxybutyrate. Dynamic study of nutrient net fluxes across the PDV showed that throughout a feeding cycle, the liver faced a constant flux of amino acids (AA), whereas volatile fatty acid and NH3 net fluxes varied in response to the meal. The present study specified, in forage-fed sheep, the partitioning of nutrient net fluxes across the PDV and the role of peptides in portal net release of AA.

Retinoic Acid Isomers Facilitate Apolipoprotein E Production and Lipidation in Astrocytes through the Retinoid X Receptor/Retinoic Acid Receptor Pathway*

PubMed Central

Zhao, Jing; Fu, Yuan; Liu, Chia-Chen; Shinohara, Mitsuru; Nielsen, Henrietta M.; Dong, Qiang; Kanekiyo, Takahisa; Bu, Guojun

2014-01-01

Apolipoprotein E (apoE) is the major cholesterol transport protein in the brain. Among the three human APOE alleles (APOE2, APOE3, and APOE4), APOE4 is the strongest genetic risk factor for late-onset Alzheimer disease (AD). The accumulation of amyloid-β (Aβ) is a central event in AD pathogenesis. Increasing evidence demonstrates that apoE isoforms differentially regulate AD-related pathways through both Aβ-dependent and -independent mechanisms; therefore, modulating apoE secretion, lipidation, and function might be an attractive approach for AD therapy. We performed a drug screen for compounds that modulate apoE production in immortalized astrocytes derived from apoE3-targeted replacement mice. Here, we report that retinoic acid (RA) isomers, including all-trans-RA, 9-cis-RA, and 13-cis-RA, significantly increase apoE secretion to ∼4-fold of control through retinoid X receptor (RXR) and RA receptor. These effects on modulating apoE are comparable with the effects recently reported for the RXR agonist bexarotene. Furthermore, all of these compounds increased the expression of the cholesterol transporter ABCA1 and ABCG1 levels and decreased cellular uptake of Aβ in an apoE-dependent manner. Both bexarotene and 9-cis-RA promote the lipidation status of apoE, in which 9-cis-RA promotes a stronger effect and exhibits less cytotoxicity compared with bexarotene. Importantly, we showed that oral administration of bexarotene and 9-cis-RA significantly increases apoE, ABCA1, and ABCG1 levels in mouse brains. Taken together, our results demonstrate that RXR/RA receptor agonists, including several RA isomers, are effective modulators of apoE secretion and lipidation and may be explored as potential drugs for AD therapy. PMID:24599963

Avian and human influenza virus compatible sialic acid receptors in little brown bats.

PubMed

Chothe, Shubhada K; Bhushan, Gitanjali; Nissly, Ruth H; Yeh, Yin-Ting; Brown, Justin; Turner, Gregory; Fisher, Jenny; Sewall, Brent J; Reeder, DeeAnn M; Terrones, Mauricio; Jayarao, Bhushan M; Kuchipudi, Suresh V

2017-04-06

Influenza A viruses (IAVs) continue to threaten animal and human health globally. Bats are asymptomatic reservoirs for many zoonotic viruses. Recent reports of two novel IAVs in fruit bats and serological evidence of avian influenza virus (AIV) H9 infection in frugivorous bats raise questions about the role of bats in IAV epidemiology. IAVs bind to sialic acid (SA) receptors on host cells, and it is widely believed that hosts expressing both SA α2,3-Gal and SA α2,6-Gal receptors could facilitate genetic reassortment of avian and human IAVs. We found abundant co-expression of both avian (SA α2,3-Gal) and human (SA α2,6-Gal) type SA receptors in little brown bats (LBBs) that were compatible with avian and human IAV binding. This first ever study of IAV receptors in a bat species suggest that LBBs, a widely-distributed bat species in North America, could potentially be co-infected with avian and human IAVs, facilitating the emergence of zoonotic strains.

Leveraging abscisic acid receptors for efficient water use in Arabidopsis

PubMed Central

Yang, Zhenyu; Liu, Jinghui; Tischer, Stefanie V.; Christmann, Alexander; Windisch, Wilhelm; Schnyder, Hans; Grill, Erwin

2016-01-01

Plant growth requires the influx of atmospheric CO2 through stomatal pores, and this carbon uptake for photosynthesis is inherently associated with a large efflux of water vapor. Under water deficit, plants reduce transpiration and are able to improve carbon for water exchange leading to higher water use efficiency (WUE). Whether increased WUE can be achieved without trade-offs in plant growth is debated. The signals mediating the WUE response under water deficit are not fully elucidated but involve the phytohormone abscisic acid (ABA). ABA is perceived by a family of related receptors known to mediate acclimation responses and to reduce transpiration. We now show that enhanced stimulation of ABA signaling via distinct ABA receptors can result in plants constitutively growing at high WUE in the model species Arabidopsis. WUE was assessed by three independent approaches involving gravimetric analyses, 13C discrimination studies of shoots and derived cellulose fractions, and by gas exchange measurements of whole plants and individual leaves. Plants expressing the ABA receptors RCAR6/PYL12 combined up to 40% increased WUE with high growth rates, i.e., are water productive. Water productivity was associated with maintenance of net carbon assimilation by compensatory increases of leaf CO2 gradients, thereby sustaining biomass acquisition. Leaf surface temperatures and growth potentials of plants growing under well-watered conditions were found to be reliable indicators for water productivity. The study shows that ABA receptors can be explored to generate more plant biomass per water transpired, which is a prime goal for a more sustainable water use in agriculture. PMID:27247417

Electro-olfactogram and multiunit olfactory receptor responses to binary and trinary mixtures of amino acids in the channel catfish, Ictalurus punctatus

PubMed Central

1989-01-01

In vivo electrophysiological recordings from populations of olfactory receptor neurons in the channel catfish, Ictalurus punctatus, clearly showed that responses to binary and trinary mixtures of amino acids were predictable with knowledge obtained from previous cross-adaptation studies of the relative independence of the respective binding sites of the component stimuli. All component stimuli, from which equal aliquots were drawn to form the mixtures, were adjusted in concentration to provide for approximately equal response magnitudes. The magnitude of the response to a mixture whose component amino acids showed significant cross-reactivity was equivalent to the response to any single component used to form that mixture. A mixture whose component amino acids showed minimal cross-adaptation produced a significantly larger relative response than a mixture whose components exhibited considerable cross-reactivity. This larger response approached the sum of the responses to the individual component amino acids tested at the resulting concentrations in the mixture, even though olfactory receptor dose-response functions for amino acids in this species are characterized by extreme sensory compression (i.e., successive concentration increments produce progressively smaller physiological responses). Thus, the present study indicates that the response to sensory stimulation of olfactory receptor sites is more enhanced by the activation of different receptor site types than by stimulus interaction at a single site type. PMID:2703818

Novel protective role of the circadian nuclear receptor retinoic acid-related orphan receptor-α in diabetic cardiomyopathy.

PubMed

Zhao, Yichao; Xu, Longwei; Ding, Song; Lin, Nan; Ji, Qingqi; Gao, Lingchen; Su, Yuanyuan; He, Ben; Pu, Jun

2017-04-01

Diabetic cardiomyopathy is a major complication that significantly contributes to morbidity and mortality in diabetics with few therapies. Moreover, antidiabetic drugs reported inconsistent or even adverse cardiovascular effects, suggesting that it is important to exploit novel therapeutic targets against diabetic cardiomyopathy. Here, we observed that the nuclear melatonin receptor, the retinoic acid-related orphan receptor-α (RORα), was downregulated in diabetic hearts. By utilizing a mouse line with RORα disruption, we demonstrated that RORα deficiency led to significantly augmented diastolic dysfunction and cardiac remodeling induced by diabetes. Microscopic and molecular analyses further indicated that the detrimental effects of RORα deficiency were associated with aggravated myocardial apoptosis, autophagy dysfunction, and oxidative stress by disrupting antioxidant gene expression. By contrast, restoration of cardiac RORα levels in transgenic mice significantly improved cardiac functional and structural parameters at 8 weeks after diabetes induction. Consistent with genetic manipulation, pharmacological activation of RORα by melatonin and SR1078 (a synthetic agonist) showed beneficial effects against diabetic cardiomyopathy, while the RORα inhibitor SR3335 significantly exacerbated cardiac impairments in diabetic mice. Collectively, these findings suggest that cardiac-targeted manipulation of nuclear melatonin receptor RORα may hold promise for delaying diabetic cardiomyopathy development. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Bile acids and their oxo derivatives: Potential inhibitors of carbonic anhydrase I and II, androgen receptor antagonists and CYP3A4 substrates.

PubMed

Trifunović, Jovana; Borčić, Vladan; Mikov, Momir

2017-05-01

Some biological properties of bile acids and their oxo derivatives have not been sufficiently investigated, although the interest in bile acids as signaling molecules is rising. The aim of this work was to evaluate physico-chemical parametar b (slope) that represents the lipophilicity of the examined molecules and to investigate interactions of bile acids with carbonic anhydrase I, II, androgen receptor and CYP450s. Thirteen candidates were investigated using normal-phase thin-layer chromatography in two solvent systems. Retention parameters were used in further quantitative structure-activity relationship analysis and docking studies to predict interactions and binding affinities of examined molecules with enzymes and receptors. Prediction of activity on androgen receptor showed that compounds 3α-hydroxy-12-oxo-5β-cholanoic and 3α-hydroxy-7-oxo-5β-cholanoic acid have stronger antiandrogen activity than natural bile acids. The inhibitory potential for carbonic anhydrase I and II was tested and it was concluded that molecules 3α-hydroxy-12-oxo-5β-cholanoic, 3α-hydroxy-7-oxo-5β-cholanoic, 3,7,12-trioxo-5β-cholanoic acid and hyodeoxycholic acid show the best results. Substrate behavior for CYP3A4 was confirmed for all investigated compounds. Oxo derivatives of bile acids show stronger interactions with enzymes and receptors as classical bile acids and lower membranolytic activity compared with them. These significant observations could be valuable in consideration of oxo derivatives as building blocks in medicinal chemistry. Copyright © 2016 John Wiley & Sons, Ltd.

Human Coronavirus HKU1 Spike Protein Uses O-Acetylated Sialic Acid as an Attachment Receptor Determinant and Employs Hemagglutinin-Esterase Protein as a Receptor-Destroying Enzyme.

PubMed

Huang, Xingchuan; Dong, Wenjuan; Milewska, Aleksandra; Golda, Anna; Qi, Yonghe; Zhu, Quan K; Marasco, Wayne A; Baric, Ralph S; Sims, Amy C; Pyrc, Krzysztof; Li, Wenhui; Sui, Jianhua

2015-07-01

Human coronavirus (hCoV) HKU1 is one of six hCoVs identified to date and the only one with an unidentified cellular receptor. hCoV-HKU1 encodes a hemagglutinin-esterase (HE) protein that is unique to the group a betacoronaviruses (group 2a). The function of HKU1-HE remains largely undetermined. In this study, we examined binding of the S1 domain of hCoV-HKU1 spike to a panel of cells and found that the S1 could specifically bind on the cell surface of a human rhabdomyosarcoma cell line, RD. Pretreatment of RD cells with neuraminidase (NA) and trypsin greatly reduced the binding, suggesting that the binding was mediated by sialic acids on glycoproteins. However, unlike other group 2a CoVs, e.g., hCoV-OC43, for which 9-O-acetylated sialic acid (9-O-Ac-Sia) serves as a receptor determinant, HKU1-S1 bound with neither 9-O-Ac-Sia-containing glycoprotein(s) nor rat and mouse erythrocytes. Nonetheless, the HKU1-HE was similar to OC43-HE, also possessed sialate-O-acetylesterase activity, and acted as a receptor-destroying enzyme (RDE) capable of eliminating the binding of HKU1-S1 to RD cells, whereas the O-acetylesterase-inactive HKU1-HE mutant lost this capacity. Using primary human ciliated airway epithelial (HAE) cell cultures, the only in vitro replication model for hCoV-HKU1 infection, we confirmed that pretreatment of HAE cells with HE but not the enzymatically inactive mutant blocked hCoV-HKU1 infection. These results demonstrate that hCoV-HKU1 exploits O-Ac-Sia as a cellular attachment receptor determinant to initiate the infection of host cells and that its HE protein possesses the corresponding sialate-O-acetylesterase RDE activity. Human coronaviruses (hCoV) are important human respiratory pathogens. Among the six hCoVs identified to date, only hCoV-HKU1 has no defined cellular receptor. It is also unclear whether hemagglutinin-esterase (HE) protein plays a role in viral entry. In this study, we found that, similarly to other members of the group 2a CoVs, sialic

Effects of high peanut meal with different crude protein level supplemented with amino acids on performance, carcass traits and nitrogen retention of Chinese Yellow broilers.

PubMed

Gou, Z Y; Jiang, S Q; Jiang, Z Y; Zheng, C T; Li, L; Ruan, D; Chen, F; Lin, X J

2016-08-01

This study assessed the effects of feeding high peanut meal diets of reduced crude protein (CP) content supplemented with essential amino acids (EAA) on growth performance, carcass traits, biochemical indices in plasma, and nitrogen (N) retention of male and female Lingnan Yellow broilers from day 22 to day 42 of age. Each of four dietary treatments (19%, 18%, 17% or 16% CP, dietary CP level reduced by the reduced dietary peanut meal) contained six replicate pens with 35 birds of each sex (males and females with equal number), separately (1680 in total). The three diets with reduced CP were supplemented with 5 EAA to meet the requirements and provide the same levels as in the 19% CP diet. Average daily gain decreased and feed:gain ratio was worse in both sexes with reduced CP% (linear, p < 0.05). Dressing percentage increased as CP% decreased in males (linear, p < 0.05) and thigh muscle percentage reduced slightly in females (linear, p < 0.05). Abdominal fat percentage of males fed the 17% CP was the lowest (quadratic, p < 0.05). The plasma metabolic indices, concentrations of triglycerides and malondialdehyde, showed linear responses to reduced CP% (p < 0.05) with triglycerides increasing while malondialdehyde decreased. Plasma uric acid increased in females (linear, p < 0.05), but not in males, as CP% decreased. Efficiency of N retention increased and N excretion strikingly decreased with lower CP diets (p < 0.001), and both variables showed significant (p < 0.05) linear and quadratic effects. It is concluded that there was a limit to which dietary CP of broilers could be reduced without adverse effects. Dietary CP could be reduced to 17% for males and 18% for females (or 18% when fed together) between day 22 and day 42, if diets are supplemented with synthetic EAA. Journal of Animal Physiology and Animal Nutrition © 2015 Blackwell Verlag GmbH.

The alpha-fetoprotein third domain receptor binding fragment: in search of scavenger and associated receptor targets.

PubMed

Mizejewski, G J

2015-01-01

Recent studies have demonstrated that the carboxyterminal third domain of alpha-fetoprotein (AFP-CD) binds with various ligands and receptors. Reports within the last decade have established that AFP-CD contains a large fragment of amino acids that interact with several different receptor types. Using computer software specifically designed to identify protein-to-protein interaction at amino acid sequence docking sites, the computer searches identified several types of scavenger-associated receptors and their amino acid sequence locations on the AFP-CD polypeptide chain. The scavenger receptors (SRs) identified were CD36, CD163, Stabilin, SSC5D, SRB1 and SREC; the SR-associated receptors included the mannose, low-density lipoprotein receptors, the asialoglycoprotein receptor, and the receptor for advanced glycation endproducts (RAGE). Interestingly, some SR interaction sites were localized on the AFP-derived Growth Inhibitory Peptide (GIP) segment at amino acids #480-500. Following the detection studies, a structural subdomain analysis of both the receptor and the AFP-CD revealed the presence of epidermal growth factor (EGF) repeats, extracellular matrix-like protein regions, amino acid-rich motifs and dimerization subdomains. For the first time, it was reported that EGF-like sequence repeats were identified on each of the three domains of AFP. Thereafter, the localization of receptors on specific cell types were reviewed and their functions were discussed.

Inhibition of lysophosphatidic acid receptors 1 and 3 attenuates atherosclerosis development in LDL-receptor deficient mice.

PubMed

Kritikou, Eva; van Puijvelde, Gijs H M; van der Heijden, Thomas; van Santbrink, Peter J; Swart, Maarten; Schaftenaar, Frank H; Kröner, Mara J; Kuiper, Johan; Bot, Ilze

2016-11-24

Lysophosphatidic acid (LPA) is a natural lysophospholipid present at high concentrations within lipid-rich atherosclerotic plaques. Upon local accumulation in the damaged vessels, LPA can act as a potent activator for various types of immune cells through its specific membrane receptors LPA 1/3. LPA elicits chemotactic, pro-inflammatory and apoptotic effects that lead to atherosclerotic plaque progression. In this study we aimed to inhibit LPA signaling by means of LPA 1/3 antagonism using the small molecule Ki16425. We show that LPA 1/3 inhibition significantly impaired atherosclerosis progression. Treatment with Ki16425 also resulted in reduced CCL2 production and secretion, which led to less monocyte and neutrophil infiltration. Furthermore, we provide evidence that LPA 1/3 blockade enhanced the percentage of non-inflammatory, Ly6C low monocytes and CD4 + CD25 + FoxP3 + T-regulatory cells. Finally, we demonstrate that LPA 1/3 antagonism mildly reduced plasma LDL cholesterol levels. Therefore, pharmacological inhibition of LPA 1/3 receptors may prove a promising approach to diminish atherosclerosis development.

Obeticholic acid, a selective farnesoid X receptor agonist, regulates bile acid homeostasis in sandwich-cultured human hepatocytes.

PubMed

Zhang, Yuanyuan; Jackson, Jonathan P; St Claire, Robert L; Freeman, Kimberly; Brouwer, Kenneth R; Edwards, Jeffrey E

2017-08-01

Farnesoid X receptor (FXR) is a master regulator of bile acid homeostasis through transcriptional regulation of genes involved in bile acid synthesis and cellular membrane transport. Impairment of bile acid efflux due to cholangiopathies results in chronic cholestasis leading to abnormal elevation of intrahepatic and systemic bile acid levels. Obeticholic acid (OCA) is a potent and selective FXR agonist that is 100-fold more potent than the endogenous ligand chenodeoxycholic acid (CDCA). The effects of OCA on genes involved in bile acid homeostasis were investigated using sandwich-cultured human hepatocytes. Gene expression was determined by measuring mRNA levels. OCA dose-dependently increased fibroblast growth factor-19 (FGF-19) and small heterodimer partner (SHP) which, in turn, suppress mRNA levels of cholesterol 7-alpha-hydroxylase (CYP7A1), the rate-limiting enzyme for de novo synthesis of bile acids. Consistent with CYP7A1 suppression, total bile acid content was decreased by OCA (1 μmol/L) to 42.7 ± 20.5% relative to control. In addition to suppressing de novo bile acids synthesis, OCA significantly increased the mRNA levels of transporters involved in bile acid homeostasis. The bile salt excretory pump (BSEP), a canalicular efflux transporter, increased by 6.4 ± 0.8-fold, and the basolateral efflux heterodimer transporters, organic solute transporter α (OST α ) and OST β increased by 6.4 ± 0.2-fold and 42.9 ± 7.9-fold, respectively. The upregulation of BSEP and OST α and OST β, by OCA reduced the intracellular concentrations of d 8 -TCA, a model bile acid, to 39.6 ± 8.9% relative to control. These data demonstrate that OCA does suppress bile acid synthesis and reduce hepatocellular bile acid levels, supporting the use of OCA to treat bile acid-induced toxicity observed in cholestatic diseases. © 2017 Intercept Pharmaceuticals. Pharmacology Research & Perspectives published by John Wiley & Sons Ltd, British Pharmacological Society and

Branched Chain Amino Acids: Beyond Nutrition Metabolism.

PubMed

Nie, Cunxi; He, Ting; Zhang, Wenju; Zhang, Guolong; Ma, Xi

2018-03-23

Branched chain amino acids (BCAAs), including leucine (Leu), isoleucine (Ile), and valine (Val), play critical roles in the regulation of energy homeostasis, nutrition metabolism, gut health, immunity and disease in humans and animals. As the most abundant of essential amino acids (EAAs), BCAAs are not only the substrates for synthesis of nitrogenous compounds, they also serve as signaling molecules regulating metabolism of glucose, lipid, and protein synthesis, intestinal health, and immunity via special signaling network, especially phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) signal pathway. Current evidence supports BCAAs and their derivatives as the potential biomarkers of diseases such as insulin resistance (IR), type 2 diabetes mellitus (T2DM), cancer, and cardiovascular diseases (CVDs). These diseases are closely associated with catabolism and balance of BCAAs. Hence, optimizing dietary BCAA levels should have a positive effect on the parameters associated with health and diseases. This review focuses on recent findings of BCAAs in metabolic pathways and regulation, and underlying the relationship of BCAAs to related disease processes.

Branched Chain Amino Acids: Beyond Nutrition Metabolism

PubMed Central

2018-01-01

Branched chain amino acids (BCAAs), including leucine (Leu), isoleucine (Ile), and valine (Val), play critical roles in the regulation of energy homeostasis, nutrition metabolism, gut health, immunity and disease in humans and animals. As the most abundant of essential amino acids (EAAs), BCAAs are not only the substrates for synthesis of nitrogenous compounds, they also serve as signaling molecules regulating metabolism of glucose, lipid, and protein synthesis, intestinal health, and immunity via special signaling network, especially phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) signal pathway. Current evidence supports BCAAs and their derivatives as the potential biomarkers of diseases such as insulin resistance (IR), type 2 diabetes mellitus (T2DM), cancer, and cardiovascular diseases (CVDs). These diseases are closely associated with catabolism and balance of BCAAs. Hence, optimizing dietary BCAA levels should have a positive effect on the parameters associated with health and diseases. This review focuses on recent findings of BCAAs in metabolic pathways and regulation, and underlying the relationship of BCAAs to related disease processes. PMID:29570613

Gamma-Aminobutyric acid and benzodiazepine receptors in the kindling model of epilepsy: a quantitative radiohistochemical study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, C.; Pedersen, H.B.; McNamara, J.O.

1985-10-01

Quantitative radiohistochemistry was utilized to study alterations of gamma-aminobutyric acid (GABA) and benzodiazepine receptors in the kindling model of epilepsy. The radioligands used for GABA and benzodiazepine receptors were (TH) muscimol and (TH)flunitrazepam, respectively. GABA receptor binding was increased by 22% in fascia dentata of the hippocampal formation but not in neocortex or substantia nigra of kindled rats. Within fascia dentata, GABA receptor binding was increased to an equivalent extent in stratum granulosum and throughout stratum moleculare; no increase was found in dentate hilus or stratum lacunosummoleculare or stratum radiatum of CA1. The increased binding was present at 24 hrmore » but not at 28 days after the last kindled seizure. The direction, anatomic distribution, and time course of the increased GABA receptor binding were paralleled by increased benzodiazepine receptor binding. The anatomic distribution of the increased GABA receptor binding is consistent with a localization to somata and dendritic trees of dentate granule cells. The authors suggest that increased GABA and benzodiazepine receptor binding may contribute to enhanced inhibition of dentate granule cells demonstrated electrophysiologically in kindled animals.« less

Human skin levels of retinoic acid and cytochrome P-450-derived 4-hydroxyretinoic acid after topical application of retinoic acid in vivo compared to concentrations required to stimulate retinoic acid receptor-mediated transcription in vitro.

PubMed Central

Duell, E A; Aström, A; Griffiths, C E; Chambon, P; Voorhees, J J

1992-01-01

Metabolism of retinoic acid to a less active metabolite, 4-hydroxyretinoic acid, occurs via cytochrome P-450 isozyme(s). Effect of a pharmacological dose of retinoic acid on the level of retinoic acid in skin and on cytochrome P-450 activity was investigated. A cream containing 0.1% retinoic acid or cream alone was applied topically to adult human skin for four days under occlusion. Treated areas were removed by a keratome and a microsomal fraction was isolated from each biopsy. In vitro incubation of 3H-retinoic acid with microsomes from in vivo retinoic acid treated sites resulted in a 4.5-fold increase (P = 0.0001, n = 13) in its transformation to 4-hydroxyretinoic acid in comparison to in vitro incubations with microsomes from in vivo cream alone treated sites. This cytochrome P-450 mediated activity was oxygen- and NADPH-dependent and was inhibited 68% by 5 microM ketoconazole (P = 0.0035, n = 8) and 51% by carbon monoxide (P = 0.02, n = 6). Cotransfection of individual retinoic acid receptors (RARs) or retinoid X receptor-alpha (RXR-alpha) and a chloramphenicol acetyl transferase (CAT) reporter plasmid containing a retinoic acid responsive element into CV-1 cells was used to determine the ED50 values for stimulation of CAT activity by retinoic acid and its metabolites. Levels of all trans and 13-cis RA in RA-treated tissues were greater than the ED50 values determined for all three RARs with these compounds. Furthermore, the level of all trans RA was greater than the ED50 for RXR-alpha whereas the 4-OH RA level was greater than the ED50 for RAR-beta and RAR-gamma but less than for RAR-alpha and RXR-alpha. These data suggest that there are sufficient amounts of retinoic acid in treated skin to activate gene transcription over both RARs and RXR-alpha. PMID:1328295

Membrane omega-3 fatty acids modulate the oligomerisation kinetics of adenosine A2A and dopamine D2 receptors

NASA Astrophysics Data System (ADS)

Guixà-González, Ramon; Javanainen, Matti; Gómez-Soler, Maricel; Cordobilla, Begoña; Domingo, Joan Carles; Sanz, Ferran; Pastor, Manuel; Ciruela, Francisco; Martinez-Seara, Hector; Selent, Jana

2016-01-01

Membrane levels of docosahexaenoic acid (DHA), an essential omega-3 polyunsaturated fatty acid (ω-3 PUFA), are decreased in common neuropsychiatric disorders. DHA modulates key cell membrane properties like fluidity, thereby affecting the behaviour of transmembrane proteins like G protein-coupled receptors (GPCRs). These receptors, which have special relevance for major neuropsychiatric disorders have recently been shown to form dimers or higher order oligomers, and evidence suggests that DHA levels affect GPCR function by modulating oligomerisation. In this study, we assessed the effect of membrane DHA content on the formation of a class of protein complexes with particular relevance for brain disease: adenosine A2A and dopamine D2 receptor oligomers. Using extensive multiscale computer modelling, we find a marked propensity of DHA for interaction with both A2A and D2 receptors, which leads to an increased rate of receptor oligomerisation. Bioluminescence resonance energy transfer (BRET) experiments performed on living cells suggest that this DHA effect on the oligomerisation of A2A and D2 receptors is purely kinetic. This work reveals for the first time that membrane ω-3 PUFAs play a key role in GPCR oligomerisation kinetics, which may have important implications for neuropsychiatric conditions like schizophrenia or Parkinson’s disease.

Olfactory receptor Olfr544 responding to azelaic acid regulates glucagon secretion in α-cells of mouse pancreatic islets.

PubMed

Kang, NaNa; Bahk, Young Yil; Lee, NaHye; Jae, YoonGyu; Cho, Yoon Hee; Ku, Cheol Ryong; Byun, Youngjoo; Lee, Eun Jig; Kim, Min-Soo; Koo, JaeHyung

2015-05-08

Olfactory receptors (ORs) are extensively expressed in olfactory as well as non-olfactory tissues. Although many OR transcripts are expressed in non-olfactory tissues, only a few studies demonstrate the functional role of ORs. Here, we verified that mouse pancreatic α-cells express potential OR-mediated downstream effectors. Moreover, high levels of mRNA for the olfactory receptors Olfr543, Olfr544, Olfr545, and Olfr1349 were expressed in α-cells as assessed using RNA-sequencing, microarray, and quantitative real-time RT-PCR analyses. Treatment with dicarboxylic acids (azelaic acid and sebacic acid) increased intracellular Ca(2+) mobilization in pancreatic α-cells. The azelaic acid-induced Ca(2+) response as well as glucagon secretion was concentration- and time-dependent manner. Olfr544 was expressed in α-cells, and the EC50 value of azelaic acid to Olfr544 was 19.97 μM, whereas Olfr545 did not respond to azelaic acid. Our findings demonstrate that Olfr544 responds to azelaic acid to regulate glucagon secretion through Ca(2+) mobilization in α-cells of the mouse pancreatic islets, suggesting that Olfr544 may be an important therapeutic target for metabolic diseases. Copyright © 2015 Elsevier Inc. All rights reserved.

Molecular size of the gamma-aminobutyric acidA receptor purified from mammalian cerebral cortex.

PubMed

Mamalaki, C; Barnard, E A; Stephenson, F A

1989-01-01

The hydrodynamic behaviour of both the soluble and purified gamma-aminobutyric acidA (GABAA) receptor of bovine or rat cerebral cortex has been investigated in solution in Triton X-100 or in 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulphonate (CHAPS). In all the hydrodynamic separations made, it was found that the binding activities for GABA, benzodiazepine, and (where detectable) t-butylbicyclophosphorothionate comigrated. Conditions were established for gel exclusion chromatography and for sucrose density gradient velocity sedimentation that maintain the GABAA receptor in a nonaggregated form. Using these conditions, the molecular weight of the bovine GABAA receptor in the above-mentioned detergents was calculated using the H2O/2H2O method. A value of Mr 230,000-240,000 was calculated for the bovine pure GABAA receptor purified in sodium deoxycholate/Triton X-100 media. A value of Mr 284,000-290,000 was calculated for the nonaggregated bovine or rat cortex receptor in CHAPS, but the Stokes radius is smaller in the latter than in the former medium and the detergent binding in CHAPS is underestimated. Thus the deduced Mr, 240,000, is the best estimate by this method.

Binding effect of fluorescence labeled glycyrrhetinic acid with GA receptors in hepatocellular carcinoma cells.

PubMed

Sun, Yu-Qi; Dai, Chun-Mei; Zheng, Yan; Shi, Shu-Dan; Hu, Hai-Yang; Chen, Da-Wei

2017-11-01

Glycyrrhetinic acid (GA) is a natural active component from licorice, which is broadly used in traditional Chinese medicine. Lots of glycyrrhetinic acid receptors (GA-R) are proved to locate on the surface of liver cells. Many reports about the hepatocellular carcinoma (HCC) treatment were dependent on GA modified carriers. However, the reality of GA-R in HCC cells was not clear. In this paper, 18β-glycyrrhetinic acid (18β-GA) was labeled with fluorescence (FITC) by chemical synthesis. Together with the binding effect of fluorescence labeled glycyrrhetinic acid (FITC-GA), the competitive action of 18β-GA with GA-R was investigated in HCC cells. The results showed that in HepG2 cells, 18β-GA and FITC-GA presented similar cytotoxicity. The specific binding saturation of GA showed the dissociation constant (K d ) was 7.457±2.122pmol/L and the maximum binding counts (B max ) was 2.385±0.175pmol/2.5×10 6 cells, respectively. FITC-GA bound to cytomembrane specifically and 18β-GA competed to bind the sites significantly in HepG2 cells. Therefore, there is binding effect between fluorescence labeled GA and GA-R. The GA-R on HCC cells is confirmed as expected, which provides a useful reference of active target modified by GA and a novel approach for receptors and ligands study. Copyright © 2017 Elsevier Inc. All rights reserved.

Clinical review: Cardiovascular consequences of ovarian disruption: a focus on functional hypothalamic amenorrhea in physically active women.

PubMed

O'Donnell, Emma; Goodman, Jack M; Harvey, Paula J

2011-12-01

Evidence indicates that hypoestrogenemia is linked with accelerated progression of atherosclerosis. Premenopausal women presenting with ovulatory disruption due to functional hypothalamic amenorrhea (FHA) are characterized by hypoestrogenemia. One common and reversible form of FHA in association with energy deficiency is exercise-associated amenorrhea (EAA). Articles were found via PubMed search for both original and review articles based on peer review publications between 1974 and 2011 reporting on cardiovascular changes in women with FHA, with emphasis placed on women with EAA. Despite participation in regular exercise training, hypoestrogenic women with EAA demonstrate paradoxical changes in cardiovascular function, including endothelial dysfunction, a known permissive factor for the progression and development of atherosclerosis. Such alterations suggest that the beneficial effects of regular exercise training on vascular function are obviated in the face of hypoestrogenemia. The long-term cardiovascular consequences of altered vascular function in response to ovulatory disruption in women with EAA remain to be determined. Retrospective data, however, suggest premature development and progression of coronary artery disease in older premenopausal women reporting a history of hypothalamic ovulatory disruption. Importantly, in women with EAA, estrogen therapy, folic acid supplementation without change in menstrual status, and resumption of menses restores endothelial function. In this review, we focus on the influence of hypoestrogenemia in association with energy deficiency in mediating changes in cardiovascular function in women with EAA, including endothelial function, regional blood flow, lipid profile, and autonomic control of blood pressure, heart rate, and baroreflex sensitivity. The influence of exercise training is also considered. With the premenopausal years typically considered to be cardioprotective in association with normal ovarian function

Light-Induced Alterations in Striatal Neurochemical Profiles

NASA Technical Reports Server (NTRS)

Sroufe, Angela E.; Whittaker, J. A.; Patrickson, J. W.

1997-01-01

Much of our present knowledge regarding circadian rhythms and biological activity during space flight has been derived from those missions orbiting the Earth. During space missions, astronauts can become exposed to bright/dark cycles that vary considerably from those that entrain the mammalian biological timing system to the 24-hour cycle found on Earth. As a spacecraft orbits the Earth, the duration of the light/dark period experienced becomes a function of the time it takes to circumnavigate the planet which in turn depends upon the altitude of the craft. Orbiting the Earth at an altitude of 200-800 km provides a light/dark cycle lasting between 80 and 140 minutes, whereas a voyage to the moon or even another planet would provide a light condition of constant light. Currently, little is known regarding the effects of altered light/dark cycles on neurochemical levels within the central nervous system (CNS). Many biochemical, physiological and behavioral phenomena are under circadian control, governed primarily by the hypothalamic suprachiasmatic nucleus. As such, these phenomena are subject to influence by the environmental light/dark cycle. Circadian variations in locomotor and behavioral activities have been correlated to both the environmental light/dark cycle and to dopamine (DA) levels within the CNS. It has been postulated by Martin-Iverson et al. that DA's role in the control of motor activity is subject to modulation by circadian rhythms (CR), environmental lighting and excitatory amino acids (EAAs). In addition, DA and EAA receptor regulated pathways are involved in both the photic entrainment of CR and the control of motor activity. The cellular mechanisms by which DA and EAA-receptor ligands execute these functions, is still unclear. In order to help elucidate these mechanisms, we set out to determine the effects of altered environmental light/dark cycles on CNS neurotransmitter levels. In this study, we focused on the striatum, a region of the brain

ISOLATION AND CHARACTERIZATION OF AXOLOTL NPDC-1 AND ITS EFFECTS ON RETINOIC ACID RECEPTOR SIGNALING

PubMed Central

Theodosiou, Maria; Monaghan, James R; Spencer, Michael L; Voss, S Randal; Noonan, Daniel J

2009-01-01

Retinoic acid, a key morphogen in early vertebrate development and tissue regeneration, mediates its effects through the binding of receptors that act as ligand-induced transcription factors. These binding events function to recruit an array of transcription co-regulatory proteins to specific gene promoters. One such co-regulatory protein, neuronal proliferation and differentiation control-1 (NPDC-1), is broadly expressed during mammalian development and functions as an in vitro repressor of retinoic acid receptor (RAR)-mediated transcription. To obtain comparative and developmental insights about NPDC-1 function, we cloned the axolotl (Ambystoma mexicanum) orthologue and measured transcript abundances among tissues sampled during the embryonic and juvenile phases of development, and also during spinal cord regeneration. Structurally, the axolotl orthologue of NPDC-1 retained sequence identity to mammalian sequences in all functional domains. Functionally, we observed that axolotl NPDC-1 mRNA expression peaked late in embryogenesis, with highest levels of expression occurring during the time of limb development, a process regulated by retinoic acid signaling. Also similar to what has been observed in mammals, axolotl NPDC-1 directly interacts with axolotl RAR, modulates axolotl RAR DNA binding, and represses cell proliferation and axolotl RAR-mediated gene transcription. These data justify axolotl as a model to further investigate NPDC-1 and its role in regulating retinoic acid signaling. PMID:17331771

The Chemical Composition and Nitrogen Distribution of Chinese Yak (Maiwa) Milk

PubMed Central

Li, Haimei; Ma, Ying; Li, Qiming; Wang, Jiaqi; Cheng, Jinju; Xue, Jun; Shi, John

2011-01-01

The paper surveyed the chemical composition and nitrogen distribution of Maiwa yak milk, and compared the results with reference composition of cow milk. Compared to cow milk, yak milk was richer in protein (especially whey protein), essential amino acids, fat, lactose and minerals (except phosphorus). The contents of some nutrients (total protein, lactose, essential amino acids and casein) were higher in the warm season than in the cold season. Higher ratios of total essential amino acids/total amino acids (TEAA/TAA) and total essential amino acids/total non essential amino acids (TEAA/TNEAA) were found in the yak milk from the warm season. However its annual average ratio of EAA/TAA and that of EAA/NEAA were similar to those of cow milk. Yak milk was rich in calcium and iron (p < 0.05), and thus may serve as a nutritional ingredient with a potential application in industrial processing. PMID:21954332

An estrogen receptor β-selective agonist inhibits non-alcoholic steatohepatitis in preclinical models by regulating bile acid and xenobiotic receptors.

PubMed

Ponnusamy, Suriyan; Tran, Quynh T; Thiyagarajan, Thirumagal; Miller, Duane D; Bridges, Dave; Narayanan, Ramesh

2017-03-01

Non-alcoholic steatohepatitis (NASH) affects 8-10 million people in the US and up to 75% of obese individuals. Despite this, there are no approved oral therapeutics to treat NASH and therefore the need for novel approaches exists. The estrogen receptor β (ER-β)-selective agonist, β-LGND2, inhibits body weight and white adipose tissue, and increases metabolism, resulting in higher energy expenditure and thermogenesis. Due to favorable effects of β-LGND2 on obesity, we hypothesized that β-LGND2 will prevent NASH directly by reducing lipid accumulation in the liver or indirectly by favorably changing body composition. Male C57BL/6 mice fed with high fat diet (HFD) for 10 weeks or methionine choline-deficient diet for four weeks and treated with vehicle exhibited altered liver weights by twofold and increased serum transaminases by 2-6-folds. These changes were not observed in β-LGND2-treated animals. Infiltration of inflammatory cells and collagen deposits, an indication of fibrosis, were observed in the liver of mice fed with HFD for 10 weeks, which were effectively blocked by β-LGND2. Gene expression studies in the liver indicate that pregnane X receptor target genes were significantly increased by HFD, and the increase was inhibited by β-LGND2. On the other hand, metabolomics indicate that bile acid metabolites were significantly increased by β-LGND2. These studies demonstrate that an ER-β agonist might provide therapeutic benefits in NASH by directly modulating the function of xenobiotic and bile acid receptors in the liver, which have important functions in the liver, and indirectly, as demonstrated before, by inhibiting adiposity. Impact statement Over 75-90% of those classified as clinically obese suffer from co-morbidities, the most common of which is non-alcoholic steatohepatitis (NASH). While there are currently no effective treatment approaches for NASH, data presented here provide preliminary evidence that an estrogen receptor β-selective ligand

Removal of acidic or basic α-amino acids in water by poorly water soluble scandium complexes.

PubMed

Hayashi, Nobuyuki; Jin, Shigeki; Ujihara, Tomomi

2012-11-02

To recognize α-amino acids with highly polar side chains in water, poorly water soluble scandium complexes with both Lewis acidic and basic portions were synthesized as artificial receptors. A suspension of some of these receptor molecules in an α-amino acid solution could remove acidic and basic α-amino acids from the solution. The compound most efficient at preferentially removing basic α-amino acids (arginine, histidine, and lysine) was the receptor with 7,7'-[1,3-phenylenebis(carbonylimino)]bis(2-naphthalenesulfonate) as the ligand. The neutral α-amino acids were barely removed by these receptors. Removal experiments using a mixed amino acid solution generally gave results similar to those obtained using solutions containing a single amino acid. The results demonstrated that the scandium complex receptors were useful for binding acidic and basic α-amino acids.

The effect of albumin on podocytes: The role of the fatty acid moiety and the potential role of CD36 scavenger receptor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawluczyk, I.Z.A., E-mail: izap1@le.ac.uk; John Walls Renal Unit, Leicester General Hospital Leicester; Pervez, A.

Evidence is emerging that podocytes are able to endocytose proteins such as albumin using kinetics consistent with a receptor-mediated process. To date the role of the fatty acid moiety on albumin uptake kinetics has not been delineated and the receptor responsible for uptake is yet to be identified. Albumin uptake studies were carried out on cultured human podocytes exposed to FITC-labelled human serum albumin either carrying fatty acids (HSA{sub +FA}) or depleted of them (HSA{sub −FA}). Receptor-mediated endocytosis of FITC-HSA{sub +FA} over 60 min was 5 times greater than that of FITC-HSA{sub −FA}. 24 h exposure of podocytes to albuminmore » up-regulated nephrin expression and induced the activation of caspase-3. These effects were more pronounced in response to HSA{sub −FA.} Individually, anti-CD36 antibodies had no effect upon endocytosis of FITC-HSA. However, a cocktail of 2 antibodies reduced uptake by nearly 50%. Albumin endocytosis was enhanced in the presence of the CD36 specific inhibitor sulfo-N-succinimidyl oleate (SSO) while knock-down of CD36 using CD36siRNA had no effect on uptake. These data suggest that receptor-mediated endocytosis of albumin by podocytes is regulated by the fatty acid moiety, although, some of the detrimental effects are induced independently of it. CD36 does not play a direct role in the uptake of albumin. - Highlights: • The fatty acid moiety is essential for receptor mediated endocytosis of albumin. • Fatty acid depleted albumin is more pathogenic to podocytes. • CD36 is not directly involved in albumin uptake by podocytes.« less

A survey of the pyrabactin resistance-like abscisic acid receptor gene family in poplar.

PubMed

Yu, Jingling; Li, Hejuan; Peng, Yajing; Yang, Lei; Zhao, Fugeng; Luan, Sheng; Lan, Wenzhi

2017-08-03

The conserved PYR/PYL/RCAR family acts as abscisic acid (ABA) receptors for land plants to adapt to terrestrial environments. Our recent study reported that the exogenous overexpression of poplar PtPYRL1 and PtPYRL5, the PYR/PYL/RCAR orthologs, promoted the sensitivity of transgenic Arabidopsis to ABA responses. Here, we surveyed the PtPYRL family in poplar, and revealed that although the sequence and structure are relatively conserved among these receptors, PtPYRL members have differential expression patterns and the sensitivity to ABA or drought treatment, suggesting that PtPYRLs might be good candidates to a future biotechnological use to enhance poplar resistance to water-stress environments.

Ondansetron and granisetron binding orientation in the 5-HT(3) receptor determined by unnatural amino acid mutagenesis.

PubMed

Duffy, Noah H; Lester, Henry A; Dougherty, Dennis A

2012-10-19

The serotonin type 3 receptor (5-HT(3)R) is a ligand-gated ion channel found in the central and peripheral nervous systems. The 5-HT(3)R is a therapeutic target, and the clinically available drugs ondansetron and granisetron inhibit receptor activity. Their inhibitory action is through competitive binding to the native ligand binding site, although the binding orientation of the drugs at the receptor has been a matter of debate. Here we heterologously express mouse 5-HT(3)A receptors in Xenopus oocytes and use unnatural amino acid mutagenesis to establish a cation-π interaction for both ondansetron and granisetron to tryptophan 183 in the ligand binding pocket. This cation-π interaction establishes a binding orientation for both ondansetron and granisetron within the binding pocket.

Evolutionary Analysis of Functional Divergence among Chemokine Receptors, Decoy Receptors, and Viral Receptors

PubMed Central

Daiyasu, Hiromi; Nemoto, Wataru; Toh, Hiroyuki

2012-01-01

Chemokine receptors (CKRs) function in the inflammatory response and in vertebrate homeostasis. Decoy and viral receptors are two types of CKR homologs with modified functions from those of the typical CKRs. The decoy receptors are able to bind ligands without signaling. On the other hand, the viral receptors show constitutive signaling without ligands. We examined the sites related to the functional difference. At first, the decoy and viral receptors were each classified into five groups, based on the molecular phylogenetic analysis. A multiple amino acid sequence alignment between each group and the CKRs was then constructed. The difference in the amino acid composition between the group and the CKRs was evaluated as the Kullback–Leibler (KL) information value at each alignment site. The KL information value is considered to reflect the difference in the functional constraints at the site. The sites with the top 5% of KL information values were selected and mapped on the structure of a CKR. The comparisons with decoy receptor groups revealed that the detected sites were biased on the intracellular side. In contrast, the sites detected from the comparisons with viral receptor groups were found on both the extracellular and intracellular sides. More sites were found in the ligand binding pocket in the analyses of the viral receptor groups, as compared to the decoy receptor groups. Some of the detected sites were located in the GPCR motifs. For example, the DRY motif of the decoy receptors was often degraded, although the motif of the viral receptors was basically conserved. The observations for the viral receptor groups suggested that the constraints in the pocket region are loose and that the sites on the intracellular side are different from those for the decoy receptors, which may be related to the constitutive signaling activity of the viral receptors. PMID:22855685

Evolutionary Analysis of Functional Divergence among Chemokine Receptors, Decoy Receptors, and Viral Receptors.

PubMed

Daiyasu, Hiromi; Nemoto, Wataru; Toh, Hiroyuki

2012-01-01

Chemokine receptors (CKRs) function in the inflammatory response and in vertebrate homeostasis. Decoy and viral receptors are two types of CKR homologs with modified functions from those of the typical CKRs. The decoy receptors are able to bind ligands without signaling. On the other hand, the viral receptors show constitutive signaling without ligands. We examined the sites related to the functional difference. At first, the decoy and viral receptors were each classified into five groups, based on the molecular phylogenetic analysis. A multiple amino acid sequence alignment between each group and the CKRs was then constructed. The difference in the amino acid composition between the group and the CKRs was evaluated as the Kullback-Leibler (KL) information value at each alignment site. The KL information value is considered to reflect the difference in the functional constraints at the site. The sites with the top 5% of KL information values were selected and mapped on the structure of a CKR. The comparisons with decoy receptor groups revealed that the detected sites were biased on the intracellular side. In contrast, the sites detected from the comparisons with viral receptor groups were found on both the extracellular and intracellular sides. More sites were found in the ligand binding pocket in the analyses of the viral receptor groups, as compared to the decoy receptor groups. Some of the detected sites were located in the GPCR motifs. For example, the DRY motif of the decoy receptors was often degraded, although the motif of the viral receptors was basically conserved. The observations for the viral receptor groups suggested that the constraints in the pocket region are loose and that the sites on the intracellular side are different from those for the decoy receptors, which may be related to the constitutive signaling activity of the viral receptors.

Efficient modulation of γ-aminobutyric acid type A receptors by piperine derivatives.

PubMed

Schöffmann, Angela; Wimmer, Laurin; Goldmann, Daria; Khom, Sophia; Hintersteiner, Juliane; Baburin, Igor; Schwarz, Thomas; Hintersteininger, Michael; Pakfeifer, Peter; Oufir, Mouhssin; Hamburger, Matthias; Erker, Thomas; Ecker, Gerhard F; Mihovilovic, Marko D; Hering, Steffen

2014-07-10

Piperine activates TRPV1 (transient receptor potential vanilloid type 1 receptor) receptors and modulates γ-aminobutyric acid type A receptors (GABAAR). We have synthesized a library of 76 piperine analogues and analyzed their effects on GABAAR by means of a two-microelectrode voltage-clamp technique. GABAAR were expressed in Xenopus laevis oocytes. Structure-activity relationships (SARs) were established to identify structural elements essential for efficiency and potency. Efficiency of piperine derivatives was significantly increased by exchanging the piperidine moiety with either N,N-dipropyl, N,N-diisopropyl, N,N-dibutyl, p-methylpiperidine, or N,N-bis(trifluoroethyl) groups. Potency was enhanced by replacing the piperidine moiety by N,N-dibutyl, N,N-diisobutyl, or N,N-bistrifluoroethyl groups. Linker modifications did not substantially enhance the effect on GABAAR. Compound 23 [(2E,4E)-5-(1,3-benzodioxol-5-yl)-N,N-dipropyl-2,4-pentadienamide] induced the strongest modulation of GABAA (maximal GABA-induced chloride current modulation (IGABA-max = 1673% ± 146%, EC50 = 51.7 ± 9.5 μM), while 25 [(2E,4E)-5-(1,3-benzodioxol-5-yl)-N,N-dibutyl-2,4-pentadienamide] displayed the highest potency (EC50 = 13.8 ± 1.8 μM, IGABA-max = 760% ± 47%). Compound 23 induced significantly stronger anxiolysis in mice than piperine and thus may serve as a starting point for developing novel GABAAR modulators.

WHIM syndrome caused by a single amino acid substitution in the carboxy-tail of chemokine receptor CXCR4

PubMed Central

Liu, Qian; Chen, Haoqian; Ojode, Teresa; Gao, Xiangxi; Anaya-O'Brien, Sandra; Turner, Nicholas A.; Ulrick, Jean; DeCastro, Rosamma; Kelly, Corin; Cardones, Adela R.; Gold, Stuart H.; Hwang, Eugene I.; Wechsler, Daniel S.; Malech, Harry L.; Murphy, Philip M.

2012-01-01

WHIM syndrome is a rare, autosomal dominant, immunodeficiency disorder so-named because it is characterized by warts, hypogammaglobulinemia, infections, and myelokathexis (defective neutrophil egress from the BM). Gain-of-function mutations that truncate the C-terminus of the chemokine receptor CXCR4 by 10-19 amino acids cause WHIM syndrome. We have identified a family with autosomal dominant inheritance of WHIM syndrome that is caused by a missense mutation in CXCR4, E343K (1027G → A). This mutation is also located in the C-terminal domain, a region responsible for negative regulation of the receptor. Accordingly, like CXCR4R334X, the most common truncation mutation in WHIM syndrome, CXCR4E343K mediated approximately 2-fold increased signaling in calcium flux and chemotaxis assays relative to wild-type CXCR4; however, CXCR4E343K had a reduced effect on blocking normal receptor down-regulation from the cell surface. Therefore, in addition to truncating mutations in the C-terminal domain of CXCR4, WHIM syndrome may be caused by a single charge-changing amino acid substitution in this domain, E343K, that results in increased receptor signaling. PMID:22596258

Altered Levels of Zinc and N-methyl-D-aspartic Acid Receptor Underlying Multiple Organ Dysfunctions After Severe Trauma

PubMed Central

Wang, Guanghuan; Yu, Xiaojun; Wang, Dian; Xu, Xiaohu; Chen, Guang; Jiang, Xuewu

2015-01-01

Background Severe trauma can cause secondary multiple organ dysfunction syndrome (MODS) and death. Oxidative stress and/or excitatory neurotoxicity are considered as the final common pathway in nerve cell injuries. Zinc is the cofactor of the redox enzyme, and the effect of the excitatory neurotoxicity is related to N-methyl-D-aspartic acid receptor (NMDAR). Material/Methods We investigated the levels of zinc and brainstem NMDAR in a rabbit model of severe trauma. Zinc and serum biochemical profiles were determined. Immunohistochemistry was used to detect brainstem N-methyl-D-aspartic acid receptor 1 (NR1), N-methyl-D-aspartic acid receptor 2A (NR2A), and N-methyl-D-aspartic acid receptor 2B (NR2B) expression. Results Brain and brainstem Zn levels increased at 12 h, but serum Zn decreased dramatically after the trauma. NR1 in the brainstem dorsal regions increased at 6 h after injury and then decreased. NR2A in the dorsal regions decreased to a plateau at 12 h after trauma. The levels of NR2B were lowest in the death group in the brainstem. Serum zinc was positively correlated with NR2A and 2B and negatively correlated with zinc in the brain. Correlations were also found between the brainstem NR2A and that of the dorsal brainstem, as well as between brainstem NR2A and changes in NR2B. There was a negative correlation between zinc and NR2A. Conclusions Severe trauma led to an acute reduction of zinc enhancing oxidative stress and the changes of NMDAR causing the neurotoxicity of the nerve cells. This may be a mechanism for the occurrence of MODS or death after trauma. PMID:26335029

Medium-chain fatty acids as ligands for orphan G protein-coupled receptor GPR84.

PubMed

Wang, Jinghong; Wu, Xiaosu; Simonavicius, Nicole; Tian, Hui; Ling, Lei

2006-11-10

Free fatty acids (FFAs) play important physiological roles in many tissues as an energy source and as signaling molecules in various cellular processes. Elevated levels of circulating FFAs are associated with obesity, dyslipidemia, and diabetes. Here we show that GPR84, a previously orphan G protein-coupled receptor, functions as a receptor for medium-chain FFAs with carbon chain lengths of 9-14. Medium-chain FFAs elicit calcium mobilization, inhibit 3',5'-cyclic AMP production, and stimulate [35S]guanosine 5'-O-(3-thiotriphosphate) binding in a GPR84-dependent manner. The activation of GPR84 by medium-chain FFAs couples primarily to a pertussis toxin-sensitive G(i/o) pathway. In addition, we show that GPR84 is selectively expressed in leukocytes and markedly induced in monocytes/macrophages upon activation by lipopolysaccharide. Furthermore, we demonstrate that medium-chain FFAs amplify lipopolysaccharide-stimulated production of the proinflammatory cytokine interleukin-12 p40 through GPR84. Our results indicate a role for GPR84 in directly linking fatty acid metabolism to immunological regulation.

Endogenous fatty acid ethanolamides suppress nicotine-induced activation of mesolimbic dopamine neurons through nuclear receptors.

PubMed

Melis, Miriam; Pillolla, Giuliano; Luchicchi, Antonio; Muntoni, Anna Lisa; Yasar, Sevil; Goldberg, Steven R; Pistis, Marco

2008-12-17

Nicotine stimulates the activity of mesolimbic dopamine neurons, which is believed to mediate the rewarding and addictive properties of tobacco use. Accumulating evidence suggests that the endocannabinoid system might play a major role in neuronal mechanisms underlying the rewarding properties of drugs of abuse, including nicotine. Here, we investigated the modulation of nicotine effects by the endocannabinoid system on dopamine neurons in the ventral tegmental area with electrophysiological techniques in vivo and in vitro. We discovered that pharmacological inhibition of fatty acid amide hydrolase (FAAH), the enzyme that catabolizes fatty acid ethanolamides, among which the endocannabinoid anandamide (AEA) is the best known, suppressed nicotine-induced excitation of dopamine cells. Importantly, this effect was mimicked by the administration of the FAAH substrates oleoylethanolamide (OEA) and palmitoylethanolamide (PEA), but not methanandamide, the hydrolysis resistant analog of AEA. OEA and PEA are naturally occurring lipid signaling molecules structurally related to AEA, but devoid of affinity for cannabinoid receptors. They blocked the effects of nicotine by activation of the peroxisome proliferator-activated receptor-alpha (PPAR-alpha), a nuclear receptor transcription factor involved in several aspects of lipid metabolism and energy balance. Activation of PPAR-alpha triggered a nongenomic stimulation of tyrosine kinases, which might lead to phosphorylation and negative regulation of neuronal nicotinic acetylcholine receptors. These data indicate for the first time that the anorexic lipids OEA and PEA possess neuromodulatory properties as endogenous ligands of PPAR-alpha in the brain and provide a potential new target for the treatment of nicotine addiction.

QUANTITATION OF ABERRANT INTERLOCUS T-CELL RECEPTOR REARRANGEMENTS IN MOUSE THYMOCYTES AND THE EFFECT OF THE HERBICIDE 2,4- DICHLOROPHENOXYACETIC ACID

EPA Science Inventory

Quantitation of aberrant interlocus T-cell receptor rearrangements in mouse thymocytes and the effect of the herbicide 2,4- Dichlorophenoxyacetic acid

Small studies in human populations have suggested a correlation between the frequency of errors in antigen receptor gene a...

Identification of amino acids in the transmembrane and juxtamembrane domains of the platelet-derived growth factor receptor required for productive interaction with the bovine papillomavirus E5 protein.

PubMed

Petti, L M; Reddy, V; Smith, S O; DiMaio, D

1997-10-01

The bovine papillomavirus E5 protein forms a stable complex with the cellular platelet-derived growth factor (PDGF) beta receptor, resulting in receptor activation and cell transformation. Amino acids in both the putative transmembrane domain and extracytoplasmic carboxyl-terminal domain of the E5 protein appear important for PDGF receptor binding and activation. Previous analysis indicated that the transmembrane domain of the receptor was also required for complex formation and receptor activation. Here we analyzed receptor chimeras and point mutants to identify specific amino acids in the PDGF beta receptor required for productive interaction with the E5 protein. These receptor mutants were analyzed in murine Ba/F3 cells, which do not express endogenous receptor. Our results confirmed the importance of the transmembrane domain of the receptor for complex formation, receptor tyrosine phosphorylation, and mitogenic signaling in response to the E5 protein and established that the threonine residue in this domain is required for these activities. In addition, a positive charge in the extracellular juxtamembrane domain of the receptor was required for E5 interaction and signaling, whereas replacement of the wild-type lysine with either a neutral or acidic amino acid inhibited E5-induced receptor activation and transformation. All of the receptor mutants defective for activation by the E5 protein responded to acute treatment with PDGF and to stable expression of v-Sis, a form of PDGF. The required juxtamembrane lysine and transmembrane threonine are predicted to align precisely on the same face of an alpha helix packed in a left-handed coiled-coil geometry. These results establish that the E5 protein and v-Sis recognize distinct binding sites on the PDGF beta receptor and further clarify the nature of the interaction between the viral transforming protein and its cellular target.

Maslinic acid ameliorates NMDA receptor blockade-induced schizophrenia-like behaviors in mice.

PubMed

Jeon, Se Jin; Kim, Eunji; Lee, Jin Su; Oh, Hee Kyong; Zhang, Jiabao; Kwon, Yubeen; Jang, Dae Sik; Ryu, Jong Hoon

2017-11-01

Schizophrenia is a chronic psychotic disorder characterized by positive, negative, and cognitive symptoms. Primary treatments for schizophrenia relieve the positive symptoms but are less effective against the negative and cognitive symptoms. In the present study, we investigated whether maslinic acid, isolated from Syzygium aromaticum (clove), can ameliorate schizophrenia-like behaviors in mice induced by MK-801, an N-methyl-d-aspartate (NMDA) receptor antagonist. After maslinic acid treatment in the MK-801 model, we examined the behavioral alteration and signaling pathways in the prefrontal cortex. Mice were treated with maslinic acid (30 mg/kg), and their behaviors were evaluated through an array of behavioral tests. The effects of maslinic acid were also examined in the signaling pathways in the prefrontal cortex. A single administration of maslinic acid blocked the MK-801-induced hyperlocomotion and reversed the MK-801-induced sensorimotor gating deficit in the acoustic startle response test. In the social novelty preference test, maslinic acid ameliorated the social behavior deficits induced by MK-801. The MK-801-induced attention and recognition memory impairments were also alleviated by a single administration of maslinic acid. Furthermore, maslinic acid normalized the phosphorylation levels of Akt-GSK-3β and ERK-CREB in the prefrontal cortex. Overall, maslinic acid ameliorated the schizophrenia-like symptoms induced by MK-801, and these effects may be partly mediated through Akt-GSK-3β and ERK-CREB activation. These findings suggest that maslinic acid could be a candidate for the treatment of several symptoms of schizophrenia, including positive symptoms, sensorimotor gating disruption, social interaction deficits, and cognitive impairments. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Dominant Mutation in Nuclear Receptor Interacting Protein 1 Causes Urinary Tract Malformations via Dysregulation of Retinoic Acid Signaling.

PubMed

Vivante, Asaf; Mann, Nina; Yonath, Hagith; Weiss, Anna-Carina; Getwan, Maike; Kaminski, Michael M; Bohnenpoll, Tobias; Teyssier, Catherine; Chen, Jing; Shril, Shirlee; van der Ven, Amelie T; Ityel, Hadas; Schmidt, Johanna Magdalena; Widmeier, Eugen; Bauer, Stuart B; Sanna-Cherchi, Simone; Gharavi, Ali G; Lu, Weining; Magen, Daniella; Shukrun, Rachel; Lifton, Richard P; Tasic, Velibor; Stanescu, Horia C; Cavaillès, Vincent; Kleta, Robert; Anikster, Yair; Dekel, Benjamin; Kispert, Andreas; Lienkamp, Soeren S; Hildebrandt, Friedhelm

2017-08-01

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of CKD in the first three decades of life. However, for most patients with CAKUT, the causative mutation remains unknown. We identified a kindred with an autosomal dominant form of CAKUT. By whole-exome sequencing, we identified a heterozygous truncating mutation (c.279delG, p.Trp93fs*) of the nuclear receptor interacting protein 1 gene ( NRIP1 ) in all seven affected members. NRIP1 encodes a nuclear receptor transcriptional cofactor that directly interacts with the retinoic acid receptors (RARs) to modulate retinoic acid transcriptional activity. Unlike wild-type NRIP1, the altered NRIP1 protein did not translocate to the nucleus, did not interact with RAR α , and failed to inhibit retinoic acid-dependent transcriptional activity upon expression in HEK293 cells. Notably, we also showed that treatment with retinoic acid enhanced NRIP1 binding to RAR α RNA in situ hybridization confirmed Nrip1 expression in the developing urogenital system of the mouse. In explant cultures of embryonic kidney rudiments, retinoic acid stimulated Nrip1 expression, whereas a pan-RAR antagonist strongly reduced it. Furthermore, mice heterozygous for a null allele of Nrip1 showed a CAKUT-spectrum phenotype. Finally, expression and knockdown experiments in Xenopus laevis confirmed an evolutionarily conserved role for NRIP1 in renal development. These data indicate that dominant NRIP1 mutations can cause CAKUT by interference with retinoic acid transcriptional signaling, shedding light on the well documented association between abnormal vitamin A levels and renal malformations in humans, and suggest a possible gene-environment pathomechanism in this disease. Copyright © 2017 by the American Society of Nephrology.

Glycyrrhizic acid prevents high calorie diet-induced metabolic aberrations despite the suppression of peroxisome proliferator-activated receptor γ expression.

PubMed

Cheng, Hong Sheng; Yaw, Hui Ping; Ton, So Ha; Choy, Siew Mei; Kong, Joana Magdelene Xiao Fang; Abdul Kadir, Khalid

2016-09-01

To investigate the effects of glycyrrhizic acid supplementation on glucose and lipid metabolism in rodents consuming a high-fat, high-sucrose diet. Twenty-four male, 8-week old Sprague Dawley rats with an initial weight of 160 to 200 g were randomised into three groups (n = 6 for each group): groups A (standard rat chow), B (high-fat, high-sucrose diet), and C (high-fat, high-sucrose diet + 100 mg/kg/d of glycyrrhizic acid via oral administration). The rats were treated accordingly for 4 wk. Glycaemic parameters, lipid profile, stress hormones, and adiponectin levels were measured after the treatment. Relative gene expressions of peroxisome proliferator-activated receptor α and γ, lipoprotein lipase as well as gluconeogenic enzymatic activities in different tissues were also determined. Consumption of high-fat, high-sucrose diet triggered hyperglycaemia, insulin resistance, and dyslipidemia, which were effectively attenuated by supplementation with glycyrrhizic acid. Glycyrrhizic acid supplementation also effectively reduced circulating adrenaline, alleviated gluconeogenic enzymes overactivity, and promoted the upregulation of lipoprotein lipase expression in the cardiomyocytes and skeletal muscles. A high calorie diet also triggered hypoadiponectinaemia and suppression of peroxisome proliferator-activated receptor γ expression, which did not improve with glycyrrhizic acid treatment. Supplementation with glycyrrhizic acid could alleviate high calorie diet-induced glucose and lipid metabolic dysregulations by reducing circulatory stress hormones, normalizing gluconeogenic enzyme activities, and elevating muscular lipid uptake. The beneficial effects of these bioactivities outweighed the adverse effects caused by diet-induced repression of peroxisome proliferator-activated receptor γ expression, resulting in the maintenance of lipid and glucose homeostasis. Copyright © 2016 Elsevier Inc. All rights reserved.

Expression pattern of the type 1 sigma receptor in the brain and identity of critical anionic amino acid residues in the ligand-binding domain of the receptor.

PubMed

Seth, P; Ganapathy, M E; Conway, S J; Bridges, C D; Smith, S B; Casellas, P; Ganapathy, V

2001-07-25

The type 1 sigma receptor (sigmaR1) has been shown to participate in a variety of functions in the central nervous system. To identify the specific regions of the brain that are involved in sigmaR1 function, we analyzed the expression pattern of the receptor mRNA in the mouse brain by in situ hybridization. SigmaR1 mRNA was detectable primarily in the cerebral cortex, hippocampus, and Purkinje cells of cerebellum. To identify the critical anionic amino acid residues in the ligand-binding domain of sigmaR1, we employed two different approaches: chemical modification of anionic amino acid residues and site-directed mutagenesis. Chemical modification of anionic amino acids in sigmaR1 with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide reduced the ligand-binding activity markedly. Since it is known that a splice variant of this receptor which lacks exon 3 does not have the ability to bind sigma ligands, the ligand-binding domain with its critical anionic amino acid residues is likely to be present in or around the region coded by exon 3. Therefore, each of the anionic amino acids in this region was mutated individually and the influence of each mutation on ligand binding was assessed. These studies have identified two anionic amino acids, D126 and E172, that are obligatory for ligand binding. Even though the ligand-binding function was abolished by these two mutations, the expression of these mutants was normal at the protein level. These results show that sigmaR1 is expressed at high levels in specific areas of the brain that are involved in memory, emotion and motor functions. The results also provide important information on the chemical nature of the ligand-binding site of sigmaR1 that may be of use in the design of sigmaR1-specific ligands with potential for modulation of sigmaR1-related brain functions.

Examining the effect of dietary electrolyte balance, energy source, and length of feeding of nitrogen-free diets on ileal endogenous amino acid losses in broilers.

PubMed

Adedokun, S A; Pescatore, A J; Ford, M J; Jacob, J P; Helmbrecht, A

2017-09-01

The effect of dietary electrolyte balance (DEB), energy source (ES), and length of feeding of nitrogen-free diet (NFD) on ileal endogenous amino acid (EAA) loss in mg/kg dry matter intake (DMI) was evaluated in broiler chickens. In Experiment 1, 720 chickens consisting of 15 replicate cages with 6 chickens/replicate were used. Treatments were arranged in a 2 × 2 × 2 factorial and consisted of 4 NFD with 2 levels (low or high) of DEB and 2 ES [corn starch (CS) or dextrose (DX)], and 2 sampling time-points (diets were fed for either 72 h (d 16 to 19) or 120 h (d 16 to 21). Experiment 2 used 360 chickens in a 2 × 2 factorial arrangement of treatments with 2 levels (low or high) of DEB and 2 ES (CS or DX). Diets were fed for 72 h (d 18 to 21). All birds had access to feed and water on an ad libitum basis. Data were analyzed using the GLM procedure of SAS appropriate for a completely randomized design for a factorial arrangement of treatments. For Experiment 1, there were interactions (P < 0.05) between the 3 main factors for nitrogen and all the AA except Trp. Broilers that were fed DX-based NFD with high DEB for 72 h had the highest (P < 0.05) EAA losses. In Experiment 2, there was no interaction between DEB and ES except for His and Lys. When ileal EAA losses from birds fed the low DEB, CS-based NFD were used to standardize apparent ileal digestibility values from a previous study, there was no effect of length of feeding on standardized ileal AA digestibility values. In conclusion, DX-based NFD with high DEB increased endogenous AA loses. Despite differences in ileal EAA losses from CS-based NFD, standardized ileal AA digestibility values were not influenced by the length of feeding of NFD. Based on the results from these studies, NFD could be fed for 72 h without influencing SIAAD values. © 2017 Poultry Science Association Inc.

Ondansetron and Granisetron Binding Orientation in the 5-HT3 Receptor Determined by Unnatural Amino Acid Mutagenesis

PubMed Central

Duffy, Noah H.; Lester, Henry A.; Dougherty, Dennis A.

2012-01-01

The serotonin type 3 receptor (5-HT3R) is a ligand-gated ion channel that mediates fast synaptic transmission in the central and peripheral nervous systems. The 5-HT3R is a therapeutic target, and the clinically available drugs ondansetron and granisetron inhibit receptor activity. Their inhibitory action is through competitive binding to the native ligand binding site, although the binding orientation of the drugs at the receptor has been a matter of debate. Here we heterologously express mouse 5-HT3A receptors in Xenopus oocytes and use unnatural amino acid mutagenesis to establish a cation-π interaction for both ondansetron and granisetron to tryptophan 183 in the ligand binding pocket. This cation-π interaction establishes a binding orientation for both ondansetron and granisetron within the binding pocket. PMID:22873819

G-protein-coupled receptors for neurotransmitter amino acids: C-terminal tails, crowded signalosomes.

PubMed Central

El Far, Oussama; Betz, Heinrich

2002-01-01

G-protein-coupled receptors (GPCRs) represent a superfamily of highly diverse integral membrane proteins that transduce external signals to different subcellular compartments, including nuclei, via trimeric G-proteins. By differential activation of diffusible G(alpha) and membrane-bound G(beta)gamma subunits, GPCRs might act on both cytoplasmic/intracellular and plasma-membrane-bound effector systems. The coupling efficiency and the plasma membrane localization of GPCRs are regulated by a variety of interacting proteins. In this review, we discuss recently disclosed protein interactions found with the cytoplasmic C-terminal tail regions of two types of presynaptic neurotransmitter receptors, the group III metabotropic glutamate receptors and the gamma-aminobutyric acid type-B receptors (GABA(B)Rs). Calmodulin binding to mGluR7 and other group III mGluRs may provide a Ca(2+)-dependent switch for unidirectional (G(alpha)) versus bidirectional (G(alpha) and G(beta)gamma) signalling to downstream effector proteins. In addition, clustering of mGluR7 by PICK1 (protein interacting with C-kinase 1), a polyspecific PDZ (PSD-95/Dlg1/ZO-1) domain containing synaptic organizer protein, sheds light on how higher-order receptor complexes with regulatory enzymes (or 'signalosomes') could be formed. The interaction of GABA(B)Rs with the adaptor protein 14-3-3 and the transcription factor ATF4 (activating transcription factor 4) suggests novel regulatory pathways for G-protein signalling, cytoskeletal reorganization and nuclear gene expression: processes that may all contribute to synaptic plasticity. PMID:12006104

Structural analysis of binding functionality of folic acid-PEG dendrimers against folate receptor.

PubMed

Sampogna-Mireles, Diana; Araya-Durán, Ingrid D; Márquez-Miranda, Valeria; Valencia-Gallegos, Jesús A; González-Nilo, Fernando D

2017-03-01

Dendrimers functionalized with folic acid (FA) are drug delivery systems that can selectively target cancer cells with folate receptors (FR-α) overexpression. Incorporation of polyethylene glycol (PEG) can enhance dendrimers solubility and pharmacokinetics, but ligand-receptor binding must not be affected. In this work we characterized, at atomic level, the binding functionality of conventional site-specific dendrimers conjugated with FA with PEG 750 or PEG 3350 as a linker. After Molecular Dynamics simulation, we observed that both PEG's did not interfere over ligand-receptor binding functionality. Although binding kinetics could be notably affected, the folate fragment from both dendrimers remained exposed to the solvent before approaching selectively to FR-α. PEG 3350 provided better solubility and protection from enzymatic degradation to the dendrimer than PEG 750. Also, FA-PEG3350 dendrimer showed a slightly better interaction with FR-α than FA-PEG750 dendrimer. Therefore, theoretical evidence supports that both dendrimers are suitable as drug delivery systems for cancer therapies. Copyright © 2017 Elsevier Inc. All rights reserved.

Inhibition of strigolactone receptors by N-phenylanthranilic acid derivatives: Structural and functional insights.

PubMed

Hamiaux, Cyril; Drummond, Revel S M; Luo, Zhiwei; Lee, Hui Wen; Sharma, Prachi; Janssen, Bart J; Perry, Nigel B; Denny, William A; Snowden, Kimberley C

2018-04-27

The strigolactone (SL) family of plant hormones regulates a broad range of physiological processes affecting plant growth and development and also plays essential roles in controlling interactions with parasitic weeds and symbiotic fungi. Recent progress elucidating details of SL biosynthesis, signaling, and transport offers many opportunities for discovering new plant-growth regulators via chemical interference. Here, using high-throughput screening and downstream biochemical assays, we identified N -phenylanthranilic acid derivatives as potent inhibitors of the SL receptors from petunia (DAD2), rice (OsD14), and Arabidopsis (AtD14). Crystal structures of DAD2 and OsD14 in complex with inhibitors further provided detailed insights into the inhibition mechanism, and in silico modeling of 19 other plant strigolactone receptors suggested that these compounds are active across a large range of plant species. Altogether, these results provide chemical tools for investigating SL signaling and further define a framework for structure-based approaches to design and validate optimized inhibitors of SL receptors for specific plant targets. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Regulating the Efficacy of Inhibition Through Trafficking of γ-Aminobutyric Acid Type A Receptors.

PubMed

Vien, Thuy N; Moss, Stephen J; Davies, Paul A

2016-11-01

Trafficking of anesthetic-sensitive receptors within the plasma membrane, or from one cellular component to another, occurs continuously. Changes in receptor trafficking have implications in altering anesthetic sensitivity. γ-Aminobutyric acid type A receptors (GABAARs) are anion-permeable ion channels and are the major class of receptor in the adult mammalian central nervous system that mediates inhibition. GABAergic signaling allows for precise synchronized firing of action potentials within brain circuits that is critical for cognition, behavior, and consciousness. This precision depends upon tightly controlled trafficking of GABAARs into the membrane. General anesthetics bind to and allosterically enhance GABAARs by prolonging the open state of the receptor and thereby altering neuronal and brain circuit activity. Subunit composition and GABAAR localization strongly influence anesthetic end points; therefore, changes in GABAAR trafficking could have significant consequences to anesthetic sensitivity. GABAARs are not static membrane structures but are in a constant state of flux between extrasynaptic and synaptic locations and are continually endocytosed and recycled from and to the membrane. Neuronal activity, posttranslational modifications, and some naturally occurring and synthetic compounds can influence the expression and trafficking of GABAARs. In this article, we review GABAARs, their trafficking, and how phosphorylation of GABAAR subunits can influence the surface expression and function of the receptor. Ultimately, alterations of GABAAR trafficking could modify anesthetic end points, both unintentionally through pathologic processes but potentially as a therapeutic target to adjust anesthetic-sensitive GABAARs.

Receptor binding proteins of Listeria monocytogenes bacteriophages A118 and P35 recognize serovar-specific teichoic acids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bielmann, Regula; Habann, Matthias; Eugster, Marcel R.

Adsorption of a bacteriophage to the host requires recognition of a cell wall-associated receptor by a receptor binding protein (RBP). This recognition is specific, and high affinity binding is essential for efficient virus attachment. The molecular details of phage adsorption to the Gram-positive cell are poorly understood. We present the first description of receptor binding proteins and a tail tip structure for the siphovirus group infecting Listeria monocytogenes. The host-range determining factors in two phages, A118 and P35 specific for L. monocytogenes serovar 1/2 have been determined. Two proteins were identified as RBPs in phage A118. Rhamnose residues in wallmore » teichoic acids represent the binding ligands for both proteins. In phage P35, protein gp16 could be identified as RBP and the role of both rhamnose and N-acetylglucosamine in phage adsorption was confirmed. Immunogold-labeling and transmission electron microscopy allowed the creation of a topological model of the A118 phage tail. - Highlights: • We present the first description of receptor binding proteins and a tail tip structure for the Siphovirus group infecting Listeria monocytogenes. • The host-range determining factors in two phages, A118 and P35 specific for L. monocytogenes serovar 1/2 have been determined. • Rhamnose residues in wall teichoic acids represent the binding ligands for both receptor binding proteins in phage A118. • Rhamnose and N-acetylglucosamine are required for adsorption of phage P35. • We preset a topological model of the A118 phage tail.« less

Evidence for a central 5-hydroxytryptamine receptor stimulation by lysergic acid diethylamide

PubMed Central

Andén, N.-E.; Corrodi, H.; Fuxe, K.; Hökfelt, T.

1968-01-01

1. Lysergic acid diethylamide (LSD) and the 5-hydroxytryptamine (5-HT) precursor, 5-hydroxytryptophan produced similar functional effects in rat spinal cord and brain to the 5-hydroxytryptamine precursor 5-hydroxytryptophan, which indicates that LSD stimulates central 5-HT receptors. 2. By means of combined histochemical and biochemical techniques it was found that LSD reduced the turnover rate of brain and spinal cord 5-HT, studied after inhibition of the tryptophan hydroxylase by α-propyldopacetamide. The turnover of brain noradrenaline but not dopamine was somewhat accelerated. 3. The functional and chemical effects by LSD were related to dose and to time. They were not observed after the LSD analogues 2-bromo-LSD and methylsergide. 4. The retardation of the 5-HT turnover by LSD may be due to negative feed-back mechanisms evoked by direct stimulation of the central 5-HT receptors. ImagesFIG. 1FIG. 2 PMID:5302837

Efficient Modulation of γ-Aminobutyric Acid Type A Receptors by Piperine Derivatives

PubMed Central

2014-01-01

Piperine activates TRPV1 (transient receptor potential vanilloid type 1 receptor) receptors and modulates γ-aminobutyric acid type A receptors (GABAAR). We have synthesized a library of 76 piperine analogues and analyzed their effects on GABAAR by means of a two-microelectrode voltage-clamp technique. GABAAR were expressed in Xenopus laevis oocytes. Structure–activity relationships (SARs) were established to identify structural elements essential for efficiency and potency. Efficiency of piperine derivatives was significantly increased by exchanging the piperidine moiety with either N,N-dipropyl, N,N-diisopropyl, N,N-dibutyl, p-methylpiperidine, or N,N-bis(trifluoroethyl) groups. Potency was enhanced by replacing the piperidine moiety by N,N-dibutyl, N,N-diisobutyl, or N,N-bistrifluoroethyl groups. Linker modifications did not substantially enhance the effect on GABAAR. Compound 23 [(2E,4E)-5-(1,3-benzodioxol-5-yl)-N,N-dipropyl-2,4-pentadienamide] induced the strongest modulation of GABAA (maximal GABA-induced chloride current modulation (IGABA-max = 1673% ± 146%, EC50 = 51.7 ± 9.5 μM), while 25 [(2E,4E)-5-(1,3-benzodioxol-5-yl)-N,N-dibutyl-2,4-pentadienamide] displayed the highest potency (EC50 = 13.8 ± 1.8 μM, IGABA-max = 760% ± 47%). Compound 23 induced significantly stronger anxiolysis in mice than piperine and thus may serve as a starting point for developing novel GABAAR modulators. PMID:24905252

ω3-Polyunsaturated fatty acids for heart failure: Effects of dose on efficacy and novel signaling through free fatty acid receptor 4.

PubMed

O'Connell, Timothy D; Block, Robert C; Huang, Shue P; Shearer, Gregory C

2017-02-01

Heart failure (HF) affects 5.7 million in the U.S., and despite well-established pharmacologic therapy, the 5-year mortality rate remains near 50%. Furthermore, the mortality rate for HF has not declined in years, highlighting the need for new therapeutic options. Omega-3 polyunsaturated fatty acids (ω3-PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are important regulators of cardiovascular health. However, questions of efficacy and mechanism of action have made the use of ω3-PUFAs in all cardiovascular disease (CVD) controversial. Here, we review recent studies in animal models of HF indicating that ω3-PUFAs, particularly EPA, are cardioprotective, with the results indicating a threshold for efficacy. We also examine clinical studies suggesting that ω3-PUFAs improve outcomes in patients with HF. Due to the relatively small number of clinical studies of ω3-PUFAs in HF, we discuss EPA concentration-dependency on outcomes in clinical trials of CVD to gain insight into the perceived questionable efficacy of ω3-PUFAs clinically, with the results again indicating a threshold for efficacy. Ultimately, we suggest that the main failing of ω3-PUFAs in clinical trials might be a failure to reach a therapeutically effective concentration. We also examine mechanistic studies suggesting that ω3-PUFAs signal through free fatty acid receptor 4 (Ffar4), a G-protein coupled receptor (GPR) for long-chain fatty acids (FA), thereby identifying an entirely novel mechanism of action for ω3-PUFA mediated cardioprotection. Finally, based on mechanistic animal studies suggesting that EPA prevents interstitial fibrosis and diastolic dysfunction, we speculate about a potential benefit for EPA-Ffar4 signaling in heart failure preserved with ejection fraction. Copyright © 2016. Published by Elsevier Ltd.

Fatty acid receptor GPR120: a novel marker for human melanoma.

PubMed

Kleemann, Johannes; Hrgovic, Igor; Ter-Nedden, Jan; Kleimann, Pia; Steinhorst, Katja; Härle, Katja; Müller, Jutta; Kaufmann, Roland; Meissner, Markus; Kippenberger, Stefan

2018-03-21

The correlation between ultraviolet radiation of the skin and melanoma incidence in humans is well established. Interestingly, epidemiologic data suggest also a correlation to an increased BMI pointing to metabolic trigger factors in melanoma pathogenesis. To substantiate this connection, we studied the expression of G-protein-coupled receptor 120 (GPR120), a receptor sensitive to unsaturated long-chain free fatty acids in melanoma tissues. One-hundred fourteen tissue sections histologically confirmed as nevi (n=32), primary melanoma (n=39), and melanoma metastasis (n=43) were immunohistochemically stained against GPR120. The staining was evaluated by three trained dermatopathologists and independently scored. Compared with nevi, primary melanoma and melanoma metastasis showed significantly higher levels of GPR120 staining. Only three out of 32 nevi showed strong GPR120 expression [median immunoreactivity-scoring system (IRS) score: 1, range: 0-10], whereas in primary melanomas 14 out of 39 were highly GPR120-positive (median IRS score: 7, range: 0-12) and in melanoma metastasis 27 out of 43 were highly GPR120-positive (median IRS score: 9, range: 0-12). GPR120 expression and tumor thickness (mm) show a statistically significant correlation in primary melanoma (P=0.011). Moreover, GPR120-positive staining was found throughout the epidermis and in sebaceous and sweat glands, which is yet not described. This study identified GPR120 as a novel marker for melanoma, indicating that melanoma cells are sensitive to free fatty acids. It is tempting to speculate that pharmacologically interfering with GPR120 signaling might improve melanoma therapy.

LAPTM4b recruits the LAT1-4F2hc Leu transporter to lysosomes and promotes mTORC1 activation.

PubMed

Milkereit, Ruth; Persaud, Avinash; Vanoaica, Liviu; Guetg, Adriano; Verrey, Francois; Rotin, Daniela

2015-05-22

Mammalian target of rapamycin 1 (mTORC1), a master regulator of cellular growth, is activated downstream of growth factors, energy signalling and intracellular essential amino acids (EAAs) such as Leu. mTORC1 activation occurs at the lysosomal membrane, and involves V-ATPase stimulation by intra-lysosomal EAA (inside-out activation), leading to activation of the Ragulator, RagA/B-GTP and mTORC1 via Rheb-GTP. How Leu enters the lysosomes is unknown. Here we identified the lysosomal protein LAPTM4b as a binding partner for the Leu transporter, LAT1-4F2hc (SLC7A5-SLAC3A2). We show that LAPTM4b recruits LAT1-4F2hc to lysosomes, leading to uptake of Leu into lysosomes, and is required for mTORC1 activation via V-ATPase following EAA or Leu stimulation. These results demonstrate a functional Leu transporter at the lysosome, and help explain the inside-out lysosomal activation of mTORC1 by Leu/EAA.

Functional analysis of free fatty acid receptor GPR120 in human eosinophils: implications in metabolic homeostasis.

PubMed

Konno, Yasunori; Ueki, Shigeharu; Takeda, Masahide; Kobayashi, Yoshiki; Tamaki, Mami; Moritoki, Yuki; Oyamada, Hajime; Itoga, Masamichi; Kayaba, Hiroyuki; Omokawa, Ayumi; Hirokawa, Makoto

2015-01-01

Recent evidence has shown that eosinophils play an important role in metabolic homeostasis through Th2 cytokine production. GPR120 (FFA4) is a G protein-coupled receptor (GPCR) for long-chain fatty acids that functions as a regulator of physiological energy metabolism. In the present study, we aimed to investigate whether human eosinophils express GPR120 and, if present, whether it possesses a functional capacity on eosinophils. Eosinophils isolated from peripheral venous blood expressed GPR120 at both the mRNA and protein levels. Stimulation with a synthetic GPR120 agonist, GW9508, induced rapid down-regulation of cell surface expression of GPR120, suggesting ligand-dependent receptor internalization. Although GPR120 activation did not induce eosinophil chemotactic response and degranulation, we found that GW9508 inhibited eosinophil spontaneous apoptosis and Fas receptor expression. The anti-apoptotic effect was attenuated by phosphoinositide 3-kinase (PI3K) inhibitors and was associated with inhibition of caspase-3 activity. Eosinophil response investigated using ELISpot assay indicated that stimulation with a GPR120 agonist induced IL-4 secretion. These findings demonstrate the novel functional properties of fatty acid sensor GPR120 on human eosinophils and indicate the previously unrecognized link between nutrient metabolism and the immune system.

Glucuronic acid and the ethanol metabolite ethyl-glucuronide cause Toll-like receptor 4 activation and enhanced pain

PubMed Central

Lewis, Susannah S.; Hutchinson, Mark R.; Zhang, Yingning; Hund, Dana K.; Maier, Steven F.; Rice, Kenner C.; Watkins, Linda R.

2013-01-01

We have previously observed that the non-opioid morphine metabolite, morphine-3-glucuronide, enhances pain via a toll-like receptor 4 (TLR4) dependent mechanism. The present studies were undertaken to determine whether TLR4-dependent pain enhancement generalizes to other classes of glucuronide metabolites. In silico modeling predicted that glucuronic acid alone and ethyl glucuronide, a minor but long-lasting ethanol metabolite, would dock to the same MD-2 portion of the TLR4 receptor complex previously characterized as the docking site for morphine-3-glucuronide. Glucuronic acid, ethyl glucuronide and ethanol all caused an increase in TLR4-dependent reporter protein expression in a cell line transfected with TLR4 and associated co-signaling molecules. Glucuronic acid-, ethyl glucuronide-, and ethanol-induced increases in TLR4 signaling were blocked by the TLR4 antagonists LPS-RS and (+)-naloxone. Glucuronic acid and ethyl glucuronide both caused allodynia following intrathecal injection in rats, which was blocked by intrathecal co-administration of the TLR4 antagonist LPS-RS. The finding that ethyl glucuronide can cause TLR4-dependent pain could have implications for human conditions such as hangover headache and alcohol withdrawal hyperalgesia, as well as suggesting that other classes of glucuronide metabolites could have similar effects. PMID:23348028

Acidic tumor microenvironment and pH-sensing G protein-coupled receptors.

PubMed

Justus, Calvin R; Dong, Lixue; Yang, Li V

2013-12-05

The tumor microenvironment is acidic due to glycolytic cancer cell metabolism, hypoxia, and deficient blood perfusion. It is proposed that acidosis in the tumor microenvironment is an important stress factor and selection force for cancer cell somatic evolution. Acidic pH has pleiotropic effects on the proliferation, migration, invasion, metastasis, and therapeutic response of cancer cells and the function of immune cells, vascular cells, and other stromal cells. However, the molecular mechanisms by which cancer cells and stromal cells sense and respond to acidic pH in the tumor microenvironment are poorly understood. In this article the role of a family of pH-sensing G protein-coupled receptors (GPCRs) in tumor biology is reviewed. Recent studies show that the pH-sensing GPCRs, including GPR4, GPR65 (TDAG8), GPR68 (OGR1), and GPR132 (G2A), regulate cancer cell metastasis and proliferation, immune cell function, inflammation, and blood vessel formation. Activation of the proton-sensing GPCRs by acidosis transduces multiple downstream G protein signaling pathways. Since GPCRs are major drug targets, small molecule modulators of the pH-sensing GPCRs are being actively developed and evaluated. Research on the pH-sensing GPCRs will continue to provide important insights into the molecular interaction between tumor and its acidic microenvironment and may identify new targets for cancer therapy and chemoprevention.

Kynurenic acid as an Antagonist of α7 Nicotinic Acetylcholine Receptors in the Brain: Facts and Challenges

PubMed Central

Albuquerque, Edson X.; Schwarcz, Robert

2013-01-01

Kynurenic acid (KYNA), a major tryptophan metabolite, is a glutamate receptor antagonist, which is also reported to inhibit α7 nicotinic acetylcholine receptors (α7nAChRs). Due to variations in experimental approaches, controversy has arisen regarding the ability of KYNA to directly influence α7nAChR function. Here we summarize current concepts of KYNA neurobiology and review evidence pertaining to the proposed role of KYNA as an endogenous modulator of α7nAChRs and synaptic transmission. As dysfunction of α7nAChRs plays a major role in the pathophysiology of central nervous system disorders, elucidation of KYNA's action on this receptor subtype has significant therapeutic implications. PMID:23270993

Inhibition of epidermal growth factor receptor by ferulic acid and 4-vinylguaiacol in human breast cancer cells.

PubMed

Sudhagar, S; Sathya, S; Anuradha, R; Gokulapriya, G; Geetharani, Y; Lakshmi, B S

2018-02-01

To examine the potential of ferulic acid and 4-vinylguaiacol for inhibiting epidermal growth factor receptor (EGFR) in human breast cancer cells in vitro. Ferulic acid and 4-vinylguaiacol limit the EGF (epidermal growth factor)-induced breast cancer proliferation and new DNA synthesis. Western blot analysis revealed both ferulic acid and 4-vinylguaiacol exhibit sustained inhibition of EGFR activation through down-regulation of Tyr 1068 autophosphorylation. Molecular docking analysis shows ferulic acid forming hydrogen bond interaction with Lys 745 and Met 793 whereas, 4-vinylguaiacol forms two hydrogen bonds with Phe 856 and exhibits stronger hydrophobic interactions with multiple amino acid residues at the EGFR kinase domain. Ferulic acid and 4-vinylguaiacol could serve as a potential structure for the development of new small molecule therapeutics against EGFR.

Branched-Chain Amino Acid Ingestion Stimulates Muscle Myofibrillar Protein Synthesis following Resistance Exercise in Humans

PubMed Central

Jackman, Sarah R.; Witard, Oliver C.; Philp, Andrew; Wallis, Gareth A.; Baar, Keith; Tipton, Kevin D.

2017-01-01

The ingestion of intact protein or essential amino acids (EAA) stimulates mechanistic target of rapamycin complex-1 (mTORC1) signaling and muscle protein synthesis (MPS) following resistance exercise. The purpose of this study was to investigate the response of myofibrillar-MPS to ingestion of branched-chain amino acids (BCAAs) only (i.e., without concurrent ingestion of other EAA, intact protein, or other macronutrients) following resistance exercise in humans. Ten young (20.1 ± 1.3 years), resistance-trained men completed two trials, ingesting either 5.6 g BCAA or a placebo (PLA) drink immediately after resistance exercise. Myofibrillar-MPS was measured during exercise recovery with a primed, constant infusion of L-[ring13C6] phenylalanine and collection of muscle biopsies pre and 4 h-post drink ingestion. Blood samples were collected at time-points before and after drink ingestion. Western blotting was used to measure the phosphorylation status of mTORC1 signaling proteins in biopsies collected pre, 1-, and 4 h-post drink. The percentage increase from baseline in plasma leucine (300 ± 96%), isoleucine (300 ± 88%), and valine (144 ± 59%) concentrations peaked 0.5 h-post drink in BCAA. A greater phosphorylation status of S6K1Thr389 (P = 0.017) and PRAS40 (P = 0.037) was observed in BCAA than PLA at 1 h-post drink ingestion. Myofibrillar-MPS was 22% higher (P = 0.012) in BCAA (0.110 ± 0.009%/h) than PLA (0.090 ± 0.006%/h). Phenylalanine Ra was ~6% lower in BCAA (18.00 ± 4.31 μmol·kgBM−1) than PLA (21.75 ± 4.89 μmol·kgBM−1; P = 0.028) after drink ingestion. We conclude that ingesting BCAAs alone increases the post-exercise stimulation of myofibrillar-MPS and phosphorylation status mTORC1 signaling. PMID:28638350

Anti-Inflammatory and Insulin-Sensitizing Effects of Free Fatty Acid Receptors.

PubMed

Miyamoto, Junki; Kasubuchi, Mayu; Nakajima, Akira; Kimura, Ikuo

2017-01-01

Chronic low-grade inflammation in macrophages and adipose tissues can promote the development of obesity and type 2 diabetes. Free fatty acids (FFAs) have important roles in various tissues, acting as both essential energy sources and signaling molecules. FFA receptors (FFARs) can modulate inflammation in various types of cells and tissues; however the underlying mechanisms mediating these effects are unclear. FFARs are activated by specific FFAs; for example, GPR40 and GPR120 are activated by medium and long chain FFAs, GPR41 and GPR43 are activated by short chain FFAs, and GPR84 is activated by medium-chain FFAs. To date, a number of studies associated with the physiological functions of G protein-coupled receptors (GPCRs) have reported that these GPCRs are expressed in various tissues and involved in inflammatory and metabolic responses. Thus, the development of selective agonists or antagonists for various GPCRs may facilitate the establishment of novel therapies for the treatment of various diseases. In this review, we summarize current literature describing the potential of GPCRs as therapeutic targets for inflammatory and metabolic disorders.

Amino acid residues in the GerAB protein important in the function and assembly of the alanine spore germination receptor of Bacillus subtilis 168.

PubMed

Cooper, Gareth R; Moir, Anne

2011-05-01

The paradigm gerA operon is required for endospore germination in response to c-alanine as the sole germinant, and the three protein products, GerAA, GerAB, and GerAC are predicted to form a receptor complex in the spore inner membrane. GerAB shows homology to the amino acid-polyamine-organocation (APC) family of single-component transporters and is predicted to be an integral membrane protein with 10 membrane-spanning helices. Site-directed mutations were introduced into the gerAB gene at its natural location on the chromosome. Alterations to some charged or potential helix-breaking residues within membrane spans affected receptor function dramatically. In some cases, this is likely to reflect the complete loss of the GerA receptor complex, as judged by the absence of the germinant receptor protein GerAC, which suggests that the altered GerAB protein itself may be unstable or that the altered structure destabilizes the complex. Mutants that have a null phenotype for Instituto de Biotecnología de León, INBIOTEC, Parque Científico de León, Av. Real, 1, 24006 León, Spain-alanine germination but retain GerAC protein at near-normal levels are more likely to define amino acid residues of functional, rather than structural, importance. Single-amino-acid substitutions in each of the GerAB and GerAA proteins can prevent incorporation of GerAC protein into the spore; this provides strong evidence that the proteins within a specific receptor interact and that these interactions are required for receptor assembly. The lipoprotein nature of the GerAC receptor subunit is also important; an amino acid change in the prelipoprotein signal sequence in the gerAC1 mutant results in the absence of GerAC protein from the spore.

The effects of added sulphur amino acids, threonine and an ideal amino acid ratio on nitrogen metabolism in mature, overweight dogs.

PubMed

Bohaty, Robin E; de Godoy, Maria R C; McLeod, Kyle R; Harmon, David L

2012-02-01

The objectives of this study were to investigate the effects of added essential amino acids in conjunction with a dietary lysine/MJ of 0.72 on nitrogen (N) metabolism in dogs. Treatments were; a control diet, a diet that provided an ideal amino acid profile (IAA), a diet with added total sulphur amino acids (TSAA), and a diet with added TSAA and threonine (TT). Diets were fed to eight overweight, mature, female hounds using a replicated 4 x 4 Latin Square design. Food intake was similar across treatments, however, food N intake was higher (p < 0.001) for TSAA than control, IAA or TT. Nitrogen absorbed was higher (p < 0.01) for TSAA than IAA and control. Urea N excretion was greater for control than TT (p < 0.05). Urine N excretion did not differ between diets. There were no differences in digestibility or N retention of diets. There were no differences in protein turnover, synthesis, or degradation. Blood metabolites were within normal ranges and did not differ due to dietary treatment. Based on the measurements made in this study, there is no benefit for added TSAA, TT or additional EAA in diets for mature dogs formulated to provide a 0.72 g lysine/MJ ME ratio.

Regulation of B cell functions by the sialic acid-binding receptors siglec-G and CD22.

PubMed

Jellusova, Julia; Nitschke, Lars

2011-01-01

B cell antigen receptor (BCR) engagement can lead to many different physiologic outcomes. To achieve an appropriate response, the BCR signal is interpreted in the context of other stimuli and several additional receptors on the B cell surface participate in the modulation of the signal. Two members of the Siglec (sialic acid-binding immunoglobulin-like lectin) family, CD22 and Siglec-G have been shown to inhibit the BCR signal. Recent findings indicate that the ability of these two receptors to bind sialic acids might be important to induce tolerance to self-antigens. Sialylated glycans are usually absent on microbes but abundant in higher vertebrates and might therefore provide an important tolerogenic signal. Since the expression of the specific ligands for Siglec-G and CD22 is tightly regulated and since Siglecs are not only able to bind their ligands in trans but also on the same cell surface this might provide additional mechanisms to control the BCR signal. Although both Siglec-G and CD22 are expressed on B cells and are able to inhibit BCR mediated signaling, they also show unique biological functions. While CD22 is the dominant regulator of calcium signaling on conventional B2 cells and also seems to play a role on marginal zone B cells, Siglec-G exerts its function mainly on B1 cells and influences their lifespan and antibody production. Both Siglec-G and CD22 have also recently been linked to toll-like receptor signaling and may provide a link in the regulation of the adaptive and innate immune response of B cells.

Stereocontrolled dopamine receptor binding and subtype selectivity of clebopride analogues synthesized from aspartic acid.

PubMed

Einsiedel, Jürgen; Weber, Klaus; Thomas, Christoph; Lehmann, Thomas; Hübner, Harald; Gmeiner, Peter

2003-10-06

Employing the achiral 4-aminopiperidine derivative clebopride as a lead compound, chiral analogues were developed displaying dopamine receptor binding profiles that proved to be strongly dependent on the stereochemistry. Compared to the D1 receptor, the test compounds showed high selectivity for the D2-like subtypes including D2(long), D2(short), D3 and D4. The highest D4 and D3 affinities were observed for the cis-3-amino-4-methylpyrrolidines 3e and the enantiomer ent3e resulting in K(i) values of 0.23 and 1.8 nM, respectively. The benzamides of type 3 and 5 were synthesized in enantiopure form starting from (S)-aspartic acid and its unnatural optical antipode.

Lysine optimization of a commercial fishmeal-free diet for hybrid striped bass (Morone chrysops x M. saxatilis)

USDA-ARS?s Scientific Manuscript database

Substitution of fishmeal with alternate proteins in aquafeeds often results in dietary imbalances of firstlimiting essential amino acids (EAA) and poorer fish performance. This growth trial was undertaken to test the hypothesis that ideal protein theory accurately predicts first-limiting amino acids...

Phytohormone abscisic acid elicits antinociceptive effects in rats through the activation of opioid and peroxisome proliferator-activated receptors β/δ.

PubMed

Mollashahi, Mahtab; Abbasnejad, Mehdi; Esmaeili-Mahani, Saeed

2018-08-05

The phytohormone abscisic acid exists in animal tissues particularly in the brain. However, its neurophysiological effects have not yet been fully clarified. This study was designed to evaluate the possible antinociceptive effects of abscisic acid on animal models of pain and determine its possible signaling mechanism. Tail-flick, hot-plate and formalin tests were used to assess the nociceptive threshold. All experiments were carried out on male Wistar rats. To determine the role of Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) and opioid receptors on the induction of abscisic acid antinociception, specific antagonists were injected 15 min before abscisic acid. The data showed that abscisic acid (5, 10 and 15 µg/rat, i.c.v.) significantly decreased pain responses in formalin test. In addition, it could also produce dose-dependent antinociceptive effect in tail-flick and hot-plate tests. Administration of PPARβ/δ antagonist (GSK0660, 80 nM, i.c.v.) significantly attenuated the antinociceptive effect of abscisic acid in all tests. The antinociceptive effects of abscisic acid were completely inhibited by naloxone (6 µg, i.c.v.) during the time course of tail-flick and hot-plate tests. The results indicated that the central injection of abscisic acid has potent pain-relieving property which is mediated partly via the PPAR β/δ and opioid signaling. Copyright © 2018 Elsevier B.V. All rights reserved.

Free fatty acid receptors and their role in regulation of energy metabolism.

PubMed

Hara, Takafumi; Kimura, Ikuo; Inoue, Daisuke; Ichimura, Atsuhiko; Hirasawa, Akira

2013-01-01

The free fatty acid receptor (FFAR) is a G protein-coupled receptor (GPCR) activated by free fatty acids (FFAs), which play important roles not only as essential nutritional components but also as signaling molecules in numerous physiological processes. In the last decade, FFARs have been identified by the GPCR deorphanization strategy derived from the human genome database. To date, several FFARs have been identified and characterized as critical components in various physiological processes. FFARs are categorized according to the chain length of FFA ligands that activate each FFAR; FFA2 and FFA3 are activated by short chain FFAs, GPR84 is activated by medium-chain FFAs, whereas FFA1 and GPR120 are activated by medium- or long-chain FFAs. FFARs appear to act as physiological sensors for food-derived FFAs and digestion products in the gastrointestinal tract. Moreover, they are considered to be involved in the regulation of energy metabolism mediated by the secretion of insulin and incretin hormones and by the regulation of the sympathetic nerve systems, taste preferences, and inflammatory responses related to insulin resistance. Therefore, because FFARs can be considered to play important roles in physiological processes and various pathophysiological processes, FFARs have been targeted in therapeutic strategies for the treatment of metabolic disorders including type 2 diabetes and metabolic syndrome. In this review, we present a summary of recent progress regarding the understanding of their physiological roles in the regulation of energy metabolism and their potential as therapeutic targets.

Mining microarray datasets in nutrition: expression of the GPR120 (n-3 fatty acid receptor/sensor) gene is down-regulated in human adipocytes by macrophage secretions.

PubMed

Trayhurn, Paul; Denyer, Gareth

2012-01-01

Microarray datasets are a rich source of information in nutritional investigation. Targeted mining of microarray data following initial, non-biased bioinformatic analysis can provide key insight into specific genes and metabolic processes of interest. Microarrays from human adipocytes were examined to explore the effects of macrophage secretions on the expression of the G-protein-coupled receptor (GPR) genes that encode fatty acid receptors/sensors. Exposure of the adipocytes to macrophage-conditioned medium for 4 or 24 h had no effect on GPR40 and GPR43 expression, but there was a marked stimulation of GPR84 expression (receptor for medium-chain fatty acids), the mRNA level increasing 13·5-fold at 24 h relative to unconditioned medium. Importantly, expression of GPR120, which encodes an n-3 PUFA receptor/sensor, was strongly inhibited by the conditioned medium (15-fold decrease in mRNA at 24 h). Macrophage secretions have major effects on the expression of fatty acid receptor/sensor genes in human adipocytes, which may lead to an augmentation of the inflammatory response in adipose tissue in obesity.

Fatty acids and hypolipidemic drugs regulate peroxisome proliferator-activated receptors alpha - and gamma-mediated gene expression via liver fatty acid binding protein: a signaling path to the nucleus.

PubMed

Wolfrum, C; Borrmann, C M; Borchers, T; Spener, F

2001-02-27

Peroxisome proliferator-activated receptor alpha (PPARalpha) is a key regulator of lipid homeostasis in hepatocytes and target for fatty acids and hypolipidemic drugs. How these signaling molecules reach the nuclear receptor is not known; however, similarities in ligand specificity suggest the liver fatty acid binding protein (L-FABP) as a possible candidate. In localization studies using laser-scanning microscopy, we show that L-FABP and PPARalpha colocalize in the nucleus of mouse primary hepatocytes. Furthermore, we demonstrate by pull-down assay and immunocoprecipitation that L-FABP interacts directly with PPARalpha. In a cell biological approach with the aid of a mammalian two-hybrid system, we provide evidence that L-FABP interacts with PPARalpha and PPARgamma but not with PPARbeta and retinoid X receptor-alpha by protein-protein contacts. In addition, we demonstrate that the observed interaction of both proteins is independent of ligand binding. Final and quantitative proof for L-FABP mediation was obtained in transactivation assays upon incubation of transiently and stably transfected HepG2 cells with saturated, monounsaturated, and polyunsaturated fatty acids as well as with hypolipidemic drugs. With all ligands applied, we observed strict correlation of PPARalpha and PPARgamma transactivation with intracellular concentrations of L-FABP. This correlation constitutes a nucleus-directed signaling by fatty acids and hypolipidemic drugs where L-FABP acts as a cytosolic gateway for these PPARalpha and PPARgamma agonists. Thus, L-FABP and the respective PPARs could serve as targets for nutrients and drugs to affect expression of PPAR-sensitive genes.

Chimeric NDP-MSH and MTII melanocortin peptides with agouti-related protein (AGRP) Arg-Phe-Phe amino acids possess agonist melanocortin receptor activity.

PubMed

Joseph, Christine G; Wilczynski, Andrzej; Holder, Jerry R; Xiang, Zhimin; Bauzo, Rayna M; Scott, Joseph W; Haskell-Luevano, Carrie

2003-12-01

Agouti-related protein (AGRP) is one of only two known endogenous antagonists of G-protein coupled receptors (GPCRs). Specifically, AGRP antagonizes the brain melanocortin-3 and -4 receptors involved in energy homeostasis, regulation of feeding behavior, and obesity. Alpha-melanocyte stimulating hormone (alpha-MSH) is one of the known endogenous agonists for these receptors. It has been hypothesized that the Arg-Phe-Phe (111-113) human AGRP amino acids may be mimicking the melanocortin agonist Phe-Arg-Trp (7-9) residue interactions with the melanocortin receptors that are important for both receptor molecular recognition and stimulation. To test this hypothesis, we generated thirteen chimeric peptide ligands based upon the melanocortin agonist peptides NDP-MSH (Ac-Ser-Tyr-Ser-Nle4-Glu-His-DPhe-Arg-Trp-Gly-Lys-Pro-Val-NH2) and MTII (Ac-Nle-c[Asp-His-DPhe-Arg-Trp-Lys]-NH2). In these chimeric ligands, the agonist DPhe-Arg-Trp amino acids were replaced by the AGRP Arg-Phe-Phe residues, and resulted in agonist activity at the mouse melanocortin receptors (mMC1R and mMC3-5Rs), supporting the hypothesis that the AGRP antagonist ligand Arg-Phe-Phe residues mimic the agonist Phe-Arg-Trp amino acids. Interestingly, the Ac-Ser-Tyr-Ser-Nle4-Glu-His-Arg-DPhe-Phe-Gly-Lys-Pro-Val-NH2 peptide possessed 7 nM mMC1R agonist potency, and is 850-fold selective for the mMC1R versus the mMC3R, 2300-fold selective for the mMC1R versus the mMC4R, and 60-fold selective for the MC1R versus the mMC5R, resulting in the discovery of a new peptide template for the design of melanocortin receptor selective ligands.

Food deprivation modulates gamma-aminobutyric acid receptors and peripheral benzodiazepine binding sites in rats.

PubMed

Weizman, A; Bidder, M; Fares, F; Gavish, M

1990-12-03

The effect of 5 days of food deprivation followed by 5 days of refeeding on gamma-aminobutyric acid (GABA) receptors, central benzodiazepine receptors (CBR), and peripheral benzodiazepine binding sites (PBzS) was studied in female Sprague-Dawley rats. Starvation induced a decrease in the density of PBzS in peripheral organs: adrenal (35%; P less than 0.001), kidney (33%; P less than 0.01), and heart (34%; P less than 0.001). Restoration of [3H]PK 11195 binding to normal values was observed in all three organs after 5 days of refeeding. The density of PBzS in the ovary, pituitary, and hypothalamus was not affected by starvation. Food deprivation resulted in a 35% decrease in cerebellar GABA receptors (P less than 0.01), while CBR in the hypothalamus and cerebral cortex remained unaltered. The changes in PBzS observed in the heart and kidney may be related to the long-term metabolic stress associated with starvation and to the functional changes occurring in these organs. The down-regulation of the adrenal PBzS is attributable to the suppressive effect of hypercortisolemia on pituitary ACTH release. The reduction in cerebellar GABA receptors may be an adaptive response to food deprivation stress and may be relevant to the proaggressive effect of hunger.

Mutagenesis Analysis Reveals Distinct Amino Acids of the Human Serotonin 5-HT2C Receptor Underlying the Pharmacology of Distinct Ligands.

PubMed

Liu, Yue; Canal, Clinton E; Cordova-Sintjago, Tania C; Zhu, Wanying; Booth, Raymond G

2017-01-18

While exploring the structure-activity relationship of 4-phenyl-2-dimethylaminotetralins (PATs) at serotonin 5-HT 2C receptors, we discovered that relatively minor modification of PAT chemistry impacts function at 5-HT 2C receptors. In HEK293 cells expressing human 5-HT 2C-INI receptors, for example, (-)-trans-3'-Br-PAT and (-)-trans-3'-Cl-PAT are agonists regarding Gα q -inositol phosphate signaling, whereas (-)-trans-3'-CF 3 -PAT is an inverse agonist. To investigate the ligand-receptor interactions that govern this change in function, we performed site-directed mutagenesis of 14 amino acids of the 5-HT 2C receptor based on molecular modeling and reported G protein-coupled receptor crystal structures, followed by molecular pharmacology studies. We found that S3.36, T3.37, and F5.47 in the orthosteric binding pocket are critical for affinity (K i ) of all PATs tested, we also found that F6.44, M6.47, C7.45, and S7.46 are primarily involved in regulating EC/IC 50 functional potencies of PATs. We discovered that when residue S5.43, N6.55, or both are mutated to alanine, (-)-trans-3'-CF 3 -PAT switches from inverse agonist to agonist function, and when N6.55 is mutated to leucine, (-)-trans-3'-Br-PAT switches from agonist to inverse agonist function. Notably, most point-mutations that affected PAT pharmacology did not significantly alter affinity (K D ) of the antagonist radioligand [ 3 H]mesulergine, but every mutation tested negatively impacted serotonin binding. Also, amino acid mutations differentially affected the pharmacology of other commercially available 5-HT 2C ligands tested. Collectively, the data show that functional outcomes shared by different ligands are mediated by different amino acids and that some 5-HT 2C receptor residues important for pharmacology of one ligand are not necessarily important for another ligand.

Bile acids override steatosis in farnesoid X receptor deficient mice in a model of non-alcoholic steatohepatitis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Weibin; Liu, Xijun; Peng, Xiaomin

Highlights: • FXR deficiency enhanced MCD diet-induced hepatic fibrosis. • FXR deficiency attenuated MCD diet-induced hepatic steatosis. • FXR deficiency repressed genes involved in fatty acid uptake and triglyceride accumulation. - Abstract: Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases, and the pathogenesis is still not well known. The farnesoid X receptor (FXR) is a member of the nuclear hormone receptor superfamily and plays an essential role in maintaining bile acid and lipid homeostasis. In this study, we study the role of FXR in the pathogenesis of NFALD. We found that FXR deficient (FXR{sup −/−})more » mice fed methionine- and choline-deficient (MCD) diet had higher serum ALT and AST activities and lower hepatic triglyceride levels than wild-type (WT) mice fed MCD diet. Expression of genes involved in inflammation (VCAM-1) and fibrosis (α-SMA) was increased in FXR{sup −/−} mice fed MCD diet (FXR{sup −/−}/MCD) compared to WT mice fed MCD diet (WT/MCD). Although MCD diet significantly induced hepatic fibrosis in terms of liver histology, FXR{sup −/−}/MCD mice showed less degree of hepatic steatosis than WT/MCD mice. Moreover, FXR deficiency synergistically potentiated the elevation effects of MCD diet on serum and hepatic bile acids levels. The super-physiological concentrations of hepatic bile acids in FXR{sup −/−}/MCD mice inhibited the expression of genes involved in fatty acid uptake and triglyceride accumulation, which may be an explanation for less steatosis in FXR{sup −/−}/MCD mice in contrast to WT/MCD mice. These results suggest that hepatic bile acids accumulation could override simple steatosis in hepatic injury during the progression of NAFLD and further emphasize the role of FXR in maintaining hepatic bile acid homeostasis in liver disorders and in hepatic protection.« less

Isoflavones enhance interleukin-17 gene expression via retinoic acid receptor-related orphan receptors α and γ

PubMed Central

Kojima, Hiroyuki; Takeda, Yukimasa; Muromoto, Ryuta; Takahashi, Miki; Hirao, Toru; Takeuchi, Shinji; Jetten, Anton M.; Matsuda, Tadashi

2018-01-01

The retinoic acid receptor-related orphan receptors α and γ (RORα and RORγ), are key regulators of helper T (Th)17 cell differentiation, which is involved in the innate immune system and autoimmune disorders. In this study, we investigated the effects of isoflavones on RORα/γ activity and the gene expression of interleukin (IL)-17, which mediates the function of Th17 cells. In doxycycline-inducible CHO stable cell lines, we found that four isoflavones, biochanin A (BA), genistein, formononetin, and daidzein, enhanced RORα- or RORγ-mediated transcriptional activity in a dose-dependent manner. In an activation assay of the Il17a promoter using Jurkat cells, these compounds enhanced the RORα- or RORγ-mediated activation of the Il17a promoter at concentrations of 1 × 10−6 M to 1 × 10−5 M. In mammalian two-hybrid assays, the four isoflavones enhanced the interaction between the RORα- or RORγ-ligand binding domain and the co-activator LXXLL peptide in a dose-dependent manner. In addition, these isoflavones potently enhanced Il17a mRNA expression in mouse T lymphoma EL4 cells treated with phorbol myristate acetate and ionomycin, but showed slight enhancement of Il17a gene expression in RORα/γ-knockdown EL4 cells. Immunoprecipitation and immunoblotting assays also revealed that BA enhanced the interaction between RORγt and SRC-1, which is a co-activator for nuclear receptors. Taken together, these results suggest that the isoflavones have the ability to enhance IL-17 gene expression by stabilizing the interactions between RORα/γ and co-activators. This also provides the first evidence that dietary chemicals can enhance IL-17 gene expression in immune cells. PMID:25583575

Ursodeoxycholic acid exerts farnesoid X receptor-antagonistic effects on bile acid and lipid metabolism in morbid obesity.

PubMed

Mueller, Michaela; Thorell, Anders; Claudel, Thierry; Jha, Pooja; Koefeler, Harald; Lackner, Carolin; Hoesel, Bastian; Fauler, Guenter; Stojakovic, Tatjana; Einarsson, Curt; Marschall, Hanns-Ulrich; Trauner, Michael

2015-06-01

Bile acids (BAs) are major regulators of hepatic BA and lipid metabolism but their mechanisms of action in non-alcoholic fatty liver disease (NAFLD) are still poorly understood. Here we aimed to explore the molecular and biochemical mechanisms of ursodeoxycholic acid (UDCA) in modulating the cross-talk between liver and visceral white adipose tissue (vWAT) regarding BA and cholesterol metabolism and fatty acid/lipid partitioning in morbidly obese NAFLD patients. In this randomized controlled pharmacodynamic study, we analyzed serum, liver and vWAT samples from 40 well-matched morbidly obese patients receiving UDCA (20 mg/kg/day) or no treatment three weeks prior to bariatric surgery. Short term UDCA administration stimulated BA synthesis by reducing circulating fibroblast growth factor 19 and farnesoid X receptor (FXR) activation, resulting in cholesterol 7α-hydroxylase induction mirrored by elevated C4 and 7α-hydroxycholesterol. Enhanced BA formation depleted hepatic and LDL-cholesterol with subsequent activation of the key enzyme of cholesterol synthesis 3-hydroxy-3-methylglutaryl-CoA reductase. Blunted FXR anti-lipogenic effects induced lipogenic stearoyl-CoA desaturase (SCD) in the liver, thereby increasing hepatic triglyceride content. In addition, induced SCD activity in vWAT shifted vWAT lipid metabolism towards generation of less toxic and more lipogenic monounsaturated fatty acids such as oleic acid. These data demonstrate that by exerting FXR-antagonistic effects, UDCA treatment in NAFLD patients strongly impacts on cholesterol and BA synthesis and induces neutral lipid accumulation in both liver and vWAT. Copyright © 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Regulation of B Cell Functions by the Sialic Acid-Binding Receptors Siglec-G and CD22

PubMed Central

Jellusova, Julia; Nitschke, Lars

2011-01-01

B cell antigen receptor (BCR) engagement can lead to many different physiologic outcomes. To achieve an appropriate response, the BCR signal is interpreted in the context of other stimuli and several additional receptors on the B cell surface participate in the modulation of the signal. Two members of the Siglec (sialic acid-binding immunoglobulin-like lectin) family, CD22 and Siglec-G have been shown to inhibit the BCR signal. Recent findings indicate that the ability of these two receptors to bind sialic acids might be important to induce tolerance to self-antigens. Sialylated glycans are usually absent on microbes but abundant in higher vertebrates and might therefore provide an important tolerogenic signal. Since the expression of the specific ligands for Siglec-G and CD22 is tightly regulated and since Siglecs are not only able to bind their ligands in trans but also on the same cell surface this might provide additional mechanisms to control the BCR signal. Although both Siglec-G and CD22 are expressed on B cells and are able to inhibit BCR mediated signaling, they also show unique biological functions. While CD22 is the dominant regulator of calcium signaling on conventional B2 cells and also seems to play a role on marginal zone B cells, Siglec-G exerts its function mainly on B1 cells and influences their lifespan and antibody production. Both Siglec-G and CD22 have also recently been linked to toll-like receptor signaling and may provide a link in the regulation of the adaptive and innate immune response of B cells. PMID:22566885

Orphan nuclear receptor oestrogen-related receptor γ (ERRγ) plays a key role in hepatic cannabinoid receptor type 1-mediated induction of CYP7A1 gene expression

PubMed Central

Zhang, Yaochen; Kim, Don-Kyu; Lee, Ji-Min; Park, Seung Bum; Jeong, Won-IL; Kim, Seong Heon; Lee, In-Kyu; Lee, Chul-Ho; Chiang, John Y.L.; Choi, Hueng-Sik

2017-01-01

Bile acids are primarily synthesized from cholesterol in the liver and have important roles in dietary lipid absorption and cholesterol homoeostasis. Detailed roles of the orphan nuclear receptors regulating cholesterol 7α-hydroxylase (CYP7A1), the rate-limiting enzyme in bile acid synthesis, have not yet been fully elucidated. In the present study, we report that oestrogen-related receptor γ (ERRγ) is a novel transcriptional regulator of CYP7A1 expression. Activation of cannabinoid receptor type 1 (CB1 receptor) signalling induced ERRγ-mediated transcription of the CYP7A1 gene. Overexpression of ERRγ increased CYP7A1 expression in vitro and in vivo, whereas knockdown of ERRγ attenuated CYP7A1 expression. Deletion analysis of the CYP7A1 gene promoter and a ChIP assay revealed an ERRγ -binding site on the CYP7A1 gene promoter. Small heterodimer partner (SHP) inhibited the transcriptional activity of ERRγ and thus regulated CYP7A1 expression. Overexpression of ERRγ led to increased bile acid levels, whereas an inverse agonist of ERRγ, GSK5182, reduced CYP7A1 expression and bile acid synthesis. Finally, GSK5182 significantly reduced hepatic CB1 receptor-mediated induction of CYP7A1 expression and bile acid synthesis in alcohol-treated mice. These results provide the molecular mechanism linking ERRγ and bile acid metabolism. PMID:26348907

Lysergic acid diethylamide-induced Fos expression in rat brain: role of serotonin-2A receptors.

PubMed

Gresch, P J; Strickland, L V; Sanders-Bush, E

2002-01-01

Lysergic acid diethylamide (LSD) produces altered mood and hallucinations in humans and binds with high affinity to serotonin-2A (5-HT(2A)) receptors. Although LSD interacts with other receptors, the activation of 5-HT(2A) receptors is thought to mediate the hallucinogenic properties of LSD. The goal of this study was to identify the brain sites activated by LSD and to determine the influence of 5-HT(2A) receptors in this activation. Rats were pretreated with the 5-HT(2A) receptor antagonist MDL 100907 (0.3 mg/kg, i.p.) or vehicle 30 min prior to LSD (500 microg/kg, i.p.) administration and killed 3 h later. Brain tissue was examined for Fos protein expression by immunohistochemistry. LSD administration produced a five- to eight-fold increase in Fos-like immunoreactivity in medial prefrontal cortex, anterior cingulate cortex, and central nucleus of amygdala. However, in dorsal striatum and nucleus accumbens no increase in Fos-like immunoreactivity was observed. Pretreatment with MDL 100907 completely blocked LSD-induced Fos-like immunoreactivity in medial prefrontal cortex and anterior cingulate cortex, but only partially blocked LSD-induced Fos-like immunoreactivity in amygdala. Double-labeled immunohistochemistry revealed that LSD did not induce Fos-like immunoreactivity in cortical cells expressing 5-HT(2A) receptors, suggesting an indirect activation of cortical neurons. These results indicate that the LSD activation of medial prefrontal cortex and anterior cingulate cortex is mediated by 5-HT(2A) receptors, whereas in amygdala 5-HT(2A) receptor activation is a component of the response. These findings support the hypothesis that the medial prefrontal cortex, anterior cingulate cortex, and perhaps the amygdala, are important regions involved in the production of hallucinations. Copyright 2002 IBRO

NR4A orphan nuclear receptors influence retinoic acid and docosahexaenoic acid signaling via up-regulation of fatty acid binding protein 5

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volakakis, Nikolaos; Joodmardi, Eliza; Perlmann, Thomas, E-mail: thomas.perlmann@licr.ki.se

2009-12-25

The orphan nuclear receptor (NR) Nurr1 is expressed in the developing and adult nervous system and is also induced as an immediate early gene in a variety of cell types. In silico analysis of human promoters identified fatty acid binding protein 5 (FABP5), a protein shown to enhance retinoic acid-mediated PPAR{beta}/{delta} signaling, as a potential Nurr1 target gene. Nurr1 has previously been implicated in retinoid signaling via its heterodimerization partner RXR. Since NRs are commonly involved in cross-regulatory control we decided to further investigate the regulatory relationship between Nurr1 and FABP5. FABP5 expression was up-regulated by Nurr1 and other NR4Amore » NRs in HEK293 cells, and Nurr1 was shown to activate and bind to the FABP5 promoter, supporting that FABP5 is a direct downstream target of NR4A NRs. We also show that the RXR ligand docosahexaenoic acid (DHA) can induce nuclear translocation of FABP5. Moreover, via up-regulation of FABP5 Nurr1 can enhance retinoic acid-induced signaling of PPAR{beta}/{delta} and DHA-induced activation of RXR. We also found that other members of the NR4A orphan NRs can up-regulate FABP5. Thus, our findings suggest that NR4A orphan NRs can influence signaling events of other NRs via control of FABP5 expression levels.« less

Different expressions and DNA methylation patterns of lysophosphatidic acid receptor genes in mouse tumor cells.

PubMed

Okabe, Kyoko; Hayashi, Mai; Wakabayashi, Naoko; Yamawaki, Yasuna; Teranishi, Miki; Fukushima, Nobuyuki; Tsujiuchi, Toshifumi

2010-01-01

Lysophosphatidic acid (LPA) receptors act as several biological effectors through LPA, which is a bioactive phospholipid. Recently, aberrant expressions of LPA receptor genes due to DNA methylation have been detected in several tumor cells. In this study, we measured expression levels and DNA methylation status of LPA receptor genes in mouse tumor cells, LL/2 lung carcinoma, B16F0 melanoma, FM3A mammary carcinoma and L1210 leukemia cells, compared with normal tissues. Total RNAs were extracted and RT-PCR analysis was performed. For DNA methylation status, bisulfite sequencing analysis was carried out, comparing outcomes with other tumor cells and normal tissues. The expressions of LPA1 gene were shown in LL/2, but not in B16F0, FM3A and L1210 cells. While the LPA2 gene was expressed in all 4 tumor cells, the LPA3 gene was unexpressed in them. The LPA1 and LPA3 unexpressed cells were highly methylated, although normal tissues were all unmethylated. The DNA methylation status was correlated with gene expression levels in cancer cells. The present results demonstrate that DNA methylation patterns of LPA receptor genes are dependent on cancer cell types, suggesting that LPA receptors may be new molecular targets for therapeutic approaches and chemoprevention. Copyright © 2011 S. Karger AG, Basel.

Mining microarray datasets in nutrition: expression of the GPR120 (n-3 fatty acid receptor/sensor) gene is down-regulated in human adipocytes by macrophage secretions

PubMed Central

Trayhurn, Paul; Denyer, Gareth

2012-01-01

Microarray datasets are a rich source of information in nutritional investigation. Targeted mining of microarray data following initial, non-biased bioinformatic analysis can provide key insight into specific genes and metabolic processes of interest. Microarrays from human adipocytes were examined to explore the effects of macrophage secretions on the expression of the G-protein-coupled receptor (GPR) genes that encode fatty acid receptors/sensors. Exposure of the adipocytes to macrophage-conditioned medium for 4 or 24 h had no effect on GPR40 and GPR43 expression, but there was a marked stimulation of GPR84 expression (receptor for medium-chain fatty acids), the mRNA level increasing 13·5-fold at 24 h relative to unconditioned medium. Importantly, expression of GPR120, which encodes an n-3 PUFA receptor/sensor, was strongly inhibited by the conditioned medium (15-fold decrease in mRNA at 24 h). Macrophage secretions have major effects on the expression of fatty acid receptor/sensor genes in human adipocytes, which may lead to an augmentation of the inflammatory response in adipose tissue in obesity. PMID:25191551

Modulation of fear memory by dietary polyunsaturated fatty acids via cannabinoid receptors.

PubMed

Yamada, Daisuke; Takeo, Jiro; Koppensteiner, Peter; Wada, Keiji; Sekiguchi, Masayuki

2014-07-01

Although the underlying mechanism remains unknown, several studies have suggested benefits of n-3 long-chain polyunsaturated fatty acid (PUFA) for patients with anxiety disorders. Elevated fear is thought to contribute to the pathogenesis of particular anxiety disorders. The aim of the present study was to evaluate whether the dietary n-3 to n-6 PUFA (3:6) ratio influences fear memory. For this purpose, the effects of various dietary 3:6 ratios on fear memory were examined in mice using contextual fear conditioning, and the effects of these diets on central synaptic transmission were examined to elucidate the mechanism of action of PUFA. We found that fear memory correlated negatively with dietary, serum, and brain 3:6 ratios in mice. The low fear memory in mice fed a high 3:6 ratio diet was increased by the cannabinoid CB1 receptor antagonist rimonabant, reaching a level seen in mice fed a low 3:6 ratio diet. The agonist sensitivity of CB1 receptor was enhanced in the basolateral nucleus of the amygdala (BLA) of mice fed a high 3:6 ratio diet, compared with that of mice fed a low 3:6 ratio diet. Similar enhancement was induced by pharmacological expulsion of cholesterol in the neuronal membrane of brain slices from mice fed a low 3:6 ratio diet. CB1 receptor-mediated short-term synaptic plasticity was facilitated in pyramidal neurons of the BLA in mice fed a high 3:6 ratio diet. These results suggest that the ratio of n-3 to n-6 PUFA is a factor regulating fear memory via cannabinoid CB1 receptors.

Role of a gamma-aminobutryic acid (GABA) receptor mutation in the evolution and spread of Diabrotica virgifera virgifera resistance to cyclodiene insecticides

USDA-ARS?s Scientific Manuscript database

An alanine to serine amino acid substitution within the Rdl subunit of the gamma-aminobutyric acid (GABA) receptor confers resistance to cyclodiene insecticides in many species. The corn rootworm, Diabrotica virgifera virgifera, is a damaging pest of cultivated corn that was partially controlled by ...

Bile acid regulates c-Jun expression through the orphan nuclear receptor SHP induction in gastric cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Won Il; Park, Min Jung; An, Jin Kwang

2008-05-02

Bile reflux is considered to be one of the most important causative factors in gastric carcinogenesis, due to the attendant inflammatory changes in the gastric mucosa. In this study, we have assessed the molecular mechanisms inherent to the contribution of bile acid to the transcriptional regulation of inflammatory-related genes. In this study, we demonstrated that bile acid induced the expression of the SHP orphan nuclear receptor at the transcriptional level via c-Jun activation. Bile acid also enhanced the protein interaction of NF-{kappa}B and SHP, thereby resulting in an increase in c-Jun expression and the production of the inflammatory cytokine, TNF{alpha}.more » These results indicate that bile acid performs a critical function in the regulation of the induction of inflammatory-related genes in gastric cells, and that bile acid-mediated gene expression provides a pre-clue for the development of gastric cellular malformation.« less

Behavioral effects of gamma-hydroxybutyrate, its precursor gamma-butyrolactone, and GABA(B) receptor agonists: time course and differential antagonism by the GABA(B) receptor antagonist 3-aminopropyl(diethoxymethyl)phosphinic acid (CGP35348).

PubMed

Koek, Wouter; Mercer, Susan L; Coop, Andrew; France, Charles P

2009-09-01

Gamma-hydroxybutyrate (GHB) is used therapeutically and recreationally. The mechanism by which GHB produces its therapeutic and recreational effects is not entirely clear, although GABA(B) receptors seem to play an important role. This role could be complex, because there are indications that different GABA(B) receptor mechanisms mediate the effects of GHB and the prototypical GABA(B) receptor agonist baclofen. To further explore possible differences in underlying GABA(B) receptor mechanisms, the present study examined the effects of GHB and baclofen on operant responding and their antagonism by the GABA(B) receptor antagonist 3-aminopropyl(diethoxymethyl)phosphinic acid (CGP35348). Pigeons were trained to peck a key for access to food during response periods that started at different times after the beginning of the session. In these pigeons, GHB, its precursor gamma-butyrolactone (GBL), and the GABA(B) receptor agonists baclofen and 3-aminopropyl(methyl)phosphinic acid hydrochloride (SKF97541) decreased the rate of responding in a dose- and time-dependent manner. CGP35348 shifted the dose-response curve of each agonist to the right, but the magnitude of the shift differed among the agonists. Schild analysis yielded a pA(2) value of CGP35348 to antagonize GHB and GBL [i.e., 3.9 (3.7-4.2)] that was different (P = 0.0011) from the pA(2) value to antagonize baclofen and SKF97541 [i.e., 4.5 (4.4-4.7)]. This finding is further evidence that the GABA(B) receptor mechanisms mediating the effects of GHB and prototypical GABA(B) receptor agonists are not identical. A better understanding of the similarities and differences between these mechanisms, and their involvement in the therapeutic effects of GHB and baclofen, could lead to more effective medications with fewer adverse effects.

Comparison in nutritional quality between wild and cultured cuttlefish Sepia pharaonis

NASA Astrophysics Data System (ADS)

Wen, Jing; Chen, Daohai; Zeng, Ling

2014-01-01

In this study, the proximate composition and the amino and fatty acid profiles of shrimp Litopenaeus vannamei (prey) and wild and cultured cuttlefish Sepia pharaonis (the latter fed the prey) were determined and compared with FAO/WHO recommendations. The resulting scores for isoleucine, phenylalanine+tyrosine, histidine, lysine, threonine, and tryptophan in cultured cuttlefish were ≥150. The ratio of EAA (essential amino acids)/nonessential amino acids in cultured cuttlefish (0.82) was higher than in the wild form (0.80). All EAA amino acid scores for cultured cuttlefish were higher than their wild counterparts, except for histidine and tryptophan. Both groups of cuttlefish possessed similar saturated fatty acid content, with the cultured containing much more total (Σ) monounsaturated fatty acids, Σ n-6 polyunsaturated fatty acids (PUFA), and eicosapentaenoic acid (C20:5 n-3) but less Σ n-3 PUFA, arachidonic acid (C20:4 n-6), and docosahexaenoic acid (C22:6 n-3) than their wild counterparts. Therefore, the present results suggest that these cultured cuttlefish were better than the wild form for human health. Notably, these results also indicate that the nutritional composition of these cuttlefish might have been significantly affected by diet.

Adiponectin receptor 1 conserves docosahexaenoic acid and promotes photoreceptor cell survival

PubMed Central

Rice, Dennis S.; Calandria, Jorgelina M.; Gordon, William C.; Jun, Bokkyoo; Zhou, Yongdong; Gelfman, Claire M.; Li, Songhua; Jin, Minghao; Knott, Eric J.; Chang, Bo; Abuin, Alex; Issa, Tawfik; Potter, David; Platt, Kenneth A.; Bazan, Nicolas G.

2015-01-01

The identification of pathways necessary for photoreceptor and retinal pigment epithelium (RPE) function is critical to uncover therapies for blindness. Here we report the discovery of adiponectin receptor 1 (AdipoR1) as a regulator of these cells’ functions. Docosahexaenoic acid (DHA) is avidly retained in photoreceptors, while mechanisms controlling DHA uptake and retention are unknown. Thus, we demonstrate that AdipoR1 ablation results in DHA reduction. In situ hybridization reveals photoreceptor and RPE cell AdipoR1 expression, blunted in AdipoR1−/− mice. We also find decreased photoreceptor-specific phosphatidylcholine containing very long-chain polyunsaturated fatty acids and severely attenuated electroretinograms. These changes precede progressive photoreceptor degeneration in AdipoR1−/− mice. RPE-rich eyecup cultures from AdipoR1−/− reveal impaired DHA uptake. AdipoR1 overexpression in RPE cells enhances DHA uptake, whereas AdipoR1 silencing has the opposite effect. These results establish AdipoR1 as a regulatory switch of DHA uptake, retention, conservation and elongation in photoreceptors and RPE, thus preserving photoreceptor cell integrity. PMID:25736573

Both retinoic-acid-receptor- and retinoid-X-receptor-dependent signalling pathways mediate the induction of the brown-adipose-tissue-uncoupling-protein-1 gene by retinoids.

PubMed Central

Alvarez, R; Checa, M; Brun, S; Viñas, O; Mampel, T; Iglesias, R; Giralt, M; Villarroya, F

2000-01-01

The intracellular pathways and receptors mediating the effects of retinoic acid (RA) on the brown-fat-uncoupling-protein-1 gene (ucp-1) have been analysed. RA activates transcription of ucp-1 and the RA receptor (RAR) is known to be involved in this effect. However, co-transfection of an expression vector for retinoid-X receptor (RXR) increases the action of 9-cis RA but not the effects of all-trans RA on the ucp-1 promoter in brown adipocytes. Either RAR-specific ¿p-[(E)-2-(5,6,7,8,-tetrahydro-5,5,8, 8-tetramethyl-2-naphthalenyl)-1-propenyl]benzoic acid¿ or RXR-specific [isopropyl-(E,E)-(R,S)-11-methoxy-3,7, 11-trimethyldodeca-2,4-dienoate, or methoprene] synthetic compounds increase the expression of UCP-1 mRNA and the activity of chloramphenicol acetyltransferase expression vectors driven by the ucp-1 promoter. The RXR-mediated action of 9-cis RA requires the upstream enhancer region at -2469/-2318 in ucp-1. During brown-adipocyte differentiation RXRalpha and RXRgamma mRNA expression is induced in parallel with UCP-1 mRNA, whereas the mRNA for the three RAR subtypes, alpha, beta and gamma, decreases. Co-transfection of murine expression vectors for the different RAR and RXR subtypes indicates that RARalpha and RARbeta as well as RXRalpha are the major retinoid-receptor subtypes capable of mediating the responsiveness of ucp-1 to retinoids. It is concluded that the effects of retinoids on ucp-1 transcription involve both RAR- and RXR-dependent signalling pathways. The responsiveness of brown adipose tissue to retinoids in vivo relies on a complex combination of the capacity of RAR and RXR subtypes to mediate ucp-1 induction and their distinct expression in the differentiated brown adipocyte. PMID:10600643

All-trans retinoic acid regulates hepatic bile acid homeostasis

PubMed Central

Yang, Fan; He, Yuqi; Liu, Hui-Xin; Tsuei, Jessica; Jiang, Xiaoyue; Yang, Li; Wang, Zheng-Tao; Wan, Yu-Jui Yvonne

2014-01-01

Retinoic acid (RA) and bile acids share common roles in regulating lipid homeostasis and insulin sensitivity. In addition, the receptor for RA (retinoid x receptor) is a permissive partner of the receptor for bile acids, farnesoid x receptor (FXR/NR1H4). Thus, RA can activate the FXR-mediated pathway as well. The current study was designed to understand the effect of all-trans RA on bile acid homeostasis. Mice were fed an all-trans RA-supplemented diet and the expression of 46 genes that participate in regulating bile acid homeostasis was studied. The data showed that all-trans RA has a profound effect in regulating genes involved in synthesis and transport of bile acids. All-trans RA treatment reduced the gene expression levels of Cyp7a1, Cyp8b1, and Akr1d1, which are involved in bile acid synthesis. All-trans RA also decreased the hepatic mRNA levels of Lrh-1 (Nr5a2) and Hnf4α (Nr2a1), which positively regulate the gene expression of Cyp7a1 and Cyp8b1. Moreover, all-trans RA induced the gene expression levels of negative regulators of bile acid synthesis including hepatic Fgfr4, Fxr, and Shp (Nr0b2) as well as ileal Fgf15. All-trans RA also decreased the expression of Abcb11 and Slc51b, which have a role in bile acid transport. Consistently, all-trans RA reduced hepatic bile acid levels and the ratio of CA/CDCA, as demonstrated by liquid chromatography-mass spectrometry. The data suggest that all-trans RA-induced SHP may contribute to the inhibition of CYP7A1 and CYP8B1, which in turn reduces bile acid synthesis and affects lipid absorption in the gastrointestinal tract. PMID:25175738

Structure--activity studies for alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid receptors: acidic hydroxyphenylalanines.

PubMed

Hill, R A; Wallace, L J; Miller, D D; Weinstein, D M; Shams, G; Tai, H; Layer, R T; Willins, D; Uretsky, N J; Danthi, S N

1997-09-26

Antagonists of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid (AMPA) receptors may have therapeutic potential as psychotropic agents. A series of mononitro- and dinitro-2- and 3-hydroxyphenylalanines was prepared, and their activity compared with willardiine, 5-nitrowillardiine, AMPA, and 2,4,5-trihydroxyphenylalanine (6-hydroxydopa) as inhibitors of specific [3H]AMPA and [3H]kainate binding in rat brain homogenates. The most active compounds were highly acidic (pKa 3-4), namely, 2-hydroxy-3,5-dinitro-DL-phenylalanine (13; [3H]AMPA IC50 approximately equal to 25 microM) and 3-hydroxy-2,4-dinitro-DL-phenylalanine (19; [3H]AMPA IC50 approximately equal to 5 microM). Two other dinitro-3-hydroxyphenylalanines, and 3,5-dinitro-DL-tyrosine, were considerably less active. Various mononitrohydroxyphenylalanines, which are less acidic, were also less active or inactive, and 2- and 3-hydroxyphenylalanine (o- and m-tyrosine) were inactive. Compounds 13 and 19, DL-willardiine (pKa 9.3, [3H]AMPA IC50 = 2 microM), and 5-nitro-DL-willardiine (pKa 6.4, [3H]AMPA IC50 = 0.2 microM) displayed AMPA > kainate selectivity in binding studies. Compound 19 was an AMPA-like agonist, but 13 was an antagonist in an AMPA-evoked norepinephrine release assay in rat hippocampal nerve endings. Also, compound 13 injected into the rat ventral pallidum antagonized the locomotor activity elicited by systemic amphetamine.

A retinoic acid receptor β2 agonist reduces hepatic stellate cell activation in nonalcoholic fatty liver disease.

PubMed

Trasino, Steven E; Tang, Xiao-Han; Jessurun, Jose; Gudas, Lorraine J

2016-10-01

Hepatic stellate cells (HSCs) are an important cellular target for the development of novel pharmacological therapies to prevent and treat nonalcoholic fatty liver diseases (NAFLD). Using a high fat diet (HFD) model of NAFLD, we sought to determine if synthetic selective agonists for retinoic acid receptor β2 (RARβ2) and RARγ can mitigate HSC activation and HSC relevant signaling pathways during early stages of NAFLD, before the onset of liver injury. We demonstrate that the highly selective RARβ2 agonist, AC261066, can reduce the activation of HSCs, marked by decreased HSC expression of α-smooth muscle actin (α-SMA), in mice with HFD-induced NAFLD. Livers of HFD-fed mice treated with AC261066 exhibited reduced steatosis, oxidative stress, and expression of pro-inflammatory mediators, such as tumor necrosis factor-alpha (TNFα), interleukin 1β (IL-1β), and monocyte chemotactic protein-1 (MCP-1). Kupffer cell (macrophage) expression of transforming growth factor-β1 (TGF-β1), which plays a critical role in early HSC activation, was markedly reduced in AC261066-treated, HFD-fed mice. In contrast, HFD-fed mice treated with an RARγ agonist (CD1530) showed no decreases in steatosis, HSC activation, or Kupffer cell TGF-β1 levels. In conclusion, our data demonstrate that RARβ2 is an attractive target for development of NAFLD therapies. • Hepatic stellate cells (HSCs) are an important pharmacological target for the prevention of nonalcoholic fatty liver diseases (NAFLD). • Retinoids and retinoic acid receptors (RARs) possess favorable metabolic modulating properties. • We show that an agonist for retinoic acid receptor-β2 (RARβ2), but not RARγ, mitigates HSC activation and NAFLD.

The 17,18-epoxyeicosatetraenoic acid-G protein-coupled receptor 40 axis ameliorates contact hypersensitivity by inhibiting neutrophil mobility in mice and cynomolgus macaques.

PubMed

Nagatake, Takahiro; Shiogama, Yumiko; Inoue, Asuka; Kikuta, Junichi; Honda, Tetsuya; Tiwari, Prabha; Kishi, Takayuki; Yanagisawa, Atsushi; Isobe, Yosuke; Matsumoto, Naomi; Shimojou, Michiko; Morimoto, Sakiko; Suzuki, Hidehiko; Hirata, So-Ichiro; Steneberg, Pär; Edlund, Helena; Aoki, Junken; Arita, Makoto; Kiyono, Hiroshi; Yasutomi, Yasuhiro; Ishii, Masaru; Kabashima, Kenji; Kunisawa, Jun

2017-12-27

Metabolites of eicosapentaenoic acid exert various physiologic actions. 17,18-Epoxyeicosatetraenoic acid (17,18-EpETE) is a recently identified new class of antiallergic and anti-inflammatory lipid metabolite of eicosapentaenoic acid, but its effects on skin inflammation and the underlying mechanisms remain to be investigated. We evaluated the effectiveness of 17,18-EpETE for control of contact hypersensitivity in mice and cynomolgus macaques. We further sought to reveal underlying mechanisms by identifying the responsible receptor and cellular target of 17,18-EpETE. Contact hypersensitivity was induced by topical application of 2,4-dinitrofluorobenzene. Skin inflammation and immune cell populations were analyzed by using flow cytometric, immunohistologic, and quantitative RT-PCR analyses. Neutrophil mobility was examined by means of imaging analysis in vivo and neutrophil culture in vitro. The receptor for 17,18-EpETE was identified by using the TGF-α shedding assay, and the receptor's involvement in the anti-inflammatory effects of 17,18-EpETE was examined by using KO mice and specific inhibitor treatment. We found that preventive or therapeutic treatment with 17,18-EpETE ameliorated contact hypersensitivity by inhibiting neutrophil mobility in mice and cynomolgus macaques. 17,18-EpETE was recognized by G protein-coupled receptor (GPR) 40 (also known as free fatty acid receptor 1) and inhibited chemoattractant-induced Rac activation and pseudopod formation in neutrophils. Indeed, the antiallergic inflammatory effect of 17,18-EpETE was abolished in the absence or inhibition of GPR40. 17,18-EpETE inhibits neutrophil mobility through GPR40 activation, which is a potential therapeutic target to control allergic inflammatory diseases. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

The type 1 lysophosphatidic acid receptor is a target for therapy in bone metastases

PubMed Central

Boucharaba, Ahmed; Serre, Claire-Marie; Guglielmi, Julien; Bordet, Jean-Claude; Clézardin, Philippe; Peyruchaud, Olivier

2006-01-01

Platelet-derived lysophosphatidic acid (LPA) supports the progression of breast and ovarian cancer metastasis to bone. The mechanisms through which LPA promotes bone metastasis formation are, however, unknown. Here we report that silencing of the type 1 LPA receptor (LPA1) in cancer cells blocks the production of tumor-derived cytokines that are potent activators of osteoclast-mediated bone destruction and significantly reduces the progression of osteolytic bone metastases. Moreover, functional blockade of LPA action on its cognate receptor LPA1 using a pharmacological antagonist mimics the effects of silencing LPA1 in tumor cells in vitro and substantially reduces bone metastasis progression in animals. Overall, these results suggest that inhibition of platelet-derived LPA action on LPA1 expressed by tumor cells may be a promising therapeutic target for patients with bone metastases. PMID:16769891

Phaseic Acid, an Endogenous and Reversible Inhibitor of Glutamate Receptors in Mouse Brain*

PubMed Central

Hou, Sheng Tao; Jiang, Susan X.; Zaharia, L. Irina; Han, Xiumei; Benson, Chantel L.; Slinn, Jacqueline; Abrams, Suzanne R.

2016-01-01

Phaseic acid (PA) is a phytohormone regulating important physiological functions in higher plants. Here, we show the presence of naturally occurring (−)-PA in mouse and rat brains. (−)-PA is exclusively present in the choroid plexus and the cerebral vascular endothelial cells. Purified (−)-PA has no toxicity and protects cultured cortical neurons against glutamate toxicity through reversible inhibition of glutamate receptors. Focal occlusion of the middle cerebral artery elicited a significant induction in (−)-PA expression in the cerebrospinal fluid but not in the peripheral blood. Importantly, (−)-PA induction only occurred in the penumbra area, indicting a protective role of PA in the brain. Indeed, elevating the (−)-PA level in the brain reduced ischemic brain injury, whereas reducing the (−)-PA level using a monoclonal antibody against (−)-PA increased ischemic injury. Collectively, these studies showed for the first time that (−)-PA is an endogenous neuroprotective molecule capable of reversibly inhibiting glutamate receptors during ischemic brain injury. PMID:27864367

Phaseic Acid, an Endogenous and Reversible Inhibitor of Glutamate Receptors in Mouse Brain.

PubMed

Hou, Sheng Tao; Jiang, Susan X; Zaharia, L Irina; Han, Xiumei; Benson, Chantel L; Slinn, Jacqueline; Abrams, Suzanne R

2016-12-30

Phaseic acid (PA) is a phytohormone regulating important physiological functions in higher plants. Here, we show the presence of naturally occurring (-)-PA in mouse and rat brains. (-)-PA is exclusively present in the choroid plexus and the cerebral vascular endothelial cells. Purified (-)-PA has no toxicity and protects cultured cortical neurons against glutamate toxicity through reversible inhibition of glutamate receptors. Focal occlusion of the middle cerebral artery elicited a significant induction in (-)-PA expression in the cerebrospinal fluid but not in the peripheral blood. Importantly, (-)-PA induction only occurred in the penumbra area, indicting a protective role of PA in the brain. Indeed, elevating the (-)-PA level in the brain reduced ischemic brain injury, whereas reducing the (-)-PA level using a monoclonal antibody against (-)-PA increased ischemic injury. Collectively, these studies showed for the first time that (-)-PA is an endogenous neuroprotective molecule capable of reversibly inhibiting glutamate receptors during ischemic brain injury. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Mechanisms controlling nucleic acid-sensing Toll-like receptors.

PubMed

Miyake, Kensuke; Shibata, Takuma; Ohto, Umeharu; Shimizu, Toshiyuki; Saitoh, Shin-Ichiroh; Fukui, Ryutaro; Murakami, Yusuke

2018-03-08

Nucleic acid (NA)-sensing Toll-like receptors (TLRs) respond to DNA/RNA derived from pathogens and dead cells. Structural studies have revealed a variety of molecular mechanisms by which TLRs sense NAs. Double-stranded RNA and single-stranded DNA directly bind to TLR3 and TLR9, respectively, whereas TLR7 and TLR8 bind to nucleosides and oligoribonucleotides derived from RNAs. Activation of ligand-bound TLRs is influenced by the functional status of TLRs. Proteolytic cleavage of NA-sensing TLRs enables ligand-dependent TLR dimerization. Trafficking of ligand-activated TLRs in endosomal and lysosomal compartments is requisite for production of type I interferons. Activation of NA-sensing TLRs is required for the control of viruses such as herpes simplex virus and endogenous retroviruses. On the other hand, excessive activation of NA-sensing TLRs drives disease progression in a variety of inflammatory diseases including systemic lupus erythematosus, heart failure, arthritis and non-alcoholic steatohepatitis. NA-sensing TLRs are targets for therapeutic intervention in these diseases. We here focus on our recent progresses in our understanding of NA-sensing TLRs.

A Receptor on Acid.

PubMed

Chen, Qiuyan; Tesmer, John J G

2017-01-26

Wacker et al. report the crystal structure of LSD in complex with one of its major targets in the brain, the 5-HT 2B receptor, the first such structure for any psychedelic drug. The results shed light on the molecular mechanisms underlying its ability to induce hallucinations with greater duration and potency than closely related compounds. Copyright © 2017 Elsevier Inc. All rights reserved.

(+)Lysergic acid diethylamide, but not its nonhallucinogenic congeners, is a potent serotonin 5HT1C receptor agonist

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burris, K.D.; Breeding, M.; Sanders-Bush, E.

Activation of central serotonin 5HT2 receptors is believed to be the primary mechanism whereby lysergic acid diethylamide (LSD) and other hallucinogens induce psychoactive effects. This hypothesis is based on extensive radioligand binding and electrophysiological and behavioral studies in laboratory animals. However, the pharmacological profiles of 5HT2 and 5HT1C receptors are similar, making it difficult to distinguish between effects due to activation of one or the other receptor. For this reason, it was of interest to investigate the interaction of LSD with 5HT1C receptors. Agonist-stimulated phosphoinositide hydrolysis in rat choroid plexus was used as a direct measure of 5HT1C receptor activation.more » (+)LSD potently stimulated phosphoinositide hydrolysis in intact choroid plexus and in cultures of choroid plexus epithelial cells, with EC50 values of 9 and 26 nM, respectively. The effect of (+)LSD in both systems was blocked by 5HT receptor antagonists with an order of activity consistent with interaction at 5HT1C receptors. Neither (+)-2-bromo-LSD nor lisuride, two nonhallucinogenic congeners of LSD, were able to stimulate 5HT1C receptors in cultured cells or intact choroid plexus. In contrast, lisuride, like (+)LSD, is a partial agonist at 5HT2 receptors in cerebral cortex slices and in NIH 3T3 cells transfected with 5HT2 receptor cDNA. The present finding that (+)LSD, but not its nonhallucinogenic congeners, is a 5HT1C receptor agonist suggests a possible role for these receptors in mediating the psychoactive effects of LSD.« less

A forward chemical screen in zebrafish identifies a retinoic acid derivative with receptor specificity.

PubMed

Das, Bhaskar C; McCartin, Kellie; Liu, Ting-Chun; Peterson, Randall T; Evans, Todd

2010-04-02

Retinoids regulate key developmental pathways throughout life, and have potential uses for differentiation therapy. It should be possible to identify novel retinoids by coupling new chemical reactions with screens using the zebrafish embryonic model. We synthesized novel retinoid analogues and derivatives by amide coupling, obtaining 80-92% yields. A small library of these compounds was screened for bioactivity in living zebrafish embryos. We found that several structurally related compounds significantly affect development. Distinct phenotypes are generated depending on time of exposure, and we characterize one compound (BT10) that produces specific cardiovascular defects when added 1 day post fertilization. When compared to retinoic acid (ATRA), BT10 shows similar but not identical changes in the expression pattern of embryonic genes that are known targets of the retinoid pathway. Reporter assays determined that BT10 interacts with all three RAR receptor sub-types, but has no activity for RXR receptors, at all concentrations tested. Our screen has identified a novel retinoid with specificity for retinoid receptors. This lead compound may be useful for manipulating components of retinoid signaling networks, and may be further derivatized for enhanced activity.

Dopamine D2High receptors stimulated by phencyclidines, lysergic acid diethylamide, salvinorin A, and modafinil.

PubMed

Seeman, Philip; Guan, Hong-Chang; Hirbec, Hélène

2009-08-01

Although it is commonly stated that phencyclidine is an antagonist at ionotropic glutamate receptors, there has been little measure of its potency on other receptors in brain tissue. Although we previously reported that phencyclidine stimulated cloned-dopamine D2Long and D2Short receptors, others reported that phencyclidine did not stimulate D2 receptors in homogenates of rat brain striatum. This study, therefore, examined whether phencyclidine and other hallucinogens and psychostimulants could stimulate the incorporation of [(35)S]GTP-gamma-S into D2 receptors in homogenates of rat brain striatum, using the same conditions as previously used to study the cloned D2 receptors. Using 10 microM dopamine to define 100% stimulation, phencyclidine elicited a maximum incorporation of 46% in rat striata, with a half-maximum concentration of 70 nM for phencyclidine, when compared with 80 nM for dopamine, 89 nM for salvinorin A (48 nM for D2Long), 105 nM for lysergic acid diethylamide (LSD), 120 nM for R-modafinil, 710 nM for dizocilpine, 1030 nM for ketamine, and >10,000 nM for S-modafinil. These compounds also inhibited the binding of the D2-selective ligand [(3)H]domperidone. The incorporation was inhibited by the presence of 200 microM guanylylimidodiphosphate and also by D2 blockade, using 10 microM S-sulpiride, but not by D1 blockade with 10 microM SCH23390. Hypertonic buffer containing 150 mM NaCl inhibited the stimulation by phencyclidine, which may explain negative results by others. It is concluded that phencyclidine and other psychostimulants and hallucinogens can stimulate dopamine D2 receptors at concentrations related to their behavioral actions.

Fatty acid amide hydrolase (FAAH) inhibition enhances memory acquisition through activation of PPAR-α nuclear receptors

PubMed Central

Mazzola, Carmen; Medalie, Julie; Scherma, Maria; Panlilio, Leigh V.; Solinas, Marcello; Tanda, Gianluigi; Drago, Filippo; Cadet, Jean Lud; Goldberg, Steven R.; Yasar, Sevil

2009-01-01

Inhibitors of fatty acid amide hydrolase (FAAH) increase endogenous levels of anandamide (a cannabinoid CB1-receptor ligand) and oleoylethanolamide and palmitoylethanolamide (OEA and PEA, ligands for α-type peroxisome proliferator-activated nuclear receptors, PPAR-α) when and where they are naturally released in the brain. Using a passive-avoidance task in rats, we found that memory acquisition was enhanced by the FAAH inhibitor URB597 or by the PPAR-α agonist WY14643, and these enhancements were blocked by the PPAR-α antagonist MK886. These findings demonstrate novel mechanisms for memory enhancement by activation of PPAR-α, either directly by administering a PPAR-α agonist or indirectly by administering a FAAH inhibitor. PMID:19403796

Absence of γ-aminobutyric acid-a receptor potentiation in central hypersomnolence disorders.

PubMed

Dauvilliers, Yves; Evangelista, Elisa; Lopez, Regis; Barateau, Lucie; Jaussent, Isabelle; Cens, Thierry; Rousset, Matthieu; Charnet, Pierre

2016-08-01

The pathophysiology of idiopathic hypersomnia (IH) remains unclear. Recently, cerebrospinal fluid (CSF)-induced enhancement of γ-aminobutyric acid (GABA)-A receptor activity was found in patients with IH compared to controls. Fifteen unrelated patients (2 males and 13 females) affected with typical IH, 12 patients (9 males and 3 females) with narcolepsy type 1, and 15 controls (9 males and 6 females) with unspecified hypersomnolence (n = 7) and miscellaneous neurological conditions (n = 8) were included. A lumbar puncture was performed in all participants to measure CSF hypocretin-1 and GABA-A response. We used a voltage-clamp assay on Xenopus oocytes injected with the RNAs that encode the α1 β2 γ2 or the α2 β2 γ2 subunits of the human GABA-A receptor. A sequence of 6 different applications (GABA, GABA/CSF, and CSF alone) with 2 to 4 oocytes per CSF sample was performed in a whole-cell voltage-clamp assay. Representative current traces from oocytes expressing human α1 β2 γ2 or α2 β2 γ2 GABA-A receptors were recorded in response to 6 successive puffs of GABA diluted in the survival medium (SM), showing stable and reliable response. GABA puffs diluted in SM/CSF solution or SM/CSF solution alone showed no significant differences in the CSF of IH, narcolepsy, or control groups. No associations were found between GABA responses, demographic features, disease duration, or disease severity in the whole population or within groups. Using the Xenopus oocyte assay, we found an absence of GABA-A receptor potentiation with CSF from patients with central hypersomnolence disorders, with no significant differences between hypocretin-deficient and non-hypocretin-deficient patients compared to controls. Ann Neurol 2016;80:259-268. © 2016 American Neurological Association.

Design and Synthesis of a Series of l-trans-4-Substituted Prolines as Selective Antagonists for the Ionotropic Glutamate Receptors Including Functional and X-ray Crystallographic Studies of New Subtype Selective Kainic Acid Receptor Subtype 1 (GluK1) Antagonist (2S,4R)-4-(2-Carboxyphenoxy)pyrrolidine-2-carboxylic Acid.

PubMed

Krogsgaard-Larsen, Niels; Delgar, Claudia G; Koch, Karina; Brown, Patricia M G E; Møller, Charlotte; Han, Liwei; Huynh, Tri H V; Hansen, Stinne W; Nielsen, Birgitte; Bowie, Derek; Pickering, Darryl S; Kastrup, Jette Sandholm; Frydenvang, Karla; Bunch, Lennart

2017-01-12

Ionotropic glutamate receptor antagonists are valuable tool compounds for studies of neurological pathways in the central nervous system. On the basis of rational ligand design, a new class of selective antagonists, represented by (2S,4R)-4-(2-carboxyphenoxy)pyrrolidine-2-carboxylic acid (1b), for cloned homomeric kainic acid receptors subtype 1 (GluK1) was attained (K i = 4 μM). In a functional assay, 1b displayed full antagonist activity with IC 50 = 6 ± 2 μM. A crystal structure was obtained of 1b when bound in the ligand binding domain of GluK1. A domain opening of 13-14° was seen compared to the structure with glutamate, consistent with 1b being an antagonist. A structure-activity relationship study showed that the chemical nature of the tethering atom (C, O, or S) linking the pyrrolidine ring and the phenyl ring plays a key role in the receptor selectivity profile and that substituents on the phenyl ring are well accommodated by the GluK1 receptor.

A High Content Drug Screen Identifies Ursolic Acid as an Inhibitor of Amyloid β Protein Interactions with Its Receptor CD36*

PubMed Central

Wilkinson, Kim; Boyd, Justin D.; Glicksman, Marcie; Moore, Kathryn J.; El Khoury, Joseph

2011-01-01

A pathological hallmark of Alzheimer disease (AD) is deposition of amyloid β (Aβ) in the brain. Aβ binds to microglia via a receptor complex that includes CD36 leading to production of proinflammatory cytokines and neurotoxic reactive oxygen species and subsequent neurodegeneration. Interruption of Aβ binding to CD36 is a potential therapeutic strategy for AD. To identify pharmacologic inhibitors of Aβ binding to CD36, we developed a 384-well plate assay for binding of fluorescently labeled Aβ to Chinese hamster ovary cells stably expressing human CD36 (CHO-CD36) and screened an Food and Drug Administration-approved compound library. The assay was optimized based on the cells' tolerance to dimethyl sulfoxide, Aβ concentration, time required for Aβ binding, reproducibility, and signal-to-background ratio. Using this assay, we identified four compounds as potential inhibitors of Aβ binding to CD36. These compounds were ursolic acid, ellipticine, zoxazolamine, and homomoschatoline. Of these compounds, only ursolic acid, a naturally occurring pentacyclic triterpenoid, successfully inhibited binding of Aβ to CHO-CD36 cells in a dose-dependent manner. The ursolic acid effect reached a plateau at ∼20 μm, with a maximal inhibition of 64%. Ursolic acid also blocked binding of Aβ to microglial cells and subsequent ROS production. Our data indicate that cell-based high-content screening of small molecule libraries for their ability to block binding of Aβ to its receptors is a useful tool to identify novel inhibitors of receptors involved in AD pathogenesis. Our data also suggest that ursolic acid is a potential therapeutic agent for AD via its ability to block Aβ-CD36 interactions. PMID:21835916

Substitution of lysine-181 to aspartic acid in the third transmembrane region of the endothelin (ET) type B receptor selectively reduces its high-affinity binding with ET-3 peptide.

PubMed

Mauzy, C; Wu, L H; Egloff, A M; Mirzadegan, T; Chung, F Z

1992-01-01

In the G protein-coupled receptor family, a highly conserved aspartic acid located within the third transmembrane domain has been shown to be involved in ligand binding. Within the endothelin (ET) peptide receptor family, this aspartic acid has been replaced by a lysine. To assess the importance of this residue in ET binding, the lysine (position 181) of rat ET type B receptor was replaced by an aspartic acid. The effects on ligand binding and phosphoinositide turnover of both the wild-type and K181D mutant receptors were examined using transient receptor expression in COS-7 cells. Using [125I]ET-1 as the radioactive peptide ligand in displacement binding studies, the wild-type receptor displayed a typical non-isopeptide-selective binding profile with similar IC50 values (0.2-0.6 nM) for all three ET peptides (ET-1, ET-2, and ET-3). The mutant receptor showed an increase in IC50 values for ET-1 (5 nM), ET-2 (27 nM), and ET-3 (127 nM). The K181D mutant receptor still elicited full inositol phosphate (IP) accumulation responses in the presence of saturating concentrations of ETs (10 nM of ET-1, 100 nM of ET-2, or 1 microM of ET-3), indicating that the mutation did not affect G protein coupling.

Dietary protein in urea cycle defects: How much? Which? How?

PubMed

Boneh, Avihu

2014-01-01

Dietary recommendations for patients with urea cycle disorders (UCDs) are designed to prevent metabolic decompensation (primarily hyperammonaemia), and to enable normal growth. They are based on the 'recommended daily intake' guidelines, on theoretical considerations and on local experience. A retrospective dietary review of 28 patients with UCDs in good metabolic control, at different ages, indicates that most patients can tolerate a natural protein intake that is compatible with metabolic stability and good growth. However, protein aversion presents a problem in many patients, leading to poor compliance with the prescribed daily protein intake. These patients are at risk of chronic protein deficiency. Failing to recognise this risk, and further restricting protein intake because of persistent hyperammonaemia may aggravate the deficiency and potentially lead to episodes of metabolic decompensation for which no clear cause is found. These patients may need on-going supplementation with essential amino acids (EAA) to prevent protein malnutrition. Current recommendations for the management of acute metabolic decompensation include cessation of protein intake whilst increasing energy (calorie) intake in the first 24h. We have found that plasma concentrations of all EAA are low at the time of admission to hospital for metabolic decompensation, with correlation between low EAA concentrations, particularly branched-chain amino acids, and hyperammonaemia. Thus, supplementation with EAA should be considered at times of metabolic decompensation. Finally, it would be advantageous to treat patients in metabolic decompensation through enteral supplementation, whenever possible, because of the contribution of the splanchnic (portal-drained viscera) system to protein retention and metabolism. Copyright © 2014 Elsevier Inc. All rights reserved.

A single amino acid residue controls Ca2+ signaling by an octopamine receptor from Drosophila melanogaster.

PubMed

Hoff, Max; Balfanz, Sabine; Ehling, Petra; Gensch, Thomas; Baumann, Arnd

2011-07-01

Rhythmic activity of cells and cellular networks plays an important role in physiology. In the nervous system oscillations of electrical activity and/or second messenger concentrations are important to synchronize neuronal activity. At the molecular level, rhythmic activity can be initiated by different routes. We have recently shown that an octopamine-activated G-protein-coupled receptor (GPCR; DmOctα1Rb, CG3856) from Drosophila initiates Ca(2+) oscillations. Here, we have unraveled the molecular basis of cellular Ca(2+) signaling controlled by the DmOctα1Rb receptor using a combination of pharmacological intervention, site-directed mutagenesis, and functional cellular Ca(2+) imaging on heterologously expressed receptors. Phosphorylation of a single amino acid residue in the third intracellular loop of the GPCR by PKC is necessary and sufficient to desensitize the receptor. From its desensitized state, DmOctα1Rb is resensitized by dephosphorylation, and a new Ca(2+) signal occurs on octopamine stimulation. Our findings show that transient changes of the receptor's surface profile have a strong effect on its physiological signaling properties. We expect that the detailed knowledge of DmOctα1Rb-dependent signal transduction fosters the identification of specific drugs that can be used for GPCR-mediated pest control, since octopamine serves important physiological and behavioral functions in arthropods.

Interactions between Human Liver Fatty Acid Binding Protein and Peroxisome Proliferator Activated Receptor Selective Drugs

PubMed Central

Velkov, Tony

2013-01-01

Fatty acid binding proteins (FABPs) act as intracellular shuttles for fatty acids as well as lipophilic xenobiotics to the nucleus, where these ligands are released to a group of nuclear receptors called the peroxisome proliferator activated receptors (PPARs). PPAR mediated gene activation is ultimately involved in maintenance of cellular homeostasis through the transcriptional regulation of metabolic enzymes and transporters that target the activating ligand. Here we show that liver- (L-) FABP displays a high binding affinity for PPAR subtype selective drugs. NMR chemical shift perturbation mapping and proteolytic protection experiments show that the binding of the PPAR subtype selective drugs produces conformational changes that stabilize the portal region of L-FABP. NMR chemical shift perturbation studies also revealed that L-FABP can form a complex with the PPAR ligand binding domain (LBD) of PPARα. This protein-protein interaction may represent a mechanism for facilitating the activation of PPAR transcriptional activity via the direct channeling of ligands between the binding pocket of L-FABP and the PPARαLBD. The role of L-FABP in the delivery of ligands directly to PPARα via this channeling mechanism has important implications for regulatory pathways that mediate xenobiotic responses and host protection in tissues such as the small intestine and the liver where L-FABP is highly expressed. PMID:23476633

Bile Acid Metabolism in Liver Pathobiology

PubMed Central

Chiang, John Y. L.; Ferrell, Jessica M.

2018-01-01

Bile acids facilitate intestinal nutrient absorption and biliary cholesterol secretion to maintain bile acid homeostasis, which is essential for protecting liver and other tissues and cells from cholesterol and bile acid toxicity. Bile acid metabolism is tightly regulated by bile acid synthesis in the liver and bile acid biotransformation in the intestine. Bile acids are endogenous ligands that activate a complex network of nuclear receptor farnesoid X receptor and membrane G protein-coupled bile acid receptor-1 to regulate hepatic lipid and glucose metabolic homeostasis and energy metabolism. The gut-to-liver axis plays a critical role in the regulation of enterohepatic circulation of bile acids, bile acid pool size, and bile acid composition. Bile acids control gut bacteria overgrowth, and gut bacteria metabolize bile acids to regulate host metabolism. Alteration of bile acid metabolism by high-fat diets, sleep disruption, alcohol, and drugs reshapes gut microbiome and causes dysbiosis, obesity, and metabolic disorders. Gender differences in bile acid metabolism, FXR signaling, and gut microbiota have been linked to higher prevalence of fatty liver disease and hepatocellular carcinoma in males. Alteration of bile acid homeostasis contributes to cholestatic liver diseases, inflammatory diseases in the digestive system, obesity, and diabetes. Bile acid-activated receptors are potential therapeutic targets for developing drugs to treat metabolic disorders. PMID:29325602

Aromatic D-amino acids act as chemoattractant factors for human leukocytes through a G protein-coupled receptor, GPR109B.

PubMed

Irukayama-Tomobe, Yoko; Tanaka, Hirokazu; Yokomizo, Takehiko; Hashidate-Yoshida, Tomomi; Yanagisawa, Masashi; Sakurai, Takeshi

2009-03-10

GPR109B (HM74) is a putative G protein-coupled receptor (GPCR) whose cognate ligands have yet to be characterized. GPR109B shows a high degree of sequence similarity to GPR109A, another GPCR that was identified as a high-affinity nicotinic acid (niacin) receptor. However, the affinity of nicotinic acid to GPR109B is very low. In this study, we found that certain aromatic D-amino acids, including D-phenylalanine, D-tryptophan, and the metabolite of the latter, D-kynurenine, decreased the activity of adenylate cyclase in cells transfected with GPR109B cDNA through activation of pertussis toxin (PTX)-sensitive G proteins. These D-amino acids also elicited a transient rise of intracellular Ca(2+) level in cells expressing GPR109B in a PTX-sensitive manner. In contrast, these D-amino acids did not show any effects on cells expressing GPR109A. We found that the GPR109B mRNA is abundantly expressed in human neutrophils. D-phenylalanine and D-tryptophan induced a transient increase of intracellular Ca(2+) level and a reduction of cAMP levels in human neutrophils. Furthermore, knockdown of GPR109B by RNA interference inhibited the D-amino acids-induced decrease of cellular cAMP levels in human neutrophils. These D-amino acids induced chemotactic activity of freshly prepared human neutrophils. We also found that D-phenylalanine and D-tryptophan induced chemotactic responses in Jurkat cells transfected with the GPR109B cDNA but not in mock-transfected Jurkat cells. These results suggest that these aromatic D-amino acids elicit a chemotactic response in human neutrophils via activation of GPR109B.

Endogenous neuropeptide Y depresses the afferent signaling of gastric acid challenge to the mouse brainstem via neuropeptide Y type Y2 and Y4 receptors.

PubMed

Wultsch, T; Painsipp, E; Thoeringer, C K; Herzog, H; Sperk, G; Holzer, P

2005-01-01

Vagal afferents signal gastric acid challenge to the nucleus tractus solitarii of the rat brainstem. This study investigated whether nucleus tractus solitarii neurons in the mouse also respond to gastric acid challenge and whether this chemonociceptive input is modified by neuropeptide Y acting via neuropeptide Y receptors of type Y2 or Y4. The gastric mucosa of female mice was exposed to different concentrations of HCl or saline, excitation of neurons in the nucleus tractus solitarii visualized by c-Fos immunohistochemistry, gastric emptying deduced from the gastric volume recovery, and gastric lesion formation evaluated by planimetry. Relative to saline, intragastric HCl (0.15-0.35 M) increased the number of c-Fos-expressing cells in the nucleus tractus solitarii in a concentration-dependent manner, inhibited gastric emptying but failed to cause significant hemorrhagic injury in the stomach. Mice in which the Y2 or Y4 receptor gene had been deleted responded to gastric acid challenge with a significantly higher expression of c-Fos in the nucleus tractus solitarii, the increases amounting to 39 and 31%, respectively. The HCl-induced inhibition of gastric emptying was not altered by deletion of the Y2 or Y4 receptor gene. BIIE0246 ((S)-N2-[[1-[2-[4-[(R,S)-5,11-dihydro-6(6H)-oxodibenz[b,e] azepin-11-yl]-1-piperazinyl]-2-oxoethyl]cyclopentyl] acetyl]-N-[2-[1,2-dihydro-3,5 (4H)-dioxo-1,2-diphenyl-3H-1,2,4-triazol-4-yl]ethyl]-argininamide; 0.03 mmol/kg s.c.), a Y2 receptor antagonist which does not cross the blood-brain barrier, did not modify the c-Fos response to gastric acid challenge. The Y2 receptor agonist peptide YY-(3-36) (0.1 mg/kg intraperitoneally) likewise failed to alter the gastric HCl-evoked expression of c-Fos in the nucleus tractus solitarii. BIIE0246, however, prevented the effect of peptide YY-(3-36) to inhibit gastric acid secretion as deduced from measurement of intragastric pH. The current data indicate that gastric challenge with acid

Inhibition of Smooth Muscle Proliferation by Urea-Based Alkanoic Acids via Peroxisome Proliferator-Activated Receptor α–Dependent Repression of Cyclin D1

PubMed Central

Ng, Valerie Y.; Morisseau, Christophe; Falck, John R.; Hammock, Bruce D.; Kroetz, Deanna L.

2007-01-01

Objective Proliferation of smooth muscle cells is implicated in cardiovascular complications. Previously, a urea-based soluble epoxide hydrolase inhibitor was shown to attenuate smooth muscle cell proliferation. We examined the possibility that urea-based alkanoic acids activate the nuclear receptor peroxisome proliferator-activated receptor α (PPARα) and the role of PPARα in smooth muscle cell proliferation. Methods and Results Alkanoic acids transactivated PPARα, induced binding of PPARα to its response element, and significantly induced the expression of PPARα-responsive genes, showing their function as PPARα agonists. Furthermore, the alkanoic acids attenuated platelet-derived growth factor–induced smooth muscle cell proliferation via repression of cyclin D1 expression. Using small interfering RNA to decrease endogenous PPARα expression, it was determined that PPARα was partially involved in the cyclin D1 repression. The antiproliferative effects of alkanoic acids may also be attributed to their inhibitory effects on soluble epoxide hydrolase, because epoxyeicosatrienoic acids alone inhibited smooth muscle cell proliferation. Conclusions These results show that attenuation of smooth muscle cell proliferation by urea-based alkanoic acids is mediated, in part, by the activation of PPARα. These acids may be useful for designing therapeutics to treat diseases characterized by excessive smooth muscle cell proliferation. PMID:16917105

Lysergic acid diethylamide (LSD) administration selectively downregulates serotonin2 receptors in rat brain.

PubMed

Buckholtz, N S; Zhou, D F; Freedman, D X; Potter, W Z

1990-04-01

A dosage regimen of lysergic acid diethylamide (LSD) that reliably produces behavioral tolerance in rats was evaluated for effects on neurotransmitter receptor binding in rat brain using a variety of radioligands selective for amine receptor subtypes. Daily administration of LSD [130 micrograms/kg (0.27 mumol/kg) intraperitoneally (IP)] for 5 days produced a decrease in serotonin2 (5-hydroxytryptamine2, 5-HT2) binding in cortex (measured 24 hours after the last drug administration) but did not affect binding to other receptor systems (5-HT1A, 5-HT1B, beta-adrenergic, alpha 1- or alpha 2-adrenergic, D2-dopaminergic) or to a recognition site for 5-HT uptake. The decrease was evident within 3 days of LSD administration but was not demonstrable after the first LSD dose. Following 5 days of LSD administration the decrease was still present 48 hours, but not 96 hours, after the last administration. The indole hallucinogen psilocybin [1.0 mg/kg (3.5 mumol/kg) for 8 days] also produced a significant decrease in 5HT2 binding, but neither the nonhallucinogenic analog bromo-LSD [1.3 mg/kg (2.4 mumol/kg) for 5 days] nor mescaline [10 mg/kg (40.3 mumol/kg) for 5 or 10 days] affected 5-HT2 binding. These observations suggest that LSD and other indole hallucinogens may act as 5-HT2 agonists at postsynaptic 5-HT2 receptors. Decreased 5-HT2 binding strikingly parallels the development and loss of behavioral tolerance seen with repeated LSD administration, but the decreased binding per se cannot explain the gamut of behavioral tolerance and cross-tolerance phenomena among the indole and phenylethylamine hallucinogens.

Phosphorylation of a conserved serine in the deoxyribonucleic acid binding domain of nuclear receptors alters intracellular localization.

PubMed

Sun, Kai; Montana, Vedrana; Chellappa, Karthikeyani; Brelivet, Yann; Moras, Dino; Maeda, Yutaka; Parpura, Vladimir; Paschal, Bryce M; Sladek, Frances M

2007-06-01

Nuclear receptors (NRs) are a superfamily of transcription factors whose genomic functions are known to be activated by lipophilic ligands, but little is known about how to deactivate them or how to turn on their nongenomic functions. One obvious mechanism is to alter the nuclear localization of the receptors. Here, we show that protein kinase C (PKC) phosphorylates a highly conserved serine (Ser) between the two zinc fingers of the DNA binding domain of orphan receptor hepatocyte nuclear factor 4alpha (HNF4alpha). This Ser (S78) is adjacent to several positively charged residues (Arg or Lys), which we show here are involved in nuclear localization of HNF4alpha and are conserved in nearly all other NRs, along with the Ser/threonine (Thr). A phosphomimetic mutant of HNF4alpha (S78D) reduced DNA binding, transactivation ability, and protein stability. It also impaired nuclear localization, an effect that was greatly enhanced in the MODY1 mutant Q268X. Treatment of the hepatocellular carcinoma cell line HepG2 with PKC activator phorbol 12-myristate 13-acetate also resulted in increased cytoplasmic localization of HNF4alpha as well as decreased endogenous HNF4alpha protein levels in a proteasome-dependent fashion. We also show that PKC phosphorylates the DNA binding domain of other NRs (retinoic acid receptor alpha, retinoid X receptor alpha, and thyroid hormone receptor beta) and that phosphomimetic mutants of the same Ser/Thr result in cytoplasmic localization of retinoid X receptor alpha and peroxisome proliferator-activated receptor alpha. Thus, phosphorylation of this conserved Ser between the two zinc fingers may be a common mechanism for regulating the function of NRs.

Design and synthesis of alkoxyindolyl-3-acetic acid analogs as peroxisome proliferator-activated receptor-γ/δ agonists.

PubMed

Gim, Hyo Jin; Li, Hua; Lee, Eun; Ryu, Jae-Ha; Jeon, Raok

2013-01-15

A series of carbazole or phenoxazine containing alkoxyindole-3-acetic acid analogs were prepared as PPARγ/δ agonists and their transactivation activities for PPAR receptor subtypes (α, γ and δ) were investigated. Structure-activity relationship studies disclosed the effect of the lipophilic tail, attaching position of the alkoxy group and N-benzyl substitution at indole. Compound 1b was the most potent for PPARδ and 3b for PPARγ. Molecular modeling suggested two different binding modes of our alkoxyindole-3-acetic acid analogs providing the insight into their PPAR activity. Copyright © 2012 Elsevier Ltd. All rights reserved.

Gi-coupled γ-aminobutyric acid-B receptors cross-regulate phospholipase C and calcium in airway smooth muscle.

PubMed

Mizuta, Kentaro; Mizuta, Fumiko; Xu, Dingbang; Masaki, Eiji; Panettieri, Reynold A; Emala, Charles W

2011-12-01

γ-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system, and exerts its actions via both ionotropic (GABA(A)) and metabotropic (GABA(B)) receptors. Although the functional expression of GABA(B) receptors coupled to the G(i) protein was reported for airway smooth muscle, the role of GABA(B) receptors in airway responsiveness remains unclear. We investigated whether G(i)-coupled GABA(B) receptors cross-regulate phospholipase C (PLC), an enzyme classically regulated by G(q)-coupled receptors in human airway smooth muscle cells. Both the GABA(B)-selective agonist baclofen and the endogenous ligand GABA significantly increased the synthesis of inositol phosphate, whereas GABA(A) receptor agonists, muscimol, and 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol exerted no effect. The baclofen-induced synthesis of inositol phosphate and transient increases in [Ca(2+)](i) were blocked by CGP35348 and CGP55845 (selective GABA(B) antagonists), pertussis toxin (PTX, which inactivates the G(i) protein), gallein (a G(βγ) signaling inhibitor), U73122 (an inhibitor of PLC-β), and xestospongin C, an inositol 1,4,5-triphosphate receptor blocker. Baclofen also potentiated the bradykinin-induced synthesis of inositol phosphate and transient increases in [Ca(2+)](i), which were blocked by CGP35348 or PTX. Moreover, baclofen potentiated the substance P-induced contraction of airway smooth muscle in isolated guinea pig tracheal rings. In conclusion, the stimulation of GABA(B) receptors in human airway smooth muscle cells rapidly mobilizes intracellular Ca(2+) stores by the synthesis of inositol phosphate via the activation of PLC-β, which is stimulated by G(βγ) protein liberated from G(i) proteins coupled to GABA(B) receptors. Furthermore, crosstalk between GABA(B) receptors and G(q)-coupled receptors potentiates the synthesis of inositol phosphate, transient increases in [Ca(2+)](i), and smooth muscle contraction through G

Ethanol impairs activation of retinoic acid receptors in cerebellar granule cells in a rodent model of fetal alcohol spectrum disorders.

PubMed

Kumar, Ambrish; Singh, Chandra K; DiPette, Donald D; Singh, Ugra S

2010-05-01

Ethanol is the main addictive and neurotoxic constituent of alcohol. Ethanol exposure during embryonic development causes dysfunction of the central nervous system (CNS) and leads to fetal alcohol spectrum disorders. The cerebellum is one of the CNS regions that are particularly vulnerable to ethanol toxic effects. Retinoic acid (RA) is a physiologically active metabolite of vitamin A that is locally synthesized in the cerebellum. Studies have shown that RA is required for neuronal development, but it remains unknown if ethanol impairs RA signaling and thus induces neuronal malformations. In this study, we tested the hypothesis that ethanol impairs the expression and activation of RA receptors in cerebellum and in cerebellar granule cells. The cerebellum of ethanol unexposed and exposed pups was used to study the expression of retinoic acid receptors (RARs or RXRs) by immunohistochemistry and by Western blot analysis. We also studied the effect of ethanol on expression of RA receptors in the cerebellar granule cells. Activation of RA receptors (DNA-binding activities) in response to high-dose ethanol was determined by electrophoretic mobility shift and supershift assays. Findings from these studies demonstrated that ethanol exposure reduced the expression of RARalpha/gamma while it increased the expression of RXRalpha/gamma in the cerebellum and in cerebellar granule neurons. Immuno-histological studies further strengthened the expression pattern of RA receptors in response to ethanol. The DNA-binding activity of RARs was reduced, while DNA-binding activity of RXRs was increased in response to ethanol exposure. For the first time, our studies have demonstrated that high-dose ethanol affects the expression and activation of RA receptors, which could impair the signaling events and induce harmful effects on the survival and differentiation of cerebellar granule cells. Taken together, these findings could provide insight into the treatment options for brain defects

Antidepressant-like effect of folic acid: Involvement of NMDA receptors and L-arginine-nitric oxide-cyclic guanosine monophosphate pathway.

PubMed

Brocardo, Patrícia de Souza; Budni, Josiane; Lobato, Kelly Ribas; Kaster, Manuella Pinto; Rodrigues, Ana Lúcia S

2008-11-19

Antidepressant-like activity of folic acid in forced swimming test and in the tail suspension test was demonstrated previously by our group. In this study we investigated the involvement of N-methyl-d-aspartate (NMDA) receptors and l-arginine-nitric oxide (NO)-cyclic guanosine monophosphate pathway in its antidepressant-like effect in the forced swimming test in mice. The antidepressant-like effect of folic acid (10 nmol/site, i.c.v.) was prevented by the pretreatment of mice with NMDA (0.1 pmol/site, i.c.v.), l-arginine (750 mg/kg, i.p., substrate for nitric oxide synthase), S-nitroso-N-acetyl-penicillamine (SNAP, 25 microg/site, i.c.v, a NO donor) or sildenafil (5 mg/kg, i.p., phosphodiesterase 5 inhibitor). The administration of 7-nitroindazole (25 and 50 mg/kg, i.p., a specific neuronal nitric oxide synthase (nNOS) inhibitor) or methylene blue (20 mg/kg, i.p., direct inhibitor of both nitric oxide synthase and soluble guanylate cyclase) in combination with a sub-effective dose of folic acid (1 nmol/site, i.c.v.) reduced the immobility time in the FST as compared with either drug alone. Together the results suggest that the antidepressant-like effect of folic acid in the forced swimming test is dependent on an inhibition of either NMDA receptors or NO and cGMP synthesis.

Activation of NMDA receptors in the brainstem, rostral ventromedial medulla, and nucleus reticularis gigantocellularis mediates mechanical hyperalgesia produced by repeated intramuscular injections of acidic saline in rats.

PubMed

Da Silva, Luis F; Desantana, Josimari M; Sluka, Kathleen A

2010-04-01

Repeated injections of acidic saline into the gastrocnemius muscle induce both muscle and cutaneous hypersensitivity. We have previously shown that microinjection of local anesthetic into either the rostral ventromedial medulla (RVM) or the nucleus reticularis gigantocellularis (NGC) reverses this muscle and cutaneous hypersensitivity. Although prior studies show that NMDA receptors in the RVM play a clear role in mediating visceral and inflammatory hypersensitivity, the role of NMDA receptors in the NGC or in noninflammatory muscle pain is unclear. Therefore, the present study evaluated involvement of the NMDA receptors in the RVM and NGC in muscle and cutaneous hypersensitivity induced by repeated intramuscular injections of acidic saline. Repeated intramuscular injections of acidic saline, 5 days apart, resulted in a bilateral decrease in the withdrawal thresholds of the paw and muscle in all groups 24 hours after the second injection. Microinjection of NMDA receptor antagonists into the RVM reversed both the muscle and cutaneous hypersensitivity. However, microinjection of NMDA receptor antagonists into the NGC only reversed cutaneous but not muscle hypersensitivity. These results suggest that NMDA receptors in the RVM mediate both muscle and cutaneous hypersensitivity, but those in the NGC mediate only cutaneous hypersensitivity after muscle insult. The current study shows that NMDA receptors in supraspinal facilitatory sites maintain noninflammatory muscle pain. Clinical studies in people with chronic widespread, noninflammatory pain, similarly, show alterations in central excitability. Thus, understanding mechanisms in an animal model could lead to improved treatment for patients with chronic muscle pain. Copyright 2010 American Pain Society. Published by Elsevier Inc. All rights reserved.

A Single Amino Acid Residue at Transmembrane Domain 4 of the α Subunit Influences Carisoprodol Direct Gating Efficacy at GABAA Receptors.

PubMed

Kumar, Manoj; Kumar, Manish; Freund, John M; Dillon, Glenn H

2017-09-01

The muscle relaxant carisoprodol has recently been controlled at the federal level as a Schedule IV drug due to its high abuse potential and consequences of misuse, such as withdrawal syndrome, delusions, seizures, and even death. Recent work has shown that carisoprodol can directly gate and allosterically modulate the type A GABA (GABA A ) receptor. These actions are subunit-dependent; compared with other GABA A receptors, carisoprodol has nominal direct gating effects in α 3 β 2 γ 2 receptors. Here, using site-directed mutagenesis and whole-cell patch-clamp electrophysiology in transiently transfected human embryonic kidney 293 cells, we examined the role of GABA A receptor α subunit transmembrane domain 4 (TM4) amino acids in direct gating and allosteric modulatory actions of carisoprodol. Mutation of α 3 valine at position 440 to leucine (present in the equivalent position in the α 1 subunit) significantly increased the direct gating effects of carisoprodol without affecting its allosteric modulatory effects. The corresponding reverse mutation, α 1(L415V), decreased carisoprodol direct gating potency and efficacy. Analysis of a series of amino acid mutations at the 415 position demonstrated that amino acid volume correlated positively with carisoprodol efficacy, whereas polarity inversely correlated with carisoprodol efficacy. We conclude that α 1(415) of TM4 is involved in the direct gating, but not allosteric modulatory, actions of carisoprodol. In addition, the orientation of alkyl or hydroxyl groups at this position influences direct gating effects. These findings support the likelihood that the direct gating and allosteric modulatory effects of carisoprodol are mediated via distinct binding sites. Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.

[Effects of ursodeoxycholic acid on the liver plasma membrane fluidity, hepatic glutathione concentration, hepatic estrogen receptors and progesterone receptors in pregnant rats with ethinylestradiol and progesterone induced intrahepatic cholestasis].

PubMed

Shi, Qing-yun; Kong, Bei-hua; Ma, Kai-dong; Zhang, Xiang-li; Jiang, Sen

2003-11-01

To explore the effects of ursodeoxycholic acid (UDCA) on the fluidity of hepatic plasma membrane, glutathione concentration in liver, hepatic estrogen receptors and progesterone receptors in pregnant rats with ethinylestradiol and progesterone induced intrahepatic cholestasis. sixty clean SD pregnant rats were selected and divided into three groups at random. Since the 13th day of pregnancy after taking blood, normal group was injected subcutaneously with refined vegetable oil 2.5 ml x kg(-1) x d(-1). Control group and treatment group were injected subcutaneously with the solution of progesterone 75 mg x kg(-1) x d(-1) and 17-alpha-ethynylestradio 1.25 mg x kg(-1) x d(-1) till the 17th day. Since the 17th day control group, normal group were fedwish 0.9% natriichloridi solution 5 ml x kg(-1) x d(-1); Treatment group was fedwish UDCA 50 mg x kg(-1) x d(-1) every day. On the 21th day, all rats were killed. Then the livers were collected for study. Membrane fluidity was measured by fluorescence polarization using 1,6-diphenyl-1,3,5-hexatriene (DPH) as a probe. Glutathione concentration was measured by 5,5'-dithionbis (2-nitrobenzoic acid) (DTNB). Estrogen receptors and progesterone receptors were measured by flow cytometry. (1) Hepatic plasma membrane fluidity and glutathione (GSH) concentration: significantly lower level of GSH concentration and higher fluorescence polarization (P) were detected in control group (GSH: 1.13 +/- 0.03, P: 0.149 +/- 0.008) in comparison with normal group (GSH: 2.11 +/- 0.07, P: 0.132 +/- 0.004, P < 0.05). However, Significantly higher level of GSH concentration and lower fluorescence polarization were detected in treatment group (GSH: 1.82 +/- 0.04, P: 0.141 +/- 0.006) in comparison with control group (P < 0.05). The level of GSH concentration and fluorescence polarization were no difference between treatment group and normal group. Hepatic estrogen receptors (ER) and progesterone receptors (PR): The expression of ER and PR in control

Folinic acid treatment for schizophrenia associated with folate receptor autoantibodies.

PubMed

Ramaekers, V T; Thöny, B; Sequeira, J M; Ansseau, M; Philippe, P; Boemer, F; Bours, V; Quadros, E V

2014-12-01

Auto-antibodies against folate receptor alpha (FRα) at the choroid plexus that block N(5)-methyltetrahydrofolate (MTHF) transfer to the brain were identified in catatonic schizophrenia. Acoustic hallucinations disappeared following folinic acid treatment. Folate transport to the CNS prevents homocysteine accumulation and delivers one-carbon units for methyl-transfer reactions and synthesis of purines. The guanosine derivative tetrahydrobiopterin acts as common co-factor for the enzymes producing dopamine, serotonin and nitric oxide. Our study selected patients with schizophrenia unresponsive to conventional treatment. Serum from these patients with normal plasma homocysteine, folate and vitamin B12 was tested for FR autoantibodies of the blocking type on serial samples each week. Spinal fluid was analyzed for MTHF and the metabolites of pterins, dopamine and serotonin. The clinical response to folinic acid treatment was evaluated. Fifteen of 18 patients (83.3%) had positive serum FR auto-antibodies compared to only 1 in 30 controls (3.3%) (χ(2)=21.6; p<0.0001). FRα antibody titers in patients fluctuated over time varying between negative and high titers, modulating folate flux to the CNS, which explained low CSF folate values in 6 and normal values in 7 patients. The mean±SD for CSF MTHF was diminished compared to previously established controls (t-test: 3.90; p=0.0002). A positive linear correlation existed between CSF MTHF and biopterin levels. CSF dopamine and serotonin metabolites were low or in the lower normal range. Administration of folinic acid (0.3-1mg/kg/day) to 7 participating patients during at least six months resulted in clinical improvement. Assessment of FR auto-antibodies in serum is recommended for schizophrenic patients. Clinical negative or positive symptoms are speculated to be influenced by the level and evolution of FRα antibody titers which determine folate flux to the brain with up- or down-regulation of brain folate intermediates

Phosphatidic acid phospholipase A1 mediates ER–Golgi transit of a family of G protein–coupled receptors

PubMed Central

Kunduri, Govind; Yuan, Changqing; Parthibane, Velayoudame; Nyswaner, Katherine M.; Kanwar, Ritu; Nagashima, Kunio; Britt, Steven G.; Mehta, Nickita; Kotu, Varshika; Porterfield, Mindy; Tiemeyer, Michael; Dolph, Patrick J.; Acharya, Usha

2014-01-01

The coat protein II (COPII)–coated vesicular system transports newly synthesized secretory and membrane proteins from the endoplasmic reticulum (ER) to the Golgi complex. Recruitment of cargo into COPII vesicles requires an interaction of COPII proteins either with the cargo molecules directly or with cargo receptors for anterograde trafficking. We show that cytosolic phosphatidic acid phospholipase A1 (PAPLA1) interacts with COPII protein family members and is required for the transport of Rh1 (rhodopsin 1), an N-glycosylated G protein–coupled receptor (GPCR), from the ER to the Golgi complex. In papla1 mutants, in the absence of transport to the Golgi, Rh1 is aberrantly glycosylated and is mislocalized. These defects lead to decreased levels of the protein and decreased sensitivity of the photoreceptors to light. Several GPCRs, including other rhodopsins and Bride of sevenless, are similarly affected. Our findings show that a cytosolic protein is necessary for transit of selective transmembrane receptor cargo by the COPII coat for anterograde trafficking. PMID:25002678

A Rationally Designed Agonist Defines Subfamily IIIA Abscisic Acid Receptors As Critical Targets for Manipulating Transpiration.

PubMed

Vaidya, Aditya S; Peterson, Francis C; Yarmolinsky, Dmitry; Merilo, Ebe; Verstraeten, Inge; Park, Sang-Youl; Elzinga, Dezi; Kaundal, Amita; Helander, Jonathan; Lozano-Juste, Jorge; Otani, Masato; Wu, Kevin; Jensen, Davin R; Kollist, Hannes; Volkman, Brian F; Cutler, Sean R

2017-11-17

Increasing drought and diminishing freshwater supplies have stimulated interest in developing small molecules that can be used to control transpiration. Receptors for the plant hormone abscisic acid (ABA) have emerged as key targets for this application, because ABA controls the apertures of stomata, which in turn regulate transpiration. Here, we describe the rational design of cyanabactin, an ABA receptor agonist that preferentially activates Pyrabactin Resistance 1 (PYR1) with low nanomolar potency. A 1.63 Å X-ray crystallographic structure of cyanabactin in complex with PYR1 illustrates that cyanabactin's arylnitrile mimics ABA's cyclohexenone oxygen and engages the tryptophan lock, a key component required to stabilize activated receptors. Further, its sulfonamide and 4-methylbenzyl substructures mimic ABA's carboxylate and C6 methyl groups, respectively. Isothermal titration calorimetry measurements show that cyanabactin's compact structure provides ready access to high ligand efficiency on a relatively simple scaffold. Cyanabactin treatments reduce Arabidopsis whole-plant stomatal conductance and activate multiple ABA responses, demonstrating that its in vitro potency translates to ABA-like activity in vivo. Genetic analyses show that the effects of cyanabactin, and the previously identified agonist quinabactin, can be abolished by the genetic removal of PYR1 and PYL1, which form subclade A within the dimeric subfamily III receptors. Thus, cyanabactin is a potent and selective agonist with a wide spectrum of ABA-like activities that defines subfamily IIIA receptors as key target sites for manipulating transpiration.

Boronic acid-tethered amphiphilic hyaluronic acid derivative-based nanoassemblies for tumor targeting and penetration.

PubMed

Jeong, Jae Young; Hong, Eun-Hye; Lee, Song Yi; Lee, Jae-Young; Song, Jae-Hyoung; Ko, Seung-Hak; Shim, Jae-Seong; Choe, Sunghwa; Kim, Dae-Duk; Ko, Hyun-Jeong; Cho, Hyun-Jong

2017-04-15

(3-Aminomethylphenyl)boronic acid (AMPB)-installed hyaluronic acid-ceramide (HACE)-based nanoparticles (NPs), including manassantin B (MB), were fabricated for tumor-targeted delivery. The amine group of AMPB was conjugated to the carboxylic acid group of hyaluronic acid (HA) via amide bond formation, and synthesis was confirmed by spectroscopic methods. HACE-AMPB/MB NPs with a 239-nm mean diameter, narrow size distribution, negative zeta potential, and >90% drug encapsulation efficiency were fabricated. Exposed AMPB in the outer surface of HACE-AMPB NPs (in the aqueous environment) may react with sialic acid of cancer cells. The improved cellular accumulation efficiency, in vitro antitumor efficacy, and tumor penetration efficiency of HACE-AMPB/MB NPs, compared with HACE/MB NPs, in MDA-MB-231 cells (CD44 receptor-positive human breast adenocarcinoma cells) may be based on the CD44 receptor-mediated endocytosis and phenylboronic acid-sialic acid interaction. Enhanced in vivo tumor targetability, infiltration efficiency, and antitumor efficacies of HACE-AMPB NPs, compared with HACE NPs, were observed in a MDA-MB-231 tumor-xenografted mouse model. In addition to passive tumor targeting (based on an enhanced permeability and retention effect) and active tumor targeting (interaction between HA and CD44 receptor), the phenylboronic acid-sialic acid interaction can play important roles in augmented tumor targeting and penetration of HACE-AMPB NPs. STATEMENT OF SIGNIFICANCE: (3-Aminomethylphenyl)boronic acid (AMPB)-tethered hyaluronic acid-ceramide (HACE)-based nanoparticles (NPs), including manassantin B (MB), were fabricated and their tumor targeting and penetration efficiencies were assessed in MDA-MB-231 (CD44 receptor-positive human adenocarcinoma) tumor models. MB, which exhibited antitumor efficacies via the inhibition of angiogenesis and hypoxia inducible factor (HIF)-1, was entrapped in HACE-AMPB NPs in this study. Phenylboronic acid located in the outer surface

Asymmetrical Macromolecular Complex Formation of Lysophosphatidic Acid Receptor 2 (LPA2) Mediates Gradient Sensing in Fibroblasts*

PubMed Central

Ren, Aixia; Moon, Changsuk; Zhang, Weiqiang; Sinha, Chandrima; Yarlagadda, Sunitha; Arora, Kavisha; Wang, Xusheng; Yue, Junming; Parthasarathi, Kaushik; Heil-Chapdelaine, Rick; Tigyi, Gabor; Naren, Anjaparavanda P.

2014-01-01

Chemotactic migration of fibroblasts toward growth factors relies on their capacity to sense minute extracellular gradients and respond to spatially confined receptor-mediated signals. Currently, mechanisms underlying the gradient sensing of fibroblasts remain poorly understood. Using single-particle tracking methodology, we determined that a lysophosphatidic acid (LPA) gradient induces a spatiotemporally restricted decrease in the mobility of LPA receptor 2 (LPA2) on chemotactic fibroblasts. The onset of decreased LPA2 mobility correlates to the spatial recruitment and coupling to LPA2-interacting proteins that anchor the complex to the cytoskeleton. These localized PDZ motif-mediated macromolecular complexes of LPA2 trigger a Ca2+ puff gradient that governs gradient sensing and directional migration in response to LPA. Disruption of the PDZ motif-mediated assembly of the macromolecular complex of LPA2 disorganizes the gradient of Ca2+ puffs, disrupts gradient sensing, and reduces the directional migration of fibroblasts toward LPA. Our findings illustrate that the asymmetric macromolecular complex formation of chemoattractant receptors mediates gradient sensing and provides a new mechanistic basis for models to describe gradient sensing of fibroblasts. PMID:25542932

Effect of common polymorphisms of the farnesoid X receptor and bile acid transporters on the pharmacokinetics of ursodeoxycholic acid.

PubMed

Hu, Miao; Fok, Benny S P; Wo, Siu-Kwan; Lee, Vincent H L; Zuo, Zhong; Tomlinson, Brian

2016-01-01

Ursodeoxycholic acid (UDCA), a natural, dihydroxy bile acid, promotes gallstone dissolution and has been attributed with several other beneficial effects. The farnesoid X receptor (FXR) may influence the pharmacokinetics of UDCA by modulating the expression of bile acid transporters. This exploratory study examined whether common functional polymorphisms in FXR and in bile acid transporter genes affect the pharmacokinetics of exogenous UDCA. Polymorphisms in genes for transporters involved in bile acid transport, solute carrier organic anion 1B1 (SLCO1B1) 388A>G and 521T>C, solute carrier 10A1 (SLC10A1) 800 C>T and ATP-binding cassette B11 (ABCB11) 1331T>C, and the FXR -1G>T polymorphism were genotyped in 26 male Chinese subjects who ingested single oral 500-mg doses of UDCA. Plasma concentrations of UDCA and its major conjugate metabolite glycoursodeoxycholic acid (GUDCA) were determined. The mean systemic exposure of UDCA was higher in the five subjects with one copy of the FXR -1G>T variant allele than in those homozygous for the wild-type allele (n = 21) (AUC0-24 h : 38.5 ± 28.2 vs. 20.9 ± 8.0 μg h/mL, P = 0.021), but this difference appeared mainly due to one outlier with the -1GT genotype and elevated baseline and post-treatment UDCA concentrations. After excluding the outlier, body weight was the only factor associated with plasma concentrations of UDCA and there were no significant associations with the other polymorphisms examined. None of the polymorphisms affected the pharmacokinetics of GUDCA. This study showed that the common polymorphisms in bile acid transporters had no significant effect on the pharmacokinetics of exogenous UDCA but an effect of the FXR polymorphism cannot be excluded. © 2015 Wiley Publishing Asia Pty Ltd.

The potent free radical scavenger alpha-lipoic acid improves memory in aged mice: putative relationship to NMDA receptor deficits.

PubMed

Stoll, S; Hartmann, H; Cohen, S A; Müller, W E

1993-12-01

alpha-Lipoic acid (alpha-LA) improved longer-term memory of aged female NMRI mice in the habituation in the open field test at a dose of 100 mg/kg body weight for 15 days. In a separate experiment, no such effect could be found for young mice. alpha-LA alleviated age-related NMDA receptor deficits (Bmax) without changing muscarinic, benzodiazepine, and alpha 2-adrenergic receptor deficits in aged mice. The carbachol-stimulated accumulation of inositol monophosphates was not changed by the treatment with alpha-LA. These results give tentative support to the hypothesis that alpha-LA improves memory in aged mice, probably by a partial compensation of NMDA receptor deficits. Possible modes of action of alpha-LA based on its free radical scavenger properties are discussed in relation to the membrane hypothesis of aging.

Successful combination immunotherapy of anti-gamma aminobutyric acid (GABA)A receptor antibody-positive encephalitis with extensive multifocal brain lesions.

PubMed

Fukami, Yuki; Okada, Hiroaki; Yoshida, Mari; Yamaguchi, Keiji

2017-08-31

A 78-year old woman who presented with akinetic mutism was admitted to our hospital. Brain MRI showed multifocal increased T 2 /FLAIR signal with extensive cortical-subcortical involvement. We suspected autoimmune encephalitis and the patient received methylprednisolone pulse. Her conscious level gradually recovered, but later relapsed again and presented with refractory status epilepticus. We treated her with intravenous immunoglobulin, plasma exchange and pulsed cyclophosphamide, with satisfactory response. A brain biopsy showed perivascular lymphocytic infiltrates and reactive gliosis. Anti-gamma aminobutyric acid (GABA) A receptor antibodies test came back to be positive after her recovery, and the diagnosis of anti-GABA A receptor antibody-positive encephalitis was made. This is a very rare case where brain biopsies were performed in a patient with anti-GABA A receptor antibody-positive encephalitis.

Synthesis of new C-25 and C-26 steroidal acids as potential ligands of the nuclear receptors DAF-12, LXR and GR.

PubMed

Dansey, María V; Del Fueyo, María C; Veleiro, Adriana S; Di Chenna, Pablo H

2017-05-01

A new methodology to obtain C-25 and C-26 steroidal acids starting from pregnenolone is described. Construction of the side chain was achieved by applying the Mukaiyama aldol reaction with a non-hydrolytic work-up to isolate the trapped silyl enol ether with higher yields. Using this methodology we synthesized three new steroidal acids as potential ligands of DAF-12, Liver X and Glucocorticoid nuclear receptors and studied their activity in reporter gene assays. Our results show that replacement of the 21-CH 3 by a 20-keto group in the side chains of the cholestane scaffold of DAF-12 or Liver X receptors ligands causes the loss of the activity. Copyright © 2017 Elsevier Inc. All rights reserved.

A Newly Discovered Antifibrotic Pathway Regulated by Two Fatty Acid Receptors: GPR40 and GPR84.

PubMed

Gagnon, Lyne; Leduc, Martin; Thibodeau, Jean-Francois; Zhang, Ming-Zhi; Grouix, Brigitte; Sarra-Bournet, Francois; Gagnon, William; Hince, Kathy; Tremblay, Mikaël; Geerts, Lilianne; Kennedy, Christopher R J; Hébert, Richard L; Gutsol, Alex; Holterman, Chet E; Kamto, Eldjonai; Gervais, Liette; Ouboudinar, Jugurtha; Richard, Jonathan; Felton, Alexandra; Laverdure, Alexandre; Simard, Jean-Christophe; Létourneau, Sylvie; Cloutier, Marie-Pier; Leblond, Francois A; Abbott, Shaun D; Penney, Christopher; Duceppe, Jean-Simon; Zacharie, Boulos; Dupuis, Jocelyn; Calderone, Angelino; Nguyen, Quang T; Harris, Raymond C; Laurin, Pierre

2018-05-01

Numerous clinical conditions can lead to organ fibrosis and functional failure. There is a great need for therapies that could effectively target pathophysiological pathways involved in fibrosis. GPR40 and GPR84 are G protein-coupled receptors with free fatty acid ligands and are associated with metabolic and inflammatory disorders. Although GPR40 and GPR84 are involved in diverse physiological processes, no evidence has demonstrated the relevance of GPR40 and GPR84 in fibrosis pathways. Using PBI-4050 (3-pentylbenzeneacetic acid sodium salt), a synthetic analog of a medium-chain fatty acid that displays agonist and antagonist ligand affinity toward GPR40 and GPR84, respectively, we uncovered an antifibrotic pathway involving these receptors. In experiments using Gpr40- and Gpr84-knockout mice in models of kidney fibrosis (unilateral ureteral obstruction, long-term post-acute ischemic injury, and adenine-induced chronic kidney disease), we found that GPR40 is protective and GPR84 is deleterious in these diseases. Moreover, through binding to GPR40 and GPR84, PBI-4050 significantly attenuated fibrosis in many injury contexts, as evidenced by the antifibrotic activity observed in kidney, liver, heart, lung, pancreas, and skin fibrosis models. Therefore, GPR40 and GPR84 may represent promising molecular targets in fibrosis pathways. We conclude that PBI-4050 is a first-in-class compound that may be effective for managing inflammatory and fibrosis-related diseases. Copyright © 2018 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

Ionotropic glutamate receptors: regulation by G-protein-coupled receptors.

PubMed

Rojas, Asheebo; Dingledine, Raymond

2013-04-01

The function of many ion channels is under dynamic control by coincident activation of G-protein-coupled receptors (GPCRs), particularly those coupled to the Gαs and Gαq family members. Such regulation is typically dependent on the subunit composition of the ionotropic receptor or channel as well as the GPCR subtype and the cell-specific panoply of signaling pathways available. Because GPCRs and ion channels are so highly represented among targets of U.S. Food and Drug Administration-approved drugs, functional cross-talk between these drug target classes is likely to underlie many therapeutic and adverse effects of marketed drugs. GPCRs engage a myriad of signaling pathways that involve protein kinases A and C (PKC) and, through PKC and interaction with β-arrestin, Src kinase, and hence the mitogen-activated-protein-kinase cascades. We focus here on the control of ionotropic glutamate receptor function by GPCR signaling because this form of regulation can influence the strength of synaptic plasticity. The amino acid residues phosphorylated by specific kinases have been securely identified in many ionotropic glutamate (iGlu) receptor subunits, but which of these sites are GPCR targets is less well known even when the kinase has been identified. N-methyl-d-aspartate, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, and heteromeric kainate receptors are all downstream targets of GPCR signaling pathways. The details of GPCR-iGlu receptor cross-talk should inform a better understanding of how synaptic transmission is regulated and lead to new therapeutic strategies for neuropsychiatric disorders.

Design of novel neurokinin 1 receptor antagonists based on conformationally constrained aromatic amino acids and discovery of a potent chimeric opioid agonist-neurokinin 1 receptor antagonist.

PubMed

Ballet, Steven; Feytens, Debby; Buysse, Koen; Chung, Nga N; Lemieux, Carole; Tumati, Suneeta; Keresztes, Attila; Van Duppen, Joost; Lai, Josephine; Varga, Eva; Porreca, Frank; Schiller, Peter W; Vanden Broeck, Jozef; Tourwé, Dirk

2011-04-14

A screening of conformationally constrained aromatic amino acids as base cores for the preparation of new NK1 receptor antagonists resulted in the discovery of three new NK1 receptor antagonists, 19 [Ac-Aba-Gly-NH-3',5'-(CF(3))(2)-Bn], 20 [Ac-Aba-Gly-NMe-3',5'-(CF(3))(2)-Bn], and 23 [Ac-Tic-NMe-3',5'-(CF(3))(2)-Bn], which were able to counteract the agonist effect of substance P, the endogenous ligand of NK1R. The most active NK1 antagonist of the series, 20 [Ac-Aba-Gly-NMe-3',5'-(CF(3))(2)-Bn], was then used in the design of a novel, potent chimeric opioid agonist-NK1 receptor antagonist, 35 [Dmt-D-Arg-Aba-Gly-NMe-3',5'-(CF(3))(2)-Bn], which combines the N terminus of the established Dmt(1)-DALDA agonist opioid pharmacophore (H-Dmt-D-Arg-Phe-Lys-NH(2)) and 20, the NK1R ligand. The opioid component of the chimeric compound 35, that is, Dmt-D-Arg-Aba-Gly-NH(2) (36), also proved to be an extremely potent and balanced μ and δ opioid receptor agonist with subnanomolar binding and in vitro functional activity.

Design of novel neurokinin 1 receptor antagonists based on conformationally constrained aromatic amino acids and discovery of a potent chimeric opioid agonist-neurokinin 1 receptor antagonist

PubMed Central

Ballet, Steven; Feytens, Debby; Buysse, Koen; Chung, Nga N.; Lemieux, Carole; Tumati, Suneeta; Keresztes, Attila; Van Duppen, Joost; Lai, Josephine; Varga, Eva; Porreca, Frank; Schiller, Peter W.; Broeck, Jozef Vanden; Tourwé, Dirk

2011-01-01

A screening of conformationally constrained aromatic amino acids as base cores for the preparation of new NK1 receptor antagonists resulted in the discovery of three new NK1 receptor antagonists, 19 [Ac-Aba-Gly-NH-3′,5′-(CF3)2-Bn], 20 [Ac-Aba-Gly-NMe-3′,5′-(CF3)2-Bn] and 23 [Ac-Tic-NMe-3′,5′-(CF3)2-Bn], which were able to counteract the agonist effect of substance P, the endogenous ligand of NK1R. The most active NK1 antagonist of the series, 20 [Ac-Aba-Gly-NMe-3′,5′-(CF3)2-Bn], was then used in the design of a novel, potent chimeric opioid agonist-NK1 receptor antagonist, 35 [Dmt-D-Arg-Aba-Gly-NMe-3′,5′-(CF3)2-Bn], which combines the N-terminus of the established Dmt1-DALDA agonist opioid pharmacophore (H-Dmt-D-Arg-Phe-Lys-NH2) and 20, the NK1R ligand. The opioid component of the chimeric compound 35, i.e. Dmt-D-Arg-Aba-Gly-NH2 36, also proved to be an extremely potent and balanced μ- and δ opioid receptor agonist with subnanomolar binding and in vitro functional activity. PMID:21413804

Characterization of Triticum aestivum Abscisic Acid Receptors and a Possible Role for These in Mediating Fusairum Head Blight Susceptibility in Wheat

PubMed Central

Gordon, Cameron S.; Rajagopalan, Nandhakishore; Risseeuw, Eddy P.; Surpin, Marci; Ball, Fraser J.; Barber, Carla J.; Buhrow, Leann M.; Clark, Shawn M.; Page, Jonathan E.; Todd, Chris D.; Abrams, Suzanne R.; Loewen, Michele C.

2016-01-01

Abscisic acid (ABA) is a well-characterized plant hormone, known to mediate developmental aspects as well as both abiotic and biotic stress responses. Notably, the exogenous application of ABA has recently been shown to increase susceptibility to the fungal pathogen Fusarium graminearum, the causative agent of Fusarium head blight (FHB) in wheat and other cereals. However roles and mechanisms associated with ABA’s modulation of pathogen responses remain enigmatic. Here the identification of putative ABA receptors from available genomic databases for Triticum aestivum (bread wheat) and Brachypodium distachyon (a model cereal) are reported. A number of these were cloned for recombinant expression and their functionality as ABA receptors confirmed by in vitro assays against protein phosphatases Type 2Cs. Ligand selectivity profiling of one of the wheat receptors (Ta_PYL2DS_FL) highlighted unique activities compared to Arabidopsis AtPYL5. Mutagenic analysis showed Ta_PYL2DS_FL amino acid D180 as being a critical contributor to this selectivity. Subsequently, a virus induced gene silencing (VIGS) approach was used to knockdown wheat Ta_PYL4AS_A (and similar) in planta, yielding plants with increased early stage resistance to FHB progression and decreased mycotoxin accumulation. Together these results confirm the existence of a family of ABA receptors in wheat and Brachypodium and present insight into factors modulating receptor function at the molecular level. That knockdown of Ta_PYL4AS_A (and similar) leads to early stage FHB resistance highlights novel targets for investigation in the future development of disease resistant crops. PMID:27755583

Characterization of Triticum aestivum Abscisic Acid Receptors and a Possible Role for These in Mediating Fusairum Head Blight Susceptibility in Wheat.

PubMed

Gordon, Cameron S; Rajagopalan, Nandhakishore; Risseeuw, Eddy P; Surpin, Marci; Ball, Fraser J; Barber, Carla J; Buhrow, Leann M; Clark, Shawn M; Page, Jonathan E; Todd, Chris D; Abrams, Suzanne R; Loewen, Michele C

2016-01-01

Abscisic acid (ABA) is a well-characterized plant hormone, known to mediate developmental aspects as well as both abiotic and biotic stress responses. Notably, the exogenous application of ABA has recently been shown to increase susceptibility to the fungal pathogen Fusarium graminearum, the causative agent of Fusarium head blight (FHB) in wheat and other cereals. However roles and mechanisms associated with ABA's modulation of pathogen responses remain enigmatic. Here the identification of putative ABA receptors from available genomic databases for Triticum aestivum (bread wheat) and Brachypodium distachyon (a model cereal) are reported. A number of these were cloned for recombinant expression and their functionality as ABA receptors confirmed by in vitro assays against protein phosphatases Type 2Cs. Ligand selectivity profiling of one of the wheat receptors (Ta_PYL2DS_FL) highlighted unique activities compared to Arabidopsis AtPYL5. Mutagenic analysis showed Ta_PYL2DS_FL amino acid D180 as being a critical contributor to this selectivity. Subsequently, a virus induced gene silencing (VIGS) approach was used to knockdown wheat Ta_PYL4AS_A (and similar) in planta, yielding plants with increased early stage resistance to FHB progression and decreased mycotoxin accumulation. Together these results confirm the existence of a family of ABA receptors in wheat and Brachypodium and present insight into factors modulating receptor function at the molecular level. That knockdown of Ta_PYL4AS_A (and similar) leads to early stage FHB resistance highlights novel targets for investigation in the future development of disease resistant crops.

Induction of cardiac Angptl4 by dietary fatty acids is mediated by peroxisome proliferator-activated receptor beta/delta and protects against fatty acid-induced oxidative stress.

PubMed

Georgiadi, Anastasia; Lichtenstein, Laeticia; Degenhardt, Tatjana; Boekschoten, Mark V; van Bilsen, Marc; Desvergne, Beatrice; Müller, Michael; Kersten, Sander

2010-06-11

Although dietary fatty acids are a major fuel for the heart, little is known about the direct effects of dietary fatty acids on gene regulation in the intact heart. To study the effect of dietary fatty acids on cardiac gene expression and explore the functional consequences. Oral administration of synthetic triglycerides composed of one single fatty acid altered cardiac expression of numerous genes, many of which are involved in the oxidative stress response. The gene most significantly and consistently upregulated by dietary fatty acids encoded Angiopoietin-like protein (Angptl)4, a circulating inhibitor of lipoprotein lipase expressed by cardiomyocytes. Induction of Angptl4 by the fatty acid linolenic acid was specifically abolished in peroxisome proliferator-activated receptor (PPAR)beta/delta(-/-) and not PPARalpha(-/-) mice and was blunted on siRNA-mediated PPARbeta/delta knockdown in cultured cardiomyocytes. Consistent with these data, linolenic acid stimulated binding of PPARbeta/delta but not PPARalpha to the Angptl4 gene. Upregulation of Angptl4 resulted in decreased cardiac uptake of plasma triglyceride-derived fatty acids and decreased fatty acid-induced oxidative stress and lipid peroxidation. In contrast, Angptl4 deletion led to enhanced oxidative stress in the heart, both after an acute oral fat load and after prolonged high fat feeding. Stimulation of cardiac Angptl4 gene expression by dietary fatty acids and via PPARbeta/delta is part of a feedback mechanism aimed at protecting the heart against lipid overload and consequently fatty acid-induced oxidative stress.

Increasing human Th17 differentiation through activation of orphan nuclear receptor retinoid acid-related orphan receptor γ (RORγ) by a class of aryl amide compounds.

PubMed

Zhang, Wei; Zhang, Jing; Fang, Leiping; Zhou, Ling; Wang, Shuai; Xiang, Zhijun; Li, Yuan; Wisely, Bruce; Zhang, Guifeng; An, Gang; Wang, Yonghui; Leung, Stewart; Zhong, Zhong

2012-10-01

In a screen for small-molecule inhibitors of retinoid acid-related orphan receptor γ (RORγ), we fortuitously discovered that a class of aryl amide compounds behaved as functional activators of the interleukin 17 (IL-17) reporter in Jurkat cells. Three of these compounds were selected for further analysis and found to activate the IL-17 reporter with potencies of ∼0.1 μM measured by EC₅₀. These compounds were shown to directly bind to RORγ by circular dichroism-based thermal stability experiments. Furthermore, they can enhance an in vitro Th17 differentiation process in human primary T cells. As RORγ remains an orphan nuclear receptor, discovery of these aryl amide compounds as functional agonists will now provide pharmacological tools for us to dissect functions of RORγ and facilitate drug discovery efforts for immune-modulating therapies.

Role of 5-HT5A and 5-HT1B/1D receptors in the antinociception produced by ergotamine and valerenic acid in the rat formalin test.

PubMed

Vidal-Cantú, Guadalupe C; Jiménez-Hernández, Mildred; Rocha-González, Héctor I; Villalón, Carlos M; Granados-Soto, Vinicio; Muñoz-Islas, Enriqueta

2016-06-15

Sumatriptan, dihydroergotamine and methysergide inhibit 1% formalin-induced nociception by activation of peripheral 5-HT1B/1D receptors. This study set out to investigate the pharmacological profile of the antinociception produced by intrathecal and intraplantar administration of ergotamine (a 5-HT1B/1D and 5-HT5A/5B receptor agonist) and valerenic acid (a partial agonist at 5-HT5A receptors). Intraplantar injection of 1% formalin in the right hind paw resulted in spontaneous flinching behavior of the injected hindpaw of female Wistar rats. Intrathecal ergotamine (15nmol) or valerenic acid (1 nmol) blocked in a dose dependent manner formalin-induced nociception. The antinociception by intrathecal ergotamine (15nmol) or valerenic acid (1nmol) was partly or completely blocked by intrathecal administration of the antagonists: (i) methiothepin (non-selective 5-HT5A/5B; 0.01-0.1nmol); (ii) SB-699551 (selective 5-HT5A; up to 10nmol); (iii) anti-5-HT5A antibody; (iv) SB-224289 (selective 5-HT1B; 0.1-1nmol); or (v) BRL-15572 (selective 5-HT1D; 0.1-1nmol). Likewise, antinociception by intraplantar ergotamine (15nmol) and valerenic acid (10nmol) was: (i) partially blocked by methiothepin (1nmol), SB-699551 (10nmol) or SB-224289 (1nmol); and (ii) abolished by BRL-15572 (1nmol). The above doses of antagonists (which did not affect per se the formalin-induced nociception) were high enough to completely block their respective receptors. Our results suggest that ergotamine and valerenic acid produce antinociception via 5-HT5A and 5-HT1B/1D receptors located at both spinal and peripheral sites. This provides new evidence for understanding the modulation of nociceptive pathways in inflammatory pain. Copyright © 2016 Elsevier B.V. All rights reserved.

Bile Acid Signaling in Metabolic Disease and Drug Therapy

PubMed Central

Li, Tiangang

2014-01-01

Bile acids are the end products of cholesterol catabolism. Hepatic bile acid synthesis accounts for a major fraction of daily cholesterol turnover in humans. Biliary secretion of bile acids generates bile flow and facilitates hepatobiliary secretion of lipids, lipophilic metabolites, and xenobiotics. In the intestine, bile acids are essential for the absorption, transport, and metabolism of dietary fats and lipid-soluble vitamins. Extensive research in the last 2 decades has unveiled new functions of bile acids as signaling molecules and metabolic integrators. The bile acid–activated nuclear receptors farnesoid X receptor, pregnane X receptor, constitutive androstane receptor, vitamin D receptor, and G protein–coupled bile acid receptor play critical roles in the regulation of lipid, glucose, and energy metabolism, inflammation, and drug metabolism and detoxification. Bile acid synthesis exhibits a strong diurnal rhythm, which is entrained by fasting and refeeding as well as nutrient status and plays an important role for maintaining metabolic homeostasis. Recent research revealed an interaction of liver bile acids and gut microbiota in the regulation of liver metabolism. Circadian disturbance and altered gut microbiota contribute to the pathogenesis of liver diseases, inflammatory bowel diseases, nonalcoholic fatty liver disease, diabetes, and obesity. Bile acids and their derivatives are potential therapeutic agents for treating metabolic diseases of the liver. PMID:25073467

Clofibric acid induces hepatic CYP 2B1/2 via constitutive androstane receptor not via peroxisome proliferator activated receptor alpha in rat.

PubMed

Ibrahim, Zein Shaban; Ahmed, Mohamed Mohamed; El-Shazly, Samir Ahmed; Ishizuka, Mayumi; Fujita, Shoichi

2014-01-01

Peroxisome proliferator activated receptor α (PPARα) ligands, fibrates used to control hyperlipidemia. We demonstrated CYP2B induction by clofibric acid (CFA) however, the mechanism was not clear. In this study, HepG2 cells transfected with expression plasmid of mouse constitutive androstane receptor (CAR) or PPARα were treated with CFA, phenobarbital (PB) or TCPOBOP. Luciferase assays showed that CFA increased CYP2B1 transcription to the same level as PB, or TCPOBOP in HepG2 transfected with mouse CAR But failed to induce it in PPARα transfected cells. CYP2B expressions were increased with PB or CFA in Wistar female rats (having normal levels of CAR) but not in Wistar Kyoto female rats (having low levels of CAR). The induction of CYP2B by PB or CFA was comparable to nuclear CAR levels. CAR nuclear translocation was induced by CFA in both rat strains. This indicates that fibrates can activate CAR and that fibrates-insulin sensitization effect may occur through CAR, while hypolipidemic effect may operate through PPARα.

Cloning and sequence analysis of the human brain beta-adrenergic receptor. Evolutionary relationship to rodent and avian beta-receptors and porcine muscarinic receptors.

PubMed

Chung, F Z; Lentes, K U; Gocayne, J; Fitzgerald, M; Robinson, D; Kerlavage, A R; Fraser, C M; Venter, J C

1987-01-26

Two cDNA clones, lambda-CLFV-108 and lambda-CLFV-119, encoding for the beta-adrenergic receptor, have been isolated from a human brain stem cDNA library. One human genomic clone, LCV-517 (20 kb), was characterized by restriction mapping and partial sequencing. The human brain beta-receptor consists of 413 amino acids with a calculated Mr of 46480. The gene contains three potential glucocorticoid receptor-binding sites. The beta-receptor expressed in human brain was homology with rodent (88%) and avian (52%) beta-receptors and with porcine muscarinic cholinergic receptors (31%), supporting our proposal [(1984) Proc. Natl. Acad. Sci. USA 81, 272 276] that adrenergic and muscarinic cholinergic receptors are structurally related. This represents the first cloning of a neurotransmitter receptor gene from human brain.

Bile Acid Metabolism and Signaling

PubMed Central

Chiang, John Y. L.

2015-01-01

Bile acids are important physiological agents for intestinal nutrient absorption and biliary secretion of lipids, toxic metabolites, and xenobiotics. Bile acids also are signaling molecules and metabolic regulators that activate nuclear receptors and G protein-coupled receptor (GPCR) signaling to regulate hepatic lipid, glucose, and energy homeostasis and maintain metabolic homeostasis. Conversion of cholesterol to bile acids is critical for maintaining cholesterol homeostasis and preventing accumulation of cholesterol, triglycerides, and toxic metabolites, and injury in the liver and other organs. Enterohepatic circulation of bile acids from the liver to intestine and back to the liver plays a central role in nutrient absorption and distribution, and metabolic regulation and homeostasis. This physiological process is regulated by a complex membrane transport system in the liver and intestine regulated by nuclear receptors. Toxic bile acids may cause inflammation, apoptosis, and cell death. On the other hand, bile acid-activated nuclear and GPCR signaling protects against inflammation in liver, intestine, and macrophages. Disorders in bile acid metabolism cause cholestatic liver diseases, dyslipidemia, fatty liver diseases, cardiovascular diseases, and diabetes. Bile acids, bile acid derivatives, and bile acid sequestrants are therapeutic agents for treating chronic liver diseases, obesity, and diabetes in humans. PMID:23897684

Ionotropic Receptors Mediate Drosophila Oviposition Preference through Sour Gustatory Receptor Neurons.

PubMed

Chen, Yan; Amrein, Hubert

2017-09-25

Carboxylic acids are present in many foods, being especially abundant in fruits. Yet, relatively little is known about how acids are detected by gustatory systems and whether they have a potential role in nutrition or provide other health benefits. Here we identify sour gustatory receptor neurons (GRNs) in tarsal taste sensilla of Drosophila melanogaster. We find that most tarsal sensilla harbor a sour GRN that is specifically activated by carboxylic and mineral acids but does not respond to sweet- and bitter-tasting chemicals or salt. One pair of taste sensilla features two GRNs that respond only to a subset of carboxylic acids and high concentrations of salt. All sour GRNs prominently express two Ionotropic Receptor (IR) genes, IR76b and IR25a, and we show that both these genes are necessary for the detection of acids. Furthermore, we establish that IR25a and IR76b are essential in sour GRNs of females for oviposition preference on acid-containing food. Our investigations reveal that acids activate a unique set of taste cells largely dedicated to sour taste, and they indicate that both pH/proton concentration and the structure of carboxylic acids contribute to sour GRN activation. Together, our studies provide new insights into the cellular and molecular basis of sour taste. Copyright © 2017 Elsevier Ltd. All rights reserved.

The interleukin-4 receptor: signal transduction by a hematopoietin receptor.

PubMed

Keegan, A D; Pierce, J H

1994-02-01

Over the last several years, the receptors for numerous cytokines have been molecularly characterized. Analysis of their amino acid sequences shows that some of these receptors bear certain motifs in their extracellular domains that define a family of receptors called the Hematopoietin receptor superfamily. Significant advances in characterizing the structure, function, and mechanisms of signal transduction have been made for several members of this family. The purpose of this review is to discuss the recent advances made for one of the family members, the interleukin (IL) 4 receptor. Other receptor systems have recently been reviewed elsewhere. The IL-4 receptor consists of, at the minimum, the cloned 140 kDa IL-4-binding chain with the potential for associating with other chains. The IL-4 receptor transduces its signal by activating a tyrosine kinase that phosphorylates cellular substrates, including the receptor itself, and the 170 kDa substrate called 4PS. Phosphorylated 4PS interacts with the SH2 domain of the enzyme PI-3'-kinase and increases its enzymatic activity. These early events in the IL-4 receptor initiated signaling pathway may trigger a series of signals that will ultimately lead to an IL-4 specific biologic outcome.

Gamma-aminobutyric acid (GABA) stimulates pancreatic cancer growth through overexpressing GABAA receptor pi subunit.

PubMed

Takehara, Akio; Hosokawa, Masayo; Eguchi, Hidetoshi; Ohigashi, Hiroaki; Ishikawa, Osamu; Nakamura, Yusuke; Nakagawa, Hidewaki

2007-10-15

Gamma-aminobutyric acid (GABA) functions primarily as an inhibitory neurotransmitter in the mature central nervous system, and GABA/GABA receptors are also present in nonneural tissues, including cancer, but their precise function in nonneuronal or cancerous cells has thus far been poorly defined. Through the genome-wide cDNA microarray analysis of pancreatic ductal adenocarcinoma (PDAC) cells as well as subsequent reverse transcription-PCR and Northern blot analyses, we identified the overexpression of GABA receptor pi subunit (GABRP) in PDAC cells. We also found the expression of this peripheral type GABAA receptor subunit in few adult human organs. Knockdown of endogenous GABRP expression in PDAC cells by small interfering RNA attenuated PDAC cell growth, suggesting its essential role in PDAC cell viability. Notably, the addition of GABA into the cell culture medium promoted the proliferation of GABRP-expressing PDAC cells, but not GABRP-negative cells, and GABAA receptor antagonists inhibited this growth-promoting effect by GABA. The HEK293 cells constitutively expressing exogenous GABRP revealed the growth-promoting effect of GABA treatment. Furthermore, GABA treatment in GABRP-positive cells increased intracellular Ca2+ levels and activated the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/Erk) cascade. Clinical PDAC tissues contained a higher level of GABA than normal pancreas tissues due to the up-regulation of glutamate decarboxylase 1 expression, suggesting their autocrine/paracrine growth-promoting effect in PDACs. These findings imply that GABA and GABRP could play important roles in PDAC development and progression, and that this pathway can be a promising molecular target for the development of new therapeutic strategies for PDAC.

Activation of mouse and human peroxisome proliferator-activated receptor alpha by perfluoroalkyl acids of different functional groups and chain lengths.

PubMed

Wolf, Cynthia J; Takacs, Margy L; Schmid, Judith E; Lau, Christopher; Abbott, Barbara D

2008-11-01

Perfluoroalkyl acids (PFAAs) are surfactants used in consumer products and persist in the environment. Some PFAAs elicit adverse effects on rodent development and survival. PFAAs can activate peroxisome proliferator-activated receptor alpha (PPARalpha) and may act via PPARalpha to produce some of their effects. This study evaluated the ability of numerous PFAAs to induce mouse and human PPARalpha activity in a transiently transfected COS-1 cell assay. COS-1 cells were transfected with either a mouse or human PPARalpha receptor-luciferase reporter plasmid. After 24 h, cells were exposed to either negative controls (water or dimethyl sulfoxide, 0.1%); positive control (WY-14643, PPARalpha agonist); perfluorooctanoic acid or perfluorononanoic acid at 0.5-100 microM; perfluorobutanoic acid, perfluorohexanoic acid, perfluorohexane sulfonate, or perfluorodecanoic acid (PFDA) at 5-100 microM; or perfluorobutane sulfonate or perfluorooctane sulfonate at 1-250 microM. After 24 h of exposure, luciferase activity from the plasmid was measured. Each PFAA activated both mouse and human PPARalpha in a concentration-dependent fashion, except PFDA with human PPARalpha. Activation of PPARalpha by PFAA carboxylates was positively correlated with carbon chain length, up to C9. PPARalpha activity was higher in response to carboxylates compared to sulfonates. Activation of mouse PPARalpha was generally higher compared to that of human PPARalpha. We conclude that, in general, (1) PFAAs of increasing carbon backbone chain lengths induce increasing activity of the mouse and human PPARalpha with a few exceptions, (2) PFAA carboxylates are stronger activators of mouse and human PPARalpha than PFAA sulfonates, and (3) in most cases, the mouse PPARalpha appears to be more sensitive to PFAAs than the human PPARalpha in this model.

Daphnia HR96 is a Promiscuous Xenobiotic and Endobiotic Nuclear Receptor

PubMed Central

Karimullina, Elina; Li, Yangchun; Ginjupalli, Gautam; Baldwin, William S.

2012-01-01

Daphnia pulex is the first crustacean to have its genome sequenced. The genome project provides new insight and data into how an aquatic crustacean may respond to environmental stressors, including toxicants. We cloned Daphnia pulex HR96 (DappuHR96), a nuclear receptor orthologous to the CAR/PXR/VDR group of nuclear receptors. In Drosophila melanogaster, (hormone receptor 96) HR96 responds to phenobarbital exposure and has been hypothesized as a toxicant receptor. Therefore, we set up a transactivation assay to test whether DappuHR96 is a promiscuous receptor activated by xenobiotics and endobiotics similar to the constitutive androstane receptor (CAR) and the pregnane X-receptor (PXR). Transactivation assays performed with a GAL4-HR96 chimera demonstrate that HR96 is a promiscuous toxicant receptor activated by a diverse set of chemicals such as pesticides, hormones, and fatty acids. Several environmental toxicants activate HR96 including estradiol, pyriproxyfen, chlorpyrifos, atrazine, and methane arsonate. We also observed repression of HR96 activity by chemicals such as triclosan, androstanol, and fluoxetine. Nearly 50% of the chemicals tested activated or inhibited HR96. Interestingly, unsaturated fatty acids were common activators or inhibitors of HR96 activity, indicating a link between diet and toxicant response. The omega-6 and omega-9 unsaturated fatty acids linoleic and oleic acid activated HR96, but the omega-3 unsaturated fatty acids alpha-linolenic acid and docosahexaenoic acid inhibited HR96, suggesting that these two distinct sets of lipids perform opposing roles in Daphnia physiology. This also provides a putative mechanism by which the ratio of dietary unsaturated fats may affect the ability of an organism to respond to a toxic insult. In summary, HR96 is a promiscuous nuclear receptor activated by numerous endo- and xenobiotics. PMID:22466357

Dietary ω-3 Polyunsaturated Fatty Acids Inhibit Tumor Growth in Transgenic ApcMin/+ Mice, Correlating with CB1 Receptor Up-Regulation

PubMed Central

Notarnicola, Maria; Tutino, Valeria; De Nunzio, Valentina; Dituri, Francesco; Caruso, Maria Gabriella; Giannelli, Gianluigi

2017-01-01

Mediterranean diet components, such as olive oil and ω-3 polyunsaturated fatty acids (ω-3 PUFAs), can arrest cell growth and promote cell apoptosis. Recently, olive oil has been demonstrated to modulate type-1 cannabinoid (CB1) receptor gene expression in both human colon cancer cells and rat colon. The aim of this study was to investigate a possible link between olive oil and ω-3 PUFAs effects and CB1 receptor expression in both intestinal and adipose tissue of ApcMin/+ mice. To confirm the role for the CB1 receptor as a negative modulator of cell proliferation in human colon cancer, CB1 receptor gene expression was also detected in tumor tissue and in surrounding normal mucosa of patients with colorectal cancer (CRC). Dietary ω-3 PUFAs significantly inhibited intestinal polyp growth in mice, correlating with CB1 receptor gene and protein expression induction. CB1 receptor gene up-regulation was also detected in adipose tissue, suggesting a close communication between cancer cells and the surrounding environment. Tissue CB1 receptor induction was associated with a concurrent inactivation of the Wnt/β-catenin pathway. Moreover, there was a significant reduction in CB1 receptor gene expression levels in cancer tissue compared to normal surrounding mucosa of patients with CRC, confirming that in cancer the “protective” action of the CB1 receptor is lost. PMID:28245562

The G Protein-Coupled Bile Acid Receptor, TGR5, Stimulates Gallbladder Filling

PubMed Central

Li, Tingting; Holmstrom, Sam R.; Kir, Serkan; Umetani, Michihisa; Schmidt, Daniel R.

2011-01-01

TGR5 is a G protein-coupled bile acid receptor present in brown adipose tissue and intestine, where its agonism increases energy expenditure and lowers blood glucose. Thus, it is an attractive drug target for treating human metabolic disease. However, TGR5 is also highly expressed in gallbladder, where its functions are less well characterized. Here, we demonstrate that TGR5 stimulates the filling of the gallbladder with bile. Gallbladder volume was increased in wild-type but not Tgr5−/− mice by administration of either the naturally occurring TGR5 agonist, lithocholic acid, or the synthetic TGR5 agonist, INT-777. These effects were independent of fibroblast growth factor 15, an enteric hormone previously shown to stimulate gallbladder filling. Ex vivo analyses using gallbladder tissue showed that TGR5 activation increased cAMP concentrations and caused smooth muscle relaxation in a TGR5-dependent manner. These data reveal a novel, gallbladder-intrinsic mechanism for regulating gallbladder contractility. They further suggest that TGR5 agonists should be assessed for effects on human gallbladder as they are developed for treating metabolic disease. PMID:21454404

Non-classical mechanism of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor channel block by fluoxetine.

PubMed

Barygin, Oleg I; Komarova, Margarita S; Tikhonova, Tatiana B; Tikhonov, Denis B

2015-04-01

Antidepressants have many targets in the central nervous system. A growing body of data demonstrates the influence of antidepressants on glutamatergic neurotransmission. In the present work, we studied the inhibition of native Ca(2+)-permeable and Ca(2+)-impermeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in rat brain neurons by fluoxetine. The Ca(2+)-impermeable AMPA receptors in CA1 hippocampal pyramidal neurons were weakly affected. The IC50 value for the inhibition of Ca(2+)-permeable AMPA receptors in giant striatal interneurons was 43 ± 7 μM. The inhibition of Ca(2+)-permeable AMPA receptors was voltage dependent, suggesting deep binding in the pore. However, the use dependence of fluoxetine action differed markedly from that of classical AMPA receptor open-channel blockers. Moreover, fluoxetine did not compete with other channel blockers. In contrast to fluoxetine, its membrane-impermeant quaternary analog demonstrated all of the features of channel inhibition typical for open-channel blockers. It is suggested that fluoxetine reaches the binding site through a hydrophobic access pathway. Such a mechanism of block is described for ligands of sodium and calcium channels, but was never found in AMPA receptors. Molecular modeling suggests binding of fluoxetine in the subunit interface; analogous binding was proposed for local anesthetics in closed sodium channels and for benzothiazepines in calcium channels. © 2014 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Integrating data on the Arabidopsis NPR1/NPR3/NPR4 salicylic acid receptors; a differentiating argument.

PubMed

Kuai, Xiahezi; MacLeod, Brandon J; Després, Charles

2015-01-01

Salicylic acid (SA) is a mandatory plant metabolite in the deployment of systemic acquired resistance (SAR), a broad-spectrum systemic immune response induced by local inoculation with avirulent pathogens. The NPR1 transcription co-activator is the central node positively regulating SAR. SA was the last of the major hormones to be without a known receptor. Recently, NPR1 was shown to be the direct link between SA and gene activation. This discovery seems to be controversial. NPR1 being an SA-receptor is reminiscent of the mammalian steroid receptors, which are transcription factors whose binding to DNA is dependent on the interaction with a ligand. Unlike steroid receptors, NPR1 does not bind directly to DNA, but is recruited to promoters by the TGA family of transcription factors to form an enhanceosome. In Arabidopsis, NPR1 is part of a multigene family in which two other members, NPR3 and NPR4, have also been shown to interact with SA. NPR3/NPR4 are negative regulators of immunity and act as substrate adaptors for the recruitment of NPR1 to an E3-ubiquitin ligase, leading to its subsequent degradation by the proteasome. In this perspective, we will stress-test in a friendly way the current NPR1/NPR3/NPR4 model.

Altered microRNA regulation of short chain fatty acid receptors in the hypertensive kidney is normalized with hydrogen sulfide supplementation.

PubMed

Weber, Gregory J; Foster, Jaleyea; Pushpakumar, Sathnur B; Sen, Utpal

2018-06-15

Hypertension affects nearly one third of the adult US population and is a significant risk factor for chronic kidney disease (CKD). An expanding body of recent studies indicates that gut microbiome has crucial roles in regulating physiological processes through, among other mechanisms, one mode of short chain fatty acids (SCFA) and their target receptors. In addition, these SCFA receptors are potential targets of regulation by host miRNAs, however, the mechanisms through which this occurs is not clearly defined. Hydrogen sulfide (H 2 S) is an important gasotransmitter involved in multiple physiological processes and is known to alleviate adverse effects of hypertension such as reducing inflammation in the kidney. To determine the role of host microRNAs in regulating short chain fatty acid receptors in the kidney as well as the gut, C57BL/6J wild-type mice were treated with or without Ang-II and H 2 S donor GYY4137 (GYY) for 4 weeks to assess whether GYY would normalize adverse effects observed in hypertensive mice and whether this was in part due to altered gut microbiome composition. We observed several changes of SCFA receptors, including Olfr78, Gpr41/43 and predicted microRNA regulators in the kidney among the different treatments. Increased expression of inflammatory markers Il6 and Rorc2, along with Tgfβ, were found in the hypertensive kidney. The glomerular filtration rate (GFR) was improved in mice treated with Ang-II + GYY compared with Ang-II only, indicating improved kidney function. The Erysipelotrichia class of bacteria, linked with high fat diets, was enriched in hypertensive animals but reduced with GYY supplementation. These data point towards a role for miRNA regulation of SCFA receptors in hypertensive kidney and are normalized by H 2 S supplementation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Molecular pharmacology of promiscuous seven transmembrane receptors sensing organic nutrients.

PubMed

Wellendorph, Petrine; Johansen, Lars Dan; Bräuner-Osborne, Hans

2009-09-01

A number of highly promiscuous seven transmembrane (7TM) receptors have been cloned and characterized within the last few years. It is noteworthy that many of these receptors are activated broadly by amino acids, proteolytic degradation products, carbohydrates, or free fatty acids and are expressed in taste tissue, the gastrointestinal tract, endocrine glands, adipose tissue, and/or kidney. These receptors thus hold the potential to act as sensors of food intake, regulating, for example, release of incretin hormones from the gut, insulin/glucagon from the pancreas, and leptin from adipose tissue. The promiscuous tendency in ligand recognition of these receptors is in contrast to the typical specific interaction with one physiological agonist seen for most receptors, which challenges the classic "lock-and-key" concept. We here review the molecular mechanisms of nutrient sensing of the calcium-sensing receptor, the G protein-coupled receptor family C, group 6, subtype A (GPRC6A), and the taste1 receptor T1R1/T1R3, which are sensing L-alpha-amino acids, the carbohydrate-sensing T1R2/T1R3 receptor, the proteolytic degradation product sensor GPR93 (also termed GPR92), and the free fatty acid (FFA) sensing receptors FFA1, FFA2, FFA3, GPR84, and GPR120. The involvement of the individual receptors in sensing of food intake has been validated to different degrees because of limited availability of specific pharmacological tools and/or receptor knockout mice. However, as a group, the receptors represent potential drug targets, to treat, for example, type II diabetes by mimicking food intake by potent agonists or positive allosteric modulators. The ligand-receptor interactions of the promiscuous receptors of organic nutrients thus remain an interesting subject of emerging functional importance.

Activation of the omega-3 fatty acid receptor GPR120 mediates anti-inflammatory actions in immortalized hypothalamic neurons.

PubMed

Wellhauser, Leigh; Belsham, Denise D

2014-03-27

Overnutrition and the ensuing hypothalamic inflammation is a major perpetuating factor in the development of metabolic diseases, such as obesity and diabetes. Inflamed neurons of the CNS fail to properly regulate energy homeostasis leading to pathogenic changes in glucose handling, feeding, and body weight. Hypothalamic neurons are particularly sensitive to pro-inflammatory signals derived locally and peripherally, and it is these neurons that become inflamed first upon high fat feeding. Given the prevalence of metabolic disease, efforts are underway to identify therapeutic targets for this inflammatory state. At least in the periphery, omega-3 fatty acids and their receptor, G-protein coupled receptor 120 (GPR120), have emerged as putative targets. The role for GPR120 in the hypothalamus or CNS in general is poorly understood. Here we introduce a novel, immortalized cell model derived from the rat hypothalamus, rHypoE-7, to study GPR120 activation at the level of the individual neuron. Gene expression levels of pro-inflammatory cytokines were studied by quantitative reverse transcriptase-PCR (qRT-PCR) upon exposure to tumor necrosis factor α (TNFα) treatment in the presence or absence of the polyunsaturated omega-3 fatty acid docosahexaenoic acid (DHA). Signal transduction pathway involvement was also studied using phospho-specific antibodies to key proteins by western blot analysis. Importantly, rHypoE-7 cells exhibit a transcriptional and translational inflammatory response upon exposure to TNFα and express abundant levels of GPR120, which is functionally responsive to DHA. DHA pretreatment prevents the inflammatory state and this effect was inhibited by the reduction of endogenous GPR120 levels. GPR120 activates both AKT (protein kinase b) and ERK (extracellular signal-regulated kinase); however, the anti-inflammatory action of this omega-3 fatty acid (FA) receptor is AKT- and ERK-independent and likely involves the GPR120-transforming growth factor

Sigma-1 receptor regulates Tau phosphorylation and axon extension by shaping p35 turnover via myristic acid.

PubMed

Tsai, Shang-Yi A; Pokrass, Michael J; Klauer, Neal R; Nohara, Hiroshi; Su, Tsung-Ping

2015-05-26

Dysregulation of cyclin-dependent kinase 5 (cdk5) per relative concentrations of its activators p35 and p25 is implicated in neurodegenerative diseases. P35 has a short t½ and undergoes rapid proteasomal degradation in its membrane-bound myristoylated form. P35 is converted by calpain to p25, which, along with an extended t½, promotes aberrant activation of cdk5 and causes abnormal hyperphosphorylation of tau, thus leading to the formation of neurofibrillary tangles. The sigma-1 receptor (Sig-1R) is an endoplasmic reticulum chaperone that is implicated in neuronal survival. However, the specific role of the Sig-1R in neurodegeneration is unclear. Here we found that Sig-1Rs regulate proper tau phosphorylation and axon extension by promoting p35 turnover through the receptor's interaction with myristic acid. In Sig-1R-KO neurons, a greater accumulation of p35 is seen, which results from neither elevated transcription of p35 nor disrupted calpain activity, but rather to the slower degradation of p35. In contrast, Sig-1R overexpression causes a decrease of p35. Sig-1R-KO neurons exhibit shorter axons with lower densities. Myristic acid is found here to bind Sig-1R as an agonist that causes the dissociation of Sig-1R from its cognate partner binding immunoglobulin protein. Remarkably, treatment of Sig-1R-KO neurons with exogenous myristic acid mitigates p35 accumulation, diminishes tau phosphorylation, and restores axon elongation. Our results define the involvement of Sig-1Rs in neurodegeneration and provide a mechanistic explanation that Sig-1Rs help maintain proper tau phosphorylation by potentially carrying and providing myristic acid to p35 for enhanced p35 degradation to circumvent the formation of overreactive cdk5/p25.

Activation of type 2 cannabinoid receptors (CB2R) promotes fatty acid oxidation through the SIRT1/PGC-1α pathway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Xuqin; Sun, Tao; Wang, Xiaodong, E-mail: xdwang666@hotmail.com

2013-07-05

Highlights: •TC, a CB2R specific agonist, stimulates SIRT1 activity by PKA/CREB pathway. •TC promotes PGC-1α transcriptional activity by increasing its deacetylation. •TC increases the expression of genes linked to FAO and promotes the rate of FAO. •The effects of TC in FAO are dependent on CB2R. •Suggesting CB2R as a target to treat diseases with lipid dysregulation. -- Abstract: Abnormal fatty acid oxidation has been associated with obesity and type 2 diabetes. At the transcriptional level, peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) has been reported to strongly increase the ability of hormone nuclear receptors PPARα and ERRα to drive transcriptionmore » of fatty acid oxidation enzymes. In this study, we report that a specific agonist of the type 2 cannabinoid receptor (CB2R) can lead to fatty acid oxidation through the PGC-1α pathway. We have found that CB2R is expressed in differentiated C2C12 myotubes, and that use of the specific agonist trans-caryophyllene (TC) stimulates sirtuin 1 (SIRT1) deacetylase activity by increasing the phosphorylation of cAMP response element-binding protein (CREB), thus leading to increased levels of PGC-1α deacetylation. This use of TC treatment increases the expression of genes linked to the fatty acid oxidation pathway in a SIRT1/PGC-1α-dependent mechanism and also drastically accelerates the rate of complete fatty acid oxidation in C2C12 myotubes, neither of which occur when CB2R mRNA is knocked down using siRNA. These results reveal that activation of CB2R by a selective agonist promotes lipid oxidation through a signaling/transcriptional pathway. Our findings imply that pharmacological manipulation of CB2R may provide therapeutic possibilities to treat metabolic diseases associated with lipid dysregulation.« less

Attenuation of excitatory amino acid toxicity by metabotropic glutamate receptor agonists and aniracetam in primary cultures of cerebellar granule cells.

PubMed

Pizzi, M; Fallacara, C; Arrighi, V; Memo, M; Spano, P F

1993-08-01

Activation of glutamate ionotropic receptors represents the primary event in the neurotoxicity process triggered by excitatory amino acids. We demonstrate here that the concentration-dependent stimulation of metabotropic glutamate receptor (mGluR) by the selective agonist trans-1-aminocyclopentane-1,3-dicarboxylate or by quisqualate counteracts both glutamate- and kainate-induced neurotoxicity in primary cultures of rat cerebellar granule cells. The mGluR-evoked responses are potentiated by aniracetam, which per se also elicits neuroprotection. Aniracetam concentration-dependently counteracted glutamate-, kainate-, or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-induced cell death and greatly facilitated neuroprotective response achieved by different concentrations of both quisqualate and trans-1-aminocyclopentane-1,3-dicarboxylate. In addition, aniracetam potentiated the mGluR-coupled stimulation of phospholipase C, as revealed by the measurement of 3H-inositol phosphate formation. Thus, mGluRs could be a suitable target for novel pharmacological strategies pointing to the treatment of neurodegenerative diseases.

Purple sweet potato color attenuates domoic acid-induced cognitive deficits by promoting estrogen receptor-α-mediated mitochondrial biogenesis signaling in mice.

PubMed

Lu, Jun; Wu, Dong-Mei; Zheng, Yuan-Lin; Hu, Bin; Cheng, Wei; Zhang, Zi-Feng

2012-02-01

Recent findings suggest that endoplasmic reticulum stress may be involved in the pathogenesis of domoic acid-induced neurodegeneration. Purple sweet potato color, a class of naturally occurring anthocyanins, has beneficial health and biological effects. Recent studies have also shown that anthocyanins have estrogenic activity and can enhance estrogen receptor-α expression. In this study, we evaluated the effect of purple sweet potato color on cognitive deficits induced by hippocampal mitochondrial dysfunction in domoic acid-treated mice and explored the potential mechanisms underlying this effect. Our results showed that the oral administration of purple sweet potato color to domoic acid-treated mice significantly improved their behavioral performance in a step-through passive avoidance task and a Morris water maze task. These improvements were mediated, at least in part, by a stimulation of estrogen receptor-α-mediated mitochondrial biogenesis signaling and by decreases in the expression of p47phox and gp91phox. Decreases in reactive oxygen species and protein carbonylation were also observed, along with a blockade of the endoplasmic reticulum stress pathway. Furthermore, purple sweet potato color significantly suppressed endoplasmic reticulum stress-induced apoptosis, which prevented neuron loss and restored the expression of memory-related proteins. However, knockdown of estrogen receptor-α using short hairpin RNA only partially blocked the neuroprotective effects of purple sweet potato color in the hippocampus of mice cotreated with purple sweet potato color and domoic acid, indicating that purple sweet potato color acts through multiple pathways. These results suggest that purple sweet potato color could be a possible candidate for the prevention and treatment of cognitive deficits in excitotoxic and other brain disorders. Crown Copyright © 2011. Published by Elsevier Inc. All rights reserved.

The Bile Acid Receptor TGR5 Does Not Interact with β-Arrestins or Traffic to Endosomes but Transmits Sustained Signals from Plasma Membrane Rafts*

PubMed Central

Jensen, Dane D.; Godfrey, Cody B.; Niklas, Christian; Canals, Meritxell; Kocan, Martina; Poole, Daniel P.; Murphy, Jane E.; Alemi, Farzad; Cottrell, Graeme S.; Korbmacher, Christoph; Lambert, Nevin A.; Bunnett, Nigel W.; Corvera, Carlos U.

2013-01-01

TGR5 is a G protein-coupled receptor that mediates bile acid (BA) effects on energy balance, inflammation, digestion, and sensation. The mechanisms and spatiotemporal control of TGR5 signaling are poorly understood. We investigated TGR5 signaling and trafficking in transfected HEK293 cells and colonocytes (NCM460) that endogenously express TGR5. BAs (deoxycholic acid (DCA), taurolithocholic acid) and the selective agonists oleanolic acid and 3-(2-chlorophenyl)-N-(4-chlorophenyl)-N, 5-dimethylisoxazole-4-carboxamide stimulated cAMP formation but did not induce TGR5 endocytosis or recruitment of β-arrestins, as assessed by confocal microscopy. DCA, taurolithocholic acid, and oleanolic acid did not stimulate TGR5 association with β-arrestin 1/2 or G protein-coupled receptor kinase (GRK) 2/5/6, as determined by bioluminescence resonance energy transfer. 3-(2-chlorophenyl)-N-(4-chlorophenyl)-N, 5-dimethylisoxazole-4-carboxamide stimulated a low level of TGR5 interaction with β-arrestin 2 and GRK2. DCA induced cAMP formation at the plasma membrane and cytosol, as determined using exchange factor directly regulated by cAMP (Epac2)-based reporters, but cAMP signals did not desensitize. AG1478, an inhibitor of epidermal growth factor receptor tyrosine kinase, the metalloprotease inhibitor batimastat, and methyl-β-cyclodextrin and filipin, which block lipid raft formation, prevented DCA stimulation of ERK1/2. Bioluminescence resonance energy transfer analysis revealed TGR5 and EGFR interactions that were blocked by disruption of lipid rafts. DCA stimulated TGR5 redistribution to plasma membrane microdomains, as localized by immunogold electron microscopy. Thus, TGR5 does not interact with β-arrestins, desensitize, or traffic to endosomes. TGR5 signals from plasma membrane rafts that facilitate EGFR interaction and transactivation. An understanding of the spatiotemporal control of TGR5 signaling provides insights into the actions of BAs and therapeutic TGR5 agonists

Variant Ionotropic Receptors in the Malaria Vector Mosquito Anopheles gambiae Tuned to Amines and Carboxylic Acids

PubMed Central

Pitts, R. Jason; Derryberry, Stephen L.; Zhang, Zhiwei; Zwiebel, Laurence J.

2017-01-01

The principal Afrotropical human malaria vector mosquito, Anopheles gambiae, remains a significant threat to global health. A critical component in the transmission of malaria is the ability of An. gambiae females to detect and respond to human-derived chemical kairomones in their search for blood meal hosts. The basis for host odor responses resides in olfactory receptor neurons (ORNs) that express chemoreceptors encoded by large gene families, including the odorant receptors (ORs) and the variant ionotropic receptors (IRs). While ORs have been the focus of extensive investigation, functional IR complexes and the chemical compounds that activate them have not been identified in An. gambiae. Here we report the transcriptional profiles and functional characterization of three An. gambiae IR (AgIr) complexes that specifically respond to amines or carboxylic acids - two classes of semiochemicals that have been implicated in mediating host-seeking by adult females but are not known to activate An. gambiae ORs (AgOrs). Our results suggest that AgIrs play critical roles in the detection and behavioral responses to important classes of host odors that are underrepresented in the AgOr chemical space. PMID:28067294

Retinoic Acid Receptor β: A Potential Therapeutic Target in Retinoic Acid Treatment of Endometrial Cancer.

PubMed

Tsuji, Keita; Utsunomiya, Hiroki; Miki, Yasuhiro; Hanihara, Mayu; Fue, Misaki; Takagi, Kiyoshi; Nishimoto, Mitsuo; Suzuki, Fumihiko; Yaegashi, Nobuo; Suzuki, Takashi; Ito, Kiyoshi

2017-05-01

Several studies have reported that retinoic acid (RA) might be used to treat malignancies. The effects of RA are mediated by the RA receptor (RAR), and RARα/RARβ especially acts as a tumor suppressor. However, little is known about its role in human endometrial cancer. In this study, we examined the effects of all-trans RA (ATRA) on progression of human endometrial cancer cell line, RL95-2 and Hec1A. We then examined the expression of RARα and RARβ in 50 endometrial cancer tissues by using immunohistochemistry. We found inhibitory effects of ATRA on cell proliferation, apoptosis, and migration in RL95-2 cells, but not in Hec1A cells. RARα or RARβ knockdown individually could not cancel out the inhibition of cell proliferation by ATRA in RL95-2 cells, but simultaneous knockdown of RARα and RARβ could block its effect on proliferation. RARα and RARβ knockdown dose dependently reduced the inhibition of migration by ATRA, but the effect was more pronounced with RARβ knockdown than with RARα knockdown. We confirmed that RARβ gene was directly regulated by ATRA in microarray and real-time reverse transcription polymerase chain reaction. Furthermore, the RARβ agonist (BMS453) significantly suppressed proliferation of RL95-2 cells. In immunohistochemical analysis, RARα expression was positively correlated with tumor grade, and RARβ showed the opposite tendency in endometrial cancer. Retinoic acid might have multiple antitumor effects, and RARβ may be a potent therapeutic target in RA treatment for endometrial cancers.

Quinolinic acid induces neuritogenesis in SH-SY5Y neuroblastoma cells independently of NMDA receptor activation.

PubMed

Hernandez-Martinez, Juan-Manuel; Forrest, Caroline M; Darlington, L Gail; Smith, Robert A; Stone, Trevor W

2017-03-01

Glutamate and nicotinamide adenine dinucleotide (NAD + ) have been implicated in neuronal development and several types of cancer. The kynurenine pathway of tryptophan metabolism includes quinolinic acid (QA) which is both a selective agonist at N-methyl-D-aspartate (NMDA) receptors and also a precursor for the formation of NAD + . The effect of QA on cell survival and differentiation has therefore been examined on SH-SY5Y human neuroblastoma cells. Retinoic acid (RA, 10 μm) induced differentiation of SH-SY5Y cells into a neuronal phenotype showing neurite growth. QA (50-150 nm) also caused a concentration-dependent increase in the neurite/soma ratio, indicating differentiation. Both RA and QA increased expression of the neuronal marker β3-tubulin in whole-cell homogenates and in the neuritic fraction assessed using a neurite outgrowth assay. Expression of the neuronal proliferation marker doublecortin revealed that, unlike RA, QA did not decrease the number of mitotic cells. QA-induced neuritogenesis coincided with an increase in the generation of reactive oxygen species. Neuritogenesis was prevented by diphenylene-iodonium (an inhibitor of NADPH oxidase) and superoxide dismutase, supporting the involvement of reactive oxygen species. NMDA itself did not promote neuritogenesis and the NMDA antagonist dizocilpine (MK-801) did not prevent quinolinate-induced neuritogenesis, indicating that the effects of QA were independent of NMDA receptors. Nicotinamide caused a significant increase in the neurite/soma ratio and the expression of β3-tubulin in the neuritic fraction. Taken together, these results suggest that QA induces neuritogenesis by promoting oxidizing conditions and affecting the availability of NAD + , independently of NMDA receptors. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Human esophageal myofibroblasts secrete proinflammatory cytokines in response to acid and Toll-like receptor 4 ligands

PubMed Central

Gargus, Matthew; Niu, Chao; Vallone, John G.; Binkley, Jana; Rubin, Deborah C.

2015-01-01

The pathophysiology of esophageal injury, repair, and inflammation in gastroesophageal reflux-disease (GERD) is complex. Whereas most studies have focused on the epithelial response to GERD injury, we are interested in the stromal response. We hypothesized that subepithelial esophageal myofibroblasts in GERD secrete proinflammatory cytokines in response to injurious agents encountered via epithelial barrier breaches or through dilated epithelial intercellular spaces. We determined the percentage of myofibroblasts [α-smooth muscle actin (α-SMA)+vimentin+CD31−] in the subepithelial GERD and normal esophageal stroma by immunomorphologic analysis. We performed α-SMA coimmunostaining with IL-6 and p65. We established and characterized primary cultures of α-SMA+vimentin+CD31−CD45− human esophageal myofibroblasts (HuEso MFs). We modeled GERD by treatment with pH 4.5-acidified media and Toll-like receptor 4 (TLR4) ligands, LPS and high-mobility group box 1 protein (HMGB1), and determined myofibroblast cytokine secretion in response to GERD injury. We demonstrate that spindle-shaped cell myofibroblasts are located near the basement membrane of stratified squamous epithelium in normal esophagus. We identify an increase in subepithelial myofibroblasts and activation of proinflammatory pathways in patients with GERD. Primary cultures of stromal cells obtained from normal esophagus retain myofibroblast morphology and express the acid receptor transient receptor potential channel vanilloid subfamily 1 (TRPV1) and TLR4. HuEso MFs stimulated with acid and TLR4 agonists LPS and HMGB1 increase IL-6 and IL-8 secretion via TRPV1 and NF-κB activation. Our work implicates a role for human subepithelial stromal cells in the pathogenesis of GERD-related esophageal injury. Findings of this study can be extended to the investigation of epithelial-stromal interactions in inflammatory esophageal mucosal disorders. PMID:25882613

Arsenic as an endocrine disruptor: arsenic disrupts retinoic acid receptor-and thyroid hormone receptor-mediated gene regulation and thyroid hormone-mediated amphibian tail metamorphosis.

PubMed

Davey, Jennifer C; Nomikos, Athena P; Wungjiranirun, Manida; Sherman, Jenna R; Ingram, Liam; Batki, Cavus; Lariviere, Jean P; Hamilton, Joshua W

2008-02-01

Chronic exposure to excess arsenic in drinking water has been strongly associated with increased risks of multiple cancers, diabetes, heart disease, and reproductive and developmental problems in humans. We previously demonstrated that As, a potent endocrine disruptor at low, environmentally relevant levels, alters steroid signaling at the level of receptor-mediated gene regulation for all five steroid receptors. The goal of this study was to determine whether As can also disrupt gene regulation via the retinoic acid (RA) receptor (RAR) and/or the thyroid hormone (TH) receptor (TR) and whether these effects are similar to previously observed effects on steroid regulation. Human embryonic NT2 or rat pituitary GH3 cells were treated with 0.01-5 microM sodium arsenite for 24 hr, with or without RA or TH, respectively, to examine effects of As on receptor-mediated gene transcription. At low, noncytotoxic doses, As significantly altered RAR-dependent gene transcription of a transfected RAR response element-luciferase construct and the native RA-inducible cytochrome P450 CYP26A gene in NT2 cells. Likewise, low-dose As significantly altered expression of a transfected TR response element-luciferase construct and the endogenous TR-regulated type I deiodinase (DIO1) gene in a similar manner in GH3 cells. An amphibian ex vivo tail metamorphosis assay was used to examine whether endocrine disruption by low-dose As could have specific pathophysiologic consequences, because tail metamorphosis is tightly controlled by TH through TR. TH-dependent tail shrinkage was inhibited in a dose-dependent manner by 0.1- 4.0 microM As. As had similar effects on RAR- and TR-mediated gene regulation as those previously observed for the steroid receptors, suggesting a common mechanism or action. Arsenic also profoundly affected a TR-dependent developmental process in a model animal system at very low concentrations. Because RAR and TH are critical for both normal human development and adult

Chlorogenic Acid Improves Late Diabetes through Adiponectin Receptor Signaling Pathways in db/db Mice

PubMed Central

Jin, Shasha; Chang, Cuiqing; Zhang, Lantao; Liu, Yang; Huang, Xianren; Chen, Zhimin

2015-01-01

The aim of this study was to examine the effects of chlorogenic acid (CGA) on glucose and lipid metabolism in late diabetic db/db mice, as well as on adiponectin receptors and their signaling molecules, to provide evidence for CGA in the prevention of type 2 diabetes. We randomly divided 16 female db/db mice into db/db-CGA and db/db-control (CON) groups equally; db/m mice were used as control mice. The mice in both the db/db-CGA and db/m-CGA groups were administered 80 mg/kg/d CGA by lavage for 12 weeks, whereas the mice in both CON groups were given equal volumes of phosphate-buffered saline (PBS) by lavage. At the end of the intervention, we assessed body fat and the parameters of glucose and lipid metabolism in the plasma, liver and skeletal muscle tissues as well as the levels of aldose reductase (AR) and transforming growth factor-β1 (TGF-β1) in the kidneys and measured adiponectin receptors and the protein expression of their signaling molecules in liver and muscle tissues. After 12 weeks of intervention, compared with the db/db-CON group, the percentage of body fat, fasting plasma glucose (FPG) and glycosylated hemoglobin (HbA1c) in the db/db-CGA group were all significantly decreased; TGF-β1 protein expression and AR activity in the kidney were both decreased; and the adiponectin level in visceral adipose was increased. The protein expression of adiponectin receptors (ADPNRs), the phosphorylation of AMP-activated protein kinase (AMPK) in the liver and muscle, and the mRNA and protein levels of peroxisome proliferator-activated receptor alpha (PPAR-α) in the liver were all significantly greater. CGA could lower the levels of fasting plasma glucose and HbA1c during late diabetes and improve kidney fibrosis to some extent through the modulation of adiponectin receptor signaling pathways in db/db mice. PMID:25849026

The nuclear bile acid receptor FXR controls the liver derived tumor suppressor histidine-rich glycoprotein.

PubMed

Deuschle, Ulrich; Birkel, Manfred; Hambruch, Eva; Hornberger, Martin; Kinzel, Olaf; Perović-Ottstadt, Sanja; Schulz, Andreas; Hahn, Ulrike; Burnet, Michael; Kremoser, Claus

2015-06-01

The nuclear bile acid receptor Farnesoid X receptor (FXR) is strongly expressed in liver and intestine, controls bile acid and lipid homeostasis and exerts tumor-protective functions in liver and intestine. Histidine-rich glycoprotein (HRG) is an abundant plasma protein produced by the liver with the proposed function as a pattern recognition molecule involved in the clearance of immune complexes, necrotic cells and pathogens, the modulation of angiogenesis, the normalization of deranged endothelial vessel structure in tumors and tumor suppression. FXR recognition sequences were identified within a human HRG promoter fragment that mediated FXR/FXR-agonist dependent reporter gene activity in vitro. We show that HRG is a novel transcriptional target gene of FXR in human hepatoma cells, human upcyte® primary hepatocytes and 3D human liver microtissues in vitro and in mouse liver in vivo. Prolonged administration of the potent nonsteroidal FXR agonist PX20606 increases HRG levels in mouse plasma. Finally, daily oral administration of this FXR agonist for seven days resulted in a significant increase of HRG levels in the plasma of healthy human male volunteers during a clinical Phase I safety study. HRG might serve as a surrogate marker indicative of liver-specific FXR activation in future human clinical studies. Furthermore, potent FXR agonists might be beneficial in serious health conditions where HRG is reduced, for example, in hepatocellular carcinoma but also other solid cancers, liver failure, sepsis and pre-eclampsia. © 2014 UICC.

Tomato PYR/PYL/RCAR abscisic acid receptors show high expression in root, differential sensitivity to the abscisic acid agonist quinabactin, and the capability to enhance plant drought resistance.

PubMed

González-Guzmán, Miguel; Rodríguez, Lesia; Lorenzo-Orts, Laura; Pons, Clara; Sarrión-Perdigones, Alejandro; Fernández, Maria A; Peirats-Llobet, Marta; Forment, Javier; Moreno-Alvero, Maria; Cutler, Sean R; Albert, Armando; Granell, Antonio; Rodríguez, Pedro L

2014-08-01

Abscisic acid (ABA) plays a crucial role in the plant's response to both biotic and abiotic stress. Sustainable production of food faces several key challenges, particularly the generation of new varieties with improved water use efficiency and drought tolerance. Different studies have shown the potential applications of Arabidopsis PYR/PYL/RCAR ABA receptors to enhance plant drought resistance. Consequently the functional characterization of orthologous genes in crops holds promise for agriculture. The full set of tomato (Solanum lycopersicum) PYR/PYL/RCAR ABA receptors have been identified here. From the 15 putative tomato ABA receptors, 14 of them could be grouped in three subfamilies that correlated well with corresponding Arabidopsis subfamilies. High levels of expression of PYR/PYL/RCAR genes was found in tomato root, and some genes showed predominant expression in leaf and fruit tissues. Functional characterization of tomato receptors was performed through interaction assays with Arabidopsis and tomato clade A protein phosphatase type 2Cs (PP2Cs) as well as phosphatase inhibition studies. Tomato receptors were able to inhibit the activity of clade A PP2Cs differentially in an ABA-dependent manner, and at least three receptors were sensitive to the ABA agonist quinabactin, which inhibited tomato seed germination. Indeed, the chemical activation of ABA signalling induced by quinabactin was able to activate stress-responsive genes. Both dimeric and monomeric tomato receptors were functional in Arabidopsis plant cells, but only overexpression of monomeric-type receptors conferred enhanced drought resistance. In summary, gene expression analyses, and chemical and transgenic approaches revealed distinct properties of tomato PYR/PYL/RCAR ABA receptors that might have biotechnological implications. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Decreased agonist sensitivity of human GABA(A) receptors by an amino acid variant, isoleucine to valine, in the alpha1 subunit.

PubMed

Westh-Hansen, S E; Rasmussen, P B; Hastrup, S; Nabekura, J; Noguchi, K; Akaike, N; Witt, M R; Nielsen, M

1997-06-25

Recombinant human GABA(A) receptors were investigated in vitro by coexpression of cDNAs coding for alpha1, beta2, and gamma2 subunits in the baculovirus/Sf-9 insect cell system. We report that a single amino acid exchange (isoleucine 121 to valine 121) in the N-terminal, extracellular part of the alpha1 subunit induces a marked decrease in agonist GABA(A) receptor ligand sensitivity. The potency of muscimol and GABA to inhibit the binding of the GABA(A) receptor antagonist [3H]SR 95531 (2-(3-carboxypropyl)-3-amino-6-(4-methoxyphenyl)pyridazinium bromide) was higher in receptor complexes of alpha1(ile 121) beta2gamma2 than in those of alpha1(val 121) beta2gamma2 (IC50 values were 32-fold and 26-fold lower for muscimol and GABA, respectively). The apparent affinity of the GABA(A) receptor antagonist bicuculline methiodide to inhibit the binding of [3H]SR 95531 did not differ between the two receptor complex variants. Electrophysiological measurements of GABA induced whole-cell Cl- currents showed a ten-fold decrease in the GABA(A) receptor sensitivity of alpha1 (val 121) beta2gamma2 as compared to alpha1(ile 121) beta2gamma2 receptor complexes. Thus, a relatively small change in the primary structure of the alpha1 subunit leads to a decrease selective for GABA(A) receptor sensitivity to agonist ligands, since no changes were observed in a GABA(A) receptor antagonist affinity and benzodiazepine receptor binding.

Immunization against exon 1 decapeptides from the lutropin/choriogonadotropin receptor or the follitropin receptor as potential male contraceptive.

PubMed

Remy, J J; Couture, L; Rabesona, H; Haertle, T; Salesse, R

1996-11-01

Pituitary gonadotropin hormones lutropin (LH) and follitropin (FSH) control steroidogenesis and gametogenesis in male and female gonads through interaction with G protein-coupled receptors, LHR and FSHR. In the male, LH acts on leydig cells and is mostly responsible for the acquisition of puberty and the production of androgens while FSH, together with androgens, regulates spermatogenesis within Sertoli cells. We have engineered filamentous phages displaying mouse LHR and human FSHR decapeptides chosen in hormone binding regions. Peptides from both receptors displayed on phages belong either to the receptor specific exon 1 (amino acids 18-27) or to the homologous exon 4 (amino acids 98-107). Vaccination of prepubertal BALB/c male mice with hybrid phages using sub-cutaneous or intraperitoneal injections induced immunity against receptors. Anti-receptor immunization produced agonist or antagonist effects depending only on the circulating levels of the antibodies. Both anti-LHR and anti-FSHR vaccines induced efficient as well as reversible male contraception, through different mechanisms: targeting LH receptors inhibited or hyperstimulated Leydig cell testosterone production while targeting FSH receptors did not affect testosterone levels.

Adolescent social defeat alters N-methyl-D-aspartic acid receptor expression and impairs fear learning in adulthood.

PubMed

Novick, Andrew M; Mears, Mackenzie; Forster, Gina L; Lei, Yanlin; Tejani-Butt, Shanaz M; Watt, Michael J

2016-05-01

Repeated social defeat of adolescent male rats results in adult mesocortical dopamine hypofunction, impaired working memory, and increased contextual anxiety-like behavior. Given the role of glutamate in dopamine regulation, cognition, and fear and anxiety, we investigated potential changes to N-methyl-D-aspartic acid (NMDA) receptors following adolescent social defeat. As both NMDA receptors and mesocortical dopamine are implicated in the expression and extinction of conditioned fear, a separate cohort of rats was challenged with a classical fear conditioning paradigm to investigate whether fear learning is altered by adolescent defeat. Quantitative autoradiography was used to measure 3H-MK-801 binding to NMDA receptors in regions of the medial prefrontal cortex, caudate putamen, nucleus accumbens, amygdala and hippocampus. Assessment of fear learning was achieved using an auditory fear conditioning paradigm, with freezing toward the auditory tone used as a measure of conditioned fear. Compared to controls, adolescent social defeat decreased adult NMDA receptor expression in the infralimbic region of the prefrontal cortex and central amygdala, while increasing expression in the CA3 region of the hippocampus. Previously defeated rats also displayed decreased conditioned freezing during the recall and first extinction periods, which may be related to the observed decreases and increases in NMDA receptors within the central amygdala and CA3, respectively. The alteration in NMDA receptors seen following adolescent social defeat suggests that dysfunction of glutamatergic systems, combined with mesocortical dopamine deficits, likely plays a role in the some of the long-term behavioral consequences of social stressors in adolescence seen in both preclinical and clinical studies. Copyright © 2016 Elsevier B.V. All rights reserved.

Age-related change in the retinoid X receptor beta gene expression in peripheral blood mononuclear cells of healthy volunteers: effect of 13-cis retinoic acid supplementation.

PubMed

Brtko, J; Rock, E; Nezbedova, P; Krizanova, O; Dvorcakova, M; Minet-Quinard, R; Farges, M-C; Ribalta, J; Winklhofer-Roob, B M; Vasson, M-P; Macejova, D

2007-01-01

The regulation of cell growth and differentiation and also expression of a number of genes by retinoids are mediated by nuclear retinoid receptors (RARs and/or RXRs). In this study we investigated age-related alteration in both RAR and RXR receptor subtypes gene expression and tissue transglutaminase (tTG) activity before and after supplementation with 13-cis retinoic acid (13cRA) in human peripheral blood mononuclear cells (PBMCs). Healthy men (40) were divided in two groups according to their age (young group: 26.1+/-4.1 years and old group: 65.4+/-3.8 years). Each volunteer received 13cRA (Curacné), 0.5mg/(kgday)) during a period of 4 weeks. We have shown that RXRbeta expression was decreased significantly (p=0.0108) in PBMCs of elderly men when compared to that of young volunteers. Distribution of retinoic acid receptor subtype expression in PBMCs was found in the order: RXRbeta>RARgamma>RXRalpha>RARalpha. The tTG activity in PBMCs reflected a trend to be enhanced after 13-cis retinoic acid supplementation. In conclusion, we demonstrate a significant decrease in the expression of RXRbeta subtype of rexinoid receptors in PBMCs of healthy elderly men. Our data suggest that in healthy elderly men reduction of RXRbeta expression in PBMCs might be a common feature of physiological senescence.

Free fatty acid receptor 3 is a key target of short chain fatty acid. What is the impact on the sympathetic nervous system?

PubMed

López Soto, Eduardo Javier; Gambino, Luisina Ongaro; Mustafá, Emilio Román

2014-01-01

Nervous system (NS) activity participates in metabolic homeostasis by detecting peripheral signal molecules derived from food intake and energy balance. High quality diets are thought to include fiber-rich foods like whole grain rice, breads, cereals, and grains. Several studies have associated high consumption of fiber-enriched diets with a reduced risk of diabetes, obesity, and gastrointestinal disorders. In the lower intestine, anaerobic fermentation of soluble fibers by microbiota produces short chain fatty acids (SCFAs), key energy molecules that have a recent identified leading role in the intestinal gluconeogenesis, promoting beneficial effects on glucose tolerance and insulin resistance. SCFAs are also signaling molecules that bind to specific G-protein coupled receptors (GPCRs) named Free Fatty Acid Receptor 3 (FFA3, GPR41) and 2 (FFA2, GPR43). However, how SCFAs impact NS activity through their GPCRs is poorly understood. Recently, studies have demonstrated the presence of FFA2 and FFA3 in the sympathetic NS of rat, mouse and human. Two studies have showed that FFA3 activation by SCFAs increases firing and norepinephrine (NE) release from sympathetic neurons. However, the recent study from the Ikeda Laboratory revealed that activation of FFA3 by SCFAs impairs N-type calcium channel (NTCC) activity, which contradicts the idea of FFA3 activation leading to increased action potential evoked NE release. Here we will discuss the scope of the latter study and the putative physiological role of SCFAs and FFAs in the sympathetic NS.

ATP7A is a novel target of retinoic acid receptor β2 in neuroblastoma cells

PubMed Central

Bohlken, A; Cheung, B B; Bell, J L; Koach, J; Smith, S; Sekyere, E; Thomas, W; Norris, M; Haber, M; Lovejoy, D B; Richardson, D R; Marshall, G M

2009-01-01

Increased retinoic acid receptor β (RARβ2) gene expression is a hallmark of cancer cell responsiveness to retinoid anticancer effects. Moreover, low basal or induced RARβ2 expression is a common feature of many human cancers, suggesting that RARβ2 may act as a tumour suppressor gene in the absence of supplemented retinoid. We have previously shown that low RARβ2 expression is a feature of advanced neuroblastoma. Here, we demonstrate that the ABC domain of the RARβ2 protein alone was sufficient for the growth inhibitory effects of RARβ2 on neuroblastoma cells. ATP7A, the copper efflux pump, is a retinoid-responsive gene, was upregulated by ectopic overexpression of RARβ2. The ectopic overexpression of the RARβ2 ABC domain was sufficient to induce ATP7A expression, whereas, RARβ2 siRNA blocked the induction of ATP7A expression in retinoid-treated neuroblastoma cells. Forced downregulation of ATP7A reduced copper efflux and increased viability of retinoid-treated neuroblastoma cells. Copper supplementation enhanced cell growth and reduced retinoid-responsiveness, whereas copper chelation reduced the viability and proliferative capacity. Taken together, our data demonstrates ATP7A expression is regulated by retinoic acid receptor β and it has effects on intracellular copper levels, revealing a link between the anticancer action of retinoids and copper metabolism. PMID:19127267

The Distribution of Charged Amino Acid Residues and the Ca2+ Permeability of Nicotinic Acetylcholine Receptors: A Predictive Model.

PubMed

Fucile, Sergio

2017-01-01

Nicotinic acetylcholine receptors (nAChRs) are cation-selective ligand-gated ion channels exhibiting variable Ca 2+ permeability depending on their subunit composition. The Ca 2+ permeability is a crucial functional parameter to understand the physiological role of nAChRs, in particular considering their ability to modulate Ca 2+ -dependent processes such as neurotransmitter release. The rings of extracellular and intracellular charged amino acid residues adjacent to the pore-lining TM2 transmembrane segment have been shown to play a key role in the cation selectivity of these receptor channels, but to date a quantitative relationship between these structural determinants and the Ca 2+ permeability of nAChRs is lacking. In the last years the Ca 2+ permeability of several nAChR subtypes has been experimentally evaluated, in terms of fractional Ca 2+ current ( Pf , i.e., the percentage of the total current carried by Ca 2+ ions). In the present study, the available Pf -values of nAChRs are used to build a simplified modular model describing the contribution of the charged residues in defined regions flanking TM2 to the selectivity filter controlling Ca 2+ influx. This model allows to predict the currently unknown Pf -values of existing nAChRs, as well as the hypothetical Ca 2+ permeability of subunit combinations not able to assemble into functional receptors. In particular, basing on the amino acid sequences, a Pf > 50% would be associated with homomeric nAChRs composed by different α subunits, excluding α7, α9, and α10. Furthermore, according to the model, human α7β2 receptors should have Pf -values ranging from 3.6% (4:1 ratio) to 0.1% (1:4 ratio), much lower than the 11.4% of homomeric α7 nAChR. These results help to understand the evolution and the function of the large diversity of the nicotinic receptor family.

Lysine supplementation of commercial fishmeal-free diet in hybrid striped bass affect growth expression genes

USDA-ARS?s Scientific Manuscript database

Substitution of fishmeal with alternate proteins in aquafeeds often results in dietary imbalances of first-limiting essential amino acids (EAA) and poorer fish performance. Previously, we conducted a growth trial to test the hypothesis that ideal protein theory accurately predicts first-limiting ami...

Similarities and differences between the responses induced in human phagocytes through activation of the medium chain fatty acid receptor GPR84 and the short chain fatty acid receptor FFA2R.

PubMed

Sundqvist, Martina; Christenson, Karin; Holdfeldt, André; Gabl, Michael; Mårtensson, Jonas; Björkman, Lena; Dieckmann, Regis; Dahlgren, Claes; Forsman, Huamei

2018-05-01

GPR84 is a recently de-orphanized member of the G-protein coupled receptor (GPCR) family recognizing medium chain fatty acids, and has been suggested to play important roles in inflammation. Due to the lack of potent and selective GPR84 ligands, the basic knowledge related to GPR84 functions is very limited. In this study, we have characterized the GPR84 activation profile and regulation mechanism in human phagocytes, using two recently developed small molecules that specifically target GPR84 agonistically (ZQ16) and antagonistically (GLPG1205), respectively. Compared to our earlier characterization of the short chain fatty acid receptor FFA2R which is functionally expressed in neutrophils but not in monocytes, GPR84 is expressed in both cell types and in monocyte-derived macrophages. In neutrophils, the GPR84 agonist had an activation profile very similar to that of FFA2R. The GPR84-mediated superoxide release was low in naïve cells, but the response could be significantly primed by TNFα and by the actin cytoskeleton disrupting agent Latrunculin A. Similar to that of FFA2R, a desensitization mechanism bypassing the actin cytoskeleton was utilized by GPR84. All ZQ16-mediated cellular responses were sensitive to GLPG1205, confirming the GPR84-dependency. Finally, our data of in vivo transmigrated tissue neutrophils indicate that both GPR84 and FFA2R are involved in neutrophil recruitment processes in vivo. In summary, we show functional similarities but also some important differences between GPR84 and FFA2R in human phagocytes, thus providing some mechanistic insights into GPR84 regulation in blood neutrophils and cells recruited to an aseptic inflammatory site in vivo. Copyright © 2018 Elsevier B.V. All rights reserved.

Discovery of a new class of ionotropic glutamate receptor antagonists by the rational design of (2S,3R)-3-(3-carboxyphenyl)-pyrrolidine-2-carboxylic acid.

PubMed

Larsen, Ann M; Venskutonytė, Raminta; Valadés, Elena Antón; Nielsen, Birgitte; Pickering, Darryl S; Bunch, Lennart

2011-02-16

The kainic acid (KA) receptors belong to the class of glutamate (Glu) receptors in the brain and constitute a promising target for the treatment of neurological and/or psychiatric diseases such as schizophrenia, major depression, and epilepsy. Five KA subtypes have been identified and named GluK1-5. In this article, we present the discovery of (2S,3R)-3-(3-carboxyphenyl)-pyrrolidine-2-carboxylic acid (1) based on a rational design process. Target compound 1 was synthesized by a stereoselective strategy in 10 steps from commercially available starting materials. Binding affinities of 1 at native ionotropic Glu receptors were determined to be in the micromolar range (AMPA, 51 μM; KA, 22 μM; NMDA 6 μM), with the highest affinity for cloned homomeric KA receptor subtypes GluK1,3 (3.0 and 8.1 μM, respectively). Functional characterization of 1 by two electrode voltage clamp (TEVC) electrophysiology at a nondesensitizing mutant of GluK1 showed full competitive antagonistic behavior with a K(b) of 11.4 μM.

ACTIVATION OF MOUSE AND HUMAN PEROXISOME PROLIFERATOR-ACTIVATED RECEPTORS (PPAR ALPHA, GAMMA, BETA DELTA) BY PERFLUOROOCTANOIC ACID (PFOA) AND PERFLUOROOCTANE SULFONATE (PFOS)

EPA Science Inventory

This study evaluates the potential for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) to activate peroxisome proliferator-activated receptors (PPARs), using a transient transfection cell assay. Cos-1 cells were cultured in DMEM with fetal bovine serum (FBS) in ...

Gintonin enhances performance of mice in rotarod test: Involvement of lysophosphatidic acid receptors and catecholamine release.

PubMed

Lee, Byung-Hwan; Kim, Jisu; Lee, Ra Mi; Choi, Sun-Hye; Kim, Hyeon-Joong; Hwang, Sung-Hee; Lee, Myung Koo; Bae, Chun-Sik; Kim, Hyoung-Chun; Rhim, Hyewon; Lim, Kiwon; Nah, Seung-Yeol

2016-01-26

Ginseng has a long history of use as a tonic for restoration of vigor. One example of ginseng-derived tonic effect is that it can improve physical stamina under conditions of stress. However, the active ingredient and the underlying molecular mechanism responsible for the ergogenic effect are unknown. Recent studies show that ginseng contains a novel ingredient, gintonin, which consists of a unique class of herbal-medicine lysophosphatidic acids (LPAs). Gintonin activates G protein-coupled LPA receptors to produce a transient [Ca(2+)]i signal, which is coupled to diverse intra- and inter-cellular signal transduction pathways that stimulate hormone or neurotransmitter release. However, relatively little is known about how gintonin-mediated cellular modulation is linked to physical endurance. In the present study, systemic administration of gintonin, but not ginsenosides, in fasted mice increased blood glucose concentrations in a dose-dependent manner. Gintonin treatment elevated blood glucose to a maximum level after 30min. This elevation in blood glucose level could be abrogated by the LPA1/3 receptor antagonist, Ki16425, or the β-adrenergic receptor antagonist, propranolol. Furthermore, gintonin-dependent enhanced performance of fasted mice in rotarod test was likewise abrogated by Ki16425. Gintonin also elevated plasma epinephrine and norepinephrine concentrations. The present study shows that gintonin mediates catecholamine release through activation of the LPA receptor and that activation of the β-adrenergic receptor is coupled to liver glycogenolysis, thereby increasing the supply of glucose and enhancing performance in the rotarod test. Thus, gintonin acts via the LPA-catecholamine-glycogenolysis axis, representing a candidate mechanism that can explain how ginseng treatment enhances physical stamina. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Functional Roles of Pattern Recognition Receptors That Recognize Virus Nucleic Acids in Human Adipose-Derived Mesenchymal Stem Cells