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1

Exploration of click reaction for the synthesis of modified nucleosides as chitin synthase inhibitors  

Microsoft Academic Search

Click reaction approach toward the synthesis of two sets of novel 1,2,3-triazolyl linked uridine derivatives 19a–19g and 21a–21g was achieved by Cu(I)-catalyzed 1,3-dipolar cycloaddition of 5?-azido-5?-deoxy-2?,3?-O-(1-methylethylidene)uridine (17) with propargylated ether of phenols 18a–18g and propargylated esters 20a–20g. Structure of one of the representative compound 19d was unambiguously confirmed by X-ray crystallography. Chitin synthase inhibition study of all these compounds 19a–19g

Preeti M. Chaudhary; Sayalee R. Chavan; Fazal Shirazi; Meenakshi Razdan; Prachi Nimkar; Shailaja P. Maybhate; Anjali P. Likhite; Rajesh Gonnade; Braja G. Hazara; Mukund V. Deshpande; Sunita R. Deshpande

2009-01-01

2

Regulation of expression, activity and localization of fungal chitin synthases  

PubMed Central

The fungal cell wall represents an attractive target for pharmacologic inhibition, as many of the components are fungal-specific. Though targeted inhibition of ?-glucan synthesis is effective treatment for certain fungal infections, the ability of the cell wall to dynamically compensate via the cell wall integrity pathway may limit overall efficacy. To date, chitin synthesis inhibitors have not been successfully deployed in the clinical setting. Fungal chitin synthesis is a complex and highly regulated process. Regulation of chitin synthesis occurs on multiple levels, thus targeting of these regulatory pathways may represent an exciting alternative approach. A variety of signaling pathways have been implicated in chitin synthase regulation, at both transcriptional and post-transcriptional levels. Recent research suggests that localization of chitin synthases likely represents a major regulatory mechanism. However, much of the regulatory machinery is not necessarily shared among different chitin synthases. Thus, an in depth understanding of the precise roles of each protein in cell wall maintenance and repair will be essential to identifying the most likely therapeutic targets.

Rogg, Luise E.; Fortwendel, Jarrod R.; Juvvadi, Praveen R.; Steinbach, William J.

2013-01-01

3

Chitin synthase homologs in three ectomycorrhizal truffles  

Microsoft Academic Search

Degenerate PCR primers were used to amplify a conserved gene portion coding chitin synthase from genomic DNA of six species of ectomycorrhizal truffles. DNA was extracted from both hypogeous fruitbodies and in vitro growing mycelium of Tuber borchii. A single fragment of about 600 bp was amplified for each species. The amplification products from Tuber magnatum, T. borchii and T.

Luisa Lanfranco; Lilia Garnero; Massimiliano Delpero; Paola Bonfante

1995-01-01

4

Inhibitory activity for chitin synthase II from Saccharomyces cerevisiae by tannins and related compounds.  

PubMed

In the course of search for potent inhibitors of chitin synthase II from natural resources, seven tannins and related compounds were isolated from the aerial part of Euphorbia pekinensis and identified as gallic acid (1), methyl gallate (2), 3-O-galloyl-(-)-shikimic acid (3), corilagin (4), geraniin (5), quercetin-3-O-(2"-O-galloyl)-beta-D-glucoside (6), and kaempferol-3-O-(2"-O-galloyl)-beta-D-glucoside (7). These and nine related compounds, (-)-quinic acid (8), (-)-shikimic acid (9), ellagic acid (10), kaempferol (11), quercetin (12), quercitrin (13), rutin (14), quercetin-3-O-(2"-O-galloyl)-beta-D-rutinoside (15) and 1,3,4,6-tetra-O-galloyl-beta-D-glucose (16), were evaluated for the inhibitory activity against chitin synthase II and III. They inhibited chitin synthase II with IC(50) values of 18-206 microM, except for two organic acids, (-)-quinic acid (8) and (-)-shikimic acid (9). Among them, 3-O-galloyl-(-)-shikimic acid (3) was the most potent inhibitor against chitin synthase II of Saccharomyces cerevisiae with an IC(50) value of 18 microM. The inhibition appears to be selective for chitin synthase II, as they did not appreciably inhibit chitin synthase III. PMID:11509967

Hwang, E I; Ahn, B T; Lee, H B; Kim, Y K; Lee, K S; Bok, S H; Kim, Y T; Kim, S U

2001-08-01

5

Chitin synthase in encysting Entamoeba invadens.  

PubMed Central

Although the cyst wall of Entamoeba invadens contains chitin, synthesis of this structural polymer during encystation has not been described before. Here we report that conditions which stimulate encystation of the parasite lead to increased chitin synthase (ChS) activity, measured by incorporation of [3H]GlcNAc ([3H]N-acetylglucosamine) from UDP-GlcNAc. The radiolabelled product was precipitable by trichloroacetic acid or ethanol and identified as chitin because it was digested by purified chitinase to radioactive chitobiose and GlcNAc. Cell fractionation indicated that approx. 60% of the enzyme is in the high-speed supernatant. pH-activity profiles showed that soluble ChS has an optimum at 6.0, whereas particulate ChS has a peak at pH 7.0-7.5. Both the activities were dependent on bivalent metal ions, especially Mn2+ and Mn2+ plus Co2+. In contrast with the ChS of other organisms, neither the particulate nor the soluble ChS of E. invadens was activated by trypsin treatment. Soluble and particulate ChS were also stimulated by digitonin and phosphatidylserine, whereas phosphatidylethanolamine stimulated only the soluble ChS. The enzyme activities were inhibited by UDP, UDP-glucose and UDP-GalNAc, but not by the analogues Polyoxin-D or Nikkomycin. This is the first report of an enzyme which is developmentally regulated during encystation of the primitive eukaryotic genus Entamoeba.

Das, S; Gillin, F D

1991-01-01

6

A nonradioactive, high throughput assay for chitin synthase activity.  

PubMed

Wheat germ agglutinin (WGA) binds with high affinity and specificity to several sites on chitin polymers. Based on these properties we have modified and adapted a previously patented (U.S. patent 5,888,757) nonradioactive, high throughput screening assay for antimicrobial agents, making it suitable as a quantitative enzymatic assay for the activity of individual chitin synthase isozymes in yeast. The procedure involves binding of synthesized chitin to a WGA-coated surface followed by detection of the polymer with a horseradish peroxidase-WGA conjugate. Horseradish peroxidase activity is then determined as an increment in absorbance at 600 nm. Absorbance values are converted to amounts of chitin using acid-solubilized chitin as a standard. The high sensitivity (lower limit of detection about 50 ng chitin), low dispersion (lower than 10%), and high throughput (96-well microtiter plate format) make this assay an excellent substitute for the conventional radioactive chitin synthase assay in cell-free extracts. We have applied this method to the differential assay of chitin synthase activities (Chs1, Chs2, and Chs3) in cell-free extracts of Saccharomyces cerevisiae. Analysis of Chs3 activity in chitosomal and plasma membrane fractions revealed that Chs3 in the plasma membrane fraction is about sixfold more active than in the chitosome. PMID:12018950

Lucero, Héctor A; Kuranda, Michael J; Bulik, Dorota A

2002-06-01

7

Immunolocalization of chitin synthase in the tobacco hornworm  

Microsoft Academic Search

To start investigation of chitin synthesis and peritrophic membrane formation in the midgut of Manduca sexta, we have cloned a cDNA fragment encoding chitin synthase. Northern blots with a corresponding RNA probe revealed a single transcript of 4.7 kb, which was most prominent in poly(A) RNA isolated from the anterior and median midgut as well as from tracheal cells. In

Lars Zimoch; Hans Merzendorfer

2002-01-01

8

Chitin Synthases from Saprolegnia Are Involved in Tip Growth and Represent a Potential Target for Anti-Oomycete Drugs  

PubMed Central

Oomycetes represent some of the most devastating plant and animal pathogens. Typical examples are Phytophthora infestans, which causes potato and tomato late blight, and Saprolegnia parasitica, responsible for fish diseases. Despite the economical and environmental importance of oomycete diseases, their control is difficult, particularly in the aquaculture industry. Carbohydrate synthases are vital for hyphal growth and represent interesting targets for tackling the pathogens. The existence of 2 different chitin synthase genes (SmChs1 and SmChs2) in Saprolegnia monoica was demonstrated using bioinformatics and molecular biology approaches. The function of SmCHS2 was unequivocally demonstrated by showing its catalytic activity in vitro after expression in Pichia pastoris. The recombinant SmCHS1 protein did not exhibit any activity in vitro, suggesting that it requires other partners or effectors to be active, or that it is involved in a different process than chitin biosynthesis. Both proteins contained N-terminal Microtubule Interacting and Trafficking domains, which have never been reported in any other known carbohydrate synthases. These domains are involved in protein recycling by endocytosis. Enzyme kinetics revealed that Saprolegnia chitin synthases are competitively inhibited by nikkomycin Z and quantitative PCR showed that their expression is higher in presence of the inhibitor. The use of nikkomycin Z combined with microscopy showed that chitin synthases are active essentially at the hyphal tips, which burst in the presence of the inhibitor, leading to cell death. S. parasitica was more sensitive to nikkomycin Z than S. monoica. In conclusion, chitin synthases with species-specific characteristics are involved in tip growth in Saprolegnia species and chitin is vital for the micro-organisms despite its very low abundance in the cell walls. Chitin is most likely synthesized transiently at the apex of the cells before cellulose, the major cell wall component in oomycetes. Our results provide important fundamental information on cell wall biogenesis in economically important species, and demonstrate the potential of targeting oomycete chitin synthases for disease control.

Guerriero, Gea; Avino, Mariano; Zhou, Qi; Fugelstad, Johanna; Clergeot, Pierre-Henri; Bulone, Vincent

2010-01-01

9

Characterization of a chitin synthase encoding gene and effect of diflubenzuron in soybean aphid, Aphis glycines.  

PubMed

Chitin synthases are critical enzymes for synthesis of chitin and thus for subsequent growth and development in insects. We identified the cDNA of chitin synthase gene (CHS) in Aphis glycines, the soybean aphid, which is a serious pest of soybean. The full-length cDNA of CHS in A. glycines (AyCHS) was 5802 bp long with an open reading frame of 4704 bp that encoded for a 1567 amino acid residues protein. The predicted AyCHS protein had a molecular mass of 180.05 kDa and its amino acid sequence contained all the signature motifs (EDR, QRRRW and TWGTR) of chitin synthases. The quantitative real-time PCR (qPCR) analysis revealed that AyCHS was expressed in all major tissues (gut, fat body and integument); however, it had the highest expression in integument (~3.5 fold compared to gut). Interestingly, the expression of AyCHS in developing embryos was nearly 7 fold higher compared to adult integument, which probably is a reflection of embryonic molts in hemimetabolus insects. Expression analysis in different developmental stages of A. glycines revealed a consistent AyCHS expression in all stages. Further, through leaf dip bioassay, we tested the effect of diflubenzuron (DFB, Dimilin ®), a chitin-synthesis inhibitor, on A. glycines' survival, fecundity and body weight. When fed with soybean leaves previously dipped in 50 ppm DFB solution, A. glycines nymphs suffered significantly higher mortality compared to control. A. glycines nymphs feeding on diflubenzuron treated leaves showed a slightly enhanced expression (1.67 fold) of AyCHS compared to nymphs on untreated leaves. We discussed the potential applications of the current study to develop novel management strategies using chitin-synthesis inhibitors and using RNAi by knocking down AyCHS expression. PMID:23139631

Bansal, Raman; Mian, M A Rouf; Mittapalli, Omprakash; Michel, Andy P

2012-10-25

10

Chitin synthases are required for survival, fecundity and egg-hatch in the red flour beetle, Tribolium castaneum  

Technology Transfer Automated Retrieval System (TEKTRAN)

The synthesis of chitin, the Beta-1,4-linked polymer of N-acetylglucosamine, is catalyzed by chitin synthase (CHS). Chitin is essential for the structural integrity of the exoskeletal cuticle and midgut peritrophic membrane (PM) of insects. To study the functions of the two chitin synthase genes, ...

11

Purification of an active, oligomeric chitin synthase complex from the midgut of the tobacco hornworm.  

PubMed

Chitin formation depends on the activity of a family II glycosyltransferase known as chitin synthase, whose biochemical and structural properties are largely unknown. Previously, we have demonstrated that the chitin portion of the peritrophic matrix in the midgut of the tobacco hornworm, Manduca sexta, is produced by chitin synthase 2 (CHS-2), one of two isoenzymes encoded by the Chs-1 and Chs-2 genes (also named Chs-A and Chs-B), and that CHS-2 is located at the apical tips of the brush border microvilli. Here we report the purification of the chitin synthase from the Manduca midgut as monitored by its activity and immuno-reactivity with antibodies to the chitin synthase. After gel permeation chromatography, the final step of the developed purification protocol, the active enzyme eluted in a fraction corresponding to a molecular mass between 440 and 670 kDa. Native PAGE revealed a single, immuno-reactive band of about 520 kDa, thrice the molecular mass of the chitin synthase monomer. SDS-PAGE and immunoblotting indicated finally that an active, oligomeric complex of the chitin synthase was purified. In summary, the chitin synthase from the midgut of Manduca may prove to be a good model for investigating the enzymes' mode of action. PMID:19576988

Maue, Lars; Meissner, Derek; Merzendorfer, Hans

2009-07-02

12

CAL1, a gene required for activity of chitin synthase 3 in Saccharomyces cerevisiae  

PubMed Central

The CAL1 gene was cloned by complementation of the defect in Calcofluor- resistant calR1 mutants of Saccharomyces cerevisiae. Transformation of the mutants with a plasmid carrying the appropriate insert restored Calcofluor sensitivity, wild-type chitin levels and normal spore maturation. Southern blots using the DNA fragment as a probe showed hybridization to a single locus. Allelic tests indicated that the cloned gene corresponded to the calR1 locus. The DNA insert contains a single open-reading frame encoding a protein of 1,099 amino acids with a molecular mass of 124 kD. The predicted amino acid sequence shows several regions of homology with those of chitin synthases 1 and 2 from S. cerevisiae and chitin synthase 1 from Candida albicans. calR1 mutants have been found to be defective in chitin synthase 3, a trypsin- independent synthase. Transformation of the mutants with a plasmid carrying CAL1 restored chitin synthase 3 activity; however, overexpression of the enzyme was not achieved even with a high copy number plasmid. Since Calcofluor-resistance mutations different from calR1 also result in reduced levels of chitin synthase 3, it is postulated that the products of some of these CAL genes may be limiting for expression of the enzymatic activity. Disruption of the CAL1 gene was not lethal, indicating that chitin synthase 3 is not an essential enzyme for S. cerevisiae.

1991-01-01

13

Different Chitin Synthase Genes Are Required for Various Developmental and Plant Infection Processes in the Rice Blast Fungus Magnaporthe oryzae  

Microsoft Academic Search

Chitin is a major component of fungal cell wall and is synthesized by chitin synthases (Chs). Plant pathogenic fungi normally have multiple chitin synthase genes. To determine their roles in development and pathogenesis, we functionally characterized all seven CHS genes in Magnaporthe oryzae. Three of them, CHS1, CHS6, and CHS7, were found to be important for plant infection. While the

Ling-An Kong; Jun Yang; Guo-Tian Li; Lin-Lu Qi; Yu-Jun Zhang; Chen-Fang Wang; Wen-Sheng Zhao; Jin-Rong Xu; You-Liang Peng

2012-01-01

14

Effects of amphotericin B, nystatin, and other polyene antibiotics on chitin synthase.  

PubMed Central

The effects of amphotericin B (AmB), nystatin, filipin, and pimaricin were tested chitin synthase (EC 2.4.1.16) (chitosomes from yeast cells of Mucor rouxii). AmB and nystatin inhibited the enzyme at concentrations greater than or equal to 10 micrograms/ml, filipin was weakly inhibitory, and pimaricin had no effect. The inhibition of chitin synthase by AmB appears to be noncompetitive, with a Ki value of about 0.13 mM. the effect of nystatin was more complex and included a sharp stimulation of chitin synthase activity at approximately 50 micrograms/ml. Our findings suggest the existence of binding sites (sterols?) on the chitosome that are selective for certain polyenes and that play a role in the operation of chitin synthase. Because the minimal growth inhibitory concentrations of AmB or nystatin are lower than the concentrations that inhibit chitin synthase in vitro, the possibility of chitosomal chitin synthase being a primary target for the antifungal action of these polyenes seems unlikely.

Rast, D M; Bartnicki-Garcia, S

1981-01-01

15

Chitin synthase III: synthetic lethal mutants and "stress related" chitin synthesis that bypasses the CSD3/CHS6 localization pathway.  

PubMed

We screened Saccharomyces strains for mutants that are synthetically lethal with deletion of the major chitin synthase gene CHS3. In addition to finding, not surprisingly, that mutations in major cell wall-related genes such as FKS1 (glucan synthase) and mutations in any of the Golgi glycosylation complex genes (MNN9 family) are lethal in combination with chs3Delta, we found that a mutation in Srv2p, a bifunctional regulatory gene, is notably lethal in the chs3 deletion. In extending studies of fks1-chitin synthase 3 interactions, we made the surprising discovery that deletion of CSD3/CHS6, a gene normally required for Chs3p delivery and activity in vivo, was not lethal with fks1 and, in fact, that lack of Csd3p/Chs6p did not decrease the high level of stress-related chitin made in the fks1 mutant. This finding suggests that "stress response" chitin synthesis proceeds through an alternate Chs3p targeting pathway. PMID:10500155

Osmond, B C; Specht, C A; Robbins, P W

1999-09-28

16

Morphology engineering of Penicillium chrysogenum by RNA silencing of chitin synthase gene.  

PubMed

Chitin synthases, that catalyze the formation of chitin the major component of cell walls in most filamentous fungi, play crucial roles in the growth and morphogenesis. To investigate the roles of chitin synthase in Penicillium chrysogenum, we developed an RNAi system to silence the class III chitin synthase gene chs4. After transformation, mutants had a slow growth rate and shorter but highly branched hyphae. All transformants either were unable to form conidia or could form only a few. Changes in chs4 expression could lead to a completely different morphology and eventually cause distinct penicillin yields. In particular, the yield of one transformant was 41 % higher than that of the original strain. PMID:23187754

Liu, Hui; Wang, Peng; Gong, Guohong; Wang, Li; Zhao, Genhai; Zheng, Zhiming

2012-11-28

17

Metabolic products of microorganisms. 181. Chitin synthase from fungi, a test model for substances with insecticidal properties.  

PubMed

Chitin synthase from Coprinus cinereus (Schaeff. ex Fr.) S. F. Gray (= C. lagopus sensu Buller) was used as a model for chitin synthase from insects. The effect of dimilin (difluorobenzuron), captan (trichloromethylsulfonyl fungicide), kitazin P (organophosphorus ester fungicide) and parathion (organophosphorus insecticide) on the fungal enzyme was compared with the effect of nikkomycin (nucleosidepeptide antibiotic). PMID:380491

Brillinger, G U

1979-04-01

18

Characterization of a chitin synthase cDNA and its increased mRNA level associated with decreased chitin synthesis in Anopheles quadrimaculatus exposed to diflubenzuron.  

PubMed

Chitin synthase (EC 2.4.1.16) is a crucial enzyme responsible for chitin biosynthesis in all chitin-containing organisms. This paper reports a complete cDNA encoding chitin synthase 1 (AqCHS1), change of AqCHS1 mRNA level in response to diflubenzuron exposure, and concentration-dependent effect of diflubenzuron on chitin synthesis in the common malaria mosquito (Anopheles quadrimaculatus). The cDNA consists of 5723 nucleotides, including an open reading frame (ORF) of 4734 nucleotides that encode 1578 amino acid residues and a non-translated region of 989 nucleotides. The deduced amino acid sequence contains all the chitin synthase signature motifs (EDR, QRRRW and SWGTR) and shows 97% identity to that of An. gambiae (AgCHS1, XM_321337). Northern blot and real-time quantitative PCR analyses revealed a significant increase of AqCHS1 mRNA level in the larvae exposed to diflubenzuron at 100 and 500 microg/L. As confirmed by real-time quantitative PCR, AqCHS1 mRNA level was enhanced by 2-fold in the larvae exposed to diflubenzuron at 500 microg/L for 24 h. In contrast, exposures of the larvae to diflubenzuron at 4.0, 20, 100 and 500 microg/L for 48 h resulted in decreases of chitin content by 9.0%, 43%, 58% and 76%, respectively. Significantly increased AqCHS1 mRNA level associated with decreased chitin synthesis may imply possible inhibition of chitin synthase, or abnormal chitin synthase translocation or chitin microfibril assembly conferred by diflubenzuron. Increased AqCHS1 expression due to increased transcription and/or increased mRNA stability may serve as a feedback mechanism to compensate such an effect in the mosquitoes. Further studies are necessary to elucidate the relationship between reduced chitin synthesis and increased expression of AqCHS1 in order to shed new light on trafficking and regulation of chitin biosynthesis in the mosquito affected by diflubenzuron. PMID:16935220

Zhang, Jianzhen; Zhu, Kun Yan

2006-06-16

19

Nucleotide sequence variation of chitin synthase genes among ectomycorrhizal fungi and its potential use in taxonomy.  

PubMed Central

DNA sequences of single-copy genes coding for chitin synthases (UDP-N-acetyl-D-glucosamine:chitin 4-beta-N-acetylglucosaminyltransferase; EC 2.4.1.16) were used to characterize ectomycorrhizal fungi. Degenerate primers deduced from short, completely conserved amino acid stretches flanking a region of about 200 amino acids of zymogenic chitin synthases allowed the amplification of DNA fragments of several members of this gene family. Different DNA band patterns were obtained from basidiomycetes because of variation in the number and length of amplified fragments. Cloning and sequencing of the most prominent DNA fragments revealed that these differences were due to various introns at conserved positions. The presence of introns in basidiomycetous fungi therefore has a potential use in identification of genera by analyzing PCR-generated DNA fragment patterns. Analyses of the nucleotide sequences of cloned fragments revealed variations in nucleotide sequences from 4 to 45%. By comparison of the deduced amino acid sequences, the majority of the DNA fragments were identified as members of genes for chitin synthase class II. The deduced amino acid sequences from species of the same genus differed only in one amino acid residue, whereas identity between the amino acid sequences of ascomycetous and basidiomycetous fungi within the same taxonomic class was found to be approximately 43 to 66%. Phylogenetic analysis of the amino acid sequence of class II chitin synthase-encoding gene fragments by using parsimony confirmed the current taxonomic groupings. In addition, our data revealed a fourth class of putative zymogenic chitin synthesis. Images

Mehmann, B; Brunner, I; Braus, G H

1994-01-01

20

Identification and characterization of two chitin synthase genes in African malaria mosquito, Anopheles gambiae.  

PubMed

Chitin synthase (CHS) represents an attractive target site for combating insect pests as insect growth and development are strictly dependent on precisely tuned chitin biosynthesis and this pathway is absent in humans and other vertebrates. Current knowledge on CHS in insects, especially their structures, functions, and regulations is still very limited. We report the identification and characterization of two chitin synthase genes, AgCHS1 and AgCHS2, in African malaria mosquito, Anopheles gambiae. AgCHS1 and AgCHS2 were predicted to encode proteins of 1,578 and 1,586 amino acid residues, respectively. Their deduced amino acid sequences show high similarities to other insect chitin synthases. Transcriptional analysis indicated that AgCHS1 was expressed in egg, larval, pupal and adult stages whereas AgCHS2 appeared to be expressed at relatively low levels, particularly during the larval stages as examined by reverse transcription (RT)-PCR and real-time quantitative PCR. Relatively high expression was detected in the carcass followed by the foregut and hindgut for AgCHS1, and the foregut (cardia included) followed by the midgut for AgCHS2. Fluorescence in situ hybridization (FISH) and immunohistochemical analysis revealed new information including the localization of the two enzymes in the ommatidia of the compound eyes, and AgCHS2 in the thoracic and abdominal inter-segmental regions of pupal integument. PMID:22683441

Zhang, Xin; Zhang, Jianzhen; Park, Yoonseong; Zhu, Kun Yan

2012-06-07

21

A multigene family related to chitin synthase genes of yeast in the opportunistic pathogen Aspergillus fumigatus.  

PubMed

Two approaches were used to isolate fragments of chitin synthase genes from the opportunistic human pathogen Aspergillus fumigatus. Firstly, regions of amino acid conservation in chitin synthases of Saccharomyces cerevisiae were used to design degenerate primers for amplification of portions of related genes, and secondly, a segment of the S. cerevisiae CSD2 gene was used to screen an A. fumigatus lambda genomic DNA library. the polymerase chain reaction (PCR)-based approach led to the identification of five different genes, designated chsA, chsB, chsC, chsD and chsE. chsA, chsB, and chsC fall into Classes I, II and III of the 'zymogen type' chitin synthases, respectively. The chsD fragment has approximately 35% amino acid sequence identity to both the zymogen type genes and the non-zymogen type CSD2 gene. chsF appears to be a homologue of CSD2, being 80% identical to CSD2 over 100 amino acids. An unexpected finding was the isolation by heterologous hybridization of another gene (chsE), which also has strong sequence similarity (54% identity at the amino acid level over the same region as chsF) to CSD2. Reverse transcriptase-PCR was used to show that each gene is expressed during hyphal growth in submerged cultures. PMID:7854320

Mellado, E; Aufauvre-Brown, A; Specht, C A; Robbins, P W; Holden, D W

1995-02-01

22

Chitin Synthases with a Myosin Motor-Like Domain Control the Resistance of Aspergillus fumigatus to Echinocandins  

PubMed Central

Aspergillus fumigatus has two chitin synthases (CSMA and CSMB) with a myosin motor-like domain (MMD) arranged in a head-to-head configuration. To understand the function of these chitin synthases, single and double csm mutant strains were constructed and analyzed. Although there was a slight reduction in mycelial growth of the mutants, the total chitin synthase activity and the cell wall chitin content were similar in the mycelium of all of the mutants and the parental strain. In the conidia, chitin content in the ?csmA strain cell wall was less than half the amount found in the parental strain. In contrast, the ?csmB mutant strain and, unexpectedly, the ?csmA/?csmB mutant strain did not show any modification of chitin content in their conidial cell walls. In contrast to the hydrophobic conidia of the parental strain, conidia of all of the csm mutants were hydrophilic due to the presence of an amorphous material covering the hydrophobic surface-rodlet layer. The deletion of CSM genes also resulted in an increased susceptibility of resting and germinating conidia to echinocandins. These results show that the deletion of the CSMA and CSMB genes induced a significant disorganization of the cell wall structure, even though they contribute only weakly to the overall cell wall chitin synthesis.

Jimenez-Ortigosa, Cristina; Aimanianda, Vishukumar; Muszkieta, Laetitia; Mouyna, Isabelle; Alsteens, David; Pire, Stephane; Beau, Remi; Krappmann, Sven; Beauvais, Anne; Dufrene, Yves F.

2012-01-01

23

Traffic of Chitin Synthase 1 (CHS-1) to the Spitzenk?rper and Developing Septa in Hyphae of Neurospora crassa: Actin Dependence and Evidence of Distinct Microvesicle Populations ? †  

PubMed Central

We describe the subcellular location of chitin synthase 1 (CHS-1), one of seven chitin synthases in Neurospora crassa. Laser scanning confocal microscopy of growing hyphae showed CHS-1–green fluorescent protein (GFP) localized conspicuously in regions of active wall synthesis, namely, the core of the Spitzenkörper (Spk), the apical cell surface, and developing septa. It was also present in numerous fine particles throughout the cytoplasm plus some large vacuoles in distal hyphal regions. Although the same general subcellular distribution was observed previously for CHS-3 and CHS-6, they did not fully colocalize. Dual labeling showed that the three different chitin synthases were contained in different vesicular compartments, suggesting the existence of a different subpopulation of chitosomes for each CHS. CHS-1–GFP persisted in the Spk during hyphal elongation but disappeared from the septum after its development was completed. Wide-field fluorescence microscopy and total internal reflection fluorescence microscopy revealed subapical clouds of particles, suggestive of chitosomes moving continuously toward the Spk. Benomyl had no effect on CHS-1–GFP localization, indicating that microtubules are not strictly required for CHS trafficking to the hyphal apex. Conversely, actin inhibitors caused severe mislocalization of CHS-1–GFP, indicating that actin plays a major role in the orderly traffic and localization of CHS-1 at the apex.

Sanchez-Leon, Eddy; Verdin, Jorge; Freitag, Michael; Roberson, Robert W.; Bartnicki-Garcia, Salomon; Riquelme, Meritxell

2011-01-01

24

Differential gene expression signatures for cell wall integrity found in chitin synthase II (chs2?) and myosin II (myo1?) deficient cytokinesis mutants of Saccharomyces cerevisiae  

Microsoft Academic Search

BACKGROUND: Myosin II-dependent contraction of the cytokinetic ring and primary septum formation by chitin synthase II are interdependent processes during cytokinesis in Saccharomyces cerevisiae. Hence, null mutants of myosin II (myo1?) and chitin synthase II (chs2?) share multiple morphological and molecular phenotypes. To understand the nature of their interdependent functions, we will seek to identify genes undergoing transcriptional regulation in

José F Rodríguez-Quińones

2009-01-01

25

The chitin synthase genes chsA and chsC are not required for cell wall stress responses in the human pathogen Aspergillus fumigatus.  

PubMed

Invasive aspergillosis is a leading cause of mortality in immunocompromised patients. The fungal cell wall is an attractive antifungal target, but it is dynamic and responsive to external stressors. The existence of multiple chitin synthases within Aspergilli is thought to reflect specialized functions in cell wall damage responses that facilitate continued growth and viability. We previously reported increased transcription of Aspergillus fumigatus chitin synthases chsA and chsC following echinocandin treatment, suggesting important roles for these chitin synthases in cell wall compensation. As only partial disruptions have been made of these genes, we generated deletion mutants of chsA and chsC singly (?chsA and ?chsC) and doubly (?chsA ?chsC). The ?chsA ?chsC strain displayed reduced total chitin synthase activity. Interestingly, deletion of these chitin synthase genes did not affect levels of chitin or ?-1,3-glucan.The ?chsA, ?chsC and ?chsA ?chsC strains produced wild-type echinocandin-mediated chitin increases, consistent with unaltered cell wall compensation. Furthermore, transcript levels of the remaining chitin synthase genes were unchanged in the mutant strains. Taken together, these results indicate that chsA and chsC do not play a direct role in the cell wall stress response. Our findings support the existence of complex post-transcriptional regulatory mechanisms controlling chitin biosynthetic machinery in response to cell wall damage. PMID:21763289

Rogg, Luise E; Fortwendel, Jarrod R; Juvvadi, Praveen Rao; Lilley, Amanda; Steinbach, William J

2011-07-05

26

The chitin synthase genes chsA and chsC are not required for cell wall stress responses in the human pathogen Aspergillus fumigatus  

PubMed Central

Invasive aspergillosis is a leading cause of mortality in immunocompromised patients. The fungal cell wall is an attractive antifungal target, but it is dynamic and responsive to external stressors. The existence of multiple chitin synthases within Aspergilli is thought to reflect specialized functions in cell wall damage responses that facilitate continued growth and viability. We previously reported increased transcription of Aspergillus fumigatus chitin synthases chsA and chsC following echinocandin treatment, suggesting important roles for these chitin synthases in cell wall compensation. As only partial disruptions have been made of these genes, we generated deletion mutants of chsA and chsC singly (?chsA and ?chsC) and doubly (?chsA ?chsC). The ?chsA ?chsC strain displayed reduced total chitin synthase activity. Interestingly, deletion of these chitin synthase genes did not affect levels of chitin or ?-1,3-glucan. The ?chsA, ?chsC and ?chsA ?chsC strains produced wild-type echinocandin-mediated chitin increases, consistent with unaltered cell wall compensation. Furthermore, transcript levels of the remaining chitin synthase genes were unchanged in the mutant strains. Taken together, these results indicate that chsA and chsC do not play a direct role in the cell wall stress response. Our findings support the existence of complex post-transcriptional regulatory mechanisms controlling chitin biosynthetic machinery in response to cell wall damage.

Rogg, Luise E.; Fortwendel, Jarrod R.; Juvvadi, Praveen Rao; Lilley, Amanda; Steinbach, William J.

2013-01-01

27

Biochemical characterization of chitin synthase activity and inhibition in the African malaria mosquito, Anopheles gambiae.  

PubMed

Abstract? Chitin synthase (CHS) is an important enzyme catalyzing the formation of chitin polymers in all chitin containing organisms and a potential target site for insect pest control. However, our understanding of biochemical properties of insect CHSs has been very limited. We here report enzymatic and inhibitory properties of CHS prepared from the African malaria mosquito, Anopheles gambiae. Our study, which represents the first time to use a nonradioactive method to assay CHS activity in an insect species, determined the optimal conditions for measuring the enzyme activity, including pH, temperature, and concentrations of the substrate uridine diphosphate N-acetyl-d-glucosamine (UDP-GlcNAc) and Mg(++) . The optimal pH was about 6.5-7.0, and the highest activity was detected at temperatures between 37°C and 44°C. Dithithreitol is required to prevent melanization of the enzyme extract. CHS activity was enhanced at low concentration of GlcNAc, but inhibited at high concentrations. Proteolytic activation of the activity is significant both in the 500 ×g supernatant and the 40?000 ×g pellet. Our study revealed only slight in vitro inhibition of A. gambiae CHS activity by diflubenzuron and nikkomycin Z at the highest concentration (2.5 ?mol/L) examined. There was no in vitro inhibition by polyoxin D at any concentration examined. Furthermore, we did not observe any in vivo inhibition of CHS activity by any of these chemicals at any concentration examined. Our results suggest that the inhibition of chitin synthesis by these chemicals is not due to direct inhibition of CHS in A. gambiae. PMID:23955856

Zhang, Xin; Yan Zhu, Kun

2012-11-22

28

Botrytis cinerea chitin synthase BcChsVI is required for normal growth and pathogenicity.  

PubMed

Fungal chitin synthase of classes V and VI (or VII), which contain an additional N-terminal myosin motor domain, have been shown to play important roles in pathogenesis. To study the function of BcChsVI in Botrytis cinerea, BcChs6 gene was disrupted through Agrobacterium tumefaciens-mediated transformation. The Bcchs6 disruption mutant exhibited a 45.5 % increasing in its chitin content when compared with wild strain. The qRT-PCR analysis revealed that in Bcchs6 mutant the expression of BcChs6 was significantly decreased, while the expression of BcChs2 and BcChs3a was increased when compared with wild type. It is probable that the disruption of this gene provoked a compensatory mechanism regulating the cellular response to cell wall damage. Interestingly, the radial growth of Bcchs6 mutant was drastically reduced when 50 % solute was removed from the regular PDA medium, and they were more sensitive to Calcofluor white and other cell wall disturbing chemicals. Pathogenicity assays on tomato leaves indicated that they were significantly reduced in their ability to cause disease. Our results demonstrated that BcChs6 is necessary for proper hyphal growth and pathogenicity of B. cinerea on tomato leaves. PMID:23722656

Cui, Zhifeng; Wang, Yanhua; Lei, Na; Wang, Kun; Zhu, Tingheng

2013-05-31

29

Wangiella (Exophiala) dermatitidis WdChs5p, a Class V Chitin Synthase, Is Essential for Sustained Cell Growth at Temperature of Infection  

Microsoft Academic Search

The chitin synthase structural gene WdCHS5 was isolated from the black fungal pathogen of humans Wangiella dermatitidis. Sequence analysis revealed that the gene has a myosin motor-like-encoding region at its 5 end and a chitin synthase (class V)-encoding region at its 3 end. Northern blotting showed that WdCHS5 is expressed at high levels under conditions of stress. Analysis of the

Hongbo Liu; Sarah Kauffman; Jeffrey M. Becker; Paul J. Szaniszlo

2004-01-01

30

Chitin synthases are required for survival, fecundity and egg hatch in the red flour beetle, Tribolium castaneum.  

PubMed

The synthesis of chitin, the beta-1,4-linked polymer of N-acetylglucosamine, is catalyzed by chitin synthase (CHS). Chitin is essential for the structural integrity of the exoskeletal cuticle and midgut peritrophic membrane (PM) of insects. To study the functions of the two chitin synthase genes, TcCHS-A and TcCHS-B, during embryonic and adult development in the red flour beetle, Tribolium castaneum, RNA interference (RNAi) experiments were carried out. When dsRNA for TcCHS-A was injected into male or female pharate adults, all insects died 5-7 d after the adult molt, and the females failed to oviposit prior to death. When dsTcCHS-A was injected into young adults 1-2 d post-eclosion, a similar lethal phenotype was obtained after 5 d and no oviposition occurred. When dsTcCHS-A injections were delayed until after adult maturation (7-10 d post-eclosion), the treated females did oviposit and the resulting embryos appeared to develop normally. However, the chitin content of the eggs was dramatically reduced, the embryos became twisted and enlarged, and the eggs did not hatch. Adults treated with dsRNA for TcCHS-B exhibited little or no chitin in their PM and died about 2 wk after injection. None of the TcCHS-B-treated females oviposited, which was probably a secondary effect caused by starvation. These results extend our previous findings that CHS genes are required for all types of molt. The present study also demonstrates that these genes have additional roles in embryonic and adult development. PMID:18718535

Arakane, Yasuyuki; Specht, Charles A; Kramer, Karl J; Muthukrishnan, Subbaratnam; Beeman, Richard W

2008-07-31

31

A Bni4-Glc7 Phosphatase Complex That Recruits Chitin Synthase to the Site of Bud EmergenceV?  

PubMed Central

Bni4 is a scaffold protein in the yeast Saccharomyces cerevisiae that tethers chitin synthase III to the bud neck by interacting with septin neck filaments and with Chs4, a regulatory subunit of chitin synthase III. We show herein that Bni4 is also a limiting determinant for the targeting of the type 1 serine/threonine phosphatase (Glc7) to the bud neck. Yeast cells containing a Bni4 variant that fails to associate with Glc7 fail to tether Chs4 to the neck, due in part to the failure of Bni4V831A/F833A to localize properly. Conversely, the Glc7-129 mutant protein fails to bind Bni4 properly and glc7-129 mutants exhibit reduced levels of Bni4 at the bud neck. Bni4 is phosphorylated in a cell cycle-dependent manner and Bni4V831A/F833A is both hyperphosphorylated and mislocalized in vivo. Yeast cells lacking the protein kinase Hsl1 exhibit increased levels of Bni4-GFP at the bud neck. GFP-Chs4 does not accumulate at the incipient bud site in either a bni4::TRP1 or a bni4V831A/F833A mutant but does mobilize to the neck at cytokinesis. Together, these results indicate that the formation of the Bni4-Glc7 complex is required for localization to the site of bud emergence and for subsequent targeting of chitin synthase.

Kozubowski, Lukasz; Panek, Heather; Rosenthal, Ashley; Bloecher, Andrew; DeMarini, Douglas J.; Tatchell, Kelly

2003-01-01

32

The Myosin Motor Domain of Fungal Chitin Synthase V Is Dispensable for Vesicle Motility but Required for Virulence of the Maize Pathogen Ustilago maydis[W  

PubMed Central

Class V chitin synthases are fungal virulence factors required for plant infection. They consist of a myosin motor domain fused to a membrane-spanning chitin synthase region that participates in fungal cell wall formation. The function of the motor domain is unknown, but it might deliver the myosin chitin synthase-attached vesicles to the growth region. Here, we analyze the importance of both domains in Mcs1, the chitin synthase V of the maize smut fungus Ustilago maydis. By quantitative analysis of disease symptoms, tissue colonization, and single-cell morphogenic parameters, we demonstrate that both domains are required for fungal virulence. Fungi carrying mutations in the chitin synthase domain are rapidly recognized and killed by the plant, whereas fungi carrying a deletion of the motor domain show alterations in cell wall composition but can invade host tissue and cause a moderate plant response. We also show that Mcs1-bound vesicles exhibit long-range movement for up to 20 ?m at a velocity of ~1.75 ?m/s. Apical Mcs1 localization depends on F-actin and the motor domain, whereas Mcs1 motility requires microtubules and persists when the Mcs1 motor domain is deleted. Our results suggest that the myosin motor domain of ChsV supports exocytosis but not long-range delivery of transport vesicles.

Treitschke, Steffi; Doehlemann, Gunther; Schuster, Martin; Steinberg, Gero

2010-01-01

33

The Tribolium chitin synthase genes TcCHS1 and TcCHS2 are specialized for synthesis of epidermal cuticle and midgut peritrophic matrix  

Microsoft Academic Search

Functional analysis of the two chitin synthase genes, TcCHS1 and TcCHS2 , in the red flour beetle, Tribolium castaneum , revealed unique and complementary roles for each gene. TcCHS1- specific RNA interference (RNAi) disrupted all three types of moult (larval-larval, larval- pupal and pupal-adult) and greatly reduced whole-body chitin content. Exon-specific RNAi showed that splice variant 8a of TcCHS1 was

Y. Arakane; S. Muthukrishnan; K. J. Kramer; C. A. Specht; Y. Tomoyasu; M. D. Lorenzen; M. Kanost; R. W. Beeman

2005-01-01

34

Catalepsy induced by nitric oxide synthase inhibitors  

Microsoft Academic Search

1.1. Previous study showed that NG-nitro-l-arginine (l-NOARG), an inhibitor of nitric oxide synthase, induces catalepsy in a dose-dependent manner in male albino-Swiss mice.2.2. The objective of the present work was to further investigate this effect, extending it to other NOS inhibitors.3.3. Results showed that l-NOARG (40–80 mg\\/kg IP), NG-nitro-l-arginine methylester (l-NAME, 40–160 mg\\/kg IP) or NG-monomethyl-l-arginine (l-NMMA, 80 mg\\/kg IP)

E. A. Del Bel; C. A. da Silva; F. S. Guimarăes

1998-01-01

35

Oligomerization of the chitin synthase Chs3 is monitored at the Golgi and affects its endocytic recycling.  

PubMed

Chs3, the catalytic subunit of chitin synthase III in Saccharomyces cerevisiae, is a complex polytopic membrane protein whose plasma membrane expression is tightly controlled: export from the ER requires interaction with Chs7; exit from the Golgi is dependent on the exomer complex, and precise bud neck localization relies on endocytosis. Moreover, Chs3 is efficiently recycled from endosomes to the TGN in an AP-1-dependent manner. Here we show that the export of Chs3 requires the cargo receptor Erv14, in a step that is independent of Chs7. Chs3 oligomerized in the ER through its N-terminal cytosolic region. However, the truncated (?126) Chs3 was still exported by Erv14, but was sent back from the Golgi to the ER in a COPI- and Rer1-dependent manner. A subset of the oligomerization-deficient Chs3 proteins evaded Golgi quality control and reached the plasma membrane, where they were enzymatically active but poorly endocytosed. This resulted in high CSIII levels, but calcofluor white resistance, explained by the reduced intercalation of calcofluor white between nascent chitin fibres. Our data show that the oligomerization of Chs3 through its N-terminus is essential for proper protein trafficking and chitin synthesis and is therefore monitored intracellularly. PMID:23926947

Sacristan, Carlos; Manzano-Lopez, Javier; Reyes, Abigail; Spang, Anne; Muńiz, Manuel; Roncero, Cesar

2013-08-26

36

Molecular Cloning, Characterization and mRNA Expression of a Chitin Synthase 2 Gene from the Oriental Fruit Fly, Bactrocera dorsalis (Diptera: Tephritidae)  

PubMed Central

Chitin synthase (CHS), a potential target for eco-friendly insecticides, plays an essential role in chitin formation in insects. In this study, a full-length cDNA encoding chitin synthase 2 (BdCHS2) was cloned and characterized in the oriental fruit fly, Bactrocera dorsalis. The BdCHS2 cDNA had 4417 nucleotides, containing an open reading frame of 4122 nucleotides, which encoded 1373 amino acid residues with a predicted molecular weight of 158.5 kDa. Phylogenetic analysis with other insect CHSs suggested that BdCHS2 belongs to insect CHS2. The BdCHS2 transcript was predominately found in midgut but was detected at low levels in fat body, Malpighian tubules, integument, and trachea. Moreover, BdCHS2 was expressed in all developmental stages, and highly expressed in the feeding stages. There was a positive relationship between BdCHS2 expression and total chitin content during development. Furthermore, both the gene expression and chitin content in midgut decreased when the insect was fed for 24 h, then starved for 24 h, while they increased dramatically and rapidly under the condition of starvation for 24 h then feeding for 24 h. These results suggest that BdCHS2 may play an important role in regulating chitin content of the midgut, and subsequently affect the growth and development of B. dorsalis.

Chen, Li; Yang, Wen-Jia; Cong, Lin; Xu, Kang-Kang; Wang, Jin-Jun

2013-01-01

37

Molecular Cloning, Characterization and mRNA Expression of a Chitin Synthase 2 Gene from the Oriental Fruit Fly, Bactrocera dorsalis (Diptera: Tephritidae).  

PubMed

Chitin synthase (CHS), a potential target for eco-friendly insecticides, plays an essential role in chitin formation in insects. In this study, a full-length cDNA encoding chitin synthase 2 (BdCHS2) was cloned and characterized in the oriental fruit fly, Bactrocera dorsalis. The BdCHS2 cDNA had 4417 nucleotides, containing an open reading frame of 4122 nucleotides, which encoded 1373 amino acid residues with a predicted molecular weight of 158.5 kDa. Phylogenetic analysis with other insect CHSs suggested that BdCHS2 belongs to insect CHS2. The BdCHS2 transcript was predominately found in midgut but was detected at low levels in fat body, Malpighian tubules, integument, and trachea. Moreover, BdCHS2 was expressed in all developmental stages, and highly expressed in the feeding stages. There was a positive relationship between BdCHS2 expression and total chitin content during development. Furthermore, both the gene expression and chitin content in midgut decreased when the insect was fed for 24 h, then starved for 24 h, while they increased dramatically and rapidly under the condition of starvation for 24 h then feeding for 24 h. These results suggest that BdCHS2 may play an important role in regulating chitin content of the midgut, and subsequently affect the growth and development of B. dorsalis. PMID:23965972

Chen, Li; Yang, Wen-Jia; Cong, Lin; Xu, Kang-Kang; Wang, Jin-Jun

2013-08-19

38

Characterization of two chitin synthase genes of the red flour beetle, Tribolium castaneum, and alternate exon usage in one of the genes during development  

Microsoft Academic Search

Two chitin synthase (CHS) genes of the red flour beetle, Tribolium castaneum, were sequenced and their transcription patterns during development examined. By screening a BAC library of genomic DNA from T. castaneum (Tc) with a DNA probe encoding the catalytic domain of a putative Tribolium CHS, several clones that contained CHS genes were identified. Two distinct PCR products were amplified

Yasuyuki Arakane; David G. Hogenkamp; Yu Cheng Zhu; Karl J. Kramer; Charles A. Specht; Richard W. Beeman; Michael R. Kanost; Subbaratnam Muthukrishnan

2004-01-01

39

CHITIN SYNTHASE GENES IN MANDUCA SEXTA: CHARACTERIZATION OF A GUT-SPECIFIC TRANSCRIPT AND DIFFERENTIAL TISSUE EXPRESSION OF ALTERNATELY SPLICED MRNAS DURING DEVELOPMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

We identified a new chitin synthase gene, MsCHS2, in the tobacco hornworm, Manduca sexta. Functional analysis of this and the previously described MsCHS1 gene in this lepidopteran species revealed unique and complementary roles for each gene, confirming earlier results from study of the beetle,Trib...

40

Inhibitors of Fatty Acid Synthase for Prostate Cancer.  

National Technical Information Service (NTIS)

The purpose of this proposal was to develop and optimize chemical scaffolds as potential inhibitors of fatty acid synthase (FASN), specifically the thioesterase (TE) domain. This line of investigation was based on a series of observation by many groups, i...

S. J. Kridel

2012-01-01

41

Farnesyl Diphosphate Synthase Inhibitors from In Silico Screening  

PubMed Central

The relaxed complex scheme is an in silico drug screening method that accounts for receptor flexibility using molecular dynamics simulations. Here, we used this approach combined with similarity searches and experimental inhibition assays to identify several low micromolar, non-bisphosphonate inhibitors, bisamidines, of farnesyl diphosphate synthase (FPPS), an enzyme targeted by some anticancer and antimicrobial agents and for the treatment of bone resorption diseases. This novel class of farnesyl diphosphate synthase inhibitors have more drug-like properties than existing bisphosphonate inhibitors, making them interesting pharmaceutical leads.

Lindert, Steffen; Zhu, Wei; Liu, Yi-Liang; Pang, Ran; Oldfield, Eric; McCammon, J Andrew

2013-01-01

42

[Thromboxane A2 synthase inhibitor and receptor antagonist].  

PubMed

Thromboxane A2 (TxA2) plays an important role in asthma. TxA2 are newly generated after cellular activation and are produced by not only platelets but also eosinophils, basophils, alveolar macrophages, and neutrophils. Pharmacological actions of TxA2 include potent bronchoconstriction, increased microvascular leakage, impairment of mucociliary clearance, and induction of airway hyperresponsiveness. Recent study demonstrated that TxA2 receptor antagonist decreased the number of eosinophils in bronchial biopsy specimens, suggesting that this type of agent possesses anti-inflammatory actions in asthma. Furthermore, addition of TxA2 synthase inhibitor significantly increased the PEF values in the persistent asthmatic patients despite the treatment with moderate-dose of inhaled corticosteroids. Therefore, these results suggest that TxA2 synthase inhibitor and receptor antagonist are useful for the treatment with symptomatic patients who had already been treated with inhaled corticosteroids. PMID:11676143

Minoguchi, K; Adachi, M

2001-10-01

43

Chitin in Diatoms and Its Association with the Cell Wall ? †  

PubMed Central

Chitin is a globally abundant polymer widely distributed throughout eukaryotes that has been well characterized in only a few lineages. Diatoms are members of the eukaryotic lineage of stramenopiles. Of the hundreds of diatom genera, two produce long fibers of chitin that extrude through their cell walls of silica. We identify and describe here genes encoding putative chitin synthases in a variety of additional diatom genera, indicating that the ability to produce chitin is more widespread and likely plays a more central role in diatom biology than previously considered. Diatom chitin synthases fall into four phylogenetic clades. Protein domain predictions and differential gene expression patterns provide evidence that chitin synthases have multiple functions within a diatom cell. Thalassiosira pseudonana possesses six genes encoding three types of chitin synthases. Transcript abundance of the gene encoding one of these chitin synthase types increases when cells resume division after short-term silicic acid starvation and during short-term limitation by silicic acid or iron, two nutrient conditions connected in the environment and known to affect the cell wall. During long-term silicic acid starvation transcript abundance of this gene and one additional chitin synthase gene increased at the same time a chitin-binding lectin localized to the girdle band region of the cell wall. Together, these results suggest that the ability to produce chitin is more widespread in diatoms than previously thought and that a subset of the chitin produced by diatoms is associated with the cell wall.

Durkin, Colleen A.; Mock, Thomas; Armbrust, E. Virginia

2009-01-01

44

SAR studies of pyridazinone derivatives as novel glucan synthase inhibitors.  

PubMed

A novel series of pyridazinone analogs has been developed as potent ?-1,3-glucan synthase inhibitors through structure-activity relationship study of the lead 5-[4-(benzylsulfonyl)piperazin-1-yl]-4-morpholino-2-phenyl-pyridazin-3(2H)-one (1). The effect of changes to the core structure is described in detail. Optimization of the sulfonamide moiety led to the identification of important compounds with much improved systematic exposure while retaining good antifungal activity against the fungal strains Candida glabrata and Candida albicans. PMID:21489787

Zhou, Gang; Ting, Pauline C; Aslanian, Robert; Cao, Jianhua; Kim, David W; Kuang, Rongze; Lee, Joe F; Schwerdt, John; Wu, Heping; Herr, R Jason; Zych, Andrew J; Yang, Jinhai; Lam, Sang; Wainhaus, Samuel; Black, Todd A; McNicholas, Paul M; Xu, Yiming; Walker, Scott S

2011-03-30

45

Structure-Based Discovery of Inhibitors of Thymidylate Synthase  

NASA Astrophysics Data System (ADS)

A molecular docking computer program (DOCK) was used to screen the Fine Chemical Directory, a database of commercially available compounds, for molecules that are complementary to thymidylate synthase (TS), a chemotherapeutic target. Besides retrieving the substrate and several known inhibitors, DOCK proposed putative inhibitors previously unknown to bind to the enzyme. Three of these compounds inhibited Lactobacillus caser TS at submillimolar concentrations. One of these inhibitors, sulisobenzone, crystallized with TS in two configurations that differed from the DOCK-favored geometry: a counterion was bound in the substrate site, which resulted in a 6 to 9 angstrom displacement of the inhibitor. The structure of the complexes suggested another binding region in the active site that could be exploited. This region was probed with molecules sterically similar to sulisobenzone, which led to the identification of a family of phenolphthalein analogs that inhibit TS in the 1 to 30 micromolar range. These inhibitors do not resemble the substrates of the enzyme. A crystal structure of phenolphthalein with TS shows that it binds in the target site in a configuration that resembles the one suggested by DOCK.

Shoichet, Brian K.; Stroud, Robert M.; Santi, Daniel V.; Kuntz, Irwin D.; Perry, Kathy M.

1993-03-01

46

Structural Studies of Pterin-Based Inhibitors of Dihydropteroate Synthase  

SciTech Connect

Dihydropteroate synthase (DHPS) is a key enzyme in bacterial folate synthesis and the target of the sulfonamide class of antibacterials. Resistance and toxicities associated with sulfonamides have led to a decrease in their clinical use. Compounds that bind to the pterin binding site of DHPS, as opposed to the p-amino benzoic acid (pABA) binding site targeted by the sulfonamide agents, are anticipated to bypass sulfonamide resistance. To identify such inhibitors and map the pterin binding pocket, we have performed virtual screening, synthetic, and structural studies using Bacillus anthracis DHPS. Several compounds with inhibitory activity have been identified, and crystal structures have been determined that show how the compounds engage the pterin site. The structural studies identify the key binding elements and have been used to generate a structure-activity based pharmacophore map that will facilitate the development of the next generation of DHPS inhibitors which specifically target the pterin site.

Hevener, Kirk E.; Yun, Mi-Kyung; Qi, Jianjun; Kerr, Iain D.; Babaoglu, Kerim; Hurdle, Julian G.; Balakrishna, Kanya; White, Stephan W.; Lee, Richard E. (Tennessee-HSC); (SJCH)

2010-01-12

47

Chitin synthase 1 gene and its two alternative splicing variants from two sap-sucking insects, Nilaparvata lugens and Laodelphax striatellus (Hemiptera: Delphacidae).  

PubMed

Chitin synthase (CHS) is an enzyme that is required for chitin formation in insect cuticles and other tissues. In this study, CHS genes from two destructive rice insect pests, the brown planthopper Nilaparvata lugens and the small brown planthopper Laodelphax striatellus, were cloned. Phylogenetic analysis showed that these genes belonged to class CHS1 of the CHS gene family. Most insects possess two CHS genes (CHS1 and CHS2); however, genome and transcriptome searches showed that N. lugens possibly possess only CHS1 in both databases. Two transcript variants (CHS1a and CHS1b) resulting from exclusively alternative splicing (exon 19a or 19b in N. lugens) were identified for each of the two rice planthopper CHS1s. Gene structure comparison using the genomes that are currently sequenced showed that the CHS1 genes in all insects except Acyrthosiphon pisum have two transcript variants. Transcription of NlCHS1a reached its highest level just after molting, whereas NlCHS1b reached its highest expression level 1-2 days before molting. Injection of the N. lugens nymphs with double-strand RNA (dsRNA) of CHS1, CHS1a and CHS1b reduced the corresponding variant transcript levels and exhibited subsequent phenotypes. Silencing of CHS1 and CHS1a resulted in elongated distal wing pads and the "wasp-waisted" or crimpled cuticle phenotypes and eventually died, whereas the phenotypes caused by injection of NlCHS1b dsRNA seem not so obvious although slightly increased mortality was observed. Our results suggest that N. lugens likely lacks CHS2 and CHS1 may be efficient target gene for RNAi-based N. lugens control. PMID:22634163

Wang, Ying; Fan, Hai-Wei; Huang, Hai-Jian; Xue, Jian; Wu, Wen-Juan; Bao, Yan-Yuan; Xu, Hai-Jun; Zhu, Zeng-Rong; Cheng, Jia-An; Zhang, Chuan-Xi

2012-05-24

48

Synthesis of Novel ?-Lactone Inhibitors of Fatty Acid Synthase  

PubMed Central

Fatty acid synthase (FAS) is necessary for growth and survival of tumor cells and is a promising drug target for oncology. Here, we report on the syntheses and activity of novel inhibitors of the thioesterase domain of FAS. Using the structure of orlistat as a starting point, which contains a ?-lactone as the central pharmacophore, 28 novel congeners were synthesized and examined. Structural features such as the length of the ?- and ?-alkyl chains, their chemical composition, and amino ester substitutions were altered and the resulting compounds explored for inhibitory activity toward the thioesterase domain of FAS. Nineteen congeners show improved potency for FAS in biochemical assays relative to orlistat. Three of that subset, including the natural product valilactone, also display an increased potency in inducing tumor cell death and improved solubility compared to orlistat. These findings support the idea that an orlistat congener can be optimized for use in a preclinical drug design and for clinical drug development.

Richardson, Robyn D.; Ma, Gil; Oyola, Yatsandra; Zancanella, Manuel; Knowles, Lynn M.; Cieplak, Piotr; Romo, Daniel; Smith, Jeffrey W.

2011-01-01

49

Spitzenk?rper Localization and Intracellular Traffic of Green Fluorescent Protein-Labeled CHS-3 and CHS-6 Chitin Synthases in Living Hyphae of Neurospora crassa? †  

PubMed Central

The subcellular location and traffic of two selected chitin synthases (CHS) from Neurospora crassa, CHS-3 and CHS-6, labeled with green fluorescent protein (GFP), were studied by high-resolution confocal laser scanning microscopy. While we found some differences in the overall distribution patterns and appearances of CHS-3-GFP and CHS-6-GFP, most features were similar and were observed consistently. At the hyphal apex, fluorescence congregated into a conspicuous single body corresponding to the location of the Spitzenkörper (Spk). In distal regions (beyond 40 ?m from the apex), CHS-GFP revealed a network of large endomembranous compartments that was predominantly comprised of irregular tubular shapes, while some compartments were distinctly spherical. In the distal subapex (20 to 40 ?m from the apex), fluorescence was observed in globular bodies that appeared to disintegrate into vesicles as they advanced forward until reaching the proximal subapex (5 to 20 ?m from the apex). CHS-GFP was also conspicuously found delineating developing septa. Analysis of fluorescence recovery after photobleaching suggested that the fluorescence of the Spk originated from the advancing population of microvesicles (chitosomes) in the subapex. The inability of brefeldin A to interfere with the traffic of CHS-containing microvesicles and the lack of colocalization of CHS-GFP with the endoplasmic reticulum (ER)-Golgi body fluorescent dyes lend support to the idea that CHS proteins are delivered to the cell surface via an alternative route distinct from the classical ER-Golgi body secretory pathway.

Riquelme, Meritxell; Bartnicki-Garcia, Salomon; Gonzalez-Prieto, Juan Manuel; Sanchez-Leon, Eddy; Verdin-Ramos, Jorge A.; Beltran-Aguilar, Alejandro; Freitag, Michael

2007-01-01

50

Sorting Signals That Mediate Traffic of Chitin Synthase III between the TGN/Endosomes and to the Plasma Membrane in Yeast  

PubMed Central

Traffic of the integral yeast membrane protein chitin synthase III (Chs3p) from the trans-Golgi network (TGN) to the cell surface and to and from the early endosomes (EE) requires active protein sorting decoded by a number of protein coats. Here we define overlapping signals on Chs3p responsible for sorting in both exocytic and intracellular pathways by the coats exomer and AP-1, respectively. Residues 19DEESLL24, near the N-terminal cytoplasmically-exposed domain, comprise both an exocytic di-acidic signal and an intracellular di-leucine signal. Additionally we show that the AP-3 complex is required for the intracellular retention of Chs3p. Finally, residues R374 and W391, comprise another signal responsible for an exomer-independent alternative pathway that conveys Chs3p to the cell surface. These results establish a role for active protein sorting at the trans-Golgi en route to the plasma membrane (PM) and suggest a possible mechanism to regulate protein trafficking.

Wang, Chao-Wen; Schekman, Randy

2012-01-01

51

REGULATION OF CHITIN SYNTHESIS IN THE LARVAL MIDGUT OF MANDUCA SEXTA  

Technology Transfer Automated Retrieval System (TEKTRAN)

In insects, chitin is not only synthesized by ectodermal cells that form chitinous cuticles, but also by endodermal cells of the midgut that secrete a chitinous peritrophic matrix. Using anti-chitin synthase (CHS) antibodies, we previously demonstrated that in the midgut of Manduca sexta, CHS is exp...

52

Regulation of chitin synthesis in the larval midgut of Manduca sexta  

Microsoft Academic Search

In insects, chitin is not only synthesized by ectodermal cells that form chitinous cuticles, but also by endodermal cells of the midgut that secrete a chitinous peritrophic matrix. Using anti-chitin synthase (CHS) antibodies, we previously demonstrated that in the midgut of Manduca sexta, CHS is expressed by two cell types, tracheal cells forming a basal tracheal network and columnar cells

L. Zimoch; D. G. Hogenkamp; K. J. Kramer; S. Muthukrishnan; H. Merzendorfer

2005-01-01

53

Nitric oxide synthase inhibitors in cardiogenic shock: present and future.  

PubMed

Cardiogenic shock (CS) accompanying myocardial infarction carries a case fatality rate of 40-50%. Profound myocardial dysfunction is partially reversible, and possibly related to a state of inflammatory storm accompanied by nitric oxide (NO) overproduction. CS survivors enjoy satisfactory longevity and quality of life. The focus of this review is to describe the available data regarding NO synthase (NOS) inhibitors in CS. In view of supportive evidence from mammalian research (inducible-NOS-knockout mice are less susceptible to ischemic and reperfusion injury), therapies mitigating NO overproduction were tested in human CS subjects. Human randomized clinical trials project excellent safety but lack of efficacy. Although the Phase III, multicenter, prospective, randomized, double-blind, placebo-controlled Study to Assess the Safety and Efficacy of Tilarginine Acetate (L-N(G)-monomethyl arginine citrate [L-NMMA]) in CS (TRIUMPH) trial demonstrated lack of clinical benefit of 5-h infusion of L-NMMA in CS, major design issues regarding the optimal timing, dosing, duration and NOS inhibitor need to be addressed prior to rendering this therapy ineffective. PMID:19804295

Kaluski, Edo; Uriel, Nir; Milo-Cotter, Olga; Klapholz, Marc

2008-03-01

54

Screening assay for the identification of deoxyhypusine synthase inhibitors.  

PubMed

The 1st step in the posttranslational hypusine [N(epsilon)-(4-amino-2-hydroxybutyl)lysine] modification of eukaryotic translation initiation factor 5A (eIF5A) is catalyzed by deoxyhypusine synthase (DHS). The eIF5A intermediate is subsequently hydroxylated by deoxyhypusine hydroxylase (DHH), thereby converting the eIF5A precursor into a biologically active protein. Depletion of eIF5A causes inhibition of cell growth, and the identification of eIF5A as a cofactor of the HIV Rev protein turns this host protein and therefore DHS into an interesting target for drugs against abnormal cell growth and/or HIV replication. The authors developed a 96-well format DHS assay applicable for the screening of DHS inhibitors. Using this assay, they demonstrate DHS inhibition by AXD455 (Semapimod, CNI-1493). This assay represents a powerful tool for the identification of new DHS inhibitors with potency against cancer and HIV. PMID:15296643

Sommer, Marc-Nicola; Bevec, Dorian; Klebl, Bert; Flicke, Birgit; Hölscher, Kerstin; Freudenreich, Tatjana; Hauber, Ilona; Hauber, Joachim; Mett, Helmut

2004-08-01

55

Chitin synthesis during in planta growth and asexual propagation of the cellulosic oomycete and obligate biotrophic grapevine pathogen Plasmopara viticola  

Microsoft Academic Search

PCR amplification of two CHS gene fragments of the obligate biotroph Plasmopara viticola, the causal agent of downy mildew of grapevine, is described. While one fragment shows homology to fungal class IV chitin synthases, the other fragment groups with other oomycete chitin synthases to form a novel class of chitin synthases most closely related to class I–III. RT-PCR experiments indicate

Stefan Werner; Ulrike Steiner; Rayko Becher; Andreas Kortekamp; Eva Zyprian; Holger B Deising

2002-01-01

56

Effects of the chitin synthesis inhibitor buprofezin on survival and development of immatures of Chrysoperla rufilabris (Neuroptera: Chrysopidae).  

PubMed

Effects of buprofezin (Applaud), a chitin synthesis inhibitor, on survival and development of eggs, three instars, and pupae of Chrysoperla rufilabris (Burmeister) were determined in the laboratory. Buprofezin at three tested concentrations (100, 500, and 1,000 mg [AI]/liter) did not affect the viability and development of eggs when the eggs were treated, or third instars and pupae when those stages were treated. Although the degree of effects by buprofezin on larvae varied with instar, buprofezin at the higher concentrations (500 and 1,000 mg [AI]/liter) reduced survival rates 17-47% and prolonged the overall development from first instars to adult emergence by 2 or 3 d when first instars were treated, indicating that the first instar is the most vulnerable stage. When second instars were treated, the survival of C. rufilabris from second instars to pupae was not significantly affected. However, the developmental time from second instar to adult emergence was longer in the treatments with the highest concentration (1,000 mg [AI]/liter) than that with the lowest concentration (100 mg [AI]/liter). The compatibility of buprofezin with natural enemies in integrated pest management programs is discussed. PMID:10826167

Liu, T X; Chen, T Y

2000-04-01

57

The efficacy of a chitin synthesis inhibitor against field populations of organophosphate-resistant Aedes aegypti in Brazil.  

PubMed

The mosquito Aedes aegypti is the main focus of dengue control campaigns. Because of widespread resistance against conventional chemical insecticides, chitin synthesis inhibitors (CSIs) are considered control alternatives. We evaluated the resistance status of four Brazilian Ae. aegypti populations to both the organophosphate temephos and the pyrethroid deltamethrin, which are used in Brazil to control larvae and adults, respectively. All vector populations exhibited high levels of temephos resistance and varying rates of alterations in their susceptibility to pyrethroids. The effect of the CSI novaluron on these populations was also investigated. Novaluron was effective against all populations under laboratory conditions. Field-simulated assays with partial water replacement were conducted to evaluate novaluron persistence. Bioassays were continued until an adult emergence inhibition of at least 70% was attained. We found a residual effect of eight weeks under indoor conditions and novaluron persisted for five-six weeks in assays conducted in an external area. Our data show that novaluron is effective against the Ae. aegypti populations tested, regardless of their resistance to conventional chemical insecticides. PMID:22510835

Fontoura, Nathalia Giglio; Bellinato, Diogo Fernandes; Valle, Denise; Lima, José Bento Pereira

2012-05-01

58

Isolation and structural determination of squalene synthase inhibitor from Prunus mume fruit.  

PubMed

Squalene synthase plays an important role in the cholesterol biosynthetic pathway. Inhibiting this enzyme in hypercholesterolemia can lower not only plasma cholesterol but also plasma triglyceride levels. A squalene synthase inhibitor was screened from Prunus mume fruit, and then purified via sequential processes of ethanol extraction, HP-20 column chromatography, ethyl acetate extraction, silica gel column chromatography, and crystallization. The squalene synthase inhibitor was identified as chlorogenic acid with a molecular mass of 354 Da and a molecular formula of C16H18O9 based on UV spectrophotometry, 1H and 13C NMRs, and mass spectrometry. Chlorogenic acid inhibited the squalene synthase of pig liver with an IC50 level of 100 nM. Since chlorogenic acid was an effective inhibitor against the squalene synthase of an animal source, it may be a potential therapeutic agent for hypercholesterolemia. PMID:18167444

Choi, Sung-Won; Hur, Nam-Yoon; Ahn, Soon-Cheol; Kim, Dong-Seob; Lee, Jae-Kwon; Kim, Dae-Ok; Park, Seung-Kook; Kim, Byung-Yong; Baik, Moo-Yeol

2007-12-01

59

Induction of protein inhibitor of neuronal nitric oxide synthase\\/cytoplasmic dynein light chain following cerebral ischemia  

Microsoft Academic Search

Administration of inhibitors of neuronal nitric oxide synthase or deletion of the encoding gene in rodents provided evidence that neuronal nitric oxide synthase activity may contribute to neuronal cell death following global and focal cerebral ischemia. In the present study, we investigated by in situ hybridization the expression of an endogenous inhibitor of neuronal nitric oxide synthase activity, designated protein

F Gillardon; H Krep; G Brinker; C Lenz; B Böttiger; K.-A Hossmann

1998-01-01

60

Total synthesis of the squalene synthase inhibitor zaragozic acid C.  

PubMed

Zaragozic acids and squalestatins were documented by Merck, Glaxo, and Tokyo Noko University/Mitsubishi Kasei Corporation as part of a program aimed at identifying novel inhibitors of squalene synthase, as well as farnesyl transferase. These natural products have attracted considerable attention from numerous synthetic chemists because of their therapeutic potential and novel architecture. This review highlights our total syntheses of zaragozic acid C by two convergent strategies. The key steps in our first-generation synthesis involve 1) simultaneous creation of the C4 and C5 quaternary stereocenters through the Sn(OTf)2-promoted aldol coupling reaction between the alpha-keto ester and silyl ketene thioacetal derived from L- and D-tartaric acids, respectively; and 2) construction of the bicyclic core structure via acid-catalyzed internal ketalization under kinetically controlled conditions. The second-generation strategy relies on a tandem carbonyl ylide formation/1,3-dipolar cycloaddition approach and features elongation of the C1 alkyl side chain through an olefin cross-metathesis as well as high convergency and flexibility. PMID:15635219

Nakamura, Seiichi

2005-01-01

61

Effect of triflumuron, a chitin synthesis inhibitor, on Aedes aegypti, Aedes albopictus and Culex quinquefasciatus under laboratory conditions  

PubMed Central

Background Resistance to traditional insecticides represents a threat to the control of disease vectors. The insect growth regulators (IGR) are a potential alternative to control mosquitoes, including resistant populations. The chitin synthesis inhibitors (CSI) are IGRs, which interfere with the insect molting process and represent one major class of compounds against Aedes aegypti populations resistant to the larvicide organophosphate temephos. In the present study, we evaluated the efficacy of the CSI triflumuron on Culex quinquefasciatus, Aedes albopictus and against several Ae. aegypti field populations. Methods The efficacy of triflumuron, against Cx. quinquefasciatus and Ae. albopictus was evaluated with laboratory strains through dose–response assays. Additionaly, this CSI was tested against seven Ae. aegypti field populations exhibiting distinct resistance levels to both temephos and the pyrethroid deltamethrin. Aedes aegypti populations were exposed to both a dose that inhibits 99% of the adult emergence of mosquitoes from the susceptible reference strain, Rockefeller, (EI99?=?3.95??g/L) and the diagnostic dose (DD), corresponding to twice the EI99. Results Our results indicate that triflumuron was effective in emergence inhibition (EI) of Cx. quinquefasciatus (EI50= 5.28??g/L; EI90= 12.47??g/L) and Ae. albopictus (EI50= 1.59??g/L; EI90= 2.63??g/L). Triflumuron was also effective against seven Ae. aegypti Brazilian populations resistant to both temephos and deltamethrin. Exposure of all the Ae. aegypti populations to the triflumuron EI99 of the susceptible reference strain, Rockefeller, resulted in complete inhibition of adult emergence, suggesting no cross-resistance among traditional insecticides and this CSI. However, a positive correlation between temephos resistance and tolerance to triflumuron was observed. Conclusion The results suggest that triflumuron represents a potential tool for the control of disease vectors in public health. Nevertheless, they point to the need of constant monitoring of the susceptibility status of vector populations to CSIs.

2013-01-01

62

Characteristics of the squalene synthase inhibitors produced by a Streptomyces species isolated from soils.  

PubMed

Microorganisms producing squalene synthase inhibitors were screened from soils. A high producer was selected and identified as a Streptomyces species. Two active inhibitors were obtained from culture broths via a series of purification processes involving solvent extraction, WK-10 cation-exchange column chromatography, HP-20 adsorption column chromatography, silica-gel column chromatography, preparative HPLC, and crystallization. The inhibitors were confirmed as macrolactins A and F with molecular weights of 402 by UV-absorption spectrometry, fast atom bombardment mass spectometry, and 13C- and 1H-NMR analyses. Kinetic results for macrolactins A and F showed that they appear to be noncompetitive inhibitors of rat liver squalene synthase with IC50 values of 1.66 and 1.53 micromol/L, respectively. Since mammalian squalene synthase was used, these inhibitors have significant potential as therapeutic agents for hyperlipemia and suppression of cholesterol biosynthesis. PMID:14735215

Choi, Sung-Won; Bai, Dong-Hoon; Yu, Ju-Hyun; Shin, Chul Soo

2003-11-01

63

Calmodulin Inhibitor-induced Apoptosis was Prevented by Glycogen Synthase Kinase3 Inhibitors in PC12 Cells  

Microsoft Academic Search

Calmodulin is known to transduce Ca2+ signals by interacting with specific target proteins. In order to determine the role of calmodulin in regulating neuronal\\u000a survival and death, we examined, whether calmodulin inhibitors induce caspase-dependent apoptotic cell death, and whether\\u000a glycogen synthase kinase-3 is involved in calmodulin inhibitor-induced cell death in PC12 cells. W13, a calmodulin specific\\u000a inhibitor increased apoptotic cell

Tsuneo Takadera; Takao Ohyashiki

2007-01-01

64

Heteroaromatic Selective Inhibitors of Neuronal Nitric Oxide Synthase.  

National Technical Information Service (NTIS)

Compounds inhibiting neuronal nitric oxide synthase (nNOS) for potential treatment in neurodegenerative diseases, such as stroke, Alzheimer's disease, Parkinson's disease, Huntington's disease, such compounds of a formula.

H. Ji R. B. Silverman

2004-01-01

65

Inhibitors of Fatty Acid Synthase for Prostate Cancer.  

National Technical Information Service (NTIS)

Fatty acid synthase (FASN), the enzyme that synthesizes fatty acid in cells, is over-expressed in prostate cancer and a potential therapeutic target. We have identified several novel chemical scaffolds with potential to inhibit FASN. An extensive series o...

S. J. Kridel

2010-01-01

66

Identification, mRNA expression, and functional analysis of chitin synthase 1 gene and its two alternative splicing variants in oriental fruit fly, Bactrocera dorsalis.  

PubMed

Two alternative splicing variants of chitin synthase 1 gene (BdCHS1) were cloned and characterized from the oriental fruit fly, Bactrocera dorsalis (Hendel). The cDNA of both variants (BdCHS1a and BdCHS1b) consisted of 5,552 nucleotides (nt), with an open reading frame (ORF) of 4,776 nt, encoding a protein of 1,592 amino acid residues, plus 685- and 88-nt of 5'- and 3'-noncoding regions, respectively. The alternative splicing site was located between positions 3,784-3,960 and formed a pair of mutually exclusive exons (a/b) that were same in size (177 nt), but showed only 65% identity at the nucleotide level. During B. dorsalis growth and development, BdCHS1 and BdCHS1a were both mainly expressed during the larval-pupal and pupal-adult transitions, while BdCHS1b was mainly expressed during pupal-adult metamorphosis and in the middle of the pupal stage. BdCHS1a was predominately expressed in the integument whereas BdCHS1b was mainly expressed in the trachea. The 20-hydroxyecdysone (20E) induced the expression of BdCHS1 and its variants. Injection of dsRNA of BdCHS1, BdCHS1a, and BdCHS1b into third-instar larvae significantly reduced the expression levels of the corresponding variants, generated phenotypic defects, and killed most of the treated larvae. Furthermore, silencing of BdCHS1 and BdCHS1a had a similar result in that the larva was trapped in old cuticle and died without tanning completely, while silencing of BdCHS1b has no effect on insect morphology. These results demonstrated that BdCHS1 plays an important role in the larval-pupal transition and the expression of BdCHS1 in B. dorsalis is regulated by 20E. PMID:23569438

Yang, Wen-Jia; Xu, Kang-Kang; Cong, Lin; Wang, Jin-Jun

2013-04-05

67

Biochemical and Cellular Pharmacology of 1843U89, a Novel Benzoquinazoline Inhibitor of Thymidylate Synthase  

Microsoft Academic Search

Studies on a series of benzoquinazoline folate analogues as inhibitors of human thymidylate synthase led to the selection of 1843U89 for further evaluation. This compound had a A, of 90 p\\\\i versus human thymidylate synthase and was noncompetitive with (6A,S)-5,10-methylenetetrahydro- folate. It was a good substrate for the addition of the second glutamate by hog liver folylpolyglutamate synthetase, having a

David S. Duch; Sheila Banks; Scott H. Dickerson; Robert Perone; Louise S. Heath; Joan Humphreys; Vincent Knick; William Pendergast; Gary K. Smith; Kathleen Waters; H. Robert Wilson

68

Chitin Research Revisited  

PubMed Central

Two centuries after the discovery of chitin, it is widely accepted that this biopolymer is an important biomaterial in many aspects. Numerous studies on chitin have focused on its biomedical applications. In this review, various aspects of chitin research including sources, structure, biosynthesis, chitinolytic enzyme, chitin binding protein, genetic engineering approach to produce chitin, chitin and evolution, and a wide range of applications in bio- and nanotechnology will be dealt with.

Khoushab, Feisal; Yamabhai, Montarop

2010-01-01

69

Antifungal thiopeptide cyclothiazomycin B1 exhibits growth inhibition accompanying morphological changes via binding to fungal cell wall chitin.  

PubMed

Cyclothiazomycin B1 (CTB1) is an antifungal cyclic thiopeptide isolated from the culture broth of Streptomyces sp. HA 125-40. CTB1 inhibited the growth of several filamentous fungi including plant pathogens along with swelling of hyphae and spores. The antifungal activity of CTB1 was weakened by hyperosmotic conditions, and hyphae treated with CTB1 burst under hypoosmotic conditions, indicating increased cell wall fragility. CTB1-sensitive fungal species contain high levels of cell wall chitin and/or chitosan. Unlike nikkomycin Z, a competitive inhibitor of chitin synthase (CHS), CTB1 did not inhibit CHS activity. Although CTB1 inhibited CHS biosynthesis, the same result was also obtained with a non-specific proteins inhibitor, cycloheximide, which did not reduce cell wall rigidity. These results indicate that the primary target of CTB1 is not CHS, and we concluded that CTB1 antifungal activity was independent of this sole inhibition. We found that CTB1 bound to chitin but did not bind to ?-glucan and chitosan. The results of the present study suggest that CTB1 induces cell wall fragility by binding to chitin, which forms the fungal cell wall. The antifungal activity of CTB1 could be explained by this chitin-binding ability. PMID:21885289

Mizuhara, Naoko; Kuroda, Manabu; Ogita, Akira; Tanaka, Toshio; Usuki, Yoshinosuke; Fujita, Ken-Ichi

2011-08-11

70

Fatty acid synthase inhibitors from plants and their potential application in the prevention of metabolic syndrome  

Microsoft Academic Search

Fatty acid synthase (FAS) a racts more and more attention recently as a potential target for metabolic syndrome, such as cancer,\\u000a obesity, diabetes and cerebrovascular disease. FAS inhibitors are widely existed in plants, consisting of diversiform compounds.\\u000a These inhibitors exist not only in herbs also in many plant foods, such as teas, allium vegetables and some fruits. These\\u000a effective components

Wei-xi Tian; Xiao-feng Ma; Shu-yan Zhang; Ying-hui Sun; Bing-hui Li

2011-01-01

71

Fatty acid synthase inhibitors from Geum japonicum Thunb. var. chinense.  

PubMed

Bioassay-guided fractionation of the MeOH extract of Geum japonicum Thunb. var. chinense using the fatty acid synthase inhibition assay led to the isolation of a new dimeric ellagitannin, gemin G (1), together with six known compounds, gemin A (2), casuarinin (3), pedunculagin (4), potentillin (5) , tellimagrandin II (6), and ellagic acid (7). Their structures were determined on the basis of spectroscopic analyses. Compounds 1-7 displayed strong inhibitory activities on fatty acid synthase with IC(50) values in the range of 0.21-41.4 microM. Compounds 1-4 exhibited significant antioxidant activities higher than vitamin C in the ORAC assay. Compounds 1 and 2 also showed weak cytotoxic effects on BGC-823 cell. PMID:19319862

Liu, Hongwei; Li, Jiankuan; Zhao, Wenhua; Bao, Li; Song, Xiaohong; Xia, Ying; Wang, Xue; Zhang, Chao; Wang, Xiaozhu; Yao, Xinsheng; Li, Ming

2009-03-01

72

MULTI-ANALYTE CHEMISTRY METHODS FOR PESTICIDES WHICH ARE ACETOLACTATE SYNTHASE (ALS) INHIBITORS IN SOIL  

EPA Science Inventory

A joint EPA/state/industry working group has developed several multi-analyte methods to analyze soils for low ppb (parts per billion) levels of herbicides (such as sulfonylureas, imidazolinones, and sulfonamides) that are acetolactate synthase (ALS) inhibitors and may cause phyto...

73

Attenuation of the Opioid Withdrawal Syndrome by Inhibitors of Nitric Oxide Synthase.  

National Technical Information Service (NTIS)

A method of attenuating the symptoms of opioid withdrawal in a human or animal subject comprises administering to the subject an effective opioid withdrawal symptom attenuating amount of an inhibitor of nitric oxide synthase (NOS) for a period of time eff...

E. D. London A. S. Kimes

1991-01-01

74

Protective effect of inducible nitric oxide synthase inhibitor on pancreas transplantation in rats  

Microsoft Academic Search

AIM: To investigate the effect of inducible nitric oxide synthase inhibitor, aminoguanidine, on pancreas transplantation in rats. METHODS: A model of pancreas transplantation was established in rats. Streptozotocin-induced diabetic male Wistar rats were randomly assigned to sham-operation control group (n = 6), transplant control group (n = 6), and aminoguanidine (AG) treatment group (n = 18). In the AG group,

Bai-Feng Li; Yong-Feng Liu; Ying Cheng; Ke-Zhong Zhang; Tie-Min Li; Ning Zhao

2007-01-01

75

Mechanism of Inhibition of Yeast Squalene Synthase by Substrate Analog Inhibitors  

Microsoft Academic Search

Squalene synthase catalyzes the reductive condensation of two identical substrate molecules, farnesyl diphosphate, to the hydrocarbon squalene via an obligatory intermediate, presqualene pyrophosphate. Since the kinetic mechanism of the transformation is sequential, two substrate binding pockets that recognize the same molecule must exist in the enzyme active site. This raises the possibility of a choice of binding pockets for inhibitors

Stephen S. Kalinowski; Kasim A. Mookhtiar

1999-01-01

76

Mechanism of action of anticandidal dipeptides containing inhibitors of glucosamine-6-phosphate synthase.  

PubMed Central

The mechanism of anticandidal action of novel synthetic dipeptides containing N3-(4-methoxyfumaroyl)-L-2,3-diaminopropanoic acid (FMDP) residues was shown to be consistent with the "warhead delivery" concept. FMDP dipeptides were shown to be transported into Candida albicans cells by the di-tripeptide permease and subsequently hydrolyzed by intracellular peptidases, especially aminopeptidase. The anticandidal activity of the particular FMDP dipeptide was influenced by the rate of its transport and, to a lower extent, by the intracellular cleavage rate. A high transport rate accompanied by a high cleavage rate resulted in the high anticandidal activity of L-norvalyl-FMDP. The strong growth-inhibitory effect of this compound was the consequence of inhibition of the enzyme glucosamine-6-phosphate synthase by the released FMDP. The action of L-norvalyl-FMDP on exponentially growing C. albicans cells resulted in a sharp decrease of incorporation of 14C label from [14C]glucose into chitin, mannoprotein, and glucan. This effect, as well as the growth-inhibitory effect, was fully reversed by exogenous N-acetyl-D-glucosamine. Glucosamine-6-phosphate synthase was proved to be the only essential target for FMDP dipeptides. Scanning electron microscopy of C. albicans cells treated with L-norvalyl-FMDP revealed highly distorted, wrinkled, and collapsed forms. Cells formed long, bulbous chains, and partial lysis occurred. Images

Milewski, S; Andruszkiewicz, R; Kasprzak, L; Mazerski, J; Mignini, F; Borowski, E

1991-01-01

77

Cyclo-Oxygenase Inhibitors and Thromboxane Synthase Inhibitors Differentially Regulate Migration Arrest, Growth Inhibition and Apoptosis in Human Glioma Cells  

Microsoft Academic Search

Summary  \\u000a ?We have previously identified thromboxane synthase as an important regulator of glioma cell migration. Inhibitors of this\\u000a enzyme abrogate cell motility and induce apoptosis. However, the formation rate of thromboxanes is indirectly dependent on\\u000a the activity of cyclo-oxygenase, which represents the rate-limiting step in the synthesis of prostaglandins and thromboxanes.\\u000a In this study we have analyzed the expression of

F. Kürzel; Ch. Hagel; S. Zapf; H. Meissner; M. Westphal; A. Giese

2002-01-01

78

Discovery of Novel Antifungal (1,3)-?-d-Glucan Synthase Inhibitors  

PubMed Central

The increasing incidence of life-threatening fungal infections has driven the search for new, broad-spectrum fungicidal agents that can be used for treatment and prophylaxis in immunocompromised patients. Natural-product inhibitors of cell wall (1,3)-?-d-glucan synthase such as lipopeptide pneumocandins and echinocandins as well as the glycolipid papulacandins have been evaluated as potential therapeutics for the last two decades. As a result, MK-0991 (caspofungin acetate; Cancidas), a semisynthetic analogue of pneumocandin Bo, is being developed as a broad-spectrum parenteral agent for the treatment of aspergillosis and candidiasis. This and other lipopeptide antifungal agents have limited oral bioavailability. Thus, we have sought new chemical structures with the mode of action of lipopeptide antifungal agents but with the potential for oral absorption. Results of natural-product screening by a series of newly developed methods has led to the identification of four acidic terpenoid (1,3)-?-d-glucan synthase inhibitors. Of the four compounds, the in vitro antifungal activity of one, enfumafungin, is comparable to that of L-733560, a close analogue of MK-0991. Like the lipopeptides, enfumafungin specifically inhibits glucan synthesis in whole cells and in (1,3)-?-d-glucan synthase assays, alters the morphologies of yeasts and molds, and produces a unique response in Saccharomyces cerevisiae strains with point mutations in FKS1, the gene which encodes the large subunit of glucan synthase.

Onishi, J.; Meinz, M.; Thompson, J.; Curotto, J.; Dreikorn, S.; Rosenbach, M.; Douglas, C.; Abruzzo, G.; Flattery, A.; Kong, L.; Cabello, A.; Vicente, F.; Pelaez, F.; Diez, M. T.; Martin, I.; Bills, G.; Giacobbe, R.; Dombrowski, A.; Schwartz, R.; Morris, S.; Harris, G.; Tsipouras, A.; Wilson, K.; Kurtz, M. B.

2000-01-01

79

Structures of a Potent Phenylalkyl Bisphosphonate Inhibitor Bound to Farnesyl and Geranylgeranyl Diphosphate Synthases  

PubMed Central

We report the x-ray crystallographic structures of the bisphosphonate N-[methyl(4-phenylbutyl)]-3-aminopropyl-1-hydroxy-1,1-bisphosphonate (BPH-210), a potent analog of pamidronate (Aredia), bound to farnesyl diphosphate synthase (FPPS) from Trypanosoma brucei as well as to geranylgeranyl diphosphate synthase from Saccharomyces cerevisiae. BPH-210 binds to FPPS, together with 3 Mg2+, with its long, hydrophobic phenylbutyl sidechain being located in the same binding pocket that is occupied by allylic diphosphates and other bisphosphonates. Binding is overwhelmingly entropy driven, as determined by isothermal titration calorimetry. The structure is of interest since it explains the lack of potency of longer chain analogs against FPPS, since these would be expected to have a steric clash with an aromatic ring at the distal end of the binding site. Unlike shorter chain FPPS inhibitors, such as pamidronate, BPH-210 is also found to be a potent inhibitor of human geranylgeranyl diphosphate synthase. In this case, the bisphosphonate binds only to the GGPP product inhibitory site, with only 1 (chain A) or 0 (chain B) Mg2+, and ?S is much smaller and ?H is ~6k cal more negative than in the case of FPPS binding. Overall, these results are of general interest since they show that some bisphosphonates can bind to more than one trans-prenyl synthase enzyme which, in some cases, can be expected to enhance their overall activity in vitro and in vivo.

Cao, Rong; Chen, Cammy K.-M.; Guo, Rey-Ting; Wang, Andrew H.-J.; Oldfield, Eric

2008-01-01

80

Facilitated diffusion of glucosamine-6-phosphate synthase inhibitors enhances their antifungal activity  

Microsoft Academic Search

N3-(4-Methoxyfumaroyl)-L-2,3-diaminopropanoic acid (FMDP) and 2-amino-2- deoxy-D-glucitol-6-phosphate (ADGP) are strong inhibitors of the essential fungal en- zyme, glucosamine-6-phosphate synthase, but their antifungal activity is poor, due to slow penetration of these agents through the cytoplasmic membrane. In the present studies we have exploited the possibility of enhancement of ADGP and FMDP antifungal activity by improving their transport properties. It has been

Agnieszka Janiak; Barbara Cybulska; Joanna Szlinder-Richert; Edward Borowski

2002-01-01

81

Docking and 3D-QSAR studies of acetohydroxy acid synthase inhibitor sulfonylurea derivatives  

Microsoft Academic Search

Docking and three dimensional quantitative-structure activity relationship (3D-QSAR) studies were performed on acetohydroxy\\u000a acid synthase (AHAS) inhibitor sulfonylurea analogues with potential herbicidal activity. The 3D-QSAR studies were carried\\u000a out using shape, spatial and electronic descriptors along with a few structural parameters. Genetic function approximation\\u000a (GFA) was used as the chemometric tool for this analysis. The whole data set (n?=?45) was

Kunal Roy; Somnath Paul

2010-01-01

82

Green Tea Epigallocatechin Gallate: A Natural Inhibitor of Fatty-Acid Synthase  

Microsoft Academic Search

We discover that epigallocatechin gallate (EGCG) from green tea is an inhibitor of fatty-acid synthase (FAS) from chicken liver. Its inhibition of FAS is composed of reversible fast-binding inhibition, through which 52 ?M EGCG can inhibit 50% of the activity of FAS, and irreversible slow-binding inactivation following saturation kinetics with the dissociation constant of 0.352 mM and limiting rate constant

Xuan Wang; Weixi Tian

2001-01-01

83

Exercise conditioning attenuates the hypertensive effects of nitric oxide synthase inhibitor in rat  

Microsoft Academic Search

Many individuals with cardiovascular diseases undergo periodic exercise conditioning with or with out medication. Therefore, this study investigated the interaction of exercise training and chronic nitric oxide synthase (NOS) inhibitor (Nitro-L-Arginine Methyl Ester, L-NAME) treatment on blood pressure and its correlation with aortic nitric oxide (NO), antioxidant defense system and oxidative stress parameters in rats. Fisher 344 rats were divided

Kazim Husain

2002-01-01

84

Expression and Regulation of Protein Inhibitor of Neuronal Nitric Oxide Synthase in Ventilatory Muscles  

Microsoft Academic Search

In skeletal muscle fibers, nitric oxide (NO) is synthesized by neuronal NO synthase (nNOS) and regulates excitation-contraction coupling, glucose uptake, and mitochondrial respiration. Recently, a novel 89- amino acid protein, designated protein inhibitor of nNOS (PIN), has been shown to interact with and spe- cifically inhibit nNOS activity. In this study, we investigated the distribution, localization, and regulation of PIN

Yang Guo; Michael T. Greenwood; Basil J. Petrof; Sabah N. A. Hussain

1999-01-01

85

Glycosphingolipid depletion in Fabry disease lymphoblasts with potent inhibitors of glucosylceramide synthase  

Microsoft Academic Search

Glycosphingolipid depletion in Fabry disease lymphoblasts with potent inhibitors of glucosylceramide synthase.BackgroundFabry disease is an inherited X-linked disorder resulting in the loss of activity of the lysosomal hydrolase ?-galactosidase A and causing the clinical manifestations of renal failure, cerebral vascular disease, and myocardial infarction. The phenotypic expression of this disorder is manifest by the accumulation of glycosphingolipids containing ?-galactosyl linkages,

Akira Abe; Lois J Arend; Lihsueh Lee; Clifford Lingwood; Roscoe O Brady; James A Shayman

2000-01-01

86

The nitric oxide synthase inhibitor N W-Nitro-L-Arginine methylester attenuates brain catalase activity in vitro  

Microsoft Academic Search

Nitric oxide has been implicated in mediating the neurotoxic effects of ischemia in the brain. However, studies of the effects of nitric oxide inhibition with nitric oxide synthase inhibitors have provided controversial results. One of the reasons for the controversy may be related to the specificity of the nitric oxide synthase inhibitors, such as Nw-nitro-L-arginine methylester (L-NAME), which has recently

S Rotzinger; C. M. G Aragon; F Rogan; S Amir; Z Amit

1995-01-01

87

Identification and evaluation of novel acetolactate synthase inhibitors as antifungal agents.  

PubMed

High-throughput phenotypic screening against the yeast Saccharomyces cerevisiae revealed a series of triazolopyrimidine-sulfonamide compounds with broad-spectrum antifungal activity, no significant cytotoxicity, and low protein binding. To elucidate the target of this series, we have applied a chemogenomic profiling approach using the S. cerevisiae deletion collection. All compounds of the series yielded highly similar profiles that suggested acetolactate synthase (Ilv2p, which catalyzes the first common step in branched-chain amino acid biosynthesis) as a possible target. The high correlation with profiles of known Ilv2p inhibitors like chlorimuron-ethyl provided further evidence for a similar mechanism of action. Genome-wide mutagenesis in S. cerevisiae identified 13 resistant clones with 3 different mutations in the catalytic subunit of acetolactate synthase that also conferred cross-resistance to established Ilv2p inhibitors. Mapping of the mutations into the published Ilv2p crystal structure outlined the chlorimuron-ethyl binding cavity, and it was possible to dock the triazolopyrimidine-sulfonamide compound into this pocket in silico. However, fungal growth inhibition could be bypassed through supplementation with exogenous branched-chain amino acids or by the addition of serum to the medium in all of the fungal organisms tested except for Aspergillus fumigatus. Thus, these data support the identification of the triazolopyrimidine-sulfonamide compounds as inhibitors of acetolactate synthase but suggest that targeting may be compromised due to the possibility of nutrient bypass in vivo. PMID:23478965

Richie, Daryl L; Thompson, Katherine V; Studer, Christian; Prindle, Vivian C; Aust, Thomas; Riedl, Ralph; Estoppey, David; Tao, Jianshi; Sexton, Jessica A; Zabawa, Thomas; Drumm, Joseph; Cotesta, Simona; Eichenberger, Jürg; Schuierer, Sven; Hartmann, Nicole; Movva, N Rao; Tallarico, John A; Ryder, Neil S; Hoepfner, Dominic

2013-03-11

88

1,6-Disubstituted indole derivatives as selective human neuronal nitric oxide synthase inhibitors.  

PubMed

A series of 1,6-disubstituted indole derivatives was designed, synthesized and evaluated as inhibitors of human nitric oxide synthase (NOS). By varying the basic amine side chain at the 1-position of the indole ring, several potent and selective inhibitors of human neuronal NOS were identified. In general compounds with bulkier side chains displayed increased selectivity for nNOS over eNOS and iNOS isoforms. One of the compounds, (R)-8 was shown to reduce tactile hyperesthesia (allodynia) after oral administration (30 mg/kg) in an in vivo rat model of dural inflammation relevant to migraine pain. PMID:21824773

Maddaford, Shawn; Renton, Paul; Speed, Joanne; Annedi, Subhash C; Ramnauth, Jailall; Rakhit, Suman; Andrews, John; Mladenova, Gabriela; Majuta, Lisa; Porreca, Frank

2011-07-22

89

Colchicine-Induced Apoptosis Was Prevented by Glycogen Synthase Kinase3 Inhibitors in PC12 Cells  

Microsoft Academic Search

The purpose of this study was to examine whether glycogen synthase kinase-3 (GSK-3) is involved in colchicine-induced cell\\u000a death in PC12 cells by using GSK inhibitors. Colchicine increased apoptotic cell death with morphological changes characterized\\u000a by cell shrinkage and nuclear condensation or fragmentation. GSK-3 inhibitors such as alsterpaullone, SB216763, and AR-A014418\\u000a prevented colchicine-induced cell death and caspase-3 activation. These results

Tsuneo Takadera; Yu Nakajima; Yuki Kanai

2010-01-01

90

A Septin-based Hierarchy of Proteins Required for Localized Deposition of Chitin in the Saccharomyces cerevisiae Cell Wall  

Microsoft Academic Search

Just before bud emergence, a Saccharomyces cerevisiae cell forms a ring of chitin in its cell wall; this ring remains at the base of the bud as the bud grows and ultimately forms part of the bud scar marking the division site on the mother cell. The chitin ring seems to be formed largely or entirely by chitin synthase III,

Douglas J. DeMarini; Alison E. M. Adams; Hanna Fares; Claudio De Virgilio; Giorgio Valle; John S. Chuang; John R. Pringle

1997-01-01

91

Structural and stereochemical studies of potent inhibitors of glucosylceramide synthase and tumor cell growth.  

PubMed

Analogs and homologs of PDMP were synthesized, based on its structure (D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol). This compound had previously been found to block the synthesis of GlcCer (glucosylceramide). Increasing the acyl chain length from 10 to 16 carbon atoms greatly enhanced the efficacy of the enzyme inhibitor, as did the use of a less polar cyclic amine, especially a pyrrolidine instead of a morpholine ring. Replacement of the phenyl ring by a chain corresponding to sphingosine also yielded a strongly inhibitory material. By using a chiral synthetic route, we showed that the isomers active against GlcCer synthase had the R,R-(D-threo)-configuration. However, strong inhibition of the growth of human cancer cells in plastico was produced by both the threo and erythro racemic compounds, showing involvement of an additional factor (beyond simple depletion of cell glycosphingolipids by blockage of GlcCer synthesis). The growth arresting effects could be correlated with increases in cellular ceramide and diglyceride levels. The aliphatic pyrrolidino compound was strongly inhibitory toward the glucosyltransferase and produced almost complete depletion of glycolipids, but did not inhibit growth or cause an accumulation of ceramide. Attempts were made to see whether the differences in growth effects could be attributed to the influence of the inhibitors on related enzymes (ceramide and sphingomyelin synthase and ceramidase and sphingomyelinase). While some stimulation of enzyme activity was noted, particularly at high inhibitor concentrations (50 microM), these findings did not explain the differing effects of the different inhibitors. The best inhibitors of GlcCer synthase compared favorably in efficacy with some cancer chemotherapeutic drugs in current use when tested with a battery of human cancer cells. PMID:7775872

Abe, A; Radin, N S; Shayman, J A; Wotring, L L; Zipkin, R E; Sivakumar, R; Ruggieri, J M; Carson, K G; Ganem, B

1995-03-01

92

Effect of a selective thromboxane synthase inhibitor on arterial graft patency and platelet deposition in dogs  

SciTech Connect

This study examined the effect of selective thromboxane synthase inhibition and nonselective cyclooxygenase inhibition on vascular graft patency and indium 111-labeled platelet deposition in 35 mongrel dogs undergoing carotid artery replacement with 4 mm X 4 cm polytetrafluoroethylene (PTFE) (one side) and Dacron (opposite side) end-to-end grafts. Aspirin-dipyridamole therapy improved one-week graft patency, from 46% in untreated dogs to 93% in treated dogs. Thromboxane synthase inhibition (U-63557A) improved graft patency in these dogs to 81%. Both drug treatments reduced platelet deposition on Dacron and PTFE grafts by 48% to 68% compared with control dogs. Dacron grafts accumulated significantly more platelets than PTFE grafts but had comparable patency rates. Low-dose aspirin therapy had no significant effect on either graft patency or platelet deposition. All treatment groups showed a 60% to 76% reduction in serum thromboxane B2, but only thromboxane synthase inhibitor treatment increased plasma 6-keto-prostaglandin F1 alpha by 100%. Selective thromboxane synthase inhibition improved small-caliber prosthetic graft patency to the same extent as did conventional cyclooxygenase inhibition in this preliminary study.

McDaniel, M.D.; Huntsman, W.T.; Miett, T.O.; Cronenwett, J.L.

1987-08-01

93

Arginine-Based Inhibitors of Nitric Oxide Synthase: Therapeutic Potential and Challenges  

PubMed Central

In the past three decades, nitric oxide has been well established as an important bioactive molecule implicated in regulation of cardiovascular, nervous, and immune systems. Therefore, it is not surprising that much effort has been made to find specific inhibitors of nitric oxide synthases (NOS), the enzymes responsible for production of nitric oxide. Among the many NOS inhibitors developed to date, inhibitors based on derivatives and analogues of arginine are of special interest, as this category includes a relatively high number of compounds with good potential for experimental as well as clinical application. Though this group of inhibitors covers early nonspecific compounds, modern drug design strategies such as biochemical screening and computer-aided drug design have provided NOS-isoform-specific inhibitors. With an emphasis on major advances in this field, a comprehensive list of inhibitors based on their structural characteristics is discussed in this paper. We provide a summary of their biochemical properties as well as their observed effects both in vitro and in vivo. Furthermore, we focus in particular on their pharmacology and use in recent clinical studies. The potential of newly designed specific NOS inhibitors developed by means of modern drug development strategies is highlighted.

Vitecek, Jan; Lojek, Antonin; Valacchi, Giuseppe; Kubala, Lukas

2012-01-01

94

Tritritionikkomycin Z, (uracil-5- sup 3 H,pyridyl-2,4- sup 3 H sub 2 ): Radiolabeling of a potent inhibitor of fungal and insect chitin synthetase  

SciTech Connect

Nikkomycin Z (NZ) (a potent fungicide, insecticide, miticide, and inhibitor of fungal and insect chitin synthetase) was converted to a mixture of specific mono-, di-, and tribromo derivatives (BrNZ, Br{sub 2}NZ, and Br{sub 3}NZ, respectively) on reaction with N-bromosuccinimide in N,N-dimethylformamide. Substitution by bromine occurred first at the 2-position of the 3-hydroxypyridyl moiety, second at the 5-position of the uracil moiety, and finally at the 4-position of the 3-hydroxypyridyl moiety as observed both for NZ and for mixtures of uridine and 3-hydroxy-6-methylpyridine as model compounds representative of the moieties of NZ. Following fractionation of the various bromonikkomycin derivatives by HPLC, their structures were assigned by NMR, MS, and UV analyses. Catalytic reductive debromination of Br{sub 3}NZ with tritium gas over palladium on carbon gave (uracil-5-{sup 3}H,pyridyl-2,4-{sup 3}H{sub 2})NZ. This material has sufficiently high specific activity ({approximately}60 Ci/mmol) and suitable positions of labeling to study its uptake, distribution, metabolism, and possible target site interactions in fungal and insect systems.

Ando, Tetsu; Tecle, B.; Toia, R.F.; Casida, J.E. (Univ. of California, Berkeley (USA))

1990-08-01

95

ATP Synthase and the Actions of Inhibitors Utilized To Study Its Roles in Human Health, Disease, and Other Scientific Areas  

PubMed Central

Summary: ATP synthase, a double-motor enzyme, plays various roles in the cell, participating not only in ATP synthesis but in ATP hydrolysis-dependent processes and in the regulation of a proton gradient across some membrane-dependent systems. Recent studies of ATP synthase as a potential molecular target for the treatment of some human diseases have displayed promising results, and this enzyme is now emerging as an attractive molecular target for the development of new therapies for a variety of diseases. Significantly, ATP synthase, because of its complex structure, is inhibited by a number of different inhibitors and provides diverse possibilities in the development of new ATP synthase-directed agents. In this review, we classify over 250 natural and synthetic inhibitors of ATP synthase reported to date and present their inhibitory sites and their known or proposed modes of action. The rich source of ATP synthase inhibitors and their known or purported sites of action presented in this review should provide valuable insights into their applications as potential scaffolds for new therapeutics for human and animal diseases as well as for the discovery of new pesticides and herbicides to help protect the world's food supply. Finally, as ATP synthase is now known to consist of two unique nanomotors involved in making ATP from ADP and Pi, the information provided in this review may greatly assist those investigators entering the emerging field of nanotechnology.

Hong, Sangjin; Pedersen, Peter L.

2008-01-01

96

The thymidylate synthase inhibitor ZD1694 potently inhibits murine and human cytomegalovirus replication in quiescent fibroblasts.  

PubMed

Tomudex (ZD1694) is a quinazoline-based folate analog and a powerful inhibitor of cellular thymidylate synthase and is approved in Europe for use in oncology. Here the first evidence of its activity against murine and human cytomegalovirus (MCMV and HCMV) is reported. ZD1694 irreversibly inhibited the replication and DNA synthesis of both viruses in quiescent fibroblasts. The corresponding 50% effective concentrations were 0.006 and 0.002 microM respectively, whereas the 50% cytotoxic concentration was >10 microM for both murine and human quiescent fibroblasts. A similar antiviral effect was observed against two ganciclovir-resistant HCMV strains isolated from AIDS patients. Taken as a whole these results demonstrate that cellular thymidylate synthase plays an essential role in viral replication and that ZD1694 merits further investigation as anticytomegaloviral agent. PMID:10996399

Lembo, D; Gribaudo, G; Riera, L; Mondo, A; Cavallo, R; Angeretti, A; Landolfo, S

2000-08-01

97

Structural study and thermodynamic characterization of inhibitor binding to lumazine synthase from Bacillus anthracis.  

PubMed

The crystal structure of lumazine synthase from Bacillus anthracis was solved by molecular replacement and refined to R(cryst) = 23.7% (R(free) = 28.4%) at a resolution of 3.5 A. The structure reveals the icosahedral symmetry of the enzyme and specific features of the active site that are unique in comparison with previously determined orthologues. The application of isothermal titration calorimetry in combination with enzyme kinetics showed that three designed pyrimidine derivatives bind to lumazine synthase with micromolar dissociation constants and competitively inhibit the catalytic reaction. Structure-based modelling suggested the binding modes of the inhibitors in the active site and allowed an estimation of the possible contacts formed upon binding. The results provide a structural framework for the design of antibiotics active against B. anthracis. PMID:20823551

Morgunova, Ekaterina; Illarionov, Boris; Saller, Sabine; Popov, Aleksander; Sambaiah, Thota; Bacher, Adelbert; Cushman, Mark; Fischer, Markus; Ladenstein, Rudolf

2010-08-13

98

Role of zinc in isoform-selective inhibitor binding to neuronal nitric oxide synthase .  

PubMed

In previous studies [Delker, S. L., et al. (2010), J. Am. Chem. Soc. 132, 5437-5442], we determined the crystal structures of neuronal nitric oxide synthase (nNOS) in complex with nNOS-selective chiral pyrrolidine inhibitors, designed to have an aminopyridine group bound over the heme where it can electrostatically interact with the conserved active site Glu residue. However, in addition to the expected binding mode with the (S,S)-cis inhibitors, an unexpected "flipped" orientation was observed for the (R,R)-cis enantiomers. In the flipped mode, the aminopyridine extends out of the active site where it interacts with one heme propionate. This prompted us to design and synthesize symmetric "double-headed" inhibitors with an aminopyridine at each end of a bridging ring structure [Xue, F., Delker, S. L., Li, H., Fang, J., Jamal, J., Marta?sek, P., Roman, L. J., Poulos, T. L., and Silverman, R. B. Symmetric double-headed aminopyridines, a novel strategy for potent and membrane-permeable inhibitors of neuronal nitric oxide synthase. J. Med. Chem. (submitted for publication)]. One aminopyridine should interact with the active site Glu and the other with the heme propionate. Crystal structures of these double-headed aminopyridine inhibitors in complexes with nNOS show unexpected and significant protein and heme conformational changes induced by inhibitor binding that result in removal of the tetrahydrobiopterin (H(4)B) cofactor and creation of a new Zn(2+) site. These changes are due to binding of a second inhibitor molecule that results in the displacement of H(4)B and the placement of the inhibitor pyridine group in position to serve as a Zn(2+) ligand together with Asp, His, and a chloride ion. Binding of the second inhibitor molecule and generation of the Zn(2+) site do not occur in eNOS. Structural requirements for creation of the new Zn(2+) site in nNOS were analyzed in detail. These observations open the way for the potential design of novel inhibitors selective for nNOS. PMID:21138269

Delker, Silvia L; Xue, Fengtian; Li, Huiying; Jamal, Joumana; Silverman, Richard B; Poulos, Thomas L

2010-12-07

99

Peripheral or central administration of nitric oxide synthase inhibitor affects feeding behavior in chicks.  

PubMed

We investigated the effect of peripheral or central administration of N(G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, on food intake in layer and broiler chicks (Gallus gallus). The intraperitoneal administration of L-NAME significantly decreased food intake in both broiler and layer chicks while the administration of D-NAME, an inactive form of L-NAME, had no effect. The intracerebroventricular (ICV) injection of L-NAME did not affect food intake in broiler chicks. However, ICV injection of L-NAME increased food intake in layer chicks while the injection of D-NAME had no effect. In addition to this, L-NAME-induced feeding was negated with the co-injection of L-arginine, suggesting that NO acts as a feeding-inhibitor signal in the brain of layer chicks. The present study revealed that administration of NO synthase inhibitor affected food intake in chicks, but the effect might be changed by chick strain and position of the injection. PMID:17618151

Khan, Md Sakirul Islam; Tachibana, Tetsuya; Hasebe, Yuko; Masuda, Naoto; Ueda, Hiroshi

2007-06-19

100

Plant-Derived Small Molecule Inhibitors of Neuronal NO-Synthase  

PubMed Central

Cigarette smoking is known to cause a decrease in NO production in man resulting in a variety of pathological effects, including vascular dysfunction. Aqueous extracts of cigarette and cigarette smoke contain chemical inhibitors to NO-synthases, a heme-containing cytochrome P450 enzymes. More recently, it was shown that freshly harvested leaves from the tobacco plant (Nicotiana tabacum, Solanaceae) also contain chemical inhibitors to neuronal NO-synthase (nNOS). Examination of leaves from 32 other plants representing diverse members of the plant kingdom showed that 17 other plants, besides tobacco, contain these chemical inhibitors. Of all these plants, 16 are members of the core asterids flowering plant group and 6 are members of the Solanaceae family. Although the identity of the chemicals is not known, perhaps the closely related plants contain the same or similar compounds that inhibit nNOS. The inhibitory effects are not attributable to nicotine. The discovery of these chemicals and their further characterization may help to explain the loss of nNOS in smokers. In this addendum, we discuss these results in light of the effect of tobacco-derived chemicals in inhibiting P450 cytochromes, as well as our thoughts on how the inactivation of nNOS leads to its selective downregulation through proteolytic degradation.

Lau, Miranda; Lowe, Ezra R

2007-01-01

101

Intracoronary administration of a thromboxane A2 synthase inhibitor relieves acetylcholine-induced coronary spasm.  

PubMed

This study sought to clarify the effectiveness of intracoronary administration of a thromboxane (TX) A2 synthase inhibitor, Ozagrel Na, to relieve coronary spasms induced by intracoronary injection of acetylcholine (ACh). An ACh spasm provocation test was performed in 92 consecutive patients with coronary spastic angina using incremental doses of 20, 50, and 80 microg into the right coronary artery, and 20, 50, and 100 microg into the left coronary artery within 20s. A coronary spasm was defined as TIMI 0 or 1 flow and an intracoronary injection of 20 mg Ozagrel Na was administered when it was provoked. Within 2 min of the administration of the TXA2 synthase inhibitor, ACh-induced coronary spasms were relieved (TIMI 3 flow) in 88.1% of procedures without complications. In only 4 cases (4.3%), it took more than 3 min to relieve the coronary spasms. Intracoronary administration of 20mg Ozagrel Na when ACh-induced spasms occurred, shortened the spasm relief time in all 7 patients (200 +/- 59s vs 111 +/- 23s, p < 0.01), improved the maximal ST segment elevation in 5 of them (3.9 +/- 3.7 mm vs 0.7 +/- 1.5 mm, p < 0.05), and stopped chest pain in 4 patients. In 4 patients who had ACh-induced coronary spasm of the left anterior descending artery, the TXB2 concentration in the coronary sinus decreased after intracoronary administration of Ozagrel Na into the left coronary artery (463 +/- 562 vs 96 +/- 45, p < 0.01). In conclusion, intracoronary administration of a TXA2 synthase inhibitor can relieve ACh-induced coronary spasms by inhibiting TXA2 synthesis in the local coronary circulation. PMID:12224820

Sueda, Shozo; Kohno, Hiroaki; Inoue, Katsuji; Fukuda, Hiroshi; Suzuki, Jun; Watanabe, Kouki; Ochi, Naoto; Kawada, Hiroyuki; Uraoka, Tadao

2002-09-01

102

Vigilance and EEG power in rats: effects of potent inhibitors of the neuronal nitric oxide synthase  

Microsoft Academic Search

We examined the effects of potent neuronal nitric oxide synthase inhibitors, 3-bromo-7-nitro indazole (3-Br-7-NI) and S-methyl-L-thiocitrulline\\u000a (S-Me-TC) on general behaviour, vigilance stages and electro-encephalographic (EEG) power spectra in rats. In addition, we\\u000a studied the effect of 7-nitro indazole (7-NI) on EEG power spectra in rats during dark and light periods. 3-Br-7-NI induced\\u000a ptosis and decrease of slow wave sleep and

Eleonora Dzoljic; Redmer van Leeuwen; René de Vries; Mihailo R. Dzoljic

1997-01-01

103

DXP synthase-catalyzed C-N bond formation: nitroso substrate specificity studies guide selective inhibitor design.  

PubMed

1-Deoxy-D-xylulose 5-phosphate (DXP) synthase catalyzes the first step in the nonmammalian isoprenoid biosynthetic pathway to form DXP from pyruvate and D-glyceraldehyde 3-phosphate (D-GAP) in a thiamin diphosphate-dependent manner. Its unique structure and mechanism distinguish DXP synthase from its homologues and suggest that it should be pursued as an anti-infective drug target. However, few reports describe any development of selective inhibitors of this enzyme. Here, we reveal that DXP synthase catalyzes C-N bond formation and exploit aromatic nitroso substrates as active site probes. Substrate specificity studies reveal a high affinity of DXP synthase for aromatic nitroso substrates compared to the related ThDP-dependent enzyme pyruvate dehydrogenase (PDH). Results from inhibition and mutagenesis studies indicate that nitroso substrates bind to E. coli DXP synthase in a manner distinct from that of D-GAP. Our results suggest that the incorporation of aryl acceptor substrate mimics into unnatural bisubstrate analogues will impart selectivity to DXP synthase inhibitors. As a proof of concept, we show selective inhibition of DXP synthase by benzylacetylphosphonate (BnAP). PMID:23824585

Morris, Francine; Vierling, Ryan; Boucher, Lauren; Bosch, Jürgen; Freel Meyers, Caren L

2013-07-03

104

Inhibitor-bound complexes of dihydrofolate reductase-thymidylate synthase from Babesia bovis.  

PubMed

Babesiosis is a tick-borne disease caused by eukaryotic Babesia parasites which are morphologically similar to Plasmodium falciparum, the causative agent of malaria in humans. Like Plasmodium, different species of Babesia are tuned to infect different mammalian hosts, including rats, dogs, horses and cattle. Most species of Plasmodium and Babesia possess an essential bifunctional enzyme for nucleotide synthesis and folate metabolism: dihydrofolate reductase-thymidylate synthase. Although thymidylate synthase is highly conserved across organisms, the bifunctional form of this enzyme is relatively uncommon in nature. The structural characterization of dihydrofolate reductase-thymidylate synthase in Babesia bovis, the causative agent of babesiosis in livestock cattle, is reported here. The apo state is compared with structures that contain dUMP, NADP and two different antifolate inhibitors: pemetrexed and raltitrexed. The complexes reveal modes of binding similar to that seen in drug-resistant malaria strains and point to the utility of applying structural studies with proven cancer chemotherapies towards infectious disease research. PMID:21904052

Begley, Darren W; Edwards, Thomas E; Raymond, Amy C; Smith, Eric R; Hartley, Robert C; Abendroth, Jan; Sankaran, Banumathi; Lorimer, Donald D; Myler, Peter J; Staker, Bart L; Stewart, Lance J

2011-08-16

105

Quantitative proteomic analysis of human lung tumor xenografts treated with the ectopic ATP synthase inhibitor citreoviridin.  

PubMed

ATP synthase is present on the plasma membrane of several types of cancer cells. Citreoviridin, an ATP synthase inhibitor, selectively suppresses the proliferation and growth of lung cancer without affecting normal cells. However, the global effects of targeting ectopic ATP synthase in vivo have not been well defined. In this study, we performed quantitative proteomic analysis using isobaric tags for relative and absolute quantitation (iTRAQ) and provided a comprehensive insight into the complicated regulation by citreoviridin in a lung cancer xenograft model. With high reproducibility of the quantitation, we obtained quantitative proteomic profiling with 2,659 proteins identified. Bioinformatics analysis of the 141 differentially expressed proteins selected by their relative abundance revealed that citreoviridin induces alterations in the expression of glucose metabolism-related enzymes in lung cancer. The up-regulation of enzymes involved in gluconeogenesis and storage of glucose indicated that citreoviridin may reduce the glycolytic intermediates for macromolecule synthesis and inhibit cell proliferation. Using comprehensive proteomics, the results identify metabolic aspects that help explain the antitumorigenic effect of citreoviridin in lung cancer, which may lead to a better understanding of the links between metabolism and tumorigenesis in cancer therapy. PMID:23990911

Wu, Yi-Hsuan; Hu, Chia-Wei; Chien, Chih-Wei; Chen, Yu-Ju; Huang, Hsuan-Cheng; Juan, Hsueh-Fen

2013-08-21

106

Quantitative Proteomic Analysis of Human Lung Tumor Xenografts Treated with the Ectopic ATP Synthase Inhibitor Citreoviridin  

PubMed Central

ATP synthase is present on the plasma membrane of several types of cancer cells. Citreoviridin, an ATP synthase inhibitor, selectively suppresses the proliferation and growth of lung cancer without affecting normal cells. However, the global effects of targeting ectopic ATP synthase in vivo have not been well defined. In this study, we performed quantitative proteomic analysis using isobaric tags for relative and absolute quantitation (iTRAQ) and provided a comprehensive insight into the complicated regulation by citreoviridin in a lung cancer xenograft model. With high reproducibility of the quantitation, we obtained quantitative proteomic profiling with 2,659 proteins identified. Bioinformatics analysis of the 141 differentially expressed proteins selected by their relative abundance revealed that citreoviridin induces alterations in the expression of glucose metabolism-related enzymes in lung cancer. The up-regulation of enzymes involved in gluconeogenesis and storage of glucose indicated that citreoviridin may reduce the glycolytic intermediates for macromolecule synthesis and inhibit cell proliferation. Using comprehensive proteomics, the results identify metabolic aspects that help explain the antitumorigenic effect of citreoviridin in lung cancer, which may lead to a better understanding of the links between metabolism and tumorigenesis in cancer therapy.

Wu, Yi-Hsuan; Hu, Chia-Wei; Chien, Chih-Wei; Chen, Yu-Ju; Huang, Hsuan-Cheng; Juan, Hsueh-Fen

2013-01-01

107

Potent, highly selective, and orally bioavailable gem-difluorinated monocationic inhibitors of neuronal nitric oxide synthase.  

PubMed

In our efforts to discover neuronal isoform selective nitric oxide synthase (NOS) inhibitors, we have developed a series of compounds containing a pyrrolidine ring with two stereogenic centers. The enantiomerically pure compounds, (S,S) versus (R,R), exhibited two different binding orientations, with (R,R) inhibitors showing much better potency and selectivity. To improve the bioavailability of these inhibitors, we have introduced a CF(2) moiety geminal to an amino group in the long tail of one of these inhibitors, which reduced its basicity, resulting in compounds with monocationic character under physiological pH conditions. Biological evaluations have led to a nNOS inhibitor with a K(i) of 36 nM and high selectivity for nNOS over eNOS (3800-fold) and iNOS (1400-fold). MM-PBSA calculations indicated that the low pK(a) NH is, at least, partially protonated when bound to the active site. A comparison of rat oral bioavailability of the difluorinated compound to the parent molecule shows 22% for the difluorinated compound versus essentially no oral bioavailability for the parent compound. This indicates that the goal of this research to make compounds with only one protonated nitrogen atom at physiological pH to allow for membrane permeability, but which can become protonated when bound to NOS, has been accomplished. PMID:20843082

Xue, Fengtian; Li, Huiying; Delker, Silvia L; Fang, Jianguo; Martásek, Pavel; Roman, Linda J; Poulos, Thomas L; Silverman, Richard B

2010-10-13

108

High-quality crystals of human haematopoietic prostaglandin D synthase with novel inhibitors  

PubMed Central

Human haematopoietic prostaglandin D synthase (H-PGDS; EC 5.3.99.2) produces prostaglandin D2, an allergic and inflammatory mediator, in mast cells and Th2 cells. H-PGDS has been crystallized with novel inhibitors with half-maximal inhibitory concentrations (IC50) in the low nanomolar range by the counter-diffusion method onboard the Russian Service Module on the International Space Station. The X-ray diffraction of a microgravity-grown crystal of H-PGDS complexed with an inhibitor with an IC50 value of 50?nM extended to 1.1?Ĺ resolution at 100?K using SPring-8 synchrotron radiation, which is one of the highest resolutions obtained to date for this protein.

Takahashi, Sachiko; Tsurumura, Toshiharu; Aritake, Kosuke; Furubayashi, Naoki; Sato, Masaru; Yamanaka, Mari; Hirota, Erika; Sano, Satoshi; Kobayashi, Tomoyuki; Tanaka, Tetsuo; Inaka, Koji; Tanaka, Hiroaki; Urade, Yoshihiro

2010-01-01

109

Effects of Sublethal Concentrations of the Chitin Synthesis Inhibitor, Hexaflumuron, on the Development and Hemolymph Physiology of the Cutworm, Spodoptera litura  

PubMed Central

The effects of sublethal concentrations 0.1, 0.5, and 1.2 µg mL-1of the chitin synthesis inhibitor, hexaflumuron, on larval growth and development, the count and proportion of hemocytes, and carbohydrate content (trehalose and glyceride) in hemolymph were investigated in the cutworm, Spodoptera litura (Fabricious) (Lepidoptera: Noctuidae). When 3rdinstar larvae were subjected to the sublethal concentrations, there were dose-dependent effects on larval weight and length of each instar larvae, percent pupation and the duration of development. Most of the larvae died during the molting process at all concentrations. Few individuals from 0.5 and 1.2 µg mL -1concentrations could develop to the 6thinstar, while the pupae emerging from the 0.1 µg mL -1concentrations did not exceed 16% of the number of the initial larvae. In 5thinstar S. litura, the total number of hemocytes was significantly increased at 24 hours post—treatment, whereas the proliferation of hemocytes was inhibited, plasmatocyte pseudopodia contracted, and granulocyte expanded at 96 hours post—treatment. The increases of plasmatocyte count and the decreases of granulocyte count were dose—dependent. The longer treatment time of the sublethal concentrations increased the content of total carbohydrate and trehalose in hematoplasma, and was dose—dependent in hemocytes. The content of glyceride in hemolymph was significantly higher at 24 hours post—treatment, but gradually returned to normal levels at 96 hours post—treatment as compared with the control. The results suggested that sublethal concentrations of hexaflumuron reduced S. litura larval survival and interfered with hemolymph physiological balances.

Zhu, Qiqi; He, Yuan; Yao, Jing; Liu, Yinzhao; Tao, Liming; Huang, Qingchun

2012-01-01

110

Furegrelate, a thromboxane synthase inhibitor, blunts the development of pulmonary arterial hypertension in neonatal piglets  

PubMed Central

The development of pulmonary arterial hypertension (PAH) in pediatric patients has been linked to the production of the arachidonic acid metabolite, thromboxane A2 (TxA2). The present study evaluated the therapeutic effect of furegrelate sodium, a thromboxane synthase inhibitor, on the development of PAH in a neonatal piglet model. Three-day-old piglets were exposed to 21 days of normoxia (N; 21% FIO2) or chronic hypoxia (CH; 10% FIO2). A third group of piglets received the oral TxA2 synthase inhibitor, furegrelate (3 mg/kg, 2 or 3 times daily) at the induction of CH. In vivo hemodynamics confirmed a 2.55-fold increase of the pulmonary vascular resistance index (PVRI) in CH piglets (104±7 WU) compared to N piglets (40±2 WU). The CH piglets treated twice daily with furegrelate failed to show improved PVRI, but furegrelate three times daily lowered the elevated PVRI in CH piglets by 34% to 69±5 WU and ameliorated the development of right ventricular hypertrophy. Microfocal X-ray computed tomography (CT) scanning was used to estimate the diameter-independent distensibility term, ? (% change in diameter per Torr). Pulmonary arterial distensibility in isolated lungs of CH piglets (?=1.0±0.1% per Torr) was lower than that of N piglets (?=1.5±0.1% per Torr) indicative of vascular remodeling. Arterial distensibility was partially restored in furegrelate-treated CH piglets (? =1.2±0.1% per Torr) and microscopic evidence showing muscularization of small pulmonary arteries also was less prominent in these animals. Finally, isolated lungs of furegrelate-treated piglets showed lower basal and vasodilator-induced transpulmonary pressures compared to CH animals. These findings suggest that pharmacological inhibition of TxA2 synthase activity by furegrelate blunts the development of hypoxia-induced PAH in an established neonatal piglet model primarily by preserving the structural integrity of the pulmonary vasculature.

Hirenallur-S., Dinesh K.; Detweiler, Neil D.; Haworth, Steven T.; Leming, Jeaninne T.; Gordon, John B.; Rusch, Nancy J.

2012-01-01

111

Regulation and function of the protein inhibitor of nitric oxide synthase (PIN)\\/dynein light chain 8 (LC8) in a human mast cell line  

Microsoft Academic Search

The protein inhibitor of nitric oxide synthase (PIN) was independently identified as an inhibitor of nitric oxide (NO) produced by neuronal nitric oxide synthase (nNOS), and as a member of the cellular dynein light chain family, dynein light chain 8 (LC8), responsible for intracellular protein trafficking. Mast cells (MC) are involved in several homeostatic and pathological processes and can be

Scott D. McCauley; Mark Gilchrist; A. Dean Befus

2007-01-01

112

Identification of Key Residues Determining Species Differences in Inhibitor Binding of Microsomal Prostaglandin E Synthase-1*  

PubMed Central

Microsomal prostaglandin E synthase-1 (MPGES1) is induced during an inflammatory reaction from low basal levels by pro-inflammatory cytokines and subsequently involved in the production of the important mediator of inflammation, prostaglandin E2. Nonsteroidal anti-inflammatory drugs prevent prostaglandin E2 production by inhibiting the upstream enzymes cyclooxygenases 1 and 2. In contrast to these conventional drugs, a new generation of NSAIDs targets the terminal enzyme MPGES1. Some of these compounds potently inhibit human MPGES1 but do not have an effect on the rat orthologue. We investigated this interspecies difference in a rat/human chimeric form of the enzyme as well as in several mutants and identified key residues Thr-131, Leu-135, and Ala-138 in human MPGES1, which play a crucial role as gate keepers for the active site of MPGES1. These residues are situated in transmembrane helix 4, lining the entrance to the cleft between two subunits in the protein trimer, and regulate access of the inhibitor in the rat enzyme. Exchange toward the human residues in rat MPGES1 was accompanied with a gain of inhibitor activity, whereas exchange in human MPGES1 toward the residues found in rat abrogated inhibitor activity. Our data give evidence for the location of the active site at the interface between subunits in the homotrimeric enzyme and suggest a model of how the natural substrate PGH2, or competitive inhibitors of MPGES1, enter the active site via the phospholipid bilayer of the membrane.

Pawelzik, Sven-Christian; Uda, Narasimha Rao; Spahiu, Linda; Jegerschold, Caroline; Stenberg, Patric; Hebert, Hans; Morgenstern, Ralf; Jakobsson, Per-Johan

2010-01-01

113

Evaluating the Role of Inducible Nitric Oxide Synthase Using a Novel and Selective Inducible Nitric Oxide Synthase Inhibitor in Septic Lung Injury Produced by Cecal Ligation and Puncture  

Microsoft Academic Search

We studied the role of inducible nitric oxide synthase (iNOS) in sep- tic lung injury using a novel and selective iNOS inhibitor (a fused pi- peridine derivative; ONO-1714) following a cecal ligation and punc- ture (CLP) procedure. All rats that received CLP died within 48 h after the intervention. The subcutaneous injection of ONO-1714 at 0.03 mg\\/kg every 12 h

IKU OKAMOTO; MASAYOSHI ABE; KAZUHIKO SHIBATA; NAOMI SHIMIZU; NORIYUKI SAKATA; TAKESHI KATSURAGI; KEIICHI TANAKA

114

A Novel Inhibitor of Inducible Nitric Oxide Synthase, ONO1714, Does Not Ameliorate Hypoxia-induced Pulmonary Hypertension in Rats  

Microsoft Academic Search

A recent study showed that long-term administration of the inducible nitric oxide synthase (iNOS) inhibitor L-NIL reduced\\u000a the development of pulmonary hypertension. The purpose of the present study was to identify the effect of an another iNOS\\u000a inhibitor, ONO-1714, on the development of pulmonary hypertensive vascular changes in chronic hypoxic pulmonary hypertension\\u000a in rats. ONO-1714 was administered to rats exposed

Bao Hua Jiang; Junko Maruyama; Ayumu Yokochi; Yoshihide Mitani; Kazuo Maruyama

2007-01-01

115

Improvement of Dolichol-linked Oligosaccharide Biosynthesis by the Squalene Synthase Inhibitor Zaragozic Acid*  

PubMed Central

The majority of congenital disorders of glycosylation (CDG) are caused by defects of dolichol (Dol)-linked oligosaccharide assembly, which lead to under-occupancy of N-glycosylation sites. Most mutations encountered in CDG are hypomorphic, thus leaving residual activity to the affected biosynthetic enzymes. We hypothesized that increased cellular levels of Dol-linked substrates might compensate for the low biosynthetic activity and thereby improve the output of protein N-glycosylation in CDG. To this end, we investigated the potential of the squalene synthase inhibitor zaragozic acid A to redirect the flow of the polyisoprene pathway toward Dol by lowering cholesterol biosynthesis. The addition of zaragozic acid A to CDG fibroblasts with a Dol-P-Man synthase defect led to the formation of longer Dol-P species and to increased Dol-P-Man levels. This treatment was shown to decrease the pathologic accumulation of incomplete Dol pyrophosphate-GlcNAc2Man5 in Dol-P-Man synthase-deficient fibroblasts. Zaragozic acid A treatment also decreased the amount of truncated protein N-linked oligosaccharides in these CDG fibroblasts. The increased cellular levels of Dol-P-Man and possibly the decreased cholesterol levels in zaragozic acid A-treated cells also led to increased availability of the glycosylphosphatidylinositol anchor as shown by the elevated cell-surface expression of the CD59 protein. This study shows that manipulation of the cellular Dol pool, as achieved by zaragozic acid A addition, may represent a valuable approach to improve N-linked glycosylation in CDG cells.

Haeuptle, Micha A.; Welti, Michael; Troxler, Heinz; Hulsmeier, Andreas J.; Imbach, Timo; Hennet, Thierry

2011-01-01

116

Improvement of dolichol-linked oligosaccharide biosynthesis by the squalene synthase inhibitor zaragozic acid.  

PubMed

The majority of congenital disorders of glycosylation (CDG) are caused by defects of dolichol (Dol)-linked oligosaccharide assembly, which lead to under-occupancy of N-glycosylation sites. Most mutations encountered in CDG are hypomorphic, thus leaving residual activity to the affected biosynthetic enzymes. We hypothesized that increased cellular levels of Dol-linked substrates might compensate for the low biosynthetic activity and thereby improve the output of protein N-glycosylation in CDG. To this end, we investigated the potential of the squalene synthase inhibitor zaragozic acid A to redirect the flow of the polyisoprene pathway toward Dol by lowering cholesterol biosynthesis. The addition of zaragozic acid A to CDG fibroblasts with a Dol-P-Man synthase defect led to the formation of longer Dol-P species and to increased Dol-P-Man levels. This treatment was shown to decrease the pathologic accumulation of incomplete Dol pyrophosphate-GlcNAc(2)Man(5) in Dol-P-Man synthase-deficient fibroblasts. Zaragozic acid A treatment also decreased the amount of truncated protein N-linked oligosaccharides in these CDG fibroblasts. The increased cellular levels of Dol-P-Man and possibly the decreased cholesterol levels in zaragozic acid A-treated cells also led to increased availability of the glycosylphosphatidylinositol anchor as shown by the elevated cell-surface expression of the CD59 protein. This study shows that manipulation of the cellular Dol pool, as achieved by zaragozic acid A addition, may represent a valuable approach to improve N-linked glycosylation in CDG cells. PMID:21183681

Haeuptle, Micha A; Welti, Michael; Troxler, Heinz; Hülsmeier, Andreas J; Imbach, Timo; Hennet, Thierry

2010-12-23

117

Visualizing inducible nitric-oxide synthase in living cells with a heme-binding fluorescent inhibitor.  

PubMed

The study of nitric-oxide synthase (NOS) physiology is constrained by the lack of suitable probes to detect NOS in living cells or animals. Here, we characterized a fluorescent inducible NOS (iNOS) inhibitor called PIF (pyrimidine imidazole FITC) and examined its utility for microscopic imaging of iNOS in living cells. PIF binding to iNOS displayed high affinity, isoform selectivity, and heme specificity, and was essentially irreversible. PIF was used to successfully image iNOS expressed in RAW264.7 cells, HEK293T cells, human A549 epithelial cells, and freshly obtained human lung epithelium. PIF was used to estimate a half-life for iNOS of 1.8 h in HEK293T cells. Our work reveals that fluorescent probes like PIF will be valuable for studying iNOS cell biology and in understanding the pathophysiology of diseases that involve dysfunctional iNOS expression. PMID:16006534

Panda, Koustubh; Chawla-Sarkar, Mamta; Santos, Cecile; Koeck, Thomas; Erzurum, Serpil C; Parkinson, John F; Stuehr, Dennis J

2005-07-08

118

1,5-Disubstituted indole derivatives as selective human neuronal nitric oxide synthase inhibitors.  

PubMed

A series of 1,5-disubstituted indole derivatives was designed, synthesized and evaluated as inhibitors of human nitric oxide synthase. A variety of flexible and restricted basic amine side chain substitutions was explored at the 1-position of the indole ring, while keeping the amidine group fixed at the 5-position. Compounds having N-(1-(2-(1-methylpyrrolidin-2-yl)ethyl)- (12, (R)-12, (S)-12 and 13) and N-(1-(1-methylazepan-4-yl)- side chains (14, 15, (-)-15 and (+)-15) showed increased inhibitory activity for the human nNOS isoform and selectivity over eNOS and iNOS isoforms. The most potent compound of the series for human nNOS (IC(50)=0.02 ?M) (S)-12 showed very good selectivity over the eNOS (eNOS/nNOS=96-fold) and iNOS (iNOS/nNOS=850-fold) isoforms. PMID:21813276

Renton, Paul; Speed, Joanne; Maddaford, Shawn; Annedi, Subhash C; Ramnauth, Jailall; Rakhit, Suman; Andrews, John

2011-07-14

119

Application of a High-throughput Fluorescent Acetyltransferase Assay to Identify Inhibitors of Homocitrate Synthase  

PubMed Central

Homocitrate synthase (HCS) catalyzes the first step of L-lysine biosynthesis in fungi by condensing acetyl-Coenzyme A and 2-oxoglutarate to form 3R-homocitrate and Coenzyme A. Due to its conservation in pathogenic fungi, HCS has been proposed as a candidate for antifungal drug design. Here we report the development and validation of a robust, fluorescent assay for HCS that is amenable to high-throughput screening for inhibitors in vitro. Using this assay, Schizosaccharomyces pombe HCS was screened against a diverse library of ~41,000 small molecules. Following confirmation, counter screens, and dose-response analysis, we prioritized over 100 compounds for further in vitro and in vivo analysis. This assay can be readily adapted to screen for small molecule modulators of other acyl-CoA-dependent acyltransferases or enzymes that generate a product with a free sulfhydryl group, including histone acetyltransferases, aminoglycoside N-acetyltransferases, thioesterases and enzymes involved in lipid metabolism.

Bulfer, Stacie L.; McQuade, Thomas J.; Larsen, Martha J.; Trievel, Raymond C.

2011-01-01

120

Phenanthrenoids from Juncus acutus L., new natural lipopolysaccharide-inducible nitric oxide synthase inhibitors.  

PubMed

The novel natural product juncutol (1), 1,4,7-trimethyl-8,9-dihydro-4H-cyclopenta[def]phenanthrene-2,6-diol, along with the three related metabolites juncusol (2), dehydrojuncusol (3), and 6-hydroxymethyl-1-methyl-5-vinyl-9,10-dihydrophenanthrene-2-ol (4), were isolated from the rhizomes of Juncus acutus L. (Juncaceae) growing in Egypt. The structural identity of 1 was determined on the basis of spectroscopic analyses, including 2D NMR spectroscopy. The inhibitory effect of these natural products on the expression of inducible nitric oxide synthase (iNOS) in lipopolysaccharide-stimulated RAW264.7 macrophage cells was determined for the first time. The unprecedented symmetrical compound juncutol (1) was found to be the most potent inhibitor against the induction of the proinflammatory iNOS protein. PMID:17666857

Behery, Fathi Abdelmohsen Abdelhalim; Naeem, Zain Elabdin Metwally; Maatooq, Galal Taha; Amer, Mohamed Mahmoud Abdelfattah; Wen, Zhi-Hong; Sheu, Jyh-Horng; Ahmed, Atallah Fouad

2007-08-01

121

ELIGLUSTAT TARTRATE: Glucosylceramide Synthase Inhibitor Treatment of Type 1 Gaucher Disease.  

PubMed

Eliglustat tartrate (Genz-112638) is a novel, orally administered agent currently in development for the treatment of lysosomal storage disorders, including type 1 Gaucher disease and Fabry disease. This glucosylceramide analogue acts as an inhibitor of glucosylceramide synthase, a Golgi complex enzyme that catalyzes the formation of glucosylceramide from ceramide and UDP-glucose and is the first step in the formation of glucocerebroside-based glycosphingolipids. Pre-clinical pharmacological studies demonstrate that the agent has a high therapeutic index, excellent oral bioavailability and limited toxicity. Phase I studies in healthy volunteers revealed limited toxicity with an excellent pharmacodynamic response, as measured by decreased plasma glucosylceramide concentrations. Phase II studies in patients with type 1 Gaucher disease have demonstrated promising clinical responses, as measured by decreases in spleen size, improvement in hemoglobin concentrations and increased platelet counts. Two randomized phase III trials testing the efficacy and safety of eliglustat tartrate are currently in progress. PMID:22563139

Shayman, J A

2010-08-01

122

Synthesis of 2-arylindole derivatives and evaluation as nitric oxide synthase and NF?B inhibitors.  

PubMed

Development of small molecule drug-like inhibitors blocking both nitric oxide synthase and NF?B could offer a synergistic therapeutic approach in the prevention and treatment of inflammation and cancer. During the course of evaluating the biological potential of a commercial compound library, 2-phenylindole (1) displayed inhibitory activity against nitrite production and NF?B with IC(50) values of 38.1 ± 1.8 and 25.4 ± 2.1 ?M, respectively. Based on this lead, synthesis and systematic optimization have been undertaken in an effort to find novel and more potent nitric oxide synthase and NF?B inhibitors with antiinflammatory and cancer preventive potential. First, chemical derivatizations of 1 and 2-phenylindole-3-carboxaldehyde (4) were performed to generate a panel of N-alkylated indoles and 3-oxime derivatives 2–7. Second, a series of diversified 2-arylindole derivatives (10) were synthesized from an array of substituted 2-iodoanilines (8) and terminal alkynes (9) by applying a one-pot palladium catalyzed Sonogashira-type alkynylation and base-assisted cycloaddition. Subsequent biological evaluations revealed 3-carboxaldehyde oxime and cyano substituted 2-phenylindoles 5 and 7 exhibited the strongest nitrite inhibitory activities (IC(50) = 4.4 ± 0.5 and 4.8 ± 0.4 ?M, respectively); as well as NF?B inhibition (IC(50) = 6.9 ± 0.8 and 8.5 ± 2.0 ?M, respectively). In addition, the 6?-MeO-naphthalen-2?-yl indole derivative 10at displayed excellent inhibitory activity against NF?B with an IC(50) value of 0.6 ± 0.2 ?M. PMID:23044819

Yu, Xufen; Park, Eun-Jung; Kondratyuk, Tamara P; Pezzuto, John M; Sun, Dianqing

2012-11-28

123

First report on chitinous holdfast in sponges (Porifera).  

PubMed

A holdfast is a root- or basal plate-like structure of principal importance that anchors aquatic sessile organisms, including sponges, to hard substrates. There is to date little information about the nature and origin of sponges' holdfasts in both marine and freshwater environments. This work, to our knowledge, demonstrates for the first time that chitin is an important structural component within holdfasts of the endemic freshwater demosponge Lubomirskia baicalensis. Using a variety of techniques (near-edge X-ray absorption fine structure, Raman, electrospray ionization mas spectrometry, Morgan-Elson assay and Calcofluor White staining), we show that chitin from the sponge holdfast is much closer to ?-chitin than to ?-chitin. Most of the three-dimensional fibrous skeleton of this sponge consists of spicule-containing proteinaceous spongin. Intriguingly, the chitinous holdfast is not spongin-based, and is ontogenetically the oldest part of the sponge body. Sequencing revealed the presence of four previously undescribed genes encoding chitin synthases in the L. baicalensis sponge. This discovery of chitin within freshwater sponge holdfasts highlights the novel and specific functions of this biopolymer within these ancient sessile invertebrates. PMID:23677340

Ehrlich, Hermann; Kaluzhnaya, Oksana V; Tsurkan, Mikhail V; Ereskovsky, Alexander; Tabachnick, Konstantin R; Ilan, Micha; Stelling, Allison; Galli, Roberta; Petrova, Olga V; Nekipelov, Serguei V; Sivkov, Victor N; Vyalikh, Denis; Born, René; Behm, Thomas; Ehrlich, Andre; Chernogor, Lubov I; Belikov, Sergei; Janussen, Dorte; Bazhenov, Vasilii V; Wörheide, Gert

2013-05-15

124

2-Alkylaminoethyl-1,1-Bisphosphonic Acids Are Potent Inhibitors of the Enzymatic Activity of Trypanosoma cruzi Squalene Synthase  

PubMed Central

As part of our efforts aimed at searching for new antiparasitic agents, the effect of representative 2-alkylaminoethyl-1,1-bisphosphonic acids on Trypanosoma cruzi squalene synthase (TcSQS) was investigated. These compounds had proven to be potent inhibitors of T. cruzi. This cellular activity had been associated with an inhibition of the enzymatic activity of T. cruzi farnesyl diphosphate synthase. 2-Alkylaminoethyl-1,1-bisphosphonic acids appear to have a dual action, since they also inhibit TcSQS at the nanomolar range.

Rodrigues-Poveda, Carlos A.; Gonzalez-Pacanowska, Dolores; Szajnman, Sergio H.

2012-01-01

125

Identification of a Glycogen Synthase Kinase-3? Inhibitor that Attenuates Hyperactivity in CLOCK Mutant Mice  

PubMed Central

Bipolar disorder is characterized by a cycle of mania and depression, which affects approximately 5 million people in the United States. Current treatment regimes include the so-called “mood-stabilizing drugs”, such as lithium and valproate that are relatively dated drugs with various known side effects. Glycogen synthase kinase-3? (GSK-3?) plays a central role in regulating circadian rhythms, and lithium is known to be a direct inhibitor of GSK-3?. We designed a series of second generation benzofuran-3-yl-(indol-3-yl)maleimides containing a piperidine ring that possess IC50 values in the range of 4 to 680 nm against human GSK-3?. One of these compounds exhibits reasonable kinase selectivity and promising preliminary absorption, distribution, metabolism, and excretion (ADME) data. The administration of this compound at doses of 10 to 25 mgkg?1 resulted in the attenuation of hyperactivity in amphetamine/ chlordiazepoxide-induced manic-like mice together with enhancement of prepulse inhibition, similar to the effects found for valproate (400 mgkg?1) and the antipsychotic haloperidol (1 mgkg?1). We also tested this compound in mice carrying a mutation in the central transcriptional activator of molecular rhythms, the CLOCK gene, and found that the same compound attenuates locomotor hyperactivity in response to novelty. This study further demonstrates the use of inhibitors of GSK-3? in the treatment of manic episodes of bipolar/mood disorders, thus further validating GSK-3? as a relevant therapeutic target in the identification of new therapies for bipolar patients.

Kozikowski, Alan P.; Gunosewoyo, Hendra; Guo, Songpo; Gaisina, Irina N.; Walter, Richard L.; Ketcherside, Ariel; McClung, Colleen A.; Mesecar, Andrew D.; Caldarone, Barbara

2012-01-01

126

Glycogen Synthase Kinase 3 (GSK3) Inhibitor, SB-216763, Promotes Pluripotency in Mouse Embryonic Stem Cells  

PubMed Central

Canonical Wnt/?-catenin signaling has been suggested to promote self-renewal of pluripotent mouse and human embryonic stem cells. Here, we show that SB-216763, a glycogen synthase kinase-3 (GSK3) inhibitor, can maintain mouse embryonic stem cells (mESCs) in a pluripotent state in the absence of exogenous leukemia inhibitory factor (LIF) when cultured on mouse embryonic fibroblasts (MEFs). MESCs maintained with SB-216763 for one month were morphologically indistinguishable from LIF-treated mESCs and expressed pluripotent-specific genes Oct4, Sox2, and Nanog. Furthermore, Nanog immunostaining was more homogenous in SB-216763-treated colonies compared to LIF. Embryoid bodies (EBs) prepared from these mESCs expressed early-stage markers for all three germ layers, and could efficiently differentiate into cardiac-like cells and MAP2-immunoreactive neurons. To our knowledge, SB-216763 is the first GSK3 inhibitor that can promote self-renewal of mESC co-cultured with MEFs for more than two months.

Noble, Brenda L.; Mendez, Daniel C.; Caseley, Paul S.; Peterson, Sarah C.; Routledge, Tyler J.; Patel, Nilay V.

2012-01-01

127

Synergistic effect of CMP/KDO synthase inhibitors with antimicrobial agents on inhibition of production and release of Vero toxin by enterohaemorrhagic Escherichia coli O157:H7.  

PubMed

Synergistic effect of CMP/KDO synthase inhibitors in LPS biosynthesis of Gram-negative bacteria with kanamycin (KM) and fosfomycin (FOM) on the production and release of Vero toxins (VTs) by Escherichia coli O157 was evaluated in vitro. While CMP/KDO synthase inhibitors, KM and FOM showed no inhibitory effect on the production/release of VTs by themselves alone, both KM and FOM showed the remarkable inhibition of VT2 release through synergistic collaboration with CMP:KDO synthase inhibitor. PMID:14698183

Kondo, Ken-ichiro; Doi, Hiroyasu; Adachi, Hayamitsu; Nishimura, Yoshio

2004-01-19

128

Syntheses and herbicidal activity of new triazolopyrimidine-2-sulfonamides as acetohydroxyacid synthase inhibitor.  

PubMed

The triazolopyrimidine-2-sulfonanilide, discovered from preparing bioisosteres of the sulfonylurea herbicides, is an important class of acetohydroxyacid synthase (AHAS, EC 4.1.3.18) inhibitors. At least over ten triazolopyrimidine sulfonanilides have been commercialized as herbicides for the control of broadleaf weeds and grass with cereal crop selectivity. Herein, a series of triazolopyrimidine-2-sulfonanilides were designed and synthesized with the aim of discovery of new herbicides with higher activity. The assay results of the inhibition activity of the synthesized compounds against Arabidopsis thatiana AHAS indicated that some compounds showed a little higher activity against flumetsulam (FS), the first commercial triazolopyrimidine-2-sulfonanilide-type herbicide. The ki values of two promising compounds 3d and 8h are respectively, 1.61 and 1.29 microM, while that of FS is 1.85 microM. Computational simulation results indicated the ester group of compound 3d formed hydrogen bonds with the surrounding residues Arg'198 and Ser653, which accounts for its 11.5-folds higher AHAS inhibition activity than Y6610. Further green house assay showed that compound 3d has comparable herbicidal activity as FS. Even at the concentration of 37.5g.ai/ha, 3d showed excellent herbicidal activity against Galium aparine, Cerastium arvense, Chenopodium album, Amaranthus retroflexus, and Rmumex acetasa, moderate herbicidal activity against Polygonum humifusum, Cyperus iria, and Eclipta prostrate. The combination of in vitro and in vivo assay indicated that 3d could be regarded as a new potential acetohydroxyacid synthase-inhibiting herbicide candidate for further study. PMID:20598554

Chen, Chao-Nan; Chen, Qiong; Liu, Yu-Chao; Zhu, Xiao-Lei; Niu, Cong-Wei; Xi, Zhen; Yang, Guang-Fu

2010-06-11

129

The Chitin Connection  

PubMed Central

ABSTRACT Chitin, a polymer of N-acetylglucosamine, is an essential component of the fungal cell wall. Chitosan, a deacetylated form of chitin, is also important in maintaining cell wall integrity and is essential for Cryptococcus neoformans virulence. In their article, Gilbert et al. [N. M. Gilbert, L. G. Baker, C. A. Specht, and J. K. Lodge, mBio 3(1):e00007-12, 2012] demonstrate that the enzyme responsible for chitosan synthesis, chitin deacetylase (CDA), is differentially attached to the cell membrane and wall. Bioactivity is localized to the cell membrane, where it is covalently linked via a glycosylphosphatidylinositol (GPI) anchor. Findings from this study significantly enhance our understanding of cryptococcal cell wall biology. Besides the role of chitin in supporting structural stability, chitin and host enzymes with chitinase activity have an important role in host defense and modifying the inflammatory response. Thus, chitin appears to provide a link between the fungus and host that involves both innate and adaptive immune responses. Recently, there has been increased attention to the role of chitinases in the pathogenesis of allergic inflammation, especially asthma. We review these findings and explore the possible connection between fungal infections, the induction of chitinases, and asthma.

Goldman, David L.; Vicencio, Alfin G.

2012-01-01

130

The occurrence of chitin in the hemocytes of invertebrates  

PubMed Central

The light-organ symbiosis of Euprymna scolopes, the Hawaiian bobtail squid, is a useful model for the study of animal–microbe interactions. Recent analyses have demonstrated that chitin breakdown products play a role in communication between E. scolopes and its bacterial symbiont Vibrio fischeri. In this study, we sought to determine the source of chitin in the symbiotic organ. We used a commercially available chitin-binding protein (CBP) conjugated to fluorescein to label the polymeric chitin in host tissues. Confocal microscopy revealed that the only cells in contact with the symbionts that labeled with the probe were the macrophage-like hemocytes, which traffic into the light-organ crypts where the bacteria reside. Labeling of extracted hemocytes by CBP was markedly decreased following treatment with purified chitinase, providing further evidence that the labeled molecule is polymeric chitin. Further, CBP-positive areas co-localized with both a halide peroxidase antibody and Lysotracker, a lysosomal marker, suggesting that the chitin-like biomolecule occurs in the lysosome or acidic vacuoles. Reverse transcriptase polymerase chain reaction (PCR) of hemocytes revealed mRNA coding for a chitin synthase, suggesting that the hemocytes synthesize chitin de novo. Finally, upon surveying blood cells from other invertebrate species, we observed CBP-positive regions in all granular blood cells examined, suggesting that this feature is a shared character among the invertebrates; the vertebrate blood cells that we sampled did not label with CBP. Although the function of the chitin-like material remains undetermined, its presence and subcellular location in invertebrate hemocytes suggests a conserved role for this polysaccharide in the immune system of diverse animals.

Heath-Heckman, Elizabeth A.C.; McFall-Ngai, Margaret J.

2011-01-01

131

Chitin and chitosan from Basidiomycetes.  

PubMed

Chitinous material was isolated from the mycelium of seven species of Basidiomycetes to evaluate the possibility of using fungal biomass as a source of chitin and chitosan. Such material was characterised for its purity, degree of acetylation and crystallinity. Chitin yields ranged between 8.5 and 19.6% dry weight and the chitosan yield was approximately 1%. The characteristics of the fungal chitins were similar to those of commercial chitin. Chitosans, with a low degree of acetylation, comparable with that of commercial chitosan, were obtained by the chemical deacetylation of fungal chitins. PMID:18023863

Di Mario, F; Rapanŕ, P; Tomati, U; Galli, E

2007-10-09

132

Evaluation of BM573, a novel TXA 2 synthase inhibitor and receptor antagonist, in a porcine model of myocardial ischemia-reperfusion  

Microsoft Academic Search

AimsTo investigate whether BM-573 (N-tert-butyl-N?-[2-(4?-methylphenylamino)-5-nitro-benzenesulfonyl]urea), an original combined thromboxane A2 synthase inhibitor and receptor antagonist, prevents reperfusion injury in acutely ischemic pigs.

Philippe Kolh; Stéphanie Rolin; Vincent Tchana-Sato; Michel Pétein; Alexandre Ghuysen; Bernard Lambermont; Julien Hanson; David Magis; Patrick Segers; Bernard Masereel; Vincent D’Orio; Jean-Michel Dogne

2006-01-01

133

Protective effect of a novel and selective inhibitor of inducible nitric oxide synthase on experimental crescentic glomerulonephritis in WKY rats  

Microsoft Academic Search

Background. Nitric oxide (NO) plays important roles in a variety of pathophysiological processes. It has been reported that inducible NO synthase (iNOS) is upregulated in the glomeruli of patients with glomerulonephritis, although there has been no direct evidence that NO generated by iNOS contributes to the progression of glomerulonephritis. ONO-1714, a novel cyclic amidine analog, is a selective inhibitor of

Daisuke Ogawa; Kenichi Shikata; Mitsuhiro Matsuda; Shinichi Okada; Hitomi Usui; Jun Wada; Naoyuki Taniguchi; Hirofumi Makino

2002-01-01

134

Effect of centrally administered C75, a fatty acid synthase inhibitor, on gastric emptying and gastrointestinal transit in mice  

Microsoft Academic Search

The central or systemic administration of 3-carboxy-4-octyl-2-methylenebutyrolactone (C75), a synthetic inhibitor of fatty acid synthase (FAS), causes anorexia and profound weight loss in rodents. The amount of food intake and gastrointestinal mobility are closely related. In this study, an attempt has been made to investigate the effects and mechanisms of C75 on gastric emptying and gastrointestinal transit after intracerebroventricular (i.c.v.)

Lai-Fu Li; Yan-Yu Lu; Wei Xiong; Juan-Ying Liu; Qiang Chen

2008-01-01

135

Effects of nitric oxide synthase inhibitor N G-nitro- l-arginine methyl ester on spatial and cued leaning  

Microsoft Academic Search

An investigation was made of the effects of the nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME) on the acquisition and retention of two operantly conditioned discrimination tasks. Twenty Long–Evans rats were conditioned to approach one of two spatial locations that was either held constant across trials (spatial task) or was associated with a visual cue (illuminated lamp) that was

B. R Knepper; D. D Kurylo

1998-01-01

136

Identification of a Glycogen Synthase Kinase-3[beta] Inhibitor that Attenuates Hyperactivity in CLOCK Mutant Mice  

SciTech Connect

Bipolar disorder is characterized by a cycle of mania and depression, which affects approximately 5 million people in the United States. Current treatment regimes include the so-called 'mood-stabilizing drugs', such as lithium and valproate that are relatively dated drugs with various known side effects. Glycogen synthase kinase-3{beta} (GSK-3{beta}) plays a central role in regulating circadian rhythms, and lithium is known to be a direct inhibitor of GSK-3{beta}. We designed a series of second generation benzofuran-3-yl-(indol-3-yl)maleimides containing a piperidine ring that possess IC{sub 50} values in the range of 4 to 680 nM against human GSK-3{beta}. One of these compounds exhibits reasonable kinase selectivity and promising preliminary absorption, distribution, metabolism, and excretion (ADME) data. The administration of this compound at doses of 10 to 25 mg kg{sup -1} resulted in the attenuation of hyperactivity in amphetamine/chlordiazepoxide-induced manic-like mice together with enhancement of prepulse inhibition, similar to the effects found for valproate (400 mg kg{sup -1}) and the antipsychotic haloperidol (1 mg kg{sup -1}). We also tested this compound in mice carrying a mutation in the central transcriptional activator of molecular rhythms, the CLOCK gene, and found that the same compound attenuates locomotor hyperactivity in response to novelty. This study further demonstrates the use of inhibitors of GSK-3{beta} in the treatment of manic episodes of bipolar/mood disorders, thus further validating GSK-3{beta} as a relevant therapeutic target in the identification of new therapies for bipolar patients.

Kozikowski, Alan P.; Gunosewoyo, Hendra; Guo, Songpo; Gaisina, Irina N.; Walter, Richard L.; Ketcherside, Ariel; McClung, Colleen A.; Mesecar, Andrew D.; Caldarone, Barbara (Psychogenics); (Purdue); (UIC); (UTSMC)

2012-05-02

137

Nitric oxide synthase inhibitor attenuates the anorexigenic effect of corticotropin-releasing hormone in neonatal chicks.  

PubMed

Nitric oxide (NO) is known as an orexigenic factor in the brain of mammals and mediates the feeding-stimulatory effect of other factors such as neuropeptide Y (NPY). In neonatal chicks, however, we recently reported that NO might have an anorexigenic effect and suggested that the feeding-regulatory mechanism in chicks might be different from that in mammals regarding NO. In the present study, we investigated the involvement of NO in the effect of other orexigenic and anorexigenic factors in neonatal chicks. Intracerebroventricular co-injection of N(G)-nitro-l-arginine methyl ester (l-NAME), a NO synthase inhibitor, did not affect NPY- and prolactin-releasing peptide-induced feeding behavior. On the other hand, the co-injection of l-NAME significantly attenuated the anorexigenic effect of corticotropin-releasing hormone (CRH). The anorexigenic effects of glucagon-like peptide-1, alpha-melanocyte-stimulating hormone and ghrelin were not affected by the l-NAME treatment. These results suggest that NO might mediate the anorexigenic effect of CRH in the brain of neonatal chicks. PMID:18280762

Khan, Md Sakirul Islam; Nakano, Yasunori; Tachibana, Tetsuya; Ueda, Hiroshi

2008-01-17

138

Blockade of tolerance to morphine but not to kappa opioids by a nitric oxide synthase inhibitor.  

PubMed Central

The nitric oxide synthase inhibitor NG-nitro-L-arginine (NO2Arg) blocks morphine tolerance in mice. After implantation of morphine pellets the analgesic response decreases from 100% on the first day to 0% on the third. Coadministration of NO2Arg along with the pellets markedly retards the development of tolerance; 60% of mice are analgesic after 3 days, and 50% of mice are analgesic after 5 days. In a daily injection paradigm the analgesic response to morphine is reduced from 60% to 0% by 5 days. Concomitant administration of morphine along with NO2Arg at doses of 2 mg/kg per day prevents tolerance for 4 weeks. A single NO2Arg dose retards morphine tolerance for several days, and dosing every 4 days is almost as effective as daily NO2Arg. NO2Arg slowly reverses preexisting tolerance over 5 days despite the continued administration of morphine along with NO2Arg. NO2Arg also reduces dependence and reverses previously established dependence. NO2Arg does not prevent tolerance to analgesia mediated by the kappa 1 agonist trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolindinyl)cyclohexyl]- benzene-acetamide (U50,488H) or the kappa 3 agent naloxone benzoylhydrazone, indicating a selective action of NO in the mechanisms of mu tolerance and dependence.

Kolesnikov, Y A; Pick, C G; Ciszewska, G; Pasternak, G W

1993-01-01

139

Allosteric inhibitor specificity of Thermotoga maritima 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase.  

PubMed

3-Deoxy-D-arabino-heptulosonate 7-phosphate synthase (DAH7PS) catalyses the first step of the shikimate pathway for the biosynthesis of aromatic amino acids. Allosteric regulation of Thermotoga maritima DAH7PS is mediated by L-Tyr binding to a discrete ACT regulatory domain appended to a core catalytic (?/?)8 barrel. Variants of T. maritima DAH7PS (TmaDAH7PS) were created to probe the role of key residues in inhibitor selection. Substitution Ser31Gly severely reduced inhibition by L-Tyr. In contrast both L-Tyr and L-Phe inhibited the TmaHis29Ala variant, while the variant where Ser31 and His29 were interchanged (His29Ser/Ser31His), was inhibited to a greater extent by L-Phe than L-Tyr. These studies highlight the role and importance of His29 and Ser31 for determining both inhibitory ligand selectivity and the potency of allosteric response by TmaDAH7PS. PMID:23916814

Cross, Penelope J; Parker, Emily J

2013-07-31

140

[Effects of dimilin, a chitin inhibitor 1 (4 chlorophenyl) 3 (2-6 difluorobenzoyl) urea on the oenocytes and molting in the processionary caterpillar (Thaumetopoea pityocampa Schiff.) (Lepidoptera) (author's transl)].  

PubMed

Te oenocytes of the processionary caterpillar show histophysiological variations during their developing cycle. Grafting experiments and culture in vitro, have not so far allowed us to reveal the least participation of the oenocytes in the determinism of molting and in the transformation of cholesterol into ecdysone. On the other hand, histochemical studies of the oenocytes during the last period of their larval state, reveal, just before nymphosis, the existence of polysaccharides which probably correspond to the synthesis of pre-cuticular substance. When the caterpillars are treated with a chitin inhibitor (pH - 60-40 = Dimilin), the polysaccharides are not longer to be seen in the oenocytes. This deficiency in cuticular material could well be the consequence of one of the most spectacular effects of this product that is a profound perturbation in the formation of the cuticle that leads to the death of animals when molting. PMID:565611

Denneulin, J C; Lamy, M

1977-01-01

141

Identification of new inhibitors of E. coli cyclopropane fatty acid synthase using a colorimetric assay  

Microsoft Academic Search

Bacterial cyclopropane synthases catalyze the cyclopropanation of unsaturated fatty acids by transferring a methylene group from S-adenosyl-l-methionine (AdoMet) to the double bond of the lipids. Mycobacterium tuberculosis cyclopropane synthases have been shown to be implicated in pathogenicity, and therefore constitute attractive targets for the development of new drugs against tuberculosis. However, no in vitro assay for these cyclopropane synthases has

Dominique Guianvarc'h; Thierry Drujon; Thearina Ear Leang; Fabienne Courtois; Olivier Ploux

2006-01-01

142

Design of selective neuronal nitric oxide synthase inhibitors for the prevention and treatment of neurodegenerative diseases.  

PubMed

Nitric oxide (NO), which is produced from L-arginine by the nitric oxide synthase (NOS) family of enzymes, is an important second-messenger molecule that regulates several physiological functions. In endothelial cells, it relaxes smooth muscle, which decreases blood pressure. Macrophage cells produce NO as an immune defense system to destroy pathogens and microorganisms. In neuronal cells, NO controls the release of neurotransmitters and is involved in synaptogenesis, synaptic plasticity, memory function, and neuroendocrine secretion. NO is a free radical that is commonly thought to contribute to oxidative damage and molecule and tissue destruction, and thus it is somewhat surprising that it has so many significant beneficial physiological effects. However, the cell is generally protected from NO's toxic effects, except under certain pathological conditions in which excessive NO is produced. In that case, tissue damage and oxidative stress can result, leading to a wide variety of diseases, including rheumatoid arthritis, Alzheimer's disease, and Parkinson's disease, among others. In this Account, we describe research aimed at identifying small molecules that can selectively inhibit only the neuronal isozyme of NOS, nNOS. By targeting only nNOS, we attained the beneficial effects of lowering excess NO in the brain without the detrimental effects of inhibition of the two isozymes found elsewhere in the body (eNOS and iNOS). Initially, in pursuit of this goal, we sought to identify differences in the second sphere of amino acids in the active site of the isozymes. From this study, the first class of dual nNOS-selective inhibitors was identified. The moieties important for selectivity in the best lead compound were determined by structure modification. Enhancement provided highly potent, nNOS-selective dipeptide amides and peptidomimetics, which were active in a rabbit model for fetal neurodegeneration. Crystal structures of these compounds bound to NOS isozymes showed a one-amino-acid difference between nNOS and eNOS in the second sphere of amino acids; this was the difference that we were searching for from the beginning of this project. With the aid of these crystal structures, we developed a new fragment-based de novo design method called "fragment hopping", which allowed the design of a new class of nonpeptide nNOS-selective inhibitors. These compounds were modified to give low nanomolar, highly dual-selective nNOS inhibitors, which we recently showed are active in a rabbit model for the prevention of neurobehavioral symptoms of cerebral palsy. These compounds could also have general application in other neurodegenerative diseases for which excess NO is responsible. PMID:19154146

Silverman, Richard B

2009-03-17

143

Histone deacetylase inhibitors stimulate mitochondrial HMG-CoA synthase gene expression via a promoter proximal Sp1 site  

PubMed Central

The expression of mitochondrial HMG-CoA synthase in the colon has been correlated with the levels of butyrate present in this tissue. We report here that the effect of butyrate on mitochondrial HMG-CoA synthase gene expression is exerted in vivo at the transcriptional level, and that trichostatin A (TSA), a specific histone deacetylase inhibitor, also induces transcriptional activity and mRNA expression of the gene in human cell lines derived from colon carcinoma. Using chromatin immunoprecipitation assays, we show that histone deacetylase 1 (HDAC1) is associated with the endogenous mitochondrial HMG-CoA synthase promoter and that TSA induction correlates with hyperacetylation of H4 histone associated with the 5? flanking region of the gene. Overexpression of HDAC1 activity leads consistently to mitochondrial HMG-CoA synthase promoter hypoacetylation and reduces its transcriptional activity. The effect of butyrate and TSA maps to a single Sp1 site present in the proximal promoter of the gene, which is able to bind Sp1 and Sp3 proteins. Interestingly, the binding affinity of Sp1 and Sp3 proteins to the Sp1 site correlates with the TSA responsiveness of the promoter. Using a one-hybrid system (GAL4-Sp1 and GAL4-Sp3), we show that both proteins can mediate responsiveness to TSA in CaCo-2 cells employing distinct mechanisms.

Camarero, Nuria; Nadal, Alicia; Barrero, Maria Jose; Haro, Diego; Marrero, Pedro F.

2003-01-01

144

Method of enhancing degradation of chitin  

US Patent & Trademark Office Database

The present invention provides a method of enhancing chitin degradation or weakening the structure of a chitin substrate comprising exposing chitin to a non-hydrolytic chitin binding protein (CBP). The invention further provides a method of enhancing chitin degradation comprising exposing chitin to a non-hydrolytic CBP and a chitin hydrolase. Compositions, including fungicides, comprising non-hydrolytic CBPs and transgenic plants comprising exogenous nucleic acid molecules encoding a non-hydrolytic CBP are also provided.

2013-02-19

145

SIN-1 reverses attenuation of hypercapnic cerebrovasodilation by nitric oxide synthase inhibitors.  

PubMed

We sought to determine whether the attenuation of the hypercapnic cerebrovasodilation associated with inhibition of nitric oxide synthase (NOS) can be reversed by exogenous NO. Rats were anesthetized (halothane) and ventilated. Neocortical cerebral blood flow (CBF) was monitored by a laser-Doppler probe. The NOS inhibitor N omega-nitro-L-arginine methyl ester (L-NAME; 40 mg/kg iv) reduced resting CBF [-36 +/- 5% (SE); P < 0.01, analysis of variance] and attenuated the increase in CBF elicited by hypercapnia (partial pressure of CO2 = 50-60 mmHg) by 66% (P < 0.01). L-NAME reduced forebrain NOS catalytic activity by 64 +/- 3% (n = 10; P < 0.001). After L-NAME, intracarotid infusion of the NO donor 3-morpholinosydnonimine (SIN-1; n = 6) increased resting CBF and reestablished the CBF increase elicited by hypercapnia (P > 0.05 from before L-NAME). Similarly, infusion of the guanosine 3',5'-cyclic monophosphate (cGMP) analogue 8-bromo-cGMP (n = 6) reversed the L-NAME-induced attenuation of the hypercapnic cerebrovasodilation. The NO-independent vasodilator papaverine (n = 6) increased resting CBF but did not reverse the attenuation of the CO2 response. SIN-1 did not affect the attenuation of the CO2 response induced by indomethacin (n = 6). The observation that NO donors reverse the L-NAME-induced attenuation of the CO2 response suggests that a basal level of NO is required for the vasodilation to occur. The findings are consistent with the hypothesis that NO is not the final mediator of smooth muscle relaxation in hypercapnia.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7519410

Iadecola, C; Zhang, F; Xu, X

1994-07-01

146

Fire ant venom alkaloid, isosolenopsin A, a potent and selective inhibitor of neuronal nitric oxide synthase.  

PubMed

Massive, multiple fire ant, Solenopsis invicta, stings are often treated aggressively, particularly in the elderly, despite limited evidence of systemic toxicity due to the venom. Over 95% of the S. invicta venom is composed of piperidine alkaloid components, whose toxicity, if any, is unknown. To assess a possible pharmacological basis for systemic toxicity, an alkaloid-rich, protein-free methanol extract of the venom from whole ants was assayed for inhibitory activity on the following nitric oxide synthase (NOS) isoforms, rat cerebellar neuronal (nNOS), bovine recombinant endothelial (eNOS), and murine recombinant immunologic (iNOS). Cytosolic NOS activity was determined by measuring the conversion of [(3)H]arginine to [(3)H]citrulline in vitro. Rat nNOS activity was inhibited significantly and in a concentration-dependent manner by the alkaloid-rich venom extract. For nNOS, enzyme activity was inhibited by approximately 50% with 0.33 +/- 0.06 microg of this venom extract, and over 95% inhibition of the three isoforms, nNOS, eNOS, and iNOS, was found with doses of 60 microg in 60 microl reaction mixture. These results indicate that the alkaloid components of S. invicta venom can produce potent inhibition of all three major NOS isoforms. Isosolenopsin A (cis-2-methyl-6-undecylpiperidine), a naturally occurring fire ant piperidine alkaloid, was synthesized and tested for inhibitory activity against the three NOS isoforms. Enzyme activities for nNOS and eNOS were over 95% inhibited with 1000 microM of isosolenopsin A, whereas the activity of iNOS was inhibited by only about 20% at the same concentration. The IC(50) for each of three NOS isoforms was approximately 18 +/- 3.9 microM for nNOS, 156 +/- 10 microM for eNOS, and >1000 microM for iNOS, respectively. Kinetic studies showed isosolenopsin A inhibition to be noncompetitive with L-arginine (K(i) = 19 +/- 2 microM). The potency of isosolenopsin A as an inhibitor of nNOS compares favorably with the inhibitory potency of widely used nNOS inhibitors. Inhibition of NOS isoforms by isosolenopsin A and structurally similar compounds may have toxicological significance with respect to adverse reactions to fire ant stings. PMID:12745988

Yi, G B; McClendon, D; Desaiah, D; Goddard, J; Lister, A; Moffitt, J; Meer, R K Vander; deShazo, R; Lee, K S; Rockhold, R W

147

Synthesis and evaluation of M. tuberculosis salicylate synthase (MbtI) inhibitors designed to probe plasticity in the active site.  

PubMed

Mycobacterium tuberculosis salicylate synthase (MbtI) catalyses the first committed step in the biosynthesis of mycobactin T, an iron-chelating siderophore essential for the virulence and survival of M. tuberculosis. Co-crystal structures of MbtI with members of a first generation inhibitor library revealed large inhibitor-induced rearrangements within the active site of the enzyme. This plasticity of the MbtI active site was probed via the preparation of a library of inhibitors based on a 2,3-dihydroxybenzoate scaffold with a range of substituted phenylacrylate side chains appended to the C3 position. Most compounds exhibited moderate inhibitory activity against the enzyme, with inhibition constants in the micromolar range, while several dimethyl ester variants possessed promising anti-tubercular activity in vitro. PMID:23108268

Manos-Turvey, Alexandra; Cergol, Katie M; Salam, Noeris K; Bulloch, Esther M M; Chi, Gamma; Pang, Angel; Britton, Warwick J; West, Nicholas P; Baker, Edward N; Lott, J Shaun; Payne, Richard J

2012-10-29

148

Chitin Biotechnology Applications  

Microsoft Academic Search

This review article describes the current status of the production and consumption of chitin and chitosan, and their current practical applications in biotechnology with some attempted uses. The applications include: 1) cationic agents for polluted waste-water treatment, 2) agricultural materials, 3) food and feed additives, 4) hypocholesterolemic agents, 5) biomedical and pharmaceutical materials, 6) wound-healing materials, 7) blood anticoagulant, antithrombogenic

Shigehiro Hirano

1996-01-01

149

Chitin Nanowhisker Aerogels  

PubMed Central

Chitin nanowhiskers are structured into mesoporous aerogels by using the same benign process used previously in our group to make cellulose nanowhisker aerogels. The nanowhiskers are sonicated in water to form a hydrogel before solvent-exchange with ethanol and drying under supercritical CO2 (scCO2). Aerogels are prepared with various densities and porosities, relating directly to the initial chitin nanowhisker content. scCO2 drying enables the mesoporous network structure to be retained as well as allowing the gel to retain its initial dimensions. The chitin aerogels have low densities (0.043–0.113 g cm?3), high porosities (up to 97 %), surface areas of up to 261 m2 g?1, and mechanical properties at the high end of other reported values (modulus between 7 and 9.3 MPa). The aerogels were further characterized by using X-ray diffraction, BET analysis, electron microscopy, FTIR, and thermogravimetric analysis. Characterization showed that the rod-like crystalline nature of the nanowhiskers was retained during the aerogel production process, making the aerogel truly an assembled structure of chitin nanocrystals. These aerogels also showed the lowest reported shrinkage during drying to date, with an average shrinkage of only 4 %.

Heath, Lindy; Zhu, Lifan; Thielemans, Wim

2013-01-01

150

Lipophilic Bisphosphonates as Dual Farnesyl/Geranylgeranyl Diphosphate Synthase Inhibitors: An X-ray and NMR Investigation  

PubMed Central

Considerable effort has focused on the development of selective protein farnesyl transferase (FTase) and protein geranylgeranyl transferase (GGTase) inhibitors as cancer chemotherapeutics. Here, we report a new strategy for anti-cancer therapeutic agents involving inhibition of farnesyl diphosphate synthase (FPPS) and geranylgeranyl diphosphate synthase (GGPPS), the two enzymes upstream of FTase and GGTase, by lipophilic bisphosphonates. Due to dual site targeting and decreased polarity, the compounds have activities far greater than do current bisphosphonate drugs in inhibiting tumor cell growth and invasiveness, both in vitro and in vivo. We explore how these compounds inhibit cell growth, how cell activity can be predicted based on enzyme inhibition data, and, using x-ray diffraction, solid state NMR and isothermal titration calorimetry, we show how these compounds bind to FPPS and/or GGPPS.

Zhang, Yonghui; Cao, Rong; Yin, Fenglin; Hudock, Michael P.; Guo, Rey-Ting; Krysiak, Kilannin; Mukherjee, Sujoy; Gao, Yi-Gui; Robinson, Howard; Song, Yongcheng; No, Joo Hwan; Bergan, Kyle; Leon, Annette; Cass, Lauren; Goddard, Amanda; Chang, Ting-Kai; Lin, Fu-Yang; Van Beek, Ermond; Papapoulos, Socrates; Wang, Andrew H.-J.; Kubo, Tadahiko; Ochi, Mitsuo; Mukkamala, Dushyant; Oldfield, Eric

2009-01-01

151

Implications of binding mode and active site flexibility for inhibitor potency against the salicylate synthase from Mycobacterium tuberculosis.  

PubMed

MbtI is the salicylate synthase that catalyzes the first committed step in the synthesis of the iron chelating compound mycobactin in Mycobacterium tuberculosis. We previously developed a series of aromatic inhibitors against MbtI based on the reaction intermediate for this enzyme, isochorismate. The most potent of these inhibitors had hydrophobic substituents, ranging in size from a methyl to a phenyl group, appended to the terminal alkene of the enolpyruvyl group. These compounds exhibited low micromolar inhibition constants against MbtI and were at least an order of magnitude more potent than the parental compound for the series, which carries a native enolpyruvyl group. In this study, we sought to understand how the substituted enolpyruvyl group confers greater potency, by determining cocrystal structures of MbtI with six inhibitors from the series. A switch in binding mode at the MbtI active site is observed for inhibitors carrying a substituted enolpyruvyl group, relative to the parental compound. Computational studies suggest that the change in binding mode, and higher potency, is due to the effect of the substituents on the conformational landscape of the core inhibitor structure. The crystal structures and fluorescence-based thermal shift assays indicate that substituents larger than a methyl group are accommodated in the MbtI active site through significant but localized flexibility in the peptide backbone. These findings have implications for the design of improved inhibitors of MbtI, as well as other chorismate-utilizing enzymes from this family. PMID:22607697

Chi, Gamma; Manos-Turvey, Alexandra; O'Connor, Patrick D; Johnston, Jodie M; Evans, Genevieve L; Baker, Edward N; Payne, Richard J; Lott, J Shaun; Bulloch, Esther M M

2012-06-07

152

A novel bisphosphonate inhibitor of squalene synthase combined with a statin or a nitrogenous bisphosphonate in vitro[S  

PubMed Central

Statins and nitrogenous bisphosphonates (NBP) inhibit 3-hydroxy-3-methylglutaryl-coenzyme-A reductase (HMGCR) and farnesyl diphosphate synthase (FDPS), respectively, leading to depletion of farnesyl diphosphate (FPP) and disruption of protein prenylation. Squalene synthase (SQS) utilizes FPP in the first committed step from the mevalonate pathway toward cholesterol biosynthesis. Herein, we have identified novel bisphosphonates as potent and specific inhibitors of SQS, including the tetrasodium salt of 9-biphenyl-4,8-dimethyl-nona-3,7-dienyl-1,1-bisphosphonic acid (compound 5). Compound 5 reduced cholesterol biosynthesis and lead to a substantial intracellular accumulation of FPP without reducing cell viability in HepG2 cells. At high concentrations, lovastatin and zoledronate impaired protein prenylation and decreased cell viability, which limits their potential use for cholesterol depletion. When combined with lovastatin, compound 5 prevented lovastatin-induced FPP depletion and impairment of protein farnesylation. Compound 5 in combination with the NBP zoledronate completely prevented zoledronate-induced impairment of both protein farnesylation and geranylgeranylation. Cotreatment of cells with compound 5 and either lovastatin or zoledronate was able to significantly prevent the reduction of cell viability caused by lovastatin or zoledronate alone. The combination of an SQS inhibitor with an HMGCR or FDPS inhibitor provides a rational approach for reducing cholesterol synthesis while preventing nonsterol isoprenoid depletion.

Wasko, Brian M.; Smits, Jacqueline P.; Shull, Larry W.; Wiemer, David F.; Hohl, Raymond J.

2011-01-01

153

Saccharomyces cerevisiae chitin biosynthesis activation by N-acetylchitooses depends on size and structure of chito-oligosaccharides  

PubMed Central

Background To explore chitin synthesis initiation, the effect of addition of exogenous oligosaccharides on in vitro chitin synthesis was studied. Oligosaccharides of various natures and lengths were added to a chitin synthase assay performed on a Saccharomyces cerevisiae membrane fraction. Findings N-acetylchito-tetra, -penta and -octaoses resulted in 11 to 25% [14C]-GlcNAc incorporation into [14C]-chitin, corresponding to an increase in the initial velocity. The activation appeared specific to N-acetylchitooses as it was not observed with oligosaccharides in other series, such as beta-(1,4), beta-(1,3) or alpha-(1,6) glucooligosaccharides. Conclusions The effect induced by the N-acetylchitooses was a saturable phenomenon and did not interfere with free GlcNAc and trypsin which are two known activators of yeast chitin synthase activity in vitro. The magnitude of the activation was dependent on both oligosaccharide concentration and oligosaccharide size.

2011-01-01

154

Inhibition of 3-hydroxy-3-methylglutaryl-CoA synthase and cholesterol biosynthesis by beta-lactone inhibitors and binding of these inhibitors to the enzyme.  

PubMed Central

The beta-lactones L-659,699 [(E,E)-11-[3-(hydroxymethyl)-4-oxo-2- oxetanyl]-3,5,7-trimethyl-2,4-undecadienoic acid) and its radioactive derivative 3H-L-668,411 (the 2,3-ditritiated methyl ester of L-659,699) inhibited a partially purified preparation of rat liver cytosolic 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase with an IC50 of 0.1 microM. These compounds were also found to inhibit the incorporation of [14C]acetate into sterols in cultured Hep G2 cells with an IC50 of 3 microM. New kinetic evidence indicated that inhibition of the isolated enzyme was irreversible. In contrast, sterol biosynthesis in cultured Hep G2 cells was rapidly restored upon removal of the compound from the medium of inhibited cultures, suggesting reversibility of inhibition in the cells. Radioactivity was found to be associated with a single cytoplasmic protein by SDS/PAGE of the cytoplasm of Hep G2 cells after incubation of the cells with the inhibitor 3H-L-668,411. This protein was identified as cytoplasmic HMG-CoA synthase. Binding of the radioactive compound to the enzyme was decreased with time if the radioactive inhibitor was removed from the medium. Exposure of a gel containing the radioactive enzyme-inhibitor complex to neutral hydroxylamine also resulted in a loss of radioactivity from the gel. The purified rat liver enzyme reacted with the 3H-ligand to form a stable enzyme-inhibitor complex which could be isolated by h.p.l.c. Radioactivity was also subsequently lost from this complex when it was incubated with neutral hydroxylamine. Incorporation of [14C]acetate into cholesterol in mouse liver was inhibited in a reversible manner after oral administration of the beta-lactone inhibitor. These studies, as well as the kinetic evidence presented, suggest that the beta-lactone inhibitors acylate HMG-CoA synthase in a reaction which appears to be irreversible in vitro, but is easily reversed in cultured cells and in animals. Images Figure 5

Greenspan, M D; Bull, H G; Yudkovitz, J B; Hanf, D P; Alberts, A W

1993-01-01

155

Phosphorylation of inhibitor-2 and activation of MgATP-dependent protein phosphatase by rat skeletal muscle glycogen synthase kinase  

SciTech Connect

Rat skeletal muscle contains a glycogen synthase kinase (GSK-M) which is not stimulated by Ca/sup 2 +/ or cAMP. This kinase has an apparent Mr of 62,000 and uses ATP but not GTP as a phosphoryl donor. GSK-M phosphorylated glycogen synthase at sites 2 and 3. It phosphorylated ATP-citrate lyase and activated MgATP-dependent phosphatase in the presence of ATP but not GTP. As expected, the kinase also phosphorylated phosphatase inhibitor 2 (I-2). Phosphatase incorporation reached approximately 0.3 mol/mol of I-2. Phosphopeptide maps were obtained by digesting /sup 32/P-labeled I-2 with trypsin and separating the peptides by reversed phase HPLC. Two partially separated /sup 32/P-labeled peaks were obtained when I-2 was phosphorylated with either GSK-M or glycogen synthase kinase 3 (GSK-3) and these peptides were different from those obtained when I-2 was phosphorylated with the catalytic subunit of cAMP-dependent protein kinase (CSU) or casein kinase II (CK-II). When I-2 was phosphorylated with GSK-M or GSK-3 and cleaved by CNBr, a single radioactive peak was obtained. Phosphoamino acid analysis showed that I-2 was phosphorylated by GSK-M or GSK-3 predominately in Thr whereas CSU and CK-II phosphorylated I-2 exclusively in Ser. These results indicate that GSK-M is similar to GSK-3 and to ATP-citrate lyase kinase. However, it appears to differ in Mr from ATP-citrate lyase kinase and it differs from GSK-3 in that it phosphorylates glycogen synthase at site 2 and it does not use GTP as a phosphoryl donor.

Hegazy, M.G.; Reimann, E.M.; Thysseril, T.J.; Schlender, K.K.

1986-05-01

156

Anti-obesity effects of 3-hydroxychromone derivative, a novel small-molecule inhibitor of glycogen synthase kinase-3.  

PubMed

Glycogen synthase kinase 3 (GSK-3) plays a central role in cellular energy metabolism, and dysregulation of GSK-3 activity is implicated in a variety of metabolic disorders, including obesity, type 2 diabetes, and cancer. Hence, GSK-3 has emerged as an attractive target molecule for the treatment of metabolic disorders. Therefore, this research focused on identification and characterization of a novel small-molecule GSK-3 inhibitor. Compound 1a, a structure based on 3-hydroxychromone bearing isothiazolidine-1,1-dione, was identified from chemical library as a highly potent GSK-3 inhibitor. An in vitro kinase assay utilizing a panel of kinases demonstrated that compound 1a strongly inhibits GSK-3?. The potential effects of compound 1a on the inactivation of GSK-3 were confirmed in human liver HepG2 and human embryonic kidney HEK293 cells. Stabilization of glycogen synthase and ?-catenin, which are direct targets of GSK-3, by compound 1a was assessed in comparison with two other GSK-3 inhibitors: LiCl and SB-415286. In mouse 3T3-L1 preadipocytes, compound 1a markedly blocked adipocyte differentiation. Consistently, intraperitoneal administration of compound 1a to diet-induced obese mice significantly ameliorated their key symptoms such as body weight gain, increased adiposity, dyslipidemia, and hepatic steatosis due to the marked reduction of whole-body lipid level. In vitro and in vivo effects were accompanied by upregulation of ?-catenin stability and downregulation of the expression of several critical genes related to lipid metabolism. From these results, it can be concluded that compound 1a, a novel small-molecule inhibitor of GSK-3, has potential as a new class of therapeutic agent for obesity treatment. PMID:23337568

Lee, Sooho; Yang, Woo Kyeom; Song, Ji Ho; Ra, Young Min; Jeong, Jin-Hyun; Choe, Wonchae; Kang, Insug; Kim, Sung-Soo; Ha, Joohun

2013-01-18

157

Protective effects of a squalene synthase inhibitor, lapaquistat acetate (TAK-475), on statin-induced myotoxicity in guinea pigs  

SciTech Connect

High-dose statin treatment has been recommended as a primary strategy for aggressive reduction of LDL cholesterol levels and protection against coronary artery disease. The effectiveness of high-dose statins may be limited by their potential for myotoxic side effects. There is currently little known about the molecular mechanisms of statin-induced myotoxicity. Previously we showed that T-91485, an active metabolite of the squalene synthase inhibitor lapaquistat acetate (lapaquistat: a previous name is TAK-475), attenuated statin-induced cytotoxicity in human skeletal muscle cells [Nishimoto, T., Tozawa, R., Amano, Y., Wada, T., Imura, Y., Sugiyama, Y., 2003a. Comparing myotoxic effects of squalene synthase inhibitor, T-91485, and 3-hydroxy-3-methylglutaryl coenzyme A. Biochem. Pharmacol. 66, 2133-2139]. In the current study, we investigated the effects of lapaquistat administration on statin-induced myotoxicity in vivo. Guinea pigs were treated with either high-dose cerivastatin (1 mg/kg) or cerivastatin together with lapaquistat (30 mg/kg) for 14 days. Treatment with cerivastatin alone decreased plasma cholesterol levels by 45% and increased creatine kinase (CK) levels by more than 10-fold (a marker of myotoxicity). The plasma CK levels positively correlated with the severity of skeletal muscle lesions as assessed by histopathology. Co-administration of lapaquistat almost completely prevented the cerivastatin-induced myotoxicity. Administration of mevalonolactone (100 mg/kg b.i.d.) prevented the cerivastatin-induced myotoxicity, confirming that this effect is directly related to HMG-CoA reductase inhibition. These results strongly suggest that cerivastatin-induced myotoxicity is due to depletion of mevalonate derived isoprenoids. In addition, squalene synthase inhibition could potentially be used clinically to prevent statin-induced myopathy.

Nishimoto, Tomoyuki; Ishikawa, Eiichiro [Pharmacology Research Laboratories I, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka 532-8686 (Japan); Anayama, Hisashi; Hamajyo, Hitomi; Nagai, Hirofumi [Development Research Center, Takeda Pharmaceutical Company Limited, 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka 532-8686 (Japan); Hirakata, Masao [Pharmacology Research Laboratories I, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka 532-8686 (Japan); Tozawa, Ryuichi [Pharmacology Research Laboratories I, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka 532-8686 (Japan)], E-mail: Ryuichi_Tozawa@takeda.co.jp

2007-08-15

158

The current state of resistance to acetohydroxyacid/acetolactate synthase inhibitors  

Technology Transfer Automated Retrieval System (TEKTRAN)

The acetohydroxyacid/acetolactate synthase (ALS) inhibiting herbicides are used for weed management in multiple crop and non-crop situations. Herbicides with this mechanism of action were introduced in the early 1980s and quickly came to dominate many cropping situations due to their broad spectrum...

159

Mass Spectrometry-Based Systems Approach for Identification of Inhibitors of Plasmodium falciparum Fatty Acid Synthase  

Microsoft Academic Search

The emergence of strains of Plasmodium falciparum resistant to the commonly used antimalarials warrants the development of new antimalarial agents. The discovery of type II fatty acid synthase (FAS) in Plasmodium distinct from the FAS in its human host (type I FAS) opened up new avenues for the development of novel antimalarials. The process of fatty acid synthesis takes place

Shilpi Sharma; Shailendra Kumar Sharma; Rahul Modak; K. Karmodiya; N. Surolia; A. Surolia

2007-01-01

160

Transmembrane BAX Inhibitor Motif Containing (TMBIM) Family Proteins Perturbs a trans-Golgi Network Enzyme, Gb3 Synthase, and Reduces Gb3 Biosynthesis*  

PubMed Central

Globotriaosylceramide (Gb3) is a well known receptor for Shiga toxin (Stx), produced by enterohemorrhagic Escherichia coli and Shigella dysenteriae. The expression of Gb3 also affects several diseases, including cancer metastasis and Fabry disease, which prompted us to look for factors involved in its metabolism. In the present study, we isolated two cDNAs that conferred resistance to Stx-induced cell death in HeLa cells by expression cloning: ganglioside GM3 synthase and the COOH terminus region of glutamate receptor, ionotropic, N-methyl-d-asparate-associated protein 1 (GRINA), a member of the transmembrane BAX inhibitor motif containing (TMBIM) family. Overexpression of the truncated form, named GRINA-C, and some members of the full-length TMBIM family, including FAS inhibitory molecule 2 (FAIM2), reduced Gb3, and lactosylceramide was accumulated instead. The change of glycolipid composition was restored by overexpression of Gb3 synthase, suggesting that the synthase is affected by GRINA-C and FAIM2. Interestingly, the mRNA level of Gb3 synthase was unchanged. Rather, localization of the synthase as well as TGN46, a trans-Golgi network marker, was perturbed to form punctate structures, and degradation of the synthase in lysosomes was enhanced. Furthermore, GRINA-C was associated with Gb3 synthase. These observations may demonstrate a new type of posttranscriptional regulation of glycosyltransferases.

Yamaji, Toshiyuki; Nishikawa, Kiyotaka; Hanada, Kentaro

2010-01-01

161

Combined treatment of ascorbic acid or alpha-tocopherol with dopamine receptor antagonist or nitric oxide synthase inhibitor potentiates cataleptic effect in mice  

Microsoft Academic Search

Rationale  Drugs like haloperidol (Hal) that decrease dopamine (DA) neurotransmission in the striatum induce catalepsy in rodents and\\u000a Parkinson disease-like symptoms in humans. Nitric oxide synthase (NOS) inhibitors interfere with motor activity, disrupting\\u000a rodent exploratory behavior and inducing catalepsy. Catalepsy induced by NOS inhibitors probably involves striatal DA-mediated\\u000a neurotransmission. Antioxidants such as ascorbic acid (vitamin C) and alpha-tocopherol (vitamin E) have

M. Lazzarini; C. Salum; E. A. Del Bel

2005-01-01

162

Identification of inhibitors of the E. coli cyclopropane fatty acid synthase from the screening of a chemical library: In vitro and in vivo studies  

Microsoft Academic Search

Using an automated coupled colorimetric assay for the Escherichia coli cyclopropane fatty acid synthase (CFAS), we have screened an academic chemical library of 3040 compounds, to identify new inhibitors of this enzyme. We identified 8 compounds as potent inhibitors of this enzyme, with IC50 ranging from 1 to 10 µM, in the presence of 750 µM S-adenosyl-l-methionine and 1 mg\\/mL phospholipids. We conducted

Dominique Guianvarc'h; Guangqi E; Thierry Drujon; Camille Rey; Qian Wang; Olivier Ploux

2008-01-01

163

The crystal structure of spermidine synthase with a multisubstrate adduct inhibitor  

Microsoft Academic Search

Polyamines are essential in all branches of life. Spermidine synthase (putrescine aminopropyltransferase, PAPT) catalyzes the biosynthesis of spermidine, a ubiquitous polyamine. The crystal structure of the PAPT from Thermotoga maritima (TmPAPT) has been solved to 1.5 Angstroms resolution in the presence and absence of AdoDATO (S-adenosyl-1,8-diamino-3-thiooctane), a compound containing both substrate and product moieties. This, the first structure of an

Sergey Korolev; Yoshihiko Ikeguchi; Tatiana Skarina; Steven Beasley; Cheryl Arrowsmith; Alexei Savchenko; Aled Edwards; Andrzej Joachimiak; Anthony E. Pegg

2001-01-01

164

Selective small molecule inhibitors of glycogen synthase kinase-3 modulate glycogen metabolism and gene transcription  

Microsoft Academic Search

Background: Glycogen synthase kinase-3 (GSK-3) is a serine\\/threonine protein kinase, the activity of which is inhibited by a variety of extracellular stimuli including insulin, growth factors, cell specification factors and cell adhesion. Consequently, inhibition of GSK-3 activity has been proposed to play a role in the regulation of numerous signalling pathways that elicit pleiotropic cellular responses. This report describes the

Matthew P Coghlan; Ainsley A Culbert; Darren AE Cross; Stacey L Corcoran; John W Yates; Nigel J Pearce; Oliver L Rausch; Gregory J Murphy; Paul S Carter; Lynne Roxbee Cox; David Mills; Murray J Brown; David Haigh; Robert W Ward; David G Smith; Kenneth J Murray; Alastair D Reith; Julie C Holder

2000-01-01

165

Sensitive Assay for Antifungal Activity of Glucan Synthase Inhibitors That Uses Germ Tube Formation in Candida albicans as an End Point  

Microsoft Academic Search

We implemented a simple, sensitive, objective, and rapid cellular assay to reveal the antifungal activity of a novel class of glucan synthase inhibitors. The assay, especially useful for early drug discovery, measures the transformation of Candida albicans from the yeast form to the hyphal form. Test compounds were ranked by potency (50% inhibitory concentration) and efficacy (percent inhibition of germ

Timothy G. Brayman; John W. Wilks

2003-01-01

166

N~-Amino-t-Arginine, an Inhibitor of Nitric Oxide Synthase, Raises Vascular Resistan_ce but Increases Mortality Rates in Awake Canines Challenged with Endotoxin  

Microsoft Academic Search

Sllmmary Inhibitors of nitric oxide synthase (NOS) have been reported to increase mean arterial pressure in animal models of sepsis and recently have been given to patients in septic shock. However, controlled studies to determine the effects of these agents on cardiovascular function and survival in awake animal models of sepsis have not been reported. To examine the therapeutic potential

J. Perren Cobb; Charles Natanson; William D. Hoffman; Robert F. Lodato; Cesar A. Koev; Michael A. Solomon; Ronald J. Elin; Jeanette M. Hosseini

1992-01-01

167

3,5-Disubstituted indole derivatives as selective human neuronal nitric oxide synthase (nNOS) inhibitors.  

PubMed

A series of 3,5-disubstituted indole derivatives was designed, synthesized and evaluated as inhibitors of human nitric oxide synthase (NOS). Various guanidine isosteric groups were explored at the 5-position of the indole ring, while keeping the basic amine side chain such as N-methylpiperidine ring, fixed at the 3-position of the indole ring. Compounds having 2-thiophene amidine and 2-furanyl amidine groups (7, 8, 10 and 12) showed increased activity for human neuronal NOS and good selectivity over endothelial and inducible NOS isoforms. Compound 8 was shown to reverse (10mg/kg, ip) thermal hyperalgesia in the L(5)/L(6) spinal nerve ligation (neuropathic pain) model and was devoid of any significant drug-drug interaction potential due to cytochrome P450 inhibition or cardiovascular liabilities associated with the inhibition of endothelial NOS. PMID:22318159

Annedi, Subhash C; Maddaford, Shawn P; Ramnauth, Jailall; Renton, Paul; Speed, Joanne; Rakhit, Suman; Andrews, John S; Porreca, Frank

2012-01-21

168

Inhibitors of the Salicylate Synthase (MbtI) from Mycobacterium tuberculosis Discovered by High-Throughput Screening  

PubMed Central

A simple steady-state kinetic high-throughput assay was developed for the salicylate synthase MbtI from Mycobacterium tuberculosis, which catalyzes the first committed step of mycobactin biosynthesis. The mycobactins are small-molecule iron chelators produced by M. tuberculosis, and their biosynthesis has been identified as a promising target for the development of new antitubercular agents. The assay was miniaturized to a 384-well plate format and high-throughput screening was performed at the National Screening Laboratory for the Regional Centers of Excellence in Biodefense and Emerging Infectious Diseases (NSRB). Three classes of compounds were identified comprising the benzisothiazolones (class I), diarylsulfones (class II), and benzimidazole-2-thiones (class III). Each of these compound series was further pursued to investigate their biochemical mechanism and structure–activity relationships. Benzimidazole-2-thione 4 emerged as the most promising inhibitor owing to its potent reversible inhibition.

Vasan, Mahalakshmi; Neres, Joao; Williams, Jessica; Wilson, Daniel J.; Teitelbaum, Aaron M.; Remmel, Rory P.; Aldrich, Courtney C.

2010-01-01

169

Inhibitors of the salicylate synthase (MbtI) from Mycobacterium tuberculosis discovered by high-throughput screening.  

PubMed

A simple steady-state kinetic high-throughput assay was developed for the salicylate synthase MbtI from Mycobacterium tuberculosis, which catalyzes the first committed step of mycobactin biosynthesis. The mycobactins are small-molecule iron chelators produced by M.?tuberculosis, and their biosynthesis has been identified as a promising target for the development of new antitubercular agents. The assay was miniaturized to a 384-well plate format and high-throughput screening was performed at the National Screening Laboratory for the Regional Centers of Excellence in Biodefense and Emerging Infectious Diseases (NSRB). Three classes of compounds were identified comprising the benzisothiazolones (class?I), diarylsulfones (class?II), and benzimidazole-2-thiones (class?III). Each of these compound series was further pursued to investigate their biochemical mechanism and structure-activity relationships. Benzimidazole-2-thione 4 emerged as the most promising inhibitor owing to its potent reversible inhibition. PMID:21053346

Vasan, Mahalakshmi; Neres, Joăo; Williams, Jessica; Wilson, Daniel J; Teitelbaum, Aaron M; Remmel, Rory P; Aldrich, Courtney C

2010-12-01

170

The nitric oxide synthase inhibitor L-NAME suppresses androgen-induced male-like pseudocopulatory behavior in whiptail lizards.  

PubMed

The synthesis of nitric oxide by the enzyme nitric oxide synthase (NOS) is involved in the androgen-dependent gating of male-typical copulatory behavior, both centrally, particularly in the preoptic area, and peripherally, notably through its role in penile erection. In the all-female whiptail lizard species Cnemidophorus uniparens, individuals display copulatory behaviors indistinguishable from males of similar species if gonadectomized and treated with testosterone. In this experiment, androgenized individuals were treated with a NOS inhibitor, which eliminated male-like behavior in half the individuals, suggesting that the central role of nitric oxide synthesis is conserved in this species. The deficit was principally in mounting, suggesting that sexual motivational systems were affected, rather than consummatory mechanisms. PMID:16023092

Sanderson, Nicholas S R; Weissler, Erik; Crews, David

2005-08-01

171

Food applications of chitin and chitosans  

Microsoft Academic Search

Chitin is the second most abundant natural biopolymer after cellulose. The chemical structure of chitin is similar to that of cellulose with 2-acetamido-2-deoxy-?-d-glucose (NAG) monomers attached via ?(1?4) linkages. Chitosan is the deacetylated (to varying degrees) form of chitin, which, unlike chitin, is soluble in acidic solutions. Application of chitinous products in foods and pharmaceuticals as well as processing aids

Fereidoon Shahidi; Janak Kamil Vidana Arachchi; You-Jin Jeon

1999-01-01

172

Epi-trichosetin, a new undecaprenyl pyrophosphate synthase inhibitor, produced by Fusarium oxysporum FKI-4553.  

PubMed

A new compound, designated epi-trichosetin (1), was isolated along with the known compound trichosetin (2) from the culture broth of Fusarium oxysporum FKI-4553 by solvent extraction, silica gel column chromatography and reversed-phase HPLC. The structure of 1 was elucidated by comparing various spectral data with those of 2, revealing that 1 was a stereoisomer of 2. Compounds 1 and 2 inhibited the undecaprenyl pyrophosphate synthase activity of Staphylococcus aureus with IC50 values of 83 and 30??M, respectively, and showed antimicrobial activity, particularly against Gram-positive bacteria, including methicillin-sensitive and -resistant S. aureus. PMID:23715038

Inokoshi, Junji; Shigeta, Naoki; Fukuda, Takashi; Uchida, Ryuji; Nonaka, Kenichi; Masuma, Rokurou; Tomoda, Hiroshi

2013-05-29

173

Effect of JGK-263 as a new glycogen synthase kinase-3? inhibitor on extrinsic apoptosis pathway in motor neuronal cells.  

PubMed

Glycogen synthase kinase-3? (GSK-3?) has been identified as one of the important pathogenic mechanisms in motor neuronal death. GSK-3? inhibitor has been investigated as a modulator of apoptosis and has been shown to confer significant protective effects on cell death in neurodegenerative diseases. However, GSK-3? is known to have paradoxical effects on apoptosis subtypes, i.e., pro-apoptotic in mitochondrial-associated intrinsic apoptosis, but anti-apoptotic in death receptor-related extrinsic apoptosis. In this study, we evaluated the effect of a new GSK-3? inhibitor (JGK-263) on motor neuron cell survival and apoptosis, by using low to high doses of JGK-263 after 48h of serum withdrawal, and monitoring changes in extrinsic apoptosis pathway components, including Fas, FasL, cleaved caspase-8, p38?, and the Fas-Daxx interaction. Cell survival peaked after treatment of serum-deprived cells with 50?M JGK-263. The present study showed that treatment with JGK-263 reduced serum-deprivation-induced motor neuronal apoptosis by inactivating not only the intrinsic, but also the extrinsic apoptosis pathway. These results suggest that JGK-263 has a neuroprotective effect through effective modulation of the extrinsic apoptosis pathway in motor neuron degeneration. PMID:23899525

Jeon, Gye Sun; Kim, Jee-Eun; Ahn, Suk-Won; Park, Kyung-Seok; Hong, Yoon-Ho; Ye, In-Hae; Park, Ji-Seon; Kim, Seung Hyun; Lee, Kwang-Woo; Kim, Sung-Min; Sung, Jung-Joon

2013-07-27

174

Effects of an endogenous nitric oxide synthase inhibitor on phorbol myristate acetate-induced acute lung injury in rats.  

PubMed

1. In the present study, we determined whether the endogenous nitric oxide (NO) synthase (NOS) inhibitor Nomega-nitro-l-arginine methyl ester (l-NAME) could ameliorate the acute lung injury (ALI) induced by phorbol myristate acetate (PMA) in rat isolated lung. 2. Typical ALI was induced successfully by PMA during 60 min of observation. At 2 micro g/kg, PMA elicited a significant increase in microvascular permeability (measured using the capillary filtration coefficient Kfc), lung weight gain, lung weight/bodyweight ratio, pulmonary arterial pressure (PAP) and protein concentration of bronchoalveolar lavage fluid. 3. Pretreatment with the NOS inhibitor l-NAME (5 mmol/L) significantly attenuated ALI. None of the parameters reflective of lung injury showed significant increase, except for PAP (P < 0.001). The addition of l-arginine (4 mmol/L) blocked the protective effective of l-NAME. Pretreatment with l-arginine exacerbated PMA-induced lung injury. 4. These data suggest that l-NAME significantly ameliorates ALI induced by PMA in rats, indicating that endogenous NO plays a key role in the development of lung oedema in PMA-induced lung injury. PMID:12859432

Lin, Hen I; Chu, Shi Jye; Wang, David; Chen, Hsing I; Hsu, Kang

175

Pharmacophore Modeling and Virtual Screening for Novel Acidic Inhibitors of Microsomal Prostaglandin E2 Synthase-1 (mPGES-1)  

PubMed Central

Microsomal prostaglandin E2 synthase-1 (mPGES-1) catalyzes prostaglandin E2 formation and is considered as a potential anti-inflammatory pharmacological target. To identify novel chemical scaffolds active on this enzyme, two pharmacophore models for acidic mPGES-1 inhibitors were developed and theoretically validated using information on mPGES-1 inhibitors from literature. The models were used to screen chemical databases supplied from the National Cancer Institute (NCI) and the Specs. Out of 29 compounds selected for biological evaluation, nine chemically diverse compounds caused concentration-dependent inhibition of mPGES-1 activity in a cell-free assay with IC50 values between 0.4 and 7.9 ?M, respectively. Further pharmacological characterization revealed that also 5-lipoxygenase (5-LO) was inhibited by most of these active compounds in cell-free and cell-based assays with IC50 values in the low micromolar range. Together, nine novel chemical scaffolds inhibiting mPGES-1 are presented that may possess anti-inflammatory properties based on the interference with eicosanoid biosynthesis.

2011-01-01

176

Hydrogen Isotopes in Beetle Chitin  

Microsoft Academic Search

\\u000a Beetles, one of the most diverse and long-lived animal groups, provide a trove of ecological and palaeoenvironmental information\\u000a largely because their exoskeletons contain chitin, a highly resistant biopolymer which preserves well in the geological record.\\u000a In addition to palaeoenvironmental inferences that can be derived from presence or absence of particular taxa, beetle chitin\\u000a records the hydrogen stable isotope ratios (D\\/H)

Darren R. Gröcke; Maarten van Hardenbroek; Peter E. Sauer; Scott A. Elias

177

Chiral linkers to improve selectivity of double-headed neuronal nitric oxide synthase inhibitors.  

PubMed

To develop potent and selective nNOS inhibitors, new double-headed molecules with chiral linkers that derive from natural amino acids or their derivatives have been designed. The new structures contain two ether bonds, which greatly simplifies the synthesis and accelerates structure optimization. Inhibitor (R)-6b exhibits a potency of 32nM against nNOS and is 475 and 244 more selective for nNOS over eNOS and iNOS, respectively. Crystal structures show that the additional binding between the aminomethyl moiety of 6b and the two heme propionates in nNOS, but not eNOS, is the structural basis for its high selectivity. This work demonstrates the importance of stereochemistry in this class of molecules, which significantly influences the potency and selectivity of the inhibitors. The structure-activity information gathered here provides a guide for future structure optimization. PMID:23993333

Jing, Qing; Li, Huiying; Chreifi, Georges; Roman, Linda J; Martásek, Pavel; Poulos, Thomas L; Silverman, Richard B

2013-08-14

178

Glycogen Synthase Kinase 3 Inhibitors in the Next Horizon for Alzheimer's Disease Treatment  

PubMed Central

Glycogen synthase kinase 3 (GSK-3), a proline/serine protein kinase ubiquitously expressed and involved in many cellular signaling pathways, plays a key role in the pathogenesis of Alzheimer's disease (AD) being probably the link between ?-amyloid and tau pathology. A great effort has recently been done in the discovery and development of different new molecules, of synthetic and natural origin, able to inhibit this enzyme, and several kinetics mechanisms of binding have been described. The small molecule called tideglusib belonging to the thiadiazolidindione family is currently on phase IIb clinical trials for AD. The potential risks and benefits of this new kind of disease modifying drugs for the future therapy of AD are discussed in this paper.

Martinez, Ana; Gil, Carmen; Perez, Daniel I.

2011-01-01

179

Endothelium-dependent hyperpolarization in isolated arteries taken from animals treated with NO-synthase inhibitors.  

PubMed

To study the effects of chronic in vivo inhibition of NO synthase on endothelium-dependent hyperpolarization, cell-membrane potential (in individual vascular smooth-muscle cells) and changes in tension (in isolated rings) were recorded from isolated canine coronary arteries and guinea-pig carotid arteries and aortas. In coronary arteries taken from control dogs and contracted with U46619, acetylcholine- and bradykinin-induced endothelium-dependent relaxations, which were unaffected by short-term in vitro exposure to indomethacin but were inhibited partially by L-nitro-arginine (LNA). In coronary arteries taken from dogs treated over the long term in vivo with LNA (30 mg/kg on the first day and 20 mg/kg the 7 following days, i.v.), the response to acetylcholine and bradykinin was inhibited when compared with arteries from control dogs. Short-term in vitro exposure to LNA or indomethacin or both did not influence the effects of either agonist. In these arteries, the hyperpolarizing response to acetylcholine, observed in the presence of LNA and indomethacin, was enhanced, whereas that to bradykinin was partially inhibited. In the guinea pig isolated aorta, the relaxation to bradykinin was abolished by long-term in vivo treatment with L-nitro-arginine-methyl-ester (L-NAME; 1.5 mg/ml, in the drinking water for > or =4 days). In the isolated guinea pig carotid artery studied in the presence of LNA and indomethacin, acetylcholine induced a hyperpolarization that was not significantly affected by long-term in vivo treatment with L-NAME. These findings indicate that endothelium-dependent hyperpolarizations are maintained during long-term inhibition of NO synthase and probably act as a back-up mechanism to elicit endothelium-dependent relaxations. PMID:9869500

Corriu, C; Félétou, M; Puybasset, L; Bea, M L; Berdeaux, A; Vanhoutte, P M

1998-12-01

180

Influence of aminoguanidine, an inhibitor of inducible nitric oxide synthase, on the pulmonary hypertensive response to microparticle injections in broilers.  

PubMed

The pulmonary hypertensive response to pulmonary vascular obstruction caused by intravenously injected microparticles is amplified by pretreatment with N(omega)nitro-L-arginine methyl ester (L-NAME). The L-NAME prevents the synthesis of the potent vasodilator nitric oxide (NO) by inhibiting both the constitutive [endothelial NO synthase (eNOS or NOS-3)] and inducible [inducible NO synthase (iNOS or NOS-2)] forms of NO synthase. In the present study we used the selective iNOS inhibitor aminoguanidine (AG) to evaluate the role of iNOS in modulating the pulmonary hypertension (PH) triggered by microparticle injections. Experiment 1 was conducted to confirm the ability of AG to inhibit NO synthesis by iNOS in broiler peripheral blood mononuclear cells exposed to bacterial lipopolysaccharide (LPS, endotoxin). Mononuclear leukocytes treated with LPS produced 10-fold more NO than untreated (control) cells. The LPS-stimulated production of NO was partially inhibited by L-NAME and was fully inhibited by AG, thereby confirming that AG inhibits LPS-mediated iNOS activation in broilers. In Experiment 2 we evaluated the responses of male progeny from a base population (MP Base) and from a derivative line selected for one generation from the survivors of an LD50 microparticle injection (MP Select). The pulmonary arterial pressure (PAP) was lower in MP Select than in MP Base broilers. Both lines exhibited similar percentage increases in PAP after microparticles were injected, and AG modestly amplified the PH triggered by microparticles in both lines. In Experiment 3 we evaluated the responses of male progeny from a second base population (PAC Base) and from a derivative line selected for 3 generations using the unilateral pulmonary artery clamp technique (PAC Select). The PAP was lower in PAC Select than in PAC Base broilers, and both lines exhibited similar percentage increases in PAP in response to the microparticles. The PH triggered by microparticles was not amplified by AG but was doubled by L-NAME. These experiments demonstrate that during the 30 min following pulmonary vascular entrapment of microparticles, iNOS modulated the PH elicited in broilers derived from the MP pedigree line, but not in broilers from the PAC pedigree line. Different NOS-mediated responses among broiler populations may affect pulmonary hemodynamic characteristics of broiler lines selected using i.v. microparticle injections. PMID:16553284

Wideman, R F; Bowen, O T; Erf, G F; Chapman, M E

2006-03-01

181

Decreased spontaneous motor activity and startle response in nitric oxide synthase inhibitor-treated rats.  

PubMed

In the central nervous system, nitric oxide has been proposed to be a retrograde messenger mediating learning and synaptic plasticity. Since only pretraining injections of nitric oxide synthesis inhibitors were shown to impair learning, we examined the possibility that systemic administration of these inhibitors might influence some non-specific aspects related to the organism's general psychophysiological status. Intraperitoneal administration of NG-nitro-L-arginine methyl ester (30 or 100 mg/kg) 60 min pre-test to adult rats resulted in: (i) altered exploratory pattern and reduced locomotion in a novel environment; (ii) reduced startle response to either acoustic or electric stimuli; and (iii) cardiovascular alterations. In addition, intracerebroventricular administration of N-nitro-L-arginine (10 microliters of a 10 mM solution) diminished the acoustic startle response. Specificity of these effects through nitric oxide was supported by the ability of the nitric oxide precursor, L-arginine, to prevent the inhibitors actions. These findings indicate that nitric oxide inhibitors interfere with the general psychophysiological status of the organism. PMID:7543413

Sandi, C; Venero, C; Guaza, C

1995-04-13

182

Ozagrel hydrochloride, a selective thromboxane A2 synthase inhibitor, alleviates liver injury induced by acetaminophen overdose in mice  

PubMed Central

Background Overdosed acetaminophen (paracetamol, N-acetyl-p-aminophenol; APAP) causes severe liver injury. We examined the effects of ozagrel, a selective thromboxane A2 (TXA2) synthase inhibitor, on liver injury induced by APAP overdose in mice. Methods Hepatotoxicity was induced to ICR male mice by an intraperitoneal injection with APAP (330 mg/kg). The effects of ozagrel (200 mg/kg) treatment 30 min after the APAP injection were evaluated with mortality, serum alanine aminotransferase (ALT) levels and hepatic changes, including histopathology, DNA fragmentation, mRNA expression and total glutathione contents. The impact of ozagrel (0.001-1 mg/mL) on cytochrome P450 2E1 (CYP2E1) activity in mouse hepatic microsome was examined. RLC-16 cells, a rat hepatocytes cell line, were exposed to 0.25 mM N-acetyl-p-benzoquinone imine (NAPQI), a hepatotoxic metabolite of APAP. In this model, the cytoprotective effects of ozagrel (1–100 muM) were evaluated by the WST-1 cell viability assay. Results Ozagel treatment significantly attenuated higher mortality, elevated serum alanine aminotransferase levels, excessive hepatic centrilobular necrosis, hemorrhaging and DNA fragmentation, as well as increase in plasma 2,3-dinor thromboxane B2 levels induced by APAP injection. Ozagrel also inhibited the hepatic expression of cell death-related mRNAs induced by APAP, such as jun oncogene, FBJ osteosarcoma oncogene (fos) and C/EBP homologous protein (chop), but did not suppress B-cell lymphoma 2-like protein11 (bim) expression and hepatic total glutathione depletion. These results show ozagrel can inhibit not all hepatic changes but can reduce the hepatic necrosis. Ozagrel had little impact on CYP2E1 activity involving the NAPQI production. In addition, ozagrel significantly attenuated cell injury induced by NAPQI in RLC-16. Conclusions We demonstrate that the TXA2 synthase inhibitor, ozagrel, dramatically alleviates liver injury induced by APAP in mice, and suggest that it is a promising therapeutic candidate for the treatment of APAP-induced liver injury.

2013-01-01

183

The crystal structure of spermidine synthase with a multisubstrate adduct inhibitor.  

SciTech Connect

Polyamines are essential in all branches of life. Spermidine synthase (putrescine aminopropyltransferase, PAPT) catalyzes the biosynthesis of spermidine, a ubiquitous polyamine. The crystal structure of the PAPT from Thermotoga maritima (TmPAPT) has been solved to 1.5 Angstroms resolution in the presence and absence of AdoDATO (S-adenosyl-1,8-diamino-3-thiooctane), a compound containing both substrate and product moieties. This, the first structure of an aminopropyltransferase, reveals deep cavities for binding substrate and cofactor, and a loop that envelops the active site. The AdoDATO binding site is lined with residues conserved in PAPT enzymes from bacteria to humans, suggesting a universal catalytic mechanism. Other conserved residues act sterically to provide a structural basis for polyamine specificity. The enzyme is tetrameric; each monomer consists of a C-terminal domain with a Rossmann-like fold and an N-terminal {beta}-stranded domain. The tetramer is assembled using a novel barrel-type oligomerization motif.

Korolev, S.; Ikeguchi, Y.; Skarina, T.; Beasley, S.; Arrowsmith, C.; Edwards, A.; Joachimiak, A.; Pegg, A. E.; Savchenko, A.; Pennsylvania State Univ. Coll. of Medicine; Milton S. Hershey Medical Center; Banting and Best Department of Medical Research; Univ. of Health Network

2002-01-01

184

Antagonism of the nitric oxide synthase inhibitor, L-NAME, of the effects of phencyclidine on latent inhibition in taste aversion conditioning  

Microsoft Academic Search

Latent inhibition (LI) is a behavioural procedure used to evaluate the potential propsychotic and antipsychotic properties of psychoactive drugs. In the present study, a conditioned taste aversion (CTA) procedure was used to investigate the effects of the nitric oxide (NO) synthase inhibitor, NG-nitro-l-arginine methyl ester (L-NAME), and the psychotomimetic drugs, phencyclidine (PCP) and d-amphetamine (d-AMP) on LI. PCP (2mg\\/kg) and

Daniel Klamer; Erik Pĺlsson; Caroline Wass; Trevor Archer; Jörgen A Engel; Lennart Svensson

2005-01-01

185

Resistance of a Rodent Malaria Parasite to a Thymidylate Synthase Inhibitor Induces an Apoptotic Parasite Death and Imposes a Huge Cost of Fitness  

Microsoft Academic Search

BackgroundThe greatest impediment to effective malaria control is drug resistance in Plasmodium falciparum, and thus understanding how resistance impacts on the parasite's fitness and pathogenicity may aid in malaria control strategy.Methodology\\/Principal FindingsTo generate resistance, P. berghei NK65 was subjected to 5-fluoroorotate (FOA, an inhibitor of thymidylate synthase, TS) pressure in mice. After 15 generations of drug pressure, the 2% DT

Francis W. Muregi; Isao Ohta; Uchijima Masato; Hideto Kino; Akira Ishih

2011-01-01

186

7-Nitroindazole, a neuronal nitric oxide synthase inhibitor, impairs passive-avoidance and elevated plus-maze memory performance in rats  

Microsoft Academic Search

The role of nitric oxide (NO) on cognitive performance in a modified elevated plus-maze (mEPM) and passive-avoidance (PA) task was investigated by using the NO synthase (NOS) inhibitor 7-nitroindazole (7-NI) and an NO precursor l-arginine. The interaction between the activation of N-methyl-d-aspartate (NMDA) receptors and NO synthesis on memory retention was also studied. 7-NI, l-arginine or MK-801, a non-competitive NMDA

Furuzan Yildiz Akar; Guner Ulak; Pelin Tanyeri; Faruk Erden; Tijen Utkan; Nejat Gacar

2007-01-01

187

Novel and orally bioavailable inducible nitric oxide synthase inhibitors: synthesis and evaluation of optically active 4,5-dialkyl-2-iminoselenazolidine derivatives  

Microsoft Academic Search

We have previously reported that (4R,5R)-5-ethyl-2-imino-4-methylthiazolidine (3) strongly inhibits inducible nitric oxide synthase (iNOS). In a successive search for strong and selective iNOS inhibitors, we, herein, describe the synthesis of the selenium analogue of 3 (4: ES-2133) and its related optically active compounds and examine their in vitro and in vivo inhibitory activity against iNOS. In addition, an alternative synthetic

Shigeo Ueda; Hideo Terauchi; Kenji Suzuki; Akihiro Yano; Masashi Matsumoto; Taeko Kubo; Hisao Minato; Yukiyo Arai; Jun-ichi Tsuji; Nobuhide Watanabe

2005-01-01

188

Design of Benzene1,2-diamines as selective inducible nitric oxide synthase inhibitors: a combined de novo design and docking analysis  

Microsoft Academic Search

Selective inhibition of inducible nitric oxide synthases (iNOS) has been a challenging problem for researchers pursuing work\\u000a in finding methods to treat inflammatory disorders, shock, etc. Though many inhibitors have been studied to date, all are\\u000a associated with selectivity or potency problems. Additionally, most of the reported compounds have several similarities and\\u000a fewer number of novel structures are being tried.

Sandrea M. Francis; Amit Mittal; Manishika Sharma; Prasad V. Bharatam

2008-01-01

189

Secondary somatosensory cortex stimulation facilitates the antinociceptive effect of the NO synthase inhibitor through suppression of spinal nociceptive neurons in the rat  

Microsoft Academic Search

Electrical stimulation of the secondary somatosensory cortex (S-II), which is clinically effective in some chronic pain patients, produces a weak antinociception by itself and also strongly facilitates the antinociceptive effect of the neuronal NO synthase inhibitor 7-nitro-indazole in laboratory animals (rats). The present study thus investigated the mechanisms by which S-II stimulation facilitates the 7-nitro-indazole-induced antinociception. S-II stimulation in combination

Ryotaro Kuroda; Naoyuki Kawao; Hiroko Yoshimura; Wakana Umeda; Motohide Takemura; Yoshio Shigenaga; Atsufumi Kawabata

2001-01-01

190

The impact of asymmetric dimethylarginine (ADAMA), the endogenous nitric oxide (NO) synthase inhibitor, to the pathogenesis of gastric mucosal damage.  

PubMed

This review was designed to provide an update on the role of asymmetric arginine (ADMA), the endogenous inhibitor of nitric oxide (NO) synthase in the pathophysiology of the upper gastrointestinal (GI) tract. Numerous studies in the past confirmed that NO is a multifunctional endogenous gas molecule involved in most of the body organs' functional and metabolic processes including the regulation of gastrointestinal (GI) secretory functions, motility, maintenance of GI integrity, gastroprotection and ulcer healing. NO is metabolized from L-arginine by enzymatic reaction in the presence of constitutive NO synthase. In upper GI tract, NO acts as a potent vasodilator known to increase gastric mucosa blood flow, regulates the secretion of mucus and bicarbonate, inhibits the gastric secretion and protects the gastric mucosa against the damage induced by a variety of damaging agents and corrosive substances. In contrast, ADMA first time described by Vallance and coworkers in 1992, is synthesized by the hydrolysis of proteins containing methylated arginine amino acids located predominantly within the nucleus of cells. This molecule has been shown to competitively inhibit NO synthase suggesting its regulatory role in the functions of vascular endothelial cells and systemic circulation in humans and experimental animals. Nowadays, ADMA is a potentially important risk factor for coronary artery diseases and a marker of cardiovascular risk. Increased plasma levels of ADMA have been documented in several conditions that are characterized by endothelial dysfunction, including hypertension, hypercholesterolemia, hyperglycemia, renal failure and tobacco exposure. The role of ADMA in other systems including GI-tract has been so far less documented. Nevertheless, ADMA was shown to directly induce oxidative stress and cell apoptosis in gastric mucosal cells in vitro and to contribute to the inflammatory reaction associated with major human pathogen to gastric mucosa, Helicobacter pylori (H.pylori). Infection of gastric mucosa with this germ or H. pylori water extract led to marked increase in the plasma concentration of ADMA and significantly inhibited bicarbonate secretion, considered as one of the important components of upper GI-tract defense system. When administered to rodents, ADMA aggravated gastric mucosal lesions injury induced by cold stress, ethanol and indomethacin and this worsening effect on gastric lesions was accompanied by the significant increase in the plasma level of ADMA. This exaggeration of gastric lesions by ADMA was coincided with the inhibition of NO, the suppression of gastric blood flow and excessive release of proinflammatory cytokine TNF-?. This metabolic analog of L-arginine applied to rats was exposed to water immersion and restraint stress and ischemia-reperfusion, causing an elevation of plasma levels of ADMA and gastric MDA content, which is the marker of lipid peroxidation. These effects, including the rise in the plasma levels of ADMA in rats with stress and ischemia-reperfusion-induced gastric lesions, were attenuated by concomitant treatment with L-arginine, the substrate for NO-synthase, and superoxide dismutase (SOD), a reactive oxygen metabolite scavenger added to ADMA. We conclude that ADMA could be considered as an important factor contributing to the pathogenesis of gastric mucosal damage and inflammatory reaction in H. pylori-infected stomach due to inhibition of NO, suppression of GI microcirculation, and the proinflammatory and proapoptotic actions of this arginine analog. PMID:22950506

Szlachcic, Aleksandra; Krzysiek-Maczka, Gracjana; Pajdo, Robert; Targosz, Aneta; Magierowski, Marcin; Jasnos, Katarzyna; Drozdowicz, Danuta; Kwiecien, Slawomir; Brzozowski, Tomasz

2013-01-01

191

Deoxyuridine triphosphatase (dUTPase) expression and sensitivity to the thymidylate synthase (TS) inhibitorD9331  

PubMed Central

Uracil DNA misincorporation and misrepair of DNA have been recognized as important events accompanying thymidylate synthase (TS) inhibition. dUTPase catalyses the hydrolysis of dUTP to dUMP, thereby maintaining low intracellular dUTP. We have addressed the relationship between dUTPase expression and cellular sensitivity to TS inhibition in four human lung tumour cell lines. Sensitivity (5-day MTT assay) to the growth inhibitory effects of the non-polyglutamatable, specific quinazoline TS inhibitor ZD9331, varied up to 20-fold (IC 50 3–70 nM). TS protein expression correlated with TS activity (r2= 0.88 P= 0.05). Intracellular concentrations of drug following exposure to ZD9331 (1 ?M, 24 h) varied by ~2-fold and dTTP pools decreased by > 80% in all cell lines. No clear associations across the cell lines between intracellular drug concentrations, TS activity/expression, or TTP depletion could be made. dUTPase activity varied 17-fold and correlated with dUTPase protein expression (r2= 0.94 P= 0.03). There was a striking variation in the amount of dUTP formed following exposure to ZD9331 (between 1.3 and 57 pmole 10–6cells) and was in general inversely associated with dUTPase activity. A large expansion in the dUTP pool was associated with increased sensitivity to a 24-h exposure to ZD9331 in A549 cells that have low dUTPase activity/expression. dUTPase expression and activity were elevated (approximately 3-fold) in two variants of a human lymphoblastoid cell line with acquired resistance to TS inhibitors, further suggesting an important role for this enzyme in TS inhibited cells. © 2000 Cancer Research Campaign

Webley, S D; Hardcastle, A; Ladner, R D; Jackman, A L; Aherne, G W

2000-01-01

192

Identification of Inhibitors against Mycobacterium tuberculosis Thiamin Phosphate Synthase, an Important Target for the Development of Anti-TB Drugs  

PubMed Central

Tuberculosis (TB) continues to pose a serious challenge to human health afflicting a large number of people throughout the world. In spite of the availability of drugs for the treatment of TB, the non-compliance to 6–9 months long chemotherapeutic regimens often results in the emergence of multidrug resistant strains of Mycobacterium tuberculosis adding to the precariousness of the situation. This has necessitated the development of more effective drugs. Thiamin biosynthesis, an important metabolic pathway of M.tuberculosis, is shown to be essential for the intracellular growth of this pathogen and hence, it is believed that inhibition of this pathway would severely affect the growth of M.tuberculosis. In this study, a comparative homology model of M.tuberculosis thiamin phosphate synthase (MtTPS) was generated and employed for virtual screening of NCI diversity set II to select potential inhibitors. The best 39 compounds based on the docking results were evaluated for their potential to inhibit the MtTPS activity. Seven compounds inhibited MtTPS activity with IC50 values ranging from 20 – 100 µg/ml and two of these exhibited weak inhibition of M.tuberculosis growth with MIC99 values being 125 µg/ml and 162.5 µg/ml while one compound was identified as a very potent inhibitor of M.tuberculosis growth with an MIC99 value of 6 µg/ml. This study establishes MtTPS as a novel drug target against M.tuberculosis leading to the identification of new lead molecules for the development of antitubercular drugs. Further optimization of these lead compounds could result in more potent therapeutic molecules against Tuberculosis.

Khare, Garima; Kar, Ritika; Tyagi, Anil K.

2011-01-01

193

Discovery of thienopyrimidine-based inhibitors of the human farnesyl pyrophosphate synthase--parallel synthesis of analogs via a trimethylsilyl ylidene intermediate.  

PubMed

Thienopyrimidine-based bisphosphonates were identified as a new class of nitrogen-containing bisphosphonate (N-BP) inhibitors of the human farnesyl pyrophosphate synthase (hFPPS). Analogs were prepared via cyclization of 2-(1-(trimethylsilyl)ethylidene)malononitrile to 2-amino-4-(trimethylsilyl)thiophene-3-carbonitrile in the presence of elemental sulfur. Direct ipso-iododesilylation of this intermediate led to selective iodination at C? of the sulfur atom in high efficiency. The synthetic protocols developed were used in the parallel synthesis of structurally diverse thieno[2,3-d]pyrimidin-4-amine-based bisphosphonate inhibitors of hFPPS. PMID:23477945

Leung, Chun-Yuen; Langille, Adrienne M; Mancuso, John; Tsantrizos, Youla S

2013-02-18

194

5-imino-1,2,4-thiadiazoles: first small molecules as substrate competitive inhibitors of glycogen synthase kinase 3.  

PubMed

Cumulative evidence strongly supports that glycogen synthase kinase-3 (GSK-3) is a pathogenic molecule when it is up-dysregulated, emerging as an important therapeutic target in severe unmet human diseases. GSK-3 specific inhibitors might be promising effective drugs for the treatment of devastating pathologies such as neurodegenerative diseases, stroke, and mood disorders. As GSK-3 has the ability to phosphorylate primed substrates, small molecules able to bind to this site should be perfect drug candidates, able to partially block the activity of the enzyme over some specific substrates. Here, we report substituted 5-imino-1,2,4-thiadiazoles as the first small molecules able to inhibit GSK-3 in a substrate competitive manner. These compounds are cell permeable, able to decrease inflammatory activation and to selectively differentiate neural stem cells. Overall, 5-imino-1,2,4-thiadiazoles are presented here as new molecules able to decrease neuronal cell death and to increase endogenous neurogenesis blocking the GSK-3 substrate site. PMID:22257026

Palomo, Valle; Perez, Daniel I; Perez, Concepcion; Morales-Garcia, Jose A; Soteras, Ignacio; Alonso-Gil, Sandra; Encinas, Arantxa; Castro, Ana; Campillo, Nuria E; Perez-Castillo, Ana; Gil, Carmen; Martinez, Ana

2012-02-03

195

Hyaluronan synthase 2 (HAS2) promotes breast cancer cell invasion by suppression of tissue metalloproteinase inhibitor 1 (TIMP-1).  

PubMed

Invasion and metastasis are the primary causes of breast cancer mortality, and increased knowledge about the molecular mechanisms involved in these processes is highly desirable. High levels of hyaluronan in breast tumors have been correlated with poor patient survival. The involvement of hyaluronan in the early invasive phase of a clone of breast cancer cell line MDA-MB-231 that forms bone metastases was studied using an in vivo-like basement membrane model. The metastatic to bone tumor cells exhibited a 7-fold higher hyaluronan-synthesizing capacity compared with MDA-MB-231 cells predominately due to an increased expression of hyaluronan synthase 2 (HAS2). We found that knockdown of HAS2 completely suppressed the invasive capability of these cells by the induction of tissue metalloproteinase inhibitor 1 (TIMP-1) and dephosphorylation of focal adhesion kinase. HAS2 knockdown-mediated inhibition of basement membrane remodeling was rescued by HAS2 overexpression, transfection with TIMP-1 siRNA, or addition of TIMP-1-blocking antibodies. Moreover, knockdown of HAS2 suppressed the EGF-mediated induction of the focal adhesion kinase/PI3K/Akt signaling pathway. Thus, this study provides new insights into a possible mechanism whereby HAS2 enhances breast cancer invasion. PMID:22016393

Bernert, Berit; Porsch, Helena; Heldin, Paraskevi

2011-10-20

196

The effect of the nitric oxide synthase inhibitor N-gamma-nitro-L-argine methyl ester on hypoxic pulmonary vasoconstriction.  

PubMed

We studied the role of nitric oxide in the regulation of pulmonary arterial tone and hypoxic pulmonary vasoconstriction. Rat pulmonary arteries (n=65, diameter=440+/-12 microm) were loaded to 17.5 mm Hg in a wire myograph and incubated with the nitric oxide synthase inhibitor N-gamma-nitro-L-argine methyl ester (L-NAME; 1, 10 or 100 microM) or distilled water (50 microl) prior to preconstriction with either 100 microM prostaglandin F(2 alpha) followed by acetylcholine (0.1-100 microM) or 5 microM prostaglandin F(2 alpha) followed by hypoxia. Concentrations of L-NAME (10 and 100 microM) which attenuated acetylcholine dilatation, elevated basal tone from 0. 2+/-0.5% to 9.4+/-2.1% (P<0.01) and 18.3+/-3.2% (P<0.001), respectively, potentiated contraction to 5 microM prostaglandin F(2 alpha) from 35.9+/-3.1% to 56.2+/-6.8% (P<0.05) and 66.4+/-5.8% (P<0.001), respectively, but had no significant effect on hypoxic pulmonary vasoconstriction. This suggests basal pulmonary nitric oxide release occurs, as well as in response to agonist-induced contraction, but not hypoxic pulmonary vasoconstriction. PMID:10940364

Jones, R D; Morice, A H

2000-08-18

197

Property-based design of a glucosylceramide synthase inhibitor that reduces glucosylceramide in the brain[S  

PubMed Central

Synthesis inhibition is the basis for the treatment of type 1 Gaucher disease by the glucosylceramide synthase (GCS) inhibitor eliglustat tartrate. However, the extended use of eliglustat and related compounds for the treatment of glycosphingolipid storage diseases with CNS manifestations is limited by the lack of brain penetration of this drug. Property modeling around the D-threo-1-phenyl-2-decanoylamino-3-morpholino-propanol (PDMP) pharmacophore was employed in a search for compounds of comparable activity against the GCS but lacking P-glycoprotein (MDR1) recognition. Modifications of the carboxamide N-acyl group were made to lower total polar surface area and rotatable bond number. Compounds were screened for inhibition of GCS in crude enzyme and whole cell assays and for MDR1 substrate recognition. One analog, 2-(2,3-dihydro-1H-inden-2-yl)-N-((1R,2R)-1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-1-hydroxy-3-(pyrrolidin-1-yl)propan-2-yl)acetamide (CCG-203586), was identified that inhibited GCS at low nanomolar concentrations with little to no apparent recognition by MDR1. Intraperitoneal administration of this compound to mice for 3 days resulted in a significant dose dependent decrease in brain glucosylceramide content, an effect not seen in mice dosed in parallel with eliglustat tartrate.

Larsen, Scott D.; Wilson, Michael W.; Abe, Akira; Shu, Liming; George, Christopher H.; Kirchhoff, Paul; Showalter, H. D. Hollis; Xiang, Jianming; Keep, Richard F.; Shayman, James A.

2012-01-01

198

Characterization of maleimide-based glycogen synthase kinase-3 (GSK-3) inhibitors as stimulators of steroidogenesis.  

PubMed

Inhibition of GSK-3? has been well documented to account for the behavioral actions of the mood stabilizer lithium in various animal models of mood disorders. Recent studies have showed that genetic or pharmacological inhibition of GSK-3? resulted in anxiolytic-like and pro-social behavior. In our ongoing efforts to develop GSK-3? inhibitors for the treatment of mood disorders, SAR studies on maleimide-based compounds were undertaken. We present herein for the first time that some of these GSK-3? inhibitors, in particular analogues 1 and 9, were able to stimulate progesterone production in the MA-10 mouse tumor Leydig cell model of steroidogenesis without any significant toxicity. These two compounds were tested in the SmartCube behavioral assay and showed anxiolytic-like signatures following daily dose administration (50 mg/kg, ip) for 13 days. Taken together, these results support the hypothesis that GSK-3? inhibition could influence neuroactive steroid production thereby mediating the modulation of anxiety-like behavior in vivo. PMID:23725591

Gunosewoyo, Hendra; Midzak, Andrew; Gaisina, Irina N; Sabath, Emily V; Fedolak, Allison; Hanania, Taleen; Brunner, Dani; Papadopoulos, Vassilios; Kozikowski, Alan P

2013-06-17

199

Pharmacodynamic and pharmacokinetic characterization of the aldosterone synthase inhibitor FAD286 in two rodent models of hyperaldosteronism: comparison with the 11beta-hydroxylase inhibitor metyrapone.  

PubMed

Aldosterone synthase (CYP11B2) inhibitors (ASIs) represent an attractive therapeutic approach for mitigating the untoward effects of aldosterone. We characterized the pharmacokinetic/pharmacodynamic relationships of a prototypical ASI, (+)-(5R)-4-(5,6,7,8-tetrahydroimidazo[1,5-a]pyridin-5-yl]benzonitrile hydrochloride (CGS020286A, FAD286, FAD) and compared these profiles to those of the 11beta-hydroxylase inhibitor metyrapone (MET) in two rodent models of secondary hyperaldosteronism and corticosteronism. In chronically cannulated Sprague-Dawley rats, angiotensin II (ANG II) (300 ng/kg bolus + 100 ng/kg/min infusion) or adrenocorticotropin (100 ng/kg + 30 ng/kg/min) acutely elevated plasma aldosterone concentration (PAC) from approximately 0.26 nM to a sustained level of approximately 2.5 nM for 9 h. Adrenocorticotropin but not ANG II elicited a sustained increase in plasma corticosterone concentration (PCC) from approximately 300 to approximately 1340 nM. After 1 h of Ang II or adrenocorticotropin infusion, FAD (0.01-100 mg/kg p.o.) or MET (0.1-300 mg/kg p.o.) dose- and drug plasma concentration-dependently reduced the elevated PACs over the ensuing 8 h. FAD was approximately 12 times more dose-potent than MET in reducing PAC but of similar or slightly greater potency on a plasma drug concentration basis. Both agents also decreased PCC in the adrenocorticotropin model at relatively higher doses and with similar dose potencies, whereas FAD was 6-fold weaker based on drug exposures. FAD was approximately 50-fold selective for reducing PAC versus PCC, whereas MET was only approximately 3-fold selective. We conclude that FAD is a potent, orally active, and relatively selective ASI in two rat models of hyperaldosteronism. MET is an order of magnitude less selective than FAD but is, nevertheless, more potent as an ASI than as an 11beta-hydroxylase inhibitor. PMID:20354176

Rigel, Dean F; Fu, Fumin; Beil, Michael; Hu, Chii-Whei; Liang, Guiqing; Jeng, Arco Y

2010-03-30

200

Chitin colonization, chitin degradation and chitin-induced natural competence of Vibrio cholerae are subject to catabolite repression.  

PubMed

Although Vibrio cholerae is a human pathogen its primary habitat are aquatic environments. In this environment, V.cholerae takes advantage of the abundance of zooplankton, whose chitinous exoskeletons provide a nutritious surface. Chitin also induces the developmental programme of natural competence in several species of the genus Vibrio. Because the chitin surface can serve as the sole carbon source for V.cholerae, the link between carbon catabolite repression and chitin-induced natural competence for transformation was investigated in this study. Provision of competing phosphoenolpyruvate: carbohydrate phosphotransferase system (PTS)-dependent carbon sources in addition to chitin significantly lowered natural transformability. These sugars are known to interfere with the accumulation of 3',5'-cyclic AMP (cAMP); therefore, the contributions of the cAMP-producing enzyme, adenylate cyclase and the cAMP receptor protein (CRP) to chitin surface colonization, chitin degradation and natural transformation were also analysed. The results provided here indicate that cAMP and CRP are important in at least three interlinked areas of the chitin-induced natural competence programme. First, cAMP and CRP are required for the efficient colonization of the chitin surface; second both contribute to chitin degradation and utilization, and third, cAMP plus CRP play a role in increasing competence gene expression. These findings highlight the complex regulatory circuit of chitin-induced natural competence in V.cholerae. PMID:22222000

Blokesch, Melanie

2012-01-06

201

Kinetics of chitinase production. I. Chitin hydrolysis.  

PubMed

As part of the development of a comprehensive mathematical model for chitinase production by Serratia marcescens QMB 1466 growing on chitin, the different mass transport and kinetic steps involved during chitin hydrolysis were studied. The experimental results for the hydrolysis of chitin by a crude preparation of chitinase show a system kinetically limited by the overall rate of chitin hydrolysis. This rate is linearly related to the concentration of enzyme adsorbed on the chitin particle. Adsorbed and bulk enzyme concentration were found to be related through a Langmuir type of isotherm. PMID:18553734

Young, M E; Bell, R L; Carroad, P A

1985-06-01

202

New developments in cancer treatment with the novel thymidylate synthase inhibitor raltitrexed ('Tomudex').  

PubMed Central

Following the demonstration of efficacy, tolerability and quality-of-life benefits of raltitrexed ('Tomudex'), principally in advanced colorectal but also in other cancers, an extensive evaluation of combination therapy with other agents in patients with colorectal and other tumour types is being undertaken. This work has been prompted by preclinical observations of enhanced activity of raltitrexed when coadministered with other cytotoxic agents or radiotherapy and by preliminary results showing the activity of raltitrexed in patients with cancers other than colorectal. Raltitrexed is currently being investigated as monotherapy in phase I and II cancer studies, including head and neck cancer, hormone-resistant prostate cancer, paediatric and adult leukaemias and solid tumours, and soft tissue sarcoma. In addition, phase I clinical trials are evaluating the drug in combination with taxanes (paclitaxel) in solid tumours, anthracyclines (doxorubicin) in gastric carcinoma, topoisomerase I inhibitors (CPT-11) and 5-fluorouracil (both infusion and bolus regimens) in advanced colorectal cancer, platinum compounds (oxaliplatin and cisplatin) in a variety of tumours and radiotherapy in rectal cancer. Preliminary reports indicate good tolerability and acceptability of the combinations being investigated, with no dose-limiting toxicity being reported to date, and some early indications of efficacy.

Blackledge, G.

1998-01-01

203

Synthesis of potent inhibitors of ?-ketoacyl-acyl carrier protein synthase III as potential antimicrobial agents.  

PubMed

Mycobacterium tuberculosis FabH, an essential enzyme in the mycolic acid biosynthetic pathway, is an attractive target for novel anti-tubercolosis agents. Structure-based design and synthesis of 1-(4-carboxybutyl)-4-(4-(substituted benzyloxy)phenyl)-1H-pyrrole-2-carboxylic acid derivatives 7a-h, a subset of eight potential FabH inhibitors, is described in this paper. The Vilsmeier-Haack reaction was employed as a key step. The structures of all the newly synthesized compounds were identified by IR, ąH-NMR, ąłC-NMR, ESI-MS and HRMS. The alamarBlue™ microassay was employed to evaluate the compounds 7a-h against Mycobacterium tuberculosis H??Rv. The results demonstrate that the compound 7d possesses good in vitro antimycobacterial activity against Mycobacterium tuberculosis H??Rv (Minimum Inhibitory Concentration value [MIC], 12.5 µg/mL).These compounds may prove useful in the discovery and development of new anti-tuberculosis drugs. PMID:22534662

Liu, Yan; Zhong, Wu; Li, Rui-Juan; Li, Song

2012-04-25

204

Effect of Calcofluor white and Congo red on fungal cell wall morphogenesis: in vivo activation of chitin polymerization.  

PubMed Central

Calcofluor White (a fluorochrome dye) affected the growth of Geotrichum lactis by causing lysis of cells at the hyphal tips. This effect was prevented by the presence of an osmotic stabilizer. The growth of Saccharomyces cerevisiae was also affected, and multicellular aggregates were formed because of incomplete separation of mother and daughter cells; fluorescence microscopy indicated the presence of abnormally thick septa. The formation of rudimentary wall material by G. lactis protoplasts was promoted by Calcofluor or Congo red (another dye). The rate of chitin synthesis in protoplasts and growing cells was enhanced by both dyes. In contrast, both dyes inhibited chitin and beta (1,3)-glucan synthases in isolated cell-free systems. Degradation rates for beta (1,3)-glucan or chitin were not affected significantly by the dyes. Wheat germ agglutinin also affected chitin synthesis in protoplasts. Images

Roncero, C; Duran, A

1985-01-01

205

Induction of hypoxia in experimental murine tumors by the nitric oxide synthase inhibitor, NG-nitro-L-arginine.  

PubMed

The nitric oxide synthase inhibitor NG-nitro-L-arginine (NOARG) was examined for its ability to alter energy metabolism in three murine tumors using 31P magnetic resonance spectroscopy. NOARG (10 mg/kg, i.v.) increased the inorganic phosphate:total phosphate ratio (Pi:total) 2-3-fold in the KHT, RIF-1, and SCCVII/Ha intradermal back tumors from 30 min to 6 h after injection, but the 31P magnetic resonance spectrum from normal tissue on the mouse back was unchanged after this treatment. NOARG (10 mg/kg, i.v.) injected 30 min before X-rays increased tumor cell survival 3-5-fold in SCCVII/Ha and 50-200-fold in RIF-1, measured using an in vivo/in vitro clonogenic assay. These effects were equivalent to those obtained from clamped tumors, indicating full radiobiological hypoxia. In KHT, only a 2-fold increase in radioresistance was observed after NOARG, which was less than the response of clamped tumors. In RIF-1 tumors, NOARG induced full radiobiological hypoxia when given from 30 min to 6 h prior to X-rays, consistent with the time course for the increase in Pi:total, measured by 31P magnetic resonance spectroscopy. Pi:total after NOARG doses of 0.1-10 mg/kg, i.v., increased in a dose-dependent manner in this tumor. Increased RIF-1 tumor radioresistance was similarly dependent on NOARG dose. The combination of the bioreductive agent RB6145 (300 mg/kg, i.p.) 15 min prior to NOARG (10 mg/kg, i.v.) produced greater than 5 decades of KHT tumor cell killing at 24 h after treatment. This combination also increased Pi:total 4.5-fold over the control value at 24 h in the KHT tumor. Histological examination of tumors at this time indicated extensive necrosis. PMID:7987843

Wood, P J; Sansom, J M; Butler, S A; Stratford, I J; Cole, S M; Szabo, C; Thiemermann, C; Adams, G E

1994-12-15

206

Stoichiometry and topology of the complex of the endogenous ATP synthase inhibitor protein IF(1) with calmodulin.  

PubMed

IF(1), the natural inhibitor protein of F(O)F(1)ATP synthase able to regulate the ATP hydrolytic activity of both mitochondrial and cell surface enzyme, exists in two oligomeric states depending on pH: an inactive, highly helical, tetrameric form above pH 6.7 and an active, inhibitory, dimeric form below pH 6.7 [ Cabezon , E. , Butler , P. J. , Runswick , M. J. , and Walker , J. E. ( 2000 ) J. Biol. Chem. 275 , 25460 -25464 ]. IF(1) is known to interact in vitro with the archetypal EF-hand calcium sensor calmodulin (CaM), as well to colocalize with CaM on the plasma membrane of cultured cells. Low resolution structural data were herein obtained in order to get insights into the molecular interaction between IF(1) and CaM. A combined structural proteomic strategy was used which integrates limited proteolysis and chemical cross-linking with mass spectrometric analysis. Specifically, chemical cross-linking data clearly indicate that the C-terminal lobe of CaM molecule contacts IF(1) within the inhibitory, flexible N-terminal region that is not involved in the dimeric interface in IF(1). Nevertheless, native mass spectrometry analysis demonstrated that in the micromolar range the stoichiometry of the IF(1)-CaM complex is 1:1, thereby indicating that binding to CaM promotes IF(1) dimer dissociation without directly interfering with the intersubunit contacts of the IF(1) dimer. The relevance of the finding that only the C-terminal lobe of CaM is involved in the interaction is two fold: (i) the IF(1)-CaM complex can be included in the category of noncanonical structures of CaM complexes; (ii) it can be inferred that the N-terminal region of CaM might have the opportunity to bind to a second target. PMID:20669893

Pagnozzi, Daniela; Birolo, Leila; Leo, Gabriella; Contessi, Stefania; Lippe, Giovanna; Pucci, Pietro; Mavelli, Irene

2010-09-01

207

Central infusion of aldosterone synthase inhibitor prevents sympathetic hyperactivity and hypertension by central Na+ in Wistar rats.  

PubMed

In Wistar rats, increasing cerebrospinal fluid (CSF) Na+ concentration ([Na+]) by intracerebroventricular (ICV) infusion of hypertonic saline causes sympathetic hyperactivity and hypertension that can be prevented by blockade of brain mineralocorticoid receptors (MR). To assess the role of aldosterone produced locally in the brain in the activation of MR in the central nervous system (CNS), Wistar rats were infused ICV with artificial CSF (aCSF), Na+ -rich (800 mmol/l) aCSF, aCSF plus the aldosterone synthase inhibitor FAD286 (100 microg x kg(-1) x day(-1)), or Na+ -rich aCSF plus FAD286. After 2 wk of infusion, rats treated with Na+ -rich aCSF exhibited significant increases in aldosterone and corticosterone content in the hypothalamus but not in the hippocampus, as well as increases in resting blood pressure (BP) and sympathoexcitatory responses to air stress, and impairment of arterial baroreflex function. Concomitant ICV infusion of FAD286 prevented the Na+ -induced increase in hypothalamic aldosterone but not corticosterone and prevented most of the increases in resting BP and sympathoexcitatory and pressor responses to air stress and the baroreflex impairment. FAD286 had no effects in rats infused with ICV aCSF. In another set of rats, 24-h BP and heart rate were recorded via telemetry before and during a 14-day ICV infusion of Na+ -rich aCSF with or without FAD286. Na+ -rich aCSF without FAD286 caused sustained increases ( approximately 10 mmHg) in resting mean arterial pressure that were absent in the rats treated with FAD286. These data suggest that in Wistar rats, an increase in CSF [Na+] may increase the biosynthesis of corticosterone and aldosterone in the hypothalamus, and mainly aldosterone activates MR in the CNS leading to sympathetic hyperactivity and hypertension. PMID:18495825

Huang, Bing S; White, Roselyn A; Ahmad, Monir; Jeng, Arco Y; Leenen, Frans H H

2008-05-21

208

Enhanced antitumor activity for the thymidylate synthase inhibitor 1843U89 through decreased host toxicity with oral folic acid.  

PubMed

The purpose of this investigation was to determine whether antitumor selectivity of the third generation thymidylate synthase inhibitor 1843U89 could be enhanced by a combination of the drug with folic acid. The effects of folic acid on toxicity of 1843U89 to the dog and mouse and on antitumor efficacy of 1843U89 in the mouse were studied. These data were compared to the effect of folic acid on the in vitro cell culture antitumor activity of 1843U89. The sensitivity of eight cancer cell lines (three ovarian, one colon, one ileocecal, one epidermoid, one osteosarcoma, and one breast line) to 1843U89 was tested in vitro in the presence and absence of folic acid. Folic acid concentrations greater than 100 microM were required to decrease 1843U89 activity in seven of the cell lines. Only the activity in HCT-8, the ileocecal line, was reserved at folic acid concentrations below 100 microM. Oral folic acid given 30 min prior to an i.v. dose of 1843U89 increased the maximally tolerated dose and the lethal dose of 1843U89, both in dogs and in thymidine-depleted mice. In mice, oral folic acid produced little or no effect upon the antitumor efficacy of 1843U89 in two of three tumor cell lines in vivo. HCT-8, the line that was sensitive to folate reversal in vitro, was also sensitive in vivo. The results show that an oral dose of folic acid 30 min prior to i.v. 1843U89 can block mouse and dog intestinal toxicity without decreasing efficacy of 1843U89 in two of three human tumor lines in the nude mouse. Thus, the data reported here indicate that the antitumor selectivity of 1843U89 may be enhanced through a combination of 1843U89 with oral folic acid. PMID:8521402

Smith, G K; Amyx, H; Boytos, C M; Duch, D S; Ferone, R; Wilson, H R

1995-12-15

209

[The effect of nitric oxide synthase inhibitor on reperfusion injury to the brain under hypothermic circulatory arrest].  

PubMed

The effect of nitric oxide synthase inhibitor-NG-nitro-L-argine methyl ester (L-NAME)-on reperfusion injury of the brain under deep hypothermic circulatory arrest was experimentally investigated in sixteen piglets weighing about 30 kg. Cardiopulmonary bypass was established and animals were cooled to a brain temperature of 20 degrees C and circulatory arrest was performed for 60 minutes followed by reperfusion of 120 minutes. The value of nitric oxide (NO) within the brain was measured with a needle electrode which was inserted into the brain. In the treatment group L-NAME was administered with a intravenous injection of 1.5 mg/kg at the beginning of the reperfusion followed by a 60-minute continuous venous infusion of 1.5 mg/kg/hour. In the control group the value of NO after 120 minutes reperfusion increased significantly compared with pre-circulatory arrest, but in the treatment group it did not. There was significant difference between the groups regarding the NO value after 120 minutes reperfusion. Blood pressure after 120 minutes reperfusion in the treatment group was a little higher than the control group, but there was no significant difference between the groups regarding cerebral blood flow, excess lactate and cerebral tissue water content. However, recovery of SEP after 120 minutes reperfusion was detected in all 8 cases of the treatment group, but only in one of the control group (p < 0.001). This data suggests that L-NAME protects the brain against the reperfusion injury under deep hypothermic circulatory arrest. PMID:9170859

Segawa, D; Hatori, N; Yoshizu, H; Tanaka, S

1997-05-01

210

The Effects of C75, an Inhibitor of Fatty Acid Synthase, on Sleep and Metabolism in Mice  

PubMed Central

Sleep is greatly affected by changes in metabolic state. A possible mechanism where energy-sensing and sleep-regulatory functions overlap is related to lipid metabolism. Fatty acid synthase (FAS) plays a central role in lipid metabolism as a key enzyme in the formation of long-chain fatty acids. We studied the effects of systemic administration of C75, an inhibitor of FAS, on sleep, behavioral activity and metabolic parameters in mice. Since the effects of C75 on feeding and metabolism are the opposite of ghrelin's and C75 suppresses ghrelin production, we also tested the role of ghrelin signaling in the actions of C75 by using ghrelin receptor knockout (KO) mice. After a transient increase in wakefulness, C75 elicited dose-dependent and long lasting inhibition of REMS, motor activity and feeding. Simultaneously, C75 significantly attenuated slow-wave activity of the electroencephalogram. Energy expenditure, body temperature and respiratory exchange ratio were suppressed. The diurnal rhythm of feeding was completely abolished by C75. There was significant correlation between the anorectic effects, the decrease in motor activity and the diminished energy expenditure after C75 injection. We found no significant difference between wild-type and ghrelin receptor KO mice in their sleep and metabolic responses to C75. The effects of C75 resemble to what was previously reported in association with visceral illness. Our findings suggest that sleep and metabolic effects of C75 in mice are independent of the ghrelin system and may be due to its aversive actions in mice.

Pellinen, Jacob; Szentirmai, Eva

2012-01-01

211

Chitin nanofibers: preparations, modifications, and applications.  

PubMed

Chitin nanofibers are prepared from the exoskeletons of crabs and prawns by a simple mechanical treatment after the removal of proteins and minerals. The obtained nanofibers have fine nanofiber networks with a uniform width of approximately 10-20 nm and a high aspect ratio. The method used for chitin-nanofiber isolation is also successfully applied to the cell walls of mushrooms. They form a complex with glucans on the fiber surface. A grinder, a Star Burst atomization system, and a high speed blender are all used in the mechanical treatment to convert chitin to nanofibers. Mechanical treatment under acidic conditions is the key to facilitate fibrillation. At pH 3-4, the cationization of amino groups on the fiber surface assists nano-fibrillation by electrostatic repulsive force. By applying this finding, we also prepared chitin nanofibers from dry chitin powder. Chitin nanofibers are acetylated to modify their surfaces. The acetyl DS can be controlled from 1 to 3 by changing the reaction time. An acetyl group is introduced heterogeneously from the surface to the core. Nanofiber morphology is maintained even in the case of high acetyl DS. Optically transparent chitin nanofiber composites are prepared with 11 different types of acrylic resins. Due to the nano-sized structure, all of the composites are highly transparent. Chitin nanofibers significantly increase the Young's moduli and the tensile strengths and decrease the thermal expansion of all acrylic resins due to the reinforcement effect of chitin nanofibers. Chitin nanofibers show chiral separation ability. The chitin nanofiber membrane transports the d-isomer of glutamic acid, phenylalanine, and lysine from the corresponding racemic amino acid mixtures faster than the corresponding l-isomer. The chitin nanofibers improve clinical symptoms and suppress ulcerative colitis in a DSS-induced mouse model of acute ulcerative colitis. Moreover, chitin nanofibers suppress myeloperoxidase activation in the colon and decrease serum interleukin-6 concentrations. PMID:22539071

Ifuku, Shinsuke; Saimoto, Hiroyuki

2012-04-27

212

Synthesis, biological evaluation, and molecular modeling of 1-benzyl-1H-imidazoles as selective inhibitors of aldosterone synthase (CYP11B2).  

PubMed

Reducing aldosterone action is beneficial in various major diseases such as heart failure. Currently, this is achieved with mineralocorticoid receptor antagonists, however, aldosterone synthase (CYP11B2) inhibitors may offer a promising alternative. In this study, we used three-dimensional modeling of CYP11B2 to model the binding modes of the natural substrate 18-hydroxycorticosterone and the recently published CYP11B2 inhibitor R-fadrozole as a rational guide to design 44 structurally simple and achiral 1-benzyl-1H-imidazoles. Their syntheses, in vitro inhibitor potencies, and in silico docking are described. Some promising CYP11B2 inhibitors were identified, with our novel lead MOERAS115 (4-((5-phenyl-1H-imidazol-1-yl)methyl)benzonitrile) displaying an IC(50) for CYP11B2 of 1.7 nM, and a CYP11B2 (versus CYP11B1) selectivity of 16.5, comparable to R-fadrozole (IC(50) for CYP11B2 6.0 nM, selectivity 19.8). Molecular docking of the inhibitors in the models enabled us to generate posthoc hypotheses on their binding modes, providing a valuable basis for future studies and further design of CYP11B2 inhibitors. PMID:20121113

Roumen, Luc; Peeters, Joris W; Emmen, Judith M A; Beugels, Ilona P E; Custers, Erica M G; de Gooyer, Marcel; Plate, Ralf; Pieterse, Koen; Hilbers, Peter A J; Smits, Jos F M; Vekemans, Jef A J; Leysen, Dirk; Ottenheijm, Harry C J; Janssen, Henk M; Hermans, J J Rob

2010-02-25

213

Systemic delivery of a glucosylceramide synthase inhibitor reduces CNS substrates and increases lifespan in a mouse model of type 2 Gaucher disease.  

PubMed

Neuropathic Gaucher disease (nGD), also known as type 2 or type 3 Gaucher disease, is caused by a deficiency of the enzyme glucocerebrosidase (GC). This deficiency impairs the degradation of glucosylceramide (GluCer) and glucosylsphingosine (GluSph), leading to their accumulation in the brains of patients and mouse models of the disease. These accumulated substrates have been thought to cause the severe neuropathology and early death observed in patients with nGD and mouse models. Substrate accumulation is evident at birth in both nGD mouse models and humans affected with the most severe type of the disease. Current treatment of non-nGD relies on the intravenous delivery of recombinant human glucocerebrosidase to replace the missing enzyme or the administration of glucosylceramide synthase inhibitors to attenuate GluCer production. However, the currently approved drugs that use these mechanisms do not cross the blood brain barrier, and thus are not expected to provide a benefit for the neurological complications in nGD patients. Here we report the successful reduction of substrate accumulation and CNS pathology together with a significant increase in lifespan after systemic administration of a novel glucosylceramide synthase inhibitor to a mouse model of nGD. To our knowledge this is the first compound shown to cross the blood brain barrier and reduce substrates in this animal model while significantly enhancing its lifespan. These results reinforce the concept that systemically administered glucosylceramide synthase inhibitors could hold enhanced therapeutic promise for patients afflicted with neuropathic lysosomal storage diseases. PMID:22912851

Cabrera-Salazar, Mario A; Deriso, Matthew; Bercury, Scott D; Li, Lingyun; Lydon, John T; Weber, William; Pande, Nilesh; Cromwell, Mandy A; Copeland, Diane; Leonard, John; Cheng, Seng H; Scheule, Ronald K

2012-08-17

214

Fabrication and characterisation of ?-chitin nanofibers and highly transparent chitin films by pulsed ultrasonication.  

PubMed

?-Chitin nanofibers were fabricated with dried shrimp shells via a simple high-intensity ultrasonic treatment under neutral conditions (60KHz, 300W, pH=7). The diameter of the obtained chitin nanofibers could be controlled within 20-200nm by simply adjusting the ultrasonication time. The pulsed ultrasound disassembled natural chitin into high-aspect-ratio nanofibers with a uniform width (19.4nm after 30min sonication). The EDS, FTIR, and XRD characterisation results verified that ?-chitin crystalline structure and molecular structure were maintained after the chemical purification and ultrasonic treatments. Interestingly, ultrasonication can slightly increase the degree of crystallinity of chitin (from 60.1 to 65.8). Furthermore, highly transparent chitin films (the transmittance was 90.2% at a 600nm) and flexible ultralight chitin foams were prepared from chitin nanofiber hydrogels. PMID:24053832

Lu, Yun; Sun, Qingfeng; She, Xilin; Xia, Yanzhi; Liu, Yixing; Li, Jian; Yang, Dongjiang

2013-07-24

215

Embryonic desiccation resistance in Aedes aegypti: presumptive role of the chitinized Serosal Cuticle  

PubMed Central

Background One of the major problems concerning dengue transmission is that embryos of its main vector, the mosquito Aedes aegypti, resist desiccation, surviving several months under dry conditions. The serosal cuticle (SC) contributes to mosquito egg desiccation resistance, but the kinetics of SC secretion during embryogenesis is unknown. It has been argued that mosquito SC contains chitin as one of its components, however conclusive evidence is still missing. Results We observed an abrupt acquisition of desiccation resistance during Ae. aegypti embryogenesis associated with serosal cuticle secretion, occurring at complete germ band extension, between 11 and 13 hours after egglaying. After SC formation embryos are viable on dry for at least several days. The presence of chitin as one of the SC constituents was confirmed through Calcofluor and WGA labeling and chitin quantitation. The Ae. aegypti Chitin Synthase A gene (AaCHS1) possesses two alternatively spliced variants, AaCHS1a and AaCHS1b, differentially expressed during Ae. aegypti embryonic development. It was verified that at the moment of serosal cuticle formation, AaCHS1a is the sole variant specifically expressed. Conclusion In addition to the peritrophic matrix and exoskeleton, these findings confirm chitin is also present in the mosquito serosal cuticle. They also point to the role of the chitinized SC in the desiccation resistance of Ae. aegypti eggs. AaCHS1a expression would be responsible for SC chitin synthesis. With this embryological approach we expect to shed new light regarding this important physiological process related to the Ae. aegypti life cycle.

Rezende, Gustavo Lazzaro; Martins, Ademir Jesus; Gentile, Carla; Farnesi, Luana Cristina; Pelajo-Machado, Marcelo; Peixoto, Alexandre Afranio; Valle, Denise

2008-01-01

216

An inhibitor of inducible nitric oxide synthase decreases forearm blood flow in patients with congestive heart failure  

Microsoft Academic Search

OBJECTIVESThe functional activation of inducible nitric oxide synthase (iNOS) was evaluated as a source of nitric oxide (NO) in the forearm of patients with heart failure.BACKGROUNDAlthough endogenous NO is normally produced by constitutive NO synthase (cNOS) in patients with congestive heart failure (CHF), expression of iNOS provides an additional source of NO. However, there are no in vivo studies showing

Yutaka Ishibashi; Toshio Shimada; Yo Murakami; Nobuyuki Takahashi; Takeshi Sakane; Takashi Sugamori; Shuzo Ohata; Shin-ichi Inoue; Yoko Ohta; Ko Nakamura; Hiromi Shimizu; Harumi Katoh; Michio Hashimoto

2001-01-01

217

Utilisation of chitinous materials in pigment adsorption.  

PubMed

The effect of adding the cells of four lactobacilli to a squid pen powder (SPP)-containing medium on prodigiosin (PG) production by Serratia marcescens TKU011 is examined. The best increase in PG productivity was shown by strain TKU012. Among the samples of strain TKU012 and the chitinous materials of cicada casting powder (CCP), shrimp shell powder (SSP), squid pen powder (SPP), ?-chitin, and ?-chitin, TKU012 cells displayed the best adsorption rate (84%) for PG, followed by CCP, SSP, SPP, ?-chitin, and ?-chitin. As for the water-soluble food colourants, Allura Red AC (R40) and Tartrazne (Y4), SPP and SSP had better adsorptive powers than pure chitin preparations, strain TKU012, and CCP. Treatment with organic solvents, hot alkali, or proteases (papain, bromelain) diminished the adsorption rates of the biosorbents. PMID:22953835

Wang, San-Lang; Chen, Yan-Cheng; Yen, Yue-Horng; Liang, Tzu-Wen

2012-05-19

218

Comparison of plasma and tissue levels of ZD1694 (Tomudex), a highly polyglutamatable quinazoline thymidylate synthase inhibitor, in preclinical models.  

PubMed Central

ZD1694 (Tomudex, raltitrexed) is a specific quinazoline antifolate thymidylate synthase inhibitor that relies on polyglutamation for high potency. Antibodies to ZD1694 have been used to establish a sensitive radioimmunoassay as an alternative to high-performance liquid chromatography (HPLC). The radioimmunoassay is reproducible, accurate and provides a means of determining low levels of ZD1694 in plasma (< 1 nM). By virtue of the high cross-reactivity of the antibodies with polyglutamated forms of ZD1694, it is also possible to measure the total concentration of drug in tissues. Results obtained in L1210 mouse leukaemia cells and in mouse tissues were similar to those previously determined using radiolabelled drug. Pharmacokinetic studies in mice have confirmed that the compound is rapidly eliminated from the plasma and that there is a prolonged terminal elimination phase. ZD1694 was measured in plasma (0.56 ng ml(-1); 1.2 pmol ml(-1)) up to 7 days after a single i.p. dose of 100 mg kg(-1) ZD1694. Liver, kidney and gut epithelium had a substantially higher level of ZD1694 immunoreactivity than plasma. For example, 24 h after a single i.p. dose at 1, 10 and 100 mg kg(-1), total drug levels in the liver were 480, 325 and 152 times higher than plasma levels respectively. In kidney and gut epithelium, total drug levels at these doses were approximately 55 and 34 times those of plasma. The high tissue to plasma ratios were maintained for at least 7 days after administration. Similarly, high tissue to plasma ratios (> 100) were found in dogs treated with a clinically relevant dose of ZD1694. These were maintained for 4 weeks in liver and kidney tissue (> 100). Total gastrointestinal concentrations of ZD1694 were approximately 10 times higher than plasma 3 days after administration, but levels were near to the limit of detection at 4 weeks. These results are consistent with extensive polyglutamation of ZD1694 within tissues in both mice and dog and provide further support for the infrequent schedule that has been used clinically. Although it has not been possible to measure individual polyglutamated forms of ZD1694, the radioimmunoassay provides a convenient means of assessing total drug levels in tissues and is currently the only method suitable for measuring the extent of drug retention in normal tissue and tumour biopsies obtained from patients treated with ZD1694.

Aherne, G. W.; Ward, E.; Lawrence, N.; Dobinson, D.; Clarke, S. J.; Musgrove, H.; Sutcliffe, F.; Stephens, T.; Jackman, A. L.

1998-01-01

219

Chitin, Chitinase Responses, and Invasive Fungal Infections  

PubMed Central

The human immune system is capable of recognizing and degrading chitin, an important cell wall component of pathogenic fungi. In the context of host-immune responses to fungal infections, herein we review the particular contributions and interplay of fungus and chitin recognition, and chitin-degrading enzymes, known as chitinases. The mechanisms of host chitinase responses may have implications for diagnostic assays as well as novel therapeutic approaches for patients that are at risk of contracting fatal fungal infections.

Vega, Karina; Kalkum, Markus

2012-01-01

220

Crystallization of calcite on chitin  

Microsoft Academic Search

Chitin, a nitrogen-containing polysaccharide which is a major component of the exoskeletons of arthropods, was found to be a substrate favouring the deposition of calcite crystals from stable supersaturated solutions at pH 8.50 and at 25°C. The crystallization was studied at constant solution supersaturation thus making it possible for relatively large amounts of the overgrowth to be formed and be

F. Manoli; S. Koutsopoulos; E. Dalas

1997-01-01

221

Multivariate SAR/QSAR of 3-aryl-4-hydroxyquinolin-2(1H)-one derivatives as type I fatty acid synthase (FAS) inhibitors.  

PubMed

Two multivariate studies, a PCA-SAR and a PLS-QSAR, of 3-aryl-4-hydroxyquinolin-2(1H)-one derivatives described as type I fatty acid synthase (FAS) inhibitors, are presented in this work. The variable selection was performed with the Fisher's weight and Ordered Predictors Selection (OPS) algorithm, respectively. In the PCA, a separation between active and inactive compounds was obtained by six descriptors (topological and geometrical). The PLS model presented five descriptors and two Latent Variables. Leave-N-out cross validation and y-randomization test showed that the model presented robustness and no chance correlation, respectively, and the descriptors indicated that the FAS inhibition depends on electronic distribution of the investigated compounds. The model obtained in this study may provide a guidance for proposition of new FAS inhibitors. PMID:20965618

de Melo, Eduardo Borges

2010-09-29

222

Glycogen Synthase Kinase 3? Inhibitor (2'Z,3'E)-6-Bromo-indirubin- 3'-Oxime Enhances Drug Resistance to 5-Fluorouracil Chemotherapy in Colon Cancer Cells  

PubMed Central

Objective To explore the effects and mechanism of glycogen synthase kinase 3? (GSK-3?) inhibitor (2'Z,3'E)-6-bromo-indirubin-3'-oxime (BIO) on drug resistance in colon cancer cells. Methods The colon cancer SW480 and SW620 cells were treated with BIO, 5-fluorouracil (5-FU) and BIO/5-FU, separately. Cell cycle distribution, apoptosis level and efflux ability of rhodamine 123 (Rh123) were detected by flow cytometry. The protein expressions of P-glycoprotein (P-gp), multidrug resistance protein 2 (MRP2), thymidylate synthase (TS), ?-catenin, E2F-1 and Bcl-2 were detected by Western blot. ?-catenin and P-gp were stained with double immunofluorescence and observed under a confocal microscope. Results BIO up-regulated ?-catenin, P-gp, MRP2 and TS, enhanced the efflux ability of Rh123, decreased Bcl-2 protein and gave the opposite effect to E2F-1 protein in SW480 and SW620 cells. Furthermore, BIO significantly inhibited cell apoptosis, increased S and G2/M phase cells, and reduced the cell apoptosis induced by 5-FU in SW480 cells, whereas the effects were slight or not obvious in SW620 cells. Conclusion GSK-3? was involved in drug resistance regulation, and activation of ?-catenin and inhibition of E2F-1 may be the most responsible for the enhancement of 5-FU chemotherapy resistance induced by GSK-3? inhibitor BIO in colon cancer.

Liu, Kun-ping; Luo, Feng; Xie, Si-ming; Tang, Li-juan; Chen, Mei-xiang; Wu, Xue-fang

2012-01-01

223

A novel lumazine synthase inhibitor derived from oxidation of 1,3,6,8-tetrahydroxy-2,7-naphthyridine to a tetraazaperylenehexaone derivative.  

PubMed

Air oxidation of 1,3,6,8-tetrahydroxy-2,7-naphthyridine afforded 2,5,8,11-tetraaza-5,11-dihydro-4,10-dihydroxyperylene-1,3,6,7,9,12-hexaone. X-ray crystallography of the product revealed that it exists in the meso form in the solid state. The mechanism of product formation most likely involves oxidative phenolic coupling and oxidation. The product proved to be a competitive inhibitor of Schizosaccharomyces pombe lumazine synthase with a Ki of 66+/-13 microM in Tris buffer and 22+/-4 microM in phosphate buffer. This is significantly more potent than the reactant (Ki 350+/-76 microM, competitive inhibition), which had previously been identified as a lumazine synthase inhibitor by high-throughput screening. Ab initio calculations indicate that the meso form is slightly less stable than the enantiomeric form, and that the two forms interconvert rapidly at room temperature. PMID:17348709

Zhang, Yanlei; Illarionov, Boris; Bacher, Adelbert; Fischer, Markus; Georg, Gunda I; Ye, Qi-Zhuang; Vander Velde, David; Fanwick, Phillip E; Song, Yunlong; Cushman, Mark

2007-03-10

224

Chitin synthetase in encysting Giardia lamblia and Entamoeba invadens  

SciTech Connect

Giardia lamblia (Gl) and Entamoeba invadens (Ei) are protozoan parasites with two morphologic stages in their life cycles. Motile trophozoites colonize the intestine of humans and reptiles respectively. Water resistant cysts, which can survive outside the host, transmit infection. In vitro cyst formation of Ei from trophozoites has been reported, and the authors have recently induced in vitro encystation of Gl. Although the cyst walls of both parasites contain chitin, it synthesis by encysting trophozoites has not been reported. The authors now show that encystation conditions greatly increase chitin synthetase (CS) specific activity (incorporation of /sup 3/H GlcNAc from UDP-GlcNAc into TCA-or alcohol-precipitable material). Extracts of encysting Gl incorporated 3.6 nmol/mg protein in 5 hr compared to < 0.005 in controls. Extracts of encysting Fi incorporated 4.8 n mol/mg protein, compared to 1.7 in the control. CS activity of both parasites requires preformed chitin. The Gl enzyme requires a reducing agent, is inhibited by digitonin and the CS inhibitors, polyoxin D and Nikkomycin, but not by tunicamycin. The product is digested by chitinase. Ei enzyme does not require a reducing agent and is stimulated by 1 mg/ml digitonin, but inhibited by higher concentrations. These studies demonstrate CS enzymes which may play important roles in encystation of Gl and Ei.

Das, S.; Gillin, F.D.

1987-05-01

225

ICI D1694, a Quinazoline Antifolate Thymidylate Synthase Inhibitor That Is a Potent Inhibitor of LI 210 Tumor Cell Growth in Vitro and in Vivo:A New Agent for Clinical Study1  

Microsoft Academic Search

AĂ­-(5-|Ar-(3,4-dihydro-2-methyl-4-oxoquinazolin-6-ylmethyl)-\\/V- methylamino)-2-thenoyl)-i.-glutamic acid (ICI D1694) is a water-soluble, folate-based thymidylate synthase (TS) inhibitor designed to be a less toxic and more potent analogue of the clinically tested \\/V'u-propargyl-5,8- dideazafolic acid. Inhibition of isolated L1210 TS by ICI D1694 is mixed noncompetitive (although tending toward competitive), with a A',of 62 n\\\\l (\\/T,,, = 960 n\\\\l). The synthetic -y-polyglutamates are up to

Ann L. Jackman; Gordon A. Taylor; William Gibson; Rosemary Kimbell; Melody Brown; A. Hilary Calvert; Ian R. Judson; Leslie R. Hughes

226

Selective growth inhibition by glycogen synthase kinase-3 inhibitors in tumorigenic HeLa hybrid cells is mediated through NF-?B-dependent GLUT3 expression  

PubMed Central

Carcinogenesis and cancer progression, driven by mutations in oncogenes and tumor-suppressor genes, result in biological differences between normal and cancer cells in various cellular processes. Specific genes and signaling molecules involved in such cellular processes may be potential therapeutic targets of agents that specifically interact with the key factors in cancer cells. Increased glucose uptake is fundamental to many solid tumors and well associated with increases in glycolysis and the overexpression of glucose transporters (GLUTs) such as GLUT1 and GLUT3 at the plasma membrane. Here, we used cell-based screening to identify glycogen synthase kinase-3? (GSK-3?) inhibitors that selectively target GLUT3-expressing tumorigenic HeLa cell hybrids as compared with non-tumorigenic hybrids that express GLUT1 alone. The GSK-3 inhibitors as well as GSK-3? RNAi suppressed GLUT3 expression at the level of transcription, leading to apoptosis. This suppression was associated with NF-?B in a p53-independent manner. Furthermore, GSK-3 inhibitors exhibited a synergistic effect with anticancer agents such as adriamycin and camptothecin in GULT3-overexpressing colon cancer cells, but little effect in non-producing A431 cells. These results suggest a potential use of GSK-3 inhibitors to selectively kill cancer cells that overexpress GLUT3.

Watanabe, M; Abe, N; Oshikiri, Y; Stanbridge, E J; Kitagawa, T

2012-01-01

227

Implantable applications of chitin and chitosan  

Microsoft Academic Search

Chitin, extracted primarily from shellfish sources, is a unique biopolymer based on the N-acetyl-glucosamine monomer. More than 40 years have lapsed since this biopolymer had aroused the interest of the scientific community around the world for its potential biomedical applications. Chitin, together with its variants, especially its deacetylated counterpart chitosan, has been shown to be useful as a wound dressing

Eugene Khor; Lee Yong Lim

2003-01-01

228

A review of chitin and chitosan applications  

Microsoft Academic Search

Chitin is the most abundant natural amino polysaccharide and is estimated to be produced annually almost as much as cellulose. It has become of great interest not only as an underutilized resource, but also as a new functional material of high potential in various fields, and recent progress in chitin chemistry is quite noteworthy. The purpose of this review is

Majeti N. V Ravi Kumar

2000-01-01

229

The Nitric Oxide Synthase Inhibitor NG-Nitro-L-Arginine Increases Basal Forebrain Acetylcholine Release during Sleep and Wakefulness  

Microsoft Academic Search

Cholinergic neurotransmission in the basal forebrain changes across the sleep\\/wake cycle, and considerable data show cor- tical activation by ACh originating from basal forebrain neurons. These findings have stimulated efforts to elucidate molecular modulators of ACh release within the basal forebrain. Basal forebrain cholinergic neurons contain nitric oxide synthase (NOS), the enzyme that produces the gaseous neuromodulator nitric oxide. This

Jacqueline Vazquez; Ralph Lydic; Helen A. Baghdoyan

230

Antiproliferative and ultrastructural effects of BPQ-OH, a specific inhibitor of squalene synthase, on Leishmania amazonensis  

Microsoft Academic Search

Parasites of the Leishmania genus require for the growth and viability the de novo synthesis of specific sterols as such as episterol and 5-dehydroepisterol because cholesterol, which is abundant in their mammalian hosts, does not fulfill the parasite sterol requirements. Squalene synthase catalyzes the first committed step in the sterol biosynthesis and has been studied as a possible target for

Juliany C. F. Rodrigues; Julio A. Urbina; Wanderley de Souza

2005-01-01

231

Cardiopulmonary Effects of Chronic Administration of the NO Synthase Inhibitor L-NAME in the Chick Embryo  

Microsoft Academic Search

Background: Experimental observations in mammalian models suggest that endothelial nitric oxide (NO) synthase (NOS) content and activity are decreased in persistent pulmonary hypertension of the newborn. Objectives: To test the hypothesis that disruption of NO signaling in the developing chick embryo lung may contribute to pulmonary hypertension. Methods: We analyzed pulmonary arterial reactivity and structure and heart morphology of 19-day

Eduardo Villamor; Carolina G. A. Kessels; Robert J. van Suylen; Jo G. R. De Mey; Carlos E. Blanco

2005-01-01

232

Glycogen synthase kinase-3 beta inhibitor suppresses Porphyromonas gingivalis lipopolysaccharide-induced CD40 expression by inhibiting nuclear factor-kappa B activation in mouse osteoblasts.  

PubMed

Bone-forming osteoblasts have been recently reported capable of expressing the critical co-stimulatory molecule CD40 upon exposure to bacterial infection, which supports the unappreciated role of osteoblasts in modulating bone inflammation. Recent studies highlight the anti-inflammatory potential of glycogen synthase kinase-3? (GSK-3?) inhibitors; however, their effect on osteoblasts remains largely unclear. In the present study, we showed that treatment with SB216763, a highly specific GSK-3? inhibitor, resulted in a dose-dependent decrease in the mRNA and protein expression of CD40, as well as production of pro-inflammatory cytokines IL-6, TNF-? and IL-1?, in the Porphyromonas gingivalis-lipopolysaccharide (LPS)-stimulated murine osteoblastic-like MC3T3-E1 cells. Furthermore, inhibition of GSK-3? remarkably represses the LPS-induced activation of the nuclear factor kappa B (NF-?B) signaling pathway by suppressing I?B? phosphorylation, NF-?Bp65 nuclear translocation, and NF-?Bp65 DNA binding activity. Closer investigation by immunoprecipitation assay revealed that ?-catenin can physically interact with NF-?Bp65. The negative regulation effect of GSK-3? inhibitor on CD40 expression is mediated through ?-catenin, for siRNA of ?-catenin attenuated the GSK-3? inhibitor-induced repression of NF-?B activation and, consequently, the expression of CD40 and production of pro-inflammatory cytokines in LPS-stimulated MC3T3-E1 cells. Thus our results elucidate the molecular mechanisms whereby GSK-3? inhibitor prevents the LPS-induced CD40 expression on osteoblasts and provide supportive evidence of the potential role of GSK-3? inhibitors in suppressing the immune function of osteoblasts in inflammatory bone diseases. PMID:22580404

Die, Liu; Yan, Peng; Jun Jiang, Zhai; Min Hua, Teng; Cai, Wen; Xing, Liang

2012-05-14

233

Antitumor activity of oxaliplatin in combination with 5-fluorouracil and the thymidylate synthase inhibitor AG337 in human colon, breast and ovarian cancers.  

PubMed

Oxaliplatin, classical [5-fluorouracil (5-FU)] and non-classical (AG337) thymidylate synthase inhibitors have shown promising activity in the treatment of cancer. This study investigates the cytotoxic effects of oxaliplatin in combination with 5-FU and AG337 in cultured human colon (HT29, CaCo2), breast (MCF-7, MDA-MB-231) and ovarian (2008) cancer cell lines, and their derived counterparts selected for their resistance to 5-FU (HT29-5-FU), doxorubicin (MCF-7mdr) or cisplatin (2008C13). Therapeutic experiments were conducted in mice bearing colon-HT29 xenografts and in the GR hormone-independent mammary carcinoma model. In vitro, oxaliplatin shows potent cytotoxic activity in colon (IC50 from 2.1 +/- 1.1 to 5.9 +/- 1.7 microM), ovarian (IC50 = 10 +/- 1.6 microM) and breast cancer cells (IC50 from 7.4 +/- 2.7 to 17.9 +/- 7.1 microM). Oxaliplatin was a potent inhibitor of DNA synthesis and bound to cellular DNA. Surprisingly, the overall amount of oxaliplatin DNA binding was significantly inferior to that induced by isocytotoxic concentrations of cisplatin in HT29 (p=0.026). In vitro, synergistic antiproliferative effects were observed when oxaliplatin was added to 5-FU and AG337. Those synergistic effects of combinations were maintained in colon HT29-5-FU cancer cells. In vivo, 5-FU increased significantly the antitumor activity of oxaliplatin in HT29 xenografts (p=0.0036), and similarly 5-FU and AG337 increased the activity of oxaliplatin in the GR tumor model (p=0.0012). These data may encourage further clinical investigation of oxaliplatin in combination with classical and non-classical thymidylate synthase inhibitors in the treatment of human cancers. PMID:9402315

Raymond, E; Buquet-Fagot, C; Djelloul, S; Mester, J; Cvitkovic, E; Allain, P; Louvet, C; Gespach, C

1997-10-01

234

Crystallization of calcite on chitin  

NASA Astrophysics Data System (ADS)

Chitin, a nitrogen-containing polysaccharide which is a major component of the exoskeletons of arthropods, was found to be a substrate favouring the deposition of calcite crystals from stable supersaturated solutions at pH 8.50 and at 25°C. The crystallization was studied at constant solution supersaturation thus making it possible for relatively large amounts of the overgrowth to be formed and be identified exclusively as calcite. The induction periods varied markedly with supersaturation. The apparent order found from kinetics data was n = 2, thus suggesting a surface diffusion-controlled mechanism.

Manoli, F.; Koutsopoulos, S.; Dalas, E.

1997-12-01

235

Endochitinase activity determination using N-fluorescein-labeled chitin  

Microsoft Academic Search

A fluorimetric method for the determination of endochitinolytic activity using N-fluorescein-labeled chitin (FITC-Chitin) is proposed, and a procedure for FITC-Chitin preparation with a degree of FITC content of 2.2 mol% (one FITC molecule per 45 glucosamine residues) is described. FITC-Chitin is capable to distinguish endochitinase and exochitinase (?-N-acetylglucosaminidase) activities.

Vladimir E Tikhonov; Luis V Lopez-Llorca; Jesús Salinas; Elena Monfort

2004-01-01

236

Chitin nanocrystals prepared by TEMPO-mediated oxidation of alpha-chitin.  

PubMed

Chitin nanocrystals dispersed in water were successfully prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) mediated oxidation of alpha-chitin in water at pH 10 under specific conditions, followed by ultrasonic treatment. When the amount of NaClO added as co-oxidant in the oxidation was 5.0 mmol/g of chitin, the weight percentage of the water-insoluble fraction in the TEMPO-oxidized chitin was 90%, and its carboxylate content reached 0.48 mmol/g. Since the TEMPO-oxidized chitin thus prepared had a crystallinity as high as that of the original alpha-chitin, the C6 carboxylate groups formed by TEMPO-mediated oxidation can be regarded as being present only on the chitin crystallite surfaces. No N-deacetylation occurred on the TEMPO-oxidized chitins. When the TEMPO-oxidized chitin was subjected to ultrasonic treatment in water, mostly individualized chitin nanocrystals were obtained, and the average nanocrystal length and width were 340 and 8 nm, respectively. PMID:18159931

Fan, Yimin; Saito, Tsuguyuki; Isogai, Akira

2007-12-27

237

Chelation of Extracellular Calcium-Induced Cell Death was Prevented by Glycogen Synthase Kinase3 Inhibitors in PC12 Cells  

Microsoft Academic Search

Calcium ion is a secondary messenger that mediates a variety of physiological responses of neurons, including cell survival\\u000a responses. To determine the role of calcium in regulating neuronal survival and death, we examined whether chelation of extracellular\\u000a calcium with EGTA induces caspase-dependent apoptotic cell death and whether glycogen synthase kinase-3 is involved in EGTA-induced\\u000a cell death in PC12 cells. EGTA

Tsuneo Takadera; Megumi Ohtsuka; Haruka Aoki

2010-01-01

238

Structure of N-acetyl-L-glutamate synthase/kinase from Maricaulis maris with the allosteric inhibitor L-arginine bound.  

PubMed

Maricaulis maris N-acetylglutamate synthase/kinase (mmNAGS/K) catalyzes the first two steps in L-arginine biosynthesis and has a high degree of sequence and structural homology to human N-acetylglutamate synthase, a regulator of the urea cycle. The synthase activity of both mmNAGS/K and human NAGS are regulated by L-arginine, although L-arginine is an allosteric inhibitor of mmNAGS/K, but an activator of human NAGS. To investigate the mechanism of allosteric inhibition of mmNAGS/K by L-arginine, we have determined the structure of the mmNAGS/K complexed with L-arginine at 2.8 Ĺ resolution. In contrast to the structure of mmNAGS/K in the absence of L-arginine where there are conformational differences between the four subunits in the asymmetric unit, all four subunits in the L-arginine liganded structure have very similar conformations. In this conformation, the AcCoA binding site in the N-acetyltransferase (NAT) domain is blocked by a loop from the amino acid kinase (AAK) domain, as a result of a domain rotation that occurs when L-arginine binds. This structural change provides an explanation for the allosteric inhibition of mmNAGS/K and related enzymes by L-arginine. The allosterically regulated mechanism for mmNAGS/K differs significantly from that for Neisseria gonorrhoeae NAGS (ngNAGS). To define the active site, several residues near the putative active site were mutated and their activities determined. These experiments identify roles for Lys356, Arg386, Asn391 and Tyr397 in the catalytic mechanism. PMID:23850694

Zhao, Gengxiang; Haskins, Nantaporn; Jin, Zhongmin; M Allewell, Norma; Tuchman, Mendel; Shi, Dashuang

2013-07-10

239

Molecular Dynamic Simulation and Inhibitor Prediction of Cysteine Synthase Structured Model as a Potential Drug Target for Trichomoniasis  

PubMed Central

In our presented research, we made an attempt to predict the 3D model for cysteine synthase (A2GMG5_TRIVA) using homology-modeling approaches. To investigate deeper into the predicted structure, we further performed a molecular dynamics simulation for 10?ns and calculated several supporting analysis for structural properties such as RMSF, radius of gyration, and the total energy calculation to support the predicted structured model of cysteine synthase. The present findings led us to conclude that the proposed model is stereochemically stable. The overall PROCHECK G factor for the homology-modeled structure was ?0.04. On the basis of the virtual screening for cysteine synthase against the NCI subset II molecule, we present the molecule 1-N, 4-N-bis [3-(1H-benzimidazol-2-yl) phenyl] benzene-1,4-dicarboxamide (ZINC01690699) having the minimum energy score (?13.0?Kcal/Mol) and a log?P value of 6 as a potential inhibitory molecule used to inhibit the growth of T. vaginalis infection.

Singh, Satendra; Singh, Atul Kumar; Gautam, Budhayash

2013-01-01

240

The chitin biosynthesis pathway in Entamoeba and the role of glucosamine-6-P isomerase by RNA interference.  

PubMed

Entamoeba histolytica, the causative agent of amoebiasis, infects through its cyst form. A thick chitin wall protects the cyst from the harsh environment outside of the body. It is known that chitin is synthesized only during encystation, but the chitin synthesis pathway (CSP) of Entamoeba is not well characterized. In this report, we have identified the genes involved in chitin biosynthesis from the Entamoeba genome database and verified their expression profile at the transcriptional level in encysting Entamoeba invadens. Semi-quantitative RT-PCR (sqRT-PCR) analysis showed that all the chitin pathway genes are entirely absent or transcribed at low levels in trophozoites. The mRNA expression of most of the CSP genes reached their maximum level between 9 and 12h after the in vitro initiation of encystation. Double-stranded RNA-mediated silencing of glucosamine-6-P isomerase (Gln6Pi) reduced chitin synthesis to 62-64%, which indicates that Gln6Pi might be a key enzyme for regulating chitin synthesis in Entamoeba. The study of different enzymes involved in glycogen metabolism revealed that stored glycogen is converted to glucose during encystation. It is clear from the sqRT-PCR analysis that the rate of glycolysis decreases as encystation proceeds. Encystation up-regulates the expression of glycogen phosphorylase, which is responsible for glycogen degradation. The significant decrease in chitin synthesis in encysting cells treated with a specific inhibitor of glycogen phosphorylase indicates that the glucose obtained from the degradation of stored glycogen in trophozoites might be one of the major sources of glucose for chitin synthesis. PMID:23058929

Samanta, Sintu Kumar; Ghosh, Sudip K

2012-10-09

241

Chitin extraction and characterization from Daphnia magna resting eggs.  

PubMed

New application areas for chitin and its derivatives have been extensively investigated and there is a solid, growing demand for new chitin sources. In this present study, chitin content of Daphnia magna resting egg (18-21%) was determined for the first time. FTIR, elemental analysis, TGA, XRD and SEM studies revealed the structural and thermal properties of extracted ?-chitin. This study suggests that D. magna resting eggs can be exploited as an attractive alternative chitin source. PMID:23973492

Kaya, Murat; Sargin, Idris; Tozak, Kabil Özcan; Baran, Talat; Erdogan, Sevil; Sezen, Göksal

2013-08-22

242

Design and synthesis of N-2,6-difluorophenyl-5-methoxyl-1,2,4-triazolo[1,5-a]-pyrimidine-2-sulfonamide as acetohydroxyacid synthase inhibitor.  

PubMed

Triazolopyrimidine-2-sulfonamide belongs to a herbicide group called acetohydroxyacid synthase inhibitors. With the aim to discover new triazolopyrimidine sulfonanilide compounds with high herbicidal activity and faster degradation rate in soil, the methyl group of Flumetsulam (FS) was modified into a methoxy group to produce a new herbicidal compound, N-2,6-difluorophenyl-5-methoxy-1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonamide (experimental code: Y6610). The enzymatic kinetic results indicated that compound Y6610 and FS have k(i) values of 3.31x10(-6) M and 3.60x10(-7) M against Arabidopsis thaliana AHAS, respectively. The 10-fold lower enzyme-inhibiting activity of Y6610 was explained rationally by further computational simulations and binding free energy calculations. In addition, compound Y6610 was found to display the same level in vivo post-emergent herbicidal activity as FS against some broad-leaf weeds and good safety to rice, maize, and wheat at the dosages of 75-300 gai/ha. Further determination of the half-lives in soil revealed that the half-life in soil of Y6610 is 3.9 days shorter than that of FS. The experimental results herein showed that compound Y6610 could be regarded as a new potential acetohydroxyacid synthase-inhibiting herbicide candidate for further study. PMID:19342247

Chen, Chao-Nan; Lv, Li-Li; Ji, Feng-Qin; Chen, Qiong; Xu, Hui; Niu, Cong-Wei; Xi, Zhen; Yang, Guang-Fu

2009-03-14

243

Cross-linking of the endogenous inhibitor protein (IF1) with rotor (gamma, epsilon) and stator (alpha) subunits of the mitochondrial ATP synthase.  

PubMed

The location of the endogenous inhibitor protein (IF1) in the rotor/stator architecture of the bovine mitochondrial ATP synthase was studied by reversible cross-linking with dithiobis(succinimidylpropionate) in soluble F1I and intact F1F0I complexes of submitochondrial particles. Reducing two-dimensional electrophoresis, Western blotting, and fluorescent cysteine labeling showed formation of alpha-IF1, IF1-IF1, gamma-IF1, and epsilon-IF1 cross-linkages in soluble F1I and in native F1F0I complexes. Cross-linking blocked the release of IF1 from its inhibitory site and therefore the activation of F1I and F1F0I complexes in a dithiothreitol-sensitive process. These results show that the endogenous IF1 is at a distance < or = 12 angstroms to gamma and epsilon subunits of the central rotor of the native mitochondrial ATP synthase. This finding strongly suggests that, without excluding the classical assumption that IF1 inhibits conformational changes of the catalytic beta subunits, the inhibitory mechanism of IF1 may involve the interference with rotation of the central stalk. PMID:12678435

Minauro-Sanmiguel, Fernando; Bravo, Concepción; García, José J

2002-12-01

244

Feeding the nitric oxide synthase inhibitor L-N(omega)nitroarginine elevates serum very low density lipoprotein and hepatic triglyceride synthesis in rats.  

PubMed

This study was conducted to study the influence of dietary L-N(omega)nitroarginine (L-NNA), a nitric oxide (NO) synthase inhibitor, on serum lipids and lipoproteins and on the activities of enzymes related to lipid metabolism in rats. Feeding rats a diet containing 0.2 g/kg L-NNA for 5 weeks elevated serum concentrations of triglyceride, cholesterol, phospholipid, and free fatty acid and reduced serum nitrate (an oxidation product of NO). The elevation in serum triglyceride was mainly due to the elevation in very low density lipoprotein (VLDL) triglyceride. Contents of cholesterol and phospholipid in the VLDL fraction also were elevated by L-NNA. L-NNA treatment caused significantly higher activity of hepatic microsomal phosphatidate phosphohydrolase (the rate-limiting enzyme in triglyceride synthesis) and lower activity of hepatic carnitine palmitoyltransferase (the rate-limiting enzyme in fatty acid oxidation). Activities of hepatic enzymes responsible for fatty acid synthesis such as glucose-6-phosphate dehydrogenase, malic enzyme, and fatty acid synthase were unaffected by L-NNA. The activity of hepatic microsomal phosphocholine cytidyltransferase (the rate-limiting enzyme in phosphatidylcholine synthesis) was reduced significantly by L-NNA. Our results suggest that lower NO production caused the elevations in hepatic triglyceride synthesis by higher esterification of fatty acid and lower fatty acid oxidation, leading to an enrichment of VLDL triglyceride. PMID:15539300

Goto, T; Ohnomi, S; Khedara, A; Kato, N; Ogawa, H; Yanagita, T

1999-05-01

245

N-Acetyl Glucosamine Obtained from Chitin by Chitin Degrading Factors in Chitinbacter tainanesis  

PubMed Central

A novel chitin-degrading aerobe, Chitinibacter tainanensis, was isolated from a soil sample from southern Taiwan, and was proved to produce N-acetyl glucosamine (NAG). Chitin degrading factors (CDFs) were proposed to be the critical factors to degrade chitin in this work. When C. tainanensis was incubated with chitin, CDFs were induced and chitin was converted to NAG. CDFs were found to be located on the surface of C. tainanensis. N-Acetylglucosaminidase (NAGase) and endochitinase activities were found in the debris, and the activity of NAGase was much higher than that of endochitinase. The optimum pH of the enzymatic activity was about 7.0, while that of NAG production by the debris was 5.3. These results suggested that some factors in the debris, in addition to NAGase and endochitinase, were crucial for chitin degradation.

Chen, Jeen-Kuan; Shen, Chia-Rui; Yeh, Chao-Hsien; Fang, Bing-Shiun; Huang, Tung-Li; Liu, Chao-Lin

2011-01-01

246

1-(Fluoroalkylidene)-1,1-bisphosphonic Acids are Potent and Selective Inhibitors of the Enzymatic Activity of Toxoplasma gondii Farnesyl Pyrophosphate Synthase  

PubMed Central

?-Fluorinated-1,1-bisphosphonic acids derived from fatty acids were designed, synthesized and biologically evaluated against Trypanosoma cruzi, the etiologic agent of Chagas disease and against Toxoplasma gondii, the responsible agent of toxoplasmosis and also towards the target parasitic enzymes farnesyl pyrophosphate synthase of T. cruzi (TcFPPS) and T gondii (TgFPPS), respectively. Interestingly, 1-fluorononylidene-1,1-bisphosphonic acid (compound 43) has proven to be an extremely potent inhibitor of the enzymatic activity of TgFPPS at the low nanomolar range exhibiting an IC50 of 30 nM. This compound was two-fold more potent than risedronate (IC50 = 74 nM) taken as a positive control. This enzymatic activity was associated to a strong cell growth inhibition against tachyzoites of T. gondii having an IC50 value of 2.7 ?M.

Szajnman, Sergio H.; Rosso, Valeria S.; Malayil, Leena; Smith, Alyssa; Moreno, Silvia N. J.; Docampo, Roberto

2012-01-01

247

Structural Basis for the Design of Potent and Species-specific Inhibitors of 3-hydroxy-3-methylglutaryl CoA Synthases  

SciTech Connect

3-Hydroxy-3-methylglutaryl CoA synthase (HMGS) catalyzes the first committed step in the mevalonate metabolic pathway for isoprenoid biosynthesis and serves as an alternative target for cholesterol-lowering and antibiotic drugs. We have determined a previously undescribed crystal structure of a eukaryotic HMGS bound covalently to a potent and specific inhibitor F-244 [(E,E)-11-[3-(hydroxymethyl)-4-oxo-2-oxytanyl]-3,5,7-trimethyl-2,4-undecadienenoic acid]. Given the accessibility of synthetic analogs of the F-244 natural product, this inhibited eukaryotic HMGS structure serves as a necessary starting point for structure-based methods that may improve the potency and species-specific selectivity of the next generation of F-244 analogs designed to target particular eukaryotic and prokaryotic HMGS.

Pojer,F.; Ferrer, J.; Richard, S.; Nagegowda, D.; Chye, M.; Bach, T.; Noel, J.

2006-01-01

248

Ni(2+), a double-acting inhibitor of neuronal nitric oxide synthase interfering with L-arginine binding and Ca(2+)/calmodulin-dependent enzyme activation.  

PubMed

Ni(2+), a toxic and carcinogenic pollutant and one of the leading causes of contact dermatitis, is shown to inhibit neuronal nitric oxide synthase (nNOS) in a competitive, reversible manner with respect to the substrate l-arginine (K(i) = 30 +/- 4 microM). The IC(50) values were dependent on calmodulin (CaM) concentration, but proved independent of Ca(2+), tetrahydrobiopterin (BH(4)) and other essential cofactors. Ni(2+) also inhibited CaM-dependent cytochrome c reduction, NADPH oxidation, and H(2)O(2) production by nNOS. Overall, the action profile of Ni(2+) was suggestive of an unusual, double-acting inhibitor of nNOS affecting l-arginine-binding and Ca(2+)/CaM-dependent enzyme activation. PMID:11437384

Palumbo, A; Astarita, G; Picardo, M; d'Ischia, M

2001-07-01

249

Efficacy of FK463, a (1,3)-?-d-Glucan Synthase Inhibitor, in Disseminated Azole-Resistant Candida albicans Infection in Mice  

PubMed Central

The efficacy of FK463, a new (1,3)-?-d-glucan synthase inhibitor, against azole-resistant Candida albicans strains has been studied. The MIC of FK463 was lower than those of azoles and amphotericin B against CDR1-expressing C26 and CaMDR-expressing C40 strains. All mice treated with FK463 (1 mg/kg) survived disseminated murine candidiasis. The fungal burden in the kidney after 6 days was markedly reduced after therapy with FK463 and amphotericin B sodium deoxycholate, and plasma (1,3)-?-d-glucan concentration was found to be lower in FK463-treated mice. In our study, FK463 was found to be a potent antifungal agent against disseminated infection with azole-resistant C. albicans.

Maesaki, Shigefumi; Hossain, Mohammad Ashraf; Miyazaki, Yoshitsugu; Tomono, Kazunori; Tashiro, Takayoshi; Kohno, Shigeru

2000-01-01

250

The effect of nitric oxide synthase inhibitors nitro-L-arginine and 7-nitroindazole on spatial learning and motor functions in Lurcher mutant and wild type mice.  

PubMed

Nitric oxide (NO) is an intercellular messenger that, among other things, plays an important role in the nervous system as a gaseous neurotransmitter, modulating long-term potentiation (LTP) induction of synaptic transmission. LTP has been suggested to be the basis of memory formation. On the other hand NO also participates in excitotoxic processes which play an important role in many neuropathological states. The aim of this work was to observe the effect of two NO synthase (NOS) inhibitors (N omega-Nitro-L-arginine, NA; 7-nitroindazole, NI) on spontaneous behaviour, spatial learning and motor functions in Lurcher (+/Lc) and wild type (+/+) mice, derived from the B6CBA strain. Heterozygous Lurcher mutant mice represent a natural model of the olivocerebellar degeneration. They suffer from postnatal, practically total, extinction of cerebellar Purkinje cells (due to the excitotoxic apoptosis) and a partial decrease of granule cells and inferior olive neurons (ION) because of the lost target of their axons. +/+ animals are healthy littermates of +/Lc. NA is a nonselective NOS inhibitor which influences, except neuronal (n), also endothelial (e) NOS with an impact on blood pressure, NI is a selective nNOS inhibitor without any circulatory effect. The adult animals of both types (+/Lc; +/+) were influenced by acute administration of both inhibitors (25 mg/kg i.p. 30 min. before experiments) and newborns only by both acute and long-term administration of NI (1 month, starting from postnatal day 2, P2). Control solutions - saline or solvents of both NA and NI inhibitors--diluted 1M HCl and dimethyl sulfoxide (DMSO) respectively, were given at a relevant volume in the same way. The effect of both inhibitors and control solutions on motor functions was tested using four standard procedures (horizontal wire, slanting ladder, rotating cylinder, foot-bridge); in newborns at the age of 14 days. Spatial learning ability was examined in five-day long procedure in the Morris water maze (MWM) (in newborns started on P21). Spontaneous behaviour was studied only in adult animals (after acutely influencing them) employing the open field method. The results showed, that neither the Lurcher mutant, nor wild type mice derived from the B6CBA strain were significantly affected by NOS inhibitors NA and NI in spatial learning after both the acute and long-term application. Only significant decrease of swimming speed was found in both types of mice after the acute administration of NI and in the wild type animals after the acute administration of NA. Motor functions were significantly negatively affected only in the Lurcher mutants after both the acute and chronic application of NI. PMID:19097389

Markvartová, V; Vozeh, F

2008-01-01

251

Purification, kinetics, inhibitors and CD for recombinant ?-amyrin synthase from Euphorbia tirucalli L and functional analysis of the DCTA motif, which is highly conserved among oxidosqualene cyclases.  

PubMed

?-Amyrin, a natural triterpene, is widely distributed in the plant kingdom, and its pentacyclic skeleton is produced by oxidosqualene cyclase (OSC). OSC enzymes are classified as membrane proteins, and they catalyze the polycyclization reaction of (3S)-2,3-oxidosqualene to yield nearly 150 different cyclic triterpene skeletons. To date, no report has described the successful purification and characterization of plant ?-amyrin synthase. The ?-amyrin synthase from Euphorbia tirucalli (EtAS) was expressed as a polyhistidine-tagged protein in Saccharomyces cerevisiae GIL77, which lacks the lanosterol synthase gene. The expression yield, determined by western blotting analysis, was 5-7 mg. By Ni(2+) -nitrilotriacetic acid affinity column chromatography and careful selection of the proper imidazole concentration during the purification processes of washing and elution, a single band was successfully obtained on SDS/PAGE. We then tested the effects of four detergents on the enzyme activity. Supplementation with Triton X-100 at a concentration of 0.05% yielded the highest activity. The optimal pH and temperature were 7.0 and 30 °C, respectively. The kinetic parameters, K(m) and k(cat) , were determined to be 33.8 ± 0.53 ?m and 46.4 ± 0.68 min(-1), respectively. To the best of our knowledge, there are no reports describing both K(m) and k(cat) for OSCs except for two examples of rat and bovine lanosterol synthases. The ?-amyrin synthase purified in this study showed a significantly higher catalytic efficiency (k(cat)/K(m)) (~ 10(3)-fold) than those of the two reported lanosterol synthases. Gel-filtration HPLC indicated that the OSC exists as a monomer, and the eluted OSC retained its activity. Furthermore, the inhibition constants K(i) and IC(50) and types of inhibition by iminosqualene, Ro48-8071 and U18666A were determined, and indicated that iminosqualene and Ro48-8071 are potent inhibitors. Additionally, this is the first report of the kinetic data of the mutated enzymes targeted for the DCTAE(485-489) motif, which is a putative initiation site for the polycyclization reaction. No activity of the D485N variant and significantly decreased activity of the C564A variant were found, definitively demonstrating that the acidic carboxyl residue Asp485 serves as a proton donor to initiate the polycyclization reaction, and that Cys564 is involved in hydrogen bond formation with the carboxyl residue Asp458 to enhance the acidity. The CD spectrum is the first to be reported for OSCs, and the CD spectra of the wild-type and the mutated EtASs were almost the same, indicating that the protein architecture was not altered by these mutations. PMID:23294602

Ito, Ryousuke; Masukawa, Yukari; Hoshino, Tsutomu

2013-02-13

252

The directionality of chitin biosynthesis: a revisit.  

PubMed

The molecular directionality of chitin biosynthesis was investigated by transmission electron microscopy (TEM) using electron crystallography methods applied to reducing-end-labelled beta-chitin microcrystals from vestimentiferan Lamellibrachia satsuma tubes and nascent beta-chitin microfibrils from the diatom Thalassiosira weissflogii. The data allowed confirmation that the microfibrils were extruded with their reducing end away from the biosynthetic loci, an orientation consistent only with elongation through polymerization at the non-reducing end of the growing chains. Such a chain-extension mechanism, which has also been demonstrated for cellulose and hyaluronan, appears to be general for glycosyltransferases that belong to the GT2 (glycosyl transferase 2) family. The data also allowed confirmation that in beta-chitin the chains are crystallized in a 'parallel-up' mode, in contrast with hypotheses proposed in previous reports. PMID:12816541

Imai, Tomoya; Watanabe, Takeshi; Yui, Toshifumi; Sugiyama, Junji

2003-09-15

253

Acetylation of ?-chitin in ionic liquids  

Microsoft Academic Search

Acetylation of ?-chitin using acetic anhydride in an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), was performed. First, a mixture of chitin and AMIMBr (2% w\\/w) was heated at 100°C for 24h for dissolution. Then, acetic anhydride (5–20equiv) was added to the solution and the mixture was heated with stirring at desired temperatures for 24h. The product was precipitated by the addition

Shozaburo Mine; Hironori Izawa; Yoshiro Kaneko; Jun-ichi Kadokawa

2009-01-01

254

Solution properties of chitin in alkali.  

PubMed

The solution properties of alpha-chitin dissolved in 2.77 M NaOH are discussed. Chitin samples in the weight-average molecular weight range 0.1 x 10(6) g/mol to 1.2 x 10(6) g/mol were prepared by heterogeneous acid hydrolysis of chitin. Dilute solution properties were measured by viscometry and light scattering. From dynamic light scattering data, relative similar size distributions of the chitin samples were obtained, except for the most degraded sample, which contained aggregates. Second virial coefficients in the range 1 to 2 x 10(-3) mL.mol.g(-2) indicated that 2.77 M NaOH is a good solvent to chitin. The Mark-Houwink-Sakurada equation and the relationship between the z-average radius of gyration (Rg) and the weight-average molecular weight (Mw) were determined to be [eta] = 0.10Mw0.68 (mL.g(-1)) and Rg = 0.17Mw0.46 (nm), respectively, suggesting a random-coil structure for the chitin molecules in alkali conditions. These random-coil structures have Kuhn lengths in the range 23-26 nm. PMID:15360323

Einbu, Aslak; Naess, Stine Nalum; Elgsaeter, Arnljot; Vĺrum, Kjell M

255

Molecular docking and pharmacophore filtering in the discovery of dual-inhibitors for human leukotriene A4 hydrolase and leukotriene C4 synthase.  

PubMed

Combination of drugs for multiple targets has been a standard treatment in treating various diseases. A single chemical entity that acts upon multiple targets is emerging nowadays because of their predictable pharmacokinetic and pharmacodynamic properties. We have employed a computer-aided methodology combining molecular docking and pharmacophore filtering to identify chemical compounds that can simultaneously inhibit the human leukotriene hydrolase (hLTA4H) and the human leukotriene C4 synthase (hLTC4S) enzymes. These enzymes are the members of arachidonic acid pathway and act upon the same substrate, LTA4, producing different inflammatory products. A huge set of 4966 druglike compounds from the Maybridge database were docked into the active site of hLTA4H using the GOLD program. Common feature pharmacophore models were developed from the known inhibitors of both the targets using Accelrys Discovery Studio 2.5. The hits from the hLTA4H docking were filtered to match the chemical features of both the pharmacophore models. The compounds that resulted from the pharmacophore filtering were docked into the active site of hLTC4S and the hits those bind well at both the active sites and matched the pharmacophore models were identified as possible dual inhibitors for hLTA4H and hLTC4S enzymes. Reverse validation was performed to ensure the results of the study. PMID:21133343

Thangapandian, Sundarapandian; John, Shalini; Sakkiah, Sugunadevi; Lee, Keun Woo

2010-12-06

256

The marine natural-derived inhibitors of glycogen synthase kinase-3? phenylmethylene hydantoins: In vitro and in vivo activities and pharmacophore modeling  

PubMed Central

The Red Sea sponge Hemimycale arabica afforded the known (Z)-5-(4-hydroxybenzylidene)-hydantoin (1). This natural phenylmethylene hydantoin (PMH) 1 and the synthetic (Z)-5-(4-(ethylthio)benzylidene)-hydantoin (2) showed potent in vitro and in vivo anti-growth and anti-invasive properties against PC-3M prostate cancer cells in MTT, spheroid disaggregation, and in mice models. To explore a possible molecular target of PMHs, the most potent synthetic analogue 2 has been virtually screened against various protein kinases. Molecular modeling study has shown that 2 can be successfully docked within the binding pocket of glycogen synthase kinase-3beta (GSK-3?) similar to the well-known GSK-3? inhibitor I-5. Several PMHs showed potent in vitro GSK-3? inhibitory activity with an IC50 range of 4–20 µM. The most potent analogue 3 showed a significant increase in liver glycogen level at the 5, 15, and 25 mg/kg dose levels, in vivo. Pharmacophore model was built and validated using in-house database of active and inactive GSK-3? inhibitors. The GSK-3? inhibitory activity of PMHs entitles them to be potential leads for the treatment of cancer, Alzheimer’s disease, bipolar disorders, stroke, different tau pathologies, and type-2 diabetes.

Khanfar, Mohammad A.; Asal, Bilal Abu; Mudit, Mudit; Kaddoumi, Amal; El Sayed, Khalid A.

2009-01-01

257

The use of aminoguanidine, a selective inducible nitric oxide synthase inhibitor, to evaluate the role of nitric oxide on periapical healing  

PubMed Central

Background: Nitric oxide (NO) is one of the many chemical mediators involved in inflammatory processes. In addition to periapical inflammation, NO can have a role in periapical healing. The purpose of this study was to evaluate the effect of aminoguanidine (AG) as a selective inhibitor of inducible nitric oxide synthase (iNOS) on the degree of healing response of periapical lesions of the canine teeth of cats. Methods: In this interventional experimental study, the root canals of 48 cat canine teeth were infected with cat dental plaque and sealed. After induction of periapical lesions, root canal therapy (RCT) was performed. On the day of RCT phase, the cats were administered either AG (experimental group) or normal saline (control group), which was continued on a daily basis until the day of sacrifice. Four canine teeth in one cat served as negative and positive controls. The animals were sacrificed 6 weeks after RCT. The healing response of the periapical zones was analyzed histologically. The mean scores of healing for the two groups were compared using Mann–Whitney U test. Results: The mean scores of healing for the AG group (2.45±0.508) were significantly higher than those of the control group (2±0.510) (P<0.05). Conclusion: The use of an iNOS selective inhibitor such as AG can accelerate the healing process in periapical lesions.

Farhad, Ali Reza; Razavi, Seyed Mohammad; Nejad, Parnian Alavi

2011-01-01

258

Altered neuronal densities in sexually dimorphic structures: comparable effects from perinatal magnetic fields with nitric oxide synthase inhibitors and postnatal hypoxia.  

PubMed

Cytometry of the neuronal density within four sexually dimorphic nuclei was completed for adult rats that had been perinatally exposed to 0.5Hz, 5-10nT magnetic fields or sham conditions while their mothers drank tap water containing the nitric oxide synthase (NOS) inhibitor L-NAME or only tap water. One week after birth the rats were rendered hypoxic for 1 min or served as controls. Exposures to either the magnetic field or the NOS inhibitor reduced the numbers of neurons within the bed nucleus of the stria terminalis by about 25%, whereas exposure to either the hypoxia or magnetic fields resulted in comparable decreases in cell numbers within the ventromedial nucleus (dorsomedial part). For comparison males had 15% fewer neurons in these nuclei compared to females. The effect sizes for the interactions involving the perinatal exposure for 8 days to the magnetic fields were comparable to the magnitudes of those associated with 1 min of hypoxia 1 week postnatally. These results show the sensitivity of specific structures of the developing brain to interactions between subtle environmental variables. PMID:19026721

McDonald, Karli K; Persinger, Michael A

2008-11-14

259

Structure Based Design of Novel Pyrimido[4,5-c]pyridazine Derivatives as Dihydropteroate Synthase (DHPS) Inhibitors with Increased Affinity  

PubMed Central

Dihydropteroate synthase (DHPS) is the validated drug target for sulfonamide antimicrobial therapy. However, due to widespread drug resistance and poor tolerance, the use of the sulfonamide antibiotics is now limited. The pterin binding pocket in DHPS has a high degree of conservation and is distinct from the sulfonamide binding site, and therefore represents an attractive alternative target for the design of novel antibacterial agents. Previously, we have structurally characterized a known pyridazine inhibitor in the Bacillus anthracis DHPS pterin site and identified a number of unfavorable interactions that appear to compromise the binding. Using this structural information, a series of 4,5-dioxo-1,4,5,6-tetrahydropyrimido[4,5-c]pyridazines was designed to improve binding affinity. Most importantly, the N-methyl ring substitution was removed to improve binding within the pterin pocket and the length of the side chain carboxylic acid was optimized to fully engage the pyrophosphate binding site. These inhibitors were synthesized and evaluated by an enzyme activity assay, X-ray crystallography, isothermal calorimetry, and surface plasmon resonance to obtain a comprehensive understanding of the binding interactions from structural, kinetic and thermodynamic perspectives. This study clearly demonstrates that compounds lacking the N-methyl substitution exhibit increased inhibition of DHPS, but the beneficial effects of optimizing the side chain length were less apparent.

Zhao, Ying; Hammoudeh, Dalia; Yun, Mi-Kyung; Qi, Jianjun; White, Stephen W.; Lee, Richard E.

2012-01-01

260

Endogenous Nitric Oxide Synthase Inhibitors in Sickle Cell Disease: Abnormal Levels and Correlations with Pulmonary Hypertension, Desaturation, Hemolysis, Organ Dysfunction and Death  

PubMed Central

Pulmonary hypertension (PH) in patients with sickle cell disease (SCD) is linked to intravascular hemolysis, impaired nitric oxide bioavailability, renal dysfunction, and early mortality. Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthases (NOS), is associated with vascular disease in other populations. We determined the plasma concentrations for several key arginine metabolites and their relationships to clinical variables in 177 patients with SCD and 29 control subjects: ADMA, symmetric dimethylarginine (SDMA), NG-monomethyl L-arginine (L-NMMA), N-omega-hydroxy-L-arginine (NOHA), arginine and citrulline. The median ADMA was significantly higher in SCD than controls (0.94 vs. 0.31 ?mol/L, p<0.001). Patients with homozygous SCD had a remarkably lower ratio of arginine to ADMA (50 vs. 237, p<0.001). ADMA correlated with markers of hemolysis, low oxygen saturation and soluble adhesion molecules. PH was associated with high levels of ADMA and related metabolites. Higher ADMA level was associated with early mortality, remaining significant in a multivariate analysis. Subjects with homozygous SCD have high systemic levels of ADMA, associated with PH and early death, implicating ADMA as a functional NOS inhibitor in these patients. These defects and others converge on the nitric oxide pathway in homozygous SCD with vasculopathy.

Kato, Gregory J.; Wang, Zeneng; Machado, Roberto F.; Blackwelder, William C.; Taylor, James G.; Hazen, Stanley L.

2010-01-01

261

Inhibition of saturated very-long-chain fatty acid biosynthesis by mefluidide and perfluidone, selective inhibitors of 3-ketoacyl-CoA synthases.  

PubMed

The trifluoromethanesulphonanilides mefluidide and perfluidone are used in agriculture as plant growth regulators and herbicides. Despite the fact that mefluidide and perfluidone have been investigated experimentally for decades, their mode of action is still unknown. In this study, we used a cascade approach of different methods to clarify the mode of action and target site of mefluidide and perfluidone. Physiological profiling using an array of biotests and metabolic profiling in treated plants of Lemna paucicostata suggested a common mode of action in very-long-chain fatty acid (VLCFA) synthesis similar to the known 3-ketoacyl-CoA synthase (KCS) inhibitor metazachlor. Detailed analysis of fatty acid composition in Lemna plants showed a decrease of saturated VLCFAs after treatment with mefluidide and perfluidone. To study compound effects on enzyme level, recombinant KCSs from Arabidopsis thaliana were expressed in Saccharomyces cerevisiae. Enzyme activities of seven KCS proteins from 17 tested were characterized by their fatty acid substrate and product spectrum. For the KCS CER6, the VLCFA product spectrum in vivo, which consists of tetracosanoic acid, hexacosanoic acid and octacosanoic acid, is reported here for the first time. Similar to metazachlor, mefluidide and perfluidone were able to inhibit KCS1, CER6 and CER60 enzyme activities in vivo. FAE1 and KCS2 were inhibited by mefluidide only slightly, whereas metazachlor and perfluidone were strong inhibitors of these enzymes with IC(50) values in ?M range. This suggests that KCS enzymes in VLCFA synthesis are the primary herbicide target of mefluidide and perfluidone. PMID:22284369

Tresch, Stefan; Heilmann, Monika; Christiansen, Nicole; Looser, Ralf; Grossmann, Klaus

2012-01-25

262

Structure-Based Design of Novel Pyrimido[4,5-c]pyridazine Derivatives as Dihydropteroate Synthase Inhibitors with Increased Affinity  

SciTech Connect

Dihydropteroate synthase (DHPS) is the validated drug target for sulfonamide antimicrobial therapy. However, due to widespread drug resistance and poor tolerance, the use of sulfonamide antibiotics is now limited. The pterin binding pocket in DHPS is highly conserved and is distinct from the sulfonamide binding site. It therefore represents an attractive alternative target for the design of novel antibacterial agents. We previously carried out the structural characterization of a known pyridazine inhibitor in the Bacillus anthracis DHPS pterin site and identified a number of unfavorable interactions that appear to compromise binding. With this structural information, a series of 4,5-dioxo-1,4,5,6-tetrahydropyrimido[4,5-c]pyridazines were designed to improve binding affinity. Most importantly, the N-methyl ring substitution was removed to improve binding within the pterin pocket, and the length of the side chain carboxylic acid was optimized to fully engage the pyrophosphate binding site. These inhibitors were synthesized and evaluated by an enzyme activity assay, X-ray crystallography, isothermal calorimetry, and surface plasmon resonance to obtain a comprehensive understanding of the binding interactions from structural, kinetic, and thermodynamic perspectives. This study clearly demonstrates that compounds lacking the N-methyl substitution exhibit increased inhibition of DHPS, but the beneficial effects of optimizing the side chain length are less apparent.

Zhao, Ying; Hammoudeh, Dalia; Yun, Mi-Kyung; Qi, Jianjun; White, Stephen W.; Lee, Richard E. (Tennessee-HSC); (SJCH)

2012-05-29

263

In vivo active aldosterone synthase inhibitors with improved selectivity: lead optimization providing a series of pyridine substituted 3,4-dihydro-1H-quinolin-2-one derivatives.  

PubMed

Pyridine substituted naphthalenes (e.g., I-III) constitute a class of potent inhibitors of aldosterone synthase (CYP11B2). To overcome the unwanted inhibition of the hepatic enzyme CYP1A2, we aimed at reducing the number of aromatic carbons of these molecules because aromaticity has previously been identified to correlate positively with CYP1A2 inhibition. As hypothesized, inhibitors with a tetrahydronaphthalene type molecular scaffold (1-11) exhibit a decreased CYP1A2 inhibition. However, tetralone 9 turned out to be cytotoxic to the human cell line U-937 at higher concentrations. Consequent structural optimization culminated in the discovery of heteroaryl substituted 3,4-dihydro-1H-quinolin-2-ones (12-26), with 12, a bioisostere of 9, being nontoxic up to 200 microM. The investigated molecules are highly selective toward both CYP1A2 and a wide range of other cytochrome P450 enzymes and show a good pharmacokinetic profile in vivo (e.g., 12 with a peroral bioavailability of 71%). Furthermore, isoquinoline derivative 21 proved to significantly reduce plasma aldosterone levels of ACTH stimulated rats. PMID:19049427

Lucas, Simon; Heim, Ralf; Ries, Christina; Schewe, Katarzyna E; Birk, Barbara; Hartmann, Rolf W

2008-12-25

264

Identification by differential display of the IF1 inhibitor peptide of ATP synthase/ATPase as a gene inducible in rat liver by pregnenolone 16alpha-carbonitrile.  

PubMed

The synthetic steroid, pregnenolone-16alpha-carbonitrile (PCN), activates hepatic metabolism and elimination of xenobiotics mediated by its interaction with the PXR, a nuclear receptor that binds PCN and such glucocorticoids as dexamethasone (Dex). We used mRNA differential display to define further the domain of genes under the control of PCN/PXR. We found 76 cDNA fragments representing mRNAs differentially expressed in the liver of rats treated with PCN or Dex. Sequence analysis of one of these revealed a PCN induced cDNA fragment as IF1, an inhibitor peptide of ATP synthase/ATPase complex. Northern blot analysis revealed that IF1 was detectable in untreated liver and was induced 2-3 fold following treatment with PCN. IF1 mRNA was not detected in lung, heart, kidney, or testes of control or PCN treated rats. We conclude that IF1 inhibitor peptide is a novel representative of an apparently large set of previously unrecognized genes coordinately controlled by the PCN/PXR system to maintain homeostasis during toxic stress. PMID:11043605

Jiménez, B D; Quattrochi, L C; Yockey, C B; Guzelian, P S

2000-09-01

265

Accelerating enzymatic hydrolysis of chitin by microwave pretreatment.  

PubMed

Response surface analysis was used to determine optimum conditions [2% (w/v) chitin, 57.5 degrees C, 38 min] for microwave irradiation of chitin to improve its enzymatic hydrolysis. V(max)/K(m) of cabbage chitinase toward untreated and microwave-irradiated chitin was found to be 21.1 and 31.7 nmol h(-1) mg(-2) mL, respectively. Similar improvement was observed in the case of pectinase in its unusual catalytic activity of chitin degradation. It was found that a greater extent of chitin hydrolysis by chitinase was possible after the substrate chitin was irradiated with microwaves. PMID:14656136

Roy, Ipsita; Mondal, Kalyani; Gupta, Munishwar N

266

A Head to Head Comparison of Eneamide and Epoxyamide Inhibitors of Glucosamine-6-P Synthase from the Dapdiamide Biosynthetic Pathway  

PubMed Central

The dapdiamides are a family of antibiotics that have been presumed to be cleaved in the target cell to enzyme-inhibitory N-acyl-2,3-diaminopropionate (DAP) warheads containing two alternative electrophilic moieties. Our prior biosynthetic studies revealed that an eneamide warhead is made first and converted to an epoxyamide via a three enzyme branch pathway. Here we provide a rationale for this logic. We report that the RR-epoxyamide warhead is a more efficient covalent inactivator of glucosamine-6-phosphate synthase by an order of magnitude over the eneamide, and this difference correlates with a more than ten-fold difference in antibiotic activity for the corresponding acyl-DAP dipeptides.

Hollenhorst, Marie A.; Ntai, Ioanna; Badet, Bernard; Kelleher, Neil L.; Walsh, Christopher T.

2011-01-01

267

Long-Lasting Antidepressant Action of Ketamine, but Not Glycogen Synthase Kinase-3 Inhibitor SB216763, in the Chronic Mild Stress Model of Mice  

PubMed Central

Background Clinical studies demonstrate that the N-methyl-D-aspartate (NMDA) receptor antagonist, ketamine, induces rapid antidepressant effects in patients with refractive major depressive disorder and bipolar depression. This rapid onset of action makes ketamine a highly attractive drug for patients, particularly those who do not typically respond to therapy. A recent study suggested that glycogen synthase kinase (GSK)-3 may underlie the rapid antidepressant action of ketamine, although the precise mechanisms are unclear. In this study, we examined the effects of ketamine and GSK-3 inhibitor SB216763 in the unpredictable, chronic mild stress (CMS) mouse model of mice. Methodology/Principal Findings Adult C57/B6 male mice were divided into 2 groups, a non-stressed control group and the unpredictable CMS (35 days) group. Then, either vehicle, ketamine (10 mg/kg), or the established GSK-3 inhibitor, SB216763 (10 mg/kg), were administered into mice in the CMS group, while vehicle was administered to controls. In the open field test, there was no difference between the four groups (control+vehicle, CMS+vehicle, CMS+ketamine, CMS+SB216763). In the sucrose intake test, a 1% sucrose intake drop, seen in CMS mice, was significantly attenuated after a single dose of ketamine, but not SB216763. In the tail suspension test (TST) and forced swimming test (FST), the increased immobility time seen in CMS mice was significantly attenuated by a single dose of ketamine, but not SB216763. Interestingly, the ketamine-induced increase in the sucrose intake test persisted for 8 days after a single dose of ketamine. Furthermore, a single administration of ketamine, but not SB216763, significantly attenuated the immobility time of the TST and FST in the control (non-stressed) mice. Conclusions/Significance These findings suggest that a single administration of ketamine, but not GSK-3 inhibitor SB216763, produces a long-lasting antidepressant action in CMS model mice.

Jia, Min; Ma, Rui; Wang, Fen; Wu, Jin; Gao, Cheng-Ge; Hashimoto, Kenji

2013-01-01

268

Coexpression of CYP11B2 or CYP11B1 with adrenodoxin and adrenodoxin reductase for assessing the potency and selectivity of aldosterone synthase inhibitors.  

PubMed

Excessive production of aldosterone has been implicated in the pathogenesis of hypertension and heart failure. One approach to ameliorate the deleterious effects of aldosterone is to suppress its biosynthesis. The enzyme aldosterone synthase (CYP11B2) is responsible for the final step of aldosterone synthesis. It requires electron transfer from the adrenodoxin/adrenodoxin reductase system to catalyze the production of aldosterone. A stable cell line simultaneously overexpressing recombinant human CYP11B2 as well as human adrenodoxin and adrenodoxin reductase was established to help maximize the enzyme activity. The homogenate of these cells was used to develop an in vitro CYP11B2 assay using 11-deoxycorticosterone as a substrate. By the same strategy, another stable cell line simultaneously overexpressing human 11beta-hydroxylase (CYP11B1), an enzyme responsible for the final step of cortisol biosynthesis, and the two electron transfer proteins was also established, and an in vitro CYP11B1 assay using 11-deoxycortisol as a substrate was likewise developed to assess the selectivity of CYP11B2 inhibitors. FAD286, a reference CYP11B2 inhibitor, inhibited CYP11B2 and CYP11B1 activities with IC(50) values of 1.6+/-0.1 and 9.9+/-0.9 nM (mean+/-SEM, n=3-6), respectively. Kinetics studies revealed that the compound inhibited the activity of both enzymes competitively with respective K(i) values of 0.8+/-0.04 and 2.2+/-0.2 nM (n=3-4). These assays can be used for assessing the potency and selectivity of CYP11B2 inhibitors for the treatment of hypertension and heart failure. PMID:19622340

LaSala, Daniel; Shibanaka, Yasuhiko; Jeng, Arco Y

2009-07-19

269

Structure determination of glycogen synthase kinase-3 from Leishmania major and comparative inhibitor structure?activity relationships with Trypanosoma brucei GSK-3  

SciTech Connect

Glycogen synthase kinase-3 (GSK-3) is a drug target under intense investigation in pharmaceutical companies and constitutes an attractive piggyback target for eukaryotic pathogens. Two different GSKs are found in trypanosomatids, one about 150 residues shorter than the other. GSK-3 short (GeneDB: Tb927.10.13780) has previously been validated genetically as a drug target in Trypanosoma brucei by RNAi induced growth retardation; and chemically by correlation between enzyme and in vitro growth inhibition. Here, we report investigation of the equivalent GSK-3 short enzymes of L. major (LmjF18.0270) and L. infantum (LinJ18{_}V3.0270, identical in amino acid sequences to LdonGSK-3 short) and a crystal structure of LmajGSK-3 short at 2 {angstrom} resolution. The inhibitor structure-activity relationships (SARs) of L. major and L. infantum are virtually identical, suggesting that inhibitors could be useful for both cutaneous and visceral leishmaniasis. Leishmania spp. GSK-3 short has different inhibitor SARs than TbruGSK-3 short, which can be explained mostly by two variant residues in the ATP-binding pocket. Indeed, mutating these residues in the ATP-binding site of LmajGSK-3 short to the TbruGSK-3 short equivalents results in a mutant LmajGSK-3 short enzyme with SAR more similar to that of TbruGSK-3 short. The differences between human GSK-3{beta} (HsGSK-3{beta}) and LmajGSK-3 short SAR suggest that compounds which selectively inhibit LmajGSK-3 short may be found.

Ojo, Kayode K.; Arakaki, Tracy L.; Napuli, Alberto J.; Inampudi, Krishna K.; Keyloun, Katelyn R.; Zhang, Li; Hol, Wim G.J.; Verlind, Christophe L.M.J.; Merritt, Ethan A.; Van Voorhis, Wesley C. (UWASH)

2012-04-24

270

CG0009, a novel glycogen synthase kinase 3 inhibitor, induces cell death through cyclin D1 depletion in breast cancer cells.  

PubMed

Glycogen synthase kinase 3?/? (GSK3?/?) is a constitutively active serine/threonine kinase involved in multiple physiological processes, such as protein synthesis, stem cell maintenance and apoptosis, and acts as a key suppressor of the Wnt-?-catenin pathway. In the present study, we examined the therapeutic potential of a novel GSK3 inhibitor, CG0009, in the breast cancer cell lines, BT549, HS578T, MDA-MB-231, NCI/ADR-RES, T47D, MCF7 and MDA-MB-435, from the NCI-60 cancer cell line panel. Assessment of cytotoxicity, apoptosis and changes in estrogen-signaling proteins was performed using cell viability assays, Western blotting and quantitative real-time PCR. CG0009 enhanced the inactivating phosphorylation of GSK3? at Ser21 and GSK3? at Ser9 and simultaneously decreased activating phosphorylation of GSK3? at Tyr216, and induced caspase-dependent apoptosis independently of estrogen receptor ? (ER?) expression status, which was not observed with the other GSK3 inhibitors examined, including SB216763, kenpaullone and LiCl. CG0009 treatment (1 µmol/L) completely ablated cyclin D1 expression in a time-dependent manner in all the cell lines examined, except T47D. CG0009 alone significantly activated p53, leading to relocation of p53 and Bax to the mitochondria. GSK3 inhibition by CG0009 led to slight upregulation of the ?-catenin target genes, c-Jun and c-Myc, but not cyclin D1, indicating that CG0009-mediated cyclin D1 depletion overwhelms the pro-survival signal of ?-catenin, resulting in cell death. Our findings suggest that the novel GSK3 inhibitor, CG0009, inhibits breast cancer cell growth through cyclin D1 depletion and p53 activation, and may thus offer an innovative therapeutic approach for breast cancers resistant to hormone-based therapy. PMID:23565238

Kim, Hyun Mi; Kim, Choung-Soo; Lee, Je-Hwan; Jang, Se Jin; Hwang, Jung Jin; Ro, Seonggu; Choi, Jene

2013-04-02

271

16-Aza-ent-beyerane and 16-Aza-ent-trachylobane: Potent Mechanism-based Inhibitors of Recombinant ent-Kaurene Synthase from Arabidopsis thaliana1  

PubMed Central

The secondary ent-beyeran-16-yl carbocation (7) is a key branch point intermediate in mechanistic schemes to rationalize the cyclic structures of many tetra- and pentacyclic diterpenes including ent-beyerene, ent-kaurene, ent-trachylobane, and ent-atiserene, presumed precursors to > 1,000 known diterpenes. (Scheme 1) To evaluate these mechanistic hypotheses, we synthesized the heterocyclic analogues, 16-aza-ent-beyerane (12) and 16-aza-ent-trachylobane (13), by means of Hg(II)- and Pb(IV)-induced cyclizations onto the ?12 double bonds of tricyclic intermediates bearing carbamoylmethyl and aminomethyl groups at C-8. The 13,16-seco 16-nor carbamate (20a) was obtained from ent-beyeran-16-one oxime (17) by Beckmann fragmentation, hydrolysis, and Curtius rearrangement. The aza analogues inhibited recombinant ent-kaurene synthase from Arabidopsis thaliana (GST-rAtKS) with inhibition constants (IC = 1 × 10 ?7 and 1 × 10?6 50 M) similar in magnitude to the pseudo-binding constant of the bicyclic ent-copalyl diphosphate substrate (Km = 3 × 10?7 M). Large enhancements of binding affinities (IC50 = 4 × 10?9 and 2 × 10?8 M) were observed in the presence of 1 mM pyrophosphate which is consistent with a tightly bound ent-beyeranyl+/pyrophosphate? ion pair intermediate in the cyclization-rearrangement catalyzed by this diterpene synthase. The weak inhibition (IC50 = 1 × 10?5 M) exhibited by ent-beyeran-16 exo-yl diphosphate (11), and its failure to undergo bridge rearrangement to kaurene, appear to rule out the covalent diphosphate as a free intermediate. 16-Aza-ent-beyerane is proposed as an effective mimic for the ent-beyeran-16-yl carbocation with potential applications as an active site probe for the various ent- diterpene cyclases, and as a novel, selective inhibitor of gibberellin biosynthesis in plants.

Roy, Arnab; Roberts, Frank G.; Wilderman, P. Ross; Zhou, Ke; Peters, Reuben J.; Coates, Robert M.

2013-01-01

272

Glycolytic glioma cells with active glycogen synthase are sensitive to PTEN and inhibitors of PI3K and gluconeogenesis  

Microsoft Academic Search

Increased glycolysis is characteristic of malignancy. Previously, with a mitochondrial inhibitor, we demonstrated that glycolytic ATP production was sufficient to support migration of melanoma cells. Recently, we found that glycolytic enzymes were abundant and some were increased in pseudopodia formed by U87 glioma (astrocytoma) cells. In this study, we examined cell migration, adhesion (a step in migration), and Matrigel invasion

Marie E Beckner; Glenn T Gobbel; Roger Abounader; Fatima Burovic; Naomi R Agostino; John Laterra; Ian F Pollack

2005-01-01

273

BN 80933, a dual inhibitor of neuronal nitric oxide synthase and lipid peroxidation: A promising neuroprotective strategy  

PubMed Central

Nitric oxide (NO) and reactive oxygen species (ROS) act independently as well as cooperatively to induce neuronal death in acute neurological disorders. Inhibition of neuronal nitric oxide synthase (nNOS) and inhibition of lipid peroxidation induced by ROS have both been proposed as neuroprotective strategies in stroke and trauma. Recently, in our laboratory, the combination of the two strategies was found to be synergistic in reducing neuronal damage. Here, we report that BN 80933 [(S)-N-{4-[4-[(3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-yl)carbonyl]-1-piperazinyl]phenyl}-2-thiophenecarboximidamide], a compound that combines potent antioxidant and selective nNOS inhibitory properties in vitro, affords remarkable neuronal protection in vivo. Intravenous administration of BN 80933 significantly reduced brain damage induced by head trauma in mice, global ischemia in gerbils, and transient focal ischemia in rats. Treatment with BN 80933 (0.3–10 mg/kg) significantly reduced infarct volume (>60% protection) and enhanced behavioral recovery in rats subjected to transient (2-h) middle cerebral artery occlusion and 48-h or 7-day reperfusion. Furthermore, treatment with BN 80933 commencing up to 8 h after the onset of ischemia resulted in a significant improvement of neurological outcome. All these results indicate that BN 80933 represents a class of potentially useful therapeutic agents for the treatment of stroke or trauma and possibly neurodegenerative disorders that involve both NO and ROS.

Chabrier, Pierre-Etienne; Auguet, Michel; Spinnewyn, Brigitte; Auvin, Serge; Cornet, Sylvie; Demerle-Pallardy, Caroline; Guilmard-Favre, Christine; Marin, Jean-Gregoire; Pignol, Bernadette; Gillard-Roubert, Veronique; Roussillot-Charnet, Christelle; Schulz, Jocelyne; Viossat, Isabelle; Bigg, Dennis; Moncada, Salvador

1999-01-01

274

XRD studies of ?-chitin from squid pen with calcium solvent  

Microsoft Academic Search

The crystalline structure of ?-chitin from squid pen was investigated by X-ray diffraction (XRD). The purified ?-chitin was prepared from bigfin reefsquid pen. ?-Chitin was treated with saturated calcium chloride dihydrate\\/alchohol (CaCl2·2H2O\\/MeOH) solvent system at different conditions for XRD studies. The change of crystallinity of ?-chitin from squid pen was studied by using the fiber photographs on imaging plates. The

H. Nagahama; T. Higuchi; R. Jayakumar; T. Furuike; H. Tamura

2008-01-01

275

Efficacy of 1400 W, a novel inhibitor of inducible nitric oxide synthase, in preventing interleukin-1beta-induced suppression of pancreatic islet function in vitro and multiple low-dose streptozotocin-induced diabetes in vivo  

Microsoft Academic Search

Objective: Nitric oxide (NO), generated by inducible nitric oxide synthase (iNOS), has been implicated in b-cell destruction in type 1 diabetes. In the present study, we tested a highly selective iNOS inhibitor, 1400 W, against interleukin-1b (IL-1b) induced suppression of rat pancreatic islets, and investigated whether 1400 W could prevent multiple low-dose streptozotocin (MLDS) induced dia- betes in mice. Furthermore,

Tobias Rydgren; Stellan Sandler

2002-01-01

276

Influence of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors on endothelial nitric oxide synthase and the formation of oxidants in the vasculature.  

PubMed

HMGCoA reductase inhibitors (statins) can have effects outside the target tissue, liver, including serious side-effects such as rhabdomyolysis as well as beneficial pleiotrophic effects. One such effect is upregulation of endothelial nitric oxide synthase (e-NOS) which generally leads to vasorelaxation. However, changing the balance between localized NO and O(2-) fluxes can also lead to oxidant stress and cellular injury through formation of reactive secondary oxidants such as peroxynitrite. We compared different statins for e-NOS subcellular localization, formation of pro-oxidants, and endothelial-dependent vascular function. Vascular relaxation in aortas of statin-dosed rats was inhibited with simvastatin (sevenfold higher EC50 for acetyl-choline induced relaxation) and atorvastatin (twofold increase) but not pravastatin. Ex vivo oxidation of the fluorescent redox probe dihydrorhodamine-123 (DHR-123) was increased in aortas from simvastatin treated rats, indicating increased reactive nitrogen and oxygen species. Human aortic endothelial cells incubated with simvastatin exhibited up to threefold higher intracellular oxidation of DHR-123 along with a twofold increase in total e-NOS protein. The elevated e-NOS was found in the Golgi/mitochondrial fraction and not in the plasma membrane, and using immunofluorescence greater e-NOS was observed proximal to Golgi and cytoskeletal structures and away from plasma membrane in simvastatin-treated cells. The data suggest that the action of lipophilic statins in endothelium can shift e-NOS localization towards intracellular domains, thereby increasing the encounter with metabolically generated O(2-) to produce peroxynitrite and related oxidants. Thus, under some conditions the direct action of lipophilic HMGCoA reductase inhibitors may unbalance NO and O(2-) fluxes and promote oxidant stress, compromising potentially beneficial vascular effects of e-NOS upregulation and increasing the potential for damage to muscle and other tissues. PMID:12860247

Parker, Rex A; Huang, Qi; Tesfamariam, Belay

2003-07-01

277

The neuronal nitric oxide synthase inhibitor, TRIM, as a neuroprotective agent: effects in models of cerebral ischaemia using histological and magnetic resonance imaging techniques.  

PubMed

Most neuroprotective compounds that appear promising in the pre-clinical phase of testing are subsequently dismissed as relatively ineffective when entered into large-scale clinical trials. Many pre-clinical studies of potential neuroprotective candidates evaluate efficacy in only one or possibly two different models of ischaemia. In this study we examined the effects of 1,2-trifluoromethylphenyl imidazole (TRIM), a novel neuronal nitric oxide synthase (nNOS) inhibitor, in three models of cerebral ischaemia (global gerbil, global rat and focal rat). In addition, to follow the progression of the pathology, we also compared traditional histology methods with more advanced magnetic resonance imaging (MRI) as endpoint measures for neurological damage and neuroprotection. TRIM (50 mg/kg i.p.) prevented ischaemia-induced hippocampal damage following global ischaemia in gerbils when administered before or immediately post-occlusion, but failed to protect when administration was delayed until 30 min post-occlusion. Further studies indicated that the compound (administered at 50 mg/kg, i.p., immediately after occlusion) also protected in a rat four-vessel occlusion (4-VO) model using both histological and diffusion-weighted (DW) imaging techniques. In a final study, TRIM (50 mg/kg i.p. 30 min after occlusion) provided a significant reduction in infarct volume at 4 and 24 h as measured using diffusion-weighted (DW) and proton density (PD)-weighted magnetic resonance imaging (MRI). This was confirmed using histological techniques. These studies confirm that nNOS inhibitors may have utility in stroke and provide evidence that combined magnetic resonance and histological methods can provide a powerful method of assessing neuronal damage in rodent models of cerebral ischaemia. PMID:14642829

Haga, Kristin K; Gregory, Lloyd J; Hicks, Caroline A; Ward, Mark A; Beech, John S; Bath, Phillip W; Williams, Steven C R; O'Neill, Michael J

2003-12-12

278

Resistance of a Rodent Malaria Parasite to a Thymidylate Synthase Inhibitor Induces an Apoptotic Parasite Death and Imposes a Huge Cost of Fitness  

PubMed Central

Background The greatest impediment to effective malaria control is drug resistance in Plasmodium falciparum, and thus understanding how resistance impacts on the parasite's fitness and pathogenicity may aid in malaria control strategy. Methodology/Principal Findings To generate resistance, P. berghei NK65 was subjected to 5-fluoroorotate (FOA, an inhibitor of thymidylate synthase, TS) pressure in mice. After 15 generations of drug pressure, the 2% DT (the delay time for proliferation of parasites to 2% parasitaemia, relative to untreated wild-type controls) reduced from 8 days to 4, equalling the controls. Drug sensitivity studies confirmed that FOA-resistance was stable. During serial passaging in the absence of drug, resistant parasite maintained low growth rates (parasitaemia, 15.5%±2.9, 7 dpi) relative to the wild-type (45.6%±8.4), translating into resistance cost of fitness of 66.0%. The resistant parasite showed an apoptosis-like death, as confirmed by light and transmission electron microscopy and corroborated by oligonucleosomal DNA fragmentation. Conclusions/Significance The resistant parasite was less fit than the wild-type, which implies that in the absence of drug pressure in the field, the wild-type alleles may expand and allow drugs withdrawn due to resistance to be reintroduced. FOA resistance led to depleted dTTP pools, causing thymineless parasite death via apoptosis. This supports the tenet that unicellular eukaryotes, like metazoans, also undergo apoptosis. This is the first report where resistance to a chemical stimulus and not the stimulus itself is shown to induce apoptosis in a unicellular parasite. This finding is relevant in cancer therapy, since thymineless cell death induced by resistance to TS-inhibitors can further be optimized via inhibition of pyrimidine salvage enzymes, thus providing a synergistic impact. We conclude that since apoptosis is a process that can be pharmacologically modulated, the parasite's apoptotic machinery may be exploited as a novel drug target in malaria and other protozoan diseases of medical importance.

Muregi, Francis W.; Ohta, Isao; Masato, Uchijima; Kino, Hideto; Ishih, Akira

2011-01-01

279

Human stem cell osteoblastogenesis mediated by novel glycogen synthase kinase 3 inhibitors induces bone formation and a unique bone turnover biomarker profile in rats.  

PubMed

Wnt activation by inhibiting glycogen synthase kinase 3 (GSK-3) causes bone anabolism in rodents making GSK-3 a potential therapeutic target for osteoporotic and osteolytic metastatic bone disease. To understand the wnt pathway related to human disease translation, the ability of 3 potent inhibitors of GSK-3 (AZD2858, AR79, AZ13282107) to 1) drive osteoblast differentiation and mineralisation using human adipose-derived stem cells (hADSC) in vitro; and 2) stimulate rat bone formation in vivo was investigated. Bone anabolism/resorption was determined using clinically relevant serum biomarkers as indicators of bone turnover and bone formation assessed in femurs by histopathology and pQCT/?CT imaging. GSK-3 inhibitors caused ?-catenin stabilisation in human and rat mesenchymal stem cells, stimulated hADSC commitment towards osteoblasts and osteogenic mineralisation in vitro. AZD2858 produced time-dependent changes in serum bone turnover biomarkers and increased bone mass over 28days exposure in rats. After 7days, AZD2858, AR79 or AZ13282107 exposure increased the bone formation biomarker P1NP, and reduced the resorption biomarker TRAcP-5b, indicating increased bone anabolism and reduced resorption in rats. This biomarker profile was differentiated from anabolic agent PTH1-34 or the anti-resorptive Alendronate-induced changes. Increased bone formation in cortical and cancellous bone as assessed by femur histopathology supported biomarker changes. 14 day AR79 treatment increased bone mineral density and trabecular thickness, and decreased trabecular number and connectivity assessed by pQCT/?CT. GSK-3 inhibition caused hADSC osteoblastogenesis and mineralisation in vitro. Increased femur bone mass associated with changes in bone turnover biomarkers confirmed in vivo bone formation and indicated uncoupling of bone formation and resorption. PMID:23872097

Gilmour, Peter S; O'Shea, Patrick J; Fagura, Malbinder; Pilling, James E; Sanganee, Hitesh; Wada, Hiroki; Courtney, Paul F; Kavanagh, Stefan; Hall, Peter A; Escott, K Jane

2013-07-18

280

Reference Genes to Study Herbicide Stress Response in Lolium sp.: Up-Regulation of P450 Genes in Plants Resistant to Acetolactate-Synthase Inhibitors  

PubMed Central

Variation in the expression of numerous genes is at the basis of plant response to environmental stresses. Non-target-site-based resistance to herbicides (NTSR), the major threat to grass weed chemical control, is governed by a subset of the genes involved in herbicide stress response. Quantitative PCR assays allowing reliable comparison of gene expression are thus key to identify genes governing NTSR. This work aimed at identifying a set of reference genes with a stable expression to be used as an internal standard for the normalisation of quantitative PCR data in studies investigating NTSR to herbicides inhibiting acetolactate synthase (ALS) in the major grass weed Lolium sp. Gene expression stability was assessed in plants resistant or sensitive to two ALS inhibitors, subjected or not to herbicide stress. Using three complementary approaches implemented in the programs BestKeeper, NormFinder and geNorm, cap-binding protein, glyceraldehyde-3-phosphate-dehydrogenase and ubiquitin were identified as the most suitable reference genes. This reference gene set can probably be used to study herbicide response in other weed species. It was used to compare the expression of the genes encoding two herbicide target enzymes (ALS and acetyl-coenzyme A carboxylase) and five cytochromes P450 (CYP) with potential herbicide-degrading activity between plants resistant or sensitive to ALS inhibitors. Overall, herbicide application enhanced CYP gene expression. Constitutive up-regulation of all CYP genes observed in resistant plants compared to sensitive plants suggested enhanced secondary metabolism in the resistant plants. Comprehensive transcriptome studies associated to gene expression analyses using the reference gene set validated here are required to unravel NTSR genetic determinants.

Duhoux, Arnaud; Delye, Christophe

2013-01-01

281

Effects of nitric oxide synthase inhibitor on decrease in peripheral arterial stiffness with acute low-intensity aerobic exercise.  

PubMed

We previously reported that even low-intensity, short-duration acute aerobic exercise decreases arterial stiffness. We aimed to test the hypothesis that the exercise-induced decrease in arterial stiffness is caused by the increased production of NO in vascular endothelium with exercise. Nine healthy men (age: approximately 22-28 yr) performed a 5-min single-leg cycling exercise (30 W) in the supine position under an intravenous infusion of NG-monomethyl-L-arginine (L-NMMA; 3 mg/kg during the initial 5 min and subsequent continuous infusion of 50 mug.kg(-1).min(-1) in saline) or vehicle (saline) in random order on separate days. The pulse wave velocity (PWV) from the femoral to posterior tibial artery was measured on both legs before and after the infusion at rest and 2 min after exercise. Under the control condition, exercised leg PWV significantly decreased after exercise (P <0.05), whereas nonexercised leg PWV did not show a significant change throughout the experiment. Under L-NMMA administration, exercised leg PWV was increased significantly by the infusion (P <0.05) but decreased significantly after the exercise (P <0.05). Nonexercised leg PWV increased with L-NMMA administration and maintained a significantly higher level during the administration compared with baseline (before the infusion, all P <0.05). The NO synthase blockade x time interaction on exercised leg PWV was not significant (P=0.706). These results suggest that increased production of NO is not a major factor in the decrease of regional arterial stiffness with low-intensity, short-duration aerobic exercise. PMID:15284073

Sugawara, Jun; Maeda, Seiji; Otsuki, Takeshi; Tanabe, Takumi; Ajisaka, Ryuichi; Matsuda, Mitsuo

2004-07-29

282

Radioisotope assay for 1-aminocyclopropane-1-carboxylic acid synthase: s-adenosylhomocysteine analogs as inhibitors of the enzyme involved in plant senescence  

SciTech Connect

A simple and rapid radioisotopic assay for 1-aminocyclopropane-1-carboxylic acid (ACC) synthase was developed, an enzyme involved in the biosynthesis of the plant hormone ethylene. The assay utilizes an AG50-X4(NH4 (+)) column which separates S-adenosyl-L-(carboxyl-/sup 14/C)methionine (AdoMet) from the product (/sup 14/C)acc, since the latter is not bound to the resin while (/sup 14/C)adoMet is. As opposed to other assays, this procedure measures ACC directly and does not require further conversion to ethylene. When an enzyme preparation from ripe-tomato fruits (Lycopersicon esculentum Mill) was assayed, an I/sub 50/ of 2.5 + or - 0.8 micrometers for sinefungin and a K/sub m/ of 27 + or - 2 micrometers for AdoMet were obtained; these values were in good agreement with previous previous determinations made with a gas-chromatographic assay. When other nucleosides were tested as inhibitors the following order of decreasing activity was found: sinefungin, S-adenosylhomocysteine (AdoHcy), AdoHcy sulfoxide, S-n-butyladenosine, 3-deaza-adenosylhomocysteine, S-isobutyladenosine, S-isobutyladenosine, S-isobutyl-l-deazaadenosine. In contrast, S-isobutyl-3-deazaadenosine, S-isobutyl-7-deazaadenosine, 3-deazaadenosine, and adenodine were not inhibitory.

Miura, G.A.; Chiang, P.K.

1985-01-01

283

Reduction in libido and fertility of male rats by administration of the nitric oxide (NO) synthase inhibitor N-nitro-L-arginine methyl ester.  

PubMed

The role of nitric oxide (NO) in libido and fertility of male rats was investigated by administration of the NO synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) (25 or 50 mg/kg/day). L-NAME caused marked reduction of precoital sexual behaviour, and a failure of most rats to mount or ejaculate during the test interval. In most matings that were successful, recovered spermatozoa were present in normal numbers. In mating experiments, L-NAME profoundly reduced the fertility of male rats. In those animals that did succeed in mating, the quantal pregnancy and the number of implants were reduced. After cessation of treatment with L-NAME, the fertility parameters returned close to normal. The inactive stereoisomer, D-NAME, caused none of the above effects when administered to rats. The results suggest that NO is essential for the expression of normal libido and fertility in male rats. It is likely that NO is required both in the male reproductive tract and in the brain. PMID:10844545

Ratnasooriya, W D; Dharmasiri, M G; Wadsworth, R M

2000-06-01

284

In vitro activity of a new oral glucan synthase inhibitor (MK-3118) tested against Aspergillus spp. by CLSI and EUCAST broth microdilution methods.  

PubMed

MK-3118, a glucan synthase inhibitor derived from enfumafungin, and comparator agents were tested against 71 Aspergillus spp., including itraconazole-resistant strains (MIC, ? 4 ?g/ml), using CLSI and EUCAST reference broth microdilution methods. The CLSI 90% minimum effective concentration (MEC(90))/MIC(90) values (?g/ml) for MK-3118, amphotericin B, and caspofungin, respectively, were as follows: 0.12, 2, and 0.03 for Aspergillus flavus species complex (SC); 0.25, 2, and 0.06 for Aspergillus fumigatus SC; 0.12, 2, and 0.06 for Aspergillus terreus SC; and 0.06, 1, and 0.03 for Aspergillus niger SC. Essential agreement between the values found by CLSI and EUCAST (± 2 log(2) dilution steps) was 94.3%. MK-3118 was determined to be a potent agent regardless of the in vitro method applied, with excellent activity against contemporary wild-type and itraconazole-resistant strains of Aspergillus spp. PMID:23229479

Pfaller, Michael A; Messer, Shawn A; Motyl, Mary R; Jones, Ronald N; Castanheira, Mariana

2012-12-10

285

Concurrent protein synthesis is required for in vivo chitin synthesis in postmolt blue crabs  

SciTech Connect

Chitin synthesis in crustaceans involves the deposition of a protein-polysaccharide complex at the apical surface of epithelial cells which secrete the cuticle or exoskeleton. The present study involves an examination of in vivo incorporation of radiolabeled amino acids and amino sugars into the cuticle of postmolt blue crabs, Callinectes sapidus. Rates of incorporation of both 3H leucine and 3H threonine were linear with respect to time of incubation. Incorporation of 3H threonine into the endocuticle was inhibited greater than 90% in the presence of the protein synthesis inhibitor, puromycin. Linear incorporation of 14C glucosamine into the cuticle was also demonstrated; a significant improvement of radiolabeling was achieved by using 14C-N-acetylglucosamine as the labeled precursor. Incorporation of 3H-N-acetylglucosamine into the cuticle of postmolt blue crabs was inhibited 89% by puromycin, indicating that concurrent protein synthesis is required for the deposition of chitin in the blue crab. Autoradiographic analysis of control vs. puromycin-treated crabs indicates that puromycin totally blocks labeling of the new endocuticle with 3H glucosamine. These results are consistent with the notion that crustacean chitin is synthesized as a protein-polysaccharide complex. Analysis of the postmolt and intermolt blue crab cuticle indicates that the exoskeleton contains about 60% protein and 40% chitin. The predominant amino acids are arginine, glutamic acid, alanine, aspartic acid, and threonine.

Horst, M.N. (Mercer Univ., Macon, GA (USA))

1990-12-01

286

Synthesis and biological evaluation of 3-benzisoxazolyl-4-indolylmaleimides as potent, selective inhibitors of glycogen synthase kinase-3?.  

PubMed

A series of novel 3-benzisoxazolyl-4-indolyl-maleimides were synthesized and evaluated for their GSK-3? inhibitory activity. Most compounds exhibited high inhibitory potency towards GSK-3?. Among them, compound 7j with an IC?? value of 0.73 nM was the most promising GSK-3? inhibitor. Preliminary structure-activity relationships were examined and showed that different substituents on the indole ring and Ną-position of the indole ring had varying degrees of influence on the GSK-3? inhibitory potency. Compounds 7c, 7f, 7j-l and 7o-q could obviously reduce A?-induced Tau hyperphosphorylation by inhibiting GSK-3? in a cell-based functional assay. PMID:23669633

Ye, Qing; Li, Meng; Zhou, Yubo; Pang, Tao; Xu, Lei; Cao, Jiayi; Han, Liang; Li, Yujin; Wang, Weisi; Gao, Jianrong; Li, Jia

2013-05-13

287

Inhibitor of neuronal nitric oxide synthase improves gas exchange in ventilator-induced lung injury after pneumonectomy  

PubMed Central

Background Mechanical ventilation with high tidal volumes may cause ventilator-induced lung injury (VILI) and enhanced generation of nitric oxide (NO). We demonstrated in sheep that pneumonectomy followed by injurious ventilation promotes pulmonary edema. We wished both to test the hypothesis that neuronal NOS (nNOS), which is distributed in airway epithelial and neuronal tissues, could be involved in the pathogenesis of VILI and we also aimed at investigating the influence of an inhibitor of nNOS on the course of VILI after pneumonectomy. Methods Anesthetized sheep underwent right pneumonectomy, mechanical ventilation with tidal volumes (VT) of 6?mL/kg and FiO2 0.5, and were subsequently randomized to a protectively ventilated group (PROTV; n?=?8) keeping VT and FiO2 unchanged, respiratory rate (RR) 25 inflations/min and PEEP 4?cm H2O for the following 8?hrs; an injuriously ventilated group with VT of 12?mL/kg, zero end-expiratory pressure, and FiO2 and RR unchanged (INJV; n?=?8) and a group, which additionally received the inhibitor of nNOS, 7-nitroindazole (NI) 1.0?mg/kg/h intravenously from 2 hours after the commencement of injurious ventilation (INJV?+?NI; n?=?8). We assessed respiratory, hemodynamic and volumetric variables, including both the extravascular lung water index (EVLWI) and the pulmonary vascular permeability index (PVPI). We measured plasma nitrite/nitrate (NOx) levels and examined lung biopsies for lung injury score (LIS). Results Both the injuriously ventilated groups demonstrated a 2–3-fold rise in EVLWI and PVPI, with no significant effects of NI. In the INJV group, gas exchange deteriorated in parallel with emerging respiratory acidosis, but administration of NI antagonized the derangement of oxygenation and the respiratory acidosis significantly. NOx displayed no significant changes and NI exerted no significant effect on LIS in the INJV group. Conclusion Inhibition of nNOS improved gas exchange, but did not reduce lung water extravasation following injurious ventilation after pneumonectomy in sheep.

2012-01-01

288

Chitin-chitosan: Properties, benefits and risks  

Microsoft Academic Search

A beneficial effect of chitin-chitosan as a food supplement is the reduction of plasma cholesterol and triglycerides due to its ability to bind dietary lipids, thereby reducing intestinal lipid absorption. The hypolipidemic influence of chitosan may also be due to interruption of the enterohepatic bile acid circulation. Plasma cholesterol in animals on cholesterol-free diet, however, is not affected, indicating that

S. S. Koide

1998-01-01

289

Chitin and chitosan: Properties and applications  

Microsoft Academic Search

Chitin is the second most important natural polymer in the world. The main sources exploited are two marine crustaceans, shrimp and crabs. Our objective is to appraise the state of the art concerning this polysaccharide: its morphology in the native solid state, methods of identification and characterization and chemical modifications, as well as the difficulties in utilizing and processing it

Marguerite Rinaudo

2006-01-01

290

DNA extraction from keratin and chitin.  

PubMed

DNA extracted from keratinous and chitinous materials can be a useful source of genetic information. To effectively liberate the DNA from these materials, buffers containing relatively high levels of DTT, proteinase K, and detergent are recommended, followed by purification using either silica-column or organic methods. PMID:22237520

Campos, Paula F; Gilbert, Thomas M P

2012-01-01

291

Spermine synthase  

Microsoft Academic Search

Spermine is present in many organisms including animals, plants, some fungi, some archaea, and some bacteria. It is synthesized\\u000a by spermine synthase, a highly specific aminopropyltransferase. This review describes spermine synthase structure, genetics,\\u000a and function. Structural and biochemical studies reveal that human spermine synthase is an obligate dimer. Each monomer contains\\u000a a C-terminal domain where the active site is located,

Anthony E. PeggAnthony; Anthony J. Michael

2010-01-01

292

Glycogen synthase kinase-3? (GSK-3?) inhibitors AR-A014418 and B6B3O prevent human immunodeficiency virus-mediated neurotoxicity in primary human neurons  

PubMed Central

Glycogen synthase kinase-3? (GSK3?) role in human immunodeficiency virus (HIV)-associated neurodegeneration has been evidenced by previous investigations. In this study, we investigated the specificity of two GSK3?-specific inhibitors, AR-A014418 (A) and B6B30 (B) to prevent direct neurotoxicity in primary human neurons exposed to HIV (BaL). Neurons were exposed to HIV (500 pg/ml) for 12-h and 6-day periods in the presence and absence of A (1 µM, 100 nM, 10 nM) and B (50 nM, 5 nM, 500 pM) to investigate acute and ongoing mechanisms of HIV neurotoxicity. Using an lactate dehydrogenase (LDH) assay to assess cytotoxicity, we observed a significant neurotoxic effect of HIV from control values (P < .01) that was not restored via coexposures of all concentrations of A and B. Additionally, no change in LDH levels were observed after 6 days. However, activity of the acute proapoptotic markers caspases 3 and 7 using a luminescence assay were measured and found to be increased by exposure to HIV (BaL) compared to controls (P = .022). This effect was ameliorated via coexposure to all concentrations of A and 50 nM B after 12 h (P < .01) and to all concentrations of A and B after 6 days (P < .01). Overall, the results from this study provide further evidence for the ability of GSK3? inhibition to be neuroprotective against HIV-associated neurotoxicity by reducing HIV associated procaspase induction. These data support a role for GSK3? as a potential therapeutic target and may have important clinical implications for treatment of HIV-associated neurocognitive disorder.

Nguyen, Timothy B.; Lucero, Ginger R.; Chana, Gursharan; Hult, Britta J.; Tatro, Erick T.; Masliah, Eliezer; Grant, Igor; Achim, Cristian L.; Everall, Ian P.

2011-01-01

293

Constitutive activation of glycogen synthase kinase-3? correlates with better prognosis and cyclin-dependent kinase inhibitors in human gastric cancer  

PubMed Central

Background Aberrant regulation of glycogen synthase kinase-3? (GSK-3?) has been implicated in several human cancers; however, it has not been reported in the gastric cancer tissues to date. The present study was performed to determine the expression status of active form of GSK-3? phosphorylated at Tyr216 (pGSK-3?) and its relationship with other tumor-associated proteins in human gastric cancers. Methods Immunohistochemistry was performed on tissue array slides containing 281 human gastric carcinoma specimens. In addition, gastric cancer cells were cultured and treated with a GSK-3? inhibitor lithium chloride (LiCl) for immunoblot analysis. Results We found that pGSK-3? was expressed in 129 (46%) of 281 cases examined, and was higher in the early-stages of pathologic tumor-node-metastasis (P < 0.001). The expression of pGSK-3? inversely correlated with lymphatic invasion (P < 0.001) and lymph node metastasis (P < 0.001) and correlated with a longer patient survival (P < 0.001). In addition, pGSK-3? expression positively correlated with that of p16, p21, p27, p53, APC, PTEN, MGMT, SMAD4, or KAI1 (P < 0.05), but not with that of cyclin D1. This was confirmed by immunoblot analysis using SNU-668 gastric cancer cells treated with LiCl. Conclusions GSK-3? activation was frequently observed in early-stage gastric carcinoma and was significantly correlated with better prognosis. Thus, these findings suggest that GSK-3? activation is a useful prognostic marker for the early-stage gastric cancer.

2010-01-01

294

Novel, druglike 1,7-disubstituted 2,3,4,5-tetrahydro-1H-benzo[b]azepine-based selective inhibitors of human neuronal nitric oxide synthase (nNOS).  

PubMed

A novel class of 1,7-disubstituted 2,3,4,5-tetrahydro-1H-benzo[b]azepine derivatives was designed, synthesized and evaluated as human nitric oxide synthase (NOS) inhibitors. Structure-activity relationship studies based on various basic amine side chains attached at the 1-position of the 2,3,4,5-tetrahydro-1H-benzo[b]azepine ring led to the identification of several potent and highly selective inhibitors (17, 18, 25, (±)-39, and (±)-40) of human neuronal NOS. The potential therapeutic application of one of these new selective nNOS inhibitors (17) was demonstrated in an in vivo spinal nerve ligation model of neuropathic pain, and various in vitro safety pharmacology studies such as the hERG K(+) channel inhibition assay and high throughput broad screen (minimal activity at 79 receptors/transporters/ion channels). PMID:22370270

Annedi, Subhash C; Ramnauth, Jailall; Cossette, Michele; Maddaford, Shawn P; Dove, Peter; Rakhit, Suman; Andrews, John S; Porreca, Frank

2012-02-09

295

Conservation of the Chitin Utilization Pathway in the Vibrionaceae? †  

PubMed Central

Vibrionaceae are regarded as important marine chitin degraders, and attachment to chitin regulates important biological functions; yet, the degree of chitin pathway conservation in Vibrionaceae is unknown. Here, a core chitin degradation pathway is proposed based on comparison of 19 Vibrio and Photobacterium genomes with a detailed metabolic map assembled for V. cholerae from published biochemical, genomic, and transcriptomic results. Further, to assess whether chitin degradation is a conserved property of Vibrionaceae, a set of 54 strains from 32 taxa were tested for the ability to grow on various forms of chitin. All strains grew on N-acetylglucosamine (GlcNAc), the monomer of chitin. The majority of isolates grew on ? (crab shell) and ? (squid pen) chitin and contained chitinase A (chiA) genes. chiA sequencing and phylogenetic analysis suggest that this gene is a good indicator of chitin metabolism but appears subject to horizontal gene transfer and duplication. Overall, chitin metabolism appears to be a core function of Vibrionaceae, but individual pathway components exhibit dynamic evolutionary histories.

Hunt, Dana E.; Gevers, Dirk; Vahora, Nisha M.; Polz, Martin F.

2008-01-01

296

Inhibitors  

MedlinePLUS

... message, please visit this page: About CDC.gov . Hemophilia Share Compartir Add this to... Ańadir en... Favorites Delicious Digg Google Bookmarks Inhibitors People with hemophilia have a higher quality of life today than ...

297

[Inhibition of chitin synthetase of Mucor rouxii in vitro by fungicides and other compounds].  

PubMed

Comparative investigations on the inhibition of chitin synthetase of Mucor rouxii revealed that in contrast to results obtained in vivo, only few fungicides and other compounds inhibit the enzyme in vitro. Besides the well-known effect of polyoxin D, an inhibition was demonstrated for terrazol, tridemorph, hinosan, and formulated preparations of dimilin (PH 60--40, 60--38). The latter preparations, however, showed growth inhibition also with fungal species which do not synthesize chitin and the pure compounds are ineffective. Inhibition by phospholipase C, unsaturated fatty acids, and the reversibility of the inhibition caused by terrazol after addition of procain-hydrochloride demonstrates that phospholipids are essential for the activity of the enzyme, whereas sterols seem to be ineffective. Action of trypsin, PCNB, pentachlorophenol, and some similar compounds results in significantly increased activity, which in the case of trypsin could be due to the hydrolysis of a protein inhibitor. Hinosan inhibits the enzyme indirectly in a still unexplored manner. PMID:753046

Lyr, H; Seyd, W

1978-01-01

298

Mesoporous silica and organosilica films templated by nanocrystalline chitin.  

PubMed

Liquid crystalline phases can be used to impart order into inorganic solids, creating materials that mimic natural architectures. Herein, mesoporous silica and organosilica films with layered structures and high surface areas have been templated by nanocrystalline chitin. Aqueous suspensions of spindle-shaped chitin nanocrystals were prepared by sequential deacetylation and hydrolysis of chitin fibrils isolated from king crab shells. The nanocrystalline chitin self-assembles into a nematic liquid-crystalline phase that has been used to template silica and organosilica composites. Removal of the chitin template by either calcination or sulfuric-acid-catalyzed hydrolysis gave mesoporous silica and ethylene-bridged organosilica films. The large, crack-free mesoporous films have layered structures with features that originate from the nematic organization of the nanocrystalline chitin. PMID:24150881

Nguyen, Thanh-Dinh; Shopsowitz, Kevin E; Maclachlan, Mark J

2013-09-25

299

Carbon, Nitrogen and Oxygen Stable Isotope Ratios in Chitin  

Microsoft Academic Search

\\u000a Stable isotope ratios in chitin are firmly imprinted during biopolymer biosynthesis and reflect dietary, metabolic, and environmental\\u000a influences. Chitin is a chemically complex amino sugar biopolymer that also includes non-amino-sugar moieties with contrasting\\u000a isotopic compositions. Reproducible N, C, O-stable isotope determinations should rely on a chemically purified chitin substrate\\u000a with limited non-amino-sugar contributions. Insecta, Crustacea and Merostomata are not distinguished

Arndt Schimmelmann

300

A selective thromboxane A2 (TXA2) synthase inhibitor, ozagrel, attenuates lung injury and decreases monocyte chemoattractant protein-1 and interleukin-8 mRNA expression in oleic acid-induced lung injury in guinea pigs.  

PubMed

This study examined the effect of ozagrel, a thromboxane A(2) synthase inhibitor, on the accumulation of leucocytes and chemokine mRNA expression in lungs experimentally injured using oleic acid (OA). OA injection into guinea pigs rapidly increased thromboxane A(2) generation and subsequently increased total protein concentration and the numbers of macrophages and neutrophils in bronchoalveolar lavage fluid and increased monocyte chemoattractant protein-1 and interleukin-8 mRNA expression in the whole lung. Administration of ozagrel prevented these changes associated with OA injection. Ozagrel is a promising drug candidate for preventing acute lung injury. PMID:19783866

Ishitsuka, Yoichi; Moriuchi, Hiroshi; Isohama, Yoichiro; Tokunaga, Hidehiro; Hatamoto, Keita; Kurita, Sumika; Irikura, Mitsuru; Iyama, Ken-ichi; Irie, Tetsumi

2009-09-26

301

Nitric oxide donors prevent while the nitric oxide synthase inhibitor L-NAME increases arachidonic acid plus CYP2E1-dependent toxicity  

SciTech Connect

Polyunsaturated fatty acids such as arachidonic acid (AA) play an important role in alcohol-induced liver injury. AA promotes toxicity in rat hepatocytes with high levels of cytochrome P4502E1 and in HepG2 E47 cells which express CYP2E1. Nitric oxide (NO) participates in the regulation of various cell activities as well as in cytotoxic events. NO may act as a protectant against cytotoxic stress or may enhance cytotoxicity when produced at elevated concentrations. The goal of the current study was to evaluate the effect of endogenously or exogenously produced NO on AA toxicity in liver cells with high expression of CYP2E1 and assess possible mechanisms for its actions. Pyrazole-induced rat hepatocytes or HepG2 cells expressing CYP2E1 were treated with AA in the presence or absence of an inhibitor of nitric oxide synthase L-N {sup G}-Nitroarginine Methylester (L-NAME) or the NO donors S-nitroso-N-acetylpenicillamine (SNAP), and (Z)-1-[-(2-aminoethyl)-N-(2-aminoethyl)]diazen-1-ium-1,2-diolate (DETA-NONO). AA decreased cell viability from 100% to 48 {+-} 6% after treatment for 48 h. In the presence of L-NAME, viability was further lowered to 23 {+-} 5%, while, SNAP or DETA-NONO increased viability to 66 {+-} 8 or 71 {+-} 6%. The L-NAME potentiated toxicity was primarily necrotic in nature. L-NAME did not affect CYP2E1 activity or CYP2E1 content. SNAP significantly lowered CYP2E1 activity but not protein. AA treatment increased lipid peroxidation and lowered GSH levels. L-NAME potentiated while SNAP prevented these changes. Thus, L-NAME increased, while NO donors decreased AA-induced oxidative stress. Antioxidants prevented the L-NAME potentiation of AA toxicity. Damage to mitochondria by AA was shown by a decline in the mitochondrial membrane potential (MMP). L-NAME potentiated this decline in MMP in association with its increase in AA-induced oxidative stress and toxicity. NO donors decreased this decline in MMP in association with their decrease in AA-induced oxidative stress and toxicity. These results indicate that NO can be hepatoprotective against CYP2E1-dependent toxicity, preventing AA-induced oxidative stress.

Wu Defeng [Department of Pharmacology and Biological Chemistry, Box 1603, One Gustave L. Levy Place, Mount Sinai School of Medicine, New York, NY 10029 (United States); Cederbaum, Arthur [Department of Pharmacology and Biological Chemistry, Box 1603, One Gustave L. Levy Place, Mount Sinai School of Medicine, New York, NY 10029 (United States)]. E-mail: arthur.cederbaum@mssm.edu

2006-10-15

302

Pulmonary hypertension triggered by lipopolysaccharide in ascites-susceptible and -resistant broilers is not amplified by aminoguanidine, a specific inhibitor of inducible nitric oxide synthase.  

PubMed

Nitric oxide (NO) is a potent pulmonary vasodilator that modulates the pulmonary vasoconstriction and pulmonary hypertension (PH) triggered by bacterial lipopolysaccharide (LPS) in broilers. The amplitude and duration of the LPS-induced PH are markedly enhanced following pretreatment with N(omega)-nitro-L-arginine methyl ester (L-NAME), which inhibits NO synthesis by both the constitutive (endothelial) and inducible (inflammatory) forms of nitric oxide synthase (eNOS and iNOS, respectively). In the present study L-NAME and the selective iNOS inhibitor aminoguanidine (AG) were administered to differentiate between iNOS and eNOS as the primary source of NO that attenuates the pulmonary vascular response to LPS. Clinically healthy male progeny from ascites-susceptible and ascites-resistant lines were anesthetized, and their pulmonary artery was cannulated. The initial pulmonary arterial pressure (PAP) was recorded, then the broilers either remained untreated (control group) or were injected i.v. with AG. Ten minutes later all birds received an i.v. injection of LPS, followed 40 min later by an i.v. injection of L-NAME. When compared with untreated controls, AG neither increased the baseline PAP nor did it increase or prolong the PH response to LPS. The ascites-susceptible broilers maintained a higher PAP than the ascites-resistant broilers throughout the experiment, and the ascites-resistant broilers exhibited greater relative increases in PAP in response to LPS than did the ascites-susceptible broilers. Within 40 min after the LPS injection, PAP subsided to a level that did not differ from the respective preinjection value for each line. Injecting L-NAME reversed the decline in PAP, and within 5 min PAP returned to hypertensive levels approaching the maximum peak PH response to LPS. The absence of any impact of AG coupled with the profound response to L-NAME indicates that NO synthesized by eNOS rather than iNOS likely modulated the acute (within 1 h) PH elicited by LPS. Evidently eNOS is activated by the increased shear stress exerted on the endothelium during the PH response to LPS, whereas LPS-mediated up-regulation of iNOS expression may take longer than 1 h before biologically effective quantities of NO are produced. PMID:16553285

Bowen, O T; Erf, G F; Anthony, N B; Wideman, R F

2006-03-01

303

Spermine synthase.  

PubMed

Spermine is present in many organisms including animals, plants, some fungi, some archaea, and some bacteria. It is synthesized by spermine synthase, a highly specific aminopropyltransferase. This review describes spermine synthase structure, genetics, and function. Structural and biochemical studies reveal that human spermine synthase is an obligate dimer. Each monomer contains a C-terminal domain where the active site is located, a central linking domain that also forms the lid of the catalytic domain, and an N-terminal domain that is structurally very similar to S-adenosylmethionine decarboxylase. Gyro mice, which have an X-chromosomal deletion including the spermine synthase (SMS) gene, lack all spermine and have a greatly reduced size, sterility, deafness, neurological abnormalities, and a tendency to sudden death. Mutations in the human SMS lead to a rise in spermidine and reduction of spermine causing Snyder-Robinson syndrome, an X-linked recessive condition characterized by mental retardation, skeletal defects, hypotonia, and movement disorders. PMID:19859664

Pegg, Anthony E; Michael, Anthony J

2009-10-27

304

Non-Bisphosphonate Inhibitors of Isoprenoid Biosynthesis Identified via Computer-Aided Drug Design  

PubMed Central

The relaxed complex scheme, a virtual-screening methodology that accounts for protein receptor flexibility, was used to identify a low-micromolar, non-bisphosphonate inhibitor of farnesyl diphosphate synthase. Serendipitously, we also found that several predicted farnesyl diphosphate synthase inhibitors were low-micromolar inhibitors of undecaprenyl diphosphate synthase. These results are of interest because farnesyl diphosphate synthase inhibitors are being pursued as both anti-infective and anticancer agents, and undecaprenyl diphosphate synthase inhibitors are antibacterial drug leads.

Durrant, Jacob D; Cao, Rong; Gorfe, Alemayehu A; Zhu, Wei; Li, Jikun; Sankovsky, Anna; Oldfield, Eric; McCammon, J Andrew

2011-01-01

305

From a Natural Product Lead to the Identification of Potent and Selective Benzofuran-3-yl-(indol-3-yl)maleimides as Glycogen Synthase Kinase 3? Inhibitors that Suppress Proliferation and Survival of Pancreatic Cancer Cells  

PubMed Central

Recent studies have demonstrated that Glycogen Synthase Kinase 3? (GSK-3?) is overexpressed in human colon and pancreatic carcinomas contributing to cancer cell proliferation and survival. Here, we report the design, synthesis, and biological evaluation of benzofuran-3-yl-(indol-3-yl)maleimides, potent GSK-3? inhibitors. Some of these compounds show picomolar inhibitory activity toward GSK-3? and an enhanced selectivity against Cyclin-dependent Kinase 2 (CDK-2). Selected GSK-3? inhibitors were tested in the pancreatic cancer cell lines MiaPaCa-2, BXPC-3, and HupT3. We determined that some of these compounds, namely compounds 5, 6, 11, 20 and 26, demonstrate antiproliferative activity against some or all of the pancreatic cancer cells at low micromolar to nanomolar concentrations. We found that the treatment of pancreatic cancer cells with GSK-3? inhibitors 5 and 26 resulted in suppression of GSK-3? activity and a distinct decrease of the X-linked Inhibitor of Apoptosis (XIAP) expression leading to significant apoptosis. The present data suggest a possible role for GSK-3? inhibitors in cancer therapy, in addition to their more prominent applications in CNS disorders.

Gaisina, Irina N.; Gallier, Franck; Ougolkov, Andrei V.; Kim, Ki H.; Kurome, Toru; Guo, Songpo; Holzle, Denise; Luchini, Doris N.; Blond, Sylvie Y.; Billadeau, Daniel D.; Kozikowski, Alan P.

2009-01-01

306

Involvement of thromboxane A2 (TXA2) in the early stages of oleic acid-induced lung injury and the preventive effect of ozagrel, a TXA2 synthase inhibitor, in guinea-pigs.  

PubMed

An intravenous injection of oleic acid into animals can produce a lung injury with hypoxaemia and pulmonary vascular hyper-permeability. Although oleic acid lung injury is used as a model of acute respiratory distress syndrome (ARDS), the precise mechanisms of the lung injury are still unclear. We have investigated whether thromboxane A(2) (TXA(2)) participated in the lung injury and have evaluated the efficacy of ozagrel, a TXA(2) synthase inhibitor, on the lung injury in guinea-pigs. Oleic acid injection increased the plasma level of TXB(2), a stable metabolite of TXA(2), and the time-course of plasma TXB(2) was similar to that of the decreased partial oxygen pressure of arterial blood (Pao(2)) induced with oleic acid. Ozagrel administered intravenously 30 min before oleic acid injection prevented the decrease in Pao(2) and pulmonary vascular hyper-permeability. It also prevented increases in lactate dehydrogenase activity, a measure of lung cell injury, TXB(2 )and its weight ratio to 6-keto prostaglandin F(1alpha) in bronchoalveolar lavage fluid. Although ozagrel administered simultaneously with oleic acid ameliorated the decrease in Pao(2), post treatment showed little effect. We suggest that TXA(2) participated in the oleic acid lung injury, as an "early phase" mediator, and rapidly-acting TXA(2) synthase inhibitors were effective in the prevention of acute lung injury. PMID:15099446

Ishitsuka, Yoichi; Moriuchi, Hiroshi; Hatamoto, Keita; Yang, Changqing; Takase, Junko; Golbidi, Saeid; Irikura, Mitsuru; Irie, Tetsumi

2004-04-01

307

Crab shell chitin whiskers reinforced natural rubber nanocomposites. 3. Effect of chemical modification of chitin whiskers.  

PubMed

The purpose of this study was to chemically modify the surface of chitin whiskers and to investigate the effect of the incorporation of these modified whiskers into a natural rubber (NR) matrix on the properties of the ensuing nanocomposite. Different chemical coupling agents were tested, namely, phenyl isocyanate (PI), alkenyl succinic anhydride (ASA) (Accosize 18 from American Cyanamid), and 3-isopropenyl-alpha,alpha'-dimethylbenzyl isocyanate (TMI). The extent of chemical modification was evaluated by Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and surface energy analysis. After chemical modification, nanocomposite films were obtained using a toluene natural rubber solution in which the whiskers were dispersed. Their mechanical properties were found to be inferior to those of unmodified chitin/NR composites presented in our previous study. In fact, even though there is an increase in filler-matrix interaction as a result of chemical modification of the chitin whiskers, this does not contribute to the improvement in the mechanical properties of the resulting nanocomposite. It is concluded that this loss of performance is due to the partial destruction of the three-dimensional network of chitin whiskers assumed to be present in the unmodified composites. PMID:14606916

Gopalan Nair, Kalaprasad; Dufresne, Alain; Gandini, Alessandro; Belgacem, Mohamed Naceur

308

The occurrence of chitin in the hemocytes of invertebrates  

Microsoft Academic Search

The light-organ symbiosis of Euprymna scolopes, the Hawaiian bobtail squid, is a useful model for the study of animal–microbe interactions. Recent analyses have demonstrated that chitin breakdown products play a role in communication between E. scolopes and its bacterial symbiont Vibrio fischeri. In this study, we sought to determine the source of chitin in the symbiotic organ. We used a

Elizabeth A. C. Heath-Heckman; Margaret J. McFall-Ngai

2011-01-01

309

The Chitinase PfCHT1 from the Human Malaria Parasite Plasmodium falciparum Lacks Proenzyme and Chitin-Binding Domains and Displays Unique Substrate Preferences  

Microsoft Academic Search

Within hours after the ingestion of a blood meal, the mosquito midgut epithelium synthesizes a chitinous sac, the peritrophic matrix. Plasmodium ookinetes traverse the peritrophic matrix while escaping the mosquito midgut. Chitinases (EC 3.2.1.14) are critical for parasite invasion of the midgut: the presence of the chitinase inhibitor, allosamidin, in an infectious blood meal prevents oocyst development. A chitinase gene,

Joseph M. Vinetz; Sanat K. Dave; Charles A. Specht; Kenneth A. Brameld; Bo Xu; Rhian Hayward; David A. Fidock

1999-01-01

310

Degradation and mineralization of chitin in an estuary  

SciTech Connect

A method for measuring microbial degradation and mineralization of radiolabeled native chitin is described. /sup 14/C-labeled chitin was synthesized in vivo by injecting shed blue crabs (Callinectes sapidus) with N-acetyl-D-(/sup 14/C)-glucosamine, allowing for its incorporation into the exoskeleton. Rates of chitin degradation and mineralization in estuarine water and sediments were determined as functions of temperature, inoculum source, and oxygen condition. Significant differences in rates between temperature treatments were evident. Q/sub 10/ values ranged from 1.2 to 2.5 for water and sediment, respectively. Increased incubation temperature also resulted in decreased lag times before onset of chitinoclastic bacterial growth and chitin degradation. The anaerobic pathway of chitin decomposition by chitinoclastic bacteria was examined with an emphasis on end product coupling to other bacterial types. Actively growing chitinoclastic bacterial isolates produced primarily acetate, hydrogen, and carbon dioxide in broth culture.

Boyer, J.

1987-01-01

311

Fine-tuning the selectivity of aldosterone synthase inhibitors: structure-activity and structure-selectivity insights from studies of heteroaryl substituted 1,2,5,6-tetrahydropyrrolo[3,2,1-ij]quinolin-4-one derivatives.  

PubMed

Pyridine substituted 3,4-dihydro-1H-quinolin-2-ones (e.g., 1-3) constitute a class of highly potent and selective inhibitors of aldosterone synthase (CYP11B2), a promising target for the treatment of hyperaldosteronism, congestive heart failure, and myocardial fibrosis. Among these, ethyl-substituted 3 possesses high selectivity against CYP1A2. Rigidification of 3 by incorporation of the ethyl group into a 5- or 6-membered ring affords compounds with a pyrroloquinolinone or pyridoquinolinone molecular scaffold (e.g., 4 and 5). It was found that these molecules are even more potent and selective CYP11B2 inhibitors than their corresponding open-chain analogues. Moreover, pyrroloquinolinone 4 exhibits no inhibition of the six most important hepatic CYP enzymes as well as a bioavailability in the range of the marketed drug fadrozole. The SAR studies disclose that subtle changes in the heterocyclic moiety are responsible for either a strong or a weak inhibition of the highly homologous 11?-hydroxylase (CYP11B1). These results are not only important for fine-tuning the selectivity of CYP11B2 inhibitors but also for the development of selective CYP11B1 inhibitors that are of interest for the treatment of Cushing's syndrome and metabolic syndrome. PMID:21384875

Lucas, Simon; Negri, Matthias; Heim, Ralf; Zimmer, Christina; Hartmann, Rolf W

2011-03-08

312

Radioisotope Assay for 1-Aminocyclopropane-1- Carboxylic Acid Synthase: S-adenosylhomocysteine Analogs as Inhibitors of the Enzyme Involved in Plant Senescence.  

National Technical Information Service (NTIS)

A simple and rapid radioisotopic assay for 1-aminocyclopropane-1-carboxylic acid (ACC) synthase was developed, an enzyme involved in the biosynthesis of the plant hormone ethylene. The assay utilizes an AG50-X4(NH4 (+)) column which separates S-adenosyl-L...

G. A. Miura P. K. Chiang

1985-01-01

313

NITRIC OXIDE SYNTHASE INHIBITORS AND NITRIC OXIDE DONORS MODULATE THE BIOSYNTHESIS OF THAXTOMIN A, A NITRATED PHYTOTOXIN PRODUCED BY STREPTOMYCES SPP  

Technology Transfer Automated Retrieval System (TEKTRAN)

Evidence for the involvement of a bacterial nitric oxide synthase (NOS) in the biosynthesis of a phytotoxin is presented. Several species of Streptomyces bacteria produce secondary metabolites with unusual nitrogen groups, such as thaxtomin A (ThxA), which contains a nitroindole moiety. ThxA is a ...

314

Homologs of the Xenopus developmental gene DG42 are present in zebrafish and mouse and are involved in the synthesis of Nod-like chitin oligosaccharides during early embryogenesis.  

PubMed Central

The Xenopus developmental gene DG42 is expressed during early embryonic development, between the midblastula and neurulation stages. The deduced protein sequence of Xenopus DG42 shows similarity to Rhizobium Nod C, Streptococcus Has A, and fungal chitin synthases. Previously, we found that the DG42 protein made in an in vitro transcription/translation system catalyzed synthesis of an array of chitin oligosaccharides. Here we show that cell extracts from early Xenopus and zebrafish embryos also synthesize chitooligosaccharides. cDNA fragments homologous to DG42 from zebrafish and mouse were also cloned and sequenced. Expression of these homologs was similar to that described for Xenopus based on Northern and Western blot analysis. The Xenopus anti-DG42 antibody recognized a 63-kDa protein in extracts from zebrafish embryos that followed a similar developmental expression pattern to that previously described for Xenopus. The chitin oligosaccharide synthase activity found in extracts was inactivated by a specific DG42 antibody; synthesis of hyaluronic acid (HA) was not affected under the conditions tested. Other experiments demonstrate that expression of DG42 under plasmid control in mouse 3T3 cells gives rise to chitooligosaccharide synthase activity without an increase in HA synthase level. A possible relationship between our results and those of other investigators, which show stimulation of HA synthesis by DG42 in mammalian cell culture systems, is provided by structural analyses to be published elsewhere that suggest that chitin oligosaccharides are present at the reducing ends of HA chains. Since in at least one vertebrate system hyaluronic acid formation can be inhibited by a pure chitinase, it seems possible that chitin oligosaccharides serve as primers for hyaluronic acid synthesis. Images Fig. 2 Fig. 4

Semino, C E; Specht, C A; Raimondi, A; Robbins, P W

1996-01-01

315

A phase I and pharmacokinetic study of 1843U89, a noncompetitive inhibitor of thymidylate synthase, in patients with advanced solid malignancies.  

PubMed

This study was performed to assess the feasibility of administering 1843U89, a potent, noncompetitive inhibitor of thymidylate synthase that does not require polyglutamation for activity, as a 2-min i.v. infusion daily for 5 days every 3 weeks, to determine whether folic acid supplementation ameliorates the toxic effects of 1843U89 and permits further dose escalation, and to recommend doses of 1843U89 administered without and with folic acid for further clinical evaluations. The study also sought to characterize the pharmacokinetic behavior of 1843U89 and to seek preliminary evidence of anticancer activity. Patients with advanced solid malignancies were treated with escalating doses of 1843U89 as a 2-min i.v. infusion daily for 5 days every 3 weeks. Initially, patients were treated in the absence of high-dose folic acid until dose-limiting toxicity was consistently noted. Next, patients were treated with escalating doses of 1843U89 preceded by 1000 mg of folic acid administered p.o. 30 min before each of the 5 daily doses of 1843U89. Patients (32) received 101 total courses of 1843U89 at doses ranging from 1 to 6 mg/m(2)/day with and without folic acid. At the 2 mg/m(2)/day dose level without folic acid, 2 of 7 new patients experienced dose-limiting toxicity, principally neutropenia, mucositis, and malaise in 3 of 11 courses. 1843U89 doses were further increased with folic acid to 6 mg/m(2)/day, but repetitive treatment was not feasible at this dose level because of an unacceptable high incidence of severe neutropenia and mucositis. Other toxicities included thrombocytopenia, rash, and fever. In contrast, repetitive treatment at the 5 mg/m(2)/day dose level was feasible. The pharmacokinetics of 1843U89 were neither dose dependent nor affected by folic acid. On day 1, clearance, terminal half-life, and steady-state volume of distribution values averaged 47.1 +/- 21.7 ml/min/m(2), 7.72 +/- 4.09 h, and 16.7 +/- 8.8 liter/m(2)/h, respectively. The results of the study indicate that the administration of 1843U89 as a 2-min infusion daily for 5 days every 3 weeks without and with folic acid is feasible at 1843U89 doses as high as 2 and 5 mg/m(2)/day, respectively. Because folic acid pretreatment results in no diminution of the antitumor activity of 1843U89 in preclinical studies and ameliorates the toxic effects of 1843U89 in both preclinical models and cancer patients, the therapeutic index of 1843U89 may be enhanced by folic acid pretreatment and, therefore, the development of 1843U89 with folic acid is warranted. However, the question of whether to administer 1843U89 at a dose of 2 mg/m(2)/day with folic acid, which is associated with negligible toxicity, or at its highest feasible dose with folic acid, 5 mg/m(2)/day, should be addressed in appropriately designed trials. PMID:11448903

Schwartz, G; Johnson, T R; Goetz, A; Burris, H; Smetzer, L; Lampkin, T; Sailstad, J; Hohneker, J A; Von Hoff, D D; Rowinsky, E K

2001-07-01

316

Salmonella Biofilm Formation on Aspergillus niger Involves Cellulose - Chitin Interactions  

PubMed Central

Salmonella cycles between host and nonhost environments, where it can become an active member of complex microbial communities. The role of fungi in the environmental adaptation of enteric pathogens remains relatively unexplored. We have discovered that S. enterica Typhimurium rapidly attaches to and forms biofilms on the hyphae of the common fungus, Aspergillus niger. Several Salmonella enterica serovars displayed a similar interaction, whereas other bacterial species were unable to bind to the fungus. Bacterial attachment to chitin, a major constituent of fungal cell walls, mirrored this specificity. Pre-incubation of S. Typhimurium with N-acetylglucosamine, the monomeric component of chitin, reduced binding to chitin beads by as much as 727-fold and inhibited attachment to A. niger hyphae considerably. A cellulose-deficient mutant of S. Typhimurium failed to attach to chitin beads and to the fungus. Complementation of this mutant with the cellulose operon restored binding to chitin beads to 79% of that of the parental strain and allowed for attachment and biofilm formation on A. niger, indicating that cellulose is involved in bacterial attachment to the fungus via the chitin component of its cell wall. In contrast to cellulose, S. Typhimurium curli fimbriae were not required for attachment and biofilm development on the hyphae but were critical for its stability. Our results suggest that cellulose–chitin interactions are required for the production of mixed Salmonella-A. niger biofilms, and support the hypothesis that encounters with chitinaceous alternate hosts may contribute to the ecological success of human pathogens.

Brandl, Maria T.; Carter, Michelle Q.; Parker, Craig T.; Chapman, Matthew R.; Huynh, Steven; Zhou, Yaguang

2011-01-01

317

Coexpression of CYP11B2 or CYP11B1 with adrenodoxin and adrenodoxin reductase for assessing the potency and selectivity of aldosterone synthase inhibitors  

Microsoft Academic Search

Excessive production of aldosterone has been implicated in the pathogenesis of hypertension and heart failure. One approach to ameliorate the deleterious effects of aldosterone is to suppress its biosynthesis. The enzyme aldosterone synthase (CYP11B2) is responsible for the final step of aldosterone synthesis. It requires electron transfer from the adrenodoxin\\/adrenodoxin reductase system to catalyze the production of aldosterone. A stable

Daniel LaSala; Yasuhiko Shibanaka; Arco Y. Jeng

2009-01-01

318

Novel chitin and chitosan nanofibers in biomedical applications.  

PubMed

Chitin and its deacetylated derivative, chitosan, are non-toxic, antibacterial, biodegradable and biocompatible biopolymers. Due to these properties, they are widely used for biomedical applications such as tissue engineering scaffolds, drug delivery, wound dressings, separation membranes and antibacterial coatings, stent coatings, and sensors. In the recent years, electrospinning has been found to be a novel technique to produce chitin and chitosan nanofibers. These nanofibers find novel applications in biomedical fields due to their high surface area and porosity. This article reviews the recent reports on the preparation, properties and biomedical applications of chitin and chitosan based nanofibers in detail. PMID:19913083

Jayakumar, R; Prabaharan, M; Nair, S V; Tamura, H

319

Heterologous expression and characterization of a "Pseudomature" form of taxadiene synthase involved in paclitaxel (Taxol) biosynthesis and evaluation of a potential intermediate and inhibitors of the multistep diterpene cyclization reaction.  

PubMed

The diterpene cyclase taxadiene synthase from yew (Taxus) species transforms geranylgeranyl diphosphate to taxa-4(5),11(12)-diene as the first committed step in the biosynthesis of the anti-cancer drug Taxol. Taxadiene synthase is translated as a preprotein bearing an N-terminal targeting sequence for localization to and processing in the plastids. Overexpression of the full-length preprotein in Escherichia coli and purification are compromised by host codon usage, inclusion body formation, and association with host chaperones, and the preprotein is catalytically impaired. Since the transit peptide-mature enzyme cleavage site could not be determined directly, a series of N-terminally truncated enzymes was created by expression of the corresponding cDNAs from a suitable vector, and each was purified and kinetically evaluated. Deletion of up to 79 residues yielded functional protein; however, deletion of 93 or more amino acids resulted in complete elimination of activity, implying a structural or catalytic role for the amino terminus. The pseudomature form of taxadiene synthase having 60 amino acids deleted from the preprotein was found to be superior with respect to level of expression, ease of purification, solubility, stability, and catalytic activity with kinetics comparable to the native enzyme. In addition to the major product, taxa-4(5),11(12)-diene (94%), this enzyme produces a small amount of the isomeric taxa-4(20), 11(12)-diene ( approximately 5%), and a product tentatively identified as verticillene ( approximately 1%). Isotopically sensitive branching experiments utilizing (4R)-[4-(2)H(1)]geranylgeranyl diphosphate confirmed that the two taxadiene isomers, and a third (taxa-3(4),11(12)-diene), are derived from the same intermediate taxenyl C4-carbocation. These results, along with the failure of the enzyme to utilize 2, 7-cyclogeranylgeranyl diphosphate as an alternate substrate, indicate that the reaction proceeds by initial ionization of the diphosphate ester and macrocyclization to the verticillyl intermediate, followed by a secondary cyclization to the taxenyl cation and deprotonation (i.e., formation of the A-ring prior to B/C-ring closure). Two potential mechanism-based inhibitors were tested with recombinant taxadiene synthase but neither provided time-dependent inactivation nor afforded more than modest competitive inhibition. PMID:10864451

Williams, D C; Wildung, M R; Jin, A Q; Dalal, D; Oliver, J S; Coates, R M; Croteau, R

2000-07-01

320

Localization and Proof of Chitin in the Opisthobranch Mollusks Aplysia californica Cooper and Bulla gmtldiana (Pilsbry), with an Enzymochromatographic Method for Chitin Demonstration  

Microsoft Academic Search

CHITIN HAS been gen erally considered as almost synonymous with th e art hropod exoskeleton. H owever, as Richards (1951) points out, other substances enter into th e structure of th e ar­ thropod exoskeleton and, conversely, some ar­ thropods are known which have no detectable chitin. It i s also true that chitin is found in ot her inverte

LINDSAY R. WINKLER

321

Chitin and Chitosan: Functional Biopolymers from Marine Crustaceans  

Microsoft Academic Search

Chitin and chitosan, typical marine polysaccharides as well as abundant biomass resources, are attracting a great deal of\\u000a attention because of their distinctive biological and physicochemical characteristics. To fully explore the high potential\\u000a of these specialty biopolymers, basic and application researches are being made extensively. This review deals with the fundamental\\u000a aspects of chitin and chitosan such as the preparation

Keisuke Kurita

2006-01-01

322

Chitin-microparticles for the control of intestinal inflammation  

PubMed Central

Chitin is a polymer of N-acetylglucosamine with the ability to regulate innate and adaptive immune responses. However, the detailed mechanisms of chitin-mediated regulation of intestinal inflammation are only partially known. In this study, Chitin-microparticles (CMPs) or PBS were orally administered to acute and chronic colitis models every three days for six consecutive weeks beginning at weaning age. The effects of this treatment were evaluated by histology, cytokine production, co-culture study and enteric bacterial analysis in DSS-induced colitis or TCR? knockout chronic colitis models. Histologically, chitin-treated mice showed significantly suppressed colitis as compared to PBS-treated mice in both animal models. The production of IFN? was upregulated in the mucosa of chitin-treated mice compared to control mice. The major source of IFN?-producing cells was CD4+ T cells. In mouse dendritic cells (DCs), we found that CMPs were efficiently internalized and processed within 48 hours. Mesenteric lymph nodes (MLNs) CD4+ T cells isolated from chitin-treated mice produced 7-fold higher amount of IFN? in the culture supernatant after being co-cultured with DCs and chitin as compared to the control. Proliferation of CFSElow CD4+ T cells in MLNs and enteric bacterial translocation rates were significantly reduced in chitin-treated mice when compared to the control. In addition, CMPs improved the imbalance of enteric bacterial compositions and significantly increased IL-10-producing cells in non-inflamed colon, indicating the immunoregulatory effects of CMPs in intestinal mucosa. In conclusion, CMPs significantly suppress the development of inflammation by modulating cytokine balance and microbial environment in colon.

Nagatani, Katsuya; Wang, Sen; Llado, Victoria; Lau, Cindy W.; Li, Zongxi; Mizoguchi, Atsushi; Nagler, Cathryn R.; Shibata, Yoshimi; Reinecker, Hans-Christian; Mora, J. Rodrigo; Mizoguchi, Emiko

2013-01-01

323

Effect of Dietary Chitin and Chitosan on Cholesterolemia of Rats  

Microsoft Academic Search

imŰnek J., BartoŔová H.: Effect of dietary chitin and chitosan on cholesterolemia of rats. Acta Vet. Brno 2005, 74: 491-499. Chitin - chitosan is being advertised as a food supplement that effectively lowers blood cholesterol concentration and controls obesity. The lard-fed rat was chosen because this model shares similarities with human hypercholesterolemia. The male rats were divided into six groups

H. BARTO

324

The Non-catalytic Chitin-binding Protein CBP21 from Serratia marcescens Is Essential for Chitin Degradation  

Microsoft Academic Search

The Gram-negative soil bacterium Serratia marc- escens uses three different family 18 chitinases to de- grade chitin, an abundant insoluble carbohydrate polymer composed of (1,4)-linked units of N-acetylglu- cosamine. We show that efficient chitin degradation additionally depends on the action of a small non- catalytic protein, CBP21, which binds to the insoluble crystalline substrate, leading to structural changes in the

G. Vaaje-Kolstad

2005-01-01

325

Structure-Bioactivity Relationship of Chitin Derivatives—Part I: The Effect of Solid Chitin Derivatives on Blood Coagulation  

Microsoft Academic Search

Chemical modification of chitin led to a series of derivatives: chi tosan, N-acetylchitosan, monoacetylchitin, dibutyrylchitin, chitosan acetate, chitosan butyrate, chitosan citrate and chitosan-poly(acrylic acid) complex. These were used to coat glass surfaces and studied with respect to their wetting properties and thrombogenic characteristics. All materials had much better wetting properties than siliconized glass surface The surface tension of these chitin

Jacek Dutkiewicz; Lidia Szosland; Magdalena Kucharska; Luba Judkiewicz; Ryszard Ciszewski

1990-01-01

326

Role of polymorphisms in factor V (FV Leiden), prothrombin, plasminogen activator inhibitor type-1 (PAI-1), methylenetetrahydrofolate reductase (MTHFR) and cystathionine ?-synthase (CBS) genes as risk factors for thrombophilias.  

PubMed

Thrombophilias are defined as a predisposition to thrombosis due to hematological changes which induce blood hypercoagulability; they can be inherited or acquired. They are individually characterized by a large phenotypic variability, even when they occur within the same family. Hereditary thrombophilias are, in most cases, due to changes related to physiological coagulation inhibitors or mutations in the genes of coagulation factors. High levels of plasma homocysteine may also be responsible for vaso-occlusive episodes and may have acquired (nutritional deficiencies of folate and vitamins B6 and B12) and/or genetic causes (mutations in the genes responsible for expression of enzymes involved in the intracellular metabolism of homocysteine). Considering that: (1) thromboses are events of multigenic and multifactorial etiopathology; (2) the presence of mutations in several genes significantly increases the risk of their occurrence; (3) the vascular territory (venous and/or arterial) affected involves different pathophysiological mechanisms and treatments, knowledge of genetic variants that may contribute to the risk and variability of the phenotypic manifestations of these diseases is extremely important. This understanding may provide support for a more individualized and therefore more effective treatment for thrombophilia carriers. Thus, this mini-review aims to address a comprehensive summary of thrombophilias and thrombosis, and discuss the role of polymorphisms in Factor V (FV Leiden), Prothrombin, Plasminogen activator inhibitor type-1 (PAI-1), Methylenetetrahydrofolate reductase (MTHFR) and Cystathionine ?-synthase (CBS) genes as risk factors for thrombophilias. PMID:22512572

Miranda-Vilela, A L

2012-09-01

327

The structures of anthranilate synthase of Serratia marcescens crystallized in the presence of (i) its substrates, chorismate and glutamine, and a product, glutamate, and (ii) its end-product inhibitor, l-tryptophan  

PubMed Central

The crystal structure of anthranilate synthase (AS) from Serratia marcescens, a mesophilic bacterium, has been solved in the presence of its substrates, chorismate and glutamine, and one product, glutamate, at 1.95 ?, and with its bound feedback inhibitor, tryptophan, at 2.4 ?. In comparison with the AS structure from the hyperthermophile Sulfolobus solfataricus, the S. marcescens structure shows similar subunit structures but a markedly different oligomeric organization. One crystal form of the S. marcescens enzyme displays a bound pyruvate as well as a putative anthranilate (the nitrogen group is ambiguous) in the TrpE subunit. It also confirms the presence of a covalently bound glutamyl thioester intermediate in the TrpG subunit. The tryptophan-bound form reveals that the inhibitor binds at a site distinct from that of the substrate, chorismate. Bound tryptophan appears to prevent chorismate binding by a demonstrable conformational effect, and the structure reveals how occupancy of only one of the two feedback inhibition sites can immobilize the catalytic activity of both TrpE subunits. The presence of effectors in the structure provides a view of the locations of some of the amino acid residues in the active sites. Our findings are discussed in terms of the previously described AS structure of S. solfataricus, mutational data obtained from enteric bacteria, and the enzyme's mechanism of action.

Spraggon, Glen; Kim, Choel; Nguyen-Huu, Xuong; Yee, Muh-Ching; Yanofsky, Charles; Mills, Stanley E.

2001-01-01

328

A head-to-head comparison of eneamide and epoxyamide inhibitors of glucosamine-6-phosphate synthase from the dapdiamide biosynthetic pathway.  

PubMed

The dapdiamides make up a family of antibiotics that have been presumed to be cleaved in the target cell to enzyme-inhibitory N-acyl-2,3-diaminopropionate (DAP) warheads containing two alternative electrophilic moieties. Our prior biosynthetic studies revealed that an eneamide warhead is made first and converted to an epoxyamide via a three-enzyme branch pathway. Here we provide a rationale for this logic. We report that the R,R-epoxyamide warhead is a more efficient covalent inactivator of glucosamine-6-phosphate synthase by 1 order of magnitude versus the eneamide, and this difference correlates with a >10-fold difference in antibiotic activity for the corresponding acyl-DAP dipeptides. PMID:21520904

Hollenhorst, Marie A; Ntai, Ioanna; Badet, Bernard; Kelleher, Neil L; Walsh, Christopher T

2011-04-26

329

Intrathecally injected Ile-Pro-Ile, an inhibitor of membrane ectoenzyme dipeptidyl peptidase IV, is antihyperalgesic in rats by switching the enzyme from hydrolase to synthase functional mode to generate endomorphin 2.  

PubMed

We have found recently that membrane-bound dipeptidyl peptidase IV (DPP-IV) generated extracellularly immunoreactive endomorphin-2 from Tyr-Pro precursor in a depolarisation-sensitive manner in rat isolated L4,5 dorsal root ganglia when the enzyme was switched to synthase mode by the hydrolase inhibitor Ile-Pro-Ile. Presently, we induced hyperalgesia in rats by injecting carrageenan into the right hindpaw and measured the reduction in nociceptive threshold (hyperalgesia) to pressure (Randall-Selitto test). The hyperalgesia, peaking at 180 min after injection, was fully reversed by intrathecal administration of 30 nmol/rat Ile-Pro-Ile. The antihyperalgesic action was antagonized by s.c. naloxone (1 mg/kg) and intrathecally injected specific antiserum to endomorphin-2 indicating that the opioid receptor-mediated effect was produced by an endogenously generated endomorphin-2-like immunoreactive substance. Intrathecal Ile-Pro-Ile was ineffective as an analgesic in the acute nociceptive test such as the rat tail-flick, whereas endomorphin-2 (EC(50)=13.3 nmol/rat), endomorphin-1 (6.8 nmol/rat), morphine (0.11 nmol/rat) and DAMGO (0.0059 nmol/rat) exerted opioid receptor-mediated analgesia given by the same route. We concluded that carrageenan-induced C-fiber barrage (wind-up) may create ideal conditions for the de novo synthesis of endomorphin-2 in rat spinal cord dorsal horns if the DPP-IV enzyme is switched to the synthase functional mode by Ile-Pro-Ile. PMID:19695241

Király, Kornél; Szalay, Balázs; Szalai, Judit; Barna, István; Gyires, Klára; Verbeken, Mathieu; Rónai, András Z

2009-08-18

330

Characterization of a Novel, Antifungal, Chitin-Binding Protein from Streptomyces tendae T?901 That Interferes with Growth Polarity  

PubMed Central

The afp1 gene, which encodes the antifungal protein AFP1, was cloned from nikkomycin-producing Streptomyces tendae Tü901, using a nikkomycin-negative mutant as a host and screening transformants for antifungal activity against Paecilomyces variotii in agar diffusion assays. The 384-bp afp1 gene has a low G+C content (63%) and a transcription termination structure with a poly(T) region, unusual attributes for Streptomyces genes. AFP1 was purified from culture filtrate of S. tendae carrying the afp1 gene on the multicopy plasmid pIJ699. The purified protein had a molecular mass of 9,862 Da and lacked a 42-residue N-terminal peptide deduced from the nucleotide sequence. AFP1 was stable at extreme pH values and high temperatures and toward commercial proteinases. AFP1 had limited similarity to cellulose-binding domains of microbial plant cell wall hydrolases and bound to crab shell chitin, chitosan, and cell walls of P. variotii but showed no enzyme activity. The biological activity of AFP1, which represents the first chitin-binding protein from bacteria exhibiting antifungal activity, was directed against specific ascomycetes, and synergistic interaction with the chitin synthetase inhibitor nikkomycin inhibited growth of Aspergillus species. Microscopy studies revealed that fluorescein-labeled AFP1 strongly bound to the surface of germinated conidia and to tips of growing hyphae, causing severe alterations in cell morphogenesis that gave rise to large spherical conidia and/or swollen hyphae and to atypical branching.

Bormann, Christiane; Baier, Daniel; Horr, Ingmar; Raps, Claudia; Berger, Jurgen; Jung, Gunther; Schwarz, Heinz

1999-01-01

331

Chitin in the Silk Gland Ducts of the Spider Nephila edulis and the Silkworm Bombyx mori.  

PubMed

Here we report the detection and localisation of chitin in the cuticle of the spinning ducts of both the spider Nephila edulis and the silkworm Bombyx mori. Our observations demonstrate that the duct walls of both animals contain chitin notwithstanding totally independent evolutionary pathways of the systems. We conclude that chitin may well be an essential component for the construction of spinning ducts; we further conclude that in both species chitin may indicate the evolutionary origin of the spinning ducts. PMID:24015298

Davies, Gwilym J G; Knight, David P; Vollrath, Fritz

2013-08-28

332

Chitin in the Silk Gland Ducts of the Spider Nephila edulis and the Silkworm Bombyx mori  

PubMed Central

Here we report the detection and localisation of chitin in the cuticle of the spinning ducts of both the spider Nephila edulis and the silkworm Bombyx mori. Our observations demonstrate that the duct walls of both animals contain chitin notwithstanding totally independent evolutionary pathways of the systems. We conclude that chitin may well be an essential component for the construction of spinning ducts; we further conclude that in both species chitin may indicate the evolutionary origin of the spinning ducts.

Davies, Gwilym J. G.; Knight, David P.; Vollrath, Fritz

2013-01-01

333

Efficacy of chitin-PAA-GTMAC gel in promoting wound healing: animal study  

Microsoft Academic Search

Acrylic grafted chitin (chitin-PAA) was modified with glycidyltrimethylammonium chloride (GTMAC) with the aim of promoting\\u000a wound healing. The chitin-PAA-GTMAC gels with different GTMAC contents were compared with the original chitin-PAA gel and\\u000a Intrasite gel for their efficacy in deep wound healing of Wistar rats. Four full-thickness wounds were made on the dorsal\\u000a skin of rats and then each was treated

Kajee Pilakasiri; Patamaporn Molee; Duangkamol Sringernyuang; Noppadon Sangjun; Somruethai Channasanon; Siriporn Tanodekaew

334

YEA! ® Elicitor Response Comparison to Chitin \\/ Chitosan in Mung Bean and Adzuki Bean Germination Experiments  

Microsoft Academic Search

YEA! ® (1 mg\\/seed) to the 0.9 mg\\/seed treatment with chitin \\/ chitosan elicited five times as much 9-1,3-glucanase enzyme activity. Secondly, lower concentrations of the chitin oligosaccharide containing six glycan moieties, N-acetylchitohexaose were studied. The importance of the chitin oligosaccharide is that short chains of chitin have been found optimal in elicitation of many types of plants. The dose

James C. Linden; Richard J. Stoner

335

Comparative protein analysis of the chitin metabolic pathway in extant organisms: A complex network approach  

Microsoft Academic Search

Chitin is a structural endogenous carbohydrate, which is a major component of fungal cell walls and arthropod exoskeletons. A renewable resource and the second most abundant polysaccharide in nature after cellulose, chitin is currently used for waste water clearing, cosmetics, medical, and veterinary applications. This work comprises data mining of protein sequences related to the chitin metabolic pathway of completely

Aristoteles Goes-Neto; Marcelo V. C. Diniz; Leonardo B. L. Santos; Suani T. R. Pinho; José G. V. Miranda; Thierry Petit Lobao; Ernesto P. Borges; Charbel Nińo El-Hani; Roberto F. S. Andrade

2010-01-01

336

Herbicide-resistant forms of Arabidopsis thaliana acetohydroxyacid synthase: characterization of the catalytic properties and sensitivity to inhibitors of four defined mutants.  

PubMed Central

Acetohydroxyacid synthase (AHAS) catalyses the first step in the synthesis of the branched-chain amino acids and is the target of several classes of herbicides. Four mutants (A122V, W574S, W574L and S653N) of the AHAS gene from Arabidopsis thaliana were constructed, expressed in Escherichia coli, and the enzymes were purified. Each mutant form and wild-type was characterized with respect to its catalytic properties and sensitivity to nine herbicides. Each enzyme had a pH optimum near 7.5. The specific activity varied from 13% (A122V) to 131% (W574L) of the wild-type and the Km for pyruvate of the mutants was similar to the wild-type, except for W574L where it was five-fold higher. The activation by cofactors (FAD, Mg2+ and thiamine diphosphate) was examined. A122V showed reduced affinity for all three cofactors, whereas S653N bound FAD more strongly than wild-type AHAS. Six sulphonylurea herbicides inhibited A122V to a similar degree as the wild-type but S653N showed a somewhat greater reduction in sensitivity to these compounds. In contrast, the W574 mutants were insensitive to these sulphonylureas, with increases in the Kiapp (apparent inhibition constant) of several hundred fold. All four mutants were resistant to three imidazolinone herbicides with decreases in sensitivity ranging from 100-fold to more than 1000-fold.

Chang, A K; Duggleby, R G

1998-01-01

337

Selective peptide inhibitors of bifunctional thymidylate synthase-dihydrofolate reductase from Toxoplasma gondii provide insights into domain-domain communication and allosteric regulation.  

PubMed

The bifunctional enzyme thymidylate synthase-dihydrofolate reductase (TS-DHFR) plays an essential role in DNA synthesis and is unique to several species of pathogenic protozoans, including the parasite Toxoplasma gondii. Infection by T. gondii causes the prevalent disease toxoplasmosis, for which TS-DHFR is a major therapeutic target. Here, we design peptides that target the dimer interface between the TS domains of bifunctional T. gondii TS-DHFR by mimicking ?-strands at the interface, revealing a previously unknown allosteric target. The current study shows that these ?-strand mimetic peptides bind to the apo-enzyme in a species-selective manner to inhibit both the TS and distal DHFR. Fluorescence spectroscopy was used to monitor conformational switching of the TS domain and demonstrate that these peptides induce a conformational change in the enzyme. Using structure-guided mutagenesis, nonconserved residues in the linker between TS and DHFR were identified that play a key role in domain-domain communication and in peptide inhibition of the DHFR domain. These studies validate allosteric inhibition of apo-TS, specifically at the TS-TS interface, as a potential target for novel, species-specific therapeutics for treating T. gondii parasitic infections and overcoming drug resistance. PMID:23813474

J Landau, Mark; Sharma, Hitesh; Anderson, Karen S

2013-08-01

338

Ultrasonication and steam-explosion as chitin pretreatments for chitin oligosaccharide production by chitinases of Lecanicillium lecanii.  

PubMed

In this study, chitin oligosaccharides have been successfully produced using chitinases from submerged fermentation of Lecanicillium lecanii. The highest Hex, Chit and Prot production was 0.14, 0.26 and 2.05 U/mg of protein, respectively, which were attained varying pH from 5 to 8 after 96 h. Culture conditions conducted at constant pH of 6 resulted in significantly lower enzyme production. The crude enzyme was partially purified by salting out with (NH4)2SO4 followed by size exclusion chromatography to isolate the chitinase mixture for further chitin hydrolysis assays. In this regard, chitin substrates were pretreated with sonication and steam explosion prior to enzymatic reaction. Structural changes were observed with steam explosion with 11.28% reduction of the crystallinity index attained with the lowest chitin/water ratio (0.1g/mL). Pretreated chitins reached the highest production of reducing sugars (0.37 mg/mL) and GlcNAc (0.59 mg/mL) in 23.6% yield. PMID:23993287

Villa-Lerma, Guadalupe; González-Márquez, Humberto; Gimeno, Miquel; López-Luna, Alberto; Bárzana, Eduardo; Shirai, Keiko

2013-08-13

339

[Methodological aspects of assessing chitin utilization by soil microorganisms].  

PubMed

A computational method for estimating specific activity of chitin decomposition by microorganisms is proposed. Spectrophotometric and gas chromatographic methods have been used to determine the rates of chitinase production, biomass accumulation, and carbon dioxide emission by pure cultures of microorganisms grown on a chitin-containing medium. Among dominants of the chitinolytic community of chernozem (Trichoderma viride, Stretomyces albolongus, Alcaligenes, and Arthrobacter), the highest chitinolytic activity is characteristic of prokaryotes. In brown desert-steppe soil, the main destructor prokaryotes are actinomycetes (S. roseolilacinus). The biomass of the fungus T. viride growth on the chitin-containing medium markedly exceeds that of prokaryotes, but the specific activity of respiration and chitinase production in actinomycetes S. roseolilacinus and S. albolongus is an order of magnitude higher than in T. viride. PMID:18956744

Manucharova, N A; Vlasenko, A N; Zenova, G M; Dobrovol'skaia, T G; Stepanov, A L

340

Adsorption of Vibrio parahaemolyticus onto Chitin and Copepods  

PubMed Central

Vibrio parahaemolyticus was observed to adsorb onto chitin particles and copepods. The efficiency of adsorption was found to be dependent on pH and on the concentration of NaCl and other ions found in seawater. Highest efficiency was observed in water samples collected from Chesapeake Bay and lowest in water from the open sea. V. parahaemolyticus was found to adsorb onto chitin with the highest efficiency of the several bacterial strains tested. Escherichia coli and Pseudomonas fluorescens did not adsorb onto chitin. The adsorption effect is considered to be one of the major factors determining the distribution of this species and affecting the annual cycle of V. parahaemolyticus in the estuarine system.

Kaneko, Tatsuo; Colwell, Rita R.

1975-01-01

341

Chitin-Induced Carbotype Conversion in Vibrio vulnificus?†  

PubMed Central

As an etiological agent of bacterial sepsis and wound infections, Vibrio vulnificus is unique among the Vibrionaceae. The most intensely studied of its virulence factors is the capsular polysaccharide (CPS). Over 100 CPS types have been identified, yet little is known about the genetic mechanisms that drive such diversity. Chitin, the second-most-abundant polysaccharide in nature, is known to induce competence in Vibrio species. Here, we show that the frequency of chitin-induced transformation in V. vulnificus varies by strain and that (GlcNAc)2 is the shortest chitin-derived polymer capable of inducing competence. Transformation frequencies (TFs) increased 8-fold when mixed-culture biofilms were exposed to a strain-specific lytic phage, suggesting that the lysis of dead cells during lytic infection increased the amount of extracellular DNA within the biofilm that was available for transfer. Furthermore, we show that V. vulnificus can undergo chitin-dependent carbotype conversion following the uptake and recombination of complete cps loci from exogenous genomic DNA (gDNA). The acquisition of a partial locus was also demonstrated when internal regions of homology between the endogenous and exogenous loci existed. This suggested that the same mechanism governing the transfer of complete cps loci also contributed to their evolution by generating novel combinations of CPS biosynthesis genes. Since no evidence that cps loci were preferentially acquired during natural transformation (random transposon-tagged DNA was readily taken up in chitin transformation assays) exists, the phenomenon of chitin-induced transformation likely plays an important but general role in the evolution of this genetically promiscuous genus.

Neiman, Jana; Guo, Yunzhi; Rowe-Magnus, Dean A.

2011-01-01

342

Biomimetic approach to forming chitin/aragonite composites.  

PubMed

Biomimetic materials which display the complexity of biominerals like nacre are synthetically difficult to prepare. The formation of chitin/calcium carbonate composites, where CaCO(3) is present as aragonite, was achieved via reacetylation of preformed chitosan scaffolds followed by the combination of presoaking of chitin templates with mineral solutions in the presence of poly(acrylic acid). The as-synthesised composites are comprised of well-ordered ribbons of aragonite crystals held within an organic matrix, mimicking the structure of nacre. PMID:22473223

Munro, Natasha H; McGrath, Kathryn M

2012-04-04

343

Timing of administration of dexamethasone or the nitric oxide synthase inhibitor, nitro-L-arginine methyl ester, is critical for effective treatment of ischaemia-reperfusion injury to rat skeletal muscle.  

PubMed

1. The effects of the nitric oxide synthase (NOS) inhibitors, NG-nitro-L-arginine-methyl ester (L-NAME), nitroiminoethyl-L-ornithine and S. methylisothiourea on skeletal muscle survival following 2 h of tourniquet ischaemia and 24 h of reperfusion were compared with those of the anti-inflammatory steroid, dexamethasone. 2. Administration of each of the NOS inhibitors or dexamethasone 30 min before reperfusion reduced the degree of skeletal muscle necrosis 24 h after reperfusion. 3. The influence of timing of drug administration was investigated. L-NAME administered 30 min before reperfusion, at 3 h after reperfusion, but not thereafter, significantly improved muscle survival compared with saline-treated controls. Dexamethasone administered 30 min before, or at 3 or 8 h after reperfusion, but not at 16 h, significantly improved muscle survival, but neither agent had protective effects when administered before ischaemia. 4. After 8 h of reperfusion of ischaemic skeletal muscle, cell-free homogenates contained Ca(2+)-independent (inducible) NOS activity which was reduced in dexamethasone-treated (2.5 mg/kg) rats. Furthermore, inducible NOS mRNA levels, as detected by reverse transcriptase-PCR, were increased after 8 h of reperfusion in saline, but not in dexamethasone-treated rats. 5. These data suggest a significant deleterious effect of endogenous NO which may be restricted to the first 3 h of the reperfusion phase of ischaemia-reperfusion injury, and raise the possibility of effective treatment of incipient reperfusion injury, even after several hours of reperfusion. PMID:9301432

Zhang, B; Knight, K R; Dowsing, B; Guida, E; Phan, L H; Hickey, M J; Morrison, W A; Stewart, A G

1997-08-01

344

Selective and transient activation of protein kinase C alpha by fumonisin B1, a ceramide synthase inhibitor mycotoxin, in cultured porcine renal cells.  

PubMed

Fumonisin B(1) (FB(1)), a potent and naturally occurring mycotoxin produced by the fungus Fusarium verticillioides, has been implicated in fatal and debilitating diseases in animals and humans. FB(1) affects a variety of cell signaling proteins including protein kinase C (PKC); a serine/threonine kinase, involved in a number of signal transduction pathways that include cytokine induction, carcinogenesis and apoptosis. The aim of this study was to investigate the short-term temporal and concentration-dependent effects of FB(1) on PKC isoforms present in LLC-PK(1) cells in relation to the FB(1)-induced accumulation of sphinganine and sphingosine utilizing various inhibitors and activators. Our studies demonstrated that FB(1) (0.1-1 microM) selectively and transiently activated PKCalpha at 5 min, without affecting PKC-delta, -epsilon and -zeta isoforms. At higher FB(1) concentrations and later time points (15-120 min), PKCalpha membrane concentrations declined to untreated levels. The observed increase in cytosol PKCalpha protein expression at 15 min was not associated with an increase in its activity or protein biosynthesis. Calphostin C, a PKC inhibitor, abrogated the FB(1)-induced translocation of PKCalpha. Pre-incubation with the PKC activator, phorbol 12-myristate 13-acetate, resulted in an additive effect on membrane translocation of PKCalpha. Intracellular sphinganine and sphingosine concentrations were unaltered at the time points tested. Myriocin, a specific inhibitor of serine palmitoyltransferase, the first enzyme in de novo sphingolipid biosynthesis, did not prevent the FB(1)-induced PKCalpha cytosol to membrane redistribution. Altering PKCalpha and its signal transduction pathways may be of importance in the ability of FB(1) to exert its toxicity via apoptosis and/or carcinogenesis. PMID:14729403

Gopee, Neera V; Sharma, Raghubir P

2004-02-01

345

Effects of taxifolin on the activity of angiotensin-converting enzyme and reactive oxygen and nitrogen species in the aorta of aging rats and rats treated with the nitric oxide synthase inhibitor and dexamethasone.  

PubMed

The action of taxifolin on the angiotensin-converting enzyme (ACE) and the formation of reactive oxygen and nitrogen species (ROS/RNS) in the aorta of aging rats and rats treated with nitric oxide synthase inhibitor (N ?-nitro-L-arginine methyl ester (L-NAME)) or dexamethasone have been studied. The ACE activity in aorta sections was determined by measuring the hydrolysis of hippuryl-L-histidyl-L-leucine, and the ROS/RNS production was measured by oxidation of dichlorodihydrofluorescein. It was shown that taxifolin at a dose of 30-100 ?g/kg/day decreases the ACE activity in the aorta of aging rats and of rats treated with L-NAME or dexamethasone to the level of the ACE activity in young control rats. Taxifolin (100 ?g/kg/day) was found to also reduce the amount of ROS/RNS in the aorta that increased as a result of L-NAME intake. L-NAME treatment increases the contribution of 5-lipoxygenase and NADPH oxidase to ROS/RNS production in the aorta, while taxifolin (100 ?g/kg/day) decreases the contribution of these enzymes to the normal level. PMID:23271616

Arutyunyan, Tamara V; Korystova, Antonina F; Kublik, Ludmila N; Levitman, Maria Kh; Shaposhnikova, Vera V; Korystov, Yuri N

2012-12-28

346

Abnormalities of endothelium-dependent responses in mesenteric arteries from Otsuka Long-Evans Tokushima Fatty (OLETF) rats are improved by chronic treatment with thromboxane A2 synthase inhibitor.  

PubMed

Thromboxane A(2) (TXA(2)) is thought to contribute to the development of diabetic complications. We tested the hypothesis that the impaired endothelial function seen in Otsuka Long-Evans Tokushima Fatty (OLETF) rats (a type 2 diabetic model) might be improved by chronic treatment with ozagrel, a TXA(2) synthase inhibitor. In mesenteric arteries from OLETF rats (40-46 weeks old) [vs. those from age-matched Long-Evans Tokushima Otsuka (LETO) rats]: (1) ACh-induced endothelium-dependent relaxation, NO-mediated relaxation, and endothelium-derived hyperpolarizing factor (EDHF)-type relaxation were all reduced; (2) ACh-induced cyclooxygenase-dependent contraction was enhanced; (3) endothelium-derived contracting factor (EDCF)-mediated contraction was enhanced; (4) ACh-stimulated nitrite production was reduced but the nitrate/nitrite ratio was increased; and (5) ACh-stimulated production of TXA(2) was increased. Chronic treatment with ozagrel (100mg/kg/day for 4 weeks, starting when they were 36-42 weeks of age) partly corrected the above abnormalities. These results suggest that ozagrel has normalizing effects on endothelial functions in OLETF mesenteric arteries, at least partly by increasing endothelium-derived relaxing factors (i.e., NO and EDHF) signaling and reducing EDCF signaling. PMID:19111834

Matsumoto, Takayuki; Takaoka, Eri; Ishida, Keiko; Nakayama, Naoaki; Noguchi, Eri; Kobayashi, Tsuneo; Kamata, Katsuo

2008-11-25

347

Sphingomyelin synthase SMS2 displays dual activity as ceramide phosphoethanolamine synthase[S  

PubMed Central

Sphingolipids are vital components of eukaryotic membranes involved in the regulation of cell growth, death, intracellular trafficking, and the barrier function of the plasma membrane (PM). While sphingomyelin (SM) is the major sphingolipid in mammals, previous studies indicate that mammalian cells also produce the SM analog ceramide phosphoethanolamine (CPE). Little is known about the biological role of CPE or the enzyme(s) responsible for CPE biosynthesis. SM production is mediated by the SM synthases SMS1 in the Golgi and SMS2 at the PM, while a closely related enzyme, SMSr, has an unknown biochemical function. We now demonstrate that SMS family members display striking differences in substrate specificity, with SMS1 and SMSr being monofunctional enzymes with SM and CPE synthase activity, respectively, and SMS2 acting as a bifunctional enzyme with both SM and CPE synthase activity. In agreement with the PM residency of SMS2, we show that both SM and CPE synthase activities are enhanced at the surface of SMS2-overexpressing HeLa cells. Our findings reveal an unexpected diversity in substrate specificity among SMS family members that should enable the design of specific inhibitors to target the biological role of each enzyme individually.

Ternes, Philipp; Brouwers, Jos F. H. M.; van den Dikkenberg, Joep; Holthuis, Joost C. M.

2009-01-01

348

Fabrication of ?-chitin whisker-reinforced poly(vinyl alcohol) nanocomposite nanofibres by electrospinning  

NASA Astrophysics Data System (ADS)

The present contribution reports, for the first time, the successful fabrication of ?-chitin whisker-reinforced poly(vinyl alcohol) (PVA) nanocomposite nanofibres by electrospinning. The ?-chitin whiskers were prepared from ?-chitin flakes from shrimp shells by acid hydrolysis. The as-prepared chitin whiskers exhibited lengths in the range 231-969 nm and widths in the range 12-65 nm, with the average length and width being about 549 and 31 nm, respectively. Successful incorporation of the chitin whiskers within the as-spun PVA/chitin whisker nanocomposite nanofibres was verified by infrared spectroscopic and thermogravimetric methods. The incorporation of chitin whiskers within the as-spun nanocomposite fibre mats increased the Young's modulus by about 4-8 times over that of the neat as-spun PVA fibre mat.

Junkasem, Jirawut; Rujiravanit, Ratana; Supaphol, Pitt

2006-09-01

349

Sonication of chitin-glucan, preparation of water-soluble fractions and characterization by HPLC.  

PubMed

A water-insoluble chitin-glucan complex, isolated from the mycelium of Aspergillus niger, was swollen in various aqueous media and treated subsequently by high-energy sonication. The concentration of the resulting water-soluble polysaccharide fractions was dependent on the swelling medium, the amount of the chitin-glucan complex in the suspension, and on the time of sonication. The yields of water-soluble chitin-glucan were within the range 13.6 to 24.4% relative to the mass of the original chitin-glucan. The nitrogen content obtained for the samples of water-soluble chitin-glucan indicated a higher content of chitin (3.45% of nitrogen in high-molecular fraction) than in the original water-insoluble chitin-glucan sample (1.8%). The distribution of the molecular weights of the water-soluble fractions prepared was determined by high-performance liquid chromatography. PMID:10769872

Mislovicová, D; Masárová, J; Bendzálová, K; Soltés, L; Machová, E

2000-04-01

350

A chalcone synthase\\/stilbene synthase DNA probe for conifers  

Microsoft Academic Search

A probe for chalcone synthase (CHS) was generated by PCR using chalcone synthase conserved sequences. The cloned PCR product has high similarity to both chalcone synthase and stilbene synthase sequences. The probe was used to examine the organization of chalcone synthase and stilbene synthase genes in Abies procera, Pinus lambertiana, P. monticola, Picea glauca, P. sitchensis, Pseudostuga menziesii, Taxus brevifolia,

S. M. Baker; E. E. White

1996-01-01

351

Comparative regional haemodynamic effects of the nitric oxide synthase inhibitors, S-methyl-L-thiocitrulline and L-NAME, in conscious rats  

PubMed Central

The regional haemodynamic effects of the putative nNOS inhibitor, S-methyl-L-thiocitrulline (SMTC), were compared with those of the nonselective NOS inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), in conscious, male Sprague–Dawley rats. SMTC (0.3 mg kg?1 bolus) produced a significant, short-lived, pressor effect associated with renal, mesenteric and hindquarters vasoconstriction; the same dose of L-NAME did not affect mean blood pressure (BP), although it caused bradycardia and mesenteric vasoconstriction. At the highest dose tested (10 mg kg?1), L-NAME produced a significantly greater bradycardia and fall in mesenteric vascular conductance than SMTC, although the initial pressor response to SMTC was greater, but less sustained, than that to L-NAME. Infusion of SMTC or L-NAME (3 mg kg?1 h?1) induced rises in BP and falls in renal, mesenteric and hindquarters vascular conductances, but the effects of L-NAME were greater than those of SMTC, and L-NAME also caused bradycardia. The renal vasodilator response to acetylcholine was markedly attenuated by infusion of L-NAME, but unaffected by SMTC. The hindquarters vasodilatation induced by salbutamol was attenuated by L-NAME, but not by SMTC. The mesenteric vasodilator response to bradykinin was modestly enhanced by SMTC, but not by L-NAME. The depressor and renal, mesenteric and hindquarters vasodilator responses to sodium nitroprusside were enhanced by L-NAME, whereas SMTC modestly enhanced the hypotensive and renal vasodilator effects of sodium nitroprusside, but attenuated the accompanying tachycardia. The results are consistent with the cardiovascular effects of low doses of SMTC being attributable to nNOS inhibition.

Wakefield, Ian D; March, Julie E; Kemp, Philip A; Valentin, Jean-Pierre; Bennett, Terence; Gardiner, Sheila M

2003-01-01

352

Adsorption of Anionic Dyes on the Biopolymer Chitin  

Microsoft Academic Search

The adsorption of the anionic dyes orange IV, orange G and xylenol orange on chitin was stud ied, employing the Langmuir isotherm. The adsorption parameters were determined utilizing var ious linear regressions of the isotherm. The results showed that the adsorption capacity is dep endent on pH. In acid pH, the polymer amino groups are protonated and the polymer chain

Elisane Longhinotti; Fabíola Pozza; Lígia Furlan; Maria de Nazaré; M. Sanchez; Marilene Klug; Mauro C. M. Laranjeira

1998-01-01

353

Characterization of Chitin and Chitosan Molecular Structure in Aqueous Solution  

SciTech Connect

Molecular dynamics simulations have been used to characterize the structure of chitin and chitosan fibers in aqueous solutions. Chitin fibers, whether isolated or in the form of a ?-chitin nanoparticle, adopt the so-called 2-fold helix with ? and ? values similar to its crystalline state. In solution, the intramolecular hydrogen bond HO3(n)?O5(n+1) responsible for the 2-fold helical motif is stabilized by hydrogen bonds with water molecules in a well-defined orientation. On the other hand, chitosan can adopt five distinct helical motifs and its conformational equilibrium is highly dependent on pH. The hydrogen bond pattern and solvation around the O3 atom of insoluble chitosan (basic pH) are nearly identical to these quantities in chitin. Our findings suggest that the solubility and conformation of these polysaccharides are related to the stability of the intrachain HO3(n)?O5(n+1) hydrogen bond, which is affect by the water exchange around the O3-HO3 hydroxyl group.

Franca, Eduardo D.; Lins, Roberto D.; Freitas, Luiz C.; Straatsma, TP

2008-12-01

354

Physiology of microbial degradation of chitin and chitosan  

Microsoft Academic Search

Chitin is produced in enormous quantities in the biosphere, chiefly as the major structural component of most fungi and invertebrates. Its degradation is chiefly by bacteria and fungi, by chitinolysis via chitinases, but also via deacetylation to chitosan, which is hydrolysed by chitosanases. Chitinases and chitosanases have a range of roles in the organisms producing them: autolytic, morphogenetic or nutritional.

Graham W. Gooday

1990-01-01

355

Chitin and collagen as universal and alternative templates in biomineralization  

Microsoft Academic Search

Biomineralized structures and tissues are composites, containing a biologically produced organic matrix and nano- or microscale amorphous or crystalline minerals. Two main examples of organic matrices – the amino-polysaccharide chitin and the asymmetric protein collagen – are presented and discussed as the basic structural modules and organo-templates for calcium and silica biomineralization in nature. Both serve as templates, providing preferential

Hermann Ehrlich

2010-01-01

356

Penetration of Ultra-Violet Rays through Chitin  

Microsoft Academic Search

ALTENBURG in 1928 found that the fluorescence of certain salts was only very slightly, if at all, affected when Drosophila melanogaster were interposed between the discharge tube of a Cooper Hewitt lamp and the salts at which the rays were directed. From this he concluded that the ultra-violet rays penetrated the chitin rather freely. His conclusion has been accepted by

G. Eloff; V. L. Bosazza

1938-01-01

357

Structural Insights into Chitinolytic Enzymes and Inhibition Mechanisms of Selective Inhibitors.  

PubMed

Chitin biodegradation is linked to fungi cell differentiation, nematode egg hatching, arthropods morphogenesis and human defense against malaria and other pathogens infection as well. Two classes of enzymes for chitin degradation include glycosyl hydrolase (GH) family 18 chitinases and family 20 ?-N-acetyl-D-hexosaminidases. However, more and more research papers have revealed that either GH 18 family chitinases or GH 20 family ?-N-acetyl-D-hexosaminidases are a family composed of a number of isoforms, each of which plays an exclusive role in different life processes. The development of novel and specific inhibitors towards chitinolytic enzymes is of great importance in the investigation of or interference with chitin biodegradation. This review focuses on identified enzymes that are specifically involved in chitin degradation. And the latest progresses on crystal structures and specific inhibitors are summarized within the realm of this field. PMID:23688083

Liu, Tian; Chen, Lei; Ma, Qiang; Shen, Xu; Yang, Qing

2013-05-13

358

Protective effect of FK506 and thromboxane synthase inhibitor on ischemia-reperfusion injury in non-heart-beating donor in rat orthotopic liver transplantation.  

PubMed

The study investigated the possibility of pharmacologically modulating hepatic allograft function from non-heart-beating donors (NHBDs) using male Lewis rats. The donors were divided into 4 groups: Group 1 in which the vehicle was administered, Group 2 in which FK506 (tacrolimus; a powerful immunosuppressive agent) was administered, Group 3 in which OKY046 (a specific thromboxane synthetase inhibitor) was administered and Group 4 in which FK506 and OKY046 were administered. The recipients received orthotopic liver transplantation. The survival rates differed significantly between the recipients that had received liver transplantation from Groups 1 and 4. The serum liver enzyme and inflammatory cytokine concentrations of the recipients which had received liver transplantation from Groups 2, 3 and 4 were significantly lower than those of the recipients that had received liver transplantation from Group 1. Although there was no significant difference, all parameters were better in the recipients that had received transplantation from Group 4 than those that had received transplantation from Groups 2 and 3. The action mechanisms of FK506 and OKY046 are completely different. Therefore, concomitant use of FK506 and OKY046 might have additive effects on liver transplantation from NHBDs. In conclusion, we demonstrated that pretreatment of NHBDs using FK506 and OKY046 ameliorated graft viability. PMID:15000260

Sasaki, Katsuya; Miyake, Hidenori; Kinoshita, Takafumi; Ikeyama, Shizuo; Tashiro, Seiki

2004-02-01

359

Stable isotopic studies on chitin. III. The D\\/H and 18 O\\/ 16 O ratios in arthropod chitin  

Microsoft Academic Search

Stable hydrogen and oxygen isotope ratios are presented for carbon-bound hydrogen and for oxygen in chitin-derived substrates from 57 arthropod species collected in 50 different locations or grown under controlled conditions in the laboratory. No systematic isotopic differences were found among Insecta, Crustacea, and Merostomata. The determination of infra- and interindividual isotopic variabilities in a lobster and among individuals of

Arndt Schimmelmann; Michael J. Deniro

1986-01-01

360

Thematic course: Natural Polysaccharides. Part II. STUDY OF THE NATURE OF CHITIN-GLUCAN BOND IN CHITIN-GLUCAN COMPLEX  

Microsoft Academic Search

The studies in the field of practical use of mycelium fungus Aspergillus niger biomass, a source of citric acid, have shown that, being the structural polysaccharides of the fungus cell walls, these chitin-glucan complexes are good enterosorbents, able to adsorb heavy metal ions (1-3), which makes it possible to use them as medicinal food additives (4). But the very fact

Natalia V. Shabrukova; Diana R. Zaynetdinova; Farid G. Khalitov; Valentina S. Gamayurova

2001-01-01

361

Peptide induced crystallization of calcium carbonate on wrinkle patterned substrate: implications for chitin formation in molluscs.  

PubMed

We here present the nucleation and growth of calcium carbonate under the influence of synthetic peptides on topographically patterned poly(dimethylsiloxane) (PDMS) substrates, which have a controlled density of defects between the wrinkles. Experiments with two lysine-rich peptides derived from the extracellular conserved domain E22 of the mollusc chitin synthase Ar-CS1, AKKKKKAS (AS8) and EEKKKKKES (ES9) on these substrates showed their influence on the calcium carbonate morphology. A transition from polycrystalline composites to single crystalline phases was achieved with the peptide AS8 by changing the pH of the buffer solution. We analyzed three different pH values as previous experiments showed that E22 interacts with aragonite biominerals more strongly at pH 7.75 than at pH 9.0. At any given pH, crystals appeared in characteristic morphologies only on wrinkled substrates, and did not occur on the flat, wrinkle-free PDMS substrate. These results suggest that these wrinkled substrates could be useful for controlling the morphologies of other mineral/peptide and mineral/protein composites. In nature, these templates are formed enzymatically by glycosyltransferases containing pH-sensitive epitopes, similar to the peptides investigated here. Our in vitro test systems may be useful to gain understanding of the formation of distinct 3D morphologies in mollusc shells in response to local pH shifts during the mineralization of organic templates. PMID:23736692

Ghatak, Anindita Sengupta; Koch, Marcus; Guth, Christina; Weiss, Ingrid M

2013-06-04

362

Glycogen synthase kinase-3beta (GSK-3beta) inhibitors AR-A014418 and B6B3O prevent human immunodeficiency virus-mediated neurotoxicity in primary human neurons.  

PubMed

Glycogen synthase kinase-3beta (GSK3beta) role in human immunodeficiency virus(HIV)-associated neurodegeneration has been evidenced by previous investigations. In this study, we investigated the specificity of two GSK3beta-specific inhibitors, AR-A014418 (A) and B6B30 (B) to prevent direct neurotoxicity in primary human neurons exposed to HIV (BaL). Neurons were exposed to HIV (500 pg/ml) for 12-h and 6-day periods in the presence and absence of A (1 microM, 100 nM, 10 nM) and B (50 nM, 5 nM, 500 pM) to investigate acute and ongoing mechanisms of HIV neurotoxicity. Using an lactate dehydrogenase (LDH) assay to assess cytotoxicity, we observed a significant neurotoxic effect of HIV from control values (P < .01) that was not restored via coexposures of all concentrations of A and B. Additionally, no change in LDH levels were observed after 6 days. However, activity of the acute proapoptotic markers caspases 3 and 7 using a luminescence assay were measured and found to be increased by exposure to HIV (BaL) compared to controls (P = .022). This effect was ameliorated via coexposure to all concentrations of A and 50 nM B after 12 h (P < .01) and to all concentrations of A and B after 6 days (P < .01). Overall, the results from this study provide further evidence for the ability of GSK3beta inhibition to be neuroprotective against HIV-associated neurotoxicity by reducing HIV associated procaspase induction. These data support a role for GSK3beta as a potential therapeutic target and may have important clinical implications for treatment of HIV-associated neurocognitive disorder. PMID:19688630

Nguyen, Timothy B; Lucero, Ginger R; Chana, Gursharan; Hult, Britta J; Tatro, Erick T; Masliah, Eliezer; Grant, Igor; Achim, Cristian L; Everall, Ian P

2009-09-01

363

The NMDA receptor antagonists, LY274614 and MK-801, and the nitric oxide synthase inhibitor, NG-nitro-L-arginine, attenuate analgesic tolerance to the mu-opioid morphine but not to kappa opioids.  

PubMed

Once daily s.c. administration of 5 mg/kg morphine, a mu-opioid agonist, or U50488H (U50), a kappa 1-opioid agonist, for 5 days in male CD-1 mice results in a 2-3-fold shift to the right of the respective analgesic (tail flick) dose-response curves, indicating the development of tolerance. Concurrent s.c. administration of the competitive NMDA receptor antagonist, LY274614 (LY), at 24 mg/kg/24 h infusion (osmotic pump) or 6 mg/kg i.p. once daily attenuates the development of morphine tolerance, when the response to saline plus morphine is compared on day 5 with LY plus morphine. Using this paradigm, once daily administration of either the non-competitive NMDA antagonist, MK-801, at 0.3 mg/kg i.p. or the nitric oxide synthase inhibitor, NG-nitro-L-arginine (NorArg), at 1 mg/kg i.p. twice daily attenuated the development of morphine tolerance. None of these drugs modify the tail-flick response or alter the ED50 for morphine. In contrast, co-administration of LY, MK-801 or NorArg, as above, failed to attenuate the development of tolerance to U50 or to the kappa 3-opioid agonist, naloxone benzoylhydrazone (NalBzoH). These results suggest that mu-opioid tolerance but not kappa 1- or kappa 3-opioid tolerance involves the mediation of NMDA receptors and the nitric oxide system. PMID:7512709

Elliott, K; Minami, N; Kolesnikov, Y A; Pasternak, G W; Inturrisi, C E

1994-01-01

364

Different content of chitin-like polysaccharides in multiple sclerosis and Alzheimer's disease brains  

Microsoft Academic Search

Chitin is an insoluble N-acetyl-glucosamine polymer coating fungi cell wall and several human parasites. It is hydrolysed by chitotriosidase (Chit); however, as chitin is absent in humans, the significance of human Chit activity is unknown.The level of plasma Chit activity positively correlates with Alzheimer's disease (AD) and multiple sclerosis (MS). A recent study revealed the presence of potentially detrimental chitin-like

Stefano Sotgiu; Salvatore Musumeci; Silvia Marconi; Beatrice Gini; Bruno Bonetti

2008-01-01

365

Viscosity–temperature behavior of chitin solutions using lithium chloride\\/DMA as solvent  

Microsoft Academic Search

Solutions of chitin in Li+\\/N,N-dimethylacetamide systems were studied via viscometry, using LiCl concentrations of 3% and 5% (m\\/v) and chitin concentrations ranging from 0.075 to 0.375gL?1. The reduced viscosity number versus concentration plot showed a minimum that was related to the formation of Li+–OC complex moieties along chitin macromolecular chains. Viscosity behavior was affected by temperature according to the Eyring

C. L. de Vasconcelos; P. M. Bezerril; M. R. Pereira; M. F. Ginani; J. L. C. Fonseca

2011-01-01

366

An infrared investigation in relation with chitin and chitosan characterization  

Microsoft Academic Search

The use of infrared spectroscopy for characterization of the composition of chitin and chitosan covering the entire range of degree of acetylation (DA) and a wide variety of raw materials is examined further. The ratio of absorbance bands selected was calibrated using 1H liquid and 13C CP-MAS solid-state NMR as absolute techniques. IR spectra of the structural units of these

J Brugnerotto; J Lizardi; F. M Goycoolea; W Argüelles-Monal; J Desbričres; M Rinaudo

2001-01-01

367

The role of chitin in uranium adsorption by R. arrhizus  

Microsoft Academic Search

In order to further refine and support the uranium biosorption mechanism hypothesis proposed for Rhizopus arrhizus, uranium competitive equilibrium uptake isotherms by chitin were determined at two different solution pH levels and in the presence of different concentrations of competing ions, namely, Cu\\/sup 2 +\\/, Zn\\/sup 2 +\\/, and Fe\\/sup 2 +\\/. The co-ion effect became more pronounced as the

Marios Tsezos

1983-01-01

368

Separation of azeotropic mixture by a biopolymer, chitin  

Microsoft Academic Search

The azeotropic mixture cannot be separated by the general distillation method. A biopolymer, chitin, packed into the straight glass column has been found to be able to separate various kinds of azeotropic mixtures at room temperature and under 1atm. The azeotropic mixtures such as cyclohexane–butanol, acetone–methanol, cyclohexane–acetone, ethyl acetate–methanol, benzene–ethanol, toluene–methanol etc., can be separated to obtain 100% pure main

Li-Yi Chen; Ji-Chao Zhang; Nan Wang; Mei-Yu Huang; Ying-Yan Jiang

2005-01-01

369

Fructose production from Jerusalem artichoke by inulinase immobilized on chitin  

Microsoft Academic Search

Summary Inulinase fromAspergillus ficuum was immobilized by cross-linking with glutaraldehyde on chitin. Batch and continuous production of fructose from Jerusalem artichoke tuber was studied using this immobililized inulinase. In a batch reactor, the extent of hydrolysis attained 90% (D-fructose\\/D-glucose :86\\/14) in 10h and 77.5g\\/L of D-fructose was produced from the Jerusalem artichoke tuber juice. In a continuous packed bed column

C. H. Kim; S. K. Rhee

1989-01-01

370

[Application of chitin and its derivatives to pharmaceutical industry for traditional Chinese medicine].  

PubMed

This paper reviewed application of chitin and its derivatives in pharmaceutical industry of traditional Chinese medicine in recent years. Chitin and its derivatives could be used as a clarificant, retaining active substances, stabiliting preparation, reducing the heavy metals of traditional Chinese medicine extraction. Because of their churacteristics in biodegradation, biocompatibility and its tendency to film easily, chitin and its derivatives was ideal assistant materials in traditional Chinese medicine. Its application was largely enhanced after chitosan was modified. The problems and prospects of the application of chitin and its derivatives were also discussed. PMID:16323536

Zhou, Bin; Gao, Wen-yuan; Zhang, Tie-jun; Chen, Hai-xia

2005-09-01

371

Effect of Inula viscosa extract on chitin synthesis in dermatophytes and Candida albicans.  

PubMed

An antimycotic effect of an extract from Inula viscosa leaves was demonstrated affecting chitin synthesis in dermatophytes and Candida albicans. The antimycotic effect was compared to the effect caused by miconazole nitrate--an antifungal drug. The inhibition effect on chitin synthesis was not correlated to the extent of growth inhibition caused by the antifungal agents: both miconazole nitrate and the I. viscosa extract inhibited the growth of dermatophytes and C. albicans. Miconazole nitrate did not affect chitin synthesis--except for M. canis--whereas I. viscosa extract caused a significant decline in chitin content. PMID:10940586

Maoz, M; Neeman, I

2000-08-01

372

Stable isotopic studies on chitin. III. The D/H and 18O/ 16O ratios in arthropod chitin  

NASA Astrophysics Data System (ADS)

Stable hydrogen and oxygen isotope ratios are presented for carbon-bound hydrogen and for oxygen in chitin-derived substrates from 57 arthropod species collected in 50 different locations or grown under controlled conditions in the laboratory. No systematic isotopic differences were found among Insecta, Crustacea, and Merostomata. The determination of infra- and interindividual isotopic variabilities in a lobster and among individuals of crustacean populations yielded small variances of about ±3 per mil for ?D values and ±0.3 per mil for ? 18O values. Molting stage and sex of crustaceans showed no systematic effects on isotopic composition. The ?D and ? 18O values of ambient water showed only weak correlations with the respective ? values of chitin-derived substrates. Positive correlation was observed between ?D values and trophic level. No temperature effects on ? 18O and ?D values from marine crustaceans were found that exceed the natural isotopic noise level. Taken together, these observations indicate that reconstruction of water isotopic composition from arthropod chitin ?D and ? 18O values will require specific information about the habits and habitats of the species involved in the analysis.

Schimmelmann, Arndt; DeNiro, Michael J.

1986-07-01

373

Polyprenyl diphosphate synthases.  

PubMed

It is noteworthy that in spite of the similarity of the reactions catalyzed by these prenyltransferases, the modes of expression of catalytic function are surprisingly different, varying according to the chain length and stereochemistry of reaction products. These enzymes are summarized and classified into four groups, as shown in Figure 13. Short-chain prenyl diphosphates synthases such as FPP and GGPP synthases require no cofactor except divalent metal ions, Mg2+ or Mn2+, which are commonly required by all prenyl diphosphate synthases. Medium-chain prenyl diphosphate synthases, including the enzymes for the synthesis of all-E-HexPP and all-E-HepPP, are unusual because they each consist of two dissociable dissimilar protein components, neither of which has catalytic activity. The enzymes for the synthesis of long-chain all-E-prenyl diphosphates, including octaprenyl (C40), nonaprenyl-(C45), and decaprenyl (C50) diphosphates, require polyprenyl carrier proteins that remove polyprenyl products from the active sites of the enzymes to maintain efficient turnovers of catalysis. The enzymes responsible for Z-chain elongation include Z,E-nonaprenyl-(C45) and Z,E-undecaprenyl (C55) diphosphate synthases, which require a phospholipid. The classification of mammalian synthases seems to be fundamentally similar to that of bacterial synthases except that no medium-chain prenyl diphosphate synthases are included. The Z-prenyl diphosphate synthase in mammalian cells is dehydrodolichyl PP synthase, which catalyzes much longer chain elongations than do bacterial enzymes. Dehydrodolichyl PP synthase will be a major target of future studies in this field in view of its involvement in glycoprotein biosynthesis. PMID:9090291

Ogura, K; Koyama, T; Sagami, H

1997-01-01

374

Chitin\\/PLGA blend microspheres as a biodegradable drug delivery system: a new delivery system for protein  

Microsoft Academic Search

Novel chitin\\/PLGAs and chitin\\/PLA based microspheres were developed for the delivery of protein. These biodegradable microspheres were prepared by polymers blending and wet phase-inversion methods. The parameters such as selected non-solvents, temperature of water and ratio of polylactide to polyglycolide were adjusted to improve thermodynamic compatibility of individual polymer (chitin and PLGAs or chitin\\/PLA), which affects the hydration and degradation

Fwu-Long Mi; Shin-Shing Shyu; Yi-Mei Lin; Yu-Bey Wu; Chih-Kang Peng; Yi-Hung Tsai

2003-01-01

375

A Bacillus amyloliquefaciens ChbB protein binds b- and a-chitin and has homologues in related strains  

Microsoft Academic Search

A small (19<8 kDa) protein was identified in Bacillus amyloliquefaciens ALKO 2718 cultures during growth in the presence of yeast extract and chitin, but not with glucose. The protein targets b-chitin best, then a-chitin, but barely any other polysaccharide. This described chitin-binding protein (ChbB) is the first of its type from a Bacillus strain and cross-reacts with antibodies raised against

Hoang Ha Chu; Viet Hoang

2001-01-01

376

Discovery of a potent, orally bioavailable and highly selective human neuronal nitric oxide synthase (nNOS) inhibitor, N-(1-(piperidin-4-yl)indolin-5-yl)thiophene-2-carboximidamide as a pre-clinical development candidate for the treatment of migraine.  

PubMed

We recently reported a series of 1,6-disubstituted indoline-based thiophene amidine compounds (5) as selective neuronal nitric oxide synthase (nNOS) inhibitors to mitigate the cardiovascular liabilities associated with hERG K(+) channel inhibition (IC(50) = 4.7 ?M) with previously reported tetrahydroquinoline-based selective nNOS inhibitors (4). The extended structure-activity relationship studies within the indoline core led to the identification of 43 as a selection candidate for further evaluations. The in vivo activity in two different pain (spinal nerve ligation and migraine pain) models, the excellent physicochemical and pharmacokinetic properties, oral bioavailability (F(po) = 91%), and the in vitro safety profile disclosed in this report make 43 an ideal candidate for further evaluation in clinical applications related to migraine pain. PMID:22840695

Annedi, Subhash C; Maddaford, Shawn P; Ramnauth, Jailall; Renton, Paul; Rybak, Taras; Silverman, Sarah; Rakhit, Suman; Mladenova, Gabriela; Dove, Peter; Andrews, John S; Zhang, Dongqin; Porreca, Frank

2012-07-14

377

Progress in the development of a chitin assay technique for measuring extraradical soilborne mycelium of V-A mycorrhizal fungi  

SciTech Connect

This investigation was conducted to replicate a chitin extraction procedure, used to identify extraradical fungal biomass, on various soil media to which chitin standards had been added. The procedure for chitin in the field soil failed each time performed. This failure is due to an incomplete reaction or a failure of nitrous acid to form in the soil media. 6 references, 1 table. (MF)

Jarstfer, A.G.; Miller, R.M.

1984-01-01

378

Cadmium removal from aqueous solutions by chitin: kinetic and equilibrium studies  

Microsoft Academic Search

A fundamental investigation on the removal of cadmium ions from aqueous solutions by chitin was conducted in batch conditions. Kinetic data and equilibrium removal isotherms were measured. The influence of different experimental parameters such as time contact, initial concentration of cadmium, chitin mass, particles size, agitation speed, temperature and the nature of cadmium salt, on the kinetics of cadmium removal

B Benguella; H Benaissa

2002-01-01

379

Molecular characterization of the modular chitin binding protein Cbp50 from Bacillus thuringiensis serovar konkukian.  

PubMed

Bacillus thuringiensis is an insecticidal bacterium whose chitinolytic system may be exploited to improve the insecticidal system of Bt-crops. A nucleotide fragment of 1368 bp from B. thuringiensis serovar konkukian S4, containing the complete coding sequence of the chitin binding protein Cbp50, was cloned and sequenced. Analyses have shown the protein to contain a modular structure consisting of an N-terminal CBM33 domain, two copies of a fibronectin-like domain and a C-terminal chitin binding domain classified as CBM5. The Cbp50 protein was heterologously expressed in Escherichia coli, purified and assessed for chitin binding activity. A deletion mutant (CBD-N; containing only the N-terminal CBM33 domain) of Cbp50 was produced to determine the role of C-terminal domains in the binding activity of the protein. The full-length Cbp50 was shown to bind ?-chitin most efficiently followed by ?-chitin, colloidal chitin and cellulose. The polysaccharide binding activity of CBD-N was drastically decreased. The data demonstrate that both the N-terminal and C-terminal domains of Cbp50 are essential for the efficient binding of chitin. The purified Cbp50 showed antifungal activity against the phytopathogenic fungus Fusarium oxysporum and the opportunistic human pathogen Aspergillus niger. This is the first report of a modular chitin binding protein in bacteria. PMID:21647612

Mehmood, Muhammad Aamer; Xiao, Xiang; Hafeez, Fauzia Yusuf; Gai, Yingbao; Wang, Fengping

2011-06-07

380

Application of chitin- and chitosan-based materials for enzyme immobilizations: a review  

Microsoft Academic Search

As functional materials, chitin and chitosan offer a unique set of characteristics: biocompatibility, biodegradability to harmless products, nontoxicity, physiological inertness, antibacterial properties, heavy metal ions chelation, gel forming properties and hydrophilicity, and remarkable affinity to proteins. Owing to these characteristics, chitin- and chitosan-based materials, as yet underutilized, are predicted to be widely exploited in the near future especially in environmentally

Barbara Krajewska

2004-01-01

381

Effect of Inula viscosa extract on chitin synthesis in dermatophytes and Candida albicans  

Microsoft Academic Search

An antimycotic effect of an extract from Inulaviscosa leaves was demonstrated affecting chitin synthesis in dermatophytes and Candidaalbicans. The antimycotic effect was compared to the effect caused by miconazole nitrate — an antifungal drug. The inhibition effect on chitin synthesis was not correlated to the extent of growth inhibition caused by the antifungal agents: both miconazole nitrate and the I.viscosa

M Maoz; I Neeman

2000-01-01

382

Bacterial Chitinolytic Communities Respond to Chitin and pH Alteration in Soil  

PubMed Central

Chitin amendment is a promising soil management strategy that may enhance the suppressiveness of soil toward plant pathogens. However, we understand very little of the effects of added chitin, including the putative successions that take place in the degradative process. We performed an experiment in moderately acid soil in which the level of chitin, next to the pH, was altered. Examination of chitinase activities revealed fast responses to the added crude chitin, with peaks of enzymatic activity occurring on day 7. PCR-denaturing gradient gel electrophoresis (DGGE)-based analyses of 16S rRNA and chiA genes showed structural changes of the phylogenetically and functionally based bacterial communities following chitin addition and pH alteration. Pyrosequencing analysis indicated (i) that the diversity of chiA gene types in soil is enormous and (i) that different chiA gene types are selected by the addition of chitin at different prevailing soil pH values. Interestingly, a major role of Gram-negative bacteria versus a minor one of Actinobacteria in the immediate response to the added chitin (based on 16S rRNA gene abundance and chiA gene types) was indicated. The results of this study enhance our understanding of the response of the soil bacterial communities to chitin and are of use for both the understanding of soil suppressiveness and the possible mining of soil for novel enzymes.

Kielak, Anna M.; Cretoiu, Mariana Silvia; Semenov, Alexander V.; S?rensen, S?ren J.

2013-01-01

383

The recovery of protein hydrolysate during enzymatic isolation of chitin from shrimp Crangon crangon processing discards  

Microsoft Academic Search

Shell waste from shrimp Crangon crangon processing is a good source of chitin and proteins, contained on a dry basis of the offals in amounts 17.8% and 40.6%, respectively. The digestion of the shells with proteolytic enzymes allow to recovery of the chitin and nutritionally valuable protein hydrolysate. These products were prepared from the shells preliminarily demineralized with 10% HCl

Józef Synowiecki; Nadia Ali Abdul Quawi Al-Khateeb

2000-01-01

384

Nitric oxide synthase in cerebral ischemia  

Microsoft Academic Search

The results of our continuing studies on the role of nitric oxide (NO) in cellular mechanisms of ischemic brain damage as\\u000a well as related reports from other laboratories are summarized in this paper. Repetitive ip administration ofN\\u000a G-nitro-L-arginine (L-NNA), a NO synthase (NOS) inhibitor, protected against neuronal necrosis in the gerbil hippocampal CA1\\u000a field after transient forebrain ischemia with a

Toshiaki Nagafuji; Masakazu Sugiyama; Toru Matsui; Atsushi Muto; Shigetaka Naito

1995-01-01

385

Antifibrotic Role of Inducible Nitric Oxide Synthase  

Microsoft Academic Search

Long-term treatment in rats with l-NAME, an isoform-non-specific inhibitor of nitric oxide synthase (NOS), leads to fibrosis of the heart and kidney, suggesting that nitric oxide (NO) may play a role in preventing tissue fibrosis. In this process, a likely target of NO is the quenching of reactive oxygen species (ROS) through peroxynitrite formation, and one possible source for this

M. G. Ferrini; D. Vernet; T. R. Magee; A. Shahed; A. Qian; J. Rajfer; N. F. Gonzalez-Cadavid

2002-01-01

386

Hybrid of chitin and humic acid as high performance sorbent for Ni(II)  

NASA Astrophysics Data System (ADS)

Hybrid of humic acid (HA) and chitin has been synthesized and the hybrid material (chitin HA) was then applied as sorbent to adsorb Ni(II). The HA was extracted from peat soil of Gambut District, South Kalimantan, Indonesia, according to the procedure recommended by IHSS (International Humic Substances Society). The chitin was isolated from crab shell waste of sea food restaurants through deproteination using NaOH 3.5% (w/v) and followed by removal of inorganic impurities using HCl 1 M. The synthesis of chitin HA was performed by reacting gelatinous chitin solution in HCl 0.5 M and HA solution in NaOH 0.5 M. Parameters investigated in this work consists of effect of medium acidity on the sorption, sorption rate (ks) and desorption rate (kd) constants, Langmuir (monolayer) and Freundlich (multilayer) sorption capacities, and energy (E) of sorption. The ks and kd were determined according to a kinetic model of first order sorption reaching equilibrium, monolayer sorption capacity (b) and energy (E) were determined according to the Langmuir isotherm model, and multilayer sorption capacity (B) was determined based on the Freundlich isotherm model. Sorption of Ni(II) on both chitin and chitin HA was maximum at pH 8.0. The kinetic expression resulted from the proposed kinetic model has been shown to be more applicable than the commonly known Lagergren equation obtained from the pseudo-first order sorption model. The application of the proposed model revealed that the presence of HA increased the ks from 0.018 min-1 for chitin to 0.031 min-1 for chitin HA. As for ks, the value of b was also bigger in the presence of HA, i.e. 7.42 × 10-5 mol/g for chitin and 9.93 × 10-5 mol/g for the chitin HA. Unlike ks and b, the value of E slightly decreased from 23.23 to 21.51 kJ/mol for the absence and presence of HA, respectively. It can also be deduced that the presence of HA on chitin contributed more to the additional layer of Ni(II) sorbed on sorbent. Without HA, B for chitin was only 6.17 times higher than b, while with the presence of HA, the enhancement of the sorption capacity from the multilayer (B) to the monolayer (b) was 19.40. The increase of ks, b, B, and the decrease of E would be very benefit in the real application of chitin HA for the recovery of Ni(II) from aqueous samples.

Santosa, Sri Juari; Siswanta, Dwi; Kurniawan, Agusta; Rahmanto, Wasino H.

2007-11-01

387

The chitobiose transporter, chbC, is required for chitin utilization in Borrelia burgdorferi  

PubMed Central

Background The bacterium Borrelia burgdorferi, the causative agent of Lyme disease, is a limited-genome organism that must obtain many of its biochemical building blocks, including N-acetylglucosamine (GlcNAc), from its tick or vertebrate host. GlcNAc can be imported into the cell as a monomer or dimer (chitobiose), and the annotation for several B. burgdorferi genes suggests that this organism may be able to degrade and utilize chitin, a polymer of GlcNAc. We investigated the ability of B. burgdorferi to utilize chitin in the absence of free GlcNAc, and we attempted to identify genes involved in the process. We also examined the role of RpoS, one of two alternative sigma factors present in B. burgdorferi, in the regulation of chitin utilization. Results Using fluorescent chitinase substrates, we demonstrated an inherent chitinase activity in rabbit serum, a component of the B. burgdorferi growth medium (BSK-II). After inactivating this activity by boiling, we showed that wild-type cells can utilize chitotriose, chitohexose or coarse chitin flakes in the presence of boiled serum and in the absence of free GlcNAc. Further, we replaced the serum component of BSK-II with a lipid extract and still observed growth on chitin substrates without free GlcNAc. In an attempt to knockout B. burgdorferi chitinase activity, we generated mutations in two genes (bb0002 and bb0620) predicted to encode enzymes that could potentially cleave the ?-(1,4)-glycosidic linkages found in chitin. While these mutations had no effect on the ability to utilize chitin, a mutation in the gene encoding the chitobiose transporter (bbb04, chbC) did block utilization of chitin substrates by B. burgdorferi. Finally, we provide evidence that chitin utilization in an rpoS mutant is delayed compared to wild-type cells, indicating that RpoS may be involved in the regulation of chitin degradation by this organism. Conclusions The data collected in this study demonstrate that B. burgdorferi can utilize chitin as a source of GlcNAc in the absence of free GlcNAc, and suggest that chitin is cleaved into dimers before being imported across the cytoplasmic membrane via the chitobiose transporter. In addition, our data suggest that the enzyme(s) involved in chitin degradation are at least partially regulated by the alternative sigma factor RpoS.

2010-01-01

388

Acetylation of alpha-chitin in ionic liquids.  

PubMed

Acetylation of alpha-chitin using acetic anhydride in an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), was performed. First, a mixture of chitin and AMIMBr (2% w/w) was heated at 100 degrees C for 24h for dissolution. Then, acetic anhydride (5-20 equiv) was added to the solution and the mixture was heated with stirring at desired temperatures for 24h. The product was precipitated by the addition of the reaction mixture into methanol. The IR spectrum of the product indicated the progress of acetylation. The degrees of substitution (DS), which were determined from the IR spectra, increased with increasing the amounts of acetic anhydride used for the reaction. The highest DS was 1.86, which was obtained by the reaction using 20 equiv of acetic anhydride at 100 degrees C. The product with this DS value was soluble in DMSO, and thus the structure of the product was further confirmed by (1)H NMR spectroscopy in DMSO-d(6). The DS value estimated by the integrated ratio of signals due to acetyl protons to a signal due to anomeric protons was in good agreement with that determined from the IR spectrum. PMID:19732868

Mine, Shozaburo; Izawa, Hironori; Kaneko, Yoshiro; Kadokawa, Jun-Ichi

2009-08-08

389

Flexible chitin films as potential wound-dressing materials: wound model studies.  

PubMed

Chitin films possessing increased flexibility, softness, transparency, and conformability have been prepared. These attributes enable the potential application of chitin films as occlusive, semipermeable film wound dressings similar to commercial products such as Opsite trade mark. The chitin films are generally nonabsorbent, exhibiting a total weight gain of only up to 120-160% in physiological fluid. Dry chitin films transpire water vapor at a rate of about 600 g/m(2)/24 h, similar to commercial polyurethane-based film dressings, but rises to 2400 g/m(2)/24 h, when wet, which is higher than the water vapor transmission rate of intact skin. The chitin films are nontoxic to human skin fibroblasts, maintaining 70-80% cell viability. Wound studies using a rat model showed no signs of allergenicity or the high inflammatory response associated with biodegradable biomaterials. The chitin films displayed accelerated wound-healing properties. Based on histological examination, wound sites dressed with the chitin films stabilized and healed faster, and appeared stronger than those dressed with Opsite trade mark and gauze dressings after 7 days of healing. PMID:12888991

Yusof, Nealda Leila Binte Muhammad; Wee, Aileen; Lim, Lee Yong; Khor, Eugene

2003-08-01

390

Pyrolysis GC/MS and IR spectroscopy in chitin analysis of molluscan shells.  

PubMed

Chitin is an insoluble component in the shells of several molluscan species. It is thought to play important roles, in biomineralization and shell structure. To date, however, reports are scarce and sometimes contradictory, and suffer from methodological problems. Only in a single cephalopod species has the chitin been identified as beta-chitin. We present data on chitin occurrence in 22 species of shell-bearing Mollusca (Conchifera) and Polyplacophora, including the first evidence for scaphopods, based on pyrolysis gas chromatography, mass spectrometry (GC-MS), and infrared spectroscopy (IR). Pyrolysis GC-MS detected chitin in every tested member of the Conchifera. IR spectroscopy before and after chitinase treatment revealed at least three distinct patterns of peak changes. The contents of the insoluble shell organics included not only chitin and proteins, but also insoluble polysaccharides, e.g., glucan. We conclude that chitin was present in the last common ancestor of the Conchifera and that its abundance in the shell matrix depends on the differentiation of the shell. PMID:19129649

Furuhashi, Takeshi; Beran, Anton; Blazso, Marianne; Czegeny, Zsuzsanna; Schwarzinger, Clemens; Steiner, Gerhard

2009-01-07

391

Structural organization of mitochondrial ATP synthase.  

PubMed

Specific modules and subcomplexes like F(1) and F(0)-parts, F(1)-c subcomplexes, peripheral and central stalks, and the rotor part comprising a ring of c-subunits with attached subunits gamma, delta, and epsilon can be identified in yeast and mammalian ATP synthase. Four subunits, alpha(3)beta(3), OSCP, and h, seem to form a structural entity at the extramembranous rotor/stator interface (gamma/alpha(3)beta(3)) to hold and stabilize the rotor in the holo-enzyme. The intramembranous rotor/stator interface (c-ring/a-subunit) must be dynamic to guarantee unhindered rotation. Unexpectedly, a c(10)a-assembly could be isolated with almost quantitive yield suggesting that an intermediate step in the rotating mechanism was frozen under the conditions used. Isolation of dimeric a-subunit and (c(10))(2)a(2)-complex from dimeric ATP synthase suggested that the a-subunit stabilizes the same monomer-monomer interface that had been shown to involve also subunits e, g, b, i, and h. The natural inhibitor protein Inh1 does not favor oligomerization of yeast ATP synthase. Other candidates for the oligomerization of dimeric ATP synthase building blocks are discussed, e.g. the transporters for inorganic phosphate and ADP/ATP that had been identified as constituents of ATP synthasomes. Independent approaches are presented that support previous reports on the existence of ATP synthasomes in the mitochondrial membrane. PMID:18485888

Wittig, Ilka; Schägger, Hermann

2008-04-27

392

Kinetics of chitinase production. II. Relationship between bacterial growth, chitin hydrolysis and enzyme synthesis.  

PubMed

A comprehensive model for chitinase production during growth of Serratia marcescens QMB 1466 on chitin was developed taking into account the rate of chitin hydrolysis in order to estimate the rate of bacterial growth. In relating growth with enzyme synthesis the total enzyme concentration was used as the sum of the enzyme present in the bulk of the fermentation broth and the enzyme adsorbed on the chitin particles. The equations constituting the proposed model were fitted to the experimental results from both continuous and batch fermentation to obtain parameters describing substrate yield, metabolic maintenance, and enzyme yields. PMID:18553735

Young, M E; Bell, R L; Carroad, P A

1985-06-01

393

Viscosity-temperature behavior of chitin solutions using lithium chloride/DMA as solvent.  

PubMed

Solutions of chitin in Li(+)/N,N-dimethylacetamide systems were studied via viscometry, using LiCl concentrations of 3% and 5% (m/v) and chitin concentrations ranging from 0.075 to 0.375 gL(-1). The reduced viscosity number versus concentration plot showed a minimum that was related to the formation of Li(+)-OC complex moieties along chitin macromolecular chains. Viscosity behavior was affected by temperature according to the Eyring model: concentration dependence of flow enthalpy of activation was correlated to polymer-polymer interactions and flow entropy of activation to the stiffness of the complexed chitosan macromolecular chain. PMID:21295769

de Vasconcelos, C L; Bezerril, P M; Pereira, M R; Ginani, M F; Fonseca, J L C

2011-01-07

394

Ionic Conductivity and Dielectric Studies of Chitin Nanofiber (CNF) Incorporated PMMA Based Polymer Electrolytes  

NASA Astrophysics Data System (ADS)

Chitin nanofibers (CNF) are synthesized from shrimp cell chitin by stepwise purification and acid hydrolysis method. PMMA based polymer electrolytes complexed with LIN (CF3SO2)2 and chitin nanofibers as nanofiller have prepared by membrane hot-press technique. The prepared composite electrolytes are subjected to FT-IR, ac impedance, dielectric and modulus analyses. The incorporation of nanofiller in the polymer matrix increases the conductivity by an order of magnitude compared with filler free electrolytes. The complexation behavior of the composite polymer electrolytes are investigated by ATR FT -IR spectroscopy. The electric modulus analysis and dielectric studies of polymer electrolytes revealed that the non Debye dielectric relaxation nature.

Shyly, P. M.; Karuppasamy, K.; Linda, T.; Thiravetyan, Paitip; Balakumar, S.; Sahaya, Shajan X.

2012-06-01

395

Preparation and characterization of chitin hydrogels by water vapor induced gelation route.  

PubMed

A novel method of chitin hydrogel preparation, called vapor induced gelation, using exposure of chitin/N-methyl-pyrrolidone/LiCl solution to water vapors is presented. Compared to gelation induced by direct immersion in water, hydrogels are characterized by smaller deformation during gelation (area shrinkage is 20% instead of 65%), larger water volume fraction (75 instead of 62%, v/v) and 10 times higher apparent compression moduli. Their nanostructure consists of thicker and larger crystalline platelets network (thickness=37 ?, apparent coherent crystalline size L???=145 ?) comparatively to direct immersion gels (25 ? and L???=95 ?). Drug delivery potential of chitin hydrogels was determined for non-interactive low molecular molecules. PMID:22676995

Vachoud, L; Pochat-Bohatier, C; Chakrabandhu, Y; Bouyer, D; David, L

2012-06-05

396

Bisphosphonates used for the treatment of bone disorders inhibit squalene synthase and cholesterol biosynthesis  

Microsoft Academic Search

Some bisphosphonates used for the treatment of bone disorders are also potent inhibitors of squalene synthase, a critical enzyme for sterol biosynthesis. Among seven drugs tested, YM 175 (cycloheptylaminomethylene-1,l-bisphosphonic acid) was the most potent inhibitor of rat liver microsomal squalene synthase (K, = 57 nM) and sterol biosynthesis from (I4C)mev- alonate in rat liver homogenate (IC50 = 17 nM). EB

Dilip Amin; Susan A. Cornell; Susan K. Gustafson; Saul J. Needle; John W. Ullrich; Glenda E. Bilder; Mark H. Perrone

397

Increased expression of inducible nitric oxide synthase (iNOS) in N-nitrosobis(2-oxopropyl)amine-induced hamster pancreatic carcinogenesis and prevention of cancer development by ONO1714, an iNOS inhibitor  

Microsoft Academic Search

Elevated protein expression of inducible nitric oxide synthase (iNOS) has been observed in human pancreatic cancers and there- fore, iNOS may play important roles in pancreatic carcinogenesis. This was examined in the present study, using an experimental model with N-nitrosobis(2-oxopropyl)amine (BOP)-treated ham- sters. Reverse transcription-polymerase chain reaction analysis demonstrated iNOS expression in a hamster pancreatic cancer cell line as well

Mami Takahashi; Tsukasa Kitahashi; Rikako Ishigamori; Michihiro Mutoh; Masami Komiya; Hidetaka Sato; Yoshihisa Kamanaka; Masao Naka; Takayuki Maruyama; Takashi Sugimura; Keiji Wakabayashi

398

Discovery of cis-N-(1-(4-(methylamino)cyclohexyl)indolin-6-yl)thiophene-2-carboximidamide: a 1,6-disubstituted indoline derivative as a highly selective inhibitor of human neuronal nitric oxide synthase (nNOS) without any cardiovascular liabilities.  

PubMed

A series of 1,6-disubstituted indoline derivatives were synthesized and evaluated as inhibitors of human nitric oxide synthase (NOS) designed to mitigate the cardiovascular liabilities associated with previously reported tetrahydroquinoline-based selective neuronal NOS inhibitors due to higher lipophilicity ( J. Med. Chem. 2011 , 54 , 5562 - 5575 ). This new series produced similar potency and selectivity among the NOS isoforms and was devoid of any cardiovascular liabilities associated with QT prolongation due to hERG activity or endothelial NOS mediated vasoconstriction effect. The SAR studies led to the identification of cis-45, which was shown to reverse thermal hyperalgesia in vivo in the spinal nerve ligation model of neuropathic pain with excellent safety profile (off-target activities at 80 CNS related receptors/ion channels/transporters). The results presented in this report make cis-45 as an ideal tool for evaluating the potential role of selective nNOS inhibitors in CNS related disorders where excess NO produced by nNOS is thought to play a crucial role. PMID:22175766

Annedi, Subhash C; Ramnauth, Jailall; Maddaford, Shawn P; Renton, Paul; Rakhit, Suman; Mladenova, Gabriela; Dove, Peter; Silverman, Sarah; Andrews, John S; Felice, Milena D; Porreca, Frank

2012-01-10

399

Discovery of N-(3-(1-methyl-1,2,3,6-tetrahydropyridin-4-yl)-1H-indol-6-yl) thiophene-2-carboximidamide as a selective inhibitor of human neuronal nitric oxide synthase (nNOS) for the treatment of pain.  

PubMed

3,6-Disubstituted indole derivatives were designed, synthesized, and evaluated as inhibitors of human nitric oxide synthase (NOS). Bulky amine containing substitution on the 3-position of the indole ring such as an azabicyclic system showed better selectivity over 5- and 6-membered cyclic amine substitutions. Compound (-)-19 showed the best selectivity for neuronal NOS over endothelial NOS (90-fold) and inducible NOS (309-fold) among the current series. Compounds 16 and (-)-19 were shown to be either inactive or very weak inhibitors of human cytochrome P450 enzymes, indicating a low potential for drug-drug interactions. Compound 16 was shown to reverse thermal hyperalgesia in vivo in the Chung model of neuropathic pain. Compound 16 was also devoid of any significant vasoconstrictive effect in human coronary arteries, associated with the inhibition of human eNOS. These results suggest that 16 may be a useful tool for evaluating the potential role of selective nNOS inhibitors in the treatment of pain such as migraine and CTTH. PMID:21923116

Annedi, Subhash C; Maddaford, Shawn P; Mladenova, Gabriela; Ramnauth, Jailall; Rakhit, Suman; Andrews, John S; Lee, David K H; Zhang, Dongqin; Porreca, Frank; Bunton, David; Christie, Lee

2011-10-05

400

Design, Synthesis, and X-ray Crystal Structure of Classical and Nonclassical 2-Amino-4-oxo-5-substituted-6-ethyl-thieno[2,3-d]pyrimidines as Dual Thymidylate Synthase and Dihydrofolate Reductase Inhibitors and as Potential Antitumor Agents  

PubMed Central

N-{4-[(2-amino-6-ethyl-4-oxo-3,4-dihydrothieno[2,3-d]pyrimidin-5-yl)thio]benzoyl}-L-glutamic acid 2 and thirteen nonclassical analogues 2a–2m were synthesized as potential dual thymidylate synthase (TS) and dihydrofolate reductase (DHFR) inhibitors and as antitumor agents. The key intermediate in the synthesis was 2-amino-6-ethyl-5-iodothieno[2,3-d]pyrimidin-4(3H)-one, 7, to which various aryl thiols were attached at the 5-position. Coupling 8 with L-glutamic acid diethyl ester and saponification afforded 2. X-ray crystal structure of 2 and 1 (the 6-methyl analogue of 2), DHFR and NADPH showed for the first time that the thieno[2,3-d]pyrimidine ring binds in a “folate” mode. Compound 2 was an excellent dual inhibitor of human TS (IC50 = 54 nM) and human DHFR (IC50 = 19 nM), and afforded nanomolar GI50 values against tumor cells in culture. The 6-ethyl substitution in 2 increases both the potency (by two- to three-orders of magnitude) as well as the spectrum of tumor inhibition in vitro compared to the 6-methyl analogue 1. Some of the nonclassical analogues were potent and selective inhibitors of DHFR from Toxoplasma gondii.

Gangjee, Aleem; Li, Wei; Kisliuk, Roy L.; Cody, Vivian; Pace, Jim; Piriano, Jennifer; Makin, Jennifer

2009-01-01

401

Structural insights into aldosterone synthase substrate specificity and targeted inhibition.  

PubMed

Aldosterone is a major mineralocorticoid hormone that plays a key role in the regulation of electrolyte balance and blood pressure. Excess aldosterone levels can arise from dysregulation of the renin-angiotensin-aldosterone system and are implicated in the pathogenesis of hypertension and heart failure. Aldosterone synthase (cytochrome P450 11B2, CYP11B2) is the sole enzyme responsible for the production of aldosterone in humans. Blocking of aldosterone synthesis by mediating aldosterone synthase activity is thus a recently emerging pharmacological therapy for hypertension, yet a lack of structural information has limited this approach. Here, we present the crystal structures of human aldosterone synthase in complex with a substrate deoxycorticosterone and an inhibitor fadrozole. The structures reveal a hydrophobic cavity with specific features associated with corticosteroid recognition. The substrate binding mode, along with biochemical data, explains the high 11?-hydroxylase activity of aldosterone synthase toward both gluco- and mineralocorticoid formation. The low processivity of aldosterone synthase with a high extent of intermediates release might be one of the mechanisms of controlled aldosterone production from deoxycorticosterone. Although the active site pocket is lined by identical residues between CYP11B isoforms, most of the divergent residues that confer additional 18-oxidase activity of aldosterone synthase are located in the I-helix (vicinity of the O(2) activation path) and loops around the H-helix (affecting an egress channel closure required for retaining intermediates in the active site). This intrinsic flexibility is also reflected in isoform-selective inhibitor binding. Fadrozole binds to aldosterone synthase in the R-configuration, using part of the active site cavity pointing toward the egress channel. The structural organization of aldosterone synthase provides critical insights into the molecular mechanism of catalysis and enables rational design of more specific antihypertensive agents. PMID:23322723

Strushkevich, Natallia; Gilep, Andrei A; Shen, Limin; Arrowsmith, Cheryl H; Edwards, Aled M; Usanov, Sergey A; Park, Hee-Won

2013-01-15

402

Chitin elicits CCL2 from airway epithelial cells and induces CCR2-dependent innate allergic inflammation in the lung  

PubMed Central

Chitin exposure in the lung induces eosinophilia and alternative activation of macrophages, and is correlated with allergic airway disease. However, the mechanism underlying chitin-induced polarization of macrophages is poorly understood. Here, we show that chitin induces alternative activation of macrophages in vivo, but does not do so directly in vitro. We further show that airway epithelial cells bind chitin in vitro and produce CCL2 in response to chitin both in vitro and in vivo. Supernatants of chitin exposed epithelial cells promoted alternative activation of macrophages in vitro, whereas antibody neutralization of CCL2 in the supernate abolished the alternative activation of macrophages. CCL2 acted redundantly in vivo, but mice lacking the CCL2 receptor, CCR2, showed impaired alternative activation of macrophages in response to chitin, as measured by arginase I, CCL17 and CCL22 expression. Furthermore, CCR2KO mice exposed to chitin had diminished ROS products in the lung, blunted eosinophil and monocyte recruitment, and impaired eosinophil functions as measured by expression of CCL5, IL13 and CCL11. Thus, airway epithelial cells secrete CCL2 in response to chitin and CCR2 signaling mediates chitin-induced alternative activation of macrophages and allergic inflammation in vivo.

Roy, Rene M.; Wuthrich, Marcel; Klein, Bruce S.

2012-01-01

403

MICROBIAL FERMENTATION OF ABUNDANT BIOPOLYMERS: CELLULOSE AND CHITIN  

SciTech Connect

Our research has dealt with seven major areas of investigation: i) characterization of cellulolytic members of microbial consortia, with special attention recently given to Clostridium phytofermentans, a bacterium that decomposes cellulose and produces uncommonly large amounts of ethanol, ii) investigations of the chitinase system of Cellulomonas uda; including the purification and characterization of ChiA, the major component of this enzyme system, iii) molecular cloning, sequence and structural analysis of the gene that encodes ChiA in C. uda, iv) biofilm formation by C. uda on nutritive surfaces, v) investigations of the effects of humic substances on cellulose degradation by anaerobic cellulolytic microbes, vi) studies of nitrogen metabolism in cellulolytic anaerobes, and vii) understanding the molecular architecture of the multicomplex cellulase-xylanase system of Clostridium papyrosolvens. Also, progress toward completing the research of more recent projects is briefly summarized. Major accomplishments include: 1. Characterization of Clostridium phytofermen