Changes of substrate configuration during trypsin hydrolysis of arginine and lysine 2-phenyl-thiazol-5-ones.
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The expression of cytochromes P450 2E1, P450 2B and P450 1A was examined in rat hepatic tissue in response to YH439, an experimental hepatoprotective agent. P450 2E1 metabolic activities relatively specific for P450 2E1 were decreased up to 57% of control activities in the hepatic microsomes prepared from rats treated with YH439 for 3 days. Immunoblot analyses showed that P450 2E1 levels were decreased below the limit of detectability in hepatic microsomes prepared from YH439-treated rats. YH439 at doses from 25 to 100 mg/kg completely suppressed isoniazid-inducible P450 2E1 levels as monitored by both metabolic activities and immunoblot analysis. RNA hybridization analysis revealed that P450 2E1 mRNA levels failed to change after YH439 treatment. These results demonstrate the YH439 effectively suppresses P450 2E1 expression in the absence of transcriptional inactivation. YH439 failed to affect P450 2B1/2 expression, whereas this agent enhanced the hepatic P450 1A1/2 levels. The hepatoprotective effects of YH439 were also examined. Animals treated with CCl4 and ethanol for 9 weeks showed hepatic injury as demonstrated by 2.5- and 2-fold increases in serum alanine aminotransferase and alkaline phosphatase activities, respectively. Concomitant YH439 treatment resulted in a significant protective effect against the experimental hepatic injury. The toxicant-induced elevation in hepatic hydroxyproline level was completely blocked by YH439 treatment. These data indicate that YH439 suppresses the expression of P450 2E1 and protects the liver against chemical-induced hepatic injury and that the selective modulation of detoxifying enzymes by YH439 may contribute to the protection of liver from xenobiotic-induced intoxication.
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The immunopharmacological effects of a newly synthesized compound in vivo, TOK-8801 (N-(2-phenylethyl)-3,6,6-trimethyl-5,6-dihydroimidazo[2,1-b]thi azo le-2- carboxamide), on the anti-SRBC plaque-forming cell (PFC) response and delayed-type hypersensitivity (DTH) reaction were investigated. Oral administration of TOK-8801 (0.1-10 mg/kg) resulted in the suppression of the PFC responses to varying doses of antigen (5 x 10(6), 2 x 10(7), 1 x 10(8)) in C3H/He strain mice (7 W) which are high responders to SRBC antigen. On the other hand, the compound augmented the PFC response in aged mice (8-9 months) in which the PFC response was markedly depressed compared with that in young mice. In the experiment of the methylated human serum albumin-induced DTH reaction, TOK-8801 augmented the reaction in low responder (C57BL/6) mice by oral administrations of 0.1-1 mg/kg for 5 days from the sensitization, whereas suppressed the reaction in high responder (ICR) mice. These immunopharmacological actions of TOK-8801 were compared in dose and activity with those of lobenzarit and bucillamine. Thus, these results suggest that TOK-8801 may act as an immunomodulating agent and would be expected to be a useful agent for autoimmune diseases such as rheumatoid arthritis.
The sensitizing potential of seven industrial antimicrobial agents was evaluated using the guinea-pig maximization test. Preventol O extra (o-phenylphenol) did not produce a sensitization reaction. Preventol ON extra (sodium salt of o-phenylphenol), Preventol GD (dichlorophene) and Proxel XL and HL containing 1,2-benzisothiazolin-3-one were weak sensitizers, while Preventol CMK and Preventol L, both containing chlorocresol, were classified as extreme potential sensitizers. Both the weak and the extreme experimental sensitizers are occasional human sensitizers. The interpretation of the test results is discussed.
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The hepatotoxicity of the 3 isomers of para-substituted thiobenzamides and the 3 isomers of 2-(para-substituted phenyl)-4-methylthiazoles was evaluated in mice depleted of glutathione (GSH) by pretreatment with buthionine sulfoximine (BSO). In accordance with previous studies with the rat, p-methoxythiobenzamide was more toxic than thiobenzamide, and conversely p-chlorothiobenzamide was markedly less toxic as assessed by serum alanine aminotransferase (ALT) activity. The hepatotoxicity of 2-phenyl-4-methylthiazole was also altered by the addition of para-substituents to the phenyl ring in the same way as observed for thiobenzamide derivatives: the rank order of toxicity was 4-methylthiazoles having p-methoxyphenyl > phenyl >> p-chlorophenyl at the 2-position. This good correlation of the rank order of hepatotoxicity between series of 2-(para-substituted phenyl)-4-methylthiazoles and para-substituted thiobenzamides supports the concept that thiobenzamides as ring cleavage metabolites play a role in the hepatotoxicity of 2-phenylthiazole derivatives.
4-(4-Methoxyphenyl)-2-aminothiazole and 3-(4-methoxyphenyl)-5-aminothiadiazole derivatives have been synthesized and evaluated as selective antagonists for human adenosine A3 receptors. A methoxy group in the 4-position of the phenyl ring and N-acetyl or propionyl substitutions of the aminothiazole and aminothiadiazole templates displayed great increases of binding affinity and selectivity for human adenosine A3 receptors. The most potent A3 antagonist of the present series, N-[3-(4-methoxy-phenyl)-[1,2,4]thiadiazol-5-yl]-acetamide (39) exhibiting a Ki value of 0.79 nM at human adenosine A3 receptors, showed antagonistic property in a functional assay of cAMP biosynthesis involved in one of the signal transduction pathways of adenosine A3 receptors. Molecular modeling study of conformation search and receptor docking experiments to investigate the dramatic differences of binding affinities between two regioisomers of thiadiazole analogues, (39) and (42), suggested possible binding mechanisms in the binding pockets of adenosine receptors.
A series of novel 9-substituted-3,7-dithia-5-azatetracyclo[9.2.1.0(2,10).0(4,8)]tetradecen-4(8)-ones-6 have been synthesized by a stereoselective hetero-Diels-Alder reaction of 5-ylidene-4-thioxo-2-thiazolidone derivatives with norbornene-2. All the compounds have been evaluated for antitumor activity in in vitro human tumor cell lines, and 10 of them possessed significant and selective cytotoxicity (MGM logGI50 approximately -4.17 to -4.98, for individual cell lines logGI50 up to -8). COMPARE analyses of differential growth inhibition patterns of compounds at the GI50 level showed high correlations with some of the antitubulin agents. The lipophilicity of the compounds was studied by RP-TLC and found to correlate well with calculated logP values. Docking and structure-activity relationship studies produced seven QSAR models with 2 or 3 variables, with correlation coefficients r2>0.9 and leave-one-out cross-validation correlation coefficients, q2>0.8.
Thiostrepton is a highly complex cyclic thiazoyl peptide antibiotic and is active against Gram-positive bacteria. Molecular mechanics, semi-empirical and ab initio studies were utilized to further understand the structural and electronic properties of this antibiotic.
A series of beta-aminoacylpiperidines bearing various fused five-membered heterocyclic rings was synthesized as dipeptidyl peptidase IV inhibitors. Potent and relatively selective inhibition could be obtained, depending on choice of heterocycle, regioisomerism, and substitution. In particular, one analog (74, DPP-IV IC50=26 nM) exhibited good oral bioavailability and acceptable half-life in the rat, albeit with rather high clearance.
Using a furanylthiazole acetic acid as a starting point, a novel series of benzoxazol-5-yl acetic acid derivatives have been identified as heparanase inhibitors. Several compounds possess an IC50 of approximately 200 nM against heparanase, for example, trans 2-[4-[3-(3,4-dichlorophenylamino)-3-oxo-1-propenyl]-2-fluorophenyl]benzoxazol-5-yl acetic acid (16e). Several of the compounds show anti-angiogenic properties. Improvement to the DMPK profile of compounds has provided compounds of potential use in in vivo models.
A quantitative structure-activity relationship study on a series of substituted benzene sulfonamide-3-pyridylethanolamines with beta3-adrenergic receptor agonist activity was made using a combination of various physiochemical descriptors. Several significant equations with good co-efficients of correlation (0.930) were obtained; the two models were selected using predictive ability of equations for test set. Both models highlight some common important structural features, that is, high electrostatic potential energy and the lipophilic nature of the molecule, favorable for beta3-adrenergic receptor agonist activity.