- Characterization of protein adducts produced by N-methyldithiocarbamate and N-methyldithiocarbamate esters
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The toxicity of N-methyldithiocarbamate may be mediated through decomposition to more biologically active compounds. Two principal products, CS2 and methyl isothiocyanate, have the potential to interact covalently with macromolecules in biological systems. In this investigation the ability of N-methyldithiocarbamate to generate methyl isothiocyanate and CS2 under physiological conditions resulting in acylation and covalent cross-linking of proteins was examined using 13C NMR and GC/MS. Two N-methyldithiocarbamate esters, S-methyl N-methyldithiocarbamate and (N-acetyl-S- methylthiocarbamoyl)cysteine, were also investigated to evaluate the acylating ability of sulfhydryl conjugates of N-methyldithiocarbamate. The predominant and most stable adduct produced by the free dithiocarbamate and its S-substituted esters was methylthiourea on ε-lysyl and N-terminal α- amino groups. Derivatization on N-terminal amino groups progressed more rapidly for the dithiocarbamate than for its mercapturate. Methylurea protein adducts were also produced by the dithiocarbamate and its esters, suggesting production of methyl isocyanate in the decomposition of N- methyldithiocarbamate. Covalent cross-linking of β-lactoglobulin by N- methyldithiocarbamate resulting from its decomposition to CS2 was observed using denaturing polyacrylamide gel electrophoresis. These results demonstrate the ability of a monoalkyldithiocarbamate to acylate protein amino groups and effect covalent cross-linking. These processes represent molecular mechanisms that may contribute to the toxicity of this class of compounds.
- Valentine,Amarnath,Amarnath,Graham
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- S-Methylation as a Bioactivation Mechanism for Mono- and Dithiocarbamate Pesticides as Aldehyde Dehydrogenase Inhibitors
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S-Methylation is a new bioactivation mechanism for metam and metabolites of methyl isothiocyanate and dazomet in mice. These soil fumigants are converted to S-methyl metam [MeNHC(S)SMe] which reaches peak levels in liver, kidney, brain, and blood 10-20 min after intraperitoneal (ip) treatment. The half-life of S-methyl metam administered ip is 8-12 min in each of these tissues. S-Methyl metam-oxon [MeNHC(O)SMe] is also detected as a metabolite of each of these soil fumigants on analysis by gas chromatography/mass spectrometry with chemical ionization. The conversion of methyl isothiocyanate to S-methyl metam and its oxon probably involves conjugation with glutathione, hydrolysis to S-(N-methylthiocarbamoyl)-cysteine, cleavage by cysteine conjugate β-lyase to release metam, and finally methylation and oxidative desulfuration. Metam and dazomet are converted to S-methyl metam by mouse liver microsomes on fortification with S-adenosylmethionine. Metam, methyl isothiocyanate, dazomet, and three metabolites (metam-oxon [MeNHC(O)SH], MeNHC(S)SMe, and MeNHC(O)SMe) administered ip to mice at 40 mg/kg inhibit low-Km liver mitochondrial aldehyde dehydrogenase and elevate ethanol-dependent blood and brain acetaldehyde levels. Several fungicides including the dialkyldithiocarbamates as the disulfide (thiram and the related alcohol-abuse drug disulfiram) and metal salts (ziram) also yield S-methyl thiocarbamate metabolites. Eight S-alkyl and S-(chloroallyl) thiocarbamate herbicides (EPTC, molinate, butylate, vernolate, pebulate, diallate, sulfallate, and triallate), but not their S-chlorobenzyl analog (thiobencarb), undergo sequential liberation of the thiocarbamic acid and then S-methylation, forming the S-methyl thiocarbamates which are new metabolites and potential aldehyde dehydrogenase inhibitors. The S-methyl mono- and dithiocarbamate metabolites of these herbicides and fungicides are easily identified by retention time on gas chromatography and by mass spectrometry giving [MH]+ plus [R1R2NCO]+ or [R1R2NCS]+, respectively, as the two major ions.
- Staub, Richard E.,Sparks, Susan E.,Quistad, Gary B.,Casida, John E.
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- Design, synthesis and biological evaluation of novel HSP70 inhibitors: N, N′-disubstituted thiourea derivatives
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As novel heat shock protein 70 (HSP70) inhibitors, N, N′-disubstituted thiourea derivatives were designed and synthesized based on the X-ray structure of the ATPase domain (nucleotide binding domain, NBD). An ATPase activity inhibition assay revealed that these compounds effectively inhibited HSP70 ATPase activity. The results revealed that the compounds 370/371/374/379/380//392/394/397/404/405 and 407 can inhibit the HSP70 ATPase turnover with high percentages of inhibition: 50.42, 38.46, 50.45, 44.12, 47.13, 50.50, 40.95, 65.36, 46.23, 35.78, and 58.37 in 200 μM, respectively. Significant synergies with lapatinib were observed for compound 379 and compound 405 in the BT474 breast cancer cell line. A structure-function analysis revealed that most of the thiourea derivatives exhibited cooperative action with lapatinib in the BT474 cancer cell line and the BT/LapR1.0 lapatinib-resistant cell line. HSP70 inhibitors may be developed as synergetic drugs in drug-resistant cancer therapy.
- Zeng, Yan-Qun,Cao, Rui-Yuan,Yang, Jian-Ling,Li, Xing-Zhou,Li, Song,Zhong, Wu
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- N-substituted Dithiocarbamates for the Treatment of Biological Disorders
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N-substituted dithiocarbamate esters in which the amine function bears a hydrogen are provides, as are methods for using the compounds in the treatment of cellular hyperproliferation and VCAM-1 mediated disease. Particularly provided is a method of treating a hyperproliferative disorder such as cancer comprising administering an antiproliferative agent in combination with a potentiating effective amount of a N-substituted dithiocarbamate ester. Also provided are methods of using the compounds in the treatment of VCAM-1 mediated diseases such as inflammation and carrdiovascular disease.
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