Glutathione carbamoylation with S-methyl N,N-diethylthiolcarbamate sulfoxide and sulfone. Mitochondrial low Km aldehyde dehydrogenase inhibition and implications for its alcohol-deterrent action.
S-Methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) and sulfone (DETC-MeSO2) both inhibit rat liver low Km aldehyde dehydrogenase (ALDH2) in vitro and in vivo (Nagendra et al., Biochem Pharmacol 47: 1465-1467, 1994). DETC-MeSO has been shown to be a metabolite of disulfiram, but DETC-MeSO2 has not. Studies were carried out to further investigate the inhibition of ALDH2 by DETC-MeSO and DETC-MeSO2. In an in vitro system containing hydrogen peroxide and horseradish peroxidase, the rate of DETC-MeSO oxidation corresponded to the rate of DETC-MeSO2 formation. Carbamoylation of GSH by both DETC-MeSO and DETC-MeSO2 was observed in a rat liver S9 fraction. Carbamoylation of GSH was not observed in the presence of N-methylmaleimide. In in vitro studies, DETC-MeSO and DETC-MeSO2 were equipotent ALDH2 inhibitors when solubilized mitochondria were used, but DETC-MeSO was approximately four times more potent than DETC-MeSO2 in intact mitochondria. In studies with rats, the dose (i.p. or oral) required to inhibit 50% ALDH2 (ED50) was 3.5 mg/kg for DETC-MeSO and approximately 35 mg/kg for DETC-MeSO2, approximately a 10-fold difference. Furthermore, maximum ALDH2 inhibition occurred 1 hr after DET(-MeSO administration, whereas maximal ALDH2 inhibition occurred 8 hr after DETC-MeSO2 dosing. DETC-MeSO is, therefore, not only a more potent ALDH2 inhibitor than DETC-MeSO2 in vivo, but also in vitro when intact mitochondria are utilized. The in vitro results thus support the in vivo findings. Since oxidation of DETC-MeSO can occur both enzymatically and non-enzymatically, it is possible that DETC-MeSO2 is formed in vivo. DETC-MeSO2, however, is not as effective as DETC-MeSO in inhibiting ALDH2, probably because it has difficulty penetrating the mitochondrial membrane. Thus, even if DETC-MeSO2 is formed in vivo from DETC-MeSO, it is the metabolite DETC-MeSO that is most likely responsible for the inhibition of ALDH2 after disulfiram administration.
Ningaraj
N S
NS
Department of Pharmacology and Toxicology, University of Kansas, Lawrence 66045, USA.
Schloss
J V
JV
Williams
T D
TD
Faiman
M D
MD
D000444:Aldehyde Dehydrogenase / Q000037:antagonists & inhibitors*; D000818:Animals; D004050:Ditiocarb / Q000031:analogs & derivatives* / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D000431:Ethanol / Q000037:antagonists & inhibitors; D005978:Glutathione / Q000378:metabolism*; D006735:Horseradish Peroxidase; D007700:Kinetics; D016014:Linear Models; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D051381:Rats
D004791:Enzyme Inhibitors; C087204:S-methyl-N,N-diethylthiolcarbamate sulfone; C073220:S-methyl N,N-diethylthiolcarbamate sulfoxide; D000431:Ethanol; D004050:Ditiocarb; D006735:Horseradish Peroxidase; D000444:Aldehyde Dehydrogenase; D005978:Glutathione