Bioactivation mechanism of S-(3-oxopropyl)-N-acetyl-L-cysteine, the mercapturic acid of acrolein.
S-(3-Oxopropyl)glutathione, the glutathione conjugate of acrolein, has been reported to be nephrotoxic. The objective of the present studies was to investigate the bioactivation mechanism of the analogues S-(3-oxopropyl)-N-acetyl-L-cysteine (1) and S-(3-oxopropyl)-N-acetyl-L-cysteine S-oxide (2) and to test the hypothesis that the cytotoxicity of 1 is associated with its latent potential to release acrolein in kidney cells. Mechanistic considerations indicated that sulfoxidation of sulfide 1 to form S-oxide 2 and a subsequent general-base-catalyzed beta-elimination reaction would release the cytotoxin acrolein. Hence the release of acrolein from 1 and 2 was studied in chemical systems, and their cytotoxicity was investigated in cultured LLC-PK1 cells and in isolated rat renal proximal tubular cells. Acrolein formation from S-oxide 2, but not from sulfide 1, was observed under basic conditions and with phosphate as the base. Kinetic analysis indicated that a general-base-catalyzed reaction was involved. Both S-conjugates 1 and 2 were cytotoxic in LLC-PK1 cells and in isolated rat renal proximal tubular cells, and the cytotoxicity of sulfide 1, but not of S-oxide 2, in isolated renal proximal tubular cells was reduced in presence of methimazole, an inhibitor of the flavin-containing monooxygenase. These findings indicate that the cytotoxicity of S-conjugate 1 is associated with a novel bioactivation mechanism that involves sulfoxidation followed by a general-base-catalyzed elimination of acrolein from S-oxide 2.
Hashmi
M
M
Department of Pharmacology, University of Rochester, New York 14642.
Vamvakas
S
S
Anders
M W
MW
D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000378:metabolism; D000171:Acrolein / Q000378:metabolism*; D000818:Animals; D001711:Biotransformation; D002384:Catalysis; D002470:Cell Survival / Q000187:drug effects; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D006899:Mixed Function Oxygenases / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344
C076175:S-(3-oxopropyl)-N-acetylcysteine; D000171:Acrolein; D006899:Mixed Function Oxygenases; D000111:Acetylcysteine