Epoxide formation from diallyl sulfone is associated with CYP2E1 inactivation in murine and human lungs

We tested the hypothesis that an epoxide formed from diallyl sulfone (DASO( 2)) is responsible for inactivation of CYP2E1 in murine and human lungs. An epoxide (1,2-epoxypropyl-3,3'-sulfonyl-1'-propene [DASO(3)]) was synthesiz ed from DASO(2) and conjugated with glutathione (GSH) to produce the conjug ates S-(1R,S-[[1-hydroxymethyl-2,3' -sulfonyl]-1'-propenyl]ethyl)glutathion e (diastereomers) and S-(1-[[2R,S-hydroxypropyl]-3,3'-sulfonyl]-1'-propenyl )glutathione (diastereomers), Analysis of these conjugates by high performa nce liquid chromatography revealed a major peak eluting at 20.5 min, This p eak was detected in incubations of murine and human lung microsomes contain ing DASO(2) and nicotinamide adenine dinucleotide phosphate (NADPH), and wa s not detected in incubations performed in the absence of DASO(2) or NADPH. The amounts of epoxide-derived GSH conjugates formed in the incubations we re concentration-dependent and achieved saturation at 0.75 mM DASO(2), Form ation of the conjugates was also time-dependent and peaked at 2.0 h after D ASO(2). The peak containing the GSH conjugates was also detected in incubat ions of CYP2E1-expressed lymphoblastoid microsomes, NADPH, and DASO(2), Max imal amounts of DASO(3), as estimated by formation of a 4-(p-nitrobenzyl)py ridine derivatized product, were detected in murine lung microsomes incubat ed for 35 min with 1 mM DASO(2), The derivatized DASO(3) was not detectable in incubations of human lung microsomes. p-Nitrophenol hydroxylation, a ca talytic activity associated with CYP2E1, was reduced in murine and human lu ng microsomes incubated with DASO(2), with decreases that were concentratio n-dependent. Dose-dependent decreases in hydroxylase activity were also fou nd in microsomes from mice treated in vivo with DASO(2) (25 to 200 mg/kg), These results supported the premise that an epoxide formed from DASO(2) med iates inactivation of lung CYP2E1, Furthermore, the findings suggested that the mouse model is relevant for studies of DASO(2) in human lung.