PULMONARY CYP2E1 BIOACTIVATES 1,1-DICHLOROETHYLENE IN MALE AND FEMALEMICE

Pulmonary cytotoxicity induced by 1,1-dichloroethylene (DCE) has been linked to the generation of reactive intermediates through a cytochrom e P450-dependent pathway. In the present studies, our objectives were to investigate and compare cytochrome P450 isozyme-selective bioactiva tion of DCE in vitro in the lungs of male and female mice. Our results showed that CYP2E1-dependent p-nitrophenol hydroxylation was signific antly higher in microsomes from female (0.45 +/- 0.01 nmol/mg protein/ min) than from male (0.38 +/- 0.02 nmol/mg protein/min) mice. Lung mic rosomes from male mice incubated in the presence of an NADPH-generatin g system and increasing amounts of DCE (5-20 mM) exhibited correspondi ng decreases in p-nitrophenol hydroxylase activity (19%-50%); however, greater decreases (26%-70%) were observed in lung microsomes from fem ale mice incubated under the same conditions. In contrast, alterations in CYP2B1-dependent 7-pentoxyresorufin O-dealkylation and CYP1A1-depe ndent 7-ethoxyresorufin O-dealkylation were not detected in any micros omal preparation incubated with DCE. Reaction with an anti-CYP2E1 anti body abolished the inhibition of p-nitrophenol hydroxylation by DCE. P rotein immunoblotting revealed significant decreases in the intensity of the bands of microsomal samples incubated previously with DCE; in c ontrast, alterations in heme content were not evoked by reaction with DCE. Our results have demonstrated that CYP2E1, and not CYP2B1 or CYP1 A1, mediated the bioactivation of DCE. Furthermore, this bioactivation occurred to a greater extent in lung microsomes from female than from male mice, which suggests that females may be at slightly greater ris k for DCE-induced pneumotoxicity.