Abstract

Cytochrome P450 (CYP) 2E1 is implicated in a variety of chemically initiated hepatotoxicities, including alcoholic liver disease. These pathological conditions arise from increased production of reactive intermediates caused by elevated enzyme concentrations. Thus, the ability to detect enhanced CYP2E1 levels would aid in identifying individuals at high risk for xenobiotic-promoted liver injury. With this in mind, the present investigation assessed in vivochlorzoxazone metabolism and compared pharmacokinetic parameters with CYP2E1 expression in blood. Twenty-two subjects were recruited and divided into two groups, control subjects and alcohol abusers, based on responses to two screening questionnaires. Those individuals with higher survey scores, i.e. those who consumed alcohol more frequently, exhibited higher rates of chlorzoxazone metabolism. Indeed, a correlation (r = 0.66, p < 0.01) was obtained when scores were compared with the pharmacokinetic parameter AUC for chlorzoxazone. Lymphocyte microsomes isolated from blood samples obtained from these same individuals were subjected to immunoblot analyses to detect CYP2E1 levels. That lymphocytes contained CYP2E1 was confirmed by reverse transcription-polymerase chain reaction and sequence analysis of the cDNA. Quantification of immunoreactive bands revealed that levels of this P450 were 2.3-fold higher in alcoholics than in control subjects. This increase in lymphocyte CYP2E1 content in alcoholic subjects coincided with a 2.1-fold increase in chlorzoxazone clearance and a 2-fold decrease in the AUC for chlorzoxazone. Importantly, a correlation (r = 0.62,p < 0.01) was observed between CYP2E1 content in lymphocytes and chlorzoxazone clearance rates. Thus, monitoring lymphocyte CYP2E1 expression may provide a substitute for estimating hepatic activity of this P450.