An Injured liver caused by Overdose of Acetaminophen has Altered Expression and Activities of P450 Enzymes and Associated Drug Efficacy During Liver Recovery and Regeneration
Acetaminophen (APAP)-induced liver injury (AILI) is the leading cause of acute liver failure in the United States. Alterations on therapeutic efficacy and adverse drug reactions (ADRs) in patients with AILI are not fully investigated. Our previous study showed that AILI could result in dose-dependent and immediate decreases in expression and activities of major hepatic drug-metabolizing cytochrome P450s (P450s) enzymes in mice. However, liver will go through regeneration after AILI. How P450-mediated drug metabolism alters during liver regeneration is unclear. The aim of the study was to investigate the alterations in expression and activities of major P450 enzymes and associated drug efficacy and ADRs during liver regeneration after AILI. Adult male C57BL6/J mice were treated with various doses of APAP at 0 (no damage control), 200 (mild damage and recoverable), 400 (severe damage but recoverable), and 600 mg/kg (life-threatening damage and unrecoverable). The mice were sacrificed at 24, 48, 72, and 96 hours after the APAP treatment. Severity of liver damage was detected by plasma levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and miR122, with further confirmation by H & E staining in liver tissue sections. The expression and activities of CYP1A2, 2B10, 2C29, 2E1, and 3A11 were measured by RT-PCR (mRNAs) and MS/MS quantification of probe drugs, respectively. Sedation efficacy of midazolam was monitored at different time points after APAP treatment at different doses. The levels of ALT and AST significantly increased at 24 hours after APAP treatment at 200 and 400 mg/kg but dropped back to normal levels at 72 and 96 hours. No mice treated with 600 mg/kg APAP could survive to 72 hours. The magnitude of liver damage was further confirmed by H & E staining. The major examined P450 enzymes showed significant decreases at 24 hours in gene expression and activity levels and recovered back to normal with the doses of 200 and 400, but not 600 mg/kg of APAP. The activities of examined major P450s are correlated with the levels of ALT, AST, and mir122. The alterations of CYP3A11 resulted in correlated changes in sedation efficacy as reflected by sleeping times with midazolam treatment. These results indicated that P450 expression and function could recover after mild and even severe, but not lethal AILI. Overall, these results suggest that ALT, AST, and miR122 are potential biomarkers for predicting how alterations in P450 activities can justify dose selection of other drugs for desired efficacy. Further studies are needed to confirm these findings in human patient populations with AILI and to understand the underlying molecular mechanisms mediating recovery of hepatic P450s during AILI.