Abstract
Tissue-specific deletion of the gene for NADPH-cytochrome P450 reductase (CPR), the essential electron donor to all microsomal cytochrome P450 (P450/CYP) enzymes, in either liver or intestine leads to up-regulation of many P450 genes in the tissue with the Cpr deletion. Here, by studying the liver-specific Cpr-null (LCN) mouse, we examined whether an inter-organ regulatory pathway exists, such that a loss of hepatic CPR would cause compensatory changes in intestinal P450 expression and capacity for first-pass metabolism of oral drugs. We show for the first time that intestinal expression of CYP2B, 2C and 3A proteins was increased in LCN mice, by 2- to 3-fold, compared with wild-type (WT) mice, accompanied by significant increases in small intestinal (SI) microsomal lovastatin-hydroxylase activity and systemic clearance of oral lovastatin (at 5 mg/kg). Additional studies showed that the hepatic Cpr deletion, which caused large decreases in bile acid (BA) levels in liver, intestine, plasma and intestinal content, led to drastic decreases in the mRNA levels of intestinal fibroblast growth factor 15 (FGF15), a target gene of the BA receptor farnesoid X receptor (FXR). Furthermore, treatment of mice with FGF19 (the human counterpart of mouse FGF15) abolished the difference between WT and LCN mice in SI CYP3A levels, at 6 h after the treatment. Our findings reveal a previously unrecognized, direct role of intestinal FGF15/19 in the regulation of SI P450 expression, and may have profound implications for the prediction of drug exposure in patients with compromised hepatic P450 function.
- Cytochrome P450
- Regulation - physiological
- Regulation - transcriptional
- Nuclear receptors (AHR, PXR, CAR, FXR, etc.)
- The American Society for Pharmacology and Experimental Therapeutics