Adaptive Hepatic and Intestinal Alterations in Mice after Deletion of NADPH-Cytochrome P450 Oxidoreductase (Cpr) in Hepatocytes

Abstract

Cytochrome P450 enzymes (P450) play an important role in firstpass metabolism in both the intestine and liver. NADPH-cytochrome P450 oxidoreductase (Cpr) is an essential electron transfer protein required for microsomal P450 activity. Mice with conditional knockout of Cpr in hepatocytes develop normally and survive even with complete loss of liver microsomal P450 activity. Our current studies were performed to determine whether alternative drugmetabolizing pathways increase in an attempt to maintain wholebody homeostasis. In addition to the liver, Cpr is mainly expressed in tissues such as lung, kidney, and gastrointestinal tract. In livers of H-Cpr-null mice, there is a marked increase in mRNA expression of phase I enzymes (Aldh1a1, 1a7, 3a2; Ces1b2, 2a6, and 2a12), antioxidant enzymes (Ho-1, Nqo1, and epoxide hydrolase), phase II enzymes (Ugt1a9; Gsta1/2, m3, m4, m6, t1, and t3; and Sult1a1 and 1d1), and drug transporters (Oatp1a4, Oct3, Mate1, Mdr1a, and Mrp3 and 4). In addition, glucuronide-conjugated bilirubin concentrations are doubled in serum of H-Cpr-null mice. Both constitutive androstane receptor (CAR) and nuclear factor erythroid 2-related factor 2 (Nrf2) protein in nuclei are higher in the livers of H-Cpr-null mice, indicating that CAR and Nrf2 are activated. In the small intestine of H-Cpr-null mice, mRNA expression of Cyp3a11 and Mdr1a, two genes critical for intestinal first-pass metabolism, are markedly up-regulated. In addition, nutrient (Pept1) and cholesterol (Npc1l1) transporters are induced in the small intestine of H-Cpr-null mice. In conclusion, in H-Cpr-null mice, adaptive regulation of alternative detoxification genes in liver and small intestine appear to partially compensate for the loss of microsomal P450 function in liver.

Contributions of Hepatic and Intestinal Metabolism to the Disposition of Niclosamide, a Repurposed Drug with Poor Bioavailability

“…2). A previous study has also reported that there was a small increase in UGT1A1 mRNA expression in the livers of the LCN mice (Cheng et al, 2014). It remains to be determined whether other niclosamide-metabolizing UGT enzymes are induced in the livers of the IECN mice and would explain the observed increases in microsomal niclosamide glucuronidation (Fig.…”

GC-MS Profile of Hua-Feng-Dan and RNA-Seq Analysis of Induced Adaptive Responses in the Liver

“…Two-dimensional clustering analysis of DEGs showed that Hua-Feng-Dan upregulated genes of cellular function, signal regulation, and circadian and signal regulation and reduced the expression of genes related to Phase-I, II, and III xenobiotic metabolism, endogenous metabolism, disease traits, and immune modulation, all pointing toward adaptive responses. For example, induction of Cyp2a4 plays roles in circadian regulation and liver detoxification ( Zhao et al, 2019 ); induction of Cyp4a14 may contribute to increased resistance to oxidative stress ( Sobocanec et al, 2010 ); induction of Fgf21 plays a role in nonalcoholic fatty liver disease (NAFLD) in humans and limits hepatotoxicity in mice ( Desai et al, 2017 ); Gm3776 is a CAR-target gene in liver of mice as an adaptive response to xenobiotics ( Cui and Klaassen, 2016 ); metallothioneins (Mt2) are sulfhydryl-rich small proteins for heavy metal detoxification and free radical scavenging ( Klaassen et al, 1999 ); glutathione S-transferase A1 (Gsta1) is a phase II enzyme playing adaptive against toxic stimuli ( Cheng et al, 2014 ); interleukin-1 receptor antagonist (Il1rn) is a member of the interleukin 1 cytokine family, inhibits the activities of interleukin 1α (IL-1α) and interleukin 1β (IL1-β), and prevents IL-1β overexpression during inflammatory responses ( Meier et al, 2019 ); and early growth response 1 (Egr1) is an important acute-phase adaptive protein ( Magee and Zhang, 2017 ). Upregulation of these genes points toward the adaptive machinery which is activated by Hua-Feng-Dan in an attempt to program the liver to produce hepatoprotective effects.…”

Effects of Diminished NADPH:cytochrome P450 Reductase in Human Hepatocytes on Lipid and Bile Acid Homeostasis

“…In liver specific Por knockdown mice gene expression phenotypes are ascribed to activation of CAR, SREBP, PPARγ and Nrf1 and repression of PPARα and FXR ( Wang et al, 2005 ; Weng et al, 2005 ; Cheng et al, 2014a ). This results in an induction of alternative detoxification enzymes in liver and the small intestine, which appears to partially compensate for the loss of microsomal P450 function.…”