Human pregnane X receptor (PXR) is critical for regulating the expression of key drug-metabolizing enzymes such as CYP3A and CYP2C. Our recent study revealed that treatment with rodent-specific PXR agonist pregnenolone-16α-carbonitrile (PCN) significantly induced hepatomegaly and promoted liver regeneration after two-thirds partial hepatectomy (PHx) in mice. However, it remains unclear whether PXR activation induces hepatomegaly and liver regeneration and simultaneously promotes metabolic function of the liver. Here, we investigated the metabolism activity of CYP1A2, CYP3A1/2 and CYP2C6/11 during PXR activation-induced liver enlargement and regeneration in rats after cocktail dosing of CYP probe drugs. For PCN-induced hepatomegaly, a notable increase in the metabolic activity of CYP3A1/2 and CYP2C6/11, as evidenced by the plasma exposure of probe substrates and the AUC ratios of the characteristic metabolites to its corresponding probe substrates. The metabolic activity of CYP1A2, CYP3A1/2 and CYP2C6/11 decreased significantly after PHx. However, PCN treatment obviously enhanced the metabolic activity of CYP2C6/11 and CYP3A1/2 in PHx rats. Furthermore, the protein expression levels of CYP3A1/2 and CYP2C6/11 in liver were up-regulated. Taken together, this study demonstrates that PXR activation not only induces hepatomegaly and liver regeneration in rats, but also promotes the protein expression and metabolic activity of the PXR downstream metabolizing enzymes such as CYP3A1/2 and CYP2C6/11 in the body.
The present study was aimed to evaluate the effects of amphiphilic copolymer micelles on six major hepatic cytochrome P450 (CYP) isoforms. A series of mPEG 2k -PCL x polymeric micelles (mPEG 2k -PCL 2k , mPEG 2k -PCL 3.5k , mPEG 2k -PCL 5k and mPEG 2k -PCL 10k ) ranging from 20 to 100 nm were prepared to investigate the inhibitory or inductive activities by in vitro incubations of rat liver microsomes and primary rat hepatocytes. Inhibition of these polymeric micelles on CYP1A2 , CYP2B1 , CYP2C6, CYP2C11 , CYP2D2 and CYP3A1/2 isoenzymes were observed above their critical micelle concentrations (>10 μg·mL −1 ) and in a concentration-dependent manner. The mPEG 2k -PCL 2k micelles showed the strongest inhibition of CYP1A2, followed by CYP2C11. The micelles with lower molecular weight PCL segment exhibited more potent inhibitory potential. Induction on CYP1A2, CYP2B1 and CYP3A1/2 activity (2.1–7.2-fold, 1.5–2.4-fold and 1.3–3.0-fold, respectively) were detected at all tested concentrations (0.1–1000 μg·mL −1 or 0.1–100 μg·mL −1 ). Accordingly, most of the mRNA levels were upregulated. As demonstrated in ex vivo fluorescence imaging results, the mPEG 2k -PCL x micelles mainly accumulated in the liver after intravenous administration. In conclusion, mPEG 2k -PCL x micelles can interfere with the normal metabolic function of CYP450s in vitro , indicating polymeric micelles as promising drug nano-carriers might cause micelle–drug interaction and the in vivo interaction deserves further investigation.
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