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Ethnopharmacological Relevance: Shengmai San (SMS) has been commonly used as a traditional Chinese medicine for the treatment of cardiovascular disorders, of which drug interactions need to be assessed for the safety concern. There is little evidence for the alterations of hepatic and intestinal drug-metabolizing enzymes after repeated SMS treatments to assess drug interactions., Aim of the Study: The studies aim to illustrate the effects of repeated treatments with SMS on cytochrome P450s (CYPs), reduced nicotinamide adenine dinucleotide (phosphate)-quinone oxidoreductase (NQO), uridine diphosphate-glucuronosyltransferase (UGT), and glutathione S-transferase (GST) using in vivo rat model., Materials and Methods: The SMS was prepared using Schisandrae Fructus, Ginseng Radix, and Ophiopogonis Radix (OR) (1:2:2). Chromatographic analyses of decoctions were performed using ultra-performance liquid chromatography (UPLC) and LC-mass spectrometry. Sprague-Dawley rats were orally treated with the SMS and its component herbal decoctions for 2 or 3 weeks. Hepatic and intestinal enzyme activities were determined. CYP3A expression and the kinetics of intestinal nifedipine oxidation (NFO, a CYP3A marker reaction) were determined., Results: Schisandrol A, schisandrin B, ginsenoside Rb1 and ophiopogonin D were identified in SMS. SMS selectively suppressed intestinal, but not hepatic, NFO activity in a dose- and time-dependent manner. Hepatic and intestinal UGT, NQO and GST activities were not affected. A 3-week SMS treatment decreased the maximal velocity of intestinal NFO by 50%, while the CYP3A protein level remained unchanged. Among SMS component herbs, the decoction of OR decreased intestinal NFO activity., Conclusions: These findings demonstrate that 3-week treatment with SMS and OR suppress intestinal, but not hepatic CYP3A function. It suggested that the potential interactions of SMS with CYP 3A drug substrates should be noticed, especially the drugs whose bioavailability depends heavily on intestinal CYP3A., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The hepatotoxin, safrole is a methylenedioxy phenyl compound, found in sassafras oil and certain other essential oils. Recombinant cytochrome P450 (CYP, P450) and human liver microsomes were studied to investigate the selective inhibitory effects of safrole on human P450 enzymes and the mechanisms of action. Using Escherichia coli-expressed human P450, our results demonstrated that safrole was a non-selective inhibitor of CYP1A2, CYP2A6, CYP2D6, CYP2E1, and CYP3A4 in the IC(50) order CYP2E1 < CYP1A2 < CYP2A6 < CYP3A4 < CYP2D6. Safrole strongly inhibited CYP1A2, CYP2A6, and CYP2E1 activities with IC(50) values less than 20 microM. Safrole caused competitive, non-competitive, and non-competitive inhibition of CYP1A2, CYP2A6 and CYP2E1 activities, respectively. The inhibitor constants were in the order CYP1A2 < CYP2E1 < CYP2A6. In human liver microsomes, 50 microM safrole strongly inhibited 7-ethoxyresorufin O-deethylation, coumarin hydroxylation, and chlorzoxazone hydroxylation activities. These results revealed that safrole was a potent inhibitor of human CYP1A2, CYP2A6, and CYP2E1. With relatively less potency, CYP2D6 and CYP3A4 were also inhibited.

Rutaecarpine is one of the main alkaloids of an herbal remedy, Evodia rutaecarpa, which has been used for the treatment of gastrointestinal disorder and headache. Effects of rutaecarpine on hepatic and renal cytochrome P450 (CYP)-dependent monooxygenase were studied in C57BL/6J mice. Treatment of mice with rutaecarpine by gastrogavage at 50 mg/kg/day for three days resulted in 57%, 41%, 6-, and 6-fold increases of hepatic microsomal benzo(a)pyrene hydroxylation, 7-ethoxycoumarin O-deethylation, 7-ethoxyresorufin O-deethylation, and 7-methoxyresorufin O-demethylation activities, respectively. However, the treatment had no effects on hepatic oxidation activities toward benzphetamine, N-nitrosodimethylamine, nifedipine, and erythromycin. In the kidney, rutaecarpine-treatment resulted in 2-fold and 42% increases of microsomal benzo(a)pyrene hydroxylation and 7-ethoxycoumarin O-deethylation activities, respectively. The treatment also increased renal 7-ethoxyresorufin O-deethylation activity to a detectable level. Immunoblot analysis of microsomal proteins showed that rutaecarpine-treatment increased the protein levels of CYP1A1 and CYP1A2 in the liver, whereas hepatic level of CYP3A-immunoreacted protein was not affected by rutaecarpine. These CYPs were not detectable in the immunoblot analyses of control and rutaecarpine-treated mouse kidney microsomes. These results indicated that rutaecarpine was a CYP1A inducer and showed potent inductive effects on both CYP1A1 and CYP1A2 in the liver.

Aflatoxin B1 (AFB1) must be activated to the electrophilic AFB1 exo-8,9-epoxide to be genotoxic and carcinogenic. A role for epoxide hydrolase in detoxication has been suggested but never directly addressed. In light of recent studies determining the instability of AFB1 exo-8,9-epoxide in H2O, a role for epoxide hydrolase appears dubious. Rat liver or recombinant rat epoxide hydrolase provided an enhancement to the already fast hydrolysis rate of up to 22%. Purified human epoxide hydrolase provided no detectable enhancement to the rate of chemical hydrolysis. Some reduction in the genotoxicity of AFB1 was observed when the ratio of rat epoxide hydrolase to cytochrome P450 was high (approximately 50-fold). An 80-fold excess of human epoxide hydrolase over cytochrome P450 only produced an effect of approximately 25% inhibition. It appears, therefore, that there is little evidence to support a role for epoxide hydrolase in the detoxication of AFB1.

Alfentanil, sufentanil, and fentanyl are synthetic opioids that are metabolized by oxidative N-dealkylation in the liver. We have previously shown that cytochrome P-450 3A4 (CYP3A4) contributes significantly to human liver microsomal alfentanil oxidation. Since identification of specific drug-metabolizing enzymes allows prediction of the variables affecting drug metabolism, the purpose of the present study was to identify the P-450 enzymes responsible for sufentanil and fentanyl metabolism in human liver microsomes. Microsomal preparations fortified with a reduced nicotinamide-adenine dinucleotide phosphate-generating system were incubated with 0.25 microM 3H-fentanyl or 3H-sufentanil. Rates of N-dealkylated metabolite formation significantly correlated with nifedipine oxidation activity (a marker of CYP3A4 activity) for fentanyl and sufentanil (r = 0.93 and 0.87, n = 18, respectively), but not with the oxidation activity for ethoxyresorufin (CYP1A2), S-mephenytoin (CYP2C19), bufuralol (CYP2D6), or chlorzoxazone (CYP2E1). Gestodene and troleandomycin (chemical inhibitors of CYP3A4) and antibody to CYP3A4 inhibited N-dealkylation of fentanyl and sufentanil. Chemical inhibitors of CYP2C, 2E1, and 2D6 did not inhibit N-dealkylation of fentanyl and sufentanil. Recombinant CYP3A4 expressed in Escherichia coli showed N-dealkylation activity of fentanyl and sufentanil, while expressed CYP1A2, 2C10, and 2E1 enzymes did not. We conclude that CYP3A4 is responsible for fentanyl and sufentanil N-dealkylation in vitro.

Pretreatments of freshwater fish tilapia, Oreochromis niloticus x O. aureus, with 3-methylcholanthrene (3-MC) and polychlorinated biphenyls (PCBs) increased liver microsomal cytochromes P450 (P450) and b5 contents, benzo[a]pyrene hydroxylation, and 7-ethoxyresorufin and 7-ethoxycoumarin O-dealkylations. The pretreatments also increased gill microsomal benzo[a]pyrene and 7-ethoxyresorufin oxidations. Immunoblot analysis of liver and gill microsomes revealed that 3-MC and PCBs induced a protein recognized by the mouse monoclonal antibody (MAb) 1-12-3 against scup P450 1A1. Northern analysis of liver and gill RNA showed that 3-MC and PCBs increased the intensity of 2.9-kb- and 1.5-kb-sized mRNA bands hybridizable to a trout P450 1A1 cDNA probe. Pretreatment with phenobarbital was without effects on the monooxygenase activity or protein or mRNA levels in liver and gill. A 3-MC-inducible P450 hemoprotein (M(r) = 59,000) and a NADPH-cytochrome P450 reductase flavoprotein (M(r) = 74,000) were purified from liver microsomes. The tilapia P450 hemoprotein showed an absorption maximum at 447 nm in CO-difference spectrum and a strong immunoreactivity with MAb 1-12-3. A reconstituted tilapia monooxygenase system consisting of P450 and NADPH-cytochrome P450 reductase was effective in the catalysis of 7-ethoxyresorufin, benzo[a]pyrene, and 7-ethoxycoumarin oxidations, but not in N-nitrosodimethylamine demethylation. These results show that 3-MC and PCBs can induce P450 1A1 in tilapia liver and gill and the tilapia P450 is highly similar to other teleost P450 1A1 with respect to spectral, immunochemical, and catalytic properties.

The effects of acetone on liver, kidney, and lung monooxygenases were studied using hamsters administered 8% acetone in drinking water. Binding of aniline to liver microsomes induced a type II difference spectrum, and the spectral binding was enhanced in hamsters pretreated with acetone. Administration of acetone caused significant increases of cytochrome P-450 and cytochrome b5 contents in liver microsomes. The increases of the hemeproteins were associated with induction of monooxygenase activities toward test substrates, aniline, N-nitrosodimethylamine, benzphetamine, benzo(a)pyrene, and 7-ethoxycoumarin. In the kidneys, acetone administration increased microsomal contents of the hemeprotein and monooxygenase activities toward aniline. N-nitrosodimethylamine, and 7-ethoxycoumarin, but not benzphetamine or benzo(a)pyrene. In the lungs, acetone pretreatment increased aniline hydroxylase activity without affecting the levels of N-nitrosodimethylamine demethylase, cytochromes P-450 and b5. In marked contrast to the inductive effects in the liver, acetone administration markedly decreased lung microsomal benzo(a)pyrene hydroxylase and 7-ethoxycoumarin O-deethylase activities. Gel electrophoresis of liver and kidney microsomes from control and acetone-treated hamsters revealed that acetone treatment enhanced the intensity of a protein band(s) in the cytochrome P-450 molecular weight region. Immunoblotting of the microsomal proteins showed that the protein band induced by acetone in hamster liver, kidney and lung was cross-reactive with antibody raised against ethanol-inducible human liver cytochrome P-450. These results demonstrate that acetone has the ability to uniformly induce a specific form of cytochrome P-450, designated as IIE1, and to cause differential changes of monooxygenase activities in the hamster tissues.(ABSTRACT TRUNCATED AT 250 WORDS)