A Comparison of Calcium Aggregation and Ultracentrifugation Methods for the Preparation of Rat Brain Microsomes for Drug Metabolism Studies

Cytochrome P450 Enzyme-Mediated Enantioselective Biotransformation of Chiral Fungicide Tebuconazole in Earthworm

Tebuconazole is widely used in agricultural practices, leading to elevated residue levels in agricultural soils. However, its biotransformation and the ecotoxicological effects of the corresponding transformation products (TPs) remain insufficiently explored. To fill this research gap, the TPs of tebuconazole in an earthworm-soil system were identified by UHPLC-QTOF/MS combined with UHPLC-QLiT/MS. Six chiral TPs were tentatively identified, with four TPs detected in both earthworms and soil, while two TPs were found exclusively in earthworm. Significant enantioselectivity was observed for tebuconazole and five TPs in earthworms, involving cytochrome P450 enzyme-mediated hydroxylation and dechlorination. In vitro metabolism experiments using earthworm microsomes revealed that CYP1A2, CYP2J2, and CYP2E1 were involved in the hydroxylation pathway of tebuconazole. Molecular docking results confirmed that S-(+)-tebuconazole produced more hydroxylated transformation products than R-(-)-tebuconazole due to its lower binding energy with these enzymes. Predictions from the ECOSAR model indicated that hydroxylation was the most significant transformation pathway for reducing the toxicity of tebuconazole. These findings provide valuable insights into the environmental fate and risk assessment of tebuconazole at the enantiomeric level.

Pregnenolone 16α-carbonitrile negatively regulates hippocampal cytochrome P450 enzymes and ameliorates phenytoin-induced hippocampal neurotoxicity

The central nervous system is susceptible to the modulation of various neurophysiological processes by the cytochrome P450 enzyme (CYP), which plays a crucial role in the metabolism of neurosteroids. The antiepileptic drug phenytoin (PHT) has been observed to induce neuronal side effects in patients, which could be attributed to its induction of CYP expression and testosterone (TES) metabolism in the hippocampus. While pregnane X receptor (PXR) is widely known for its regulatory function of CYPs in the liver, we have discovered that the treatment of mice with pregnenolone 16α-carbonitrile (PCN), a PXR agonist, has differential effects on CYP expression in the liver and hippocampus. Specifically, the PCN treatment resulted in the induction of cytochrome P450, family 3, subfamily a, polypeptide 11 (CYP3A11), and CYP2B10 expression in the liver, while suppressing their expression in the hippocampus. Functionally, the PCN treatment protected mice from PHT-induced hippocampal nerve injury, which was accompanied by the inhibition of TES metabolism in the hippocampus. Mechanistically, we found that the inhibition of hippocampal CYP expression and attenuation of PHT-induced neurotoxicity by PCN were glucocorticoid receptor dependent, rather than PXR independent, as demonstrated by genetic and pharmacological models. In conclusion, our study provides evidence that PCN can negatively regulate hippocampal CYP expression and attenuate PHT-induced hippocampal neurotoxicity independently of PXR. Our findings suggest that glucocorticoids may be a potential therapeutic strategy for managing the neuronal side effects of PHT.