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Chlorzoxazone-based One-Sample Method for Estimating In Vivo CYP2E1 Activity in Mice
Cunzhen Zhang1, Rui Yang1, Jun Ma1
1Institute of Clinical Pharmacology, School of Basic Medical Sciences, Zhengzhou University; Zhengzhou, 450001, China.
Introduction:
Cytochrome P450 2E1 (CYP2E1) plays a crucial role in metabolism and disease, making it highly significant to establish a simpler, sensitive method for evaluating its in vivo activity compared to traditional pharmacokinetic (PK) parameters.
Methods:
A high-performance liquid chromatography-ultraviolet (HPLC-UV) method was developed and validated for determining chlorzoxazone (CZX) and its metabolite 6-hydroxy CZX (6-OH CZX) in plasma. Four mouse models with distinct CYP2E1 activity were constructed: high activity induced by isoniazid, and low activity via Q11 (a CYP2E1 inhibitor), Cyp2e1 knockout, or carbon tetrachloride (CCl₄). PK experiments were conducted, with activity changes verified by in vitro CYP2E1 protein expression and microsomal activity. Additionally, the sensitivity of PK parameters and the plasma 6-OH CZX/CZX ratio (metabolite ratio, MR) for characterizing CYP2E1 activity, as well as correlations between MR at different time points and both microsomal CYP2E1 activity and CZX half-life (t₁/₂), were analyzed.
Results:
The HPLC-UV method met analytical requirements in terms of specificity, linearity, and intra-day and inter-day precision. Microsomal activity and protein expression experiments confirmed the successful establishment of the four models. For CYP2E1 activity characterization, CZX t₁/₂ was more sensitive than its area under the curve (AUC) and clearance (CL); MR values at 15 and 7 minutes outperformed those at 2 minutes, with 15-minute MR showing stronger correlations with microsomal activity (r = 0.57, P = 0.007) and CZX t₁/₂ (r = 0.83, P < 0.01).
Discussion:
This study addresses limitations of traditional PK parameters (multiple samplings, non-metabolic interference) and existing MR methods (unclear optimal time points). The 15-min MR and CZX t₁/₂ offer simplified evaluation, with CZX's high CYP2E1 specificity enhancing translation. Limitations include focus on male C57BL/6J mice and single-point MR's inability to reflect dynamic activity.
Conclusion:
Four representative mouse models with distinct CYP2E1 activity were successfully constructed. CZX t₁/₂ exhibits higher sensitivity and applicability in characterizing in vivo CYP2E1 activity changes, while the 15-minute MR better represents activity changes. This research lays a foundation for characterizing CYP2E1 variations in disease and pathological processes.
