Zamora Francisco Gonzales, Bigelow Hannah, Yang Hong, Jimenez Tania Perez
Animal Clinic Veterinary Hospital, Lima, Peru.
Relief Veterinarian, Sahuarita, AZ, United States.
Front Vet Sci. 2025 Jul 22;12:1511341. doi: 10.3389/fvets.2025.1511341. eCollection 2025.
Cytochrome P450 (CYP) 1A2 plays a key role in the metabolism of various drugs in dogs. However, the impact of genetic variation on differences in CYP1A2 metabolism among dogs remains unclear. Recent studies have identified variability in the copy number of the CYP1A2 gene, ranging from two to five copies. Additionally, a genetic polymorphism (stop codon) has been identified which results in the expression of an inactive protein, this has been investigated and changes in the pharmacokinetics of some clinically used drugs have been described. If these additional copies are functional, dogs with more CYP1A2 gene copies may exhibit faster drug clearance, potentially affecting appropriate drug dosing. To investigate this possibility, a well-characterized dog liver bank ( = 58) was analyzed to determine whether CYP1A2 copy number variation (CNV) correlates with CYP1A2 protein levels and enzyme activity. Real-time PCR was used to assess CYP1A2 CNV, while label-free mass spectrometry measured CYP1A2 protein concentration in liver microsomes. Theobromine N-3 demethylation was examined as a marker of canine CYP1A2 activity using commercially available recombinant CYPs and liver microsomes from dogs treated with isoform-selective enzyme inducers. Only CYP1A1 and CYP1A2 demonstrated the ability to catalyze theobromine N-3 demethylation, and this activity was induced exclusively by β-naphthoflavone. Liver microsome theobromine N-3 demethylation activity showed a moderate correlation with CYP1A2 protein levels ( = 0.46; = 0.0003). Among the 58 liver samples genotyped for CYP1A2 CNV, nine dogs had two copies, 20 had three copies, 23 had four copies, and six had five copies. However, CYP1A2 CNV did not significantly correlate with CYP1A2 protein concentration ( = -0.14; = 0.30) and showed a weak negative correlation with theobromine N-3 demethylation activity ( = -0.45; = 0.00035). These findings suggest that CYP1A2 CNV is not a strong predictor of increased CYP1A2 protein expression or activity. According to the literature, CNV might not be relevant, but the genetic polymorphism (stop codon) could potentially be. The studies available show relationships between the stop codon and protein inactivity in the metabolizing of clinically used drugs. Further studies are necessary to validate these preliminary results.
细胞色素P450（CYP）1A2在犬类多种药物的代谢中起关键作用。然而，基因变异对犬类中CYP1A2代谢差异的影响仍不清楚。最近的研究已确定CYP1A2基因拷贝数存在变异性，范围从两个拷贝到五个拷贝。此外，还发现了一种基因多态性（终止密码子），其导致无活性蛋白的表达，对此已进行了研究，并描述了一些临床使用药物的药代动力学变化。如果这些额外的拷贝具有功能，那么具有更多CYP1A2基因拷贝的犬可能表现出更快的药物清除率，这可能会影响适当的药物剂量。为了研究这种可能性，对一个特征明确的犬肝脏库（n = 58）进行了分析，以确定CYP1A2拷贝数变异（CNV）是否与CYP1A2蛋白水平和酶活性相关。使用实时PCR评估CYP1A2 CNV，同时采用无标记质谱法测量肝微粒体中CYP1A2蛋白浓度。使用市售重组CYP和经同工型选择性酶诱导剂处理的犬的肝微粒体，检测可可碱N-3去甲基化作为犬CYP1A2活性的标志物。只有CYP1A1和CYP1A2表现出催化可可碱N-3去甲基化的能力，并且这种活性仅由β-萘黄酮诱导。肝微粒体可可碱N-3去甲基化活性与CYP1A2蛋白水平呈中度相关（r = 0.46；P = 0.0003）。在对58个肝脏样本进行CYP1A2 CNV基因分型中，9只犬有两个拷贝，20只犬有三个拷贝，23只犬有四个拷贝，6只犬有五个拷贝。然而，CYP1A2 CNV与CYP1A2蛋白浓度无显著相关性（r = -0.14；P = 0.30），并且与可可碱N-3去甲基化活性呈弱负相关（r = -0.45；P = 0.00035）。这些发现表明，CYP1A2 CNV不是CYP1A2蛋白表达或活性增加的有力预测指标。根据文献，CNV可能无关，但基因多态性（终止密码子）可能有潜在关联。现有研究表明了终止密码子与临床使用药物代谢中蛋白无活性之间的关系。需要进一步研究来验证这些初步结果。
