Ai Chun-Zhi, Liu Yong, Li Wei, Chen De-Meng, Zhu Xin-Xing, Yan Ya-Wei, Chen Du-Chu, Jiang Yi-Zhou
Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China.
Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, Guangdong, China.
PLoS One. 2017 Jun 19;12(6):e0179333. doi: 10.1371/journal.pone.0179333. eCollection 2017.
EGFR inhibitors, even with therapeutics superiorities in anticancer, can cause idiosyncratic pulmonary and hepatic toxicities that are associated with the reactive electrophile bioactivated by Cytochrome P450s (P450s). Until now, neither has the electrophilic intermediate been caught experimentally, nor has the subtle mechanism been declared. Herein, the underlying mechanism of bioactivation mediated by P450s was explored by DFT calculations for a case of EGFR inhibitor, Erlotinib. Based on the calculation and analysis, we suggest that with other metabolites, reactive electrophiles of Erlotinib: epoxide and quinine-imine, can be generated by several steps along the oxidative reaction pathway. The generation of epoxide needs two steps: (1) the addition of Erlotinib to Compound I (Cpd I) and (2) the rearrangement of protons. Whereas, quinine-imine needs a further oxidation step (3) via which quinone is generated and ultimately turns into quinine-imine. Although both reactive electrophiles can be produced for either face-on or side-on pose of Erlotinib, the analysis of energy barriers indicates that the side-on path is preferred in solvent environment. In the rate-determining step, e.g. the addition of Erlotinib to the porphyrin, the reaction barrier for side-on conformation is decreased in aqueous and protein environment compared with gas phase, whereas, the barrier for face-on pose is increased in solvent environment. The simulated mechanism is in good agreement with the speculation in previous experiment. The understanding of the subtle mechanism of bioactivation of Erlotinib will provide theoretical support for toxicological mechanism of EGFR inhibitors.
表皮生长因子受体（EGFR）抑制剂尽管在抗癌治疗方面具有优势，但可引发特异性肺毒性和肝毒性，这些毒性与细胞色素P450（P450s）生物活化产生的反应性亲电试剂有关。到目前为止，既没有通过实验捕获亲电中间体，也没有阐明其微妙机制。在此，通过密度泛函理论（DFT）计算，针对EGFR抑制剂厄洛替尼的案例，探究了由P450s介导的生物活化潜在机制。基于计算与分析，我们认为，与其他代谢产物一样，厄洛替尼的反应性亲电试剂：环氧化物和喹宁-亚胺，可沿氧化反应途径经几步反应生成。环氧化物的生成需要两步：（1）厄洛替尼与化合物I（Cpd I）加成；（2）质子重排。而喹宁-亚胺则需要进一步的氧化步骤（3），通过该步骤生成醌并最终转化为喹宁-亚胺。尽管对于厄洛替尼的正面或侧面构象都可产生这两种反应性亲电试剂，但能垒分析表明，在溶剂环境中，侧面途径更占优势。在速率决定步骤中，例如厄洛替尼与卟啉的加成反应，与气相相比，在水相和蛋白质环境中，侧面构象的反应能垒降低，而正面构象的能垒在溶剂环境中升高。模拟机制与先前实验中的推测高度吻合。对厄洛替尼生物活化微妙机制的理解将为EGFR抑制剂的毒理学机制提供理论支持。
