黄芩苷调控CYP3A表达影响环孢素人体药代动力学的机制

Baicalin monomer and Chinese medicine including baicalin as the main bioactive constituent are widely used in clinical therapy of many diseases, such as acute and chronic hepatitis. Cyclosporine is extensively metabolized by CYP3A and used in patients undergoing liver or renal transplantation as an immunosuppressant. Inhibition of CYP3A causes the variation of the plasma concentration, which in turn leads to unanticipated toxic reactions of cyclosporine. Little research is reported about baicalin’s effects on cyclosporine pharmacokinetics in human. Our earlier study showed that multiple doses of baicalin significantly decreased the expression and activity of CYP3A in rat liver. Based on that, we proposed that baicalin may represse the expression of CYP3A potentially through regulation of nuclear receptors including PXR, PPARα and FXR, decrease metabolism of cyclosporine and increase AUC in human. To test this hypothesis, we will employ the ChIP, qRT-PCR, western blot, luminescent assay and LC-MS to evaluate the effect of baicalin on cyclosporine pharmacokinetics in healthy volunteers and liver-transplant-patients, to explore the mechanism of CYP3A down-regulation induced by baicalin in HepG2 cells, primary human hepatocytes. The results of the study would be helpful for revealing the influence of baicalin on the CYP3A in human and providing direction on clinical reasonable application of baicalin and CYP3A substrate drugs.

黄芩苷及以其为主要活性成分的中药复方临床应用广泛，如辅助治疗急、慢性肝炎等。环孢素广泛用于肝、肾移植患者的治疗，CYP3A被抑制是其血药浓度升高产生毒性反应的重要原因。迄今关于黄芩苷对环孢素人体药动学的影响仍知之甚少。本研究前期结果提示黄芩苷多次给药可降低大鼠肝CYP3A的表达和活性。为此，我们提出假说：黄芩苷可能通过核受体PXR、PPARα、FXR等抑制CYP3A表达而减慢环孢素代谢，增加其AUC。为了验证这一假说，我们将通过HepG2细胞系、人原代肝细胞、人体试验，采用ChIP、qRT-PCR、Western blot、荧光素酶报告基因、LC-MS等手段，从分子、细胞、整体等多方面探讨黄芩苷对健康志愿者及肝移植病人环孢素药动学的影响，明确黄芩苷抑制CYP3A的分子调控机制。本研究将为揭示黄芩苷对人CYP3A的作用和机制奠定基础，为黄芩苷及CYP3A底物药物的临床合理应用提供新的思路。

本项目系统研究了黄芩苷对环孢素药动学的影响及机制。结果表明静脉多剂量给予黄芩苷（80 mg/kg，7 d）对大鼠体内环孢素的药动学参数无显著影响。黄芩苷（80、160 mg/kg，i.g.）单次和多次给药（7 d）可显著降低大鼠体内环孢素的暴露量；且多次灌胃给予黄芩苷（80 mg/kg）后大鼠肠道P-gp 表达显著上升。离体肠囊外翻实验表明，黄芩苷（10 μM）可显著抑制环孢素（10 μM）在大鼠小肠内的吸收；黄芩苷（2、10及20 μM）作用于MDCK-Pgp 细胞后P-gp 活性和蛋白表达水平显著增加。由此可知，大鼠灌胃给予黄芩苷可显著降低其体内环孢素暴露量，可能与黄芩苷抑制环孢素肠道吸收、上调肠道中P-gp的活性及表达有关。进一步的人体试验结果显示，健康志愿者单次合用黄芩苷（500 mg，p.o.）后体内环孢素（200 mg）的药动学参数无显著变化，表明单次口服合用黄芩苷不影响环孢素健康人体药动学。人体试验与动物实验不一致的主要原因可能与不同种属的肝脏、肠道中代谢酶及转运体的表达量存在较大差异等有关。本项目的研究结果可为临床合理制定环孢素给药方案提供理论依据。. 基于黄芩苷具有抗炎、抗氧化及免疫调节等多层次、多靶点的药理作用，我们进一步拓展了研究内容，探讨了黄芩苷对首发精神分裂症患者和精神分裂症小鼠模型阴性症状及认知障碍的改善作用。结果显示，与奥氮平单用组相比，合用黄芩苷可显著改善首发精神分裂症患者的阴性症状及认知障碍。此外，黄芩苷也可改善精神分裂症模型小鼠的情感障碍和非空间认知障碍。本研究可为精神分裂症辅助治疗提供新的思路和方向。