Mechanisms of adverse effects of anti-tuberculosis drugs

描述(申请人提供)：药物性肝损伤是抗结核(TB)化疗的一个主要安全问题。我们研究的长期目标是改善抗结核病药物的安全性。该应用的目的是确定利福平和异烟肼联合治疗所致肝损伤的机制。先前已经进行了广泛的研究来研究利福平和异烟肼对小鼠或大鼠的肝损伤；然而，这些研究都没有模拟人类的肝毒性。啮齿动物和人类对利福平和/或异烟肼的反应存在物种差异。孕烷X受体(PXR)是一种转录因子，调节参与外源和内源代谢的基因网络。化学物质激活PXR的能力因物种而异。利福平是一种人特异性PXR激活剂，对人PXR有很强的激活作用，但对小鼠PXR的作用很弱。为了克服配体依赖的PXR激活的物种差异，我们建立了PXR人源化的小鼠模型。通过使用这些PXR人源化的小鼠，我们注意到利福平和异烟肼诱导的肝损伤是人类PXR依赖的。然而，利福平介导的PXR激活不会改变异烟肼的代谢。通过使用代谢组学的方法，我们发现利福平和异烟肼联合治疗引起原卟啉IX(PP-IX)的蓄积，特别是在肝脏，这是人类PXR依赖的。PP-IX是一种合成卟啉的中间体，先前的研究表明PP-IX具有肝毒性。根据我们的初步数据和以前的报道，我们假设利福平和异烟肼联合治疗干扰了卟啉的合成，PP-IX在肝脏中的积聚介导了肝脏毒性。为了验证我们的假设，我们将追求以下两个具体目标：(1)确定利福平和异烟肼联合治疗所致肝损伤中的毒性介质(S)。我们的工作假设是PP-IX在肝脏中的蓄积是利福平和异烟肼联合治疗引起肝毒性的关键介质；以及(2)确定利福平和异烟肼联合治疗中导致肝毒性的人类PXR依赖途径(S)。我们的工作假设是，人类PXR介导的氨基酮丙酸合成酶1上调，在利福平和异烟肼联合治疗引起的肝毒性中是关键的。这些研究结果有望为从机制上理解利福平和异烟肼肝毒性提供一个新的范式。基于人类PXR、氨基酮丙酸合成酶1和PP-IX的新策略可以被开发来预测、预防和治疗利福平和异烟肼联合治疗引起的肝损伤。

DESCRIPTION (provided by applicant): Drug-induced liver injury is a major safety issue in anti-tuberculosis (TB) chemotherapy. The long- term goal of our research is to improve the safety profile of medication with anti-TB drugs. The objective of this application is to determine the mechanism of liver injury associated with rifampicin and isoniazid co-therapy. Extensive studies have been conducted previously to investigate the liver injury caused by rifampicin and isoniazid in mice or rats; however, none of these studies mimicked the hepatotoxicity in humans. Species differences between rodents and humans in responding to rifampicin and/or isoniazid are expected. Pregnane X receptor (PXR) is a transcription factor regulating a gene network involved in the metabolism of xenobiotics and endobiotics. The ability of chemicals to activate PXR is species- dependent. Rifampicin is a human specific PXR activator, which strongly activates human PXR, but has a very weak effect on mouse PXR. To overcome the species differences in ligand-dependent PXR activation, we generated a PXR-humanized mouse model. By using these PXR-humanized mice, we noted that rifampicin and isoniazid-induced liver injury is human PXR-dependent. However, rifampicin- mediated PXR activation does not alter isoniazid metabolism. By using a metabolomic approach, we found that rifampicin and isoniazid co-treatment caused protoporphyrin IX (PP-IX) accumulation, specifically in liver, and this is human PXR-dependent. PP-IX is an intermediate in porphyrin synthesis, and has been shown to be hepatotoxic in previous studies. Based upon our preliminary data and previous reports, we hypothesize that rifampicin and isoniazid co-treatment disturbs porphyrin synthesis, and the accumulation of PP-IX in liver mediates the hepatotoxicity. To test our hypothesis, we will pursue the following two specific aims: (1) identify the toxic mediator(s) in the liver injury caused by rifampicin and isoniazid co-therapy. Our working hypothesis is that the accumulation of PP-IX in liver is the key mediator of the hepatotoxicity caused by rifampicin and isoniazid co-therapy; and (2) determine the human PXR-dependent pathway(s) responsible for the hepatotoxicity in rifampicin and isoniazid co- therapy. Our working hypothesis is that human PXR-mediated up-regulation of aminolevulinic acid synthase 1, the rate-limiting enzyme in porphyrin synthesis in liver, is critical in the hepatotoxicity caused by rifampicin and isoniazid co-therapy. The results from these studies are expected to provide a new paradigm for the mechanistic understanding of rifampicin and isoniazid-induced hepatotoxicity. Novel strategies, based upon human PXR, aminolevulinic acid synthase 1, and PP-IX, can be developed to predict, prevent, and treat the liver injury caused by rifampicin and isoniazid co-therapy.