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.
Rifampicin and isoniazid co-therapy frequently causes liver injury, and even liver failure. This proposed project will provide a novel mechanistic understanding of the liver injury induced by rifampicin and isoniazid co-therapy, which can be applied to predict, prevent, and treat this toxic event.
|Sachar, Madhav; Ma, Xiaochao (2016) Role of ABCG2 in liver injury associated with erythropoietic protoporphyria. Hepatology 64:305|
|Wang, Pengcheng; Pradhan, Komal; Zhong, Xiao-Bo et al. (2016) Isoniazid metabolism and hepatotoxicity. Acta Pharm Sin B 6:384-392|
|Sachar, Madhav; Anderson, Karl E; Ma, Xiaochao (2016) Protoporphyrin IX: the Good, the Bad, and the Ugly. J Pharmacol Exp Ther 356:267-75|
|Li, Feng; Wang, Pengcheng; Liu, Ke et al. (2016) A High Dose of Isoniazid Disturbs Endobiotic Homeostasis in Mouse Liver. Drug Metab Dispos 44:1742-1751|
|Shehu, Amina I; Li, Guangming; Xie, Wen et al. (2016) The pregnane X receptor in tuberculosis therapeutics. Expert Opin Drug Metab Toxicol 12:21-30|
|Liu, Ke; Yan, Jiong; Sachar, Madhav et al. (2015) A metabolomic perspective of griseofulvin-induced liver injury in mice. Biochem Pharmacol 98:493-501|
|Gonzalez, Frank J; Fang, Zhong-Ze; Ma, Xiaochao (2015) Transgenic mice and metabolomics for study of hepatic xenobiotic metabolism and toxicity. Expert Opin Drug Metab Toxicol 11:869-81|
|Tien, Yun-Chen; Liu, Ke; Pope, Chad et al. (2015) Dose of Phenobarbital and Age of Treatment at Early Life are Two Key Factors for the Persistent Induction of Cytochrome P450 Enzymes in Adult Mouse Liver. Drug Metab Dispos 43:1938-45|
|Ling, Xiaoxi; Zhang, Shaojuan; Shao, Pin et al. (2015) Synthesis of a reactive oxygen species responsive heterobifunctional thioketal linker. Tetrahedron Lett 56:5242-5244|
|Liu, Ke; Li, Feng; Lu, Jie et al. (2014) Role of CYP3A in Isoniazid Metabolism In Vivo. Drug Metab Pharmacokinet 29:219-22|
Showing the most recent 10 out of 12 publications