Anti-TB Drugs, Isoniazid and Rifampicin Produce Hepatic Fibrosis Through a Oxidative Stress-Dependent Mechanism

Abstract

Background and Aims: Chronic hepatitis has emerged as a distinct clinical outcome in large DILI registries. AT drugs being the commonest DILI agents in India, we investigated the pathways that mediate the development of hepatic fibrosis in long-term treatment of AT drugs in mice. Methods: In a combined in vivo and in vitro experiment-based study, the extent of liver injury and development of hepatic fibrosis were evaluated in wild type BALB/c mice at different time points of AT drugs (cotreatment of INH 50 mg/kg and RMP 100 mg/kg body weight) treatment for 24 weeks. Markers of oxidative stress, hepatic inflammation, apoptosis and fibrosis were evaluated. In vitro studies with mediators released from INH treated E47 cells on LX2 cells were carried out to establish the pathways in greater detail. Results: Development of hepatic oxidative stress associated with increased expression of NADPH oxidase was observed in mice during long-term treatment of AT drugs in mice. Immunohistochemistry and quantitative polymerase chain reaction demonstrated a gradual increase of HSC activation during AT drugs treatment. Histological evidence of liver fibrosis was first observed at 3 months of these drugs treatment. In addition, increasing apoptosis of hepatocytes associated with duration of AT drugs treatment accelerated hepatic fibrosis, suggesting a causative contribution of apoptosis in this process. In vitro study on stable human cell lines also confirmed the involvement of mediators (products of oxidative stress) released from INH-treated hepatocytes in the activation of hepatic stellate cell and increased collagen synthesis. Conclusions: In mice, long-term treatment of AT drugs contributes HSC activation leading to development of hepatic fibrosis. These findings will help in understanding of the pathobiology of AT druginduced liver fibrosis.