Endoplasmic reticulum stress inhibition preserves mitochondrial function and cell survival during the early onset of isoniazid-induced oxidative stress

A comprehensive understanding of isoniazid (INH)-mediated hepatotoxic effects is essential for developing strategies to predict and prevent severe liver toxicity in tuberculosis treatment. In this study, we used multi-omics profiling in vitro to investigate the toxic effects of INH, revealing significant involvement of endoplasmic reticulum (ER) stress, mitochondrial impairment, redox imbalance, and altered metabolism. Additional analysis using transcriptomics data from repeated time-course INH treatments on human hepatic microtissues revealed that cellular responses to ER stress and oxidative stress happened prior to disturbances in mitochondrial complexes. Mechanistic validation studies using time-lapse measurements of cytosolic and mitochondrial reactive oxygen species (ROS) revealed that INH initially triggered cytosolic ROS increasement and Nrf2 signaling pathway activation before mitochondrial ROS accumulation. Molecular imaging showed that INH subsequently disrupted mitochondrial function by impairing respiratory complexes I–IV and caused mitochondrial membrane proton leakage without affecting mitochondrial complex V, leading to mitochondrial depolarization and reduced ATP production. These disturbances enhanced mitochondrial fission and mitophagy. Our findings highlight the potential of inhibiting ER stress during early INH exposure to mitigate cytosolic and mitochondrial oxidative stress. We also revealed the critical role of Nrf2 signaling in protecting hepatocytes under INH-induced oxidative stress by maintaining redox homeostasis and enabling metabolic reprogramming through regulating antioxidant gene expression and cellular lipid abundance. Alternative antioxidant pathways, including selenocompound metabolism, HIF-1 signaling, and the pentose phosphate pathway, also responded to INH-induced oxidative stress. Collectively, our study emphasizes the importance of ER stress, redox imbalance, metabolic changes, and mitochondrial dysfunction that underlie INH-induced hepatotoxicity.