Induction of Heme oxygenase 1 protects hepatocytes from Isoniazid – Rifampicin induced cell death: an in vitro study.

Background: Anti tuberculosis therapy agent isoniazid (INH) and rifampicin (RMP) injure hepatocytes. Heme oxygenase-1(HO-1) is a stress induced protein which seems to have some cellular protective function. We examined the protective function of HO-1 during INH-RMP induced cell death of hepatocytes by induction of HO-1 using hemin chloride or by silencing HO-1 gene using small interfering RNA (siRNA).

Methods: The role of HO-1 induction on INH-RMP induced cell death was examined on HepG2 cells overexpressing human CYP2E1 gene (E47 cells) during short term culture. The E47 cells were treated with hemin chloride to induce HO-1 expression during INH-RMP treatment. In other set of experiments, transient knockdown of HO-1 gene using siRNA was carried out before treatment of INH-RMP. Cell viability using Trypan blue, intracellular reactive oxygen species (ROS), cell death were evaluated by FACS analysis at different time points of INH-RMP treatment.

Results: INH-RMP treatment to E47 cells induced expression of cytoplasmic HO-1 protein at early hours of drug treatment with minimum loss of cell viability and cell death. At later hours, failiure to express HO-1 protein resulted in loss of cell viability and increased cell death. Addition of Hemin chloride during treatment of INH-RMP induced HO-1 in E47 cells and reversed the drug induced liver injury. Silencing the HO-1 gene using siRNA potentiated INH-RMP induced cell death of the E47 cells

Conclusion: Induction of HO-1 ameliorated INH-RMP induced cell death of hepatocytes. This may be a potential target for future therapeutic option in INH-RMP induced drug induced liver injury.