Autophagy as a rescue mechanism in efavirenz-induced mitochondrial dysfunction: a lesson from hepatic cells

Efavirenz (EFV) is the most widely used non-nucleoside reverse transcriptase inhibitor applied in highly active antiretroviral therapy (HAART), the combined pharmacological treatment of the human immunodeficiency virus infection. Its use has been associated with the development of several adverse events including hepatotoxicity. The molecular pathogenesis of this effect is poorly understood but recent reports have highlighted features of mitochondrial dysfunction in hepatic cells exposed to clinically relevant concentrations of EFV. In this study, we investigated the activation of autophagy and, in particular, mitophagy, in human hepatic cells exposed to EFV. We detected the presence of altered mitochondria with abnormal morphology and relative increase in mitochondrial mass. Several autophagic markers reveal specific induction of autophagy. Of special note, while moderate levels of EFV activate autophagy, higher concentrations exceeding the threshold of mitochondrial dysfunction, lead to a blockage in the autophagic flux, thus promoting "autophagic stress". Pharmacological inhibition of autophagy exacerbates the deleterious effect of EFV on cell survival/proliferation thereby promoting apoptosis, a finding which points to the fact that autophagy is triggered as a rescue mechanism enabling cell survival. The effect described in this study could be involved in the EFV-associated hepatotoxicity. It may constitute a new mechanism implicated in the genesis of pharmacological liver damage and in the recovery of hepatic homeostasis upon a drug-induced cellular insult.