Hepatotoxicity is a very common side effect associated with the pharmacological treatment of human immunodeficiency virus (HIV) infection and its pathogenesis is poorly understood. Efavirenz (EFV) is the most widely used nonnucleoside reverse transcriptase inhibitor administered for the control of HIV and some of its toxic effects in hepatic cells have been recently shown to display features of mitochondrial dysfunction. Here we studied the activation of autophagy and, in particular, mitophagy, the main mitochondrial turnover mechanism, in human hepatic cells treated with clinically relevant concentrations of this drug. EFV-treated cells had altered mitochondria, characterized by a relative increase in mitochondrial mass and defective morphology. This was followed by induction of autophagy as shown by the presence of autophagic vacuoles and the presence of the specific autophagic marker proteins microtubule-associated protein 1A/1B light chain 3 and Beclin-1. Importantly, whereas moderate levels of EFV activated autophagy, higher concentrations led to blockage in the autophagic flux, a condition that promotes "autophagic stress" and produces severe cellular damage. Finally, pharmacological inhibition of autophagy exacerbated the deleterious effect of EFV on cell survival/proliferation promoting apoptosis, which suggests that autophagy acts as an adaptive mechanism of cell survival.
Conclusion: Clinical concentrations of EFV induce autophagy and, in particular, mitophagy in hepatic cells. Activation of this process promotes cell survival, but exceeding a certain threshold of mitochondrial dysfunction is associated with an autophagic overload or stress. This effect could be involved in the EFV-associated hepatotoxicity and may constitute a new mechanism implicated in the genesis of drug-induced liver damage.
Copyright © 2011 American Association for the Study of Liver Diseases.