Mitochondrial toxicity in HAART: an overview of in vitro evidence

The combined antiretroviral therapeutic approach currently employed for the treatment of HIV infection, known as Higly Active Antiretroviral Therapy (HAART), has dramatically reduced AIDS-related morbidity and mortality. However, the adverse reactions associated with the long term use of this therapy have now become a major issue and researchers have focused on understanding the cellular mechanisms underlying these drug-induced detrimental effects which englobe a large list of different events including rash and hypersensibility reactions, hepatotoxicity, metabolic disturbances including lipodystrophy, and other metabolic syndrome-like disturbances such as hyperlactatemia, hyperlipedimia, insulin resistance and pancreatitis. Other events include CNS toxic effects, peripheral neuropathies as well as nephrotoxicity and increased risk of cardiovascular diseases. Many of these reactions have been shown to develop as e result of mitochondrial dysfunction. The mitochondrial effect of N(t)RTI (Nucleos(t)ide Reverse Transcriptase Inhibitors) class of drugs, which has been widely studied, is believed to originate from the inhibitory action of these drugs on DNA polymerase gamma, the enzyme responsible for replication of mitochondrial DNA. However, additional mitochondrial targets have also been described and need to be considered. As to NNRTI (Non-Nucleoside-Transcriptase Inhibitor) or PI (Protease Inhibitors), evidence of the implication of mitochondria has also been reported, however the details of the mechanisms underlying these actions are still not fully known. This review covers the current knowledge of mitochondrial toxicities, particularly the available in vitro evidence, regarding the most commonly used groups of HIV drugs. Novel findings of mtDNA-independent mitochondrial dysfunction have received special attention.