Abstract

Despite combination antiretroviral therapies (cART), a significant proportion of HIV-infected patients develop HIV-associated neurocognitive disorders (HAND). Ongoing viral replication in the CNS due to poor brain penetration of cART may contribute to HAND. However, it has also been proposed that toxic effects of long-term cART may contribute to HAND. A better understanding of the neurotoxic potential of cART is critically needed in light of the use of CNS penetrating cART to contend with virus reservoir in brain. The Efavirenz (EFV) metabolites 7-hydroxyefavirenz (7-OH-EFV) and 8-hydroxyefavirenz (8-OH-EFV) were synthesized, purified, and chemical structures confirmed by mass spectrometry and NMR. The effects of EFV, 7-OH-EFV and 8-OH-EFV on calcium, dendritic spine morphology, and survival were determined in primary neurons. EFV, 7-OH-EFV and 8-OH-EFV each induced neuronal damage in a dose dependent manner. However, 8-OH-EFV was at-least an order of magnitude more toxic than EFV or 7-OH-EFV, inducing considerable damage to dendritic spines at a 10 nM concentration. The 8-OH-EFV metabolite evoked calcium flux in neurons, which was primarily mediated by L-type voltage operated calcium channels. Blockade of L-type VOCCs protected dendritic spines from 8-OH-EFV-induced damage. Concentrations of EFV and 8-OH-EFV in the cerebral spinal fluid of HIV-infected subjects taking EFV were within the range that damaged neurons in culture. These findings demonstrate that the 8-OH metabolite of EFV is a potent neurotoxin and highlight the importance of directly determining the effects of antiretroviral drugs, and drug metabolites on neurons and other brain cells.