HIV-1 Vpr causes neuronal apoptosis and in vivo neurodegeneration

Despite the introduction of highly active antiretroviral therapy, dementia caused by human immunodeficiency virus-1 (HIV-1) infection remains a devastating and common neurological disorder. Although the mechanisms governing neurodegeneration during HIV-1 infection remain uncertain, the HIV-1 accessory protein, viral protein R (Vpr), has been proposed as a neurotoxic protein. Herein, we report that Vpr protein and transcript were present in the brains of HIV-infected persons. Moreover, soluble Vpr caused neuronal apoptosis, involving cytochrome c extravasation, p53 induction, and activation of caspase-9 while exerting a depressive effect on whole-cell currents in neurons (p < 0.05), which was inhibited by iberiotoxin. Vpr-activated glial cells secreted neurotoxins in a concentration- dependent manner (p < 0.001). Transgenic (Tg) mice expressing Vpr in brain monocytoid cells displayed the transgene principally in the basal ganglia (p < 0.05) and cerebral cortex (p < 0.01) compared with hindbrain expression. Vpr was released from cultured transgenic macrophages, which was cytotoxic to neurons and was blocked by anti-Vpr antibody (p < 0.05). Neuronal injury was observed in Tg animals compared with wild-type littermates, chiefly affecting GAD65 (p < 0.01) and vesicular acetylcholine transferase (p < 0.001) immunopositive neuronal populations in the basal ganglia. There was also a loss of subcortical synaptophysin (p < 0.001) immunoreactivity as well as an increase in activated caspase-3, which was accompanied by a hyperexcitable neurobehavioral phenotype (p < 0.05). Thus, HIV-1 Vpr caused neuronal death through convergent pathogenic mechanisms with ensuing in vivo neurodegeneration, yielding new insights into the mechanisms by which HIV-1 injures the nervous system.