HIV-1 Tat neurotoxicity: a model of acute and chronic exposure, and neuroprotection by gene delivery of antioxidant enzymes

HIV-associated neurocognitive disorder (HAND) is an increasingly common, progressive disease characterized by neuronal loss and progressively deteriorating CNS function. HIV-1 gene products, particularly gp120 and Tat elicit reactive oxygen species (ROS) that lead to oxidant injury and cause neuron apoptosis. Understanding of, and developing therapies for, HAND requires accessible models of the disease. We have devised experimental approaches to studying the acute and chronic effects of Tat on the CNS. We studied acute exposure by injecting recombinant Tat protein into the caudate-putamen (CP). Ongoing Tat expression, which more closely mimics HIV-1 infection of the brain, was studied by delivering Tat-expression over time using an SV40-derived gene delivery vector, SV(Tat). Both acute and chronic Tat exposure induced lipid peroxidation and neuronal apoptosis. Finally, prior administration of recombinant SV40 vectors carrying antioxidant enzymes, copper/zinc superoxide dismutase (SOD1) or glutathione peroxidase (GPx1), protected from Tat-induced apoptosis and oxidative injury. Thus, injection of recombinant HIV-1 Tat and the expression vector, SV(Tat), into the rat CP cause respectively acute or ongoing apoptosis and oxidative stress in neurons and may represent useful animal models for studying the pathogenesis and, potentially, treatment of HIV-1 Tat-related damage.