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Preventing HIV-1 Tat-induced neuronal apoptosis using antioxidant enzymes: mechanistic and therapeutic implications
Lokesh Agrawal1, Jean-Pierre Louboutin, David S Strayer
1Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Room 251, 1020 Locust Street, Philadelphia, PA 19107, USA.
Abstract:
HIV-1 proteins, especially gp120 and Tat, elicit reactive oxygen species (ROS) and cause neuron apoptosis. We used antioxidant enzymes, Cu/Zn superoxide dismutase (SOD1) and glutathione peroxidase (GPx1) to study signaling and neuroprotection from Tat-induced apoptosis. SOD1 converts superoxide to peroxide; GPx1 converts peroxide to water. Primary human neurons were transduced with SV40-derived vectors carrying SOD1 and GPx1, then HIV-1 Tat protein was added. Both SV(SOD1) and SV(GPx1) delivered substantial transgene expression. Tat decreased endogenous cellular, but not transduced, SOD1 and GPx1. Tat rapidly increased neuron [Ca(2+)](i), which effect was not altered by SV(SOD1) or SV(GPx1). However, both vectors together blocked Tat-induced [Ca(2+)](i) fluxes. Similarly, neither SV(SOD1) nor SV(GPx1) protected neurons from Tat-induced apoptosis, but both vectors together did. Tat therefore activates multiple signaling pathways, in one of which superoxide acts as an intermediate while the other utilizes peroxide. Gene delivery to protect neurons from Tat must therefore target both.
Insights
HIV-1 Tat protein induces neuron apoptosis via reactive oxygen species. Targeting both superoxide and peroxide pathways with antioxidant enzymes is necessary for neuroprotection against Tat-induced cell death.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- HIV-1 proteins, particularly gp120 and Tat, are known to induce oxidative stress and neuronal apoptosis.
- Antioxidant enzymes like Cu/Zn superoxide dismutase (SOD1) and glutathione peroxidase (GPx1) play crucial roles in managing reactive oxygen species (ROS).
Purpose of the Study:
- To investigate the roles of SOD1 and GPx1 in neuroprotection against HIV-1 Tat-induced apoptosis.
- To elucidate the signaling pathways involving ROS in Tat-induced neuronal cell death.
Main Methods:
- Primary human neurons were transduced with SV40-derived vectors expressing SOD1 and GPx1.
- Neurons were subsequently exposed to HIV-1 Tat protein.
- Changes in intracellular calcium ([Ca(2+)](i)), endogenous SOD1/GPx1 levels, and apoptosis were measured.
Main Results:
- HIV-1 Tat exposure decreased endogenous SOD1 and GPx1 levels but not transduced levels.
- Tat rapidly increased intracellular calcium, an effect not mitigated by individual SOD1 or GPx1 expression.
- Co-delivery of both SOD1 and GPx1 vectors blocked Tat-induced calcium fluxes and prevented neuronal apoptosis.
- Tat-induced apoptosis involves at least two distinct signaling pathways, one involving superoxide and another involving peroxide.
Conclusions:
- Neuroprotection against HIV-1 Tat requires targeting both superoxide and peroxide-mediated signaling pathways.
- Gene delivery strategies aiming to protect neurons from Tat toxicity must simultaneously address both ROS intermediates.
