Astrocytes mediate HIV-1 Tat-induced neuronal damage via ligand-gated ion channel P2X7R.

Abstract

During human immunodeficiency virus (HIV)-1 infection, perturbations in neuron–glia interactions may culminate in neuronal damage. Recently, purinergic receptors have been implicated in the promotion of virus-induced neurotoxicity and supporting the viral life cycle at multiple stages. The astrocytes robustly express purinergic receptors. We therefore sought to examine if P2X7R, a P2X receptor subtype, can mediate HIV-1 Tat-induced neuronal apoptosis. Tat augmented the expression of P2X7R in astrocytes. Our data reveal the involvement of P2X7R in Tat-mediated release of monocyte chemoattractant protein (MCP-1) /chemokine (C-C motif) ligand 2 (CCL2) from the astrocytes. P2X7R antagonists, such as the oxidized ATP, A438079, brilliant blue G, and broad spectrum P2 receptor antagonist suramin, attenuated Tat-induced CCL2 release in a calcium- and extracellular signal-regulated kinase (ERK)1/2-dependent manner. Calcium chelators, (1,2-bis(o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid) acetoxymethyl ester and EGTA, and ERK1/2 inhibitor U0126 abolished chemokine (C-C motif) ligand 2 release from astrocytes. Furthermore, in human neuronal cultures, we demonstrated P2X7R involvement in Tat-mediated neuronal death. Importantly, in the TUNEL assay, the application of P2X7R-specific antagonists or the knockdown of P2X7R in human astrocytes reduced HIV-Tat-induced neuronal death significantly, underlining the critical role of P2X7R in Tat-mediated neurotoxicity. Our study provides novel insights into astrocyte-mediated neuropathogenesis in HIV-1 infection and a novel target for therapeutic management of neuroAIDS. We investigated the role of P2X7R in Tat-mediated neuroinflammation and neuronal damage. We proposed the following cascade for Tat-mediated CCL2 release from astrocytes: Tat mediates increase in P2X7R expression, which on activation evokes increase in intracellular calcium, which further leads to phosphorylation of ERK1/2 followed by the release of CCL2 from astrocytes. Tat also leads to direct and indirect (mediated via astrocytes) neuronal death that can be abrogated by inhibiting P2X7R. We believe that these finding should provide new insights into the role of astrocytes in HIV-1 Tat-mediated neurotoxicity.