HIV-1 Tat enhances purinergic P2Y4 receptor signaling to mediate inflammatory cytokine production and neuronal damage via PI3K/Akt and ERK MAPK pathways

Abstract

Background HIV-associated neurocognitive disorders (HANDs) afflict more than half of HIV-1-positive individuals. The transactivator of transcription (Tat) produced by HIV virus elicits inflammatory process and is a major neurotoxic mediator that induce neuron damage during HAND pathogenesis. Activated astrocytes are important cells involved in neuroinflammation and neuronal damage. Purinergic receptors expressed in astrocytes participate in a positive feedback loop in virus-induced neurotoxicity. Here, we investigated that whether P2Y4R, a P2Y receptor subtype, that expressed in astrocyte participates in Tat-induced neuronal death in vitro and in vivo. Methods Soluble Tat protein was performed to determine the expression of P2Y4R and proinflammatory cytokines in astrocytes using siRNA technique via real-time PCR, Western blot, and immunofluorescence assays. Cytometric bead array was used to measure proinflammatory cytokine release. The TUNEL staining and MTT cell viability assay were analyzed for HT22 cell apoptosis and viability, and the ApopTag® peroxidase in situ apoptosis detection kit and cresyl violet staining for apoptosis and death of hippocampal neuron in vivo. Results We found that Tat challenge increased the expression of P2Y4R in astrocytes. P2Y4R signaling in astrocytes was involved in Tat-induced inflammatory cytokine production via PI3K/Akt- and ERK1/2-dependent pathways. Knockdown of P2Y4R expression significantly reduced inflammatory cytokine production and relieved Tat-mediated neuronal apoptosis in vitro. Furthermore, in vivo challenged with Tat, P2Y4R knockdown mice showed decreased inflammation and neuronal damage, especially in hippocampal CA1 region. Conclusions Our data provide novel insights into astrocyte-mediated neuron damage during HIV-1 infection and suggest a potential therapeutic target for HANDs. Electronic supplementary material The online version of this article (10.1186/s12974-019-1466-8) contains supplementary material, which is available to authorized users.

Purinergic signaling in infectious diseases of the central nervous system

“…Tat also induces the overexpression of P2Y 4 receptor in astrocytes. This purinergic receptor induces cytokine and chemokine release that contributes to apoptosis and neuronal death (Zhou et al, 2019). Furthermore, Tat protein induces monocyte/macrophage infiltration in the CNS, thereby contributing to HIV-dementia development, as this condition is associated with immune cell infiltration (Pu et al, 2003).…”

“… Fekete et al (2018) Astrocytes P2 receptors: P2X4; P2X7; P2Y1; P2Y 2 ; P2Y 4 ; P2Y 6 P2Y 12 ; P2Y 13 ; P2Y 14 HIV: P2Y4 induces cytokine and chemokine release. Zhou et al (2019) HIV: P2X7 is upregulated, inducing neuronal death. Tewari et al (2014) P1 receptors: A 1 ; A 2A ; A 2B ; A 3 Undefined roles in CNS infections.…”

“… Wang et al (2015) HIV: astrocytic P2Y4 induces apoptosis and neuronal death. Zhou et al (2019) HIV: astrocytic P2X7 contributes to neuronal death Tewari et al (2014) P1 receptors: A 1 ; A 2A ; A 2B ; A 3 HIV: A1 has neuroprotective effects. Pingle et al (2007) NTPDase3/CD39L3; CD73 Undefined roles in CNS infections.…”

Rh-relaxin-2 attenuates degranulation of mast cells by inhibiting NF-κB through PI3K-AKT/TNFAIP3 pathway in an experimental germinal matrix hemorrhage rat model

“…Brain tissues were collected and stored in a -80 o C freezer after being perfused with cold PBS (0.1 M, pH 7.4). Western blot was performed as described previously [14,20]. After extraction of protein samples, protein quantification was performed using Lowry methodology (BioRad, USA).…”

Rh-relaxin-2 Attenuates Degranulation of mast cells by Inhibiting NF-κB through PI3K-AKT/TNFAIP3 Pathway in an Experimental Germinal Matrix Hemorrhage Rat Model

“…Brain tissues were collected and stored in -80 o C freezer after being perfused with cold PBS (0.1M, pH 7.4). Western blot was performed as described previously (14) (19). After extraction of protein samples, protein quantification was performed using Lowry methodology (BioRad, USA).…”