Molecular interplay of HIV Tat, cocaine, and cART in microglial pyroptosis: Role of NLRP3 inflammasome

Abstract: Despite the advent of combination antiretroviral therapy (cART), HIV-associated neurocognitive disorders (or NeuroHIV) remain prevalent, affecting 30-50% of patients and presenting persistent challenges in managing neurological complications. Glial cell dysregulation, particularly microglia and astrocytes, drives chronic neuroinflammation in the central nervous system (CNS), exacerbated by HIV proteins such as the Transactivator of Transcription (Tat). While previous research has implicated inflammasomes, notably the NLRP3 inflammasome, and toll-like receptors (TLRs) in mediating neuroinflammation, the precise mechanisms by which HIV, cART, and substances like cocaine modulate inflammasome activation and subsequent neuroinflammatory responses remain poorly understood. Also, pyroptosis, a highly inflammatory form of programmed cell death, emerges as crucial in inflammatory diseases, including NeuroHIV. Characterized by membrane pore formation and the release of proinflammatory cytokines like interleukin-1β (IL-1β) and IL-18, pyroptosis exacerbates inflammation and tissue damage. However, the link between inflammasome-mediated pyroptosis and microglial activation in the context of HIV Tat, cocaine, and cART, contributing to neuroinflammation in NeuroHIV, remains elusive and forms the crux of this proposal. This proposed study aims to address these critical knowledge gaps by elucidating the molecular mechanisms underlying the interplay between HIV Tat, cocaine, and cART in activating NLRP3 inflammasome signaling pathways, leading to pyroptosis and microglial activation. We hypothesize that these factors collectively contribute to microglial activation and exacerbate neuroinflammation through distinct regulatory mechanisms called microglial pyroptosis. This hypothesis will be tested with two specific aims: 1. determining the molecular mechanism(s) underlying NLRP3-mediated pyroptosis in microglia exposed to HIV Tat, cocaine, and cART in vitro; 2. validating the combined effects of HIV Tat, cocaine, and cART on NLRP3-mediated pyroptosis and microglial activation in vivo and isolated ex vivo adult microglia. Archival macaque brain tissues will also be utilized to validate the microglial pyroptosis and neuroinflammation. This comprehensive investigation into the molecular mechanisms of microglial pyroptosis and neuroinflammation induced by HIV Tat, cocaine, and cART holds significant promise for developing novel therapeutic strategies to alleviate neuroinflammatory responses in NeuroHIV and substance abuse disorders. Furthermore, the identification of these pathways may uncover new drug targets for the treatment of other neuroinflammatory diseases, underscoring the broader implications of this research.