Triggering receptor expressed on myeloid cells 2 (TREM2) is involved in neuroinflammation and HIV-associated neurocognitive impairment (NCI). People with HIV (PWH) using cannabis exhibit lower inflammation and neurological disorders. We hypothesized that TREM2 dysfunction mediates HIV neuropathogenesis and can be reversed by cannabinoids. EcoHIV-infected wildtype (WT) and TREM2^R47H mutant mice were used to study HIV’s impact on TREM2 and behavior. TREM2 and related gene expressions were examined in monocyte-derived macrophages (MDMs) from PWH (n = 42) and people without HIV (PWoH; n = 19) with varying cannabis use via RNA sequencing and qPCR. Differences in membrane-bound and soluble TREM2 (sTREM2) were evaluated using immunocytochemistry (ICC) and ELISA. EcoHIV increased immature and C-terminal fragment forms of TREM2 in WT mice but not in TREM2^R47H mice, with increased IBA1 protein in TREM2^R47H hippocampi, correlating with worse memory test performance. TREM2 mRNA levels increased with age in PWoH but not in PWH. Cannabidiol (CBD) treatment increased TREM2 mRNA alone and with IL1β. RNA-seq showed the upregulation of TREM2-related transcripts in cannabis-using PWH compared to naïve controls. IL1β increased sTREM2 and reduced membrane-bound TREM2, effects partially reversed by CBD. These findings suggest HIV affects TREM2 expression modulated by cannabis and CBD, offering insights for therapeutic strategies.

E-cigarette use has been marketed as a safer alternative to traditional cigarettes, as a means of smoking cessation, and are used at a higher rate than the general population in people with HIV (PWH). Early growth receptor 2 (EGR2) and Activity-Regulated Cytoskeleton-Associated Protein (ARC) have a role in addiction, synaptic plasticity, inflammation, and neurodegeneration. This study showed that 10 days of exposure to e-cigarette vapor altered gene expression in the brains of 6-month-old, male, Sprague Dawley rats. Specifically, the e-cigarette solvent vapor propylene glycol (PG) downregulated EGR2 and ARC mRNA expression in frontal cortex, an effect which was reversed by nicotine (NIC) and THC, suggesting that PG could have a protective role against NIC and cannabis dependence. However, in vitro, PG upregulated EGR2 and ARC mRNA expression at 18 h in cultured C6 rat astrocytes suggesting that PG may have neuroinflammatory effects. PG-induced upregulation of EGR2 and ARC mRNA was reversed by NIC but not THC. The HIV antiretroviral DTG reversed the effect NIC had on decreasing PG-induced upregulation of EGR2, which is concerning because EGR2 has been implicated in HIV latency reversal, T-cell apoptosis, and neuroinflammation, a process that underlies the development of HIV-associated neurocognitive disorders.

Background/Objectives: HIV-associated neurocognitive impairment (NCI) remains a prevalent issue among people with HIV (PWH) despite advancements in antiretroviral therapy (ART). The pathogenesis of HIV-associated NCI is linked to chronic neuroinflammation caused by HIV, even in those with successful viral suppression. Growth Differentiation Factor 15 (GDF15), a protein involved in inflammatory and metabolic stress responses, has emerged as a key player and potential biomarker for various neurological conditions. This study investigates the relationship between GDF15 expression and HIV-associated NCI. Methods: PWH from the California NeuroAIDS Tissue Network (CNTN) underwent comprehensive neuropsychological exams within 12 months before death and were categorized based on cognitive performance. We examined GDF15 levels in their CSF (Cerebrospinal Fluid) and brain tissues using immunoblotting, immunohistochemistry, double immunolabeling, and ELISA. Results: The cohort was of a similar age across HIV-associated NCI statuses (mean = 40.5), with a predominance of males (77%). The mean plasma viral load was 3.56 log₁₀ copies/mL for Neurocognitively Unimpaired (NUI) PWH and 5.38 log10 copies/mL for people with HIV-associated NCI. GDF15 protein levels were significantly elevated in the frontal cortices of PWH with NCI compared to NUI PWH. Conclusions: The findings indicate that GDF15 may play a role in the pathogenesis of HIV-associated NCI, possibly through neuroinflammatory mechanisms. The strong association between GDF15 levels and cognitive impairment severity suggests its potential as a biomarker for the early detection and monitoring of NCI in PWH.

Objectives: With the success of antiretroviral therapy (ART), people with HIV (PWH) are living longer. As they age, they increasingly face age-related comorbidities, including neurodegenerative conditions. The astrocyte–neuron lactate shuttle (ANLS) is a key mechanism that couples astrocytic glycolysis to neuronal oxidative metabolism, ensuring an adequate energy supply for synaptic activity. Disruption of this system has been implicated in both Alzheimer’s disease (AD) and HIV-associated neurocognitive impairment (HIV-NCI), conditions characterized by some overlapping cognitive deficits yet distinct pathological drivers. Methods: We investigated the expression of major ANLS transporters, including glucose transporters (GLUT1, GLUT3) and monocarboxylate transporters (MCT1, MCT2, MCT4), in postmortem frontal cortex from individuals with AD and PWH. There were two HIV cohorts based on viral suppression (suppressed/non-suppressed), and both were stratified by neurocognitive status (neurocognitively normal/ neurocognitively impaired), while AD participants were compared to cognitively healthy participants. Quantitative immunoblotting and immunofluorescence imaging characterized disease-specific alterations. Results: In AD, both endothelial (GLUT1 _55 kDa ) and astrocytic (GLUT1 _45 kDa ) isoforms were significantly reduced, along with MCT1, indicating widespread impairment of glucose and lactate transport. GLUT3, the neuronal glucose transporter, also showed a marked reduction. In contrast, in virally non-suppressed (VNS) PWH, GLUT1 _45 kDa and MCT4 were downregulated, while virally suppressed (VS) PWH maintained preserved expression. Correlation analyses revealed strong GLUT3–MCT1 coupling in AD, suggestive of coordinated neuronal–astrocytic adaptation, but disrupted GLUT1–MCT4 relationships in VNS PWH, reflecting ANLS uncoupling under viremia. Conclusions: These findings identify shared and distinct patterns of metabolic disruption: degeneration-driven ANLS failure in AD versus inflammation-driven uncoupling in HIV-NCI.

(1) Background: Triggering receptor expressed on myeloid cells 2 (TREM2) is involved in neu-roinflammation and HIV-associated neurocognitive impairment (NCI). People with HIV (PWH) using cannabis exhibit lower inflammation and neurological disorders. We hypothesized TREM2 dysfunction mediates HIV neuropathogenesis and can be reversed by cannabinoids. (2) Methods: EcoHIV-infected wildtype (WT) and TREM2R47H mutant mice were used to study HIV's impact on TREM2 and behavior. TREM2 and related gene expressions were examined in mono-cyte-derived macrophages (MDMs) from PWH (n=42) and people without HIV (PWoH; n=19) with varying cannabis use via RNA sequencing and qPCR. Differences in membrane-bound and soluble TREM2 (sTREM2) were evaluated using immunocytochemistry (ICC) and ELISA. (3) Results: EcoHIV increased immature and C-terminal fragment forms of TREM2 in WT mice but not in TREM2R47H mice, with increased IBA1 protein in TREM2R47H hippocampi, correlating with worse memory test performance. TREM2 mRNA levels increased with age in PWoH but not PWH. Cannabidiol (CBD) treatment increased TREM2 mRNA alone and with IL1β. RNA-seq showed upregulation of TREM2-related transcripts in cannabis-using PWH compared to naïve controls. IL1β increased sTREM2 and reduced membrane-bound TREM2, effects partially re-versed by CBD. (4) Conclusions: These findings suggest HIV affects TREM2 expression modu-lated by cannabis and CBD, offering insights for therapeutic strategies.