Contrasting Cannabinoid Receptor 2 (CB2R)-Associated Responses in Two Different Cerebrovascular Endothelial Cell Lines in a Blood Brain Barrier Model in the Context of HIV

Despite the success of suppressive antiretrovirals, infection with human immunodeficiency virus (HIV) is associated with several comorbidities which include negative consequences to the central nervous system (CNS), where disruption of the blood-brain barrier (BBB) is a major underlying factor in the resulting chronic inflammation and contribution to the pathogenesis of neuroHIV. Currently, the use of cannabis and cannabinoid derivatives among persons living with HIV (PWH) is common. Despite perceived benefits, we have previously identified context-dependent effects of cannabis use, including its impact on vascular biomarkers. In this study, we used an in vitro polycellular BBB model with two different human cerebrovascular endothelial cell lines (hCMEC/D3 and HBMEC/ci18) to test the effects of cannabinoids and their receptors on barrier integrity and function in the context of the latent HIV brain environment, mimicked by the addition of conditioned media from HIV latently infected promonocytes. We found that the two brain endothelial cell lines had similar responses to HIV-conditioned media by increasing permeability to dextran and decreased expression of tight junction proteins. However, their response to cannabinoids, particularly via the cannabinoid receptor 2 (CB2R), was markedly different, with hCMEC/D3 cells showing improvement of BBB integrity by all measures, but HBMEC/ci18 cells showing no benefits or aggravation of damage. While the contrasting effects were not due to differences in cell viability or proliferation, differences CB2R-elicited baseline G protein-coupled receptor (GPCR) response thresholds between the two cell lines were significant, revealed by forskolin-induced cAMP levels that were 50–200-fold higher in hCMEC/D3 cells in comparison to HBMEC/ci18. This was correlated to higher baseline CB2R expression in hCMEC/D3, and was not an HIV-induced signaling defect in HBMEC/ci18. The CBD/THC-induced phosphorylation of p38 MAPK was also significantly stronger in hCMEC/D3 compared to HBMEC/ci18, was abrogated by a CB2R inverse agonist/antagonist. Motivated by the need to identify predictors of positive response to cannabinoids, our study suggests that CB2R levels and GPCR activation thresholds in cerebrovascular endothelium may be important candidate mechanistic biomarkers to be tested in primary cells, animal models, and longitudinal clinical cohorts, with the goal of distinguishing beneficial versus aggravating effects of cannabis to the BBB, particularly in the context of HIV.