Molecular effects of cannabinoids on the Blood Brain Barrier in HIV-infected brain

Molecular effects of cannabinoids on the Blood Brain Barrier in HIV-infected brain Infection with the human immunodeficiency virus (HIV) causes significant disease morbidity in the brain, largely due to HIV-associated blood-brain barrier (BBB) disruption, inflammation, and persistence of HIV-infected CNS target cells such as microglia and macrophages, in spite of antiretroviral therapies (ART). Cannabis is a commonly used drug by people with HIV (PWH). Recently, we made the important observation that the impact of cannabis on BBB integrity markers is context-dependent, with signs of BBB disruption in non-HIV subjects, but paradoxically improving BBB integrity in PWH. This observation makes it a high priority to understand the mechanistic basis of this dichotamous influence of cannabis on the BBB. Cannabis and HIV interact in multifactorial ways that are still poorly understood. Importantly, HIV brain target cells microglia/macrophages express the cannabinoid receptor 2 (CB2R), while endothelial cells of the blood brain barrier (BBB) express both CB1R and CB2R and other cannabinoid receptors such as GPR55. It is also unknown how cannabis influences HIV-associated brain inflammation or the active/latent status of HIV in infected microglia. By protecting vascular integrity, it follows that cannabis will not only affect the select transport of substrates into the CNS, it will also directly influence the infiltration of inflammatory cells and the passage of ART or other treatments to the brain. The goal of this application is to test the hypothesis that cannabinoids positively impact BBB integrity in the HIV-infected brain environment, leading to reduced inflammatory cell infiltration and ultimately protection from HIV-associated neurocognitive disorders. Our analysis of two human brain microvascular endothelial cell (HBMEC) lines (hCMEC/D3 and HBMEC/ci18) with opposing vascular integrity responses to cannabinoids in the context of HIV suggest a molecular mechanism that can explain the context-dependent effects of cannabis in human BBB properties. Based on this preliminary data, our hypothesis posits that beneficial effects of cannabinoids in the context of HIV occur via CB2R, while cannabinoid signaling via GPR55 may be damaging. In the proposed studies we will model the human BBB in vitro using multicellular systems containing the two HBMEC lines in parallel, along with pericytes, astrocytes and microglia, to replicate HIV-induced vascular phenotypes characterized by loss of tight junction proteins and increased permeability to fluorescent labelled- dextran. Implications to infection in the brain will be validated in vivo using the EcoHIV mouse model, which develops BBB disorders. Successful completion of these experiments will define the molecular mechanisms that underlie the dichotomous influence of cannabis on the BBB in the context of HIV, forming the basis of new approaches aimed at optimizing BBB integrity.