Activation of CB2R by synthetic CB2R agonist, PM289, improves brain endothelial barrier properties, decreases inflammatory response and enhances endothelial repair

Abstract The Cannabinoid 2 Receptor (CB2R) has been found to provide immunological modulation in different cell types. More recently, detection of CB2R in the cerebral endothelium suggests a possible role in the resolution of inflammation at the level of the blood–brain–barrier (BBB). Here, the notion that CB2R upregulation in brain endothelial cells could be exploited to promote vascular protection and BBB integrity was evaluated. Targeting and activation of CB2R was accomplished by a novel and highly specific chromenopyrazole based CB2R agonist, PM289. This study demonstrates that CB2R upregulation is induced as early as 8 h in the cortical vasculature in an experimental mouse model of TBI. Unlike CB2R, CB1R was marginally detected and not significantly induced. In the human brain endothelial cell line, hCMEC/D3 cells, similar induction of CB2R was observed upon stimulation with TNFα. Analysis of transendothelial electrical resistance shows that PM289 markedly prevented the barrier-leakiness induced by TNFα. The BBB is also responsible for maintaining an immunological barrier. The five-fold increase in ICAM1 expression in stimulated endothelial cells was significantly diminished due to CB2R activation. Utilizing wounding assays, results showed that wound repair could be accomplished in nearly half the time when the novel CB2R agonist is present compared to the untreated control. Lastly, mechanistically, the effects of CB2R may be explained by the observed inhibition of the p65 NFκB subunit. Overall, these studies support the notion that targeting and activating CB2R in the brain vasculature could aid in BBB and vascular protection in the context of neuroinflammation.