Activation of Cannabinoid Receptor 2 Attenuates Leukocyte–Endothelial Cell Interactions and Blood–Brain Barrier Dysfunction under Inflammatory Conditions

Authors:
  • JHJános Haskó
    János Haskó
  • ASAndrew Skuba
    Andrew Skuba
  • SFShongshan Fan
    Shongshan Fan
  • HDHolly Dykstra
    Holly Dykstra
  • RMRyan McCormick
    Ryan McCormick
  • NRNancy Reichenbach
    Nancy Reichenbach
  • IKIstvan Krizbai
    Istvan Krizbai
  • AMAnu Mahadevan
    Anu Mahadevan
  • MZMing Zhang
    Ming Zhang
  • RTRonald Tuma
    Ronald Tuma
  • YSYoung-Jin Son
    Young-Jin Son
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Abstract
Previous studies have shown that modulation of the receptor-mediated cannabinoid system during neuroinflammation can produce potent neuroprotective and anti-inflammatory effects. However, in this context, little is known about how selective activation of the cannabinoid type-2 receptor (CB2R) affects the activated state of the brain endothelium and blood–brain barrier (BBB) function. Using human brain tissues and primary human brain microvascular endothelial cells (BMVECs), we demonstrate that the CB2R is highly upregulated during inflammatory insult. We then examined whether the CB2R agonists could attenuate inflammatory responses at the BBB using a mouse model of LPS-induced encephalitis and highly selective CB2R agonists. Visualization by intravital microscopy revealed that administration of JWH133 [(6aR,10aR)-3-(1,1-dimethylbutyl)-6a,7,10,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran] or a novel resorcinol-based compound, O-1966 (1-[4-(1,1-dimethyl-heptyl)-2,6-dimethoxy-phenyl]-3-methyl-cyclohexanol), greatly attenuated leukocyte adhesion in surface pial vessels and in deep ascending cortical postcapillary venules. BBB permeability assessments with small and large fluorescent tracers showed that CB2R agonists were effective at preventing barrier leakiness after LPS administration. To determine whether the effects by CB2R agonists on barrier protection are not only due to the CB2R modulation of immune cell function, we tested the agonistsin vitrowith barrier-forming primary BMVECs. Remarkably, the addition of CB2R agonist increased transendothelial electrical resistance and increased the amount of tight junction protein present in membrane fractions. Furthermore, CB2R agonists decreased the induction of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 surface expression in BMVECs exposed to various proinflammatory mediators. Together, these results suggest that pharmacological CB2R ligands offer a new strategy for BBB protection during neuroinflammation.

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