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

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 endothelial cells (BMVEC) 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 or a novel resorcinol-based compound O-1966, greatly attenuated leukocyte adhesion in surface pial vessels and in deep ascending cortical post-capillary 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 agonists in-vitro with barrier forming primary BMVEC. Remarkably, the addition of CB2R agonist increased trans-endothelial electrical resistance and increased the amount of tight junction protein present in membrane fractions. Furthermore, CB2R agonists decreased the induction of ICAM-1 and VCAM-1 surface expression in BMVEC exposed to various pro-inflammatory mediators. Together, these results suggest that pharmacological CB2R ligands offer a new strategy for BBB protection during neuroinflammation.

The Endocannabinoid/Endovanilloid N-Arachidonoyl Dopamine (NADA) and Synthetic Cannabinoid WIN55,212-2 Abate the Inflammatory Activation of Human Endothelial Cells

“…Therefore, the detection of CB 2 R in EC cultures may depend on several factors, including the EC niche, detection method, and inflammatory state, and on the health, passage number, or growth conditions of the ECs. Nonetheless, the synthetic CB 2 R agonists JWH133, HU-308, and O-1966 have been reported to reduce the LPS-and TNF␣-induced inflammatory activation of both HCAEC and HMVEC-brain and protect barrier function in LPS-treated HMVEC-brain (73,77). Consistent with these results, we observed an anti-inflammatory trend with HU-308 when administered to activated HMVEC-lung.…”

Targeting the endocannabinoid system with cannabinoid receptor agonists: pharmacological strategies and therapeutic possibilities

“…These include the relief of various kinds of pain and the treatment of pruritus, of certain types of cancer, of cough and of some neurodegenerative, immunological, inflammatory, cardiovascular, hepatic, renal and bone disorders (table 1). There is also evidence, first, that CB 2 receptor activation can ameliorate neuroinflammation by protecting the blood-brain and blood-spinal cord barriers [67,68]), and second that activation of these receptors can reduce inflammation following spinal cord injury by lowering the expression of toll-like receptors [68]). …”

Poly(ADP-ribose) Polymerase-1 Inhibition in Brain Endothelium Protects the Blood—Brain Barrier under Physiologic and Neuroinflammatory Conditions

“…IVM for in vivo leukocyte adhesion was performed in animals that underwent craniotomy and cranial window implantation. 8,9 For IC injection, the head of the mouse was positioned in a stereotactic head holder. A 1-cm area of skin on the dorsal surface of the skull over the right hemisphere was excised.…”

“…To explore this idea, we tested whether inhibition of PARP would reduce leukocyte adhesion in vivo in an animal model of localized aseptic meningitis. We used IVM for surveillance of cerebral vascular changes and leukocyteendothelium interactions, 8,9 where TNFα was introduced IC via a cannula located next to a cranial window ( Figure 1A). First, we established the concentration and time of the inflammatory responses in the mouse brain ( Figure 1B).…”

“…In this study, we tested whether inhibition of PARP would reduce leukocyte adhesion in vivo in an animal model of localized aseptic meningitis (induced by intracerebral injection of tumor necrosis factor alpha (TNFα)), utilizing intravital videomicroscopy (IVM) for surveillance of cerebral vascular changes and leukocyte-endothelial interactions. 8,9 Inactivation of PARP resulted in a significant decrease in leukocyte adhesion to and migration across the CNS endothelium in vivo. In addition, we showed that PARP inhibition caused reduction in leukocyte adhesion and migration in an in vitro blood-brain barrier (BBB) model, thereby preserving barrier functions.…”