The cannabinoid receptor CB1 has been linked to a modulation of blood pressure and atherogenic inflammation, although the precise underlying molecular mechanisms are not yet fully understood. Endothelial cells respond to the changes of local haemodynamic shear stress by modulating intracellular signalling, which leads to alterations of gene expression, cell morphology, and structural remodeling. Among the genes regulated by shear stress is endothelial nitric oxide synthase, which catalyzes the production of the vasodilator nitric oxide and thereby limits endothelial cell activation. Here, we addressed the question whether endothelial CB1 expression is affected by shear stress.

 

Methods: Murine samples were collected from atherogenic mice with apolipoprotein E deficiency (Apoe-/-) and mice with selective endothelial CB1 deficiency (Apoe-/- Bmx^Cre Cnr1^flox/flox). In situ hybridization for detection of the CB1 expressing gene Cnr1 and immunostainings of caveolin 1 (CAV1) adhesion (ICAM1) and junctional molecules (VE-Cadherin) were performed with murine aortic arch sections and whole mounted arteries. The inner curvature of the aortic arch, exposed to low oscillatory shear stress (OSS) was analyzed as atheroprone area, and the descending aorta, exposed to high laminar shear stress (LSS) as atheroprotective area. Perfusion cultures with the ibidi system were performed to study OSS (4 dyn/cm²) and LSS (10 dyn/cm²) responses in human umbilical vein endothelial cells (HUVECs) and human aortic endothelial cells (HAECs). Gene expression levels were determined by qPCR.

 

Results: Endothelial Cnr1 expression was more pronounced in atheroprone OSS areas compared to atheroprotective LSS areas of Apoe-/- aortas. CNR1 mRNA levels in HUVECs and HAECs were also upregulated by OSS compared to static condition or LSS in perfusion culture. HAEC treatment with CB1 agonist (ACEA) under LSS condition resulted in enhanced inflammation (ICAM1, VCAM1), lipid transcytosis (CAV1) and glycolysis (PFKFB3), while decreasing vasodilatory (NOS3) mRNA levels. En face stained aortas of atherogenic mice with selective endothelial CB1 deficiency revealed decreased ICAM1 and increased VE-Cadherin expression in atheroprone areas, supporting reduced endothelial inflammation and permeability in absence of CB1. 

 

Conclusion: Our results indicate that CB1 expression is upregulated by atheroprone flow conditions in vivo and in vitro, which is linked to proinflammatory effects and supports a therapeutic benefit for blocking CB1 signalling.