Cannabinoid-1 receptor activation induces reactive oxygen species-dependent and -independent mitogen-activated protein kinase activation and cell death in human coronary artery endothelial cells

Background and purpose: Impaired endothelial activity and/or cell death play a critical role in the development of vascular dysfunction associated with congestive heart failure, diabetic complications, hypertension, coronary artery disease and atherosclerosis. Increasing evidence suggests that cannabinoid 1 (CB₁) receptor inhibition is beneficial in atherosclerosis and cardiovascular inflammation both in experimental models, as well as in humans. Here, we investigated the effects of CB₁ receptor activation with the endocannabinoid anandamide (AEA) or synthetic agonist HU210 on cell death and interrelated signal transduction pathways in human primary coronary artery endothelial cells (HCAECs). Experimental approach: Cell death, CB₁ receptor expression, reactive oxygen species (ROS) generation and activation of signal transduction pathways in HCAECs were determined by flow cytometry and molecular biology tools. Key results: In HCAECs expressing CB₁ receptors (demonstrated by Western immunoblot and flow cytometry) AEA (5-15 μM) or HU210 (30-1000 nM) triggered concentration- and time-dependent activation of p38 and c-Jun NH₂-terminal protein kinase (JNK)-mitogen-activated protein kinases (MAPKs), cell death and ROS generation. The AEA- or HU210-induced cell death and MAPK activation were attenuated by CB₁ antagonists [SR141716 (rimonabant) and AM281], inhibitors of p38 and JNK-MAPKs or the antioxidant N-acetylcysteine. N-acetylcysteine alone prevented AEA- or HU210-induced ROS generation, but only partially attenuated MAPK activation and cell death. In contrast, in combination with CB₁ antagonists, N-acetylcysteine completely prevented these effects. Conclusions and implications: CB₁ receptor activation in endothelial cells may amplify the ROS-MAPK activation-cell death pathway in pathological conditions when the endocannabinoid synthetic or metabolic pathways are dysregulated by excessive inflammation and/or oxidative/nitrosative stress, thereby contributing to the development of endothelial dysfunction and pathophysiology of multiple cardiovascular diseases.