Rimonabant inhibits TNF-α-induced endothelial IL-6 secretion via CB1 receptor and cAMP-dependent protein kinase pathway

Aim: To investigate whether rimonabant, a cannabinoid receptor antagonist, had inhibitory effects on inflammatory reactions in human umbilical vein endothelial cells (HUVEC). Methods: TNF-alpha-induced IL-6 production was measured by ELISA and effects on related signaling pathways were investigated by immunoblot analysis. Cellular cAMP level was measured using kinase-coupled luciferase reaction. Results: Rimonabant at 1 and 10 mu mol/L significantly inhibited TNF-a-induced IL-6 production when added 15, 30 and 60 minutes before TNF-alpha treatment. Rimonabant also inhibited TNF-a-induced phosphorylation of I kappa B kinase (IKK) alpha/beta and I kappa B-alpha degradation. ACEA, a cannabinoid receptor subtype 1 (CB1) agonist, added before rimonabant abolished the former effects of rimonabant. H-89, an inhibitor of cAMP-dependent protein kinase (PKA), abolished the inhibitory effects of rimonabant on TNF-alpha induced IL-6 production. Rimonabant also increased the phosphorylation of PKA regulatory subunit II (PKA-RII), implying the essential role of PKA activation in the inhibitory effects of rimonabant. Treatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor, wortmannin did not abolish the inhibitory effects of rimonabant on TNF-alpha induced IL-6 production. Conclusion: Rimonabant had anti-inflammatory effects on endothelial cells and inhibited TNF-alpha-induced IKK alpha/beta phosphorylation, I kappa B-alpha degradation and IL-6 production in HUVEC. This effect was related to CB1 antagonism and PKA activation.