CB1 Receptor Inhibition Research Articles

Cannabinoid 1 Receptor Promotes Cardiac Dysfunction, Oxidative Stress, Inflammation, and Fibrosis in Diabetic Cardiomyopathy

Endocannabinoids and cannabinoid (CB)1 receptors have been implicated in cardiac dysfunction, inflammation, and cell death associated with various forms of shock, heart failure, and atherosclerosis. We explored the role of CB1 receptors in cardiac dysfunction, inflammation and cell death using a mouse model of type 1 diabetic cardiomyopathy. Diabetic cardiomyopathy was characterized by increased myocardial endocannabinoid anandamide levels, oxidative/nitrative stress, activation of p38/Jun kinase, mitogen‐activated protein kinases, enhanced inflammation, increased expression of CB1, advanced glycation end product and angiotensin II type 1 receptors[AT(1)R], p47(phox), β‐myosin heavy chain isozyme switch, accumulation of AGE, fibrosis, and decreased expression of sarcoplasmic/endoplasmic reticulum Ca(2+)‐ATPase. Pharmacological inhibition or genetic deletion of CB1 receptors attenuated the diabetes‐induced cardiac dysfunction and the above‐mentioned pathological alterations. Activation of CB1 receptors by endocannabinoids may play an important role in the pathogenesis of diabetic cardiomyopathy by facilitating MAPK activation, AT(1)R expression/signaling, AGE accumulation, oxidative/nitrative stress, inflammation, and fibrosis. Conversely, CB1 receptor inhibition may be beneficial in the treatment of diabetic cardiovascular complications.

CB1 receptor inhibition leads to decreased vascular AT1 receptor expression, inhibition of oxidative stress and improved endothelial function

Inhibition of the cannabinoid receptor CB(1) (CB(1)-R) exerts numerous positive cardiovascular effects such as modulation of blood pressure, insulin sensitivity and serum lipid concentrations. However, direct vascular effects of CB(1)-R inhibition remain unclear. CB(1)-R expression was validated in vascular smooth muscle cells (VSMCs) and aortic tissue of mice. Apolipoprotein E-deficient (ApoE-/-) mice were treated with cholesterol-rich diet and the selective CB(1)-R antagonist rimonabant or vehicle for 7 weeks. CB(1)-R inhibition had no effect on atherosclerotic plaque development, collagen content and macrophage infiltration but led to improved aortic endothelium-dependent vasodilation and decreased aortic reactive oxygen species (ROS) production and NADPH oxidase activity. Treatment of cultured VSMC with rimonabant resulted in reduced angiotensin II-mediated but not basal ROS production and NADPH oxidase activity. CB(1)-R inhibition with rimonabant and AM251 led to down-regulation of angiotensin II type 1 receptor (AT1-R) expression, whereas stimulation with the CB(1)-R agonist CP 55,940 resulted in AT1-R up-regulation, indicating that AT1-R expression is directly regulated by the CB(1)-R. CB(2)-R inhibition had no impact on AT1-R expression in VSMC. Consistently, CB(1)-R inhibition decreased aortic AT1-R expression in vivo. CB(1)-R inhibition leads to decreased vascular AT1-R expression, NADPH oxidase activity and ROS production in vitro and in vivo. This antioxidative effect is associated with improved endothelial function in ApoE-/- mice, indicating beneficial direct vascular effects of CB(1)-R inhibition.

Abstract 5224: CB1 Receptor Inhibition Leads to Decreased Vascular AT1 Receptor Expression, Inhibition of Oxidative Stress and Improved Endothelial Function

Inhibition of the cannabinoid receptor CB1 (CB1-R) exerts numerous effects such as modulation of blood pressure, insulin sensitivity and lipid concentrations. However, direct vascular effects of CB1-R inhibition remain unclear. Methods and Results: CB1-R expression was validated in vascular smooth muscle cells (VSMC) and aortic tissue of mice (real-time RT-PCR). Treatment of cultured VSMC with the selective CB1-R antagonist rimonabant resulted in reduced angiotensin II (ang II)-mediated reactive oxygen species (ROS) production (DCF fluorescence) and NADPH oxidase activity (lucigenin-enhanced chemiluminescence). Because rimonabant inhibited ang II-induced but not basal ROS production, and ang II activates NADPH oxidase through ang II type-1 receptor (AT1-R) stimulation, we analyzed AT1-R expression in VSMC. CB1-R inhibition with rimonabant or AM251 led to down-regulation of AT1-R protein expression (Western blot), stimulation with the CB1-R agonist CP55,940 resulted in AT1-R up-regulation, and co-incubation with CP55,940 abolished the effect of rimonabant, indicating that AT1-R expression is directly regulated by the CB1-R. The expression of rac1 and MnSOD was not affected. VSMC showed no significant expression of the CB2-R under basal conditions (real-time PCR, Western blot), and CB2-R inhibition had no impact on AT1-R expression in VSMC. To investigate the relevance of CB1-R inhibition in vivo, apolipoprotein E-deficient (ApoE−/−) mice were treated with cholesterol-rich diet and rimonabant or vehicle for 7 weeks. Consistent with the in vitro findings, CB1-R inhibition decreased AT1-R expression (real-time RT-PCR, Western blot), NADPH oxidase activity, and ROS production (L-012 chemiluminescence) in the aortic wall. Importantly, CB1-R inhibition improved endothelium-dependent vasodilation of isolated aortic segments (organ chamber experiments), indicating a functional relevance in vivo. Conclusions: CB1-R inhibition leads to decreased vascular AT1-R expression, NADPH oxidase activity and ROS production in vitro and in vivo. This antioxidative effect is associated with improved endothelial function in ApoE−/− mice, indicating beneficial direct vascular effects of CB1-R inhibition.

UP-1.008: Inhibition of CB1 Receptor Protects against Cisplatin-Induced Nephrotoxicity

UP-1.008: Inhibition of CB1 Receptor Protects against Cisplatin-Induced Nephrotoxicity

Cannabinoid CB1 receptor inhibition decreases vascular smooth muscle migration and proliferation

Vascular smooth muscle proliferation and migration triggered by inflammatory stimuli and chemoattractants such as platelet‐derived growth factor (PDGF) are key events in the development and progression of atherosclerosis and restenosis. Cannabinoids may modulate cell proliferation and migration in various cell types through cannabinoid receptors. Here we investigated the effects of CB1 receptor antagonist rimonabant (SR141716A), which has recently been shown to have anti‐atherosclerotic effects both in mice and humans on PDGF‐induced proliferation, migration, and signal transduction of human coronary artery smooth muscle cells (HCASMCs). PDGF‐induced Ras and ERK 1/2 activation, while increasing pro‐liferation and migration of HCASMCs, which were dose dependently attenuated by CB1 antagonist, rimonabant. These findings suggest that in addition to improving plasma lipid alterations and decreasing inflammatory cell migration and inflammatory response, CB1 antagonists may exert beneficial effects in atherosclerosis and restenosis by decreasing vascular smooth muscle proliferation and migration.

Cannabinoid CB1 receptor inhibition decreases vascular smooth muscle migration and proliferation

Vascular smooth muscle proliferation and migration triggered by inflammatory stimuli and chemoattractants such as platelet-derived growth factor (PDGF) are key events in the development and progression of atherosclerosis and restenosis. Cannabinoids may modulate cell proliferation and migration in various cell types through cannabinoid receptors. Here we investigated the effects of CB1 receptor antagonist rimonabant (SR141716A), which has recently been shown to have anti-atherosclerotic effects both in mice and humans, on PDGF-induced proliferation, migration, and signal transduction of human coronary artery smooth muscle cells (HCASMCs). PDGF induced Ras and ERK 1/2 activation, while increasing proliferation and migration of HCASMCs, which were dose dependently attenuated by CB1 antagonist, rimonabant. These findings suggest that in addition to improving plasma lipid alterations and decreasing inflammatory cell migration and inflammatory response, CB1 antagonists may exert beneficial effects in atherosclerosis and restenosis by decreasing vascular smooth muscle proliferation and migration.

Antagonism of endocannabinoid receptor CB1 directly increases basal and insulin‐stimulated glucose transport activity in soleus muscle of lean Zucker rats

The endocannabinoid system is emerging as a new pharmacological target in the treatment of obesity and insulin resistance. It is known that endocannabinoid receptors (CB1 subtype) are expressed in rat skeletal muscle. However, it is currently unknown what role, if any, modulation of these receptors might have on the glucose transport system in skeletal muscle. Therefore, the goal of this study was to determine whether glucose transport activity in soleus muscle of lean Zucker rats is directly affected by selective CB1 receptor inhibition. Soleus muscle strips from lean Zucker rats were incubated for 60 min in the absence or presence of a maximally‐effective insulin concentration (5 mU/ml) and increasing concentrations (25–1000 nM) of the CB1 receptor antagonist, SR 141716. In the absence of insulin, SR141716 at 100–200 nM activated glucose transport (2‐deoxyglucose uptake) by 33% (p<0.05), with an EC50 of ~50 nM. Insulin‐stimulated glucose transport was enhanced 37% (p<0.05) by 100 nM SR141716, again with an EC50 of ~50 nM. These SR141716‐mediated increases were substantially reduced at the highest concentrations of the CB1 receptor antagonist. These results support the hypothesis that the glucose transport system in rat skeletal muscle is directly and positively modulated by CB1 receptor antagonism.

N-arachidonylethanolamide relaxation of bovine coronary artery is not mediated by CB1 cannabinoid receptor.

It has been reported that the endogenous cannabinoid N-arachidonylethanolamide (AEA), commonly referred to as anandamide, has the characteristics of an endothelium-derived hyperpolarizing factor in rat mesenteric artery. We have carried out studies to determine whether AEA affects coronary vascular tone. The vasorelaxant effects of AEA were determined in isolated bovine coronary artery rings precontracted with U-46619 (3 x 10(-9) M). AEA decreased isometric tension, producing a maximal relaxation of 51 +/- 9% at a concentration of 10(-5) M. Endothelium-denuded coronary arteries were not significantly affected by AEA. The CB1 receptor antagonist SR-141716A (10(-6)M) failed to reduce the vasodilatory effects of AEA, suggesting that the CB1 receptor is not involved in this action of AEA. Because AEA is rapidly converted to arachidonic acid and ethanolamine in brain and liver by a fatty acid amide hydrolase (FAAH), we hypothesized that the vasodilatory effect of AEA results from its hydrolysis to arachidonic acid followed by enzymatic conversion to vasodilatory eicosanoids. In support of this hypothesis, bovine coronary arteries incubated with [3H]AEA for 30 min hydrolyzed 15% of added substrate; approximately 9% of the radiolabeled product was free arachidonic acid, and 6% comigrated with the prostaglandins (PGs) and epoxyeicosatrienoic acids (EETs). A similar result was obtained in cultured bovine coronary endothelial cells. Inhibition of the FAAH with diazomethylarachidonyl ketone blocked both the metabolism of [3H]AEA and the relaxations to AEA. Whole vessel and cultured endothelial cells prelabeled with [3H]arachidonic acid synthesized [3H]PGs and [3H]EETs, but not [3H]AEA, in response to A-23187. Furthermore, SR-141716A attenuated A-23187-stimulated release of [3H]arachidonic acid, suggesting that it may have actions other than inhibition of CB1 receptor. These experiments suggest that AEA produces endothelium-dependent vasorelaxation as a result of its catabolism to arachidonic acid followed by conversion to vasodilatory eicosanoids such as prostacyclin or the EETs.