Modulating the endocannabinoid system in human health and disease: successes and failures

The discovery of the endocannabinoid system (ECS; comprising of G-protein coupled cannabinoid 1 and 2 receptors, their endogenous lipid ligands or endocannabinoids, and synthetic and metabolizing enzymes, triggered an avalanche of experimental studies that have implicated the ECS in a growing number of physiological/pathological functions. They also suggested that modulating ECS activity holds therapeutic promise for a broad range of diseases, including neurodegenerative, cardiovascular and inflammatory disorders, obesity/metabolic syndrome, cachexia, chemotherapy-induced nausea and vomiting, tissue injury and pain, among others. However, clinical trials with globally acting CB1 antagonists in obesity/metabolic syndrome, and other studies with peripherally restricted CB1/2 agonists and inhibitors of the endocannabinoid metabolizing enzyme in pain introduced unexpected complexities, and suggested that better understanding of the pathophysiological role of the ECS is required in order to devise clinically successful treatment strategies, which will be critically reviewed in this brief synopsis.