Endocannabinoid and immune system alterations at moderate (18 m/min) and endurance (32 m/min) exercise intensities were assessed and compared to controls. Rats were exercised for 60 minutes/day, 5 days/week for 16 weeks. Immune effector cell proportions (T cell subtypes, B cells, NK cells, and neutrophils) and endocannabinoid serum levels were determined. Anandamide (ANA) and 2 arachidonyl-glycerol (2-AG) serum levels increased with endurance type of exercise. mRNA expression of the CB1 receptor increased together with ANA in the same group. Apoptotic index increased while immune effector cells responded divergently. B lymphocyte percentage decreased while T lymphocyte and NK cell percentage increased in blood. CD8+ subtypes increased whereas CD11b+ cell and CD25+ cell numbers decreased in the spleen in the endurance type of exercise group. Rats were grouped as the control, the endurance type of exercise, the AM281 (CB1 receptor antagonist) and the AM281+AM630 (CB2 receptor antagonist) groups in the second part of the study. Flow cytometry and microarray analyses of the spleen and the thymus were conducted. Endurance type of exercise associated significantly to immunological changes particularly to that of the T lymphocytes. T lymphocytes increased whereas cytolytic T lymphocytes decreased in blood. T cell and double positive T cell percentages significantly increased in the spleen. Activated T cells and NK like T cells furthermore decreased in the spleen. AM281 and/or AM630 could partially reverse the effect of exercise in blood but not in the spleen. Alterations in the thymus were not observed. Exercise altered 302 genes, some of them related with the immune system. Up-regulation of heat-shock protein coding genes was the most significant ones.

The endogenous cannabinoids (endocannabinoids) anandamide (AEA) and 2-arachidonylglycerol (2-AG) exert their effects predominantly through cannabinoid CB1 and CB2 receptors, but these actions are short-lived because of rapid hydrolysis by fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), respectively. Selective inhibition of either enzyme elevates CNS levels of the appropriate endocannabinoid and produces analgesic effects with fewer psychomimetic side effects than Δ9-tetrahydrocannabinol (THC), the primary active constituent of marijuana. While cannabinoid receptor agonists and FAAH inhibitors reliably produce anti-inflammatory and anti-hyperalgesic effects in the carrageenan test and other inflammatory pain models, much less is known about the consequences of inhibiting MAGL in these assays. Here, we tested whether the selective MAGL inhibitor JZL184 would reduce nociceptive behavior in the carrageenan test. JZL184 significantly attenuated carrageenan-induced paw edema and mechanical allodynia, whether administered before or after carrageenan. Complementary genetic and pharmacological approaches revealed that JZL184’s anti-allodynic effects required both CB1 and CB2 receptors, but only CB2 receptors mediated its anti-edematous actions. Importantly, the anti-edematous and anti-allodynic effects of JZL184 underwent tolerance following repeated injections of high dose JZL184 (16 or 40 mg/kg), but repeated administration of low dose JZL184 (4 mg/kg) retained efficacy. Interestingly, the anti-allodynic effects of the combination of low dose of JZL184 (4mg/kg) and high dose of the selective and long-acting FAAH inhibitor PF-3845 (10 mg/kg) was augmented compared with each drug alone. On the contrary, the combination treatment did not reduce edema more than either JZL184 or PR-3845 given alone. These results suggest that low doses of MAGL inhibitors alone or in combination with FAAH inhibitors, reduce inflammatory nociception through the activation of both CB1 and CB2 receptors with no evidence of tolerance following repeated administration.