The enzymatic activities involved in 2-AG hydrolysis are regulated by cannabinoid receptors during aging

PASCUAL, A.C.; GAVEGLIO, V.L.; GIUSTO, N.M.; PASQUARÉ, S.J.

Waterville Valley, NH

Seminario; Gordon Research Seminar: "Cannabinoid Function in the CNS"; 2013

Endocannbinoid 2-arachidonoylglycerol (2-AG) is an endogenous ligand of the cannabinoid receptors CB1 and CB2. 2-AG is synthesized and released in response either to an increase in intracellular calcium or to the action of metabotropic agonists. The enzymes responsible for its synthesis are diacylglycerol lipase (DAGL) and lysophosphatidate phosphohydrolase (LPAase). Its hydrolysis is carried out mainly by the enzyme monoacylglycerol lipase (MAGL) although other enzymes are involved in its breakdown, such as fatty acid amide hydrolase (FAAH) and serine hydrolase ABHD. Although it is well known that endocannabinoids play a role as neuroprotectors in pathological senescent processes, their role in physiological senescent processes has not been fully elucidated to date. Our previous findings on aged rat cerebral cortex (CC) synaptosomes showed that 2-AG hydrolysis increases while its synthesis decreases. We have also demonstrated that a) in adult synaptosomes 75% of 2-AG hydrolysis corresponds to MAGL whereas the remaining 25% corresponds to FAAH, and b) although MAGL and FAAH are mainly responsible for 2-AG hydrolysis in aged synaptosomes, the participation of other serine hydrolases, such as ABHD, cannot be discarded. We thus suggest that both the synthetic and hydrolitic enzymes which control 2-AG level could be regulated by cannabinoid receptors themselves. The aim of this study was to characterize the regulation of 2-AG hydrolysis by CB1 and CB2 agonists and/or antagonists during aging. To this end, CC synaptosomes from adult (3 mo) and aged (28 mo) rats were isolated by differential centrifugation and purified in ficoll gradients. MAGL activity was assayed using 2-arachidonoyl-[3H]glycerol and the radiolabeled product [3H]glycerol was quantified from aqueous phase by liquid scintillation. Our results in aged synaptosomes show that the expression of CB receptors decreases and that 2-AG hydrolysis is inhibited in the presence of CB1 and/or CB2 antagonists. Our findings therefore confirm a modulation of 2-AG hydrolysis by CB1/CB2 antagonists in the aging process, thus suggesting a relevant therapeutic target to control 2-AG metabolism in physiological aging.