Cannabinoid-induced autophagy regulates suppressor of cytokine signaling-3 in intestinal epithelium

Abstract

Koay LC, Rigby RJ, Wright KL. Cannabinoid-induced autophagy regulates suppressor of cytokine signaling-3 in intestinal epithelium. Am J Physiol Gastrointest Liver Physiol 307: G140-G148, 2014. First published May 15, 2014; doi:10.1152/ajpgi.00317.2013.-Autophagy is a catabolic process involved in homeostatic and regulated cellular protein recycling and degradation via the lysosomal degradation pathway. Emerging data associate impaired autophagy, increased activity in the endocannabinoid system, and upregulation of suppressor of cytokine signaling-3 (SOCS3) protein expression during intestinal inflammation. We have investigated whether these three processes are linked. By assessing the impact of the phytocannabinoid cannabidiol (CBD), the synthetic cannabinoid arachidonyl-2=-chloroethylamide (ACEA), and the endocannabinoid N-arachidonoylethanolamine (AEA) on autophagosome formation, we explored whether these actions were responsible for cyclic SOCS3 protein levels. Our findings show that all three cannabinoids induce autophagy in a dose-dependent manner in fully differentiated Caco-2 cells, a model of mature intestinal epithelium. ACEA and AEA induced canonical autophagy, which was cannabinoid type 1 receptor-mediated. In contrast, CBD was able to bypass the cannabinoid type 1 receptor and the canonical pathway to induce autophagy, albeit to a lesser extent. Functionally, all three cannabinoids reduced SOCS3 protein expression, which was reversed by blocking early and late autophagy. In conclusion, the regulatory protein SOCS3 is regulated by autophagy, and cannabinoids play a role in this process, which could be important when therapeutic applications for the cannabinoids in inflammatory conditions are considered.cannabinoid; autophagy; suppressor of cytokine signaling-3 AUTOPHAGY EXHIBITS MANY physiological roles in the cellular process. Regulation and induction of autophagy correspond to an outcome for the cell: survival or death. During nutrient starving or growth factor deprivation, autophagy acts as the catabolic process to maintain homoeostasis in the cellular context. Stress-induced autophagy will recycle cellular content by transferring energy from a nonessential process to a more crucial cellular process (7,27,40). In contrast to the survival function, autophagy is utilized as a defense mechanism to eliminate the invasion of microbial content (18,23,30). In normal colonic cells, autophagy is required for renewal of the colonic epithelium. Autophagy is active at the lower part of the crypt of the colonic gland, where proliferation of stem cell populations is sustained (11). The importance of autophagy regulation in maintaining homeostasis has linked this system to various pathologies (22,45). Studies have revealed polymorphisms of various autophagy-associated genes (ATG16L1 and IRGM) with increased susceptibility to Crohn's disease (CD) (29,33). Intestinal epithelial cells line the entire gastrointestinal (GI) tract, providing a barrier to microbes and, as such, encounter high exposure to inflammatory st...

Endocannabinoid signalling and the deteriorating brain

“…Evidence shows that autophagy is reduced in aged tissues and that rapamycin, and hence mTOR inhibition, increases lifespan mainly through induction of autophagy 95 . Interestingly, autophagy measured in cancer cells is also induced by eCB signalling 96–98 . However, the underlying mechanism of this latter response is unlikely to involve the above-mentioned CB1 activation of mTOR, as this mechanism inhibits (rather than stimulates) autophagy.…”

Interplay of oxidative, nitrosative/nitrative stress, inflammation, cell death and autophagy in diabetic cardiomyopathy

“…Pharmacological inhibition or genetic deletion of CB 1 receptors was associated with attenuated diabetes-induced myocardial inflammation, decreased MAPK activation, oxidative/nitrative stress, β-MHC isoenzyme switch, AT 1 R up-regulation, myocardial RAGE and AGE expression/accumulation, MAPK activation, and largely diminished cell death and better preservation of cardiac function [38]. Recent studies indicate that cannabinoids (especially CB1 agonists) may be important inductors of autophagy in preimplantation mouse embryos [138] and in human epithelial colorectal adenocarcinoma cells (CaCo2) [139]. Although, the evidences outlined here clearly show that inflammation is one of the key therapeutically important components associated with diabetic cardiomyopathy, to see if pharmacologic modulation of cytokine as well as cannabinoid signalling and thereby autophagy has therapeutic potential, further experimental studies are required.…”

The role of CB 1 in intestinal permeability and inflammation

“…Within 2 wk, 3 to 4 clonal populations of cells were selected, passaged, and cultured for experiments with continued selection pressure. Transfection efficiency was checked by immunoblotting for CB 1 receptor expression using CB 1 receptor antibody (1: 1000, 10006590; Cambridge Bioscience, Cambridge, United Kingdom) (29). Two clones were further assessed for CB 1 receptor knockdown by the [ 35 S] GTP‐γS binding assay using the synthetic CB 1 receptor agonist arachidonyl‐2'‐chloroethylamide as described in Shore et al (30).…”