Mireille Alhouayek

Increasing endogenous 2-arachidonoylglycerol levels counteracts colitis and related systemic inflammation

Inflammatory bowel diseases (IBDs) are chronic inflammatory conditions for which new therapeutic approaches are needed. Genetic and pharmacological data point to a protective role of CB1 and CB2 cannabinoid receptor activation in IBD experimental models. Therefore, increasing the endogenous levels of 2‐arachidonoylglycerol, the main full agonist of these receptors, should have beneficial effects on colitis. 2‐Arachidonoylglycerol levels were raised in the trinitrobenzene sulfonic acid (TNBS)‐induced colitis mouse model by inhibiting monoacylglycerol lipase (MAGL), the primary enzyme responsible for hydrolysis of 2‐arachidonoylglycerol, using the selective inhibitor JZL184. MAGL inhibition in diseased mice increased 2‐arachidonoylglycerol levels, leading to a reduction of macroscopic and histological colon alterations, as well as of colonic expression of proinflammatory cytokines. The restored integrity of the intestinal barrier function after MAGL inhibition resulted in reduced endotoxemia as well as reduced peripheral and brain inflammation. Coadministration of either CB1 (SR141716A) or CB2 (AM630) selective antagonists with JZL184 completely abolished the protective effect of MAGL inhibition on TNBS‐induced colon alterations, thus demonstrating the involvement of both cannabinoid receptors. In conclusion, increasing 2‐arachidonoylglycerol levels resulted in a dramatic reduction of colitis and of the related systemic and central inflammation. This could offer a novel pharmacological approach for the treatment of IBD based on the new protective role of 2‐arachidonoylglycerol described here.—Alhouayek, M., Lambert, D. M., Delzenne, N. M., Cani, P. D., Muccioli, G. G. Increasing endogenous 2‐arachidonoylglycerol levels counteracts colitis and related systemic inflammation. FASEB J. 25, 2711‐2721 (2011). www.fasebj.org

COX-2-derived endocannabinoid metabolites as novel inflammatory mediators

Cyclooxygenase-2 (COX-2) is an enzyme that plays a key role in inflammatory processes. Classically, this enzyme is upregulated in inflammatory situations and is responsible for the generation of prostaglandins (PGs) from arachidonic acid (AA). One lesser-known property of COX-2 is its ability to metabolize the endocannabinoids, N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG). Endocannabinoid metabolism by COX-2 is not merely a means to terminate their actions. On the contrary, it generates PG analogs, namely PG-glycerol esters (PG-G) for 2-AG and PG-ethanolamides (PG-EA or prostamides) for AEA. Although the formation of these COX-2-derived metabolites of the endocannabinoids has been known for a while, their biological effects remain to be fully elucidated. Recently, several studies have focused on the role of these PG-G or PG-EA in vivo. In this review we take a closer look at the literature concerning these novel bioactive lipids and their role in inflammation.

The endocannabinoid system in inflammatory bowel diseases: from pathophysiology to therapeutic opportunity

Crohns disease and ulcerative colitis are two major forms of inflammatory bowel diseases (IBD), which are chronic inflammatory disorders of the gastrointestinal tract. These pathologies are currently under investigation to both unravel their etiology and find novel treatments. Anandamide and 2-arachidonoylglycerol are endogenous bioactive lipids that bind to and activate the cannabinoid receptors, and together with the enzymes responsible for their biosynthesis and degradation [fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL)] constitute the endocannabinoid system (ECS). The ECS is implicated in gut homeostasis, modulating gastrointestinal motility, visceral sensation, and inflammation, as well as being recently implicated in IBD pathogenesis. Numerous subsequent studies investigating the effects of cannabinoid agonists and endocannabinoid degradation inhibitors in rodent models of IBD have identified a potential therapeutic role for the ECS.

Implication of the anti-inflammatory bioactive lipid prostaglandin D2-glycerol ester in the control of macrophage activation and inflammation by ABHD6

Significance 2-Arachidonoylglycerol (2-AG) is an endogenous bioactive lipid implicated in numerous (patho)physiological processes. 2-AG classically activates the cannabinoid receptors, and its activity is terminated by enzymatic hydrolysis. The main enzyme studied in this context is monoacylglycerol lipase (MAGL). Although its inhibition, to increase 2-AG levels, has proven beneficial, it is hindered by psychotropic side effects due to drastically elevated brain 2-AG. Here we show the anti-inflammatory effects of inhibition of another 2-AG hydrolase, α/β-hydrolase domain 6, without the side effects associated with MAGL inhibition. We also show that 2-AG decreases macrophage activation and this effect is not mediated by its classical receptors. Furthermore, we demonstrate that a cyclooxygenase-2–derived metabolite of 2-AG, prostaglandin D2-glycerol ester, is responsible for the documented effects. Proinflammatory macrophages are key mediators in several pathologies; thus, controlling their activation is necessary. The endocannabinoid system is implicated in various inflammatory processes. Here we show that in macrophages, the newly characterized enzyme α/β-hydrolase domain 6 (ABHD6) controls 2-arachidonoylglycerol (2-AG) levels and thus its pharmacological effects. Furthermore, we characterize a unique pathway mediating the effects of 2-AG through its oxygenation by cyclooxygenase-2 to give rise to the anti-inflammatory prostaglandin D2-glycerol ester (PGD2-G). Pharmacological blockade of cyclooxygenase-2 or of prostaglandin D synthase prevented the effects of increasing 2-AG levels by ABHD6 inhibition in vitro, as well as the 2-AG–induced increase in PGD2-G levels. Together, our data demonstrate the physiological relevance of the interaction between the endocannabinoid and prostanoid systems. Moreover, we show that ABHD6 inhibition in vivo allows for fine-tuning of 2-AG levels in mice, therefore reducing lipopolysaccharide-induced inflammation, without the characteristic central side effects of strong increases in 2-AG levels obtained following monoacylglycerol lipase inhibition. In addition, administration of PGD2-G reduces lipopolysaccharide-induced inflammation in mice, thus confirming the biological relevance of this 2-AG metabolite. This points to ABHD6 as an interesting therapeutic target that should be relevant in treating inflammation-related conditions, and proposes PGD2-G as a bioactive lipid with potential anti-inflammatory properties in vivo.

Adipose tissue NAPE-PLD controls fat mass development by altering the browning process and gut microbiota

Obesity is a pandemic disease associated with many metabolic alterations and involves several organs and systems. The endocannabinoid system (ECS) appears to be a key regulator of energy homeostasis and metabolism. Here we show that specific deletion of the ECS synthesizing enzyme, NAPE-PLD, in adipocytes induces obesity, glucose intolerance, adipose tissue inflammation and altered lipid metabolism. We report that Napepld-deleted mice present an altered browning programme and are less responsive to cold-induced browning, highlighting the essential role of NAPE-PLD in regulating energy homeostasis and metabolism in the physiological state. Our results indicate that these alterations are mediated by a shift in gut microbiota composition that can partially transfer the phenotype to germ-free mice. Together, our findings uncover a role of adipose tissue NAPE-PLD on whole-body metabolism and provide support for targeting NAPE-PLD-derived bioactive lipids to treat obesity and related metabolic disorders.

Harnessing the anti-inflammatory potential of palmitoylethanolamide

Palmitoylethanolamide (PEA) is a peroxisome proliferator-activated receptor alpha (PPAR-α) ligand that exerts anti-inflammatory, analgesic and neuroprotective actions. PEA is synthetized from phospholipids through the sequential actions of N-acyltransferase and N-acylphosphatidylethanolamine-preferring phospholipase D (NAPE-PLD), and its actions are terminated by its hydrolysis by two enzymes, fatty acid amide hydrolase (FAAH) and N-acylethanolamine-hydrolysing acid amidase (NAAA). Here, we review the impact of PEA administration in inflammatory and neurodegenerative settings and the differential role of FAAH and NAAA in controlling PEA levels. Recent studies with NAAA inhibitors put forth this enzyme as capable of increasing PEA levels in vivo in inflammatory processes, and identified it as an interesting target for drug discovery research. Thus, PEA hydrolysis inhibitors could constitute potential therapeutic alternatives in chronic inflammatory and neurodegenerative diseases.

N-Acylethanolamine-hydrolyzing acid amidase inhibition increases colon N-palmitoylethanolamine levels and counteracts murine colitis

N‐Palmitoylethanolamine or palmitoylethanolamide (PEA) is an anti‐inflammatory compound that was recently shown to exert peroxisome proliferator‐activated receptor‐α‐dependent beneficial effects on colon inflammation. The actions of PEA are terminated following hydrolysis by 2 enzymes: fatty acid amide hydrolase (FAAH), and the less‐studied N‐acylethanolaminehydrolyzing acid amidase (NAAA). This study aims to investigate the effects of inhibiting the enzymes responsible for PEA hydrolysis in colon inflammation in order to propose a potential therapeutic target for inflammatory bowel diseases (IBDs). Two murine models of IBD were used to assess the effects of NAAA inhibition, FAAH inhibition, and PEA on macroscopic signs of colon inflammation, macrophage/neutrophil infiltration, and the expression of proinflammatory mediators in the colon, as well as on the colitis‐related systemic inflammation. NAAA inhibition increases PEA levels in the colon and reduces colon inflammation and systemic inflammation, similarly to PEA. FAAH inhibition, however, does not increase PEA levels in the colon and does not affect the macroscopic signs of colon inflammation or immune cell infiltration. This is the first report of an anti‐inflammatory effect of a systemically administered NAAA inhibitor. Because NAAA is the enzyme responsible for the control of PEA levels in the colon, we put forth this enzyme as a potential therapeutic target in chronic inflammation in general and IBD in particular.—Alhouayek, M., Bottemanne, P., Subramanian, K. V., Lambert, D. M., Makriyannis, A., Cani, P. D., and Muccioli, G. G. N‐Acylethanolamine‐hydrolyzing acid amidase inhibition increases colon N‐palmitoylethanolamine levels and counteracts murine colitis. FASEB J. 29, 650‐661 (2015). www.fasebj.org

Budesonide-loaded nanostructured lipid carriers reduce inflammation in murine DSS-induced colitis

The challenge for the treatment of inflammatory bowel disease (IBD) is the delivery of the drug to the site of inflammation. Because nanoparticles have the ability to accumulate in inflamed regions, the aim of the present study was to evaluate nanostructured lipid carriers (NLCs) as nanoparticulate drug delivery systems for the treatment of IBD. Budesonide (BDS) was chosen as a candidate anti-inflammatory drug. BDS-loaded NLCs (BDS-NLC) produced by high-pressure homogenization had a size of 200 nm and a negative zeta potential. BDS-NLCs reduced the TNF-α secretion by activated macrophages (J774 cells). BDS-NLCs were more active in a murine model of dextran sulfate-induced colitis when compared with Blank-NLCs or a BDS suspension: BDS-NLCs decreased neutrophil infiltration, decreased the levels of the pro-inflammatory cytokines IL-1β and TNF-α in the colon and improved the histological scores of the colons. These data suggest that NLCs could be a promising alternative to polymeric nanoparticles as a targeted drug delivery system for IBD treatment.

Controlling 2-arachidonoylglycerol metabolism as an anti-inflammatory strategy.

The endocannabinoid system is implicated in, and regulates, several physiological processes, ranging from food intake and energy balance to pain and inflammation. 2-Arachidonoylglycerol (2-AG) is a full agonist at the cannabinoid receptors which classically mediate its effects. The activity of this bioactive lipid is dependent on its endogenous levels, which are tightly controlled by several hydrolases, monoacylglycerol lipase and α/β-hydrolase domain 6 and 12. Moreover, 2-AG is also a substrate of cyclooxygenase-2, and this reaction leads to the formation of prostaglandin glycerol esters, the effects of which remain to be fully elucidated. In this review we discuss the multiple mechanisms by which 2-AG controls inflammation and the therapeutic potential of 2-AG metabolism inhibitors.

A comparative study of curcumin-loaded lipid-based nanocarriers in the treatment of inflammatory bowel disease

Selective drug delivery to inflamed tissues is of widespread interest for the treatment of inflammatory bowel disease (IBD). Because a lack of physiological lipids has been described in patients suffering IBD, and some lipids present immunomodulatory properties, we hypothesize that the combination of lipids and anti-inflammatory drugs together within a nanocarrier may be a valuable strategy for overcoming IBD. In the present study, we investigated and compared the in vitro and in vivo efficacy of three lipid-based nanocarriers containing curcumin (CC) as an anti-inflammatory drug for treating IBD in a murine DSS-induced colitis model. These nanocarriers included self-nanoemulsifying drug delivery systems (SNEDDS), nanostructured lipid carriers (NLC) and lipid core-shell protamine nanocapsules (NC). In vitro, a 30-fold higher CC permeability across Caco-2 cell monolayers was obtained using NC compared to SNEDDS (NC>SNEDDS>NLC and CC suspension). The CC SNEDDS and CC NLC but not the CC NC or CC suspension significantly reduced TNF-α secretion by LPS-activated macrophages (J774 cells). In vivo, only CC NLC were able to significantly decrease neutrophil infiltration and TNF-α secretion and, thus, colonic inflammation. Our results show that a higher CC permeability does not correlate with a higher efficacy in IBD treatment, which suggests that lipidic nanocarriers exhibiting increased CC retention at the intestinal site, rather than increased CC permeability are efficient treatments of IBD.