The endocannabinoid 2-arachidonoylglycerol (2-AG) regulates neurotransmission and neuroinflammation by activating CB 1 cannabinoid receptors on neurons and CB 2 cannabinoid Correspondence should be addressed to N.S. (nstella@uw.edu). 11 These authors contributed equally to this work.Note: Supplementary information is available on the Nature Neuroscience website. Competing Financial Interests:The authors declare no competing financial interests.Reprints and permissions information is available online at http://www.nature.com/reprintsandpermissions/. NIH Public Access Author ManuscriptNat Neurosci. Author manuscript; available in PMC 2011 February 1. Published in final edited form as:Nat Neurosci. 2010 August ; 13(8): 951-957. doi:10.1038/nn.2601. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript receptors on microglia. Enzymes that hydrolyze 2-AG, such as monoacylglycerol lipase, regulate the accumulation and efficacy of 2-AG at cannabinoid receptors. We found that the recently described serine hydrolase α-β-hydrolase domain 6 (ABHD6) also controls the accumulation and efficacy of 2-AG at cannabinoid receptors. In cells from the BV-2 microglia cell line, ABHD6 knockdown reduced hydrolysis of 2-AG and increased the efficacy with which 2-AG can stimulate CB 2 -mediated cell migration. ABHD6 was expressed by neurons in primary culture and its inhibition led to activitydependent accumulation of 2-AG. In adult mouse cortex, ABHD6 was located postsynaptically and its selective inhibition allowed the induction of CB 1 -dependent long-term depression by otherwise subthreshold stimulation. Our results indicate that ABHD6 is a rate-limiting step of 2-AG signaling and is therefore a bona fide member of the endocannabinoid signaling system.In the nervous system, the endocannabinoids (eCBs) arachidonoylethanolamide (anandamide) and 2-AG are produced and inactivated by neurons and glia 1,2 . The production of eCBs increases in response to specific stimuli, including membrane receptor activation, ion channel opening and calcium influx 2 . eCBs are inactivated by cellular uptake followed by intracellular enzymatic hydrolysis 3,4 . The balance between this production and inactivation dictates the levels of extracellular eCB accumulation and the ensuing activation of CB 1 receptors expressed by neurons (regulating neurotransmitter release) and CB 2 receptors expressed by microglia (regulating their motility and ability to produce immunomodulators) [4][5][6][7] . Thus, the enzymatic steps that control the production and inactivation of eCBs constitute promising molecular targets for indirectly modulating CB 1 and CB 2 receptor activity, and thereby controlling neurotransmission and neuroinflammation.Of all the steps that control the accumulation of eCBs, the hydrolytic enzymes that inactivate anandamide and 2-AG represent the most promising pharmacological and genetic targets for fine-tuning the local accumulation of these lipid transmitters. Inhibition of fatty acid amide hydrolase (FAAH) increases...

Chronic bacterial infections associated with biofilm formation are often difficult to resolve without extended courses of antibiotic therapy. Mesenchymal stem cells (MSC) exert antibacterial activity in vitro and in acute bacterial infection models, but their activity in chronic infection with biofilm models has not been previously investigated. Therefore, we studied the effects of MSC administration in mouse and dog models of chronic infections associated with biofilms. Mice with chronic Staphylococcus aureus implant infections were treated by i.v. administration of activated or non-activated MSC, with or without antibiotic therapy. The most effective treatment protocol was identified as activated MSC co-administered with antibiotic therapy. Activated MSC were found to accumulate in the wound margins several days after i.v. administration. Macrophages in infected tissues assumed an M2 phenotype, compared to untreated infections which contained predominately M1 macrophages. Bacterial killing by MSC was found to be mediated in part by secretion of cathelicidin and was significantly increased by antibiotics. Studies in pet dogs with spontaneous chronic multi drug-resistant wound infections demonstrated clearance of bacteria and wound healing following repeated i.v. administration of activated allogeneic canine MSC. Thus, systemic therapy with activated MSC may be an effective new, non-antimicrobial approach to treatment of chronic, drug-resistant infections.

Cellular therapy with allogeneic or autologous mesenchymal stem cells (MSC) has emerged as a promising new therapeutic strategy for managing inflammatory bowel disease (IBD). However, MSC therapy ideally requires a convenient and relatively homogenous cell source (typically bone marrow or adipose tissues) and the ability to generate cells with stable phenotype and function. An alternative means of generating allogeneic MSC is to derive them from induced pluripotent stem cells (iPSC), which could in theory provide an indefinite supply of MSC with well‐defined phenotype and function. Therefore, we compared the effectiveness of iPSC‐derived MSC (iMSC) and adipose‐derived MSC (adMSC) in a mouse model of IBD (dextran sodium sulfate‐induced colitis), and investigated mechanisms of intestinal protection. We found that iMSC were equivalent to adMSC in terms of significantly improving clinical abnormalities in treated mice and reducing lesion scores and inflammation in the gut. Administration of iMSC also stimulated significant intestinal epithelial cell proliferation, increased in the numbers of Lgr5+ intestinal stem cells, and increased intestinal angiogenesis. In addition, the microbiome alterations present in mice with colitis were partially restored to resemble those of healthy mice following treatment with iMSC or adMSC. Thus, iMSC administration improved overall intestinal health and healing with equivalent potency to treatment with adMSC. This therefore is the first report of the effectiveness of iMSC in the treatment of IBD, along with a description of unique mechanisms of action with respect to intestinal healing and microbiome restoration. stem cells translational medicine 2018;7:456–467

Mesenchymal stem cells (MSC) have been shown to improve wound healing and sup-press inflammatory immune responses. Newer research also indicates that MSC exhibit antimicrobial activity, although the mechanisms underlying this activity have not been fully elucidated. Therefore, we conducted in vitro and in vivo studies to examine the ability of resting and activated MSC to kill bacteria, including multidrug resistant strains. We investigated direct bacterial killing mechanisms and the interaction of MSC with host innate immune responses to infection. In addition, the activity of MSC against chronic bacterial infections was investigated in a mouse biofilm infection model. We found that MSC exhibited high levels of spontaneous direct bactericidal activity in vitro. Moreover, soluble factors secreted by MSC inhibited Staphylococcus aureus biofilm formation in vitro and disrupted the growth of established biofilms. Secreted factors from MSC also elicited synergistic killing of drug-resistant bacteria when combined with several major classes of antibiotics. Other studies demonstrated interactions of activated MSC with host innate immune responses, including triggering of neutrophil extracellular trap formation and increased phagocytosis of bacteria. Finally, activated MSC administered systemically to mice with established S. aureus biofilm infections significantly reduced bacterial numbers at the wound site and improved wound healing when combined with antibiotic therapy. These results indicate that MSC generate multiple direct and indirect, immunologically mediated antimicrobial activities that combine to help eliminate chronic bacterial infections when the cells are administered therapeutically.