Altered microbiome-enteric glial cell-NADPH oxidase axis is key to deployment-associated gastrointestinal inflammatory phenotypes

Most veterans who return from war theater report clinical symptoms of gastrointestinal disorders characterized by bloating, pain constipation, and diarrhea similar to inflammatory bowel disease (IBS). Our previous studies have linked some of these symptoms to an altered gut microbiome which results in inflammation and oxidative damage in the gut. Of emerging significance are enteric glial cells (EGC) which reside in close proximity to enteric neurons and have recently been found to regulate the gut microenvironment in homeostatic and diseased states in IBS and IBD. Moreover, they are known to change to a reactive phenotype in the presence of pathogenic bacteria mediated by nitosative stress. In this study, using both in-vivo and in-vitro models, we hypothesize that an altered microbiome correlates with a reactive EGC phenotype which contributes to oxidative stress in deployment associated gastrointestinal disorders. Our results show that EGC in mice treated with war theatre chemicals (PB and Permethrin) changed to a reactive phenotype via TLR4-S100β/RAGE-NO pathway, that correlated well with downstream NOX-2 activation. Furthermore, there was an increase in nitrosative stress and inflammation, which was not observed in mice treated with antibiotics suggesting that the downstream redox signaling in EGCs were mediated by an altered microbiome. Mechanistically, EGC cells treated with LPS-RS, a TLR4 blocker and NADPH oxidase inhibitor apocynin showed a decreased activation of S100β/RAGE-NO pathway, with attenuated inflammation compared to LPS treated groups. The results show that targeting NOX2 production in reactive EGC may hold promising therapeutic potential in treating deployment-related gastrointestinal inflammatory functional disorders.