[Abstract unavailable

Many of the symptoms of Gulf War Illness (GWI) that include neurological abnormalities, neuroinflammation, chronic fatigue and gastrointestinal disturbances have been traced to Gulf War chemical exposure. Though the association and subsequent evidences are strong, the mechanisms that connect exposure to intestinal and neurological abnormalities remain unclear. Using an established rodent model of Gulf War Illness, we show that chemical exposure caused significant dysbiosis in the gut that included increased abundance of phylum Firmicutes and Tenericutes, and decreased abundance of Bacteroidetes. Several gram negative bacterial genera were enriched in the GWI-model that included Allobaculum sp. Altered microbiome caused significant decrease in tight junction protein Occludin with a concomitant increase in Claudin-2, a signature of a leaky gut. Resultant leaching of gut caused portal endotoxemia that led to upregulation of toll like receptor 4 (TLR4) activation in the small intestine and the brain. TLR4 knock out mice and mice that had gut decontamination showed significant decrease in tyrosine nitration and inflammatory mediators IL1β and MCP-1 in both the small intestine and frontal cortex. These events signified that gut dysbiosis with simultaneous leaky gut and systemic endotoxemia-induced TLR4 activation contributes to GW chemical-induced neuroinflammation and gastrointestinal disturbances.

Aryl hydrocarbon receptor (AhR) has been shown to have profound influence on T cell differentiation and use of distinct AhR ligands has shown that while some ligands induce Tregs, others induce Th17 cells. In the current study, we tested the ability of dietary AhR ligands (indole-3-carbinol; I3C and 3,3'-diindolylmethane; DIM), and an endogenous AhR ligand, 6-Formylindolo(3,2-b)carbazole (FICZ), on the differentiation and functions of Tregs and Th17 cells. Treatment of C57BL/6 mice with indoles (I3C or DIM), attenuated DTH response to mBSA and generation of Th17 cells while promoting Tregs. In contrast, FICZ exacerbated the DTH response and promoted Th17 cells. Indoles decreased the induction of IL-17 while promoted IL-10 and FoxP3 expression. Also, indoles caused reciprocal induction of Tregs and Th17 cells only in wild-type (AhR+/+) but not in AhR knockout (AhR−/−) mice. Upon analysis of microRNA (miR) profile in draining lymph nodes of mice with DTH, treatment with I3C and DIM decreased the expression of several miRs (miR-31, miR-219, and miR-490) that targeted FoxP3, while increasing the expression of miR-495 and miR-1192 that were specific to IL-17. Interestingly, treatment with FICZ had precisely the opposite effects on these miRs. Transfection studies using mature miR mimics of miR-490 and miR-1192 that target FoxP3 and IL-17 respectively or scrambled miR (mock) or inhibitors confirmed that these miRs specifically targeted FoxP3 and IL-17 genes. Our studies demonstrate for the first time that the ability of AhR ligands to regulate the differentiation of Tregs versus Th17 cells may depend on miR signature profile.

Background and Aims Progression from steatosis to steatohepatitic lesions is hypothesized to require a second hit. These lesions have been associated with increased oxidative stress, often ascribed to high levels of leptin and other proinflammatory mediators. Here we have examined the role of leptin in inducing oxidative stress and Kupffer cell activation in CCl4-mediated steatohepatitic lesions of obese mice. Methods Male C57BL/6 mice fed with a high fat diet (60%kcal) at 16 weeks were administered CCl4 to induce steatohepatitic lesions. Approaches included use of immuno-spin trapping for measuring free radical stress, gene-deficient mice for leptin, p47 phox, iNOS and adoptive transfer of leptin primed macrophages in vivo. Results Diet-induced obese (DIO) mice, treated with CCl4 increased serum leptin levels. Oxidative stress was significantly elevated in DIO mice liver but not in OB/OB mice, or in DIO mice treated with leptin antibody. In OB/OB mice, leptin supplementation restored markers of free radical generation. Markers of free radical formation were significantly decreased by the peroxynitrite decomposition catalyst FeTPPS, the iNOS inhibitor 1400W, the NADPH oxidase inhibitor apocynin, or in iNOS or p47 phox-deficient mice. These results correlated with the decreased expression of TNF-alpha and MCP-1. Kupffer cell depletion eliminated oxidative stress and inflammation, whereas in macrophage-depleted mice, the adoptive transfer of leptin-primed macrophages significantly restored inflammation. Conclusions These results, for the first time, suggest that leptin action in macrophages of steatotic liver through induction of iNOS and NADPH oxidase caused peroxynitrite-mediated oxidative stress thus activating Kupffer cells.