BioProject

NLRX1 is a mitochondrial-associated NOD-like receptor that modulates antiviral immunity, cellular stress, autophagy, and reactive oxygen species (ROS) production. More...

NLRX1 is a mitochondrial-associated NOD-like receptor that modulates antiviral immunity, cellular stress, autophagy, and reactive oxygen species (ROS) production. The role of NLRX1 in inflammatory bowel disease (IBD) remains largely unknown. This study aimed to characterize NLRX1-mediated mechanisms of protection from IBD. We investigated the ability of NLRX1 to modulate global colonic gene expression, gut pathology, inflammation and immunity by using loss-of-function approaches in dextran sodiu sulfate (DSS) and CD4+CD45RBhigh transfer colitis models. Colons, spleens, and mesenteric lymph nodes (MLN) were excised for characterizing immune cell subsets, histological analyses, cytokine, RNA sequencing analyses, and autophagy expression, NF-κB activity, and ROS production. The loss of NLRX1 increased severity of disease and colonic histopathology in both models of IBD. Colons of NLRX1-/- mice had significantly increased epithelial ulceration and leukocyte infiltration mostly in the form of neutrophils, lymphocytes, and macrophages in the DSS model, while recipients of NLRX1-/- CD4+ T cells had increased leukocytic infiltration, proliferation, fibrosis, and crypt abscessation in both colon and ileum. The loss of NLRX1 increased numbers of effector T helper (Th1), Th17, and regulatory T cells (Treg) cells in the colonic mucosa and spleen, increased colonic NF-κB activity, upregulation of IL-17, IFNγ and TNF-α production, and increased ROS production. Global transcriptomic analyses demonstrates that NLRX1 regulates immunity and lipid metabolism pathways. NLRX1 ameliorates intestinal pathology during IBD by acting as an internal thermostat that modulates the balance of effector versus regulatory CD4+ T cell responses, and suppressing colonic NF-κB activity, inflammatory cytokine expression, lipid metabolism gene expression, ROS production and autophagy. Overall design: NLRX1 is a mitochondrial-associated NLR and has been proposed to act as an anti-inflammatory entity that prevents overzealous inflammation. Many important inflammatory pathways such as NF-κB modulation, ROS production, and autophagy have been linked to NLRX1, although exact mechanisms remain controversial. Given its multifactorial effects, NLRX1 presents as a highly powerful and novel molecule in the study of chronic immunologic diseases. In addition, the current controversy surrounding cellular and molecular mechanisms of action of NLRX1 sets the stage for further investigation. We have developed a series of experiments characterizing the effect of NLRX1 deletion on sensitivity of mice to both acute and chronic models of inflammatory bowel disease, focusing not only on clinical and immunologic differences but also exploring several mechanisms by which NLRX1 provides protection from experimental IBD. First, we show that NLRX1 deletion promotes effector T cell phenotypes in murine models of IBD; an exciting finding opening new doors for NLRX1’s effects on immune-mediated disease. NLRX1 knockout mice are more sensitive to dextran sodium sulfate induced-colitis than their wild-type counterparts, and also that lack of NLRX1 in T cells in an adoptive transfer model results in similarly increased pathology at both the tissue level and immune cell level. Indeed, expression of NLRX1 in wild-type mice under active experimental IBD conditions is significantly suppressed, highlighting its importance as a potential regulatory molecule. We further analyze the molecular pathways influencing NLRX1 during IBD and show clearly that modulation of reactive oxygen species, NF-κB activity, inflammatory cytokine production, and autophagy are all implicated. Thus, NLRX1 represents a novel and potential therapeutic target for IBD. Our findings are of great interest not only to researchers of IBD and other immune-mediated diseases, but also to the study of the lesser-known NLRs and their functions. This dataset was created using the acute DSS model. Less...