Molina, Jose G.

Abstract Regulatory T-cell (Treg) deficiency causes lethal, CD4+T cell-driven autoimmune diseases. Stem cell transplantation is used to treat these diseases, but this procedure is limited by the availability of a suitable donor. The intestinal microbiota drives host immune homeostasis by regulating the development of Treg, Th1 and Th2 cells. It is currently unclear if Treg-deficiency autoimmune disorders can be treated by targeting the enteric microbiota. Our aims are to determine the autoimmunity, gut microbiota, and plasma metabolomics affected by probiotic Lactobacillus reuteri DSM 17938 (LR), and to further identify the mechanism of modulated metabolite(s) in suppressing autoimmunity in Treg-deficient scurfy (SF) mice. We demonstrated that Foxp3+Treg deficiency results in gut microbial dysbiosis and autoimmunity over the lifespan of SF mouse. Remodeling microbiota with LR prolonged survival and reduced multi-organ inflammation in SF mice. LR changed the metabolomics profile disrupted by Treg-deficiency with a major effect of restoring levels of the purine metabolite inosine. Feeding inosine itself prolonged life and inhibited multi-organ inflammation by reducing Th1/Th2 cells and their associated cytokines. Mechanistically, the inhibition of inosine on the differentiation of Th1 and Th2 cells in vitro depended on adenosine A2A receptors. Both A2A receptor specific antagonist or genetically knockout A2A to SF mice reversed the anti-inflammatory effects of both inosine and LR in vivo. In conclusions, A2A receptors mediate a substantial protective effect of inosine and LR. The LR-modulated-microbiota-inosine-A2A axis might represent a potential avenue for combatting autoimmune diseases mediated by Treg dysfunction.

Abstract Adenosine signaling has been implicated in chronic lung diseases such as asthma and chronic obstructive pulmonary disease; however, the specific roles of the various adenosine receptors in processes central to these disorders are not well understood. In this study, we have investigated the role(s) of the A3 adenosine receptor in adenosine-dependent pulmonary inflammation observed in adenosine deaminase (ADA)-deficient mice. The A3 receptor (A3R) was found to be expressed in eosinophils and mucus-producing cells in the airways of ADA-deficient mice. Treatment of ADA-deficient mice with MRS 1523, a selective A3R antagonist, prevented airway eosinophilia and mucus production. Similar findings were seen in the lungs of ADA/A3 double knockout mice. Although eosinophils were decreased in the airways of ADA-deficient mice following antagonism or removal of the A3R, elevations in circulating and lung interstitial eosinophils persisted, suggesting signaling through the A3R is needed for the migration of eosinophils into the airways. These findings identify an important role for the A3R in regulating lung eosinophilia and mucus production in an environment of elevated adenosine.

Abstract Adenosine is a signaling molecule produced during conditions that cause cellular stress or damage. This signaling pathway is implicated in the regulation of pulmonary disorders through the selective engagement of adenosine receptors. The goal of this study was to examine the involvement of the A3 adenosine receptor (A3R) in a bleomycin model of pulmonary inflammation and fibrosis. Results demonstrated that A3R-deficient mice exhibit enhanced pulmonary inflammation that included an increase in eosinophils. Accordingly, there was a selective up-regulation of eosinophil-related chemokines and cytokines in the lungs of A3R-deficient mice exposed to bleomycin. This increase in eosinophil numbers was accompanied by a decrease in the amount of extracellular eosinophil peroxidase activity in lavage fluid from A3R-deficient mice exposed to bleomycin, an observation suggesting that the A3R is necessary for eosinophil degranulation in this model. Despite an increase in inflammatory metrics associated with A3R-deficient mice treated with bleomycin, there was little difference in the degree of pulmonary fibrosis. Examination of fibrotic mediators demonstrated enhanced transforming growth factor (TGF)-β1 expression, but not a concomitant increase in TGF-β1 activity. This was associated with the loss of expression of matrix metalloprotease 9, an activator of TGF-β1, in alveolar macrophages and airway mast cells in the lungs of A3R-deficient mice. Together, these results suggest that the A3R serves antiinflammatory functions in the bleomycin model, and is also involved in regulating the production of mediators that can impact fibrosis.