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BackgroundAspergillus fumigatus is a well-known opportunistic pathogen that causes a range of diseases including the often-fatal disease, invasive pulmonary aspergillosis (IPA), in immunocompromised populations. The severity of IPA is dependent on both host- and pathogen-derived signaling molecules that mediate host immunity and fungal growth. Oxylipins are bioactive oxygenated fatty acids known to influence host immune response and Aspergillus developmental programs. Aspergillus synthesizes 8-HODE and 5,8-diHODE that have structural similarities to 9-HODE and 13-HODE, which are known ligands of the host G-protein-coupled receptor G2A (GPR132).Materials and methodsOxylipins were extracted from infected lung tissue to assess fungal oxylipin production and the Pathhunter β-arrestin assay was used to assess agonist and antagonist activity by fungal oxylipins on G2A. An immunocompetent model of A. fumigatus infection was used to assess changes in survival and immune responses for G2A-/- mice.ResultsHere we report that Aspergillus oxylipins are produced in lung tissue of infected mice and in vitro ligand assays suggest 8-HODE is a G2A agonist and 5,8-diHODE is a partial antagonist. To address the hypothesis that G2A could be involved in the progression of IPA, we assessed the response of G2A-/- mice to A. fumigatus infection. G2A-/- mice showed a survival advantage over wild-type mice; this was accompanied by increased recruitment of G2A-/- neutrophils and increased levels of inflammatory markers in A. fumigatus-infected lungs.ConclusionsWe conclude that G2A suppresses host inflammatory responses to Aspergillus fumigatus although it remains unclear if fungal oxylipins are involved in G2A activities.

Glucagon, an essential regulator of glucose and lipid metabolism, also promotes weight loss, in part through potentiation of fibroblast growth factor 21 (FGF21) secretion. However, FGF21 is only a partial mediator of metabolic actions ensuing from glucagon receptor (GCGR) activation, prompting us to search for additional pathways. Intriguingly, chronic GCGR agonism increases plasma bile acid levels. We hypothesized that GCGR agonism regulates energy metabolism, at least in part, through farnesoid X receptor (FXR). To test this hypothesis, we studied whole-body and liver-specific FXR-knockout (Fxr∆liver) mice. Chronic GCGR agonist (IUB288) administration in diet-induced obese (DIO) Gcgr, Fgf21, and Fxr whole-body or liver-specific knockout (∆liver) mice failed to reduce body weight when compared with wild-type (WT) mice. IUB288 increased energy expenditure and respiration in DIO WT mice, but not Fxr∆liver mice. GCGR agonism increased [14C]palmitate oxidation in hepatocytes isolated from WT mice in a dose-dependent manner, an effect blunted in hepatocytes from Fxr∆liver mice. Our data clearly demonstrate that control of whole-body energy expenditure by GCGR agonism requires intact FXR signaling in the liver. This heretofore-unappreciated aspect of glucagon biology has implications for the use of GCGR agonism in the therapy of metabolic disorders. [ABSTRACT FROM AUTHOR]

Previous in vitro experiments demonstrated that acute-phase protein, alpha 1-antitrypsin (AAT), could act either as an enhancer or as a suppressor of lipopolysaccharide (LPS)-induced cell activation depending on treatment time. Here we investigate how AAT regulates inflammatory responses in the short term when administrated post LPS challenge. Similar experimental setup was used both in vitro and in vivo: human monocytes and neutrophils were stimulated with LPS for 2 h followed by AAT for a total time of 4 h, and C57BL/6 mice were treated intranasally with LPS and 2 h later with AAT and sacrificed after 4 h. Bronchial lavage (BAL) and lung homogenates were analyzed using bio-plex cytokine assay. BAL cell counts were assessed. Within 4 h, AAT enhanced LPS-induced tumor necrosis factor-alpha (TNFα), interleukin (IL)-6, and IL-8 release from monocytes and neutrophils. Mice challenged for 4 h with LPS followed by AAT at 2 h showed no changes in BAL cell counts and higher levels of almost all measured cytokines, specifically RANTES in BAL and IL-12, IL-13, granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF), and IL-10 levels in lung homogenates, than in mice treated with LPS only. Within the short term, AAT enhances the magnitude of LPS-induced specific cytokine/chemokine production, which may play an important role in amplification and resolution of acute-phase inflammatory reactions in vivo. [ABSTRACT FROM AUTHOR]

ALR mice are unusually resistant to T1D. Genetic elements responsible for the ALR-derived T1D resistance were identified via analysis of outcross/backcross cohorts of ALR with T1D-prone NOD. We have previously demonstrated that NADPH Oxidase (NOX) in ALR cells is inhibited. Genetic analyses have mapped inhibited NOX to a locus on Chromosome (Chr.) 3 [Suppressor of Superoxide Production (Susp)] that is also in linkage disequilibrium with ALR-derived T1D resistance. To directly determine the impact of NOX inhibition on T1D initiation, NOX-inactive NOD mice (NOD-Ncf1µ) were bred. NOD-Ncf1µ mice have significantly reduced incidence of T1D (10%) versus 85% in Ncf1 intact littermate controls and were resistant to the adoptive transfer of diabetogenic BDC2.5 CD4+ T cell clones, demonstrating that NOX plays an important role in T1D pathogenesis. To identify the gene encoded by Susp and determine the mechanism of protection, ten recombinant congenic strains (RCS), with overlapping intervals on Chr. 3, have been generated. ALR x NOD F1 hybrids demonstrated an intermediate O2• production compared to ALR (Low O2• production) and NOD (High O2• production) supporting co-dominant mode of inheritance. Using the RCS we have reduced the size of the interval containing Susp from 45 cM to 19 cM. Experiments have also been performed comparing immune system function from mice with and without NOX activity that result in T1D protection.. Splenocytes from NOD, NOD-Ncf1µ, and ALR mice were activated to assess cytokine production. Activation of NOD splenocytes led to a Th1 cytokine secretion profile as exemplified by higher levels of IFN-γ (p<0.05) and TNFα (p<0.05) synthesis when compared to NOD-Ncf1µ or ALR splenocytes. In contrast, activated NOD-Ncf1µ and ALR splenocytes secreted a cytokine profile indicative of a Th17 response as observed by higher levels of IL-17 (p<0.01) and IL-10 (p<0.05) in comparison to NOD splenocytes. In conclusion, inhibition of NOX is protective against T1D and inhibition of immune cell O2• appears to skew immune responses away from a pathogenic Th1 and towards a potentially non-pathogenic Th17 response. These results also support a role for 02• production in polarizing an immune response. [ABSTRACT FROM AUTHOR]