The Endogenous Th17 Response in NO<inf>2</inf>-Promoted Allergic Airway Disease Is Dispensable for Airway Hyperresponsiveness and Distinct from Th17 Adoptive Transfer

Severe, glucocorticoid-resistant asthma comprises 5-7% of patients with asthma. IL-17 is a biomarker of severe asthma, and the adoptive transfer of Th17 cells in mice is sufficient to induce glucocorticoid-resistant allergic airway disease. Nitrogen dioxide (NO2) is an environmental toxin that correlates with asthma severity, exacerbation, and risk of adverse outcomes. Mice that are allergically sensitized to the antigen ovalbumin by exposure to NO2 exhibit a mixed Th2/Th17 adaptive immune response and eosinophil and neutrophil recruitment to the airway following antigen challenge, a phenotype reminiscent of severe clinical asthma. Because IL-1 receptor (IL-1R) signaling is critical in the generation of the Th17 response in vivo, we hypothesized that the IL-1R/Th17 axis contributes to pulmonary inflammation and airway hyperresponsiveness (AHR) in NO2-promoted allergic airway disease and manifests in glucocorticoid-resistant cytokine production. IL-17A neutralization at the time of antigen challenge or genetic deficiency in IL-1R resulted in decreased neutrophil recruitment to the airway following antigen challenge but did not protect against the development of AHR. Instead, IL-1R-/- mice developed exacerbated AHR compared to WT mice. Lung cells from NO2-allergically inflamed mice that were treated in vitro with dexamethasone (Dex) during antigen restimulation exhibited reduced Th17 cytokine production, whereas Th17 cytokine production by lung cells from recipient mice of in vitro Th17-polarized OTII T-cells was resistant to Dex. These results demonstrate that the IL-1R/Th17 axis does not contribute to AHR development in NO2-promoted allergic airway disease, that Th17 adoptive transfer does not necessarily reflect an endogenously-generated Th17 response, and that functions of Th17 responses are contingent on the experimental conditions in which they are generated. © 2013 Martin et al

Anti-Inflammatory Effects of Levalbuterol-Induced 11β-Hydroxysteroid Dehydrogenase Type 1 Activity in Airway Epithelial Cells

Airway epithelial NF-kB activation is observed in asthmatic subjects and is a cause of airway inflammation in mouse models of allergic asthma. Combination therapy with inhaled short-acting b2-agonists and corticosteroids significantly improves lung function and reduces inflammation in asthmatic subjects. Corticosteroids operate through a number of mechanisms to potently inhibit NF-kB activity. Since b-agonists can induce expression of 11b-HSD1, which converts inactive 11-keto corticosteroids into active 11-hydroxy corticosteroids, thereby potentiating the effects of endogenous glucocorticoids, we examined whether this mechanism is involved in the inhibition of NF-kB activation induced by the b-agonist albuterol in airway epithelial cells. Treatment of transformed murine Club cells (MTCC) with (R)-albuterol (levalbuterol), but not with (S)- or a mixture of (R+S)- (racemic) albuterol, augmented mRNA expression of 11b-HSD1. MTCC were stably transfected with luciferase (luc) reporter constructs under transcriptional regulation by NF-kB (NF-kB/luc) or glucocorticoid response element (GRE/luc) consensus motifs. Stimulation of NF-kB/luc MTCC with lipopolysaccharide (LPS) or tumor necrosis factor-α (TNFα) induced luciferase activity, which was inhibited by pretreatment with (R)-, but not (S)- or racemic albuterol. Furthermore, pretreatment of GRE/luc MTCC with (R)-albuterol augmented 11-keto corticosteroid (cortisone) induced luciferase activity, which was diminished by the 11β-HSD inhibitor glycyrrhetinic acid (18β-GA). LPS- and TNFα-induced NF-kB/luc activity was diminished in MTCC cells treated with a combination of cortisone and (R)-albuterol, an effect that was inhibited by 18β-GA. Finally, pretreatment of MTCC cells with the combination of cortisone and (R)-albuterol diminished LPS- and TNFα-induced pro-inflammatory cytokine production. These results demonstrate that levalbuterol augments conversion of inactive 11-keto corticosteroids into the active 11-hydroxy form

Airway Epithelial Indoleamine 2,3-Dioxygenase Inhibits CD4+ T Cells during Aspergillus fumigatus Antigen Exposure

Indoleamine 2,3-dioxygenase (IDO) suppresses the functions of CD4+ T cells through its ability to metabolize the essential amino acid tryptophan. Although the activity of IDO is required for the immunosuppression of allergic airway disease by the Toll-Like-Receptor 9 (TLR9) agonist, oligonucleotides comprised of cytosine and guanine nucleotides linked by phosphodiester bonds (CpG) DNA, it is unclear whether IDO expression by resident lung epithelial cells is sufficient to elicit these effects. Therefore, we created a transgenic mouse inducibly overexpressing IDO within nonciliated airway epithelial cells. Upon inhalation of formalin-fixed Aspergillus fumigatus hyphal antigens, the overexpression of IDO from airway epithelial cells of these mice reduced the number of CD4+ T cells within the inflamed lung and impaired the capacity of antigen-specific splenic CD4+ effector T cells to secrete the cytokines IL-4, IL-5, IL-13, and IFN-γ. Despite these effects, allergic airway disease pathology was largely unaffected in mice expressing IDO in airway epithelium. In support of the concept that dendritic cells are the major cell type contributing to the IDO-inducing effects of CpG DNA, mice expressing TLR9 only in the airway epithelium did not augment IDO expression subsequent to the administration of CpG DNA. Furthermore, the systemic depletion of CD11c+ cells rendered mice incapable of CpG DNA-induced IDO expression. Our results demonstrate that an overexpression of IDO within the airway epithelium represents a novel mechanism by which the number of CD4+ T cells recruited to the lung and their capacity to produce cytokines can be diminished in a model of allergic airway disease, and these results also highlight the critical role of dendritic cells in the antiasthmatic effects of IDO induction by CpG DNA

LncRNA U90926 is dispensable for the development of obesity‐associated phenotypes in vivo

Abstract Obesity is a global health problem characterized by excessive fat accumulation, driven by adipogenesis and lipid accumulation. Long non‐coding RNAs (lncRNAs) have recently been implicated in regulating adipogenesis and adipose tissue function. Mouse lncRNA U90926 was previously identified as a repressor of in vitro adipogenesis in 3T3‐L1 preadipocytes. Consequently, we hypothesized that, in vivo, U90926 may repress adipogenesis, and hence its deletion would increase weight gain and adiposity. We tested the hypothesis by applying U90926‐deficient (U9‐KO) mice to a high‐throughput phenotyping pipeline. Compared with WT, U9‐KO mice showed no major differences across a wide range of behavioral, neurological, and other physiological parameters. In mice fed a standard diet, we have found no differences in obesity‐related phenotypes, including weight gain, fat mass, and plasma concentrations of glucose, insulin, triglycerides, and free fatty acids, in U9‐KO mice compared to WT. U90926 deficiency lacked a major effect on white adipose tissue morphology and gene expression profile. Furthermore, in mice fed a high‐fat diet, we found increased expression of U90926 in adipose tissue stromal vascular cell fraction, yet observed no effect of U90926 deficiency on weight gain, fat mass, adipogenesis marker expression, and immune cell infiltration into the adipose tissue. These data suggest that the U90926 lacks an essential role in obesity‐related phenotypes and adipose tissue biology in vivo