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Smooth muscle IL-4 receptor activation induces airway hyper-responsiveness

ABSTRACT: Selective stimulation of IL-4 receptor on smooth muscle induces airway hyper-responsiveness in mice. Abstract: Production of the cytokines IL-4 and IL-13 is increased in both human asthma and mouse asthma models and Stat6 activation by the common IL-4/IL-13R drives most mouse model pathophysiology, including airway hyperresponsiveness (AHR). However, the precise cellular mechanisms through which IL-4Rα induces AHR remain unclear. Overzealous bronchial smooth muscle constriction is thought to underlie AHR in human asthma, but the smooth muscle contribution to AHR has never been directly assessed. Furthermore, differences in mouse vs. human airway anatomy and observations that selective IL-13 stimulation of Stat6 in airway epithelium induces murine AHR raise questions about the importance of direct IL-4R effects on smooth muscle in murine asthma models and relevance of these models to human asthma. Using transgenic mice in which smooth muscle is the only cell type that expresses or fails to express IL-4Rα, we demonstrate that direct smooth muscle activation by IL-4, IL-13, or allergen is sufficient, but not necessary, to induce AHR and show that 5 genes known to promote smooth muscle migration, proliferation and contractility are activated by IL-13 in smooth muscle in vivo. These observations demonstrate that IL-4Rα promotes AHR through multiple mechanisms and provide a model for testing smooth muscle-directed asthma therapeutics.

ORGANISM(S): Mus musculus

PROVIDER: GSE26476 | GEO | 2011/01/07

SECONDARY ACCESSION(S): PRJNA136527

REPOSITORIES: GEO

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Project description:Selective stimulation of IL-4 receptor on smooth muscle induces airway hyper-responsiveness in mice. Abstract: Production of the cytokines IL-4 and IL-13 is increased in both human asthma and mouse asthma models and Stat6 activation by the common IL-4/IL-13R drives most mouse model pathophysiology, including airway hyperresponsiveness (AHR). However, the precise cellular mechanisms through which IL-4Rα induces AHR remain unclear. Overzealous bronchial smooth muscle constriction is thought to underlie AHR in human asthma, but the smooth muscle contribution to AHR has never been directly assessed. Furthermore, differences in mouse vs. human airway anatomy and observations that selective IL-13 stimulation of Stat6 in airway epithelium induces murine AHR raise questions about the importance of direct IL-4R effects on smooth muscle in murine asthma models and relevance of these models to human asthma. Using transgenic mice in which smooth muscle is the only cell type that expresses or fails to express IL-4Rα, we demonstrate that direct smooth muscle activation by IL-4, IL-13, or allergen is sufficient, but not necessary, to induce AHR and show that 5 genes known to promote smooth muscle migration, proliferation and contractility are activated by IL-13 in smooth muscle in vivo. These observations demonstrate that IL-4Rα promotes AHR through multiple mechanisms and provide a model for testing smooth muscle-directed asthma therapeutics. For the microarray aspect of of the study, there were three groups of mice: 1. IL4R gene knockout (KO) mice 2. WT mice 3. IL4R KO mice that were also transgenic for a gene construct that expressed IL4R under the control of the smooth muscle-specific promoter from the SMP8 gene All mice were subjected to intratracheal IL13 exposure for 7 days, and whole lung RNA was prepared for microarray analysis 24 hours after the last instillation. Per treatment and genotype: Two RNA pools were made from four mice each. These were labeled and hybridized to make a total of 6 microarrays. RNA was labeled with the standard Affymetrix 3' labeling protocol to make cDNA that was hybridized to Mouse MOE 430 plus 2.0 GeneChips. Gene transcripts were identified that differed in their relative expression as a function of IL4R expression on the smooth muscle cells.

Project description:Mechanisms by which regulatory T (Treg) cells fail to control inflammation in asthma remain poorly understood. We show that a severe asthma-associated polymorphism in the interleukin-4 receptor alpha chain (IL-4Rα-R576) biases induced Treg (iTreg) cells towards a T helper 17 (TH17) cell fate. This skewing reflects the recruitment by IL-4Rα-R576 of the adaptor protein growth factor receptor-bound protein 2 (GRB2), which drives IL-17 expression by an extracellular signal-regulated kinase-, IL-6- and STAT3-dependent mechanism. We showed that the IL-4Rα-R576 mutation elicits TH17 airway responses in vivo, in a house dust mite (HDM)- or ovalbumin (OVA)-driven model of airway inflammation in the mice carry the IL-4Rα-R576 mutation (Il4raR576 mice). Treg cell-specific deletion of genes encoding IL-6Rα or the master TH17 cell regulator Retinoid-related Orphan Receptor γt (RORγt), but not IL-4 and IL-13, protected mice against exacerbated airway inflammation induced by IL-4Rα--576. Analysis of lung tissue Treg cells revealed that the expression of IL-17 and the TH17 cell-associated chemokine receptor CCR6 was largely overlapping and highly enriched in Treg and conventional T (Tconv) cells of allergen-treated Il4raR576 mice. To further characterize the subset of IL-17 producing Foxp3+ Treg in the lung of OVA-treated mice we utilized CCR6 as a marker of Treg cells committed towards the TH17 cell lineage to examine their functional, epigenetic and transcriptional profiles. CCR6+Foxp3EGFP+ Treg cells isolated from OVA-sensitized and challenged Il4raR576 mice, by FACS (Fluorescence Activated Cell Sorting) exhibited decreased methylation of the Foxp3 CNS2 locus comparing to CCR6–Foxp3EGFP+ Treg cells from same animals, indicative of decreased stability. They also exhibited profoundly decreased suppressive function as compared to CCR6– WT and CCR6– Il4raR576 counterparts. Transcriptional profiling of CCR6+Foxp3EGFP+ Treg cells revealed increased relative expression in CCR6+ Il4raR576 Treg cells of genes associated with a TH17 cell signature, including Rorc, Ccr6, Il23r, Il17a, Il17f, Il1r1, Nr1d1, Cstl, and Ahr comparing to CCR6–Foxp3EGFP+ Treg cells from same animals.

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Smooth muscle IL-4 receptor activation induces airway hyper-responsiveness

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