title: MAPK regulation of IL-4/IL-13 receptors contributes to the synergistic increase in CCL11/eotaxin-1 in response to TGF-β1 and IL-13 in human airway fibroblasts.
abstract: CCL11/eotaxin-1 is a potent eosinophilic CC chemokine expressed by primary human fibroblasts. The combination of TGF-β1 and IL-13 synergistically increases CCL11 expression, but the mechanisms behind the synergy are unclear. To address this, human airway fibroblast cultures from normal and asthmatic subjects were exposed to IL-13 alone or TGF-β1 plus IL-13. Transcriptional (nuclear run-on) and posttranscriptional (mRNA stability) assays confirmed that transcriptional regulation is critical for synergistic expression of CCL11. TGF-β1 plus IL-13 synergistically increased STAT-6 phosphorylation, nuclear translocation, and binding to the CCL11 promoter as compared with IL-13 alone. STAT-6 small interfering RNA significantly knocked down both STAT-6 mRNA expression and phosphorylation and inhibited CCL11 mRNA and protein expression. Regulation of the IL-4Rα complex by TGF-β1 augmented IL-13 signaling by dampening IL-13Rα2 expression, overcoming IL-13's autoregulation of its pathway and enhancing the expression of CCL11. Our data suggest that TGF-β1 induced activation of the MEK/ERK pathway reduces IL-13Rα2 expression induced by IL-13. Thus, TGF-β1, a pleiotropic cytokine upregulated in asthmatic airways, can augment eosinophilic inflammation by interfering with IL-13's negative feedback autoregulatory loop under MEK/ERK-dependent conditions.
authors.affiliation: University of Pittsburgh Asthma Institute, University of Pittsburgh School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
authors.forename: Xiuxia
authors.initials: X
authors.lastname: Zhou
authors.forename: Haizhen
authors.initials: H
authors.lastname: Hu
authors.forename: Silvana
authors.initials: S
authors.lastname: Balzar
authors.forename: John B
authors.initials: JB
authors.lastname: Trudeau
authors.forename: Sally E
authors.initials: SE
authors.lastname: Wenzel
mesh_terms: D001249:Asthma / Q000276:immunology / Q000378:metabolism*; D015153:Blotting, Western; D054413:Chemokine CCL11 / Q000276:immunology / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000276:immunology* / Q000378:metabolism; D005347:Fibroblasts / Q000276:immunology / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D007249:Inflammation / Q000276:immunology / Q000378:metabolism; D018793:Interleukin-13 / Q000276:immunology / Q000378:metabolism; D008168:Lung / Q000276:immunology / Q000378:metabolism*; D053660:Receptors, Interleukin-13 / Q000276:immunology / Q000378:metabolism; D019948:Receptors, Interleukin-4 / Q000276:immunology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050800:STAT6 Transcription Factor / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D053773:Transforming Growth Factor beta1 / Q000276:immunology / Q000378:metabolism*
chemical_list: C515456:CCL11 protein, human; D054413:Chemokine CCL11; D018793:Interleukin-13; D053660:Receptors, Interleukin-13; D019948:Receptors, Interleukin-4; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D053773:Transforming Growth Factor beta1; D048049:Extracellular Signal-Regulated MAP Kinases