title: IL-9 induces IL-8 production via STIM1 activation and ERK phosphorylation in epidermal keratinocytes: A plausible mechanism of IL-9R in atopic dermatitis.
abstract: BACKGROUND
  IL-9 and its receptor play important roles in the pathogenesis of asthma. Its role in atopic dermatitis (AD) was examined in just a few studies, including nucleotide polymorphisms, increased transcriptional levels of IL-9 and IL-9R in diseased skin, and an association of blood IL-9 levels with clinical severity.
  
  
  OBJECTIVE
  Little was known about the pathophysiological regulation of IL-9/IL-9R in AD skin. We asked whether IL-9R was expressed in epidermal keratinocytes; if so, what the functional outcome, cytokine production, and signaling pathway of IL-9/IL-9R in keratinocytes are.
  
  
  METHODS
  We measured and compared the expression of IL-9R in skin from AD patients and controls by immunofluorescence. We also performed in vitro studies on the IL-9-treated primary keratinocytes, including flow cytometry for IL-9R expressions, Western blotting for mTOR, S6K, ERK, p38, and STAT3 activations, ELISA for cytokine levels, and immunofluorescence for STIM1.
  
  
  RESULTS
  We found that IL-9R was indeed expressed in keratinocytes but not in fibroblasts. Its expression in keratinocytes was enhanced by IL-4 but not by TGF-beta1. IL-9 induced a moderate production of IL-8 but not CXCL16, CCL22, TSLP, nor IL-33. IL-9 induced formation of STIM1-puncta. IL-9 induced ERK phosphorylation both dose- and time-dependently, but not mTOR, S6K, p38, or STAT3. Pretreatment with U0126 (ERK inhibitor) but not rapamycin (mTOR inhibitor) abrogated the IL-9-mediated IL-8 production. Blockage of STIM1 with BTP2 or SKF96265 abrogated ERK phosphorylation and IL-8 production induced by IL-9.
  
  
  CONCLUSIONS
  This study represents the first to show the regulation of the IL-9-STIM1-ERK-IL-8 axis in keratinocyte, and how the axis might play an important role in the pathophysiology of AD.
authors.affiliation: Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Dermatology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan; Department of Dermatology, National Yang-Ming University College of Medicine, Taipei, Taiwan.
authors.forename: Chien-Hui
authors.initials: CH
authors.lastname: Hong
authors.affiliation: Department of Biochemistry, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Kee-Lung
authors.initials: KL
authors.lastname: Chang
authors.affiliation: Department of Urology, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
authors.forename: Hung-Jen
authors.initials: HJ
authors.lastname: Wang
authors.affiliation: Department of Dermatology, Kaohsiung Medical University, Kaohsiung, Taiwan; National Environmental Health Research Center, National Health Research Institute, Miao-Li, Taiwan. Electronic address: dermyu@nhri.org.tw.
authors.forename: Hsin-Su
authors.initials: HS
authors.lastname: Yu
authors.affiliation: Department of Dermatology, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan; Department of Dermatology, Chang Gung University College of Medicine, Taoyuan, Taiwan. Electronic address: dermlee@gmail.com.
authors.forename: Chih-Hung
authors.initials: CH
authors.lastname: Lee
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003876:Dermatitis, Atopic / Q000209:etiology*; D000078404:Epidermal Cells; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D006801:Humans; D015847:Interleukin-4 / Q000494:pharmacology; D016209:Interleukin-8 / Q000096:biosynthesis*; D016906:Interleukin-9 / Q000494:pharmacology*; D015603:Keratinocytes / Q000378:metabolism*; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009363:Neoplasm Proteins / Q000502:physiology*; D010766:Phosphorylation; D053651:Receptors, Interleukin-9 / Q000502:physiology*; D000071737:Stromal Interaction Molecule 1
chemical_list: C508045:IL9R protein, human; D016209:Interleukin-8; D016906:Interleukin-9; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D053651:Receptors, Interleukin-9; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D015847:Interleukin-4; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: ERK; IL-8; IL-9; IL-9R; Keratinocytes; STIM1