title: Induction of GITRL expression in human keratinocytes by Th2 cytokines and TNF-α: implications for atopic dermatitis.
abstract: BACKGROUND
  Glucocorticoid-induced TNF receptor-related protein ligand (GITRL), a ligand for the T cell co-stimulatory molecule GITR, is expressed by keratinocytes and involved in chemokine production. The expression of GITRL in skin inflammation remains unknown.
  
  
  OBJECTIVE
  This study investigated cytokine regulation of keratinocyte GITRL expression.
  
  
  METHODS
  Glucocorticoid-induced TNF receptor expression was evaluated in cytokine-treated human epidermal keratinocytes (HEK)s, murine PAM 212 cell line, murine and human skin explants by real time PCR, flow cytometry and immunostaining. Functional responses to GITR fusion protein were examined by real time PCR and ELISA. GITRL expression in AD and psoriasis was studied by immunohistochemistry.
  
  
  RESULTS
  Skin biopsies from STAT6VT transgenic mice, which develop spontaneous atopic skin inflammation, were found by immunofluoresence, to have increased keratinocyte GITRL expression. Exposure to Th2 cytokines augmented GITRL mRNA expression in the murine PAM 212 keratinocytic cell line and murine skin explants. In contrast, GITRL mRNA and protein expression was only increased in HEKs and human skin explants in the presence of the combination of TNF-α and Th2 cytokines. A synergistic effect of Th2 cytokines and GITR fusion protein on production of CCL17, the Th2 chemokine, by murine keratinocytes was demonstrated. Immunohistochemical staining showed that acute AD lesions have increased expression of GITRL compared with normal skin, chronic AD lesions and psoriatic plaques.
  
  
  CONCLUSIONS
  Our studies demonstrate that GITRL expression is augmented by Th2 cytokines and TNF-α in keratinocytes. Increased GITRL expression in acute AD skin lesions is shown. This observation suggests a link between cytokine-regulated keratinocyte GITRL expression and its role in inflammatory responses in AD.
authors.affiliation: Department of Pediatrics, National Jewish Health, 1400 Jackson Street, Denver, CO 80206, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Byrne
authors.forename: E
authors.initials: E
authors.lastname: Goleva
authors.forename: F
authors.initials: F
authors.lastname: Chouiali
authors.forename: M H
authors.initials: MH
authors.lastname: Kaplan
authors.forename: Q A
authors.initials: QA
authors.lastname: Hamid
authors.forename: D Y M
authors.initials: DY
authors.lastname: Leung
mesh_terms: D000818:Animals; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D003876:Dermatitis, Atopic / Q000276:immunology / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000276:immunology / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D060888:Real-Time Polymerase Chain Reaction; D018418:Th2 Cells / Q000276:immunology / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism*; D048069:Tumor Necrosis Factors / Q000276:immunology / Q000378:metabolism*
chemical_list: D016207:Cytokines; C478967:TNFSF18 protein, human; D014409:Tumor Necrosis Factor-alpha; D048069:Tumor Necrosis Factors