title: Vitamin D Activation and Function in Human Corneal Epithelial Cells During TLR-Induced Inflammation.
abstract: OBJECTIVE
  Vitamin D is recognized to be an important modulator of the immune system. In the eye, studies have shown that deficiencies and genetic differences in vitamin D-related genes have a significant impact on the development of various ocular diseases. Our current study examines the ability of human corneal epithelial cells (HCEC) to activate vitamin D and the effect of vitamin D treatment on antimicrobial peptide production and cytokine modulation during inflammation, with the ultimate goal of using vitamin D therapeutically for corneal inflammation.
  
  
  METHODS
  Human corneal epithelial cells were treated with 10-7M vitamin D3 (D3) or 25-hydroxyvitamin D3 (25D3) for 24 hours and 1,25-dihydroxyvitamin D3 (1,25D3) detected by immunoassay. Human cathelicidin (LL-37) expression was examined by RT-PCR, immunoblot, and immunostaining following 1,25D3 treatment and antimicrobial activity of 1,25D3-treated cells was determined. Cells were stimulated with TLR3 agonist polyinosinic-polycytidylic acid (Poly[I:C]) for 24 hours and cytokine levels measured by RT-PCR, ELISA, and Luminex. Immunostaining determined expression of vitamin D receptor (VDR) and retinoic acid inducible gene-1 receptor (RIG-1) as well as NF-κB nuclear translocation.
  
  
  RESULTS
  When treated with inactive vitamin D metabolites, HCEC produced active 1,25D3, leading to enhanced expression of the antimicrobial peptide, LL-37, dependent on VDR. 1,25-D3 decreased the expression of proinflammatory cytokines (IL-1β, IL-6, TNFα, and CCL20) and MMP-9 induced by Poly(I:C) as well as pattern recognition receptor expression (TLR3, RIG-1, MDA5). However, early activation of NF-κB was not affected.
  
  
  CONCLUSIONS
  These studies demonstrate the protective ability of vitamin D to attenuate proinflammatory mediators while increasing antimicrobial peptides and antipseudomonas activity in corneal cells, and further our knowledge on the immunomodulatory functions of the hormone.
authors.forename: Rose Yvonne
authors.initials: RY
authors.lastname: Reins
authors.forename: Hasna
authors.initials: H
authors.lastname: Baidouri
authors.forename: Alison Marie
authors.initials: AM
authors.lastname: McDermott
mesh_terms: D002102:Cadaver; D002117:Calcitriol / Q000494:pharmacology*; D002478:Cells, Cultured; D003315:Cornea / Q000276:immunology* / Q000473:pathology; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects*; D007249:Inflammation / Q000276:immunology*; D051193:Toll-Like Receptors / Q000037:antagonists & inhibitors*; D014807:Vitamin D / Q000378:metabolism*
chemical_list: D051193:Toll-Like Receptors; D014807:Vitamin D; D002117:Calcitriol