title: Sinonasal epithelial cells synthesize active vitamin D, augmenting host innate immune function.
abstract: BACKGROUND
  Vitamin D, long recognized for its role in bone metabolism and calcium homeostasis, has been increasingly shown to augment innate immunity. 1-α-Hydroxylase, the enzyme responsible for the synthesis of active vitamin D, has been shown to have extrarenal expression in multiple cell types, including airway epithelial cells. The purpose of this study is to explore whether sinonasal epithelial cells (SNECs) express 1-α-hydroxylase, allowing for the local production of active vitamin D, thereby augmenting innate immune function.
  
  
  METHODS
  Human SNECs were grown in culture and stimulated by inactive vitamin D. Expression of 1-α-hydroxylase was measured by real-time polymerase chain reaction and immunocytochemistry. Active vitamin D production was measured by enzyme-linked immunosorbent assay (ELISA). The expression of cathelicidin, an antimicrobial peptide, was measured by real-time polymerase chain reaction and immunocytochemistry.
  
  
  RESULTS
  SNECs constitutively express the enzyme 1-α-hydroxylase resulting in active vitamin D production. SNECs exposed to inactive vitamin D had a significant 8-fold increase in cathelicidin expression when compared to controls.
  
  
  CONCLUSIONS
  SNECs can generate active vitamin D, which significantly increases expression of the antimicrobial peptide cathelicidin. © 2013 ARS-AAOA, LLC.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21287-0910, USA.
authors.forename: Babar
authors.initials: B
authors.lastname: Sultan
authors.forename: Murugappan
authors.initials: M
authors.lastname: Ramanathan
authors.forename: Joan
authors.initials: J
authors.lastname: Lee
authors.forename: Lindsey
authors.initials: L
authors.lastname: May
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Lane
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000378:metabolism*; D023181:Antimicrobial Cationic Peptides / Q000378:metabolism*; D002117:Calcitriol / Q000378:metabolism*; D002908:Chronic Disease; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D007113:Immunity, Innate; D009297:Nasal Mucosa / Q000276:immunology; D010256:Paranasal Sinuses / Q000276:immunology; D060888:Real-Time Polymerase Chain Reaction; D012220:Rhinitis / Q000276:immunology* / Q000378:metabolism; D012852:Sinusitis / Q000276:immunology* / Q000378:metabolism; D054804:Cathelicidins
chemical_list: D023181:Antimicrobial Cationic Peptides; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D002117:Calcitriol; D054804:Cathelicidins