title: Calcitriol May Down-Regulate mRNA Over-Expression of Toll-Like Receptor-2 and -4, LL-37 and Proinflammatory Cytokines in Cultured Human Keratinocytes.
abstract: BACKGROUND
  Although vitamin D analogs have been used in the topical treatment of psoriasis, their mechanisms of action are not well understand. Calcitriol, the hormonally active vitamin D3 metabolite, has been demonstrated to exert immunomodulatory effects in the skin by down-regulating the expression of Toll-like receptors (TLRs) and proinflammatory cytokines.
  
  
  OBJECTIVE
  We investigated the effects of calcitriol on the expression of TLR2, TLR4, antimicrobial peptide LL-37, and proinflammatory cytokines in cultured human keratinocytes.
  
  
  METHODS
  The mRNA expression levels of TLR2, TLR4, tumor necrosis factor α (TNF-α), interleukin (IL)-1β and LL-37 in cultured human keratinocytes were measured by real-time polymerase chain reaction (PCR) and reverse transcription (RT). Furthermore, we measured supernatant TNF-α levels by an enzyme-linked immunosorbent assay (ELISA) to confirm the effects of calcitriol on TLR2 and TLR4.
  
  
  RESULTS
  As measured by RT-PCR and real-time PCR, calcitriol was found to suppress the lipopolysaccharide- and ultraviolet B radiation-mediated induction of expression of TLRs, LL-37 and proinflammatory cytokines such as TNF-α and IL-1β in normal human keratinocytes. The supernatant TNF-α levels measured by ELISA were also suppressed after treatment with calcitriol.
  
  
  CONCLUSIONS
  Calcitriol may down-regulate inflammatory stated over-expression of LL-37 and proinflammatory cytokines.
authors: Department of Dermatology, Chung-Ang University Hospital, Seoul, Korea.
authors: Mi Sook
authors: MS
authors: Jeong
authors: Department of Dermatology, Chung-Ang University Hospital, Seoul, Korea.
authors: Ji-Yun
authors: JY
authors: Kim
authors: Department of Dermatology, Chung-Ang University Hospital, Seoul, Korea.
authors: He In
authors: HI
authors: Lee
authors: Department of Dermatology, Chung-Ang University Hospital, Seoul, Korea.
authors: Seong Jun
authors: SJ
authors: Seo
keywords: Calcitriol; TLR2; TLR4