Ann Dermatol.  2014 Jun;26(3):296-302.

Calcitriol May Down-Regulate mRNA Over-Expression of Toll-Like Receptor-2 and -4, LL-37 and Proinflammatory Cytokines in Cultured Human Keratinocytes

• Jeong MS
• Kim JY
• Lee HI
• Seo SJ

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 alpha (TNF-alpha), interleukin (IL)-1beta 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-alpha 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-alpha and IL-1beta in normal human keratinocytes. The supernatant TNF-alpha levels measured by ELISA were also suppressed after treatment with calcitriol.
CONCLUSION
Calcitriol may down-regulate inflammatory stated over-expression of LL-37 and proinflammatory cytokines.

Keyword

Calcitriol; TLR2; TLR4

MeSH Terms

Calcitriol*
Cholecalciferol
Cytokines*
Enzyme-Linked Immunosorbent Assay
Humans
Interleukins
Keratinocytes*
Psoriasis
Real-Time Polymerase Chain Reaction
Reverse Transcription
RNA, Messenger*
Skin
Toll-Like Receptors
Tumor Necrosis Factor-alpha
Vitamin D
Calcitriol
Cholecalciferol
Cytokines
Interleukins
RNA, Messenger
Toll-Like Receptors
Tumor Necrosis Factor-alpha
Vitamin D

Figure

• 

  Fig. 1 The expression of TLR2 and TLR4 mRNA in keratinocytes increased in response to LPS or UVB irradiation. The increased TLR2 and TLR4 mRNA expression was down-regulated upon treatment with 10 nM calcitriol. (A) Reverse transcription-polymerase chain reaction. (B) Real-time polymerase chain reaction. TLR: Toll-like receptor, LPS: lipopolysaccharide, UVB: ultraviolet B, CA: calcitriol. *p<0.05.

• 

  Fig. 2 The expression of TNF-α mRNA in keratinocytes increased in response to LPS or UVB irradiation. The increase in TNF-α mRNA expression was suppressed upon treatment with calcitriol. Expression levels of TNF-α mRNA was measured by real-time polymerase chain reaction. TNF: tumor necrosis factor, LPS: lipopolysaccharide, UVB: ultraviolet B, CA: Calcitriol. *p<0.05.

• 

  Fig. 3 The levels of secretory cytokine TNF-α in the supernatant increased in response to LPS or UVB irradiation. The increased TNF-α was down-regulated upon treatment with calcitriol. The expression level of TNF-α was quantified by enzyme-linked immunosorbent assay. TNF: tumor necrosis factor, LPS: lipopolysaccharide, UVB: ultraviolet B, CA: Calcitriol. *p<0.05.

• 

  Fig. 4 The expression of IL-1β mRNA in keratinocytes increased in response to LPS or UVB irradiation. The increase in IL-1β mRNA expression was suppressed upon treatment with calcitriol. Expression levels of IL-1β mRNA were measured by real-time polymerase chain reaction. IL: interleukin, LPS: lipopolysaccharide, UVB: ultraviolet B, CA: Calcitriol. *p<0.05.

• 

  Fig. 5 The expression of LL-37 mRNA in keratinocytes increased in response to LPS or UVB irradiation. The increase in LL-37 mRNA expression was suppressed upon treatment with calcitriol. Expression levels of LL-37 mRNA were measured by real-time polymerase chain reaction. LPS: lipopolysaccharide, UVB: ultraviolet B, CA: Calcitriol. *p<0.05.

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