Vitamin D boosts the skin's natural antimicrobial peptide LL‑37 in lab‑grown sebocyte cells by activating the vitamin D receptor, suggesting that adequate vitamin D may help strengthen skin defenses against microbes.

Antimicrobial peptides (AMPs) have been widely accepted as major contributors to cutaneous innate non-specific immunity, which is the first line of defense against invading pathogens. Altered expression of AMPs has been described in chronic inflammatory disorders of the skin. This study was conducted to clarify the expression of AMPs, including psoriasin, human β-defensin (hBD)-2, hBD-3, and LL-37, in cultured sebocytes and to evaluate the changes in the expression of AMPs in cultured sebocytes after treatment with vitamin D. Primary culture of sebocytes obtained from hair follicles of the scalp was used for this study. Cultured sebocytes were treated with vitamin D (10(-10)-10(-6) M). In addition, vitamin D (10(-10), 10(-8) and 10(-6) M) was added to sebocytes treated with vitamin D receptor (VDR) siRNA. Reverse transcription-polymerase chain reaction for psoriasin, hBD-2, hBD-3, and hCAP-18 was performed using cultured sebocytes and sebocytes treated with VDR siRNA. Western blotting for psoriasin, hBD-2, hBD-3, and hCAP-18 was also performed using sebocytes treated with vitamin D (10(-10), 10(-8), and 10(-6) M). Gene and protein expression of hCAP-18 (p < 0.05) showed an increase in sebocytes treated with vitamin D. Gene expression of hCAP-18 by treatment with vitamin D was blocked in sebocytes treated with VDR siRNA. In conclusion, treatment with vitamin D resulted in increased expression of LL-37 through the vitamin D receptor of cultured sebocytes.