Effects of 25-hydroxyvitamin D3 on cathelicidin production and antibacterial function of human oral keratinocytes

Vitamin D and its metabolites have been recognized as key determinants in innate immune modulation. In this study, we investigated the regulation of antibacterial functions of oral keratinocyte cells by 25-hydroxyvitamin D-3 (25VD(3)). OKF6/TERT2 cells, an immortalized human oral keratinocyte cell line, were transfected with or without 24-hydroxylase small interfering RNA (siRNA) and incubated with different amounts of 25VD(3). These epithelial cells expressed high levels of inactivating 24-hydroxylase (CYP24A1) and relatively low levels of activating 1 alpha-hydroxylase (CYP27B1) in the presence of 25VD(3). 25VD(3) influenced the expression of vitamin D-driven genes and cathelicidin in a dose-related manner. SiRNA specific to 24-hydroxylase augmented the cathelicidin production and subseqently influenced the antibacterial activity on multispecies of oral pathogens. These observations suggest that 25VD(3) is capable of stimulating cathelicidin production and modulating antibacterial function upon CYP24A1 knochdown in oral epithelial cells, and indicate novel mechanisms that 25VD(3) may enhance antibacterial ability in oral keratinocytes. (C) 2013 Elsevier Inc. All rights reserved.