1,25-Dihydroxyvitamin-D(3) Induces Avian β-Defensin Gene Expression in Chickens

Host defense peptides (HDPs) play a critical role in innate immunity. Specific modulation of endogenous HDP synthesis by dietary compounds has been regarded as a novel approach to boost immunity and disease resistance in animal production. 1,25-dihydroxy vitamin D(3) (1,25D(3)) is well known as a powerful HDP inducer in humans, but limited information about the effect of 1,25D(3) on HDPs in poultry is available. Here, we sought to examine whether 1,25D(3) could stimulate avian β-defensin (AvBD) expression in chickens. We used chicken embryo intestinal epithelial cells (CEIEPCs) and peripheral blood mononuclear cells (PBMCs) to study the effect of 1,25D(3) on the expression of AvBDs. We observed that 1,25D(3) is able to up-regulate the expression of several AvBDs in CEIEPCs and PBMCs, whereas it increased the amounts of AvBD4 mRNA in CEIEPCs only in the presence of lipopolysaccharide (LPS). On the other hand, LPS treatment not only inhibited the expression of CYP24A1 but also altered the expression pattern of VDR in CEIEPCs. Furthermore, AvBDs were not directly regulated by 1,25D(3), as cycloheximide completely blocked 1,25D(3)-induced expression of AvBDs. Our observations suggest that 1,25D(3) is capable of inducing AvBD gene expression and is a potential antibiotic alternative through augmentation of host innate immunity as well as disease control in chickens.