Vitamin D3 modulates yellow catfish (Pelteobagrus fulvidraco) immune function in vivo and in vitro and this involves the vitamin D3/VDR-type I interferon axis

Vitamin D₃ (VD₃) has been shown to regulate immune function in mammals. 1,25-dihydroxyvitamin (1,25(OH)₂D₃) is the active form of vitamin D₃, which is also known as calcitriol. The current study investigated the immunomodulatory effects of 1,25(OH)₂D₃ on the innate immune response of yellow catfish (Pelteobagrus fulvidraco) after in vivo and in vitro immune challenge. The in vivo results showed that increasing dietary vitamin D₃ decreased mortality, enhanced the immune protective rate, and increased serum lysozyme, catalase and SOD activities in yellow catfish infected with Edwardsiella Ictaluri (p < 0.05). The in vitro results showed that 1,25(OH)₂D₃ (0, 1, 10, 100, 200 pM) dose-dependently attenuated the rate of apoptosis and production or reactive oxygen species and increased the phagocytic activity of head kidney macrophages stimulated with 10 mg/L lipopolysaccharide (LPS) and 100 mg/L of Poly(I:C) (p < 0.05). Real-time quantitative PCR results showed that increasing dietary vitamin D₃ content in vivo and increasing the level of 1,25(OH)₂D₃in vitro partially regulated the expression of VD₃/VDR-type I interferon axis genes (vdr, irf-3, ifn-a, jak1, stat1, ifi56 and ifp35) after immune challenge. These results indicated that vitamin D₃ content helped yellow catfish to resist oxidative stress and inflammation caused by immune challenge, and immunomodulation involved the VD₃/VDR-type I interferon action axis.