Vitamin D protects against necrotising enterocolitis in newborn mice by activating the ERK signalling pathway.

Necrotising enterocolitis (NEC) is a serious intestinal disease that occurs in the neonatal period. The present study aimed to investigate the protective effect of vitamin D on NEC and the underlying mechanisms. Artificial feeding and hypoxia-cold stimulation were used to establish a mouse NEC model. IEC-6 cells were treated with lipopolysaccharide (LPS) to establish thein vitroNEC model. Changes in the levels of interleukin (IL)-6, IL-1 beta and tumour necrosis factor (TNF)-alpha, and activities of malondialdehyde (MDA) and glutathione peroxidase (GPx) were investigated via ELISA kits. In addition, mRNA expression of IL-6, IL-1 beta and TNF-alpha and protein expression of phosphorylated (p)-ERK1/2, Ki67, cleaved caspase-3 and Bcl-2 in intestinal tissues were determined via reverse transcription-quantitative PCR and western blotting. Cell proliferation and apoptosis were also analysed via MTT assay and flow cytometry. In NEC mice, vitamin D reduced intestinal tissue damage, decreased the mRNA expression of IL-6, IL-1 beta and TNF-alpha, and decreased the protein expression of cleaved caspase-3 and MDA. Whereas, vitamin D increased the protein expression of Bcl-2 and Ki67 and GPx, as well as the p-ERK1/2/ERK1/2 ratio, in NEC mice. Furthermore, vitamin D improved cell viability, increased the ratio of p-ERK1/2/ERK1/2, inhibited apoptosis, and decreased the mRNA expression of IL-6, IL-1 beta and TNF-alpha in LPS-treated IEC-6 cells. The dual-specificity mitogen-activated protein kinase kinase inhibitor PD98059 reversed the effects of vitamin D on the proliferation, apoptosis and inflammation of LPS-treated IEC-6 cells. Overall, vitamin D relieved NEC in mice. Vitamin D promoted proliferation, and inhibited apoptosis and inflammation of LPS-treated IEC-6 cells by activating the ERK signalling pathway.