TJP2 and inflammatory bowel disease: While the underlying mechanism is still unclear, accumulating evidences indicate that vitamin D play a preventive role in IBD development via regulating immune response, modulating the release of inflammatory cytokines [27, 28], improving intestinal epithelial barrier function by increasing the expression of some tight junction proteins such as Occludin, Zo-1, Zo-2, Vinculin and Claudins [29, 30], inducing colon cells senescence to secret senescence-associated inflammatory cytokines [11], and increasing antimicrobial peptide synthesis and secretion [31].