Background: The vitamin D receptor (VDR) is a nuclear receptor that is expressed in many tissues throughout the body, but is particularly abundant within the colon. Despite this, there is not much known about the specific role VDR plays in the gut, although its activation by calcitriol has been shown to have both cytoprotective and anti-inflammatory actions. VDR is activated by the active form of vitamin D, calcitriol as well as the secondary bile acid lithocholic acid (LCA). Vitamin D deficiency is common in patients with Inflammatory Bowel Disease (IBD) and may be a key factor underlying loss of intestinal barrier function during IBD pathogenesis. Aim: To determine if VDR activation by calcitriol is protective against cytokine-induced apoptosis in colonic epithelial cells. Methods: Using the cytokines TNFα and IFNγ, cytokine induced apoptosis was modelled in polarised monolayers of T84 colonic epithelial cells. Calcitriol (1-100nM) was used to activate VDR and the VDR target protein, CYP24A1, was used to verify activation of the receptor. Barrier function and apoptosis were measured as changes in TER (transepithelial electrical resistance) and expression of the apoptosis marker, cleaved PARP, by western blot. All experiments have at least an n=3. GraphPad Prism 8 was used to do the statistical analysis for each experiment. The paired t-test was used for the comparison of paired treatments between 2 groups. While for more than 2 groups, ANOVA was used. Results: Gene expression of CYP24A1, a marker of VDR activation, significantly increased with treatment of calcitriol, whereas the activity of another nuclear bile acid receptor, farnesoid x receptor (FXR) was not altered. Barrier function in cytokine-treated colonic epithelial cells (as measured by TER) was significantly reduced compared to controls. Cytokine treatment also increased levels of cleaved PARP indicating that apoptosis was occurring. In cells pre-treated with 1-100nM calcitriol, cytokine-induced reductions in TER were not altered and PARP cleavage was not inhibited. Conclusion: Activation of the VDR by calcitriol does not prevent cytokine-induced epithelial apoptosis or loss of barrier function in vitro. Thus, previously reported protective effects of VDR in colitis are likely due to other actions, such as mucosal immune suppression or modulation of the microbiome. Further studies to elucidate the anti-inflammatory effects of VDR in the colon are required.