1,25-Dihydroxyvitamin D₃ and dietary vitamin D reduce inflammation in mice lacking intestinal epithelial cell Rab11a

A number of studies have examined the effects of 1,25-dihydroxyvitamin D₃ (1,25(OH)₂ D₃ ) on intestinal inflammation driven by immune cells, while little information is currently available about its impact on inflammation caused by intestinal epithelial cell (IEC) defects. Mice lacking IEC-specific Rab11a a recycling endosome small GTPase resulted in increased epithelial cell production of inflammatory cytokines, notably IL-6 and early onset of enteritis. To determine whether vitamin D supplementation may benefit hosts with epithelial cell-originated mucosal inflammation, we evaluated in vivo effects of injected 1,25(OH)₂ D₃ or dietary supplement of a high dose of vitamin D on the gut phenotypes of IEC-specific Rab11a knockout mice (Rab11a^ΔIEC ). 1,25(OH)₂ D₃ administered at 25 ng, two doses per mouse, by intraperitoneal injection, reduced inflammatory cytokine production in knockout mice compared to vehicle-injected mice. Remarkably, feeding mice with dietary vitamin D supplementation at 20,000 IU/kg spanning fetal and postnatal developmental stages led to improved bodyweights, reduced immune cell infiltration, and decreased inflammatory cytokines. We found that these vitamin D effects were accompanied by decreased NF-κB (p65) in the knockout intestinal epithelia, reduced tissue-resident macrophages, and partial restoration of epithelial morphology. Our study suggests that dietary vitamin D supplementation may prevent and limit intestinal inflammation in hosts with high susceptibility to chronic inflammation.