Vitamin D Improves Cognitive Function and Modulates T_h17/T_reg Cell Balance After Hepatectomy in Mice

It is known that surgery-induced tissue damage activates the peripheral immune system resulting in the release of inflammatory mediators and cognitive impairment in aged mice. Vitamin D has been shown to have immunomodulatory function, but the molecular basis for it has not been well understood. In this study, we mainly investigated the efficacy and mechanism of vitamin D against postoperative cognitive dysfunction (POCD). The treatment of C57BL mice with vitamin D significantly preserves postoperative cognitive function, markedly inhibits surgery-induced interleukin (IL)-17, IL-6, transforming growth factor beta (TGF-β), and retinoic acid-related orphan receptor (RORγt) production, and obviously induces IL-10 and forkhead box p3 (Foxp3) expression. These findings indicate that vitamin D amelioration of POCD is, to a large extent, due to inhibit inflammatory CD4_T cell lineage, T helper 17 (T_h17) cells, accompanied with expansion in regulatory T cells (T_reg cells), a subset of CD4_T cells that are important in inhibiting inflammation. Our results suggest that T_h17 and T_reg cell imbalance may play a role in the development of POCD. Vitamin D is useful in the control of inflammatory diseases.