1,25-Dihydroxyvitamin D_3 and its analogs exert immunoregulatory activitives / 医学研究生学报

ABSTRACT

The active form of vitamin D,1,25-Dihydroxyvitamin D3 \,is a secosteroid hormone that binds to the vitamin D receptor(VDR),a member of the superfamily of nuclear receptors for steroid hormones,thyroid hormone,and retinoic acid.1,25-Dihydroxyvitamin D3 and its analogue regulate calcium and bone metabolism,control cell proliferation and differentiation,and exert immunoregulatory activities.Recent advances in understanding their functions and novel insights into the immunomodulatory mechanisms they control suggest a wider applicability in the treatment of autoimmune diseases and induction of allograft tolerance.In addition to direct effects on T cell activation,1,25-Dihydroxyvitamin D3 and its analogue modulate with different mechanisms the phenotype and function of antigen-presenting cells(APC),and,in particular,of dendritic cells(DC).In vitro and in vivo experiments have shown that 1,25-Dihydroxyvitamin D3 and its analogue induce DC to acquire tolerogenic properties that favor the induction of regulatory rather than effector T cells.These intriguing actions of 1,25-Dihydroxyvitamin D3 and its nanlogue have been demonstrated in several experimental models and could be exploited,in principle,to treat a variety of human autoimmune diseases,or inhibit allograft rejection.