VD/VDR

Vitamin D is a secosteroidalprohormone, it can be synthesized at sufficient levels in skin, given adequate skin exposure to UV B radiation from sunlight. Vitamin D modulates its biological effects by directly regulating target gene expression through the Vitamin D receptor (VDR), a ligand-regulated transcription factor and a member of the nuclear receptor superfamily. Whether synthesized in the skin or ingested, vitamin D requires two hydroxylation steps to become the biologically active hormone, 1,25-dyhydroxyvitamin D₃ [1,25(OH)₂D₃], a form that signals through the VDR. The hormone-bound VDR modulates target gene transcription in response to vitamin D. VDR acts as a master transcriptional regulator of autophagy. Activation of the VDR by vitamin D induces autophagy and an autophagic transcriptional signature in breast cancer (BC) cells.

There are 2 forms of vitamin D. Vitamin D₂ (ergocalciferol) comes from irradiation of the yeast and plant sterol ergosterol, and vitamin D₃ (cholecalciferol) is found in oily fish and cod liver oil and is made in the skin. Vitamin D represents vitamin D₂ and vitamin D₃.

Topical agents containing active vitamin D₃ (calcitriol, 1α, 25- dihydroxyvitaminD₃, VD₃) analogues such as Tacalcitol, Calcipotriol and Maxacalcitol are widely used for psoriasis therapy.