25-Hydroxytachysterol3 is the metabolite of Vitamin D3. 25-Hydroxytachysterol3 inhibits the proliferation of epidermal keratinocytes and dermal fibroblasts, stimulates the expression of differentiation- and antioxidant-related genes in keratinocytes. 25-Hydroxytachysterol3 activates vitamin D receptor ( VDR ) and aryl hydrocarbon receptor ( AhR ), liver X receptor α/β ( LXR α/β ) and peroxisome proliferator-activated receptor γ ( PPARγ ), stimulates the expression of CYP24A1.