[Novel pharmacological activity of a vitamin (novel pharmacological action of vitamin D)].

The endocrine system to maintain calcium homeostasis involves the active vitamin D, as well as parathyloid hormone (PTH). Based on this 'classical' calcium-regulatory function, 1,25-(OH)2D3 and 1 alpha OHD3 was developed as the drug for vitamin D resistant rickets, renal dystrophy, and osteoporosis. Psoriasis is a chronic skin disease which is characterized by hyperproliferation and abnormal differentiation of epidermis. As an anti-psoriatic drug, 1,24R-(OH)2D3 has been on clinical use. The efficacy for psoriasis is explainable by the differentiation-inducing activity of this compound. 1,25-(OH)2D3 was also reported to suppress proliferation and induce differentiation of tumor cells including breast cancer, colon cancer and so forth, suggesting the possible therapy of malignant tumors. In immune system, active vitamin D3 exerts various effects; 1,25-(OH)2D3 suppresses proliferation and cytokine production in T cells and antibody production in B cells. Animal models of autoimmune diseases and skin-graft suggest active vitamin D becomes a novel immuno suppressant. Since 1,25-(OH)2D3 induces the synthesis of nerve growth factor (NGF), it will be a new therapy for the treatment of neuronal degenerative diseases.