الفهرس 
Vitamin DOnly 14 pages are availabe for public view
 |  | from | 32 |  |  |
| | | from | 32 | | |
Abstract
Vitamin D is an ancient vitamin which was discovered many years ago and was well known for its effect on calcium metabolism. Lately, vitamin D is known also for its non calcemic actions as it regulates the growth and differentiation of multiple cell types, and displays immunoregulatory and anti-inflammatory properties.
It has many influences on the innate (macrophages, dendritic cells, TLRs, AMPs) and adaptive (T-cells) immune systems. Vitamin D exerts all of its actions through the VDR gene which is present in all the cells targeted by the vitamin D including most of the cells of the immune system. Accordingly polymorphisms in the VDR gene is one of the factors involved in the aetiopathogenesis of many skin disorders.
In the skin, calcitriol regulates the growth of epidermal cells by inhibiting proliferation and induction of the terminal differentiation of keratinocytes, and enhances immunosuppressive and anti-inflammatory pathways.
Analogues of 1,25(OH)2D are being developed to achieve specificity for non skeletal target tissues such as the cancer and immune cells to avoid the hypercalcemia resulting from 1,25(OH)2D itself, as vitamin D analogues might offer a new approach in the therapy of very common skin diseases.
Vitamin D deficiency has been related to a number of disorders including psoriasis, skin cancer, infection, vitiligo, atopic dermatitis etc...
Psoriasis is an immunologically mediated, probably autoimmune disease in which T helper type 1 cytokines play an important role, it is characterized by hyperplasia and altered differentiation of epidermal keratinocytes. Vitamin D and its analogues have the capacity to modulate both antigen presenting cells (APCs) and T-cells thus interfering with psoriasis pathogenesis.
The association between low serum levels of vitamin D and incidence and mortality of several types of tumors points to the anti carcinogenic role of vitamin D.
Therapies targeting vitamin D signaling provide novel approaches for the treatment of infectious and inflammatory skin diseases by affecting both innate and adaptive immune functions through AMP regulation.
Many autoimmune conditions have been found to be associated with reduced vitamin D levels. However, little is known about the association between them and reduced vitamin D levels and further studies are needed.
Vitiligo is an acquired skin disorder caused by the disappearance of pigment cells from the epidermis .The difference in serum vitamin D levels between vitiligo patients and the healthy controls refers to the possible effect of vitamin D in its pathogenesis.
Atopic dermatitis (AD) is a chronic inflammatory skin disorder usually presenting with severe pruritus and flaring eczematous lesions in varying localizations depending on the age of the patient. Oral supplementation of vitamin D precursors is beneficial in AD, as vitamin D increases cathelicidin expression and antimicrobial activity in keratinocytes.