Editorial: The role of vitamin D as an immunomodulator

Résumé

The role of vitamin D as an immunomodulatorThe metabolism and immunomodulatory role of vitamin D: An abbreviated overview Considered as a vitamin and a pre-hormone, vitamin D, in its biologically active form (1,25-dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ]) is able to immunomodulate the functional activities of both innate and adaptive immune cells (1), including B-cells (2), T-cells (3), monocytes (4), macrophages (5), dendritic cells (6), neutrophils (7), and platelets (8), as these cells express the vitamin D receptor (VDR), a nuclear receptor and ligand-activated transcription factor/a ligand-dependent transcription regulator molecule belonging to the superfamily of nuclear receptors (9).Mechanistically, the action of the 1,25(OH) 2 D 3 on the target cells is performed by its binding to the VDR in the cytoplasm, followed by its heterodimerization with the retinoid X receptor-a (RXR-a) in the nucleus, resulting in the formation of the 1,25(OH) 2 D 3 -RXR-VDR complex that binds to vitamin D response elements (VDRE) located on DNA (10) (Figure 1).Humans and some animals have the ability to synthesize vitamin D in the form of previtamin D 3 in the skin as a result of localized conversion of 7-dehydrocholesterol (7-DHC) when exposed to solar ultraviolet B rays (UVB, 290-320 nm) (11-13).Previtamin D 3 isomerizes to vitamin D 3 (cholecalciferol) in the skin, in a thermo-sensitive but noncatalytic process (14), and both previtamin D 3 and vitamin D 3 are converted into a variety of photoproducts thanks to UVB radiation (15).Vitamin D 3 is considered to be best metabolized by the body.Its metabolism takes place consecutively in the liver, where it undergoes a first hydroxylation at the carbon 25-position into calcifediol/calcidiol ([25 (OH)D 3 ]) by the enzyme microsomal vitamin D 25-hydroxylase, also known as a cytochrome p450 2R1, which is encoded in humans by the CYP2R1 gene (16), and then, according to the cell needs and in response to cellular signals, it is hydrolyzed mainly in the kidneys at the 1a-position into 1,25(OH) 2 D 3 , i.e., calcitriol (17) by the enzyme 25- Frontiers in Immunology frontiersin.

Citer ce document

Accès au document

Ce document est hébergé sur son dépôt institutionnel d'origine.

Auteur(s)

Statistiques

Consultations : 1

Téléchargements : 0