TY - JOUR
T1 - Vitamin D-binding protein controls T cell responses to vitamin D
AU - Kongsbak, Martin
AU - von Essen, Marina Rode
AU - Levring, Trine Bøegh
AU - Schjerling, Peter
AU - Woetmann, Anders
AU - Ødum, Niels
AU - Bonefeld, Charlotte Menné
AU - Geisler, Carsten
PY - 2014/9/18
Y1 - 2014/9/18
N2 - Background: In vitro studies have shown that the active form of vitamin D, 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3), can regulate differentiation of CD4+ T cells by inhibiting Th1 and Th17 cell differentiation and promoting Th2 and Treg cell differentiation. However, the serum concentration of 1,25(OH)D is far below the effective concentration of 1,25(OH)2D3 found in studies, and it has been suggested that 1,25(OH)2D3 must be produced locally from the inactive precursor 25-hydroxyvitamin D3 (25(OH)D3) to affect ongoing immune responses . Although it has been reported that activated T cells express the 25(OH)D-1α-hydroxylase CYP27B1 that converts 25(OH)D3 to 1,25(OH2)D3, it is still controversial whether activated T cells have the capacity to produce sufficient amounts of 1,25(OH2)D3 to affect vitamin D-responsive genes. Furthermore, it is not known how the vitamin D-binding protein (DBP) found in high concentrations in serum affects T cell responses to 25(OH)D3. Results: We found that activated T cells express CYP27B1 and have the capacity to produce sufficient 1,252)D3 to affect vitamin D-responsive genes when cultured with physiological concentrations of 25(OH)D3 in serum-free medium. However, if the medium was supplemented with serum or purified DBP, DBP strictly inhibited the production of 1,252)D3 and 25(OH)D3-induced T cell responses. In contrast, DBP did not inhibit the effect of exogenous 1,252)D3. Actin, arachidonic acid and albumin did not affect the sequestration of 252)D3 by DBP, whereas carbonylation of DBP did. Conclusions: Activated T cells express CYP27B1 and can convert 25(OH)D3 to 1,252)D3 in sufficiently high concentrations to affect vitamin D-responsive genes when cultured in serum-free medium. However, DBP sequesters 25(OH)D3 and inhibits the production of 1,252)D3 in T cells. To fully exploit the immune-regulatory potential of vitamin D, future studies of the mechanisms that enable the immune system to exploit 25(OH)D3 and convert it to 1,252)D3 are required.
AB - Background: In vitro studies have shown that the active form of vitamin D, 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3), can regulate differentiation of CD4+ T cells by inhibiting Th1 and Th17 cell differentiation and promoting Th2 and Treg cell differentiation. However, the serum concentration of 1,25(OH)D is far below the effective concentration of 1,25(OH)2D3 found in studies, and it has been suggested that 1,25(OH)2D3 must be produced locally from the inactive precursor 25-hydroxyvitamin D3 (25(OH)D3) to affect ongoing immune responses . Although it has been reported that activated T cells express the 25(OH)D-1α-hydroxylase CYP27B1 that converts 25(OH)D3 to 1,25(OH2)D3, it is still controversial whether activated T cells have the capacity to produce sufficient amounts of 1,25(OH2)D3 to affect vitamin D-responsive genes. Furthermore, it is not known how the vitamin D-binding protein (DBP) found in high concentrations in serum affects T cell responses to 25(OH)D3. Results: We found that activated T cells express CYP27B1 and have the capacity to produce sufficient 1,252)D3 to affect vitamin D-responsive genes when cultured with physiological concentrations of 25(OH)D3 in serum-free medium. However, if the medium was supplemented with serum or purified DBP, DBP strictly inhibited the production of 1,252)D3 and 25(OH)D3-induced T cell responses. In contrast, DBP did not inhibit the effect of exogenous 1,252)D3. Actin, arachidonic acid and albumin did not affect the sequestration of 252)D3 by DBP, whereas carbonylation of DBP did. Conclusions: Activated T cells express CYP27B1 and can convert 25(OH)D3 to 1,252)D3 in sufficiently high concentrations to affect vitamin D-responsive genes when cultured in serum-free medium. However, DBP sequesters 25(OH)D3 and inhibits the production of 1,252)D3 in T cells. To fully exploit the immune-regulatory potential of vitamin D, future studies of the mechanisms that enable the immune system to exploit 25(OH)D3 and convert it to 1,252)D3 are required.
U2 - 10.1186/s12865-014-0035-2
DO - 10.1186/s12865-014-0035-2
M3 - Journal article
C2 - 25230725
SN - 1471-2172
VL - 15
SP - 1
EP - 13
JO - BMC Immunology
JF - BMC Immunology
M1 - 35
ER -