Involvement of the vitamin D receptor in the regulation of NF-kappaB activity in fibroblasts.
We have used mouse embryonic fibroblasts (MEFs) derived from VDR(+/-) and VDR(-/-) mice to determine whether the nuclear vitamin D receptor (VDR) is directly involved in the regulation of NF-kappaB activation. We found that the basal IkappaBalpha protein level was markedly decreased in VDR(-/-) MEFs compared to VDR(+/-) MEFs; however, degradation of IkappaBalpha and its phosphorylation were not altered in VDR(-/-) cells, neither were the levels of IKKalpha and IKKbeta proteins. Consistently, p65 nuclear translocation was increased in unstimulated VDR(-/-) cells. The physical interaction between VDR and p65 was absent in VDR(-/-) MEFs, which may free p65 and increase its activity. Consequently, these alterations combined led to a marked increase in NF-kappaB transcriptional activity. Consistently, induction of IL-6 by TNFalpha or IL-1beta was much more robust in VDR(-/-) than in VDR(+/-) cells, indicating that VDR(-/-) cells are more susceptible to inflammatory stimulation. Therefore, fibroblasts lacking VDR appear to be more pro-inflammatory due to the intrinsic high NF-kappaB activity. The reduction of IkappaBalpha in VDR(-/-) MEFs may be partially explained by the lack of VDR-mediated stabilization of IkappaBalpha by 1,25(OH)(2)D(3). These data suggest that VDR plays an inhibitory role in the regulation of NF-kappaB activation.
Szeto
Frances L
FL
Committee on Molecular Metabolism and Nutrition, Biological Science Division, The University of Chicago, Chicago, IL 60637, USA.
Sun
Jun
J
Kong
Juan
J
Duan
Yingli
Y
Liao
Anne
A
Madara
James L
JL
Li
Yan Chun
YC
D000818:Animals; D002460:Cell Line; D005347:Fibroblasts; D015850:Interleukin-6 / Q000096:biosynthesis; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism*; D018167:Receptors, Calcitriol / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
D015850:Interleukin-6; D016328:NF-kappa B; D018167:Receptors, Calcitriol