Takeuchi A, Reddy G S, Kobayashi T, Okano T, Park J, Sharma S
Department of Pathology, Roger Williams Medical Center, Brown University, Providence, RI 02908, USA.
J Immunol. 1998 Jan 1;160(1):209-18.
The molecular basis of the immunomodulatory properties of 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3) remains elusive. We demonstrate here that 1alpha,25(OH)2D3-mediated suppressive effects on the inducible expression of cytokine genes in human T cells may, in part, be due to diminished activity of the transcription factor NFAT. The vitamin D3 receptor (VDR) and its heterodimeric partner retinoid X receptor alpha (RXR alpha) specifically bound to the distal NFAT site in the human IL-2 promoter, and this binding was abolished by mutating unique regions in the NFAT oligonucleotide. In vitro inhibition of NFAT complex formation was noted when VDR-RXR alpha heterodimers were added to DNA binding reactions containing nuclear extracts from activated B or T cells, whereas in vitro NFkappaB complex formation was not significantly influenced. Furthermore, 1alpha,25(OH)2D3 treatment of activated T cells resulted in decreased formation of NFAT complexes detected upon incubation of nuclear extracts from these cells with 32P-labeled probe. Transient expression of both VDR and RXR alpha, but not of a single component, was capable of inhibiting expression of a NFAT-driven reporter gene in stimulated jurkat cells in a ligand-dependent manner. These results suggest that NFAT plays a crucial role in 1alpha,25(OH)2D3-mediated immunosuppressive activity.
1α,25 - 二羟基维生素D3（1α,25(OH)2D3）免疫调节特性的分子基础仍不清楚。我们在此证明，1α,25(OH)2D3对人T细胞中细胞因子基因诱导表达的抑制作用，部分可能归因于转录因子NFAT的活性降低。维生素D3受体（VDR）及其异源二聚体伴侣视黄酸X受体α（RXRα）特异性结合于人白细胞介素 - 2启动子中的远端NFAT位点，并且通过突变NFAT寡核苷酸中的独特区域可消除这种结合。当将VDR - RXRα异源二聚体添加到含有活化B细胞或T细胞核提取物的DNA结合反应中时，可观察到体外对NFAT复合物形成的抑制作用，而体外NFκB复合物的形成未受到显著影响。此外，用1α,25(OH)2D3处理活化的T细胞会导致，在用32P标记的探针孵育这些细胞的核提取物时检测到的NFAT复合物形成减少。VDR和RXRα两者的瞬时表达，而非单一成分的表达，能够以配体依赖的方式抑制刺激的Jurkat细胞中NFAT驱动的报告基因的表达。这些结果表明，NFAT在1α,25(OH)2D3介导的免疫抑制活性中起关键作用。
