Sølvsten H, Svendsen M L, Fogh K, Kragballe K
Department of Dermatology, Marselisborg Hospital, Aarhus, Denmark.
Arch Dermatol Res. 1997 May;289(6):367-72. doi: 10.1007/s004030050206.
The natural biologically active form of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), possesses antiproliferative, prodifferentiating and immunomodulatory properties. The actions of 1,25(OH)2D3 are mediated through the intracellular vitamin D receptor (VDR), and the level of VDR is believed to determine the cellular responsiveness to vitamin D3. In the present study we examined the effects of 1,25(OH)2D3 on the expression of VDR and its message in cultured human keratinocytes. Western analysis showed the mean VDR content to be higher in undifferentiated cultures (175 pg/microgram protein) than in differentiated cultures (90 pg/microgram protein). Incubation with 1,25(OH)2D3 induced an increase in the VDR in both undifferentiated and differentiated keratinocytes. The VDR increase was detectable after 2 h and maximal (approximately two-fold stimulation) after 8 h. The 1,25(OH)2D3-induced stimulation of VDR levels was dose dependent with a maximum at 10(-7) M. The VDR mRNA levels as determined by the ribonuclease protection assay showed a peak (50% stimulation) after approximately 2 h. Although this increase in VDR mRNA was not statistically significant, the results indicate that the ligand-induced upregulation of VDR involves increased transcription. The upregulation of VDR levels may increase the responsiveness to 1,25(OH)2D3 and may, therefore, be an important mechanism for regulating the effects of 1,25(OH)2D3 on keratinocyte proliferation and differentiation.
维生素D3的天然生物活性形式，1,25 - 二羟基维生素D3（1,25(OH)2D3），具有抗增殖、促分化和免疫调节特性。1,25(OH)2D3的作用是通过细胞内维生素D受体（VDR）介导的，并且VDR的水平被认为决定了细胞对维生素D3的反应性。在本研究中，我们检测了1,25(OH)2D3对培养的人角质形成细胞中VDR表达及其信使核糖核酸的影响。蛋白质印迹分析显示，未分化培养物中的平均VDR含量（175 pg/微克蛋白质）高于分化培养物中的（90 pg/微克蛋白质）。用1,25(OH)2D3孵育可诱导未分化和分化的角质形成细胞中VDR增加。2小时后可检测到VDR增加，8小时后达到最大值（约两倍刺激）。1,25(OH)2D3诱导的VDR水平刺激呈剂量依赖性，在10^(-7) M时达到最大值。通过核糖核酸酶保护分析测定的VDR信使核糖核酸水平在约2小时后出现峰值（50%刺激）。虽然VDR信使核糖核酸的这种增加在统计学上不显著，但结果表明配体诱导的VDR上调涉及转录增加。VDR水平的上调可能会增加对1,25(OH)2D3的反应性，因此可能是调节1,25(OH)2D3对角质形成细胞增殖和分化作用的重要机制。
