Halicka H Dorota, Zhao Hong, Li Jiangwei, Traganos Frank, Studzinski George P, Darzynkiewicz Zbigniew
Brander Cancer Research Institute and Department of Pathology, New York Medical College, Valhalla, NY 10595, USA.
Aging (Albany NY). 2012 Apr;4(4):270-8. doi: 10.18632/aging.100450.
In addition to its traditional role in the regulation of calcium homeostasis and bone metabolism, vitamin D also exhibits immunomodulatory, anti-proliferative and cancer preventive activities. Molecular mechanisms that confer the chemo-preventive properties to vitamin D are poorly understood. We previously reported that constitutive phosphorylation of histone H2AX on Ser139 (γH2AX) and activation of ATM (Ser1981 phosphorylation), seen in untreated normal or tumor cells predominantly in S phase of the cell cycle, is to a large extent indicative of DNA replication stress occurring as a result of persistent DNA damage caused by endogenous oxidants, by-products of oxidative metabolism. In the present study we observed that exposure of mitogenically stimulated human lymphocytes, pulmonary carcinoma A549 and lymphoblastoid TK6 cells to 1,25-dihydroxyvitamin D3 (1,25-VD) reduced the level of constitutive expression of γH2AX and ATM-S1981P. We also observed that the H2O2-induced rise in the level of γH2AX in lymphocytes was attenuated by 1,25-VD. Whereas in lymphocytes 1,25-VD reduced by 50-70% the level of endogenous oxidants as determined by their ability to oxidize 2,7-dichlorodihydrofluorescein (DCFH) in A549 and TK6 cells the attenuation of DNA damage signaling by 1,25-VD was seen in the absence of detectable reduction in DCFH oxidation. These findings suggest that while the anti-oxidant activity of 1,25-VD may contribute to a reduction in the intensity of DNA replication stress in lymphocytes, other factors play a role in the 1,25-VD effects seen in A549 and TK6 cells. The data are consistent with the recent report on the interaction between DNA damage signaling (ATM activation) and 1,25D receptor (VDR) phosphorylation that lead to enhancement of DNA repair efficiency, and provide further support for the chemo-preventive and anti-aging properties of this vitamin/hormone.
除了在调节钙稳态和骨代谢方面的传统作用外，维生素D还具有免疫调节、抗增殖和预防癌症的活性。赋予维生素D化学预防特性的分子机制尚不清楚。我们之前报道过，在未处理的正常或肿瘤细胞中，主要在细胞周期的S期观察到组蛋白H2AX在Ser139位点的组成型磷酸化（γH2AX）和ATM（Ser1981磷酸化）的激活，这在很大程度上表明DNA复制应激是由内源性氧化剂（氧化代谢的副产物）引起的持续性DNA损伤所致。在本研究中，我们观察到有丝分裂原刺激的人淋巴细胞、肺癌A549细胞和淋巴母细胞TK6细胞暴露于1,25 - 二羟基维生素D3（1,25 - VD）后，γH2AX和ATM - S1981P的组成型表达水平降低。我们还观察到，1,25 - VD减弱了H2O2诱导的淋巴细胞中γH2AX水平的升高。在淋巴细胞中，1,25 - VD使内源性氧化剂水平降低了50 - 70%（通过其氧化A549和TK6细胞中2,7 - 二氯二氢荧光素（DCFH）的能力来确定），而在未检测到DCFH氧化有明显降低的情况下，1,25 - VD对DNA损伤信号传导有减弱作用。这些发现表明，虽然1,25 - VD的抗氧化活性可能有助于降低淋巴细胞中DNA复制应激的强度，但其他因素在A549和TK6细胞中观察到的1,25 - VD效应中起作用。这些数据与最近关于DNA损伤信号传导（ATM激活）与1,25D受体（VDR）磷酸化之间相互作用导致DNA修复效率提高的报道一致，并为这种维生素/激素的化学预防和抗衰老特性提供了进一步支持。
