Bogojević Desanka, Poznanović Goran, Grdović Nevena, Grigorov Ilijana, Vidaković Melita, Dinić Svetlana, Mihailović Mirjana
Institute for Biological Research Siniša Stanković, University of Belgrade, Despot Stephen Blvd. 142, 11060, Belgrade, Serbia.
Radiat Environ Biophys. 2011 Mar;50(1):167-79. doi: 10.1007/s00411-010-0331-z. Epub 2010 Sep 17.
Previously, we showed that administration of the acute-phase protein α(2)-macroglobulin (α(2)M) to rats before total-body irradiation with 6.7 Gy (LD(50/30)) of X-rays provides the same level of radioprotection as amifostine. Here, we compare the cytoprotective effects of α(2)M and amifostine on rat liver. The potential of the liver to replenish cells destroyed by ionizing radiation was assessed by immunoblot analysis with antibody to proliferating cell nuclear antigen (PCNA). After irradiation, in unprotected rats PCNA decreased 6-fold from the basal level. In rats pretreated with either α(2)M or amifostine, PCNA was increased throughout a 4 week follow-up period, indicating that hepatocyte proliferation was unaffected. Since PCNA is an important component of the repair machinery, its increased expression was accompanied by significantly lower DNA damage in α(2)M- and amifostine-treated rats. At 2 weeks after irradiation, the Comet assay revealed a 15-fold increase in DNA damage in unprotected rats, while in α(2)M- and amifostine-treated rats we observed 3- and 4-fold rise in damage, respectively. The improved protection to DNA damage was supported by elevated activity of the antioxidant systems. Compared to untreated rats, pretreatments with α(2)M and amifostine led to similar increases in levels of the inflammatory cytokine IL-6 and the redox-sensitive transcription factor NFκB, promoting upregulation of MnSOD, the major component of the cell's antioxidant axis, and subsequent increases in Mn/CuZnSOD and catalase enzymatic activities. The results show that α(2)M induces protein factors whose interplay underlies radioprotection and support the idea that α(2)M is the central effector of natural radioprotection in the rat.
此前，我们发现，在给大鼠全身照射6.7 Gy（半数致死剂量LD(50/30)）的X射线之前，给予急性期蛋白α(2)-巨球蛋白（α(2)M），其提供的辐射防护水平与氨磷汀相同。在此，我们比较了α(2)M和氨磷汀对大鼠肝脏的细胞保护作用。通过使用增殖细胞核抗原（PCNA）抗体进行免疫印迹分析，评估肝脏补充被电离辐射破坏的细胞的潜力。照射后，未受保护的大鼠体内PCNA从基础水平下降了6倍。在用α(2)M或氨磷汀预处理的大鼠中，在整个4周的随访期内PCNA均增加，表明肝细胞增殖未受影响。由于PCNA是修复机制的重要组成部分，其表达增加伴随着α(2)M和氨磷汀处理的大鼠体内DNA损伤显著降低。照射后2周，彗星试验显示未受保护的大鼠DNA损伤增加了15倍，而在α(2)M和氨磷汀处理的大鼠中，我们分别观察到损伤增加了3倍和4倍。抗氧化系统活性升高支持了对DNA损伤的更好保护。与未处理的大鼠相比，用α(2)M和氨磷汀预处理导致炎症细胞因子IL-6水平和氧化还原敏感转录因子NFκB出现类似的升高，促进了细胞抗氧化轴的主要成分MnSOD的上调，以及随后Mn/CuZnSOD和过氧化氢酶活性的增加。结果表明，α(2)M诱导了其相互作用构成辐射防护基础的蛋白质因子，并支持α(2)M是大鼠天然辐射防护的核心效应因子这一观点。
