Golubnitschaja Olga, Moenkemann Heike, Trog Daniela B, Blom Henk J, De Vriese An S
Department of Radiology, Division of Molecular/Experimental Radiology, University of Bonn, Germany, and Renal Unit, Department of Internal Medicine, University Hospital, Gent, Belgium.
Med Sci Monit. 2006 Feb;12(2):BR68-74. Epub 2006 Jan 26.
Oxidative stress was proposed as a critical factor in diabetic complications. The etiology of cell degeneration in diabetes mellitus (DM)-induced cardiomyopathy is unclear. The transition between apoptotic degeneration and cell proliferation under stress conditions is regulated at cell-cycle checkpoints. This study was aimed at elucidating the role of a potent cellular stress-response system of the p53-dependent checkpoint genes, i.e. P21WAF1/CIP1 and 14-3-3 sigma, in the heart in diabetes.
MATERIAL/METHODS: Target gene expression levels were analyzed ex vivo in cardiomyocytes of streptozotocin-induced rats by Western blots and two-dimensional immunoblots. The levels of DNA damage/repair in diabetic cardiomyocytes were evaluated by "comet assay" and compared with a control group.
Whereas no detectable expression of 14-3-3 sigma and only traces of both p53 and p21WAF1/CIP1 were found in cardiomyocytes of the controls, high expression rates of all three genes were observed in the DM group. Individual levels of DNA breakage were significantly lower in diabetic than in non-diabetic cardiomyocytes.
We propose a dual role for cell-cycle regulation under diabetic conditions: the expressions of both p21WAF1/CIP1 and 14-3-3 sigma genes, activated via p53 function, trigger cell-cycle arrest and DNA repair, preventing replication of mutated DNA and increasing stress resistance of heart tissue at least in early diabetes. However, the double cell-cycle arrest ultimately inhibits the replication of cells, which consequently accumulate in the G1 and G2 phases; this could lead to retarded proliferative activity and tissue degeneration in diabetic myocardium in later diabetes.
氧化应激被认为是糖尿病并发症的关键因素。糖尿病（DM）诱导的心肌病中细胞变性的病因尚不清楚。应激条件下细胞凋亡性变性与细胞增殖之间的转变在细胞周期检查点受到调控。本研究旨在阐明p53依赖性检查点基因（即P21WAF1/CIP1和14-3-3 sigma）这一强大的细胞应激反应系统在糖尿病心脏中的作用。
材料/方法：通过蛋白质免疫印迹法和二维免疫印迹法对链脲佐菌素诱导的大鼠心肌细胞进行离体分析，以检测目标基因的表达水平。采用“彗星试验”评估糖尿病心肌细胞中的DNA损伤/修复水平，并与对照组进行比较。
在对照组心肌细胞中未检测到14-3-3 sigma的表达，p53和p21WAF1/CIP1也仅有微量表达，而在糖尿病组中观察到这三个基因的高表达率。糖尿病心肌细胞中单个DNA断裂水平显著低于非糖尿病心肌细胞。
我们提出糖尿病条件下细胞周期调控具有双重作用：通过p53功能激活的p21WAF1/CIP1和14-3-3 sigma基因的表达触发细胞周期停滞和DNA修复，防止突变DNA的复制，并至少在糖尿病早期增加心脏组织的应激抗性。然而，双重细胞周期停滞最终会抑制细胞复制，导致细胞在G1期和G2期积累；这可能导致糖尿病后期糖尿病心肌中增殖活性受阻和组织变性。
