Instituto de Fisiología Experimental (IFISE-CONICET), Argentina.
J Endocrinol. 2010 May;205(2):187-200. doi: 10.1677/JOE-09-0462. Epub 2010 Feb 17.
In this study, we analyzed the contribution of hydroxyl radical in the liver apoptosis mediated by hyperglycemia through the Bax-caspase pathway and the effects of insulin protection against the apoptosis induced by hyperglycemia. Male adult Wistar rats were randomized in three groups: control (C) (sodium citrate buffer, i.p.), streptozotocin (STZ)-induced diabetic (SID) (STZ 60 mg/kg body weight, i.p.), and insulin-treated SID (SID+I; 15 days post STZ injection, SID received insulin s.c., twice a day, 15 days). Rats were autopsied on day 30. In liver tissue, diabetes promoted a significant increase in hydroxyl radical production which correlated with lipid peroxidation (LPO) levels. Besides, hyperglycemia significantly increased mitochondrial BAX protein expression, cytosolic cytochrome c levels, and caspase-3 activity leading to an increase in apoptotic index. Interestingly, the treatment of diabetic rats with desferoxamine or tempol (antioxidants/hydroxyl radical scavengers) significantly attenuated the increase in both hydroxyl radical production and in LPO produced by hyperglycemia, preventing apoptosis by reduction of mitochondrial BAX and cytosolic cytochrome c levels. Insulin treatment showed similar results. The finding that co-administration of antioxidants/hydroxyl radical scavengers together with insulin did not provide any additional benefit compared with those obtained using either inhibitors or insulin alone shows that it is likely that insulin prevents oxidative stress by reducing the effects of hydroxyl radicals. Importantly, insulin significantly increased apoptosis inhibitor protein expression by induction of its mRNA. Taken together, our studies support that, at least in part, the hydroxyl radical acts as a reactive intermediate, which leads to liver apoptosis in a model of STZ-mediated hyperglycemia. A new anti-apoptosis signal for insulin is shown, given by an increase of apoptosis inhibitor protein.
在这项研究中，我们通过 Bax-caspase 途径分析了羟自由基在高血糖介导的肝凋亡中的作用，以及胰岛素对高血糖诱导的凋亡的保护作用。雄性成年 Wistar 大鼠随机分为三组：对照组（C）（柠檬酸钠缓冲液，腹腔内注射）、链脲佐菌素（STZ）诱导的糖尿病（SID）（STZ60mg/kg 体重，腹腔内注射）和胰岛素治疗的 SID（SID+I；STZ 注射后 15 天，SID 每天两次皮下注射胰岛素，15 天）。大鼠在第 30 天进行尸检。在肝组织中，糖尿病导致羟自由基产生显著增加，与脂质过氧化（LPO）水平相关。此外，高血糖显著增加线粒体 BAX 蛋白表达、胞浆细胞色素 c 水平和 caspase-3 活性，导致凋亡指数增加。有趣的是，用去铁胺或替普（抗氧化剂/羟自由基清除剂）治疗糖尿病大鼠可显著降低高血糖引起的羟自由基产生和 LPO 的增加，通过降低线粒体 BAX 和胞浆细胞色素 c 水平来预防凋亡。胰岛素治疗也显示出类似的结果。抗氧化剂/羟自由基清除剂与胰岛素联合使用与单独使用抑制剂或胰岛素相比没有提供任何额外益处的发现表明，胰岛素可能通过减少羟自由基的作用来预防氧化应激。重要的是，胰岛素通过诱导其 mRNA 显著增加凋亡抑制剂蛋白的表达。总之，我们的研究支持至少部分羟自由基作为一种反应性中间体，导致 STZ 介导的高血糖模型中的肝凋亡。显示了胰岛素的一种新的抗凋亡信号，即通过增加凋亡抑制剂蛋白。
