Department of Biological and Clinical Sciences, University of Torino, Orbassano, Turin, Italy.
Pflugers Arch. 2011 Aug;462(2):219-33. doi: 10.1007/s00424-011-0970-1. Epub 2011 May 5.
Postconditioning (PostC) modifies the early post-ischemic pH, redox environment, and activity of enzymes. We hypothesized that early acidosis in PostC may affect superoxide dismutase (SOD) and catalase (CAT) activities, may reduce 3-nitrotyrosine (3-NT) protein levels, and may increase S-nitrosylated (SNO) protein levels, thus deploying its protective effects. To verify this hypothesis, we studied the early (7(th) min) and late (120(th) min) phases of reperfusion (a) endogenous SOD and CAT activities and (b) 3-NT protein levels and SNO protein levels. Isolated rat hearts underwent 30-min ischemia/120-min reperfusion (I/R) or PostC (5 cycles of 10-s I/R at the beginning of 120-min reperfusion) either with or without exogenous CAT or SOD infused during the initial 3 min of reperfusion. The effects of early reperfusion with acid buffer (AB, pH 6.8) on endogenous antioxidant enzymes were also tested. Pressure, infarct size, and lactate dehydrogenase release were also measured. At the 7(th) min, PostC induced a significant decrease in SOD activity with no major change both in Mn and Cu/Zn SOD levels and in CAT activity and level. PostC also reduced 3-NT and increased SNO levels. Exogenous SOD, but not CAT, abolished PostC cardioprotection. In late reperfusion (120-min), I/R increased SOD activity but decreased CAT activity and Cu/Zn SOD levels; these effects were reversed by PostC; 3-NT was not affected, but SNO was increased by PostC. AB reproduced PostC effects on antioxidant enzymes. The conclusions are as follows: PostC downregulates endogenous SOD and preserves CAT activity, thus increasing SNO and reducing 3-NT levels. These effects are triggered by early post-ischemic acidosis. Yet acidosis-induced SOD downregulation may limit denitrosylation, thus contributing to PostC triggering. Hence, exogenous SOD, but not CAT, interferes with PostC triggering. Prolonged SOD downregulation and SNO increase may contribute to PostC and AB beneficial effects.
预处理（PostC）可改变缺血后早期的 pH 值、氧化还原环境和酶活性。我们假设预处理早期的酸中毒可能会影响超氧化物歧化酶（SOD）和过氧化氢酶（CAT）的活性，可能会降低 3-硝基酪氨酸（3-NT）蛋白水平，并可能增加 S-亚硝基化（SNO）蛋白水平，从而发挥其保护作用。为了验证这一假设，我们研究了再灌注的早期（第 7 分钟）和晚期（第 120 分钟）阶段：（a）内源性 SOD 和 CAT 活性；（b）3-NT 蛋白水平和 SNO 蛋白水平。分离的大鼠心脏经历 30 分钟缺血/120 分钟再灌注（I/R）或预处理（在 120 分钟再灌注开始时进行 5 个 10 秒的 I/R 循环），无论是否在再灌注的最初 3 分钟内输注外源性 CAT 或 SOD。还测试了早期用酸性缓冲液（AB，pH 6.8）再灌注对内源性抗氧化酶的影响。还测量了压力、梗死面积和乳酸脱氢酶释放。在第 7 分钟时，PostC 诱导 SOD 活性显著降低，Mn 和 Cu/Zn SOD 水平以及 CAT 活性和水平均无明显变化。PostC 还降低了 3-NT 并增加了 SNO 水平。外源性 SOD，但不是 CAT，消除了 PostC 的心脏保护作用。在晚期再灌注（120 分钟）中，I/R 增加了 SOD 活性，但降低了 CAT 活性和 Cu/Zn SOD 水平；PostC 逆转了这些作用；3-NT 没有受到影响，但 SNO 则增加了。AB 再现了预处理对抗氧化酶的影响。结论如下：PostC 下调内源性 SOD 并保持 CAT 活性，从而增加 SNO 并降低 3-NT 水平。这些作用是由缺血后早期酸中毒触发的。然而，酸中毒诱导的 SOD 下调可能会限制去硝化作用，从而促进 PostC 的触发。因此，外源性 SOD，但不是 CAT，会干扰 PostC 的触发。延长的 SOD 下调和 SNO 增加可能有助于 PostC 和 AB 的有益作用。
