Intracellular signal transduction via acitive oxygen production in cardiac myocytes-role of redox regulation in Mn-SOD induction-

为了探讨活性氧/氧自由基代谢在心肌应激反应的细胞内信号转导中的作用，我们研究了活化心肌细胞中活性氧的产生和应激蛋白的诱导以及两者之间的关系。在第一年，我们证明过氧化氢在使用过氧化氢敏感染料DCFH刺激TNF-α的心肌细胞中产生。TNF-α也增强心肌细胞中Mn-SOD的表达。因为清除过氧化氢的2-巯基丙酰甘氨酸（MPG）阻断了与Mn-SOD表达直接相关的心肌细胞中TNF-α产生的过氧化氢对心肌细胞Mn-SOD的诱导。第二年，我们在体内检测了TNF-α对心肌细胞Mn-SOD的诱导作用。在大鼠踏车运动模型中，运动后48小时心肌细胞TNFα和IL-1β浓度升高，Mn-SOD蛋白和活性升高。TNFα和IL-1β抗体可减弱运动对Mn-SOD的诱导作用。MPG还能减弱运动对Mn-SOD的诱导作用。上述结果提示，运动等生理应激在心肌细胞中产生细胞因子，细胞因子通过过氧化氢介导的信号转导通路激活，诱导心肌中抗氧化酶Mn-SOD的产生。

To investigate the role of active oxygen/ oxygen radical metabolism in intracellular signal transduction of myocardial stress response, we examined the production of active oxygen species and the induction of stress proteins in activated cardiac myocytes and the relationship between these two phenomena. In the first year, we demonstrated that hydrogen peroxide was produced in cardiac myocytes stimulated with TNF-α using hydrogen peroxide sensitive dye, DCFH. TNF-α also augmented Mn-SOD expression in cardiac myocytes. Because 2-mercaptopropionyl glycine (MPG), which scavenge hydrogen peroxide, blocked Mn-SOD induction in cardiac myocytes by TNF-α hydrogen peroxide produced by TNF-α in cardiac myocytes directly linked to the expression of Mn-SOD. In the second year, we examined whether the induction of Mn-SOD in cardiac myocytes by TNF-α occurred in vivo. In treadmill exercise model of rat, concentration of TNFα and IL-1β in cardiac myocytes increased soon after exercise together with the augmentation of Mn-SOD protein and activity 48 hr after exercise. Antibody to TNFα and IL-1β attenuated the induction of Mn-SOD by exercise. MPG could also attenuated Mn-SOD induction by exercise. These results suggest that physical stress such as exercise produced cytokines in cardiac myocytes and the cytokines, thus produced, induced antioxidative enzyme, Mn-SOD, in myocardium through the activation of signal transduction pathway mediated by hydrogen peroxide.