Molecular mechanisms of particular defense system against oxidative stress induced by the control of signaling

蛋白激酶C （PKC）是生理条件下细胞间信号通路的关键分子。PKC是一种由钙离子和磷脂酰丝氨酸和1,2-二酰基甘油（DAG）等脂质激活的酶。近年来，越来越多的证据表明脂质过氧化参与了好氧生物生理和病理中的细胞内信号转导。我们进一步证明了1,2-二酰基甘油过氧化氢（氧化- dag）激活大鼠脑PKC的效率与强效人工PKC活化剂佛波酯一样高。在本研究中，为了阐明氧化dag对PKC信号异常过度激活和细胞损伤的新型特异性防御系统的机制，我们在四氯化碳（CCl4）处理的大鼠肝脏和缺血再灌注（IR）损伤的大鼠脑两种动物模型中观察了氧化dag含量和PKC δ SV （PKC δ剪接变体，可能被认为是PKC δ分子的显性负突变体）的表达。此外，利用PKCδ SV过表达的PC12细胞，分析了PKCδ SV对氧化应激的保护作用。氧化DAG在两种模型中均显著升高。PKC δ SV在正常和四氯化碳处理的大鼠肝脏中几乎检测不到。另一方面，过度表达PKC SV的PC12细胞可以抵抗PKC信号的过度激活。这些结果表明，氧化DAG是氧化应激的关键分子，PKC δ SV可能对氧化DAG引起的氧化应激具有特殊的保护作用。

Protein kinase C (PKC) is a key molecule for intercellular signaling pathway in physiological conditions. PKC is an enzyme which is activated by calcium ion and lipids such as phosphatidylserine and 1,2-diacylglycerol (DAG). In recent years, many evidences that lipid peroxidation participates in intracellular signal transduction in physiology and pathology of aerobic organisms have been presented. We further demonstrated that 1,2-diacylglycerol hydroperoxide (oxidized-DAG) activated rat brain PKC as efficiently as phorbol ester, powerful artificial PKC activator . In this study, to elucidate the mechanism of novel and specific defence system against aberrant over-activation of PKC signaling by oxidized-DAG and subsequent to cell injury, we observed oxidized-DAG content and the expression of PKC δ SV (which is PKC δ splicing variant and may be considered as a dominant negative mutant of PKC δ molecule) in two animal models such as carbon tetrachloride (CCl4)-treated rat liver and ischemia-reperfusion (IR)-injured rat brain. In addition, the protective effects of PKC δ SV on oxidative stress were analyzed using PKCδ SV over-expressed PC12 cell. Oxidized DAG was significantly increased in both models. PKC δ SV was barely detected in normal and carbon tetrachloride-treated rat liver. On the other hands, PC12 cells over-expressing PKC SV resistant to over-activation of PKC signaling. These results suggested that oxidized-DAG is a key molecule for oxidative stress and PKC δ SV may have a specific function for the protection of oxidative stress caused by oxidized DAG.