We previously reported that heat shock protein 27 (HSP27) phosphorylation plays an important role in the activation of glucose-6-phosphate dehydrogenase (G6PD), resulting in the upregulation of the pentose phosphate pathway and antioxidant effects against cerebral ischemia–reperfusion injury. The present study investigated the effect of geranylgeranylacetone, an inducer of HSP27, on ischemia–reperfusion injury in male rats as a preliminary study to see if further research of the effects of geranylgeranylacetone on the ischemic stroke was warranted. In all experiments, male Wistar rats were used. First, we conducted pathway activity profiling based on a gas chromatography–mass spectrometry to identify ischemia–reperfusion-related metabolic pathways. Next, we investigated the effects of geranylgeranylacetone on the pentose phosphate pathway and ischemia–reperfusion injury by real-time polymerase chain reaction (RT-PCR), immunoblotting, and G6PD activity, protein carbonylation and infarct volume analysis. Geranylgeranylacetone or vehicle was injected intracerebroventricularly 3 h prior to middle cerebral artery occlusion or sham operation. Pathway activity profiling demonstrated that changes in the metabolic state depended on reperfusion time and that the pentose phosphate pathway and taurine-hypotaurine metabolism pathway were the most strongly related to reperfusion among 137 metabolic pathways. RT-PCR demonstrated that geranylgeranylacetone did not significantly affect the increase in HSP27 transcript levels after ischemia–reperfusion. Immunoblotting showed that geranylgeranylacetone did not significantly affect the elevation of HSP27 protein levels. However, geranylgeranylacetone significantly increase the elevation of phosphorylation of HSP27 after ischemia–reperfusion. In addition, geranylgeranylacetone significantly affected the increase in G6PD activity, and reduced the increase in protein carbonylation after ischemia–reperfusion. Accordingly, geranylgeranylacetone significantly reduced the infarct size (median 31.3% vs 19.9%, p = 0.0013). As a preliminary study, these findings suggest that geranylgeranylacetone may be a promising agent for the treatment of ischemic stroke and would be worthy of further study. Further studies are required to clearly delineate the mechanism of geranylgeranylacetone-induced HSP27 phosphorylation in antioxidant effects, which may guide the development of new approaches for minimizing the impact of cerebral ischemia–reperfusion injury.

中文翻译：

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Geranylgeranylacetone 通过增强 HSP 27 磷酸化减轻大鼠脑缺血再灌注损伤：一项初步研究

我们之前报道过热休克蛋白 27 (HSP27) 磷酸化在葡萄糖 6-磷酸脱氢酶 (G6PD) 的激活中起重要作用，导致磷酸戊糖途径的上调和对脑缺血再灌注损伤的抗氧化作用。本研究调查了香叶基香叶基丙酮（HSP27 的诱导剂）对雄性大鼠缺血-再灌注损伤的影响，作为初步研究，以确定是否有必要进一步研究香叶基香叶基丙酮对缺血性中风的影响。在所有实验中，使用雄性 Wistar 大鼠。首先，我们基于气相色谱-质谱法进行了通路活性分析，以确定与缺血-再灌注相关的代谢通路。下一个，我们通过实时聚合酶链反应 (RT-PCR)、免疫印迹和 G6PD 活性、蛋白质羰基化和梗塞体积分析研究了香叶基香叶基丙酮对磷酸戊糖途径和缺血-再灌注损伤的影响。在大脑中动脉闭塞或假手术前 3 小时，在脑室内注射香叶基香叶基丙酮或载体。通路活性分析表明，代谢状态的变化取决于再灌注时间，在 137 条代谢通路中，磷酸戊糖通路和牛磺酸-次牛磺酸代谢通路与再灌注的相关性最强。RT-PCR 表明，香叶基香叶基丙酮对缺血再灌注后 HSP27 转录水平的增加没有显着影响。免疫印迹显示香叶基香叶基丙酮对 HSP27 蛋白水平的升高没有显着影响。然而，香叶基香叶基丙酮显着增加缺血再灌注后 HSP27 的磷酸化水平。此外，香叶基香叶基丙酮显着影响 G6PD 活性的增加，并减少缺血再灌注后蛋白质羰基化的增加。因此，香叶基香叶基丙酮显着减少了梗塞面积（中位数为 31.3% 对 19.9%，p = 0.0013）。作为一项初步研究，这些发现表明香叶基香叶基丙酮可能是治疗缺血性中风的有希望的药物，值得进一步研究。需要进一步的研究来清楚地描述香叶基香叶基丙酮诱导的 HSP27 磷酸化在抗氧化作用中的机制，