State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, China.
Jiangsu Key Laboratory of TCM Evaluation and Translational Research, Department of Pharmacology of Chinese Materia Medica, China Pharmaceutical University, Nanjing, China.
Biochim Biophys Acta Mol Basis Dis. 2017 Nov;1863(11):2835-2847. doi: 10.1016/j.bbadis.2017.07.017. Epub 2017 Jul 21.
Altered mitochondrial oxidation increases vulnerability to cardiac ischemia/reperfusion (I/R) injury in metabolic disorders. However, the metabolic signaling responsible for the dysfunction remains partly unknown. We sought to test whether or not hypoxic succinate accumulation could inhibit pyruvate dehydrogenase (PDH) activity and subsequently aggravate I/R injury. Results showed that saturated fatty acid palmitate stimulation increased fatty acid oxidation and induced hypoxia in cardiomyocytes, leading to succinate accumulation. Intracellular succinate induced hypoxia inducible factor-1α (HIF-1α) expression and impaired PDH activity via upregulation of pyruvate dehydrogenase kinase 4 (PDK4) expression. Luciferase reporter assay showed that succinate increased PDK4 expression through gene promoter induction in a HIF-1α-dependent manner. Palmitate also induced the release of succinate into extracellular space. By activating GRP91, extracellular succinate induced the translocation of PKCδ to mitochondria and further exacerbated PDH impairment. These results demonstrated that succinate impaired PDH activity via GPR91-dependent and independent pathways. Ginsenoside Rb1 (a major compound isolated from ginseng) and trimetazidine (fatty acid β-oxidation inhibitor) prevented hypoxic succinate accumulation in cardiomyocytes and improved PDH activity by blocking succinate-associated HIF-1α activation and GPR91 signaling. Through improving PDH activity, Rb1 and trimetazidine prevented cardiac acidification, ameliorated mitochondrial dysfunction and thereby reduced apoptosis during hypoxia/reoxygenation insult. In isolated working rat hearts perfused with palmitate and in high-fat diet-fed mice, early intervention of Rb1 and trimetazidine reduced succinate production and resultantly increased heart resistance to ischemia/reperfusion injury. Taken together, our findings demonstrated that early intervention by targeting inhibition of succinate accumulation-induced PDH impairment is an effective strategy to alleviate I/R injury.
线粒体氧化功能改变会增加代谢紊乱患者发生心肌缺血/再灌注（I/R）损伤的易感性。然而，导致这种功能障碍的代谢信号通路仍不完全清楚。本研究旨在探讨缺氧琥珀酸积累是否会抑制丙酮酸脱氢酶（PDH）的活性，进而加重 I/R 损伤。结果表明，饱和脂肪酸棕榈酸刺激会增加脂肪酸氧化，并诱导心肌细胞缺氧，导致琥珀酸积累。细胞内琥珀酸诱导低氧诱导因子-1α（HIF-1α）表达，并通过上调丙酮酸脱氢酶激酶 4（PDK4）的表达来损害 PDH 活性。荧光素酶报告基因实验表明，琥珀酸通过 HIF-1α依赖性基因启动子诱导增加 PDK4 的表达。棕榈酸也会将琥珀酸释放到细胞外空间。通过激活 GRP91，细胞外琥珀酸诱导 PKCδ向线粒体易位，并进一步加重 PDH 损害。这些结果表明，琥珀酸通过 GPR91 依赖和非依赖途径损害 PDH 活性。人参皂苷 Rb1（从人参中分离得到的主要化合物）和曲美他嗪（脂肪酸β氧化抑制剂）通过阻断与琥珀酸相关的 HIF-1α激活和 GPR91 信号通路，防止心肌细胞中缺氧琥珀酸的积累，并改善 PDH 活性。通过改善 PDH 活性，Rb1 和曲美他嗪可防止心脏酸化，改善线粒体功能障碍，从而减少缺氧/复氧损伤时的细胞凋亡。在灌注棕榈酸的分离工作大鼠心脏和高脂饮食喂养的小鼠中，早期干预 Rb1 和曲美他嗪可减少琥珀酸的产生，并使心脏对 I/R 损伤的抵抗力增加。综上所述，我们的研究结果表明，通过靶向抑制琥珀酸积累诱导的 PDH 损害的早期干预，是减轻 I/R 损伤的有效策略。
