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Drp1-mediated mitochondrial abnormalities link to synaptic injury in diabetes model.

ABSTRACT: Diabetes has adverse effects on the brain, especially the hippocampus, which is particularly susceptible to synaptic injury and cognitive dysfunction. The underlying mechanisms and strategies to rescue such injury and dysfunction are not well understood. Using a mouse model of type 2 diabetes (db/db mice) and a human neuronal cell line treated with high concentration of glucose, we demonstrate aberrant mitochondrial morphology, reduced ATP production, and impaired activity of complex I. These mitochondrial abnormalities are induced by imbalanced mitochondrial fusion and fission via a glycogen synthase kinase 3β (GSK3β)/dynamin-related protein-1 (Drp1)-dependent mechanism. Modulation of the Drp1 pathway or inhibition of GSK3β activity restores hippocampal long-term potentiation that is impaired in db/db mice. Our results point to a novel role for mitochondria in diabetes-induced synaptic impairment. Exploration of the mechanisms behind diabetes-induced synaptic deficit may provide a novel treatment for mitochondrial and synaptic injury in patients with diabetes.

SUBMITTER: Huang S

PROVIDER: S-EPMC4407851 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature

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Drp1-mediated mitochondrial abnormalities link to synaptic injury in diabetes model.

Huang Shengbin S Wang Yongfu Y Gan Xueqi X Fang Du D Zhong Changjia C Wu Long L Hu Gang G Sosunov Alexander A AA McKhann Guy M GM Yu Haiyang H Yan Shirley ShiDu SS

Diabetes 20141120 5

Diabetes has adverse effects on the brain, especially the hippocampus, which is particularly susceptible to synaptic injury and cognitive dysfunction. The underlying mechanisms and strategies to rescue such injury and dysfunction are not well understood. Using a mouse model of type 2 diabetes (db/db mice) and a human neuronal cell line treated with high concentration of glucose, we demonstrate aberrant mitochondrial morphology, reduced ATP production, and impaired activity of complex I. These mi ...[more]

PMID: 25412623

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Project description:Mitochondrial dysfunction is a salient feature of myocardial ischemia/reperfusion injury (MIRI), while the potential mechanism of mitochondrial dynamics disorder remains unclear. This study sought to explore whether activation of Adenosine monophosphate-activated protein kinase (AMPK) could alleviate MIRI by regulating GTPase dynamin-related protein 1 (Drp1)-mediated mitochondrial dynamics. Isolated mouse hearts in a Langendorff perfusion system were subjected to ischemia/reperfusion (I/R) treatment, and H9C2 cells were subjected to hypoxia /reoxygenation (H/R) treatment in vitro. The results showed that AICAR, the AMPK activator, could significantly improve the function of left ventricular, decrease arrhythmia incidence and myocardial infarction area of isolated hearts. Meanwhile, AICAR increased superoxide dismutase (SOD) activity and decreased malondialdehyde (MDA) content in myocardial homogenate. Mechanistically, AICAR inhibited the phosphorylation of Drp1 at Ser 616 while enhanced phosphorylation of Drp1 at Ser 637. In addition, AICAR reduced the expression of inflammatory cytokines including TNF-ɑ, IL-6, and IL-1β, as well as mitochondrial fission genes Mff and Fis1, while improved the expression of mitochondrial fusion genes Mfn1 and Mfn2. Similar results were also observed in H9C2 cells. AICAR improved mitochondrial membrane potential (MMP), reduced reactive oxygen species (ROS) production, and inhibited mitochondrial damage. To further prove if Drp1 regulated mitochondrial dynamics mediated AMPK protection effect, the mitochondrial fission inhibitor Mdivi-1 was utilized. We found that Mdivi-1 significantly improved MMP, inhibited ROS production, reduced the expression of TNF-a, IL-6, IL-1β, Fis1, and Mff, and improved the expression of Mfn1 and Mfn2. However, the protection effect of Mdivi-1 was not reversed by AMPK inhibitor Compound C. In conclusion, this study confirmed that activation of AMPK exerted the protective effects on MIRI, which were largely dependent on the inhibition of Drp1-mediated mitochondrial fission.

Project description:AimsGenetic and pharmacological inhibition of mitochondrial fission induced by acute myocardial ischaemia/reperfusion injury (IRI) has been shown to reduce myocardial infarct size. The clinically used anti-hypertensive and heart failure medication, hydralazine, is known to have anti-oxidant and anti-apoptotic effects. Here, we investigated whether hydralazine confers acute cardioprotection by inhibiting Drp1-mediated mitochondrial fission.Methods and resultsPre-treatment with hydralazine was shown to inhibit both mitochondrial fission and mitochondrial membrane depolarisation induced by oxidative stress in HeLa cells. In mouse embryonic fibroblasts (MEFs), pre-treatment with hydralazine attenuated mitochondrial fission and cell death induced by oxidative stress, but this effect was absent in MEFs deficient in the mitochondrial fission protein, Drp1. Molecular docking and surface plasmon resonance studies demonstrated binding of hydralazine to the GTPase domain of the mitochondrial fission protein, Drp1 (KD 8.6±1.0 µM), and inhibition of Drp1 GTPase activity in a dose-dependent manner. In isolated adult murine cardiomyocytes subjected to simulated IRI, hydralazine inhibited mitochondrial fission, preserved mitochondrial fusion events, and reduced cardiomyocyte death (hydralazine 24.7±2.5% vs. control 34.1±1.5%, P=0.0012). In ex vivo perfused murine hearts subjected to acute IRI, pre-treatment with hydralazine reduced myocardial infarct size (as % left ventricle: hydralazine 29.6±6.5% vs. vehicle control 54.1±4.9%, P=0.0083), and in the murine heart subjected to in vivo IRI, the administration of hydralazine at reperfusion, decreased myocardial infarct size (as % area-at-risk: hydralazine 28.9±3.0% vs. vehicle control 58.2±3.8%, P<0.001).ConclusionWe show that, in addition to its antioxidant and anti-apoptotic effects, hydralazine, confers acute cardioprotection by inhibiting IRI-induced mitochondrial fission, raising the possibility of repurposing hydralazine as a novel cardioprotective therapy for improving post-infarction outcomes.

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Drp1-mediated mitochondrial abnormalities link to synaptic injury in diabetes model.

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Drp1-mediated mitochondrial abnormalities link to synaptic injury in diabetes model.

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