Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), Achucarro Basque Center for Neuroscience and Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Leioa, Spain.
Department of Neuroscience, Physiology, & Pharmacology, University College London, London, UK.
Glia. 2020 Sep;68(9):1743-1756. doi: 10.1002/glia.23802. Epub 2020 Feb 14.
Mitochondrial fission mediated by cytosolic dynamin related protein 1 (Drp1) is essential for mitochondrial quality control but may contribute to apoptosis as well. Blockade of Drp1 with mitochondrial division inhibitor 1 (mdivi-1) provides neuroprotection in several models of neurodegeneration and cerebral ischemia and has emerged as a promising therapeutic drug. In oligodendrocytes, overactivation of AMPA-type ionotropic glutamate receptors (AMPARs) induces intracellular Ca overload and excitotoxic death that contributes to demyelinating diseases. Mitochondria are key to Ca homeostasis, however it is unclear how it is disrupted during oligodendroglial excitotoxicity. In the current study, we have analyzed mitochondrial dynamics during AMPAR activation and the effects of mdivi-1 on excitotoxicity in optic nerve-derived oligodendrocytes. Sublethal AMPAR activation triggered Drp1-dependent mitochondrial fission, whereas toxic AMPAR activation produced Drp1-independent mitochondrial swelling. Accordingly, mdivi-1 efficiently inhibited Drp1-mediated mitochondrial fission and did not prevent oligodendrocyte excitotoxicity. Unexpectedly, mdivi-1 also induced mitochondrial depolarization, ER Ca depletion and modulation of AMPA-induced Ca signaling. These off-target effects of mdivi-1 sensitized oligodendrocytes to excitotoxicity and ER stress and eventually produced oxidative stress and apoptosis. Interestingly, in cultured astrocytes mdivi-1 induced nondetrimental mitochondrial depolarization and oxidative stress that did not cause toxicity or sensitization to apoptotic stimuli. In summary, our results provide evidence of Drp1-mediated mitochondrial fission during activation of ionotropic glutamate receptors in oligodendrocytes, and uncover a deleterious and Drp1-independent effect of mdivi-1 on mitochondrial and ER function in these cells. These off-target effects of mdivi-1 limit its therapeutic potential and should be taken into account in clinical studies.
细胞质动力相关蛋白 1（Drp1）介导的线粒体分裂对于线粒体质量控制至关重要，但也可能导致细胞凋亡。线粒体分裂抑制剂 1（mdivi-1）阻断 Drp1 在几种神经退行性变和脑缺血模型中提供神经保护作用，并已成为一种有前途的治疗药物。在少突胶质细胞中，AMPA 型离子型谷氨酸受体（AMPAR）的过度激活会导致细胞内 Ca 超载和兴奋性毒性死亡，从而导致脱髓鞘疾病。线粒体是 Ca 稳态的关键，但尚不清楚在少突胶质细胞兴奋毒性过程中如何破坏 Ca 稳态。在本研究中，我们分析了 AMPAR 激活过程中线粒体动力学的变化以及 mdivi-1 对少突胶质细胞兴奋毒性的影响。亚致死 AMPAR 激活触发了 Drp1 依赖性线粒体分裂，而毒性 AMPAR 激活则导致 Drp1 非依赖性线粒体肿胀。因此，mdivi-1 有效地抑制了 Drp1 介导的线粒体分裂，但不能防止少突胶质细胞兴奋毒性。出乎意料的是，mdivi-1 还诱导了线粒体去极化、内质网 Ca 耗竭和调节 AMPA 诱导的 Ca 信号。mdivi-1 的这些非靶点效应使少突胶质细胞对兴奋毒性和内质网应激敏感，并最终产生氧化应激和细胞凋亡。有趣的是，在培养的星形胶质细胞中，mdivi-1 诱导了非有害的线粒体去极化和氧化应激，而不会导致毒性或对凋亡刺激物的敏感性。总之，我们的研究结果为少突胶质细胞中离子型谷氨酸受体激活时 Drp1 介导的线粒体分裂提供了证据，并揭示了 mdivi-1 对这些细胞中线粒体和内质网功能的有害且 Drp1 非依赖性的影响。mdivi-1 的这些非靶点效应限制了其治疗潜力，在临床研究中应加以考虑。
