Role of hypoxia-inducible factor-prolyl-hydroxylase (HIF-PHD) in mitochondrial pathways of ischemic neuronal death

在阿尔茨海默病和帕金森氏病等神经退行性疾病中，以及脑缺血或创伤性脑损伤后，决定脑组织和功能不可逆性丧失的神经元死亡的潜在机制共享共同的细胞程序性死亡信号通路。在神经元中，这些程序化的细胞死亡途径进入线粒体，线粒体是能量新陈代谢的关键细胞器，负责产生ATP，从而确保神经元的功能和生存。这种线粒体的死亡与线粒体膜通透性有关，以及促凋亡蛋白，如凋亡诱导因子(AIF)、Smac/Diablo或细胞色素c从膜间隙释放到胞浆和细胞核，在那里它们协调一个确定的细胞死亡程序。现在人们普遍认为，线粒体损伤标志着所谓的程序性细胞死亡无法恢复的点，这意味着线粒体受损的细胞无法生存。因此，新发现的神经元死亡信号关键触发因素之间的机械联系，如破坏钙稳态或氧化应激，与线粒体损伤可能成为创新的靶点，以克服目前治疗退行性神经疾病的治疗选择的警告。坏死性下垂和铁性下垂是两种新出现的调节性坏死，分别由RIP1/RIP3激酶激活和铁依赖的酶级联反应调节。我们最近的数据表明，在神经细胞中，这些调控细胞死亡的范例可能与线粒体完整性和功能的丧失有关，特别是对代谢平衡、ROS稳态和钙调节以及死亡信号的影响。此外，低氧诱导因子(HIF)的脯氨基-4-羟基酶(PhDS)在体外和体内的氧化应激与铁性下垂和坏死性下垂信号相关的范例中被认为是线粒体保护的靶标。我们假设，HIF-PhD可能作为与缺氧/缺血性脑损伤相关的调节性坏死的范例中的潜在治疗靶点。这些发现的结果将使我们能够在坏死性下垂和铁性下垂的范例中剖析PHD参与细胞死亡信号的机制，以及它们与线粒体完整性和功能的潜在联系，在体外氧化应激和氧糖剥夺诱导的神经细胞死亡模型系统中，以及在体内缺氧缺血后的有害应激反应中。此外，我们将讨论在培养的小胶质细胞、脑片和体内缺氧缺血后，PHD在调节神经炎性反应中的关键作用。结合本项目申请者的专业知识，可以提供一幅关于博士在神经退行性变和神经炎症机制中的作用的独特和统一的图景，这可能导致神经保护和再生的新策略。

In neurodegenerative diseases such as Alzheimers and Parkinsons disease, and after cerebral ischemia or traumatic brain injury, the underlying mechanisms of neuronal death determining the irreversible loss of brain tissue and functions share common signaling pathways of programmed cell death. In neurons, these programmed cell death pathways funnel into mitochondria, the key organelles of energy metabolism that are in charge to produce ATP thereby securing neuronal function and survival. Such mitochondrial demise is associated with mitochondrial membrane permeabilization, and the release of pro-apoptotic proteins, such as apoptosis inducing factor (AIF), SMAC/DIABLO or cytochrome c from the intermembrane space into the cytosol and the cell nucleus, where they orchestrate a determined cell death program. It is now well accepted that mitochondrial damage marks the so-called point of no return of programmed cell death, meaning that cells with impaired mitochondria cannot survive. Thus, newly identified mechanistic links between key triggers of neuronal death signaling, such as disrupted Ca2+-homeostasis or oxidative stress, and mitochondrial damage may serve as innovative targets to overcome the current caveat of therapeutic options in the treatment of degenerating neural diseases. Necroptosis and ferroptosis are two emerging forms of regulated necrosis that are regulated by activation of RIP1/RIP3 kinase activation and iron-dependent enzymatic cascades, respectively. Our recent data suggest that in neuronal cells, these paradigms of regulated cell death may be linked to loss of mitochondrial integrity and function with particular impact on the metabolic balance, ROS homeostasis and Ca2+ regulation, and death signaling. In addition, hypoxia-inducible factor (HIF) prolyl-4-hydroxylases (PHDs) emerged as promising target candidates for mitochondrial protection in paradigms of oxidative stress associated with ferroptosis and necroptosis signaling in vitro and in vivo. We hypothesize that HIF-PHDs may serve as potential therapeutic targets in paradigms of regulated necrosis relevant to hypoxic/ischemic brain damage. The outcome of these findings will allow us to dissect the mechanistic involvement of PHDs in cell death signaling in paradigms of necroptosis and ferroptosis, and their potential link to mitochondrial integrity and function in detrimental stress responses in model systems of neuronal cell death induced by oxidative stress and oxygen glucose deprivation in vitro, and after hypoxia-ischemia in vivo. Further, we will address the proposed key role of PHDs in the regulation of neuroinflammatory responses in cultured microglial cells, in brain slices, and after hypoxia ischemia in vivo. Combining the expertise of the applicants in this project allows for providing a unique and unifying picture of the role of PHDs in mechanisms of neurodegeneration and neuroinflammation that may lead to novel strategies of neuroprotection and regeneration.