Pyruvate: Powerful Brain Protection after Cardiac Arrest

描述（由申请人提供）：心脏骤停是美国死亡的主要原因，对大脑和其他内脏器官造成严重缺血。即使心律恢复，大多数心脏骤停患者最终还是会死于不可逆转的脑损伤的毁灭性影响，许多幸存者还会遭受持续的、使人衰弱的神经损伤。尽管进行了广泛的临床前和临床研究，但预防心脏骤停患者脑损伤的实际治疗方法仍然难以捉摸。最近的研究表明，促红细胞生成素通过激活细胞保护信号级联来抑制神经元凋亡和抑制破坏性炎症，从而保护脑免受缺血性损伤。然而，由于促红细胞生成素不能轻易地穿过血脑屏障，需要大剂量才能达到显著的神经保护作用，最近在心脏骤停患者中静脉注射促红细胞生成素的临床试验结果令人失望。神经元和星形胶质细胞可以表达和合成促红细胞生成素，在脑内诱导促红细胞生成素的表达可以在绕过血脑屏障的同时赋予强大的神经保护作用。最近，我们证明了丙酮酸，一种天然的中间代谢物和抗氧化剂，诱导新的促红细胞生成素表达和信号传导阻滞心肌；重要的是，这些反应在丙酮酸清除后4小时仍保持强劲。此外，在心肺复苏（CPR）期间静脉输注丙酮酸可以防止心脏骤停后3天的神经损伤和神经元凋亡。血脑屏障内的高亲和力，高容量运输机制有效地将丙酮酸输送到脑实质。本研究将验证丙酮酸通过诱导脑内促红细胞生成素的表达和信号传导来预防心脏骤停后脑损伤和维持神经认知功能的假设。这一假设将在遭受心室颤动、心脏骤停、心肺复苏术、除颤反击和恢复的狗身上得到解决。在心肺复苏术和恢复前55分钟静脉输注丙酮酸盐或对照NaCl，或在心律和脑灌注恢复后120-180分钟延迟输注。在心脏骤停复苏后5 h、2 d和4 d进行活检，检测易感脑区促红细胞生成素mRNA和蛋白含量、信号激酶激活、中性粒细胞浸润、促凋亡半胱天酶、促炎基质金属蛋白酶和细胞保护酶内皮型一氧化氮合酶的活性。关于丙酮酸的神经保护机制及其在脑内诱导促红细胞生成素信号的能力的重要信息将为最终临床利用这种脑保护现象提供必要的基础。

DESCRIPTION (provided by applicant): The leading cause of death in the United States, cardiac arrest imposes profound ischemia on the brain and other internal organs. Even when cardiac rhythm is restored, most cardiac arrest victims eventually succumb to the devastating effects of irreversible brain damage, and many survivors suffer persistent, debilitating neurological impairment. Despite extensive preclinical and clinical research, a practical treatment to prevent brain damage in cardiac arrest victims remains elusive. Recently the hormone erythropoietin was shown to protect brain from ischemic injury by activating cytoprotective signaling cascades which suppress neuronal apoptosis and dampen destructive inflammation. However, because erythropoietin cannot readily traverse the blood-brain barrier, massive dosages are required to achieve significant neuroprotection, and outcomes of recent clinical trials of intravenous erythropoietin in cardiac arrest victims have been disappointing. Neurons and astrocytes can express and synthesize erythropoietin, and induction of erythropoietin expression within the brain could confer powerful neuroprotection while circumventing the blood brain barrier. Recently, we demonstrated that pyruvate, a natural intermediary metabolite and antioxidant, induced novel erythropoietin expression and signaling in arrested myocardium; importantly, these responses remained robust 4 hours after pyruvate had cleared. Moreover, intravenous pyruvate infusion during cardiopulmonary resuscitation (CPR) prevented subsequent neurological impairment and neuronal apoptosis 3 days after cardiac arrest. A high-affinity, high-capacity transport mechanism within the blood brain barrier efficiently delivers pyruvate to the brain parenchyma. This investigation will test the hypothesis that pyruvate prevents brain injury and preserves neurocognitive function after cardiac arrest by inducing erythropoietin expression and signaling within the brain. This hypothesis will be addressed in dogs subjected to ventricular fibrillation cardiac arrest, CPR, defibrillatory countershocks and recovery. Pyruvate or control NaCl will be infused intravenously during CPR and the first 55 min recovery, or in a delayed manner 120-180 min after restoration of cardiac rhythm and brain perfusion. Erythropoietin mRNA and protein content, signaling kinase activation, neutrophil infiltration, and activities of proapoptotic caspases, pro-inflammatory matrix metalloproteinases, and the cytoprotective enzyme endothelial nitric oxide synthase will be measured in vulnerable brain regions biopsied at 5 h, 2 d and 4 d after cardiac arrest-resuscitation. Crucial information on pyruvate's neuroprotective mechanisms and its ability to induce erythropoietin signaling within the brain will provide the essential foundation for eventual clinical exploitation of this cerebroprotective phenomenon.