Blood-Brain Barrier Ion Transport in Cerebral Ischemia

脑缺血中的血脑屏障离子转运

• 批准号: 8720068
• 负责人: Martha E O'Donnell
• 金额: $ 32.7万
• 依托单位: UNIVERSITY OF CALIFORNIA AT DAVIS
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2017-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8720068
• 关键词: Animals; Attenuated; Bicarbonates; Biological Assay; Blood; Blood - brain barrier anatomy; Blood Glucose; Brain; Brain Edema; Brain Injuries; Bumetanide; Cause of Death; Cells; Cerebral Edema; Cerebral Ischemia; Cerebrum; Comorbidity; Diabetes Mellitus; Edema; Endothelial Cells; Evaluation; Goals; Grant; Hour; Human; Hyperglycemia; Hypoxia; In Situ; In Vitro; Individual; Infarction; Intravenous; Ion Transport; Ions; Ischemia; Ischemic Stroke; Magnetic Resonance Imaging; Mediating; Membrane; Methods; Middle Cerebral Artery Occlusion; Modeling; Nuclear Magnetic Resonance; Outcome; Patients; Perfusion; Population; Process; Proteins; Rattus; Sodium; Sodium-Potassium-Chloride Symporters; Streptozocin; Stroke; Swelling; Testing; Therapeutic; Translating; Vasopressins; Water; Western Blotting; Work; diabetic; effective therapy; in vivo; inhibitor/antagonist; intravenous administration; public health relevance; research study; response; therapeutic target; uptake

DESCRIPTION (provided by applicant): The long term goal of this project is to identify blood-brain barrier (BBB) ion transporters that mediate ischemia-induced brain edema. During the early hours of ischemic stroke, edema forms in the presence of an intact BBB by a process involving BBB transport of Na and Cl from blood into brain. Our previous studies have shown that Na-K-Cl cotransport (NKCC) and Na/H exchange (NHE), present in the luminal BBB membrane, are stimulated by ischemic factors, including hypoxia, aglycemia and vasopressin (AVP) and that inhibiting BBB NKCC and/or NHE activity reduces brain edema in the rat middle cerebral artery occlusion (MCAO) model of stroke. In preliminary studies we have now found evidence that a BBB Na-HCO3 cotransporter (NBC) constitutes a 3rd prominent BBB Na transporter that is also stimulated during ischemia to substantially participate in cerebral edema formation. This gives us an important additional therapeutic target for reducing the highly injurious early edema formation in ischemic stroke. While our studies indicate that NKCC, NHE and NBC appear to be promising therapeutic targets for reducing edema in otherwise healthy stroke patients, it must be recognized that hyperglycemia, a common co-morbidity in stroke present in ~30% of patients, causes greater cerebral edema and worsened outcome. The underlying mechanisms for this are poorly understood. However, in recent studies we have found that hyperglycemia increases expression and activity of BBB NKCC, NHE and NBC and augments their stimulation by ischemic factors. Further, we have also found evidence that the hyperglycemia exacerbation of brain edema in MCAO is reduced by inhibition of BBB NKCC, NHE and NBC. Our hypothesis is that BBB NKCC, NHE and/or NBC participate in the hyperglycemia-induced augmentation of cerebral edema formation and constitute effective therapeutic targets in hyperglycemic stroke. The first aim is to determine whether NBC protein is present at the luminal BBB membrane and is stimulated by ischemic factors. We will use Western blot and immunoEM to evaluate BBB NBC protein in CMEC and in BBB in situ, and microspectrofluorometry to assess ischemic factor effects on CMEC NBC activity. The second aim is to determine whether hyperglycemic conditions increase expression and activity of BBB NKCC, NHE and/or NBC and augment stimulation of these Na transporters by ischemic factors. We will use Western blot, microspectrofluorometry and radioisotopic flux assays to test the effects of hyperglycemia on CMEC NKCC, NHE and NBC protein and activity. We will also use immunoEM to evaluate NKCC, NHE and NBC in BBB in situ of hyperglycemic rats. The third aim is to determine whether inhibition of BBB NKCC, NHE and/or NBC attenuates ischemia-induced edema in hyperglycemic animals. Here, we will examine the effects of inhibiting BBB NKCC, NHE and NBC on ischemia-induced changes in rat brain Na and water, using nuclear magnetic resonance methods and rats with STZ-induced hyperglycemia. We will also assess the efficacy of NKCC, NHE and NBC inhibitors for reduction of edema when administered after the onset of ischemia.

描述（由申请人提供）：该项目的长期目标是确定介导缺血引起的脑水肿的血脑屏障（BBB）离子转运蛋白。在缺血性中风的早期，水肿是在完整 BBB 存在的情况下通过 BBB 将 Na 和 Cl 从血液转运到大脑的过程形成的。我们之前的研究表明，存在于管腔 BBB 膜中的 Na-K-Cl 共转运 (NKCC) 和 Na/H 交换 (NHE) 受到缺血因素的刺激，包括缺氧、血糖和加压素 (AVP)，并且抑制 BBB NKCC 和/或 NHE 活性可减轻大鼠大脑中动脉闭塞 (MCAO) 模型中的脑水肿。 中风。在初步研究中，我们现在发现证据表明 BBB Na-HCO3 协同转运蛋白 (NBC) 构成第三种重要的 BBB Na 转运蛋白，在缺血期间也会受到刺激，从而显着参与脑水肿的形成。这为我们减少缺血性中风中高度伤害性的早期水肿形成提供了一个重要的额外治疗靶点。虽然我们的研究表明 NKCC、NHE 和 NBC 似乎是减少其他方面健康的中风患者水肿的有希望的治疗靶点，但必须认识到，高血糖是约 30% 患者中存在的中风常见并发症，会导致更大的脑水肿和恶化的结果。人们对此的基本机制知之甚少。然而，在最近的研究中，我们发现高血糖会增加 BBB NKCC、NHE 和 NBC 的表达和活性，并增强缺血因素对它们的刺激。此外，我们还发现证据表明，通过抑制 BBB NKCC、NHE 和 NBC，可以减轻 MCAO 中脑水肿的高血糖恶化。我们的假设是，BBB NKCC、NHE 和/或 NBC 参与高血糖诱导的脑水肿形成的增强，并构成高血糖中风的有效治疗靶点。第一个目的是确定 NBC 蛋白是否存在于管腔 BBB 膜上并受到缺血因素的刺激。我们将使用蛋白质印迹和免疫电镜来评估 CMEC 和原位 BBB 中的 BBB NBC 蛋白，并使用显微分光荧光法来评估缺血因子对 CMEC NBC 活性的影响。第二个目的是确定高血糖条件是否会增加 BBB NKCC、NHE 和/或 NBC 的表达和活性，并增强缺血因子对这些 Na 转运蛋白的刺激。我们将使用蛋白质印迹、显微荧光分光光度法和放射性同位素通量测定来测试高血糖对 CMEC NKCC、NHE 和 NBC 蛋白和活性的影响。我们还将使用免疫电镜来评估高血糖大鼠 BBB 中的 NKCC、NHE 和 NBC。第三个目的是确定抑制 BBB NKCC、NHE 和/或 NBC 是否可以减轻高血糖动物中缺血引起的水肿。在这里，我们将使用核磁共振方法和 STZ 诱导的高血糖大鼠，研究抑制 BBB NKCC、NHE 和 NBC 对缺血引起的大鼠脑钠和水变化的影响。我们还将评估 NKCC、NHE 和 NBC 抑制剂在缺血发作后服用时减轻水肿的功效。