Mechanism of thrombin-induced tolerance to brain injury

说明(申请人提供)：凝血酶是一种丝氨酸蛋白酶，是凝血级联反应的重要组成部分。它是在脑出血(ICH)或多种脑损伤后血脑屏障破裂后立即在大脑中产生的。体内和体外的证据表明，脑实质中高浓度的凝血酶可能是有害的。然而，低浓度的凝血酶具有神经保护作用。因此，我们已经证明，小剂量凝血酶(凝血酶预适应，TPC)脑内预处理可减轻脑出血、脑缺血和帕金森病所致的脑损伤。为了阐明TPC诱导的神经保护的细胞机制，我们设计了一种新的大鼠脑出血模型。这采用了海马区内注射血液(或血液成分)的方法。与造成更多弥漫性损伤的大鼠脑出血模型相比，这具有导致容易量化的神经元丢失的优势。我们实验室的工作还表明，蛋白质合成(例如铁处理蛋白和热休克蛋白)在凝血酶诱导的神经保护中是必不可少的。在这项研究中，我们将研究凝血酶、蛋白酶激活受体-1(PAR-1，一种凝血酶受体)、磷脂酰肌醇3激酶(PI3K)/核糖体蛋白S6激酶(P70 S6K)和细胞外信号调节激酶(ERK)/p70 S6K通路在介导脑出血后神经元死亡保护中的作用。P70S6K的磷酸化是蛋白质合成的重要调节因子。我们将测试以下两个具体目标。1.确定凝血酶预适应是否通过激活PAR-1减少脑出血后神经元死亡。2.确定凝血酶是否通过激活PI3K/p70 S6K和ERK/p70 S6K通路而产生神经保护作用。公共卫生相关性：我们项目的目的是调查TPC所涉及的机制。凝血酶诱导的脑保护似乎是PAR-1介导的，与缺血预适应相比，这极大地促进了分析。这些研究的长期目标是找到可以用来限制脑出血后脑损伤的机制。在低浓度时，凝血酶保护大脑。研究如何调节凝血酶将使我们能够创造新的方法来限制脑出血、脑缺血和帕金森病后的脑损伤，并有利于公众健康。

DESCRIPTION (provided by applicant): Thrombin, a serine protease, is an essential component of the coagulation cascade. It is produced immediately in the brain after an intracerebral hemorrhage (ICH) or after the blood- brain barrier breakdown that occurs following many kinds of brain injury. Evidence, both in vivo and in vitro, indicates that high concentrations of thrombin within the brain parenchyma can be deleterious. However, low concentrations of thrombin are neuroprotective. Thus, we have demonstrated that intracerebral pretreatment with a low dose of thrombin (thrombin preconditioning, TPC) reduces brain injury induced by ICH, cerebral ischemia and Parkinson's disease. In order to elucidate the cellular mechanisms involved in TPC-induced neuroprotection we have devised a new rat ICH model. This employs intrahippocampal injection of blood (or blood component). This has the advantage of causing easily quantifiable neuronal loss in contrast to the intracaudate model of ICH in the rat which causes more diffuse injury. Work from our laboratory also suggests that protein synthesis (e.g. iron-handling proteins and heat shock proteins) is essential in thrombin-induced neuroprotection. In this proposal, we will examine the role of thrombin, protease-activated receptor-1 (PAR-1, a thrombin receptor) and the activation of phosphatidylinositol 3 kinase (PI3K)/ ribosomal protein S6 kinases (p70 S6K) and extracellular signal-regulated kinases (ERK)/p70 S6K pathways in mediating protection from neuronal death following ICH. Phosphorylation of p70 S6K is a crucial regulator of protein synthesis. We will test the following two specific aims. 1. To determine whether or not thrombin preconditioning reduces ICH-induced neuronal death through PAR-1 activation. 2. To determine whether or not thrombin-induced neuroprotection results from activation of the PI3K/p70 S6K and ERK/p70 S6K pathways. PUBLIC HEALTH RELEVANCE: The purpose of our project is to investigate the mechanisms involved in TPC. Thrombin- induced brain protection seems to be PAR-1 mediated, greatly facilitating analysis compared to ischemic preconditioning. The long term goal of these studies is to find mechanisms that can be used to limit brain injury after ICH. At low concentrations, thrombin protects the brain. Researching how to mediate thrombin will allow us to create new ways to limit brain injury after intracerebral hemorrhage, cerebral ischemia, and Parkinson's disease, and benefit public health.