小胶质细胞/巨噬细胞在脑出血脑损伤过程中的作用机制

Intracerebral hemorrhage (ICH) results from the rupture of cerebral vessels leading to the development of a hematoma in the brain parenchyma. ICH accounts for approximately 15-20 % of all strokes and it carries a worse prognosis than ischemic strokes. Effective medical treatment for ICH has been unsatisfactory. When ICH occurs, blood collects in the brain and causes brain damage and cell death. This is followed by an inflammatory response including microglia/macrophages activation, enzyme activation, release of many mediators of injury, and tissue breakdown and repair. We reported that when whole blood and blood components including leukocytes, matrix metalloproteinases (MMPs) and thrombin, were injected into the rodent brain parenchyma, they activated microglia/macrophages in a dose- and time-dependent manner. Moreover, the extent of brain damage, neuronal death, and activation of microglia/macrophage were reduced in MMP-3, -9, -12 null mice compared to wildtype controls. Nonetheless, despite inhibition of MMPs and thrombin, and despite minocycline (which has inactivating properties for microglia/macrophages) treatment, a substantial degree of brain damage and neuronal death still existed after ICH, thus necessitating new insights or targets in the condition. We propose to target more comprehensively the activation of microglia/macrophages to further alleviate ICH damage for several reasons. First, brain damage and neuronal death are always accompanied by the activation of microglia/macrophages in ICH injury, even though we do not know whether the activation of microglia/macrophages is a cause or a result of the insult. Second, the activation of microglia/microphages in ICH is is a major source of MMPs and other cytotoxic mediators. The overall hypothesis to be tested in this proposal is that the activation of microglia/macrophages is a key factor in promoting neuronal injury in the acute period after ICH and that blocking, inhibiting and deleting microglia/macrophages will attenuate brain injury in ICH. Moreover, as other brain cell type and infiltrating leukocyte subsets in ICH also produce mediators of injury such as proteases, we propose that the combination of microglia/macrophage inhibitors with the inhibition of protease activity in the acute period after ICH will further alleviate brain injury. We will use cell cultures and blood-induced ICH model in mice to test the hypotheses. The specific aims are: 1. To determine whether factors relevant to ICH trigger the activation of microglia and production of MMPs in vitro and in mice. 2. To determine the mechanisms by which activated microglia kill neurons. 3. To determine if ICH injury is decreased by inhibiting microglia activation in vitro and in microglia null mice. 4: To determine if the simultaneous inhibition of the activation of microglia/macrophages and MMPs will significantly improve histological and functional outcomes following ICH.

脑出血后激活的小胶质细胞/巨噬细胞及其表达的基质金属蛋白酶可能是加重脑损伤的重要机制。预实验表明脑出血后小胶质细胞被激活及基质金属蛋白酶大量表达。拟证实脑出血急性期激活的小胶质细胞/巨噬细胞是造成脑出血后神经损伤的重要因素，阻断小胶质细胞/巨噬细胞的激活能明显减轻脑出血后的脑损伤。其他神经细胞和白细胞也能产生蛋白酶和细胞因子等损伤介质，因此假设在脑出血的急性期抑制小胶质细胞/巨噬细胞的激活及蛋白酶活性能进一步减轻脑出血后的脑损伤并改善神经功能的恢复。拟用培养的人类胚胎神经细胞和小鼠自体血诱导的脑出血动物模型（这个模型可以最大限度的模拟脑出血病人）、CD11b-胸腺激酶转基因小鼠（当用更昔洛韦）时可以杀死增殖的小胶质细胞/巨噬细胞及其他基因敲除小鼠探讨小胶质细胞/巨噬细胞及基质金属蛋白酶在脑出血后的作用，为筛选脑出血的治疗新药（小胶质细胞激活抑制因子及基质金属蛋白酶抑制因子）提供科学依据。

脑出血是临床上最常见的脑卒中亚型，具有高发病率、高死亡率和高致残率等特点，严重危害人类健康。脑出血后激活的小胶质细胞/巨噬细胞是脑出血急性期引起神经损伤的重要因素，抑制小胶质细胞/巨噬细胞活动可以减少脑出血后的脑损伤，并且联合抑制基质金属蛋白酶和小胶质细胞/巨噬细胞的激活能进一步减少脑损伤。本研究深入研究了激活的小胶质细胞/巨噬细胞是脑出血急性期引起神经损伤的调节机制，并且发现抑制小胶质细胞/巨噬细胞活动可以减少脑出血后的脑损伤。本研究应用培养的人类胚胎神经细胞和小鼠自体血诱导的脑出血动物模型、CD11b-胸腺激酶转基因小鼠可以杀死增殖的小胶质细胞/巨噬细胞及其他基因敲除小鼠探讨小胶质细胞/巨噬细胞及基质金属蛋白酶在脑出血后的作用，为筛选脑出血的治疗新药提供科学依据。