Role For Inflammatory Cytokines In Neurodegeneration

趋化因子已被证明参与脑发育、正常脑稳态的维持以及神经胶质细胞和神经元细胞的迁移、分化和增殖。趋化因子和趋化因子受体表达可通过炎性介质增加，并且与许多神经炎性和神经障碍相关，包括多发性硬化、创伤、中风、阿尔茨海默病、肿瘤进展和AIDS痴呆。趋化因子作用的一个新兴领域是神经内分泌和免疫系统之间的通讯。现在很明显，趋化因子及其受体代表了一个多功能多能蛋白质家族，其对CNS的作用不限于神经炎症。这些分子构成了生理和发育过程中细胞通讯的重要调节因子。我们以前已经表明，人类神经元细胞表达的细胞表面趋化因子受体，这似乎介导神经元细胞迁移和细胞内钙离子的增加。此外，我们发现SDF-1a和HIV蛋白gp 120能够与神经元表面的CXCR 4结合，导致程序性神经元细胞死亡。尽管有这些发现，仍然是非常少的了解其他趋化因子受体在神经元和神经胶质细胞表面的生物学作用。在这项研究中，我们研究了各种趋化因子的直接和间接作用，更具体地说，这里的MCP-1和MIP-2（我们已经证明了神经元上存在细胞表面受体），以诱导神经元细胞死亡或存活。我们已经发现MCP-1和MIP-2通过特异性细胞表面趋化因子受体，通过产生活性氧产生（例如，一氧化氮或NO），通过半胱天冬酶活化和谷氨酸释放。此外，我们还发现，这些趋化因子直接激活星形胶质细胞，产生大量的炎性细胞因子和分子，这些细胞因子和分子似乎对人类和啮齿动物分化的神经元有毒。事实上，趋化因子诱导的星形胶质细胞神经毒性似乎部分是由于代谢活跃的星形胶质细胞和小胶质细胞释放谷氨酸。我们认为，CNS趋化因子在神经炎症的发生和与创伤和神经系统疾病相关的各种病理后遗症中起重要作用。在急性和慢性神经退行性和神经炎症过程中，趋化因子是否有共同的潜在生化和分子机制介导其作用仍有待确定。其他研究集中在阿尔茨海默病（AD）发展中的趋化因子和各种炎症介质。这种疾病的标志性病理特征是b-淀粉样蛋白（Ab）斑块的积累，随后AD患者脑内的神经变性和神经炎症。有几种形式的抗体，包括抗体1 -40和1-42，每一种表现出不同的细胞协会以及神经毒性的潜力。例如，Ab 1-40主要与反应性星形胶质细胞相关，而Ab 1-42与活化的小胶质细胞/巨噬细胞相关，并且表现出比Ab 1-40更大的神经毒性效力。在这两种情况下，激活的神经胶质细胞的存在下，在生产的趋化因子和炎性细胞因子，我们认为这可能介导以及加剧抗体诱导的神经毒性。利用cDNA微阵列技术，我们分析了两种形式的抗体肽对神经元和星形胶质细胞群体的影响及其诱导差异基因表达的能力。一些促炎（包括趋化因子和几个CCR），凋亡，谷氨酸受体相关基因被发现在人类星形胶质细胞和神经元细胞上调。我们目前正在研究这些基因在抗体介导的激活和细胞死亡中的具体作用，以及检查对照老年人和AD脑组织的组织学切片中有关基因的RNA和蛋白质表达。我们相信这些研究可以阐明神经胶质细胞可能直接或间接介导神经炎症，神经退行性变和AD病理的途径。除了上述工作，我们最近获得了高度明确的海马组织从AD患者沿着与年龄匹配的同行，希望建立一个模型，定义AD的炎症机制，以及抗体和趋化因子诱导的神经毒性和星形胶质细胞活化。该项目的目标是使用cDNA微阵列分析来表征和比较从急性（创伤）和慢性（AD）疾病损伤过程中获得的中枢神经系统组织的基因表达谱。我们已经进行了这些研究，目前正在处理数据。目前正在进行免疫组织学分析和PCR确认，以证实我们的发现。总体而言，我们认为在急性和慢性神经退行性和神经炎症过程中存在共同的潜在生化和分子机制。本项目的最终目标是：1）使用cDNA微阵列分析表征和比较从急性（创伤）和慢性（AD）疾病-损伤过程中获得的CNS组织的遗传谱; 2）确定在神经变性的急性和慢性阶段是否调节特异性炎症标记物，其可以是诊断性的或表型的;和3）确定特定的信号传导途径是否在各种神经变性过程中被利用，特别强调神经胶质。

Chemokines have been shown to be involved in brain development, in the maintenance of normal brain homeostasis, and in the migration, differentiation, and proliferation of glial and neuronal cells. Chemokine and chemokine receptor expression can be increased by inflammatory mediators and have been associated with a number of neuroinflammatory and neurological disorders including multiple sclerosis, trauma, stroke, Alzheimer's disease, tumor progression, and AIDS dementia. An emerging area of interest for chemokine action is represented by the communication between the neuroendocrine and the immune system. It is now evident that chemokines and their receptors represent a multifunctional pluripotent family of proteins whose actions on the CNS are not restricted to neuroinflammation. These molecules constitute crucial regulators of cellular communication in physiological and developmental processes. We have previously shown that human neuronal cells express a number of cell surface chemokine receptors, which appear to mediate neuronal cell migration and increases in intracellular calcium. In addition, we have found that SDF-1a and the HIV protein, gp120, are able to bind to CXCR4 on the surface of neurons resulting in a programmed neuronal cell death. Despite these findings, there is still very little known about the biological role of other chemokine receptors on the surface of neurons and glia cells. In this study, we have examined the direct and indirect effects of a variety of chemokines, more specifically here MCP-1 and MIP-2 (for which we have demonstrated the presence of cell surface receptors on neurons), to induce neuronal cell death or survival. We have found that the MCP-1 and MIP-2 directly and specifically induce differentiated hippocampal neuron death via specific cell surface chemokine receptors, through the generation of reactive oxygen species production (e.g., nitric oxide or NO), through caspase activation, and glutamate release. In addition, we have also found that these chemokines directly activate astrocytes to produce a number of inflammatory cytokines and molecules that appear to be toxic to human and rodent differentiated neurons. In fact, chemokine-induced astrocyte neurotoxicity appears to be partially due to the release of glutamate by metabolically active astrocytes and microglia. We believe that CNS chemokines play an important role in the genesis of neuroinflammation and the various pathological sequelae associated with trauma and neurological diseases. Whether there are common underlying biochemical and molecular mechanisms in which chemokines mediate their effects in both acute and chronic neurodegenerative and neuroinflammatory processes remains to be determined. Additional studies have focused on chemokines and various inflammatory mediators in the development of Alzheimers Disease (AD). The hallmark pathological feature of this disease is the accumulation of b-amyloid (Ab) plaques, the ensuing neurodegeneration and neuroinflammation within the brains of AD patients. There are several forms of Ab, including Ab1-40 and 1-42, each exhibiting differing cellular associations as well as neurotoxic potency. For example, Ab 1-40 is primarily associated with reactive astrocytes, while Ab 1-42 is associated with activated microglia/macrophages and exhibits greater neurotoxic potency than Ab 1-40. The presence of activated glia in both cases results in the production of chemokines and inflammatory cytokines, which we believe may mediate as well as exacerbate Ab-induced neurotoxicity. Using cDNA microarray technology, we have analyzed the effect of the two forms of Ab peptide on neuronal and astroglial populations and their ability to induce differential gene expression. A number of proinflammatory (including chemokines and several CCRs), apoptotic, and glutamate receptor-associated genes were found to be upregulated in human astrocytes and neuronal cells. We are currently examining the specific role of these genes in Ab-mediated activation and cell death as well as examining histological sections of control aged and AD brain tissue for the RNA and protein expression of the genes in question. We believe these studies may elucidate the pathways via which glia cells may directly and indirectly mediate neuroinflammation, neurodegeneration and AD pathology. In addition to the work above, we have recently acquired highly defined hippocampal tissue from AD patients along with age-matched counterparts with the hope of building a model defining the inflammatory mechanisms of AD as well as Ab- and chemokine-induced neurotoxicity and astrocyte activation. The goals of this project are to characterize and compare the gene expression profile of CNS tissue obtained from acute (trauma) and chronic (AD) disease-injury processes using cDNA microarray analysis. We have already performed these studies and are currently processing the data. Immunohistological analyses and PCR confirmations are currently underway to confirm our findings. Overall, we believe there are common underlying biochemical and molecular mechanisms involved in both acute and chronic neurodegenerative and neuroinflammatory processes. The ultimate goals of this project are: 1) to characterize and compare the genetic profile of CNS tissue obtained from acute (trauma) and chronic (AD) disease-injury processes using cDNA microarray analysis; 2) to determine whether specific inflammatory markers are modulated during acute and chronic phases of neurodegeneration that may be diagnostic or phenotypic; and 3) to determine whether specific signaling pathways are being utilized in various neurodegenerative processes with specific emphasis on neuroglia.