细菌内毒素耐受小鼠的细胞凋亡及信号转导相关分子研究

发布时间：2018-01-02 14:14

本文关键词：细菌内毒素耐受小鼠的细胞凋亡及信号转导相关分子研究　出处：《第二军医大学》2006年博士论文　论文类型：学位论文

【摘要】：内毒素(endotoxin)是革兰氏阴性细菌(GNB)细胞壁外膜层的主要组成成分,其主要组成成分是脂多糖(LPS)。由亲水性的多糖(O-特异性多糖、核心多糖)和疏水性的类脂A(Lipid A)组成。其中Lipid A是LPS中最为保守的部分,无种属特异性,是LPS的主要生物活性成分。研究发现Lipid A结构的完整性与LPS的毒性相关。LPS在细菌生长繁殖、死亡破裂或人工方法裂解后释放。一旦进入人或其他敏感动物体内,将对宿主各系统、器官产生广泛影响。LPS不仅是决定GNB感染(如脓毒症和感染性休克)的主要致病因子,而且与人类其他许多疾病关系密切,是一种危及人类健康乃至生命的最为重要的病原相关模式分子(PAMPs)。随着有创技术、免疫抑制剂、细胞毒化疗,以及广谱抗生素使用的增多,脓毒症和感染性休克的发病率自20世纪50年代以来一直呈增多趋势,在美国每年因其死亡的人数达近20万,儿童脓毒症病死率为10%-15%,成人则高达40%。我国还没有此方面的详细报道。内毒素的致病机制主要是LPS通过持续刺激机体单核巨噬细胞系统,使之产生大量的细胞因子,包括TNF-α,IL-6,IL-12等,活性氧、溶酶体酶、NO等活性物质,引起细胞损伤和凋亡,最终导致失控性炎症反应,并伴有较高的机体死亡率。尽管宿主细胞在细菌产物的作用下出现以细胞凋亡为特征的细胞死亡现象,但是宿主在细菌致病产物的作用下并非总是被动的。他们积极主动的调动宿主抗御死亡的机制来对抗细菌的攻击,降低并缓解细菌对宿主的损害程度。当宿主多次接触细菌内毒素,再次给予高剂量的细菌内毒素时,宿主仅出现轻微的反应或不反应,这种现象被定义为内毒素耐受或称之为低应答(hyporesponsiveness),它被认为是机体的一种适应性反应,可以有效的抑制单核巨噬细胞过度表达引起的炎症反应及败血症休克。内毒素耐受现象一个世纪前就已经被认识到,但其作用机制至今尚未研究清楚,而且内毒素耐受的出现与细胞凋亡的抑制是否有关,也是一个倍受关注的问题。因此,本研究首先诱导小鼠出现内毒素耐受现象,检测耐受后的小鼠的肝组织细胞中是否出现凋亡现象。在此基础上,我们探讨了耐受现象与细胞凋亡及机体死亡之间的关系。研究在耐受出现后,动物组织细胞中凋亡相关信号分子及LPS相关信号分子的变化。一、小鼠内毒素耐受模型的建立
[Abstract]:Endotoxin (endotoxin) is a major component of the outer membrane of the cell wall of Gram-negative bacteria (GNB). Its main component is lipopolysaccharide (LPS). Core polysaccharides) and hydrophobic lipopolipid A). Lipid A is the most conserved part of LPS and has no species specificity. It is found that the integrity of Lipid A structure is related to the toxicity of LPS. Death ruptures or artificial cleavage after release. Once entered into humans or other sensitive animals, the host system will be affected. LPs is not only the main pathogenic factor in determining GNB infection (such as sepsis and septic shock), but also closely related to many other human diseases. It is one of the most important pathogen-related model molecules that endanger human health and even life. With the increase of invasive technology, immunosuppressant, cytotoxic chemotherapy, and the use of broad-spectrum antibiotics. The incidence of sepsis and septic shock has been increasing since 1950s. In the United States, the number of deaths per year is nearly 200,000, and the mortality of children with sepsis is 10-15%. The pathogenic mechanism of endotoxin is that LPS continuously stimulates the mononuclear macrophage system to produce a large number of cytokines. Including TNF- 伪, IL-6, IL-12, reactive oxygen species, lysosomal enzyme no and other active substances, resulting in cell damage and apoptosis, eventually leading to uncontrolled inflammatory response. With higher body mortality. Although the host cells under the action of bacterial products, cell death characterized by cell apoptosis. But the host is not always passive under the action of the bacterial pathogenic product. They actively mobilize the host to resist the death mechanism to resist the bacterial attack. Reduce and alleviate the degree of bacterial damage to the host. When the host is exposed to bacterial endotoxin for several times and given a high dose of bacterial endotoxin again, the host has only a slight or no reaction. This phenomenon is defined as endotoxin tolerance or hyporesponsiveness, which is considered to be an adaptive response of the body. It can effectively inhibit the inflammatory response and septicemia shock caused by the excessive expression of mononuclear macrophages. The phenomenon of endotoxin tolerance has been recognized a century ago, but the mechanism of endotoxin tolerance has not been studied, and whether the occurrence of endotoxin tolerance is related to the inhibition of apoptosis. Therefore, this study first induced the phenomenon of endotoxin tolerance in mice, and detected whether there was apoptosis in the liver tissue cells of mice after tolerance. We investigated the relationship between tolerance, apoptosis and death, and studied the changes of apoptosis-related signaling molecules and LPS related signaling molecules in animal tissue cells after tolerance. 1. Establishment of mouse endotoxin tolerance model
【学位授予单位】：第二军医大学
【学位级别】：博士
【学位授予年份】：2006
【分类号】：R363

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