The Role of MKP-1 in innate immune responses to LPS

描述(由申请人提供)：在美国，败血症每年导致约751,000人住院和215,000人死亡，每年的成本近170亿美元。严重脓毒症的死亡率从30%到50%不等。严重的脓毒症常伴有严重低血压、大量血管扩张、休克和多器官衰竭。导致心血管衰竭的机制尚不完全清楚。由此可见，炎症细胞因子的过度产生导致一氧化氮的合成，在大量血管扩张和心功能抑制中起着关键作用。许多炎性细胞因子，特别是肿瘤坏死因子-α和白介素1-β，在介导这一病理生理过程中起着重要作用。MAP激酶在调节包括肿瘤坏死因子-α和白介素1-β在内的细胞因子的产生中起着至关重要的作用。我的实验室率先发现了MAP-1在负调控细胞因子表达中的作用。我们发现，MKP-1是一种中枢负性调节因子，可以抑制暴露于细菌成分的巨噬细胞产生的肿瘤坏死因子-α和白介素6。最近，我们发现在小鼠中敲除MKP-1后，在IPS攻击时，肿瘤坏死因子-α和IL-6的产生显著增加。这些MKP-1-/-小鼠表现出严重的低血压，肺、肝和肾脏严重异常，死亡率显著增加。基于这些结果，我们推测MKP-1起作用是为了防止先天免疫系统对细菌攻击的过度反应，从而维持心血管功能。在目前的应用中，我们建议研究MKP-1在严重脓毒症中的作用。我们的具体目的是：1)验证MKP-1基因敲除小鼠比野生型小鼠更容易受到内毒素休克的假设，因为它加剧了造血细胞系和心肌细胞的炎症反应，从而导致心脏组织受损；2)测试霍乱毒素B亚单位，一种有效的MKP-1诱导剂，可预防内毒素诱导的死亡。拟议研究的完成将为防止先天免疫系统过度反应的调节机制提供关键的见解。更重要的是，这些研究可能为脓毒症及其相关性休克和多器官衰竭综合征的治疗提供新的治疗靶点。

DESCRIPTION (provided by applicant): Sepsis accounts for approximately 751,000 hospitalizations and 215,000 deaths annually in the United States, with annual costs of nearly $17 billion. The mortality rate from severe sepsis ranges from 30-50%. Severe sepsis is often associated with profound hypotension, massive vasodilation, shock, and multiple organ failure. The mechanisms leading to the cardiovascular collapse are not fully understood. It appears that induction of nitric oxide synthesis as a result of excessive inflammatory cytokine production plays a critical role in the massive vasodilation and the depression of heart function. A number of inflammatory cytokines, particularly TNF-alpha and IL-1beta, play an important role in mediating this pathophysiological process. The MAP kinases play a crucial role in mediating the production of cytokines, including TNF-alpha and IL- 1beta. My laboratory has pioneered the role of MAP kinase phosphatases (MKP)-1 in the negative control of cytokine expression. We found that MKP-1 acts as a central negative regulator to restrain the production of TNF-alpha and IL-6 in macrophages exposed to bacterial components. Recently, we found that knockout of MKP-1 in mice resulted in dramatic increases in the production of TNF-alpha and IL-6 upon challenge with IPS. These MKP-1 -/-mice exhibited severe hypotension, profound abnormalities in lung, liver, and kidney, and a marked increase in mortality. Based on these results, we hypothesize that MKP-1 acts to prevent the over-reaction of the innate immune system to bacterial insult, and thereby maintains cardiovascular function. In the present application, we propose to study the function of MKP-1 during severe sepsis. Our Specific Aims are: 1) To test the hypothesis that MKP-1 knockout mice are more susceptible than are wild type mice to endotoxic shock due to exacerbated inflammatory responses by both the hematopoietic cell lineage and cardiomyocytes and resulting damage to the cardiac tissues; 2) To test the hypothesis that cholera toxin B subunit, a potent MKP-1-inducing agent, offers protection against LPS-induced mortality. Completion of the proposed studies will provide critical insights into the regulatory mechanisms that prevent the over-reaction of the innate immune system. More importantly, these studies may reveal novel therapeutic targets for treating sepsis and sepsis-associated shock and multiple organ failure syndrome.