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

描述（由申请人提供）：脓毒症在美国每年约有751，000例住院治疗和215，000例死亡，年费用近170亿美元。严重脓毒症的死亡率为30- 50%。严重脓毒症常伴有严重低血压、大血管扩张、休克和多器官功能衰竭。导致心血管崩溃的机制尚未完全了解。由于过度的炎性细胞因子的产生而引起的一氧化氮合成的诱导似乎在大量的血管舒张和心脏功能的抑制中起着关键作用。许多炎性细胞因子，特别是TNF-α和IL-1 β，在介导这一病理生理过程中发挥重要作用。MAP激酶在介导包括TNF-α和IL-1 β在内的细胞因子的产生中起关键作用。我的实验室率先研究了MAP激酶磷酸酶（MKP）-1在细胞因子表达负调控中的作用。我们发现，MKP-1作为一个中央负调节器，以抑制TNF-α和IL-6的生产在巨噬细胞暴露于细菌成分。最近，我们发现敲除小鼠中的MKP-1导致在用IPS攻击时TNF-α和IL-6的产生显著增加。这些MKP-1 -/-小鼠表现出重度低血压，肺、肝和肾严重异常，死亡率显著增加。基于这些结果，我们假设MKP-1的作用是防止先天免疫系统对细菌损伤的过度反应，从而维持心血管功能。在本申请中，我们提出研究MKP-1在严重脓毒症期间的功能。我们的具体目标是：1）检验MKP-1基因敲除小鼠比野生型小鼠更易发生内毒素休克的假设，这是由于造血细胞谱系和心肌细胞的炎症反应加剧以及导致的心脏组织损伤; 2）检验霍乱毒素B亚单位（一种强效MKP-1诱导剂）提供针对LPS诱导死亡的保护的假设。完成拟议的研究将为防止先天免疫系统过度反应的调控机制提供重要见解。更重要的是，这些研究可能揭示治疗脓毒症和脓毒症相关休克和多器官衰竭综合征的新的治疗靶点。

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.