The roles of MKP-1 in Gram-negative bacterial sepsis and colitis

描述(申请人提供)：炎症反应的失调在包括感染性休克和炎症性肠病(IBD)在内的大量人类疾病的发病机制中起着重要作用。丝裂原活化蛋白激酶磷酸酶(MKP)-1在抑制细菌感染时的炎症反应中起着至关重要的作用。MKP-1是p38和JNK的诱导性负性调节因子，可抑制促炎细胞因子的产生。当同时受到Toll样受体配体和细菌的攻击时，MKP-1缺陷(MKP-1-/-)小鼠比野生型小鼠表现出更强烈的炎症反应。由于炎症有助于抑制和清除微生物病原体，我们推测MKP-1-/-小鼠应该表现出更有效的杀灭入侵病原体的能力。令人惊讶的是，当感染大肠杆菌时，MKP-1-/-小鼠表现出比野生型小鼠更大的细菌负担，尽管炎症反应更强烈。这些数据表明，MKP-1不仅作为重要的抗炎调节因子发挥作用，而且在协调先天免疫机制的杀菌活性方面也发挥着重要作用。除了炎性细胞因子，MKP-1-/-小鼠还产生显著更高水平的抗炎细胞因子IL-10。这导致我们假设，过度产生IL-10会损害MKP-1-/-小鼠的抗菌防御。为了了解IL-10在MKP-1-/-小鼠中的作用，我们培育了同时缺乏IL-10和MKP-1基因的小鼠。已知，在常规但不是无病原体的条件下饲养的IL-10-/-小鼠会患上与直肠脱垂相关的结肠炎。相反，即使在无病原体的情况下，MKP-1和IL-10的缺失也会导致严重的直肠脱垂。MKP-1/IL-10双基因敲除小鼠也出现了眼部异常，这是一种类似于IBD眼部表现的新表型。综上所述，这些数据表明，MKP-1缺乏会加剧IL-10-/-小鼠的结肠炎表型。我们建议利用IL-10-/-小鼠IBD模型来确定MKP-1-/-小鼠杀菌缺陷的分子机制，并确定MKP-1在结肠炎发病机制中的作用。我们的具体目标是确定：1)。MKP-1-/-小鼠杀菌活性缺陷的内在免疫系统缺陷；2)IL-10过度产生是否导致MKP-1-/-小鼠杀菌活性缺陷；以及3)MKP-1缺乏是否会加重IL-10-/-小鼠结肠炎的严重程度。拟议的研究将揭开控制感染免疫反应和预防慢性小肠结肠炎的关键调控机制，并可能导致治疗脓毒症和IBD的新策略。公共卫生相关性：免疫反应异常是人类疾病的主要原因，包括感染性休克和炎症性肠病。在这项拨款申请中，我们建议研究MKP-1在革兰氏阴性细菌败血症和结肠炎中的作用。这些研究将揭示关键的免疫调节机制，并可能导致治疗脓毒症和炎症性肠病的新策略。

DESCRIPTION (provided by applicant): Dysregulation of the inflammatory response plays an important role in the pathogenesis of a plethora of human diseases, including septic shock and inflammatory bowel disease (IBD). Mitogen-activated protein kinase phosphatase (MKP)-1 is crucial for restraining the inflammatory response during bacterial infection. MKP-1 acts as an inducible negative regulator of p38 and JNK, and serves to restrict the production of pro-inflammatory cytokines. MKP-1-deficient (MKP-1-/-) mice exhibit a more robust inflammatory response than do wild-type mice when challenged with both toll-like receptor ligands and bacteria. Since inflammation facilitates the containment and clearance of microbial pathogens, we reasoned that MKP-1-/- mice should exhibit more efficient killing of invading pathogens. Surprisingly, when infected with Escherichia coli, MKP-1-/- mice exhibited substantially greater bacterial burdens than do wild-type mice in spite of a more robust inflammatory response. These data suggest that MKP-1 not only functions as a crucial anti-inflammatory regulator but also plays an important role in orchestrating the bactericidal activity of the innate immune mechanism. In addition to inflammatory cytokines, MKP-1-/- mice also produce substantially higher levels of the anti-inflammatory cytokine IL-10. This led us to hypothesize that excessive IL-10 production impairs the antimicrobial defense in MKP-1-/- mice. To understand the role of IL-10 in MKP-1-/- mice, we generated mice that lack both the IL-10 and MKP-1 genes. IL-10-/- mice housed in conventional but not pathogen-free conditions are known to develop colitis associated with rectal prolapse. Conversely, deletion of both MKP-1 and IL-10 caused severe rectal prolapse even in pathogen-free conditions. The MKP-1/IL-10 double knockout mice also developed ocular abnormalities, a novel phenotype resembling the ocular manifestation of IBD. Taken together, these data suggest that MKP-1 deficiency exacerbates the colitis phenotype of IL-10-/- mice. We propose to define the molecular mechanisms underlying the bactericidal defects of MKP-1-/- mice and to define the role of MKP-1 in the pathogenesis of colitis using the IL-10-/- mouse model of IBD. Our specific aims are to determine: 1). The defects in the innate immune system underlying the faulty bactericidal activity of MKP-1-/- mice; 2) Whether excessive IL-10 production contributes to the defects in the bactericidal activity of MKP-1-/- mice; and 3) Whether MKP-1 deficiency exacerbates the severity of colitis in IL-10-/- mice. The proposed studies will unravel critical regulatory mechanisms that govern the immune response to infection and prevent chronic enterocolitis and may lead to novel strategies for the treatment of sepsis and IBD. PUBLIC HEALTH RELEVANCE: Abnormal immune responses are a major cause of human illnesses, including septic shock and inflammatory bowel disease. In this grant application we propose to study the roles of MKP-1 in Gram-negative bacterial sepsis and colitis. These studies will uncover critical immune regulatory mechanisms, and may lead to novel strategies for the treatment of sepsis and inflammatory bowel disease.