MRSA Activation of Human Keratinocyte Signaling

描述（由申请人提供）：S。金黄色葡萄球菌USA 300是一种从美国大多数人皮肤和软组织感染中分离出来的可怕的人病原体。我们推测角质形成细胞是USA 300感染引起的大部分病理的原因，并且是预防或治疗的潜在靶点。在目标#1中，我们将确定USA 300和我们将研究的测序临床分离株表达的一组特定的葡萄球菌基因产物促进了人角质形成细胞对生物体的内吞作用，它们从内体逃逸并激活caspase-1介导的炎性体信号传导的能力。葡萄球菌诱导角质形成细胞焦亡，释放IL-1和HMGB 1刺激中性粒细胞局部积聚，引起特征性化脓性感染。我们预期阻断角质形成细胞的焦亡反应可以预防S。金黄色葡萄球菌通过角质形成细胞屏障侵入。葡萄球菌的内吞作用主要是由5 - 1整合素介导的，整合素激活PI 3 K-Akt信号传导和增殖，这表明葡萄球菌内吞作用可能与葡萄球菌的内吞作用有关。金黄色葡萄球菌感染也触发角质细胞增殖。在目标#2中，我们将确定如何积极地 具有增加的β 1表面受体可用性的复制角质形成细胞有助于细菌摄取，从而促进持续的局部感染。在第三个目标中，在体外器官型培养物中和在具有人皮肤异种移植物的SCID：hu小鼠中使用人角质形成细胞，我们将确定靶向角质形成细胞信号传导;用半胱天冬酶-1或钙蛋白酶抑制剂阻断角质形成细胞凋亡和阻断PI 3 K-Akt介导的角质形成细胞增殖是否将预防角质形成细胞凋亡和随后的中性粒细胞募集。这些研究将为预防或治疗S.金黄色皮肤感染。公共卫生影响：葡萄球菌皮肤感染是急诊室就诊的最常见原因之一，与巨大的发病率和成本相关。尽管USA 300 MRSA仍然对许多抗生素敏感，但这些微生物仍然存在。该项目将确定角质形成细胞信号传导，我们假设是负责这些生物体引起的大部分病理，提供治疗靶点，以防止葡萄球菌感染。

DESCRIPTION (provided by applicant): S. aureus USA300 is a formidable human pathogen isolated from the majority of human skin and soft tissue infections in the US. We postulate that the keratinocyte is responsible for much of the pathology induced by USA300 infection and is a potential target for prevention or therapy. In Aim #1 we will establish that the expression of a specific group of staphylococcal gene products by USA300 and the sequenced clinical isolates that we will study facilitates the endocytosis of the organisms by human keratinocytes, their ability to escape from the endosome and to activate caspase-1 mediated inflammasome signaling. Staphylococcal induction of keratinocyte pyroptosis, release of IL-1 and HMGB1 stimulate the local accumulation of neutrophils causing the characteristic pyogenic infection. We expect that blocking keratinocyte pyroptosis pharmacologically could prevent S. aureus invasion through the keratinocyte barrier. Staphylococcal endocytosis is mediated primarily by 5 1 integrins that activate PI3K-Akt signaling and proliferation, indicating the likelihood that S. aureus infection also triggers keratinocyte proliferation. In Aim #2 we will determine how actively replicating keratinocytes with increased availability of 5 1 surface receptors contribute to the bacterial uptake, thus fueling persistent local infection. In the third aim, using human keratinocytes in organotypic cultures in vitro and in SCID:hu mice with human skin xenografts, we will establish if targeting keratinocyte signaling; blocking keratinocyte pytoptosis with caspase-1 or calpain inhibitors and blocking PI3K-Akt mediated keratinocyte proliferation will prevent pyroptosis and subsequent neutrophil recruitment. These studies would provide novel targets to prevent or treat S. aureus skin infection. Public Health Implications: Staphylococcal skin infections are among the most common reasons for ER visits, associated with tremendous morbidity and cost. Although even the USA 300 MRSA is still susceptible to many antibiotics, these organisms nonetheless persist. This project will determine if keratinocyte signaling, which we postulate is responsible for much of the pathology evoked by these organisms, provides therapeutic targets to prevent staphylococcal infection.