MRSA Activation of Human Keratinocyte Signaling

描述(由申请人提供)：金黄色葡萄球菌USA300是一种可怕的人类病原体，从美国大多数人类皮肤和软组织感染中分离出来。我们推测角质形成细胞是USA300感染引起的大部分病理改变的原因，是预防或治疗的潜在靶点。在目标1中，我们将确定USA300和我们将要研究的临床分离株的一组特定的葡萄球菌基因产物的表达促进了人角质形成细胞对生物的内吞作用，即它们逃离内小体并激活caspase-1介导的炎症信号的能力。葡萄球菌诱导角质形成细胞下垂，释放IL-1和HMGB1刺激中性粒细胞局部聚集，导致典型的化脓性感染。我们期望从药理上阻断角质形成细胞下垂可以阻止金黄色葡萄球菌通过角质形成细胞屏障入侵。金黄色葡萄球菌内吞作用主要由5 1整合素介导，5 1整合素激活PI3K-Akt信号转导和增殖，提示金黄色葡萄球菌感染也可能触发角质形成细胞的增殖。在目标2中，我们将确定如何积极 复制角质形成细胞，增加5 1表面受体的可用性，有助于细菌的摄取，从而促进持续的局部感染。在第三个目标中，利用体外器官培养中的人角质形成细胞和SCID：HU小鼠与人皮肤移植，我们将确定是否针对角质形成细胞信号转导；用caspase-1或calain抑制剂阻断角质形成细胞的降解，以及阻断PI3K-Akt介导的角质形成细胞增殖，以防止角质形成细胞下垂和随后的中性粒细胞募集。这些研究将为预防或治疗金黄色葡萄球菌皮肤感染提供新的靶点。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有关。尽管即使是美国300种耐甲氧西林金黄色葡萄球菌仍然对许多抗生素敏感，但这些细菌仍然存在。这个项目将确定角质形成细胞信号是否提供了预防葡萄球菌感染的治疗靶点。我们假设角质形成细胞信号是导致这些微生物引起的大部分病理变化的原因。

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.