Pathogen and host-derived lipid membranes governing Staphylococcus aureus-mediated skin inflammation

人类皮肤被一个复杂的微生物群定植，不断释放促炎微生物相关分子模式（MAMP）分子。在入侵的病原体仍然导致快速的促炎反应的情况下，如何避免永久性皮肤炎症在很大程度上仍然不清楚。角质化的死亡角质细胞形成皮肤上层，被包裹在脂质层膜的保护层中，这可能阻止细菌分子到达对mamp有反应的活角质细胞。特应性皮炎（AD）患者表现出皮肤屏障功能的主要缺陷，特别是脂质板层膜的完整性。病原菌金黄色葡萄球菌是阿尔茨海默病患者皮肤炎症的常见原因。它通过释放细菌脂蛋白（toll样受体（TLR） 2的强效激动剂）激活活的角质形成细胞。我们在项目的第一阶段分析了生物活性细菌和宿主肽如何促进激活和炎症。我们发现，只有在表面活性剂样酚溶性调节素（PSM）肽的帮助下，金黄色葡萄球菌才能有效地释放脂蛋白，PSM肽以一种不清楚的方式动员疏水脂蛋白。初步数据表明，psm可促进金黄色葡萄球菌中含有膜包埋脂蛋白的膜泡（MVs）的释放。基于这些发现，我们提出：(i)金黄色葡萄球菌主要通过含有脂蛋白的mv激活AD中的角化细胞，（ii）这些mv在健康皮肤中被皮肤板层膜保留，而在皮肤板层膜完整性受损的AD患者中，它们很容易到达表达tlr2的角化细胞，从而引起炎症。我们建议通过阐明金黄色葡萄球菌如何以及何时释放MVs，是否大多数细菌脂蛋白与MVs相关，以及它们如何离开MVs激活角质形成细胞中的TLR2来研究这些假设。体外和体内实验旨在阐明板层膜功能障碍是否以及如何影响tlr2依赖性皮肤炎症，以及在AD皮肤中补充脂质鸡尾酒是否有助于阻止金黄色葡萄球菌脂蛋白进入mamp反应性角质形成细胞。我们的项目将有助于阐明细菌MAMP释放和皮肤屏障功能的关键过程，并应启发更好的临床干预AD患者和其他慢性炎症性皮肤病的皮肤炎症。

Human skin is colonized by a complex microbiome constantly releasing pro-inflammatory microbe-associated molecular pattern (MAMP) molecules. It has remained largely unclear how permanent skin inflammation is avoided while invading pathogens still lead to rapid pro-inflammatory responses. The keratinized, dead corneocytes forming the upper skin layers are embedded in a protective layer of lipid lamellar membranes, which may prevent bacterial molecules from reaching MAMP-responsive live keratinocytes. Atopic dermatitis (AD) patients exhibit major defects in skin barrier function, in particular in the integrity of lipid lamellar membranes. The bacterial pathogen Staphylococcus aureus is a frequent cause of skin inflammation in AD patients. It activates live keratinocytes by releasing bacterial lipoproteins, potent agonists of the Toll-like receptor (TLR) 2. We analysed in the first phase of the project how bioactive bacterial and host peptides contribute to activation and inflammation. We found that lipoproteins can only be efficiently released by S. aureus with the help of surfactant-like phenol-soluble modulin (PSM) peptides, which mobilize the hydrophobic lipoproteins in an unclear fashion. Preliminary data suggest that PSMs promote the release of membrane vesicles (MVs) containing the membrane-embedded lipoproteins from S. aureus. Based on these findings we propose that (i) S. aureus activates keratinocytes in AD largely by lipoprotein-containing MVs and that (ii) such MVs are retained by skin lamellar membranes in healthy skin while they can easily reach TLR2-expressing keratinocytes in AD patients with compromised skin lamellar membrane integrity to cause inflammation.We propose to investigate these hypotheses by elucidating how and when S. aureus releases MVs, if most bacterial lipoproteins are associated with MVs, and how they can leave MVs to activate TLR2 in keratinocytes. In vitro and in vivo experiments are envisaged to elucidate if and how lamellar membrane dysfunction impacts on TLR2-dependent skin inflammation and if supplementation of AD skin with lipid cocktails can help to prevent the access of S. aureus lipoproteins to MAMP-responsive keratinocytes. Our project will help to elucidate key processes of bacterial MAMP releases and of skin barrier function and it should inspire better clinical interventions against skin inflammation in AD patients and other chronic inflammatory skin diseases.