Immune mechanisms that promote S. aureus persistence during craniotomy-associated biofilm infection

神经外科手术，以减轻危及生命的水肿(去骨瓣减压术)或获得临时进入 脑部肿瘤切除术(开颅手术)需要切除一部分头骨(即骨瓣)。感染 开颅手术后的发病率从0.8-12%不等，其中相当一部分是由甲氧西林引起的。 耐药金黄色葡萄球菌(MRSA)，在骨瓣的两面形成生物膜。生物膜是细菌的 被包裹在自我产生的基质中的群落，由于其新陈代谢而对抗生素产生顽固性 休眠。我们实验室建立了金黄色葡萄球菌开颅相关生物被膜感染的小鼠模型 这与人类疾病具有重要的超微结构和核磁共振特征，可以用来识别 感染持久性的机制。我们已经确定了S。 金黄色开颅模型，即中性粒细胞(PMN)优先募集和趋化因子在颅脑损伤中的表达 而单核细胞在大脑中更突出。髓系来源的抑制细胞 (MDSCs)是一种具有抗炎特性的未成熟粒细胞群，在这两种情况下都存在 舱室，但在银河最丰富。我们的初步研究已经确定了IL-10在 促进金黄色葡萄球菌在大脑和大脑中的存活，表明IL-10可能是编程的关键 胶质细胞和渗入的白细胞进入抗炎状态，以促进生物膜的持久性。尽管IL- 10在大脑和大脑中都有表达，这种细胞因子可能会抑制细胞的抗菌活性。 在任一部位富含的类型，即PMN和MDSCs(Galea)与小胶质细胞、星形胶质细胞和 单核细胞(脑)。在分子机制方面，我们的初步数据表明，金黄色葡萄球菌- 衍生乳酸盐诱导MDSCs产生IL-10由于乳酸是一种组蛋白脱乙酰酶抑制物(HDACi) 而IL-10启动子受组蛋白乙酰化调控，这支持金黄色葡萄球菌生物被膜- 衍生乳酸是一种外源性HDACi，可促进IL-10的表达并抑制血管内皮细胞的抗菌反应 通过分别靶向MDSCs/PMN和小胶质细胞/星形胶质细胞/单核细胞来促进大脑和大脑 感染持续性。IL-10与大脑和分子之间的串扰 将在以下具体目标中测试造成这种区分的专一性的机制。1) 金黄色葡萄球菌开颅手术中MDSC来源的IL-10对中性粒细胞抗菌活性的影响 相关生物膜感染；2)确定IL-10是否促进金黄色葡萄球菌在脑内的持续存在 开颅手术相关的生物膜感染，使神经胶质细胞和单核细胞向抗炎状态极化； 3)证实金黄色葡萄球菌生物膜衍生乳酸盐通过抑制HDAC活性而促进IL-10的产生。 更好地理解开颅手术生物被膜感染时的免疫区划可能是 被用来增强大脑和大脑的抗菌活性和生物膜清除。我们的发现 提示IL-10是探索这一目的的有吸引力的候选者。

Neurosurgery to relieve life-threatening edema (decompressive craniectomy) or gain temporary access to the brain for tumor resection (craniotomy) requires removal of a portion of the skull (i.e. bone flap). The infection incidence after craniotomy/craniectomy ranges from 0.8-12%, with a significant number caused by methicillin- resistant S. aureus (MRSA), which forms a biofilm on both surfaces of the bone flap. Biofilms are bacterial communities encased in a self-produced matrix that are recalcitrant to antibiotics due to their metabolic dormancy. Our laboratory has developed a mouse model of S. aureus craniotomy-associated biofilm infection that shares important ultrastructural and MRI attributes with human disease, which can be exploited to identify mechanisms for infection persistence. We have identified a unique immune compartmentalization in the S. aureus craniotomy model, namely preferential neutrophil (PMN) recruitment and chemokine expression in the subcutaneous galea, whereas monocytes are more prominent in the brain. Myeloid-derived suppressor cells (MDSCs), an immature granulocyte population with anti-inflammatory properties, are present in both compartments, but most abundant in the galea. Our preliminary studies have identified a role for IL-10 in promoting S. aureus survival in both the galea and brain, suggesting that IL-10 may be critical for programming glia and infiltrating leukocytes towards an anti-inflammatory state to promote biofilm persistence. Although IL- 10 is expressed in both the galea and brain, the cytokine is poised to inhibit the antibacterial activity of cell types that are enriched at either site, namely PMNs and MDSCs (galea) vs. microglia, astrocytes, and monocytes (brain). In terms of molecular mechanisms, our preliminary data demonstrate that S. aureus- derived lactate induces IL-10 production in MDSCs. Since lactate is a histone deacetylase inhibitor (HDACi) and the IL-10 promoter is regulated by histone acetylation, this supports the hypothesis that S. aureus biofilm- derived lactate is an exogenous HDACi that promotes IL-10 expression and inhibits antimicrobial responses in the galea and brain by targeting MDSCs/PMNs vs. microglia/astrocytes/monocytes, respectively, to promote infection persistence. The crosstalk between IL-10 and galeal vs. brain populations and the molecular mechanisms responsible for this compartmentalized specificity will be tested in the following Specific Aims. 1) Identify the role of MDSC-derived IL-10 on PMN antimicrobial activity in the galea during S. aureus craniotomy- associated biofilm infection; 2) Determine whether IL-10 promotes S. aureus persistence in the brain during craniotomy-associated biofilm infections by polarizing glia and monocytes towards an anti-inflammatory state; and 3) Establish that S. aureus biofilm-derived lactate enhances IL-10 production by inhibiting HDAC activity. An improved understanding of the immune compartmentalization during craniotomy biofilm infection may be leveraged to enhance antimicrobial activity and biofilm clearance in both the galea and brain. Our findings suggest that IL-10 represents an attractive candidate to explore for this purpose.