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 用于肿瘤切除术（开颅术）的脑需要移除颅骨的一部分（即骨瓣）。感染 开颅术/颅骨切除术后的发病率范围为0.8- 12%，其中大量是由甲氧西林引起的， 耐甲氧西林金黄色葡萄金黄色葡萄球菌（MRSA），其在骨瓣的两个表面上形成生物膜。生物膜是细菌 由于它们的新陈代谢， 休眠本实验室建立了一种S.金黄色葡萄球菌开颅相关生物膜感染 它与人类疾病具有重要的超微结构和MRI属性，可用于识别 感染持久性的机制。我们已经确定了一个独特的免疫区室化的S。 金黄色葡萄球菌开颅模型，即优先中性粒细胞（PMN）募集和趋化因子表达， 皮下帽状细胞，而单核细胞在大脑中更突出。髓源性抑制细胞 MDSC是一种具有抗炎特性的未成熟粒细胞群， 隔间，但最丰富的盔瓣。我们的初步研究已经确定了IL-10在 促进S.金黄色葡萄球菌在帽状软骨和大脑中的存活，表明IL-10可能对编程至关重要， 神经胶质细胞和浸润的白细胞朝向抗炎状态以促进生物膜持久性。虽然， 10在帽状软骨和脑中表达，该细胞因子准备抑制细胞的抗菌活性， 在任一位点富集的类型，即PMN和MDSC（帽状细胞）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，S。金黄色， 衍生的乳酸盐诱导MDSC中的IL-10产生。由于乳酸盐是一种组蛋白脱乙酰酶抑制剂（HDACi） IL-10启动子受组蛋白乙酰化调控，支持S.金黄色葡萄球菌生物膜- 衍生的乳酸盐是一种外源性HDACi，其促进IL-10表达并抑制抗微生物应答， 通过分别靶向MDSC/PMN与小胶质细胞/星形胶质细胞/单核细胞，促进 感染持续性IL-10和帽状细胞与脑细胞群之间的串扰以及分子生物学效应。 将在以下特定目的中测试负责这种区室化特异性的机制。第一章 鉴定MDSC衍生的IL-10对S.金耳开颅术- 相关生物膜感染; 2）确定IL-10是否促进S.金黄色葡萄球菌在大脑中的持久性， 通过使神经胶质细胞和单核细胞向抗炎状态极化的开颅术相关的生物膜感染; （3）建立S.金黄色葡萄球菌生物膜衍生的乳酸盐通过抑制HDAC活性增强IL-10产生。 对开颅手术生物膜感染期间免疫区室化的更好理解可能是 用于增强帽状体和脑中的抗微生物活性和生物膜清除。我们的研究结果 表明IL-10代表了用于该目的探索的有吸引力的候选物。

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.