Rice Teresa C, Pugh Amanda M, Xia Brent T, Seitz Aaron P, Whitacre Brynne E, Gulbins Erich, Caldwell Charles C
Division of Research, Department of Surgery, University of Cincinnati, Cincinnati, OH Department of Molecular Biology, University of Duisburg-Essen, Essen, Germany.
J Am Coll Surg. 2017 Oct;225(4):538-547. doi: 10.1016/j.jamcollsurg.2017.06.010. Epub 2017 Jul 6.
Pseudomonas aeruginosa is a major cause of morbidity and mortality among burn patients, despite antibiotic therapy. There is a need to identify innate immune defenses that prevent P aeruginosa infection in injured adults in an effort to find therapeutic alternatives to antibiotics. Here, we tested our hypothesis that microvesicles (MVs) in bronchoalveolar (BAL) fluid have a role in the immunity of the lung in response to pathogens.
Microvesicles were isolated from murine BAL fluid, quantified using Nanoparticle Tracking Analysis, and injected into burn-injured mice before P aeruginosa infection. Survival was assessed and BAL bacterial loads enumerated. Neutrophil number and interleukin 6 activity were determined. Lungs were harvested and sphingosine (SPH) content analyzed via immunohistochemistry. Antimicrobial effects of MVs and SPH-enriched MVs were assessed in an in vitro assay.
Burn-injured mice have reduced BAL MV number and SPH content compared with sham. When BAL MVs from healthy mice are administered to injured mice, survival and bacterial clearance are improved robustly. We also observed that intranasal administration of MVs restores SPH levels after burn injury, MVs kill bacteria directly, and this bacterial killing is increased when the MVs are supplemented with SPH.
Using a preclinical model, BAL MVs are reduced after scald injury and BAL MV restoration to injured mice improves survival and bacterial clearance. The antimicrobial mechanisms leading to improved survival include the quantity and SPH content of BAL MVs.
尽管进行了抗生素治疗，但铜绿假单胞菌仍是烧伤患者发病和死亡的主要原因。有必要确定可预防成年伤者感染铜绿假单胞菌的天然免疫防御机制，以便找到抗生素的替代治疗方法。在此，我们检验了我们的假设，即支气管肺泡（BAL）液中的微泡（MVs）在肺部对病原体的免疫反应中发挥作用。
从鼠BAL液中分离微泡，使用纳米颗粒跟踪分析进行定量，并在铜绿假单胞菌感染前注射到烧伤小鼠体内。评估存活率并计算BAL细菌载量。测定中性粒细胞数量和白细胞介素6活性。采集肺组织并通过免疫组织化学分析鞘氨醇（SPH）含量。在体外试验中评估MVs和富含SPH的MVs的抗菌作用。
与假手术组相比，烧伤小鼠的BAL MV数量和SPH含量降低。当将健康小鼠的BAL MVs给予受伤小鼠时，存活率和细菌清除率显著提高。我们还观察到，鼻内给予MVs可恢复烧伤后SPH水平，MVs可直接杀死细菌，并且当MVs补充SPH时，这种细菌杀伤作用增强。
使用临床前模型，烫伤后BAL MVs减少，将BAL MVs恢复至受伤小鼠可提高存活率和细菌清除率。导致存活率提高的抗菌机制包括BAL MVs的数量和SPH含量。
