Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
Biomedical Institute, Fluminense Federal University, Niterói, Brazil.
Cell Microbiol. 2020 Jul;22(7):e13195. doi: 10.1111/cmi.13195. Epub 2020 Mar 5.
Neutrophils are leukocytes that are capable of eliminating both intra- and extracellular pathogens by mechanisms such as phagocytosis, degranulation, and release of neutrophil extracellular traps (NETs). Histoplasma capsulatum var. capsulatum (H. capsulatum) is a dimorphic fungus with a global distribution that causes histoplasmosis, a disease that is endemic in different geographic areas and is spreading worldwide. The release of NETs has been described as an important host defense mechanism against different fungi; however, there are no reports demonstrating that this process is implicated in neutrophil response to H. capsulatum infection. Therefore, the aim of this work is to investigate whether isolated human neutrophils release NETs in response to H. capsulatum and the potential mechanisms involved, as well as delineate the NETs antifungal activity. Using both confocal fluorescence and scanning electron microscopy techniques, we determined that NETs are released in vitro in response to H. capsulatum via an oxidative mechanism that is downstream of activation of the Syk and Src kinase pathways and is also dependent on CD18. NETs released in response to H. capsulatum yeasts involve the loss of neutrophil viability and are associated with elastase and citrullinated histones, however also can occur in a PAD4 histone citrullination independent pathway. This NETs also presented fungicidal activity against H. capsulatum yeasts. Our findings may contribute to the understanding of how neutrophils recognize and respond as immune effector cells to H. capsulatum, which may lead to better knowledge of histoplasmosis pathophysiology and treatment.
中性粒细胞是白细胞的一种，能够通过吞噬作用、脱颗粒和释放中性粒细胞胞外陷阱（NETs）等机制来消除细胞内和细胞外的病原体。荚膜组织胞浆菌变种（H. capsulatum）是一种具有全球分布的二态真菌，可引起组织胞浆菌病，这是一种在不同地理区域流行并在全球范围内传播的疾病。NETs 的释放已被描述为一种重要的宿主防御机制，可抵御不同的真菌；然而，目前尚无报道表明该过程与中性粒细胞对荚膜组织胞浆菌感染的反应有关。因此，本研究旨在探讨人中性粒细胞是否会因荚膜组织胞浆菌的感染而释放 NETs，以及涉及的潜在机制，同时还研究了 NETs 的抗真菌活性。通过共聚焦荧光和扫描电子显微镜技术，我们确定 NETs 可通过氧化机制在体外响应荚膜组织胞浆菌的刺激而释放，该机制是在 Syk 和 Src 激酶途径激活的下游发生的，并且还依赖于 CD18。荚膜组织胞浆菌酵母诱导的 NETs 涉及中性粒细胞活力的丧失，与弹性蛋白酶和瓜氨酸化组蛋白有关，但也可在依赖于 PAD4 组蛋白瓜氨酸化的非依赖性途径中发生。这些 NETs 对荚膜组织胞浆菌酵母也具有杀菌活性。我们的发现可能有助于理解中性粒细胞如何作为免疫效应细胞识别和响应荚膜组织胞浆菌，这可能有助于更好地了解组织胞浆菌病的病理生理学和治疗方法。
