线粒体是多功能的细胞器,其超微结构与细胞生理学密切相关。越来越多的证据表明,线粒体重塑对免疫反应有影响,但是我们目前对线粒体结构的理解,互动,免疫细胞的形态变化,主要是嗜酸性粒细胞,仍然鲜为人知。这里,我们应用透射电子显微镜(TEM),单细胞成像分析,和电子层析成像,一种以高分辨率提供三维(3D)视图的技术,研究在培养物中以及在以募集和激活这些细胞为特征的炎症性疾病的背景下发展的小鼠嗜酸性粒细胞的线粒体动力学(哮喘的小鼠模型,甲型H1N1流感病毒(IAV)感染,和曼氏血吸虫病)。首先,定量分析显示,在嗜酸性粒细胞发育过程中(从未分化的前体细胞到成熟的嗜酸性粒细胞),线粒体面积减少了70%.线粒体自噬,TEM在未成熟但在成熟的嗜酸性粒细胞中揭示了一致的过程,在嗜酸性粒细胞生成过程中可能在线粒体清除中起作用。在发育中的嗜酸性粒细胞中还检测并定量了线粒体相互作用(细胞器膜间接触)的事件,包括线粒体-内质网,线粒体-线粒体,和线粒体分泌颗粒,与成熟细胞相比,未成熟细胞中的所有细胞数量均显着增加。此外,单线粒体分析显示,随着嗜酸性粒细胞的成熟,线粒体cr的数量显着增加,并重塑为层状形态。嗜酸性粒细胞对炎症性疾病的反应没有改变(哮喘)或减少(IAV和血吸虫感染)其线粒体质量。然而,哮喘和血吸虫病,但不是IAV感染,诱导线粒体数量和体积的扩增。线粒体cr重塑发生在所有炎症条件下,线粒体的比例仅包含层状或管状,或混合cr(仅在组织嗜酸性粒细胞中看到的超微结构方面)取决于组织/疾病微环境。线粒体与颗粒相互作用的能力,主要是动员的,在参与所有炎性疾病的嗜酸性粒细胞中通过TEM显着捕获。总之,我们证明了嗜酸性粒细胞生成和炎症诱导的激活过程会干扰小鼠嗜酸性粒细胞内的线粒体动力学,从而导致cr重塑和细胞器间接触。了解线粒体动力学如何促进嗜酸性粒细胞免疫功能是一个开放的有趣领域。
Mitochondria are multifunctional organelles of which ultrastructure is tightly linked to cell physiology. Accumulating evidence shows that mitochondrial remodeling has an impact on immune responses, but our current understanding of the mitochondrial architecture, interactions, and morphological changes in immune cells, mainly in eosinophils, is still poorly known. Here, we applied transmission electron microscopy (TEM), single-cell imaging analysis, and electron tomography, a technique that provides three-dimensional (3D) views at high resolution, to investigate mitochondrial dynamics in mouse eosinophils developing in cultures as well as in the context of inflammatory diseases characterized by recruitment and activation of these cells (mouse models of asthma, H1N1 influenza A virus (IAV) infection, and schistosomiasis mansoni). First, quantitative analyses showed that the mitochondrial area decrease 70% during eosinophil development (from undifferentiated precursor cells to mature eosinophils). Mitophagy, a consistent process revealed by TEM in immature but not in mature eosinophils, is likely operating in mitochondrial clearance during
eosinophilopoiesis. Events of mitochondria interaction (inter-organelle membrane contacts) were also detected and quantitated within developing eosinophils and included mitochondria-endoplasmic reticulum, mitochondria-mitochondria, and mitochondria-secretory granules, all of them significantly higher in numbers in immature compared to mature cells. Moreover, single-mitochondrion analyses revealed that as the eosinophil matures, mitochondria cristae significantly increase in number and reshape to lamellar morphology. Eosinophils did not change (asthma) or reduced (IAV and Schistosoma infections) their mitochondrial mass in response to inflammatory diseases. However, asthma and schistosomiasis, but not IAV infection, induced amplification of both cristae numbers and volume in individual mitochondria. Mitochondrial cristae remodeling occurred in all inflammatory conditions with the proportions of mitochondria containing only lamellar or tubular, or mixed cristae (an ultrastructural aspect seen just in tissue eosinophils) depending on the tissue/disease microenvironment. The ability of mitochondria to interact with granules, mainly mobilized ones, was remarkably captured by TEM in eosinophils participating in all inflammatory diseases. Altogether, we demonstrate that the processes of
eosinophilopoiesis and inflammation-induced activation interfere with the mitochondrial dynamics within mouse eosinophils leading to cristae remodeling and inter-organelle contacts. The understanding of how mitochondrial dynamics contribute to eosinophil immune functions is an open interesting field to be explored.