O'Dea Kieran P, Tan Ying Ying, Shah Sneh, V Patel Brijesh, C Tatham Kate, Wilson Mike R, Soni Sanooj, Takata Masao
Section of Anaesthetics, Pain Medicine & Intensive Care, Imperial College London, Chelsea & Westminster Hospital, London, UK.
J Extracell Vesicles. 2020 Jan 5;9(1):1706708. doi: 10.1080/20013078.2019.1706708. eCollection 2020.
Microvesicles (MVs), a plasma membrane-derived subclass of extracellular vesicles, are produced and released into the circulation during systemic inflammation, yet little is known of cell/tissue-specific uptake of MVs under these conditions. We hypothesized that monocytes contribute to uptake of circulating MVs and that their increased margination to the pulmonary circulation and functional priming during systemic inflammation produces substantive changes to the systemic MV homing profile. Cellular uptake of i.v.-injected, fluorescently labelled MVs (J774.1 macrophage-derived) in vivo was quantified by flow cytometry in vascular cell populations of the lungs, liver and spleen of C57BL6 mice. Under normal conditions, both Ly6C and Ly6C monocytes contributed to MV uptake but liver Kupffer cells were the dominant target cell population. Following induction of sub-clinical endotoxemia with low-dose i.v. LPS, MV uptake by lung-marginated Ly6C monocytes increased markedly, both at the individual cell level (2.5-fold) and through substantive expansion of their numbers (8-fold), whereas uptake by splenic macrophages was unchanged and uptake by Kupffer cells actually decreased (~50%). Further analysis of MV uptake within the pulmonary vasculature using a combined model approach of in vivo macrophage depletion, ex vivo isolated perfused lungs and in vitro lung perfusate cell-based assays, indicated that Ly6C monocytes possess a high MV uptake capacity (equivalent to Kupffer cells), that is enhanced directly by endotoxemia and ablated in the presence of phosphatidylserine (PS)-enriched liposomes and β3 integrin receptor blocking peptide. Accordingly, i.v.-injected PS-enriched liposomes underwent a redistribution of cellular uptake during endotoxemia similar to MVs, with enhanced uptake by Ly6C monocytes and reduced uptake by Kupffer cells. These findings indicate that monocytes, particularly lung-marginated Ly6C subset monocytes, become a dominant target cell population for MVs during systemic inflammation, with significant implications for the function and targeting of endogenous and therapeutically administered MVs, lending novel insights into the pathophysiology of pulmonary vascular inflammation.
微泡（MVs）是细胞外囊泡的一个源自质膜的亚类，在全身炎症期间产生并释放到循环中，但在这些情况下，关于MVs的细胞/组织特异性摄取知之甚少。我们假设单核细胞有助于循环MVs的摄取，并且它们在全身炎症期间增加向肺循环的边缘化和功能启动会导致全身MV归巢谱发生实质性变化。通过流式细胞术对C57BL6小鼠肺、肝和脾的血管细胞群体中静脉注射的荧光标记MVs（J774.1巨噬细胞来源）的细胞摄取进行定量。在正常条件下，Ly6C单核细胞和Ly6C⁻单核细胞都有助于MV摄取，但肝库普弗细胞是主要的靶细胞群体。在用低剂量静脉注射脂多糖诱导亚临床内毒素血症后，肺边缘的Ly6C单核细胞对MV的摄取在个体细胞水平上显著增加（约2.5倍），并且通过其数量的实质性增加（约8倍），而脾巨噬细胞的摄取没有变化，库普弗细胞的摄取实际上减少了（约50%）。使用体内巨噬细胞耗竭、离体分离灌注肺和基于体外肺灌注液细胞的检测的联合模型方法对肺血管内MV摄取的进一步分析表明，Ly6C单核细胞具有高MV摄取能力（等同于库普弗细胞），内毒素血症可直接增强该能力，并且在存在富含磷脂酰丝氨酸（PS）的脂质体和β₃整合素受体阻断肽的情况下被消除。因此，静脉注射的富含PS的脂质体在内毒素血症期间经历了与MVs类似的细胞摄取重新分布，Ly6C单核细胞的摄取增加，库普弗细胞的摄取减少。这些发现表明，单核细胞，特别是肺边缘的Ly6C亚群单核细胞，在全身炎症期间成为MVs的主要靶细胞群体，这对内源性和治疗性施用的MVs的功能和靶向具有重要意义，为肺血管炎症的病理生理学提供了新的见解。
