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 Ly6Chigh and Ly6Clow 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 Ly6Chigh 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 Ly6Chigh 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 Ly6Chigh monocytes and reduced uptake by Kupffer cells. These findings indicate that monocytes, particularly lung-marginated Ly6Chigh 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.

中文翻译：

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在低度全身性炎症过程中，单核细胞介导循环微泡归巢到肺血管。

微囊泡（MVs）是细胞膜囊泡的质膜来源的亚类，在全身性炎症过程中产生并释放到循环系统中，但在这些条件下细胞/组织特异性摄取MV的情况鲜为人知。我们假设单核细胞有助于循环MV的摄取，并且它们在系统性炎症过程中对肺循环和功能性启动的增加的边缘作用会导致系统性MV归巢模式发生实质性变化。通过流式细胞术在C57BL6小鼠的肺，肝和脾的血管细胞群中，对体内静脉注射荧光标记的MV（J774.1巨噬细胞衍生）的细胞摄取进行定量。在正常条件下，Ly6Chigh和Ly6Clow单核细胞均促进MV摄取，但肝Kupffer细胞是主要的靶细胞群。用低剂量静脉内LPS诱导亚临床内毒素血症后，肺边缘Ly6Chigh单核细胞的MV摄取在单个细胞水平（〜2.5倍）和其数量的实质性扩展（〜8倍）上均显着增加。 ，而脾脏巨噬细胞的摄取却没有改变，而库普弗细胞的摄取却实际上减少了（〜50％）。使用体内巨噬细胞耗竭，离体分离的灌注肺和体外肺灌注液细胞的联合分析方法对肺血管内的MV摄取进行进一步分析，表明Ly6Chigh单核细胞具有很高的MV摄取能力（相当于Kupffer细胞） ），可通过内毒素血症直接增强，并在富含磷脂酰丝氨酸（PS）的脂质体和β3整联蛋白受体阻断肽存在下消融。因此，iv 内毒素血症期间，注射了PS的富含PS的脂质体会发生细胞摄取的重新分布，类似于MV，Ly6Chigh单核细胞的摄取增加，而Kupffer细胞的摄取减少。这些发现表明，单核细胞，特别是肺边缘的Ly6Chigh亚型单核细胞，成为全身性炎症期间MV的主要靶细胞群，对内源性和治疗性MV的功能和靶向具有重要意义，从而为肺血管的病理生理学提供了新的见解炎。