Abstract：
Endothelial dysfunction plays a pivotal role in the pathogenesis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Dipeptidyl peptidase IV (DPP-4), a cell surface glycoprotein, has been implicated in endothelial inflammation and barrier dysfunction. In this study, the role of DPP-4 on lipopolysaccharide (LPS)-induced pulmonary microvascular endothelial cells (HPMECs) dysfunction and the underlying mechanism were investigated by siRNA-mediated knockdown of DPP-4. Our results indicated that LPS (1 μg/ml) challenge resulted in either the production and releasing of DPP-4, as well as the secretion of IL-6 and IL-8 in HPMECs. DPP-4 knockdown inhibited chemokine releasing and monolayer hyper-permeability in LPS challenged HPMECs. When cocultured with human polymorphonuclear neutrophils (PMNs), DPP4 knockdown suppressed LPS-induced neutrophil-endothelial adhesion, PMN chemotaxis and trans-endothelial migration. Western blotting showed that DPP-4 knockdown attenuated LPS-induced activation of TLR4/NF-κB pathway. Immunoprecipitation and liquid chromatography-tandem mass spectrometry revealed that DPP-4 mediated LPS-induced endothelial inflammation by interacting with integrin-α5β1. Moreover, exogenous soluble DPP-4 treatment sufficiently activated integrin-α5β1 downstream FAK/AKT/NF-κB signaling, thereafter inducing ICAM-1 upregulation in HPMECs. Collectively, our results suggest that endothelia synthesis and release DPP-4 under the stress of endotoxin, which interact with integrin-α5β1 complex in an autocrine or paracrine manner to exacerbate endothelial inflammation and enhance endothelial cell permeability. Therefore, blocking DDP-4 could be a potential therapeutic strategy to prevent endothelial dysfunction in ALI/ARDS.
摘要：
内皮功能障碍在急性肺损伤（ALI）/急性呼吸窘迫综合征（ARDS）的发病机制中起着关键作用。二肽基肽酶IV(DPP-4),细胞表面糖蛋白，与内皮炎症和屏障功能障碍有关。在这项研究中,通过siRNA介导的DPP-4敲低研究了DPP-4在脂多糖(LPS)诱导的肺微血管内皮细胞(HPMECs)功能障碍中的作用及其机制。我们的结果表明，LPS（1μg/ml）攻击导致HPMEC中DPP-4的产生和释放以及IL-6和IL-8的分泌。DPP-4敲低抑制LPS攻击的HPMECs中趋化因子的释放和单层高通透性。当与人多形核中性粒细胞（PMN）共培养时，DPP4敲低抑制LPS诱导的中性粒细胞-内皮粘附，PMN趋化性和跨内皮迁移。Westernblotting显示DPP-4敲低可减弱LPS诱导的TLR4/NF-κB通路的激活。免疫沉淀和液相色谱-串联质谱显示DPP-4通过与整合素-α5β1相互作用介导LPS诱导的内皮炎症。此外，外源可溶性DPP-4处理充分激活了FAK/AKT/NF-κB信号下游的整合素-α5β1，此后在HPMECs中诱导ICAM-1上调。总的来说，我们的结果表明，内毒素应激下内皮合成和释放DPP-4，其与整合素-α5β1复合物以自分泌或旁分泌方式相互作用以加剧内皮炎症并增强内皮细胞通透性。因此,阻断DDP-4可能是预防ALI/ARDS患者内皮功能障碍的潜在治疗策略.
