Department of Anesthesiology, University of California San Francisco, San Francisco, CA 94143.
Department of Anesthesiology, University of California San Francisco, San Francisco, CA 94143
J Immunol. 2019 Oct 1;203(7):1961-1972. doi: 10.4049/jimmunol.1801534. Epub 2019 Aug 26.
Human mesenchymal stem cell (MSC) extracellular vesicles (EV) can reduce the severity of bacterial pneumonia, but little is known about the mechanisms underlying their antimicrobial activity. In the current study, we found that bacterial clearance induced by MSC EV in pneumonia in C57BL/6 mice was associated with high levels of leukotriene (LT) B in the injured alveolus. More importantly, the antimicrobial effect of MSC EV was abrogated by cotreatment with a LTB BLT1 antagonist. To determine the role of MSC EV on LT metabolism, we measured the effect of MSC EV on a known ATP-binding cassette transporter, multidrug resistance-associated protein 1 (MRP1), and found that MSC EV suppressed MRP1 mRNA, protein, and pump function in LPS-stimulated Raw264.7 cells in vitro. The synthesis of LTB and LTC from LTA are competitive, and MRP1 is the efflux pump for LTC Inhibition of MRP1 will increase LTB production. In addition, administration of a nonspecific MRP1 inhibitor (MK-571) reduced LTC and subsequently increased LTB levels in C57BL/6 mice with acute lung injury, increasing overall antimicrobial activity. We previously found that the biological effects of MSC EV were through the transfer of its content, such as mRNA, microRNA, and proteins, to target cells. In the current study, miR-145 knockdown abolished the effect of MSC EV on the inhibition of MRP1 in vitro and the antimicrobial effect in vivo. In summary, MSC EV suppressed MRP1 activity through transfer of miR-145, thereby resulting in enhanced LTB production and antimicrobial activity through LTB/BLT1 signaling.
人骨髓间充质干细胞（MSC）细胞外囊泡（EV）可减轻细菌性肺炎的严重程度，但对其抗菌活性的机制知之甚少。在本研究中，我们发现 MSC EV 在 C57BL/6 小鼠肺炎中诱导的细菌清除与受损肺泡中白三烯（LT）B 水平升高有关。更重要的是，LTB/BLT1 拮抗剂的共同治疗可消除 MSC EV 的抗菌作用。为了确定 MSC EV 对 LT 代谢的作用，我们测量了 MSC EV 对已知的三磷酸腺苷结合盒转运蛋白多药耐药相关蛋白 1（MRP1）的影响，发现 MSC EV 在体外抑制 LPS 刺激的 Raw264.7 细胞中 MRP1 mRNA、蛋白和泵功能。LTA 合成的 LTB 和 LTC 是竞争性的，MRP1 是 LTC 的外排泵。抑制 MRP1 将增加 LTB 的产生。此外，给予非特异性 MRP1 抑制剂（MK-571）可减少 C57BL/6 小鼠急性肺损伤中的 LTC，并随后增加 LTB 水平，从而提高整体抗菌活性。我们之前发现 MSC EV 的生物学效应是通过将其内容物（如 mRNA、microRNA 和蛋白质）转移到靶细胞来实现的。在本研究中，miR-145 的敲低消除了 MSC EV 对体外抑制 MRP1 和体内抗菌作用的影响。总之，MSC EV 通过转移 miR-145 抑制 MRP1 活性，从而通过 LTB/BLT1 信号增强 LTB 产生和抗菌活性。
