Department of Clinical Laboratory, Fujian Medical University Union Hospital, Fuzhou, 350001, People's Republic of China.
Central Laboratory, Fujian Medical University Union Hospital, Fuzhou, 350001, People's Republic of China.
Cell Mol Biol Lett. 2023 Nov 13;28(1):92. doi: 10.1186/s11658-023-00505-1.
Hypervirulent Klebsiella pneumoniae (hvKp) infection-induced sepsis-associated acute lung injury (ALI) has emerged as a significant clinical challenge. Increasing evidence suggests that activated inflammatory macrophages contribute to tissue damage in sepsis. However, the underlying causes of widespread macrophage activation remain unclear.
BALB/c mice were intravenously injected with inactivated hvKp (iHvKp) to observe lung tissue damage, inflammation, and M1 macrophage polarization. In vitro, activated RAW264.7 macrophage-derived exosomes (iHvKp-exo) were isolated and their role in ALI formation was investigated. RT-PCR was conducted to identify changes in exosomal miRNA. Bioinformatics analysis and dual-luciferase reporter assays were performed to validate MSK1 as a direct target of miR-155-5p. Further in vivo and in vitro experiments were conducted to explore the specific mechanisms involved.
iHvKp successfully induced ALI in vivo and upregulated the expression of miR-155-5p. In vivo, injection of iHvKp-exo induced inflammatory tissue damage and macrophage M1 polarization. In vitro, iHvKp-exo was found to promote macrophage inflammatory response and M1 polarization through the activation of the p38-MAPK pathway. RT-PCR revealed exposure time-dependent increased levels of miR-155-5p in iHvKp-exo. Dual-luciferase reporter assays confirmed the functional role of miR-155-5p in mediating iHvKp-exo effects by targeting MSK1. Additionally, inhibition of miR-155-5p reduced M1 polarization of lung macrophages in vivo, resulting in decreased lung injury and inflammation induced by iHvKp-exo or iHvKp.
The aforementioned results indicate that exosomal miR-155-5p drives widespread macrophage inflammation and M1 polarization in hvKp-induced ALI through the MSK1/p38-MAPK Axis.
高毒力肺炎克雷伯菌（hvKp）感染引起的脓毒症相关急性肺损伤（ALI）已成为一个重大的临床挑战。越来越多的证据表明，激活的炎症性巨噬细胞有助于脓毒症中的组织损伤。然而，广泛的巨噬细胞激活的根本原因尚不清楚。
用失活的 hvKp（iHvKp）静脉注射 BALB/c 小鼠，观察肺组织损伤、炎症和 M1 巨噬细胞极化。体外分离激活的 RAW264.7 巨噬细胞衍生的外泌体（iHvKp-exo），并研究其在 ALI 形成中的作用。进行 RT-PCR 以鉴定外泌体 miRNA 的变化。进行生物信息学分析和双荧光素酶报告基因检测，以验证 MSK1 是 miR-155-5p 的直接靶标。进一步进行体内和体外实验以探索涉及的特定机制。
iHvKp 成功地在体内诱导了 ALI，并上调了 miR-155-5p 的表达。在体内，注射 iHvKp-exo 诱导了炎症性组织损伤和巨噬细胞 M1 极化。体外，发现 iHvKp-exo 通过激活 p38-MAPK 途径促进巨噬细胞炎症反应和 M1 极化。RT-PCR 显示 iHvKp-exo 中 miR-155-5p 的水平随暴露时间的增加而增加。双荧光素酶报告基因检测证实 miR-155-5p 通过靶向 MSK1 发挥调节 iHvKp-exo 作用的功能作用。此外，抑制 miR-155-5p 减少了体内肺巨噬细胞的 M1 极化，从而降低了 iHvKp-exo 或 iHvKp 诱导的肺损伤和炎症。
上述结果表明，外泌体 miR-155-5p 通过 MSK1/p38-MAPK 轴驱动 hvKp 诱导的 ALI 中广泛的巨噬细胞炎症和 M1 极化。
