Department of Emergency, Anhui Provincial Children's Hospital, No. 39 Wangjiang East Road, Hefei, Anhui Province, 230022, China.
J Cardiothorac Surg. 2024 Sep 2;19(1):509. doi: 10.1186/s13019-024-02995-2.
Streptococcus pneumoniae (Spn) is a major causative agent of pneumonia, which can disseminate to the bloodstream and brain. Pneumonia remains a leading cause of death among children aged 1-59 months worldwide. This study aims to investigate the role of Kruppel-like factor 2 (KLF2) in lung injury caused by Spn in young mice.
Young mice were infected with Spn to induce pneumonia, and the bacterial load in the bronchoalveolar lavage fluid was quantified. KLF2 expression in lung tissues was analyzed using real-time quantitative polymerase chain reaction and Western blotting assays. Following KLF2 overexpression, lung tissues were assessed for lung wet-to-dry weight ratio and Myeloperoxidase activity. The effects of KLF2 on lung injury and inflammation were evaluated through hematoxylin and eosin staining and enzyme-linked immunosorbent assay. Chromatin immunoprecipitation and dual-luciferase assay were conducted to examine the binding of KLF2 to the promoter of microRNA (miR)-222-3p and cyclin-dependent kinase inhibitor 1B (CDKN1B), as well as the binding of miR-222-3p to CDKN1B. Levels of miR-222-3p and CDKN1B in lung tissues were also determined.
In young mice with pneumonia, KLF2 and CDKN1B were downregulated, while miR-222-3p was upregulated in lung tissues. Overexpression of KLF2 reduced lung injury and inflammation, evidenced by decreased bacterial load, reduced lung injury, and lower levels of proinflammatory factors. Co-transfection of miR-222-3p-WT and oe-KLF2 significantly reduced luciferase activity, suggesting that KLF2 binds to the promoter of miR-222-3p and suppresses its expression. Transfection of CDKN1B-WT with miR-222-3p mimics significantly reduced luciferase activity, indicating that miR-222-3p binds to CDKN1B and downregulates its expression. Overexpression of miR-222-3p or downregulation of CDKN1B increased bacterial load in BALF, lung wet/dry weight ratio, MPO activity, and inflammation, thereby reversing the protective effect of KLF2 overexpression on lung injury in young mice with pneumonia.
KLF2 alleviates lung injury in young mice with Spn-induced pneumonia by transcriptional regulation of the miR-222-3p/CDKN1B axis.
肺炎链球菌（Spn）是导致肺炎的主要病原体，它可以传播到血液和大脑中。肺炎仍然是全世界 1-59 个月儿童死亡的主要原因。本研究旨在探讨 Kruppel 样因子 2（KLF2）在幼鼠 Spn 引起的肺损伤中的作用。
用 Spn 感染幼鼠诱导肺炎，并定量分析支气管肺泡灌洗液中的细菌负荷。实时定量聚合酶链反应和 Western blot 检测肺组织中 KLF2 的表达。过表达 KLF2 后，评估肺湿重/干重比和髓过氧化物酶活性。通过苏木精和伊红染色和酶联免疫吸附试验评估 KLF2 对肺损伤和炎症的影响。通过染色质免疫沉淀和双荧光素酶报告基因检测，研究 KLF2 与 microRNA（miR）-222-3p 和细胞周期蛋白依赖性激酶抑制剂 1B（CDKN1B）启动子的结合，以及 miR-222-3p 与 CDKN1B 的结合。还测定了肺组织中 miR-222-3p 和 CDKN1B 的水平。
在患肺炎的幼鼠中，KLF2 和 CDKN1B 在肺组织中下调，而 miR-222-3p 上调。KLF2 的过表达减少了细菌负荷，减轻了肺损伤，降低了促炎因子水平，从而减轻了肺损伤和炎症。miR-222-3p-WT 和 oe-KLF2 的共转染显著降低了荧光素酶活性，表明 KLF2 结合到 miR-222-3p 的启动子并抑制其表达。miR-222-3p 模拟物与 CDKN1B-WT 的转染显著降低了荧光素酶活性，表明 miR-222-3p 结合到 CDKN1B 并下调其表达。miR-222-3p 的过表达或 CDKN1B 的下调增加了 BALF 中的细菌负荷、肺湿重/干重比、MPO 活性和炎症，从而逆转了 KLF2 过表达对肺炎幼鼠肺损伤的保护作用。
KLF2 通过转录调节 miR-222-3p/CDKN1B 轴缓解 Spn 诱导的肺炎幼鼠的肺损伤。
