Qingfei Litan decoction alleviated Klebsiella pneumoniae-induced pneumonia by targeting the TLR4/MyD88/NF-κB axis via miR-146a-5p.

ETHNOPHARMACOLOGICAL RELEVANCE: Klebsiella pneumoniae (Kp) is a significant pathogen responsible for various clinical bacterial infections, including pneumonia, sepsis, and even death. However, effective treatment options remain limited due to the rising prevalence of antimicrobial resistance. Traditional Chinese medicine (TCM) has shown potential in the treatment of bacterial pneumonia. Qingfei Litan decoction (QFLT) has been reported to alleviate symptoms in patients with bacterial pneumonia, though its precise mechanisms in regulating pulmonary inflammation remain unclear.

AIM OF THE STUDY: This study aimed to investigate the therapeutic potential of QFLT in Kp-induced pneumonia and to elucidate its underlying molecular mechanisms.

MATERIAL AND METHODS: In vivo, a murine pneumonia model was established through intratracheal instillation of Kp, and QFLT was administered by oral gavage. miR-146a-5p expression was downregulated by tail vein injection of an antagomir. The therapeutic effects of QFLT on pulmonary pathology, inflammatory factors, and miR-146a-5p expression were evaluated using qRT-PCR, flow cytometry, and other methods. Bioinformatics tools were employed to predict miR-146a-5p targets and associated inflammatory pathways. In vitro, an alveolar macrophage inflammation model was established by stimulating MH-S cells with heat-inactivated Klebsiella pneumoniae (iKp), followed by QFLT treatment. Inhibition of miR-146a-5p was achieved through transfection with specific inhibitors. The effects of QFLT on inflammatory responses, miR-146a-5p expression, and TLR4/MyD88/NF-κB signaling were assessed using qRT-PCR, Western blotting (WB) and other methods.

RESULTS: Kp infection significantly exacerbated pulmonary inflammation and downregulated miR-146a-5p expression in both lung tissues and MH-S cells. QFLT treatment alleviated inflammatory responses and upregulated miR-146a-5p expression. Bioinformatics analysis demonstrated that miR-146a-5p targeted TRAF6, a key mediator of the TLR4/MyD88/NF-κB pathway. Western blot analysis further confirmed that QFLT reduced Kp-induced upregulation of the TLR4/MyD88/NF-κB pathway in MH-S cells. Moreover, inhibition of miR-146a-5p exacerbated inflammatory responses in both lung tissues and MH-S cells, whereas QFLT treatment effectively attenuated these inflammatory effects. Furthermore, miR-146a-5p suppression resulted in elevated expression of proteins in the TLR4/MyD88/NF-κB signaling pathway in MH-S cells, while QFLT administration significantly reduced the expression levels of these signaling components.

CONCLUSIONS: These findings demonstrated that QFLT ameliorated Kp-induced pneumonia by modulating the TLR4/MyD88/NF-κB axis via miR-146a-5p.