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Updated: Jul 19, 2025
Inducing Acute Lung Injury in Mice by Direct Intratracheal Lipopolysaccharide Instillation
Published on: July 6, 2019
Grape Seed Proanthocyanidin Ameliorates LPS-induced Acute Lung Injury By Modulating M2a Macrophage Polarization Via
Xin Qiao1, Hua Wang1, Yulin He1
1Department of Pulmonary and Critical Care Medicine, The First Hospital of China Medical University, Shenyang, China.
Abstract:
Acute lung injury (ALI) is an acute and progressive pulmonary inflammatory disease that is difficult to cure and has a poor prognosis. Macrophages, which have various phenotypes and diverse functions, play an essential role in the pathogenesis of ALI. Grape seed proanthocyanidin (GSP) has received much attention over several decades, and many biological activities such as anti-apoptotic, antioxidant, and anti-inflammatory have been identified. This study aimed to determine the effect of GSP on lipopolysaccharide (LPS)-induced ALI. In this study, we established an ALI mouse model by tracheal instillation of LPS, and by pre-injection of GSP into mice to examine the effect of GSP on the ALI mouse model. Using H&E staining, flow cytometry, and ELISA, we found that GSP attenuated LPS-induced lung pathological changes and decreased inflammatory cytokine expression in ALI mice. In addition, GSP reduced the recruitment of monocyte-derived macrophages to the lung and significantly promoted the polarization of primary mouse lung macrophages from M1 to M2a induced by LPS. In vitro, GSP also decreased the expression levels of inflammatory cytokines such as TNF-α, IL-6, IL-1β, and M1 macrophage marker iNOS induced by LPS in MH-S cells, while increasing the expression levels of M2a macrophage marker CD206. Bioinformatics analysis identified TREM2 and the PI3K/Akt pathway as candidate targets and signaling pathways that regulate M1/M2a macrophage polarization in ALI, respectively. Furthermore, GSP activated PI3K/Akt and increased TREM2 expression in vivo and in vitro. Meanwhile, GSP's impact on M2a polarization and inflammation suppression was attenuated by the PI3K inhibitor LY294002 or siRNA knockdown TREM2. In addition, GSP-enhanced PI3K/Akt activity was prevented by TREM2 siRNA. In conclusion, this study demonstrated that GSP could ameliorate LPS-induced ALI by modulating macrophage polarization from M1 to M2a via the TREM2/PI3K/Akt pathway.
Insights
Grape seed proanthocyanidin (GSP) treats acute lung injury (ALI) by shifting inflammatory M1 macrophages to anti-inflammatory M2a types. This modulation occurs through the TREM2/PI3K/Akt pathway, reducing lung inflammation and pathology.
Area of Science:
- Immunology
- Pharmacology
- Cell Biology
Background:
- Acute lung injury (ALI) is a severe inflammatory lung condition with limited treatment options.
- Macrophages play a critical role in ALI pathogenesis, with their polarization state influencing disease progression.
- Grape seed proanthocyanidin (GSP) exhibits known anti-inflammatory and antioxidant properties.
Purpose of the Study:
- To investigate the therapeutic effects of GSP on lipopolysaccharide (LPS)-induced ALI.
- To elucidate the mechanisms by which GSP influences macrophage polarization in ALI.
- To identify potential molecular targets of GSP in ALI treatment.
Main Methods:
- Establishment of an LPS-induced ALI mouse model.
- Administration of GSP and assessment of lung pathology via H&E staining.
- Flow cytometry and ELISA to analyze inflammatory cytokines and macrophage populations.
- In vitro studies using MH-S cells to assess GSP's effect on macrophage polarization markers.
- Bioinformatic analysis to identify molecular pathways involved.
Main Results:
- GSP significantly attenuated LPS-induced lung pathological damage and reduced inflammatory cytokine levels.
- GSP decreased monocyte-derived macrophage recruitment and promoted M1 to M2a macrophage polarization.
- GSP activated the PI3K/Akt pathway and increased TREM2 expression, crucial for its anti-inflammatory effects.
- Inhibition of PI3K/Akt or TREM2 abolished GSP's beneficial effects on macrophage polarization and inflammation.
Conclusions:
- GSP ameliorates LPS-induced ALI by modulating macrophage polarization from M1 to M2a.
- The therapeutic mechanism of GSP involves the TREM2/PI3K/Akt signaling pathway.
- GSP represents a potential therapeutic agent for ALI, targeting macrophage polarization.
