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Updated: Aug 26, 2025
Bronchoalveolar Lavage Exosomes in Lipopolysaccharide-induced Septic Lung Injury
Published on: May 21, 2018
Macrophage-Derived Exosomes in TLR9-/- Mice Ameliorate Sepsis-Induced Mitochondrial Oxidative Stress and Apoptosis in
Xiang Li1, Junyu Luo1, Yanmei Li2
1The First Affiliated Hospital of Yunnan University of Traditional Chinese Medicine, Kunming 650021, China.
Objective:
To explore the mechanisms of TLR9 from macrophages on mitochondrial apoptosis in cardiomyocytes at early stage of sepsis.
Methods:
The in vivo and in vitro sepsis mice were bone marrow transplantation (BMT) with wild type (WT) or (toll-like receptor 9) TLR9 knockout (-/- or KO) myeloid cells and then constructed by cecum ligation and puncture (CLP) as vivo experiment and cardiomyocytes cocultured with WT or TLR9-deficient macrophages treated with LPS as vitro experiment, respectively. Sepsis model were performed by CLP. The expression levels of exosome, PI3K/AKT, and ERK1/2, inflammatory factors, and apoptotic proteins were tested by western blot in vivo. Besides, associated apoptotic proteins and JC-1 fluorescence assay were tested in vitro.
Results:
The expressions of p-PI3K, p-AKT, exosome markers (CD9, CD63, and TSG101), p-ERK1/2, TNF-α, IFN-γ, IL-1β, and cleaved-caspase-3/-9 were significantly increased in septic mice vs. control mice, and these proteins were declined dramatically in TLR9-/- BMT mice vs. WT BMT mice in sepsis mice models. Meanwhile, the protein expression of cytochrome C, cleaved-caspase-3, and cleaved-caspase-9 increased significantly in primary mouse myocardial cells cocultured with TLR9-/- or WT macrophages stimulated with LPS, and these mitochondrial apoptotic proteins as well as the green 5,5',6,6'-tetrachloro-1,1',3,3'- tetraethylbenzimidazolcarbocyanine iodide (JC-1) fluorescence were dramatically lower in LPS-stimulated cardiomyocytes cocultured with TLR9-/- than with WT macrophages.
Conclusion:
TLR9-/- in macrophages suppressed the inflammatory reaction as well as the exosome secretion and resulted in the inhibition of apoptosis and oxidative stress in sepsis-induced cardiomyopathy.
Insights
Toll-like receptor 9 (TLR9) in macrophages promotes sepsis-induced cardiomyopathy by increasing inflammation and apoptosis. Eliminating TLR9 in macrophages protects against sepsis-induced cardiac injury.
Area of Science:
- Immunology
- Cardiology
- Molecular Biology
Background:
- Sepsis can lead to cardiomyopathy, a serious complication affecting heart function.
- Toll-like receptor 9 (TLR9) plays a role in immune responses, but its specific involvement in sepsis-induced cardiac apoptosis requires further investigation.
Purpose of the Study:
- To elucidate the role of TLR9 in macrophages during the early stages of sepsis-induced mitochondrial apoptosis in cardiomyocytes.
Main Methods:
- Established in vivo (cecum ligation and puncture model) and in vitro (macrophage-cardiomyocyte co-culture) sepsis models.
- Utilized wild-type and TLR9 knockout bone marrow-derived myeloid cells for transplantation and co-culture experiments.
- Assessed protein expression (exosomes, PI3K/AKT, ERK1/2, inflammatory factors, apoptotic markers) via Western blot and JC-1 fluorescence assay.
Main Results:
- Septic mice exhibited increased expression of pro-inflammatory cytokines, exosome markers, and apoptotic proteins compared to controls.
- TLR9 knockout in myeloid cells significantly reduced these inflammatory and apoptotic markers in vivo.
- In vitro, TLR9-deficient macrophages suppressed LPS-induced apoptosis and mitochondrial damage in cardiomyocytes.
Conclusions:
- TLR9 in macrophages exacerbates sepsis-induced cardiomyopathy by promoting inflammation, exosome secretion, and mitochondrial apoptosis.
- Targeting TLR9 in macrophages offers a potential therapeutic strategy to mitigate cardiac dysfunction during sepsis.
