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Updated: Jun 5, 2025
Isolation and In Vitro Culture of Murine and Human Alveolar Macrophages
Published on: April 20, 2018
Monocyte-Derived Macrophages Induce Alveolar Macrophages Death via TNF-α in Acute Lung Injury
Junjie Xiao1,2, Fei Hou1,2,3, Huan Wang4
1College of Pulmonary & Critical Care Medicine, Chinese PLA General Hospital, Beijing, China.
Introduction:
Acute lung injury (ALI) and its subsequent progression to acute respiratory distress syndrome (ARDS) are severe respiratory conditions. They are marked by rapid lung function deterioration and extensive pulmonary inflammation, often resulting in critical patient outcomes. Alveolar macrophages (AMs) and monocyte-derived macrophages (MDMs) are two distinct subsets of lung macrophages present in the alveoli during ALI. Both are critical mediators of pulmonary inflammation. Our study examined the interplay between AMs and MDMs in the inflammatory environment of ALI/ARDS.
Methods:
Mice were treated with lipopolysaccharide (LPS) to establish ALI models. The lung tissues of mice were subjected to hematoxylin-eosin staining to observe the degree of tissue damage. In vivo, CCR2-deficient mice or depleting peripheral blood mononuclear cells by clodronate liposomes were used to reduce MDMs recruitment. The bronchoalveolar lavage fluid (BALF) supernatants were used for cytokine and total protein analyses. AMs and MDMs in the BALF were analyzed by flow cytometry. The levels of AMs death were determined through propidium iodide staining and measured by flow cytometry. In vitro, primary AMs were exposed to MDM-conditioned medium or TNF-α, and their death levels were assessed under a fluorescence microscope with propidium iodide staining.
Results:
AMs significantly decrease in number and undergo extensive cell death during ALI. The reduced MDMs recruitment can increase the number of AMs, reduce AMs death, and alleviate lung injury. In vitro, MDM-conditioned medium can induce AMs death and TNF-α is one of the major secretions. It indicates that TNF-α stimulation in vitro promotes AMs death. In vivo, MDMs are identified as the primary cells secreting TNF-α. Additionally, the treatment with TNF-α antagonists can reduce AMs death and the severity of lung injury.
Conclusion:
Our study demonstrates that MDMs contribute to AMs death during ALI through TNF-α. Targeting TNF-α may offer a therapeutic strategy to mitigate AMs death and lung injury in ALI/ARDS.
Insights
Monocyte-derived macrophages (MDMs) cause alveolar macrophage (AMs) death in acute lung injury (ALI) via TNF-α. Targeting TNF-α may treat ALI and acute respiratory distress syndrome (ARDS).
Area of Science:
- Immunology
- Pulmonary Medicine
- Cell Biology
Background:
- Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are critical conditions characterized by lung inflammation and function loss.
- Alveolar macrophages (AMs) and monocyte-derived macrophages (MDMs) are key immune cells in the lungs during ALI, mediating inflammation.
Purpose of the Study:
- To investigate the interaction between AMs and MDMs in the inflammatory environment of ALI/ARDS.
- To elucidate the mechanisms by which MDMs influence AMs during lung injury.
Main Methods:
- Established ALI models in mice using lipopolysaccharide (LPS).
- Utilized CCR2-deficient mice and clodronate liposomes to modulate MDM recruitment.
- Analyzed macrophage populations, cell death, cytokine levels, and protein in bronchoalveolar lavage fluid (BALF).
- Conducted in vitro experiments exposing AMs to MDM-conditioned medium and TNF-α.
Main Results:
- AMs numbers decreased significantly, with increased cell death during ALI.
- Reduced MDM recruitment led to increased AMs, decreased AMs death, and alleviated lung injury.
- MDM-conditioned medium induced AMs death in vitro, with TNF-α identified as a key mediator.
- MDMs were the primary source of TNF-α in vivo, and TNF-α antagonists reduced AMs death and lung injury.
Conclusions:
- MDMs contribute to AMs death in ALI through TNF-α secretion.
- Targeting TNF-α presents a potential therapeutic strategy for mitigating AMs death and lung injury in ALI/ARDS.
