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Alveolar Macrophage Phagocytosis and Bacteria Clearance in Mice

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Published on: March 2, 2019

The Role and Phagocytic Mechanisms of Alveolar Macrophages in Inflammatory Responses Induced by Diesel Exhaust

Dongyang Han¹, Renzhen Peng¹, Bin Pan^1,2

¹Department of Environmental Health, School of Public Health, Fudan University, Shanghai 200032, China.

Environmental Science & Technology

|July 16, 2025

Abstract:

Alveolar macrophages, the most abundant innate immune cells in the distal lung parenchyma, are not only essential for maintaining pulmonary homeostasis but also orchestrate pulmonary and thus systemic responses to ambient particulate matter. However, their specific role in the development of adverse health effects related to ambient fine particulate matter (PM_2.5) exposure remains insufficiently understood. In this study, we used both mouse models and cultured cells to document their role in the development of pulmonary inflammation due to exposure to diesel exhaust particles (DEP), the main component of urban PM_2.5. The results revealed that DEP induced pulmonary inflammation as well as an acute phase response in the lung and liver within 24 h, which gradually diminished over the subsequent week. Depletion of alveolar macrophages alleviated the DEP-induced pulmonary inflammation and acute phase response. Furthermore, this study showed that Msr1 may be the primary receptor responsible for the phagocytosis of DEP in macrophages, while the PIP2-mediated nonbiological phagocytic signaling pathway appeared to be nonsignificant. All of the results in the present study reveal the key role of alveolar macrophages in DEP-induced pulmonary inflammation, enhancing our understanding of the complex interactions among DEP, alveolar macrophages, and inflammatory responses.

Insights

Alveolar macrophages are key drivers of lung inflammation caused by diesel exhaust particles (DEP), a major component of fine particulate matter (PM2.5). Removing these cells reduces inflammation, clarifying their central role in particulate matter toxicity.

Area of Science:

Pulmonary immunology
Environmental toxicology
Innate immune cell function

Background:

Alveolar macrophages are crucial for lung homeostasis and responses to particulate matter.
The precise role of alveolar macrophages in PM2.5-induced adverse health effects is not fully understood.
Diesel exhaust particles (DEP) are a primary component of urban PM2.5.

Purpose of the Study:

To investigate the role of alveolar macrophages in pulmonary inflammation induced by DEP exposure.
To identify the mechanisms by which DEP affects lung and systemic responses.
To elucidate the specific receptors and signaling pathways involved in DEP phagocytosis by macrophages.

Main Methods:

Utilized mouse models and cultured cell systems to study DEP exposure.
Depleted alveolar macrophages to assess their impact on inflammation.
Investigated the expression of scavenger receptor class A member 1 (Msr1) and the role of PIP2 signaling.

Main Results:

DEP exposure induced acute pulmonary and hepatic inflammation within 24 hours, which resolved over a week.
Depletion of alveolar macrophages significantly reduced DEP-induced inflammation and acute phase responses.
Msr1 was identified as a potential primary receptor for DEP phagocytosis, while PIP2 signaling was found to be non-significant.

Conclusions:

Alveolar macrophages play a critical role in mediating pulmonary inflammation following DEP exposure.
Understanding this interaction is vital for comprehending the health impacts of urban air pollution.
Msr1 is implicated in the macrophage response to DEP, offering potential therapeutic targets.

Read full analysis

Keywords:

alveolar macrophages diesel exhaust particles inflammation response macrophage scavenger receptor 1 phagocytosis

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