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Depletion of alveolar macrophages by treatment with 2-chloroadenosine aerosol
Y Kubota1, Y Iwasaki, H Harada
1Second Department of Medicine, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Abstract:
Alveolar macrophages (AMs) are localized in the alveoli and alveolar ducts of the lung and are the only macrophages living in an aerobic environment. Recent studies have demonstrated that AMs play a central role in lung diseases, such as pneumonia and acute respiratory distress syndrome. It has become important to find a simple, effective way to eliminate AMs in order to investigate the function of AMs in vivo. 2-Chloroadenosine (2-CA), a purine analog, is reported to be selectively cytotoxic to cultured macrophages, and we hypothesized that it would deplete the number of AMs in the bronchoalveolar lavage fluid (BALF) of mice without any effect on neutrophil or lymphocyte counts. After mice had inhaled 1 mM aerosolized 2-CA for 2 h, AMs were found to be significantly depleted at 0 h [(4.42 +/- 0.16) x 10(4)/ml], 24 h [(4.17 +/- 0.89) x 10(4)/ml], 48 h [(3.17 +/- 0.21) x 10(4)/ml], and 72 h [(5.00 +/- 0.64) x 10(4)/ml] compared with concentrations in untreated controls [(12.1 +/- 0.21) x 10(4)/ml]. Neutrophil and lymphocyte counts in BALF did not change and histological changes in the lung were not observed after 2-CA treatment. The lung wet-to-dry weight ratio did not change at 0, 24, and 48 h after 2-CA aerosol application. The 2-CA aerosol had no effect on lung vascular permeability, as assessed by the intravenous administration of Evans blue, or on other phagocytes, as assessed by Kupffer cell counts. Our study demonstrates the efficacy of 2-CA in reducing AM numbers in vivo.
Insights
A novel method using 2-Chloroadenosine (2-CA) effectively depletes alveolar macrophages (AMs) in mice. This technique allows for in vivo studies of AM function without impacting other immune cells or lung tissue.
Area of Science:
- Pulmonary immunology
- Cell biology
- Pharmacology
Background:
- Alveolar macrophages (AMs) are crucial immune cells in the lung's aerobic environment.
- AMs play a significant role in lung diseases like pneumonia and ARDS.
- Investigating AM function in vivo requires effective depletion methods.
Purpose of the Study:
- To evaluate the efficacy of 2-Chloroadenosine (2-CA) in depleting AMs in vivo.
- To assess the safety and specificity of 2-CA treatment on lung tissue and other immune cells.
Main Methods:
- Mice inhaled aerosolized 1 mM 2-Chloroadenosine (2-CA) for 2 hours.
- Alveolar macrophage counts were measured in bronchoalveolar lavage fluid (BALF) at various time points.
- Neutrophil and lymphocyte counts, lung histology, lung wet-to-dry weight ratio, lung vascular permeability, and Kupffer cell counts were assessed.
Main Results:
- 2-CA significantly depleted AMs in BALF at 0, 24, 48, and 72 hours post-inhalation compared to controls.
- Neutrophil and lymphocyte counts remained unchanged.
- No significant histological changes, altered lung wet-to-dry ratio, or increased vascular permeability were observed. Kupffer cell counts were unaffected.
Conclusions:
- Aerosolized 2-CA is an effective and specific method for reducing AM numbers in vivo.
- 2-CA treatment does not adversely affect lung tissue integrity or other immune cell populations.
- This approach provides a valuable tool for studying AM roles in lung physiology and pathology.