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Published on: August 1, 2012
Identification of a distinct glucocorticosteroid-insensitive pulmonary macrophage phenotype in patients with chronic
Kirandeep K Chana1, Peter S Fenwick1, Andrew G Nicholson2
1Airway Disease, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
Background:
In patients with chronic obstructive pulmonary disease (COPD), pulmonary macrophages increase in number, release increased levels of inflammatory mediators, and respond poorly to glucocorticosteroids. Whether this is due to a change in macrophage phenotype or localized activation is unknown.
Objective:
We sought to investigate whether macrophages from patients with COPD are a distinct phenotype.
Methods:
Macrophage populations were isolated from human lung tissue from nonsmokers, smokers, and patients with COPD by using Percoll density gradients. Five macrophage populations were isolated on the basis of density (1.011-1.023, 1.023-1.036, 1.036-1.048, 1.048-1.061, and 1.061-1.073 g/mL), and cell-surface expression of CD14, CD16, CD163, CD40, and CD206 was assessed by using flow cytometry. Release of active matrix metalloproteinase 9, TNF-α, CXCL8, and IL-10 was measured by using ELISA.
Results:
The 2 least dense fractions were more than 90% apoptotic/necrotic, with the remaining fractions greater than 70% viable. Macrophages from nonsmokers and smokers were CD163(+), CD206(+), CD14(+), and CD40(-), whereas macrophages from patients with COPD were less defined, showing significantly lower expression of all receptors. There were no differences in receptor expression associated with density. Macrophages from patients with COPD of a density of 1.036 to 1.048 g/mL released higher levels of active matrix metalloproteinase 9 compared with cells from nonsmokers, with no difference between the remaining fractions. This population of macrophages from patients with COPD was less responsive to budesonide compared with those from nonsmokers and smokers when stimulated with LPS. Glucocorticosteroid insensitivity was selective for proinflammatory cytokines because budesonide inhibition of LPS-stimulated IL-10 release was similar for all macrophages.
Conclusions:
This study identifies a specific macrophage phenotype in the lungs of patients with COPD who are glucocorticosteroid insensitive with a density of 1.036 to 1.048 g/mL but do not correspond to the current concept of macrophage phenotypes.
Insights
Pulmonary macrophages in chronic obstructive pulmonary disease (COPD) exhibit a distinct, glucocorticosteroid-insensitive phenotype. This specific macrophage subset, identified by density, contributes to disease pathology and reduced treatment efficacy in COPD patients.
Area of Science:
- Pulmonary immunology
- Cell biology
- Respiratory medicine
Background:
- Pulmonary macrophages are elevated in COPD, releasing more inflammatory mediators.
- Their poor response to glucocorticosteroids in COPD is not fully understood.
- It remains unclear if this is due to altered macrophage phenotype or localized activation.
Purpose of the Study:
- To investigate if macrophages from COPD patients represent a distinct phenotype.
- To characterize cell-surface receptor expression and mediator release.
- To assess glucocorticosteroid responsiveness.
Main Methods:
- Macrophage isolation from human lung tissue (nonsmokers, smokers, COPD patients) via Percoll density gradients.
- Flow cytometry analysis of cell-surface markers (CD14, CD16, CD163, CD40, CD206).
- ELISA measurement of matrix metalloproteinase 9, TNF-α, CXCL8, and IL-10 release.
Main Results:
- COPD macrophages showed significantly lower expression of CD14, CD163, CD40, and CD206 compared to controls.
- A specific density fraction (1.036-1.048 g/mL) of COPD macrophages released higher matrix metalloproteinase 9.
- These COPD macrophages were less responsive to budesonide treatment for inflammatory cytokine release.
Conclusions:
- A distinct glucocorticosteroid-insensitive macrophage phenotype exists in COPD lungs.
- This phenotype is characterized by specific cell-surface marker expression and density.
- These findings challenge current macrophage phenotype classifications in COPD.
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