Effects of corticosteroids on COPD lung macrophage phenotype and function

Area of Science:

• Immunology
• Pulmonary Medicine
• Pharmacology

Background:

• Macrophages are elevated in chronic obstructive pulmonary disease (COPD) lungs, exhibiting impaired microbial phagocytosis and efferocytosis.
• Inhaled corticosteroids (ICSs) are standard COPD anti-inflammatory treatments, but their effects on COPD macrophage phenotype and function beyond cytokine suppression are not well understood.

Purpose of the Study:

• To investigate the impact of corticosteroids on the phenotype and function of lung macrophages from COPD patients.
• To explore potential mechanisms of therapeutic benefit for corticosteroids in COPD.

Main Methods:

• Lung macrophages from control and COPD subjects were treated with corticosteroids.
• Gene and protein expression of macrophage markers (CD163, CD164, CD206, MERTK, CD64, CD80, CD86) were analyzed.
• Functional assays assessed the uptake of hemoglobin-haptoglobin complexes (via CD163) and efferocytosis of apoptotic neutrophils (via MERTK).

Main Results:

• Corticosteroids upregulated CD163, CD164, CD206, and MERTK expression while downregulating CD64, CD80, and CD86.
• Significant increases were observed in CD163-mediated hemoglobin-haptoglobin uptake (59% to 81%) and MERTK-mediated efferocytosis (15% to 28%).
• Bacterial phagocytosis remained unaffected by corticosteroid treatment.

Conclusions:

• Corticosteroids modulate the phenotype and function of COPD lung macrophages.
• These alterations may contribute to therapeutic benefits in COPD by limiting iron availability for bacterial growth and improving efferocytosis of apoptotic cells.