ABSTRACT
Exacerbations of chronic obstructive pulmonary disease (COPD) are an increasing cause of hospitalisations and are associated with accelerated progression of airflow obstruction. Approximately half of COPD exacerbations are associated with bacteria and many patients have lower airways colonisation. This suggests that bacterial infection in COPD could be due to reduced pathogen removal. This study investigated whether bacterial clearance by macrophages is defective in COPD. Phagocytosis of fluorescently labelled polystyrene beads and Haemophillus influenzae and Streptococcus pneumoniae by alveolar macrophages and monocyte-derived macrophages (MDM) was assessed by fluorimetry and flow cytometry. Receptor expression was measured by flow cytometry. Alveolar macrophages and MDM phagocytosed polystyrene beads similarly. There was no difference in phagocytosis of beads by MDM from COPD patients compared with cells from smokers and nonsmokers. MDM from COPD patients showed reduced phagocytic responses to S. pneumoniae and H. influenzae compared with nonsmokers and smokers. This was not associated with alterations in cell surface receptor expression of toll-like receptor (TLR)2, TLR4, macrophage receptor with collagenous structure, cluster of differentiation (CD)163, CD36 or mannose receptor. Budesonide, formoterol or azithromycin did not suppress phagocytosis suggesting that reduced responses in COPD MDM were not due to medications. COPD macrophage innate responses are suppressed and may lead to bacterial colonisation and increased exacerbation frequency.
Subject(s)
Macrophages, Alveolar/immunology , Phagocytosis/immunology , Pulmonary Disease, Chronic Obstructive/immunology , Pulmonary Disease, Chronic Obstructive/microbiology , Cells, Cultured , Female , Flow Cytometry , Fluorometry , Haemophilus influenzae/immunology , Humans , Male , Microbial Viability , Microscopy, Confocal , Middle Aged , Polystyrenes , Streptococcus pneumoniae/immunologyABSTRACT
Pulmonary macrophages are a target for inhaled therapies. Combinations of long-acting beta(2)-agonists (LABA) and glucocorticosteroids have been developed for asthma and chronic obstructive pulmonary disease (COPD). This study examined two LABA, salmeterol and formoterol, and the glucocorticosteroid, budesonide, on cytokine release from monocyte-derived macrophages (MDM) to determine whether anti-inflammatory effects observed in patients are due to inhibition of macrophages. MDM were incubated in the absence or presence of LABA or budesonide prior to stimulation with lipopolysaccharide (LPS). Tumour necrosis factor (TNF)-alpha, granulocyte macrophage-colony stimulating factor (GM-CSF) and CXC chemokine ligand (CXCL)8 were measured by ELISA. Formoterol and salmeterol inhibited LPS-stimulated release of TNF-alpha (mean effective concentration (EC(50)) 2.4+/-1.8 and 3.5+/-2.7 nM, respectively; n = 11-16), GM-CSF (EC(50) 24.6+/-2.1 and 52.4+/-40.8 nM, respectively, n = 11-12) but not CXCL8 from LPS-stimulated MDM. Budesonide inhibited release of all three cytokines (EC(50) TNF-alpha: 1.2+/-0.4 nM; GM-CSF: 0.4+/-0.2 nM; CXCL8: 0.4+/-0.1 nM; n = 3-4). Formoterol but not salmeterol elevated cAMP in these cells. These effects were attenuated by beta-adrenoceptor antagonists, propranolol and ICI118551. Salmeterol (10(-7) M) also inhibited formoterol-induced cAMP and formoterol-mediated attenuation of cytokine release. Combining budesonide (0.3 nM) with formoterol, inhibited TNF-alpha release additively. LABA may inhibit inflammatory cytokine release from macrophages in a cAMP-independent manner and act additively with budesonide.
