MMP-8, MMP-9 and Neutrophil Elastase in Peripheral Blood and Exhaled Breath Condensate in COPD

Chronic obstructive pulmonary disease (COPD) is characterised by progressive and irreversible airflow limitation associated with chronic inflammation involving cytokines and metalloproteinases (MMPs). MMP-8, MMP-9 and neutrophil elastase (NE) are known to be implicated in COPD but the factors influencing activation and suppression remain unclear. This study aimed to compare MMP-8, MMP-9 and NE in the peripheral blood of COPD patients and controls and to likewise assess exhaled breath condensate (EBC) for these MMPs. Peripheral blood micro(mi)RNA139-5p levels, which may regulate MMPs in COPD, were also measured. Blood and EBC were collected from COPD patients (stable and during exacerbations) and healthy controls. Expression of mRNA for MMP-8, MMP-9, NE and miRNA-139-5p expression in peripheral blood mononuclear cells (PBMCs) was measured using qRT-PCR. MMP-8, MMP-9 and NE protein in plasma as well as MMP-8 and MMP-9 protein in EBC were analysed by enzyme-linked immunoassays. PBMCs from COPD patients showed greater expression of mRNA for MMP-8 (p = 0.0004), MMP-9 (p = 0.0023) and NE (p = 0.0019). PBMC expression of mRNA for NE was significantly higher in COPD exacerbations compared to stable cases (p < 0.05). Expression of mRNA for MMP-9 and NE correlated negatively with spirometry in patients (p < 0.05). Plasma from COPD patients showed greater levels of protein for MMP-8 (p = 0.003), MMP-9 (p = 0.046) and NE (p = 0.018). MMP-8 protein levels were lower in the EBC of COPD patients (p < 0.0001). In PBMCs, enhanced expression of mRNA for MMP-9 and NE is associated with COPD and may correlate with disease severity and exacerbations.