Airway inflammation in Japanese COPD patients compared with smoking and nonsmoking controls

To assess the importance of inflammation in chronic obstructive pulmonary disease (COPD) by measuring airway and systemic inflammatory biomarkers in Japanese patients with the disease and relevant control groups.

This was the first study of its type in Japanese COPD patients. It was a non-treatment study in which 100 participants were enrolled into one of three groups: nonsmoking controls, current or ex-smoking controls, and COPD patients. All participants underwent standard lung function assessments and provided sputum and blood samples from which the numbers of inflammatory cells and concentrations of biomarkers were measured, using standard procedures.

The overall trends observed in levels of inflammatory cells and biomarkers in sputum and blood in COPD were consistent with previous reports in Western studies. Increasing levels of neutrophils, interleukin 8 (IL-8), surfactant protein D (SP-D), and Krebs von den Lungen 6 (KL-6) in sputum and clara cell 16 (CC-16), high-sensitivity C-reactive protein (hs-CRP), and KL-6 in serum and plasma fibrinogen were seen in the Japanese COPD patients compared with the non-COPD control participants. In sputum, significant correlations were seen between total cell count and matrix metalloproteinase 9 (MMP-9; P<0.001), neutrophils and MMP-9 (P<0.001), macrophages and KL-6 (P<0.01), total cell count and IL-8 (P<0.05), neutrophils and IL-8 (P<0.05), and macrophages and MMP-9 (P<0.05). Significant correlations were also observed between some inflammatory cells in sputum and biomarkers in serum, with the most significant between serum CC-16 and both total cell count (P<0.005) and neutrophils (P<0.005) in sputum.

These results provide evidence for the first time that COPD in Japanese patients is a multicomponent disease, involving both airway and systemic inflammation, in addition to airway obstruction. Therefore, intervention with anti-inflammatory therapy may provide additional benefit in disease management of COPD in Japan.