Association between the Reduced Expression of RECK and Neutrophilic Inflammation in Chronic Obstructive Pulmonary Disease

<b><i>Introduction:</i></b> Reversion-inducing cysteine-rich protein with Kazal motifs (RECK), a recently discovered inhibitor of matrix metalloproteinase (MMP). There is a large number of chronic obstructive pulmonary disease (COPD) patients worldwide; however, the role of RECK on COPD has not been studied. This study explored the expression of RECK in COPD patients and its effect on neutrophil function to provide a new scientific basis for the prevention and treatment of COPD. <b><i>Method:</i></b> Fifty patients with acute exacerbation of COPD and fifty healthy controls were enrolled in the study. RECK was detected in lung tissue, sputum, and plasma of subjects as well as in BEAS-2B cells stimulated with cigarette smoke extract (CSE) by immunohistochemistry, ELISA, and qRT-PCR. Meanwhile, lung function (FEV1%pred) and inflammatory cytokines (IL-6 and IL-8) were examined, and correlation analysis was performed with RECK expression. The effect of RECK on proliferation, apoptosis, migration, and inflammatory cytokines and its potential mechanism was further quantified by neutrophil stimulated with recombinant human RECK protein (rhRECK) combined with CSE using CCK8, flow cytometry, Transwell assay, qRT-PCR, ELISA, and Western analysis. <b><i>Results:</i></b> RECK was mainly expressed on airway epithelial cells in normal lung tissue and was significantly diminished in COPD patients. The levels of RECK in sputum and plasma were also significantly decreased in COPD patients. Pearson correlation analysis showed that RECK level in plasma was positively correlated with FEV1%pred (<i>r</i> = 0.458, <i>p</i> &lt; 0.001) and negatively correlated with IL-6 and IL-8 (<i>r</i> = −0.386, −0.437; <i>p</i> = 0.006, 0.002) in COPD patients. The expression of RECK was decreased in BEAS-2B stimulated with CSE. The migration, inflammation, and MMP-9 expression of neutrophils were promoted by CSE, while inhibited by rhRECK. <b><i>Conclusion:</i></b> RECK is low expressed in COPD patients and negatively correlated with inflammation. It may inhibit the inflammation and migration of neutrophils by downregulating MMP-9.