S100 Calcium Binding Protein A9 in Sputum of Patients with Steroid Naive Asthma: Relation with Airway Obstruction and Nneutrophilc Inflammation

Background: We previously reported elevation of S100 calcium bindingprotein A9 (S100A9) protein in sputum of neutrophilic severe uncontrolled asthmatics in spite of high dose inhaled corticosteroid treatment compared with stable asthmatics. The aim of this study was to evaluate the relation of S100A9 protein with neutrophilic inflammation in the steroid naive - mild to severe asthmatics and lung function. Materials and Methods: Sputum were obtained from 132 never-smoking or ex-smoking asthmatics (<10 pack-years). S100A9 proteins were measured in inhaled or systemic corticosteroid naïve asthmatic (SNBA, n=103), inhaled and systemic steroid treated asthmatic (STBA, n=29) and normal controls (NC, n=35) using an enzyme-linked immunosorbent assay. Correlations between S100A9 levels and inflammatory cells, FEV1, and annual rate of exacerbation were analyzed. Results: The S100A9 levels were significantly higher in sputum of both SNBA and STNA than that of normal controls (P=0.008, and 0.001 respectively) and were comparable between SNBA and STNA (P=0.734). In bronchial asthma (BA), S100A9 levels were significantly correlated with the percentages of neutrophils (r=0.267, p=0.002) and those of eosinophils (r= -0.195, p=0.025) in sputum. The correlations were persistently observed in SNBA. When BA was divided into 4 groups: Neutrophil dominant (70% or more), eosinophil dominant (3% or more), co-dominant and pauci-granulocytic group. The S100A9 levels was the highest in the neutrophilic group (13.51 pg/ug) compared to the eosinophilic (9.06 pg/ug), co-dominant (5.96 pg/ug) and pauci-granulocytic (7.87 pg/ug) groups. S100A9 levels was significantly increased in the subject experiencing exacerbation compared to those not experiencing exacerbation. Conclusion: Our data suggest that S100A9 protein was elevated in sputum of asthma compared to normal control. The levels were correlated with percentage of neutrophil in sputum and were regardless of steroid treatment.