Abstract
Interleukin (IL)-18 is suggested to contribute to the pathophysiology of asthma by modulating airway inflammation. However, the involvement of IL-18 on chronic airway inflammation and airway remodelling which are characterizing refractory asthma, has not been assessed. Aim of this study was to investigate IL-18 levels in refractory asthma and its relation to eosinophilic airway inflammation and remodelling.
IL-18 levels were measured in sputum supernatants obtained from mild asthmatic patients (33 smokers and 32 non smokers), patients with refractory asthma (n=32) and healthy subjects (17 smokers and 17 non-smokers). Eosinophilic airway inflammation was assessed by measuring ECP, eosinophil counts in sputum and AHR to methacholine. Airway remodelling was assessed by measuring IL-13, VEGF and transforming growth factor (TGF)-b1 in induced sputum.
Patients with refractory asthma and smoking asthmatics had significantly lower IL-18 levels in sputum compared to non smoking asthmatics (p=0.004 and p=0.049, respectively). No correlation was found between IL-18, ECP, eosinophils and AHR in patients with refractory asthma, although the correlations in mild smoking and non smoking asthmatics were documented (r=-0.636, p=0.026 for PD20meth, and r=-0.495, p=0.043 for FEV1% pred, in non smoking asthmatics, and r=0.765, p=0.006 for PD20meth and r=0.768, p<=0.001, in smoking asthmatics). Significant correlations were found between IL-18 levels and (TGF)-b1, and IL-13 (r=0.803, p<0.001, and r=0.640, p=0.10, respectively).
These findings suggest that in refractory asthma IL-18 is possibly involved in chronic airway inflammation and airway remodelling through an eosinophil independent pathway.
- © 2011 ERS
