Background Active cigarette smoking has detrimental effects on asthma morbidity and severity. Angiopoietin-1 has been shown to protect the microvessels against plasma leakage, whereas angiopoietin-2 enhances vascular permeability and subsequently induces airway mucosal oedema. Therefore, it is recently thought that angiopoietin-2 may contribute to the pathophysiology of asthma.
Objective To determine whether angiopoietin-2 levels in the airways are associated with clinical profiles in smoking asthmatics.
Methods We measured angiopoietin-1 and -2 levels in induced sputum in 35 normal controls (18 non-smokers and 17 smokers) and 49 asthmatics (24 non-smokers and 25 smokers) before and after inhaled beclomethasone dipropionate (BDP: 800 μg/day) therapy for 12 weeks.
Results Angiopoietin-1 and -2 levels in induced sputum were significantly higher in asthmatics than in normal controls. Moreover, angiopoietin-2 levels were significantly higher in smoking asthmatics than in non-smoking asthmatics (P=0.0001). The airway vascular permeability index was also higher in smoking asthmatics than in non-smoking asthmatics. Moreover, the angiopoietin-2 level was positively correlated with the airway vascular permeability index (non-smoking asthmatics: r=0.87, P<0.001, smoking asthmatics: r=0.64, P=0.002). After BDP therapy, angiopoietin-1 levels were significantly decreased in non-smoking asthmatics, smoking-cessation asthmatics, and active-smoking asthmatics. In contrast, angiopoietin-2 levels did not differ from before to after BDP therapy in non-smoking asthmatics and active-smoking asthmatics. However, its levels were significantly decreased from before to after BDP therapy in smoking-cessation asthmatics (P=0.002). Although forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) before BDP therapy was comparable in all subgroups, this parameter after BDP therapy was significantly lower in active-smoking asthmatics than in non-smoking and smoking-cessation asthmatics. Moreover, the reduction in angiopoietin-2 levels after BDP therapy in smoking-cessation asthmatics was significantly correlated with an mprovement in FEV1/FVC.
Conclusion Angiopoietin-2 levels were elevated in the airways of smoking asthmatics, and its levels were associated with impaired airway responses.