Cigarette smoke extract induces thymic stromal lymphopoietin expression, leading to TH2-type immune responses and airway inflammation

Background: Both active and passive smoking are considered to be risk factors for asthma development. However, the precise mechanisms involved remain elusive. Recently, thymic stromal lymphopoietin (TSLP) has been shown to play a key role in the development of T(H)2-type allergic inflammation in patients with asthma. Objective: The aim of this study was to investigate whether there was a causal relationship between cigarette smoke exposure and TSLP expression in the lung. Methods: We examined the effects of repeated intranasal exposure of cigarette smoke extract (CSE) on TSLP mRNA and protein expression in the mouse lung by means of real-time PCR, Western blotting, and immunohistochemistry. We also examined the effects of intranasal exposure of CSE plus ovalbumin (OVA) on T(H)2-type immune responses and lung pathology. Results: Repeated exposure of CSE induced TSLP mRNA and protein expression, which was inhibited by treatment with antioxidative N-acetylcysteine and by TNF-alpha receptor I deficiency. In addition, the intranasal exposure of CSE simultaneously with OVA induced OVA-specific T(H)2-type immune responses and airway inflammation, which were inhibited by the blockade of the TSLP activity. Conclusion: CSE induced TSLP expression in the mouse lung in an oxidative stress-dependent and TNF-a receptor I-dependent manner, and when challenged simultaneously with an antigen, CSE promoted the development of airway inflammation in association with TH2-type immune responses. (J Allergy Clin Immunol 2008;122:1208-14.)