Abstract
OBJECTIVE: Exposure to cigarette smoke is a risk factor for chronic rhinosinusitis. Current literature confirms complement fragments are activated in human nasal mucosa. The mechanism(s) responsible for this activation is unclear. We investigated the effects of cigarette smoke on nasal mucosa in vitro and via a model of cigarette smoke exposure by using animals deficient in complement components. STUDY DESIGN: Prospective, controlled animal and in vitro human cell line study. SETTING: University laboratory. SUBJECTS AND METHODS: Human respiratory epithelial cells were exposed to five, 10, and 20 percent cigarette smoke extract (CSE) in vitro in the presence or absence of human serum. Complement activation was assessed by enzyme-linked immunosorbent assay and immunofluorescent techniques. Complement-deficient (C3(-/-), n = 6; factor B(-/-), n = 50) and sufficient mice (wild type, n = 10) were exposed to the smoke of four cigarettes per exposure for two exposures per day for three days. Mice were sacrificed 12 hours after the last exposure, and the nasal cavity was surgically removed. Histological characteristics were analyzed by the use of a subjective scale and quantitative image analysis scoring systems. RESULTS: In vitro analysis of respiratory cell cultures demonstrated that exposure of serum to CSE resulted in complement activation. Furthermore, immunofluorescent staining for C3d could only be demonstrated in CSE-exposed cultures. In vivo analysis demonstrated that complement deficiency, either C3 or factor B deficiency, resulted in a significant reduction in histological evidence of damage as compared with wild-type control mice (wild type vs C3(-/-), P = 0.02; wild type vs factor B(-/-), P = 0.07; no significant difference between C3(-/-) vs factor B(-/-)). CONCLUSION: These data demonstrate that cigarette smoke activates the complement system. Furthermore, complement deficiency protected against smoke-induced mucosal damage in this small series.