The Effect Of Smoking On Expressions Of Matrix Metalloproteinase-9 In Tracheal Epithelium Of Rats

Objective To investigate the effect of different smoking dosage,different continuous time of smoking and smoking cessation on expressions of matrix metalloproteinase-9(MMP-9) mRNA and proteins in tracheal epithelium of rats,and the relationship between smoking or smoking cessation and trachea remodeling in chronic obstructive pulmonary disease(COPD).Methods Forty Wistar rats were randomly divided into the normal control group,the smoking group of long term and large dosage,the smoking group of short term and large dosage,the smoking group of long term and small dosage and the smoking cessation group which was exposed to room air for 10 weeks after long term and large dosage smoking.The expressions of MMP-9 mRNA and proteins in tracheal epithelium of rats were detected by in situ hybridization and immunohistochemistry respectively.Results(1) The pathological changes of emphysema were observed in the lung tissue of every smoking rat.(2) Compared with the normal control group(0.88±0.88,2.80±1.66),the expressions of MMP-9 mRNA and proteins in tracheal epithelium of rats were remarkable elevated in the smoking group of long term and large dosage(22.01±2.86,20.81±2.46),the smoking group of short term and large dosage(14.94±3.46,13.68±2.00),the smoking group of long term and small dosage(6.92±2.71,8.84±1.80) and the smoking cessation group (19.00±3.36,14.82±1.74).The P values were all less than 0.01.(3) Compared with the smoking group of long term and large dosage,the expressions of MMP-9 in tracheal epithelium of rats were decreased in the smoking group of short term and large dosage,the smoking group of long term and small dosage and the smoking cessation group.The P values were all less than 0.05.Conclusions Smoking could increase the expression of MMP-9 mRNA and proteins in tracheal epithelium of rats.The expression could be more remarkable with longer smoking time and larger dosage and could be decreased after smoking cessation.Smoking could cause trachea damage and remodeling.Smoking cessation could ease trachea remodeling and be the effective method to prevent COPD.