The Effect of Azithromycin on Airway Remodeling of Asthmatic Rats
|Keywords||Azithromycin Asthma airway remodeling TGF-β1 MMP-9 VEGF|
Background It has been a research hotspot of numerous scholars that airway remodeling is as one of the important pathological feathers of asthma. The new direction of asthma treatment is inhibition or reversion of airway remodeling. Azithromycin is a new generation of macrolide antibiotic. It has determinate clinical value because of its immune regulation action in fighting against asthma. Recently, a study found that it can inhibit airway remodeling, but the mechanism is not clear.Objectives The purpose of this experiment is to observe the effect of azithromycin on airway remodeling of asthmatic rats and its possible mechanism through determine airway morphology index and the expression of transforming growth factor-β1(TGF-β1), matrix metalloproteinase-9(MMP-9), vascular endothelium growth factor(VEGF) and meanwhile,offer logical proofs for its clinical applying.Methods Thirty-two clean Sprauge-Dawley(SD) rats were divided randomly into four groups on average:the normal control group(group C), the asthma model group(group M), the Dexamethasone treated group(group D), the Azithromycin treated group(group A). Each group contained eight rats. The rat models of airway remodeling of asthma were established with the ovalbumin(OVA) sensitization and stimulation. Rats in the M,A and D group were sensitized intraperitoneally on the first day and eighth day with100mg of OVA and100mg of Al(OH)3in1ml of normal saline. The rats were challenged by2%OVA continuous inhalation from the15th day,20minutes per day for4weeks. The rats in A and D group were separately given azithromycin for50mg·kg-1d-1or dexamethasone for0.5mg·kg-1·d-1daily intraperitoneally before atomizing challenged every time. And meanwhile the rats in M group were given lml of normal saline intraperitoneally. The rats in C group were injections intraperitoneally on the first day and eighth day with1ml of normal saline. From the15th day, the rats inhaled normal saline for20minutes per day for4weeks.Twenty-four hours after the final antigen challenge, the rats in every group were executed and the right lung tissues were harvested and then made into pathological sections. The lung tissue sections were stained with hematoxylin and eosin for pathologic changes and Masson for collagen deposition in airway wall and PAS for mucus secretion. Parameters of airway remodeling were determined by medical image analysis system. The expression of TGF-β1,MMP-9,VEGF in rat lung tissue were observed by immunohistochemistry. Then all datas were reported by the way of "mean±standard deviation". SPSS13.0statistics software was adopted for analysis of these datas. P<0.05was considered statistically significant.Results (1)The general condition changes in each group:rats in M group appeared symptoms such as tachypnea, restlessness, scratching fur on their face and gatism among or after the challenge. After repeated provocation, fur of the rats lost luster, the spirit depressed, the response slowed, the weight growth slowly or lighten. Compared with the M group, the symptom of rats in A and D group alleviated obviously. There was no significant symptom in C group.(2)The pulmonary histopathological changes in each group:rats in M group demonstrated that inflammatory cells infiltrated around the bronchus and the vascular which were mainly lymphocytes, eosinophils, neutrophils and macrophagocytes with the bronchial spasm, epithelial shed, airway wall thickness, collagen deposition and the mucs production increased. There were different changes in A and D group, and the histopathological changes were much lighter than those of M group. The above-mentioned changes were not significant in C group.(3)The determination of parameters of airway remodeling:the thickness of airway wall and smooth muscle in A and D group was significantly lower than that of M group,but higher than that of C group(P<0.01). But there was no significant difference in A and D group(P>0.05).(4)The results of immunohistochemistry:the protein expression of the TGF-β1, MMP-9,VEGF in M group were significantly higher than that of C group (P<0.01). The expression in A and D group were decreased significantly than that of M group(P<0.01).(5)The results of correlation analysis:the results demonstrated that there was a significantly positive correlation between the thickness of smooth muscle and the protein expression of the TGF-β1, MMP-9, VEGF in lung tissue (P<0.01). And among these three index, the expression was pairwise correlation (P<0.01).Conclusions (1) Persistently allergen stimulate can lead to airway remodeling.(2) Azithromycin can improve the process of airway remodeling through reducing the protein expression of the TGF-β1, MMP-9, VEGF in lung tissue, but can not convert.