| Background: Referred to as asthma, Bronchial Asthma, the most common chronic childhood respiratory disease, is a kind of chronic airway inflammation by a variety of cells such as mast cells, eosinophils, T lymphocytes, and others involving, manifested as recurrent episodes of wheezing, difficulty breathing, chest tightness or cough. The incidence of asthma shows an up trend in the global. Continuous airway inflammation in the airway induced repeatedly airway injuring and repairing, which may lead to structural changes known as airway remodeling which includes airway smooth muscle hypertrophy and hyperplasia, collagen deposition to sub-epithelial basement membrane, hyperplasia of goblet cells, and an increase in vascularity, etc. Extracellular matrix (ECM) protein deposition beneath the basement membrane is characteristic of the airway wall of an asthmatic individual. Matrix metalloproteinases (MMPs) were the main rate-limiting enzymes in ECM metabolism, which could degrade the majority components of ECM. Tissue inhibitor of metalloproteinases (TIMP) -1, which interacted 1: 1 with the domain of MMP-9, inhibited the activity of MMP-9. The imbalance of MMP-9/TIMP-1 leading to abnormal metabolism of extracellular matrix, may be involved in the process of airway remodeling in asthma. Regulated upon activation normal T cell expressed and secreted (RANTES) are cysteine - cysteine type chemokine, also known as CCL5, is a secretion of a variety of inflammatory cells, such as eosinophils, monocytes, dendritic cells, lymphocytes, NK cells and so on. RANTES, which has chemotactic effects, especially for a powerful eosinophil chemotactic role, could aggravate airway inflammation of asthma, and may also be involved in airway remodeling from occurring. Objectives: To learn the situation of airway remodeling by observing dthe rats airway pathological changes with light microscopy, and quantifiing the airway wall thickening of rats bronchi with multi-function color pathological image analysis system.To observe the expression of MMP-9, TIMP-1 in the lung tissue and RANTES in bronchoalveolar lavage fluid (BALF) of each group rats and study the correlation between MMP-9/TIMP-1 and RANTES.Methods: Thirty-six young male Wistar rats were randomly divided into three groups: asthmtic model group (Group A), Dexamethason (DEX) intervention group (Group B) and normal control group (Group C). At 1, 7, 14 days, 10% of Ovalbumin (OVA) and aluminum hydroxide [Al2(OH)3] compound preparation (1 ml) was applied to sensitize the rats in Group A and B by injection Intraperitoneally each. Group C were given intraperitoneal injection of normal saline at the same dosage as normal control. On the 21th day, the rats in Group A and B inhaled 1% of OVA atomization 30 min each time to excite wheezing, every other day for 6 weeks, Group C inhalation with normal saline instead. One week after the excitation, Group B began to be intervened via tail vein injection with DEX (0.5mg/Kg) half an hour before inhalation three times a week, Group A and C tail vein injection with normal saline. At the last meeting 24 hours after inhalation the rats of three groups were taken thoracotomy under anesthesia with an intraperitoneal injection of 1% pentobarbital sodium (0.2ml/Kg). The left lung main bronchus of the rats was ligated and cut to be fixed and embedded. The BALF of right lungs were collected.Pathological changes in left lung airway of each group were observed in the left lung organization slices. Bronchial basement membrane perimeter (Pbm),airway smooth muscle area (WAm), inner way area (WAi) were measured by multi-function color pathological image analysis system, and WAm/Pbm and WAi/Pbm taken as indicators of airway remodeling. Immunohistochemistry assays was used to determine the status of MMP-9 and TIMP-1 expression in the left lung organization slices, and mean integral ?optical density (IOD) of MMP-9 and TIMP-1 were also measured by multi-function color pathological image analysis system. The contents of RANTES in BALF of right lungs were determined by enzyme linked immunosorbent assay (ELISA).All data were processed by SPSS 10.0 statistical software. Data comparisons between groups were tested by One-Way ANOVA analysis, and the correlation coefficient of correlation analysis between MMP-9/TIMP-1 and RANTES was calculated, P <0.05 as statistically significant difference.Results: There is wheezing onset of the rats in asthmatic model group during OVA inhalation. Airway remodeling such as airway wall and smooth muscle thickening could observed in the left lung bronchial biopsy. WAm/Pbm and WAi/Pbm of the rats left airway in asthmatic model group slices are 5.78±1.36μm~2/μm, 15.10±3.99μm~2/μm, higher than that in normal control group (P<0.05). The rats in DEX intervention group wheeze after OVA inhalation in the first week, and there is a relief after DEX intervention in the following weeks. Airway remodeling in DEX intervention group was not seen. WAm/Pbm and WAi/Pbm of the rats left airway in DEX intervention group slices are 3.98±1.25μm~2/μm, 9.86±2.47μm~2/μm, lower than that in asrhmatic model group (P<0.05).The MMP-9 and TIMP-1 mean IOD values (1.7655±1.0476, 1.958±0.0927)of rats left lung and the RANTES expression (18.20±4.00 pg/ml ) of rats right BALF in asthmatic model group are significantly higher than those in normal control group and DEX intervention group (P<0.05). The MMP-9 and TIMP-1 mean IOD values (0.8525±0.0231, 0.876±0.0302) of rats left lung and the RANTES expression (9.28±2.26pg/ml) of rats right BALF in DEX intervention group are no differences with those in normal control group. The imbalance of MMP-9/TIMP-1 in asthmatic model group was negatively correlated with RANTES of BALF (r=-0.141, P<0.05).Conclusions: The expression of MMP-9, TIMP-1 and RANTES all increase conspicuously in asthma, which could promote the progress of airway inflammation. The imbalance of MMP-9/TIMP-1 in asthmatic model group was negatively correlated with RANTES, contribution to ECM degradation and deposition related to participation in the occurrence of airway remodeling. DEX could inhibite MMP-9, TIMP-1 and RANTES expression, reducing airway remodeling. |
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