| Effects of Erythromycin on Expression Levels ofαSmooth Muscle Actin and Transforming Growth Factor-β1 in Emphysema Rat ModelIntroductionCOPD is characterized by airflow obstruction due to chronic airway inflammation. The airflow obstruction is generally progressive and may be partially irreversible. Airway remodeling plays an important role as a "bridge" beween airflow obstruction and airway inflammation. The consensus that has prevailed since is that airway smooth muscle cell is an end-response effector cell, however exciting new evidence, mainly from in vitro studies, supports the concept that in addition to contraction and relaxation, this structural cell fulfills other diverse functions,α-smooth muscle actin is the main sign protein of smooth muscle cell and myofibroblast, and denoting the proliferation and function change of smooth muscle cell. Transforming growth factor-β1 is demonstrated to be a modulator of inflammation and a potent stimulator of collagen, and produced by many cell types, including platelets, epithelia cells, mesothelial cells, T leukocytes activated by antigen, monocyte activated by Lipopolysaccharide, B leukocytes, and macrophages. Macrolide antibiotics such as erythromycin are known tbr their therapeutic uses as antibacterial agents, but just as importantly, they are also effective anti-inflammatory, immunoloregulation and anti-fibrosis agents, and definitely effective against chronic inflammatory airway diseases particularly diffuse panbronchiolitis.In this study, we established the rat model of emphysema by intratracheal instillation of lipopolysaccharide and daily exposure to cigarette smog. To observed the action of erythromycin on the expression of transforming growth factor-β1 andα-smooth muscle actin and to evaluated the protective and therapeutic effects of erythromycin.Materials and methods1. Animal model and tissue preparationThirty-six male Wistar rats were assigned randomized to normal control(group A, n=6), emphysema model(group B, n=15), Erythromycin prevention(group C, n=15) Groups, the animals of 10 weeks age were weighted about 220±20g at the time of experimenting.The rat model of emphysema was established by intratracheal instillation of lipopolysaccharide(LPS) twice at the time of 1st and 14th days respectively and daily exposure to cigarette smog for four weeks, the rats of Group C were subjected to gastric erythromycin perfusion daily from three early days of experiment. After 4 weeks from exposure to cigarette smog, animals were sacrificed by cervica dislocation, lungs were removed and manufactured histologic specimens.2. Experimental methodshematoxylin and eosin staining and be observed, Masson trichrome staining and Verhoeff elastic fiber staining, the morphological changes of lungs were compared and immunohistochemical analysis was used to quantify the levels of expression of transforming growth factor-β1 andα-smooth muscle actin localized in peripheral airways.3. Statistical AnalysisData are presented as(?)±s, P＜0.05 was considered significant. All statistical analyses were performed with SPSS13.0 statistical package.Results 1. Histological analysisIn the hematoxylin-eosin stain study, specimens in normal control group neither airway nor alveolus showed abnormal findings, All cases of model group by light microscopy showed wide spread inflammatory changes in bronchiole and severe emphysema, the extent of inflammation and emphysema was significantly reduced in treatment group.2. Morphological analysisBoth mean length interval(44.93±4.7)μm and mean alveolus number (154.5±43.7)/mm~2 obtained from the group B were statistically different in comparison with animals of group C(28.52±3.78)μm, (361.8+72.2)/mm~2 respectively (P＜0.05), mean alveolus number(239.6±63.9)/mm~2 in group C were higher than those in group A (P＜0.05);In group B the thickness of smooth muscles layer in the bronchi was increased and mean area proportion(9.67±1.63)%, namely smooth muscles area divided totel area were significant differences as compared to those(6.42±1.43)% of group A(P＜0.05); in group C the thickness of bronchiolar walls were increased unconspicuously, mean thickness proportion(7.75±1.31)% and mean area proportion(14.7±4.1)% were significant differences as compared to those (9.67±1.63)% , (19.6±3.9)% of group B(P＜0.05).3. ImmunoistochemistryTGF-β1 expression in cytoplasm of bronchiolar epithelia were observed in animals of various group, and higher than those in both airway smooth muscle cell and alveolus macrophages. TGF-β1 expression in group A were lower, and absorbency of TGF-β1 in bronchiolar epithelia in group B(0.369±0.071)and in group C (0.314±0.058) were significantly higher than(0.174±0.023) in groupA (P＜0.05); relative content ofα-SMA in group B(0.434±0.043)and group C(0.353±0.035) were significantly higher than those(0.261±0.024)inl groupA; there was statistical significance between group Band groupC (P＜0.05).4. Relativity analysisThe relative level ofα-SMA expression in airway smooth muscle was significantly correlated with TGF-β1 expression in cytoplasm of bronchiolar epithelia (r=0.631, P＜0.01) and mean thickness proportion(r=0.781, P＜0.01). In addition, the levels of TGF-β1 expression were correlated with mean thickness proportion(r=0.477, P＜0.01).ConclusionsThe increased expression of TGF-β1 in cytoplasm of bronchiolar epithelia andα-SMA in airway smooth muscle cell were positive correlated with each other, which might indicate TGF-β1 participate in airway smooth muscle cell proliferation. Erythromycin could reduce airway inflammation and downregulate the expression of TGF-β1 in bronchiolar epithelia andα-SMA in airway smooth muscle cell, and may prevent airway remodeling to some degree.
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