Changes Of Pulmonary AT₁R,TGF-β1,Collagen Type Ⅰ And Ⅲ In OLETF Rats

Objectives:Diabetes mellitus (DM) is a metabolic disorder of chronic hyperglycemia which is caused by multitude factors. At present,a lot of studies were done to heart, brain, kidney, retina and nervous system chronic complications of diabetes,but chronic lung damage caused by diabetes was not well understood.The studies about lungs of diabetes at home and abroad were mainly focused on lung function,lung tissue morphology and lung tissue ultrastructural at present and there were few studies about pathogenesis of lung damage caused by diabetes. In recent years studies had found that the local RAS activation in tissue might play an important role in the pathogenesis of fibrosis,but studies about the change of local RAS components in lung tissue of diabetic were not found. AngⅡis the main effector molecule of RAS and it is mainly bound to type 1 receptor.This experiment by immunohistochemistry measured the expression of AT1R,TGF-β1 and collagen typeⅠ,Ⅲin lung tissue of diabetic state in order to explore the changes of AT1R and TGF-β1 and pathogenesis of pulmonary fibrosis and provide a theoretical basis for clinical intervention.Methods:4 weeks spontaneous type 2 diabetes mellitus model 30 OLETF rats and the same department non-diabetic control of them 8 LETO rats were reared in single cage with standard feed in specific pathogen-free conditions.They were made OGTT on a regular basis. To 30 weeks,there were 16 OLETF rats modelled successfully. We selected 8 OLETF rats randomly from them as DM group and the LETO rats as N group. They continued to be fed for 12 weeks,then they were killed by the femoral artery bleeding and the lung samples were obtained. Put them in 10% neutral formalin to fix,anhydrate% transparent dip wax,embed and slice:①Observed the structural changes of lung tissue under light microscope by HE staining;②Observed collagen deposition in lung tissue of each group by Masson staining;③Detected the expression of AT1R,TGF-β1 collagen typeⅠ,Ⅲby immunohistochemistry,then observed staining intensity and calculated the percentage of positive cells of AT1R and TGF-β1 under light microscope and determined collagen typeⅠ,Ⅲratios of the positive reactive area of view and mean optical density by the image analysis system.Results:(1) Compared with LETO rats, OLETF rats were fatter,acted slowly,lazy and dry dull coat color.During experiment, the body mass of DM group were significantly higher than N group(P<0.01).(2)HE staining:N group had normal alveolar structure.The lung organizational structure of DM group disordered, bronchial wall,alveolar wall thickening,alveolar epithelial cells showed unclear, alveolar atrophy,collapse,extracellular matrix and fibroblasts of pulmonary interstitial and perivascular increased, and there were inflammatory cell infiltration. (3)Masson staining:Pulmonary interstitial and perivascular of N group had little collagen fibers and in DM group they increased and disordered. (4)Immunohistochemistry:①AT1R:In DM group bronchial epithelial cell,typeⅡalveolar epithelial cell,fibroblast,macrophages and little capillary endothelial cells cytoplasm could be seen many positive particles and in N group could be seen little positive particles.AT1R expression in DM group compared with N group was different(P<0.01).②TGF-β1:In DM group bronchial epithelial cells,alveolar epithelial cells,fibroblast,macrophages and little capillary endothelial cells cytoplasm could be seen many positive particles and N group had little. TGF-β1 expression in DM group compared with N group was different(P<0.01).③collagen typeⅠ,Ⅲ:Pulmonary interstitial collagen typeⅠandⅢof DM group could see a lot of positive expression, N group showed little. Collagen typeⅠ,Ⅲratios of the positive reactive area of view and mean optical density in DM group compared with N group was different(P<0.01).(5)Pearson correlation analysis:The expression of AT1R had positive correlation with that of TGF-β1 expression in DM group.Conclusions:(1)Pathological changes and collagen fibers deposition occured in lung tissue of DM group,indicating that DM group had more fibers and the lung was another target organ of diabetes.(2)AT1R expression increased in lung tissue of DM group,suggesting that lung tissue of DM group exist activation of local RAS components.It may be play a role in the pathogenesis of pulmonary fibrosis.(3) TGF-β1 expression in lung tissue of DM group increased and showed positive correlation with the expression of AT1R, suggesting that AngⅡby AT1R for the occurrence of pulmonary interstitial fibrosis may be partly mediated by TGF-β1.