Budesonide Impact On The Expression Of Pulmonary Surfactant Protein-A (SP-A) In Hyperoxia-induced Lung Injury In Neonatal Rats

Objectives:1. To establish a model of hyperoxia-induced lung injury in neonatal rats;2. To observe the histopathological changes in neonatal rat lung of hyperoxia-inducedinjury as well as its affecting the expression of SP-A mRNA and protein by comparingwith control group, and to study the role of SP-A in the development of hyperoxia-inducedlung injury;3. To observe whether the inhaled corticosterroids, budesonide, has a protective effectto hyperoxia-induced injury and affects the expression of SP-A, and in order to provide atheoretical evident for clinical treatments of hyperoxia-induced lung injury.Method:The108neonatal SD rats (less than1day after birth, no male or female) wererandomly divided into3groups: Group Ⅰ,Air Group (Control Group); Group Ⅱ,Hyperoxygen and Saline Group (Hyperoxia Group); Group Ⅲ,Hyperoxygen andBudesonide Group (Interfering Group). Each group had36rats.Group Ⅰ was incubated in normal air. Group Ⅱ and Ⅲwere both exposed in specialoxygen boxes, and the oxygen concentration was continuously to90%-95%.In daily GroupⅡ was inhaled10ml of saline. And at the same time, Group Ⅲwas inhaled10ml ofdissolved BUD saline (with BUD2mg).The rats were executed on the3th,7thand14thday. Using bronchoalveolar lavaging tomeasure the protein level in lavaging fluid; Taking the lung tissue to weight, afterwise dry,and calculate the wet/dry proportion;Using HE to observe the histopathologicalchanges;Using Westen Blot to measure the level of SP-A protein in lungs;Using RT-PCRto detect the expression level of SP-A mRNA. Result:1. The general condition: Group Ⅰ (Air Group) was viable and fed well. Group Ⅱ(Hyperoxia Group) was dull, apathetic, less active, even dyspnea after hyperoygen abortion.The situation of Group Ⅲ (Interfering Group) was between the former two.2. Lung histopathology: In Group Ⅰ (Air Group), the size, shape and distrubution ofalveoli were normal. No inflamation can be found. In Group Ⅱ (Hyperoxia Group), after3days of hyperoxygen, the small blood vessels expanded congestion, alveolar cavityenlarged and appeared red blood and inflammatory cells, pulmonary septal area fractured.After7days of hyperoxygen, inflammation, pulmonary edema, pulmonary hemorrhagewere more obvious, the pulmonary septal area got wider and the structure of lung tissuewas arranged disorder. After14days of hyperoxygen, the changes were more obvious, thestructure of lung tissue was more disorder, the pulmonary septal area got severe wider,significant fibrosis could be seen, the numbers of alveoli reduced evidently, alveolar cavityenlarged obviously. In Group Ⅲ (Interfering Group), comparing with Group Ⅱ, thestructure and morphology in the lung tissue were milder.3. The wet/dry porpotion (W/D) of lung tissue: on the3thand7thday of this study, theW/D in Group Ⅱis higher than Group Ⅰ (P<0.01). And on the14thday, it is moresignificantly higher than Group Ⅰ (P<0.01). However, comparing with Group Ⅱ, the W/Don the3th,7thand14thday is obviously reduced in Group Ⅲ (P<0.01).4. The level of the protein in bronchoalveolar lavage fluid (BLAF): on the3th,7thand14thday, the BLAF protein level in Group Ⅱ is higher than Group Ⅰ, the differences arestatistically significant (P<0.01). However, on the3thday the protein in Group Ⅲisdecreased comparing with Group Ⅱ (P<0.05),and on the7thand14thday the protein levelis significantly lower (P<0.01).5. The variation of the expression level of SP-A protein in lung tissue: the WestenBlot shows that on the3thday, the expression level of SP-A protein in Group Ⅱ is higherthan GroupⅠ(P<0.01), and on the7thand14thday the expression level is significantlylower (P<0.01). On the3thday, the expression level of SP-A protein in Group Ⅲisbetween Group Ⅰa nd GroupⅡ（P<0.05）, and on the7thand14thday the expression levelis significantly increased comparing with Group Ⅱ(P<0.05).6. The variation of the expression level of SP-A mRNA in lung tissue: the RT-PCRshows that on the3thday, the expression level of SP-A mRNA in Group Ⅱis higher than GroupⅠ (P<0.05), on the7thday the expression level is lower and on the14thday theexpression level is significantly lower (P<0.01). On the3thday, the expression level ofSP-A mRNA in Group Ⅲ is between Group Ⅰ and GroupⅡ（P<0.05）, and on the7thand14thday the expression level is significantly increased comparing with Group Ⅱ(P<0.05).Conclusion:1. The hyperoxygen treatment will cause lung injury in rats, and the injury willincrease with the extension of oxygen time.The main histopathological changes of lungtissue are local hyperemia, hemorrhage, inflammatory exudate, structure disorder,development disturbance, decrease in the number of alveolar and interstitial pulmonaryfibrosis.2. In the hyperoxia-induced lung injury, the expression level of SP-A mRNA andprotein is increased firstly and then decreased. The level is parallel with the degree of lunginjury. These findings suggest that there is a certain protective mechanism of the body inthe process of hyperoxia-induced lung injury, and the decrease or dysfunction ofpulmonary surfactant protein is an important factor.3. The inhaled corticosterroids, budesonide may promote the expression of SP-AmRNA and protein by enhancing antioxidation and antiinflammation, alleviate the lunginjury, and play a protective effect to hyperoxia-induced lung injury.