The Effects Of Cigarette Smoke And Lipopolysaccharide On SP-B Protein Expression In Rat Iung

Background Inflammation and cigarette smoke are risk factors for chronic respiratory insufficiency. With the process of chronic inflammatory lung tissue damage, fibrous tissue hyperplasia, alveolar epithelial cells degeneration, alveolar active material quantity and activity decline were the important causes resulting in chronic respiratory dysfunction, this process is the precondition of respiratory dysfunction. SP-B is the most important protein of lung alveolar surfactant pulmonary surfactant.The Gram-negative bacteria were the main pathogens which lead to lung infections and even lung exhaustion. Lipopolysac-charides are a major component of the cell walls of Gram-negative bacteria, and it is bioactive substances of gram-negative bacteria.In this study, cigarette smoke exposed rats was choosed to be research object, lipopolysaccharide drip into these rats trachea (lipopolysaccharide endotracheal instillation) that simulated inflammation conditions of COPD airway, to observe the effects of cigarette smoke and lipopolysaccharide on SP-B expression in rat lung, explore mechanism of this process, we hope this study is helpful to the prevention and treatment for chronic respiratory dysfunction is the basis and theoretical basis.Objectives To explore the effects of cigarette smoke and lipopolysaccharide on SP-B protein expression in rat lung by testing Respiration curve parameters, arterial partial pressure of oxygen, arterial partial pressure of carbon dioxide, and SP-B protein and mRNA expression in lung tissue.Methods Totally 40 SD rats were divided into 4 groups at random:normal control group(Ⅰ group), smoke exposure group(Ⅱ group), Lipopolysaccharide group(Ⅲ group), and smoke exposure+Lipopolysaccharide group(IVgroup),10 rats in each group. Rats of Ⅰ group were divided into normal control group with the no-treatment group.Rats of Ⅱ group were just exposured to smoke 2 times daily every time 30 mins for 28 days. Rats of III group were just treated by intratracheal instillation of 1 mg.Kg-1lipopolysaccharide in first day and fourteenth day. Rats of III group were treated by smoke exposure 2 times daily every time 30 mins for 28 days and intratracheal instillation of 1 mg.Kg-1lipopoly-saccharide in first day and fourteenth day, the group is also called experimental group.On the twenty-ninth day, all rats were anaesthesia by 4% chloral hydrate solution (10ml.kg-1), place endotracheal intubation and Left carotid artery catheterization, the diaphragm are connected with BL-420 biological signal collect and analysis system through needle electrode for recording respiratory curve. Respiratory curve dates of four groups were retained to comparative analysis,2ml arterial blood were got to test arterial partial pressure of oxygen and arterial partial pressure of carbon dioxide, then rats were sacrificed, lung tissue samples were divided into threeparts, the first part was for HE staining to test the morphological changes of lung tissue, the second part was for immunohistochemical staining to test the expression of SP-B protein; the third part was for enzyme-linked immuno sorbent assay to test the content of SP-B protein in lung tissue homogenate, the fourth part was for reverse transcription-polymerase chain reaction to test the level of SP-B protein in lung tissue homogenate. All datas were retained, analysed through SPSS 13.0 statistical software, statistical methods include Spearman rank sum test, Independent t-test and chi-square test (size of test a=0.05).Result ①The inspiratory phase time and frequency of IV group(experimental group) was shorter than Ⅱ group and Ⅲ group, these of Ⅱ group and Ⅲ group was shorter thanl group.There is on difference in respiratory amplitude between Ⅱ group with Ⅲ group, but the inspiratory phase time of Ⅱ group was shorter than Ⅲ group. The expiratory phase time and frequency of IV group(experimental group) was higher than Ⅱ group and Ⅲ group, the expiratory phase time and frequency of Ⅱ group and Ⅲ group was higher thanl group. There is on difference in expiratory phase between Ⅱ group with Ⅲ group. ②Blood acid-alkali indexes results:The arterial partial pressure of oxygen of IV group was obviously lower than Ⅱ group and III group, that of Ⅱ group and Ⅲ group was obviously lower than Ⅰ group, there is no difference in arterial partial pressure of oxygen between Ⅱ group with Ⅲ group. The arterial partial pressure of carbon dioxide of IV group was obviously higher than Ⅱ group, The arterial partial pressure of carbon dioxide of Ⅱ group was obviously higher than Ⅲ group, that of Ⅲ group was obviously higher than Ⅰ group.③the content of SP-B protein in lung tissue homogenate of Ⅳ group was obviously lower than Ⅱ group, that of Ⅱ group was obviously lower than Ⅲ group, that of Ⅲ group was obviously lower than Ⅰ group.④Hematoxylin-eosin staining results:there was pathological phenomenon which is destruction of the structure and pathological changes of interstitial pneumonia in lung tissues of IV group, there was also this pathological phenomenon in Ⅱ group, this phenomenon of Ⅱ group is lighter than IV group, there is inflammatory injury in lung tissues of Ⅲ group, there was normal lung tissue structure in Ⅰ group. Immunohistochemical detection results:the SP-B protein expression of IV group was obviously lower than Ⅱ group, that of Ⅱ group was obviously lower than Ⅲ group, that of Ⅲ group was obviously lower than Ⅰ group.⑤Reverse transcription-polymerase chain reaction results:the level of SP-B protein in lung tissue homogenate of of Ⅳ group was obviously lower than Ⅱ group, that of Ⅱ group was obviously lower than Ⅲ group, that of Ⅲ group was obviously lower than Ⅰ group. All above results have statistical significance.Conclusion Cigarette smoke alone can reduce the expression of SP-B in rat lung, lipopolysaccharide alone also can reduce expression of SP-B in rat lung, the common role of cigarette smoke and lipopolysaccharide can further reinforce down-regulation the expression of SP-B in rat lung. This may further decreases respiratory function of rats with down-regulation of SP-B expression.