The Pathogenesis Of Rat Chronic Obstructive Pulmonary Disease Model Induced By Intratracheal Instillation Of Lipopolysaccharide And Passive Smoking And The Effect Of Spearmint Oil On COPD

Chronic obstructive pulmonary disease is a common respiratory disease,with high morbidity and mortality rates,although has been paid extensive attention,there is still a lack of effective prevention and treatment.The main pathological feature of COPD is airway inflammation and the destruction of lung parenchyma or emphysema.Airway inflammation,especially small airway inflammation is the main lesion and the pathogenesis of COPD.However,the understanding of the essence,characteristics and inflammatory mechanisms of airway inflammation is currently not yet very clear.In this experiment,Spearmint oil is a volatile oil.Its main components are limonene 42.43%, carvone 35.37%,octanol 4.70%,dihydrocarvon 2.27%by gas chromatography analysis. Experimental study showed that the spearmint has obvious inhibition on local acute inflammation caused by egg white,xylene,and has anti-allergic and anti-asthmatic effects.Our experiments have shown that the protective effect of Spearmint oil on rat COPD model induced by intratracheal instillation of Klebsiella pneumonia and lipopolysaccharide(LPS).In order to further confirm that the protective effect of Spearmint oil on COPD inflammation and its mechanism,we use rat COPD model induced by intratracheal instillation of lipopolysaccharide(LPS) and passive smoking to study the Spearmint oil for the treatment of COPD and its mechanism.OBJECTIVE:To explore the pathogenesis of chronic obstructive pulmonary disease (COPD),to investigate the effect of Spearmint oil on airway inflammation and the expression of interleukin-8(IL-8)and CCR2 in rats with chronic obstructive pulmonary disease(COPD).METHODS:Eighty-six SD rats were randomly divided into seven groups:①control group;②COPD model group;③Spearmint oil 300 mg.kg^-1 group;④Spearmint oil 100 mg.kg^-1 group;⑤Spearmint oil 30 mg.kg^-1 group;⑥dexamethasone treatment group(0.01 mg.kg^-1).COPD model was induced by intratracheal instillation of lipopolysaccharide(LPS) and passive smoking for 12 weeks in rats,and COPD rats were treated with Spearmint oil for 4 weeks.Pathological changes in rat model of COPD,the different concentrations of methacholine(Mch)-induced airway resistance(R_L) and lung compliance(C_dyn) in rats,total and differential cell count in bronchoalveolar lavage fluid(BALF) were measured.The pathologic changes of lung tissue were observed by HE,AB-PAS and Masson staining,semi-quantitative score and morphological measurement and analysis of pathological images.IL-8 content in lung tissue was detected by ELISA and CCR2 expression in lung tissue was measured by immunohistochemistry.The effect of Spearmint oil on these changes was determined. Statistical software SPSS16.0 was used for all data analysis.RESULTS:(1) There were lots of infiltrating inflammation cells in the bronchial mucus and lung tissue,the destruction of the alveolar wall was observed,it was accorded with the COPD pathologic change.(2) In MCH 0.5,1.0,2.0,8.0 mg·mL^-1 stimulation,the airway resistances in COPD rats were significantly higher than those in controls(P＜0.05).In MCH 1.0 mg·mL^-1,the airway resistances in Spearmint oil 300 mg·mL^-1 were significantly lower than those in COPD group(P＜0.05).In Mch 2.0 mg·mL^-1,the lung compliances in COPD group were significantly higher than those in controls(P＜0.05),there wasn't significant difference between Spearmint oil group and COPD group(P＞0.05).(3) The leucocyte,including neutrophile,lymphocyte and macrophage numbers in BALF were significantly higher in COPD group than those in control group (P＜0.001),Spearmint oil 30,100 and 300 mg·kg^-1 group and dexamethasone treatment group were significantly lower than those in control group(P＜0.01). (4) The varying degree of bronchiolitis,pulmonary interstitial inflammation and inflammation cell infiltration were observed in COPD group.Spearmint oil 30, 100 and 300 mg·kg^-1 group attenuated bronchiolitis,pulmonary interstitial inflammation and reduced inflammation cell infiltration and significantly reduced the degree of pathology inflammation in lung tissue.(5) The thickness of collagen deposition in COPD group was significantly thicker than that of the control group(P＜0.001),Spearmint oil 300 mg·kg^-1 group significantly reduced the thickness of collagen deposition compared to COPD group(P＜0.001).(6) In COPD group,we observed that alveoli vary in size,alveolar structural disorder, alveolar wall thinning,varying degrees of tearing and integration into the bulla. Compared with the control group,the lung mean linear intercept(Lm) in COPD group significantly increased,mean alveolar number in unit area(MAN) significantly reduced,bronchiole wall thickness/diameter ratio significantly increased,bronchiole wall markedly thickened.Compared with COPD group, Spearmint oil 30,100 and 300 mg·kg^-1 group were significantly increased MAN, reduced alveolar damage;bronchiole wall thickness/diameter ratio was significantly lower,bronchiole wall significantly thinned.(7) Compared with control group,goblet cell of bronchus,bronchioles in COPD group significantly proliferated,goblet cell-positive%was significantly higher.Spearmint oil 30,100 and 300 mg·kg^-1 group and dexamethasone treatment group significantly reduced the goblet cell proliferation and goblet cell-positive%in COPD group.(8) ELISA analysis showed that IL-8 in lung homogenate of COPD group were significantly higher than that in control group(P＜0.001),IL-8 in Spearmint oil 300 and 100 mg·kg^-1 group was significantly lower than that in COPD group(P＜0.01); there wasn't significant difference between Spearmint oil 30 mg.kg^-1 group and COPD group(P＞0.05).(9) Immunohistochemical image analysis results showed that CCR2 expression in lung tissue of COPD group was significantly higher than that in control group(P＜0.01), CCR2 expression in Spearmint oil 300 mg·kg^-1 group was significantly lower than that in COPD group(P＜0.01),CCR2 expression in Spearmint oil 30,100mg·kg^-1 group and dexamethasone treatment group was significantly lower than that in COPD group(P＜0.001).(10) IL-8 in lung homogenate did not correlate with neutrophile.In model group,IL-8 in lung homogenate was inverse correlated with the gray of CCR2(r=-0.774, P＜0.05);in Spearmint oil 30,100 and 300 mg.kg^-1 group,IL-8 in lung homogenate was inverse correlated with the gray of CCR2(r=-0.668,P＜0.05;r=-0.867,P＜0.05; r=-0.732,P＜0.05).CONCLUSION:Spearmint oil has protective effect on lung injury in COPD rats,since it reduced pulmonary inflammation,attenuates bronchiolitis,pulmonary interstitial inflammation and reduces inflammation cell infiltration,airway resistances and collagen deposition,improves emphysema and inhibits goblet cell proliferation.The mechanism may include reducing IL-8 content and decreasing CCR2 expression in lung tissue.