Effect Of Simvastatin On Airway Inflammation, Vascular Endothelial Growth Factor And Its Receptors In Asthmatic Rat

Objective: To investigate the effect of simvastatin on airway inflammationand remodeling in asthma rats,and to explore the regulating role of simvastatinon airway inflammation,VEGF and VCGFR2.Methods: Forty cleaning SD rats (male, six weeks old, weights from130to150grams) were randomly divided into five groups: a control group, anasthma group,a S1group (simvastatin20mg/kg), a S2group (simvastatin40mg/kg) and a S3group(simvastatin60mg/kg). The asthma group rats weresensitized on the first day and the8th day with OVA(100mg) andAL(OH)3(100mg) by intraperitoneal injection. And then those rats werechallenged with inhaling atomization OVA(The concentration of OVA wasincreased from1%to1.5%,2%,2.5%,3%, every four times)in a not closetightly box from the fifteen day to the end. Rats were inhaled30minutes eachtime, every other day,20times altogether. S1,2,3group rats were givenintragastric adminstration with Simvastatin (20mg/kg,40mg/kg,60mg/kg)30minutes prior OVA atomization, the others were same as the asthmagroup.The control group rats used normal saline instead of OVA,the otherswas same with asthma model group.After24hours of last challeng,rats wereanesthesiaed by1%pentobarbitalin, and measured pulmonary function byanimal lung function meter. The number of total cells and eosinophils in theBALF were counted. Lung tissue was sliced and stained with HE. Theexpression of VEGF and VEGFR₂in lung tissues were observed byimmunohistochemistry combined with the micro-image analysis, and meanoptical density of VEGF and VEGFR₂were measured by image analysissoftware. The parameters such as vascular counts and thickness of airway wallwere measured by image analysis system. The level of IL-4, IFN-γ and VEGF in serum was measured by ELISA.Results:1,Result of pulmonary function observation:The basic peaks of airway pressure was not significantly different amongfive groups(P>0.05). The peaks of airway pressure reduced in asthma group,S1group S2group, S3group,the difference was statistically significant(P<0.05).But no significant diffrence in control group after injecting Ach(P<0.05).2,The number of total cells and eosinophils in BALF(×106/L):The asthma group (32.55±3.20,7.78±0.95)was the highest among the fivegroups.The control group(9.49±2.84,0.83±0.42) was lower than S1group(22.68±2.92,4.33±0.55), S2group(16.93±2.71,2.67±0.56), S3group(13.20±3.66,1.83±0.51). S1group was higher than S2group. S2group was higher S3group. The difference was statistically significant(P<0.05).3,Pathological findings:The obvious inflammatory cells infiltration,goblet cells proliferation,mucus excreted more and hyperplasia of vascular, smooth muscle,basementmembrane and airway wall thickeness can be found in the lung tissue ofasthmatic rats. After the treatment with simvastatin,the change of the abovementioned pathology character were decreased.4,The number of airway wall thickness and vascular counts were measured bythe image analysis:Asthma group(96.71±5.54,23.13±1.89) was the highest among the fivegroups (P<0.05).The control group(60.83±6.42,12.01±0.82) was lower thanthe S1group(86.57±6.79,18.50±0.93), S2group(78.32±2.69,16.83±0.98), S3group (69.08±7.02,15.17±0.75)(P<0.05), S1group was high-er than S2group.S2group was higher S3group. The difference was statistica-lly significant(P<0.05).5,The expression of VEGF and VEGFR₂in airway tissues were observed byimmunohistochemistry and the system of micro-image analysis.The average light density values of VEGF and VEGFR₂was used as statistic: Asthma group(0.37±0.02,0.41±0.02)was the highest among the fivegroups.The control group(0.19±0.04,0.20±0.02) was lower than the S1group(0.32±0.04,0.35±0.03), S2group(0.27±0.05,0.30±0.03), S3group (0.23±0.03,0.25±0.03). S1group was higher than S2group. S3group was higher S3group.The difference was statistically significant(P<0.05).6,The serum level of IL-4, VEGF and IFN-γ were measured by ELISA:The level of IL-4, VEGF: Asthma group(475.71±55.56,48.20±5.23)wasthe highest among the five groups. The control group(174.34±40.64,14.94±3.18)was lower than the S1group(362.91±37.59,37.25±4.20), S2group(284.62±34.15,30.27±2.91), S3group(225.18±26.92,22.77±3.54). S1group was higher than S2group. S2group was higher S3group. Thedifference was statistically significant(P<0.05).The level of IFN-γ: The asthma group(11.86±3.17) was the lowest amongthe five groups. The control group(51.26±8.59)was higher than the S1group(22.11±4.82), S2group(34.52±4.95), S3group(44.70±4.16), S1groupwas lower than S2group. S2group was lower S3group. The difference wasstatistically significant(P<0.05).7,Result of correlation analysis:There was a significant positive correlation between airway wall thicknessand vascular counts (r=0.893,P<0.01), was a significant negatively correlationbetween the level of IL-4and IFN–γ(r=-0.867,P<0.01).In asthma group theprotein expressin of VEGF were positively correlation with that ofVEGFR₂,vascular counts, airway wall thickness, the level of IL-4inserum(r=0.859,P<0.01;r=0.852,P<0.01; r=0.858, P<0.01;r=0.824,P<0.01),andwas negatively correlation with that of the level of IFN–γ inserum(r=-0.866,P<0.05).Conclusion:1,We Succesfully to created the asthmatic model of rats by sensitized withovalbumin and aluminum hydroxide, and challenged with repeated exposureto aerosolized ovalbumin.2,The concentration of VEGF in serum of asthma group rats was significantly higher than that of control group rats,as well as the protein expression ofVEGF and VEGFR₂in asthma group rats have a significantly increased. Thelung tissue expression of VEGF were positive correlation with VEGFR₂,airway wall thickness and IL-4. It was indicated that it was interactionbetween VEGF and asthma inflammation factors. And VEGF involved inairway inflammation and airway remodeling.3, Simvastatin can modulate asthma airway resistance, reduce airwayinflammation, regulating Th1/Th2imbalance by elevating levels of IFN-γ andreducing the IL-4.4, Simvastatin can inhibit asthma airway inflammation and airwayremodeling by suppressing VEGF and VEGFR₂expression levels.5,It was indicated that the effect of simvastatin on asthma is associated withthe dose.