Protective Effect And Mechanism Of Allicin On Airway Inflammation And Airway Remodeling In Asthmatic Mice

Objective:To explore the effect and mechanism of allicin on improving airway inflammation and airway remodeling in mice with bronchial asthma,and to provide a theoretical basis for the clinical application of allicin in the treatment of asthma.Methods:Twenty-four healthy female BALB/c mice were randomly divided into three groups:control group（Control group）,asthma model group（OVA group）and allicin intervention group（Allicin group）,with 8 mice in each group.The mice in OVA group and Allicin group were sensitized by intraperitoneal injection of 0.2 m L suspension of 100 ug ovalbumin（OVA）and1 mg aluminum hydroxide（Al₂OH₃）at 0,7 and 14 days,respectively,while mice in Control group were intraperitoneally injected with 0.2m L saline.From the 21st day of the experiment,mice in OVA group and Allicin group were put into a self-made atomization box,and 5%OVA atomization solution was given for continuous atomization excitation,once every other day,every time for30min,for 6 weeks,while mice in Control group were atomized with the same amount of normal saline.The mice in Allicin group were given allicin 20mg/kg intragastrically one hour before stimulation,and were anesthetized and killed by intraperitoneal injection of chloral hydrate within 24 hours after the last stimulation.The bronchoalveolar lavage fluid（BALF）of mice was taken for inflammatory cell count;The lung tissues of mice were stained with HE and Masson,and the pathological changes and airway remodeling were observed.The expression ofα-smooth muscle actin（α-SMA）in lung tissues was detected by immunohistochemistry.The expression levels of interleukin-4（IL-4）and interferon-γ（IFN-γ）in serum were detected by ELISA.The expression levels of TGF-β1,Smad2 and Smad7 in mouse lung tissue were detected by Western blotting method.Results:1.Symptoms of mice in each group:mice in Control group are active,with smooth hair and weight gain,without symptoms such as wheezing and dyspnea;After atomization stimulation,OVA group mice showed symptoms such as scratching ears and scratching nose,shortness of breath,abdominal muscle contraction,wheezing,etc.Some mice showed irritability,poor spirit after repeated stimulation,decreased diet and activity,messy and dull hair,and slow or even gradual decline in weight growth.In Allicin group,the symptoms of wheezing,scratching ears and scratching nose were mild,and there was no obvious weight loss after stimulation for 6 weeks.2.Inflammatory cells and cytokines:（1）The number of inflammatory cells in BALF:Compared with Control group,the total number of inflammatory cells,neutrophils and eosinophilia in BALF of OVA group were significantly higher（P<0.05）,which were 27.50±3.67 vs 2.75±1.91,6.63±1.06 vs 0.38±0.52,4.63±1.19 vs0.25±0.46,respectively.Compared with OVA group,the total number of inflammatory cells,neutrophils and eosinophils in BALF of mice in Allicin group were significantly lower（P<0.05）,which were 9.00±1.60 vs 27.50±3.67,1.63±0.92 vs 6.63±1.06,1.50±0.93 vs 4.63±1.19,respectively.（2）Serum cytokine level:Compared with Control group,the level of IL-4 in serum of OVA group was increased significantly（P<0.05）,which was 29.62±4.86 vs15.44±2.87,and the level of IFN-γdecreased significantly（P<0.05）,which was51.45±16.94 vs 108.68±19.37.Compared with OVA group,the level of IL-4 in serum of Allicin group decreased significantly（P<0.05）,which was 19.57±4.11vs 29.62±4.86,and the level of IFN-γincreased significantly（P<0.05）,which was 90.68±11.17 vs 51.45±16.94.3.Lung histopathology:In the Control group,the airway structure of mice was intact,with no obvious inflammatory infiltration and little mucus secretion.In OVA group,the airway epithelial cells of mice were necrotic and exfoliated,the lumen was narrow,a large number of inflammatory secretions were found in the lumen,some or even completely occluded,a large number of inflammatory cells infiltrated under the mucosa and around the blood vessels,and the airway smooth muscle was obviously thickened.The above airway pathological manifestations were obviously alleviated after intervention of allicin.Compared with Control group,the expression ofα-SMA in lung tissue of OVA group was significantly higher（P<0.05）,which was 2039.67±398.18 vs 785.63±120.75,while that of Allicin group was significantly lower than that of OVA group（P<0.05）,which was1352.79±145.79 vs 2039.67±398.18.4.Changes of signal pathway:Compared with Control group,the expression of TGF-β1 and Smad2 protein in lung tissue of OVA group was significantly higher（P<0.05）,which were 0.440±0.063 vs0.067±0.022,0.460±0.008 vs 0.069±0.010,respectively,while the expression of Smad7 protein was significantly lower,which was 0.168±0.025 vs0.625±0.004.Compared with OVA group,TGF-β1 and Smad2 protein levels in lung tissue of mice in Allicin group were significantly decreased（P<0.05）,which were 0.170±0.050 vs 0.440±0.063 and 0.177±0.018 vs 0.460±0.008,respectively,while Smad7 protein levels was significantly increased（P<0.05）,which was 0.454±0.027 vs 0.168±0.025.Conclusion:1.Allicin can reduce the infiltration of inflammatory cells in lung tissue of asthmatic mice,reduce the count of inflammatory cells in bronchoalveolar lavage fluid,especially the number of eosinophils,reduce the level of IL-4 in serum,and increase the level of IFN-γat the same time,indicating that allicin can inhibit airway inflammation in asthma.2.Allicin can reduce the expression level of TGF-β1 and Smad2 and increase the expression level of Smad7 in lung tissue to some extent,indicating that allicin can improve airway remodeling in asthmatic mice by regulating TGF-β1/Smads pathway.