Apolipoprotein E(ApoE)alleviates Murine Allergic Airway Inflammation Via Suppressing The Activation Of NLRP3 Inflammasome And Oxidative Stress

BackgroundAs a chronic airway inflammatory disease,bronchial asthma exists in every age group of human beings.It not only seriously affects our normal work and life,but also brings heavy burden to many families and society.At present,glucocorticoids are the first-line drugs for the treatment of asthma,but glucocorticoids have no effect on many patients or the effect is very weak,so it is necessary to find new targets or mechanisms for the treatment of asthma.Activation of NLRP3 inflammasome can induce or aggravate airway inflammation in asthma.Apo E has been reported as a steroid-nonresponsive gene and as a negative regulator of AHR and goblet cell proliferation in dust mite-challenged mice.ROS and RNS have effects on airway inflammation and are determinants of disease severity.Antioxidant therapy has been shown to be effective in both asthmatic patients and asthma murine models.In asthmatic alveolar macrophages,Apo E plays a role by activating NLRP3 inflammasome and secreting IL-1β.However,whether Apo E can regulate the activity of NLRP3inflammasomes and oxidative stress remains unclear,and the role of Apo E in ovalbumin（OVA）-induced allergic airway inflammation and its mechanism remain unclear.Objectives:To investigate the role of Apo E in OVA induced allergic airway inflammation,and reveal whether the activation of NLRP3 inflammasome and oxidative stress represented a mechanism underlying the effect of Apo E.Methods:Female wild-type（WT）C57BL/6 mice and Apo E^-/-mice were maintained on C57BL/6 background.Mice were randomly divided into four groups:Blank group,Apo E^-/-group,OVA group,and Apo E^-/-OVA model group.Wright-Giemsa staining was used for differential cell counts including eosinophil,lymphocyte,neutrophil and monocyte in a blind manner.Inflammatory cell infiltration and goblet cell proliferation were detected by Hematoxylin-Eosin（H&E）staining and Periodate scheffer staining（PAS）staining,respectively.NLRP inflammatory body markers in lung tissues were detected by protein imprinting method:NLRP3,caspase-1（p20）,IL-1β（p17）;Oxidative stress markers:Nitrotyrosine,SOD2,8-OHd G;Mitochondrial division and fusion markers:Fis1,OPA1,Mfn2,DRP1 and internal reference:GAPDH;Serum total OVA specific Ig E level was determined by ELISA.The levels of 8-OHd G,Nitrotyrosine and SOD2 in lung tissues were detected by immunohistochemistry.Results:（1）The total number of leukocytes,eosinophils,lymphocytes,monocytes,neutrophils and serum total Ig E in the Apo E^-/-group were not significantly different from those in the blank group（P>0.05）.NLRP3,caspase-1（p20）,IL-1β（p17）had no significant difference compared with the blank group（P>0.05）.Nitrotyrosine,SOD2,8-OHd G had no significant difference compared with blank group（P>0.05）.There were no significant differences in the levels of OPA1,Mfn2,DRP1 and Fis1 compared with the blank group（P>0.05）,and the differences were not statistically significant.（2）Compared with the blank group,the total number of leucocytes,eosinophils,lymphocytes,monocytes,neutrophils and serum total Ig E in OVA group were significantly increased（P<0.01）.The levels of NLRP3 and IL-1β（p17）were significantly increased（P<0.01）;The levels of Nitrotyrosine,SOD2 and 8-OHd G were significantly increased（P<0.01）;The levels of OPA1,Mfn2,DRP1 and Fis1 were significantly increased（P<0.01）;The level of caspase-1（P20）was increased（P<0.05）;The differences were statistically significant.（3）Compared with the Apo E^-/-group,the total number of leucocytes,eosinophils,lymphocytes,monocytes,neutrophils and serum total Ig E levels in Apo E^-/-OVA group were significantly increased（P<0.01）.The levels of NLRP3 and IL-1β（p17）were significantly increased（P<0.01）;The levels of Nitrotyrosine,SOD2 and 8-OHd G were significantly increased（P<0.01）;The levels of OPA1,Mfn2,DRP1and Fis1 were significantly increased（P<0.01）,and the level of Caspase-1（P20）was significantly increased（P<0.05）;The differences were statistically significant.（4）Compared with the OVA group,the total number of leucocytes,eosinophils,lymphocytes,monocytes,neutrophils and serum total Ig E levels in the Apo E^-/-OVA group were significantly increased（P<0.01）;The levels of NLRP3and IL-1β（p17）were significantly increased（P<0.01）;The levels of Nitrotyrosine,SOD2 and 8-OHd G were significantly increased（P<0.01）;The levels of OPA1,Mfn2,DRP1and Fis1 were significantly increased（P<0.01）;The level of caspase-1（P20）increased（P<0.05）,and the differences were statistically significant.Conclusions:Apolipoprotein E is involved in the regulation of NLRP3 inflammasome activation and oxidative stress,thereby regulating OVA-induced allergic airway inflammation.