Role Of Antioxidant Peptide SS31 In The Ozone Exposure OVA Sensitization And Challenge Mouse Model

Background and ObjectiveThere is increasing evidence of the negative health impact resulting from ozone,an important constituent of environmental pollution,in particular that associated with asthma and other respiratory diseases.A causative relationship between single acute ozone exposure and an airway neutrophilia with bronchial hyperresponsiveness(AHR)associated with increased airway smooth muscle contractility has been proved in rodents.Compared to non-asthmatics,asthmatics have increased susceptibility to the adverse effects of ozone.Therefore,further extensive and more comprehensive ozone studies performing with asthmatic animal models are needed.Oxidative stress-related mechanisms play an important role in ozone-induced effects in asthma,which include airway inflammation,smooth muscle cells contraction and AHR.Szeto-Schiller(SS)-31 is a novel antioxidant selectively targeting cardiolipin on the inner mitochondrial membrane.SS31 serves to inhibit lipid peroxidation caused by ROS and alter membrane properties,which will improve mitochondrial bioenergetics to protect cells from oxidative stress.The purpose of this study is:(1)to explore the influence of ozone exposure on airway/lung inflammation,AHR and airway hypersecretion in Ovalbumin(OVA)sensitized/challenged asthmatic mouse model;and(2)explore the ability of SS31 to protect against ozone repeated exposure induced deleterious effects.MethodsOVA sensitization was performing by intraperitoneal(i.p.)injection.Ozone exposures(2ppm or 3ppm for 3hours)were given one hour.after OVA challenges(once every other day,4times).Lung function,Liu’s staining of BALF cell smear,hematoxylin-eosin(HE)staining and Periodic Acid-Schiff stain(PAS)staining of lung were performed and analyzed.Then,the mice were randomly divided into saline-treated groups and SS31-treated groups.Before each OVA challenges,the mice were given i.p.injection of SS31 or saline.ELISA analyses were performed for proinflammatory cytokines(interleukin,IL;IL-1ɑ,IL-4,IL-13 and IL-18)and8-hydroxy-2’-deoxyguanosine(8-OHdG).superoxide dismutase(SOD)activity,the levels of reduced glutathione(GSH)and malondialdehyde(MDA)were colorimetrically estimated.ResultRepeat ozone exposures down-regulated the airway resistance of mice undergoing OVA sensitization and challenge,which did not mean improvement of asthma since inflammation in BALF and lung was increased.In addition,epithelial hypersecretion,structural changes including subepithelial and airway wall fibrosis,alveolar destruction,smooth muscle thickening and vascularity were observed.IL-1ɑ,IL-4,and IL-13 were elevated.8-OHdG and MDA increased in BALF,since GSH concentration decreased and SOD activity was inhibited.No influence of SS31 occurred in control group for airway inflammation,AHR,lung inflammation,epithelial secretion,and oxidative stress.For mice undergoing ozone exposure and OVA sensitization and challenge,SS31 i.p.injection suppressed airway neutrophilic and eosinophilic inflammation,improved airway epithelial hypersecretion,reduced eosinophils infiltration in lung,and down-regulated the levels of IL-1α,IL-4 and IL-13.8-OHdG and MDA decreased in BALF.GSH increased and SOD activity was up-regulated in lung.ConclusionFor mice undergoing ozone exposure and OVA sensitization and challenge,AHR is not an accurate indicator of the severity of asthma or the effect of therapeutic intervention.Attention should be focused on the airway/lung inflammation andbronchial epithelial hypersecretio.Mitochondia-targeted peptide SS31 protects the asthmatic mouse from the sustained ozone-induced oxidative stress.The protective effect is served to inhibit airway inflammation and epithelial hypersecretion.