Objective To explor the antioxidant effects of heme oxygenase-1(HO-1) for asthma and its mechanism.Methods Thirty two months old healthy male guinea pigs were randomly assigned to 3 groups,all of them were feed under the same management condition.Asthmatic group,refering to Huston′s research results,were sensitized by exposure to aerosolized ovalbumin(OVA) in order to build the guinea pig modle of asthma.Dexamethasone group(DG),were also sensitized by exposur to aerosolized ovalbumin as well as the asthmatic group had done and then treated with dexamethasone.Normal control group(NCG):were treated with 0.9% sterile sodium chloride.All the tested animals were measured the activity of lung HO-1,levels of malondialdehyde (MDA) in the lung tissue or serum and bilirubin in the serum by spectrophotometry.And the pathology and expression of HO-1protein in the lung tissue were observed.Results In the OVA induced asthmatic group,the HO-1 activity and level of MDA in lung tissue or serum were markedly increased compared with the groups of NCG and DG (P<0.01) and the expression of lung HO-1 protein was as 3~4 grade.While level of bilirubin was markedly reduced compared with NCG and DG.For example,in asthmatic group,the activity of lung HO-1 was,the level of bilirubin formed,(901.12±321.53)pmol/(mg MDA was(69.38±7.49)nmol/mg protein,and the level of bilirubin in serum was (0.54±0.23)pmol/L.In DG,the data of HO-1 and MDA as described above were markedly reduced compared with the OVA induced asthmatic group(P<0.01),and lung protein expression was 1~2 grade,while the level of bilirubin in the serum was increased(P<0.01).But,all datas of DG had no significant difference compared with NCG(P>0.05).Conclusion The guinea pigs′ in vivo lipid peroxide level increases and the level of bilirubin,an antioxidant,markedly decrease during asthma attacks,which induce the imbalance of oxidant and antioxidant.Content level and activity of HO-1 protein can increase in asthma body in order to compensate the reduce of bilirubin level,regulate the imbalance of oxidant and antioxidant,protect lung tissues from oxidizing reaction damage and relieve allergy or asthma symptoms.