Abstract: Objective To study the protective effect of housefly maggot chitosan(HMC)on the damage of brain microvascular endotheliocyte induced by H₂O₂ in vitro.Methods Normal cells,damaged cells induced by H₂O₂ were cultured in modified minimal essential medium(DMEM),together with different doses of HMC.The survival rates of the cells were tested with 3-(4,5 dimethythiazol-2-yl)-2,5 diphenyl-tetrazolium bromide(MTT)assay.Vasoactive substance contents such as nitric oxide(NO)and endothelin(ET)in cell culture fluid were tested with biochemistry and radioimmunity method.In addition,superoxide dismutase(SOD)and malonodialdehyde(MDA)contents in culture fluid of H₂O₂ damaged cells were detected with biochemistry method.Results In MTT experiment,A values for cell survival rate of moderate and high dose HMC+hydrogen peroxide groups were 0.714 0±0.059 5 and 0.811 9±0.059 7,which were higher than that of hydrogen peroxide treated groups(P<0.01).In all HMC+hydrogen peroxide groups,SOD levels were 14.76±1.59, 16.99±1.69,and 19.22±2.31NU/mL,respectively,which were higher than those of hydrogen peroxide treated groups (P<0.05,P<0.01).In all HMC+hydrogen peroxide groups,MDA levels were 10.11±1.91,8.23±1.64,and 6.74±1.26 nmol/L,respectively,which were lower than that of hydrogen peroxide treated groups(P<0.01).NO levels were higher (P<0.05,P<0.01)and ET contents were lower(P<0.01)than those of H₂O₂ treated group(P<0.01).Conclusion HMC could protect vascular endothelial cell and could elevate cell survival rate,promote the releasing of NO from damaged cell induced by H₂O₂,restrain the releasing of ET,preserve the structural and functional integrity of the cell.HMC could activate SOD,enhance its anti-oxidation effect.