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Studying lactobacillus with different anti-oxidation capacity in vitro inhibiting mucosal oxidative stress and barrier dysfunction of colon in dextran sulfate sodium-induced colitic mice in order to provide a theoretical basis for the practical application of lactobacillus.Determining the scavenging rates of 9 lactobacillus to DPPH , OH·and O2-·after different pretreatment （ aritificial gastric juice and pancreatic juice , pH3.5 buffer , pH4 buffer ） in vitro. To evaluate the resistance of 9 lactobacillus to ROS, their survival in the presence of 1 mmol/L hydrogen peroxide, 0.4 mmol/L hydroxyl radicals and superoxide anions induced by paraquat was tested. The model of DSS-induced colitic was used to study the anti-oxidation capacity of lactobacillus in vivo. Sixty-three mice were randomly divided into 7 groups.Control group,and DSS group drank pure water. The rest four groups drank bacteria suspension of L. plantarum Fn008, L. casei Fn012, L. acidophilus Fn022, L. sakei Fn034, L. acidophilus Fn037. Seven days later, control group drank pure water as before. The rest six groups drank 3% DSS solution for 7 days. Body weight loss, stool consistency, and rectal bleeding were measured everyday. Oxidation-related indicators （ ROS, T-AOC, MDA, GSH ） were determined. Mucosal barrier function-related indicators （ D- xylose in serum, endotoxin in liver, mesenteric lymph node and Peyer‘s patches, expression of tight junction genes ZO-1,ZO-2, Occludin、Claudin1）were sdudied. Mucosal inflammation was evaluated by MPO in colon and IL-10, IL-8, TNF-αsecreted by ileum macrophage. Colon flora was also analysed.After incubating with aritificial gastric juice and pancreatic juice , pH3.5 buffer and pH4 buffer , the scavenging rates of lactobacillus to DPPH were lower than nomal and the scavenging rates of lactobacillus to OH·were higher than nomal. After incubating with aritificial gastric juice and pancreatic juice the scavenging rates of lactobacillus to O2-·were higher than nomal. In vivo compared with Control group, the DAI of DSS group was higher , DSS did induce oxidative stress, enhanced the level of free radicals in colon content and MDA of colon significantly, decrease the antioxidant activity and counts of lactobacillus in colon , increase the counts of enterococci and E.coli significantly,increase the transposition of endotoxin due to enhanced permeability of colon mucosa . IL-10 in supernate of culturing ileum macrophage in vitro was lower than Control group, TNF-αand IL-8 higher.The expression of tight junction genes ZO-1, ZO-2, Occludin, Claudin1 was significantly lower than Control group. But the DAI of lactobacillus-intervened groups were lower significantly than DSS group. L. plantarum Fn008+DSS group and L. acidophilus Fn037 +DSS group could decrease the level of free radicals colon content significantly, increase the antioxidant activity and counts of lactobacillus in colon, decrease the counts of enterococci and E.coli significantly,suppress the transposition of endotoxin . IL-10 in supernate of culturing ileum macrophage in vitro was higher than DSS group, TNF-αand IL-8 lower. The expression of tight junction genes ZO-1, ZO-2, Occludin, Claudin 1 was significantly higher than DSS group. The resistance of lactobacillus to H2O2 was correlated with DAI （r=0.898 ,P=0.038） ,ROS of colon chime （r=-0.927,P<0.0001）,MPO and MDA of colon （ r=-0.722,P=0.000;r=-0.903,P=0.000）. The resistance of lactobacillus to H2O2 and OH·was correlated with mucosa permeability（r=-0.955,P=0.011;r=-0.910, P=0.018） and the counts of enterococci （r=-0.92,P=0.025;r=-0.902,P=0.0361）.After induced by DSS, ROS, the counts of enterococci and E.coli in colon chime increased, T-AOC and the counts of lactobacillus decreased. The resistance of lactobacillus to H2O2 was correlated with preventing colitis, reducing ROS and maintaining mucosa permeability. Fn008 and Fn037 with stronger resistance to H2O2 and OH·could significantly restrain oxidative stress, injury of mucosa barrier and colitis induced by DSS.
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