关键词: 巴西日圆线虫, 抗炎作用, 黏膜修复, 溃疡性结肠炎, 炎症性肠病, 小鼠

Abstract: Objective　To investigate the alleviation of Nippostrongylus brasiliensis infection on dextran sulfate sodium salt (DSS)⁃induced ulcerative colitis in mice, and to explore the underlying mechanism. Methods　Thirty male C57BL/6J mice of the SPF grade, each weighing approximately 25 g, were randomly divided into three groups, including the blank control group (NC group), DSS modeling group (DSS group), and N. brasiliensis treatment group (Nb + DSS group), of 10 mice in each group. Mice in the DSS group were orally administered with 3.5% DSS daily since day 1 (D0) for 6 successive days, and given normal drinking water since D6, and animals in the Nb + DSS group were subcutaneously injected with the third⁃stage larvae of N. brasiliensis at a dose of 500 larvae per mice 5 days prior to D0, followed by oral administration with 3.5% DSS daily since D0 for 6 successive days and normal drinking water since D6, while mice in the NC group were given normal drinking water. Mouse body weight and stool were observed and the disease activity index (DAI) was scored in each group during the study period. All mice were sacrificed on D9. The mouse colon length was measured, and mouse colon specimens were subjected to hematoxylin⁃eosin (HE) staining and histopathological scoring. In addition, the mRNA and protein expression of interleukin (IL)⁃1β and IL⁃10 was quantified in mouse colon specimens using quantitative fluorescent real⁃time PCR (qPCR) assay and enzyme⁃linked immunosorbent assay (ELISA), and the mRNA and protein expression of mucosal repair⁃associated molecules zonula occludens⁃1 (ZO⁃1), mucin 2 (MUC2) and claudin⁃1 was detected in mouse colon specimens using qPCR assay and immunofluorescence assay. Results　The mice body weights, DAI scores and colon lengths were (26.26 ± 1.93), (22.39 ± 1.65), (25.00 ± 1.58) g (F = 8.06, P < 0.01); (1.89 ± 0.34), (0.47 ± 0.39), 0 points (F = 57.61, P < 0.000 1); and (42.50 ± 5.75), (56.20 ± 5.96) mm and (61.17 ± 7.88) mm (F = 13.72, P < 0.001) in the NC, DSS and Nb + DSS groups on D9, respectively, and elevated mouse body weight (P < 0.05), reduced DAI score (P < 0.000 1) and increased colon length (P < 0.01) were observed in the Nb + DSS group relative to the DSS group on D9. Pathological examinations showed that the colonic crypts were relatively intact and the inflammatory cell infiltration was lower in the mouse colon specimens in the Nb + DSS group than in DSS the group. There was a significant difference in the histopathological scores of mouse colon specimens among the NC group (0 point), the DSS group [(2.00 ± 1.22) points] and the Nb + DSS group [(0.20 ± 0.45) points] (F = 10.71, P < 0.01), respectively, and the histopathological score of mouse colon specimens was significantly higher in the DSS group than in the NC and Nb + DSS groups (both P values < 0.01). qPCR assay quantified that the relative IL⁃10 and IL⁃1β mRNA expression was 1.25 ± 0.08, 0.44 ± 0.14 and 1.30 ± 0.45 (F = 10.66, P < 0.01), and 0.22 ± 0.13, 1.14 ± 0.31 and 0.41 ± 0.19 (F = 16.89, P < 0.001) in mouse colon specimens in the NC, DSS and Nb + DSS groups, respectively, and higher IL⁃10 mRNA expression and lower IL⁃1β mRNA expression were found in mouse colon specimens in the Nb + DSS group than in the DSS group (both P values < 0.01). The relative MUC2, claudin⁃1 and ZO⁃1 mRNA expression was 0.87 ± 0.25, 0.34 ± 0.26 and 4.21 ± 0.55 (F = 121.60, P < 0.000 1), 1.05 ± 0.41, 0.16 ± 0.09 and 0.22 ± 0.11 (F = 14.00, P < 0.01), and 1.03 ± 0.10, 0.60 ± 0.11 and 1.64 ± 0.28 (F = 32.16, P < 0.000 1) in mouse colon specimens in the NC, DSS and Nb + DSS groups, respectively, and significantly higher MUC2 and ZO⁃1 mRNA expression was quantified in mouse colon specimens in the Nb + DSS group than in the DSS group (both P values < 0.05). The mean fluorescence intensities of ZO⁃1 and claudin⁃1 were 17.18 ± 2.08, 12.38 ± 1.21 and 18.06 ± 2.59 (F = 8.95, P < 0.01) and 13.50 ± 1.63, 9.66 ± 2.03 and 13.61 ± 0.97 (F = 6.96, P < 0.05) in mouse colon specimens in the NC, DSS and Nb + DSS groups, respectively, and the mean fluorescence intensities of ZO⁃1 and claudin⁃1 were significantly greater in mouse colon specimens in the Nb + DSS group than in the DSS group (both P values < 0.05).  Conclusion　N. brasiliensis infection may remarkably alleviate DSS⁃induced ulcerative colitis in mice through promoting expression of anti⁃inflammatory cytokines, inhibiting expression of pro⁃inflammatory cytokines and facilitating mucosal repair in colon tissues.

Key words: ippostrongylus brasiliensis, Anti?inflammatory effect, Mucosal repair, Ulcerative colitis, Inflammatory bowel disease, Mouse