Objective:To investigate the effects of adherent-invasive Escherichia coli ( E. coli) LF82 on the structure and function of intestinal barrier in mice with ulcerative colitis (UC). Methods:Twenty-four specific pathogen free (SPF) C57BL/6 mice were divided into UC with E. coli LF82 group, UC group and healthy control group with eight mice in each group. The UC mice model was induced by dextran sulfate sodium (DSS). One week before modeling, the mice of UC with E. coli LF82 group were intragastric administrated with 1×10 9 colony-forming unit (CFU) E. coli LF82 to colonize the bacteria strain. The effects of E. coli LF82 on colitis of mice with UC were evaluated by disease activity index (DAI), gross morphological injury score, colonic mucosal injury index (CMDI), myeoloperoxidase (MPO) activity and pathological features. The ultrastructure and the changes of cytoskeleton F-actin of mice colonic tissues were detected by transmission electron microscope (TEM) and direct immunofluorescence. The ability of colonic mucin production and degree of fibrosis were estimated by periodic acid Schiff reaction (PAS) stain and sirius red stain. T test, least significant difference, repeated measurement analysis of variance and one-way analysis of variance were used for statistical analysis. Results:On the fourth, fifth, sixth and seventh day after the modeling, the DAI scores of UC with E. coli LF82 group were all higher than those of UC group ((2.53±0.38) points vs. (2.01±0.53) points, (3.02±0.62) points vs. (2.67±0.24) points, (3.13±0.61) points vs. (2.20±0.24) points, (3.27±0.28) points vs. (2.20±0.69) points, respectively), and the differences were statistically significant ( t=3.37, 2.25, 9.56 and 10.24, all P<0.05). The gross morphological injury score of mice colon of UC with E. coli LF82 group was higher than that of UC group ((6.17±1.94) points vs. (2.83±0.98) points), and the difference was statistically significant ( t=-3.75, P<0.05). The CMDI and MPO activity of UC with E. coli LF82 group were both higher than those of UC group ((16.80±2.79) points vs. (11.80±3.11) points, (729.3±77.5) U/mg vs. (594.4±31.9) U/mg), and the differences were statistically significant ( t=-2.83; mean difference=134.82, 95% confidence interval ( CI) 72.12 to 197.51; both P<0.05). The results of TEM showed that the E. coli LF82 could invade the submucosa of colon and caused further injury of colonic tissues in mice. The distribution of cytoskeleton F-actin of mice colonic tissues changed. The results of PAS staining showed that the percentages of PAS positive cells of UC with E. coli LF82 group and UC group were both lower than that of healthy control group ((32.40±8.02)% and (41.90±8.99)% vs. (57.70±11.52)%), and the difference was statistically significant ( F=17.63, P<0.01). The percentage of PAS positive cells of UC with E. coli LF82 group was lower than that of UC group, and the difference was statistically significant (mean difference=-9.50, 95% CI -18.33 to -0.67, P<0.05). The results of sirius red staining showed that the villous epithelium of colon mucosa of UC with E. coli LF82 group was partially injured and collagen fibers hyperplasia was serious. The area ratios of collagen fiber of UC with E. coli LF82 group and UC group were both higher than that of healthy control group ((51.83±5.78)% and (37.11±5.59)% vs. (15.41±2.25) %), and the difference was statistically significant ( F=86.72, P<0.01). The area ratio of collagen fiber of UC with E. coli LF82 group was higher than that of UC group, the difference was statistically significant (mean difference=14.83, 95% CI 8.91 to 20.76, P<0.05). Conclusions:E. coli LF82 can aggravate DSS-induced colitis in UC mice, leading to changes in colon ultrastructure and cytoskeleton, it can also reduce the ability of mucus secretion of colon of mice and increase the degree of colonic tissues fibrosis.

【Objective】 To investigate the expressions of NLRP1 and NLRP3 in the colon of ulcerative colitis (UC) patients and analyze the correlation of the expressions with severity of UC, endoscopic manifestations and related laboratory indicators. 【Methods】 We collected biopsical specimens obtained with colonoscopy in 46 patients with UC (22 mild cases and 24 moderate to severe cases) and 20 cases of normal control group. We used the disease activity index to evaluate the Mayo UC inflammatory activity and immunohistochemical method to detect the protein expression levels of intestinal mucosal NLRP1 and NLRP3 in the tissue. RT-PCR was used to detect the expressions of NLRP1 and NLRP3 mRNA in intestinal mucosal tissues. Meanwhile, the colonoscopy, serum uric acid, C-reactive protein, serum sedimentation rate, platelet count, low-density lipoprotein, and cholesterol of UC patients were also counted to further analyze the relationship between NLRP1 and NLRP3. 【Results】 The expressions of NLRP1 and NLRP3 protein and mRNA in colonic mucosal tissues of UC patients were significantly higher than those of normal controls (P<0.05). Compared with that in mild UC, the expression of NLRP1 in colonic mucosal tissues of moderate and severe UC patients was significantly increased (P<0.05). There was no significant difference in the expressions of NLRP1 and NLRP3 in colonic mucosal tissues of UC patients with different lesion ranges. NLRP1 expression was positively correlated with Mayo overall score, Mayo endoscopic score, erythrocyte sedimentation rate, and C-reactive protein (P<0.05), NLRP3 expression was positively correlated with C-reactive protein (P<0.05), but not correlated with Mayo overall score, Mayo endoscopic score, or erythrocyte sedimentation rate. NLRP1 expression was positively correlated with low-density lipoprotein and platelet (P<0.05), but not with uric acid or cholesterol. NLRP3 was positively correlated with low-density lipoprotein, uric acid and cholesterol (P<0.05), but not with platelet. 【Conclusion】 NLRP1 and NLRP3 may be involved in the pathogenesis of UC and related to disease activity. Therefore, they can be used as molecular targets for targeted therapy, and NLRP1 can be used as a predictor of mucosal healing.