Objective To investigate the relationship between the expression of NOD-like receptor protein 3 (NLRP3) inflammasome in colonic mucosal tissues of ulcerative colitis (UC) patients and UC mice model and the activity of UC.Methods From December 2016 to January 2018,at Department of Gastroenterology,the First Affiliated Hospital of Zhejiang Traditional Chinese Medicine University,60 patients with UC were recruited,of which 15 cases at remission phase,15 cases at mild activity phase,and 15 cases at moderate activity phase,and 15 cases at severe activity phase;and 15 healthy subjects were selected as healthy control group.UC mice models were established by dextran sulfate sodium (DSS).Forty-eight BALB/c mice were divided into 2.5％ DSS group,5.0％ DSS group and 7.5％ DSS group and control group.The colon tissues of UC patients and UC mice models were pathologically scored.The expression of NLRP3,cysteinyl aspartate specific proteinase 1 (caspase-1) and apoptosis-associated speck-like protein containing CARD (ASC)at mRNA level in colon tissues of UC patients and UC mice models were determined by real time fluorescence quantitative polymerase chain reaction (PCR).The expression of NLRP3,caspase-1 and ASC at protein level in colon tissues of UC patients and UC mice models were detected by Western blotting.One-way analysis of variance and SNK-t test were performed for statistical analysis.Results The histopathological scores of colon tissues of UC patients at remission phase,at mild activity phase,at moderate activity phase,at severe activity phase and healthy controls were 2.37 ± 0.46,4.84 ± 1.29,6.82 ± 0.96,9.42 ± 1.13 and 1.23 ± 0.55,respectively;the differences were statistically significant (F =67.68,P ＜ 0.01).The higher the degree of inflammation,the higher the pathological score,and the differences were statistically significant (all P ＜ 0.05).The pathological scores of colon tissues of mice in the 2.5％ DSS group,5.0％ DSS group and 7.5％ DSS group were 4.54±0.74,6.02± 1.00 and 8.43 ± 1.46,respectively;the higher the dose of DSS,the higher the pathological score,and the differences were statistically significant (all P ＜ 0.05).The expression of NLRP3 at mRNA level of UC at remission phase,mild activity phase,moderate activity phase,severe activity phase and healthy controls were 1.15 ±0.10,1.49 ±0.13,2.00±0.25,2.05 ±0.33 and 0.61 ±0.09,respectively;the expression ofcaspase-1 at mRNA level were 1.13 ±0.08,1.51 ±0.19,2.10 ±0.23,2.88 ±0.33 and 0.61 ±0.11,respectively;the expression of ASC at mRNA level were 1.12 ± 0.08,1.88 ± 0.33,2.53 ± 0.22,3.20 ± 0.24 and 0.59 ± 0.12,respectively;the differences between groups were statistically significant (F =108.43,63.25 and 105.25,all P ＜ 0.01).The higher the degree of inflammation,the higher the mRNAexpression levels of NLRP3,caspase-1 and ASC,and the differences were statistically significant (all P ＜0.01).The higher the dose of DSS,the higher the protein expression levels of NLRP3,caspase-1 and ASC at mRNA level.The higher the degree of inflammation,the higher expression of NLRP3,caspase-1 and ASC in colon tissues of UC patients.The higher dose of DSS,the higher the protein expression levels of NLRP3,caspase-1 and ASC in colon tissues of mice.Conclusions The expression level of NLRP3 inflammasome is different in different stages of UC,the higher degree of inflammatory activity,the higher the expressie level.It is helpful to evaluate the activity of UC by detecting the expression level of NLRP3 inflammasome.