Effect of Buzhong Yiqiwan on NLRP3 Inflammasome Pathway of DSS-induced Colitis Model Mice at Different Pathological Stages / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo explore the intervention effect and mechanism of Buzhong Yiqiwan （BZYQ） on colitis mice. MethodSixty-four C57BL/6 mice were randomly divided into 2 weeks blank group， 2 weeks model group， 2 weeks high-dose BZYQ （12 g·kg-1） group， 2 weeks low-dose BZYQ （6 g·kg-1） group， 4 weeks blank group， 4 weeks model group， 4 weeks high-dose BZYQ （12 g·kg-1） group， and 4 weeks low-dose BZYQ （6 g·kg-1） group. The colitis model was induced in mice by feeding 3% dextran sodium sulfate （DSS） for 7 days. The mice received BZYQ （12 and 6 g·kg-1） by gavage on the 8th day after modeling， once per day， and sacrificed on the 2nd and 4th weeks， correspondingly. The colon length and weight of mice in each group were measured. Hematoxylin-eosin （HE） staining was used for pathological observation and colonic mucosal inflammation was scored. The mRNA and protein expression of NOD-like receptor thermoprotein domain 3 （NLRP3）， apoptosis-associated speck-like protein containing a CARD （ASC）， and cysteinyl aspartate-specific protease-1 （Caspase-1） was detected by real-time quantitative polymerase chain reaction （Real-time PCR） and Western blot， respectively. Enzyme-linked immunosorbent assay （ELISA） was used to detect the content of inflammatory cytokines， such as interleukin （IL）-1β， IL-18， and IL-33 in colonic tissues. ResultCompared with the 2 weeks blank group， the 2 weeks model group showed shortened colon length， increased colon weight （P<0.05）， loss of epithelial cells， destruction of gland structure， infiltration of a large number of inflammatory cells in mucosa and submucosa， local crypt abscess， and increase in mucosal inflammation score （P<0.01） as revealed by light microscopy， elevated levels of IL-1β， IL-18， and IL-33 in colonic tissues （P<0.05）， and increased mRNA and protein expression of NLRP3， ASC， and Caspase-1 （P<0.05）. The intervention of BZYQ （12 g·kg-1） restored colon length， alleviated mucosal injury （P<0.05）， down-regulated the content of IL-18 （P<0.05）， reduced the mRNA expression of NLRP3 and ASC as well as the protein expression of ASC and Caspase-1 compared with the conditions in the 2 weeks model group. Compared with the 4 weeks blank group， the 4 weeks model group showed decreased colon length， increased colon weight （P<0.05）， decreased glands in the mucosal layer， expansion of glandular cavity， atrophy of crypt， local connective tissue hyperplasia and lymphocyte infiltration， increased inflammation score （P<0.01） as revealed by the light microscopy， increased expression of IL-1β， IL-18， and IL-33 （P<0.05）， and elevated mRNA and expression of NLRP3 inflammasome complex （P<0.05）. Compared with the conditions in the 4 weeks model group， the intervention of BZYQ （12 and 6 g·kg-1） could improve colon length and weight （P<0.05）， and the intervention of BZYQ （12 g·kg-1） could also improve the inflammation score of the colon （P<0.05）. Different from the acute stage， the intervention of BZYQ （12 and 6 g·kg-1） increased the content of IL-33 in the intestinal mucosa and up-regulated the mRNA and protein expression of NLRP3 inflammasome complexes ASC and Caspase-1 （P<0.05）. ConclusionBZYQ can relieve the injury of colitis induced by DSS in mice. The mechanism is related to the regulation of intestinal immune response mediated by NLRP3 inflammasome， and it has different regulatory effects in acute and chronic inflammation stages.