ObjectiveTo evaluate and analyze the syndrome characteristics of Qi and Yin deficiency accompanied by Qi stagnation and blood stasis in a rhein-induced cathartic colon （CC） rat model. MethodsTwenty-four rats were divided into a normal group and a model group （CC group）. The rats were administered equal volumes of physiological saline or 2% rhein suspension by gavage to establish the model over three cycles （approximately 118 days）. The first cycle lasted 46 days， with a dosage of 12 mL·kg^-1·d^-1， administered every other day. The second cycle lasted 37 days， with a dosage of 12 mL·kg^-1·d^-1， administered for 5 consecutive days followed by 2 days of cessation. The third cycle lasted 35 days， with a dosage of 16 mL·kg^-1·d^-1， also administered for 5 consecutive days followed by 2 days of cessation. Each cycle ended when 80% of the rats no longer exhibited loose stools. Body mass， 24 h food intake， coat condition， and coat red （R）， green （G）， and blue （B） values were recorded. The open field test （OFT） was used to measure the total distance traveled to evaluate Qi deficiency. The body mass coefficient and 24 h water intake were recorded to assess Yin deficiency. The sucrose preference test （SPT） was used to determine the sucrose preference rate （SPR）， and the average speed in OFT was measured to evaluate depressive status （liver depression and Qi stagnation）. Tongue images and their R， G， and B values were recorded. Whole blood viscosity （WBV） and plasma viscosity （PV） were measured using an automatic hemorheological analyzer to evaluate blood stasis. A carbon ink propulsion test was performed to determine the intestinal transit rate （ITR） for disease model evaluation. Hematoxylin-eosin （HE） staining was used to observe histopathological changes in the colon. Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） was used to detect the mRNA expression of transient receptor potential ankyrin 1 （TRPA1） and tryptophan hydroxylase 1 （TPH1） in colon tissue. Western blot was used to detect the protein expression of TRPA1 and TPH1. ResultsIn terms of syndrome indicators， compared with the normal group， the body mass of the CC group decreased （P<0.05）， while 24 h food intake increased （P<0.01）. The coats of the CC group appeared withered， disheveled， and dull， and the R， G， and B values of the coat decreased （P<0.01）. The total distance traveled in OFT decreased （P<0.01）. The body mass coefficient decreased （P<0.01）， while 24 h water intake increased （P<0.05， P<0.01）. The SPR decreased （P<0.01）， and the average speed in OFT slowed （P<0.01）. The tongue appeared dark red， and the R， G， and B values of tongue images decreased （P<0.01）. WBV and PV increased （P<0.01）. Regarding disease indicators， compared with the normal group， the ITR decreased in the CC group （P<0.01）. Pathologically， HE staining showed necrosis and shedding of colonic mucosal epithelial cells， disruption of mucosal continuity， and infiltration of inflammatory cells in the lamina propria in the CC group. Semi-quantitative analysis showed increased HAI scores （P<0.05） and increased inflammatory cell counts and area proportion （P<0.05）. In terms of molecular biological indicators， compared with the normal group， the mRNA and protein expression levels of TRPA1 and TPH1 in colon tissue decreased in the CC group （P<0.05， P<0.01）. ConclusionThe rhein-induced CC rat model conforms to the traditional Chinese medicine syndrome characteristics of Qi and Yin deficiency accompanied by Qi stagnation and blood stasis.

Ulcerative colitis （UC）， a chronic inflammatory bowel disease affecting the colorectum with high morbidity and prevalence， has become a global burden. However， the causes and pathogenesis are still unclear. Available studies have verified that the imbalance of intestinal microenvironment is crucial in the occurrence and development of UC. Intestinal microenvironment is mainly composed of intestinal microbiota and intestinal mucosal cells， which are involved in the physiological and pathological activities of the body through the intestinal microbial barrier， chemical barrier， mechanical barrier， and immune barrier. Thus， probiotic agents， 5-aminosalicylic acid preparations， corticosteroids， immunosuppressants， biological preparations and other drugs are commonly used in western medicine for the treatment of UC， which， however， have limitations. Therefore， it is the key task for the prevention and treatment of UC to find new therapies. In recent years， it has been found that traditional Chinese medicine （TCM） has unique advantages in the prevention and treatment of UC. Chinese medicine compounds and Chinese medicine monomers can regulate the intestinal microenvironment through multiple pathways and targets， thereby intervening the occurrence and development of UC. It has gradually become a hot spot in the prevention and treatment of UC and attracted extensive attention. Therefore， this study first discussed the correlation between intestinal microenvironment imbalance and UC and then summarized the mechanisms of TCM against UC from the aspects of regulating intestinal flora， improving chemical barrier， protecting mechanical barrier， and inhibiting immune inflammatory response， in order to provide new ideas for the research on TCM in the treatment of UC.