ObjectiveTo explore the potential mechanism of Changji'an Formula （肠激安方） on intestinal permeability for rats with diarrhea-predominant irritable bowel syndrome （IBS-D） of liver depression and spleen deficiency syndrome by the microRNA-29b-3p （miR-29b-3p）/tumor necrosis factor receptor-associated factor 3 （TRAF3）/nuclear factor-κB （NF-κB）/myosin light chain kinase （MLCK） axis. MethodsTwenty-four 1-day-old male Sprague-Dawley （SD） suckling rats were selected， and the IBS-D rat model of liver depression and spleen deficiency syndrome was established via a three-factor method，i.e. maternal separation plus acetic acid stimulation and restraint stress， for 6 consecutive weeks. After successful modeling， the rats were randomly divided into a model group， pinaverium bromide group， low-dose and high-dose Changji'an Formula groups， with 6 rats in each group. Another 6 age-matched non-modeled SD rats were included as the control group. The low-dose and high-dose Changji'an Formula groups were given intragastric administration of Changji'an Formula solution at doses of 16.74 g/（kg·d） and 33.48 g/（kg·d）， respectively； the pinaverium bromide group received intragastric administration of pinaverium bromide tablets at 0.018 g/（kg·d）； and the control group was given distilled water at 10 ml/（kg·d） via intragastric gavage. The intervention was conducted once daily for 14 consecutive days. After the gavage treatment， the fecal water content of rats in each group was measured. Enzyme-linked immunosorbent assay （ELISA） was used to detect the serum levels of intestinal permeability indicators， including D-lactic acid （D-LA）， diamine oxidase （DAO）， and lipopolysaccharide （LPS）. Quantitative real-time polymerase chain reaction （qRT-PCR） was conducted to determine the mRNA expression levels of miR-29b-3p， TRAF3， tumor necrosis factor-α （TNF-α）， p65， p50， and MLCK in colonic tissues. Western Blot analysis was employed to detect the protein expression levels of TRAF3， TNF-α， p65， phosphorylated p65 （p-p65）， MLCK， myosin light chain （MLC）， phosphorylated MLC （p-MLC）， and tight junction proteins including junctional adhesion molecule-A （JAM-A）， Occludin， and Claudin-1 in colonic tissues. ResultsCompared with the control group， the model group exhibited significantly increased fecal water content and serum levels of D-LA， DAO， and LPS， along with decreased protein expression levels of JAM-A， Occludin， and Claudin-1 in colonic tissues （P＜0.05 or P＜0.01）. Additionally， in the model group， the mRNA expression levels of miR-29b-3p， TNF-α， p65， p50， and MLCK in colonic tissues were up-regulated， while the mRNA and protein expression levels of TRAF3 were down-regulated； the protein levels of TNF-α and MLCK， as well as the ratios of p-p65/p65 and p-MLC/MLC， significantly elevated （P＜0.01）. Compared with the model group， all treatment groups showed reduced fecal water content and serum levels of D-LA， DAO， and LPS， along with down-regulated mRNA expression levels of miR-29b-3p， TNF-α， p65， p50， and MLCK， and up-regulated TRAF3 mRNA expression in colonic tissues. Moreover， the pinaverium bromide group and high-dose Changji'an Formula group presented increased protein levels of Occludin， Claudin-1， and TRAF3， as well as decreased protein levels of TNF-α and MLCK， and reduced ratios of p-p65/p65 and p-MLC/MLC in colonic tissues （P＜0.05 or P＜0.01）. Compared with the low-dose Changji'an Formula group， the high-dose group had lower fecal water content and serum levels of DAO and LPS （P＜0.01）. In comparison with the pinaverium bromide group， the high-dose Changji'an Formula group showed a significant decrease in serum DAO level （P＜0.01）. ConclusionsChangji'an Formula can reduce intestinal permeability and restore intestinal barrier function in IBS-D rats of liver depression and spleen deficiency syndrome by regulating the miR-29b-3p/TRAF3/NF-κB/MLCK axis.