Moluodan promotes DSS-induced intestinal inflammation involving the reprogram of macrophage function and polarization

Ethnopharmacological relevance: Moluodan (MLD) is a traditional Chinese medicine that is composed of 18 herbal medicines based on traditional Chinese medicine theory and practice. It has long been used in treating chronic gastritis and its components were traditionally used in dealing with intestinal inflammation. However, its specific pharmacological mechanism is still unclear.

Aim of the study: The upper and lower digestive tract diseases are correlated. In clinical practice, some chronic gastritis patients are also accompanied by intestinal inflammation. Due to the unclear pharmacological mechanism of MLD and its effect on intestinal inflammation, there is doubt whether MLD is still suitable for this type of patient. Therefore, this study aims to elucidate the pharmacological mechanism of MLD and identify its effect in the mouse model of intestinal inflammation.

Materials and methods: Mice intestinal inflammation model was induced by 2.5% dextran sulfate sodium (DSS). The mice were given different concentrations of MLD via oral gavage (0.25, 0.5 g/kg b.w.). Pharmacodynamic Indicators were assessed including body weight, colon length, disease activity index (DAI), bloody stool score, inflammatory factors, histological change, etc. RAW264.7 macrophage cells were used for in vitro experiments that illuminated the role of MLD in reprogramming macrophage function and polarization. RT-qPCR and western blots were performed to measure the mRNA and protein levels of macrophage polarization marker and effector molecules. The functions of polarized macrophages were tested using ROS detection probes, Edu assay and wound healing assay.

Results: The administration of MLD exhibited obvious hemostatic effects, while unexpectedly accentuating various aspects of the DSS-induced intestinal inflammation in mice, including increased body weight loss and colon shortening, elevated disease activity index, and intensified colonic tissue damage. Additionally, MLD treatment induced more severe inflammatory cell infiltration and higher proinflammatory cytokines expression in colon tissue. Further results showed that MLD promoted M1 macrophage polarization and stimulated its proinflammatory cytokines expression, while only slightly affecting the function of M2 macrophage. Western blot analysis revealed that MLD induced the phosphorylation of Akt and NF-κB. The polarization of M1 macrophages induced by MLD was inhibited by either an Akt Inhibitor or a NF-κB Inhibitor.

Conclusions: Although MLD has an obvious hemostatic effect, it generally promoted the severity of DSS-induced colitis in mice by facilitating macrophage polarization toward the M1 phenotype through the Akt/NF-κB pathway. Our study suggested that although MLD may not be suitable for colitis, especially during the acute inflammation stage.

AKT/NF-κB; Gastrointestinal inflammation; Macrophage polarization; Moluodan.