Effect of polysaccharides from Sijunzi decoction on Ca²⁺ related regulators during intestinal mucosal restitution

Sijunzi decoction, a representative Chinese herbal formula of reinforcing Qi strengthening spleen, has been widely used for treating patients with gastrointestinal diseases and spleen-deficiency syndrome, however, the exact effects and mechanisms are remained unclear.

The migration of intestinal epithelial (IEC-6) cells has been demonstrated to be one of the major repair modalities during the healing of mucosal wounds. Ca²⁺ is the key factor in regulating cell migration. Thus, this study aimed to elucidate the potential effects and mechanisms of polysaccharides (SJZDP) extracted from Sijunzi decoction in intestinal mucosal restitution.

Cell migration was detected by scratch method with micropipette tip. Western blotting was adopted to evaluate the expression of STIM1 and STIM2 proteins. Immunofluorescence was carried out to assess the translocation of STIM1 protein. Immunoprecipitation was used to determine the levels of STIM1/TRPC1 and STIM1/STIM2 complexes. A indomethacin-induced intestinal mucosal injury rat model was applied. The content of polyamines in intestinal mucosa was detected by high-performance liquid chromatography. The morphological changes in the intestinal mucosa were observed at the end of animal experiment.

The results showed that treatment with SJZDP significantly promoted cell migration, enhanced the level of STIM1 protein and STIM1/TRPC1 complexes, reduced the level of STIM2 protein and STIM1/STIM2 complexes. Further more, SJZDP exposure promoted the translocation of STIM1 to the plasma membrane. In vivo experiment results, the administration of SJZDP effectively reduced intestinal mucosal injury.

These results revealed that SJZDP promotes intestinal epithelial restitution after wounding, presumably by regulating cellular levels of STIM1 and STIM2 differentially, stimulating the translocation of STIM1, and inducing STIM1/TRPC1 association as well as decreasing the level of STIM1/STIM2.