Shenling Baizhu Decoction treats ulcerative colitis of spleen-deficiency and dampness obstruction types by targeting 'gut microbiota and galactose metabolism-bone marrow' axis.

Ethnopharmacological Relevance: Shenlin Baizhu Decoction (SLBZD), which comes from 'Taiping Huimin Heji Ju Fang', belongs to a classical prescription for treating spleen deficiency and dampness obstruction (SQDDS)-type ulcerative colitis (UC) in traditional Chinese medicine. However, the mechanism of SLBZD in treating UC with SQDDS remains unclear.

Aim Of The Study: This study aims to investigate the mechanism of SLBZD against SQDDS-type UC of based on the "gut microbiota and metabolism - bone marrow" axis to induce endogenous bone marrow mesenchymal stem cells (BMSCs) homing.

Materials And Methods: Ultra-performance liquid chromatography-mass spectrometry was used to analysis of SLBZD qualitatively. The efficacy of SLBZD in SQDDS-type UC was evaluated based on the following indicators: the body weight, colon length, disease activity index (DAI) score, Haemotoxylin and Eosin (H&E) pathological sections, and intestinal permeability proteins (occluding and ZO-1). 16S rRNA gene sequencing and non-target metabolomics were performed to identify gut microbiota changes and its metabolites in feces, respectively. BMSCs in each group was collected, cultured, and analyzed. Optimal passaged BMSCs were injected by tail vein into UC rats of SQDDS types. BMSCs homing to the colonic mucosal tissue was observed by immunofluorescent. Finally, the repairing effect of BMSCs homing to the colonic mucosal tissue after SLBZD treatment was analyzed by transmission electron microscopy, qRT-PCR, and immunohistochemistry.

Results: SLBZD effectively improved the colonic length and the body weight, reduced DAI and H&E scores, and increased the expression of the intestinal permeability proteins, including occluding and ZO-1, to treat SQDDS-type UC. After SLBZD treatment, the α-diversity and β-diversity of the gut microbiota were improved. The differential microbiota was screened as Aeromonadaceae, Lactobacillaceae, and Clostridiaceae at the family level, and Aeromonas, Lactobacillus, Clostridium_sensu_stricto_1 at the genus level. Meanwhile, the main metabolic pathway was the galactose metabolism pathway. SLBZD treatment timely corrected the aberrant levels of β-galactose in peripheral blood and bone marrow, senescence-associate-β-galactosidase in BMSCs, and galactose kinase-2, galactose mutase, and galactosidase beta-1 in peripheral blood to further elevate the expression levels of senescence-associated (SA) proteins (p16, p53, p21, and p27) in BMSCs. The Spearman's correlation analysis demonstrated the relationship between microbiota and metabolism, and the relationship between the galactose metabolism pathway and SA proteins. After BMSCs in each group injection via the tail vein, the pharmacodynamic effects were consistent with those of SLBZD in SQDDS-type UC rats. Furthermore, BMSCs have been homing to colonic mucosal tissue. BMSCs from the SLBZD treatment group had stronger restorative effects on intestinal permeability function due to increasing protein and mRNA expressions of occludin and ZO-1, and decreasing the proteins and mRNA expressions of SDF-1 and CXCR4 in colon.

Conclusions: SLBZD alleviated the damaged structure of gut microbiota and regulated their metabolism, specifically the galactose metabolism, to treat UC of SDDOS types. SLBZD treatment promotes endogenous BMSCs homing to colonic mucosal tissue to repaire the intestinal permeability. The current exploration revealed an underlying mechanism wherein SLBZD activates endogenous BMSCs by targeting 'the gut microbiota and its metabolism-bone marrow' axis and repairs colonic mucosal damage to treat SDDOS-type UC.