Gut bacteria inhibited liver tumor growth during Rheum officinale Baill. treatment in mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Rheum officinale Baill. (Dahuang, DH) was first documented in the Shennong Bencaojing (Shennong's Classic of Materia Medica), and used in traditional Chinese medicine to purge accumulation, clear heat, and detoxify. Modern research confirms the anti-inflammatory, antioxidant, and anti-tumor properties. However, the anti-tumor mechanisms remained unclear in hepatocellular carcinoma.

AIM OF THE STUDY: To investigate the mechanism by which DH inhibits the growth of liver cancer.

MATERIALS AND

METHODS

Yinchenhao Decoction (YCHD) contains DH, Artemisia capillaris Thunb. (Yinchen, YC), and Gardenia jasminoides Ellis (Zhizi, ZZ). A subcutaneous Hepa1-6 tumor xenograft model was established. Mice were gavaged with YCHD, DH, or YZ (YCHD without DH), and the tumor-suppressive effects were evaluated. Oil Red O staining was performed to detect lipid droplet (LD) accumulation in tumor. 16S rRNA and Internal transcribed spacer region (ITS) sequencing were used to analyze the structures and compositions of bacteria and fungi in the gut, respectively. Periodic acid-schiff (PAS) staining was applied to quantify goblet cell numbers, and immunohistochemistry was conducted to determine the expression levels of Zonula occludens-1 (ZO-1) and Occludin in colon. A pseudo-germ-free model induced by antibiotics water (ATB) was established to investigate whether DH inhibits liver cancer growth through modulation of the gut bacteria. Finally, ultra performance liquid chromatography-mass spectrometry (UPLC/MS) was used to characterize the water extracts of DH, YZ, and YCHD.

RESULTS

DH suppressed liver tumor growth in mice, which LD accumulation was decreased in tumor and the structures and compositions of bacteria and fungi were reshaped in gut. Further, DH increased goblet cell numbers and ZO-1 expression level. In a pseudo-germ-free model induced by ATB, DH inhibited liver tumor growth potentially via gut bacteria remodeling.

CONCLUSION

DH inhibited liver tumor growth in mice, potentially via gut microbiota remodeling, intestinal barrier improvement, and reduced LD accumulation.