American ginseng attenuates azoxymethane/dextran sodium sulfate-induced colon carcinogenesis in mice

Abstract

Background: Colorectal cancer is a leading cause of cancer-related death, and inflammatory bowel disease is a risk factor for this malignancy. We previously reported colon cancer chemoprevention potential using American ginseng (AG) in a xenograft mice model. However, the nude mouse model is not a gut-specific colon carcinogenesis animal model.

Methods: In this study, an experimental colitis and colitis-associated colorectal carcinogenesis mouse model, chemically induced by azoxymethane/dextran sodium sulfate (DSS) was established and the effects of oral AG were evaluated. The contents of representative ginseng saponins in the extract were determined.

Results: AG significantly reduced experimental colitis measured by the disease activity index scores. This suppression of the experimental colitis was not only evident during DSS treatment, but also very obvious after the cessation of DSS, suggesting that the ginseng significantly promoted recovery from the colitis. Consistent with the anti-inflammation data, we showed that ginseng very significantly attenuated azoxymethane/DSS-induced colon carcinogenesis by reducing the colon tumor number and tumor load. The ginseng also effectively suppressed DSS-induced proinflammatory cytokines activation using an enzyme-linked immunosorbent assay array, in which 12 proinflammatory cytokine levels were assessed, and this effect was supported subsequently by real-time polymerase chain reaction data.

Conclusion: AG, as a candidate of botanical-based colon cancer chemoprevention, should be further investigated for its potential clinical utility.

Keywords: American ginseng; azoxymethane; carcinogenesis; chemoprevention; dextran sodium sulfate.

Fig. 1

Experimental protocol. Experimental A/J mice were divided into three groups, i.e., control (or negative control) group, model group, and American ginseng (AG) group. Animals in the model and AG groups initially received a single intraperitoneal injection of azoxymethane (AOM; 7.5 mg/kg). One week after the AOM administration (set as Day 1), mice in the model and AG groups received 2.5% dextran sodium sulfate (DSS) in drinking water for 8 consecutive days. Mice in the AG group also received oral AG extract 30 mg/kg/day for 90 consecutive days (Day 1–14 is the acute phase and then up to 90 days is the chronic phase).

Fig. 2

Major ginsenosides in American ginseng (AG) extract. (A) Chemical structures of 11 ginsenosides. (B) Typical chromatograph of AG extract. (C) Contents of the major ginsenosides in the AG extract. Glc, β-D-glucopyranosyl; Xyl, β-D-xylopyranosyl; Rha, α-L-rhamnopyranosyl; Ara(f), α-L-arabinofuranosyl; Ara(p), α-L-arabinopyranosyl.

Fig. 3

Effects of American ginseng (AG) on azoxymethane/dextran sodium sulfate-induced change in acute colitis (n = 6 per group). (A) Representative hematoxylin and eosin stained histological sections of control (or negative control), model, and AG groups. (B) AG ameliorates the colitis, expressed as disease activity index. Data from the control (or negative control) group are all zeros from Day 1 to Day 14, shown as a thick horizontal line.

Fig. 4

Effects of American ginseng extract (AG) on azoxymethane/dextran sodium sulfate-induced colon carcinogenesis (n = 6 per group). (A) Representative macroscopic morphology of colon tumors in the control (or negative control), model, and AG groups. Arrows indicate the azoxymethane/dextran sodium sulfate-induced tumors. (B) Representative hematoxylin and eosin stained histological sections of control, model, and AG groups. (C) Number of colon tumor and load reduced very significantly in the AG group compared to the model group (p < 0.01 and p < 0.001, respectively).

Fig. 5

Acute inflammatory responses in azoxymethane/dextran sodium sulfate model and American ginseng (AG) treatment groups. Protein lysis was prepared using colonic tissue from six mice, which was collected on Day 14. Cytokine expressions were analyzed using the mouse cytokine Multi-Analyte ELISArray. *p < 0.05, compared to the model group. **p < 0.01, compared to the model group. G-CSF, granulocyte colony-stimulating factor; GM-CSF, granulocyte–macrophage colony-stimulating factor; IFN, interferon; IL, interleukin, TNF, tumor necrosis factor.

Fig. 6

Expression of inflammatory cytokine genes in colon tissues in the acute phase at Day 14 (A) and chronic phase at Day 90 (B). Colonic tissues from six mice were collected and used for total RNA isolation. Real-time polymerase chain reaction was used to determine cytokine gene expression. *p < 0.01, compared to the model group. G-CSF, granulocyte colony-stimulating factor; GM-CSF, granulocyte–macrophage colony-stimulating factor; IFN, interferon; IL, interleukin, TNF, tumor necrosis factor.