Glycyrrhetic Acid Ameliorates Dextran Sulfate Sodium-Induced Ulcerative Colitis in Vivo

Abstract

Glycyrrhizae Radix (GR) is a Korean traditional herb medicine that is widely used in clinical health care. Glycyrrhetic acid (GA) is an aglycone saponin extracted from GR that has anti-inflammatory, anti-cancer, and anti-viral effects. However, the anti-inflammatory effects of GA in colitis have not been reported. This study investigated the role of GA on ulcerative colitis in a dextran sulfate sodium (DSS)-induced mouse colitis model. DSS-treated mice displayed weight loss and shortened colon length compared with control mice. Mice administered GA showed less weight loss and longer colon length than the DSS-treated group. Interleukin (IL)-6, IL-1β, and tumor necrosis factor-alpha were decreased by GA treatment. GA treatment also reduced DSS-induced microscopic damage to colon tissue. GA regulates the phosphorylation of transcription factors including nuclear factor-kappa B (NF-κB) and IκB alpha, and regulates the expression of cycloxygenase-2 and prostaglandin E₂. GA thus showed beneficial effects in a mouse model of colitis, implicating GA might be a useful herb-derived medicine in the treatment of ulcerative colitis.

Keywords: anti-inflammation; dextran sulfate sodium; glycyrrhetic acid; ulcerative colitis.

Figure 1

Effects of GA on clinical signs in DSS-induced colitis. (A) Body weight was measured at the same time on the experimental days; (B) Disease activity index score in the five study groups. Values represent mean ± S.E.M. (n = 6). Data were analyzed by Student’s t-test (^# p < 0.05 vs. control and * p < 0.05 vs. DSS alone).

Figure 2

Effects of GA on DSS-induced colon shortening. (A) Average colon length in cm measured after 10 days at the time of sacrifice; (B) Representative colons of each group. Values represent mean ± S.E.M. (n = 6). Data were analyzed by Student’s t-test (^# p < 0.05 vs. control and * p < 0.05 vs. DSS alone).

Figure 3

Effects of inflammatory cytokines levels in DSS-induced UC. (A) IL-6 production in mouse serum at day 10; (B) TNF-α production in mouse serum at day 10; (C) IL-1β production in mouse serum at day 10. Values represent mean ± S.E.M. (n = 6). Data were analyzed by Student’s t-test (^# p < 0.05 vs. control and * p < 0.05 vs. DSS alone).

Figure 4

Effects of GA on transcription factors in DSS-induced UC. (A) Phosphorylation of IκBα and phosphorylation of NF-κB were assayed by Western blot; (B) Relative ratio of phospho-IκBα and NF-κB p65 calculated using an image analyzer. Values represent mean ± S.E.M. (n = 6). Data were analyzed by Student’s t-test (^# p < 0.05 vs. control and * p < 0.05 vs. DSS alone).

Figure 5

Effects of GA on epithelial injury in DSS-induced UC. (A) Paraffin sections of colonic tissue were stained with hematoxylin & eosin, and then observed by microscope (10× and 40×); (B) Microscopic scores. Values represent mean ± S.E.M. (n = 6). Data were analyzed by Student’s t-test (^# p < 0.05 vs. control and * p < 0.05 vs. DSS alone).

Figure 6

Effects of GA on COX-2 and PGE₂ expression in DSS-induced UC. COX-2 levels were determined by western blot analysis, and PGE₂ levels using PGE₂ assay kits. (A) Western blot analysis was used to determine COX-2 levels in colonic tissues. Data shown are representative of three independent experiments; (B) COX-2/GAPDH ratios were determined by densitometry; (C) PGE₂ production in colonic tissues. Values represent mean ± S.E.M. (n = 6). Data were analyzed by Student’s t-test (^# p < 0.05 vs. control and * p < 0.05 vs. DSS alone).