Regulatory effects of glycyrrhizae radix extract on DSS-induced ulcerative colitis

Abstract

Background: Glycyrrhizae Radix (GR) is a Korean traditional herb medicine that is widely-used in clinical health care. The clinical functions of GR include relief of toxicity, anti-cancer, regulating blood cholesterol and anti-inflammation. This study investigated the role of GR on ulcerative colitis in a dextran sulfate sodium (DSS)-induced mouse model of colitis.

Method: Western blot analysis and enzyme-linked immunosorbent assay (ELISA) analyses were done on male BALB/c mice administered 5 % DSS during the experimental period. Ethanol extracts of GR were orally administered at same time daily to control mice. The severity of colitis was measured by body weight change and colon length.

Result: DSS-treated mice displayed weight loss and shortened colon length compared with control mice. Mice were administered GR showed less weight loss and longer colon length than the DSS-treated group. Inflammatory cytokines were decreased by GR treatment. Treatment also reduced DSS-induced microscopic damage to colon tissue. GR regulated the phosphorylation of transcription factors such as NF-κB p65 and IκB α.

Conclusions: GR has beneficial effects in a colitis model. GR might be a useful herb medicine in the treatment of ulcerative colitis.

Keywords: COX-2; Colon; Dextran sulfate sodium; Glycyrrhizae radix; PGE2; Ulcerative colitis.

Fig. 1

Effect of Glycyrrhizae Radix (GR) on dextran-sulfate-sodium (DSS)-induced clinical signs. Ulcerative colitis was induced in male BALB/c mice by administering 5 % DSS in the drinking water for 10 days. Over the same period, GR (25 mg/kg, 50 mg/kg) and the reference compound 5-aminosalicylic acid (5-ASA; 50 mg/kg) were given orally daily. a Body weight was measured at the same time on the experimental days. Weight changes are given by percentage (%). b Disease activity index score in the five study groups. Values represent mean ± S.E.M. ($n$ = 6). Data were analyzed by Tukey post hoc test (^# P < 0.05 versus control and ^* P < 0.05 versus DSS alone)

Fig. 2

Effect of GR on DSS-induced colon shortening. Ulcerative colitis was induced and GR and 5-ASA administered as described in the legend to Fig. 1. Colon length steadily shortened in mice receiving DSS. a Colon was harvested on day 10, and colon lengths were measured. b Colon lengths in the five groups. Values represent mean ± S.E.M (n = 6). Data were analyzed by Tukey post hoc test (^# P < 0.05 versus control and ^* P < 0.05 versus DSS alone)

Fig. 3

Effect of GR on levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-$\alpha$) in DSS-induced colitis. Ulcerative colitis was induced and GR and 5-ASA administered as described in the legend to Fig. 1. Cytokine production was determined by ELISA. a IL-6 production in mouse serum at day 10. b TNF-α production in mouse serum at day 10. c IL-6 production in colon tissue. d TNF-α production in colon tissue. Values represent mean ± S.E.M. ($n$ = 6). Data were analyzed by Tukey post hoc test (^# $P$ < 0.05 versus control and ^* $P$ < 0.05 versus DSS alone)

Fig. 4

Efect of GR on transcription factors in DSS-induced colitis. Ulcerative colitis was induced and GR and 5-ASA administered as described in the legend to Fig. 1. a Phosphorylation of IκB α and phosphorylation of NF-κB were assayed by Western blot. b Relative ratio of phospho-IκB α and NF-κB p65 calculated using an image analyzer. c Relative ratio of phospho-NF-κB and NF-κB p65 calculated using an image analyzer. Values represent mean ± S.E.M. ($n$ = 6). Data were analyzed by Tukey post hoc test (^# P < 0.05 versus control and ^* P < 0.05 versus DSS alone)

Fig. 5

Effect of GR on COX-2 and PGE₂ abundance in DSS-induced colitis. Ulcerative colitis was induced and GR and 5-ASA administered as described in the legend to Fig. 1. 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 Tukey post hoc test (^# P < 0.05 versus control and ^* P < 0.05 versus DSS alone)

Fig. 6

Effect of GR on epithelial injury in DSS-induced colitis. Ulcerative colitis was induced and GR and 5-ASA administered as described in the legend to Fig. 1. a Paraffin sections of colonic tissue were stained with hematoxylin and eosin observed by microscope (100× and 400×). b Microscopic scores. Values represent mean ± S.E.M. ($n$ = 6). Data were analyzed by Tukey post hoc test (^# P < 0.05 versus control and ^* P < 0.05 versus DSS alone)

Fig. 7

HPLC elution profile of GR extract