Anti-inflammatory Effects of Flavonoids on TNBS-induced Colitis of Rats

Abstract

It has been shown that the extracts including eupatilin and quercetin-3-β-D-glucuronopyranoside had mucoprotective effects on the esophagus and stomach through their antioxidant activities. This study was designed to investigate the anti-inflammatory effect of these flavonoid compounds in an animal model of inflammatory bowel disease induced by 2,4,6-trinitrobenzene sulfonic acid. Experimental colitis was induced by intracolonic administration of 2,4,6-trinitrobenzene sulfonic acid. Extracts including eupatilin or quercetin-3-β-D-glucuronopyranoside were orally administered to animals 48, 24, and 1 h prior to the induction of colitis and then again 24 h later. The animals were sacrificed 48 h after by 2,4,6-trinitrobenzene sulfonic acid treatment and the macroscopic appearance of the colonic lesions was scored in a blinded manner on a scale of 1 to 10. The inflammatory response to colitis induction was assessed by measuring myeloperoxidase activity, nitric oxide production, tumor necrosis factor-α expression, total glutathione levels, and malondialdehyde concentrations in the colon. The results indicated that extracts including eupatilin and extracts including quercetin-3-β-D-glucuronopyranoside dose-dependently improved the morphology of the lesions induced by 2,4,6-trinitrobenzene sulfonic acid and reduced the ulcer index accordingly. In addition, rats receiving extracts including eupatilin and extracts including quercetin-3-β-D-glucuronopyranoside showed significantly decreased levels of mucosal myeloperoxidase activity, nitric oxide production, tumor necrosis factor-α expression, and malondialdehyde levels, and increased total glutathione levels. Extracts including eupatilin and extracts including quercetin-3-β-D-glucuronopyranoside ameliorated the inflammatory response and colonic injury in acute colitis by decreasing oxidative stress and neutrophil activation. Extracts including eupatilin and extracts including quercetin-3-β-D-glucuronopyranoside may inhibit acute colitis.

Keywords: Colitis; Flavonoids; Inflammation; Quercetin; Reactive oxygen species.

Fig. 1

Chemical structures of Eupatilin (5,7-Dihydroxy- 3',4',6-trimethoxyflavone) and QGC (quercetin-3-O-β-D-glucuronopyranoside).

Fig. 2

Effect of EIE and EIQ administration on colonic injury in rats with TNBS-induced acute colitis. The image show representative colonic tissues from the in normal control group (A), TNBS and no treatment group (B), TNBS and EIE 100 mg/kg group (C), and TNBS and EIQ 30 mg/kg (D). TNBS lesions are characterized by focal ulceration, and treatment with the flavonoid glycosides EIE and EIQ reduced the severity of the lesions.

Fig. 3

Effect of acute administration of EIE, and EIQ on macroscopic colon damage in rats with TNBS-induced acute colitis. Macroscopic damage to the colon resulting from TNBS was scored on a scale of 0 to 10. EIE and EIQ dose-dependently diminished the macroscopic scores. The data are expressed as mean±S.E.M. ^###p<0.001 vs. the control group and ^*p<0.05, ^**p<0.01 and ^***p<0.001 vs. the TNBS alone group.

Fig. 4

Effect of EIE and EIQ administration on the colon weight to length ratio in rats with TNBS-induced acute colitis. Colon weight to length ratios were dose-dependently decreased by administration of EIE and EIQ. The data are expressed as mean±S.E.M. ^###p<0.001 vs. the control group and ^*p<0.05 and ^***p<0.01 vs. the TNBS alone group.

Fig. 5

Effect of EIE and EIQ administration on MPO activity in rats with TNBS-induced acute colitis. MPO activity was significantly increased by TNBS instillation compared with control group. However, MPO activity was significantly decreased by EIE (50 and 100 mg/kg) and EIQ (30 mg/kg). The data are expressed as mean±S.E.M. ^###p<0.001 vs. the control group and ^**p<0.01 and ^***p<0.001 vs. the TNBS alone group.

Fig. 6

Effect of EIE and EIQ administration on NO production with TNBS-induced colitis. After TNBS instillation, nitrite production was significantly increased compared with the control group. However, NO production was significantly decreased with EIE (50 and 100 mg/kg) or EIQ (30 mg/kg). The data are expressed as mean±S.E.M. ^###p<0.001 vs. the control group and ^**p<0.01 and ^***p<0.001 vs. the TNBS alone group.

Fig. 7

Effect of EIE and EIQ administration on TNF-α expression in rats with TNBS-induced acute colitis. After TNBS instillation, TNF-α expression was significantly increased compared with the control group. However, TNF-α expression was significantly decreased by EIE (100 mg/kg) and EIQ (30 mg/kg). The data are expressed as mean±S.E.M. ^###p<0.001 vs. the control group and ^*p<0.05 and ^***p<0.001 vs. the TNBS alone group.

Fig. 8

Effect of EIE and EIQ administration on GSH levels in rats with TNBS-induced acute colitis. After TNBS instillation, total GSH levels were significantly decreased compared with the control group. However, GSH levels were significantly increased by administration of EIE (50 and 100 mg/kg) and EIQ (30 mg/kg). The data are expressed as mean±S.E.M. ^###p<0.001 vs. the control group and ^**p<001 and ^***p<0.001 vs. the TNBS alone group.

Fig. 9

Effect of EIE and EIQ administration on MDA levels in rats with TNBS-induced acute colitis. After TNBS instillation, MDA levels were significantly increased compared with control group. However, MDA was significantly decreased by administration of EIE (50 and 100 mg/kg) and EIQ (10 and 30 mg/kg). The data are expressed as mean±S.E.M. ^###p<0.001 vs. the control group and ^*p<0.05, ^**p<0.01, and ^***p<0.001 vs. the TNBS alone group.