Effect of taurine on oxidative stress and apoptosis-related protein expression in trinitrobenzene sulphonic acid-induced colitis

Abstract

Ulcerative colitis (UC) is a multi-factorial inflammatory disease of the colon and rectum. The present study was undertaken to investigate the effect of taurine, an anti-oxidant amino acid, on oxidative stress and the expression of apoptosis-related proteins, pro-apoptotic Bax and anti-apoptotic B cell lymphoma-2 (Bcl-2) in colon tissue in rats with 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced colitis. Rats received taurine (1.5% w/v) in drinking water for 15 days before and 15 days after administration of TNBS solution. Then, colonic myeloperoxidase (MPO) activity, malondialdehyde (MDA) and glutathione (GSH) levels, and Bax and Bcl-2 expression were measured. TNBS-induced colitis caused significantly increased MPO activity and MDA levels and decreased GSH levels in colon tissue compared to controls. Increase in Bax expression and decrease in Bcl-2 expression were detected in colon of rats with TNBS-induced colitis. Taurine treatment was associated with amelioration in macroscopic and microscopic colitis scores, decreased colonic MPO activity and MDA levels and increased GSH levels in TNBS-induced colitis. In addition, taurine reduced the expression of Bax and prevented the loss of Bcl-2 proteins in colon tissue of rats with TNBS-induced colitis. The results of this study show that taurine administration may exert beneficial effects in UC by decreasing inflammatory reactions, oxidative stress and apoptosis.

Figures

Fig. 1

Histopathological appearance of colonic tissue in rats. (a) Normal colonic mucosa of control rats [haematoxylin and eosin (H&E) × 40]. (b) Normal colonic mucosa of taurine-treated rats (H&E × 200). (c) Colonic mucosa of 2,4,6-trinitrobenzene sulphonic acid (TNBS)-treated rats. Large ulcerations (arrows) (H&E × 100). (d) Colonic mucosa of TNBS + taurine-treated rats. Moderated inflammatory cell infiltration (arrows) (H&E × 400).

Fig. 2

Macroscopic and microscopic colitis scores of control, taurine (Tau)-, 2,4,6-trinitrobenzene sulphonic acid (TNBS)- and TNBS plus taurine (TNBS + Tau)-treated rats. Each value is expressed as mean ± standard deviation. Values not sharing a common superscript letter are significantly different by Kruskal–Wallis test (P < 0.05).

Fig. 3

Myeloperoxidase (MPO) activity in the colon tissue of control, taurine (Tau)-, 2,4,6-trinitrobenzene sulphonic acid (TNBS)- and TNBS plus taurine (TNBS + Tau)-treated rats. Each value is expressed as mean ± standard deviation. Values not sharing a common superscript letter are significantly different by Kruskal–Wallis test (P < 0.05).

Fig. 4

Malondialdehyde (MDA) levels in the colon tissue of control, taurine (Tau)-, 2,4,6-trinitrobenzene sulphonic acid (TNBS)- and TNBS plus taurine (TNBS + Tau)-treated rats. Each value is expressed as mean ± standard deviation. Values not sharing a common superscript letter are significantly different by analysis of variance (P < 0.05).

Fig. 5

Glutathione levels in the colon tissue of control, taurine (Tau)-, 2,4,6-trinitrobenzene sulphonic acid (TNBS)- and TNBS plus taurine (TNBS + Tau)-treated rats. Each value is expressed as mean ± standard deviation. Values not sharing a common superscript letter are significantly different by Kruskal–Wallis test (P < 0.05).

Fig. 6

Western blot analysis of colonic Bax (a), B cell lymphoma-2 (Bcl-2) (b) expression and β-tubulin (c) expression as an index of the adequency of sample loading in control, taurine (Tau)-, 2,4,6-trinitrobenzene sulphonic acid (TNBS)- and TNBS plus taurine (TNBS + Tau)-treated rats.

Fig. 7

Densitometric quantification of colonic Bax and B cell lymphoma-2 (Bcl-2) and β-tubulin expression in control, taurine (Tau)-, 2,4,6-trinitrobenzene sulphonic acid (TNBS)- and TNBS plus taurine (TNBS + Tau)-treated groups. Results are average values of four or six animals. Values not sharing a common superscript letter are significantly different by analysis of variance (P < 0.05).

Fig. 8

Immunohistochemistry of colonic Bax expression in the colon tissue of rats. (a) Control (× 100); (b) taurine- (× 250); (c) 2,4,6-trinitrobenzene sulphonic acid- (× 100); and (d) TNBS plus taurine-treated groups (× 100).

Fig. 9

Immunohistochemistry of colonic B cell lymphoma-2 (Bcl-2) expression in the colon tissue of rats. (a) Control (× 250); (b) taurine- (× 100); (c) 2,4,6-trinitrobenzene sulphonic acid (TNBS)- (× 100); and (d) TNBS plus taurine-treated groups (× 100).