The effects of oxidative DNA damage and mutations in the p53 protein on cells of the colonic mucosa with and without the fecal stream: an experimental study in rats

Abstract

Objective. The aim of this study was to investigate the levels of oxidative DNA damage and p53 mutations in an experimental model of diversion colitis. Material and methods. Sixty rats were divided into three groups with 20 animals in accordance with the sacrifice was carried out 6, 12 and 18 weeks. For each group, 15 animals were subjected to diversion of the fecal stream through colostomy in the left proximal colon and distal mucous fistula (experimental group), and five to a laparotomy without deviation of the fecal stream (control group). The presence of colitis was evaluated by inflammatory grading scale. Mutations in the p53 protein were evaluated by immunohistochemistry with primary antibody with cross-reactivity for rats. The oxidative DNA damage was measured using the comet assay. To statistical analysis were used the Student's t, Mann-Whitney and Kruskal-Wallis test adopting a significance level of 5% (p < 0.05). Results. Colon segments without fecal stream showed greater degree of inflammation when compared to animals with preserved fecal stream (p = 0.01). The levels of oxidative stress were significantly higher in segments without fecal stream (p < 0.0001) and increased with the time of fecal diversion (p = 0.007). The levels of oxidative DNA damage are directly related to tissue degree of inflammation. There were no mutations in the p53 protein in the segments without fecal stream regardless of time of exclusion considered. Conclusion. Despite higher levels of oxidative damage to nuclear DNA on segments without fecal stream that developed colitis mutations in the p53 protein were not detected.

Key Words::

• Colitis
• colon
• comet assay
• DNA damage
• fatty acids
• oxidative stress
• tumor suppressor protein p53
• volatile

Acknowledgements

CARM thanks Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) for financial support. (Process: 06-02306-6.)

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.