Analysis of oxidative DNA damage in patients with colorectal cancer.

PURPOSE: The aim of this study was to measure the levels of oxidative DNA damage in cells isolated from the colon mucosa in patients with colorectal cancer and to compare normal and neoplastic tissues and make correlations with anatomopathologic variables. PATIENTS AND METHODS: Thirty-three patients with colorectal adenocarcinoma were studied. The oxidative DNA damage was evaluated by means of the alkaline version of the comet assay. RESULTS: For all the patients studied, it was found that the cells obtained from the neoplastic tissue presented oxidative DNA damage greater than in the cells from normal tissue. The cells isolated from the neoplastic mucosal tissue of the colon presented significantly greater mean extent of DNA strand breakage than the cells isolated from normal tissue. Additionally, the patients at earlier stages of the Dukes and TNM classifications presented higher levels of oxidative damage than those at more advanced stages. CONCLUSION: Assessment of the levels of oxidative damage at the different stages of colorectal carcinogenesis is of great interest because it enables evaluation of the effectiveness of antioxidant substances that could be used as preventive measures against the initial oxidative aggressive action on the colonic mucosa.

Protective effects of mate tea (Ilex paraguariensis) on H2O2-induced DNA damage and DNA repair in mice.

Yerba mate (Ilex paraguariensis) is rich in several bioactive compounds that can act as free radical scavengers. Since oxidative DNA damage is involved in various pathological states such as cancer, the aim of this study was to evaluate the antioxidant activity of mate tea as well as the ability to influence DNA repair in male Swiss mice. Forty animals were randomly assigned to four groups. The animals received three different doses of mate tea aqueous extract, 0.5, 1.0 or 2.0 g/kg, for 60 days. After intervention, the liver, kidney and bladder cells were isolated and the DNA damage induced by H(2)O(2) was investigated by the comet assay. The DNA repair process was also investigated for its potential to protect the cells from damage by the same methodology. The data presented here show that mate tea is not genotoxic in liver, kidney and bladder cells. The regular ingestion of mate tea increased the resistance of DNA to H(2)O(2)-induced DNA strand breaks and improved the DNA repair after H(2)O(2) challenge in liver cells, irrespective of the dose ingested. These results suggest that mate tea could protect against DNA damage and enhance the DNA repair activity. Protection may be afforded by the antioxidant activity of the mate tea's bioactive compounds.

Influence of oxidative stress and alpha tocopherol supplementation on urothelial cells of the urinary bladder in ovariectomised rats.

The present study was designed to investigate whether vitamin E supplementation would influence the levels of oxidative stress and the damage to urothelial cell DNA in the bladders of castrated rats. A total of 30 rats of the Wistar breed were divided into 3 groups of 10 animals each. Group 1 underwent a sham procedure and was killed after 30 days; group 2 underwent bilateral oophorectomy and was killed after 30 days without receiving vitamin E supplementation and group 3 underwent bilateral oophorectomy and received vitamin E supplementation at a dose of 1,000 IU/kg once a week intra-muscularly for 30 days. Four weeks after the procedure, the rats were anesthetised and their bladders were rapidly removed, frozen and stored at -70 degrees C for Comet assaying, which was carried out on lymphocytes and vesicular urothelium cells. The 8-isoprostane concentration in plasma was also determined to confirm the presence of oxidative stress. The 8-isoprostane levels found were higher in oophorectomised rats that had not received vitamin E supplementation than in the sham group and the oophorectomised group with vitamin replacement. Tail moment analysis on the urothelial cells demonstrated that the oophorectomised group presented DNA damage that was statistically significant in comparison with the other groups. On the basis of the above data, vitamin E decreased the effects of oophorectomy on lipid peroxidation and avoided the DNA damage observed in urothelial cells.