Genotoxic effect of bile acids on human normal and tumour colon cells and protection by dietary antioxidants and butyrate.
BACKGROUND
Colorectal cancer is the second cause of death for tumour worldwide. Among the risk factors for this disease the dietary habits seem to have a pivotal role. An elevated intake of fats causes a high release in the gut lumen of bile acids that are positively correlated with colorectal cancer, since they act as detergents and proliferation promoters. Recently, it was evidenced that bile acids can also be able to induce DNA damage.


OBJECTIVE
In this study the genotoxicity of deoxycholic acid (DCA) and chenodeoxycholic acid CDCA) has been evaluated in human normal colonocytes derived from 60 colon biopsies and in tumour cells. The involvement of reactive oxygen species (ROS) and the oxidative DNA damage was assessed. In addition, the protective effect exerted by both two well-known antioxidants commonly present in the diet, beta-carotene and alpha-tocopherol, and butyrate which is known to be involved in the regulation of several cellular functions, has also been tested.


METHODS
The DNA damage was evaluated by the "comet assay" or single cell gel electrophoresis (SCGE) both in its conventional use and by the Endonuclease III modified method, which allow to detect the presence of oxidized pyrimidines.


RESULTS
Bile acids (CDA and CDCA) resulted genotoxic on both normal and tumour human colon cells. The inclusion of the endonuclease III digestion step in the comet assay demonstrated that bile acids induced an oxidative DNA damage. In addition, treatment of colonocytes with bile acids in the presence of the antioxidants (beta-carotene, alpha-tocopherol) and Na-butyrate caused a reduction of DNA damage.


CONCLUSIONS
Our results suggest that bile acids may be involved in the tumour initiation by inducing a DNA oxidative damage, and so add further evidences to the preventive properties of antioxidants present in the Mediterranean diet.
Rosignoli
Patrizia
P
Dept Specialità Medico-Chirurgiche e Sanità Pubblica, Università degli Studi di Perugia, Perugia, Italy.
Fabiani
Roberto
R
De Bartolomeo
Angelo
A
Fuccelli
Raffaela
R
Pelli
Maria Antonietta
MA
Morozzi
Guido
G
D000975:Antioxidants / Q000494:pharmacology*; D001647:Bile Acids and Salts / Q000633:toxicity*; D001706:Biopsy; D002087:Butyrates / Q000494:pharmacology*; D002478:Cells, Cultured; D003106:Colon / Q000187:drug effects / Q000473:pathology; D015179:Colorectal Neoplasms / Q000517:prevention & control*; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects*; D004273:DNA, Neoplasm / Q000187:drug effects; D019073:HT29 Cells; D006801:Humans; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D017382:Reactive Oxygen Species
D000975:Antioxidants; D001647:Bile Acids and Salts; D002087:Butyrates; D004273:DNA, Neoplasm; D017382:Reactive Oxygen Species