Genotoxic potential of microcystin-LR and nodularin in vitro in primary cultured rat hepatocytes and in vivo in rat liver

• Published in: Environmental toxicology Vol. 20; no. 3; pp. 341 - 347
• Main Authors: Bouaicha, N, Maatouk, I, Plessis, M.J, Perin, F
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.06.2005; Wiley
• Subjects: 32P postlabeling; 8-oxo-dG; Animal, plant and microbial ecology; Animals; Applied ecology; Biological and medical sciences; Biomarkers - analysis; Cell Culture Techniques; Deoxyguanosine - analogs & derivatives; Deoxyguanosine - analysis; DNA adducts; DNA Damage; Ecotoxicology, biological effects of pollution; Enzyme Inhibitors - toxicity; Fundamental and applied biological sciences. Psychology; General aspects; genotoxicity; Hepatocytes; hepatotoxicity; I compounds; in vitro studies; in vivo studies; laboratory animals; liver; Liver - drug effects; Liver - pathology; Liver Neoplasms - chemically induced; Male; microcystin-LR; Microcystins; nodularin; Oxidative Stress; Peptides, Cyclic - toxicity; Rats; Rats, Sprague-Dawley; toxicity testing; Ecotoxicology; Rat; Toxicity; Liver; I compounds; Rodentia; Genotoxicity; 32P postlabeling; Postlabeling; In vitro; 8-oxo-dG; nodularin; In vivo; Vertebrata; Mammalia; Hepatocyte; DNA; Environment; DNA adducts; microcystin-LR
• ISSN: 1520-4081; 1522-7278
• DOI: 10.1002/tox.20110

Microcystin-LR (MCYST-LR) and nodularin (NOD) are known as tumor promoters in experimental animals and so present potential health threats for humans. Although their hepatotoxic mechanisms have been very well documented, many other effects of these toxins are relatively undescribed, indeed controversial, notably those related to their genotoxicity. In the present investigation, we examined how these toxins could induce DNA damage using a combination of in vitro and in vivo approaches. We first used the 32P-postlabeling assay to test hydrophobic adduct formation on DNA from primary cultured rat hepatocytes treated with noncytotoxic concentrations of MCYST-LR and NOD (2 and 10 ng/mL). Analysis of the autoradiograms of DNA digests isolated from the hepatocytes did not show any hydrophobic DNA adduct formation. However, these toxins significantly decreased the amount of hydrophobic endogenous adducts, termed I compounds. We next investigated oxidative DNA damage by using the 32P-postlabeling assay to analyze 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) content as a biomarker of possible DNA lesions. Both MCYST-LR and NOD significantly enhanced 8-oxo-dG in time- and dose-dependent manner in vitro in primary cultured hepatocytes and in vivo in rat liver cells. Thus, it appears that the depletion of endogenous DNA adducts (I compounds) and/or the increase of 8-oxo-dG levels by MCYST-LR and NOD could be involved in the formation of hepatic tumors during long-term exposure to these cyanobacterial hepatotoxins.