Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 7-Day Trial for You or Your Team.

Learn More →

Cylindrospermopsin Genotoxicity and Cytotoxicity: Role Of Cytochrome P-450 and Oxidative Stress

Cylindrospermopsin Genotoxicity and Cytotoxicity: Role Of Cytochrome P-450 and Oxidative Stress Cylindrospermopsin (CYN) is a cyanobacterial toxin found in drinking-water sources world wide. It was the likely cause of human poisonings in Australia and possibly Brazil. Although CYN itself is a potent protein synthesis inhibitor, its acute toxicity appears to be mediated by cytochrome p-450 (CYP450)-generated metabolites. CYN also induces genotoxic effects both in vitro and in vivo, and preliminary evidence suggests that tumors are generated by oral exposure to CYN. To understand the role of CYP450-activated CYN metabolites on in vitro genotoxicity, this study quantified the process in primary mouse hepatocytes using the COMET assay in both the presence and absence of CYP450 inhibitors known to block acute CYN cytotoxicity. CYN was cytotoxic at concentrations above 0.1 μM(EC50 = 0.5 μM) but produced significant increases in Comet tail length, area, and tail moment at 0.05 μM and above; hence genotoxicity is unlikely to be secondary to metabolic disruption due to toxicity. The CYP450 inhibitors omeprazole (100 μM) and SKF525A (50 μM) completely inhibited the genotoxicity induced by CYN. The toxin also inhibits production of glutathione (GSH), a finding confirmed in this study. This could potentiate cytotoxicity, and by implication genotoxicity, via reduced reactive oxygen species (ROS) quenching. The lipid peroxidation marker, malondialdehyde (MDA) was quantified in CYN-treated cells, and the effect of the reduced glutathione (GSSG) reductase (GSSG-rd.) inhibitor 1,3-bis(chloroethyl)-l-nitrosourea (BCNU) on both MDA production and lactate dehydrogenase (LDH) leakage was examined. MDA levels were not elevated by CYN treatment, and block of GSH regeneration by BCNU did not affect lipid peroxidation or cytotoxicity. It therefore seems likely that CYP450-derived metabolites are responsible for both the acute cytotoxicity and genotoxicity induced by CYN. This work was funded by the Cooperative Research Centre for Water Quality and Treatment. The authors thank Yvette de Graaf for help with the COMET assay, and Dr. Tanya Lewanowitsch for useful and timely advice. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Toxicology & Environmental Health Part A: Current Issues Taylor & Francis

Cylindrospermopsin Genotoxicity and Cytotoxicity: Role Of Cytochrome P-450 and Oxidative Stress

Download PDF
15 pages

Loading next page...
 
/lp/taylor-francis/cylindrospermopsin-genotoxicity-and-cytotoxicity-role-of-cytochrome-p-4Chwj0eDdw

References (36)

Publisher
Taylor & Francis
Copyright
Copyright Taylor & Francis Group, LLC
ISSN
1087-2620
eISSN
1528-7394
DOI
10.1080/15287390590925465
pmid
16020200
Publisher site
See Article on Publisher Site

Abstract

Cylindrospermopsin (CYN) is a cyanobacterial toxin found in drinking-water sources world wide. It was the likely cause of human poisonings in Australia and possibly Brazil. Although CYN itself is a potent protein synthesis inhibitor, its acute toxicity appears to be mediated by cytochrome p-450 (CYP450)-generated metabolites. CYN also induces genotoxic effects both in vitro and in vivo, and preliminary evidence suggests that tumors are generated by oral exposure to CYN. To understand the role of CYP450-activated CYN metabolites on in vitro genotoxicity, this study quantified the process in primary mouse hepatocytes using the COMET assay in both the presence and absence of CYP450 inhibitors known to block acute CYN cytotoxicity. CYN was cytotoxic at concentrations above 0.1 μM(EC50 = 0.5 μM) but produced significant increases in Comet tail length, area, and tail moment at 0.05 μM and above; hence genotoxicity is unlikely to be secondary to metabolic disruption due to toxicity. The CYP450 inhibitors omeprazole (100 μM) and SKF525A (50 μM) completely inhibited the genotoxicity induced by CYN. The toxin also inhibits production of glutathione (GSH), a finding confirmed in this study. This could potentiate cytotoxicity, and by implication genotoxicity, via reduced reactive oxygen species (ROS) quenching. The lipid peroxidation marker, malondialdehyde (MDA) was quantified in CYN-treated cells, and the effect of the reduced glutathione (GSSG) reductase (GSSG-rd.) inhibitor 1,3-bis(chloroethyl)-l-nitrosourea (BCNU) on both MDA production and lactate dehydrogenase (LDH) leakage was examined. MDA levels were not elevated by CYN treatment, and block of GSH regeneration by BCNU did not affect lipid peroxidation or cytotoxicity. It therefore seems likely that CYP450-derived metabolites are responsible for both the acute cytotoxicity and genotoxicity induced by CYN. This work was funded by the Cooperative Research Centre for Water Quality and Treatment. The authors thank Yvette de Graaf for help with the COMET assay, and Dr. Tanya Lewanowitsch for useful and timely advice.

Journal

Journal of Toxicology & Environmental Health Part A: Current Issues – Taylor & Francis

Published: May 1, 2005

There are no references for this article.