| Brevetoxin Forms Covalent DNA Adducts in Rat Lung Following Intratracheal Exposure Faisal F.Y. Radwan1,2 and John S. Ramsdell1 1Marine Biotoxins Program, Center for Coastal Environmental Health and Biomolecular Research, National Oceanic and Atmospheric Administration/National Ocean Service, Charleston, South Carolina, USA; 2Sohag University, Faculty of Science, Sohag, Egypt Abstract
Background: Human exposure to brevetoxins produced by the red tide organism, Karenia brevis, is an increasing public health concern. Using in vitro exposure of rat liver cells to brevetoxin B (PbTx-2) , the primary toxin product of K. brevis, we previously showed that it formed C27,28-epoxy brevetoxin metabolites capable of covalently binding to nucleic acids, a common initiation step for carcinogenesis. Objective: This study was undertaken to evaluate nucleic acid adduction in lung following in vitro and in vivo brevetoxin exposures. Methods: To clarify reactions of brevetoxin epoxide with DNA, we analyzed reaction products of PbTx-6 (a C27,28 epoxide metabolite of brevetoxin B) with nucleosides. We also analyzed adducts from nucleic acid hydrolysates of isolated rat lung cells treated with PbTx-2 or PbTx-6 in vitro and lung tissue from rats after intratracheal exposure to PbTx-2 or PbTx-6 at 45 µg toxin/kg body weight. Results: Our results indicate that PbTx-2 forms DNA adducts with cytidine aftertreatment of isolated lung cells, and forms DNA adducts with adenosine and guanosine after intratracheal exposure. Conclusions: These results are consistent with metabolic activation of highly reactive brevetoxin intermediates that bind to nucleic acid. These findings provide a basis for monitoring exposure and assessing the hazard associated with depurination of brevetoxin–nucleotide adducts in lung tissue. Key words: brevetoxin, DNA adducts, epoxidation, harmful algal bloom, Karenia brevis, lung, metabolism. Environ Health Perspect 116:930–936 (2008) . doi:10.1289/ehp.11068 available via http://dx.doi.org/ [Online 24 March 2008]
Address correspondence to J.S. Ramsdell, Harmful Algal Bloom & Analytical Response Branch, NOAA, 219 Fort Johnson Rd., Charleston, SC 29412, USA. Telephone: (843) 762–8510. Fax: (843) 762–8700. E-mail: john.ramsdell@noaa.gov We thank J. Pritchett (IAS Inc., Burlingame, CA) for mass spectrometry analyses. This work was performed while F.F.Y.R held a National Research Council Associateship Award at the Marine Biotoxins Program, NOAA/NOS/CCEHBR. This work was funded by the National Oceanic and Atmospheric Administration/National Ocean Service (NOAA/NOS) . The NOS does not approve, recommend, or endorse any proprietary product or material mentioned in this publication. No reference shall be made to NOS, or to this publication furnished by NOS, in any advertising or sales promotion which would indicate or imply that NOS approves, recommends, or endorses any proprietary product or proprietary material mentioned herein or which has as its purpose any intent to cause directly or indirectly the advertised product to be used or purchased because of NOS publication. The authors declare they have no competing financial interests. Received 14 November 2007 ; accepted 21 March 2008.
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