Brevetoxin Forms Covalent DNA Adducts in Rat Lung Following Intratracheal Exposure

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 C(27,28)-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 C(27,28) 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 microg toxin/kg body weight. RESULTS Our results indicate that PbTx-2 forms DNA adducts with cytidine after treatment 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.