Immune function in Trachemys scripta following exposure to a predominant brevetoxin congener, PbTx-3, as a model for potential health impacts for sea turtles naturally exposed to brevetoxins
Many species of marine life in southwestern Florida, including sea turtles, are impacted by blooms of the toxic dinoflagellate, Karenia brevis. Sublethal exposure to toxins produced by K. brevis has been shown to impact sea turtle health. Since all sea turtles in the Gulf of Mexico have protected status, a freshwater turtle, Trachemys scripta, was used as a model for immune system effects following experimental exposure to a predominant brevetoxin congener in K. brevis blooms, PbTx-3. Exposure to PbTx-3 was oral or intratracheal and health effects were assessed using a suite of immune function parameters: innate immune function (phagocytosis, plasma lysozyme activity), adaptive immune function (lymphocyte proliferation), and measures of oxidative stress (superoxide dismutase (SOD) and glutathione-S-transferase (GST) activity in plasma). Inflammation was also measured using plasma protein electrophoresis. In addition, differential expression of genes in peripheral blood leukocytes was determined using suppression subtractive hybridization followed by real-time PCR of specific genes. The primary immune effects of sublethal brevetoxin exposure in T. scripta following PbTx-3 administration, appear to be an increase in oxidative stress, a decrease in lysozyme activity, and modulation of immune function through lymphocyte proliferation responses. Plasma protein electrophoresis showed a decreased A:G ratio which may indicate potential inflammation. Genes coding for oxidative stress, such as thioredoxin and GST, were upregulated in exposed animals. That sublethal brevetoxin exposures impact immune function components suggests potential health implications for sea turtles naturally exposed to toxins. Knowledge of physiological stressors induced by brevetoxins may contribute to the ultimate goal of developing directed treatment strategies in exposed animals for reduced mortality resulting from red tide toxin exposure in sea turtles.
KeywordsBrevetoxins Red tide Immune system Pond slider Freshwater turtle
enzyme-linked immunosorbent assay
polymerase chain reaction
suppression subtractive hybridization
hen egg white lysozyme
peripheral blood leukocytes
heat shock protein
The authors would like to acknowledge funding from NOAA NOS National Center for Coastal Ocean Science (Grant No. NA11NOS4780058). The authors would like to acknowledge Mote Marine Laboratory for use of facilities; J Balmer and C Coppola for roles in initial experiments; B Carter and P Larkin for conducting SSH, primer design, and qPCR experiments. The research was funded by NOAA Grant numbers NA11NOS4780031 (SLM) and NA11NOS4780058 (CJW) and is publication number ECO878 from the Ecology and Oceanography of Harmful Algal Blooms Program (ECOHAB).
This research was funded by NOAA Grant numbers NA11NOS4780031 (SLM) and NA11NOS4780058 (CJW).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. The protocols with animals were approved by FAU IACUC. This article does not contain studies with human participants performed by any of the authors.
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