The paralytic shellfish toxin, saxitoxin, enters the cytoplasm and induces apoptosis of oyster immune cells through a caspase-dependent pathway

• Published in: Aquatic Toxicology
• Main Authors: Abi-Khalil, Celina, Finkelstein, Darren S., Conejero, Geneviève, Du Bois, Justin, Destoumieux-Garzon, Delphine, Rolland, Jean Luc
• Other Authors: Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Department of Chemistry, Biochimie et Physiologie Moléculaire des Plantes (BPMP), Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: Shellfish; Toxin; Harmful algae; Phytoplankton; crassostrea gigas; hémocyte; réaction hémocytaire; [SDV]Life Sciences [q-bio]; Crassostrea gigas
• Online Access: https://hal.science/hal-01561503; https://hal.science/hal-01561503/document; https://hal.science/hal-01561503/file/Abi-KhalilC.-et%20al-PrePrint-AquaticToxico.-2017_%7B5391CD15-5587-4D24-A8CB-EEE879DFA9DB%7D.pdf; https://doi.org/10.1016/j.aquatox.2017.07.001

Article accepté Exposure of the toxin-producing dinoflagellate Alexandrium catenella (A. catenella) was previously demonstrated to cause apoptosis of hemocytes in the oyster species Crassostrea gigas. In this work, a coumarin-labeled saxitoxin appeared to spread throughout the cytoplasm of the hemocytes. PSTs, including saxitoxin, were also shown to be directly responsible for inducing apoptosis in hemocytes, a process dependent on caspase activation and independent of reactive oxygen species (ROS) production. A series of in vitro labeling and microscopy experiments revealed that STX and analogs there of induced nuclear condensation, phosphatidylserine exposure, membrane permeability, and DNA fragmentation of hemocytes. Unlike in vertebrates, gonyautoxin-5 (GTX5), which ispresent in high concentrations in A. catenella, was found to be more toxic than saxitoxin (STX) to oyster immune cells. Altogether, results show that PSTs produced by toxic dinoflagellates enter the cytoplasm and induce apoptosis of oyster immune cells through a caspase-dependent pathway. Because of the central role of hemocytes in mollusc immune defense, PST-induced death of hemocytes could negatively affect resistance of bivalvemolluscs to microbial infection.