Simone Puiseux-Dao

Proteomic and phosphoproteomic analysis of cellular responses in medaka fish (Oryzias latipes) following oral gavage with microcystin-LR ☆

Chronic and subchronic toxicity resulting from exposure to microcystins (MCs) receives increasing attention due to the risk of bioaccumulation of these toxins by aquatic animals, including fish. The mechanisms of action of MCs that target the liver, involve modifications of protein phosphorylation resulting from phosphatases 1 and 2A inhibition. Therefore, studying phosphoprotein modifications by using a specific phosphoprotein stain Pro-Q Diamond in fish liver contaminated with MC-leucine-arginine (MC-LR), the most toxic MC, should help dissecting disturbed signaling and metabolic networks. We have recently used this technology to identify several proteins that are modulated either in expression or phosphorylation in the liver of medaka following short-term exposure to MC-LR by balneation. In the present study, we have decided to use an alternative way of introducing the toxin into fish; that is by gavage (force-feeding). This was first achieved using tritiated MC-LR and allowed us to quantify the quantity of toxin incorporated into fish and to demonstrate that the toxin is mainly accumulated in liver. Afterwards a proteomics study limited to liver cytosolic proteins of contaminated animals showed that several proteins were up or down regulated either in quantity or in phosphorylation or both. Some of them had been previously detected as modified in balneation experiments but new molecules were identified as involved in signal transduction pathways activated by the toxin. In addition, in the conditions used (5 microg toxin/g body weight) anatomopathological studies supported a process of apoptonecrosis established after 24h, which was suggested to proceed by the evolution of some of the proteins after 2h contamination.

Effect of antibacterial plant flavanones on the intracellular calcium compartment involved in the first cleavage of sea urchin eggs

Two plant flavanones, (Sigmoidin A and B) having noticeable antibacterial activity, were assayed using a preparation for the study of sea urchin egg cleavage. When added after insemination, both toxins inhibit egg division with a half maximal dose of 7.5 microM for Sigmoidin A and 12 microM for Sigmoidin B. The first Ca2+ signal following fertilization was not modified by the molecules, however, the intracellular storage of calcium in isolated non-mitochondrial compartments was reduced in a dose-dependent manner by Sigmoidin A and Sigmoidin B. Both trigger a complete discharge of the sequestered calcium. In vivo the flavanones dramatically reduced the capacity of storage of non-mitochondrial intracellular calcium compartments necessary to the cyclical elevation of cytosolic free calcium during the cell cycle.

Effects of cadmium and copper contamination on calcium content of the bivalve Ruditapes decussatus

Abstract Heavy metals, such as Cu, Cd and Hg are known to disturb Ca homeostasis in marine invertebrates. Accumulation of Cu and Cd was studied in the clam Ruditapes decussatus . Animals were exposed to Cu (30 and 150 μg/ litre) or Cd (200 and 500 μg/litre). Metal concentrations were measured in the gills, visceral masses and remainders. Exposure to Cd increased Cd concentrations in all organs studied. In Cu experiments, a significant increase in Cu and Ca concentrations was noted in the organs studied. This increase in Ca may be induced by the action of copper. Such an increase was not observed in Cd-treated animals. Following a detoxication period of 8 days, the body content of Cu decreased strongly (ca 50% after 3 days), whereas that of Cd remained unchanged, suggesting that Cd is more firmly bound than Cu in R. decussatus .

Effect of maitotoxin on sea urchin egg fertilization and on Ca2+ permeabilities of eggs and intracellular stores

Summary— Maitotoxin (MTX), a potent marine toxin involved in ciguatera poisoning, inhibited sea urchin egg fertilization in a dose‐dependent manner with an IC50 of 7.5 × 10−3 MU (mouse‐unit)/ml. It did not affect male gametes fertilizing capabilities but provoked exocytosis in female gametes. It induced a K+ loss simultaneously with a Na+ entry into unfertilized eggs and increased the Ca2+ influx at higher concentrations. On isolated cortex preparations, high concentrations of MTX reduced the rate of ATP‐dependent ca2+ accumulation into reticulum compartments and caused a leakage of Ca2+ from a preparation pre‐loaded with 45Ca2+. Verapamil (10−4 M) similarly blocked the increase of egg permeability to Ca2+ and the effect on Ca2+ sequesting into intracellular compartment, induced by MTX. Ion transport perturbations which evolved relatively slowly are probably not the direct cause of fertilization inhibition which could be related to a modification of the plasma membrane of the female gametes by this hydrophilic toxin.

The mysid Siriella armata as a test organism in toxicology: Effects of cadmium

Abstract A shrimp-like crustacean of the coastal Zooplankton in the north-western Mediterranean Sea, the mysid Siriella armata, offers a test organism whose life cycle is entirely controllable under laboratory conditions. The effects of the heavy metal cadmium were studied on adults and juveniles cultured in the laboratory including acute toxicity, bioaccumulation and effects on growth, ingestion and moult cycle.

Maitotoxin, Okadaic Acid, and Microcystins: Toxins That Disturb Signal Transduction and Phosphorylations

Seafood poisoning surveys point out the increasingly wide occurrence of illness risk due to toxins found in molluscs or fish consumed by humans. Some poisonings such as paralytic shellfish poisoning induce neurologic symptoms; in others, digestive disorders are predominant, as in diarrhetic shellfish poisoning (DSP). The toxins isolated from these animals are, in fact, synthesized by microalgae, in general dinoflagellates but also diatoms or cyanobacteria, and they accumulate along the food chain.