The possibility of reactive oxygen species (ROS)-independent toxic effects of Cochlodinium polykrikoides on damselfish (Chromis caerulea).
ABSTRACT To elucidate the ichthyotoxic mechanism of the harmful dinoflagellate Cochlodinium polykrikoides, a bioassay using damselfish was conducted. After exposure to a live-cell suspension of C. polykrikoides, all the fish were died within 90 min. In the presence of catalase and superoxide dismutase (SOD), no significant reduction in the toxicity of C. polykrikoides on the fish was observed. Furthermore, no significant levels of reactive oxygen species (ROS) were detected in five strains of C. polykrikoides isolated in Japan. Our results support the idea that certain toxic substances, rather than ROS, are mainly responsible for the fish-killing activity of C. polykrikoides.
SourceAvailable from: Ying Zhong Tang[Show abstract] [Hide abstract]
ABSTRACT: Harmful algal blooms (HABs) caused by the dinoflagellate Cochlodinium poly krikoides have increased in geographic extent, frequency, and duration in coastal areas worldwide. These blooms have negatively impacted many coastal fisheries, causing mass mortalities of both wild and farmed fish. Forage fish species may be particularly susceptible to HABs as they feed on plankton and are highly abundant in coastal ecosystems where these blooms occur. While mortalities associated with HABs have been well documented for juvenile and adult fish, the potential impacts to early life stages (i.e. embryos and eleutheroembryos) have not been explored. We conducted a series of toxicity experiments using a clonal laboratory culture of C. polykrikoides and 3 forage fish species (Atlantic silverside Menidia menidia, inland silverside M. beryllina, and sheepshead minnow Cyprinodon variegatus) all common on the US East Coast. Our experiments demonstrated that C. polykrikoides caused mortalities in both embryos and eleutheroembryos, but that sensitivity to acute toxicity differed among fish species (M. beryllina > M. menidia > C. variegatus) and among life stages (eleutheroembryos > embryos). Although embryos were somewhat resistant to C. polykrikoides biotoxins until they hatched, once they hatched, they experienced rapid mortality and impaired swimming ability. By testing ecologically relevant exposure times to C. polykrikoides, we found that eleutheroembryos can become incapacitated relatively quickly (i.e. within hours), and that surviving fish could recover swimming ability following removal from C. polykrikoides exposure. This research provides the first evidence of sublethal impacts on fish exposed to C. polykrikoides, and advances understanding of the potential ecosystem impacts of this harmful alga.Marine Ecology Progress Series 05/2014; 505:81-94. DOI:10.3354/meps10793 · 2.64 Impact Factor
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ABSTRACT: In this research, we investigated the cytotoxic mechanisms of Cochlodinium polykrikoidescell lysate on isolated rat liver hepatocytes.This micro algae is responsible for a severe and widespread harmful algal bloom in the Persian Gulf and Gulf of Oman (2008-2009). Isolated hepatocytes were obtained by collagenase perfusion of Sprague-Dawley rat liver.According to our results, incubation of algal lysate with isolated rat hepatocytescaused hepatocyte membrane lysis, reactive oxygen species (ROS) formation, glutathione depletion, collapse of mitochondrial membrane potential,ATP depletion and increase in ADP/ATP ratio, cytochrome c release in to the hepatocyte cytosol,activation of caspase-3 (final mediator of apoptosis) and appearance of apoptosis phenotype. On the other hand, pre-treatment of antioxidants (α-tocopherol succinate and BHT), radical scavengers (mannitol and DMSO), mitochondrial permeability transition (MPT) pore sealing agents (cyclosporine A, carnitine and trifluoperazine), NADPH P450 reductase inhibitor (Diphenyliodonium chloride), CYP2E1 inhibitors (Phenylimidazole and 4-Methylpyrazole) and ATP generators (L-glutamine, Fructose and Xylitol)inhibitedcaspase-3 activation and cell death in algal lysate treated hepatocytes.Our data also confirmed that algal lysate activates apoptosis signaling via oxidative stress and mitochondrial pathway. Thus, ROS formation caused by the lysate exposure could directly be involved in mitochondrial MPT pore opening and activation of caspase-3 leading to C.polykrikoides lysateinduced apoptosis on rat hepatocytes. These findings contribute to a better understanding of C.polykrikoides-toxic effects on mammalian liver cells.Iranian journal of pharmaceutical research (IJPR) 02/2013; 12(4):829-44. · 0.51 Impact Factor
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ABSTRACT: Harmful algal blooms produced by the marine ichthyotoxic dinoflagellate Cochlodinium polykrikoides are responsible for mass mortalities of wild and farmed fish globally. This study compared the cytotoxic mechanisms of C. polykrikoides total extract on both trout and rat liver hepatocytes. Trout hepatocytes were more sensitive than rat hepatocytes against C. polykrikoides extract. The effective concentration 50 after 3 hour incubation (EC503hr) concentrations found for C. polykrikoides extract in trout and rat hepatocytes (i.e., 50% membrane lysis in 3 hr) were Eq. 1 cell/ml and Eq. 240 cell/ml, respectively. C. polykrikoides extract exposure in both isolated trout and rat hepatocytes resulted in membrane lysis, reactive oxygen species formation, glutathione depletion, collapse of mitochondrial membrane potential, ATP depletion, increase in adenosine diphosphate (ADP)/adenosine triphosphate (ATP) ratio, cytochrome c release into the hepatocyte cytosol, and activation of caspases cascade. Trout hepatocyte toxicity was also associated with lysosomal membrane injury. Mitochondrial permeability transition in both trout and rat hepatocytes produced cytochrome c release from the mitochondrial intramembrane space into the cytosol. Thus, the cytochrome c release triggered activation of caspase-3 and apoptosis. Finally, data demonstrated that C. polykrikoides extract may induce more apoptotic phenotype in rat than trout hepatocytes, which in the latter favored predominantly necrotic mode of cell death.Toxicological and Environmental Chemistry 07/2014; 96(6-ahead-of-print):1-14. DOI:10.1080/02772248.2014.980132 · 0.72 Impact Factor