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Progress in Understanding Algal Bloom-Mediated Fish Kills: The Role of Superoxide Radicals, Phycotoxins and Fatty Acids.

Dorantes-Aranda JJ, Seger A, Mardones JI, Nichols PD, Hallegraeff GM - PLoS ONE (2015)

Bottom Line: The effect of purified phycotoxins and crude extracts was compared, and the effect of fatty acids is discussed.However, the paralytic shellfish toxins (PST) GTX1&4, C1&C2, and STX did not account for Alexandrium ichthyotoxicity.Only aqueous extracts of Alexandrium were cytotoxic (≤65% decrease of viability), whereas crude methanol and acetone extracts of Chattonella, Fibrocapsa, Heterosigma, Karlodinium and Prymnesium decreased cell viability down to 0%.

View Article: PubMed Central - PubMed

Affiliation: Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia.

ABSTRACT
Quantification of the role of reactive oxygen species, phycotoxins and fatty acids in fish toxicity by harmful marine microalgae remains inconclusive. An in vitro fish gill (from rainbow trout Oncorhynchus mykiss) assay was used to simultaneously assess the effect in superoxide dismutase, catalase and lactate dehydrogenase enzymatic activities caused by seven species of ichthyotoxic microalgae (Chattonella marina, Fibrocapsa japonica, Heterosigma akashiwo, Karenia mikimotoi, Alexandrium catenella, Karlodinium veneficum, Prymnesium parvum). Quantification of superoxide production by these algae was also performed. The effect of purified phycotoxins and crude extracts was compared, and the effect of fatty acids is discussed. The raphidophyte Chattonella was the most ichthyotoxic (gill cell viability down to 35%) and also the major producer of superoxide radicals (14 pmol cell-1 hr-1) especially after cell lysis. The raphidophyte Heterosigma and dinoflagellate Alexandrium were the least toxic and had low superoxide production, except when A. catenella was lysed (5.6 pmol cell-1 hr-1). Catalase showed no changes in activity in all the treatments. Superoxide dismutase (SOD) and lactate dehydrogenase exhibited significant activity increases of ≤23% and 51.2% TCC (total cellular content), respectively, after exposure to C. marina, but SOD showed insignificant changes with remaining algal species. A strong relationship between gill cell viability and superoxide production or superoxide dismutase was not observed. Purified brevetoxins PbTx-2 and -3 (from Karenia brevis, LC50 of 22.1 versus 35.2 μg mL-1) and karlotoxin KmTx-2 (from Karlodinium; LC50 = 380 ng mL-1) could almost entirely account for the fish killing activity by those two dinoflagellates. However, the paralytic shellfish toxins (PST) GTX1&4, C1&C2, and STX did not account for Alexandrium ichthyotoxicity. Only aqueous extracts of Alexandrium were cytotoxic (≤65% decrease of viability), whereas crude methanol and acetone extracts of Chattonella, Fibrocapsa, Heterosigma, Karlodinium and Prymnesium decreased cell viability down to 0%. These and our previous findings involving the role of fatty acids confirm that superoxide radicals are only partially involved in ichthyotoxicity and point to a highly variable contribution by other compounds such as lipid peroxidation products (e.g. aldehydes).

No MeSH data available.


Related in: MedlinePlus

Viability of gill cells after exposure to (A) Karlodinium veneficum and equivalent karlotoxin (KmTx-2) concentrations, (B) karlotoxin at different pH, and (C) karlotoxin at higher concentrations.Error bars represent standard deviations of four replicates. The interrupted line in C shows LC50 values: 380 (3 hrs), 293 (4 hrs), and 203 ng mL-1 (5 hrs). Letters or asterisk on top of columns or next to the symbols in the lines indicate significant differences among treatments.
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pone.0133549.g009: Viability of gill cells after exposure to (A) Karlodinium veneficum and equivalent karlotoxin (KmTx-2) concentrations, (B) karlotoxin at different pH, and (C) karlotoxin at higher concentrations.Error bars represent standard deviations of four replicates. The interrupted line in C shows LC50 values: 380 (3 hrs), 293 (4 hrs), and 203 ng mL-1 (5 hrs). Letters or asterisk on top of columns or next to the symbols in the lines indicate significant differences among treatments.

Mentions: Purified brevetoxin PbTx-2 was more toxic than PbTx-3, with LC50 of 22.1 and 35.2 μg mL-1, respectively (Fig 8A). The difference in toxicity was significant at concentrations ≥20 μg mL-1 (p = 0.0002), PbTx-2 decreased gill cell viability by 44% and PbTx-3 by 30%. A decrease of gill cell viability of 99% and 55% was observed at the highest concentration of PbTx-2 and PbTx-3 (40 μg mL-1), respectively (Fig 8A). Among the PST toxins tested, GTX1&4 was the most toxic (p = 0.0002), followed by STX and C1&C2. Gonyautoxins 1 and 4 were supplied as a cocktail, as well as C1&2; LC50 observed for each toxin were 0.09 μg mL-1 GTX1 with 0.03 μg mL-1 GTX4, 1.71 μg mL-1 for STX, and 3.58 μg mL-1 C1 with 1.07 μg mL-1 C2 (Fig 8B). Karlotoxin KmTx-2 showed a comparable toxicity with live and lysed Karlodinium veneficum cells (<38% loss of viability; Fig 9A). Toxicity of karlotoxin did not vary between pH 7.5 and 9.0 (17–35% loss of viability; Fig 9B). Low toxicity was observed in a 2-hr exposure (≤26% loss of gill cell viability) but a significant increase in toxicity was observed with time, particularly at a concentration of 1000 ng mL-1 (Fig 9C) (p≤0.0347). Lower LC50 values were observed as exposure time was increased. LC50 calculated at 3, 4 and 5 hrs were 380, 293, and 203 ng mL-1, respectively (previously reported in Place et al. [44]).


Progress in Understanding Algal Bloom-Mediated Fish Kills: The Role of Superoxide Radicals, Phycotoxins and Fatty Acids.

Dorantes-Aranda JJ, Seger A, Mardones JI, Nichols PD, Hallegraeff GM - PLoS ONE (2015)

Viability of gill cells after exposure to (A) Karlodinium veneficum and equivalent karlotoxin (KmTx-2) concentrations, (B) karlotoxin at different pH, and (C) karlotoxin at higher concentrations.Error bars represent standard deviations of four replicates. The interrupted line in C shows LC50 values: 380 (3 hrs), 293 (4 hrs), and 203 ng mL-1 (5 hrs). Letters or asterisk on top of columns or next to the symbols in the lines indicate significant differences among treatments.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4509671&req=5

pone.0133549.g009: Viability of gill cells after exposure to (A) Karlodinium veneficum and equivalent karlotoxin (KmTx-2) concentrations, (B) karlotoxin at different pH, and (C) karlotoxin at higher concentrations.Error bars represent standard deviations of four replicates. The interrupted line in C shows LC50 values: 380 (3 hrs), 293 (4 hrs), and 203 ng mL-1 (5 hrs). Letters or asterisk on top of columns or next to the symbols in the lines indicate significant differences among treatments.
Mentions: Purified brevetoxin PbTx-2 was more toxic than PbTx-3, with LC50 of 22.1 and 35.2 μg mL-1, respectively (Fig 8A). The difference in toxicity was significant at concentrations ≥20 μg mL-1 (p = 0.0002), PbTx-2 decreased gill cell viability by 44% and PbTx-3 by 30%. A decrease of gill cell viability of 99% and 55% was observed at the highest concentration of PbTx-2 and PbTx-3 (40 μg mL-1), respectively (Fig 8A). Among the PST toxins tested, GTX1&4 was the most toxic (p = 0.0002), followed by STX and C1&C2. Gonyautoxins 1 and 4 were supplied as a cocktail, as well as C1&2; LC50 observed for each toxin were 0.09 μg mL-1 GTX1 with 0.03 μg mL-1 GTX4, 1.71 μg mL-1 for STX, and 3.58 μg mL-1 C1 with 1.07 μg mL-1 C2 (Fig 8B). Karlotoxin KmTx-2 showed a comparable toxicity with live and lysed Karlodinium veneficum cells (<38% loss of viability; Fig 9A). Toxicity of karlotoxin did not vary between pH 7.5 and 9.0 (17–35% loss of viability; Fig 9B). Low toxicity was observed in a 2-hr exposure (≤26% loss of gill cell viability) but a significant increase in toxicity was observed with time, particularly at a concentration of 1000 ng mL-1 (Fig 9C) (p≤0.0347). Lower LC50 values were observed as exposure time was increased. LC50 calculated at 3, 4 and 5 hrs were 380, 293, and 203 ng mL-1, respectively (previously reported in Place et al. [44]).

Bottom Line: The effect of purified phycotoxins and crude extracts was compared, and the effect of fatty acids is discussed.However, the paralytic shellfish toxins (PST) GTX1&4, C1&C2, and STX did not account for Alexandrium ichthyotoxicity.Only aqueous extracts of Alexandrium were cytotoxic (≤65% decrease of viability), whereas crude methanol and acetone extracts of Chattonella, Fibrocapsa, Heterosigma, Karlodinium and Prymnesium decreased cell viability down to 0%.

View Article: PubMed Central - PubMed

Affiliation: Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia.

ABSTRACT
Quantification of the role of reactive oxygen species, phycotoxins and fatty acids in fish toxicity by harmful marine microalgae remains inconclusive. An in vitro fish gill (from rainbow trout Oncorhynchus mykiss) assay was used to simultaneously assess the effect in superoxide dismutase, catalase and lactate dehydrogenase enzymatic activities caused by seven species of ichthyotoxic microalgae (Chattonella marina, Fibrocapsa japonica, Heterosigma akashiwo, Karenia mikimotoi, Alexandrium catenella, Karlodinium veneficum, Prymnesium parvum). Quantification of superoxide production by these algae was also performed. The effect of purified phycotoxins and crude extracts was compared, and the effect of fatty acids is discussed. The raphidophyte Chattonella was the most ichthyotoxic (gill cell viability down to 35%) and also the major producer of superoxide radicals (14 pmol cell-1 hr-1) especially after cell lysis. The raphidophyte Heterosigma and dinoflagellate Alexandrium were the least toxic and had low superoxide production, except when A. catenella was lysed (5.6 pmol cell-1 hr-1). Catalase showed no changes in activity in all the treatments. Superoxide dismutase (SOD) and lactate dehydrogenase exhibited significant activity increases of ≤23% and 51.2% TCC (total cellular content), respectively, after exposure to C. marina, but SOD showed insignificant changes with remaining algal species. A strong relationship between gill cell viability and superoxide production or superoxide dismutase was not observed. Purified brevetoxins PbTx-2 and -3 (from Karenia brevis, LC50 of 22.1 versus 35.2 μg mL-1) and karlotoxin KmTx-2 (from Karlodinium; LC50 = 380 ng mL-1) could almost entirely account for the fish killing activity by those two dinoflagellates. However, the paralytic shellfish toxins (PST) GTX1&4, C1&C2, and STX did not account for Alexandrium ichthyotoxicity. Only aqueous extracts of Alexandrium were cytotoxic (≤65% decrease of viability), whereas crude methanol and acetone extracts of Chattonella, Fibrocapsa, Heterosigma, Karlodinium and Prymnesium decreased cell viability down to 0%. These and our previous findings involving the role of fatty acids confirm that superoxide radicals are only partially involved in ichthyotoxicity and point to a highly variable contribution by other compounds such as lipid peroxidation products (e.g. aldehydes).

No MeSH data available.


Related in: MedlinePlus