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  • Interactive effects of CO₂ and trace metals on the proteasome activity and cellular stress response of marine bivalves Crassostrea virginica and Mercenaria mercenaria.

Interactive effects of CO₂ and trace metals on the proteasome activity and cellular stress response of marine bivalves Crassostrea virginica and Mercenaria mercenaria.

Aquatic toxicology (Amsterdam, Netherlands) (2014-02-28)
Sandra Götze, Omera B Matoo, Elia Beniash, Reinhard Saborowski, Inna M Sokolova
초록

Increased anthropogenic emission of CO2 changes the carbonate chemistry and decreases the pH of the ocean. This can affect the speciation and the bioavailability of metals in polluted habitats such as estuaries. However, the effects of acidification on metal accumulation and stress response in estuarine organisms including bivalves are poorly understood. We studied the interactive effects of CO2 and two common metal pollutants, copper (Cu) and cadmium (Cd), on metal accumulation, intracellular ATP/ubiquitin-dependent protein degradation, stress response and energy metabolism in two common estuarine bivalves-Crassostrea virginica (eastern oyster) and Mercenaria mercenaria (hard shell clam). Bivalves were exposed for 4-5 weeks to clean seawater (control) and to either 50 μg L(-1) Cu or 50 μg L(-1) Cd at one of three partial pressures of CO2 ( [Formula: see text] ∼ 395, ∼ 800 and ∼ 1500 μatm) representative of the present-day conditions and projections of the Intergovernmental Panel for Climate Change (IPCC) for the years 2100 and 2250, respectively. Clams accumulated lower metal burdens than oysters, and elevated [Formula: see text] enhanced the Cd and Cu accumulation in mantle tissues in both species. Higher Cd and Cu burdens were associated with elevated mRNA expression of metal binding proteins metallothionein and ferritin. In the absence of added metals, proteasome activities of clams and oysters were robust to elevated [Formula: see text] , but [Formula: see text] modulated the proteasome response to metals. Cd exposure stimulated the chymotrypsin-like activity of the oyster proteasome at all CO2 levels. In contrast, trypsin- and caspase-like activities of the oyster proteasome were slightly inhibited by Cd exposure in normocapnia but this inhibition was reversed at elevated [Formula: see text] . Cu exposure inhibited the chymotrypsin-like activity of the oyster proteasome regardless of the exposure [Formula: see text] . The effects of metal exposure on the proteasome activity were less pronounced in clams, likely due to the lower metal accumulation. However, the general trends (i.e. an increase during Cd exposure, inhibition during exposure to Cu, and overall stimulatory effects of elevated [Formula: see text] ) were similar to those found in oysters. Levels of mRNA for ubiquitin and tumor suppressor p53 were suppressed by metal exposures in normocapnia in both species but this effect was alleviated or reversed at elevated [Formula: see text] . Cellular energy status of oysters was maintained at all metal and CO2 exposures, while in clams the simultaneous exposure to Cu and moderate hypercapnia (∼ 800 μatm [Formula: see text] ) led to a decline in glycogen, ATP and ADP levels and an increase in AMP indicating energy deficiency. These data suggest that environmental CO2 levels can modulate accumulation and physiological effects of metals in bivalves in a species-specific manner which can affect their fitness and survival during the global change in estuaries.

MATERIALS
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Sigma-Aldrich
Cadmium, granular, ≥99%, 5-20 mesh
Sigma-Aldrich
Cadmium, powder, −100 mesh, 99.5% trace metals basis
Sigma-Aldrich
Cadmium, shot, 3 mm, 99.999% trace metals basis
Sigma-Aldrich
Cadmium, granular, 30-80 mesh, ≥99%
Cadmium, foil, 6mm disks, thickness 0.25mm, as rolled, 99.9%
Cadmium, foil, 6mm disks, thickness 0.125mm, as rolled, 99.95%
Cadmium, foil, not light tested, 50x50mm, thickness 0.01mm, 99.7+%
Cadmium, foil, light tested, 25x25mm, thickness 0.01mm, 99.7+%
Cadmium, tube, 500mm, outside diameter 2.29mm, inside diameter 1.27mm, wall thickness 0.51mm, 99.95+%
Cadmium, foil, 50mm disks, thickness 0.5mm, as rolled, 99.95%
Cadmium, foil, not light tested, 100x100mm, thickness 0.01mm, 99.7+%
Cadmium, foil, not light tested, 50x50mm, thickness 0.005mm, 99.7+%
Cadmium, foil, not light tested, 25x25mm, thickness 0.01mm, 99.7+%
Cadmium, foil, 4mm disks, thickness 0.5mm, as rolled, 99.95%
Cadmium, rod, 300mm, diameter 10.0mm, as drawn, 99.99+%
Cadmium, foil, not light tested, 100x100mm, thickness 0.025mm, 99.7+%
Cadmium, foil, not light tested, 25x25mm, thickness 0.025mm, 99.7+%
Cadmium, foil, light tested, 100x100mm, thickness 0.025mm, 99.7+%
Cadmium, foil, 8mm disks, thickness 1.0mm, as rolled, 99.95%
Cadmium, foil, 6mm disks, thickness 0.25mm, as rolled, 99.95%
Cadmium, wire reel, 0.1m, diameter 0.5mm, hard, 99.99+%
Cadmium, foil, light tested, 50x50mm, thickness 0.01mm, 99.7+%
Cadmium, foil, 50mm disks, thickness 0.25mm, as rolled, 99.95%
Cadmium, rod, 500mm, diameter 5.0mm, as drawn, 99.99+%
Cadmium, rod, 25mm, diameter 40mm, 99.9%
Cadmium, foil, light tested, 100x100mm, thickness 0.015mm, 99.7+%
Cadmium, wire reel, 0.1m, diameter 0.5mm, hard, 99.95+%
Cadmium, foil, 8mm disks, thickness 0.125mm, as rolled, 99.99+%
Cadmium, foil, 6mm disks, thickness 0.005mm, 99.7+%
Cadmium, foil, 8mm disks, thickness 0.05mm, as rolled, 99.99+%