Victor P. Chelomin

Cadmium-Induced Oxidative Stress in the Bivalve Mollusk Modiolus modiolus

Cadmium-induced oxidative stress in the bivalve Modiolus modiolus is studied from the standpoint of the universality of the mechanism of free-radical oxidation. The kinetics of cadmium accumulation by the bivalve was revealed in a laboratory experiment. The gills accumulated higher Cd levels than the digestive gland. In the process of cadmium accumulation, there was an increase in lipid peroxidation products (malondialdehyde and lipofuscin) and a reduction in the total oxiradical scavenging capacity (TOSC). Cadmium induces oxidative stress in molluscan tissues through damage to the antioxidation system. Thus, TOSC can provide a useful biochemical indicator of early pathological changes in the cell or the organism, as well as of the environmental effects of heavy metal pollution.

Evaluation of the genotoxicity of cadmium in gill cells of the clam Corbicula japonica using the comet assay

Cadmium-induced DNA degradation in gill cells of the clam Corbicula japonica was assessed using the comet assay (single-cell gel electrophoresis). Accumulation of highly toxic cadmium in the gill cells of bivalve is accompanied by damage to the cell genome, which is revealed as DNA migration in the comet assay. The main mechanisms of Cd effects on the integrity of the DNA structure are discussed.

The adaptation of mussels Crenomytilus grayanus to cadmium accumulation result in alterations in organization of microsomal enzyme-membrane complex (non-specific phosphatase).

The kinetic parameters (V(m), K(m) and slope) of membrane-bound microsomal non-specific phosphatase (NPase, with G6P as the substrate) from the digestive gland of unexposed and cadmium adapted (45 days for 100 µg Cd(2+)/l) mussels were investigated. In vivo and in vitro approaches were used. Adaptation of mussels (Crenomytilus grayanus) to cadmium resulted in a 1.6-fold increase in NPase activity. V(m) was increased by 1.6-fold, but K(m) was the same in terms of enzyme kinetics. This indicates that the total concentration of the enzymes in the digestive gland increased. Cd(2+) (1 mM) did not significantly alter the activity of the membrane-bound enzyme in vitro both for unexposed and for cadmium adapted mussels, meaning that cadmium ions are not a direct inhibitor of the membrane-bound enzyme in this concentration. The microsomal NPase activity in both unexposed and cadmium adapted mussels was inhibited by in vitro solubilization of microsomes with non-ionic detergent (Triton X100, 0.01%). This inhibition was uncompetitive for microsomes of unexposed mussels (K(m) decreased 3.1-fold). The most drastic events were observed in cadmium adapted mussels, where inhibition was mixed (K(m) decreased 7.2-fold). The simultaneous actions of detergent and cadmium ions did not alter NPase activity significantly in comparison with action of the detergent alone. The differences in the types and the extents of inhibition of the enzymes activity by membrane disordering agent (Triton X100) indicated that the enzyme-membrane complex (NPase) has been altered as a result of adaptation of mussels to cadmium accumulation. We conclude that the mussels produced a new enzyme-membrane complex, with the same K(m) as the previous complex, but with other detergent sensitivity and greater amounts. Thus, the adaptation capacity of this enzyme is reduced as result of adaptation of mussels to cadmium accumulation.

DNA damage in the gill cells of the marine scallop Mizuhopecten yessoensis during anoxic stress and aerobic recovery

Anoxia-induced DNA damage in the gill cells of the marine scallop Mizuhopecten yessoensis was assessed with the alkaline comet assay (single-cell gel electrophoresis). The alkaline comet assay method for detecting DNA strand breaks and alkali labile sites in individual cells. DNA damage was determened in the scallops (M. yessoensis) gill cells. The scallops were exposed to air for 8 h showing a clear increase in the levels of DNA damage. After the air exposure, M. yessoensis were re-submersed for a period of 12 h, leading values to return to a pre-aerial exposure level. Control animals were kept immersed during the whole period. The resulting data demonstrate that natural influences, such as oxygen depletion (anoxia) in seawater, can be responsible for the induction of DNA damage. If the scallops were re-immersed in oxic conditions, the anoxically induced breaks were repaired. The main mechanisms influencing the integrity of the DNA structure are discussed in this paper.

In vitro effect of copper ions on transbilayer distribution of aminophospholipids in synaptosomal membrane of walleye pollock (Theragra chalcogramma)

Effect of copper ions on lipid matrix organization of synaptosomal membrane of the marine fish Theragra chalcogramma was investigated. It was demonstrated that interaction of copper ions with these membrane stimulated the process of lipid peroxidation and caused changes in the transbilayer distribution of aminophospholipids. Accessibility of phosphatidylethanolamine was increased more than twice, and of phosphatidylserine more than ten times, that can be explained by changes in asymmetrical structure of lipid matrix of synaptosomal membrane. We suggested, that the main mechanism of copper-stimulated damage in transbilayer organization of the membrane is oxidation of membrane protein sulfhydryl groups.

Using Heavy Metal Content and Lipid Peroxidation Indicators in the Tissues of the Mussel Crenomytilus grayanus for Pollution Assessment After Marine Environmental Remediation.

We examined the effects of environmental remediation on the heavy metal concentration and lipid peroxidation activity in the digestive gland and gills of the marine mussel Crenomytilus grayanus. Changes in heavy metal concentrations and lipid peroxidation biomarkers in the tissues of mussels collected at a contaminated site were compared with those obtained from a reference site. Prior to remediation the concentration of Pb, Cu, Cd, Fe and Zn and the levels of malondialdehyde, conjugated dienes and lipofuscin in mussels collected from the contaminated site were significantly increased compared with those obtained from the reference site. Three years after remediation, these parameters did not significantly exceed the reference site parameters, except Pb, whose concentration, though markedly decreased, yet was much higher than in tissues of mussels from the reference site.

Glutathione S-transferase activity in marine invertebrates from Peter the Great Bay in the Sea of Japan

A total of 23 species of marine invertebrates from Peter the Great Bay belonging to five taxonomic groups were screened for the activity of glutathione S-transferase, which is one of the main enzymes for the detoxification of organic xenobiotics. Significant variation of the enzyme activity (7.1 to 36900 nmol/min/mg of protein) was found among the different groups of organisms. The possible reasons for the differences in enzyme activity are discussed based on the example of bivalve mollusks.

The genotoxicity of copper oxide nanoparticles to marine organisms based on the example of the Pacific mussel Mytilus trossulus gould, 1850 (Bivalvia: Mytilidae)

The accumulation of CuO nanoparticles causes destructive changes in the DNA molecule in the gill and digestive gland cells of the Pacific mussel Mytilus trossulus. The gill cells of the mollusk were found to be more sensitive to the genotoxic effect of CuO nanoparticles than the digestive-gland cells.

Genotoxic potential of copper oxide nanoparticles in the bivalve mollusk Mytilus trossulus

Copper oxide nanoparticles (CuO-NPs) are among the most widely used metal oxide nanoparticles, which increases the chance of their being released into the marine environment. As the applications of these particles have increased in recent years, their potential impact on the health of marine biota has also increased. However, the toxicological effects of these NPs in the marine environment are poorly known. In the present study, the DNA damaging potential of CuO-NPs in the marine eastern mussel Mytilus trossulus was evaluated and compared to that of dissolved copper exposures. Genotoxicity was assessed by the single cell gel electrophoresis (comet) assay in mussel gill and digestive gland cells. The results showed that copper in both forms (CuO-NPs and dissolved copper) was accumulated to different extents in mussel tissues. The mussel exposed to the dissolved copper attained higher concentrations of copper in the gills than in the digestive gland. In contrast to these results, it was found that CuO-NPs could induce much higher copper accumulation in the digestive gland than in the gills. A clear and statistically significant increase in DNA damage was found in both tissues of the Cu-exposed group compared to the control mussels. Our results indicated that the CuO-NP exposure produced remarkable effects and increased DNA damage significantly in mussel gill cells only. It should be noted that the digestive gland cells were prone to accumulation following CuO-NPs when compared to the gill cells, while the gill cells were more sensitive to the genotoxic effects of CuO-NPs. These results also suggested the need for a complete risk assessment of engineered particles before its arrival in the consumer market.

An analysis of the quality of the marine environment based on determination of the genotoxicity of DNA in the gill cells of the Yesso Scallop, Mizuhopecten yessoensis (Jay, 1856)

This study showed that chronic pollution of the aquatic environment causes destructive changes to DNA in the gill cells of the Yesso Scallop, Mizuhopecten yessoensis.