Mercury‐induced micronuclei in skin fibroblasts of beluga whales

Abstract

Abstract-Beluga whales (Delphinapterus leucas) inhabiting the St. Lawrence estuary are highly contaminated with environmental pollutants and have a high incidence of cancer. Environmental contaminants may be partly responsible for the high incidence of cancer observed in this population. DNA damage plays an important role in the development of cancer. The micronuclei assay was used to test the genotoxic potential of mercury compounds in skin fibroblasts of an Arctic beluga whale. Both mercuric chloride (Hg) and methylmercury (MeHg) induced a highly significant (p Ͻ 0.001) dose-response increase of micronucleated cells. Statistically significant increases in micronucleated cells were observed for 0.5, 5, and 20 g/ml Hg and 0.05, 0.5, and 2 g/ml MeHg when compared to control cultures. Concentrations of 0.5, 5, and 20 g/ml Hg induced a two-, three-and fourfold increase of micronucleated cells, respectively. Treatment with MeHg was one order of magnitude more potent in inducing micronuclei and in inhibiting cell proliferation than Hg. Although results of this in vitro study do not imply that mercury compounds are involved in the etiology of cancer in St. Lawrence beluga whales, significant increases in micronuclei frequency were found at low concentrations of MeHg (0.05 and 0.5 g/ml) that are believed to be comparable to concentrations present in certain whales of this population.

Marine Mammal Neoplasia: A Review

“…64 Mercury methyl hemoglobin is another suspected carcinogen in St. Lawrence belugas (D. leucas) and has been documented to produce multimicronucleation in fibroblasts because of genotoxic effects. 33 Endocrine disruption by PCBs is well documented. A role in the development of thyroid neoplasia may result from a decrease in plasma concentrations of thyroid hormones followed by a compensatory increase in thyroid stimulating hormone (TSH) secretion by the hypophysis;.…”

“…40 In addition, organochlorine compounds and mercury induced micronuclei in beluga skin fibroblasts. 33,34 Biomarkers of DNA damage in marine mammals include micronuclei, sister chromatid exchange, and chromosome aberration. 33,35 DDT, toxaphene, and chlordane compounds were the major pesticide derivatives found in the St. Lawrence beluga whales (D. leucas), and all of these compounds had direct genotoxicity in beluga whale fibroblasts in vitro.…”

“…33,34 Biomarkers of DNA damage in marine mammals include micronuclei, sister chromatid exchange, and chromosome aberration. 33,35 DDT, toxaphene, and chlordane compounds were the major pesticide derivatives found in the St. Lawrence beluga whales (D. leucas), and all of these compounds had direct genotoxicity in beluga whale fibroblasts in vitro. 34 Low concentrations of toxaphene may be involved in the etiology of cancer in St. Lawrence beluga whales (D. leucas) by posing a long-term genetic hazard.…”

Meeting Report: Methylmercury in Marine Ecosystems—From Sources to Seafood Consumers

“…The direct effects of elevated MeHg on marine biota can include impacts on neurologic end points and memory, locomotion, and cognition, as well as changes in brain neurochemical receptor density (Basu et al 2005; Scheuhammer et al 2008). Adverse effects may further manifest as immunosuppression, which may make individuals more susceptible to disease, as has been measured in cetaceans and pinnipeds (Gauthier et al 1998; Lalancette et al 2003). Direct reproductive effects associated with high Hg levels have been documented in bird species in freshwater ecosystems (Burgess and Meyer 2008; Evers et al 2008), and Braune et al (2006) documented egg Hg concentrations in the ivory gull that exceed twice the adverse effect threshold for eggs in the common loon (Evers et al 2003), suggesting that seabirds may be experiencing similar reproductive effects as freshwater birds.…”

Metal Levels in Southern Right Whales (Eubalaena australis) from Península Valdés, Argentina

“…Specifically, in cetaceans, metal exposure has been correlated with infectious disease mortality, parasitic infections and pneumonias and histopathological changes in lung and kidney tissues [7][8][9]. Cetacean cell culture studies showed that metals can induce cytotoxic, immunotoxic and genotoxic effects [10][11][12][13][14][15][16][17]. Thus, animal and tissue culture studies suggest that metals could be a health concern to cetaceans.…”