Changes in Metallothionein Levels in Freshwater Mussels Exposed to Urban Wastewaters: Effects from Exposure to Heavy Metals?

Abstract

Municipal effl uents are complex mixtures of compounds such as heavy metals, aromatic and aliphatic hydrocarbons, and micro-organisms and are released in aquatic ecosystems. The purpose of this study was to verify whether changes in metallothioneins (MT) were associated with the accumulation of labile metals in tissue of freshwater mussels exposed to the dispersion plume of a major municipal effl uent. Mussels were placed in experimental cages deployed at sites 1.5 km upstream, 8 km downstream and 12 km downstream of the outfall of a major, primary-treated municipal effl uent in the St. Lawrence River (Québec, Canada). Mussels were analysed for MT and labile zinc levels in their gonads, gills and digestive glands. Lipogenic enzyme (isocitrate and glucose-6-phosphate dehydrogenase) and arachidonic acid cyclooxygenase (COX) activities were also measured in gonad and gill tissues. Although MT was induced in all the tissues examined, the results showed that labile zinc levels were signifi cantly reduced in gill and gonad tissues, with an increase observed only at the 12 km downstream site in the digestive gland. COX activity was readily induced in gills and gonads. Glucose-6-phosphate dehydrogenase activity was reduced at both downstream sites, but isocitrate dehydrogenase activity was signifi cantly induced at the farthest (12 km) site. Analysis of covariance revealed that MT levels in gills were more infl uenced by COX activity than with distance in the dispersion plume and was negatively correlated with labile zinc levels. In conclusion, MT induction was inversely related to the levels of labile zinc but positively so with the infl ammation biomarker COX. Hence, the induction of MT in mussels exposed to the municipal effl uent of a large city appears to be associated with either infl ammatory processes or as compensation for the loss of labile essential metals. We propose that the simple and complimentary parameters of labile zinc and COX evaluations be used to link MT induction with divalent heavy metal exposure in environmental studies dealing with various type of contaminants in such complex contaminant mixture effl uents.

Characterization of phospholipid hydroperoxide glutathione metabolizing peroxidase (gpx4) isoforms in Coho salmon olfactory and liver tissues and their modulation by cadmium

“…In our GST study, the loss of olfactory GST expression was accompanied by a strong and concomitant increase in the expression of metallonthionein, a sensitive marker of heavy metal exposures in fish (Bigot et al, 2011; Falfushynska et al, 2011; Gagne et al, 2007; Kim et al, 2010). In addition to observed effects at the mRNA level, Cd can inhibit GPx catalytic activities in several species, with the loss of catalytic capacity associated with GSH depletion or the formation of a chemical complex between Cd and selenium at the active site of the enzyme (Cuypers et al, 2010; Gambhir and Nath, 1992; Quig, 1998).…”

Novel antifouling agent zinc pyrithione: determination, acute toxicity, and bioaccumulation in marine mussels (Mytilus galloprovincialis)

“…It is well known that in mussel cells, metallothioneins bind Zn, as well as other heavy metals such as Cu and Cd, to provide protection against metal toxicity [38,39].…”

Assessment of the Health Status of Mussels Mytilus galloprovincialis Along the Campania Coastal Areas: A Multidisciplinary Approach

“…A variety of contaminant/stress-related biomarkers have been suggested to be monitored for an integrated assessment of contaminants, as well as their effects in different seas ( Lehtonen et al, 2014 ). These include tissue end-points, represented by histopathological alterations at a bivalve digestive gland, neoplastic and inflammatory lesions, levels of metallothionein gene expression ( Knapen et al, 2007 ; Gagné et al, 2007 ), superoxide dismutase (SOD) specific activity and mitochondrial function ( Abele et al, 2007 ; Cravo et al, 2009 ).…”