Metallothionein is up-regulated in molluscan responses to cadmium, but not aluminum, exposure

Abstract

Metallothionein (MTs) is a family of low molecular weight peptides with high cysteine content. In aquatic invertebrates, MTs play an important role in the detoxification of metals and they are often cited as useful biomarkers for toxic metal stress. The change in concentrations of metallothionein in response to aluminum and cadmium exposure was investigated in the soft tissues of two freshwater molluscs: Lymnaea stagnalis and Dreissena polymorpha that have contrasting feeding behavior and therefore metal accumulation profiles. The majority of added Al had precipitated in the bottom of tanks within 24 h, with an average of only 15.4% and 26.2% remaining in the water column of tanks containing snails and mussels, respectively. In contrast, most of the Cd did not precipitate but remained in solution (81.1% and 82.7%, respectively) between water changes. Both metals accumulated in the soft tissues of both animals, but only cadmium exposure led to an increase in metallothionein concentrations in the soft tissues. However, no significant difference was observed in the level of total protein in both tested molluscs upon exposure to Al and Cd compared to the corresponding control. Therefore, care should be taken in the use of metallothioneins as biomarkers for metal stress, since not all metallic stressors induce their expression.

Biomarkers of environmental stress in gills of ribbed mussel Aulacomya atra atra (Nuevo Gulf, Northern Patagonia)

“…MT readily associates with metal ions with low charge states such as Cd. They are not expected to associate as readily with 'hard' metal ions such as Al, which has high charge states (Desouky, 2012). In that sense, Desouky (2012) did not found an induction of MT by Al in two species of freshwater molluscs.…”

Origin, exposure routes and xenobiotics impart nanoplastics with toxicity on freshwater bivalves

“…They could have also react to metals or additives released in the tissues after absorption of NPs in the cells to sequester or excrete them. The fact that Al did not trigger an up-regulation of mt was already described in the literature in freshwater molluscs such as Dreissena polymorpha 35 . But considering the very low bioaccumulation observed in tissues, the weak concentrations of Al may also have not been sufficient to implement a response towards the mt gene, even if this metal generated an oxidative stress ( cat induction).…”

Evaluation of metallothionein response in Lymnaea stagnalis pond snail exposured to trace metals and thiocarbamate fungicide

“…3A). The exposure of L. stagnalis to extremely high concentration of Cd (50 mg L −1 ) during 20 days also caused an increase in total metallothionein concentration [6].…”