engleski

Effects of cadmium exposure on biomarker responses and gene expression in acanthocephalans

Acanthocephalans are increasingly used as bioindicators of environmental quality due to effective metal accumulation, orders of magnitude higher than in other bioindicator organisms (such as fish, crustaceans, and mollusks). However, the mechanism of metal homeostasis and accumulation in acanthocephalans is still unexplained. Therefore we investigated the effects of in vitro Cd2+ exposure on metal accumulation, biomarkers of metal exposure (metallothioneins, MT) and general stress (total cytosolic proteins, TP) and gene expression in Dentitruncus truttae Sinzar, 1955 hosted in brown trout (Salmo trutta Linnaeus, 1758) from the Krka River. Parasites were exposed in culture to 2 and 10 mg Cd2+ l-1 for 3 and 5 days and Cd2+ levels in the organisms were determined using HR ICP-MS. Measurement of TP was performed spectrophotometrically by the Lowry method and of MT by differential pulse voltammetry (DVP). Next-generation RNA-Seq technology was utilized to explore genome-wide differentially expressed gene profiles between control and Cd2+ treated acanthocephalan specimens. Our results confirmed efficient Cd2+ accumulation in parasites, which levels in unexposed parasites and fish intestine were 391.90 µg kg-1 and 196.80 µg kg-1, respectively. When exposed to 10 mg Cd2+ l-1, acanthocephalans accumulated 188.6 mg g-1 after three days and 267 mg g-1 after five days. Both biomarkers decreased with increasing Cd2+ concentration, probably due to the inhibitory effect of Cd2+ on protein synthesis. Concentrations of MT and TP represent one of the first data reported for acanthocephalans and their baseline levels (mg g-1 wet tissue) were 0.80 and 56.3, respectively. High number of differentially expressed genes was identified for 2 mg l-1 (4826 genes) and 10 mg l-1 (5809 genes) dose of Cd2+. Gene ontology analysis showed that the top enriched biological processes included protein digestion and absorption, gap junction, focal adhesion, apoptosis and genes connected with infections and diseases. Our results confirmed the ability of acanthocephalans to accumulate high concentrations of metals, but at the same time toxic effect on their metabolism was recorded. Exposure of acanthocephalans to high concentrations of Cd2+ altered the expression of thousands of genes and simultaneously several stress response systems

Dentitruncus truttae ; Krka River ; parasites ; bioindicators

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