Cytosolic Distribution of Metals (Cd, Cu) and Metalloids (As, Se) in Livers and Gonads of Field-Collected Fish Exposed to an Environmental Contamination Gradient: An SEC-ICP-MS Analysis

Nastassia Urien,Patrice Couture,Sabrina Jacob,Peter Campbell

doi:10.3390/environments5090102

Nastassia Urien, Patrice Couture + Show 2 more

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https://doi.org/10.3390/environments5090102

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Journal: Environments	Publication Date: Sep 5, 2018
Citations: 10	License type: CC BY 4.0

Affiliation: Institut National de la Recherche Scientifique

Abstract

The distribution of As, Cd, Cu and Se among biomolecules of different molecular weight (MW) in the heat-treated cytosolic fraction of livers and gonads of white suckers (WS; Catostomus commersonii) collected in a reference lake and in a lake subject to multi-metal contamination was investigated. Distribution profiles were obtained by separation of the heat-stable protein and peptide (HSP) fractions using size-exclusion high performance-liquid chromatography, coupled online to an inductively coupled plasma mass spectrometer, to quantify the associated metals. Metal-handling strategies did not vary between the reference and exposed fish, with the exception of As. Cadmium and Cu appeared associated with the heat-stable peptides metallothioneins (MTs), indicating their reasonable detoxification and regulation in WS. In contrast, Se and As were not bound to MTs, but rather, to biomolecules of lower MW (<2 kDa). Arsenic was found associated with the same biomolecules in fish from both lakes, but their proportions changed between reference and exposed fish. For future work, the identification of the Se and As binding biomolecules would be of great interest to determine if these metalloids are detoxified or if, conversely, the biomolecules are metal-sensitive and their binding to Se or As represents a threat for the health of these fish.

Highlights

Trace element exposure in the environment may lead to accumulation in aquatic organisms and cause toxic effects
One of the most used approaches involves successive differential centrifugation steps, followed by a heat-treatment that enables the discrimination between cytosolic trace elements associated with heat-denaturable proteins (HDP; e.g., cytosolic enzymes) and those bound to heat-stable proteins or peptides (HSP) such as MT or MTLP
In the SEC-ICP-MS analysis of metal-binding profiles, metal-binding biomolecule pools were operationally defined as medium molecular weight (MMW), low molecular weight (LMW) and very low molecular weight (VLMW)

Summary

Introduction

Trace element exposure in the environment may lead to accumulation in aquatic organisms and cause toxic effects. Once they interact with biota, trace elements can penetrate into cells and bind to, or interact with, cytosolic molecules and interfere with cell function, leading eventually to deleterious effects [1]. The investigation of subcellular trace element forms within organisms and organs can provide valuable insights into how these elements are handled within living cells, i.e., information on whether they are detoxified or present in biologically sensitive pools, and how they exert their toxicity [4,5]. Metallothioneins are low molecular weighted (6–7 kDa), cysteine-rich cytosolic peptides that can complicate various metals by binding to the numerous thiol groups present in its constituent cysteine residues (≈30% of its amino acids)

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