title: Insights into the mechanisms underlying mercury-induced oxidative stress in gills of wild fish (Liza aurata) combining (1)H NMR metabolomics and conventional biochemical assays.
abstract: Oxidative stress has been described as a key pathway to initiate mercury (Hg) toxicity in fish. However, the mechanisms underlying Hg-induced oxidative stress in fish still need to be clarified. To this aim, environmental metabolomics in combination with a battery of conventional oxidative stress biomarkers were applied to the gills of golden grey mullet (Liza aurata) collected from Largo do Laranjo (LAR), a confined Hg contaminated area, and São Jacinto (SJ), selected as reference site (Aveiro Lagoon, Portugal). Higher accumulation of inorganic Hg and methylmercury was found in gills of fish from LAR relative to SJ. Nuclear magnetic resonance (NMR)-based metabolomics revealed changes in metabolites related to antioxidant protection, namely depletion of reduced glutathione (GSH) and its constituent amino acids, glutamate and glycine. The interference of Hg with the antioxidant protection of gills was corroborated through oxidative stress endpoints, namely the depletion of glutathione peroxidase and superoxide dismutase activities at LAR. The increase of total glutathione content (reduced glutathione+oxidized glutathione) at LAR, in parallel with GSH depletion aforementioned, indicates the occurrence of massive GSH oxidation under Hg stress, and an inability to carry out its regeneration (glutathione reductase activity was unaltered) or de novo synthesis. Nevertheless, the results suggest the occurrence of alternative mechanisms for preventing lipid peroxidative damage, which may be associated with the enhancement of membrane stabilization/repair processes resulting from depletion in the precursors of phosphatidylcholine (phosphocholine and glycerophosphocholine), as highlighted by NMR spectroscopy. However, the observed decrease in taurine may be attributable to alterations in the structure of cell membranes or interference in osmoregulatory processes. Overall, the novel concurrent use of metabolomics and conventional oxidative stress endpoints demonstrated to be sensitive and effective towards a mechanistically based assessment of Hg toxicity in gills of wild fish, providing new insights into the toxicological pathways underlying the oxidative stress.
authors.affiliation: Department of Biological and Environmental Sciences, University of Messina, 98166 Messina, Italy. Electronic address: tcappello@unime.it.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Cappello
authors.affiliation: Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: fatimabrandao@ua.pt.
authors.forename: Fátima
authors.initials: F
authors.lastname: Brandão
authors.affiliation: Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Sofia
authors.initials: S
authors.lastname: Guilherme
authors.affiliation: Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Maria Ana
authors.initials: MA
authors.lastname: Santos
authors.affiliation: Department of Biological and Environmental Sciences, University of Messina, 98166 Messina, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Maisano
authors.affiliation: Department of Biological and Environmental Sciences, University of Messina, 98166 Messina, Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Mauceri
authors.affiliation: Centro de Química Estrutural, Instítuto Superíor Técnico, Universidade de Lisboa, 1049-001 Lisbon, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Canário
authors.affiliation: Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Mário
authors.initials: M
authors.lastname: Pacheco
authors.affiliation: Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Patrícia
authors.initials: P
authors.lastname: Pereira
mesh_terms: D000818:Animals; D001681:Biological Assay; D015415:Biomarkers / Q000378:metabolism; D005880:Gills / Q000187:drug effects / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D008628:Mercury / Q000378:metabolism* / Q000633:toxicity; D055442:Metabolome / Q000502:physiology; D055432:Metabolomics; D018384:Oxidative Stress; D011174:Portugal; D066244:Proton Magnetic Resonance Spectroscopy; D023701:Smegmamorpha / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism* / Q000633:toxicity
chemical_list: D015415:Biomarkers; D014874:Water Pollutants, Chemical; D005979:Glutathione Peroxidase; D008628:Mercury; D005978:Glutathione
keywords: Environmental health assessment; Fish; Gills; Mercury; Metabolomics; Oxidative stress