title: Relevance of the bioavailable fraction of DDT and its metabolites in freshwater sediment toxicity: New insight into the mode of action of these chemicals on Dictyostelium discoideum.
abstract: In this work, the toxicity of lake sediments contaminated with DDT and its metabolites DDD and DDE (collectively, DDX) was evaluated with widely used toxicity tests (i.e., Vibrio fischeri, Daphnia magna, Pseudokirchneriella subcapitata, and Lumbriculus variegatus) and with the social amoeba Dictyostelium discoideum, a model organism that is also suitable for studying pollutant-induced alterations at the molecular and cellular levels. Although the DDX concentration in the sediments was high (732.5 ppb), the results suggested a minimal environmental risk; in fact, no evidence of harmful effects was found using the different bioassays or when we considered the results of more sensitive sublethal biomarkers in D. discoideum amoebae. In line with the biological results, the chemical data showed that the concentration of DDX in the pore water (in general a highly bioavailable phase) showed a minimal value (0.0071ppb). To confirm the importance of the bioavailability of the toxic chemicals in determining their biological effects and to investigate the mechanisms of DDX toxicity, we exposed D. discoideum amoebae to 732.5ppb DDX in water solution. DDX had no effect on cell viability; however, a strong reduction in amoebae replication rate was observed, which depended mainly on a reduction in endocytosis rate and on lysosomal and mitochondrial alterations. In the presence of a moderate and transient increase in reactive oxygen species, the glutathione level in DDX-exposed amoebae drastically decreased. These results highlight that studies of the bioavailability of pollutants in environmental matrices and their biological effects are essential for site-specific ecological risk assessment. Moreover, glutathione depletion in DDX-exposed organisms is a new finding that could open the possibility of developing new pesticide mixtures that are more effective against DDT-resistant malaria vectors.
authors.affiliation: Department of Sciences and Technological Innovation (DiSIT), University of Piemonte Orientale "A. Avogadro", V.le T. Michel 11, 15121 Alessandria, Italy.
authors.forename: Susanna
authors.initials: S
authors.lastname: Sforzini
authors.affiliation: Department of Sciences and Technological Innovation (DiSIT), University of Piemonte Orientale "A. Avogadro", V.le T. Michel 11, 15121 Alessandria, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Governa
authors.affiliation: Department of Sciences and Technological Innovation (DiSIT), University of Piemonte Orientale "A. Avogadro", V.le T. Michel 11, 15121 Alessandria, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Boeri
authors.affiliation: Department of Sciences and Technological Innovation (DiSIT), University of Piemonte Orientale "A. Avogadro", V.le T. Michel 11, 15121 Alessandria, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Oliveri
authors.affiliation: Renewable Energy & Environmental R&D Center - Istituto eni Donegani, via G. Fauser 4, 28100 Novara, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Oldani
authors.affiliation: Renewable Energy & Environmental R&D Center - Istituto eni Donegani, via G. Fauser 4, 28100 Novara, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Vago
authors.affiliation: Department of Sciences and Technological Innovation (DiSIT), University of Piemonte Orientale "A. Avogadro", V.le T. Michel 11, 15121 Alessandria, Italy. Electronic address: aldo.viarengo@uniupo.it.
authors.forename: Aldo
authors.initials: A
authors.lastname: Viarengo
authors.affiliation: Renewable Energy & Environmental R&D Center - Istituto eni Donegani, via G. Fauser 4, 28100 Novara, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Borrelli
mesh_terms: D048908:Aliivibrio fischeri / Q000187:drug effects; D000818:Animals; D001682:Biological Availability; D000460:Chlorophyta / Q000187:drug effects; D003634:DDT / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*; D003621:Daphnia / Q000187:drug effects; D004023:Dictyostelium / Q000187:drug effects* / Q000378:metabolism; D004784:Environmental Monitoring / Q000379:methods*; D005618:Fresh Water / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry*; D010575:Pesticides / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*; D018675:Toxicity Tests; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*
chemical_list: D010575:Pesticides; D014874:Water Pollutants, Chemical; D003634:DDT
keywords: Bioavailability; DDT; Dictyostelium discoideum; Environmental risk; GSH; Toxicity mechanisms