Paloma Fernández Freire

Toxicity of silver nanoparticles to a fish gill cell line: Role of medium composition

Abstract In aqueous solutions, silver nanoparticle (AgNP) behavior is affected by a variety of factors which lead to altered AgNP size and toxicity. Our research aims to explore the effect of media composition on citrate-coated AgNP (cit-AgNP) behavior and toxicity to the cell line from rainbow trout (Oncorhynchus mykiss) gill, RTgill-W1. Three different exposure media (L15/ex, L15/ex w/o Cl and d-L15/ex) were used. These were characterized by varying ionic strength and chloride content, both of which had a dominant effect on the behaviour of cit-AgNP. Comparing the behaviour and toxicity of cit-AgNP in the different media, stronger agglomeration of cit-AgNP correlated with higher toxicity. Deposition of cit-AgNP on cells might explain the higher toxicity of agglomerated cit-AgNP compared to that of suspended cit-AgNP. The cit-AgNP concentration-response curves as a function of dissolved silver ions, and the limited prevention of toxicity by silver ligands, indicated that cit-AgNP elicited a particle-specific effect on the cells. Furthermore, the lysosomal membrane integrity was significantly more sensitive to cit-AgNP exposure than cellular metabolic activity or cell membrane integrity and showed the weakest protection by silver ligands. This revealed that cit-AgNP toxicity seems to particularly act on RTgill-W1 cell lysosomes. The newly developed low ionic strength medium, d-L15/ex, which can stabilize cit-AgNP and better mimic the freshwater environment, offers an excellent exposure solution to study cellular and molecular effects of NP to gill cells.

Oxidative DNA damage contributes to the toxic activity of propylparaben in mammalian cells

Propyl p-hydroxybenzoate, commonly referred to as propylparaben, is the most frequently used preservative to inhibit microbial growth and extend shelf life of a range of consumer products. The objective of this study was to provide further insight into the toxicological profile of this compound, because of the current discrepancy in the literature with regard to the safety of parabens. The Vero cell line, derived from the kidney of the green monkey, was selected to evaluate the adverse effects of propylparaben by use of a set of mechanistically relevant endpoints for detecting cytotoxicity and genotoxic activities. Our results demonstrate that exposure to the compound for 24h causes changes in cell-proliferation rates rather than in cell viability. A significant and dose-dependent decline in the percentage of mitotic cells was observed at the lowest concentration tested, mainly due to cell-cycle arrest at the G0/G1 phase. Immunodetection techniques revealed that induction of DNA double-strand breaks and oxidative damage underlies the cytostatic effect observed in treated Vero cells. Additional studies are in progress to extend these findings, which define a novel mode of action of propylparaben in cultured mammalian cells.

The antioxidant butylated hydroxyanisole potentiates the toxic effects of propylparaben in cultured mammalian cells.

Butylated hydroxyanisole and propylparaben are phenolic preservatives commonly used in food, pharmaceutical and personal care products. Both chemicals have been subjected to extensive toxicological studies, due to the growing concern regarding their possible impacts on environmental and human health. However, the cytotoxicity and underlying mechanisms of co-exposure to these compounds have not been explored. In this study, a set of relevant cytotoxicity endpoints including cell viability and proliferation, oxidative stress, DNA damage and gene expression changes were analyzed to assess whether the antioxidant butylated hydroxyanisole could prevent the pro-oxidant effects caused by propylparaben in Vero cells. We demonstrated that binary mixtures of both chemicals induce greater cytotoxic effects than those reported after single exposureto each compound. Simultaneous treatment with butylated hydroxyanisole and propylparaben caused G0/G1 cell cycle arrest as a result of enhanced generation of oxidative stress and DNA double strand breaks. DNA microarray analysis revealed that a cross-talk between transforming growth factor beta (TGFβ) and ataxia-telangiectasia mutated kinase (ATM) pathways regulates the response of Vero cells to the tested compounds in binary mixture. Our findings indicate that butylated hydroxyanisole potentiates the pro-oxidant effects of propylparaben in cultured mammalian cells and provide useful information for their safety assessment.

Toxicological assessment of third generation (G3) poly (amidoamine) dendrimers using the Allium cepa test

Abstract Despite the expected increase of nanotechnology applications, limited information is currently available on the occurrence, fate and negative impact of engineered nanosized particles in the environment. Plants are an integral and essential part of the ecosystems and their response to nanomaterials exposure is therefore of great interest. In this work, different parameters including root growth, mitotic index and chromosome aberrations were used to estimate the potential ecotoxicity of low generation (G3) hydroxyl- and amine-terminated poly(amidoamine) dendrimers using the Allium cepa test. The findings of the present study indicate that both tested dendrimers produce toxic effects in a higher plant system. The analysis of macroscopic parameters, used in testing for general toxicity, revealed reduction of mean root length in bulbs exposed to high concentrations. In parallel, we observed a decrease in the mitotic activity of root meristems which was associated with severe defects in chromosome segregation. Our results may greatly contribute to characterize the toxicological profile and risk of these potentially emerging pollutants in the environment.

Endoplasmic reticulum stress as a novel cellular response to di (2-ethylhexyl) phthalate exposure.

Di (2-ethylhexyl) phthalate is a high-production chemical widely used as a plasticizer for polyvinyl chloride products. Due to its ubiquitous presence in environmental compartments and the constant exposure of the general population through ingestion, inhalation, and dermal absorption, this compound has been subjected to extensive in vivo and in vitro toxicological studies. Despite the available information, research on the cytotoxicity of di (2-ethylhexyl) phthalate in mammalian cells is relatively limited.In this paper, an in vitro multi-parametric approach was used to provide further mechanistic data on the toxic activity of this chemical in Vero and HaCaT cells. Our results reveal that a 24 h exposure to di (2-ethylhexyl) phthalate causes, in both cell lines, an inhibition of cell proliferation that was linked to cell cycle delay at the G1 phase. Concomitantly, the tested compound induces mild endoplasmic reticulum stress which leads to an adaptive rather than a pro-apoptotic response in mammalian cells. These findings demonstrate that there are multiple potential cellular targets of di (2-ethylhexyl) phthalate-induced toxicity and the need to develop further experimental studies for the risk assessment of this ubiquitous plasticizer.

A moderate exposure to perfluorooctanoic acid causes persistent DNA damage and senescence in human epidermal HaCaT keratinocytes

Perfluorooctanoic acid has been used widespread, during the last decades, in a number of consumer and industrial products. Although this compound has been subjected to extensive epidemiological and toxicological studies, limited data are available concerning its potential dermal toxicity in mammalian cells. In this study, we used a two-stage approach with relevant cytotoxicity endpoints including cell viability and proliferation, oxidative stress, DNA damage and cell senescence to assess the immediate and the long-lasting or delayed cytotoxicity caused by the compound in HaCaT keratinocytes. Our results suggest that a single exposure to perfluorooctanoic acid causes concentration-dependent changes in cell proliferation that were not restored during a 48 h recovery period. Furthermore, we demonstrate that a moderate treatment with this perfluorochemical causes persistent DNA damage, which ultimately leads to development of the senescence-associated secretory phenotype in HaCaT cells. This paper provides unprecedented data and insights regarding the cytotoxic effects of perfluorooctanoic acid in human cells that could be of special relevance for use in comparative in vitro-in vivo studies. Moreover, our findings highlight the importance of considering both the immediate and long-lasting or delayed cytotoxic responses caused by chemical exposure, to ensure the accurate identification of toxicity in cell-based systems.