Uptake and intracellular effects of different size-shape polystyrene microplastics in a Caco-2 monolayer

Our current understanding of the human toxicity of plastic particles constitutes a major knowledge gap. MPs can vary largely in their characteristics, and parameters such as size, shape, and chemical composition need to be included in risk assessment strategies. In the present study, we aimed to evaluate the impact of shape on uptake and intracellular effects of MPs comparing both spherical and irregularly shaped polystyrene particles in a human epithelial colorectal adenocarcinoma (Caco-2) cell line. Two sizes of carboxylated polystyrene spheres (200 nm and 2 μm) and self-synthesized irregularly-shaped polystyrene particles (average length and diameter: 8.9 μm and 1.14 μm respectively) were used to study on one hand their ability to penetrate cells, and on the other hand their potential to induce changes in metabolic activity, membrane integrity, general reactive oxygen species levels, mitochondrial DNA content and expression of oxidative stress-related genes. Altogether, our study demonstrates that both spheres and irregularly-shaped MPs are internalized by Caco-2 cells in a size-dependent manner, i.e., smaller particles are more easily taken up after 24 h exposure. Intracellularly, a lowering in H 2 O 2 levels was observed for all MPs. This was complemented with mitochondrial changes after exposure to the 200 nm spheres and irregularly-shaped particles, while differential expression of pro-and anti-oxidative genes, namely HMOX1, CAT and GPX1, was observed during exposure to the 2 μm spheres. These adverse (anti)-oxidative responses indicate that effects are related to the physicochemical and toxicokinetic characteristics of the particles, and highlight the importance of particle characterization to acquire fundamental insights vital for proper hazard profiling. Exposure to mercury (Hg) in the communities of the Mojana Bolivarense, is given by the mining activities in the area, carried out in the Magdalena and Cauca rivers, which generate waste from the gold amalgamation processes and imply a risk of contamination and consumption of fish, being the developing child population a cause for concern, given the conditions of the socioeconomic and environmental vulnerability of the populations. The objective of this research was to evaluate the levels of total Hg (T-Hg) in hair and blood in children and adolescents between 6-12 years of age, potentially exposed to Hg contamination, as well as its relationship with consumption, hema-tological markers, biochemical and cognitive development factors. The Ethics Committee of the University of Cartagena approved the study and each participant signed informed consent. For the characterization of the population and selection of the participants, the health survey was applied. A total of 215 hair samples and 206 blood samples were collected from children living in the municipality of Magangue and Arjona as a reference point. T-Hg levels were measured with a direct mercury analyzer; hematology was evaluated with an automated hematology analyzer; biochemical parameters were quantified in serum using commercial kits; to assess IQ in participants Wechsler Test for Children (WISC-V) and variables of verbal comprehension, perceptual reasoning, working memory and processing speed were measured. The mean concentrations of T-Hg in hair and blood of the entire population were 0.50 μg/g and 1.02 μg/L, respectively. T-Hg levels in the hair (0.82 μg/g) and in the blood (1.32 μg/L) were higher in the Magangue participants depending on the reference site. With ranges from 0.14 to 2.47 μg/g in hair, of which 29% showed Hg concentrations above the USEPA threshold (1 μg/g). Blood Hg levels did not exceed 5 μg/L, however, levels of 0.49 to 3.59 μg/L were observed. The levels of Hg in hair showed a positive correlation with the levels of Hg in blood, the level of platelets (PCT), the absolute value of granulocytes (GRA), and a negative correlation with the percentage of lymphocytes (LYM%). The IQ evaluation showed significant differences between the study population and the reference point. The Processing Speed Index score is negatively correlated with Hg levels in hair and blood. In conclusion, it was possible to evidence and infer alterations in hematological analyzes and IQ indices of children and adolescents exposed to mercury due to environmental exposure and consumption. Minciencias-SGR (Grant BPIN-2020000100001); and 727, 2015. Colombia is one of the developing countries that use mercury to extract gold from ore in small-scale mining areas. Exposure to mercury in these mining communities is a serious health hazard, especially for the minors who live there. The objective of this research was to evaluate the levels of Total-Hg (T-Hg) in hair and blood, as well as its relationship with hematological parameters, in children and adolescents from Achi, a community belonging to the agricultural, and mining of the Mojana Bolivarense. This study was approved by the ethics committee of the University of Cartagena and each participant signed informed consent. 99 hair and blood samples were collected in the municipality of Achi-Bolivar and 122 samples from participants S140 Abstracts / Toxicology Letters 368S1 (2022) S84-S283

Jaar van publicatie:2022

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