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Poly-lactic Acid Nanoplastics Bioccumulate in Developing Zebrafish and Induce Epigenetic Changes
Summary
PLA nanoplastics were found to bioaccumulate in zebrafish embryos and larvae during development, and exposure induced epigenetic changes including altered DNA methylation patterns, raising concern about transgenerational effects from biodegradable plastic degradation products.
Plastics at the micro or nano scale (MPs-NPs) have been detected in the tissues of both aquatic and terrestrial organisms, including humans. Therefore, the increasing demand for alternatives to conventional plastics has led to the development of biodegradable polymers, which are eco-friendly but warrant further investigation regarding potential health risks. Since the potential adverse effects of biodegradable polymers during the developmental process are poorly investigated, in this study we examined the effects of the biodegradable polymer polylactic acid nanoplastics (PLA-NPs) on zebrafish embryo development. The zebrafish embryos/larvae were exposed to Rhodamine B-labelled PLA-NPs (red) of 180 nm, at 0.1, 1 and 10 mg/L concentrations and incubated at 28°C at a 14:10 h day/night light regimen, up to five days. Bioaccumulation assay was performed on zebrafish embryos/larvae through their in vivo observation under the fluorescence microscope at different time points (24, 48, 72, 96 and 120 hours post fertilization, hpf). Larvae at 120 hpf were used for DNA extraction and the evaluation of global DNA methylation status (% 5metC/Total DNA) was measured by ELISA assay. Lastly, Immunofluorescence (IF) analysis was carried out to assess any difference in the regional distribution of 5metC within developing larvae vs. controls. The results demonstrate that PLA-NPs bioaccumulate within the embryos already at 24hpf, suggesting their ability to pass the chorion and further distribute at the nervous system (eye) and intestinal level, up to 120 hpf in a concentration-dependent manner. At 120 hpf, PLA-NPs changes the global DNA methylation status at 0,1 mg/L dose only (p<0.05 vs control). IF analysis confirm PLA NPs bioaccumulation within the nervous system and gastrointestinal tract; furthermore, 5metC increases dose-dependently around the eye and within intestine, confirming epigenetic modification related to PLA-NPs exposure. Taken together, PLA-NPs bioaccumulate in zebrafish embryo and induce epigenetic changes in global DNA methylation status. The PLA-NPs induced changes in DNA status warrant investigations suggesting a possible involvement in the development of the nervous central system and gastroenteric system. Funding: NGEU, MUR, PRIN-PNRR2022, CODE: P2022AA47Y- CUP I53D23007130001, Project title: Poly(Lactic Acid) plastics contamination (PLASTAMINATION): organ injuries and underlying molecular mechanisms.