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Toxicity and Functional Tissue Responses of Two Freshwater Fish after Exposure to Polystyrene Microplastics.

ABSTRACT: Microplastics (MPs)' ingestion has been demonstrated in several aquatic organisms. This process may facilitate the hydrophobic waterborne pollutants or chemical additives transfer to biota. In the present study the suitability of a battery of biomarkers on oxidative stress, physiology, tissue function and metabolic profile was investigated for the early detection of adverse effects of 21-day exposure to polystyrene microplastics (PS-MPs, sized 5-12 μm) in the liver and gills of zebrafish Danio rerio and perch, Perca fluviatilis, both of which are freshwater fish species. An optical volume map representation of the zebrafish gill by Raman spectroscopy depicted 5 μm diameter PS-MP dispersed in the gill tissue. Concentrations of PS-MPs close to the EC₅₀ of each fish affected fish physiology in all tissues studied. Increased levels of biomarkers of oxidative damage in exposed fish in relation to controls were observed, as well as activation of apoptosis and autophagy processes. Malondialdehyde (MDA), protein carbonyls and DNA damage responses differed with regard to the sensitivity of each tissue of each fish. In the toxicity cascade gills seemed to be more liable to respond to PS-MPs than liver for the majority of the parameters measured. DNA damage was the most susceptible biomarker exhibiting greater response in the liver of both species. The interaction between MPs and cellular components provoked metabolic alterations in the tissues studied, affecting mainly amino acids, nitrogen and energy metabolism. Toxicity was species and tissue specific, with specific biomarkers responding differently in gills and in liver. The fish species that seemed to be more susceptible to MPs at the conditions studied, was P. fluviatilis compared to D. rerio. The current findings add to a holistic approach for the identification of small sized PS-MPs' biological effects in fish, thus aiming to provide evidence regarding PS-MPs' environmental impact on wild fish populations and food safety and adequacy.

SUBMITTER: Kaloyianni M

PROVIDER: S-EPMC8625933 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Plastics are persistent synthetic polymers that accumulate in the marine environment as waste. Microplastic (MP) particles are derived from the breakdown of larger debris or can enter the environment as microscopic fragments. Filter-feeder organisms ingest MP while feeding and are likely to be impacted by MP pollution. To assess the impact of polystyrene microspheres (PS) on the physiology of the Pacific oyster, adult oysters were experimentally exposed to virgin micro-PS (2 and 6 Âµm in diameter; 32 Âµg L-1) for two months during a reproductive cycle. Effects were investigated on transcriptomic responses, in digestive gland gonads and oocytes of exposed oysters. Transcriptomic profiles in the tissues of the exposed oyster showed endocrine disrupting signals, notably highlighting alteration in glucocorticoid response, insulin pathway and fatty-acid metabolism in response to micro-PS exposition. In oocytes from exposed females, several transcripts coding for proteins involved in Ca2+ binding were differentially expressed suggesting a disruption of the Ca2+ signaling pathway with crucial consequences on oocyte maturation. To assess the impact of polystyrene microspheres (PS) on the physiology of the Pacific oyster, adult oysters were experimentally exposed to virgin micro-PS (2 and 6 Âµm in diameter; 32 Âµg L-1) for two months during a reproductive cycle and compared to control oysters. Adults were sampled 2 and 8 weeks after the beginning of exposure (corresponding to T1 and T3, respectively, 8-9 replicates per time of sampling and condition for a total of 56). Tissues were immediately dissected from each oyster, frozen in liquid nitrogen, then crushed to a fine powder at -196Â°C with an oscillating mill mixer and stored in liquid nitrogen until RNA extraction. Oocytes were collected from 5 females per condition, filtered in a 40 Âµm sieve, counted and transferred into 1.5 mL of Extract-all reagent (Eurobio, Courtaboeuf, France) (20,000 oocytes). Total RNA was isolated using 1.5 mL of Extract-all Reagent per 50 mg of gonad powder. For microarray hybridizations, 200 ng of total RNA were indirectly labeled with Cy3 using the Low Input Quick Amp Labeling kit One-Color. Hybridization was performed using the Agilent Gene expression hybridization kit (5188-5242), with 1.65 Î¼g of labeled RNA, for 16 h at 65 Â°C. The employed arrays were Agilent 60-mer 4x44K custom microarrays, containing 31,918 C. gigas ESTs, designed by Dheilly et al. (2011). Slides were scanned on an Agilent Technologies G2565AA Microarray Scanner system at 5 Î¼m resolution, using default parameters. Features were extracted using the Agilent Feature Extraction software 6.1.

Project description:BackgroundMicroplastics (MPs), which are smaller in size and difficult to degrade, can be easily ingested by marine life and enter mammals through the food chain. Our previous study demonstrated that following acute exposure to MPs, the serum testosterone content reduced and sperm quality declined, resulting in male reproductive dysfunction in mice. However, the toxic effect of long-term exposure to MPs at environmental exposure levels on the reproductive system of mammals remains unclear.ResultsIn vivo, mice were given drinking water containing 100 μg/L and 1000 μg/L polystyrene MPs (PS-MPs) with particle sizes of 0.5 μm, 4 μm, and 10 μm for 180 consecutive days. We observed alterations in testicular morphology and reductions in testosterone, LH and FSH contents in serum. In addition, the viability of sperm was declined and the rate of sperm abnormality was increased following exposure to PS-MPs. The expression of steroidogenic enzymes and StAR was downregulated in testis tissues. In vitro, we used primary Leydig cells to explore the underlying mechanism of the decrease in testosterone induced by PS-MPs. First, we discovered that PS-MPs attached to and became internalized by Leydig cells. And then we found that the contents of testosterone in the supernatant declined. Meanwhile, LHR, steroidogenic enzymes and StAR were downregulated with concentration-dependent on PS-MPs. We also confirmed that PS-MPs decreased StAR expression by inhibiting activation of the AC/cAMP/PKA pathway. Moreover, the overexpression of LHR alleviated the reduction in StAR and steroidogenic enzymes levels, and finally alleviated the reduction in testosterone induced by PS-MPs.ConclusionsPS-MPs exposure resulted in alterations in testicular histology, abnormal spermatogenesis, and interference of serum hormone secretion in mice. PS-MPs induced a reduction in testosterone level through downregulation of the LH-mediated LHR/cAMP/PKA/StAR pathway. In summary, our study showed that chronic exposure to PS-MPs resulted in toxicity of male reproduction under environmental exposure levels, and these potential risks may ring alarm bells of public health.

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Toxicity and Functional Tissue Responses of Two Freshwater Fish after Exposure to Polystyrene Microplastics.

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