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.

Nanoplastics and Microplastics May Be Damaging Our Livers

“…Human SMMC-7721 cells also had elevated levels of apoptosis after exposure to NPs [ 129 ]. After exposure to PS-MPs, the Bax/Bcl-2 ratio and the level of caspase, a biomarker for detecting apoptosis in fish [ 130 ], were increased in the liver of zebrafish and sea bass [ 131 ]. In addition, the ratio of Bax/Bcl2 reflects the activation of procaspase and the occurrence of apoptosis [ 132 ].…”

“…Both LC3II/I and SQSTM1 ratios are widely used as indicators of autophagy [ 148 , 149 , 150 ]. Zebrafish and sea bass were exposed to PS-MPs, and the LC3 II/I ratio was increased, and SQSTM1/p62 levels were decreased in the livers of both fish after exposure to PS-MPs, compared with the controls [ 131 ]. This result suggests the development of hepatocyte autophagy.…”

Genotoxicity of Particles From Grinded Plastic Items in Caco-2 and HepG2 Cells

“…The exposure time is much longer in non-human species (i.e., typically weeks in ecotoxicology as compared to hours-days in human toxicology). It is also interesting that the ecotoxicological studies indicate that even large polystyrene particles with diameters larger than 1 μm are genotoxic in the comet assay ( 14 , 23 , 25 , 28 , 29 , 31 , 33 ). On the contrary, studies on human cells have indicated very little effect on levels of DNA strand breaks measured by the comet assay.…”

Polystyrene microplastics induce apoptosis and necroptosis in swine testis cells via ROS/MAPK/HIF1α pathway

“…4 At present, MPs have been found in the tissues of various organisms, and their toxic manifestations are also diverse, such as causing intestinal flora imbalance, liver lipid metabolism disorders, impaired skeletal muscle regeneration, oxidative or inflammatory injury of organs, and neurological disorders of brain. [5][6][7][8][9] Notably, increasing evidences have demonstrated that MPs can cross the tissue barrier and enter the reproductive organs of male or female animals, causing reproductive toxicity, which seriously threatens the physiological health of animals. For example, polystyrene microplastics (PS-MPs) exposure can target the testicular tissue in mice and lead to poor sperm quality by activating the nuclear factor erythroid 2-related factor 2/heme oxygenase-1/nuclear factor-kappa B (Nrf2/HO-1/NF-κB) pathway.…”

“…MPs can easily enter animals or humans through the food chain, posing a serious threat to health and safety 4 . At present, MPs have been found in the tissues of various organisms, and their toxic manifestations are also diverse, such as causing intestinal flora imbalance, liver lipid metabolism disorders, impaired skeletal muscle regeneration, oxidative or inflammatory injury of organs, and neurological disorders of brain 5–9 . Notably, increasing evidences have demonstrated that MPs can cross the tissue barrier and enter the reproductive organs of male or female animals, causing reproductive toxicity, which seriously threatens the physiological health of animals.…”