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Plastics, particularly mesoplastics, dominate beach debris and act as carriers of hazardous chemicals, either initially present in plastics or absorbed from the surrounding environment. In this study, mesoplastics were collected from five beaches in the southern region of Spain to investigate their potential impact on marine life. In vitro assays employing fish liver cells (PLHC-1) were conducted to evaluate the toxicity of methanolic extracts derived from intact mesoplastics and after simulated photodegradation. LC-MS analysis of the methanolic extracts revealed the presence of organophosphate esters, phthalates, and phthalate alternatives. The extracts from photodegraded plastics generally showed higher cytotoxicity, ability to generate reactive oxygen species (ROS), and genotoxicity (micronuclei formation) than those from intact mesoplastics. All the extracts induced EROD activity in PLHC-1 cells, indicating the presence of significant amounts of CYP1A inducers in beach mesoplastics. Thus, mesoplastics contain chemicals able to induce cytotoxicity and genotoxicity in PLHC-1 cells, and further photodegradation of mesoplastics facilitates the release of additional chemicals, increasing the overall toxicity. This work also highlights the usefulness of cell-based assays to better define the risks of plastic pollution.

This study investigates the toxicity of methanolic extracts obtained from compostable plastics (BPs) and conventional plastics (both virgin and recycled). Additionally, it explores the potential influence of plastic photodegradation and composting on toxic responses using a battery of in vitro assays conducted in PLHC-1 cells. The extracts of BPs, but not those of conventional plastics, induced a significant decrease in cell viability (<70%) in PLHC-1 cells after 24 h of exposure. Toxicity was enhanced by either photodegradation or composting of BPs. Extracts of conventional plastics, and particularly those of recycled plastics, induced 7-ethoxyresorufin-O-deethylase (EROD) activity and micronucleus formation in exposed cells, indicating the presence of significant amounts of CYP1A inducers and genotoxic compounds in the extracts, which was enhanced by photodegradation. These findings highlight the importance of investigating the effects of degradation mechanisms such as sunlight and composting on the toxicity of BPs. It is also crucial to investigate the composition of newly developed formulations for BPs, as they may be more harmful than conventional ones.

Fish liver cell lines are valuable tools to understand the toxicity of chemicals in aquatic vertebrates. While conventional 2D cell cultures grown in monolayers are well established, they fail to emulate toxic gradients and cellular functions as in in-vivo conditions. To overcome these limitations, this work focuses on the development of Poeciliopsis lucida (PLHC-1) spheroids as a testing platform to evaluate the toxicity of a mixture of plastic additives. The growth of spheroids was monitored over a period of 30 days, and spheroids 2-8 days old and sized between 150 and 250 µm were considered optimal for conducting toxicity tests due to their excellent viability and metabolic activity. Eight-day-old spheroids were selected for lipidomic characterization. Compared to 2D-cells, the lipidome of spheroids was relatively enriched in highly unsaturated phosphatidylcholines (PCs), sphingosines (SPBs), sphingomyelins (SMs) and cholesterol esters (CEs). When exposed to a mixture of plastic additives, spheroids were less responsive in terms of decreased cell viability and generation of reactive oxygen species (ROS), but were more sensitive than cells growing in monolayers for lipidomic responses. The lipid profile of 3D-spheroids was similar to a liver-like phenotype and it was strongly modulated by exposure to plastic additives. The development of PLHC-1 spheroids represents an important step towards the application of more realistic in-vitro methods in aquatic toxicity studies.

Lipid metabolism is essential in maintaining energy homeostasis in multicellular organisms. In vertebrates, the peroxisome proliferator-activated receptors (PPARs, NR1C) regulate the expression of many genes involved in these processes. Atlantic cod (Gadus morhua) is an important fish species in the North Atlantic ecosystem and in human nutrition, with a highly fatty liver. Here we study the involvement of Atlantic cod Ppar a and b subtypes in systemic regulation of lipid metabolism using two model agonists after in vivo exposure. WY-14,643, a specific PPARA ligand in mammals, activated cod Ppara1 and Ppara2 in vitro. In vivo, WY-14,643 caused a shift in lipid transport both at transcriptional and translational level in cod. However, WY-14,643 induced fewer genes in the fatty acid beta-oxidation pathway compared to that observed in rodents. Although GW501516 serves as a specific PPARB/D ligand in mammals, this compound activated cod Ppara1 and Ppara2 as well as Pparb in vitro. In vivo, it further induced transcription of Ppar target genes and caused changes in lipid composition of liver and plasma. The integrative approach provide a foundation for understanding how Ppars are engaged in regulating lipid metabolism in Atlantic cod physiology. We have shown that WY-14,643 and GW501516 activate Atlantic cod Ppara and Pparb, affect genes in lipid metabolism pathways, and induce changes in the lipid composition in plasma and liver microsomal membranes. Particularly, the combined transcriptomic, proteomics and lipidomics analyses revealed that effects of WY-14,643 on lipid metabolism are similar to what is known in mammalian studies, suggesting conservation of Ppara functions in mediating lipid metabolic processes in fish. The alterations in the lipid profiles observed after Ppar agonist exposure suggest that other chemicals with similar Ppar receptor affinities may cause disturbances in the lipid regulation of fish. Model organism: Atlantic cod (Gadus morhua). LSID: urn:l

Plastics production and usage has exponentially increased in the last decades around the world. Due to the insufficient waste management, a significant amount of plastic ends up in the environment, where they tend to fragment into micro- and nano-plastics (NPs), and accumulate in aquatic organisms with still unknown effects. Although studies have indicated that lipid metabolism is a main target of NPs, this mechanism has not been extensively explored. In this study, we evaluated changes in the lipidome of mussel hemocytes after exposure to polystyrene (PS) NPs of 50 and 500 nm, at two different concentrations (106 and 109 particles/mL) for 24 h. The lipidome of hemocytes, analyzed by FIA-ESI (±) Orbitrap, was characterized by a relatively high abundance of cholesteryl esters (CEs) and phosphatidylcholine-plasmalogens (PC–Os/PC-Ps), involved in cell's defense against oxidative stress and membrane reorganization. In hemocytes exposed to PS NPs, a number of highly unsaturated membrane lipids were down-regulated, indicating a reorganization of the cell membranes after exposure to the particles and an oxidation of lipids with a high number of double bonds. This reduction was more evident after exposure to 50 nm NPs –both concentrations- and 500 nm NPs –high concentration–. The analysis of culture medium suggested increased release of vesicles enriched in triglycerides (TGs). The relevance of these responses to NP exposure on the immune function of hemocytes remains to be investigated.

There is increasing awareness that exposure to endocrine disrupters interferes with lipid homeostasis in vertebrates, including fish. Many of these compounds exert their action by binding to nuclear receptors, such as peroxisome proliferator-activated receptors and retinoid X receptor. This work investigates the use of fish liver cells (PLHC-1 and ZFL cells) for the screening of metabolic and lipid disrupters in the aquatic environment by assessing changes in the cell’s lipidome after exposure to the model compounds, tributyltin chloride and all-trans retinoic acid. Lipid extracts, analyzed by FIA-ESI (+/-) Orbitrap, evidenced the intracellular accumulation of triglycerides and diglycerides in both cell models after exposure 100 and 200 nM tributyltin chloride for 24 h. Exposure to 1 µM all-trans retinoic acid led to a significant accumulation of triglycerides in PLHC-1 cells, while few triglycerides were accumulated in ZFL cells. Retinoic acid (cyp26b1, cyp3a65, lrata) and lipid metabolism (fasn, scd, elovl6) related genes were up-regulated by tributyltin chloride and all-trans retinoic acid, while only all-trans retinoic acid down-regulated the expression of dgat1a. The two cell models show sensitivity and responses to tributyltin chloride and all-trans retinoic acid comparable to those previously reported in mammalian cells. These results support the use of fish liver cells as alternative models for the detection of contaminants that act as lipid disrupters in the aquatic environment.

As plastics in the environment break down to smaller particles, contain additives, trap environmental pollutants and cross cell membranes, there is growing concern about the toxicological consequences for humans and vulnerable aquatic species. Recent studies have shown the ability of plastic additives to disrupt oxidative metabolism and cause damage to macromolecules as part of their mechanism of action. This article focuses on human and fish cell models because they serve to unravel the mechanisms of action of plastic additives and to predict the consequences of exposure. In addition, some in vivo studies revealing the action of plastics and its additives on oxidative stress parameters in aquatic organisms are reviewed. The selected works highlight an alteration of the oxidative stress balance as one accepted mechanism of action of plastics and warn about the negative consequences on humans and wildlife.