Mixture toxicity of 6PPD-quinone and polystyrene nanoplastics in zebrafish

• Published in: Environmental pollution (1987) 2024-05, Vol.348, p.123835-123835, Article 123835
• Main Authors: Varshney, Shubham, O'Connor, Olivia L., Gora, Adnan Hussain, Rehman, Saima, Kiron, Viswanath, Siriyappagouder, Prabhugouda, Dahle, Dalia, Kögel, Tanja, Ørnsrud, Robin, Olsvik, Pål A.
• Format: Article
• Language: English
• Subjects: adults; biosynthesis; cholesterol metabolism; Combined toxicity; Danio rerio; EthoVision system; fatty acid metabolism; histology; Intestinal transcriptomics; Liver transcriptomics; mitochondria; muscle tissues; nanoplastics; neurotransmitters; ozone; phenotype; pollution; polystyrenes; risk; sterols; Synergy; toxic substances; toxicity; transcriptomics; Tyre-wear pollution
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2024.123835

Plastic pollution, including micro- and nanoplastics, is a growing concern. Tyre-wear particles (TWPs) are the second largest source of microplastics in the ocean following abrasion of synthetic fibres. In addition to the particles themselves, TWPs contain many harmful chemicals, including 6PPD. This chemical reacts with atmospheric ozone and forms the toxic compound 6PPD-quinone (6PPDq), which poses a danger to aquatic life. There is a knowledge gap in understanding risks associated with the combined toxicity of nanoplastics (NPs) and 6PPDq. The present study aimed to investigate the toxicity of NPs and 6PPDq on adult zebrafish using phenotypic (behaviour, histology) and transcriptomic endpoints. Zebrafish were exposed to four treatments: control (contaminant-free), 50 μg/L 6PPDq, 3 mg/L polystyrene (PS)-NPs, and a combination of 50 μg/L 6PPDq and 3 mg/L PS-NPs. We did not observe locomotory dysregulation in zebrafish exposed to NPs. However, we found significant hyperlocomotion in zebrafish exposed to 6PPDq and this effect was even more substantial after co-exposure with PS-NPs. This study explores the molecular mechanisms behind these effects, identifying genes associated with neurotransmitters and fatty acid metabolism that were dysregulated by the co-exposure. Transcriptomic analysis further showed that both 6PPDq and PS-NPs impacted cellular processes associated with sterol biosynthesis, cholesterol metabolism, and muscle tissue development. The effects on these mechanisms were stronger in co-exposed zebrafish, indicating a heightened risk to cellular integrity and mitochondrial dysfunction. These results highlight the significance of mixture toxicity when studying the effects of NPs and associated chemicals like 6PPDq. [Display omitted] •Nanoplastics exposure did not affect behaviour but caused mitochondrial dysfunction.•6PPDq exposure caused behavioural changes in adult zebrafish.•6PPDq exposure also affected metabolic pathways in the liver and intestine.•Nanoplastics enhanced behavioural and transcriptional toxicity of 6PPDq