POLYSTYRENE NANOPARTICLES IN ZEBRAFISH: THEIR ROLE IN OCULAR STRESS AND LIPID METABOLIC IMBALANCE

Nanoplastics (NP) pollution poses a growing environmental threat, with potential toxic effects on aquatic organisms. In this study, Raman microscopy was employed to monitor 150 nm polystyrene (PS) bioaccumulation during zebrafish early developmental stages. Raman imaging enabled the detection of PS in eye at 96 hours post-fertilization (hpf), as previously reported in the literature.1 PS induced proteins structural changes as demonstrated from the identification of amide I and amide III peaks, at 1663 cm⁻¹ and 1250 cm⁻¹ respectively, detected exclusively in treated samples. These peaks, according to the literature, are closely associated with inflammatory processes and oxidative stress.2 The eyes revealed alterations in pigmentation patterns that could relate to inflammatory and oxidative stress processes. This hypothesis is supported by RT-PCR results, which show increased gene expression of inflammation- and oxidative stress-related genes, such as il-1β, sod1, cat, and gstm. Particularly noteworthy is the increased expression of the rpe65c gene, specific to the retinal pigment epithelium and essential for visual function. Dysregulation of rpe65c has been associated with ocular diseases in various experimental models, highlighting the potential impact of polystyrene nanoparticles on eye physiology.3 Furthermore, we performed RT-PCR analysis of genes involved in eye development and regeneration, including rpe65 (retinal pigment epithelium-specific protein 65), sox2 (SRY-box transcription factor 2), and pax6a (paired box gene 6a). These genes were also significantly upregulated after PS treatment, indicating a regenerative response likely triggered by tissue injury. Finally, Oil Red O staining revealed a marked increase in neutral lipid accumulation in PS-treated larvae, particularly in the head, yolk sac, and body, indicating systemic lipid metabolism disruption following nanoparticle exposure. These findings demonstrate that polystyrene nanoplastics can bioaccumulate during critical stages of zebrafish development, inducing oxidative stress, inflammation, retinal gene dysregulation, and lipid metabolic imbalance. 1. Quiang L. and Cheng J. Ecotoxicology and Environmental Safety Vol. 176, 2019, Pages 226-2332. Hana Y., et al., Toxicology and Applied Pharmacology Vol. 327, 2017, Pages 39-513. Kiser Philip D. Progress in Retinal and Eye Research. Vol. 88, 2022, 101013