Uptake, Distribution, and Toxicological Mechanisms of Micro(nano)plastics in Fish

Abstract

Aquatic ecosystems are the typical reservoirs for plastic wastes, which can crumble into smaller pieces with particle size less than 5 mm [termed as micro(nano)plastics, MNPs] under various physical and chemical processes. MNPs in aquatic ecosystems are easily ingested by fish unintentionally, thereby inducing adverse endpoints. The primary objectives of this thesis were to investigate the uptake, distribution, and impacts of MNPs on fish tissues. Uptake and distribution kinetics of MNPs in fish tissues were tracked using newly developed second near-infrared aggregated-induced emission fluorophore-labeled MNPs sensors. We tested that gastrointestinal (GI) tract and gill were the key targets for MNPs accumulation in fish, while MNPs were also detected in other tissues including liver, brain, eye, and skin, highlighting the overlooked but important transport of MNPs among fish tissues via blood circulation. The impacts and respective toxicological mechanisms of MNPs in fish organs were mainly examined based on bioinformatic analysis, including 16S rRNA gene sequencing, bulk RNA sequencing, metabolomics, and single cell RNA sequencing. Waterborne and foodborne exposure of MNPs induced hepatic genotoxicity via different pathways, with waterborne exposure mainly enriched in circadian rhythm and hippo signaling pathway, while foodborne exposure mainly enriched in TNF signaling pathway, C-type lectin receptor signaling pathway, and TGF-beta signaling pathway. Additionally, MPs were observed to induce higher respiratory damages in fish compared to NPs, as evidenced by the upregulation of egln3 and nadk (gene), and the downregulation of isocitrate (metabolite). Ion regulation and ammonia excretion of fish were confirmed to be disturbed by MNPs via a novel gut-gill bacteria axis. Based on the results of the advanced single cell RNA sequencing, immune and physiological heterogeneities of fish gills to MNPs were investigated, which further highlighted fibroblasts as a potential sensitive cell-type biomarker for MNPs.

Date of Award	20 Nov 2024
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Wenxiong WANG (Supervisor)