Polystyrene microplastic exposure induces hepatic damage via immune-modulated autophagy and ferroptosis in Nile...

Hepatic damage in fish induced by microplastic exposure has garnered increasing concern, yet its molecular mechanisms remain insufficiently elucidated. In this study, 30 days after hatching (dah) Nile tilapia were subjected to sub-chronic exposure to polystyrene microplastics (PS; 100 nm) for 14 days. Histopathological examination revealed evident inflammatory cell infiltration in the livers of PS-exposed fish compared to the control fish. Transmission electron microscopy showed elevated mitochondrial rupture and increased autophagosome formation. Immunofluorescence and Western blot analyses showed upregulated Lc3b and downregulated P62 protein levels, suggesting enhanced hepatic autophagy. Transcriptomic profiling of liver tissues and subsequent KEGG enrichment analysis highlighted significant upregulation of genes involved in the MAPK, NOD-like receptor, Toll-like receptor, and autophagy signaling pathways. Metabolomic profiling indicated notable enrichment in glutathione metabolism, ferroptosis, cysteine and methionine metabolism, and the NOD-like receptor pathway. Integrated transcriptomic and metabolomic KEGG analysis consistently identified ferroptosis as a centrally enriched pathway. Further gene expression and metabolite analyses demonstrated marked upregulation of immune-related genes, autophagy-related genes, and ferroptosis-pathway genes. Concurrently, ferroptosis-related metabolites including glutathione and cysteine were significantly decreased. Meanwhile, levels of lipid metabolites such as 2-oleoylglycerol were also reduced, whereas lipid peroxidation products represented by 4-hydroxynonenal were significantly increased. Additional validation confirmed increased expression of inflammatory factors (il-1β, tgf-β, nlrp3) and altered iron homeostasis in the PS-exposed fish liver. These findings indicate that sub-chronic PS exposure promotes hepatic ferroptosis via immune-mediated activation of autophagy, ultimately leading to liver injury in Nile tilapia. Our study provides novel insights into the mechanisms underlying microplastic-induced tissue damage in aquatic organisms.