Impact of polystyrene microplastic exposure on gilthead seabream (Sparus aurata Linnaeus, 1758): Differential inflammatory and immune response between anterior and posterior intestine

Plastics are the most widely discharged waste into the aquatic ecosystems, where they break down into microplastics (MPs) and nanoplastics (NPs). MPs are ingested by several marine organisms, including benthic and pelagic fish spe-cies, contributing to organ damage and bioaccumulation.This study aimed to assess the effects of MPs ingestion on gut innate immunity and barrier integrity in gilthead seabreams (Sparus aurataLinnaeus, 1758) fed for 21 days with a diet enriched with polystyrene (PS-MPs; 1-20 mu m; 0, 25 or 250 mg /kg b.w./die). Physiological fish growth and health status were not impacted by PS-MPs treatments at the end of experimental period. Inflammation and immune alterations were revealed by molecular analyses in both anterior (AI) and posterior intes-tine (PI) and were confirmed by histological evaluation. PS-MPs triggered TLR-Myd88 signaling pathway with follow-ing impairment of cytokines release. Specifically, PS-MPs increased pro-inflammatory cytokines gene expression (i.e., IL-1 beta, IL-6 and COX-2) and decreased anti-inflammatory ones (i.e., IL-10). Moreover, PS-MPs also induced an increase in other immune-associated genes, such as Lys, CSF1R and ALP. TLR-Myd88 signaling pathway may also lead to the mitogen-activated protein kinases (MAPK) signaling pathway activation. Here, MAPK (i.e., p38 and ERK) were activated by PS-MPs in PI, following the disruption of intestinal epithelial integrity, as evidenced by reduced gene ex-pression of tight junctions (i.e. ZO-1, Cldn15, Occludin, and Tricellulin), integrins (i.e., Itgb6) and mucins (i.e., Muc2-like and Muc13-like). Thus, all the obtained results suggest that the subchronic oral exposure to PS-MPs induces inflamma-tory and immune alterations as well as an impact on intestinal functional integrity in gilthead seabream, with a more evident effect in PI.

Automated summary

This study aimed to assess the effects of microplastics ingestion on gut innate immunity and barrier integrity in gilthead seabreams. The results showed that ingesting polystyrene microplastics can cause inflammation and immune alterations, as well as disrupt intestinal epithelial integrity.