Environ Pollut 2025 Apr 21;375:126291. doi: 10.1016/j.envpol.2025.126291.

Microplastic and nanoplastic exposure induced transcriptional and physiological alterations and triggered immune responses in the sea cucumber, Holothuria leucospilota.

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Microplastics (MPs) and nanoplastics (NPs) are pervasive pollutants widely distributed across aquatic ecosystems. They have gained significant attention due to their potential adverse effects on marine organisms. Many marine species, particularly sea cucumbers, inadvertently ingest these plastic particles due to their non-selective feeding behavior. In this study we carried out a 14-day exposure experiment and investigated the effects of polyethylene MPs and NPs on gene expression, oxidative stress, immune condition and histology of a tropical sea cucumber, Holothuria leucospilota, a most abundant sea cucumbers species in the world. The results showed that MPs and NPs dramatically altered gene expression in discrepant profiles. NPs caused down-regulation of the majority of genes related to metabolic processes. In contrast to the enrichment of GO terms which related to regulation, differentiation and development after being exposed to MPs, metabolome-related GO terms were significantly enriched in NPs exposure. The toxicity mechanism associated with the NPs and MPs exposure involves the activation of the antioxidant defense system and the disruption of immune balance. Furthermore, histological destruction of the respiratory tree in NP and MP groups provided robust evidence for the unstable physiological condition. Our study deepens the comprehension of size-dependent plastic toxicity on marine benthic invertebrates, thereby posing a potential hazard to marine ecosystems.

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