Exposure to polystyrene nanoplastics induces apoptosis, autophagy, histopathological damage, and intestinal microbiota dysbiosis of the Pacific whiteleg shrimp (Litopenaeus vannamei)

Nanoplastics (NPs) are widely distributed environmental pollutants that can disrupt intestinal immunity of crustaceans. In this study, the effects of NPs on gut immune enzyme activities, cell morphology, apoptosis, and microbiota diversity of Litopenaeus vannamei were investigated. L. vannamei was exposed to five concentrations of NPs (0, 0.1, 1, 5, and 10 mg/L) for 28 days. The results showed that higher concentrations of NPs damaged the intestinal villi, promoted formation of autophagosomes, increased intestinal non-specific immunoenzyme activities, and significantly increased apoptosis at 10 mg/L. In response to exposure to NPs, the expression levels of ATG3, ATG4, ATG12, Caspase-3, p53, and TNF initially increased and then decreased. In addition, the concentration of NPs was negatively correlated to the expression levels of the genes of interest and intestinal enzyme activities, suggesting that exposure to NPs inhibited apoptosis and immune function. The five dominant phyla of the gut microbiota (Proteobacteria, Firmicutes, Bacteroidetes, Acidobacteria, and Actinomycetes) were similar among groups exposed to different concentrations of NPs, but the abundances tended to differ. Notably, exposure to NPs increased the abundance of pathogenic bacteria. These results confirm that exposure to NPs negatively impacted intestinal immune function of L. vannamei. These findings provide useful references for efficient breeding of L. vannamei.

Polystyrene nanoplastics exposure alters muscle amino acid composition and nutritional quality of Pacific whiteleg shrimp (Litopenaeus vannamei)

Litopenaeus vannamei were exposed to 80-nm polystyrene nanoplastics (NPs) at different concentrations (0, 0.1, 1, 5, and 10 mg/L) for 28 days to study the effects on muscle nutritional quality. Our results showed that with increasing NPs concentrations, the survival rate, specific gain rate, and protein efficiency ratio decreased but the feed conversion ratio increased. There was no significant difference in moisture, ash, and crude lipid content in the muscle, and a general decrease in crude protein content was observed. However, the total amino acid and semi-essential amino acid contents decreased. The spacing between muscle fibers and the melting morphology of muscle increased. The hardness of muscle flesh texture increased, but springiness, cohesiveness, and chewiness decreased. Regarding antioxidant enzyme activity, the activity of catalase decreased, but the total antioxidant capacity, superoxide dismutase activity, and reduced glutathione first increased and then decreased. The expression level of the growth-related genes retinoid X receptor (RXR), chitin synthase (CHS), and calmodulin A (CaM) first increased then decreased, but calcium/calmodulin-dependent protein kinase I (CaMKI), ecdysteroid receptor (EcR), chitinase 5 (CHT5), cell division cycle 2 (Cdc2), and cyclin-dependent kinase 2 (CDK2) decreased. Our results suggest that exposure to NPs can inhibit growth by inducing oxidative stress, which leads to muscle tissue damage and changes in amino acid composition. These results will provide a theoretical reference for the risk assessment of NPs and the ecological health aquaculture of shrimp.

Polystyrene nanoplastics induce lipid metabolism disorder and alter fatty acid composition in the hepatopancreas of Pacific whiteleg shrimp (Litopenaeus vannamei)

The impact of nanoplastics (NPs) on environmental pollution and aquatic organisms has gradually attracted attention, but there are relatively few reports of the effects of NPs on the lipid metabolism of crustaceans. In this study, we exposed Pacific whiteleg shrimp (Litopenaeus vannamei) to different concentrations of polystyrene NPs (0, 0.1, 1, 5, and 10 mg/L) for 28 days. We then evaluated the effects of NP exposure on metabolite content, histology, lipid metabolism-related enzyme activity, and gene expression. Our results showed that with increasing NPs concentrations and exposure time, (1) the crude protein and crude fat content decreased and fatty acid composition changed; (2) the tissue structure was destroyed and the number of lipid droplets increased in the hepatopancreas; (3) the activities of acetyl-CoA carboxylase, fatty acid synthase, carnitine palmitoyl transferase-1, pyruvate kinase and low-density lipoprotein content tended to decrease and that of lipase and high-density lipoprotein content first increased and then decreased; the content of triglycerides and total carbohydrate first decreased and then increased; (4) the expression of fatty acid synthesis-related genes (Fas, SREBP, and FAD), fatty acid transport-related genes (FATP, FABP, and ACBP), and fatty acid decomposition-related genes (Ampk and lip1) first increased and then decreased. These results indicate that exposure to NPs can cause physiological disorders of fat metabolism in L.vannamei and that high concentrations of NPs have a negative impact on lipid metabolism. These results of this study provide valuable ecotoxicological data for better interpretation of the mechanism of action of NPs in crustaceans.

Polystyrene nanoplastics decrease nutrient accumulation, disturb sex hormones, and inhibit reproductive development in juvenile Macrobrachium nipponense

The biological effects of nanoplastics has grown exponentially over the past few years. However, little is known about the effects of nanoplastic exposure on gonadal development in crustaceans. Thus, juvenile oriental river prawns (Macrobrachium nipponense) were exposed to different concentrations of 75-nm polystyrene nanoplastics (0, 5, 10, 20, and 40 mg/L) for 28 days to study the effects of exposure to nanoplastics on gonadal development. The genes encoding extracellular signal-regulated kinase (ERK) and mitogen-activated protein kinase kinase (MEK) were selected and the nutrient composition, sex hormone level, and gonad development-related gene expression were determined. Crude lipid and crude protein decreased with exposure to higher concentrations of nanoplastics, whereas there were no significant differences in levels of ash or moisture (P > 0.05). Full-length Mn-ERK and Mn-MEK cDNAs were cloned from M. nipponense and homologous comparisons showed that the genes had conserved functional sequences and had evolved consistently in invertebrates. With nanoplastics concentration increased, the serum sex hormone (estradiol, progesterone, and testosterone) levels of juvenile shrimp first increased and then decreased. In addition, the expression of gonad development-related genes (Vitellogenin, Vitellogenin receptor, Cyclin B, Gametocyte Specific Factor 1, Vasa, and PL10), MEK and ERK initially increased and then decreased with increasing nanoplastic concentration. This suggests that polystyrene nanoplastics reduce the accumulation of nutrients and lead to suppression of gonadal development in juvenile M. nipponense and, thus, provides basic information on the toxic effects of nanoplastics that could extend to other crustaceans.