Interplay Between Nanoplastics and the Immune System of the Mediterranean Sea Urchin Paracentrotus lividus

Abstract

The present study highlights for the first time the interplay between model nanoplastics, such as the carboxyl-modified polystyrene nanoparticles (PS-COOH, 60 nm) NPs and the coelomocytes of the sea urchin Paracentrotus lividus, a benthic grazer widely distributed in Mediterranean coastal area, upon acute in vitro exposure (4 h) (5 and 25 μg mL–1). Insight into PS-COOH trafficking (uptake and clearance) and effects on immune cell functions (i.e., cell viability, lysosomal membrane stability, and phagocytosis) are provided. Dynamic Light Scattering analysis reveals that PS NP suspensions in CF undergo a quick agglomeration, more pronounced for PS-COOH (608.3 ± 43 nm) compared to PS-NH2 (329.2 ± 5 nm). However, both PS NPs are still found as nano-scale agglomerates in CF after 4 h of exposure, as shown by the polydispersity index > 0.3 associated with the presence of different PS NP size populations in the CF. The observed changes in ζ-potential upon suspension in CF (–11.1 ± 3 mV and –12.1 ± 4 mV for PS-COOH and PS-NH2, respectively) confirm the formation of a bio-corona on both PS NPs. Optical fluorescence microscopy and fluorimetric analyses using fluorescently labeled PS-COOH (60 nm) reveal a fast uptake of PS-COOH primarily by phagocytes within 1 h of exposure. Upon transfer to PS NP-free CF, a significant decrease in fluorescence signal is observed, suggesting a fast cell clearance. No effect on cell viability is observed after 4 h of exposure to PS-COOH, however a significant decrease in lysosomal membrane stability (23.7 ± 4.8%) and phagocytic capacity (63.43 ± 3.4%) is observed at the highest concentration tested. Similarly, a significant reduction in cell viability, lysosomal membrane stability and phagocytosis is found upon exposure to PS-NH2 (25 μg mL–1), which confirms the important role of surface charges in triggering immunotoxicity. Overall, our results show that, although being quickly internalized, PS-COOH can be easily eliminated by the coelomocytes but may still be able to trigger an immune response upon long-term exposure scenarios. Taking into account that sediments along Mediterranean coasts are a sink for micro- and nanoplastics, the latter can reach concentrations able to exceed toxicity-thresholds for marine benthic species.

Impact of Microbial Colonization of Polystyrene Microbeads on the Toxicological Responses in the Sea Urchin Paracentrotus lividus

“…Similar findings have been already reported in our previous study upon exposure to only virgin micro-PS regardless of their size, 29 while no changes in coelomocyte sub-populations including red versus white amoebocytes were observed by short-term in vitro exposure of coelomocytes to PS nanoparticles (60−50 nm). 68 In agreement with previous findings in other biological systems, the increasing trend of ROS over time together with the concomitant decrease of RNS found in coelomocytes of specimens exposed to colonized micro-PS suggested NO scavenging by ROS through the formation of peroxynitrite by reaction between NO and superoxide anions. 69−71 ROS levels increase in larvae, tissues, and immune cells of some marine invertebrate species upon MP exposure.…”

“…Therefore, the presence of bacteria on the surface of colonized micro-PS could have stimulated such immunological responses with an increased production of the red pigment. Similar findings have been already reported in our previous study upon exposure to only virgin micro-PS regardless of their size, while no changes in coelomocyte sub-populations including red versus white amoebocytes were observed by short-term in vitro exposure of coelomocytes to PS nanoparticles (60–50 nm) …”

U–Pb geochronology of Variscan granitoids from the Moroccan Meseta (Northwest Africa): Tectonic implications

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Polystyrene microplastic particles induce endothelial activation

“…Using the same model organism, Kelpsiene et al reported a reduced life-time upon exposure to polystyrene nanoplastics [ 20 ]. Of note, some studies reported translocation in a surface charge-dependent manner in both marine organisms and rats [ 8 , 21 ]. Based on these observations and the fact that due to weathering processes and subsequent surface oxidation, microplastic particles are expected to acquire carboxylic groups (-COOH) and hence are negatively charged [ 22 ], we therefore have used carboxylated PS particles in our study as well.…”