Molecular Impacts of Dietary Exposure to Nanoplastics Combined or Not with Arsenic in the Caribbean Mangrove Oysters (Isognomon alatus)

Abstract

Nanoplastics (NPs) are anthropogenic contaminants that raise concern, as they cross biological barriers. Metals’ adsorption on NPs’ surface also carries ecotoxicological risks to aquatic organisms. This study focuses on the impacts of three distinct NPs on the Caribbean oyster Isognomon alatus through dietary exposure. As such, marine microalgae Tisochrysis lutea were exposed to environmentally weathered mixed NPs from Guadeloupe (NPG), crushed pristine polystyrene nanoparticles (PSC), and carboxylated polystyrene nanoparticles of latex (PSL). Oysters were fed with NP-T. lutea at 10 and 100 µg L−1, concentrations considered environmentally relevant, combined or not with 1 mg L−1 pentoxide arsenic (As) in water. We investigated key gene expression in I. alatus’ gills and visceral mass. NP treatments revealed significant induction of cat and sod1 in gills and gapdh and sod1 in visceral mass. As treatment significantly induced sod1 expression in gills, but once combined with any of the NPs at both concentrations, basal mRNA levels were observed. Similarly, PSL treatment at 100 µg L−1 that significantly induced cat expression in gills or sod1 in visceral mass showed repressed mRNA levels when combined with As (reduction of 2222% and 34%, respectively, compared to the control). This study suggested a protective effect of the interaction between NPs and As, possibly by decreasing both contaminants’ surface reactivity.

Origin, exposure routes and xenobiotics impart nanoplastics with toxicity on freshwater bivalves

“…This could underline a disturbance of the energetic balance leading to an oxidative stress in clams after NP-L entry. Similar trends were observed in previous studies on the pacific oyster I. alatus exposed through the direct route to NPs, with the up-regulation of cav, 12S and cat genes 33 , whereas it was not observed after dietary exposure 15 . Surprisingly, no response was observed towards apoptosis in gills, with a global inhibition of gadd45, p53 and bax in all conditions tested (except Al).…”

“…These results are quite different from other studies made under marine conditions on the pacific oysters. The expression of cox1 in gills of Isognomon alatus was not modulated after neither water- nor diet borne exposures to environmental NPs for 7 days 15 , 31 . However, the expression of 12s was up-regulated in gills of I. alatus after direct exposure to environmental NPs 31, 33 while it was down-regulated in the present study.…”

“…It could result from a lower bioavailability of Al in presence of NPs, potentially due to Al adsorption onto NPs’ surface. It has been suggested that NPs can be directly rejected through pseudo-faeces or mucus secretion 30, 31 and that the bioavailability of a metalloid such as arsenic was lowered in presence of NPs in mangrove oysters, due to its adsorption to the surface of NPs 15 . On the assumption that a part of Al is bound to NPs, it could explain, at least partly, the low accumulation of Al in gills and visceral mass in conditions with NPs.…”

“…Several studies have reported their toxic effects, in particular on growth, locomotion, energetic metabolism, associated with the production of reactive oxygen species (ROS) that can lead to death [11][12][13][14][15] . These important interactions with the aquatic life suggest that NPs can play a key role in the functioning of ecosystems.…”

Early molecular responses of mangrove oysters to nanoplastics using a microfluidic device to mimic environmental exposure

“…The authors showed that these environmentally relevant NPs could impact algae and bivalves by inhibiting the cell growth of Scenedesmus subspicatus and incrementing the fecal and pseudofecal production of Corbicula fluminea (Baudrimont et al, 2020). Another study on mangrove oysters Isognomon alatus demonstrated that dietary exposure to nanoplastics (10-100 µg/L) produced from microplastics collected on Caribbean beaches could modulate genes involved in oxidative stress (up-regulation of the catalase gene) (Lebordais et al, 2021). Moreover, a recent study on Isognomon alatus demonstrated the synergic effect of arsenic (1 mg/L), when combined to NP exposures (7.5 to 15 µg/L) on response against oxidative stress (up-regulation of cat) and apoptosis (up-regulation of bax and p53 genes) (Arini et al, 2022).…”