Functionalized Nanoplastics (NPs) Increase the Toxicity of Metals in Fish Cell Lines

Abstract

Nanoplastics (NPs) are one of the most abundant environment-threatening nanomaterials on the market. The objective of this study was to determine in vitro if functionalized NPs are cytotoxic by themselves or increase the toxicity of metals. For that, we used 50 nm polystyrene nanoparticles with distinct surface functionalization (pristine, PS-Plain; carboxylic, PS-COOH; and amino PS-NH2) alone or combined with the metals arsenic (As) and methylmercury (MeHg), which possess an environmental risk to marine life. As test model, we chose a brain-derived cell line (SaB-1) from gilthead seabream (Sparus aurata), one of the most commercial fish species in the Mediterranean. First, only the PS-NH2 NPs were toxic to SaB-1 cells. NPs seem to be internalized into the cells but they showed little alteration in the transcription of genes related to oxidative stress (nrf2, cat, gr, gsta), cellular protection against metals (mta) or apoptosis (bcl2, bax). However, NPs, mainly PS-COOH and PS-NH2, significantly increased the toxicity of both metals. Since the coexistence of NPs and other pollutants in the aquatic environment is inevitable, our results reveal that the combined effect of NPs with the rest of pollutants deserves more attention.

Uptake and toxicity of polystyrene micro/nanoplastics in gastric cells: Effects of particle size and surface functionalization

“…Therefore, lack of elevation in Bcl-2 expression while increase in BAX and Caspase-8 in cells treated with PS particles, indicate tipping of balance favoring apoptosis onset. Gonza ´lez-Ferna ´ndez et al had also observed increased transcription of BAX genes, concomitant with decreased gene expression of Bcl-2 in SaB-1 cells exposed to 50 nm aminated PS particle treatment compared to carboxyl or plain PS particles [74].…”

Nanoplastics Increase Fish Susceptibility to Nodavirus Infection and Reduce Antiviral Immune Responses

“…Commercial PS-NH 2 and PS-COOH displayed positive and negative charges, respectively, in ultrapure water. However, once resuspended in the culture medium, all the particles reduced their ζ-potential and showed a similar negative charge very close to the medium alone (−9.1 ± 1.0 mV) [29]. This charge reduction could be associated with the adsorption of proteins and lipids in the culture medium [31].…”

“…Clathrin-mediated endocytosis is also the primary route of internalization of virus into the cell [33]. Although we have not investigated the mechanism, we have reported that SaB-1 cells internalize NPs and suffer a strong and general stress state [29]. Therefore, the increased endocytic mechanism in cells leading to NP internalization might also contribute to increase the NNV attachment and entry, which has been suggested for GS cells [15].…”

“…In this study, we used a brain cell line (SaB-1), which has been demonstrated to show good replication of the NNV virus [28], to study the mechanisms of infection and the immune response in a tissue-specific manner. In addition, we already showed that SaB-1 cells are susceptible to NP internalization [29], being a suitable model to study NP-cellular interactions. Cell lines are frequently used as experimental models due to their easy replicability and maintenance.…”

“…The SaB-1 cell line, derived from the brain of gilthead seabream (Sparus aurata) [28], was cultured in L-15 Leibowitz medium (ThermoFisher Scientific, Waltham, MA, USA) supplemented with 15% fetal bovine serum (FBS, ThermoFisher Scientific, Waltham, MA, USA) and antibiotics [29]. Cells were sub-cultured by routine trypsinization methods, and viability was always higher than 95%.…”