Impact of multigenerational exposure to AgNO3 or NM300K Ag NPs on antioxidant defense and oxidative stress in Caenorhabditis elegans

Lisa M Rossbach,Deborah H Oughton,Erica Maremonti,Dag M Eide,Dag A Brede

doi:10.1016/j.ecoenv.2021.112178

Lisa M Rossbach, Deborah H Oughton + Show 3 more

Open Access

https://doi.org/10.1016/j.ecoenv.2021.112178

Copy DOI

Abstract

Adaptation of the nematode Caenorhabditis elegans towards NM300K silver nanoparticles (Ag NPs) has previously been demonstrated. In the current study, the sensitivity to a range of secondary stressors (CeO2 NP, Ce3+, Cu2+, Cd2+, and Paraquat) following the multigenerational exposure to silver nanoparticles (Ag NPs NM300K) or AgNO3 was investigated. This revealed improved tolerance to the ROS inducer Paraquat with higher fecundity after pre-exposure to Ag NP, indicating an involvement of reactive oxygen species (ROS) metabolism in the adaptive response to NM300K. The potential contribution of the antioxidant defenses related to adaptive responses was investigated across six generations of exposure using the sod-1::GFP reporter (GA508), and the Grx1-roGFP2 (GRX) biosensor strains. Results showed an increase in sod-1 expression by the F3 generation, accompanied by a reduction of GSSG/GSH ratios, from both AgNO3 and Ag NP exposures. Continuous exposure to AgNO3 and Ag NP until the F6 generation resulted in a decreased sod-1 expression, with a concomitant increase in GSSG/GSH ratios. The results thus show that despite an initial enhancement, the continuous exposure to Ag caused a severe impairment of the antioxidant defense capacity in C. elegans.

Highlights

Silver nanoparticles (Ag NPs) have received a great deal of attention in ecotoxicological studies due to their wide use acting as antibacterial agents in consumer products (Fung and Bowen, 1996; Park et al, 2009)
Transmission electron microscopy (TEM) analysis of the NM300K Ag NPs in ddH2O (15 MΩ cm) showed particles to be spherical with a median size of 23.9 ± 21.8 nm (Fig. S2)
The current study was undertaken to investigate the activation of the antioxidant defenses and the effects on oxidative stress response following a multigenerational exposure towards either AgNO3 or NM300K Ag NP

Summary

Introduction

Silver nanoparticles (Ag NPs) have received a great deal of attention in ecotoxicological studies due to their wide use acting as antibacterial agents in consumer products (Fung and Bowen, 1996; Park et al, 2009). The EU reference Ag NPs NM300K have been subject to a wide range of toxicological studies, and is amongst the best charac terized nanomaterials available (Bicho et al, 2016; Kleiven et al, 2018; Koser et al, 2017; van der Ploeg et al, 2014; Volker et al, 2015). In our previous work we showed that the chronic six generational exposure towards the NM300K Ag NPs, resulted in an increased susceptibility towards AgNO3 exposure, while the multigenerational exposures towards AgNO3 resulted in a decrease in sensitivity towards Ag NPs (Rossbach et al, 2019)

Objectives

Methods

Results

Discussion

Conclusion