Abstract

Silver nanoparticles (AgNPs) are one of the most widely used nanomaterials. The level of exposure to nanosilver is constantly raising, and a growing body of research highlights that it is harmful to the health, especially the nervous system, of humans. The potential pathways through which nanosilver affects neurons include the release of silver ions and the associated induction of oxidative stress. To better understand the mechanisms underlying the neurotoxicity of nanosilver, in this study we exposed male Wistar rats to 0.5 mg/kg body weight of AgNPs coated with bovine serum albumin (BSA), polyethylene glycol (PEG), or citrate, or to AgNO3 as a source of silver ions for 28 days and assessed the expression of antioxidant defense markers in the hippocampus of the exposed animals after 1 week of spatial memory training. We also evaluated the influence of AgNPs coating on neurosteroidogenesis in the rat hippocampus. The results showed that AgNPs disrupted the antioxidant system in the hippocampus and induced oxidative stress in a coating-dependent manner, which could potentially be responsible for neurodegeneration and cognitive disorders. The analysis of the influence of AgNPs on neurosteroids also indicated coating-dependent modulation of steroid levels with a significant decrease in the concentrations of progesterone and 17α-progesterone in AgNPs(BSA), AgNPs(PEG), and Ag+ groups. Furthermore, exposure to AgNPs or Ag+ resulted in the downregulation of selected genes involved in antioxidant defense (Cat), neurosteroid synthesis (Star, Hsd3b3, Hsd17b1, and Hsd17b10), and steroid metabolism (Ar, Er1, and Er2). In conclusion, depending on the coating material used for their stabilization, AgNPs induced oxidative stress and modulated the concentrations of steroids as well as the expression of genes involved in steroid synthesis and metabolism.

Highlights

  • The beginning of the 21st century saw rapid development of nanotechnology in almost every branch of modern science and technology, facilitating its use in a wide range of commercially available products [1]

  • Considering the extensive application of nanosilver in consumer products and increased human exposure, in this study we investigated the neurotoxic impact of AgNPs by analyzing the effects of differently coated AgNPs on the antioxidant parameters, oxidative stress, and neurosteroid metabolism in the hippocampus of orally exposed rats after 1 week of memory training

  • The results of ANOVA revealed that the concentrations of all neurosteroids in the rat hippocampus were significantly influenced by AgNPs depending on the type of coating used on the nanoparticles

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Summary

Introduction

The beginning of the 21st century saw rapid development of nanotechnology in almost every branch of modern science and technology, facilitating its use in a wide range of commercially available products [1]. The nanomaterial most commonly found in consumer products is nanosilver according to the Nanodatabase [2]. Due to their desirable physicochemical properties, antimicrobial effect, and ease of synthesis, silver nanoparticles (AgNPs) have been successfully applied in hygiene products, cosmetics, textiles, toys, food containers, and dietary supplements [1,3]. The widespread use of AgNPs has increased the level of human exposure to these nanomaterials, mainly by inhalation, dermal contact, and ingestion [4]. Numerous studies in recent years have shown that AgNPs elicit toxic effects in various tissues, including the nervous system [5,6,7,8], which raises legitimate concerns about their possible impact on human health.

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