Sex-related response in mice after sub-acute intraperitoneal exposure to silver nanoparticles

Highlights

• Favourable AgNP deposition in female compared to male liver.

• Most apparent sex-differences in oxidative stress response observed in the lungs.

• Higher levels of ROS/GSH in kidney and liver of animals exposed to TRF- vs. PVP-AgNPs.

Abstract

Silver nanoparticles (AgNPs) are among the most commercialized nanomaterials in biomedicine due to their antimicrobial and anti-inflammatory properties. Nevertheless, possible health hazards of exposure to AgNPs are yet to be understood and therefore raise public concern in regards of their safety.

In this study, sex-related differences, role of steroidal hormones and influence of two different surface stabilizing agents (polymer vs. protein) on distribution and adverse effects of AgNPs were investigated in vivo. Intact and gonadectomised male and female mice were treated with seven AgNPs doses administered intraperitoneally during 21 days. After treatment, steroid hormone levels in serum, accumulation of Ag levels and oxidative stress biomarkers in liver, kidneys, brain and lungs were determined.

Sex-related differences were observed in almost all tissues. Concentration of Ag was significantly higher in the liver of females compared to males. No significant difference was found for AgNP accumulation in lungs between females and males, while the lungs of intact males showed significantly higher Ag accumulation compared to gonadectomised group. Effect of surface coating was also observed, as Ag accumulation was significantly higher in kidneys and liver of intact females, as well as in kidneys and brain of intact males treated with protein-coated AgNPs compared to polymeric AgNPs. Oxidative stress response to AgNPs was the most pronounced in kidneys where protein-coated AgNPs induced stronger effects compared to polymeric AgNPs. Interestingly, protein-coated AgNPs reduced generation of reactive oxygen species in brains of females and gonadectomised males. Although there were no significant differences in levels of hormones in the AgNP-exposed animals compared to controls, sex-related differences in oxidative stress parameters were observed in all organs.

Results of this study highlight the importance of including the sex-related differences and effects of protein corona in biosafety evaluation of AgNPs exposure.

Introduction

Silver nanoparticles (AgNPs) are used today in a wide range of commercial products, while the market size of AgNP-based products is steadily increasing (Syafiuddin et al., 2017). Due to biocidal and anti-inflammatory properties, AgNPs have gained particular interest in biomedicine, pharmacy, food and textile industry (Carbone et al., 2016; Chen and Schluesener, 2008; Hebeish et al., 2011). However, their extensive use raises concerns about their safety and health-related risks (Li and Cummins, 2020). Given that, despite many promising benefits, the possible health hazards associated with exposure to AgNPs are not well understood.

Besides dermal exposure, which is the main route of exposure to AgNPs after human use of AgNPs-impregnated textile or products related to wound healing, AgNPs may enter the human body through respiratory and gastrointestinal systems. Irrespective of the exposure pathway, existing in vivo studies demonstrated that AgNPs may enter the blood circulation via different exposure routes, with subsequent accumulation in different organs and interference with normal physiological mechanisms (Exbrayat et al., 2015; Li and Cummins, 2020). Pathological changes in all major organs after the short- or long-term in vivo exposure to AgNPs have been well documented in existing scientific literature (Barbir et al., 2019; Kim et al., 2010; Strużyńska and Skalska, 2018; Sung et al., 2009; Wang et al., 2020; Xu et al., 2020). Alteration of cellular permeability, reactive oxygen species (ROS) generation and inflammatory response have been described as the most important key events that lead to adverse health outcomes of exposure to AgNPs (Docea et al., 2020; Korani et al., 2015; Shrivastava et al., 2016). Accumulated ROS can lead to lipid peroxidation, dysfunction of many proteins and biomolecules, enzyme inhibition, DNA damage and finally cell death (Flores-López et al., 2019; Valko et al., 2007). Moreover, AgNPs interact with proteins and other biomolecules in every biological compartment, which leads to the formation of a biomolecular corona on their surface (Capjak et al., 2017; Del Pilar Chantada-Vázquez et al., 2019; Durán et al., 2015; Monteiro-Riviere et al., 2013). Once formed, protein corona provides a new biological identity to AgNPs and modifies their uptake, activity, clearance, and toxicity (Capjak et al., 2017; Monteiro-Riviere et al., 2013). The effects of a protein corona formation on the biological actions and fate of NPs has been studied in only few in vivo studies (Barbir et al., 2019; Bertrand et al., 2017; Garza-Ocañas et al., 2010) where NPs were functionalized with albumin (Barbir et al., 2019; Garza-Ocañas et al., 2010) or metallothionein (Barbir et al., 2019). Moreover, we found that biodistribution and stress response to AgNPs exposure are dependent on the character of protein corona (Barbir et al., 2019). In the same study, we found the sex-related differences in the distribution of these AgNPs in liver, kidneys and blood of laboratory animals. Despite plenty of published data on in vivo effects to AgNPs, sex differences in responses are still not well understood and are described to only a limited extent. Greater AgNPs deposition (by 2–4 times) was found in kidneys of female rats compared to males after subacute oral and subchronic inhalatory exposure (Dong et al., 2013; Kim et al., 2009, Kim et al., 2010, Kim et al., 2008; Song et al., 2013). More recent study evidenced sex differences in AgNP accumulation in a number of organs being significantly higher in females than males, especially in the kidney, liver, jejunum and colon (Boudreau et al., 2016). Contrary to the results on AgNPs accumulation, there are evidences that male animals treated with AgNPs had a higher decrease in kidney function than females (Sung et al., 2009). Sex-dependent differences after in vivo exposure to AgNPs were also found for changes in hepatic and kidney gene expression pathways related to metabolism and cell signaling (Dong et al., 2013; Kim et al., 2016). In these studies, male rats showed a higher expression of genes involved in pathways related to diabetes triggering and xenobiotic metabolism compared to females, which could partially explain the differences in renal clearance and AgNPs accumulation. Brief overview of most in vivo studies on the biodistribution and toxicological effects of AgNPs published recently has been presented as supporting information to our previous paper (Barbir et al., 2019).

Within this study, we aimed to investigate the sex-related differences and possible role of steroidal hormones in the distribution and oxidative stress response to AgNPs after sub-acute exposure in adult mice, also considering the impact on protein vs. polymer surface stabilization of particles. For this purpose, intact and gonadectomised male and female mice were treated intraperitoneally with seven AgNP doses of 1 mg Ag per kg body weight (b.w.) during the period of 21 days. Protein-coated AgNPs were prepared by using transferrin (TRF) as surface coating agent, while polymer-coated AgNPs were prepared by colloidal stabilization with polyvinylpyrrolidone (PVP). TRF was selected due to the expression of TRF receptors on the surface of many cell types, including those of the blood-brain barrier (BBB) (Mo et al., 2019). Overexpression of TRF receptors was noticed also on the surface of tumor cells owed to their increased need for iron (Shen et al., 2018) and made them attractive target for the delivery of therapeutic agents into cancer cells as well as across the BBB (Dixit et al., 2015). The PVP-AgNPs were included as one of the most widely studied polymer-coated AgNPs. Distribution and toxicity effects of PVP-AgNPs and TRF-AgNPs were evaluated in the kidney, liver, lung and brain of mice by measuring the total Ag level using inductively coupled plasma-mass spectrometry (ICPMS), as well as the levels of intracellular GSH, peroxy and superoxide radicals. Steroidal hormones were measured only in serum of control and treated mice using liquid chromatography with tandem mass spectrometry (LC-MS/MS).

Obtained results provide additional information on the role of surface decoration of AgNPs with proteins in triggering the biological responses in males vs. females to promote further relevant sex-related approach in nanotoxicology.