Abstract
Silver nanoparticles (AgNPs) are widely used in the household, medical and industrial sectors due to their effective bactericidal activities and unique plasmonic properties. Despite the promising advantages, safety concerns have been raised over the usage of AgNPs because they pose potential hazards. However, the mechanistic basis behind AgNPs toxicity, particularly the sublethal effects at the organismal level, has remained unclear. In this study, we used a powerful in vivo platform Drosophila melanogaster to explore a wide spectrum of adverse effects exerted by dietary AgNPs at the organismal, cellular and molecular levels. Lethal doses of dietary AgNPs caused developmental delays and profound lethality in developing animals and young adults. In contrast, exposure to sublethal doses, while not deadly to developing animals, shortened the adult lifespan and compromised their tolerance to oxidative stress. Importantly, AgNPs mechanistically resulted in tissue-wide accumulation of reactive oxygen species (ROS) and activated the Nrf2-dependent antioxidant pathway, as demonstrated by an Nrf2 activity reporter in vivo. Finally, dietary AgNPs caused a variety of ROS-mediated stress responses, including apoptosis, DNA damage, and autophagy. Altogether, our study suggests that lethal and sublethal doses of AgNPs, have acute and chronic effects, respectively, on development and longevity by inducing ROS-mediated stress responses.
Highlights
Nanotechnology—the creation, manipulation, and application of materials with nanoscale structures (1–100 nm)—has turned out to be a popular field of research in the 21st century
The EDX qualitative analysis validated that the primary particles of AgNPs are composed of nearly 100% elemental silver (the components of a TEM grid contributed to the detection of carbon and copper signal peaks) (Fig. 1a)
Due to the effective antimicrobial activity and unique plasmonic properties of AgNPs, these nanoparticles have been of particular interest for application in various sectors, such as commodity, healthcare, and electronic industries
Summary
Nanotechnology—the creation, manipulation, and application of materials with nanoscale structures (1–100 nm)—has turned out to be a popular field of research in the 21st century. In 2009, the human dietary intake of silver, owing to the widespread use of silver compounds, was estimated at 70–90 μg.day−1 24 This number likely underestimates the actual exposure levels; there has been a recent increase in the use of AgNPs in the food industry as components of the coatings of containers/processing machines or as packaging materials intended to prevent bacterial proliferation[25]. Drosophila melanogaster has been considered a powerful model system for toxicological studies (referred to as drosophotoxicology), including the assessment of nanotoxicity[34] This model system is used because of its relatively short life cycle and because of its ease of genetic manipulation. The purpose of this study was to explore the toxic effects and mechanisms of AgNPs at the organismal, cellular and molecular levels by using the Drosophila model system. Our results showed that lethal and sublethal doses of AgNPs have acute and chronic effects, respectively, on development and longevity by inducing ROS-mediated stress responses
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