Glucose availability determines silver nanoparticles toxicity in HepG2.
BACKGROUND
The increasing body of evidence suggest that nanomaterials toxicity is associated with generation of oxidative stress. In this paper we investigated the role of respiration in silver nanoparticles (AgNPs) generated oxidative stress and toxicity. Since cancer cells rely on glucose as the main source of energy supply, glucose availability might be an important determinant of NPs toxicity.


METHODS
AgNPs of 20 nm nominal diameter were used as a model NPs. HepG2 cells were cultured in the media with high (25 mM) or low (5.5 mM) glucose content and treated with 20 nm AgNPs. AgNPs-induced toxicity was tested by neutral red assay. Generation of H2O2 in mitochondria was evaluated by use of mitochondria specific protein indicator HyPer-Mito. Expression of a 77 oxidative stress related genes was assessed by qPCR. The activity of antioxidant enzymes was estimated colorimetrically by dedicated methods in cell homogenates.


RESULTS
AgNPs-induced dose-dependent generation of H2O2 and toxicity was observed. Toxicity of AgNPs towards cells maintained in the low glucose medium was significantly lower than the toxicity towards cells growing in the high glucose concentration. Scarceness of glucose supply resulted in upregulation of the endogenous antioxidant defence mechanisms that in turn alleviated AgNPs dependent ROS generation and toxicity.


CONCLUSIONS
Glucose availability can modify toxicity of AgNPs via elevation of antioxidant defence triggered by oxidative stress resulted from enhanced oxidative phosphorylation in mitochondria and associated generation of ROS. Presented results strengthen the idea of strong linkage between NPs toxicity and intracellular respiration and possibly other mitochondria dependent processes.
Department of Molecular Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Banacha 12/16, 90-237, Lodz, Poland. zuberek.mariusz@gmail.com.
Mariusz
M
Zuberek
Department of Molecular Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Banacha 12/16, 90-237, Lodz, Poland. d.wojciechowska4@gmail.com.
Dominika
D
Wojciechowska
Department of Molecular Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Banacha 12/16, 90-237, Lodz, Poland. damiank@biol.uni.lodz.pl.
Damian
D
Krzyzanowski
Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195, Warsaw, Poland. s.meczynska@ichtj.waw.pl.
Sylwia
S
Meczynska-Wielgosz
Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195, Warsaw, Poland. m.kruszewski@ichtj.waw.pl.|Faculty of Medicine, University of Information Technology and Management in Rzeszow, Sucharskiego 2, 35-225, Rzeszow, Poland. m.kruszewski@ichtj.waw.pl.|Department of Molecular Biology and Translational Research, Institute of Rural Health, Jaczewskiego 2, 20-090, Lublin, Poland. m.kruszewski@ichtj.waw.pl.
Marcin
M
Kruszewski
Department of Molecular Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Banacha 12/16, 90-237, Lodz, Poland. agrzelak@biol.uni.lodz.pl.
Agnieszka
A
Grzelak
D000975:Antioxidants / Q000378:metabolism; D003470:Culture Media; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005947:Glucose / Q000378:metabolism*; D056945:Hep G2 Cells; D006801:Humans; D057446:Hydrodynamics; D006861:Hydrogen Peroxide / Q000378:metabolism; D053768:Metal Nanoparticles / Q000633:toxicity*; D008928:Mitochondria / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000235:genetics; D010316:Particle Size; D012834:Silver / Q000633:toxicity*; D055672:Static Electricity
D000975:Antioxidants; D003470:Culture Media; D012834:Silver; D006861:Hydrogen Peroxide; D005947:Glucose