title: Mechanistic study on the biological effects of silver and gold nanoparticles in Caco-2 cells--induction of the Nrf2/HO-1 pathway by high concentrations of silver nanoparticles.
abstract: The most commonly used metal nanoparticles (NPs) across diverse applications, including in agro-food applications, include silver (AgNPs) and gold (AuNPs). In the present study, we aimed to investigate the biological responses and possible toxicological effects of AgNPs and AuNPs in the Caco-2 cells as an in vitro human GI tract model. Both AgNPs and AuNPs were internalized into the cytoplasm of Caco-2 cells, but not within the nucleus and only exposure to high concentrations of AgNPs, but not AuNPs, caused acute cytotoxicity and depolarization of the mitochondrial membrane potential. In addition, only AgNPs significantly depleted the total intracellular glutathione level, induced the activation of the stress-responsive gene, Nrf2, and dramatically increased the expression of heme oxygenase-1 (HO-1). Furthermore, siRNA silencing of Nrf2 transcripts significantly reduced the AgNP-induced HO-1 mRNA induction, suggesting a key role for Nrf2 in the control of HO-1 expression. Taken together, AgNPs but not AuNPs induced acute cytotoxicity and cellular responses via the oxidative stress-related activation of Nrf2/HO-1 signaling pathway in Caco-2 cells. The expression of HO-1 transcripts may be useful as a sensitive marker for safety evaluation of AgNPs in the GI tract of humans.
authors.affiliation: Nano Safety and Risk Assessment Laboratory, National Nanotechnology Center, National Science and Technology Development Agency (NSTDA), Pathum Thani 12120, Thailand. Electronic address: sasitorn@nanotec.or.th.
authors.forename: Sasitorn
authors.initials: S
authors.lastname: Aueviriyavit
authors.forename: Duangkamol
authors.initials: D
authors.lastname: Phummiratch
authors.forename: Rawiwan
authors.initials: R
authors.lastname: Maniratanachote
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D018938:Caco-2 Cells; D005786:Gene Expression Regulation / Q000187:drug effects; D006046:Gold / Q000633:toxicity*; D051547:Heme Oxygenase-1 / Q000502:physiology*; D006801:Humans; D053768:Metal Nanoparticles / Q000633:toxicity*; D051267:NF-E2-Related Factor 2 / Q000502:physiology*; D018384:Oxidative Stress / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*; D012834:Silver / Q000633:toxicity*
chemical_list: D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D012834:Silver; D006046:Gold; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D000111:Acetylcysteine
keywords: 2′,7′-dichlorofluorescein; 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide; 3-morpholinosydnonimine hydrochloride; 5-thio-2-nitrobenzoic acid; ARE; AgNPs; AuNPs; CM; Caco-2 cells; DCF; DLS; GAPDH; GI; GSH; GSTP1; Gastrointestinal system; Gold nanoparticles; HO-1; Heme oxygenase-1; Keap1; Kelch-like ECH-associated protein 1; MAPKs; MTT; Mrp1; N-acetylcysteine; NAC; NPs; Nrf2; PBS; ROS; SIN-1; Silver nanoparticles; TEM; TMRE; TNB; UDP glucuronosyltransferase 1A1; UGT1A1; antioxidant-responsive element; complete culture media; dynamic light scattering; gastrointestinal tract; glutathione; glutathione S-transferase P1; glyceraldehyde 3-phosphate dehydrogenase; gold nanoparticles; heme oxygenase-1; mitogen-activated protein kinase C; multidrug resistance protein; nanoparticles; nuclear factor (erythroid-derived 2)-like 2; phosphate buffered saline; qRT-PCR; quantitative real time reverse transcriptase polymerase chain reaction; reactive oxygen species; silver nanoparticles; tetramethylrhodamine ethyl ester; transmission electron microscopy