Silver Nanoparticles Induce Degradation of the Endoplasmic Reticulum Stress Sensor Activating Transcription Factor-6 Leading to Activation of the NLRP-3 Inflammasome

Simard, Jean-Christophe; Vallières, Francis; de Liz, Rafaël; Lavastre, Valérie et Girard, Denis (2015). Silver Nanoparticles Induce Degradation of the Endoplasmic Reticulum Stress Sensor Activating Transcription Factor-6 Leading to Activation of the NLRP-3 Inflammasome Journal of Biological Chemistry , vol. 290 , nº 9. pp. 5926-39. DOI: 10.1074/jbc.M114.610899.

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Résumé

In the past decade, the increasing amount of nanoparticles (NPs) and nanomaterials used in multiple applications led the scientific community to investigate the potential toxicity of NPs. Many studies highlighted the cytotoxic effects of various NPs, including titanium dioxide, zinc oxide and silver nanoparticles (AgNPs). In a few studies, endoplasmic reticulum (ER) stress was found to be associated with NP cytotoxicity leading to apoptosis in different cell types. In this study, we report for the first time that silver nanoparticles of 15 nm (AgNP15), depending on the concentration, induced different signature ER stress markers in human THP-1 monocytes leading to a rapid ER stress response with degradation of the ATF-6 sensor. Also, AgNP15 induced pyroptosis and activation of the NLRP-3 inflammasome as demonstrated by the processing and increased activity of caspase-1, secretion of IL-1beta and ASC pyroptosome formation. Transfection of THP-1 cells with siRNA targeting NLRP-3 decreased the AgNP15-induced IL-1beta production. Absence of caspase-4 expression resulted in a significant reduction of pro-IL-1beta. However, caspase-1 activity was significantly higher in caspase-4 deficient cells compared to WT cells. Inhibition of AgNP15-induced ATF-6 degradation with Site-2 protease inhibitors completely blocked the effect of AgNP15 on pyroptosis and secretion of IL-1beta, indicating that ATF-6 is crucial for the induction of this type of cell death. We conclude that AgNP15 induce degradation of the ER stress sensor ATF-6, leading to activation of the NLRP-3 inflammasome regulated by caspase-4 in human monocytes.

Type de document:	Article
Mots-clés libres:	Caspase; Caspase 1 (CASP1); Caspase 4; Endoplasmic Reticulum Stress (ER Stress); Inflammasome; NLRP-3 Inflammasome; Nanotechnology; Pyroptosis; Silver Nanoparticles
Centre:	Centre INRS-Institut Armand Frappier
Date de dépôt:	03 avr. 2017 21:00
Dernière modification:	03 avr. 2017 21:00
URI:	https://espace.inrs.ca/id/eprint/3255

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