Mapping the dynamics of Nrf2 antioxidant and NFκB inflammatory responses by soft electrophilic chemicals in human liver cells defines the transition from adaptive to adverse responses. (October 2022)

• Record Type: Journal Article
• Authors: ter Braak, Bas; Klip, Janna E.; Wink, Steven; Hiemstra, Steven; Cooper, Sarah L.; Middleton, Alistair; White, Andrew; van de Water, Bob
• Is Part Of: Toxicology in vitro. Volume 84(2022)
• Publication Date: 2022-10
• Subjects: Oxidative stress -- Inflammation -- New approach method -- Reporter assay -- HepG2 BAC GFP -- Dynamic regulation; Toxicity testing -- In vitro -- Periodicals; Toxicology -- Periodicals; 615.9
• DOI: 10.1016/j.tiv.2022.105419
• Languages: English
• ISSNs: 0887-2333

Abstract

Abstract: A comprehensive understanding of the dynamic activation and crosstalk between different cellular stress response pathways that drive cell adversity is crucial in chemical safety assessment. Various chemicals have electrophilic properties that drive cell injury responses in particular oxidative stress signaling and inflammatory signaling. Here we used bacterial artificial chromosome-based GFP cellular stress reporters with live cell confocal imaging, to systematically monitor the differential modulation of the dynamics of stress pathway activation by six different soft electrophiles: sulforaphane, andrographolide, diethyl maleate, CDDO-Me, ethacrynic acid and tert-butyl hydroquinone. The various soft electrophiles showed differential potency and dynamics of Nrf2 activation and nuclear translocation. These differences in Nrf2 dynamics correlated with distinct activation pattern of Nrf2 downstream targets SRNX1 and HMOX1. All soft electrophiles caused a strong dose dependent suppression of a cytokine-induced NFĸB response represented by suppression of NFĸB nuclear oscillation and inhibition of the downstream target gene activation A20 and ICAM1, which followed the potency of Nrf2 modulation but occurred at higher concentration close to saturation of Nrf2 activation. RNAi-based depletion of RelA resulted in a prolonged presence of Nrf2 in the nucleus after soft electrophile treatment; depletion of Nrf2 caused the induction of NFĸB signaling and activation of its downstream targets A20 and ICAM1. A systematic transcriptome analysis confirmed these effects by soft electrophiles on Nrf2 and NFκB signaling crosstalk in human induced-pluripotent stem cell-derived hepatocyte-like cells. Altogether our data indicate that modulation of Nrf2 by soft electrophiles may have consequences for efficient inflammatory signaling. Highlights: Dynamic activation of Nrf2 and NFĸB pathways was investigated using HepG2 reporters. Soft electrophiles induce the Nrf2 pathway, yet inhibit the NFĸB response. This opposite regulation is conserved between different hepatocyte test systems.