Stimulation of de novo glutathione synthesis by nitrofurantoin for enhanced resilience of hepatocytes

Abstract

Toxicity is not only a function of damage mechanisms, but is also determined by cellular resilience factors. Glutathione has been reported as essential element to counteract negative influences. The present work hence pursued the question how intracellular glutathione can be elevated transiently to render cells more resistant toward harmful conditions. The antibiotic nitrofurantoin (NFT) was identified to stimulate de novo synthesis of glutathione in the human hepatoma cell line, HepG2, and in primary human hepatocytes. In intact cells, activation of NFT yielded a radical anion, which subsequently initiated nuclear-factor-erythroid 2-related-factor-2 (Nrf2)-dependent induction of glutamate cysteine ligase (GCL). Application of siRNA-based intervention approaches confirmed the involvement of the Nrf2-GCL axis in the observed elevation of intracellular glutathione levels. Quantitative activation of Nrf2 by NFT, and the subsequent rise in glutathione, were similar as observed with the potent experimental Nrf2 activator diethyl maleate. The elevation of glutathione levels, observed even 48 h after withdrawal of NFT, rendered cells resistant to different stressors such as the mitochondrial inhibitor rotenone, the redox cycler paraquat, the proteasome inhibitors MG-132 or bortezomib, or high concentrations of NFT. Repurpose of the antibiotic NFT as activator of Nrf2 could thus be a promising strategy for a transient and targeted activation of the endogenous antioxidant machinery.

Development of a Physiologically Based Pharmacokinetic Model for Nitrofurantoin in Rabbits, Rats, and Humans

“…Such stress pathway activity is known to vary strongly amongst individuals [ 39 , 40 ], which may contribute to liver toxicity in specific subpopulations independent of renal impairment. In the case of NFT exposure, this concerns especially NRF2- and ATF4-mediated signaling [ 11 ]; hence, the expression of proteins involved in these pathways might represent additional risk factors. Future integration of our PBPK model with stress pathway models may allow the prediction of the effect of interindividual variability, renal function, and various dosage regimens on NFT disposition, stress biomarkers, and potential liver injury.…”

“…Severe fatalities due to hepatic toxicity have been reported [ 7 , 8 ], and autoimmune-like hepatitis has been identified as the most common cause [ 9 , 10 ]. Although the mechanisms by which NFT causes DILI are not fully resolved, in vitro studies have suggested that NFT may cause liver injury by hyper-activation of several cellular stress pathways [ 11 ].…”

G × E interactions as a basis for toxicological uncertainty

“…Moreover, export carriers of hepatocytes can be upregulated to protect the cells from cytotoxicity due to overloading with bile acids or xenobiotics (Ghallab et al 2019a ). The use of stress response pathways differs largely, so that a given insult may be innocuous for one cell type, but detrimental for another (Gutbier et al 2018b ; Harris et al 2018 ; Smirnova et al 2015 ; Wijaya et al 2022 ). According to the toxicological concept of the adverse outcome pathway (AOP) (Leist et al 2017 ), it is possible to include resilience factors as a “modulatory influence” on key events and within the description of key event relationships.…”

Application of high throughput in vitro metabolomics for hepatotoxicity mode of action characterization and mechanistic-anchored point of departure derivation: a case study with nitrofurantoin

“…The activation of cellular oxidative stress response pathways by nitrofurantoin has been previously demonstrated (Wijaya et al 2021 ). At low doses, nitrofurantoin has been shown to activate the endogenous antioxidant machinery by being a potent stimulator of intracellular glutathione synthesis (Wijaya et al 2022 ), at high concentrations however, it has been linked to oxidative stress-related hepatotoxicity (Wang et al 2008 ). Because of its characteristic dose-related biological responses nitrofurantoin was considered as a suitable compound to assess the applicability of the high throughput targeted metabolomics to provide a basis for a mechanistic-grounded PoD determination.…”