GPX4 degradation contributes to fluoride-induced neuronal ferroptosis and cognitive impairment via mtROS-chaperone-mediated autophagy.

Ferroptosis is a newly recognized type of programmed cell death that is implicated in the pathophysiological process of neurological disorders. Our previous studies have revealed that exposure to high concentrations of fluoride for long periods of time induces hippocampal neural injury and cognitive deficits. However, whether ferroptosis is involved in fluoride-induced neuronal death and the underlying mechanism remain unknown. In this study, the results indicated that exposure to high fluoride triggered ferroptosis in SH-SY5Y cells and in the hippocampus of mice. Fluoride exposure accelerated the lysosomal degradation of GPX4 and led to neuronal ferroptosis, while GPX4 overexpression protected SH-SY5Y cells against fluoride-induced neurotoxicity. Intriguingly, the enhanced chaperone-mediated autophagy (CMA) induced by fluoride stimulation was responsible for GPX4 degradation because the inhibition of CMA activity by LAMP2A knockdown effectively prevented fluoride-induced GPX4 loss. Furthermore, mitochondrial ROS (mtROS) accumulation caused by fluoride contributed to CMA activation-mediated GPX4 degradation and subsequent neuronal ferroptosis. Notably, the ferroptosis-specific inhibitor ferrostatin-1 (Fer-1) or the ROS scavenger N-acetyl-L-cysteine (NAC) alleviated fluoride-evoked hippocampal neuronal death and synaptic injury as well as cognitive deficits in mice. The present studies indicates that ferroptosis is a novel mechanism of fluoride-induced neurotoxicity and that chronic fluoride exposure facilitates GPX4 degradation via mtROS chaperone-mediated autophagy, leading to neuronal ferroptosis and cognitive impairment.

Resveratrol alleviated 5-FU-induced cardiotoxicity by attenuating GPX4 dependent ferroptosis.

The clinical use of 5-fluorouracil (5-FU), a potent antitumor agent, was limited by severe cardiotoxic effects. The present study was aimed to investigate the protective effects of resveratrol (Res) on 5-FU-induced cardiotoxicity and to explore its potential mechanisms.The cardiotoxicity model was intraperitoneal injection of 5-FU at the dose of 30 mg/kg for 7 consecutive days. Plasma enzymes activities, cardiac tissues were assessed after treatment with Res for 3 weeks. Ferrostatin-1 (Fer-1) was used as ferroptosis inhibitor. In H9c2 cardiomyocyte cells, cell viability, generation of reactive oxygen species (ROS), mitochondrial activity and cellular Fe2+ levels were measured. Western-blot assay was performed to evaluate the protein level of ferroptosis in vitro and in vivo. In the mice model, Res reduced 5-FU-induced cardiomyocyte injury (ferroptosis, myofibrillar loss and vacuolization). In addition, increased serum creatine kinase (CK), lactate dehydrogenase (LDH), malonaldehyde (MDA) and Fe2+ activity and decreased activities of glutathione (GSH) were observed in 5-FU group. These changes were prevented by treatment with Res. In H9c2 cardiomyocyte cells, Res increased the cell viability and attenuated cell ferroptosis as measured by DCFH-DA, TMRE and Calcein AM staining. In addition, 5-FU induced a reduction in GPX4, FTH1, Nrf2 and NQO1 and activation of TfR and P53 compared with the control group. However, Res effectively inhibited the changes in ferroptosis associated proteins in vitro and in vivo. Res possessed the cardioprotective potential against 5-FU induced cardiotoxicity. Moreover, Res attenuates 5-FU-induced cardiotoxicity via inhibiting GPX4 dependent ferroptosis.

A Class of Disulfide Compounds Suppresses Ferroptosis by Stabilizing GPX4.

Ferroptosis is a nonapoptotic form of cell death characterized by iron-dependent lipid peroxidation and has been implicated in multiple pathological conditions. Glutathione peroxidase 4 (GPX4) plays an essential role in inhibiting ferroptosis by eliminating lipid peroxide using glutathione (GSH) as a reductant. In this study, we found Ellman's reagent DTNB and a series of disulfide compounds, including disulfiram (DSF), an FDA-approved drug, which protect cells from erastin-induced ferroptosis. Mechanistically, DTNB or DSF is conjugated to multiple cysteine residues in GPX4 and disrupts GPX4 interaction with HSC70, an adaptor protein for chaperone mediated autophagy, thus preventing GPX4 degradation induced by erastin. In addition, DSF ameliorates concanavalin A induced acute liver injury by suppressing ferroptosis in a mouse model. Our work reveals a novel regulatory mechanism for GPX4 protein stability control. We also discover disulfide compounds as a new class of ferroptosis inhibitors and suggest therapeutic repurposing of DSF in treating ferroptosis-related diseases.

FTY720 induces ferroptosis and autophagy via PP2A/AMPK pathway in multiple myeloma cells.

AIMS: Multiple myeloma (MM) is the second hematological plasma cell malignany and sensitive to fingolimod (FTY720), a novel immunosuppressant. Previous study shows FTY720-induced apoptosis and autophagy can cause cell death in MM cells, however, the high death rate cannot fully be explained. The study aims to investigate further mechanism of how FTY720 kills MM cells. MATERIALS AND METHODS: Experiments are performed on 25 human primary cell samples and two MM cell lines by flow cytometry, fluorescence microscopy, and transmission electron microscopy. Expressions of relative factors are tested by qRT-PCR or western blot. KEY FINDINGS: Ferroptosis-specific inhibitors, deferoxamine mesylate (DFOM) and ferropstatin-1 (Fer-1), reverse FTY720-induced cell death in MM cells. Glutathione peroxidase 4 (GPX4) and soluble carrier family 7 member 11 (SLC7A11), key regulators of ferroptosis, are highly expressed in primary MM cells and can be decreased by FTY720 at the mRNA and protein level in MM cells. In addition, FTY720 induces other characteristic changes of ferroptosis. Furthermore, FTY720 can dephosphorylate AMP-activated protein kinase subunit ɑ (AMPKɑ) at the Thr172 site by activating protein phosphatase 2A (PP2A) and reduce the expression of phosphorylated eukaryotic elongation factor 2 (eEF2), finally cause MM cell death. Using LB-100, a PP2A inhibitor, AICAR, an agonist of AMPK, and bafilomycin A1 (Baf-A1), an autophagy inhibitor, we discover that FTY720 induces ferroptosis and autophagy through the PP2A/AMPK pathway, and ferroptosis and autophagy can reinforce each other. SIGNIFICANCE: These results provide a new perspective on the treatment of MM.