Farnesoid X Receptor suppresses lipid peroxidation and ferroptosis

Abstract

Objective: Ferroptosis is a regulated cell death modality that occurs upon iron-dependent lipid peroxidation. The recent decade of research has uncovered many regulators driving ferroptosis as well as cellular gatekeepers preventing ferroptosis. Yet, many processes and networks remain to be elucidated. Methods and results: In this study, we performed a chemical screen using small molecules with known mode of action and identified two agonists (Turofexorate and Fexaramine) of the nuclear receptor Farnesoid X Receptor (FXR), also known as NR1H4, to suppress ferroptosis, but not apoptosis or necroptosis. Further, we demonstrate that in liver cells with high FXR protein levels, inhibition of FXR sensitizes cells to undergo ferroptotic cell death, while activation of FXR inhibits ferroptosis. Importantly, FXR also inhibits ferroptosis in ex vivo primary mouse hepatocytes. Activation of FXR by Turofexorate and Fexaramine significantly reduces lipid peroxidation. Mechanistically, overexpression of FXR or activation of FXR by bile acids upregulates the ferroptosis-inhibitory regulators FSP1, PPARa, GPX4, SCD1, and ACSL3 to reduce peroxidized lipids and to counteract ferroptosis. Conclusion: In this study, we demonstrate that activation of FXR inhibits ferroptotic cell death via upregulation of a number of ferroptosis-inhibitory proteins (FSP1, PPARa, GPX4, SCD1, and ACSL3) to reduce lipid peroxidation. Hence, modulating FXR activity may be beneficial to overcome ferroptosis-mediated degenerative diseases.

Ferroptosis: Iron-mediated cell death linked to disease pathogenesis

“…Apart from the fatty acid metabolic processes mentioned earlier and implicated in ferroptosis regulation, bile acid metabolism also connects to ferroptosis. For example, Tschuck et al have shown that the activation of the nuclear receptor Farnesoid X receptor, triggered by bile acids, leads to the upregulation of pivotal genes, namely GPX4, FSP1, and ACSL3, that curtail ferroptosis [76] . In essence, the network of lipid metabolism plays a pivotal role in both the initiation and modulation of lipid peroxidation during ferroptosis [76] .…”

Suppression of ferroptosis by vitamin A or antioxidants is essential for neuronal development

“…Spheroids were cultured according to the protocol previously described 15 . In brief, HT-1080 were seeded into 96-well round bottom microplates (CellCarrier Spheroid ULA, PerkinElmer) with a density of 2,000 cells per well.…”

“…Immunostaining of HT-1080 with anti-4-Hydroxynonenal-antibody (4-HNE, ab46545, Abcam) was performed as previously described 15 . In brief, ferroptotic cell death was induced via 300 nM RSL3 for 2 h and cells were co-treated with 20 µM ATRA or 2 µM ferrostatin-1.…”

“…Flow cytometry: C11-BODIPY staining and flow cytometry was performed as previously described 15 . Ferroptosis was induced for 2 h with 250 nM RSL3 and cells were co-treated with 20 µM ATRA or 2 µM ferrostatin-1.…”

“…Ferroptosis is another RCD, which occurs through iron-dependent lipid peroxidation 3,8 . It is controlled by a number of cellular gatekeepers including the system-xc -/glutathione peroxidase 4 (GPX4)/glutathione axis 3 , the ferroptosis suppressor protein 1 (FSP1)/ubiquinol/vitamin k axis [9][10][11] , the GTP cyclohydrolase 1 (GCH1)/tetrahydrobiopterin (BH4)/dihydrofolate reductase (DHFR) axis 12,13 , and the nuclear receptor Farnesoid X receptor (FXR) 14,15 , amongst others.…”