Moderate mechanical stress suppresses chondrocyte ferroptosis in osteoarthritis by regulating NF-κB p65/GPX4 signaling pathway

Ferroptosis is a recently identified form of programmed cell death that plays an important role in the pathophysiological process of osteoarthritis (OA). Herein, we investigated the protective effect of moderate mechanical stress on chondrocyte ferroptosis and further revealed the internal molecular mechanism. Intra-articular injection of sodium iodoacetate (MIA) was conducted to induce the rat model of OA in vivo, meanwhile, interleukin-1 beta (IL-1β) was treated to chondrocytes to induce the OA cell model in vitro. The OA phenotype was analyzed by histology and microcomputed tomography, the ferroptosis was analyzed by transmission electron microscope and immunofluorescence. The expression of ferroptosis and cartilage metabolism-related factors was analyzed by immunohistochemical and Western blot. Animal experiments revealed that moderate-intensity treadmill exercise could effectively reduce chondrocyte ferroptosis and cartilage matrix degradation in MIA-induced OA rats. Cell experiments showed that 4-h cyclic tensile strain intervention could activate Nrf2 and inhibit the NF-κB signaling pathway, increase the expression of Col2a1, GPX4, and SLC7A11, decrease the expression of MMP13 and P53, thereby restraining IL-1β-induced chondrocyte ferroptosis and degeneration. Inhibition of NF-κB signaling pathway relieved the chondrocyte ferroptosis and degeneration. Meanwhile, overexpression of NF-κB by recombinant lentivirus reversed the positive effect of CTS on chondrocytes. Moderate mechanical stress could activate the Nrf2 antioxidant system, inhibit the NF-κB p65 signaling pathway, and inhibit chondrocyte ferroptosis and cartilage matrix degradation by regulating P53, SLC7A11, and GPX4.

Aldehyde dehydrogenase 3a2 protects AML cells from oxidative death and the synthetic lethality of ferroptosis inducers

Metabolic alterations in cancer represent convergent effects of oncogenic mutations. We hypothesized that a metabolism-restricted genetic screen, comparing normal primary mouse hematopoietic cells and their malignant counterparts in an ex vivo system mimicking the bone marrow microenvironment, would define distinctive vulnerabilities in acute myeloid leukemia (AML). Leukemic cells, but not their normal myeloid counterparts, depended on the aldehyde dehydrogenase 3a2 (Aldh3a2) enzyme that oxidizes long-chain aliphatic aldehydes to prevent cellular oxidative damage. Aldehydes are by-products of increased oxidative phosphorylation and nucleotide synthesis in cancer and are generated from lipid peroxides underlying the non-caspase-dependent form of cell death, ferroptosis. Leukemic cell dependence on Aldh3a2 was seen across multiple mouse and human myeloid leukemias. Aldh3a2 inhibition was synthetically lethal with glutathione peroxidase-4 (GPX4) inhibition; GPX4 inhibition is a known trigger of ferroptosis that by itself minimally affects AML cells. Inhibiting Aldh3a2 provides a therapeutic opportunity and a unique synthetic lethality to exploit the distinctive metabolic state of malignant cells.

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.

The Emerging Roles of Ferroptosis in Huntington's Disease

Huntington's disease (HD) is an autosomal dominant and fatal neurodegenerative disorder, which is caused by an abnormal CAG repeat in the huntingtin gene. Despite its well-defined genetic origin, the molecular mechanisms of neuronal death are unclear yet, thus there are no effective strategies to block or postpone the process of HD. Ferroptosis, a recently identified iron-dependent cell death, attracts considerable attention due to its putative involvement in neurodegenerative diseases. Accumulative data suggest that ferroptosis is very likely to participate in HD, and inhibition of the molecules and signaling pathways involved in ferroptosis can significantly eliminate the symptoms and pathology of HD. This review first describes evidence for the close relevance of ferroptosis and HD in patients and mouse models, then summarizes advances for the mechanisms of ferroptosis involved in HD, finally outlines some therapeutic strategies targeted ferroptosis. Comprehensive understanding of the emerging roles of ferroptosis in the occurrence of HD will help us to explore effective therapies for slowing the progression of this disease.