Ferroptosis induces detrimental effects in chronic EAE and its implications for progressive MS

Abstract

Ferroptosis is a form of lipid peroxidation-mediated cell death and damage triggered by excess iron and insufficiency in the glutathione antioxidant pathway. Oxidative stress is thought to play a crucial role in progressive forms of multiple sclerosis (MS) in which iron deposition occurs. In this study we assessed if ferroptosis plays a role in a chronic form of experimental autoimmune encephalomyelitis (CH-EAE), a mouse model used to study MS. Changes were detected in the mRNA levels of several ferroptosis genes in CH-EAE but not in relapsing–remitting EAE. At the protein level, expression of iron importers is increased in the earlier stages of CH-EAE (onset and peak). While expression of hemoxygenase-1, which mobilizes iron from heme, likely from phagocytosed material, is increased in macrophages at the peak and progressive stages. Excess iron in cells is stored safely in ferritin, which increases with disease progression. Harmful, redox active iron is released from ferritin when shuttled to autophagosomes by ‘nuclear receptor coactivator 4’ (NCOA4). NCOA4 expression increases at the peak and progressive stages of CH-EAE and accompanied by increase in redox active ferrous iron. These changes occur in parallel with reduction in the antioxidant pathway (system xCT, glutathione peroxidase 4 and glutathione), and accompanied by increased lipid peroxidation. Mice treated with a ferroptosis inhibitor for 2 weeks starting at the peak of CH-EAE paralysis, show significant improvements in function and pathology. Autopsy samples of tissue sections of secondary progressive MS (SPMS) showed NCOA4 expression in macrophages and oligodendrocytes along the rim of mixed active/inactive lesions, where ferritin+ and iron containing cells are located. Cells expressing NCOA4 express less ferritin, suggesting ferritin degradation and release of redox active iron, as indicated by increased lipid peroxidation. These data suggest that ferroptosis is likely to contribute to pathogenesis in CH-EAE and SPMS.

Role of ferroptosis in neuroimmunity and neurodegeneration in multiple sclerosis revealed by multi‐omics data

“… 6 The ferroptotic signalling pathway and its resulting phenotypes can be alleviated by anti‐ferroptotic compounds. 6 , 48 …”

Targeted RNAseq Revealed the Gene Expression Signature of Ferroptosis-Related Processes Associated with Disease Severity in Patients with Multiple Sclerosis

“…Besides its contribution to microglia-related EAE disease severity and neuronal damage [ 26 ], the sensitization to ferroptosis by activation of NOX2 was suggested in cancers [ 27 ]. With regard to iron regulation and utilization, a recent study has presented the dysregulated expression of genes involved in these processes, following increased lipid peroxidation in a chronic EAE, but not a relapsing–remitting EAE model [ 9 ]. The complexity of disease, including relapse, remission and progression phases, was reflected by gene expression changes through stages of EAE, showing the peak of SLC11A2/DMT1 expression at the peak of chronic EAE, decreasing to pre-onset levels in the progressive stage.…”

“…Another recent study has shown that transcriptional changes related to ferroptosis were more prominent during acute EAE and relapse, while demyelination progressively increased over time [ 11 ]. Expression of GPX4 , often assigned as the hallmark defense enzyme in ferroptosis that is required for glutathione-mediated antioxidant defense, remained unchanged between RR and chronic EAE [ 9 ]. The GPX4 gene expression and plasma protein levels were not different between MS phenotypes in our study.…”

“…The first experimental evidence that linked a loss of oligodendrocytes with the expression of several markers of ferroptosis was provided in a mouse model of cuprizone diet-induced demyelination [ 8 ]. Recent evidence suggests that treatment with ferroptosis inhibitors can restore the antioxidant defense and lead to a reduction in lesion size and a clinical improvement in the late stage of EAE [ 9 ]. Furthermore, it was shown that ferroptosis mediated the activation of T cells in EAE, which involved the infiltration and activation of CD4+ T cells in the CNS, while implementation of ferroptosis inhibitors led to a reduction in neuroinflammation and prevention of neuronal death in EAE mice [ 10 ].…”

Oxidative Stress Markers in Multiple Sclerosis

“…Jhelum et al [ 184 ] reported increased peroxidation, increased mRNA levels of several ferroptosis genes, increased nuclear receptor coactivator 4 (NCOA4) expression (assessed using qRT-PCR), decreased GPx4 activity (assessed using Western blot analysis), and decreased total glutathione (assessed using spectrophotometry) in the brain of female mice with EAE of C57BL/6. C57BL/6 OlaHSD [ 15 ] and C57BL/6 female mice with EAE [ 185 ] showed increased levels of acrolein or their metabolites (assessed using Western blot [ 15 ] or liquid chromatography/tandem mass spectrometry [ 185 ]) in the spinal cord and urine.…”