IFITM3 knockout alleviates neuronal parthanatos by restoring astrocytic glutamate uptake in intracerebral hemorrhage mice

Introduction: Intracerebral hemorrhage (ICH) causes severe neurological deficits mainly attributable to secondary brain injury. Parthanatos is a subtype of regulated cell death triggered by glutamate excitotoxicity. Interferon-induced transmembrane protein 3 (IFITM3) is an immune regulatory molecule involved in neuronal death in various neurodegenerative disorders. However, it remains unclear whether and how IFITM3 and parthanatos participate in secondary brain injury after ICH.

Objectives: This study aims to investigate whether IFITM3 aggravates neuronal parthanatos by impairing astrocytic glutamate uptake after ICH and to elucidate the underlying mechanisms.

Methods: Bioinformatics analysis of transcriptome datasets from ICH human patients and mouse models was performed to identify the IFITM3 expression and its potential functions. IFITM3 knockout mice and mice with AAV-mediated astrocytic IFITM3 overexpression were subjected to the ICH model by autologous blood injection. Neurobehavioral tests, Western blot, immunofluorescence staining, glutamate uptake assay, and pharmacological approaches were employed to elucidate the role of IFITM3 in glutamate uptake and neuronal parthanatos.

Results: IFITM3 was upregulated and served as a hub gene in immune response and cell death after ICH. IFITM3 knockout improved the sensorimotor and cognitive functions of ICH mice. Conversely, astrocytic IFITM3 overexpression reversed these neuroprotective effects. Specifically, IFITM3 knockout alleviated neuronal excitotoxicity and parthanatos by restoring astrocytic glutamate uptake in the perihematomal region, as evidenced by decreased glutamate levels, oxidative damage, PARP-1 overactivation, PAR overproduction, and nuclear translocation of the AIF-MIF complex. Additionally, IFITM3 knockout reduced p38 MAPK phosphorylation and increased the expression of glutamate transporter EAAT2. Administration of a p38 MAPK Inhibitor in IFITM3-overexpressing mice restored EAAT2 expression and attenuated neuronal parthanatos after ICH.

Conclusion: Astrocytic IFITM3 upregulation causes impaired glutamate uptake, excitotoxicity, parthanatos, and neurological deficits through p38 MAPK/EAAT2 pathway, highlighting IFITM3 and parthanatos as potential therapeutic targets for ICH.