Inhibition of ferroptosis after intracerebral hemorrhage

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Inhibition of ferroptosis after intracerebral hemorrhage Spontaneous intracerebral hemorrhage (ICH) is the stroke subtype with the highest mortality and morbidity. Because large amounts of blood are released into the extracellular space during ICH, the metabolism of hemoglobin/free heme is very important for brain recovery. Heme is degraded by heme oxygenase into iron, biliverdin, and carbon monoxide. Importantly, iron accumulation within the brain contributes to secondary brain injury after ICH. Indeed, iron toxicity contributes to collagenase-induced hemorrhagic brain injury in mice, and reducing iron accumulation with iron chelators can improve neuronal survival. Recently, ferroptosis, an iron- dependent form of non-apoptotic cell death, was identified in cancer cells and in organotypic hippocampal slice cultures after glutamate exposure. It is triggered by small molecules or by conditions that inhibit glutathione biosynthesis or glutathione peroxidase 4 (GPX4) activity. This regulated cell death is characterized by extensive iron-dependent lipid peroxidation, which can be suppressed by lipophilic antioxidant ferrostatin-1 or liproxstatin- 1. Ferroptotic cell death also has been shown to occur in brain cells. To date, it has been reported in mouse models of Parkinson disease and ICH. Whether inhibition of ferroptosis by ferrostain-1 or liproxstain-1 reduces ICH injury and improves functional outcomes in aged animals remains unknown. Therefore, this research is intended to characterize ferroptotic cell death in the context of ICH in aged animals. Our long-term goal is to limit ICH injury and improve functional outcomes. The scientific objective of this proposal is to test the hypothesis that inhibition of ferroptosis by ferrostain-1 or liproxstain-1 protects ICH brain and improves functional outcomes. We will further determine whether augmentation of GPX4 activity inhibits ferroptosis and provides cerebroprotection after ICH. In pilot studies, ferroptotoic cell death, characterized by shrunken mitochondria, was detected by transmission electron microscopy in the mouse ICH brain. Additionally, mice treated with ferrostatin-1 after ICH had better neurologic outcomes than mice treated with vehicle. A second, independent, ferroptosis inhibitor, liproxstatin-1, also exhibited marked protection against ICH injury. Together, these novel observations strongly support the premise that inhibition of ferroptosis might reduce ICH injury in aged animals. The first specific aim will determine whether suppression of iron-dependent lipid peroxidation improves histologic and functional outcomes after ICH in aged mice of both sexes. The second specific aim will determine whether overexpression of GPX4 is cerebroprotective after ICH. This study will provide novel evidence that ferroptotic cell death, in addition to other regulated cell death pathways, is prominent in the brains of aged animals with ICH. It will also provide insight into the molecular mechanism by which increased GPX4 activity prevents post-ICH ferroptosis. Work on the proposed project could render new drugs/treatments for patients with ICH. Successful validation of lipid peroxidation inhibitors in the ICH models of aged animals will provide the rationale and proof-of-concept for future preclinical and clinical trials.