Subarachnoid haemorrhage (SAH) introduces a large erythrocyte burden into the subarachnoid space (SAS) and cerebrospinal fluid (CSF). Most mechanistic studies have focused on events after erythrocyte lysis, when cell-free haemoglobin (Hb), haem, iron, and other erythrocyte-derived mediators promote vascular dysfunction, oxidative injury, and inflammation. Before membrane rupture, however, erythrocytes can remain within clot or CSF, undergo transport towards extracranial drainage pathways, or become associated with and internalised by local cells. Evidence from human CSF studies, experimental SAH models, and other haemorrhagic brain injury models indicates that these processes involve heterogeneous erythrocyte populations and need not occur in a fixed sequence. We propose that the erythrocyte burden after SAH is dynamically partitioned among retained cellular, extracranially transported, cell-associated, and extracellular molecular pools. The biological consequences of this redistribution depend on both the rate of transfer between pools and whether lymphatic, phagocytic, haemoglobin-binding, haem-processing, and iron-storage systems become capacity-limited. This framework distinguishes direct evidence from mechanistic inference and generates testable predictions about when erythrocyte removal, cellular uptake, or molecular scavenging will reduce injury rather than redistribute it. Defining erythrocyte fate quantitatively may identify therapeutic opportunities both before and after extracellular erythrolysis.
Successful recanalization after endovascular thrombectomy does not always restore microvascular perfusion, highlighting the need for adjunctive strategies. Ischemic postconditioning (IPostC) involves brief, controlled cycles of flow interruption and restoration at the onset of reperfusion to attenuate ischemia-reperfusion injury. In the parent INSPIRE trial, IPostC, delivered in situ as four cycles of 2-minute balloon inflation followed by 2-minute deflation at the previously occluded arterial segment immediately after successful recanalization, reduced infarct growth from baseline to 48 h. This exploratory secondary analysis included all 60 randomized patients. We investigated whether IPostC was associated with early changes in immunothrombosis, coagulation, and microvascular transit and explored associated plasma proteomic and metabolomic profiles. Arterial blood obtained approximately 15 min after successful recanalization was analyzed using flow cytometry and thromboelastography. Quantitative digital subtraction angiography–derived microcirculation time was analyzed in 55 patients, and plasma proteomic and metabolomic profiling was performed in 29 patients. Compared with controls, patients receiving IPostC had lower neutrophil CD11b expression (median, 52.15 versus 64.27 mean fluorescence intensity ×10²; P = 0.011), a lower thromboelastography α-angle (65.15° versus 67.95°; P = 0.037), and shorter microcirculation time (2.11 versus 3.03 s; P = 0.020). Longer microcirculation time was associated with greater infarct growth (r = 0.533; P < 0.001). Proteomic and metabolomic analyses identified signals involving blood–brain barrier and extracellular-matrix organization and mitochondrial bioenergetics. Biomarker comparisons were not adjusted for multiple comparisons; in the omics analyses, no protein and 17 metabolites remained significant after false discovery rate correction. In summary, IPostC was associated with lower neutrophil activation, slower clot propagation, and faster microvascular transit after recanalization, and multi-omics profiling pointed to blood–brain barrier integrity and mitochondrial bioenergetics as candidate pathways. These findings are hypothesis-generating and require validation in larger studies. Trial registration: NCT06545734, registered 9 August 2024.
We report findings from a Phase 1/2a clinical trial (EUCT No. 2024-514590-22-00, STOP-DCI), an interventional, randomized, double-blind, placebo-controlled, multiple ascending-dose, first-in-human trial to determine safety and evaluate clinical outcome for the MEK 1/2 inhibitor EDV2209 in patients with severe spontaneous subarachnoid hemorrhage (SAH). In Phase 1b (N = 11), three cohorts received a single intracerebral ventricular (ICV) bolus (8.55 µg, 17–28.5 µg). In Phase 2a (N = 16), two cohorts were given three ICV injections of 28.5 µg EDV2209 or placebo over 18 h, beginning within 8 h of SAH onset. The study found an equal distribution of adverse events between treatment and placebo with no treatment-associated safety concerns. Outcomes and mortality were as expected or better for patients with severe SAH in the patients treated with EDV2209. Pharmacokinetics were reproducibly stable in the CSF with no detectable levels of EDV2209 in plasma. Treatment with EDV2209 was considered safe and was interpreted to provide potential benefit for improving patient outcome following severe SAH. These results provide a rationale to continue with a Phase 2b / 3 study powered to determine efficacy as well as safety.
Erythrocyte-derived metabolites released from the hematoma contribute substantially to secondary brain injury after intracerebral hemorrhage (ICH), and enhancing endogenous hematoma clearance is a promising therapeutic strategy. Hexokinase 2 (HK2), a key glycolytic enzyme predominantly expressed in microglia, regulates microglial function, but its role in hematoma resolution after ICH remains unclear. We therefore investigated whether HK2 governs microglia/macrophage-mediated erythrophagocytosis and thereby influences hematoma clearance and neurological recovery after ICH. ICH was induced in male C57BL/6 mice by striatal collagenase injection, and HK2 was selectively inhibited with 3-bromopyruvate (3-BP). Neurobehavioral outcomes, hematoma volume, and hemoglobin content were quantified, and mechanisms were examined in hemoglobin- or erythrocyte-stimulated BV2 microglia and RAW 264.7 macrophages using pharmacological inhibition, glucose-6-phosphate (G-6-P) rescue, and lentiviral HK2 overexpression. After ICH, HK2 was localized predominantly to peri-hematomal microglia/macrophages, and nuclear HK2 increased progressively, peaking at 72 h. HK2 inhibition exacerbated neurological deficits, reduced M2-like (Arg-1⁺) microglia/macrophages, and delayed hematoma clearance without affecting initial hematoma formation. In vitro, G-6-P restored ATP levels suppressed by 3-BP but only partially rescued phagocytosis, indicating a non-glycolytic mechanism: HK2 upregulated peroxisome proliferator-activated receptor γ (PPARγ) and CD36, and pharmacological blockade of PPARγ abolished HK2-enhanced erythrophagocytosis. These findings identify HK2 as a contributor to endogenous hematoma clearance that promotes microglia/macrophage erythrophagocytosis at least in part through PPARγ/CD36 signaling, and support further genetic and cell-specific studies before HK2 is advanced as a therapeutic target for ICH.
In large-core ischemic stroke, outcomes after thrombectomy remain heterogeneous, and imaging markers that capture treatment-modifiable injury beyond lesion extent are needed. We investigated whether lesion water content on noncontrast CT, quantified as net water uptake (NWU), predicts 12-month functional outcome and modifies the effect of endovascular thrombectomy (EVT). This secondary analysis of the randomized TENSION trial included 198 patients with admission CT suitable for NWU quantification and available 12-month modified Rankin Scale (mRS) scores; 168 had paired 24-h CT for follow-up NWU (NWUFU) assessment. The primary outcome was ordinal 12-month mRS. Multivariable ordinal and logistic regression tested associations and the NWU × EVT interaction, with discrimination assessed by area under the receiver operating characteristic curve (AUC). Median baseline NWU was 16.4
