Perihematomal edema (PHE) significantly aggravates secondary brain injury in patients with intracerebral hemorrhage (ICH), yet its detailed mechanisms remain elusive. Neutrophil extracellular traps (NETs) are known to exacerbate neurological deficits and worsen outcomes after stroke. This study explores the potential role of NETs in the pathogenesis of brain edema following ICH. The rat ICH model was created, immunofluorescence and Western blot were used to examine neutrophil accumulation, NET markers citrullinated histone H3 (CitH3) and myeloperoxidase (MPO), tight junction proteins (ZO-1 and Occludin), Aquaporin-4 (AQP4), matrix metalloproteinase-9 (MMP-9), and ERK phosphorylation (p-ERK) in brain tissues surrounding the hematoma. TUNEL staining and behavioral tests were employed to evaluate neuronal apoptosis and neurological dysfunction, while blood–brain barrier (BBB) permeability and brain edema were also measured by Evans blue and brain water content. Furthermore, the molecular mechanisms related to NETs-induced PHE were investigated using NETs, ERK, MMP-9 and AQP4 regulators, respectively. Ly6G⁺ neutrophils surrounding the hematoma developed NETs within 3 days post-ICH. NETs decreased tight junction proteins, destroyed BBB integrity, promoted brain edema, increased neuronal apoptosis, and exacerbated neurological deficits. Conversely, inhibition of NETs mitigated PHE, reduced neuronal apoptosis, and improved neurological functions. Mechanistically, NET-induced PHE was originated from impairment of BBB tight junction via ERK/MMP9 pathway, coupled with ERK-mediated AQP4 downregulation in perihematomal regions. These findings elucidated the effects of NETs on PHE, which offered promising insights for targeting NETs to relieve brain edema and secondary brain injury post-ICH.

Secondary blood-brain barrier (BBB) disruption and vasogenic edema drive neurological deterioration after intracerebral hemorrhage (ICH), but targeted therapies remain lacking. PTEN-induced putative kinase 1 (PINK1) is a neuroprotective kinase, yet its role in ICH-induced BBB damage is unclear. This study investigates whether MTK458, a novel PINK1 agonist, protects BBB integrity after ICH and elucidates mechanisms. An ICH mouse model was employed and MTK458 (10, 50, 100 mg/kg) were administered intraperitoneally. The effects of MTK458 were evaluated using brain water content measurements, BBB integrity detection and neurological impairment assessments. A hemoglobin-stimulated BV2 microglia-bEnd.3 endothelial cell co-culture system was established to assess the effects of MTK458 on microglia-mediated tight junctions loss of BBB in vitro. PINK1 expression was significantly downregulated after ICH, with its lowest level observed at 72 h. MTK458 (50 mg/kg) reduced Evans blue extravasation and brain edema, attenuated microglial activation and neuroinflammation, decreased neuronal apoptosis, and improved both acute and subacute neurological function in vivo. MTK458 reversed hemoglobin-induced PINK1 loss in BV2 cells and reduced BV2-mediated damage to bEnd.3 tight junctions in vitro. Mechanistically, MTK458 restored microglial PINK1 expression, inhibited ROS production and cytosolic mtDNA leakage, and thereby suppressed activation of the cGAS-STING-NF-κB signalling pathway, leading to MMP-9 suppression and ZO-1/occludin protection. Consistent with this, the STING agonist dimeric amidobenzimidazole (diABZI) reversed the inhibitory effect of MTK458 on MMP-9, abolished its protection of tight junctions, and compromised BBB integrity. MTK458 activates PINK1, inhibits the cGAS-STING-NF-κB pathway, reduces microglial MMP-9 release, protects BBB integrity, alleviates edema and neuroinflammation, and improves neurological outcomes, providing a novel therapeutic strategy for secondary ICH injury.