CCL2 knockdown attenuates post-traumatic external cerebral herniation by suppressing JAK-STAT signaling following traumatic brain injury.

BACKGROUND: C-C motif chemokine ligand 2 (CCL2) contributes to post-traumatic neuroinflammation and blood-brain barrier (BBB) disruption, but its role in post-traumatic external cerebral herniation and endothelial JAK-STAT signaling remains unclear. METHODS: CCL2-knockdown BEND3 cells were subjected to 4 h oxygen-glucose deprivation and 24 h reoxygenation. Recombinant CCL2 rescue and the JAK-STAT inhibitor SC99 were used to assess pathway directionality. Cell injury, apoptosis, JAK2/STAT1/STAT3 phosphorylation, transendothelial electrical resistance, permeability and tight junction proteins were evaluated. In mice, sh-CCL2 was delivered before traumatic brain injury (TBI). Neurological function, inflammatory mediators, BBB integrity, intracranial pressure, cerebral perfusion, venous morphology, external cerebral herniation and histological injury were assessed. RESULTS: CCL2 knockdown reduced LDH release and apoptosis, suppressed JAK2, STAT1 and STAT3 phosphorylation, increased transendothelial electrical resistance, reduced permeability and restored ZO-1, Occludin and Claudin-5. Recombinant CCL2 partially reversed these effects, supporting an upstream contribution of CCL2 to JAK-STAT activation. In vivo, sh-CCL2 improved mNSS but not Garcia score or brain water content (85.29 ± 3.50% in TBI vs. 84.73 ± 3.23% in TBI + sh-CCL2; P = 0.829). It also reduced inflammatory mediators and Evans blue extravasation, decreased mean intracranial pressure from 20.60 ± 0.76 to 12.19 ± 0.44 mmHg, increased cerebral blood flow from 62.10 ± 3.13 to 83.43 ± 4.65 mL/100 g/min and reduced external cerebral herniation volume from 18.70 ± 0.55 to 7.94 ± 0.38 mm3. CONCLUSION: CCL2 promotes OGD/R-induced endothelial injury partly through JAK-STAT activation. CCL2 knockdown may alleviate TBI-related neurovascular dysfunction and post-traumatic external cerebral herniation by preserving endothelial barrier integrity and improving cerebral venous and perfusion abnormalities.