Hemin activates interleukin-17 signaling and CCAAT/enhancer-binding protein beta to promote neuroinflammation and blood-brain barrier disruption

Heme overload, a feature of hemolytic conditions and cellular injury, can initiate oxidative stress and inflammatory cascades that perturb neurovascular homeostasis. However, the molecular mechanisms by which peripheral heme exposure disrupts blood-brain barrier (BBB) integrity remain incompletely defined. Here, we investigated key molecular mediators linking peripheral hemin challenge to neurovascular injury. Intraperitoneal administration of hemin induced marked BBB permeability in mice, accompanied by immune cell infiltration into the brain parenchyma, microglial pro-inflammatory activation, and neuronal DNA damage. In this study, we aimed to elucidate how hemin challenge activates inflammatory signaling pathways that disrupt neurovascular homeostasis. Transcriptomic profiling of the spleen revealed robust activation of the interleukin-17 (IL-17) signaling pathway. Consistently, hemin exposure increased IL-17A levels both in vivo and in vitro and enhanced the expression of downstream signaling components, including phosphorylated NF-κB p65 (p-p65) and matrix metalloproteinase 9 (MMP9). Functional studies showed that in vivo IL-17A neutralization attenuated neuroinflammatory responses and improved BBB integrity, while in vitro blockade with Secukinumab similarly mitigated inflammatory responses and endothelial barrier dysfunction. Mechanistically, hemin upregulated CCAAT/enhancer-binding protein beta (CEBPB), partly dependent on IL-17 signaling. Knockdown of CEBPB alleviated hemin-induced inflammatory responses and endothelial barrier dysfunction, supporting its role as a downstream effector. In addition, reduced DNA methylation at the CEBPB promoter was observed, suggesting a potential contribution of epigenetic regulation. Collectively, these findings provide insight into a peripheral-to-central inflammatory mechanism linking heme burden to BBB impairment, and suggest that IL-17 signaling, in part through CEBPB, contributes to hemolysis- associated neurovascular injury.