HIF-1α/Netrin-4 Axis Mediates RIPC-Induced Angiogenesis and Neurogenesis After Ischemic Stroke.

Abstract

Remote ischemic postconditioning (RIPC) confers neuroprotection in ischemic stroke partly via promoting angiogenesis and neurogenesis, but its precise molecular mechanisms remain unclear; here, we investigated the role of the secreted guidance protein Netrin-4 (NTN4) and its upstream regulator hypoxia-inducible factor 1α (HIF-1α) in mediating RIPC's reparative effects, using endothelial-specific Ntn4 knockout (KO) mice subjected to transient middle cerebral artery occlusion (MCAO) and RIPC, alongside in vitro assays with brain microvascular endothelial cells (BMECs) and neural stem cells (NSCs) and molecular interaction analyses, including DNA pull-down and chromatin immunoprecipitation (ChIP), finding that RIPC significantly upregulated NTN4 expression in the ischemic penumbra of MCAO mice, that endothelial-specific Ntn4 knockout abolished RIPC's protective effects-impairing neurological recovery, angiogenesis and neurogenesis, which were rescued by recombinant NTN4 administration, that NTN4 promoted BMEC proliferation and tube formation via an integrin β1-PI3K/AKT pathway while conditioned medium from Ntn4-overexpressing BMECs enhanced NSC neuronal differentiation through an integrin β1-MAPK/ERK axis, and that RIPC stabilised HIF-1α, which directly bound the Ntn4 promoter to drive its transcription, collectively establishing that RIPC orchestrates brain repair by stabilising HIF-1α to transcriptionally activate endothelial NTN4, which signals through integrin β1 to drive parallel PI3K/AKT and MAPK/ERK pathways for angiogenesis and neurogenesis, highlighting this axis as a key therapeutic target in stroke.