Nuclear heme oxygenase-1 enhances blood–spinal cord barrier repair via corticotropin-releasing hormone-mediated tight junction phosphorylation

OBJECTIVE: The hallmark of secondary spinal cord injury (SCI) is destruction of the blood-spinal cord barrier (BSCB). Nuclear heme oxygenase-1 (NHO-1) is involved in neuroprotection in the central nervous system. Previously, we demonstrated that adenoviral delivery of nuclear-targeted HO-1 (NHO-1) alleviates BSCB disruption, but the molecular mechanisms remain to be clarified. This study was conducted to investigate the specific regulatory mechanisms regulating tight junctions in the BSCB. METHODS: A moderate T10 contusion SCI was induced in adult male Sprague-Dawley rats. Nuclear-targeted HO-1 was delivered by adenoviral pretreatment 7 days before injury. Spinal cords were collected at 24 h post-SCI for RNA-seq and quantitative real-time-PCR validation. BSCB permeability (Evans Blue), tight junction phosphorylation (western blot), and locomotor function (Basso, Beattie, and Bresnahan score and footprint analysis) were assessed, with intrathecal corticotropin-releasing hormone (CRH)-R1 agonist (Cortagine) or antagonist (Antalarmin) administered after SCI. RESULTS: RNA-seq identified 10 overlapping differentially expressed genes across pairwise comparisons; subsequent Venn-based prioritization and quantitative real-time-PCR validation identified Crh as the most consistently regulated candidate. Functional assays demonstrated that nuclear HO-1, particularly when combined with CRH receptor activation, decreased leakage of BSCB via enhancing phosphorylation of tight junction protein which disappears after application of CRH inhibitor. CONCLUSION: These results indicate that nuclear-targeted HO-1 promotes BSCB repair after SCI by transcriptionally upregulating Crh and enhancing CRH-dependent phosphorylation of tight junction proteins (Claudin-5 and Occludin).