Restoration of the Blood‐Spinal Cord Barrier after Spinal Cord Injury through 5‐HT1F Receptor Mediated Mitochondrial Biogenesis

Abstract

Vascular and mitochondrial dysfunction are well‐established consequences of spinal cord injury (SCI). Evidence suggests mitigating these dysfunctions may be an effective approach in treating SCI. We propose to restore vascular and mitochondrial dysfunction following SCI through pharmacological induction of mitochondrial biogenesis (MB). We previously reported that 5‐hydroxytryptamine receptor 1F (5‐HT1F) agonism induces MB in the spinal cord and promotes locomotor recovery with drug initiation beginning at a clinically relevant time point of 8h post‐SCI. The goal of this study was to elucidate if MB induction with the newer selective 5‐HT1F receptor agonist lasmiditan can enhance restoration of the blood‐spinal cord barrier (BSCB) after SCI. C57BL/6J mice were subjected to moderate SCI using a force‐controlled impactor‐induced contusion model followed by daily administration of lasmiditan (0.1 mg/kg, i.p.) beginning 1h after injury. Integrity of the BSCB was assessed using Evans Blue dye extravasation. SCI increased dye extravasation at 1, 3, and 7d, and lasmiditan‐treated mice displayed reduced dye accumulation at 7d post‐SCI, suggesting accelerated BSCB recovery. Levels of tight junction proteins occludin and zonula occludens‐1 were decreased in vehicle‐treated mice and returned to sham levels with lasmiditan treatment by d7. These findings led us to investigate if lasmiditan induces MB in endothelial cells. Primary cultures of cerebral microvascular endothelial cells from C57BL6 mice were treated with lasmiditan. A Seahorse Biosciences flux analyzer was used to quantify FCCP‐uncoupled oxygen consumption rate (OCR), a marker of MB. Lasmiditan increased FCCP‐uncoupled OCR, nuclear‐ and mitochondrial‐encoded proteins (PGC‐1a, COX1, TFAM), and mitochondrial number, confirming MB. Lastly, treatment with lasmiditan enhanced endothelial branching morphogenesis and migration, indicating a role of the 5‐HT1F receptor activation in angiogenic pathways. Collectively, these data reveal that 5‐HT1F receptor agonist‐induced MB occurs in endothelial cells and may accelerate restoration of the BSCB after SCI.Support or Funding InformationThis study was supported by the National Institutes of Health National Institute of General Medical Sciences: GM084147 (R.G.S), and the Biomedical Laboratory Research and Development Program of the Department of Veterans Affairs: BX: 000851 (R.G.S.).