HGSNAT alleviates oxygen-glucose deprivation- induced endothelial injury by suppressing ER stress: implications for Moyamoya disease.

OBJECTIVES: Moyamoya disease (MMD) is a progressive cerebrovascular disorder characterized by chronic cerebral hypoperfusion and ischemic microenvironments that critically impact brain microvascular endothelial cells. Oxygen-glucose deprivation (OGD) models have been extensively employed in MMD research to recapitulate the ischemic conditions relevant to MMD pathophysiology. This study aims to explore the functional involvement and molecular basis of HGSNAT in human brain microvascular endothelial cells (HBMECs) following OGD-induced injury, to establish a theoretical foundation for elucidating the pathogenesis of vascular endothelial injury associated with MMD. METHODS: An in vitro model of hypoxic-ischemic injury was established by subjecting HBMECs to OGD. After HGSNAT overexpression, endoplasmic reticulum stress (ERS) activator Tunicamycin treatment, and GPX8 silencing, cell viability, angiogenic capacity, and migratory ability were evaluated using the CCK-8 assay, tube formation assay, and scratch wound healing assay, respectively. Enzyme-linked immunosorbent assay (ELISA) was employed to evaluate the secretion of inflammatory cytokines, while intracytoplasmic reactive oxygen species (ROS) levels were examined using DCFH-DA staining. Additionally, Western blotting was performed to assess the abundance of factors linked to the ERS cascade. RESULTS: OGD exposure significantly downregulated HGSNAT mRNA expression and enzymatic activity. HGSNAT overexpression markedly enhanced the viability of OGD-treated HBMECs and improved angiogenic and migratory capacities, while reducing the secretion of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). Functional studies uncovered that HGSNAT overexpression reduced ROS accumulation and suppressed activation of the PERK-eIF2α-ATF4 cascade; these effects were abrogated by Tunicamycin treatment. Furthermore, the study found that GPX8 knockout could weaken the protective effect mediated by HGSNAT, resulting in decreased cell survival, impaired angiogenesis and migratory ability, elevated inflammatory levels, and reactivation of the ERS pathway. This indicates that the efficacy of HGSNAT required for maintaining endothelial homeostasis depends on the function of GPX8. CONCLUSION: Overexpression of HGSNAT is associated with maintaining or enhancing GPX8 levels under OGD stress, thereby protecting HBMECs from OGD-induced endoplasmic reticulum stress and endothelial damage. GPX8 knockdown partially abolished these protective effects, suggesting that GPX8 contributes to HGSNAT-mediated inhibition of the PERK-eIF2α-ATF4 ER stress pathway, oxidative stress, and inflammation.