High-altitude hypoxia caused a marked increase in permeability.
Retinal cell apoptosis was significantly increased due to high-altitude hypoxia.
VE-cadherin phosphorylation in endothelial cells was notably elevated, contributing to barrier disruption.
(NMN) intervention reduced both endothelial cell apoptosis and permeability.
NMN protected the endothelial barrier by regulating levels.
Inhibition of Src phosphorylation and downregulation of the Pi3k/Akt signaling pathway were observed with NMN treatment.
Simplified
PURPOSE: High-altitude retinopathy (HAR) is primarily caused by hypobaric hypoxia, leading to hemodynamic changes in the retina and disruption of the (BRB), which results in vasogenic edema. Currently, treatment strategies for this condition are limited. In this study, we investigated the protective effect of (NMN) against high-altitude hypoxia-induced BRB disruption and its potential molecular mechanisms.
METHODS: We established a mouse model of high-altitude BRB injury using a simulated high-altitude environment chamber. Vascular leakage was observed through the Evans Blue dye leakage assay, and retinal Nicotinamide adenine dinucleotide (NAD+) levels were measured using the WST-8 assay. Human umbilical vein endothelial cells (HUVECs) were cultured in a hypoxic chamber, and the permeability of a confluent monolayer to FITC-dextran was monitored. With or without NMN intervention, VE-cadherin expression or phosphorylation at cell junctions was analyzed by Western blot and/or immunofluorescence. Apoptosis levels were assessed via Western blot, TUNEL staining, or flow cytometry, whereas (ROS) levels were observed using DCFH-DA, MitoSOX, or DHE probes. DNA damage levels were measured using 8-Oxoguanine immunofluorescence staining, and phosphorylation levels of the Src/Pi3k/Akt signaling pathway were analyzed via Western blot.
RESULTS: High-altitude hypoxia led to increased retinal cell apoptosis and significant phosphorylation of VE-cadherin in endothelial cells, which resulted in a marked increase in BRB permeability. Both in vitro and in vivo experiments showed that NMN intervention reduced endothelial cell apoptosis and permeability. Additionally, NMN protected the endothelial barrier by regulating ROS levels in endothelial cells, inhibiting Src phosphorylation, and downregulating the downstream Pi3k/Akt signaling pathway.
CONCLUSIONS: These findings establish the role of NMN and the ROS-mediated Src/Pi3k/Akt signaling pathway in protecting the endothelial barrier, and identify a potential therapeutic strategy for protecting against hypoxia-related BRB leakage.
Key numbers
11.9×
Evans Blue Permeability Increase
Evans blue permeability surface area product in the 7 Km 24 hours group compared to control.
2.3×
FITC-Dextran Permeability Increase
FITC-dextran permeability surface area product in the 7 Km 24 hours group compared to control.
100 mg/kg/day
NAD+ Level Increase
Dose of administered to mice before hypoxia exposure.
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