Ascorbic acid prevents VEGF-induced increases in endothelial barrier permeability

Area of Science:

• Biochemistry
• Cell Biology
• Ophthalmology

Background:

• Diabetic retinopathy is linked to increased vascular endothelial growth factor (VEGF), which elevates endothelial barrier permeability and may cause macular edema.
• Vitamin C (ascorbic acid) is known to enhance endothelial barrier function.

Purpose of the Study:

• To investigate whether ascorbic acid can prevent VEGF-induced increases in endothelial permeability in human umbilical vein endothelial cells (HUVECs).

Main Methods:

• HUVECs were treated with VEGF and varying concentrations of ascorbic acid.
• Cell permeability was measured using radiolabeled inulin.
• Reactive oxygen species (ROS) generation and endothelial nitric oxide synthase (eNOS) activity were assessed.
• The role of nitric oxide synthase (NOS) was investigated using L-NAME and sepiapterin.

Main Results:

• VEGF increased HUVEC permeability in a concentration-dependent manner.
• Ascorbic acid progressively inhibited VEGF-induced leakage, with significant effects at 13 µM and complete inhibition at 50 µM.
• Ascorbic acid reduced basal and VEGF-induced ROS generation.
• VEGF treatment decreased intracellular ascorbate levels, suggesting ascorbate oxidation is linked to VEGF-induced leakage.
• VEGF-induced leakage was blocked by L-NAME and sepiapterin, indicating eNOS uncoupling.

Conclusions:

• VEGF-induced barrier leakage appears to involve the uncoupling of eNOS.
• Ascorbic acid may prevent this by scavenging reactive oxygen species or by recycling tetrahydrobiopterin, thereby maintaining eNOS function.
• Ascorbate repletion could be a potential therapeutic strategy for diabetic macular edema.