Ascorbate Suppresses VEGF Expression in Retinal Pigment Epithelial Cells

Area of Science:

• Epigenetics and Molecular Biology
• Ophthalmology
• Cell Biology

Background:

• Vascular Endothelial Growth Factor (VEGF) plays a critical role in angiogenesis and is implicated in various ocular diseases.
• DNA hydroxymethylation is an epigenetic modification that can influence gene expression.
• Ascorbate (Vitamin C) is an essential nutrient with potential roles in cellular processes beyond its antioxidant functions.

Purpose of the Study:

• To investigate the impact of ascorbate on DNA hydroxymethylation.
• To determine how ascorbate-mediated DNA hydroxymethylation affects VEGF expression in retinal pigment epithelial (RPE) cells.

Main Methods:

• Utilized dot-blot and hydroxymethylated DNA immunoprecipitation sequencing to assess DNA hydroxymethylation changes induced by ascorbate in ARPE-19 cells.
• Performed RNA sequencing (RNA-seq) to analyze global transcriptome alterations.
• Quantified VEGF transcription and secretion using quantitative RT-PCR and ELISA in various RPE cell models and in vivo (Gulo-/- mice).

Main Results:

• Ascorbate treatment increased 5-hydroxymethycytosine (5hmC) levels and altered genome-wide 5hmC profiles in RPE cells.
• A significant shift in the transcriptome was observed, with many differentially expressed genes correlating with altered 5hmC.
• VEGFA, encoding VEGF, was notably downregulated by ascorbate, independent of HIF-1α, and correlated with increased gene body 5hmC. This effect was confirmed in primary RPE cells and in Gulo-/- mice, showing reduced VEGF in ocular tissues.

Conclusions:

• Ascorbate inhibits VEGF expression in RPE cells, likely through epigenetic mechanisms involving DNA hydroxymethylation.
• These findings suggest a potential therapeutic role for ascorbate in managing diseases characterized by aberrant VEGF production, such as age-related macular degeneration (AMD).