Homocysteine Increases the Expression of Vascular Endothelial Growth Factor by a Mechanism Involving Endoplasmic Reticulum Stress and Transcription Factor ATF4

Academic Article

Abstract

  • Vascular endothelial growth factor (VEGF) plays a key role in the development and progression of diabetic retinopathy. We previously demonstrated that amino acid deprivation and other inducers of endoplasmic reticulum-stress (ER stress) up-regulate the expression of VEGF in the retinal-pigmented epithelial cell line ARPE-19. Because homocysteine causes ER stress, we hypothesized that VEGF expression is increased by ambient homocysteine. DL-Homocysteine-induced VEGF expression was investigated in confluent ARPE-19 cultures. Northern analysis showed that homocysteine increased steady state VEGF mRNA levels 4.4-fold. Other thiol-containing compounds, including L-homocysteine thiolactone and DTT, induced VEGF expression 7.9- and 8.8-fold. Transcriptional run-on assays and mRNA decay studies demonstrated that the increase in VEGF mRNA levels was caused by increased transcription rather than mRNA stabilization. VEGF mRNA induction paralleled that of the ER-stress gene GRP78. Homocysteine treatment caused transient phosphorylation of eIF2α and an increase in ATF4 protein level Overexpression of a dominant-negative ATF4 abolished the VEGF response to homocysteine treatment and to amino acid deprivation. VEGF mRNA expression by ATF4-/- MEF did not respond to homocysteine treatment and the response was restored with expression of wild-type ATF4. These studies indicate that expression of the pro-angiogenic factor VEGF is increased by homocysteine and other thiol-containing reductive compounds via ATF4-dependent activation of VEGF transcription.
  • Authors

    Published In

    Digital Object Identifier (doi)

    Pubmed Id

  • 3540991
  • Author List

  • Roybal CN; Yang S; Sun CW; Hurtado D; Vander Jagt DL; Townes TM; Abcouwer SF
  • Start Page

  • 14844
  • End Page

  • 14852
  • Volume

  • 279
  • Issue

  • 15