Previously, we demonstrated that
cysteamine releases
endothelin-1 in the rat duodenal mucosa, followed by increased expression of early growth response factor-1 (egr-1). We hypothesized that egr-1 is a key mediator gene in the multifactorial mechanisms of
duodenal ulcer development and healing because its
protein,
transcription factor product Egr-1, regulates the expression of angiogenic
growth factors. We wanted to determine the effect of egr-1
antisense oligonucleotide on
cysteamine-induced
duodenal ulcers as well as on the expression of bFGF, PDGF, and
VEGF, of which synthesis is modulated by Egr-1. An
antisense oligonucleotide to egr-1 was used to inhibit the synthesis of Egr-1 and to determine its effect on
ulcer formation in the rat model of
cysteamine-induced duodenal ulceration. Real-time RT-PCR and Western blot analysis were used to assess the expression of Egr-1
mRNA and
protein as well as ERK, bFGF, PDGF, and
VEGF. The antisense Egr-1
oligonucleotide inhibited the expression of egr-1
mRNA and
protein and increased the
duodenal ulcer size from 8.1 +/- 1.8 mm(2) in controls to 20.7 +/- 4.0 mm(2) (P < 0.01).
Cysteamine induced phosphorylation of ERK1/2 and enhanced the synthesis of bFGF, PDGF, and
VEGF in the preulcerogenic stages of duodenal ulceration, whereas egr-1
antisense oligonucleotide markedly decreased the expression of these
growth factors in the duodenal mucosa. We also demonstrated that Egr-1 expression relates to the ulcerogenic effect of
cysteamine because these actions were not exerted by the toxic analog
ethanolamine. Thus Egr-1 seems to play a critical role in duodenal ulceration because Egr-1 downregulation aggravates experimental
duodenal ulcers, most likely through the transcriptional inhibition of bFGF, PDGF, and
VEGF synthesis.