Our recent Studies demonstrated a critical role of enhanced transcriptional activity of early growth response factor-1 (Egr-1) in early stages of cysteamine-induced duodenal ulcer in rats. Since cysteamine is also a reducing agent, the aims of this study were to determine the effect of cysteamine oil proximal duodenal mucosa: (a) redox status, (b) mucosal oxygenation, (c) expression of hypoxia-inducible factor 1 (HIF-1alpha) and its binding to DNA, and (d) HIF-1alpha, interaction with Egr-1 and other redox-sensitive transcription factors. Here we demonstrate for the first time that cysteamine treatment reduced the duodenal oxygenation by 19% (vs. baseline) and markedly increased the redox Status in duodenal mucosa (p < 0.05). Cysteamine increased HIF-1alpha expression, its binding to DNA, and enhanced the HIF-1alpha interactions with Egr-1 and other transcription factors (e.g., AP-1, AP-2, L-III BP, NF-E1, NF-E2, STAT4, and MRE), their binding to DNA. Thus, these data demonstrate the involvement of the redox-dependent regulatory mechanisms in the early stages of duodenal ulceration. Published by Elsevier Inc.