Colitis increased local hepcidin-25 expression, which was associated with the IL-6/Stat-3 signaling pathway. An increase in local iron sequestration was also observed, but additional studies are needed to determine whether this sequestration is a defensive or pathological response to intestinal inflammation.
-Context -Intestinal inflammation can induce a local reduction in oxygen levels that triggers an adaptive response centered on the expression of hypoxia-inducible factors (HIFs). Nitric oxide, a well-described inflammatory mediator, may interfere with hypoxia signaling. Objectives -We aimed to evaluate the role of nitric oxide in hypoxia signaling during colonic inflammation. Method -Colitis was induced by single (acute) or repeated (reactivated colitis) trinitrobenzenosulfonic acid administration in rats.In addition, one group of rats with reactivated colitis was also treated with Nw-Nitro-L-arginine methyl ester hydrochloride to block nitric oxide synthase. Colitis was assessed by macroscopic score and myeloperoxidase activity in the colon samples. Hypoxia was determined using the oxygen-dependent probe, pimonidazole. The expression of HIF-1a and HIF-induced factors (vascular endothelial growth factor -VEGF and apelin) was assessed using Western blotting. Results -The single or repeated administration of trinitrobenzenosulfonic acid to rats induced colitis which was characterized by a high macroscopic score and myeloperoxidase activity. Hypoxia was observed with both protocols. During acute colitis, HIF-1a expression was not increased, but VEGF and apelin were increased. HIF-1a expression was inhibited during reactivated colitis, and VEGF and apelin were not increased. Nw-Nitro-L-arginine methyl ester hydrochloride blockade during reactivated colitis restored HIF-1a, VEGF and apelin expression. Conclusions -Nitric oxide could interfere with hypoxia signaling during reactivated colitis inflammation modifying the expression of proteins regulated by HIF-1a. HEADINGS -Colitis. Hypoxia-inducible factor 1. Nitric oxide. NG-Nitroarginine methyl ester. Endothelial growth factors.
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