98 Unique Expression of Cytoglobin/Stellate Cell Activation-Associated Protein As An Oxygen Supplier Before Angiogenesis During Gastric Ulcer Healing in Rats

Abstract

Background and Aims: Cytoglobin/stellate cell activation-associated protein (Cygb/STAP) discovered by a proteome analysis on the rat hepatic stellate cells as one of the hemeproteins may act as an oxygen transporter like hemoglobin and myoglobin. Induction of angiogenesis is involved in remodeling of the injured tissues including gastric ulcer mediated by the supply of oxygen as well as nutrient for the regenerating tissues. To examine the physiological roles of Cygb/STAP, we investigated the expression and localization of Cygb/ STAP in the ulcerated gastric tissues as well as hypoxia inducible factor (HIF)-1, a key factor under the hypoxic condition, and vascular endothelial growth factor (VEGF), a key angiogenic factor regulated by HIF-1. Methods: Gastric ulcers in rats (8-week-old Wistar rat) were produced by acetic acid. Rats were sacrificed on days 3, 11, 18, or 25 after production of the gastric ulcer. To determine the expressions of Cygb/STAP, VEGF, and HIF-1 at the ulcerated tissue, western blotting was performed. Each mRNA expression of HIF-1 and VEGF of the ulcerated gastric tissues was measured by real time RT-PCRmethod. Localization of Cygb/STAP, VEGF, HIF-1, and von Willebrand factor (VWF) for angiogenesis at the ulcerated gastric tissues was examined by the immunohistochemical study. Results: Expression of Cygb/STAP was increased at the ulcerated tissue on day 11 compared with the intact tissues from sham-operated rats, and then gradually decreased in correspondence with the process of ulcer healing. Changes in both protein and mRNA expression levels of HIF-1 were in parallel with Cygb/STAP expression. However, protein and mRNA expressions of VEGF began to increase after the reduction of Cygb/STAP and HIF-1 expression. Cygb/ STAP was localized in the cytoplasm of mesenchymal cells in lamina propria mucosae in the intact stomach. Number of Cygb/STAP-positive cells was increased at the regenerative mucosa of ulcerated gastric tissues. It was not co-localized at the VWF expression in the early phase of regenerated areas. Notable angiogenesis was induced on day 18 when VEGF expression but not Cygb/STAP and HIF-1 expressions was significantly increased in the ulcerated tissues. Treatment with anti-ulcer drug initially enhanced an increase in Cygb/ STAP protein expression at the ulcerated tissues in the early phase of healing. Conclusion: These results suggested that Cygb/STAP act as a transient oxygen supplier for the immature regenerative mucosa during the ulcer healing until an appropriate angiogenesis was recognized at that area.