Expression and immunolocalization of heat shock proteins in the healing of gastric ulcers in rats

Abstract

Background: Heat shock proteins are induced when cells are subjected to noxious stimuli. They afford cytoprotection and increase the resistance of the tissue to damage. However, their roles in the healing of gastric ulcers have not been well established. In this study, the expression and immunolocalization of three heat shock proteins (HSPs); namely inducible HSP70 (iHSP70), HSP47, and HSP32 during ulcer healing were investigated in rats with gastric ulcer. Methods: Gastric ulcers (kissing ulcers) were induced by luminal application of acetic acid solution. Gastric tissue samples were obtained from the ulcer base, ulcer margin, and non-ulcerated area around the ulcer margin at different time intervals after ulcer induction. The protein levels and distributions of HSPs were analyzed with Western blotting and immunohistochemical methods, respectively. Results: It was found that all HSPs were expressed in normal, non-ulcerated, and gastric ulcer tissues. HSP32 was elevated during inflammation (1-8 days after ulcer induction), while HSP47 expression was exacerbated at the ulcer base and margin during ulcer healing (3-12 days). Decreased expression of iHSP70 was observed at the ulcer base immediately after ulcer induction, but returned to normal level by the end of the healing stage (8-12 days). Inducible HSP70 was found distributed in the gastric glands and injured tissues in the inflamed areas. Wide distribution of HSP47 was detected in granulation tissues and collagen producing cells, while HSP32 was localized in the gastric glands and inflammatory cells. Conclusions: The findings indicate that iHSP70, HSP47, and HSP32 play different roles during ulcer healing. HSP32 seems to act as an inflammatory defensive factor, and HSP47 as a collagen-specific molecular chaperon contributing significantly to gastric ulcer healing. However, the role of iHSP70 in the ulcer healing process is still undefined.