Dr. Chang has been interested in the cell and molecular biology of the intestinal epithelial cell. His investigations fall into two major areas: 1) Mechanisms of mucosal cytoprotection to inflammation and immune-associated injury, and 2) Na absorptive mechanisms of the epithelial cell. The first area primarily involves the study of inducible heat shock proteins, which are a family of highly conserved proteins which bind and stabilize specific cell proteins during conditions of stress or injury such as the glucocorticoid receptor. In epithelial cells, many aspects of hsp induction and substrate targets appear unique. The actions of several compounds used for the treatment of IBD also appear to involve and require the induction of hsps. Dr. Chang is also examining the role of a novel gastric mucosal peptide (AMP-18) which appears to promote wound healing and provide protein to the gastric epithelium. This peptide may have a pivotal role in the pathogenesis of NSAID and H. pylori induced gastric mucosal injury. Dr. Changs interest in intestinal Na absorption is focused on defining the role and regulatory mechanisms of Na-H exchange proteins in gut and renal cells. The four isoforms expressed by these epithelia have region- and cell-specific expression and differ in their physiological roles. Dr. Chang is currently studying how these isoforms reach different parts of the epithelial cell membrane and the cellular mechanisms involved in regulating their activities.