Transforming growth factor-alpha and epidermal growth factor receptor in colonic mucosa in active and inactive inflammatory bowel disease

Transforming growth factor-alpha (TGF-alpha) is overexpressed in colonic ca rcinomas and promotes mucosal wound healing. It may be implicated in chroni c inflammatory bowel disease (IBD), We analyzed the expression of TGF-alpha and its receptor, epidermal growth factor receptor (EGF-r), in the colonic mucosa of patients with Crohn's disease (CD) or ulcerative colitis (UC), i n active or inactive stages, as compared with controls. Proteins and mRNA w ere detected in biopsies from the right and left colon and in surgical colo nic specimens. Immunoblot analysis revealed TGF-alpha protein as a 29kDa ba nd. This band was normally expressed in uninvolved colonic mucosa of patien ts with CD or UC whether in active or inactive stages, but decreased or abs ent in involved mucosa of active IBD, even when TGF-alpha mRNA and EGF-r pr otein were detected. In the unaffected mucosa of CD, the intensity of TGF-a lpha immunoreactivity was similar to that of controls in the right colon bu t stronger (P = 0.05) in the left colon. There was no TGF-alpha overexpress ion in dysplastic regions. In conclusion, in active IBD disease, the decrea sed TGF-alpha protein amount seems not only related to epithelial cell loss but reflects a down-regulation at least at the protein level. We speculate that TGF-alpha does not play a role within the active stage but may be imp licated later in the repair process.