Peptide gene expression in gastrointestinal mucosal ulceration: ordered sequence or redundancy?

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Abstract
The gastrointestinal tract is subjected to a wide variety of mucosal challenges. Helicobacter pyloriassociated ulcer disease, non-steroidal anti-inflammatory drug (NSAID) associated ulcers, alcohol induced mucosal injury, and a variety of inflammatory conditions, including ulcerative colitis and Crohn's disease. No matter what the cause of the ulceration, the mucosa usually responds rapidly by triggering off a cascade of repair mechanisms to stimulate repair and restore mucosal integrity. Many genes are induced by the damage: apart from early response genes such as c-fos, c-jun,egr-1, and Sp-1, genes encoding peptides are particularly well represented; there is increasing evidence that at least 30 such genes are involved in the process. In the main, most investigators have pursued the time honoured reductionist approach, singling out individual peptides for detailed attention. However, these peptides are not all expressed at the same time, but follow an apparently ordered sequence. One point which does not seem to have been at all tackled in this field is that many of these peptides have similar actions, prompting the reasonable question—is gene expression after mucosal damage largely redundant, or is there an ordered sequence, with intrinsic interdependency? In this article, we will examine the importance of these peptides in the ulcer healing process, and attempt to identify the sequential gene expression of these peptides after ulceration.