Background and aims: Ulcerative colitis is a chronic inflammatory condition characterized by an altered intestinal immunoinflammatory response. Since increasing evidence indicates that neuropeptides play a key role in the regulation of gastrointestinal immune function, the aims of this study were: a) to determine tissue and plasma levels of Vasoactive Intestinal Polypeptide, Substance P, and Calcitonin Gene-Related Peptide in patients with ulcerative colitis, and b) to ascertain whether a relationship exists between tissue concentrations of neuropeptides and the histological grading of mucosal inflammation.
Methods: A total of 29 patients with active and 39 with inactive ulcerative colitis, and 16 control subjects took part in the study. Biopsy specimens of colonic mucosa and blood samples were obtained from each subject, and neuropeptide concentrations were measured by sensitive and specific radioimmunoassays.
Results: Both Vasoactive Intestinal Polypeptide and Substance P concentrations were found to be significantly reduced in endoscopic biopsy specimens of patients with ulcerative colitis compared to controls (p < 0.01 and p = 0.05, respectively), and the reduction appeared to be related to the degree of mucosal inflammation; in contrast, Calcitonin Gene-Related Peptide tissue levels were unchanged. In addition, there was no significant difference in the neuropeptide plasma levels between ulcerative colitis patients and control subjects.
Conclusions: Taken together, our results suggest that the reduction of Vasoactive Intestinal Polypeptide and Substance P is probably a secondary phenomenon, correlated with the degree of mucosal inflammation; whatever the mechanism, the decreased availability of these neuropeptides in the local microenvironment may play an important role in the pathogenesis of ulcerative colitis, by affecting many components of the normal immune response. Moreover, based on our data, the measurement of neuropeptide plasma concentrations does not appear to be a useful tool to monitor disease activity.