The effects of disease activities on neuropeptide levels in patients with ulcerative colitis

Ulcerative colitis (UC) is a chronic relapsing inflammatory bowel disease. The mechanisms triggering the initial attack and relapses, however, are not well understood. Intestinal mucosa is heavily innervated with peptidergic neurons. Substance P (SP) and Calcitonin gene-related peptide (CGRP), which are largely co-expressed in sensory neurons, have dual role in mucosal healing and inflammation while VIP has anti-inflamatory effects. Differential effects of these peptides might be related to their localization such that neuronal peptides might have protective effects while non-neuronal ones participate in inflammation. Up to our knowledge changes in neuronal and non-neuronal levels of SP, CGRP and VIP in UC is not studied in detail previously. Furthermore the effects of anti-inflammatory treatment on these peptides is not known. In this research, we aimed to determine changes in SP, CGRP and VIP levels in patients with UC and the effects of anti-inflamatory treatment on these possible changes. Neprilysin (NEP) is a membrane-associated neutral peptidase, also known as CD10 and has peptidase activity on SP and CGRP. We here also determined the changes in NEP levels before and after treatment in patients with UC. Biopsies of involved mucosa from 74 patients with UC were obtained. Patients who underwent colonoscopy because of possible malignancy or iron deficiency anemia and had no visible and microscopic pathology was used as control (n=28). Biopsies were also obtained from 33 of UC who were in clinical remission 3 months after treatment. Study was approved by Committee of Ethics at Faculty of Medicine, Akdeniz University, and informed consents were obtained from patients. Changes in neuronal and non-neuronal peptide levels were determined using two-step acetic acid extraction of colonic mucosa followed by ELISA. CD10 immunohistochemistry was performed on tissue from the cases in the department of pathology. Tissues from all patients were assessed histologically using the grading scale developed by Geboes. Both neuronal and non-neuronal SP levels were increased in patients with UC after treatment. Interestingly, non-neuronal SP levels were increased after treatment when compare to healty tissues. Besides, we found that neuronal SP levels in the inflamed mucosa of the pancolitis were repressed compared to uninvolved mucosa. Similarly, only neuronal CGRP levels were increased in treated patients. We found that NEP immunostaining in healty and non-inflamed enteric mucosa was uniformly positive while expression was variable it was lost in the active colitis. Neuronal VIP levels were significantly lower in colonic mucosa of patients with UC compared to healthy control group. We also observed that VIP levels were lower in inflamed mucosa compared to non-inflamed mucosa in distal colitis. Furthermore in patients who are in remission neuronal and non-neuronal VIP levels were increased. In conclusion we found that SP, CGRP, VIP and NEP levels increased in patients treated with effective medication (corticosteroids and/or non-steroid anti-inflammatory/immunosuppressive drugs). Anti-inflammatory treatment increased CGRP and SP levels especially in the neuronal compartment of healed mucosa. Both CGRP and SP may increase healing process. Similarly VIP has a well-known anti-inflammatory effects. Since SP, CGRP and VIP levels markedly increased in healed mucosa, it is likely that these neuropeptides have protective effects in UC. Similarly the level of NEP, a peptidase which hydrolysis SP and CGRP to bioactive fragments increased in healty and healed mucosa. Our results in conjuction with previously published data demonstrates that decreased levels of VIP, CGRP and SP levels as well as NEP expression is involved in pathophysiology of inflammatory bowel diseases