Pronounced substance P innervation in irradiation-induced enteropathy - a study on human colon

The immunohistochemical expression of various neuropeptides, including subs tance P (SP), and the substance P receptor (SPR), was examined in irradiati on-induced enteropathy in man. Samples from irradiated and non-irradiated p atients operated on for rectal carcinoma were examined. The samples were fr om the sigmoid and corresponded macroscopically to non-cancerous sigmoid co lon. There was a marked atrophy, ulcerations and inflammatory reactions in the irradiation-influenced mucosa. In this mucosa, there was a very pronoun ced innervation of varicose nerve fibers showing SP-like immunoreactivity ( LI). The degree of SP-LI in the ganglionic cells of the submucous plexus wa s increased as compared to non-irradiated patients. There were only few or no nerve fibers showing immunoreaction for other neuropeptides examined (CG RP, enkephalin, NPY) in the irradiation-influenced mucosa. A marked SPR imm unoreaction was detected in cells in the lamina propria which were interpre ted as representing polymorphonuclear leukocytes. The marked expression of SP in the irradiation-damaged mucosa and the presence of SPR immunoreactive leukocytes suggest that SP is highly involved in the inflammatory reaction s that occur in response to radiotherapy. The observations also suggest tha t SP, but not NPY, CGRP and enkephalin, has an important role in the reorga nisation processes that take place in the mucosa in irradiation-induced ent eropathy. (C) 2000 Elsevier Science B.V. All rights reserved.