Nitric oxide synthase immunoreactivity of interstitial cells of Cajal in experimental colitis.

OBJECTIVE: There is functional and morphological evidence that interstitial cells of Cajal (ICC) may play a role in nitric oxide (NO) dependent signal transduction. However, little is known about the nitric oxide synthase (NOS) containing ICC during inflammation. MATERIALS AND METHODS: Immunocytochemical methods were used for the ultrastructural localization of NOS1-containing ICC in the wall of the colon of rats in experimental colitis. RESULTS: Large numbers of NOS immunoreactive (IR) nerve terminals were found in very close vicinity to smooth muscle cells as well as to blood vessels. IR nerves were found in close relationship with the ICC. The gap between the NOS IR nerve fibers and the membrane of smooth muscle cells and of ICC was 20-250 nm. In experimental colitis the number of NOS IR nerve fibers slightly decreased, however, large numbers (24%) of the ICC became IR for NOS. In the noninflamed area and in the controls, all these cells were immunonegative for NOS. CONCLUSIONS: Our light- and ultrastructural study suggests that some of the ICC can also synthesize NO, at least during inflammation. Therefore the change in the number and structure of ICC could play an important role in the pathogenesis of a variety of motility disorders.

Neuroimmune interactions in experimental colitis. An immunoelectron microscopic study.

With its abundance of neurons and immunocytes, the gut is a potentially important site for the study of the interaction between the nervous and immune systems. In this electron microscopic study we have investigated the distribution of substance P (SP)- and vasoactive intestinal polypeptide (VIP)-immunoreactive (IR) nerve terminals and the immunocytes during experimental colitis in the rat. A mild colitis was induced by a luminal enema containing trinitrobenzene sulfonic acid. The most severe inflammation was detected after 2 days and the density and the distribution of the SP- and VIP-IR nerve terminals as well as the immunocompetent cells were studied at that time. Many SP- and VIP-IR nerve terminals were observed in a very close situation to the inflammatory cells. The number of VIP-IR nerve terminals slightly increased in the inflamed area. The gap between the axolemma of the nerve terminals and immunocytes was 20-200 nm. Some lymphocytes and plasma cells were also IR for SP in the inflamed area, whereas no IR immunocytes were observed in the control and in noninflamed area from the same animal. The very close apposition of the SP- and VIP-IR nerve terminals to the inflammatory cells as well as the presence of SP-IR immunocytes in inflamed area support the suggestion that bidirectional neuroimmunomodulation exists in the colon.