Immunoreactivity for high-affinity choline transporter colocalises with VAChT in human enteric nervous system
BACKGROUND The body has not only a neuronal but also a nonneuronal cholinergic system. Both systems are likely to be very important, particularly in inflammatory conditions. The patterns and importance of the nonneuronal cholinergic system in patients with ulcerative colitis (UC) are largely unknown. METHODS The colons of UC and non-UC patients were examined for expression patterns of choline acetyltransferase (ChAT), vesicular acetylcholine transporter (VAChT), and the muscarinic receptor of the M(2) subtype. RESULTS ChAT and VAChT immunoreactions and mRNA reactions for ChAT were detected in epithelial and endocrine cells, in cells in the lamina propria, and in blood vessel walls. Furthermore, a marked M(2) immunoreaction was noted for epithelium, blood vessel walls, and smooth musculature. ChAT and VAChT immunoreactions were significantly higher in endocrine and epithelial cells, respectively, in non-UC mucosa than in UC mucosa. On the other hand, there was a tendency toward higher M(2) levels in epithelium of UC patients. CONCLUSIONS There is a pronounced nonneuronal cholinergic system in the colon, which has previously been ignored when discussing cholinergic influences in UC. Furthermore, it is evident that certain changes in the nonneuronal cholinergic system occur in response to inflammation/derangement in UC. Cholinergic effects in the colon can be considered to be related not only to nerve-related effects but also to effects of acetylcholine from nonneuronal local cells. Thus, the recently discussed phenomenon of a "cholinergic antiinflammatory pathway" in the intestine may have a pronounced nonneuronal component.