Exposure to stress is associated with susceptibility to disease and one stress mediator, norepinephrine, has been reported to enhance the adherence of enterohemorrhagic Escherichia coli O157:H7 (EHEC) to the colonic mucosa. We tested the hypothesis that adrenocorticotropic hormone (ACTH) and other stress-related hormones may act in a similar fashion. Explants of distal colonic mucosa from young pigs were mounted in Ussing chambers and their luminal aspect was exposed to EHEC strain 700728 for 30-90 min. When added to the contraluminal, but not luminal bathing medium, ACTH increased EHEC adherence within 90 min in a concentration-dependent manner (EC50 = 1.2 nM), but did not alter tissue electrical conductance. ACTH had no effect on the adherence of a pig-adapted non-O157 E. coli strain. The effect of 0.1 μM ACTH on luminal EHEC adherence was prevented in tissues pretreated contraluminally with the type 2 melanocortin receptor antagonist ACTH7-38, the neuronal conduction blocker saxitoxin, or the muscarinic cholinergic antagonist atropine. Moreover, ACTH7-38 decreased EHEC adherence in the absence of ACTH. These results suggest that ACTH acts via melanocortin receptors located on enteric nerves to enhance mucosal adherence of EHEC.
- Enteric nervous system
- Melanocortin receptor
- Stress-related intestinal infection