The sympathetic neurotransmitter norepinephrine has been found to increase mucosal adherence of enterohemorrhagic Escherichia coli O157:H7 in explants of murine cecum and porcine distal colon. In the present study, we tested the hypothesis that norepinephrine augments the initial, loose adherence of this important pathogen to the intestinal mucosa. In mucosal sheets of porcine cecum or proximal, spiral and distal colon mounted in Ussing chambers, norepinephrine (10 μM, contraluminal addition) increased mucosal adherence of wild-type E. coli O157:H7 strain 85-170; in the cecal mucosa, this effect occurred within 30-90 min after bacterial inoculation. In addition, norepinephrine transiently increased short-circuit current in cecal and colonic mucosal sheets, a measure of active anion transport. Norepinephrine was effective in promoting cecal adherence of a non-O157 E. coli strain as well as E. coli O157:H7 eae or espA mutant strains that are incapable of intimate mucosal attachment. Nerve fibers immunoreactive for the norepinephrine synthetic enzyme dopamine β-hydroxylase appeared in close proximity to the cecal epithelium, and the norepinephrine reuptake blocker cocaine, like norepinephrine and the selective α2-adrenoceptor agonist UK-14,304, increased E. coli O157:H7 adherence. These results suggest that norepinephrine, acting upon the large bowel mucosa, modulates early, non-intimate adherence of E. coli O157:H7 and probably other mucosa-associated bacteria. Sympathetic nerves innervating the cecocolonic mucosa may link acute stress exposure or psychostimulant abuse with an increased microbial colonization of the intestinal surface. This in turn may alter host susceptibility to enteric infections.
Bibliographical noteFunding Information:
We thank Melissa A. Casey and H. Noel Opitz for excellent technical assistance. This investigation was supported by National Institutes of Health Grants AI-44918 and MH-50431 (M.L.) and DA-10200 (D.R.B.). M.P.S. gratefully acknowledges the support of the Biotechnology and Biological Sciences Research Council, UK (C518022). Salary support for C.C. was provided by NIH training grant T32 DA-007239.
- Enteric nervous system
- Mucosa-adherent bacterium
- Type III secretion system