Cholinergic Signaling Attenuates Pro-Inflammatory Interleukin-8 Response in Colonic Epithelial Cells

Abstract

Infants affected by Hirschsprung disease (HSCR), a neurodevelopmental congenital disorder, lack ganglia of the intrinsic enteric nervous system (aganglionosis) in a variable length of the colon, and are prone to developing severe Hirschsprung-associated enterocolitis (HAEC). HSCR patients typically show abnormal dense innervation of extrinsic cholinergic nerve fibers throughout the aganglionic rectosigmoid. Cholinergic signaling has been reported to reduce inflammatory response. Consequently, a sparse extrinsic cholinergic innervation in the mucosa of the rectosigmoid correlates with increased inflammatory immune cell frequencies and higher incidence of HAEC in HSCR patients. However, whether cholinergic signals influence the pro-inflammatory immune response of intestinal epithelial cells (IEC) is unknown. Here, we analyzed colonic IEC isolated from 43 HSCR patients with either a low or high mucosal cholinergic innervation density (fiber-low versus fiber-high) as well as from control tissue. Compared to fiber-high samples, IEC purified from fiber-low rectosigmoid expressed significantly higher levels of IL-8 but not TNF-α, IL-10, TGF-β1, Muc-2 or tight junction proteins. IEC from fiber-low rectosigmoid showed higher IL-8 protein concentrations in cell lysates as well as prominent IL-8 immunoreactivity compared to IEC from fiber-high tissue. Using the human colonic IEC cell line SW480 we demonstrated that cholinergic signals suppress lipopolysaccharide-induced IL-8 secretion via the alpha 7 nicotinic acetylcholine receptor (a7nAChR). In conclusion, we showed for the first time that the presence of a dense mucosal cholinergic innervation is associated with decreased secretion of IEC-derived pro-inflammatory IL-8 in the rectosigmoid of HSCR patients likely dependent on a7nAChR activation. Owing to the association between IL-8 and enterocolitis-prone, fiber-low HSCR patients, targeted therapies against IL-8 might be a promising immunotherapy candidate for HAEC treatment.

A Novel Method for Identifying the Transition Zone in Long-Segment Hirschsprung Disease: Investigating the Muscle Unit to Ganglion Ratio

“…Overall, this suggests that more subtle changes in the ENS may underly the development of HAEC. Reductions in enteric cholinergic innervation of the gut mucosa and serotonin production have been found in HAEC patients [ 21 , 22 , 47 ]. It is now recognised that the ENS communicates with the gut immune system and has an important role in immune activation and suppression [ 48 , 49 , 50 ].…”

Neuroimmune regulation in Hirschsprung’s disease associated enterocolitis

“…Another study shows that cholinergic innervation in rectosigmoid colon in HSCR patients is associated with secretion of proinflammatory IL-8, which increases the risk of HAEC (22).…”

“…HAEC-mediated 5-hydroxytryptaminergic neuronal damage may lead to colonic dysfunction and recurrent enterocolitis ( 21 ). Another study shows that cholinergic innervation in rectosigmoid colon in HSCR patients is associated with secretion of pro-inflammatory IL-8, which increases the risk of HAEC ( 22 ).…”

“…Studies have shown that cholinergic signaling can reduce inflammatory responses and α7nAChR plays an important role in the neuroimmune signaling pathways. Thus, sparse exogenous cholinergic innervation in the sigmoid mucosa and antagonism of α7nAChR are associated with increased frequency of inflammatory immune cells and higher incidence of HAEC in patients with HSCR ( 22 ).…”

Associations of Mucosal Nerve Fiber Innervation Density with Hirschsprung-Associated Enterocolitis: A Retrospective Three-Center Cohort Study

“…Recently, our group discovered that the lack of mucosal cholinergic innervation in the distal colon of HSCR patients was associated with increased inflammatory immune cell status and enterocolitis in a prospective study set up. [17,37,38].…”