Neuro-anatomical evidence indicating indirect modulation of macrophages by vagal efferents in the intestine but not in the spleen.
BACKGROUND
Electrical stimulation of the vagus nerve suppresses intestinal inflammation and normalizes gut motility in a mouse model of postoperative ileus. The exact anatomical interaction between the vagus nerve and the intestinal immune system remains however a matter of debate. In the present study, we provide additional evidence on the direct and indirect vagal innervation of the spleen and analyzed the anatomical evidence for neuroimmune modulation of macrophages by vagal preganglionic and enteric postganglionic nerve fibers within the intestine.


METHODS
Dextran conjugates were used to label vagal preganglionic (motor) fibers projecting to the small intestine and spleen. Moreover, identification of the neurochemical phenotype of the vagal efferent fibers and enteric neurons was performed by immunofluorescent labeling. F4/80 antibody was used to label resident macrophages.


RESULTS
Our anterograde tracing experiments did not reveal dextran-labeled vagal fibers or terminals in the mesenteric ganglion or spleen. Vagal efferent fibers were confined within the myenteric plexus region of the small intestine and mainly endings around nNOS, VIP and ChAT positive enteric neurons. nNOS, VIP and ChAT positive fibers were found in close proximity of intestinal resident macrophages carrying α7 nicotinic receptors. Of note, VIP receptors were found on resident macrophages located in close proximity of VIP positive nerve fibers.


CONCLUSIONS
In the present study, we show that the vagus nerve does not directly interact with resident macrophages in the gut or spleen. Instead, the vagus nerve preferentially interacts with nNOS, VIP and ChAT enteric neurons located within the gut muscularis with nerve endings in close proximity of the resident macrophages.
Tytgat Institute for Liver and Intestinal Research, Academic Medical Center (AMC), Amsterdam, The Netherlands.
Cathy
C
Cailotto
Department of Gastroenterology, University Hospital Leuven, Catholic University of Leuven, Leuven, Belgium.
Pedro J
PJ
Gomez-Pinilla
Tytgat Institute for Liver and Intestinal Research, Academic Medical Center (AMC), Amsterdam, The Netherlands.
Léa M
LM
Costes
Tytgat Institute for Liver and Intestinal Research, Academic Medical Center (AMC), Amsterdam, The Netherlands.
Jan
J
van der Vliet
Department of Gastroenterology, University Hospital Leuven, Catholic University of Leuven, Leuven, Belgium.
Martina
M
Di Giovangiulio
Department of Gastroenterology, University Hospital Leuven, Catholic University of Leuven, Leuven, Belgium.
Andrea
A
Némethova
Department of Gastroenterology, University Hospital Leuven, Catholic University of Leuven, Leuven, Belgium.
Gianluca
G
Matteoli
Department of Gastroenterology, University Hospital Leuven, Catholic University of Leuven, Leuven, Belgium.
Guy E
GE
Boeckxstaens
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D004525:Efferent Pathways; D005260:Female; D007421:Intestine, Small / Q000166:cytology / Q000294:innervation* / Q000378:metabolism; D008198:Lymph Nodes / Q000166:cytology; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009197:Myenteric Plexus / Q000166:cytology / Q000502:physiology; D009333:Neck; D009414:Nerve Growth Factors / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D013154:Spleen / Q000166:cytology / Q000294:innervation*; D014630:Vagus Nerve / Q000502:physiology*; D064569:alpha7 Nicotinic Acetylcholine Receptor / Q000378:metabolism
C072167:CAT development factor; D009414:Nerve Growth Factors; D064569:alpha7 Nicotinic Acetylcholine Receptor; D052248:Nitric Oxide Synthase Type I; C496321:Nos1 protein, mouse; D000109:Acetylcholine