Communication between mast cells and rat submucosal neurons

Abstract

Histamine is a mast cell mediator released e.g. during food allergy. The aim of the project was to identify the effect of histamine on rat submucosal neurons and the mechanisms involved. Cultured submucosal neurons from rat colon express H1, H2 and H3 receptors as shown by immunocytochemical staining confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) with messenger RNA (mRNA) isolated from submucosal homogenates as starting material. Histamine evoked a biphasic rise of the cytosolic Ca(2+) concentration in cultured submucosal neurons, consisting in a release of intracellularly stored Ca(2+) followed by an influx from the extracellular space. Although agonists of all three receptor subtypes evoked an increase in the cytosolic Ca(2+) concentration, experiments with antagonists revealed that mainly H1 (and to a lesser degree H2) receptors mediate the response to histamine. In coculture experiments with RBL-2H3 cells, a mast cell equivalent, compound 48/80, evoked an increase in the cytosolic Ca(2+) concentration of neighbouring neurons. Like the response to native histamine, the neuronal response to the mast cell degranulator was strongly inhibited by the H1 receptor antagonist pyrilamine and reduced by the H2 receptor antagonist cimetidine. In rats sensitized against ovalbumin, exposure to the antigen induced a rise in short-circuit current (I sc) across colonic mucosa-submucosa preparations without a significant increase in paracellular fluorescein fluxes. Pyrilamine strongly inhibited the increase in I sc, a weaker inhibition was observed after blockade of protease receptors or 5-lipoxygenase. Consequently, H1 receptors on submucosal neurons seem to play a pivotal role in the communication between mast cells and the enteric nervous system.

The antinociception of oxytocin on colonic hypersensitivity in rats was mediated by inhibition of mast cell degranulation via Ca2+-NOS pathway

“…Histamine mainly exists in mast cells, and its release is considered as a reliable indicator of mast cell degranulation 41 . Besides, histamine is reported to cause activation of submucosal neurons mainly mediated by histamine H 1 receptors on the neurons in rat 42 . Histamine has been demonstrated to increases Nav1.8 expression in primary afferent neurons via histamine H 2 receptor-mediated pathway and thereby contributes to neuropathic pain 43 .…”

Epithelial propionyl‐ and butyrylcholine as novel regulators of colonic ion transport

“…Relative changes in the cytosolic Ca 2 + concentration of neurons in intact submucosal ganglia were measured using the Ca 2 + ‐sensitive fluorescent dye fura‐2 as described previously (Bell et al ., ). The isolated submucosae were transferred to an experimental chamber mounted on an inverted microscope (IX‐50; Olympus, Hamburg, Germany) equipped with an epifluorescence set‐up and an image analysis system (Till Photonics, Martinsried, Germany).…”

Imaging of mast cells

“…Similarly, neuropeptides released by nerves can modulate mast cell activation, and hence degranulation. Most of the studies on nerve‐MC signaling focused on experiments in cell culture and rodent animal models . Under normal conditions, and even more so during inflammation, neurons generate impulses, resulting in the release of adenosine triphosphate, vasoactive intestinal peptide (VIP), substance P (SP), and calcitonin gene‐related peptide (CGRP), all of which are believed to contribute to nerve triggered mast cell activation …”