Mechanosensitive ion channel Piezo2 is important for enterochromaffin cell response to mechanical forces

Abstract

The enterochromaffin (EC) cell in GI epithelium is the source of nearly all systemic serotonin (5-hydroxytryptamine, 5-HT), which is an important neurotransmitter and endocrine, autocrine and paracrine hormone. The EC cell is a specialized mechanosensor, and it is well known that it releases 5-HT in response to mechanical forces. However, the EC cell mechanotransduction mechanism is unknown. The aim of this work was to determine whether Piezo2 is involved in EC cell mechanosensation. Piezo2 mRNA was expressed in human jejunum and mouse mucosa from all segments of small bowel. Piezo2 immunoreactivity localized specifically within EC cells of human and mouse small bowel epithelium. The EC cell model released 5-HT in response to stretch, and had Piezo2 mRNA & protein, and a mechanically-sensitive inward non-selective cation current characteristic of Piezo2. Both inward currents and 5-HT release were inhibited by Piezo2 siRNA and antagonists (Gd³⁺ and D-GsMTx4). Jejunum mucosal pressure increased 5-HT release and short circuit current via submucosal 5HT3 and 5HT4 receptors. Pressure-induced secretion was inhibited by the mechanosensitive ion channel antagonists Gd³⁺, ruthenium red and D-GsMTx4. We conclude that the EC cells in human and mouse small bowel GI epithelium selectively express the mechanosensitive ion channel Piezo2, and activation of Piezo2 by force leads to inward currents, 5-HT release and an increase in mucosal secretion. Therefore, Piezo2 is critical to EC cell mechanosensitivity and downstream physiologic effects.

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