Prox1-positive cells monitor and sustain the murine intestinal epithelial cholinergic niche

Abstract

The enteric neurotransmitter acetylcholine governs important intestinal epithelial secretory and immune functions through its actions on epithelial muscarinic Gq-coupled receptors such as M3R. Its role in the regulation of intestinal stem cell function and differentiation, however, has not been clarified. Here, we find that nonselective muscarinic receptor antagonism in mice as well as epithelial-specific ablation of M3R induces a selective expansion of DCLK1positive tuft cells, suggesting a model of feedback inhibition. Cholinergic blockade reduces Lgr5-positive intestinal stem cell tracing and cell number. In contrast, Prox1-positive endocrine cells appear as primary sensors of cholinergic blockade inducing the expansion of tuft cells, which adopt an enteroendocrine phenotype and contribute to increased mucosal levels of acetylcholine. This compensatory mechanism is lost with acute irradiation injury, resulting in a paucity of tuft cells and acetylcholine production. Thus, enteroendocrine tuft cells appear essential to maintain epithelial homeostasis following modifications of the cholinergic intestinal niche.

Acetylcholine From Tuft Cells: The Updated Insights Beyond Its Immune and Chemosensory Functions

“…Therefore, the distribution of tuft cells in human lung still needs to be carefully investigated. The knockout of Pou2f3 gene indicates the specific deletion of tuft cells and Pou2f3 –/– mice exhibit impaired mucosal type 2 responses and epithelial regeneration ( Gerbe et al, 2016 ; Middelhoff et al, 2020 ). In this respect, the long term targeting on IL17RB to monitor tuft cell-like human colorectal cancer still needs further research to avoid the potential damage to the homeostasis of colorectal mucosa.…”

“…Using electron microscopy, researchers have made it clear that the expressions of ChAT in mice localize in the cytosol as well as the nucleus ( Kummer and Krasteva-Christ, 2014 ; Friedman et al, 2019 ). A recent study in intestinal epithelium has demonstrated that increased ChAT expression is related to the expansion of tuft cells following the increase of ACh secretion ( Middelhoff et al, 2020 ).…”

“…Previous studies have found that tuft cell ablation would lead to impaired intestinal regeneration, suggesting the role of tuft cells in maintaining epithelial homeostasis ( Westphalen et al, 2014 ; Middelhoff et al, 2020 ). An experiment on human intestinal organoid indicated that endogenous ACh increased cell division and differentiation to maintain the homeostasis of intestine ( Takahashi et al, 2018 ; Brinkman et al, 2019 ).…”

“…These expanded tuft cells may also orchestrate with submucosal cholinergic nerve fibers to increase the secretion of ACh. Interestingly, mature tuft cells already existing in epithelium show no response to the reduced cholinergic signaling ( Middelhoff et al, 2020 ). Lgr5 has been defined as a marker of intestinal stem cells (ISCs) with self-renewal ability ( Barker et al, 2007 ).…”

Helminth Sensing at the Intestinal Epithelial Barrier—A Taste of Things to Come

“…Although the close interaction between airway tuft cells and cholinergic neurons has been previously demonstrated ( 37 ), with recent demonstrations of tuft cell acetylcholine driving ciliary beating in a Trpm5-dependent fashion ( 38 ), their role in cholinergic neuron signaling in the intestine is less clear. There is evidence that during genetic and antagonist muscarinic receptor blockade, small intestinal tuft cells arise with an enteroendocrine-like phenotype to sustain the murine intestinal epithelial cholinergic niche ( 39 ). Moreover, as acetylcholine receptors are also expressed on diverse cell types, including goblet cells (where acetylcholine promotes mucus secretion), dendritic cells, macrophages, as well as B and T cells ( 40 , 41 ), there is the unexplored possibility that tuft cells may also play a larger role in anthelmintic immunity via their production of acetylcholine.…”