A succinate/SUCNR1-brush cell defense program in the tracheal epithelium

Abstract

Host-derived succinate accumulates in the airways during bacterial infection. Here, we show that luminal succinate activates murine tracheal brush (tuft) cells through a signaling cascade involving the succinate receptor 1 (SUCNR1), phospholipase Cβ2, and the cation channel transient receptor potential channel subfamily M member 5 (TRPM5). Stimulated brush cells then trigger a long-range Ca 2+ wave spreading radially over the tracheal epithelium through a sequential signaling process. First, brush cells release acetylcholine, which excites nearby cells via muscarinic acetylcholine receptors. From there, the Ca 2+ wave propagates through gap junction signaling, reaching also distant ciliated and secretory cells. These effector cells translate activation into enhanced ciliary activity and Cl − secretion, which are synergistic in boosting mucociliary clearance, the major innate defense mechanism of the airways. Our data establish tracheal brush cells as a central hub in triggering a global epithelial defense program in response to a danger-associated metabolite.

Tuft cell IL-17RB restrains IL-25 bioavailability and reveals context-dependent ILC2 hypoproliferation

“…High expression of Itpr2 in tuft cells from the human intestine indicates that this function might be conserved [26,39]. In tracheal tuft cells, an elevation in intracellular calcium is linked to acetylcholine release that stimulates surrounding epithelial cells and triggers Ca 2+ waves, thereby promoting ciliary activity and Cl − secretion [22]. Small intestinal tuft cells may employ similar mechanisms to produce IL-25.…”

“…We therefore hypothesized that increasing cytosolic Ca 2+ is a critical step in tuft cells for their production of IL-25. To test this, we visualized Ca 2+ activity in isolated villi using the genetically encoded fast Ca 2+ sensor GCaMP6f, expressed in TRPM5 + tuft cells, as recently published for tracheal tuft cells [22,23]. In these Trpm5 Cre ;R26 GCaMP6f mice, temporally and spatially resolved Ca 2+ signals can be recorded by confocal imaging in tuft cells in their native cellular environment in small intestinal villus epithelium (Fig.…”

“…We used the following mouse strains: Vil1 Cre (B6.Cg-Tg(Vil1-cre)997Gum/J; JAX, 004586); Nmur1 iCre- Leibundgut-Landmann); Il5 Red5 (B6(C)-Il5 tm1.1(iCre)Lky /J; JAX, 030926); Il25 fl-tdTomato ([3], B6(C)-Il25 tm1.1Lky /J); Il25 iCre ([28], B6(C)-Il25 tm2.1(cre)Lky /J); Tg CAG-lsl-Gq-DREADD (B6N;129-Tg(CAG-CHRM3*,-mCitrine)1Ute/J; JAX, 026220). Except for Trpm5 Cre ;R26 GcaMP6f mice [22,23], all lines were crossed to Arg1 Yarg ;Il13 Smart13 double reporter (B6.129S4-Arg1 tm1Lky /J; JAX, 015857; B6.129S4(C)-Il13 tm2.1Lky /J; JAX, 031367). All mice were on a C57BL/6 background.…”

“…Intracellular Ca 2+ was monitored with either GCaMP6f expressed in the tuft cells of Trpm5 Cre ;R26 GcaMP6f mice or the Ca 2+ indicator Cal630-AM loaded into tracheal epithelial cells using a similar technique as described previously for the tracheal epithelium [22]. Cal630-AM (AAT-Bioquest CAT# 20720) was dissolved in a solution of DMSO and freshly prepared 20% Pluronic F-127 in DMSO, then further diluted in extracellular solution (see above), and briefly sonicated.…”

“…eGFP ([21], from D. Artis and C. Klose); Il17rb fl/fl ([15], from U. Siebenlist); Il17rb -/mice with global Il17rb deletion were generated from Vil1 Cre ; Il17rb fl/fl mice in which Cre is active with high frequency in the male germline; Itpr2 -/-([55], from A. Saab); Trpm5 Cre ;R26 GCaMP6f[22,23]; Il17rc -/-(from S.…”