BQ788 Reveals Glial ETB<sub>R</sub> Modulation of Neuronal Cholinergic and Nitrergic Pathways to Inhibit Intestinal Motility: ETB<sub>R</sub> Signaling is Linked to POI
pubmed: wnt1 2023-06-01
Br J Pharmacol. 2023 May 17. doi: 10.1111/bph.16145. Online ahead of print.
BACKGROUND AND PURPOSE: ET-1 signaling modulates intestinal motility and inflammation, but the role of ET-1/ETBR signaling is poorly understood. Enteric glia modulate normal motility and inflammation. We investigated whether glial ETBR signaling is a mechanism regulating neural-motor pathways of intestinal motility and inflammation.
EXPERIMENTAL APPROACH: We studied ETBR signaling using: ETBR drugs (ET-1, SaTX, BQ788), activity-dependent stimulation of neurons (high K+ -depolarization, EFS), gliotoxins, Tg (Ednrb-EGFP) EP59Gsat/Mmucd mice, cell-specific mRNA in Sox10CreERT2; Rpl22-HAflx or ChATCre; Rpl22-HAflx mice, Sox10CreERT2 ::GCaMP5g-tdT, Wnt1Cre2 ::GCaMP5g-tdT mice, muscle tension recordings, fluid-induced peristalsis, ET-1 expression, qPCR, western blots, 3-D LSM-immunofluorescence co-labeling studies in LMMP-CM and a POI model of intestinal inflammation (P<0.01 is significant).
KEY RESULTS: In the muscularis externa ETBR is expressed exclusively in glia. ET-1 is expressed in RiboTag (ChAT)-neurons, isolated ganglia and intra-ganglionic varicose-nerve fibers co-labeled with peripherin or SP. Pharmacological analysis of neural evoked glial responses indicates that ET-1 release provides activity-dependent glial ETBR modulation of Ca2+ waves. BQ788 reveals amplification of glial and neuronal Ca2+ responses and excitatory cholinergic contractions. The BQ788 effect is sensitive to L-NAME. Gliotoxins disrupt SaTX-induced glial-Ca2+ waves and prevent BQ788 amplification of contractions. ETBR is linked to inhibition of contractions and peristalsis. Inflammation causes glial ETBR upregulation, SaTX-hypersensitivity and glial amplification of ETBR signaling. In vivo BQ788 (i.p.,1mg/Kg) attenuates intestinal inflammation in POI.
CONCLUSION AND IMPLICATIONS: Enteric glial ET-1/ETBR signaling provides dual modulation of neural-motor circuits to inhibit motility - It inhibits excitatory cholinergic neural-motor pathways and stimulates inhibitory nitrergic motor pathways. Amplification of glial ETBR is linked to muscularis externa inflammation and possibly pathogenic mechanisms of postoperative ileus.