Ca2+ signalling in interstitial cells of Cajal contributes to generation and maintenance of tone in mouse and monkey lower esophageal sphincters

• Published in: The Journal of physiology 2022-03, Vol.600 (11), p.2613-2636
• Main Authors: Drumm, Bernard T., Hannigan, Karen I., Lee, Ji Yeon, Rembetski, Benjamin E., Baker, Salah A., Koh, Sang Don, Cobine, Caroline A., Sanders, Kenton M.
• Format: Article
• Language: English
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/JP282570

The lower esophageal sphincter (LES) generates tone and prevents reflux of gastric contents. LES smooth muscle cells (SMCs) are relatively depolarized, facilitating activation of Ca v 1.2 channels to sustain contractile tone. We hypothesised that intramuscular interstitial cells of Cajal (ICC-IM), through activation of Ca 2+ -activated-Cl − channels (ANO1), set membrane potentials of SMCs favorable for activation of Ca v 1.2 channels. In some gastrointestinal muscles, ANO1 channels in ICC-IM are activated by Ca 2+ transients, but no studies have examined Ca 2+ dynamics in ICC-IM within the LES. Immunohistochemistry and qPCR were used to determine expression of key proteins and genes in ICC-IM and SMCs. These studies revealed that Ano1 and its gene product, ANO1 are expressed in c-Kit + cells (ICC-IM) in mouse and monkey LES clasp muscles. Ca 2+ signaling was imaged in situ , using mice expressing GCaMP6f specifically in ICC (Kit-KI-GCaMP6f). ICC-IM exhibited spontaneous Ca 2+ transients from multiple firing sites. Ca 2+ transients were abolished by CPA or caffeine but were unaffected by tetracaine or nifedipine. Maintenance of Ca 2+ transients depended on Ca 2+ influx and store reloading, as Ca 2+ transient frequency was reduced in Ca 2+ free solution or by Orai antagonist. Spontaneous tone of LES muscles from mouse and monkey was reduced ~80% either by Ani9, an ANO1 antagonist or by the Ca v 1.2 channel antagonist nifedipine. Membrane hyperpolarisation occurred in the presence of Ani9. These data suggest that intracellular Ca 2+ activates ANO1 channels in ICC-IM in the LES. Coupling of ICC-IM to SMCs drives depolarization, activation of Ca v 1.2 channels, Ca 2+ entry and contractile tone.