Pacemaker function and neural responsiveness of subserosal interstitial cells of Cajal in the mouse colon

Abstract

Key pointsr Rhythmic action potentials and intercellular Ca 2+ waves are generated in smooth muscle cells of colonic longitudinal muscles (LSMC).r Longitudinal muscle excitability is tuned by input from subserosal ICC (ICC-SS), a population of ICC with previously unknown function.r ICC-SS express Ano1 channels and generate spontaneous Ca 2+ transients in a stochastic manner.r Release of Ca 2+ and activation of Ano1 channels causes depolarization of ICC-SS and LSMC, leading to activation of L-type Ca 2+ channels, action potentials, intercellular Ca 2+ waves and contractions in LSMC.r Nitrergic neural inputs regulate the Ca 2+ events in ICC-SS. r Pacemaker activity in longitudinal muscle is an emergent property as a result of integrated processes in ICC-SS and LSMC.Abstract Much is known about myogenic mechanisms in circular muscle (CM) in the gastrointestinal tract, although less is known about longitudinal muscle (LM). Two Ca 2+ signalling behaviours occur in LM: localized intracellular waves not causing contractions and intercellular waves leading to excitation-contraction coupling. An Ano1 channel antagonist inhibited intercellular Ca 2+ waves and LM contractions. Ano1 channels are expressed by interstitial cells of Cajal (ICC) but not by smooth muscle cells (SMCs). We investigated Ca 2+ signalling in a novel population of ICC that lies along the subserosal surface of LM (ICC-SS) in mice expressing GCaMP6f in ICC. ICC-SS fired stochastic localized Ca 2+ transients. Such events have been linked to activation of Ano1 channels in ICC. Ca 2+ transients in ICC-SS occurred by release from stores most probably via inositol trisphosphate receptors. This activity relied on influx via store-operated Bernard T. Drumm received his PhD in Physiology in 2013. His research investigates how Ca 2+ signalling impacts the functions of visceral smooth muscle organs in the gastrointestinal and urinary tracts. His doctoral work, studying Ca 2+ wave propagation in urethral cells, was followed by a postdoctoral position and later research track faculty position at the University of Nevada, Reno (UNR), where he studied the regulation of pacemaker and neuroeffector mechanisms in gastrointestinal interstitial cells. Dr Drumm took up a position as Lecturer in the

Ca2+ signaling driving pacemaker activity in submucosal interstitial cells of Cajal in the murine colon

“…Store-operated Ca 2+ entry (SOCE) has been established as a mechanism for filling stores upon depletion [44,45]. Contributions from SOCE via STIM and Orai interactions are essential for maintenance of Ca 2+ stores in other types of ICC [46][47][48][49].…”

Ca2+signaling driving pacemaker activity in submucosal interstitial cells of Cajal in the colon

“…CICR would tend toward negligible when Ca 2+ entry falls below threshold levels. Concentrations of thapsigargin and CPA that blocked Ca 2+ transients quantitatively in other ICC [51,81,88] caused partial block of Ca 2+ transients in ICC-SM. In fact, these drugs caused a marked narrowing of the duration of the CTCs, and this led us to analyze the temporal characteristics of Ca 2+ transients within clusters.…”

“…Store-operated Ca 2+ entry (SOCE) has been established as a mechanism for filling stores upon depletion [47,48]. Contributions from SOCE via STIM and Orai interactions are essential for maintenance of Ca 2+ stores in other types of ICC [49][50][51][52].…”

Disrupted endothelial cell heterogeneity and network organization impair vascular function in prediabetic obesity

“…Compared to control responses (no drug) and in contrast to U73312 (2 μM), U73343 (2 μM), did not reduce steady-state Ca 2+ responses or the number of active cells although the first peak was reduced. Two IP 3 receptor (IP 3 R) inhibitors, 2-aminoethoxydiphenyl borate (2-APB, 100 μM) and caffeine (10 mM; [ [53] , [54] , [55] ]), each inhibited ACh-evoked increases in Ca 2+ . The broad-spectrum transient receptor potential channel antagonist, ruthenium red (RuR, 5 μM), did not reduce ACh-evoked endothelial Ca 2+ activity.…”