Dominant role of interstitial cells of Cajal in nitrergic relaxation of murine lower oesophageal sphincter

Abstract

Key pointsr Nitric oxide (NO) is an important inhibitory neurotransmitter in the gastrointestinal tract.Oesophageal achalasia may result from impairment of nitrergic relaxation.r Smooth muscle cells (SMCs) have been accepted to be the major targets for neuronal NO to mediate relaxation. However, besides SMCs, the receptor for NO, NO-sensitive guanylyl cyclase (NO-GC), has been shown in interstitial cells of Cajal (ICC).r Using cell-specific knockout mice, this study shows that NO-GC in SMC and ICC modulates lower oesophagus sphincter tone in vitro and in vivo.r More importantly, NO-GC in ICC possesses a dominant role in mediating swallowing-induced relaxation. Lack of functional nitrergic signalling, thus, results in deficits in relaxation of the lower oesophagus sphincter as seen in achalasic patients.Abstract Oesophageal achalasia is a disease known to result from reduced relaxation of the lower oesophageal sphincter (LES). Nitric oxide (NO) is one of the main inhibitory transmitters. NO-sensitive guanylyl cyclase (NO-GC) acts as the key target of NO and, by the generation of cGMP, mediates nitrergic relaxation in the LES. To date, the exact mechanism of nitrergic LES relaxation is still insufficiently elucidated. To clarify the role of NO-GC in LES relaxation, we used cell-specific knockout (KO) mouse lines for NO-GC. These include mice lacking NO-GC in smooth muscle cells (SMC-GCKO), in interstitial cells of Cajal (ICC-GCKO) and in both SMC/ICC (SMC/ICC-GCKO). We applied oesophageal manometry to study the functionality of LES in vivo. Isometric force studies were performed to monitor LES responsiveness to exogenous NO and electric field stimulation of intrinsic nerves in vitro. Cell-specific expression/deletion of NO-GC was monitored by immunohistochemistry. Swallowing-induced LES relaxation is strongly reduced by deletion of NO-GC in ICC. Basal LES tone is affected by NO-GC deletion in either SMC or ICC. Lack of NO-GC in both cells leads to a complete interruption of NO-induced relaxation and, therefore, to an achalasia-like phenotype similar to that seen in global GCKO mice. Our data indicate that regulation of basal LES tone is based on a dual mechanism mediated by NO-GC in SMC and ICC whereas swallow-induced LES relaxation is mainly regulated by nitrergic mechanisms in ICC.

The cells and conductance mediating cholinergic neurotransmission in the murine proximal stomach

“…This has been reported to be successful with respect to obtaining maximal gene knockdown in the GI tract (Groneberg et al . ).…”

Decrease of Nitrergic Innervation in the Esophagus of Patients with Chagas Disease: Correlation with Loss of Interstitial Cells of Cajal

“…Although data from correlation analyses should not be interpreted as causative, those data in conjunction with data from previous studies suggest that alterations in both nitrergic innervation and ICC density may be viewed as inter-dependent events. A decrease in ICCs density in the muscle layers has been associated with reduction of the NO-dependent inhibitory response [33] and several other studies in the literature have implicated ICCs in NO-dependent neurotransmission [11,18,29,34]. Moreover, NO is considered to be a cytoprotective molecule that affects the survival of the ICCs [35,36].…”

“…Structural damage of the Enteric Nervous System (ENS), denervation above 90% in the myenteric plexus [7], ganglionitis and periganglionitis have been widely described in the digestive form of Chagas disease [8,9]. It is well known, however, that motility regulation in the GI tract and lower esophageal sphincter relaxation is influenced not only by neuromediators, as Nitric Oxide (NO), but also by Interstitial Cells of Cajal (ICCs) [10][11][12][13]. ative decrease in the number of neurons in colon of chagasic patient with megacolon [25].…”

Treatment with low doses of aspirin during chronic phase of experimental Chagas’ disease increases oesophageal nitrergic neuronal subpopulation in mice

“…In humans, it has been reported in the literature that there is a dual mechanism of relaxation for the LES by NO through the SMC and ICC (Groneberg et al . ). In this study, we saw the maintenance of nitrergic neurons, but we were unaware of possible alterations that could have occurred in the ICC.…”

“…NO is the principal inhibitory neurotransmitter responsible for relaxation of the lower oesophageal sphincter (LES), where guanylate cyclase is the enzyme target (GC‐NO) (Groneberg et al . ), which results in the synthesis of cyclic guanosine monophosphate (cGMP) (Friebe & Koesling ) in various target cells. The expression of GC‐NO was identified in various parts of the gastrointestinal tract, including smooth muscle cells (SMC) and interstitial cells of Cajal (ICC) (Lino et al .…”