Pacemaker currents modulated by C-type natriuretic peptide in interstitial cells of Cajal from murine small intestine

Abstract

Although the presence of C-type natriuretic peptide (CNP) in gastrointestinal tract has been demonstrated, the effect of CNP on interstitial cells of Cajal (ICC), pacemaker cells in gastrointestinal tract, is still unclear. This study was designed to investigate the effect of CNP on pacemaker currents of ICC and possible mechanisms. We used immunocytochemistry techniques to exhibit natriuretic peptide receptors (NPR) and recorded membrane currents by using whole-cell patch clamp technique on cultured ICC. Our experiment showed that NPR-A and NPR-B were expressed in ICC from murine small intestine. Whole cell recordings further showed that the amplitude of pacemaker currents in intestinal small networks of ICC was 322+/-22pA and the frequency was 16.25+/-0.95Hz. CNP significantly reduced the amplitude of pacemaker currents in small networks of ICC in a dose-dependent manner, and the amplitude was inhibited by 23.95%, 61.76% and 81.67%, the amplitude values in 329+/-28.0pA, 311.2+/-14.8pA and 295+/-26.5pA before treatment with CNP and 237.9+/-27.5pA, 119.6+/-18.5pA and 57.2+/-13.5pA after treatment with 0.01 micromolxL(-1), 0.1 micromolxL(-1) and 1pmolxL(-1) CNP, respectively. The frequencies of pacemaker currents were also significantly reduced from 16.25+/-0.95Hz of control to 13+/-0.9Hz, 12+/-0.8Hz and 3+/-0.2Hz by 0.01micromolxL 1, 0.1micromolxL(-1) and 1 micromol x L(-1) CNP, respectively. CNP also inhibited the amplitude of pacemaker currents in single ICC. The inhibitory effect of CNP was mimicked by 8-Br-cGMP, a membrane permeable cGMP analogue, which suggests that CNP could inhibit pacemaker currents via NPR-B-particulate guanylate cyclase (pGC)-cGMP signal pathway.

Electroacupuncture promotes the gastrointestinal motility of diabetic mice by CNP/NPR‐B‐cGMP and PDE3A‐cGMP signaling

“…Some studies demonstrated that the mSCF content was obviously decreased when CNP was added in cultured GSMCs . Zhang et al verified that rhythmic spontaneous currents of ICC from murine small intestine were completely suppressed by up‐regulating the CNP/NPR‐B signaling and gradually recovered after breaking off the CNP supplement. In the current study, we analyzed the correlations between the mSCF mRNA expression and the NPR‐B mRNA expression in the stomach and colon of mice; our results show the significant negative correlation between mSCF and NPR‐B both in the stomach and in the colon, indicating that up‐regulated mSCF/c‐Kit signaling by EA may be mediated partially via down‐regulation of CNP/NPR‐B signaling in the gut of diabetic mice.…”

Transmembrane guanylate cyclase in intestinal pathophysiology

“…ANP/GC-A is a classical regulator of sodium flux in the intestine and has recently been shown to regulate CFTR expression in IECs [43]. CNP/GC-B regulates circular smooth muscle relaxation and may act directly in the ICC to control small bowel pacemaker currents [44,45]. Notably, although genetic deletion of GC-B in mice does not result in a severe gastrointestinal phenotype, two separately reported GC-B truncation mutants result in a lethal loss of intestinal motility [42,46,47].…”

“…Expression and/or activity of GC-A, GC-B, and their ligands can be found in the intestinal tract of rabbits, rodents, and humans in a wide variety of cell types including IECs, smooth muscle, myenteric and submucosal neurons, myofibroblasts and the interstitial cells of Cajal (ICC) [2 , [42][43][44][45]. ANP/GC-A is a classical regulator of sodium flux in the intestine and has recently been shown to regulate CFTR expression in IECs [43].…”

Pacemaking activity is regulated by membrane stretch via the CICR pathway in cultured interstitial cells of Cajal from murine intestine

“…The cells were allowed to settle for 30 min before adding SMGM medium (Clonetics Corp., San Diego, CA, USA) supplemented with 2% antibiotic/antimycotic (Gibco Invitrogen Corp., Grand Island, USA) and murine stem cell factor (SCF, 5 ng/ml, Sigma Aldrich, St. Louis, MO, US). Cells were incubated at 37 1C in a 5% CO 2 incubator (Zhang et al, 2006).…”