Mind the gap (junction): cGMP induced by nitric oxide in cardiac myocytes originates from cardiac fibroblasts

Abstract

Background and Purpose: The intracellular signalling molecule cGMP, formed by NO-sensitive GC (NO-GC), has an established function in the vascular system.Despite numerous reports about NO-induced cGMP effects in the heart, the underlying cGMP signals are poorly characterized.Experimental Approach: Therefore, we analysed cGMP signals in cardiac myocytes and fibroblasts isolated from knock-in mice expressing a FRET-based cGMP indicator.Key Results: Whereas in cardiac myocytes, none of the known NO-GC-activating substances (NO, GC activators, and GC stimulators) increased cGMP even in the presence of PDE inhibitors, they induced substantial cGMP increases in cardiac fibroblasts.As cardiac myocytes and fibroblasts are electrically connected via gap junctions, we asked whether cGMP can take the same route. Indeed, in cardiomyocytes cocultured on cardiac fibroblasts, NO-induced cGMP signals were detectable, and two groups of unrelated gap junction inhibitors abolished these signals. Conclusion and Implication:We conclude that NO-induced cGMP formed in cardiac fibroblasts enters cardiac myocytes via gap junctions thereby turning cGMP into an intercellular signalling molecule. The findings shed new light on NO/cGMP signalling in the heart and will potentially broaden therapeutic opportunities for cardiac disease.Abbreviations: % CER, % change of emission ratio; 8MMX, 8-methoxymethyl-IBMX; Ang II, angiotensin II; ANP, atrial natriuretic peptide; BAY60, BAY60-7550; BNP, brain natriuretic peptide; CNP, C-type natriuretic peptide; ES cells, embryonic stem cells; GSNO, Snitrosoglutathione; NO-GC, NO-sensitive GC; ROI, region of interest; α/βGlycA, 18-α/βglycyrrhetinic acid

Enhanced Cardiomyocyte Function in Hypertensive Rats With Diastolic Dysfunction and Human Heart Failure Patients After Acute Treatment With Soluble Guanylyl Cyclase (sGC) Activator

“…Interestingly, connexin 43 appeared to be reduced and disrupted at the intercalated disk in DSS rats, an effect partially reversed after treatment. Taken together, these findings suggest that a functional NO-sGC-cGMP pathway preserves the intercalated disk, the site of mechanical and electrical conduction between cardiomyocytes and perhaps also fibroblasts (Menges et al, 2019) and endothelial cells (Yuan et al, 2015;Johnson and Camelliti, 2018). Connexin 43 expressed in endothelial cells modulates monocyte-endothelial adhesion by regulating cell adhesion proteins, an interaction that is decreased upon reduced connexin 43 (Yuan et al, 2015).…”

Angiotensin II-Induced Cardiovascular Fibrosis Is Attenuated by NO-Sensitive Guanylyl Cyclase1

“…While the occurrence of NO-induced cGMP signals in cardiac cells has been a matter of debate [24][25][26][27][28], a recent publication revealed pronounced NO-induced cGMP responses in cardiac fibroblasts but none in isolated cardiac myocytes [9]. The occurrence of NO-GC in cardiac fibroblasts is compatible with an antifibrotic action.…”

“…Whereas NO/cGMP-induced vasorelaxation as prototypical biological NO response has been known for decades, the protective role of NO-induced cGMP in cardiovascular events such as cardiovascular remodeling and fibrosis is a matter of current research [1,3]. A possible role of NO-dependent cGMP in fibrosis development is further underlined by the finding of comparably high NO-induced cGMP signals in cardiac fibroblasts and their recently described absence in cardiac myocytes [9]. As AngII induces cardiovascular remodeling/fibrosis, NO-GC1 KOs challenged by AngII treatment were analyzed to verify the protective role of NO/cGMP in these events.…”

“…Recently, measurements of NO-induced cGMP signals in cardiac cells revealed NO-GC-dependent cGMP to be exclusively produced in cardiac fibroblasts whereas in cardiac myocytes only the natriuretic peptide CNP induces cGMP production [9]. The occurrence of NO-induced cGMP in cardiac fibroblasts prompted us to speculate about a possible role of cGMP in fibrosis.…”

cGMP: a unique 2nd messenger molecule – recent developments in cGMP research and development

“…However, cardiomyocyte-specific deletion of sGC in mice had a negative effect on cardioprotective signaling following acute myocardial infarction in vivo (Frankenreiter et al 2018). Intriguingly cardiac fibroblasts/fibroblast-like cells can serve as major source of cGMP for cardiomyocytes (Menges et al 2019). Isolated murine cardiomyocytes expressing the Förster resonance energy transfer (FRET) indicator cGi-500 (EC 50 500 nM) were neither responsive to NO donors at high concentrations nor did sGC activators or stimulators in the presence of IBMX induce changes in cGMP measured by using the FRET technique (Doris Koesling, Bochum).…”