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

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

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

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 co-cultured on cardiac fibroblasts, NO-induced cGMP signals were detectable, and two groups of unrelated gap junction inhibitors abolished these signals.