NRSF-GNAO1 Pathway Contributes to the Regulation of Cardiac Ca2+ Homeostasis.

BACKGROUND: During the development of heart failure, a fetal cardiac gene program is reactivated and accelerates pathological cardiac remodeling. We previously reported that a transcriptional repressor, NRSF (neuron restrictive silencer factor), suppresses the fetal cardiac gene program, thereby maintaining cardiac integrity. The underlying molecular mechanisms remain to be determined, however. METHODS: We aim to elucidate molecular mechanisms by which NRSF maintains normal cardiac function. We generated cardiac-specific NRSF knockout mice and analyzed cardiac gene expression profiles in those mice and mice cardiac-specifically expressing a dominant-negative NRSF mutant. RESULTS: We found that cardiac expression of Gαo, an inhibitory G protein encoded in humans by GNAO1, is transcriptionally regulated by NRSF and is increased in the ventricles of several mouse models of heart failure. Genetic knockdown of Gnao1 ameliorated the cardiac dysfunction and prolonged survival rates in these mouse heart failure models. Conversely, cardiac-specific overexpression of GNAO1 in mice was sufficient to induce cardiac dysfunction. Mechanistically, we observed that increasing Gαo expression increased surface sarcolemmal L-type Ca2+ channel activity, activated CaMKII (calcium/calmodulin-dependent kinase-II) signaling, and impaired Ca2+ handling in ventricular myocytes, which led to cardiac dysfunction. CONCLUSIONS: These findings shed light on a novel function of Gαo in the regulation of cardiac Ca2+ homeostasis and systolic function and suggest Gαo may be an effective therapeutic target for the treatment of heart failure.

Successful balloon aortic valvuloplasty as a bridge therapy to transcatheter aortic valve implantation during the proctoring period.

In Japan, transcatheter aortic valve implantation (TAVI) with Edwards-SAPIEN XT valve (Edwards Lifesciences Inc., Irvine, CA, USA) started in October 2013. All institutions should undergo a training period to perform TAVI independently. Balloon aortic valvuloplasty (BAV) as a bridge to TAVI during the training period should be performed with caution to avoid severe aortic regurgitation (AR) because bailout TAVI is not possible. We present a case in which BAV was successfully performed as a bridge to TAVI during the training period. The patient was an 85-year-old man with medically uncontrollable congestive heart failure due to severe aortic valve stenosis. The aortic valve area was 0.60 cm2 with a left ventricular ejection fraction of 20%. TAVI was considered a safe but high-risk strategy owing to the unstable hemodynamic condition. We chose BAV as a bridge therapy to TAVI. The aortic annulus diameter was 25.3 mm on computed tomography scans. We chose a 20-mm balloon catheter to avoid BAV-induced AR. Transfemoral TAVI was performed successfully 16 days after BAV using a 26-mm SAPIEN XT valve. The postoperative course was uneventful. The case demonstrated BAV as a bridge therapy to TAVI can be safely and effectively performed during the training period. .