a-pacing-controlled-procedure-for-assessment-heart-rate-dependent

A Pacing-Controlled Procedure for the Assessment of Heart Rate-Dependent Diastolic Functions in Murine Heart Failure Models

Heart failure with preserved ejection fraction (HFpEF) is a condition characterized by diastolic dysfunction and exercise intolerance. While ...

The University of Tokyo Hospital

the university of tokyo

Three-Dimensional Visualization of Hypoxia-Induced Pulmonary Vascular Remodeling in Mice.

Cyclic guanosine monophosphate (cGMP), produced by guanylate cyclase (GC), activates protein kinase G (PKG) and regulates cardiac remodeling. cGMP/PKG signal is activated by two intrinsic pathways: nitric oxide (NO)-soluble GC and natriuretic peptide (NP)-particulate GC (pGC) pathways. Activation of these pathways has emerged as a potent therapeutic strategy to treat patients with heart failure, given cGMP-PKG signaling is impaired in heart failure with reduced ejection fraction (HFrEF) and preserved ejection fraction (HFpEF). Large scale clinical trials in patients with HFrEF have shown positive results with agents that activate cGMP-PKG pathways. In patients with HFpEF, however, benefits were observed only in a subgroup of patients. Further investigation for cGMP-PKG pathway is needed to develop better targeting strategies for HFpEF. This review outlines cGMP-PKG pathway and its modulation in heart failure.

Cyclic GMP and PKG Signaling in Heart Failure.

Heart failure with preserved ejection fraction (HFpEF), characterized by diastolic dysfunction and insufficient exercise capacity, is a growing health problem worldwide. One major difficulty with experimental research on HFpEF is the lack of methods to consistently detect diastolic dysfunction in mouse models. We developed a pacing-controlled pressure-volume (PV) loop protocol for the assessment of diastolic function at different heart rates in mice and tested if the protocol could detect diastolic dysfunction specific to a HFpEF model. A HFpEF model was generated by high-fat diet (HFD) feeding with concomitant -nitro-l-arginine methyl ester administration, and a pressure-overload hypertrophy (PO) model was produced by surgical constriction of the transverse aorta (TAC). Heart rate (HR) was slowed below 400 beats/min by intraperitoneal injection of ivabradine. PV loop data were acquired and analyzed at HR incrementing from 400 to 700 beats/min via atrial pacing using a miniature pacing catheter inserted into the esophagus, and comparisons were made among control, HFpEF, and PO mice. At baseline without pacing, no diastolic abnormalities were detected in either PO or HFpEF models. Frequency-diastolic relations, however, revealed the significant diastolic impairment specific to the HFpEF model; both relaxation time constant (Tau) and end-diastolic pressure-volume relationship (EDPVR) were worsened as heart rate increased. Peak positive first derivative of left ventricular pressure (dP/d) was significantly lower in HFpEF versus controls only at a high HR of 700 beats/min. A pacing-controlled protocol would be a feasible and potent method to detect diastolic dysfunction specific to a mouse HFpEF model. We developed a pacing-controlled PV loop protocol for the assessment of diastolic function at different heart rates in mice, which is a feasible and potent method for the characterization of diastolic dysfunction in a murine HFpEF model whose diastolic dysfunction might be difficult to be detected under resting conditions without pacing.

A pacing-controlled protocol for frequency-diastolic relations distinguishes diastolic dysfunction specific to a mouse HFpEF model.

Dopamine D1 receptor (D1R), coded by the Drd1 gene, is induced in cardiomyocytes of failing hearts, triggering heart failure-associated ventricular arrhythmia, and therefore could be a potential therapeutic target for chronic heart failure. The regulation of D1R expression, however, is not fully understood. Here, we explored the molecular mechanism by which cardiomyocyte D1R is induced in failing hearts. We performed motif analysis for the promoter region of the Drd1 gene using the transcription factor affinity prediction (TRAP) method and identified nuclear factor-kappa B (NF-κB) as a candidate transcriptional factor regulating the expression of the Drd1 gene. We next employed murine models of heart failure from chronic pressure overload by transverse aortic constriction (TAC), and assessed myocardial Drd1 expression levels and NF-κB activity, as well as endoplasmic reticulum (ER) stress, which has been implicated in the pathogenesis of heart failure. Drd1 induction in TAC hearts was dependent on the severity of heart failure, and was associated with NF-κB activation and ER stress, as assessed by p65 phosphorylation and the expression of ER stress-related genes, respectively. We further tested if Drd1 was induced by ER stress via NF-κB activation in cultured neonatal rat ventricular myocytes. Tunicamycin activated NF-κB pathway in an ER stress-dependent manner and increased Drd1 expression. Importantly, inhibition of NF-κB pathway by pretreatment with Bay11-7082 completely suppressed the tunicamycin-induced upregulation of Drd1, suggesting that NF-κB activation is essential to this regulation. Our study demonstrates the pivotal role for the ER stress-induced NF-κB activation in the induction of D1R in cardiomyocytes. Intervention of this pathway might be a potential new therapeutic strategy for heart failure-associated ventricular arrhythmia.

Endoplasmic reticulum stress-activated nuclear factor-kappa B signaling pathway induces the upregulation of cardiomyocyte dopamine D1 receptor in heart failure.

Acute vasoreactivity test with inhaled nitric oxide (NO) is performed during diagnostic right heart catheterization (RHC) to identify patients with pulmonary arterial hypertension (PAH) who respond to calcium channel blockers. Our purpose was to investigate the prognostic importance of follow-up vasoreactivity test after treatment.

Genri Numata

Department of Cardiovascular Medicine

The University of Tokyo Hospital

A Pacing-Controlled Procedure for the Assessment of Heart Rate-Dependent Diastolic Functions in Murine Heart Failure Models

Genri Numata

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Cardiovascular Medicine

The University of Tokyo Hospital

A Pacing-Controlled Procedure for the Assessment of Heart Rate-Dependent Diastolic Functions in Murine Heart Failure Models

Department of Cardiovascular Medicine