Adam Nabeebaccus

Extracellular matrix secretion by cardiac fibroblasts: role of microRNA-29b and microRNA-30c.

Rationale: MicroRNAs (miRNAs), in particular miR-29b and miR-30c, have been implicated as important regulators of cardiac fibrosis. Objective: To perform a proteomics comparison of miRNA effects on extracellular matrix secretion by cardiac fibroblasts. Methods and Results: Mouse cardiac fibroblasts were transfected with pre-/anti-miR of miR-29b and miR-30c, and their conditioned medium was analyzed by mass spectrometry. miR-29b targeted a cadre of proteins involved in fibrosis, including multiple collagens, matrix metalloproteinases, and leukemia inhibitory factor, insulin-like growth factor 1, and pentraxin 3, 3 predicted targets of miR-29b. miR-29b also attenuated the cardiac fibroblast response to transforming growth factor-&bgr;. In contrast, miR-30c had little effect on extracellular matrix production but opposite effects regarding leukemia inhibitory factor and insulin-like growth factor 1. Both miRNAs indirectly affected cardiac myocytes. On transfection with pre–miR-29b, the conditioned medium of cardiac fibroblasts lost its ability to support adhesion of rat ventricular myocytes and led to a significant reduction of cardiac myocyte proteins (&agr;-actinin, cardiac myosin-binding protein C, and cardiac troponin I). Similarly, cardiomyocytes derived from mouse embryonic stem cells atrophied under pre–miR-29 conditioned medium, whereas pre–miR-30c conditioned medium had a prohypertrophic effect. Levels of miR-29a, miR-29c, and miR-30c, but not miR-29b, were significantly reduced in a mouse model of pathological but not physiological hypertrophy. Treatment with antagomiRs to miR-29b induced excess fibrosis after aortic constriction without overt deterioration in cardiac function. Conclusions: Our proteomic analysis revealed novel molecular targets of miRNAs that are linked to a fibrogenic cardiac phenotype. Such comprehensive screening methods are essential to define the concerted actions of miRNAs in cardiovascular disease.Rationale: MicroRNAs (miRNAs), in particular miR-29b and miR-30c, have been implicated as important regulators of cardiac fibrosis. Objective: To perform a proteomics comparison of miRNA effects on extracellular matrix secretion by cardiac fibroblasts. Methods and Results: Mouse cardiac fibroblasts were transfected with pre-/anti-miR of miR-29b and miR-30c, and their conditioned medium was analyzed by mass spectrometry. miR-29b targeted a cadre of proteins involved in fibrosis, including multiple collagens, matrix metalloproteinases, and leukemia inhibitory factor, insulin-like growth factor 1, and pentraxin 3, 3 predicted targets of miR-29b. miR-29b also attenuated the cardiac fibroblast response to transforming growth factor-β. In contrast, miR-30c had little effect on extracellular matrix production but opposite effects regarding leukemia inhibitory factor and insulin-like growth factor 1. Both miRNAs indirectly affected cardiac myocytes. On transfection with pre–miR-29b, the conditioned medium of cardiac fibroblasts lost its ability to support adhesion of rat ventricular myocytes and led to a significant reduction of cardiac myocyte proteins (α-actinin, cardiac myosin-binding protein C, and cardiac troponin I). Similarly, cardiomyocytes derived from mouse embryonic stem cells atrophied under pre–miR-29 conditioned medium, whereas pre–miR-30c conditioned medium had a prohypertrophic effect. Levels of miR-29a, miR-29c, and miR-30c, but not miR-29b, were significantly reduced in a mouse model of pathological but not physiological hypertrophy. Treatment with antagomiRs to miR-29b induced excess fibrosis after aortic constriction without overt deterioration in cardiac function. Conclusions: Our proteomic analysis revealed novel molecular targets of miRNAs that are linked to a fibrogenic cardiac phenotype. Such comprehensive screening methods are essential to define the concerted actions of miRNAs in cardiovascular disease. # Novelty and Significance {#article-title-44}

NADPH oxidases and cardiac remodelling.

A heart under chronic stress undergoes cardiac remodelling, a process that comprises structural and functional changes including cardiomyocyte hypertrophy, interstitial fibrosis, contractile dysfunction, cell death and ventricular dilatation. Reactive oxygen species (ROS)-dependent modulation of intracellular signalling is implicated in the development of cardiac remodelling. Among the different ROS sources that are present in the heart, NADPH oxidases (NOXs) are particularly important in redox signalling. NOX isoforms are expressed in multiple cell types including cardiomyocytes, fibroblasts, endothelial cells and inflammatory cells—with the two main isoforms expressed in the heart being NOX2 and NOX4. Recent studies indicate that NOX-dependent signalling is involved in the development of cardiomyocyte hypertrophy, interstitial fibrosis and post-MI remodelling. NOXs may also be involved in the genesis of contractile dysfunction and myocyte apoptosis. Here, we review the main effects of NOXs in the pathogenesis of cardiac remodelling and the redox-sensitive signalling pathways that underlie these effects. The elucidation of mechanisms involved in NOX-dependent regulation of cardiac remodelling may lead to new therapeutic targets for heart failure.

Novel aspects of ROS signalling in heart failure

Heart failure and many of the conditions that predispose to heart failure are associated with oxidative stress. This is considered to be important in the pathophysiology of the condition but clinical trials of antioxidant approaches to prevent cardiovascular morbidity and mortality have been unsuccessful. Part of the reason for this may be the failure to appreciate the complexity of the effects of reactive oxygen species. At one extreme, excessive oxidative stress damages membranes, proteins and DNA but lower levels of reactive oxygen species may exert much more subtle and specific regulatory effects (termed redox signalling), even on physiological signalling pathways. In this article, we review our current understanding of the roles of such redox signalling pathways in the pathophysiology of heart failure, including effects on cardiomyocyte hypertrophy signalling, excitation–contraction coupling, arrhythmia, cell viability and energetics. Reactive oxygen species generated by NADPH oxidase proteins appear to be especially important in redox signalling. The delineation of specific redox-sensitive pathways and mechanisms that contribute to different components of the failing heart phenotype may facilitate the development of newer targeted therapies as opposed to the failed general antioxidant approaches of the past.

Endoplasmic Reticulum Stress and Nox-Mediated Reactive Oxygen Species Signaling in the Peripheral Vasculature: Potential Role in Hypertension

SIGNIFICANCE Reactive oxygen species (ROS) are produced during normal endoplasmic reticulum (ER) metabolism. There is accumulating evidence showing that under stress conditions such as ER stress, ROS production is increased via enzymes of the NADPH oxidase (Nox) family, especially via the Nox2 and Nox4 isoforms, which are involved in the regulation of blood pressure. Hypertension is a major contributor to cardiovascular and renal disease, and it has a complex pathophysiology involving the heart, kidney, brain, vessels, and immune system. ER stress activates the unfolded protein response (UPR) signaling pathway that has prosurvival and proapoptotic components. RECENT ADVANCES Here, we summarize the evidence regarding the association of Nox enzymes and ER stress, and its potential contribution in the setting of hypertension, including the role of other conditions that can lead to hypertension (e.g., insulin resistance and diabetes). CRITICAL ISSUES A better understanding of this association is currently of great interest, as it will provide further insights into the cellular mechanisms that can drive the ER stress-induced adaptive versus maladaptive pathways linked to hypertension and other cardiovascular conditions. More needs to be learnt about the precise signaling regulation of Nox(es) and ER stress in the cardiovascular system. FUTURE DIRECTIONS The development of specific approaches that target individual Nox isoforms and the UPR signaling pathway may be important for the achievement of therapeutic efficacy in hypertension.

Drug treatment effects on outcomes in heart failure with preserved ejection fraction: a systematic review and meta-analysis

Background Clinical drug trials in patients with heart failure and preserved ejection fraction have failed to demonstrate improvements in mortality. Methods We systematically searched Medline, Embase and the Cochrane Central Register of Controlled Trials for randomised controlled trials (RCT) assessing pharmacological treatments in patients with heart failure with left ventricular (LV) ejection fraction≥40% from January 1996 to May 2016. The primary efficacy outcome was all-cause mortality. Secondary outcomes were cardiovascular mortality, heart failure hospitalisation, exercise capacity (6-min walk distance, exercise duration, VO2 max), quality of life and biomarkers (B-type natriuretic peptide, N-terminal pro-B-type natriuretic peptide). Random-effects models were used to estimate pooled relative risks (RR) for the binary outcomes, and weighted mean differences for continuous outcomes, with 95% CI. Results We included data from 25 RCTs comprising data for 18101 patients. All-cause mortality was reduced with beta-blocker therapy compared with placebo (RR: 0.78, 95%CI 0.65 to 0.94, p=0.008). There was no effect seen with ACE inhibitors, aldosterone receptor blockers, mineralocorticoid receptor antagonists and other drug classes, compared with placebo. Similar results were observed for cardiovascular mortality. No single drug class reduced heart failure hospitalisation compared with placebo. Conclusion The efficacy of treatments in patients with heart failure and an LV ejection fraction≥40% differ depending on the type of therapy, with beta-blockers demonstrating reductions in all-cause and cardiovascular mortality. Further trials are warranted to confirm treatment effects of beta-blockers in this patient group.

Echocardiographic evaluation of diastolic function in mouse models of heart disease

Background Mouse models of heart disease are extensively employed. The echocardiographic characterization of contractile function is usually focused on systolic function with fewer studies assessing diastolic function. Furthermore, the applicability of diverse echocardiographic parameters of diastolic function that are commonly used in humans has not been extensively evaluated in different pathophysiological models in mice. Methods and results We used high resolution echocardiography to evaluate parameters of diastolic function in mouse models of chronic pressure overload (aortic constriction), volume overload (aorto-caval shunt), heart failure with preserved ejection fraction (HFpEF; DOCA-salt hypertension), and acute sarcoplasmic reticulum dysfunction induced by thapsigargin - all known to exhibit diastolic dysfunction. Left atrial area increased in all three chronic models while mitral E/A was difficult to quantify at high heart rates. Isovolumic relaxation time (IVRT) and Doppler E/E′ increased significantly and the peak longitudinal strain rate during early filling (peak reverse longitudinal strain rate) decreased significantly after aortic constriction, with the changes being proportional to the magnitude of hypertrophy. In the HFpEF model, reverse longitudinal strain rate decreased significantly but changes in IVRT and E/E′ were non-significant, consistent with less severe dysfunction. With volume overload, there was a significant increase in reverse longitudinal strain rate and decrease in IVRT, indicating a restrictive physiology. Acute thapsigargin treatment caused significant prolongation of IVRT and decrease in reverse longitudinal strain rate. Conclusion These results indicate that the combined measurement of left atrial area plus reverse longitudinal strain rate and/or IVRT provide an excellent overall assessment of diastolic function in the diseased mouse heart, allowing distinction between different types of pathophysiology.

Asymptomatic aortic stenosis: the influence of the systemic vasculature on exercise time.

BACKGROUND Changes in the peripheral vasculature occur in patients with aortic stenosis (AS). The aims of the present study were to characterize peripheral arterial waveforms and aortic pulsewave velocity (PWV) in patients with AS and to determine their relationship to exercise time. METHODS The study included 101 patients with a median age of 68 years (range, 27-84 years) with at least moderate AS. Patients underwent transthoracic echocardiography, an assessment of the radial artery waveform and PWV using a SphygmoCor device, and a treadmill exercise stress test. RESULTS The mean brachial systolic blood pressure was 143 ± 23 mm Hg in patients with severe AS and 135 ± 15 mm Hg in patients with moderate AS (P = .04). The mean radial augmentation index was 102 ± 20% in patients with severe AS and 89 ± 16% in those with moderate AS (P < .001). The radial augmentation index was related to the effective valve orifice area (R = -0.45, P = .001), the peak transvalvular pressure difference (R = 0.33, P = .001), and the mean transvalvular pressure difference (R = 0.33, P = .001). On univariate analysis, exercise time was related to systemic arterial compliance (R = 0.312, P = .008) and PWV (R = -0.44, P < 0.001). On multivariate analysis, after adjusting for age, AS severity, and PWV, only age was a significant predictor of exercise time (β = -0.46; P = .006; 95% confidence interval, -15 to -3). CONCLUSIONS In patients with asymptomatic moderate to severe AS, exercise capacity is influenced only by age, not by resting measures of aortic valve stenosis or aortic stiffness.

Heart failure—potential new targets for therapy

INTRODUCTION/BACKGROUND Heart failure is a major cause of cardiovascular morbidity and mortality. This review covers current heart failure treatment guidelines, emerging therapies that are undergoing clinical trial, and potential new therapeutic targets arising from basic science advances. SOURCES OF DATA A non-systematic search of MEDLINE was carried out. International guidelines and relevant reviews were searched for additional articles. AREAS OF AGREEMENT Angiotensin-converting enzyme inhibitors and beta-blockers are first line treatments for chronic heart failure with reduced left ventricular function. AREAS OF CONTROVERSY Treatment strategies to improve mortality in heart failure with preserved left ventricular function are unclear. GROWING POINTS Many novel therapies are being tested for clinical efficacy in heart failure, including those that target natriuretic peptides and myosin activators. A large number of completely novel targets are also emerging from laboratory-based research. Better understanding of pathophysiological mechanisms driving heart failure in different settings (e.g. hypertension, post-myocardial infarction, metabolic dysfunction) may allow for targeted therapies. AREAS TIMELY FOR DEVELOPING RESEARCH Therapeutic targets directed towards modifying the extracellular environment, angiogenesis, cell viability, contractile function and microRNA-based therapies.

Cardiac-targeted NADPH oxidase 4 in the adaptive cardiac remodelling of the murine heart.

BACKGROUND The mechanisms that determine whether the heart adapts to overload stress, or fails, are poorly understood. NADPH oxidase (NOX) proteins produce reactive oxygen species (ROS) involved in redox signalling, and our recent studies have found that an increase in Nox4 during pressure overload protects the heart against failure. We aimed to identify novel Nox4-driven cardioprotective mechanisms that promote adaptive cardiac remodelling. METHODS We first undertook a proteomic comparison of heart tissue from cardiac-targeted Nox4-overexpressing mice and controls. The Nox4 cardiac metabolome was then investigated by (1)H nuclear magnetic resonance (NMR) spectroscopy. Effects on cardiac metabolism were assessed by ex-vivo working heart perfusions and isolated mitochondrial respiration studies. Ex-vivo cardiac energetics were assessed by (31)P NMR. Alterations to cardiac fatty acid oxidation were explored in primary cardiomyocytes (extracellular flux analysis). FINDINGS Cardiac-targeted Nox4 overexpression profoundly remodelled the cardiac proteome in an isoform-specific manner, both in the unstressed and stressed heart. Glycolysis and fatty acid oxidation were identified as the most enriched pathways that were altered by Nox4. Metabolomic analysis showed a 2·2 times increase in acetylcarnitine concentrations (p=0·002). Ex-vivo heart perfusions demonstrated a profound increase in palmitate oxidation relative to wild-type hearts (3·6 times increase, p=0·01), with opposite findings observed in primary cardiomyocytes with a knockdown of Nox4. A preference for fatty acid oxidation in Nox4 hearts correlated with a better energetic state (phosphocreatine:ATP ratio) when subjected to increasing doses of isoprenaline stress under baseline and pressure-overload. INTERPRETATION In this study we identified a novel role for Nox4 in the regulation of cardiac fatty acid oxidation. Cardiomyocyte-targeted Nox4 hearts preferentially oxidised fatty acids for energy provision, improving myocardial energetics under stress. Enhancing fatty acid oxidation might have an adaptive role in the setting of pressure-overload hypertrophy. These data provide novel insights into ROS-dependent metabolic programming. FUNDING UK Medical Research Council, British Heart Foundation.

Reporting trends of randomised controlled trials in heart failure with preserved ejection fraction: a systematic review.

Background Heart failure with preserved ejection fraction (HFpEF) causes significant cardiovascular morbidity and mortality. Current consensus guidelines reflect the neutral results from randomised controlled trials (RCTs). Adequate trial reporting is a fundamental requirement before concluding on RCT intervention efficacy and is necessary for accurate meta-analysis and to provide insight into future trial design. The Consolidated Standards of Reporting Trials (CONSORT) 2010 statement provides a framework for complete trial reporting. Reporting quality of HFpEF RCTs has not been previously assessed, and this represents an important validation of reporting qualities to date. Objectives The aim was to systematically identify RCTs investigating the efficacy of pharmacological therapies in HFpEF and to assess the quality of reporting using the CONSORT 2010 statement. Methods MEDLINE, EMBASE and CENTRAL databases were searched from January 1996 to November 2015, with RCTs assessing pharmacological therapies on clinical outcomes in HFpEF patients included. The quality of reporting was assessed against the CONSORT 2010 checklist. Results A total of 33 RCTs were included. The mean CONSORT score was 55.4% (SD 17.2%). The CONSORT score was strongly correlated with journal impact factor (r=0.53, p=0.003) and publication year (r=0.50, p=0.003). Articles published after the introduction of CONSORT 2010 statement had a significantly higher mean score compared with those published before (64% vs 50%, p=0.02). Conclusions Although the CONSORT score has increased with time, a significant proportion of HFpEF RCTs showed inadequate reporting standards. The level of adherence to CONSORT criteria could have an impact on the validity of trials and hence the interpretation of intervention efficacy. We recommend improving compliance with the CONSORT statement for future RCTs.