High-dose enalapril treatment reverses myocardial fibrosis in experimental uremic cardiomyopathy

Oxytocin alleviates liver fibrosis via hepatic macrophages

Background & Aims

Previous studies demonstrated oxytocin treatment effectiveness in reducing mortality and reversing liver fibrosis in mice. However, the underlying mechanism remains obscure, given the absence of oxytocin receptor expression in hepatic stellate cells, the primary liver fibrosis effector cells.

Methods

A comprehensive map of cell populations in fibrotic liver was generated using single-cell sequencing. The map enabled our study of the target cells of oxytocin action in the liver in more dimensions. Furthermore, we elucidated the mechanism of the oxytocin signaling system in hepatic macrophages using oxytocin receptor-specific knockout mice and liver fibrosis animal models.

Results

The carbon tetrachloride-induced hepatic fibrosis and bile duct ligation hepatic fibrosis mouse models demonstrated that oxytocin reversed hepatic fibrosis in mice. The mapped liver cell populations demonstrated that oxytocin promoted the phenotypic switch from Ly6high to Ly6Clow in myeloid-derived macrophages. The phenotypic control of oxytocin signaling system activation on this phenotypic switch was validated using myeloid-specific oxytocin receptor knockout mice. Subsequent studies demonstrated that the calcium inward flow induced by oxytocin receptor activation activated the key orphan nuclear receptor NR4A1, which controls macrophage phenotypic switching. Specifically, calcium ions activated CREB, a key target regulator of NR4A1 expression.

Conclusions

The findings established hepatic macrophages as a hub responsible for the oxytocin-mediated alleviation of liver fibrosis. This study revealed a novel pathway where oxytocin regulates macrophage phenotype.

Impact and implications

Previous studies revealed for the first time the expression of oxytocin receptors in the liver. The present study shows that oxytocin reverses hepatic fibrosis and that hepatic macrophages are the central hub of oxytocin-mediated alleviation of hepatic fibrosis by promoting a phenotypic switch in hepatic macrophages, transitioning from Ly6high to Ly6Clow expression. The present study reveals a novel pathway by which oxytocin regulates macrophage phenotype. In addition, the potential applications of oxytocin and its analogues, as traditional drugs for clinical application, in the treatment of liver fibrosis deserve to be further explored.

Effects of intensive blood pressure control on left ventricular hypertrophy in aortic valve disease

BACKGROUND

Hypertension adds to the pressure overload on the left ventricle (LV) in combination with aortic valve (AV) disease, but the optimal blood pressure (BP) targets for patients with AV disease remain unclear. We tried to investigate whether intensive BP control reduces LV hypertrophy in asymptomatic patients with aortic stenosis (AS) or aortic regurgitation (AR).

METHODS

A total of 128 hypertensive patients with mild to moderate AS (n = 93) or AR (n = 35) were randomly assigned to intensive therapy, targeting a systolic BP <130 mm Hg, or standard therapy, targeting a systolic BP <140 mm Hg. The primary end point was the change in LV mass from baseline to the 24-month follow-up. Secondary end points included changes in severity of AV disease, LV volumes, ejection fraction and global longitudinal strain (GLS).

RESULTS

The treatment groups were generally well balanced regarding the baseline characteristics. The mean (±SD) age of the patients was 68 ± 8 years and 48% were men. The mean BP was 145 ± 12/81 ± 10 mm Hg at baseline. Medication at baseline was similar between the 2 groups. The 2 treatment strategies resulted in a rapid and sustained difference in systolic BP (P < .05). At 24-month, the mean systolic BP was 129 ± 12 mm Hg in the intensive therapy group and 135 ± 14 mm Hg in the standard therapy group. No patient died or underwent AV surgery during follow-up in either of the groups. LV mass was changed from 189.5 ± 41.3 to 185.6 ± 41.5 g in the intensive therapy group (P = .19) and from 183.8 ± 38.3 to 194.0 ± 46.4 g in the standard therapy group (P < .01). The primary end point of change in LV mass was significantly different between the intensive therapy and the standard therapy group (-3.9 ± 20.2 g vs 10.3 ± 20.4 g; P = .0007). The increase in LV mass index was also significantly greater in the standard therapy group (P = .01). No significant differences in secondary end points (changes in severity of AV disease, LV volumes, ejection fraction and GLS) were observed between the treatment groups.

CONCLUSIONS

Among hypertensive patients with AV disease, intensive hypertensive therapy resulted in a significant reduction in LV hypertrophy, although progression of AV disease was similar between the treatment groups.

CLINICAL TRIAL REGISTRATION

http://ClinicalTrials.gov (Number NCT03666351).

Heart Failure with Improved Ejection Fraction: Insight into the Variable Nature of Left Ventricular Systolic Function

The progress of contemporary cardiovascular therapy has led to improved survival in patients with myocardial disease. However, the development of heart failure (HF) represents a common clinical challenge, regardless of the underlying myocardial pathology, due to the severely impaired quality of life and increased mortality comparable with malignant neoplasms. Left ventricular ejection fraction (LVEF) is the main index of systolic function and a key predictor of mortality among HF patients, hence its improvement represents the main indicator of response to instituted therapy. The introduction of complex pharmacotherapy for HF, increased availability of cardiac-implantable electronic devices and advances in the management of secondary causes of HF, including arrhythmia-induced cardiomyopathy, have led to significant increase in the proportion of patients with prominent improvement or even normalization of LVEF, paving the way for the identification of a new subgroup of HF with an improved ejection fraction (HFimpEF). Accumulating data has indicated that these patients share far better long-term prognoses than patients with stable or worsening LVEF. Due to diverse HF aetiology, the prevalence of HFimpEF ranges from roughly 10 to 40%, while the search for reliable predictors and genetic associations corresponding with this clinical presentation is under way. As contemporary guidelines focus mainly on the management of HF patients with clearly defined LVEF, the present review aimed to characterize the definition, epidemiology, predictors, clinical significance and principles of therapy of patients with HFimpEF.

Hypertension in aortic stenosis: a focused review and recommendations for clinical practice

: In patients with aortic stenosis, the presence of hypertension negatively affects the hemodynamic severity of the stenosis, and worsens adverse left ventricular remodeling. It accelerates the progression of the stenosis and is associated with worse prognosis. Proper management of hypertension is thus crucial but there are concerns about the safety and efficacy of antihypertensive medications as well as uncertainty about optimal blood pressure (BP) targets and their impact on left ventricular mass regression and survival benefits. In the present review, we discuss these issues based on the evidence available in the current literature. Focus is first directed on the consequences of a persistently elevated BP before and after surgical aortic valve replacement or transcatheter valve implantation, and the clinical significance of an abnormal BP response during exercise in patients with significant aortic stenosis. Available data on use of antihypertensive drugs are then critically addressed, the conclusion being that calcium channel blockers may be associated with lower survival, and that diuretics may have disadvantages in patients with left ventricular hypertrophy and smaller left ventricular cavity dimensions, β-blockers may be well tolerated and a better choice for patients with concomitant coronary artery disease and arrhythmias. Renin--angiotensin system blockers improve survival given either before or after valve intervention. Emphasis is placed on the fact that evidence is not derived from randomized trials but only from observational studies. Finally, we discuss the optimal SBP level to reach in patients with aortic stenosis. Again, randomized trials are not available but observational evidence suggests that values between 130 and 139 mmHg systolic and 70-90 mmHg diastolic might represent the best option, and lower BP targets should probably be avoided.

Microvascular disease in chronic kidney disease: the base of the iceberg in cardiovascular comorbidity

Chronic kidney disease (CKD) is a relentlessly progressive disease with a very high mortality mainly due to cardiovascular complications. Endothelial dysfunction is well documented in CKD and permanent loss of endothelial homeostasis leads to progressive organ damage. Most of the vast endothelial surface area is part of the microcirculation, but most research in CKD-related cardiovascular disease (CVD) has been devoted to macrovascular complications. We have reviewed all publications evaluating structure and function of the microcirculation in humans with CKD and animals with experimental CKD. Microvascular rarefaction, defined as a loss of perfused microvessels resulting in a significant decrease in microvascular density, is a quintessential finding in these studies. The median microvascular density was reduced by 29% in skeletal muscle and 24% in the heart in animal models of CKD and by 32% in human biopsy, autopsy and imaging studies. CKD induces rarefaction due to the loss of coherent vessel systems distal to the level of smaller arterioles, generating a typical heterogeneous pattern with avascular patches, resulting in a dysfunctional endothelium with diminished perfusion, shunting and tissue hypoxia. Endothelial cell apoptosis, hypertension, multiple metabolic, endocrine and immune disturbances of the uremic milieu and specifically, a dysregulated angiogenesis, all contribute to the multifactorial pathogenesis. By setting the stage for the development of tissue fibrosis and end organ failure, microvascular rarefaction is a principal pathogenic factor in the development of severe organ dysfunction in CKD patients, especially CVD, cerebrovascular dysfunction, muscular atrophy, cachexia, and progression of kidney disease. Treatment strategies for microvascular disease are urgently needed.

Stachydrine Ameliorates Cardiac Fibrosis Through Inhibition of Angiotensin II/Transformation Growth Factor β1 Fibrogenic Axis

Cardiovascular diseases, the leading cause of death worldwide, are tightly associated with the pathological myocardial fibrosis. Stachydrine (Sta), a major active compound in Chinese motherwort Leonurus heterophyllus, was reported to effectively attenuate cardiac fibrosis, but the cellular and molecular mechanism remains unclear. In this study, the anti-fibrotic effect of Sta and mechanism underlying were explored in a mouse model of pressure overload and AngII stimulated cardiac fibroblasts (CFs). Mice were randomly divided into sham, transverse aorta constriction with saline (TAC+Sal), TAC with telmisartan (TAC+Tel), and TAC with Sta (TAC+Sta) groups. Cardiac morphological and functional changes were evaluated by echocardiography and histological methods, and the molecular alterations were detected by western blotting. Primary cultured neonatal mouse CFs were treated with or without angiotensin II (AngII, 10⁻⁷ M), transformation growth factor β1 (TGFβ1, 10 ng/mL), and different dosage of Sta (10⁻⁶–10⁻⁴ M) for up to 96 h, and cell proliferation, cytotoxicity, morphology and related signals were also detected. The in vivo results revealed that TAC prominently induced cardiac dysfunction, left ventricular dilation, myocardial hypertrophy, and elevated myocardial collagen deposition, accompanied with increased fibrotic markers including α-smooth muscle actin (α-SMA) and periostin. However, Sta treatment partially reversed cardiac morphological and functional deteriorations, and significantly blunted cardiac fibrosis as well as Tel. Increments of myocardial angiotensinogen (AGT), angiotensin converting enzyme (ACE), AngII type 1 receptor (AT1R), and TGFβ1 transcripts, together with increased protein levels of ACE and AngII, after TAC were dramatically down-regulated by Sta treatment. Coincidently, in vitro experiments demonstrated that AngII stimulation in CFs led to up-regulation of AT1R and TGFβ1, and therefore promoted CFs trans-differentiating into hyper-activated myocardial fibroblasts (MFs) as evidenced by increased cell proliferation, collagen and fibrotic makers. On the contrary, Sta potently down-regulated but not directly inhibited AT1R, suppressed TGFβ1 production, and the pro-fibrotic effect of AngII in CFs. Moreover, activation of TGFβ1/Smads signal in the fibrotic process were observed both TAC model and in AngII stimulated CFs, which were also notably blunted by Sta. However, Sta failed to abolish the activation of CFs triggered by TGFβ1. Taken together, it was demonstrated in this study that Sta suppressed ACE/AngII/AT1R-TGFβ1 profibrotic axis, especially on the de novo production of AngII via down-regulating AGT/ACE and AT1R, and therefore inactivated CFs and blunted MFs transition, which ultimately prevented cardiac fibrosis.

Association of Renin-Angiotensin Inhibitor Treatment With Mortality and Heart Failure Readmission in Patients With Transcatheter Aortic Valve Replacement

IMPORTANCE

Data are lacking on the effect of a renin-angiotensin system (RAS) inhibitor prescribed after transcatheter aortic valve replacement (TAVR). Treatment with a RAS inhibitor may reverse left ventricular remodeling and improve function.

OBJECTIVE

To investigate the association of prescription of a RAS inhibitor and outcomes after TAVR.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study of TAVR procedures performed in the United States (using the Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapies Registry) between July 2014 and January 2016 that were linked to Medicare claims data (final date of follow-up: March 31, 2017). To account for differences in demographics, echocardiographic findings, and in-hospital complications, 1:1 propensity matching was performed.

EXPOSURES

Initial hospital discharge prescription of a RAS inhibitor after TAVR.

MAIN OUTCOMES AND MEASURES

Primary outcomes were all-cause death and readmission due to heart failure at 1 year after discharge, which were considered separately. The secondary outcome was health status assessed by the Kansas City Cardiomyopathy Questionnaire (KCCQ; score range: 0-100, with a higher score indicating less symptom burden and better quality of life; a small effect size was defined as 5 points) at 1 year.

RESULTS

Among 21 312 patients who underwent TAVR at 417 US sites, 8468 patients (39.7%) were prescribed a RAS inhibitor at hospital discharge. After propensity matching, 15 896 patients were included (mean [SD] age, 82.4 [6.8] years; 48.1% were women; mean [SD] left ventricular ejection fraction [LVEF], 51.9% [11.5%]). Patients with a prescription for a RAS inhibitor vs those with no prescription had lower mortality rates at 1 year (12.5% vs 14.9%, respectively; absolute risk difference [ARD], -2.4% [95% CI, -3.5% to -1.4%]; hazard ratio [HR], 0.82 [95% CI, 0.76 to 0.90]) and lower heart failure readmission rates at 1 year (12.0% vs 13.8%; ARD, -1.8% [95% CI, -2.8% to -0.7%]; HR, 0.86 [95% CI, 0.79 to 0.95]). When stratified by LVEF, having a prescription for a RAS inhibitor vs no prescription was associated with lower 1-year mortality among patients with preserved LVEF (11.1% vs 13.9%, respectively; ARD, -2.81% [95% CI, -3.95% to -1.67%]; HR, 0.78 [95% CI, 0.71 to 0.86]), but not among those with reduced LVEF (18.8% vs 19.5%; ARD, -0.68% [95% CI, -3.52% to 2.20%]; HR, 0.95 [95% CI, 0.81 to 1.12]) (P = .04 for interaction). Of 15 896 matched patients, 4837 (30.4%) were included in the KCCQ score analysis and improvements at 1 year were greater in patients with a prescription for a RAS inhibitor vs those with no prescription (median, 33.3 [interquartile range, 14.2 to 51.0] vs 31.3 [interquartile range, 13.5 to 51.1], respectively; difference in improvement, 2.10 [95% CI, 0.10 to 4.06]; P < .001), but the effect size was not clinically meaningful.

CONCLUSIONS AND RELEVANCE

Among patients who underwent TAVR, receiving a prescription for a RAS inhibitor at hospital discharge compared with no prescription was significantly associated with a lower risk of mortality and heart failure readmission. However, due to potential selection bias, this finding requires further investigation in randomized trials.

Effects of the angiotensin-converting enzyme inhibitor alacepril in dogs with mitral valve disease

Alacepril is a relatively novel angiotensin-converting enzyme inhibitor; however, the safety, tolerance, and efficacy of alacepril in terms of cough suppression in dogs with mitral valve disease (MVD) remain unknown. The aim of this study was to investigate the safety, tolerance, and cough suppression efficacy of alacepril in dogs with MVD. This was a multi-center, prospective study. Forty-two dogs with echocardiographic or radiographic evidence of cardiac enlargement in addition to cough were enrolled. Dogs were treated with alacepril (1.0-3.0 mg/kg/day) for at least 4 weeks. One dog (2.4%) developed complications, including appetite loss, lethargy, and vomiting. Thirty-six dogs were re-evaluated after 4 weeks of treatment. Cough resolved or improved in 20 dogs (55.6%) after treatment. Based on the efficacy of alacepril, the dogs were divided into an effective group (n=20) and an ineffective group (n=16). After treatment, the left ventricular end-diastolic internal diameter corrected for body weight was significantly increased from baseline in the ineffective group but was significantly decreased in the effective group. Univariate binomial logistic regression analyses showed that high atrial natriuretic peptide level, N-terminal pro-B-type natriuretic peptide level, and E wave velocity at baseline were significantly correlated with alacepril inefficacy. Alacepril as treatment for MVD is well tolerated in most dogs, and different conditions of cardiac loading may influence the effect of the drug. Alacepril is expected to improve the quality of life of dogs with early stage MVD.

Regulation of fibrosis in muscular dystrophy

The production of force and power are inherent properties of skeletal muscle, and regulated by contractile proteins within muscle fibers. However, skeletal muscle integrity and function also require strong connections between muscle fibers and their extracellular matrix (ECM). A well-organized and pliant ECM is integral to muscle function and the ability for many different cell populations to efficiently migrate through ECM is critical during growth and regeneration. For many neuromuscular diseases, genetic mutations cause disruption of these cytoskeletal-ECM connections, resulting in muscle fragility and chronic injury. Ultimately, these changes shift the balance from myogenic pathways toward fibrogenic pathways, culminating in the loss of muscle fibers and their replacement with fatty-fibrotic matrix. Hence a common pathological hallmark of muscular dystrophy is prominent fibrosis. This review will cover the salient features of muscular dystrophy pathogenesis, highlight the signals and cells that are important for myogenic and fibrogenic actions, and discuss how fibrosis alters the ECM of skeletal muscle, and the consequences of fibrosis in developing therapies.

Resolution of organ fibrosis

Fibrosis is the excessive accumulation of extracellular matrix that often occurs as a wound healing response to repeated or chronic tissue injury, and may lead to the disruption of organ architecture and loss of function. Although fibrosis was previously thought to be irreversible, recent evidence indicates that certain circumstances permit the resolution of fibrosis when the underlying causes of injury are eradicated. The mechanism of fibrosis resolution encompasses degradation of the fibrotic extracellular matrix as well as elimination of fibrogenic myofibroblasts through their adaptation of various cell fates, including apoptosis, senescence, dedifferentiation, and reprogramming. In this Review, we discuss the present knowledge and gaps in our understanding of how matrix degradation is regulated and how myofibroblast cell fates can be manipulated, areas that may identify potential therapeutic approaches for fibrosis.

Regression of Established Cardiac Fibrosis in Hypertensive Heart Disease

Established cardiac fibrosis (ECF) with symptomatic heart failure preserved ejection fraction represents an ever-increasing segment of the hypertensive population. The regression of ECF with attendant improvement in myocardial stiffness and symptomatic failure represents an unmet health care need. Is the regression of ECF in hypertensive heart disease feasible and will stiffness and symptomatic failure be improved? What is the cellular/molecular signaling involved in its regression? What incremental knowledge is needed to proceed effectively? These issues are addressed in this Review.

Microvascular ischemia in hypertrophic cardiomyopathy: new insights from high-resolution combined quantification of perfusion and late gadolinium enhancement

BACKGROUND

Microvascular ischemia is one of the hallmarks of hypertrophic cardiomyopathy (HCM) and has been associated with poor outcome. However, myocardial fibrosis, seen on cardiovascular magnetic resonance (CMR) as late gadolinium enhancement (LGE), can be responsible for rest perfusion defects in up to 30% of patients with HCM, potentially leading to an overestimation of the ischemic burden. We investigated the effect of left ventricle (LV) scar on the total LV ischemic burden using novel high-resolution perfusion analysis techniques in conjunction with LGE quantification.

METHODS

30 patients with HCM and unobstructed epicardial coronary arteries underwent CMR with Fermi constrained quantitative perfusion analysis on segmental and high-resolution data. The latter were corrected for the presence of fibrosis on a pixel-by-pixel basis.

RESULTS

High-resolution quantification proved more sensitive for the detection of microvascular ischemia in comparison to segmental analysis. Areas of LGE were associated with significant reduction of myocardial perfusion reserve (MPR) leading to an overestimation of the total ischemic burden on non-corrected perfusion maps. Using a threshold MPR of 1.5, the presence of LGE caused an overestimation of the ischemic burden of 28%. The ischemic burden was more severe in patients with fibrosis, also after correction of the perfusion maps, in keeping with more severe disease in this subgroup.

CONCLUSIONS

LGE is an important confounder in the assessment of the ischemic burden in patients with HCM. High-resolution quantitative analysis with LGE correction enables the independent evaluation of microvascular ischemia and fibrosis and should be used when evaluating patients with HCM.

Apocynin Attenuates Cardiac Injury in Type 4 Cardiorenal Syndrome via Suppressing Cardiac Fibroblast Growth Factor-2 With Oxidative Stress Inhibition

Background

Type 4 cardiorenal syndrome (CRS) refers to the cardiac injury induced by chronic kidney disease. We aimed to assess oxidative stress and cardiac injury in patients with type 4 CRS, determine whether the antioxidant apocynin attenuated cardiac injury in rats with type 4 CRS, and explore potential mechanisms.

Methods and Results

A cross-sectional study was conducted among patients with type 4 CRS (n=17) and controls (n=16). Compared with controls, patients with type 4 CRS showed elevated oxidative stress, which was significantly correlated with cardiac hypertrophy and decreased ejection fraction. In vivo study, male Sprague-Dawley rats underwent 5/6 subtotal nephrectomy and sham surgery, followed with apocynin or vehicle treatment for 8 weeks. Eight weeks after surgery, the 5/6 subtotal nephrectomy rats mimicked type 4 CRS, showing increased serum creatinine, cardiac hypertrophy and fibrosis, and decreased ejection fraction compared with sham-operated animals. Cardiac malondialdehyde, NADPH oxidase activity, fibroblast growth factor-2, and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation increased significantly in the 5/6 subtotal nephrectomy rats. These changes were significantly attenuated by apocynin. In vitro study showed that apocynin reduced angiotensin II–induced NADPH oxidase–dependent oxidative stress, upregulation of fibroblast growth factor-2 and fibrosis biomarkers, and ERK1/2 phosphorylation in cardiac fibroblasts. Importantly, the ERK1/2 inhibitor U0126 reduced the upregulation of fibroblast growth factor-2 and fibrosis biomarkers in angiotensin II–treated fibroblasts.

Conclusions

Oxidative stress is a candidate mediator for type 4 CRS. Apocynin attenuated cardiac injury in type 4 CRS rats via inhibiting NADPH oxidase–dependent oxidative stress-activated ERK1/2 pathway and subsequent fibroblast growth factor-2 upregulation. Our study added evidence to the beneficial effect of apocynin in type 4 CRS.

Long-term effects of ACE inhibitor on vascular remodelling

The long-term pathomorphological changes of the injured vessels under angiotensin-converting-enzyme (ACE) inhibitor are still not known. Therefore, we assessed the alternations of vascular architecture after three-month therapy with ACE inhibitor and identified new target cells for this medication. Carotid arteries of spontaneously hypertensive rats underwent balloon angioplasty. 14 days prior intervention, half of the animals was treated with ACE inhibitor. After three months of vascular trauma, the injured vessels were explored by histomorphology and immunohistochemistry for angiotensin-II receptor (AT1R), dendritic and HSP47+ cells. The neointimal growth decreased significantly only up to 28 days under ACE inhibitor. In contrast, the reductive effect of ACE inhibitor on media area persisted up to three months after intervention. A significant fraction of early neointimal cells was of a dendritic cell type. The relevant portion of these cells showed an expression of AT1R and HSP47. AT1R was present in 70% and HSP47 in 18% of all early neointimal cells in both groups. ACE inhibitor may at least temporarily diminish remodelling processes in injured vessels. The detection of AT1R on dendritic cells identifies these cells as important targets for therapeutic strategies involving modulation of the renin-angiotensin system.

The biological significance of angiotensin-converting enzyme inhibition to combat kidney fibrosis

Both angiotensin-converting enzyme inhibitor (ACE-I) and angiotensin II receptor blocker have been recognized as renin-angiotensin system (RAS) inhibitors. These two RAS inhibitors are rarely recognized as drugs with distinct pharmacological effects in the clinic or most clinical trials. Some preclinical basic research and clinical trials indicate that ACE-I might display superior organ-protective effects, especially anti-fibrotic effects. Such anti-fibrotic effects of ACE-I could be associated with an endogenous anti-fibrotic peptide, N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP). In this review, we focused on the anti-fibrotic effects of RAS inhibition and the endogenous anti-fibrotic peptide AcSDKP.

Paricalcitol downregulates myocardial renin-angiotensin and fibroblast growth factor expression and attenuates cardiac hypertrophy in uremic rats

BACKGROUND

Vitamin D attenuates uremic cardiac hypertrophy, possibly by suppressing the myocardial renin-angiotensin system (RAS) and fibroblast growth factors (FGFs). We compared the suppression of cardiac hypertrophy and myocardial expression of RAS and FGF receptor genes offered by the vitamin D analog paricalcitol (Pc) or the angiotensin-converting enzyme inhibitor enalapril (E) in experimental uremia.

METHODS

Rats with 5/6 nephrectomy received Pc or E for 8 weeks. Renal function, systolic blood pressure, and cardiac hypertrophy were evaluated. Myocardial expression of RAS genes, brain natriuretic peptide (BNP), and FGF receptor-1 (FGFR-1) were determined using quantitative reverse-transcription (pRT)-PCR.

RESULTS

Blood pressure, proteinuria, and serum creatinine were significantly higher in untreated uremic animals. Hypertension was significantly reduced by E but only modestly by Pc; however, cardiac hypertrophy in the untreated group was similarly attenuated by Pc or E. Upregulation of myocardial expressions of renin, angiotensinogen, FGFR-1, and BNP in untreated uremic animals was reduced similarly by Pc and E, while the angiotensin II type 1 receptor was downregulated only by E.

CONCLUSIONS

Uremic cardiac hypertrophy is associated with activation of the myocardial RAS and the FGFR-1. Downregulation of these genes induced by Pc and E results in similar amelioration of left ventricular hypertrophy despite the different antihypertensive effects of these drugs.

Speckle tracking echocardiography detects uremic cardiomyopathy early and predicts cardiovascular mortality in ESRD

Cardiovascular mortality is high in ESRD, partly driven by sudden cardiac death and recurrent heart failure due to uremic cardiomyopathy. We investigated whether speckle-tracking echocardiography is superior to routine echocardiography in early detection of uremic cardiomyopathy in animal models and whether it predicts cardiovascular mortality in patients undergoing dialysis. Using speckle-tracking echocardiography in two rat models of uremic cardiomyopathy soon (4-6 weeks) after induction of kidney disease, we observed that global radial and circumferential strain parameters decreased significantly in both models compared with controls, whereas standard echocardiographic readouts, including fractional shortening and cardiac output, remained unchanged. Furthermore, strain parameters showed better correlations with histologic hallmarks of uremic cardiomyopathy. We then assessed echocardiographic and clinical characteristics in 171 dialysis patients. During the 2.5-year follow-up period, ejection fraction and various strain parameters were significant risk factors for cardiovascular mortality (primary end point) in a multivariate Cox model (ejection fraction hazard ratio [HR], 0.97 [95% confidence interval (95% CI), 0.95 to 0.99; P=0.012]; peak global longitudinal strain HR, 1.17 [95% CI, 1.07 to 1.28; P<0.001]; peak systolic and late diastolic longitudinal strain rates HRs, 4.7 [95% CI, 1.23 to 17.64; P=0.023] and 0.25 [95% CI, 0.08 to 0.79; P=0.02], respectively). Multivariate Cox regression analysis revealed circumferential early diastolic strain rate, among others, as an independent risk factor for all-cause mortality (secondary end point; HR, 0.43; 95% CI, 0.25 to 0.74; P=0.002). Together, these data support speckle tracking as a postprocessing echocardiographic technique to detect uremic cardiomyopathy and predict cardiovascular mortality in ESRD.

Pediatric cardiomyopathies: causes, epidemiology, clinical course, preventive strategies and therapies

Pediatric cardiomyopathies, which are rare but serious disorders of the muscles of the heart, affect at least one in every 100,000 children in the USA. Approximately 40% of children with symptomatic cardiomyopathy undergo heart transplantation or die from cardiac complications within 2 years. However, a significant number of children suffering from cardiomyopathy are surviving into adulthood, making it an important chronic illness for both pediatric and adult clinicians to understand. The natural history, risk factors, prevalence and incidence of this pediatric condition were not fully understood before the 1990s. Questions regarding optimal diagnostic, prognostic and treatment methods remain. Children require long-term follow-up into adulthood in order to identify the factors associated with best clinical practice including diagnostic approaches, as well as optimal treatment approaches. In this article, we comprehensively review current research on various presentations of this disease, along with current knowledge about their causes, treatments and clinical outcomes.

Myocardial T1 mapping and extracellular volume quantification: a Society for Cardiovascular Magnetic Resonance (SCMR) and CMR Working Group of the European Society of Cardiology consensus statement

Rapid innovations in cardiovascular magnetic resonance (CMR) now permit the routine acquisition of quantitative measures of myocardial and blood T1 which are key tissue characteristics. These capabilities introduce a new frontier in cardiology, enabling the practitioner/investigator to quantify biologically important myocardial properties that otherwise can be difficult to ascertain clinically. CMR may be able to track biologically important changes in the myocardium by: a) native T1 that reflects myocardial disease involving the myocyte and interstitium without use of gadolinium based contrast agents (GBCA), or b) the extracellular volume fraction (ECV)-a direct GBCA-based measurement of the size of the extracellular space, reflecting interstitial disease. The latter technique attempts to dichotomize the myocardium into its cellular and interstitial components with estimates expressed as volume fractions. This document provides recommendations for clinical and research T1 and ECV measurement, based on published evidence when available and expert consensus when not. We address site preparation, scan type, scan planning and acquisition, quality control, visualisation and analysis, technical development. We also address controversies in the field. While ECV and native T1 mapping appear destined to affect clinical decision making, they lack multi-centre application and face significant challenges, which demand a community-wide approach among stakeholders. At present, ECV and native T1 mapping appear sufficiently robust for many diseases; yet more research is required before a large-scale application for clinical decision-making can be recommended.

Oxidative stress, fibrosis, and early afterdepolarization-mediated cardiac arrhythmias

Animal and clinical studies have demonstrated that oxidative stress, a common pathophysiological factor in cardiac disease, reduces repolarization reserve by enhancing the L-type calcium current, the late Na, and the Na-Ca exchanger, promoting early afterdepolarizations (EADs) that can initiate ventricular tachycardia and ventricular fibrillation (VT/VF) in structurally remodeled hearts. Increased ventricular fibrosis plays a key facilitatory role in allowing oxidative-stress induced EADs to manifest as triggered activity and VT/VF, since normal non-fibrotic hearts are resistant to arrhythmias when challenged with similar or higher levels of oxidative stress. The findings imply that antifibrotic therapy, in addition to therapies designed to suppress EAD formation at the cellular level, may be synergistic in reducing the risk of sudden cardiac death.

Differential Ly-6C expression identifies the recruited macrophage phenotype, which orchestrates the regression of murine liver fibrosis

Although macrophages are widely recognized to have a profibrotic role in inflammation, we have used a highly tractable CCl(4)-induced model of reversible hepatic fibrosis to identify and characterize the macrophage phenotype responsible for tissue remodeling: the hitherto elusive restorative macrophage. This CD11B(hi) F4/80(int) Ly-6C(lo) macrophage subset was most abundant in livers during maximal fibrosis resolution and represented the principle matrix metalloproteinase (MMP) -expressing subset. Depletion of this population in CD11B promoter-diphtheria toxin receptor (CD11B-DTR) transgenic mice caused a failure of scar remodeling. Adoptive transfer and in situ labeling experiments showed that these restorative macrophages derive from recruited Ly-6C(hi) monocytes, a common origin with profibrotic Ly-6C(hi) macrophages, indicative of a phenotypic switch in vivo conferring proresolution properties. Microarray profiling of the Ly-6C(lo) subset, compared with Ly-6C(hi) macrophages, showed a phenotype outside the M1/M2 classification, with increased expression of MMPs, growth factors, and phagocytosis-related genes, including Mmp9, Mmp12, insulin-like growth factor 1 (Igf1), and Glycoprotein (transmembrane) nmb (Gpnmb). Confocal microscopy confirmed the postphagocytic nature of restorative macrophages. Furthermore, the restorative macrophage phenotype was recapitulated in vitro by the phagocytosis of cellular debris with associated activation of the ERK signaling cascade. Critically, induced phagocytic behavior in vivo, through administration of liposomes, increased restorative macrophage number and accelerated fibrosis resolution, offering a therapeutic strategy to this orphan pathological process.

Liver fibrosis: a bidirectional model of fibrogenesis and resolution

Liver fibrosis is the generic response to chronic injury of varying aetiologies. A number of common mechanisms link this response to the pathogenesis of fibrosis in other organs. While long thought to be relentlessly progressive, there is now excellent evidence in both human liver disease and animal models that hepatic fibrosis is potentially reversible. The liver therefore provides an excellent bidirectional model for the study of fibrogenesis and fibrosis resolution. In this article, we will review the evidence for the reversibility of liver fibrosis. We will highlight some of the mechanisms responsible for fibrogenesis and fibrosis regression, focussing on the role of hepatic myofibroblast activation and apoptosis, the importance of matrix metalloproteinases and their tissue inhibitors and the central involvement of hepatic macrophages in orchestrating this process. Finally, we will briefly discuss what renders liver fibrosis irreversible and how this accumulating knowledge base could lead to badly needed anti-fibrotic therapies in the future.

Inhibition of signal transducer and activator of transcription 3 (STAT3) attenuates interleukin-6 (IL-6)-induced collagen synthesis and resultant hypertrophy in rat heart

IL-6 has been shown to play a major role in collagen up-regulation process during cardiac hypertrophy, although the precise mechanism is still not known. In this study we have analyzed the mechanism by which IL-6 modulates cardiac hypertrophy. For the in vitro model, IL-6-treated cultured cardiac fibroblasts were used, whereas the in vivo cardiac hypertrophy model was generated by renal artery ligation in adult male Wistar rats (Rattus norvegicus). During induction of hypertrophy, increased phosphorylation of STAT1, STAT3, MAPK, and ERK proteins was observed both in vitro and in vivo. Treatment of fibroblasts with specific inhibitors for STAT1 (fludarabine, 50 μM), STAT3 (S31-201, 10 μM), p38 MAPK (SB203580, 10 μM), and ERK1/2 (U0126, 10 μM) resulted in down-regulation of IL-6-induced phosphorylation of specific proteins; however, only S31-201 and SB203580 inhibited collagen biosynthesis. In ligated rats in vivo, only STAT3 inhibitors resulted in significant decrease in collagen synthesis and hypertrophy markers such as atrial natriuretic factor and β-myosin heavy chain. In addition, decreased heart weight to body weight ratio and improved cardiac function as measured by echocardiography was evident in animals treated with STAT3 inhibitor or siRNA. Compared with IL-6 neutralization, more pronounced down-regulation of collagen synthesis and regression of hypertrophy was observed with STAT3 inhibition, suggesting that STAT3 is the major downstream signaling molecule and a potential therapeutic target for cardiac hypertrophy.

Elevation of the antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline: a blood pressure-independent beneficial effect of angiotensin I-converting enzyme inhibitors

Blockade of the renin-angiotensin system (RAS) is well recognized as an essential therapy in hypertensive, heart, and kidney diseases. There are several classes of drugs that block the RAS; these drugs are known to exhibit antifibrotic action. An analysis of the molecular mechanisms of action for these drugs can reveal potential differences in their antifibrotic roles. In this review, we discuss the antifibrotic action of RAS blockade with an emphasis on the potential importance of angiotensin I-converting enzyme (ACE) inhibition associated with the antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP).

Targeting cardiac fibrosis: a new frontier in antiarrhythmic therapy?

Cardiac fibrosis is known to alter cardiac conduction and promote reentry. Recent evidence indicates that fibrosis characterized by increased interstitial collagen accumulation and increased myofibroblast proliferation also promotes enhanced automaticity and early afterdepolarizations (EADs) causing triggered activity. Fibrosis then becomes an effective therapeutic target for the management of lethal cardiac arrhythmias. While oxidative stress with hydrogen peroxide (H(2)O(2)) is shown to readily promote EADs and triggered activity in isolated rat and rabbit ventricular myocytes however, this same stress fails to cause EADs in well-coupled, non-fibrotic hearts due to source-to-sink mismatches arising from cell-to-cell coupling. The triggered activity in the aged fibrotic hearts causes focal ventricular tachycardia (VT) that degenerates within seconds to ventricular fibrillation (VF) after the emergence of spatially discordant action potential duration alternans leading to wavebreak, reentry and VF. Computer simulations in 2D tissue incorporating variable degrees of fibrosis showed that intermediate (but not mild or very severe) fibrosis promoted EADs and TA. Human studies have shown that myocardial fibrosis was an independent predictor for arrhythmias including sustained VT and VF. A variety of drug classes including, torsemide, a loop diuretic, that inhibits the enzyme involved in the myocardial extracellular generation of collagen type I molecules and the inhibitors of the renin-angiotensin-aldosterone system (RAAS), the mineralocorticoid receptors and endothelin receptors reduce cardiac fibrosis with reduction of myocardial stiffness and improved ventricular function. It is hoped that in the near future effective antifibrotic drug regimen would be developed to reduce the risk of fibrosis related VT and VF.