Cardiomyocyte hypertrophy, oncosis, and autophagic vacuolization predict mortality in idiopathic dilated cardiomyopathy with advanced heart failure

Progressive Left Ventricular Remodeling for Predicting Mortality in Children With Dilated Cardiomyopathy: The Pediatric Cardiomyopathy Registry

BACKGROUND

Pediatric dilated cardiomyopathy often leads to death or cardiac transplantation. We sought to determine whether changes in left ventricular (LV) end-diastolic dimension (LVEDD), LV end-diastolic posterior wall thickness, and LV fractional shortening (LVFS) over time may help predict adverse outcomes.

METHODS AND RESULTS

We studied children up to 18 years old with dilated cardiomyopathy, enrolled between 1990 and 2009 in the Pediatric Cardiomyopathy Registry. Changes in LVFS, LVEDD, LV end-diastolic posterior wall thickness, and the LV end-diastolic posterior wall thickness:LVEDD ratio between baseline and follow-up echocardiograms acquired ≈1 year after diagnosis were determined for children who, at the 1-year follow-up had died, received a heart transplant, or were alive and transplant-free. Within 1 year after diagnosis, 40 (5.0%) of the 794 eligible children had died, 117 (14.7%) had undergone cardiac transplantation, and 585 (73.7%) had survived without transplantation. At diagnosis, survivors had higher median LVFS and lower median LVEDD Z scores. Median LVFS and LVEDD Z scores improved among survivors (Z score changes of +2.6 and -1.1, respectively) but remained stable or worsened in the other 2 groups. The LV end-diastolic posterior wall thickness:LVEDD ratio increased in survivors only, suggesting beneficial reverse LV remodeling. The risk for death or cardiac transplantation up to 7 years later was lower when LVFS was improved at 1 year (hazard ratio [HR], 0.83; P=0.004) but was higher in those with progressive LV dilation (HR, 1.45; P<0.001).

CONCLUSIONS

Progressive deterioration in LV contractile function and increasing LV dilation are associated with both early and continuing mortality in children with dilated cardiomyopathy. Serial echocardiographic monitoring of these children is therefore indicated.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT00005391.

Remodeling of Cardiomyocytes: Study of Morphological Cellular Changes Preceding Symptomatic Ischemic Heart Failure

Although major pathogenesis mechanisms of heart failure (HF) are well established, the significance of early (mal)adaptive structural changes of cardiomyocytes preceding symptomatic ischemic HF remains ambiguous. The aim of this study is to present the morphological characterization of changes in cardiomyocytes and their reorganization of intermediate filaments during remodeling preceding symptomatic ischemic HF in an adult human heart. A total of 84 myocardial tissue samples from middle-left heart ventricular segments were analyzed histomorphometrically and immunohistochemically, observing the cardiomyocyte's size, shape, and desmin expression changes in the remodeling process: Stage A of HF, Stage B of HF, and Stages C/D of HF groups (ACC/AHA classification). Values p < 0.05 were considered significant. The cellular length, diameter, and volume of Stage A of HF increased predominantly by the diameter vs. the control group (p < 0.001) and continued to increase in Stage B of HF in a similar pattern (p < 0.001), increasing even more in the C/D Stages of HF predominantly by length (p < 0.001). Desmin expression was increased in Stage A of HF vs. the control group (p < 0.001), whereas it was similar in Stages A and B of HF (p > 0.05), and most intense in Stages C/D of HF (p < 0.001). Significant morphological changes of cardiomyocytes and their cytoskeletal reorganization were observed during the earliest remodeling events preceding symptomatic ischemic HF.

Relationship Between Results of Pathological Evaluation of Endomyocardial Biopsy and Echocardiographic Indices in Patients With Non-Ischemic Cardiomyopathy

Background: Endomyocardial biopsy (EMB) is a useful modality in diagnosing the origin of cardiomyopathy and the condition of the impaired myocardium. However, the usefulness of obtaining an EMB from the right and left ventricles (RV and LV, respectively), and its associations with echocardiographic parameters, have not been explored. Methods and Results: Ninety-five consecutive patients with non-ischemic cardiomyopathy excluding myocarditis who underwent EMB between July 2017 and May 2019 were studied. Seventy-nine RV and 93 LV biopsy specimens were pathologically analyzed. The relationships among echocardiographic data before EMB and pathologically measured cardiomyocyte diameter (CMD) and interstitial fibrosis (IF) were evaluated. CMD in both LV and RV specimens correlated with echocardiographic LV morphology, but only CMD in the LV was significantly correlated with cardiac function evaluation, including LV ejection fraction, E' and E/E'. In contrast, there were no significant correlations between IF in either the LV or RV and any echocardiographic parameters measured. Furthermore, CMD of both ventricles was significantly correlated with B-type natriuretic peptide (BNP) concentration at EMB, whereas IF of the LV was barely related and IF of the RV was not significantly correlated with BNP concentrations. Conclusions: Pathologically evaluated CMD of EMB specimens of the LV may be more related to functional parameters for heart failure status and LV geometry on echocardiographic examination, than IF.

Chronic high‑salt intake induces cardiomyocyte autophagic vacuolization during left ventricular maladaptive remodeling in spontaneously hypertensive rats

The role of autophagy in high-salt (HS) intake associated hypertensive left ventricular (LV) remodeling remains unclear. The present study investigated the LV autophagic change and its association with the hypertensive LV remodeling induced by chronic HS intake in spontaneously hypertensive rats (SHR). Wistar Kyoto (WKY) rats and SHR were fed low-salt (LS; 0.5% NaCl) and HS (8.0% NaCl) diets and were subjected to invasive LV hemodynamic analysis after 8, 12 and 16 weeks of dietary intervention. Reverse transcription-quantitative PCR and western blot analysis were performed to investigate the expression of autophagy-associated key components. The LV morphologic staining was performed at the end of the study. The rat H9c2 ventricular myoblast cell-associated experiments were performed to explore the mechanism of HS induced autophagic change. A global autophagy-associated key component, as well as increased cardiomyocyte autophagic vacuolization, was observed after 12 weeks of HS intake. During this period, the heart from HS-diet-fed SHR exhibited a transition from compensated LV hypertrophy to decompensation, as shown by progressive impairment of LV function and interstitial fibrosis. Myocardial extracellular [Na⁺] and the expression of tonicity-responsive enhancer binding protein (TonEBP) was significantly increased in HS-fed rats, indicating myocardial interstitial hypertonicity by chronic HS intake. The global autophagic change and overt deterioration of LV function were not observed in LS-fed SHR and HS-fed WKY rats. The study of rat H9c2 cardiomyocytes demonstrated a cytosolic [Na⁺] elevation-mediated, reactive oxygen species-dependent the autophagic change occurred when exposed to an increased extracellular [Na⁺]. The present findings demonstrated that a myocardial autophagic change participates in the maladaptive LV remodeling induced by chronic HS intake in SHR, which provides a possible target for future intervention studies on HS-induced hypertensive LV remodeling.

Echocardiography phenotyping in murine genetic reference population of BXD strains reveals significant QTLs associated with cardiac function and morphology

The genetic reference population of recombinant inbred BXD mice has been derived from crosses between C57BL/6J and DBA/2J strains. The DBA/2J parent exhibits cardiomyopathy phenotypes, whereas C57BL/6J has normal heart. BXD mice are sequenced for studying genetic interactions in cardiomyopathies. The study aimed to assess cardiomyopathy traits in BXDs and investigate the quantitative genetic architecture of those traits. Echocardiography, blood pressure, and cardiomyocyte size parameters obtained from 44 strains of BXD family (n > 5/sex) at 4-5 mo of age were associated with heart transcriptomes and expression quantitative trait loci (eQTL) mapping was performed. More than twofold variance in ejection fraction (EF%), fractional shortening (FS%), left ventricular volumes (LVVols), internal dimensions (LVIDs), mass (LVM), and posterior wall (LVPW) thickness was found among BXDs. In male BXDs, eQTL mapping identified Ndrg4 on chromosome 8 QTL to be positively correlated with LVVol and LVID and negatively associated with cardiomyocyte diameter. In female BXDs, significant QTLs were found on chromosomes 7 and 3 to be associated with LVPW and EF% and FS%, respectively, and Josd2, Dap3, and Tpm3 were predicted as strong candidate genes. Our study found variable cardiovascular traits among BXD strains and identified multiple associated QTLs, suggesting an influence of genetic background on expression of echocardiographic and cardiomyocyte diameter traits. Increased LVVol and reduced EF% and FS% represented dilated cardiomyopathy, whereas increased LV mass and wall thickness indicated hypertrophic cardiomyopathy traits. The BXD family is ideal for identifying candidate genes, causal and modifier, that influence cardiovascular phenotypes.NEW & NOTEWORTHY This study aimed to establish a cardiac phenotype-genotype correlation in murine genetic reference population of BXD RI strains by phenotyping the echocardiography, blood pressure, and cardiomyocyte diameter traits and associating each collected phenotype with genetic background. Our study identified several QTLs and candidate genes that have significant association with cardiac hypertrophy, ventricular dilation, and function including systolic hyperfunction and dysfunction.

Nuclear translocation of MLKL enhances necroptosis by a RIP1/RIP3-independent mechanism in H9c2 cardiomyoblasts

Accumulating evidence suggests that necroptosis of cardiomyocytes contributes to cardiovascular diseases. Lethal disruption of the plasma membrane in necroptosis is induced by oligomers of mixed lineage kinase domain-like (MLKL) that is translocated to the membrane from the cytosol. However, the role played by cytoplasmic-nuclear shuttling of MLKL is unclear. Here, we tested the hypothesis that translocation of MLKL to the nucleus promotes the necroptosis of cardiomyocytes. Activation of the canonical necroptotic signaling pathway by a combination of TNF-α and zVAD (TNF/zVAD) increased nuclear MLKL levels in a RIP1-activity-dependent manner in H9c2 cells, a rat cardiomyoblast cell line. By use of site-directed mutagenesis, we found a nuclear export signal sequence in MLKL and prepared its mutant (MLKL-L280/283/284A), though a search for a nuclear import signal was unsuccessful. MLKL-L280/283/284A localized to both the cytosol and the nucleus. Expression of MLKL-L280/283/284A induced necroptotic cell death, which was attenuated by GppNHp, an inhibitor of Ran-mediated nuclear import, but not by inhibition of RIP1 activity or knockdown of RIP3 expression. GppNHp partly suppressed H9c2 cell death induced by TNF/zVAD treatment. These results suggest that MLKL that is translocated to the nucleus via RIP1-mediated necroptotic signaling enhances the necroptosis of cardiomyocytes through a RIP1-/RIP3-independent mechanism.

Enhanced nuclear localization of phosphorylated MLKL predicts adverse events in patients with dilated cardiomyopathy

AIMS

The role of necroptosis in dilated cardiomyopathy (DCM) remains unclear. Here, we examined whether phosphorylation of mixed lineage kinase domain-like protein (MLKL), an indispensable event for execution of necroptosis, is associated with the progression of DCM.

METHODS AND RESULTS

Patients with DCM (n = 56, 56 ± 15 years of age; 68% male) were enrolled for immunohistochemical analyses of biopsies. Adverse events were defined as a composite of death or admission for heart failure or ventricular arrhythmia. Compared with the normal myocardium, increased signals of MLKL phosphorylation were detected in the nuclei, cytoplasm, and intercalated discs of cardiomyocytes in biopsy samples from DCM patients. The phosphorylated MLKL (p-MLKL) signal was increased in enlarged nuclei or nuclei with bizarre shapes in hypertrophied cardiomyocytes. Nuclear p-MLKL level was correlated negatively with septal peak myocardial velocity during early diastole (r = -0.327, P = 0.019) and was correlated positively with tricuspid regurgitation pressure gradient (r = 0.339, P = 0.023), while p-MLKL level in intercalated discs was negatively correlated with mean left ventricular wall thickness (r = -0.360, P = 0.014). During a median follow-up period of 3.5 years, 10 patients (18%) had adverse events. To examine the difference in event rates according to p-MLKL expression levels, patients were divided into two groups by using the median value of nuclear p-MLKL or intercalated disc p-MLKL. A group with high nuclear p-MLKL level (H-nucMLKL group) had a higher adverse event rate than did a group with low nuclear p-MLKL level (L-nucMLKL group) (32% vs. 4%, P = 0.012), and Kaplan-Meier survival curves showed that the adverse event-free survival rate was lower in the H-nucMLKL group than in the L-nucMLKL group (P = 0.019 by the log-rank test). Such differences were not detected between groups divided by a median value of intercalated disc p-MLKL. In δ-sarcoglycan-deficient (Sgcd-/- ) mice, a model of DCM, total p-MLKL and nuclear p-MLKL levels were higher than in wild-type mice.

CONCLUSION

The results suggest that increased localization of nuclear p-MLKL in cardiomyocytes is associated with left ventricular diastolic dysfunction and future adverse events in DCM.

Asthma can Promote Cardiomyocyte Mitophagy in a Rat Model

Clinical observations have shown the risk of cardiovascular disease during asthmatic changes. Whether and how asthma causes heart failure is the subject of debate. Here, we aimed to investigate the possibility of cardiomyocyte mitophagy in a rat model of asthma. Twelve mature Wistar rats were randomly allocated into the Control and Asthmatic rats (n = 6). To induce asthma, ovalbumin was injected intraperitoneally on days 1 and 8 and procedure followed by nebulization from days 14 to 32. After 2 weeks, we performed the pathological examination of both lungs and heart using Hematoxylin-Eosin staining. Real-time PCR analysis was used to measure the expression of mitophagic factors, such as Optineurin, Pink1, and mitofusin 1 and 2. Typical changes like increased inter-alveolar septa thickness and interstitial pneumonia were evident in asthmatic lungs. In cardiac tissue, slight inflammatory response, and hydropic degeneration with an eosinophilic appearance were detected in the cytoplasm of cardiomyocytes. Real-time PCR analysis showed mitophagic response in pulmonary and cardiac tissues via upregulation of mitophagy-related genes like Optineurin and Pink-1 in asthmatic lungs and hearts compared to the control group (p < 0.05). Likewise, asthmatic changes increased the expression of genes associated with mitochondrial fusion in the lungs and heart. The expression of mitofusin1 and 2 was significantly increased following inflammatory response in pulmonary and cardiac tissues (p < 0.05). Our findings showed the expression of certain factors related to mitophagy during chronic asthmatic conditions. The findings open a new avenue in the understanding of cardiomyocyte injury during asthma.

The Role of Circulating Collagen Turnover Biomarkers and Late Gadolinium Enhancement in Patients with Non-Ischemic Dilated Cardiomyopathy

Background: Myocardial scarring is a primary pathogenetic process in nonischemic dilated cardiomyopathy (NIDCM) that is responsible for progressive cardiac remodeling and heart failure, severely impacting the survival of these patients. Although several collagen turnover biomarkers have been associated with myocardial fibrosis, their clinical utility is still limited. Late gadolinium enhancement (LGE) determined by cardiac magnetic resonance imaging (CMR) has become a feasible method to detect myocardial replacement fibrosis. We sought to evaluate the association between collagen turnover biomarkers and replacement myocardial scarring by CMR and, also, to test their ability to predict outcome in conjunction with LGE in patients with NIDCM. Method: We conducted a prospective study on 194 patients (48.7 ± 14.3 years of age; 74% male gender) with NIDCM. The inclusion criteria were similar to those for the definition of NIDCM, performed exclusively by CMR: (1) LV dilation with an LV end-diastolic volume (LVEDV) of over 97 mL/m2; (2) global LV dysfunction, expressed as a decreased LVEF of under 45%. CMR was used to determine the presence and extent of LGE. Several collagen turnover biomarkers were determined at diagnosis, comprising galectin-3 (Gal3), procollagen type I carboxy-terminal pro-peptide (PICP) and N-terminal pro-peptide of procollagen type III (PIIINP). A composite outcome (all-cause mortality, ventricular tachyarrhythmias, heart failure hospitalization) was ascertained over a median of 26 months. Results: Gal3, PICP and PIIINP were considerably increased in those with LGE+ (p < 0.001), also being directly correlated with LGE mass (r2 = 0.42; r2 = 0.44; r2 = 0.31; all p < 0.001). Receiver operating characteristic (ROC) analysis revealed a significant ability to diagnose LGE, with an area under the ROC of 0.816 for Gal3, 0.705 for PICP, and 0.757 for PIIINP (all p < 0.0001). Kaplan−Meier analysis showed that at a threshold of >13.8 ng/dL for Gal3 and >97 ng/dL for PICP, they were able to significantly predict outcome (HR = 2.66, p < 0.001; HR = 1.93, p < 0.002). Of all patients, 17% (n = 33) reached the outcome. In multivariate analysis, after adjustment for covariates, only LGE+ and Gal3+ remained independent predictors for outcome (p = 0.008; p = 0.04). Nonetheless, collagen turnover biomarkers were closely related to HF severity, providing incremental predictive value for severely decreased LVEF of under 30% in patients with NIDCM, beyond that with LGE alone. Conclusions: In patients with NIDCM, circulating collagen turnover biomarkers such as Gal3, PICP and PIIINP are closely related to the presence and extent of LGE and can significantly predict cardiovascular outcome. The joint use of LGE with Gal3 and PICP significantly improved outcome prediction.

The combination of carboxy-terminal propeptide of procollagen type I blood levels and late gadolinium enhancement at cardiac magnetic resonance provides additional prognostic information in idiopathic dilated cardiomyopathy - A multilevel assessment of myocardial fibrosis in dilated cardiomyopathy

Aims

To determine the prognostic value of multilevel assessment of fibrosis in dilated cardiomyopathy (DCM) patients.

Methods and results

We quantified fibrosis in 209 DCM patients at three levels: (i) non‐invasive late gadolinium enhancement (LGE) at cardiac magnetic resonance (CMR); (ii) blood biomarkers [amino‐terminal propeptide of procollagen type III (PIIINP) and carboxy‐terminal propeptide of procollagen type I (PICP)], (iii) invasive endomyocardial biopsy (EMB) (collagen volume fraction, CVF). Both LGE and elevated blood PICP levels, but neither PIIINP nor CVF predicted a worse outcome defined as death, heart transplantation, heart failure hospitalization, or life‐threatening arrhythmias, after adjusting for known clinical predictors [adjusted hazard ratios: LGE 3.54, 95% confidence interval (CI) 1.90–6.60; P < 0.001 and PICP 1.02, 95% CI 1.01–1.03; P = 0.001]. The combination of LGE and PICP provided the highest prognostic benefit in prediction (likelihood ratio test P = 0.007) and reclassification (net reclassification index: 0.28, P = 0.02; and integrated discrimination improvement index: 0.139, P = 0.01) when added to the clinical prediction model. Moreover, patients with a combination of LGE and elevated PICP (LGE+/PICP+) had the worst prognosis (log‐rank P < 0.001). RNA‐sequencing and gene enrichment analysis of EMB showed an increased expression of pro‐fibrotic and pro‐inflammatory pathways in patients with high levels of fibrosis (LGE+/PICP+) compared to patients with low levels of fibrosis (LGE‐/PICP‐). This would suggest the validity of myocardial fibrosis detection by LGE and PICP, as the subsequent generated fibrotic risk profiles are associated with distinct cardiac transcriptomic profiles.

Conclusion

The combination of myocardial fibrosis at CMR and circulating PICP levels provides additive prognostic value accompanied by a pro‐fibrotic and pro‐inflammatory transcriptomic profile in DCM patients with LGE and elevated PICP.

Sacubitril/Valsartan Inhibits Cardiomyocyte Hypertrophy in Angiotensin II-Induced Hypertensive Mice Independent of a Blood Pressure-Lowering Effect

Background

Hypertensive left ventricular hypertrophy is associated with the risk of heart failure, coronary heart disease and cerebrovascular disease. Although sacubitril/valsartan (SAC/VAL), a first-in-class angiotensin receptor neprilysin inhibitor, reduces the risks of death and hospitalization for patients with heart failure, its mechanism of action is not fully understood. We hypothesized that SAC/VAL is superior to other conventional drugs in reducing cardiac hypertrophy.

Methods

Male C57BL/6J mice were implanted with an osmotic pump containing angiotensin II (Ang II). After 7 days of Ang II infusion, mice were also treated with either SAC/VAL, valsartan, enalapril or vehicle alone each day for 2 weeks. Blood pressure measurement was done weekly, and echocardiography was performed before and 3 weeks after infusion of Ang II. Histological analyses were done using extracted heart to investigate cardiac hypertrophy and fibrosis.

Results

Ang II markedly elevated blood pressures in all of the treatment groups, and there were no differences in the degree of blood pressure reduction among the SAC/VAL-, valsartan- and enalapril-treated groups. Echocardiography showed that SAC/VAL significantly suppressed the increase in left ventricular (LV) wall thickness and tended to decrease LV mass. In a histological analysis, SAC/VAL inhibited Ang II-induced cardiomyocyte hypertrophy, and individual cardiomyocytes in the SAC/VAL group were smaller than those in the valsartan and enalapril groups. Although previous studies using animal models of heart failure have indicated that SAC/VAL attenuates cardiac fibrosis, we found no supporting evidence in this setting.

Conclusions

SAC/VAL, valsartan and enalapril all attenuated cardiomyocyte hypertrophy in a mouse model of Ang II-induced cardiac hypertrophy. Of note, SAC/VAL most strongly suppressed hypertrophy in spite of similar blood pressure-lowering effects as valsartan and enalapril. The present study suggests that SAC/VAL may have a beneficial effect on the early stage of hypertensive heart disease.

Activated FMS-like tyrosine kinase 3 ameliorates angiotensin II-induced cardiac remodelling

AIM

FMS-like receptor tyrosine kinase 3 (Flt3) has been reported to be increased in cardiomyocytes responding to ischaemic stress. This study was to determine whether Flt3 activation could ameliorate pressure overload-induced heart hypertrophy and fibrosis, and to elucidate the mechanisms of action.

METHODS

In vivo cardiac hypertrophy and remodelling experiments were conducted by infusing angiotensin II (Ang II) chronically in male C57BL/6 mice. Flt3-specific ligand (FL) was administered intraperitoneally every two days (5 µg/mouse). In vitro experiments on hypertrophy, apoptosis and autophagy mechanism were performed in neonatal rat cardiomyocytes (NRCMs) and H9c2 cells with adenovirus vector-mediated overexpression of Flt3.

RESULTS

Our results demonstrated that following chronic Ang II infusion for 4 weeks, the mice exhibited heart hypertrophy, fibrosis, apoptosis and contractile dysfunction. Meanwhile, Ang II induced autophagic responses in mouse hearts, as evidenced by increased LC3 II and decreased P62 expression. These pathological alterations in Ang II-treated mice were significantly ameliorated by Flt3 activation with FL administration. In NRCMs and Flt3-overexpressed H9c2 cells, FL attenuated Ang II-induced pathological autophagy and inactivated AMPK/mTORC1/FoxO3a signalling, thereby efficiently mitigating cell hypertrophy and apoptosis. Conversely, the AMPK activator metformin or the mTORC1 inhibitor rapamycin reversed the effects of FL on the alterations of autophagy, hypertrophy and apoptosis in cardiomyocytes induced by Ang II.

CONCLUSION

Flt3 activation ameliorates cardiac hypertrophy, fibrosis and contractile dysfunction in the mouse model of chronic pressure overload, most likely via suppressing AMPK/mTORC1/FoxO3a-mediated autophagy. These results provide new evidence supporting Flt3 as a novel therapeutic target in maladaptive cardiac remodelling.

Overexpression of FNTB and the activation of Ras induce hypertrophy and promote apoptosis and autophagic cell death in cardiomyocytes

Farnesyltransferase (FTase) is an important enzyme that catalyses the modification of protein isoprene downstream of the mevalonate pathway. Previous studies have shown that the tissue of the heart in the suprarenal abdominal aortic coarctation (AAC) group showed overexpression of FTaseβ (FNTB) and the activation of the downstream protein Ras was enhanced. FTase inhibitor (FTI) can alleviate myocardial fibrosis and partly improve cardiac remodelling in spontaneously hypertensive rats. However, the exact role and mechanism of FTase in myocardial hypertrophy and remodelling are not fully understood. Here, we used recombinant adenovirus to transfect neonatal rat ventricular cardiomyocytes to study the effect of FNTB overexpression on myocardial remodelling and explore potential mechanisms. The results showed that overexpression of FNTB induces neonatal rat ventricular myocyte hypertrophy and reduces the survival rate of cardiomyocytes. FNTB overexpression induced a decrease in mitochondrial membrane potential and increased apoptosis in cardiomyocytes. FNTB overexpression also promotes autophagosome formation and the accumulation of autophagy substrate protein, LC3II. Transmission electron microscopy (TEM) and mCherry‐GFP tandem fluorescent‐tagged LC3 (tfLC3) showed that FNTB overexpression can activate autophagy flux by enhancing autophagosome conversion to autophagolysosome. Overactivated autophagy flux can be blocked by bafilomycin A1. In addition, salirasib (a Ras farnesylcysteine mimetic) can alleviate the hypertrophic phenotype of cardiomyocytes and inhibit the up‐regulation of apoptosis and autophagy flux induced by FNTB overexpression. These results suggest that FTase may have a potential role in future treatment strategies to limit the adverse consequences of cardiac hypertrophy, cardiac dysfunction and heart failure.

Dilated cardiomyopathy: from epidemiologic to genetic phenotypes: A translational review of current literature

Dilated cardiomyopathy (DCM) is characterized by left ventricular dilatation and, consecutively, contractile dysfunction. The causes of DCM are heterogeneous. DCM often results from myocarditis, exposure to alcohol, drugs or other toxins and metabolic or endocrine disturbances. In about 35% of patients, genetic mutations can be identified that usually involve genes responsible for cytoskeletal, sarcomere and nuclear envelope proteins. Due to its heterogeneity, a detailed diagnostic work-up is necessary to identify the specific underlying cause and exclude other conditions with phenotype overlap. Patients with DCM show typical systolic heart failure symptoms, but, with progress of the disease, diastolic dysfunction is present as well. Depending on the underlying pathology, DCM patients also become apparent through arrhythmias, thromboembolic events or cardiogenic shock. Disease progression and prognosis are mostly driven by disease severity and reverse remodelling within the heart. The worst prognosis is seen in patients with lowest ejection fractions or severe diastolic dysfunction, leading to terminal heart failure with subsequent need for left ventricular assist device implantation or heart transplantation. Guideline-based heart failure medication and device therapy reduces the frequency of heart failure hospitalizations and improves survival.

Sodium (±)-5-bromo-2-(α-hydroxypentyl) benzoate ameliorates pressure overload-induced cardiac hypertrophy and dysfunction through inhibiting autophagy

Sodium (±)-5-bromo-2-(a-hydroxypentyl) benzoate (generic name: brozopine, BZP) has been reported to protect against stroke-induced brain injury and was approved for Phase II clinical trials for treatment of stroke-related brain damage by the China Food and Drug Administration (CFDA). However, the role of BZP in cardiac diseases, especially in pressure overload-induced cardiac hypertrophy and heart failure, remains to be investigated. In the present study, angiotensin II stimulation and transverse aortic constriction were employed to induce cardiomyocyte hypertrophy in vitro and in vivo, respectively, prior to the assessment of myocardial cell autophagy. We observed that BZP administration ameliorated cardiomyocyte hypertrophy and excessive autophagic activity. Further results indicated that AMP-activated protein kinase (AMPK)-mediated activation of the mammalian target of rapamycin (mTOR) pathway likely played a role in regulation of autophagy by BZP after Ang II stimulation. The activation of AMPK with metformin reversed the BZP-induced suppression of autophagy. Finally, for the first time, we demonstrated that BZP could protect the heart from pressure overload-induced hypertrophy and dysfunction, and this effect is associated with its inhibition of maladaptive cardiomyocyte autophagy through the AMPK-mTOR signalling pathway. These findings indicated that BZP may serve as a promising compound for treatment of pressure overload-induced cardiac remodelling and heart failure.

Biological Cardiac Tissue Effects of High-Energy Heavy Ions - Investigation for Myocardial Ablation

Noninvasive X-ray stereotactic treatment is considered a promising alternative to catheter ablation in patients affected by severe heart arrhythmia. High-energy heavy ions can deliver high radiation doses in small targets with reduced damage to the normal tissue compared to conventional X-rays. For this reason, charged particle therapy, widely used in oncology, can be a powerful tool for radiosurgery in cardiac diseases. We have recently performed a feasibility study in a swine model using high doses of high-energy C-ions to target specific cardiac structures. Interruption of cardiac conduction was observed in some animals. Here we report the biological effects measured in the pig heart tissue of the same animals six months after the treatment. Immunohistological analysis of the target tissue showed (1.) long-lasting vascular damage, i.e. persistent hemorrhage, loss of microvessels, and occurrence of siderophages, (2.) fibrosis and (3.) loss of polarity of targeted cardiomyocytes and wavy fibers with vacuolization. We conclude that the observed physiological changes in heart function are produced by radiation-induced fibrosis and cardiomyocyte functional inactivation. No effects were observed in the normal tissue traversed by the particle beam, suggesting that charged particles have the potential to produce ablation of specific heart targets with minimal side effects.

Analysis of the Correlation between the Myocardial Expression of DPP-4 and the Clinical Parameters of Patients with Heart Failure

Dipeptidyl peptidase-4 (DPP-4) inhibitors are widely used as antidiabetic drugs. We recently reported that DPP-4 inhibition has beneficial effects on heart failure (HF) mice model. Furthermore, we confirmed that myocardial DPP-4 activity was significantly increased in HF mice compared with non-HF mice. The aim of this study was to investigate the level of myocardial CD26 (DPP-4) expression and its association to clinical parameters in HF patients.Endomyocardial biopsy (EMB) specimens (n = 33) were obtained from HF patients who were admitted to Chiba University Hospital from June 2006 to July 2012. EMB specimens were fixed in formaldehyde and stained with Masson's trichrome staining or with anti-CD26 antibody. Patients were divided into the high CD26 density (CD26-H) or low CD26 density groups (CD26-L). DPP-4 density was compared with blood brain natriuretic peptide (BNP) level and echocardiographic parameters at one year after EMB. Although there were no significant differences in echocardiographic parameters between the CD26-H group and CD26-L group, blood BNP levels were higher in the CD26-H group than in the CD26-L group at one year after EMB. Multivariate regression analysis showed that CD26 density was also an independent determinant of blood BNP levels at one year after EMB.The level of myocardial CD26 expression might be a predictive marker of prognosis in patients with HF.

Prognostic value of fibrosis-related markers in dilated cardiomyopathy: A link between osteopontin and cardiovascular events

INTRODUCTION

Serum markers of fibrosis provide an insight into extracellular matrix (ECM) fibrosis in heart failure (HF) and dilated cardiomyopathy (DCM). However, their role as predictors of cardiovascular (CV) events in DCM is poorly understood.

METHODS

This is an observational, prospective cohort study. 70 DCM patients (48±12.1years, ejection fraction - EF 24.4±7.4) were recruited. Markers of collagen type I and III synthesis - procollagen type I and III carboxy- and amino-terminal peptides (PICP, PIIICP, PINP, PIIINP), fibrosis controlling factors - ostepontin (OPN), transforming growth factor (TGF1-β) and connective tissue growth factor (CTGF), and matrix metalloproteinases (MMP-2, MMP-9) and tissue inhibitor (TIMP-1), were measured in serum. All patients underwent endomyocardial biopsy. The end-point was combined with CV death and urgent HF hospitalization. Patients were divided into two groups: those who did (group 1, n=45) and did not reach (group 2, n=25) an end-point.

RESULTS

Over a 12-month period of observation, 6 CV deaths and 19 HF hospitalizations occurred. Qualitative and quantitative measures of ECM fibrosis were similar in both groups. The levels of all of the markers of collagen synthesis, TGF1-β, MMP-9 and TIMP-1 were similar, however, OPN, CTGF and MMP-2 were significantly lower in group 1.

CONCLUSIONS

Invasively-determined fibrosis levels were not related with CV outcomes in DCM. Out of the 11 markers of fibrosis under study, only OPN was found to be related to CV outcomes. OPN is not only the pivotal protein controlling fibrosis, but may also serve as a biomarker associated with prognosis.

Cardiac myosin-binding protein C is a novel marker of myocardial injury and fibrosis in aortic stenosis

Objective

Cardiac myosin-binding protein C (cMyC) is an abundant sarcomeric protein and novel highly specific marker of myocardial injury. Myocyte death characterises the transition from hypertrophy to replacement myocardial fibrosis in advanced aortic stenosis. We hypothesised that serum cMyC concentrations would be associated with cardiac structure and outcomes in patients with aortic stenosis.

Methods

cMyC was measured in two cohorts in which serum had previously been prospectively collected: a mechanism cohort of patients with aortic stenosis (n=161) and healthy controls (n=46) who underwent cardiac MRI, and an outcome cohort with aortic stenosis (n=104) followed for a median of 11.3 years.

Results

In the mechanism cohort, cMyC concentration correlated with left ventricular mass (adjusted β=11.0 g/m² per log unit increase in cMyC, P<0.001), fibrosis volume (adjusted β=8.0 g, P<0.001) and extracellular volume (adjusted β=1.3%, P=0.01) in patients with aortic stenosis but not in controls. In those with late gadolinium enhancement (LGE) indicative of myocardial fibrosis, cMyC concentrations were higher (32 (21–56) ng/L vs 17 (12–24) ng/L without LGE, P<0.001). cMyC was unrelated to coronary calcium scores. Unadjusted Cox proportional hazards analysis in the outcome cohort showed greater all-cause mortality (HR 1.49 per unit increase in log cMyC, 95% CI 1.11 to 2.01, P=0.009).

Conclusions

Serum cMyC concentration is associated with myocardial hypertrophy, fibrosis and an increased risk of mortality in aortic stenosis. The quantification of serum sarcomeric protein concentrations provides objective measures of disease severity and their clinical utility to monitor the progression of aortic stenosis merits further study.

Clinical trial registration

NCT1755936; Post-results.

Autophagic vacuoles in cardiomyocytes of dilated cardiomyopathy with initially decompensated heart failure predict improved prognosis

Autophagy is a process of bulk protein degradation and organelle turnover, and is a current therapeutic target in several diseases. The present study aimed to clarify the significance of myocardial autophagy of patients with dilated cardiomyopathy (DCM). Left ventricular endomyocardial biopsy was performed in 250 consecutive patients with DCM (54.9±13.9 years; male, 79%), initially presenting with decompensated heart failure (HF). The association of these findings with HF mortality or recurrence was examined. Myofilament changes, which are apparent in the degenerated cardiomyocytes of DCM, were recognized in 164 patients (66%), and autophagic vacuoles in cardiomyocytes were identified in or near the area of myofilament changes in 86 patients (34%). Morphometrically, fibrosis (odds ratio [OR], 0.96; 95% confidence interval [CI], 0.93 to 0.99) and mitochondrial abnormality (OR, 2.24; 95% CI, 1.23 to 4.08) were independently related with autophagic vacuoles. During the follow-up period of 4.9±3.9 y, 24 patients (10%) died, including 10 (4%) who died of HF, and 67 (27%) were readmitted for HF recurrence. Multivariate analysis identified a family history of DCM (hazard ratio [HR], 2.117; 95% CI, 1.199 to 3.738), hemoglobin level (HR, 0.845; 95% CI, 0.749 to 0.953), myofilament changes (HR, 13.525; 95% CI, 5.340 to 34.255), and autophagic vacuoles (HR, 0.214; 95% CI, 0.114 to 0.400) as independent predictors of death or readmission due to HF recurrence. In conclusion, autophagic vacuoles in cardiomyocytes are associated with a better HF prognosis in patients with DCM, suggesting autophagy may play a role in the prevention of myocardial degeneration.

Outcomes and predictors of recovery in acute-onset cardiomyopathy: A single-center experience of patients undergoing endomyocardial biopsy for new heart failure

BACKGROUND

About one-third of patients with unexplained acute-onset heart failure (HF) recover left ventricular (LV) function; however, characterization of these patients in the setting of contemporary HF therapies is limited. We aim to describe baseline characteristics and predictors of recovery in patients with acute-onset cardiomyopathy.

METHODS

We previously described 851 patients with unexplained HF undergoing endomyocardial biopsy. In this study, 235 patients with acute-onset HF were further retrospectively examined.

RESULTS

Follow-up LV ejection fraction (LVEF) was available for 138 patients. At 1 year, 48 of 138 (33%) had LVEF recovery (follow-up LVEF ≥50%), and 90 of 138 (65%) had incomplete or lack of recovery. Higher cardiac index (P=.019), smaller LV diastolic diameter (P=.002), and lack of an intraventricular conduction delay (IVCD) (P=.002) were associated with LVEF recovery. IVCD (P=.001) and myocarditis (P=.016) were independent predictors of the composite end point of death, LV assist device placement, and/or transplant at 1 year. Those with an IVCD had a significantly lower 1-year survival than those without (P=.007).

CONCLUSIONS

Patients with a smaller LV end-diastolic diameter, higher cardiac index, and lack of IVCD at presentation for acute-onset HF were more likely to have LVEF recovery. IVCD was a poor prognostic marker in all patients presenting with acute cardiomyopathy.

Intensive Hemodialysis Preserved Cardiac injury

Cardiac injury triggers cellular responses involving both cardiomyocytes and nonmuscle cells to process cardiac structural remodeling. End-stage renal disease (ESRD), despite conventional dialysis, is associated with adverse cardiac remodeling and increased cardiovascular events. Intensification of hemodialysis with nocturnal home hemodialysis (NHD; five sessions per week; 6-8 hours per treatment) was associated with regression of left ventricular hypertrophy and downregulation of genes in apoptosis and fibrosis. In this pilot study, we hypothesize that NHD achieves its cardiac effects in part through attenuation of innate immune activation resulting in amelioration of cardiomyocytes apoptosis and fibrosis. Eight patients (4M:4F; age, 59 ± 9 years) with ESRD were studied. Half of the cohort was converted to NHD, whereas the rest of the patients were maintained on conventional hemodialysis (CHD). At baseline, CHD was associated with an increase in cardiomyocyte apoptosis detected by flow cytometry using Annexin V (mean fluorescence index in CHD and in normal control is 1.00 ± 0.05 vs. 0.66 ± 0.01, p < 0.05). After conversion to NHD, cardiomyocyte apoptosis was reduced compared with baseline CHD situation (p < 0.05) and approached that of normal control (0.59 ± 0.09 vs. 0.66 ± 0.01, p > 0.05). The CHD serum was associated with a coordinated augmentation innate immunity pathway, significantly increasing myeloid differentiation factor-88 and interleukin-1 receptor-associated kinase-4; NHD was able to reduce their levels. Heat shock protein 60 was augmented during CHD condition and fell after NHD. In addition, CHD increased fibroblast proliferation and myofibroblast transformation. Uremia is associated with activation of common innate immune signaling pathways leading to fibrosis and apoptosis. Amelioration of uremic clearance by NHD may attenuate this pathological signaling cascade.

Narrow time window of metabolic changes associated with transition to overt heart failure in Tgaq*44 mice

BACKGROUND

The timing and consequences of alternations in substrate utilization in heart failure (HF) and their relationship with structural changes remain unclear. This study aimed to analyze metabolic changes associated with transition to overt heart failure in transgenic mouse model of HF resulting from cardiac-specific overexpression of constitutively active Gαq*.

METHODS

Structural changes quantified by morphometry, relative cardiac mRNA and protein expression of PPARα, FAT/CD36, CPT-1, GLUT-4 and glycolytic efficiency following administration of 1-(13)C glucose were investigated in 4-14-month-old Tgαq*44 mice (TG), compared with age-matched FVB wild type mice (WT).

RESULTS

Initial hypertrophy in TG (4-10-month of age) was featured by an accelerated glycolytic pathway that was not accompanied by structural changes in cardiomyocytes. In 10-month-old TG, cardiomyocyte elongation and hypertrophic remodeling and increased glycolytic flux was accompanied by relatively low expression of FAT/CD36, CPT-1 and PPARα. During the transition phase (12-month-old TG), a pronounced increase in PPARα with an increase in relative fatty acid (FA) flux was associated with anomalies of cardiomyocytes with accumulation of lipid droplets and glycogen as well as cell death. At the stage of overt heart failure (14-month-old TG), an accelerated glycolytic pathway with a decline in FA oxidation was accompanied by further structural changes.

CONCLUSION

Tgαq*44 mice display three distinct phases of metabolic/structural changes during hypertrophy and progression to HF, with relatively short period of increase in FA metabolism, highlighting a narrow metabolic changes associated with transition to overt heart failure in Tgaq*44 mice that have therapeutic significance.

Mas receptor mediates cardioprotection of angiotensin-(1-7) against Angiotensin II-induced cardiomyocyte autophagy and cardiac remodelling through inhibition of oxidative stress

Angiotensin II (Ang II) plays an important role in the onset and development of cardiac remodelling associated with changes of autophagy. Angiotensin1-7 [Ang-(1-7)] is a newly established bioactive peptide of renin-angiotensin system, which has been shown to counteract the deleterious effects of Ang II. However, the precise impact of Ang-(1-7) on Ang II-induced cardiomyocyte autophagy remained essentially elusive. The aim of the present study was to examine if Ang-(1-7) inhibits Ang II-induced autophagy and the underlying mechanism involved. Cultured neonatal rat cardiomyocytes were exposed to Ang II for 48 hrs while mice were infused with Ang II for 4 weeks to induce models of cardiac hypertrophy in vitro and in vivo. LC3b-II and p62, markers of autophagy, expression were significantly elevated in cardiomyocytes, suggesting the presence of autophagy accompanying cardiac hypertrophy in response to Ang II treatment. Besides, Ang II induced oxidative stress, manifesting as an increase in malondialdehyde production and a decrease in superoxide dismutase activity. Ang-(1-7) significantly retarded hypertrophy, autophagy and oxidative stress in the heart. Furthermore, a role of Mas receptor in Ang-(1-7)-mediated action was assessed using A779 peptide, a selective Mas receptor antagonist. The beneficial responses of Ang-(1-7) on cardiac remodelling, autophagy and oxidative stress were mitigated by A779. Taken together, these result indicated that Mas receptor mediates cardioprotection of angiotensin-(1-7) against Ang II-induced cardiomyocyte autophagy and cardiac remodelling through inhibition of oxidative stress.

Isosorbide dinitrate inhibits mechanical stress-induced cardiac hypertrophy and autophagy through downregulation of angiotensin II type 1 receptor

Mechanical stress can induce cardiac hypertrophy and autophagy. Recently, it has been reported that nitric oxide donors inhibited autophagy in human chondrocytes. Therefore, the effect of isosorbide dinitrate (ISDN) on cardiac hypertrophy and autophagy induced by mechanical stress was investigated in this study. A 48-hour mechanical stretch and a 4-week transverse aortic constriction were performed to induce cardiomyocyte hypertrophy in vitro and in vivo, respectively, before the assessment of myocardial autophagy using LC3b-II. ISDN was found to significantly reduce mechanical stretch-induced LC3b-II upregulation. Furthermore, mechanical stress was shown to upregulate angiotensin II (AngII) type 1 (AT1) receptor expression in both cultured cardiomyocytes and in mouse hearts, whereas ISDN was demonstrated to significantly suppress the upregulation of the AT1 receptor. It was concluded that ISDN could inhibit mechanical stress-induced cardiac hypertrophy and autophagy through the downregulation of AT1 receptor expression.

The case for inhibiting p38 mitogen-activated protein kinase in heart failure

This minireview discusses the evidence that the inhibition of p38 mitogen-activated protein kinases (p38 MAPKs) maybe of therapeutic value in heart failure. Most previous experimental studies, as well as past and ongoing clinical trials, have focussed on the role of p38 MAPKs in myocardial infarction and acute coronary syndromes. There is now growing evidence that these kinases are activated within the myocardium of the failing human heart and in the heart and blood vessels of animal models of heart failure. Furthermore, from a philosophical viewpoint the chronic activation of the adaptive stress pathways that lead to the activation of p38 MAPKs in heart failure is analogous to the chronic activation of the sympathetic, renin-aldosterone-angiotensin and neprilysin systems. These have provided some of the most effective therapies for heart failure. This minireview questions whether similar and synergistic advantages would follow the inhibition of p38 MAPKs.

High-density lipoprotein inhibits mechanical stress-induced cardiomyocyte autophagy and cardiac hypertrophy through angiotensin II type 1 receptor-mediated PI3K/Akt pathway

Mechanical stress triggers cardiac hypertrophy and autophagy through an angiotensin II (Ang II) type 1 (AT1) receptor-dependent mechanism. Low level of high density lipoprotein (HDL) is an independent risk factor for cardiac hypertrophy. This study was designed to evaluate the effect of HDL on mechanical stress-induced cardiac hypertrophy and autophagy. A 48-hr mechanical stretch and a 4-week transverse aortic constriction were employed to induce cardiomyocyte hypertrophy in vitro and in vivo, respectively, prior to the assessment of myocardial autophagy using LC3b-II and beclin-1. Our results indicated that HDL significantly reduced mechanical stretch-induced rise in autophagy as demonstrated by LC3b-II and beclin-1. In addition, mechanical stress up-regulated AT1 receptor expression in both cultured cardiomyocytes and in mouse hearts, whereas HDL significantly suppressed the AT1 receptor. Furthermore, the role of Akt phosphorylation in HDL-mediated action was assessed using MK-2206, a selective inhibitor for Akt phosphorylation. Our data further revealed that MK-2206 mitigated HDL-induced beneficial responses on cardiac remodelling and autophagy. Taken together, our data revealed that HDL inhibited mechanical stress-induced cardiac hypertrophy and autophagy through downregulation of AT1 receptor, and HDL ameliorated cardiac hypertrophy and autophagy via Akt-dependent mechanism.

Design of magnetic nanoparticles for hepatocellular carcinoma treatment using the control mechanisms of the cell internal nucleus and external membrane

Nanoparticle drugs and relevant treatment technologies have achieved widespread attention in recent years. Hepatocellular carcinoma (HCC) remains a challenging malignancy of worldwide importance since it is one of the worst malignant tumors. In this study, magnetic Fe₃O₄ nanoparticles are prepared via a co-precipitation reaction with self-assembled surface monolayers of oleic acid molecules. For synthesizing the nanoparticle anti-tumor drug used against HCC, the liquid photo-immobilization method is used to bond the photoactive N-isopropylacrylamide derivative (NIPAm-AA) onto the oleic acid monolayer for subsequently embedding doxorubicin, photoactive tumor necrosis factor-α (TNF-α)/interferon-γ (IFN-γ), and folic acid (FOL). We investigate how the nanoparticle drug inhibits the growth of human hepatocellular carcinoma HepG2 cells in vitro and in vivo. Remarkably, our characterizations show that the nanoparticle drug demonstrates much higher anticancer efficacy (94.7%) in vitro than previously reported drugs. It is revealed that the programmed cell death induced by the drug is mainly oncosis, a new programmed cell death pathway, different from earlier proposed mechanisms. This oncosis mechanism is also confirmed in the other two hepatocellular carcinoma cells (BEL-7402 and Huh-7). This study may be helpful for developing a new type of nanoparticle drug capable of assuring molecular control of both the cell inner nucleus and outer membrane as a means to enormously increase the drug efficacy in human hepatocellular carcinoma.

Protease 3C of hepatitis A virus induces vacuolization of lysosomal/endosomal organelles and caspase-independent cell death

BACKGROUND

3C proteases, the main proteases of picornaviruses, play the key role in viral life cycle by processing polyproteins. In addition, 3C proteases digest certain host cell proteins to suppress antiviral defense, transcription, and translation. The activity of 3C proteases per se induces host cell death, which makes them critical factors of viral cytotoxicity. To date, cytotoxic effects have been studied for several 3C proteases, all of which induce apoptosis. This study for the first time describes the cytotoxic effect of 3C protease of human hepatitis A virus (3Cpro), the only proteolytic enzyme of the virus.

RESULTS

Individual expression of 3Cpro induced catalytic activity-dependent cell death, which was not abrogated by the pan-caspase inhibitor (z-VAD-fmk) and was not accompanied by phosphatidylserine externalization in contrast to other picornaviral 3C proteases. The cell survival was also not affected by the inhibitors of cysteine proteases (z-FA-fmk) and RIP1 kinase (necrostatin-1), critical enzymes involved in non-apoptotic cell death. A substantial fraction of dying cells demonstrated numerous non-acidic cytoplasmic vacuoles with not previously described features and originating from several types of endosomal/lysosomal organelles. The lysosomal protein Lamp1 and GTPases Rab5, Rab7, Rab9, and Rab11 were associated with the vacuolar membranes. The vacuolization was completely blocked by the vacuolar ATPase inhibitor (bafilomycin A1) and did not depend on the activity of the principal factors of endosomal transport, GTPases Rab5 and Rab7, as well as on autophagy and macropinocytosis.

CONCLUSIONS

3Cpro, apart from other picornaviral 3C proteases, induces caspase-independent cell death, accompanying by cytoplasmic vacuolization. 3Cpro-induced vacuoles have unique properties and are formed from several organelle types of the endosomal/lysosomal compartment. The data obtained demonstrate previously undocumented morphological characters of the 3Cpro-induced cell death, which can reflect unknown aspects of the human hepatitis A virus-host cell interaction.

Pathophysiology and the cardiorenal connection in heart failure. Circulating hormones: biomarkers or mediators

Heart failure (HF) is a syndrome characterized by a complex pathophysiology which involves multiple organ systems, with the kidney playing a major role. HF can present with reduced ejection fraction (EF), HFrEF, or with preserved EF (HFpEF). The interplay between diverse organ systems contributing to HF is mediated by the activation of counteracting neurohormonal pathways focused to re-establishing hemodynamic homeostasis. During early stages of HF, these biochemical signals, consisting mostly of hormones and neurotransmitters secreted by a variety of cell types, are compensatory and the patient is asymptomatic. However, with disease progression, the attempt to reverse or delay cardiac dysfunction is deleterious, leading to multi-organ congestion, fibrosis and decompensation and finally symptomatic HF. In conclusion, these neurohormonal pathways mediate the evolution of HF and have become a way to monitor HF. Specifically, these mediators have become important in the diagnosis and prognosis of this highly fatal cardiovascular disease. Finally, while these multiple neurohumoral factors serve as important HF biomarkers, they can also be targeted for more effective and curative HF treatments.

Neuregulin-1/erbB activities with focus on the susceptibility of the heart to anthracyclines

Neuregulin-1 (NRG1) signaling through the tyrosine kinase receptors erbB2 and erbB4 is required for cardiac morphogenesis, and it plays an essential role in maintaining the myocardial architecture during adulthood. The tyrosine kinase receptor erbB2 was first linked to the amplification and overexpression of erbb2 gene in a subtype of breast tumor cells, which is indicative of highly proliferative cells and likely a poor prognosis following conventional chemotherapy. The development of targeted therapies to block the survival of erbB2-positive cancer cells revealed that impaired NRG1 signaling through erbB2/erbB4 heterodimers combined with anthracycline chemotherapy may lead to dilated cardiomyopathy in a subpopulation of treated patients. The ventricular-specific deletion of either erbb2 or erbb4 manifested dilated cardiomyopathy, which is aggravated by the administration of doxorubicin. Based on the exacerbated toxicity displayed by the combined treatment, it is expected that the relevant pathways would be affected in a synergistic manner. This review examines the NRG1 activities that were monitored in different model systems, focusing on the emerging pathways and molecular targets, which may aid in understanding the acquired dilated cardiomyopathy that occurs under the conditions of NRG1-deficient signaling.

Increased Na⁺/Ca²⁺ exchanger expression/activity constitutes a point of inflection in the progression to heart failure of hypertensive rats

Spontaneously hypertensive rat (SHR) constitutes a genetic model widely used to study the natural evolution of hypertensive heart disease. Ca²⁺-handling alterations are known to occur in SHR. However, the putative modifications of Ca²⁺-handling proteins during the progression to heart failure (HF) are not well established. Moreover, the role of apoptosis in SHR is controversial. We investigated intracellular Ca²⁺, Ca²⁺-handling proteins and apoptosis in SHR vs. control Wistar rats (W) from 3 to 15 months (mo). Changes associated with the transition to HF (i.e. lung edema and decrease in midwall fractional shortening), occurred at 15 mo in 38% of SHR (SHRF). In SHRF, twitch and caffeine-induced Ca²⁺ transients, significantly decreased relative to 6/9 mo and 15 mo without HF signs. This decrease occurred in association with a decrease in the time constant of caffeine-Ca²⁺ transient decay and an increase in Na⁺/Ca²⁺ exchanger (NCX) abundance (p<0.05) with no changes in SERCA2a expression/activity. An increased Ca²⁺-calmodulin-kinase II activity, associated with an enhancement of apoptosis (TUNEL and Bax/Bcl2) was observed in SHR relative to W from 3 to 15 mo.

CONCLUSIONS

1. Apoptosis is an early and persistent event that may contribute to hypertrophic remodeling but would not participate in the contractile impairment of SHRF. 2. The increase in NCX expression/activity, associated with an increase in Ca²⁺ efflux from the cell, constitutes a primary alteration of Ca²⁺-handling proteins in the evolution to HF. 3. No changes in SERCA2a expression/activity are observed when HF signs become evident.

Mechanical stress triggers cardiomyocyte autophagy through angiotensin II type 1 receptor-mediated p38MAP kinase independently of angiotensin II

Angiotensin II (Ang II) type 1 (AT1) receptor is known to mediate a variety of physiological actions of Ang II including autophagy. However, the role of AT1 receptor in cardiomyocyte autophagy triggered by mechanical stress still remains elusive. The aim of this study was therefore to examine whether and how AT1 receptor participates in cardiomyocyte autophagy induced by mechanical stresses. A 48-hour mechanical stretch and a 4-week transverse aorta constriction (TAC) were imposed to cultured cardiomyocytes of neonatal rats and adult male C57B/L6 mice, respectively, to induce cardiomyocyte hypertrophy prior to the assessment of cardiomyocyte autophagy using LC3b-II. Losartan, an AT1 receptor blocker, but not PD123319, the AT2 inhibitor, was found to significantly reduce mechanical stretch-induced LC3b-II upregulation. Moreover, inhibition of p38MAP kinase attenuated not only mechanical stretch-induced cardiomyocyte hypertrophy but also autophagy. To the contrary, inhibition of ERK and JNK suppressed cardiac hypertrophy but not autophagy. Intriguingly, mechanical stretch-induced autophagy was significantly inhibited by Losartan in the absence of Ang II. Taken together, our results indicate that mechanical stress triggers cardiomyocyte autophagy through AT1 receptor-mediated activation of p38MAP kinase independently of Ang II.

Role of cardiac magnetic resonance in the evaluation of dilated cardiomyopathy: diagnostic contribution and prognostic significance

Dilated cardiomyopathy (DCM) represents the final common morphofunctional pathway of various pathological conditions in which a combination of myocyte injury and necrosis associated with tissue fibrosis results in impaired mechanical function. Recognition of the underlying aetiology of disease and accurate disease monitoring may be crucial to individually optimize therapeutic strategies and stratify patient's prognosis. In this regard, CMR has emerged as a new reference gold standard providing important information for differential diagnosis and new insight about individual risk stratification. The present review article will focus on the role of CMR in the evaluation of present condition, analysing respective strengths and limitations in the light of current literature and technological developments.

End-systolic elastance and ventricular-arterial coupling reserve predict cardiac events in patients with negative stress echocardiography

Background. A maximal negative stress echo identifies a low-risk subset for coronary events. However, the potentially prognostically relevant information on cardiovascular hemodynamics for heart-failure-related events is unsettled. Aim of this study was to assess the prognostic value of stress-induced variation in cardiovascular hemodynamics in patients with negative stress echocardiography. Methods. We enrolled 891 patients (593 males mean age 63 ± 12, ejection fraction 48 ± 17%), with negative (exercise 172, dipyridamole 482, and dobutamine 237) stress echocardiography result. During stress we assessed left ventricular end-systolic elastance index (E_LVI), ventricular arterial coupling (VAC) indexed by the ratio of the E_LVI to arterial elastance index (E_aI), systemic vascular resistance (SVR), and pressure-volume area (PVA). Changes from rest to peak stress (reserve) were tested as predictors of main outcome measures: combined death and heart failure hospitalization. Results. During a median followup of 19 months (interquartile range 8–36), 50 deaths and 84 hospitalization occurred. Receiver-operating-characteristic curves identified as best predictors E_LVI reserve for exercise (AUC = 0.871) and dobutamine (AUC = 0.848) and VAC reserve (AUC = 0.696) for dipyridamole. Conclusions. Patients with negative stress echocardiography may experience an adverse outcome, which can be identified by assessment of E_LVI reserve and VAC reserve during stress echo.

Biochemistry of cardiomyopathy in the mitochondrial disease Friedreich's ataxia

FRDA (Friedreich's ataxia) is a debilitating mitochondrial disorder leading to neural and cardiac degeneration, which is caused by a mutation in the frataxin gene that leads to decreased frataxin expression. The most common cause of death in FRDA patients is heart failure, although it is not known how the deficiency in frataxin potentiates the observed cardiomyopathy. The major proposed biochemical mechanisms for disease pathogenesis and the origins of heart failure in FRDA involve metabolic perturbations caused by decreased frataxin expression. Additionally, recent data suggest that low frataxin expression in heart muscle of conditional frataxin knockout mice activates an integrated stress response that contributes to and/or exacerbates cardiac hypertrophy and the loss of cardiomyocytes. The elucidation of these potential mechanisms will lead to a more comprehensive understanding of the pathogenesis of FRDA, and will contribute to the development of better treatments and therapeutics.

Tbx20 functions as an important regulator of estrogen-mediated cardiomyocyte protection during oxidative stress

BACKGROUND

As a transcription factor mainly expressed in cardiovascular system, T-box 20 (Tbx20) plays an important role in embryonic cardiovascular system development and adult heart function. Here, we determined the mechanism by which Tbx20 regulates cardiomyocyte apoptosis and cardiomyopathies.

METHODS

We analyzed Tbx20 expression levels and apoptosis rates in normal and heart failure human autopsy heart samples. Female C57BL/6 mice were ovariectomized and treated with 17β-estradiol to determine Tbx20 expression levels. ROS production, TUNEL, DNA laddering, qRT-PCR, Western blot, immunohistochemistry and ChIP analyses were performed on male C57BL/6 transverse aortic constriction-induced heart failure samples and on neonatal rat ventricular myocytes that were treated with H2O2 to investigate the role of Tbx20 in estrogen-mediated heart protection.

RESULTS

Tbx20 expression was down regulated during heart failure, accompanied by elevated cardiomyocyte apoptotic levels in humans and mice. H2O2 led to a concurrent decrease in Tbx20 expression and increase in apoptosis in cultured neonatal rat cardiomyocytes. Tbx20 overexpression reduced H2O2-induced cardiomyocyte apoptosis and was associated with a profound inhibition of p38MAPK, Bax and caspase3 and the activation of Bcl-2. Estrogen was able to protect cardiomyocytes from H2O2-induced apoptosis by upregulating Tbx20 expression in a concentration-dependent manner. Tbx20 silencing increased oxidative stress-induced apoptosis in H9c2 cells. Moreover, Tbx20 directly regulated Esrra expression to enhance the heart-protective effect of estrogen.

CONCLUSIONS

These results indicate that Tbx20 functions as an important regulator of estrogen-mediated cardiomyocyte protection during oxidative stress, suggesting that estorgen-Tbx20-ERR-α may represent a crucial regulatory cascade and a potential therapeutic target for heart failure.

Doxorubicin and NRG-1/erbB4-Deficiency Affect Gene Expression Profile: Involving Protein Homeostasis in Mouse

The accumulating evidence demonstrates the essential role of neuregulin-1 signaling in the adult heart, and, moreover, indicates that an impaired neuregulin signaling exacerbates the doxorubicin-mediated cardiac toxicity. Despite this strong data, the specific cardiomyocyte targets of the active erbB2/erbB4 heterodimer remain unknown. In this paper, we examined pathways involved in cardiomyocyte damage as a result of the cardiac sensitization to anthracycline toxicity in the ventricular muscle-specific erbB4 knockout mouse. We performed morphological analyses to evaluate the ventricular remodeling and employed a cDNA microarray to assess the characteristic gene expression profile, verified data by real-time RT-PCR, and then grouped into functional categories and pathways. We confirm the upregulation of genes related to the classical signature of a hypertrophic response, implicating an erbB2-dependent mechanism in doxorubicin-treated erbB4-KO hearts. Our results indicate the remarkable downregulation of IGF-I/PI-3′ kinase pathway and extends our current knowledge by uncovering an altered ubiquitin-proteasome system leading to cardiomyocyte autophagic vacuolization.

The role of TWEAK/Fn14 in cardiac remodeling

The pathophysiological basis of heart failure is cardiac remodeling, a process that comprises structural and functional changes including cardiomyocyte proliferation, hypertrophy, necrosis, apoptosis, autophagy, interstitial fibrosis, contractile dysfunction and ventricular dilatation. Accumulating evidence demonstrate that tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is involved in the process by binding its receptor fibroblast growth factor-inducible molecule 14 (Fn14). In this review, we will discuss the potential role of the TWEAK/Fn14 axis in cardiac remodeling, elucidate its possible mechanisms and explore new therapeutic targets for heart failure.

Autophagy and cardiovascular aging: lesson learned from rapamycin

The biological aging process is commonly associated with increased risk of cardiovascular diseases. Several theories have been put forward for aging-associated deterioration in ventricular function, including attenuation of growth hormone (insulin-like growth factors and insulin) signaling, loss of DNA replication and repair, histone acetylation and accumulation of reactive oxygen species. Recent evidence has depicted a rather unique role of autophagy as another important pathway in the regulation of longevity and senescence. Autophagy is a predominant cytoprotective (rather than self-destructive) process. It carries a prominent role in determination of lifespan. Reduced autophagy has been associated with aging, leading to accumulation of dysfunctional or damaged proteins and organelles. To the contrary, measures such as caloric restriction and exercise may promote autophagy to delay aging and associated comorbidities. Stimulation of autophagy using rapamycin may represent a novel strategy to prolong lifespan and combat aging-associated diseases. Rapamycin regulates autophagy through inhibition of the nutrient-sensing molecule mammalian target of rapamycin (mTOR). Inhibition of mTOR through rapamycin and caloric restriction promotes longevity. The purpose of this review is to recapitulate some of the recent advances in an effort to better understand the interplay between rapamycin-induced autophagy and decelerating cardiovascular aging.