Ischemic Cardiomyopathy Hearts Research Articles

Defining the Sarcomeric Proteoform Landscape in Ischemic Cardiomyopathy by Top-Down Proteomics.

Ischemic cardiomyopathy (ICM) is a prominent form of heart failure, but the molecular mechanisms underlying ICM remain relatively understudied due to marked phenotypic heterogeneity. Alterations in post-translational modifications (PTMs) and isoform switches in sarcomeric proteins play important roles in cardiac pathophysiology. Thus, it is essential to define sarcomeric proteoform landscape to better understand ICM. Herein, we have implemented a top-down liquid chromatography (LC)-mass spectrometry (MS)-based proteomics method for the identification and quantification of sarcomeric proteoforms in the myocardia of donors without heart diseases (n = 16) compared to end-stage ICM patients (n = 16). Importantly, quantification of post-translational modifications (PTMs) and expression reveal significant changes in various sarcomeric proteins extracted from ICM tissues. Changes include altered phosphorylation and expression of cardiac troponin I (cTnI) and enigma homologue 2 (ENH2) as well as an increase in muscle LIM protein (MLP) and calsarcin-1 (Cal-1) phosphorylation in ICM hearts. Our results imply that the contractile apparatus of the sarcomere is severely dysregulated during ICM. Thus, this is the first study to uncover significant molecular changes to multiple sarcomeric proteins in the LV myocardia of the end-stage ICM patients using liquid chromatography-mass spectrometry (LC-MS)-based top-down proteomics. Raw data are available via the PRIDE repository with identifier PXD038066.

Ectonucleoside triphosphate diphosphohydrolase-1 (CD39) impacts TGF-β1 responses: insights into cardiac fibrosis and function following myocardial infarction.

Extracellular purine nucleotides and nucleosides released from activated or injured cells influence multiple aspects of cardiac physiology and pathophysiology. Ectonucleoside triphosphate diphosphohydrolase-1 (ENTPD1; CD39) hydrolyzes released nucleotides and thereby regulates the magnitude and duration of purinergic signaling. However, the impact of CD39 activity on post-myocardial infarction (MI) remodeling is incompletely understood. We measured the levels and activity of ectonucleotidases in human left ventricular samples from control and ischemic cardiomyopathy (ICM) hearts and examined the impact of ablation of Cd39 expression on post-myocardial infarction remodeling in mice. We found that human CD39 levels and activity are significantly decreased in ICM hearts (n = 5) compared with control hearts (n = 5). In mice null for Cd39, cardiac function and remodeling are significantly compromised in Cd39-/- mice following myocardial infarction. Fibrotic markers including plasminogen activator inhibitor-1 (PAI-1) expression, fibrin deposition, α-smooth muscle actin (αSMA), and collagen expression are increased in Cd39-/- hearts. Importantly, we found that transforming growth factor β1 (TGF-β1) stimulates ATP release and induces Cd39 expression and activity on cardiac fibroblasts, constituting an autocrine regulatory pathway not previously appreciated. Absence of CD39 activity on cardiac fibroblasts exacerbates TGF-β1 profibrotic responses. Treatment with exogenous ectonucleotidase rescues this profibrotic response in Cd39-/- fibroblasts. Together, these data demonstrate that CD39 has important interactions with TGF-β1-stimulated autocrine purinergic signaling in cardiac fibroblasts and dictates outcomes of cardiac remodeling following myocardial infarction. Our results reveal that ENTPD1 (CD39) regulates TGF-β1-mediated fibroblast activation and limits adverse cardiac remodeling following myocardial infarction.NEW & NOTEWORTHY We show that CD39 is a critical modulator of TGF-β1-mediated fibroblast activation and cardiac remodeling following myocardial infarction via modulation of nucleotide signaling. TGF-β1-induced CD39 expression generates a negative feedback loop that attenuates cardiac fibroblast activation. In the absence of CD39 activity, collagen deposition is increased, elastin expression is decreased, and diastolic dysfunction is worsened. Treatment with ecto-apyrase attenuates the TGF-β1-induced profibrotic cardiac fibroblast phenotype, revealing a novel approach to combat post-myocardial infarction cardiac fibrosis.

Resolving the intertwining of inflammation and fibrosis in human heart failure at single-cell level.

Inflammation and fibrosis are intertwined mechanisms fundamentally involved in heart failure. Detailed deciphering gene expression perturbations and cell-cell interactions of leukocytes and non-myocytes is required to understand cell-type-specific pathology in the failing human myocardium. To this end, we performed single-cell RNA sequencing and single T cell receptor sequencing of 200,615 cells in both human dilated cardiomyopathy (DCM) and ischemic cardiomyopathy (ICM) hearts. We sampled both lesion and mild-lesion tissues from each heart to sequentially capture cellular and molecular alterations to different extents of cardiac fibrosis. By which, left (lesion) and right ventricle (mild-lesion) for DCM hearts were harvest while infarcted (lesion) and non-infarcted area (mild-lesion) were dissected from ICM hearts. A novel transcription factor AEBP1 was identified as a crucial cardiac fibrosis regulator in ACTA2+ myofibroblasts. Within fibrotic myocardium, an infiltration of a considerable number of leukocytes was witnessed, especially cytotoxic and exhausted CD8+ T cells and pro-inflammatory CD4+ T cells. Furthermore, a subset of tissue-resident macrophage, CXCL8hiCCR2+HLA-DRhi macrophage was particularly identified in severely fibrotic area, which interacted with activated endothelial cell via DARC, that potentially facilitate leukocyte recruitment and infiltration in human heart failure.

Defining decreased protein succinylation of failing human cardiac myofibrils in ischemic cardiomyopathy

Succinylation is a post-translational modification of protein lysine residues with succinyl groups derived from succinyl CoA. Succinylation is considered a significant post-translational modification with the potential to impact protein function which is highly conserved across numerous species. The role of succinylation in the heart, especially in heart failure and myofibril mechanics, remains largely unexplored. Mechanical parameters were measured in myofibrils isolated from failing hearts of ischemic cardiomyopathy patients and non-failing donor controls. We employed mass spectrometry to quantify differential protein expression in myofibrils from failing ischemic cardiomyopathy hearts compared to non-failing hearts. In addition, we combined peptide enrichment by immunoprecipitation with liquid chromatography tandem mass spectrometry to quantitatively analyze succinylated lysine residues in these myofibrils. Several key parameters of sarcomeric mechanical interactions were altered in myofibrils isolated from failing ischemic cardiomyopathy hearts, including lower resting tension and a faster rate of activation. Of the 100 differentially expressed proteins, 46 showed increased expression in ischemic heart failure, while 54 demonstrated decreased expression in ischemic heart failure. Our quantitative succinylome analysis identified a total of 572 unique succinylated lysine sites located on 181 proteins, with 307 significantly changed succinylation events. We found that 297 succinyl-Lys demonstrated decreased succinylation on 104 proteins, while 10 residues demonstrated increased succinylation on 4 proteins. Investigating succinyl CoA generation, enzyme activity assays demonstrated that α-ketoglutarate dehydrogenase and succinate dehydrogenase activities were significantly decreased in ischemic heart failure. An activity assay for succinyl CoA synthetase demonstrated a significant increase in ischemic heart failure. Taken together, our findings support the hypothesis that succinyl CoA production is decreased and succinyl CoA turnover is increased in ischemic heart failure, potentially resulting in an overall decrease in the mitochondrial succinyl CoA pool, which may contribute to decreased myofibril protein succinylation in heart failure.

Dysregulation of H11 Kinase in the Failing Left Ventricular Myocardium

Background: Increased expression of H11 kinase (H11K) has been observed in Left Ventricular (LV) myocardium of failed human hearts. Its potential role as a contributor to the progression of Heart Failure (HF) remains uncertain. In the present study we examined the expression of H11K in cytosolic and mitochondrial fractions of failing human and dog LV myocardium and assessed its interaction with Akt (cell-survival enzyme) and p38MAPK (programmed cell death enzyme). Methods: Total RNA and Sodium-Dodecyl Sulfate (SDS) extracts were prepared from homogenate of LV specimens of 6 dogs with intracoronary microembolization-induced HF, 6 normal (NL) dogs, 7 explanted failed human hearts due to Idiopathic Dilated Cardiomyopathy (IDC), 7 failed human hearts due to Ischemic Cardiomyopathy (ICM) and 7 non-failing human donor hearts (DNR). SDS extracts were also prepared from cytosolic and mitochondrial fractions isolated from LV specimens. Results: H11K mRNA and protein levels normalized to GAPDH increased significantly in LV tissue from ICM and IDC hearts compared to DNR hearts and in HF dogs compared with NL dogs. H11K protein levels increased in cytosolic fractions but decreased in mitochondrial fractions of both failed human and dog hearts compared to DNR hearts and NL dog hearts. Immunoprecipitation studies in specimens from HF dogs showed that H11K cytosolic fractions interacted predominantly with p38MAPK and least with Akt when compared with NL dogs. Conclusions: Enhanced interaction of H11K with p38MAPK in HF can promote cell death thus contributing to progressive LV dysfunction. Therapeutic modalities that restore interaction of H11K with Akt and augment H11K translocation to mitochondria can potentially and partially reverse the progression of LV dysfunction by promoting cell survival.

Cardiac Proteome Profiling in Ischemic and Dilated Cardiomyopathy Mouse Models

Heart failure (HF) is a worldwide pandemic with an unacceptable high level of morbidity and mortality. Understanding the different pathophysiological mechanisms will contribute to prevention and individualized therapy of HF. We established mouse models for ischemic cardiomyopathy (ICM) and dilated cardiomyopathy (DCM) by inducing myocardial infarction (MI) and Coxsackievirus B3 infection, respectively. Isobaric tags for relative and absolute quantitation and liquid chromatography coupled with tandem mass spectrometry technology was used to identify the protein expression profiles in control and failing hearts. A total of 1,638 proteins were identified and compared in this proteomics analysis. Among them, 286 proteins were differently expressed. Gene ontology, KEGG pathway and ingenuity pathway analysis was performed to systematically assess the potential connections of the differentially expressed proteins to biological functions. Compared with control group, the differentially expressed proteins derived from the hearts of ICM and DCM mice were partially similar and mainly modulated in oxidative phosphorylation, metabolism and protein folding pathways. Moreover, difference still existed, the differentially expressed proteins between DCM and ICM hearts were significantly modulated in oxidative phosphorylation, metabolic and AMPK signaling pathways. Confirmatory western bolt analysis demonstrated that SDHB was down-regulated in both ICM and DCM hearts, while UQCRQ, GLUT4 and adiponectin were up-regulated in ICM hearts. Adenosine triphosphate (ATP) concentration significantly decreased in both DCM and ICM hearts. The protein expression of phospho-AMPKα decreased significantly in DCM hearts, but increased in ICM. In summary, oxidative phosphorylation, cardiac metabolism, and protein folding play critical roles in the pathogenesis of HF. The diverse changes in protein expression profiles between failing hearts induced by either MI or CVB3 infection demonstrated the heterogeneity of HF. Understanding the differences in proteome profiles could offer more precise therapeutic options for HF.

HEAT SHOCK PRE-TREATMENT OF EXPLANT-DERIVED CARDIAC STEM CELLS PROTECTS AGAINST ISCHEMIC STRESS

Transplant of explant-derived cardiac stem cells (EDCs) provides therapeutic regeneration of ischemic cardiomyopathy (ICM) through stimulation of angiogenesis and the generation of new cardiomyocytes- despite negligible long-term engraftment of transplanted cells. To offset the relentless ongoing loss of transplanted cells in ICM hearts, we investigated the ability of heat shock proteins (HSPs) to protect EDCs from cellular stress. Increasing EDCs exposure to heat shock culture conditions (43°C at 5% oxygen) progressively enhanced HSP70 transcript expression while HSP90 transcript expression remained unchanged. HSP70 expression plateaued 2012±736 fold above baseline after exposure to 3 hours of heat shock conditions and this pre-treatment duration was used for subsequent experiments. Heat shock treatment increased EDC proliferation within ischemic (1% oxygen) serum free conditions designed to mimic the ICM heart (population doubling time: 75±4 vs. 103±7 hours with no heat shock treatment, p=0.01, n=4). After 48 hours of exposure to hypoxic serum free conditions, heat shock pre-treatment increased the number of proliferating (Ki-67+) EDCs by 60±13% (p < 0.0001, n=6). Heat shock pre-treatment also conferred resistance to direct noxious stimuli. After 18 hours of exposure to 2ul of 100mM staurosporine, heat shock pre-treatment reduced cell death by 45±7% (p=0.03 vs. non heat shock pre-treated cells, n=5) and annexin V+ cells by 27±6% (p=0.04 vs. non heat shock pre-treated cells, n=5). Heat shock pre-treatment provides a simple inexpensive strategy to increase EDC survival in conditions mirroring the inhospitable remodeled ICM heart. We anticipate this strategy will synergize with biomaterial-based approaches that boost acute engraftment without supporting long-term cell survival.

Long non-coding RNAs link extracellular matrix gene expression to ischemic cardiomyopathy.

Ischemic cardiomyopathy (ICM) resulting from myocardial infarction is a major cause of heart failure (HF). Recently, thousands of long non-coding RNAs (lncRNAs) have been discovered and implicated in a variety of biological processes. However, the role of most lncRNAs in HF remains largely unknown. The aim of this study is to test the hypothesis that the expression and function of lncRNAs are differentially regulated in diseased hearts. In this study, we performed RNA deep sequencing of protein-coding and non-coding RNAs from cardiac samples of patients with ICM ( n = 15) and controls ( n = 15). Genome-wide transcriptome analysis confirmed that many protein-coding genes previously known to be involved in HF were altered in ICM hearts. Among the 145 differentially expressed lncRNAs identified in ICM hearts, we found a set of 35 lncRNAs that display strong positive expression correlation. Expression correlation coefficient analyses of differentially expressed lncRNAs and protein-coding genes revealed a strong association between lncRNAs and extracellular matrix (ECM) protein-coding genes. We overexpressed or knocked down selected lncRNAs in cardiac fibroblasts and our results suggest that lncRNAs are important regulators of fibrosis and the expression of ECM synthesis genes. Moreover, we show that lncRNAs participate in the TGF-β pathway to modulate the expression of ECM genes and myofibroblast differentiation. Our studies demonstrate that the expression of many lncRNAs is dynamically regulated in ICM. lncRNAs regulate the expression and function of ECM and cardiac fibrosis during the development of ICM. Our results further indicate that lncRNAs may represent novel regulators of heart function and cardiac disorders, including ICM.

Calmodulin Regulation of Ryanodine Receptors (RyR2) Differs in Failing and Non-Faling Human Hearts due to Differences in RyR2 Phosphorylation

The RyR2 is a macromolecular complex comprising a Ca2+ channel and many accessory proteins that regulate channel activity. In animal models, the binding of intracellular calmodulin (CaM, ∼45 nM in the cytoplasm) partially inhibits calcium release in cardiomyocytes due to its ability to inhibit RyR2 channel opening. Single channel studies of RyR2 in lipid bilayers find that CaM inhibits RyR2 from animal hearts with an IC50 of 100 nM.In this study, RyR2 was isolated from healthy human donor hearts and hearts with ischemic cardiomyopathy (ICM) with ethics approval (UoN H-2009-0369; Univ Sydney #2012/2814; QUT EC28114) and incorporated into lipid bilayers. We found that RyR2 from healthy human hearts were not inhibited by CaM at concentrations up to 500 nM whereas for RyR2 from human hearts with ICM, CaM caused a reduction in open probability of 57% ± 6%. Dephosphorylating these RyR2 channels with Protein Phosphatase 1 prior to experiments abolished the effect of CaM, suggesting that increased RyR2 phosphorylation in ICM hearts mediates CaM inhibition in humans.

Abstract 19706: CD39/CD73 Pathway in End-stage Human Ischemic Cardiomyopathy

Introduction: CD39 (ectonucleoside triphosphate diphosphohydrolase) is a nucleotidase expressed on endothelial cells, vascular smooth muscles cells, and leukocytes. CD39 plays a key role in vascular homeostasis, hydrolyzing extracellular ATP or ADP to AMP. CD73 (ecto-5’-nculeotidase) hydrolyzes AMP to adenosine. Both CD39 and CD73 are key modulators of purinergic signaling and have been shown to be important in ischemic preconditioning and ischemia reperfusion in animal models. Hypothesis: We hypothesized that the expression of the purine nucleotide-metabolizing pathway consisting of CD39 and CD73 in human hearts with ischemic cardiomyopathy is unregulated in response to ischemia. Methods: We compared the expression of CD39 and CD73 in left ventricular samples from patients with end-stage ischemic cardiomyopathy and normal hearts. Left ventricular tissue obtained from 7 end-stage ischemic cardiomyopathy hearts and 7 normal hearts not used for transplantation were homogenized and the levels of CD39 and CD73 mRNA were measured by qRT-PCR. Using the same tissue, immunoblot analysis for the protein level of CD39 and CD73 was conducted. Furthermore, immunohistochemical analysis of CD39 and CD73 expression was conducted on left ventricular tissue from the same subjects. Results: The total mRNA levels of CD39 and CD73 were increased in patients with end-stage ischemic cardiomyopathy. However, while there was a reduction in the total CD73 protein levels that did not reach significance, there was a marked reduction in the the total protein level of CD39 in ICM hearts (Figure). Immunohistochemical analysis demonstrated that the expression pattern of CD39 was significantly different in ICM hearts compared to normal hearts. Conclusions: These data provide important evidence that the extracellular nucleotide metabolizing pathway is altered in ICM. CD39 protein levels are significantly reduced in human end-stage ischemic cardiomyopathy.

189 Regulation of the Mitochondrial Proteins Mitofilin and Porin in Explanted Failing Human Hearts

Purpose: The concept that the failing heart is energy starved is supported by observations of abnormal energy production by the mitochondria respiratory chain. We previously showed that the physiologic processes of mitochondria biogenesis, fission and fusion are abnormal in the failing human heart and give rise to mitochondria hyperplasia, reduced organelle size and poor respiration. This study examined the regulation of two key mitochondrial proteins; porin (PO), the outer membrane protein that forms the aqueous channel for metabolite flux between mitochondria and cytosol, and mitofilin (MF), a critical organizer of mitochondria cristae morphology and thus indispensible for normal mitochondrial function. Methods and Materials: Studies were performed in LV tissue homogenate obtained from 6 normal (NL) donor human hearts, 6 explanted failing human hearts with dilated cardiomyopathy (DCM) and 6 explanted failing human hearts with ischemic cardiomyopathy (ICM). Protein expression of PO, MF and glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a housekeeping protein, was measured with specific antibodies and Western blotting and bands quantified in densitometric units (du). Results: Compared to NL donor hearts, MF was significantly reduced in ICM and DCM hearts while expression of PO and GAPDH were unchanged (Table).

Etiology-dependency of ionic remodeling in cardiomyopathic rabbits

Background Both dilated (DCM) and ischemic cardiomyopathy (ICM) are associated with action potential (AP) prolongation due to ionic remodeling. In humans, AP prolongation is more pronounced in myocytes isolated from explanted DCM than ICM hearts. However, there is a large variability due to confounding factors, including age, sex, concomitant disease, drug treatment, and progression of the disease at the time of heart transplantation. Here, we investigated the etiology-dependency of ionic remodeling in standardized rabbit models of ICM and DCM. Methods ICM and DCM were induced by chronic infarction or combined volume and pressure overload, respectively. APs and membrane currents were measured using patch-clamp methodology. Results Both ICM and DCM caused hypertrophy, but this hypertrophy was more prominent in DCM rabbits that also developed heart failure (DCM F), as revealed by the presence of ascites. Animals of either model showed AP prolongation. While the AP prolongation was similar by the same degree of hypertrophy, AP prolongation in DCM F was more pronounced. In all models, L-type Ca 2+ current, inward rectifier K + current, and rapid delayed rectifier K + current were unaltered, but the transient outward K + current ( I to1) density was significantly reduced. The I to1 decrease was not associated with differences in voltage-dependency of (in)activation. I to1 downregulation was similar in ICM and DCM with the same degree of hypertrophy, but was more pronounced in DCM F. Conclusions The amount of ionic remodeling and AP prolongation in cardiomyopathic rabbits is due to differences in the amount of hypertrophy rather than differences in the etiology of the cardiomyopathy.

Regional Heterogeneity of Decreased Myocardial Norepinephrine and Increased Lipid Peroxidation Levels in Patients With End-stage Failing Heart Secondary to Dilated or Ischemic Cardiomyopathy

Regional alterations in norepinephrine (NE) and lipid peroxidation in the myocardium of patients with heart failure is not well known. This study was designed to investigate regional myocardial NE levels and lipid peroxidation index and their relationships with the functional parameters in two pathologic conditions: dilated cardiomyopathy (DCM) and ischemic cardiomyopathy (ICM). Biopsied heart samples were obtained from 13 DCM and 10 ICM patients (orthotopic cardiac transplantation). Tissue NE was assayed by high-pressure liquid chromatography with electrochemical detection. Tissue lipid peroxidation (malondialdehyde, MDA) was evaluated by the thiobarbituric acid (TBA) reaction. Non-failing hearts (controls, n = 4) were included in this study for comparison. Left ventricular dysfunction was present at rest with a mean left ventricular ejection fraction (LVEF) of 19.1 +/- 2.6% for DCM patients and 17.4 +/- 2.0% for ICM patients. The amount of NE in control hearts was significantly lower (p < 0.05) than in DCM or ICM hearts. For all patients, there were several differences in distribution of NE among the sub-divisions of the atria and ventricles studied. NE content was significantly higher in the right atria than in the left atria or ventricles. A significant correlation between LVEF and NE concentrations was observed in the left septum of ICM and DCM patients and in the left ventricle of the ICM group. In DCM and ICM patients, some parts of the left ventricle showed higher levels of lipid peroxides compared with controls. MDA levels in patients with DCM varied little from one region to another, whereas in ICM patients there was considerable variation. This study is the first demonstration of a correlation between the values of pre-operative LVEF and cardiac NE concentrations in specific parts of the myocardium. This effect could not be generalized to the entire heart. The pattern of myocardial MDA distribution did not follow that of the NE distribution.

Cambios nucleares y expresión de p62 en la miocardiopatía isquémica y dilatada

The study's objectives were to investigate nuclear stereology and to determine the level of p62, a protein involved in nuclear transport, in human cardiomyocytes from patients with heart failure due to ischemic cardiomyopathy (ICM) or dilated cardiomyopathy (DCM). We studied 23 human hearts: 10 had ICM, 10 had DCM, and three were from control subjects. The size of the nucleus was significantly increased in ICM and DCM hearts compared with those from controls (by 60% and 66%, respectively, P=.03), as was the size of the nucleolus (by 59%, P=.02 and 75%, P=.03, respectively). In addition, the p62 level was significantly increased in both forms of cardiomyopathy compared with controls (ICM 110%, P=.01; and DCM 145%, P=.04). In the ICM group, there were correlations between the p62 level and nuclear size (r=0.615, P=.05) and between the p62 level and the heterochromatin percentage (r=-0.707; P=.02). In conclusion, cardiomyocytes from hearts affected by ICM and DCM showed changes in nuclear and nucleolar morphology. The p62 level had doubled in both forms of cardiomyopathy and, in ICM hearts, there was a correlation with nuclear changes.

Influence of nitric oxide synthase inhibition and endothelin-1 receptor blockade on acetylcholine-induced coronary artery contraction in vitro in dilated and ischemic cardiomyopathies.

The normal dilatory response to acetylcholine (ACH) is reduced in coronary vessels from patients with dilated cardiomyopathy (DCM) and reversed to a contraction in patients with coronary artery disease (CAD) and ischemic cardiomyopathy (ICM). This study investigated the influence of nitric oxide synthase inhibition and endothelin (ET)-1 receptor blockade on the reactivity to ACH of coronary arteries isolated from patients with end-stage congestive heart failure (CHF) associated or not with CAD. Small (approximately 400 microm) epicardial right coronary arteries were isolated from explanted hearts of patients undergoing transplantation for DCM or ICM. Segments were mounted on a wire myograph to record changes in isometric tension. ACH (1 microM) dilated pre-contracted vessels from DCM hearts but contracted pre-contracted vessels from ICM hearts. In the absence of pre-contraction, ACH (10(-9)-3 x 10(-5) M) induced a small contraction of rings from DCM hearts and a larger contraction (p < 0.05) of rings from ICM hearts. N(omega)-nitro-L-arginine (L-NNA, 100 microM), a NO synthase inhibitor, increased (p < 0.05) sensitivity and maximal response to ACH of vessels from DCM hearts only. In the presence of L-NNA, blockade of ET(A) with BQ123 (1 microM) prevented the effects of L-NNA in DCM, whereas blockade of ET(A/B) receptors with bosentan (10 microM) only reduced vascular sensitivity to ACH without significantly reducing the maximal contraction to ACH in DCM. The antagonists had no effects in vessels from ICM hearts. ACH, however, induced similar contractions of vessels without endothelium in DCM and ICM. These results suggest that ACH induces a contraction by stimulating smooth muscle muscarinic receptors. In coronary arteries isolated from DCM hearts, the contraction is regulated by NO and ET-1, whereas these factors seem to have little influence in ICM. This suggests that endothelial muscarinic receptors are either not expressed or uncoupled in ICM hearts.

Differential expression of heat shock proteins in normal and failing human hearts.

Heat shock proteins (hsp) constitute an endogenous stress response that protects cells from injury. Most work on these important proteins has focused on the immediate response to acute stress in cell culture systems and mammalian models of heart disease. Little is known about the expression of the hsps in human hearts. We were interested in whether there was increased expression of the hsps in heart failure, a setting of chronic, sustained stress. Five different hsps were examined: hsp27, hsp60, hsp72, hsc70 and hsp90. Three groups of explanted hearts were studied: dilated cardiomyopathy (DCM), ischemic cardiomyopathy (IHD), and normal controls. Western-blotting with a standard curve of purified protein on each blot was used to quantify the expression of the hsps. Hsp27 was increased almost two-fold in DCM compared to normal hearts, and was significantly greater than in IHD hearts. Levels of hsp60 were doubled in both DCM and IHD hearts (P < 0.05). Hsp72, hsc70 and hsp90 were not significantly changed. This study shows for the first time that differential changes in hsp levels occur in end-stage heart failure. Since hsps can render cells resistant to apoptosis, and are associated with the mitochondria and the cytoskeleton, which are known to be abnormal in heart failure, these studies may lead to new insights into the pathogenesis of cardiac decompensation.

Stem cell factor in mast cells and increased mast cell density in idiopathic and ischemic cardiomyopathy.

We compared cardiac mast cell (HHMC) density and the immunological and nonimmunological release of mediators from mast cells isolated from heart tissue of patients with idiopathic dilated (DCM) (n=24) and ischemic cardiomyopathy (ICM) (n = 10) undergoing heart transplantation and from control subjects (n = 10) without cardiovascular disease. HHMC density in DCM (18.4+/-1.6 cells/mm2) and ICM (18.4+/-1.5 cells/mm2) was higher than that in control hearts (5.3+/-0.7 cells/mm2; P<.01). The histamine and tryptase contents of DCM and ICM hearts were higher than those of control hearts. The histamine content of the hearts was correlated with mast cell density (r(s)=.91; P<.001). Protein A/gold staining of heart tissue revealed stem cell factor (SCF), the principal growth, differentiating, and activating factor of human mast cells, in HHMC secretory granules. Histamine release from cardiac mast cells caused by immunological (anti-IgE and rhSCF) and nonimmunological stimuli (Ca2+ ionophore A23187) was higher in patients with DCM and ICM compared with control subjects. Immunological activation of HHMC induced a significantly greater release of tryptase and LTC4 in patients with DCM and ICM compared with control subjects. Histamine and tryptase content and mast cell density are higher in failing hearts than in control hearts. SCF, present in secretory granules of HHMC, might represent an autocrine factor sustaining mast cell hyperplasia in heart tissue in these patients. The increased local release of fibrogenic factors (eg, histamine, tryptase, and leukotriene C4) might contribute to collagen accumulation in the hearts of patients with cardiomyopathy.