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Biomedical subjects

Michael R Bristow

Publications and source records attributed to Michael R Bristow.

At least 19 recordsLinked to original sources
PubMed2026

Subgroups and Special Populations in Heart Failure Clinical Trials: Insights From the HFC-ARC Expert Consensus Panel.

In the evolving landscape of heart failure (HF) management, the identification and analysis of subgroups and special populations within clinical trials are crucial for enhancing clinical decision-making, guiding further research, and understanding heterogeneity in study outcomes. This expert consensus document results from the collaborative efforts of the Heart Failure Collaboratory and the Heart Failure Collaboratory Academic Research Consortium, which brought together stakeholders from academia, industry, the U.S. Food and Drug Administration, and patient representatives. The purpose of this assembly was to propose standardized definitions and critical endpoint considerations essential for shaping the design and conduct of clinical trials for drugs and devices in the field of HF. In this context, we propose definitions and endpoints for specific subgroups and special populations in the spectrum of HF. We enhanced the precision, efficacy, and applicability of clinical research and promote more "personalized" approaches to interpretation of clinical trials. Furthermore, we explore the burgeoning field of gene therapy as a promising avenue for addressing the genetic basis of certain cardiomyopathies within these specialized patient groups. We focus especially on methodological considerations for subgroup analyses in large-scale trials, highlighting the importance of proper interpretation of subgroups and best practices for identifying heterogeneity suggestive of differential treatment effects, including when these analyses should be considered hypothesis-generating and requiring subsequent validation. We advocate for a methodical approach to clinical trial design, one that prioritizes the strategic identification of subgroups and employs appropriate statistical methodologies to ensure the reliability and clinical relevance of findings. Through this lens, we envision a pathway toward more personalized and effective treatments for HF, ultimately aiming to improve patient outcomes by leveraging the insights garnered from meticulously designed and comprehensively analyzed clinical trials.

Humans↗
PubMed2025

β1- and β2-adrenergic Receptor Haplotypes Regulate Therapeutic Responses to Placebo and the Biased Ligand β-blocker Bucindolol.

BACKGROUND: ADRB1 and ADRB2, encoding cardiac myocyte &#x3b2;1- and &#x3b2;2-adrenergic receptors (ARs) that mediate pathologic myocardial remodeling in response to chronically increased signaling, contain N-terminus haplotype variants capable of influencing agonist- or biased ligand-induced receptor internalization that uncouples canonical signaling and initiates EGFR/ERK1/2 cardioprotection. METHODS: In two heart failure (HF) clinical trial genetic substudies we investigated effects of internalizing vs. internalization-resistant ADRB1/ADRB2 haplotypes on clinical or biomarker responses to the biased ligand &#x3b2;-blocker bucindolol vs. placebo or vs. the nonbiased &#x3b2;1-antagonist metoprolol, and in haplotyped isolated human heart preparations we measured ERK1/2 activation in response to these same interventions. RESULTS: In subjects with &#x2265;3 internalizing ADRB1+ADRB2 haplotypes (6.7% subcohort) placebo treatment was associated with fewer clinical events compared to subjects with internalization-resistant haplotypes (Odds Ratio (OR) 0.28, 95% CI (0.10, 0.82)). In contrast, placebo treatment in subjects with &#x2265;3 internalization-resistant haplotypes (70% subcohort) was associated with more clinical events in comparison to subjects with internalizing haplotype counterparts (OR 1.64 (1.46, 1.84)). Bucindolol treatment was equal to placebo in the &#x2265;3 internalizing subcohort, but was superior to placebo in the internalization-resistant subcohort (bucindolol vs. placebo OR 0.49 (0.41, 0.58)). In subjects with all 4 haplotypes internalization-resistant (25% subcohort), bucindolol vs. placebo reduced time to first event rates by 62.3&#xb1;17.5% (P <0.01, 1.68&#xb1;0.34 fold > the all-haplotypes parent population and additive to 1.92&#xb1;0.58 fold when the ADRB1 haplotype contained Arg389 rather than Gly389). The same bucindolol vs. placebo pattern was observed for NT-proBNP or norepinephrine reduction vs. metoprolol. In these comparisons ADRB2 and ADRB1 haplotypes behaved similarly, and although the haplotypes differed in frequency between Black and non-Black subjects, within haplotypes there were no by-race differences in therapeutic effects. Bucindolol but not metoprolol activated ERK1/2 signaling in isolated ventricular preparations with &#x2265;3 internalization-resistant haplotypes. CONCLUSIONS: 1) Both &#x3b2;1- and &#x3b2;2-AR haplotypes regulate therapeutic responses in HF; internalizing species confer protection against clinical events in placebo-treated subjects, while in internalization-resistant haplotypes the biased ligand &#x3b2;-blocker bucindolol but not the non-biased ligand metoprolol is associated with favorable effects. 2) The biased ligand cardioprotective effect may be related to internalization-dependent or -independent ERK1/2 activation.

Beta Adrenergic Receptors↗
PubMed2006

Predictors of sudden cardiac death and appropriate shock in the Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION) Trial.

BACKGROUND: The factors that determine the risk for sudden death or implantable cardioverter defibrillator therapy in patients receiving cardiac resynchronization therapy (CRT) therapies are largely unknown. METHODS AND RESULTS: We hypothesized that clinical measures of heart failure severity and the presence of comorbid conditions would predict the risk of malignant arrhythmias in the 1520 patients enrolled in the Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION) Trial. Outcomes in the CRT group after implantable cardioverter defibrillator therapy were also evaluated. The CRT-defibrillator device reduced the risk of sudden death by 56% compared with drug therapy (17 of 595 [2.9%] versus 18 of 308 [5.8%], P<0.02). CRT therapy was not associated with sudden death risk reduction (48 of 617 [7.8%]). Other factors associated with reduced sudden death risk were left ventricular ejection fraction >20% (HR, 0.55 [95% CI, 0.35 to 0.87]; P=0.01), QRS duration >160 ms (HR, 0.63 [95% CI, 0.40 to 0.997]; P=0.05), and female gender (HR, 0.56 [95% CI, 0.34 to 0.94]; P=0.003). The risk for sudden death was increased by advanced New York Heart Association class IV heart failure (HR, 2.62 [95% CI, 1.61 to 4.26]; P<0.011) and renal dysfunction (HR, 1.69 [95% CI, 1.06 to 2.69]; P=0.03). An appropriate shock was experienced in 88 (15%) of the 595 CTR-D patients. In the CRT-defibrillator patients, female gender (HR, 0.54 [95 % CI, 0.31 to 0.94]; P=0.03) and use of neurohormonal antagonists were associated with reduced risk. Class IV heart failure status increased risk. Appropriate implantable cardioverter defibrillator therapy was positively associated with risk of death or all-cause hospitalization (HR, 1.57; P<0.002), pump failure death or hospitalization (HR, 2.35; P<0.001), and sudden death (HR, 2.99; P=0.03), but not total mortality (HR, 1.3; P=0.28). CONCLUSIONS: In CRT candidates, sudden cardiac death risk is associated with higher New York Heart Association class and renal dysfunction. In CRT-defibrillator recipients, reduction in the risk of an appropriate shock is associated with medical therapy with neurohormonal antagonists, female gender, and New York Heart Association functional class III versus IV clinical status. Shock therapy was associated with worse outcome.

Aged↗
PubMed2006

Canonical transient receptor potential channels promote cardiomyocyte hypertrophy through activation of calcineurin signaling.

The calcium/calmodulin-dependent phosphatase calcineurin plays a central role in the control of cardiomyocyte hypertrophy in response to pathological stimuli. Although calcineurin is present at high levels in normal heart, its activity appears to be unaffected by calcium during the course of a cardiac cycle. The mechanism(s) whereby calcineurin is selectively activated by calcium under pathological conditions has remained unclear. Here, we demonstrate that diverse signals for cardiac hypertrophy stimulate expression of canonical transient receptor potential (TRPC) channels. TRPC consists of a family of seven membrane-spanning nonselective cation channels that have been implicated in the nonvoltage-gated influx of calcium in response to G protein-coupled receptor signaling, receptor tyrosine kinase signaling, and depletion of internal calcium stores. TRPC3 expression is up-regulated in multiple rodent models of pathological cardiac hypertrophy, whereas TRPC5 expression is induced in failing human heart. We demonstrate that TRPC promotes cardiomyocyte hypertrophy through activation of calcineurin and its downstream effector, the nuclear factor of activated T cells transcription factor. These results define a novel role for TRPC channels in the control of cardiac growth, and suggest that a TRPC-derived pool of calcium contributes to selective activation of calcineurin in diseased heart.

Anilides↗
PubMed2006

A polymorphism within a conserved beta(1)-adrenergic receptor motif alters cardiac function and beta-blocker response in human heart failure.

Heterogeneity of heart failure (HF) phenotypes indicates contributions from underlying common polymorphisms. We considered polymorphisms in the beta(1)-adrenergic receptor (beta(1)AR), a beta-blocker target, as candidate pharmacogenomic loci. Transfected cells, genotyped human nonfailing and failing ventricles, and a clinical trial were used to ascertain phenotype and mechanism. In nonfailing and failing isolated ventricles, beta(1)-Arg-389 had respective 2.8 +/- 0.3- and 4.3 +/- 2.1-fold greater agonist-promoted contractility vs. beta(1)-Gly-389, defining enhanced physiologic coupling under relevant conditions of endogenous expression and HF. The beta-blocker bucindolol was an inverse agonist in failing Arg, but not Gly, ventricles, without partial agonist activity at either receptor; carvedilol was a genotype-independent neutral antagonist. In transfected cells, bucindolol antagonized agonist-stimulated cAMP, with a greater absolute decrease observed for Arg-389 (435 +/- 80 vs. 115 +/- 23 fmol per well). Potential pathophysiologic correlates were assessed in a placebo-controlled trial of bucindolol in 1,040 HF patients. No outcome was associated with genotype in the placebo group, indicating little impact on the natural course of HF. However, the Arg-389 homozygotes treated with bucindolol had an age-, sex-, and race-adjusted 38% reduction in mortality (P = 0.03) and 34% reduction in mortality or hospitalization (P = 0.004) vs. placebo. In contrast, Gly-389 carriers had no clinical response to bucindolol compared with placebo. Those with Arg-389 and high baseline norepinephrine levels trended toward improved survival, but no advantage with this allele and exaggerated sympatholysis was identified. We conclude that beta(1)AR-389 variation alters signaling in multiple models and affects the beta-blocker therapeutic response in HF and, thus, might be used to individualize treatment of the syndrome.

Adrenergic beta-Antagonists↗
PubMed2006

Importance of right ventricular end-systolic regional wall stress in idiopathic pulmonary arterial hypertension: a new method for estimation of right ventricular wall stress.

RV dysfunction in idiopathic (primary) pulmonary hypertension (IPAH) is often characterized by chamber dilation, ventricular hypertrophy, and impaired systolic function. In this study we characterize right ventricular (RV) chamber size, end-diastolic thickness, myocardial mass, and ejection fraction in patients with right ventricular heart failure from IPAH, n = 16 and compare these characteristics to a control population of cardiac transplant patients (TX, n = 4) and a group of normal subjects (N, n = 5). Subjects underwent both gated cardiac magnetic resonance imaging (MRI) of the right ventricle and right heart catheterization (RHC). Using parameters from both the MRI and RHC, an estimate of RV end-systolic relative wall stress (RWS) was calculated. RV RWS was 34.7 +/- 8.4 and 17.3 +/- 3.8 Kdynes/cm2 in the cardiac transplant and control subjects respectively and was significantly elevated 104.1 Kdynes/cm2 in IPAH patients (IPAH vs N and TX; p = 0.004 and 0.008 ). RV ejection fraction RVEF was lower in IPAH patients 0.36 +/- .10 than in N and TX 0.57 +/- .04 and 0.55 +/- .08 respectively, (p = 0.0006 N and 0.0007 TX). An inverse linear correlation was demonstrated between RWS and RVEF (y = 215- 332x; R = .80, p < or = .0001). Right ventricular RWS is significantly elevated in IPAH and may provide a useful quantitative monitoring tool in patients with IPAH to assess the benefit of different therapeutic interventions and provide prognostic information.

Cardiomegaly↗
PubMed2006

Serial gene expression profiling in the intact human heart.

BACKGROUND: In chronic heart failure due to a dilated cardiomyopathy phenotype, the molecular bases for contractile dysfunction and chamber remodeling remain largely unidentified. METHODS: To investigate the feasibility of measuring global gene expression serially in the intact failing human heart, we performed repeated messenger RNA (mRNA) expression profiling using RNA extracted from endomyocardial biopsy specimens and gene chip methodology in 8 subjects with idiopathic dilated cardiomyopathy. In patients treated with beta-blocking agents or placebo, myocardial gene expression was measured in endomyocardial biopsy material and radionuclide ejection fraction was measured at baseline and after 4 to 12 months of treatment. Gene expression was measured for 12,625 gene sequences by using Affymetrix U95 gene chips and commercially available software. For 6 mRNAs, gene chip results were compared with measurements made by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: In an unfiltered composite analysis of changes in expression detected in the patients with high-signal intensity chips, 241 genes showed an increase and 331 genes a decrease in mRNA abundance. There was good agreement between changes measured by quantitative RT-PCR and those determined by gene chips. There was less variance between differences in phenotype in patients sampled serially as compared between subjects with similar phenotypes sampled at baseline. CONCLUSIONS: Serial gene expression profiling with association to phenotypic change is feasible in the intact human heart and may offer advantages to cross-sectional expression profiling. This study suggests that the intact failing remodeled human heart is in an activated state of gene expression, with a large net reduction in gene expression occurring as phenotypic improvement occurs.

Adolescent↗
PubMed2006

A beta1-adrenergic receptor CaM kinase II-dependent pathway mediates cardiac myocyte fetal gene induction.

Beta-adrenergic signaling plays an important role in the natural history of dilated cardiomyopathies. Chronic activation of beta-adrenergic receptors (beta1-AR and beta2-AR) during periods of cardiac stress ultimately harms the failing heart by mechanisms that include alterations in gene expression. Here, we show that stimulation of beta-ARs with isoproterenol in neonate rat ventricular myocytes causes a "fetal" response in the relative activities of the human cardiac fetal and/or adult gene promoters that includes repression of the human and rat alpha-myosin heavy chain (alpha-MyHC) promoters with simultaneous activation of the human atrial natriuretic peptide (ANP) and rat beta-MyHC promoters. We also show that the promoter changes correlate with changes in endogenous gene expression as measured by mRNA expression. Furthermore, we show that these changes are specifically mediated by the beta1-AR, but not the beta2-AR, and are independent of alpha1-AR stimulation. We also demonstrate that the fetal gene response is independent of cAMP and protein kinase A, whereas inhibition of Ca2+/calmodulin-dependent protein kinase (CaMK) pathway blocks isoproterenol-mediated fetal gene program induction. Finally, we show that induction of the fetal program is dependent on activation of the L-type Ca2+ channel. We conclude that in neonatal rat cardiac myocytes, agonist-occupied beta1-AR mobilizes Ca2+ stores to activate fetal gene induction through cAMP independent pathways that involve CaMK.

Actins↗
PubMed2006

Alterations in myocardial gene expression as a basis for cardiomyopathies and heart failure.

Heart muscle disease and one of its consequences, chronic heart failure, are caused by altered gene expression. There are three general types of changes in gene expression that can cause or affect the natural history of heart muscle disease. These are: (1) mutations in genes that lead to changes in important functional properties of proteins critical to myocardial structure and/or function; (2) polymorphic variation in disease modifying genes and proteins, leading to altered function of a common gene product variant; and (3), regulated altered expression of a wild type gene and protein gene product. The role of these alterations in gene expression in the cause, progression and interaction with therapy of heart muscle disease and heart failure is discussed.

Cardiomyopathies↗
PubMed2005

Cost effectiveness of cardiac resynchronization therapy in the Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION) trial.

OBJECTIVES: The analysis goal was to estimate incremental cost-effectiveness ratios (ICERs) for the Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION) trial patients who received cardiac resynchronization therapy (CRT) via pacemaker (CRT-P) or pacemaker-defibrillator (CRT-D) in combination with optimal pharmacological therapy (OPT) relative to patients with OPT alone. BACKGROUND: In the COMPANION trial, CRT-P and CRT-D reduced the combined risk of all-cause mortality or first hospitalization among patients with advanced heart failure and intraventricular conduction delays, but the cost effectiveness of the therapy remains unknown. METHODS: In this analysis, intent-to-treat trial data were modeled to estimate the cost effectiveness of CRT-D and CRT-P relative to OPT over a base-case seven-year treatment episode. Exponential survival curves were derived from trial data and adjusted by quality-of-life trial results to yield quality-adjusted life-years (QALYs). For the first two years, follow-up hospitalizations were based on trial data. The model assumed equalized hospitalization rates beyond two years. Initial implantation and follow-up hospitalization costs were estimated using Medicare data. RESULTS: Over two years, follow-up hospitalization costs were reduced by 29% for CRT-D and 37% for CRT-P. Extending the cost-effectiveness analysis to a seven-year base-case time period, the ICER for CRT-P was 19,600 dollars per QALY and the ICER for CRT-D was 43,000 dollars per QALY relative to OPT. CONCLUSIONS: For the COMPANION trial patients, the use of CRT-P and CRT-D was associated with a cost-effectiveness ratio below generally accepted benchmarks for therapeutic interventions of 50,000 dollars per QALY to 100,000 dollars per QALY. This suggests that the clinical benefits of CRT-P and CRT-D can be achieved at a reasonable cost.

Cardiac Output, Low↗
PubMed2005

Mode of death in advanced heart failure: the Comparison of Medical, Pacing, and Defibrillation Therapies in Heart Failure (COMPANION) trial.

OBJECTIVES: The aim of this study was to evaluate the mode of death in patients with advanced chronic heart failure (HF) and intraventricular conduction delay treated with optimal pharmacologic therapy (OPT) alone or OPT with biventricular pacing to provide cardiac resynchronization therapy (CRT) or CRT + an implantable defibrillator (CRT-D). BACKGROUND: Limited data are available on mode of death in advanced HF. No data have existed on mode of death in these patients who also have an intraventricular conduction delay and are treated with CRT or CRT-D. METHODS: Using prespecified definitions and source materials, seven cardiologists assessed mode of death among the 313 deaths that occurred in the Comparison of Medical, Pacing, and Defibrillation Therapies in Heart Failure (COMPANION) trial. RESULTS: A primary cardiac cause was present in 78% of deaths. Pump failure (44.4%) was the most common mode of death followed by sudden cardiac death (SCD) (26.5%). Compared with OPT, CRT-D significantly reduced the number of cardiac deaths (38%, p = 0.006), whereas CRT alone was associated with a non-significant 14.5% reduction (p = 0.33). Both CRT and CRT-D tended to reduce pump failure deaths (29%, p = 0.11 and 27%, p = 0.14, respectively). The CRT-D significantly reduced SCD (56%, p = 0.02), but CRT alone did not. CONCLUSIONS: Pump failure deaths are the predominant mode of death in patients with advanced HF and are modestly reduced by both CRT and CRT-D. Only CRT-D reduced SCD and thus produced a favorable effect on cardiac mortality.

Cardiac Output, Low↗
PubMed2005

The PPAR-alpha activator fenofibrate fails to provide myocardial protection in ischemia and reperfusion in pigs.

Rodent studies suggest that peroxisome proliferator-activated receptor-alpha (PPAR-alpha) activation reduces myocardial ischemia-reperfusion (I/R) injury and infarct size; however, effects of PPAR-alpha activation in large animal models of myocardial I/R are unknown. We determined whether chronic treatment with the PPAR-alpha activator fenofibrate affects myocardial I/R injury in pigs. Domestic farm pigs were assigned to treatment with fenofibrate 50 mg.kg(-1).day(-1) orally or no drug treatment, and either a low-fat (4% by weight) or a high-fat (20% by weight) diet. After 4 wk, 66 pigs underwent 90 min low-flow regional myocardial ischemia and 120 min reperfusion under anesthetized open-chest conditions, resulting in myocardial stunning. The high-fat group received an infusion of triglyceride emulsion and heparin during this terminal experiment to maintain elevated arterial free fatty acid (FFA) levels. An additional 21 pigs underwent 60 min no-flow ischemia and 180 min reperfusion, resulting in myocardial infarction. Plasma concentration of fenofibric acid was similar to the EC50 for activation of PPAR-alpha in vitro and to maximal concentrations achieved in clinical use. Myocardial expression of PPAR-alpha mRNA was prominent but unaffected by fenofibrate treatment. Fenofibrate increased expression of carnitine palmitoyltransferase (CPT)-I mRNA in liver and decreased arterial FFA and lactate concentrations (each P < 0.01). However, fenofibrate did not affect myocardial CPT-I expression, substrate uptake, lipid accumulation, or contractile function during low-flow I/R in either the low- or high-fat group, nor did it affect myocardial infarct size. Despite expression of PPAR-alpha in porcine myocardium and effects of fenofibrate on systemic metabolism, treatment with this PPAR-alpha activator does not alter myocardial metabolic or contractile responses to I/R in pigs.

Animals↗
PubMed2005

Alpha-myosin heavy chain: a sarcomeric gene associated with dilated and hypertrophic phenotypes of cardiomyopathy.

BACKGROUND: Mutations in the beta-myosin heavy-chain (betaMyHC) gene cause hypertrophic (HCM) and dilated (DCM) forms of cardiomyopathy. In failing human hearts, downregulation of alphaMyHC mRNA or protein has been correlated with systolic dysfunction. We hypothesized that mutations in alphaMyHC could also lead to pleiotropic cardiac phenotypes, including HCM and DCM. METHODS AND RESULTS: A cohort of 434 subjects, 374 (134 affected, 214 unaffected, 26 unknown) belonging to 69 DCM families and 60 (29 affected, 30 unaffected, 1 unknown) in 21 HCM families, was screened for alphaMyHC gene (MYH6) mutations. Three heterozygous MYH6 missense mutations were identified in DCM probands (P830L, A1004S, and E1457K; 4.3% of probands). A Q1065H mutation was detected in 1 of 21 HCM probands and was absent in 2 unaffected offspring. All MYH6 mutations were distributed in highly conserved residues, were predicted to change the structure or chemical bonds of alphaMyHC, and were absent in at least 300 control chromosomes from an ethnically similar population. The DCM carrier phenotype was characterized by late onset, whereas the HCM phenotype was characterized by progression toward dilation, left ventricular dysfunction, and refractory heart failure. CONCLUSIONS: This study suggests that mutations in MYH6 may cause a spectrum of phenotypes ranging from DCM to HCM.

Cardiomyopathy, Dilated↗
PubMed2005

Thyroid hormone induces cardiac myocyte hypertrophy in a thyroid hormone receptor alpha1-specific manner that requires TAK1 and p38 mitogen-activated protein kinase.

Alterations in TR [thyroid hormone (TH) receptor]1 isoform expression have been reported in models of both physiologic and pathologic cardiac hypertrophy as well as in patients with heart failure. In this report, we demonstrate that TH induces hypertrophy as a direct result of binding to the TRalpha1 isoform and, moreover, that overexpression of TRalpha1 alone is also associated with a hypertrophic phenotype, even in the absence of ligand. The mechanism of TH and TRalpha1-specific hypertrophy is novel for a nuclear hormone receptor and involves the transforming growth factor beta-activated kinase (TAK1) and p38. Mitigating TRalpha1 effects, both TRalpha2 and TRbeta1 attenuate TRalpha1-induced myocardial growth and gene expression by diminishing TAK1 and p38 activities, respectively. These findings refine our previous observations on TR expression in the hypertrophied and failing heart and suggest that manipulation of thyroid hormone signaling in an isoform-specific manner may be a relevant therapeutic target for altering the pathologic myocardial program.

Adenoviridae↗
PubMed2005

Thymopoietin (lamina-associated polypeptide 2) gene mutation associated with dilated cardiomyopathy.

Thymopoietin or TMPO (indicated by its alternative gene symbol, LAP2, in this work) has been proposed as a candidate disease gene for dilated cardiomyopathy (DCM), since a LAP2 product associates with nucleoplasmic lamins A/C, which are encoded by the DCM gene LMNA. We developed a study to screen for genetic mutations in LAP2 in a large collection of DCM patients and families. A total of 113 subjects from 88 families (56 with familial DCM (FDC) and 32 with sporadic DCM) were screened for LAP2 mutations using denaturing high-performance liquid chromatography and sequence analysis. We found a single putative mutation affecting the LAP2alpha isoform in one FDC pedigree. The mutation predicts an Arg690Cys substitution (c.2068C>T; p.R690C) located in the C-terminal domain of the LAP2alpha protein, a region that is known to interact with lamin A/C. RT-PCR, Western blot analyses, and immunolocalization revealed low-level LAP2alpha expression in adult cardiac muscle, and localization to a subset of nuclei. Mutated Arg690Cys LAP2alpha expressed in HeLa cells localized to the nucleoplasm like wild-type LAP2alpha, with no effect on peripheral and nucleoplasmic lamin A distribution. However, the in vitro interaction of mutated LAP2alpha with the pre-lamin A C-terminus was significantly compromised compared to the wild-type protein. LAP2 mutations may represent a rare cause of DCM. The Arg690Cys mutation altered the observed LAP2alpha interaction with A-type lamins. Our finding implicates a novel nuclear lamina-associated protein in the pathogenesis of genetic forms of dilated cardiomyopathy.

Cardiomyopathy, Dilated↗
PubMed2005

Increased reactive oxygen species production and functional alterations in antioxidant enzymes in human failing myocardium.

BACKGROUND: The nature of oxidative stress and the activity of antioxidant enzyme systems are incompletely characterized in the failing human heart. METHODS AND RESULTS: We obtained ventricular myocardium from failing, explanted human hearts in patients with nonischemic dilated cardiomyopathy at the time of heart transplant to examine whether reactive oxygen species (ROS) production and antioxidant enzyme activity or expression were altered in end-stage human heart failure. Nonfailing myocardium was obtained from organ donors who were not eligible for transplantation. Electroparamagnetic resonance (EPR) with the O(2)(-) spin trap 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide demonstrated that formation of superoxide anion was increased more than 2-fold in the failing (P < .001 vs. nonfailing) myocardium. Manganese superoxide dismutase (MnSOD) mRNA and catalase mRNA expression were increased by 52% (P=.05) and 116% (P < .05), respectively, in failing vs. nonfailing hearts. Copper-zinc superoxide dismutase (CuZnSOD) mRNA and glutathione peroxidase-1 (GPx-1) mRNA were unchanged. The expression of MnSOD, CuZnSOD, and catalase mRNA showed moderate correlation, suggesting coordinate regulation of gene expression. Activity was no different with regard to catalase, GPx-1, and glucose-6-phosphate dehydrogenase. MnSOD activity accounted for approximately 90% of total SOD activity, and was markedly decreased in failing hearts (by 61%, P < .05). MnSOD protein expression by western blot analysis was decreased in the failing group (P < .05 vs. nonfailing). CONCLUSION: The decrease in MnSOD activity in failing myocardium, in the setting of increased mRNA expression, may reflect decreased translation or processing, or a posttranslational modification of MnSOD. The increase in MnSOD mRNA in failing hearts is consistent with the thesis that there is increased oxidative stress in failing myocardium that leads to increase transcription of antioxidant enzymes. The source of this direct measure of ROS is likely superoxide. These observations have implications for the pathophysiology and treatment of heart failure.

Adult↗