Molecular and cellular biology of heart failure

In recent years, the striking development of molecular biology and molecular genetic has brought completely new insights into the understanding of heart failure. Two aspects for which significant progress has been made in 1995 are discussed in this review: the genetic mechanisms of inherited cardiomyopathies and the molecular basis of heart failure due to chronic hemodynamic overload. In familial hypertrophic cardiomyopathy, a novel disease gene was found. It encodes myosin binding protein C, whose structure and function are poorly understood. Contractile deficits associated with the myosin mutations were demonstrated, and all this strengthened the hypothesis that hypertrophy is a compensatory mechanism that occurs in presence of a sarcomeric defect. These studies have important prognostic and clinical implications, but new and unexpected concerns have arisen, because a widespread difference in phenotype can be seen in patients harboring similar genotypes. In familial dilated cardiomyopathy, the main findings were the identification of four disease loci, but the genes are still unknown. With respect to the consequences of chronic hemodynamic overload on myocyte function and phenotype, recent data gave rise to lively discussions in the fields of reexpression of fetal troponin T isoforms and of decreased function and expression of the sarco(endo)plasmic reticulum Ca2+ ATPase in the failing human heart; at the moment it is difficult to draw definitive conclusions. Interestingly, three new concepts emerged in the understanding of the pathogenesis of heart failure: the increased contribution of the Na(+)-Ca2+ exchange, the possible recruitment of an inositol phosphate-sensitive calcium pool for myofibrillar activation, and the involvement of apoptotic myocyte and nonmyocyte cell death in myocardial remodeling.

Differential expression of alpha- and beta-enolase genes during rat heart development and hypertrophy

We have analyzed the transition between isoforms of the glycolytic enzyme enolase (2-phospho-D-glycerate hydrolyase; EC 4.2.1.11) in rat heart during normal and pathological growth. A striking fall in embryonic alpha-enolase gene expression occurs during cardiac development, mostly controlled at pretranslational steps. In fetal and neonatal hearts, muscle-specific beta-enolase gene expression is a minor contributor to total enolase. Control mechanisms of beta-enolase gene expression must include posttranscriptional steps. Aortic stenosis induces a rapid and drastic decrease in beta-enolase transcript level in cardiomyocytes, followed by the fall in beta-subunit level. In contrast, alpha-enolase transcript level is not significantly altered, although the corresponding subunit level increases in nonmuscle cells. We conclude that, like fetal heart, hypertrophic heart is characterized by a high ratio of alpha- to beta-enolase subunit concentrations. This study indicates that the decrease in beta-enolase gene expression may be linked to beneficial energetic changes in contractile properties occurring during cardiac hypertrophy.

Cardiac myosin binding protein-C gene splice acceptor site mutation is associated with familial hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy (FHC) is an autosomal dominant disease characterized by a ventricular hypertrophy predominantly affecting the interventricular septum and associated with a large extent of myocardial and myofibrillar disarray. It is the most common cause of sudden death in the young. In the four disease loci found, three genes have been identified which code for beta-myosin heavy chain, cardiac troponin T and alpha-tropomyosin. Recently the human cardiac myosin binding protein-C (MyBP-C) gene was mapped to chromosome 11p11.2 (ref. 8), making this gene a good candidate for the fourth locus, CMH4 (ref. 5). Indeed, MyBP-C is a substantial component of the myofibrils that interacts with several proteins of the thick filament of the sarcomere. In two unrelated French families linked to CMH4, we found a mutation in a splice acceptor site of the MyBP-C gene, which causes the skipping of the associated exon and could produce truncated cardiac MyBP-Cs. Mutations in the cardiac MyBP-C gene likely cause chromosome 11-linked hypertrophic cardiomyopathy, further supporting the hypothesis that hypertrophic cardiomyopathy results from mutations in genes encoding contractile proteins.

Removal of the financial barrier to health care: does it impact on prostate cancer at presentation and survival? A comparative study between black and white men in a Veterans Affairs system

OBJECTIVES

African-American men are known to have a higher incidence and mortality rate from prostate cancer than American-Caucasian men. It is also known that African Americans have a higher incidence of advanced stage disease at diagnosis. One hypothesis for the latter is a delay in diagnosis due to lack of financial access to health care. Because eligibility for medical care in Veterans Affairs Medical Centers (VAMCs) is similar for both black and white patients, less disparity of stage at diagnosis, and therefore survival between blacks and whites, would be expected.

METHODS

Cases for this study included only those histologically confirmed, newly diagnosed prostate cancers at the Allen Park VAMC in Wayne County, Michigan, between 1973 and 1992. Trained Surveillance, Epidemiology, and End Result (SEER) abstractors determined the stage at diagnosis, according to SEER criteria. Data analyses include descriptive statistics and survival analysis.

RESULTS

The distribution of race and annual income of all male patients seen at the VAMC in Allen Park is similar. Over the entire 20-year period (1973 to 1992), there were a total of 358 prostate cancers in white patients and 383 in black patients. The ages of black and white patients were comparable. The proportion of white and black men presenting with localized disease is similar (57% and 54%, respectively). A significantly greater proportion of black patients with prostate cancer were classified as having distant disease compared with white patients (25% versus 19%; P = 0.045). A racial "crossover" effect in survival occurred around age 70 years, with white men demonstrating improved survival under 70 years of age, and black men 70 years and older tending to have better survival.

CONCLUSIONS

These data suggest that financial access to care has no apparent influence on the higher proportion of distant disease and poorer survival of African-American patients with prostate cancer compared with American-Caucasian men.

The recurring evolution of lipoprotein(a). Insights from cloning of hedgehog apolipoprotein(a)

The lipoprotein Lp(a), a major inherited risk factor for atherosclerosis, consists of a low density lipoprotein-like particle containing apolipoprotein B-100 plus the distinguishing component apolipoprotein(a) (apo(a)). Human apo(a) contains highly repeated domains related to plasminogen kringle four plus single kringle five and protease-like domains. Apo(a) is virtually confined to primates, and the gene may have arisen during primate evolution. One exception is the occurrence of an Lp(a)-like particle in the hedgehog. Cloning of the hedgehog apo(a)-like gene shows that it is distinctive in form and evolutionary history from human apo(a), but that it has acquired several common features. It appears that the primate and hedgehog apo(a) genes evolved independently by duplication and modification of different domains of the plasminogen gene, providing a novel type of "convergent" molecular evolution.

Calcium transport proteins in the nonfailing and failing heart: gene expression and function

In heart failure alterations of intracellular Ca2+ handling are thought to be a major reason for impaired contraction and relaxation. Peak Ca2+ transients are reduced, resting Ca2+ levels elevated, and the time course of diastolic Ca2+ decline is markedly prolonged in failing hearts. The proteins of the sarcoplasmic reticulum and the sarcolemmal Na+/Ca2+ exchanger are the most important tools for Ca2+ homeostasis in the cardiomyocyte, and their molecular cloning has allowed prediction of structure/function analysis. The investigation of function and gene expression of these proteins in failing myocardium has been an area of intensive research in recent years in order to provide a more detailed understanding of the pathophysiology of heart failure. Quantitative changes in expression of the sarcoplasmic reticulum Ca(2+)-ATPase, the ryanodine receptor, and the Na+/Ca2+ exchanger with correlations to functional alterations have been reported both in experimental animal models and in the human failing heart. However, in human heart failure these findings are currently the subject of a lively discussion because observations have apparently been in part contradictory. This review discusses the proteins involved in myocardial Ca2+ handling and describes the current state of research on expressional and functional alterations and their potential implication in the pathomechanism of heart failure.

Mutations in the laminin alpha 2-chain gene (LAMA2) cause merosin-deficient congenital muscular dystrophy

Congenital muscular dystrophies (CMDs), are heterogeneous autosomal recessive disorders. Their severe manifestations consist of early hypotonia and weakness, markedly delayed motor milestones and contractures, often associated with joint deformities. Histological changes seen in muscle biopsies consist of large variations in muscle fibre size, a few necrotic and regenerating fibres and a marked increase in endomysial collagen tissue. Diagnosis is based on clinical features and on morphological changes. In several CMD cases, we have demonstrated an absence of one of the components of the extracellular matrix around muscle fibres, the merosin M chain, now referred to as the alpha 2 chain of laminin-2 (ref.3). We localized this CMD locus to chromosome 6q2 by homozygosity mapping and linkage analysis. The laminin alpha 2 chain gene (LAMA2) maps to the same region on chromosome 6q22-23 (ref. 5). We therefore investigated LAMA2 for the presence of disease-causing mutations in laminin alpha 2 chain-deficient CMD families and now report splice site and nonsense mutations in two families leading presumably to a truncated laminin alpha 2 protein.

Response and immunoresistance to botulinum toxin injections

Botulinum toxin antibodies (ABS) may be a reason why occasionally patients do not have a response to injections with botulinum toxin type A (BTX). We tested 86 patients with cervical or oromandibular dystonia for the presence of BTX ABS; 20 were positive and 66 were negative. All patients who tested positive had no response to BTX injections on at least two consecutive treatment sessions. When compared with 22 randomly selected patients with negative BTX ABS results, the patients with positive BTX ABS tests had an earlier age at onset (mean age: 31.8 +/- 16.7 years versus 43.4 +/- 10.5; p < 0.05), higher mean dose per visit (249.2 +/- 32.5 U versus 180.8 +/- 68.7, p < 0.0005), and higher total cumulative dose (mean dose: 1,709 +/- 638 U versus 1,066 +/- 938; p < 0.01). Four out of five patients with positive ABS tests later had a response to botulinum toxin type F injections. Of 26 patients with negative BTX ABS results who were tested because of poor response on at least one visit, 21 had good response after subsequent injection and five had no effect. Except for young age at onset and higher dosages, there were no other factors that could reliably predict which patients would become immunoresistant to BTX type A injections. Treatment with alternate serotypes may offer clinical benefit to this group of patients. Absence of detectable BTX ABS may occur in patients with poor response to BTX injections because of inadequate dosage, injections of inappropriate muscles, or poor sensitivity of the BTX ABS bioassay.

Readjusting the localization of long QT syndrome gene on chromosome 11p15

Long QT syndrome (LQT) is an autosomal dominant cardiac disease characterized by ventricular arrhythmia. A first locus for LQT has been identified on chromosome 11p15.5 (LQT1), closely linked to HRAS. To refine the location of LQT1, microsatellites were genotyped in 8 French families and the following order was determined: tel-HRAS-DRD4-D11S922-D11S4046- IGF2-INS-TH-D11S1318-D11S1323-D11S1338-D11S90 9-D11S1346-cen. By haplotype analysis, 12 crossing-over events were identified in affected and unaffected subjects, delineating the LQT1 candidate region to 7 cM. This new delineated localization between D11S1318 and D11S1323 is in a more centromeric region than previously thought and is 5 cM proximal to HRAS.

The COX8 gene is not the disease gene of the CMH4 locus in familial hypertrophic cardiomyopathy

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The relationship of counselor and peer alliance to drug use and HIV risk behaviors in a six-month methadone detoxification program

The purpose of this study was to examine the relationship of treatment outcomes in opioid detoxification to levels of counselor and peer alliance. Forty-one subjects were recruited from a larger, 180-day study of psychosocial treatment. Beginning at day 90, subjects completed monthly measures of alliance. Outcome measures included treatment retention, drug use and self-reported HIV risk. Measures of alliance were found to be internally consistent and moderately stable over time. During the final 30 days of the methadone taper, higher levels of both types of alliance were associated with less use of illicit opioids. Alliance with counselor was associated with less frequent needle sharing. For subjects who could be located for 30-day follow-up, greater alliance with peers was associated with more frequent HIV (sexual) risk behaviors. Results suggest that treatment outcome may be improved through approaches that address a patient's alliance with both counselor and peers.

Tremor and longevity in relatives of patients with Parkinson's disease, essential tremor, and control subjects

To study the relation between essential tremor (ET) and Parkinson's disease (PD), we compared the frequency of familial tremor in relatives of patients with PD (N = 391), ET (N = 140), and the combination of ET and PD (N = 125) with the frequency in patients with progressive supranuclear palsy (PSP) (N = 99) and normal age-matched controls (N = 104). Tremor was present in 96 (5.1%) of 1,874 parents and siblings of patients with PD, 152 of 650 (23.4%) relatives of patients with ET, 91 (20.7%) of 439 relatives of patients with ET-PD, 12 of 462 (2.6%) relatives of patients with PSP, and 10 of 448 (2.2%) relatives of normal controls. The high frequency of familial tremor among relatives of patients with PD, and especially those with the ET-PD combination, compared with relatives of patients with PSP or of normal controls suggests that there is an association of PD and familial tremor. Since the most common form of familial tremor is ET, our study provides support for the notion that ET and PD are pathogenetically related. We also found that parents with tremor lived on the average 9.2 years longer than those without tremor. The association of familial tremor with significantly increased longevity suggests that familial tremor confers some anti-aging influence. Alternatively, tremor may be a simple byproduct of the aging process.

[Hypertrophic cardiomyopathy: practical application of genetic research]

Hypertrophic cardiomyopathy is usually familial with an autosomal dominant mode of transmission. The condition is genetically heterogeneous. The first defective gene to be described was that of the beta heavy chain of cardiac myosin (beta-MHC, chromosome 14 q11-q12) where over 20 different localised false sense mutations and a hot point of mutation in exon 13 have been reported. This locus seems to be implicated in 30% of families studied. Systematic screening of the genome has led to the detection of new sites on chromosomes 1, 11 and 15. No gene has yet been identified in these three new loci. For all new families, present strategy consists in determining the locus responsible for the disease by linkage analysis. For beta-MHC locus a panel of several markers (the two MYO I and MYO II microsatellites of the beta-MHC gene and two new AFN microsatellites) has been established which allows accurate detection of whether the haplotype cosegregates with the disease, even in relatively small families. It is then necessary to define the mutation by PCR amplification of the exons followed by electrophoresis on Hydrolink-MDE gels and sequencing of the mutant exons. Some subjects are genotypically affected but phenotypically normal and it seems the penetrance varies with the type of mutation. Analysis of the genotype/phenotype relationship should be continued in order to improve our knowledge of the consequences of each mutation. The genotype diagnosis is therefore complex and cannot be undertaken at present of the examination of the propositus. Whole families must be sampled.(ABSTRACT TRUNCATED AT 250 WORDS)

Patterns of expression of sarcoplasmic reticulum Ca(2+)-ATPase and phospholamban mRNAs during rat heart development

This study reports the clonal analysis and sequence of rat phospholamban (PLB) cDNA clones and the temporal appearance and patterns of distribution of the mRNAs encoding sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA2) and PLB in the developing rat heart determined by in situ hybridization. Both proteins play a critical role in the contraction-relaxation cycle of the heart. SERCA2 mRNA is already abundantly present in the first stage studied, in the cardiogenic plate of the 9-day-old presomite embryo, before the occurrence of the first contractions. This very early expression makes it an excellent marker for the study of early heart development. Subsequently, SERCA2 mRNA becomes expressed in a craniocaudal gradient, being highest at the venous pole and decreasing in concentration toward the arterial pole of the heart. PLB mRNA can be detected in hearts from 12 days of development onward in a virtually opposite gradient. In essence, these patterns do not change during further development. PLB mRNA levels remain highest in the ventricle and outflow tract, whereas SERCA2 mRNA prevails in the inflow tract and atrium, although the difference between atrium and ventricle becomes less pronounced. These observations are compatible with a model in which the upstream part of the heart (inflow tract and atrium) would have a greater capacity to clear calcium and hence would have a longer duration of the diastole than the downstream compartments (atrioventricular canal, ventricle, and outflow tract), similar to the observed pattern of contraction of the embryonic heart. The sinoatrial and atrioventricular nodes do not reveal an expression pattern of SERCA2 and PLB mRNA that allows one to distinguish them from the surrounding atrial working myocardium. However, the ventricular part of the conduction system, comprising atrioventricular bundle and bundle branches, are almost devoid of SERCA2 mRNA.