Silent myocardial ischemia: Current perspectives and future directions

Silent myocardial ischemia (SMI) is increasingly being recognized as part of the spectrum of ischemic heart disease. The spectrum of SMI ranges from asymptomatic coronary artery disease to critical illness necessitating intensive care. Although many diagnostic tools have been used to identify low- and high-risk subgroups, their use is limited by modest sensitivities and specificities. The present review identifies current concepts in the management of SMI in various clinical settings, as well as emerging technologies that may simplify the diagnosis and treatment of this condition.     

Neutrophil elastase produces 52-kD and 30-kD glucocorticoid receptor fragments in the cytosol of human leukemia cells

Characterization of glucocorticoid receptors in leukemia cells is important to understand mechanisms of glucocorticoid resistance but has been impeded by receptor fragmentation in cytosol extracts. We recently found that formation of 52- and 30-kilodalton (kD) glucocorticoid receptor fragments in cytosol of leukemia cells is due to proteolysis and is blocked by diisopropylfluorophosphate (DFP). In the present study, we identify a 28-kD serine protease in cytosol of leukemia cells that binds [3H]DFP and correlates with the formation of 52- and 30-kD receptor fragments. This protease is immunoprecipitated by antiserum to neutrophil elastase. Limited digestion of [3H]dexamethasone-21-mesylate- labeled receptors by purified neutrophil elastase produces 52- and 30- kD receptor fragments. Receptor fragmentation in the cytosol of leukemia cells in inhibited by methoxysuccinyl-alanyl-alanyl-prolyl- valyl-chloromethylketone, a highly specific inhibitor of neutrophil elastase. The addition of as few as 5% neutrophils to a lymphoid cell suspension provides sufficient elastase to produce receptor fragmentation. Our findings indicate that neutrophil elastase is responsible for receptor fragmentation in the cytosol of leukemia cells. The neutrophil elastase may be endogenous to the leukemia cells or may come from neutrophils that contaminate leukemia cell suspensions.     

Deficiency of intact thrombospondin and membrane glycoprotein Ia in platelets with defective collagen-induced aggregation and spontaneous loss of disorder

Platelets from a patient with a severe lifelong bleeding tendency, which later spontaneously disappeared, lacked intact thrombospondin and glycoprotein (GP) Ia. Before disappearance of the bleeding disorder, results of coagulation studies and platelet aggregation in response to adenosine diphosphate (ADP), arachidonic acid, thrombin, A23187, epinephrine, and ristocetin were normal. In contrast, aggregation only occurred in the presence of collagen or wheat germ agglutinin at unusually high doses of these agonists. The platelets adhered normally to purified bovine and human type I collagen, and they did not spread in the presence of methylated type I collagen. No collagen-induced clot retraction was observed. Two-dimensional gel electrophoretic analyses of platelet proteins and immunologic studies showed that intact thrombospondin and GP Ia were absent. Aggregation in response to collagen could be restored by adding thrombospondin. Disappearance of the bleeding tendency occurred at the onset of menopause; subsequent analyses revealed that thrombospondin and GP Ia were present in platelets and that collagen-induced platelet aggregation was normal. These results suggest that both thrombospondin and GP Ia are essential in collagen-induced platelet aggregation. The spontaneous disappearance of the bleeding tendency may have been related to hormonal influences.     

The obesity-associated peptide leptin induces hypertrophy in neonatal rat ventricular myocytes

One of the major manifestations of obesity is increased production of the adipocyte-derived 16-kDa peptide leptin, which is also elevated in heart disease, including congestive heart failure. However, whether leptin can directly alter the cardiac phenotype is not known. We therefore studied the effect of leptin as a potential hypertrophic factor in cultured myocytes from 1- to 4-day-old neonatal rat heart ventricles. Using RT-PCR, we demonstrate that these cells express the short-form (OB-Ra) leptin receptor. Twenty-four hours of exposure to leptin (0.31 to 31.3 nmol/L) produces a significantly increased cell surface area that peaked at 0.63 nmol/L. Subsequent experiments were done with 3.1 nmol/L leptin, which significantly increased cell area by 42%, protein synthesis by 32%, and alpha-skeletal actin and myosin light chain-2 expression by 250% and 300%, respectively. These events occurred in the absence of any increased cell death. Hypertrophy was preceded by rapid activation of the mitogen-activated protein kinase system including p38 and p44/42 as early as 5 minutes after leptin addition, whereas hypertrophy was inhibited by the p38 inhibitor SB203580 but not by the p44/42 inhibitor PD98059. Our results demonstrate a direct hypertrophic effect of leptin and may offer a biological link between hypertrophy and hyperleptinemic conditions such as obesity.     

Therapeutic opportunities for cell cycle re-entry and cardiac regeneration

Over the last two decades, considerable effort has been made to better understand putative regulators and molecular switches that govern the cell cycle in attempts to reactivate cell cycle progression of cardiac muscle. Rapid advancements on the field of stem cycle biology including evidence of cardiac progenitors within the adult myocardium itself and reports of cardiomyocyte DNA synthesis, which each suggest that the adult myocardium may in fact have the capacity for de novo myocyte regeneration. Augmenting cardiomyocyte number by targeting specific cell cycle regulatory genes or by stimulating cardiac progenitor cells to differentiate into cardiac muscle may be of therapeutic value in repopulating the adult myocardium with functionally active cells in patients with end-stage heart failure. Advancements in the area of cardiomyocyte cell cycle control and regeneration and their therapeutic potential are discussed.     

Detection of platelet-directed immunoglobin G in sera using the peroxidase-anti-peroxidase (PAP) slide technique

An immunohistochemical procedure for the detection of immunoglobulin G adherent to platelets is described. The peroxidase anti-peroxidase method is used to detect antibody activity directed against platelets from normal donors in the sera from 305 individuals. These subjects were divided into three groups: group 1, patients referred for tissue typing; group 2, healthy normal females; group 3, healthy normal males. In group 1, 28% of the sera were found to be positive; in most of these a history of prior transfusions was obtained. In group 2, 7.4% were found to be positive, most having previous pregnancies. Only 1% were found to be positive in group 3, and no reason for presensitization was found. Results from the indirect immunofluorescence technique served as a control and as a means to compare the sensitivity. Under the conditions chosen, the peroxidase anti-peroxidase test was two to eight times more sensitive than the immunofluorescence technique. Specificity of the peroxidase anti-peroxidase technique was demonstrated using a monospecific anti-PLA1 antiserum. It is concluded that the peroxidase anti-peroxidase slide technique may be a useful tool in the study of platelet-related immunophenomena.     

Apoptosis of ventricular myocytes: a means to an end

One of the most compelling issues to impact on contemporary cardiology is arguably the phenomenon of programmed cell death or apoptosis. Studies in the nematode Caenorhabditis elegans provided the first indication that determinants of cell fate crucial for normal worm development were under genetic influences of the ced-3 and ced-9 genes, which promote or prevent cell death, respectively. Extrapolation of these seminal findings led to the discovery of the mammalian ced-3 and ced-9 homologs, which broadly encompass a family of cellular cysteine proteases known collectively as caspases and the Bcl-2 proteins. In quiescent cells, caspases exist as inactive zymogens that are readily activated by autocatalytic processes or by other caspases following a death signal. The caspase-dependent cleavage of intracellular substrates results in the biochemical dismantling of the cell and morphological features characteristic of apoptosis. Recently, a mitochondrial death pathway for apoptosis has been proposed. Perturbations to mitochondria resulting in the loss of mitochondrial membrane potential, DeltaPsim, permeability transition pore (PTP) opening and the release of pro-apoptotic factors by mitochondria including cytochrome c, second mitochondrial activator of caspases/direct IAP binding protein with low pI (Smac/DIABLO), AIF, and others are considered terminal events in the apoptotic pathway. Bcl-2 and related family members are characterized by their ability to promote or prevent cell death. These proteins exert their pro- or anti-apoptosis function by impinging on components of the cell death pathway that underlie caspase activation, mitochondrial dysfunction or both. The limited regenerative potential of the adult cardiac muscle itself, together with the heightened and exciting possibility of regenerating cardiac muscle with cardiac progenitor cells, acknowledges the need for new strategies to suppress and/or prevent inappropriate cardiac cell death in patients with ischemic heart disease or heart failure patients as a therapeutic means of preserving cardiac pump function after injury.     

Lovastatin therapy for hypercholesterolemia in cardiac transplant recipients

Hypercholesterolemia (type II hyperlipidemia) after cardiac transplantation is common and may play a role in the accelerated rate of coronary atherosclerosis seen following the procedure. However, conventional cholesterol-lowering drugs are either ineffective or contraindicated for use in transplant recipients. The presence of type II hyperlipidemia was identified in 11 cardiac transplant recipients during a mean follow-up period of 15 months (range 3 to 41) after transplantation. Lovastatin, at an initial dosage of 20 mg/day, was administered for a period of 1 year. The maximal dosage of lovastatin was 60 mg/day. All patients received maintenance dosages of immunosuppressive agents, including cyclosporine-A, prednisone and, in some instances, azathioprine. Lipid profiles, hepatic transaminases, serum creatinine, creatine kinase and cyclosporine-A serum trough levels were measured quarterly. Total cholesterol decreased by 27% (354 +/- 50 vs 258 +/- 36 mg/dl, p less than 0.01) after 3 months and remained stable thereafter. Similarly, low density lipoprotein cholesterol decreased by 34% (221 +/- 51 vs 146 +/- 40 mg/dl, p less than 0.01) after 3 months and remained constant. Triglycerides, high density lipoprotein, hepatic transaminases, creatinine, creatine kinase and trough cyclosporine-A levels remained stable during the 1-year follow-up period. Lovastatin was uniformly well tolerated in this study group. When given in modest dosages, lovastatin appears to be a safe, effective and well-tolerated therapy for hypercholesterolemia in cardiac transplant recipients.     

Interactions in the aetiology,presentation and management of synchronous and metachronous adenocarcinoma of the prostate and rectum

Adenocarcinoma of the prostate and rectum are common male pelvic cancers and may present synchronously or metachronously and, due to their anatomic proximity. The treatment of rectal or prostate cancer (in particular surgery and/or radiotherapy) may alter the presentation, incidence and management should a metachronous tumour develop. This review focuses on the interaction between prostatic and rectal cancer diagnosis and management. We have restricted the scope of this large topic to general considerations, management of rectal cancer after prostate cancer treatment and vice versa, management of synchronous disease and cancer follow-up issues.     

Pregnancy outcome in patients with Takayasu’s arteritis: cohort study and review of the literature

Objective: The objective of this study is to investigate the clinical features of pregnancy in women with Takayasu’s arteritis managed in a tertiary medical center and review the literature in order to establish the course and recommended follow up and treatment for these pregnancies.

Materials and methods: Retrospective analysis of 20 pregnancies in 6 women with Takayasu’s arteritis. Patients were recruited from the high risk pregnancy clinics at Sheba Medical Center, where follow up included strict control of blood pressure and treatment of obstetric and disease-related complications.

Results: Mean maternal age was 29.3?±?3 years. Thirty-six patients had both supra and infradiaphragmatic arterial disease, of them two had an abdominal aorta involvement and three out of six patients had an isolated supradiaphragmatic disease. Of 20 pregnancies, six pregnancies (30%) resulted in early spontaneous miscarriages, and one pregnancy was terminated at 17 weeks due to fetal anomalies. The remaining 13 pregnancies (65%) resulted in live births. Three out of 13 (23%) neonates were small-for-gestational-age. The most common complication was maternal hypertension affecting 8/13 (61.5%) pregnancies. Preeclampsia occurred in one pregnancy. Four out of 13 (30.7%) pregnancies necessitated preterm induction of labor due to obstetric indications or uncontrolled disease.

Conclusions: Although Takayasu’s arteritis is associated with pregnancy complications, tight preconception disease control, strict follow up, and targeted treatment of high blood pressure can result in positive pregnancy outcome.