Application of cDNA microarrays in determining molecular phenotype in cardiac growth, development, and response to injury

Gene expression patterns and related pathways in the hearts of rhesus monkeys subjected to prolonged myocardial ischemia

After myocardial infarction (MI) occurs, progressive pathological cardiac remodeling results in heart dysfunction and even heart failure during the following months or years. The present study explored the molecular mechanisms underlying the late phase of MI at the global transcript level. A rhesus monkey model of myocardial ischemia induced by left anterior descending (LAD) artery ligation was established, and the heart tissue was collected eight weeks after ligation for transcriptome analysis by DNA microarray technology. Differentially expressed genes in the core infarcted area and remote infarcted area of the ischemic heart were detected with significance analysis of microarray (SAM), and related pathways were detected by Gene Ontology (GO)/pathway analysis. We found that compared to the sham condition, prolonged ischemia increased the levels of 941 transcripts, decreased the levels of 380 transcripts in the core infarcted area, and decreased the levels of 8 transcripts in the remote area in monkey heart tissue. Loss of coordination between the expression of genes, including natriuretic peptide A (NPPA), NPPB, and corin (Corin, serine peptidase), may aggravate cardiac remodeling. Furthermore, imbalance in the enriched significantly changed pathways, including fibrosis-related pathways, cardioprotective pathways, and the cardiac systolic pathway, likely also plays a key role in regulating the development of heart remodeling.

The Body-wide Transcriptome Landscape of Disease Models

Virtually all diseases affect multiple organs. However, our knowledge of the body-wide effects remains limited. Here, we report the body-wide transcriptome landscape across 13–23 organs of mouse models of myocardial infarction, diabetes, kidney diseases, cancer, and pre-mature aging. Using such datasets, we find (1) differential gene expression in diverse organs across all models; (2) skin as a disease-sensor organ represented by disease-specific activities of putative gene-expression network; (3) a bone-skin cross talk mediated by a bone-derived hormone, FGF23, in response to dysregulated phosphate homeostasis, a known risk-factor for kidney diseases; (4) candidates for the signature activities of many more putative inter-organ cross talk for diseases; and (5) a cross-species map illustrating organ-to-organ and model-to-disease relationships between human and mouse. These findings demonstrate the usefulness and the potential of such body-wide datasets encompassing mouse models of diverse disease types as a resource in biological and medical sciences. Furthermore, the findings described herein could be exploited for designing disease diagnosis and treatment.

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Body-wide multi-organ transcriptome datasets encompassing diverse disease models

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Skin is a disease-sensor organ, and FGF23 mediates a bone-skin cross talk in diseases

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Diverse putative inter-organ cross talk selectively associates with diseases

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A cross-species map illustrating the mouse-human relationships

Analysis of region specific gene expression patterns in the heart and systemic responses after experimental myocardial ischemia

Aims

Ischemic myocardial injury leads to the activation of inflammatory mechanisms and results in ventricular remodeling. Although great efforts have been made to unravel the molecular and cellular processes taking place in the ischemic myocardium, little is known about the effects on the surrounding tissue and other organs. The aim of this study was to determine region specific differences in the myocardium and in distant organs after experimental myocardial infarction by using a bioinformatics approach.

Methods and Results

A porcine closed chest reperfused acute myocardial infarction model and mRNA microarrays have been used to evaluate gene expression changes. Myocardial infarction changed the expression of 8903 genes in myocardial-, 856 in hepatic- and 338 in splenic tissue. Identification of myocardial region specific differences as well as expression profiling of distant organs revealed clear gene-regulation patterns within the first 24 hours after ischemia. Transcription factor binding site analysis suggested a strong role for Kruppel like factor 4 (Klf4) in the regulation of gene expression following myocardial infarction, and was therefore investigated further by immunohistochemistry. Strong nuclear Klf4 expression with clear region specific differences was detectable in porcine and human heart samples after myocardial infarction.

Conclusion

Apart from presenting a post myocardial infarction gene expression database and specific response pathways, the key message of this work is that myocardial ischemia does not end at the injured myocardium. The present results have enlarged the spectrum of organs affected, and suggest that a variety of organ systems are involved in the co-ordination of the organism´s response to myocardial infarction.

Genetic markers: Potential candidates for cardiovascular disease

The effective prevention of cardiovascular disease depends upon the ability to recognize the high-risk individuals at an early stage of the disease or long before the development of adverse events. Evolving technologies in the fields of proteomics, metabolomics, and genomics have played a significant role in the discovery of cardiovascular biomarkers, but so far these methods have achieved the modest success. Hence, there is a crucial need for more reliable, suitable, and lasting diagnostic and therapeutic markers to screen the disease well in time to start the clinical aid to the patients. Gene polymorphisms associated with the cardiovascular disease play a decisive role in the disease onset. Therefore, the genetic marker evaluation to classify high-risk patients from low-risk patients trends an effective approach to patient management and care. Currently, there are no genetic markers available for extensive adoption as risk factors for coronary vascular disease, yet, there are numerous promising, biologically acceptable candidates. Many of these gene biomarkers, alone or in combination, can play an essential role in the prediction of cardiovascular risk. The present review highlights some putative emerging genetic biomarkers that could facilitate more authentic and fast diagnosis of CVD. This review also briefly describes few technological approaches employed in the biomarker search.

Long-acting beneficial effect of percutaneously intramyocardially delivered secretome of apoptotic peripheral blood cells on porcine chronic ischemic left ventricular dysfunction

The quantity of cells with paracrine effects for use in myocardial regeneration therapy is limited. This study investigated the effects of catheter-based endomyocardial delivery of secretome of 2.5 × 10(9) apoptotic peripheral blood mononuclear cells (APOSEC) on porcine chronic post-myocardial infarction (MI) left ventricular (LV) dysfunction and on gene expression. Closed-chest reperfused MI was induced in pigs by 90-min occlusion followed by reperfusion of the mid-LAD (day 0). At day 30, animals were randomized to receive porcine APOSEC (n = 8) or medium solution (control; n = 8) injected intramyocardially into the MI border zone using 3D NOGA guidance. At day 60, cardiac MRI with late enhancement and diagnostic NOGA (myocardial viability) were performed. Gene expression profiling of the infarct core, border zone, and normal myocardium was performed using microarray analysis and confirmed by quantitative real-time PCR. Injection of APOSEC significantly decreased infarct size (p < 0.05) and improved cardiac index and myocardial viability compared to controls. A trend towards higher LV ejection fraction was observed in APOSEC vs. controls (45.4 ± 5.9% vs. 37.4 ± 8.9%, p = 0.052). Transcriptome analysis revealed significant downregulation of caspase-1, tumor necrosis factor and other inflammatory genes in APOSEC-affected areas. rtPCR showed higher expression of myogenic factor Mefc2 (p < 0.05) and downregulated caspase genes (p < 0.05) in APOSEC-treated pigs. In conclusion, overexpression of MEF2c and repression of caspase was related to decreased infarct size and improved cardiac function in secretome-treated animals. Altered gene expression 1-month post-APOSEC treatment proved the long-acting effects of cell-free therapy with paracrine factors.

Will global transcriptome analysis allow the detection of novel prognostic markers in coronary artery disease and heart failure?

Coronary artery disease (CAD) is one of the leading causes of death in the developed countries. Myocardial infarction (MI) is an acute episode of CAD that results in myocardial injury and subsequent heart failure (HF). In the acute phase of MI several risk factors for future cardiovascular events have been found. The molecular mechanisms of these disorders are still unknown, but altered gene expression may play an important role in the development and progression of cardiovascular diseases. High-throughput techniques should greatly facilitate the elucidation of the mechanisms and provide novel insights into the pathophysiology of cardiovascular diseases. In this review we focus on the perspectives of gene-expression profiling conducted on cardiac tissues and blood for the determination of novel diagnostic and prognostic markers and therapeutic targets.

Downregulation of miR-151-5p contributes to increased susceptibility to arrhythmogenesis during myocardial infarction with estrogen deprivation

Estrogen deficiency is associated with increased incidence of cardiovascular diseases. But merely estrogen supplementary treatment can induce many severe complications such as breast cancer. The present study was designed to elucidate molecular mechanisms underlying increased susceptibility of arrhythmogenesis during myocardial infarction with estrogen deprivation, which provides us a new target to cure cardiac disease accompanied with estrogen deprivation. We successfully established a rat model of myocardial ischemia (MI) accompanied with estrogen deprivation by coronary artery ligation and ovariectomy (OVX). Vulnerability and mortality of ventricular arrhythmias increased in estrogen deficiency rats compared to non estrogen deficiency rats when suffered MI, which was associated with down-regulation of microRNA-151-5p (miR-151-5p). Luciferase Reporter Assay demonstrated that miR-151-5p can bind to the 3′-UTR of FXYD1 (coding gene of phospholemman, PLM) and inhibit its expression. We found that the expression of PLM was increased in (OVX+MI) group compared with MI group. More changes such as down-regulation of Kir2.1/I_K1, calcium overload had emerged in (OVX+MI) group compared to MI group merely. Transfection of miR-151-5p into primary cultured myocytes decreased PLM levels and [Ca²⁺]_i, however, increased Kir2.1 levels. These effects were abolished by the antisense oligonucleotides against miR-151-5p. Co-immunoprecipitation and immunofluorescent experiments confirmed the co-localization between Kir2.1 and PLM in rat ventricular tissue. We conclude that the increased ventricular arrhythmias vulnerability in response to acute myocardial ischemia in rat is critically dependent upon down-regulation of miR-151-5p. These findings support the proposal that miR-151-5p could be a potential therapeutic target for the prevention of ischemic arrhythmias in the subjects with estrogen deficiency.

Transcriptional profiling of HMGB1-induced myocardial repair identifies a key role for Notch signaling

Exogenous high-mobility group box 1 protein (HMGB1) administration to the mouse heart, during acute myocardial infarction (MI), results in cardiac regeneration via resident c-kit(+) cell (CPC) activation. Aim of the present study was to identify the molecular pathways involved in HMGB1-induced heart repair. Gene expression profiling was performed to identify differentially expressed genes in the infarcted and bordering regions of untreated and HMGB1-treated mouse hearts, 3 days after MI. Functional categorization of the transcripts, accomplished using Ingenuity Pathway Analysis software (IPA), revealed that genes involved in tissue regeneration, that is, cardiogenesis, vasculogenesis and angiogenesis, were present both in the infarcted area and in the peri-infarct zone; HMGB1 treatment further increased the expression of these genes. IPA revealed the involvement of Notch signaling pathways in HMGB1-treated hearts. Importantly, HMGB1 determined a 35 and 58% increase in cardiomyocytes and CPCs expressing Notch intracellular cytoplasmic domain, respectively. Further, Notch inhibition by systemic treatment with the γ-secretase inhibitor DAPT, which blocked the proteolytic activation of Notch receptors, reduced the number of CPCs, their proliferative fraction, and cardiomyogenic differentiation in HMGB1-treated infarcted hearts. The present study gives insight into the molecular processes involved in HMGB1-mediated cardiac regeneration and indicates Notch signaling as a key player.

Identification of temporal and region-specific myocardial gene expression patterns in response to infarction in swine

Molecular mechanisms associated with pathophysiological changes in ventricular remodelling due to myocardial infarction (MI) remain poorly understood. We analyzed changes in gene expression by microarray technology in porcine myocardial tissue at 1, 4, and 6 weeks post-MI.MI was induced by coronary artery ligation in 9 female pigs (30-40 kg). Animals were randomly sacrificed at 1, 4, or 6 weeks post-MI (n = 3 per group) and 3 healthy animals were also included as control group. Total RNA from myocardial samples was hybridized to GeneChip® Porcine Genome Arrays. Functional analysis was obtained with the Ingenuity Pathway Analysis (IPA) online tool. Validation of microarray data was performed by quantitative real-time PCR (qRT-PCR).More than 8,000 different probe sets showed altered expression in the remodelling myocardium at 1, 4, or 6 weeks post-MI. Ninety-seven percent of altered transcripts were detected in the infarct core and 255 probe sets were differentially expressed in the remote myocardium. Functional analysis revealed 28 genes de-regulated in the remote myocardial region in at least one of the three temporal analyzed stages, including genes associated with heart failure (HF), systemic sclerosis and coronary artery disease. In the infarct core tissue, eight major time-dependent gene expression patterns were recognized among 4,221 probe sets commonly altered over time. Altered gene expression of ACVR2B, BID, BMP2, BMPR1A, LMNA, NFKBIA, SMAD1, TGFB3, TNFRSF1A, and TP53 were further validated.The clustering of similar expression patterns for gene products with related function revealed molecular footprints, some of them described for the first time, which elucidate changes in biological processes at different stages after MI.

Coordinated regulation of cardiac Na(+)/Ca (2+) exchanger and Na (+)-K (+)-ATPase by phospholemman (FXYD1)

Phospholemman (PLM) is the founding member of the FXYD family of regulators of ion transport. PLM is a 72-amino acid protein consisting of the signature PFXYD motif in the extracellular N terminus, a single transmembrane (TM) domain, and a C-terminal cytoplasmic tail containing three phosphorylation sites. In the heart, PLM co-localizes and co-immunoprecipitates with Na(+)-K(+)-ATPase, Na(+)/Ca(2+) exchanger, and L-type Ca(2+) channel. The TM domain of PLM interacts with TM9 of the α-subunit of Na(+)-K(+)-ATPase, while its cytoplasmic tail interacts with two small regions (spanning residues 248-252 and 300-304) of the proximal intracellular loop of Na(+)/Ca(2+) exchanger. Under stress, catecholamine stimulation phosphorylates PLM at serine(68), resulting in relief of inhibition of Na(+)-K(+)-ATPase by decreasing K(m) for Na(+) and increasing V(max), and simultaneous inhibition of Na(+)/Ca(2+) exchanger. Enhanced Na(+)-K(+)-ATPase activity lowers intracellular Na(+), thereby minimizing Ca(2+) overload and risks of arrhythmias. Inhibition of Na(+)/Ca(2+) exchanger reduces Ca(2+) efflux, thereby preserving contractility. Thus, the coordinated actions of PLM during stress serve to minimize arrhythmogenesis and maintain inotropy. In acute cardiac ischemia and chronic heart failure, either expression or phosphorylation of PLM or both are altered. PLM regulates important ion transporters in the heart and offers a tempting target for development of drugs to treat heart failure.

Controlled reoxygenation cardiopulmonary bypass is associated with reduced transcriptomic changes in cyanotic tetralogy of Fallot patients undergoing surgery

In cyanotic patients undergoing repair of heart defects, high level of oxygen during cardiopulmonary bypass (CPB) leads to greater susceptibility to myocardial ischemia and reoxygenation injury. This study investigates the effects of controlled reoxygenation CPB on gene expression changes in cyanotic hearts of patients undergoing surgical correction of tetralogy of Fallot (TOF). We randomized 49 cyanotic TOF patients undergoing corrective cardiac surgery to receive either controlled reoxygenation or hyperoxic/standard CPB. Ventricular myocardium biopsies were obtained immediately after starting and before discontinuing CPB. Microarray analyses were performed on samples, and array results validated with real-time PCR. Gene expression profiles before and after hyperoxic/standard CPB revealed 35 differentially expressed genes with three upregulated and 32 downregulated. Upregulated genes included two E3 Ubiquitin ligases. The products of downregulated genes included intracellular signaling kinases, metabolic process proteins, and transport factors. In contrast, gene expression profiles before and after controlled reoxygenation CPB revealed only 11 differentially expressed genes with 10 upregulated including extracellular matrix proteins, transport factors, and one downregulated. The comparison of gene expression following hyperoxic/standard vs. controlled reoxygenation CPB revealed 59 differentially expressed genes, with six upregulated and 53 downregulated. Upregulated genes included PDE1A, MOSC1, and CRIP3. Downregulated genes functionally clustered into four major classes: extracellular matrix/cell adhesion, transcription, transport, and cellular metabolic process. This study provides direct evidence that hyperoxic CPB decreases the adaptation and remodeling capacity in cyanotic patients undergoing TOF repair. This simple CPB strategy of controlled reoxygenation reduced the number of genes whose expression was altered following hyperoxic/standard CPB.

Contribution of lysosomal cysteine proteases in cardiac and renal diseases

Cardiac and renal diseases (CRDs) are characterized by extensive remodeling of the extracellular matrix (ECM) architecture of the cardiorenal system. Among the many extracellular proteolytic enzymes present in cardiorenal cells and involved in ECM remodeling, members of the matrix metalloproteinase family and serine protease family have received the most attention. However, recent findings from laboratory and clinical studies have indicated that cysteine protease cathepsins also participate in pathogenesis of the heart and kidney. Deficiency and pharmacological inhibition of cathepsins have allowed their in vivo evaluation in the setting of pathological conditions. Furthermore, recent studies evaluating the feasibility of cathepsins as a diagnostic tool have suggested that the serum levels of cathepsins L, S and K and their endogenous inhibitor cystatin C have predictive value as biomarkers in patients with coronary artery disease and heart and renal failure. The goal of this review is to highlight recent discoveries regarding the contributions of cathepsins in CRDs, particularly hypertensive heart failure and proteinuric kidney disease.

Phospholemman deficiency in postinfarct hearts: enhanced contractility but increased mortality

Phospholemman (PLM) regulates [Na(+) ](i), [Ca(2+)](i) and contractility through its interactions with Na(+)-K(+)-ATPase (NKA) and Na(+) /Ca(2+) exchanger (NCX1) in the heart. Both expression and phosphorylation of PLM are altered after myocardial infarction (MI) and heart failure. We tested the hypothesis that absence of PLM regulation of NKA and NCX1 in PLM-knockout (KO) mice is detrimental. Three weeks after MI, wild-type (WT) and PLM-KO hearts were similarly hypertrophied. PLM expression was lower but fractional phosphorylation was higher in WT-MI compared to WT-sham hearts. Left ventricular ejection fraction was severely depressed in WT-MI but significantly less depressed in PLM-KO-MI hearts despite similar infarct sizes. Compared with WT-sham myocytes, the abnormal [Ca(2+) ], transient and contraction amplitudes observed in WT-MI myocytes were ameliorated by genetic absence of PLM. In addition, NCX1 current was depressed in WT-MI but not in PLM-KO-MI myocytes. Despite improved myocardial and myocyte performance, PLM-KO mice demonstrated reduced survival after MI. Our findings indicate that alterations in PLM expression and phosphorylation are important adaptations post-MI, and that complete absence of PLM regulation of NKA and NCX1 is detrimental in post-MI animals.

Phospholemman: a novel cardiac stress protein

Phospholemman (PLM), a member of the FXYD family of regulators of ion transport, is a major sarcolemmal substrate for protein kinases A and C in cardiac and skeletal muscle. In the heart, PLM co-localizes and co-immunoprecipitates with Na(+)-K(+)-ATPase, Na(+)/Ca(2+) exchanger, and L-type Ca(2+) channel. Functionally, when phosphorylated at serine(68), PLM stimulates Na(+)-K(+)-ATPase but inhibits Na(+)/Ca(2+) exchanger in cardiac myocytes. In heterologous expression systems, PLM modulates the gating of cardiac L-type Ca(2+) channel. Therefore, PLM occupies a key modulatory role in intracellular Na(+) and Ca(2+) homeostasis and is intimately involved in regulation of excitation-contraction (EC) coupling. Genetic ablation of PLM results in a slight increase in baseline cardiac contractility and prolongation of action potential duration. When hearts are subjected to catecholamine stress, PLM minimizes the risks of arrhythmogenesis by reducing Na(+) overload and simultaneously preserves inotropy by inhibiting Na(+)/Ca(2+) exchanger. In heart failure, both expression and phosphorylation state of PLM are altered and may partly account for abnormalities in EC coupling. The unique role of PLM in regulation of Na(+)-K(+)-ATPase, Na(+)/Ca(2+) exchanger, and potentially L-type Ca(2+) channel in the heart, together with the changes in its expression and phosphorylation in heart failure, make PLM a rational and novel target for development of drugs in our armamentarium against heart failure. Clin Trans Sci 2010; Volume 3: 189-196.

Identification of a core set of genes that signifies pathways underlying cardiac hypertrophy

Although the molecular signals underlying cardiac hypertrophy have been the subject of intense investigation, the extent of common and distinct gene regulation between different forms of cardiac hypertrophy remains unclear. We hypothesized that a general and comparative analysis of hypertrophic gene expression, using microarray technology in multiple models of cardiac hypertrophy, including aortic banding, myocardial infarction, an arteriovenous shunt and pharmacologically induced hypertrophy, would uncover networks of conserved hypertrophy-specific genes and identify novel genes involved in hypertrophic signalling. From gene expression analyses (8740 probe sets, n = 46) of rat ventricular RNA, we identified a core set of 139 genes with consistent differential expression in all hypertrophy models as compared to their controls, including 78 genes not previously associated with hypertrophy and 61 genes whose altered expression had previously been reported. We identified a single common gene program underlying hypertrophic remodelling, regardless of how the hypertrophy was induced. These genes constitute the molecular basis for the existence of one main form of cardiac hypertrophy and may be useful for prediction of a common therapeutic approach. Supplementary material for this article can be found at: http://www.interscience.wiley.com/jpages/1531-6912/suppmat

Hawley H. Seiler Resident Award. Transcriptional profile of brain injury in hypothermic circulatory arrest and cardiopulmonary bypass

BACKGROUND

Little is known about the molecular mechanisms of neurologic complications after hypothermic circulatory arrest (HCA) with cardiopulmonary bypass (CPB). Canine genome sequencing allows profiling of genomic changes after HCA and CPB alone. We hypothesize that gene regulation will increase with increased severity of injury.

METHODS

Dogs underwent 2-hour HCA at 18 degrees C (n = 10), 1-hour HCA (n = 8), or 2-hour CPB at 32 degrees C alone (n = 8). In each group, half were sacrificed at 8 hours and half at 24 hours after treatment. After neurologic scoring, brains were harvested for genomic analysis. Hippocampal RNA isolates were analyzed using canine oligonucleotide expression arrays containing 42,028 probes.

RESULTS

Consistent with prior work, dogs that underwent 2-hour HCA experienced severe neurologic injury. One hour of HCA caused intermediate clinical damage. Cardiopulmonary bypass alone yielded normal clinical scores. Cardiopulmonary bypass, 1-hour HCA, and 2-hour HCA groups historically demonstrated increasing degrees of histopathologic damage (previously published). Exploratory analysis revealed differences in significantly regulated genes (false discovery rate < 10%, absolute fold change > or = 1.2), with increases in differential gene expression with injury severity. At 8 hours and 24 hours after insult, 2-hour HCA dogs had 502 and 1,057 genes regulated, respectively; 1-hour HCA dogs had 179 and 56 genes regulated; and CPB alone dogs had 5 and 0 genes regulated.

CONCLUSIONS

Our genomic profile of canine brains after HCA and CPB revealed 1-hour and 2-hour HCA induced markedly increased gene regulation, in contrast to the minimal effect of CPB alone. This adds to the body of neurologic literature supporting the safety of CPB alone and the minimal effect of CPB on a normal brain, while illuminating genomic results of both.

Off-pump coronary artery bypass surgery is associated with fewer gene expression changes in the human myocardium in comparison with on-pump surgery

Off-pump coronary artery bypass surgery reduces the myocardial injury associated with on pump surgery with cardiopulmonary bypass (CPB) and ischemic-cardioplegic arrest (CA). We sought to find a mechanistic explanation for this by comparing the transcriptomic changes in the myocardium of patients undergoing on- and off-pump surgery. Transcriptomic analyses were performed on left ventricular biopsies obtained from patients prior to (pre-op) and after completion of all coronary anastomoses (post-op). Microarray results were validated with real-time polymerase chain reaction. In on-pump group, 68 genes were upregulated in post-op vs. pre-op biopsies (P < 0.01, >or=2-fold). They included inflammatory genes CCL3 and CCL4, apoptotic gene GADD45B and prostaglandin synthesis gene PTGS2 (COX-2). In the off-pump group, 17 genes were upregulated in post-op vs. pre-op biopsies (P < 0.01, >or=2-fold), all shared with on-pump patients. To uncover the genes implicated in CPB and ischemic-CA response, we compared the postoperative gene profiles of the two groups. Thirty-eight genes were upregulated in the on-pump vs. off-pump patients (P < 0.01, >or=2-fold). On-pump surgery induces injury-related response, as demonstrated by the upregulation of apoptosis and remodeling markers, whereas off-pump surgery ameliorates that by mainly upregulating a cytoprotective genetic program. Blood levels of the identified cytokines and chemokines followed the same pattern obtained by transcriptomics, suggesting that the myocardium is a likely source for these proteomic changes. In conclusion, off-pump surgery is associated with fewer alterations in gene expression connected with inflammation, apoptosis, and remodeling seen after on-pump surgery with CPB and ischemic-CA.

Effect of Guanxin No.2 decoction on gene expression in different areas of the myocardial infarcted heart of rats using microarray technology

Objectives

We have used microarray technology to detect the effect of Guanxin No.2 decoction on gene expression in different areas of the myocardial infarcted heart of rats.

Methods

Male Sprague-Dawley rats (180–200 g) were randomly divided into three groups: sham-operated; coronary artery ligation; and coronary artery ligation plus administration of Guanxin No.2 decoction (10.0 g raw materials/kg per day by gavage). The experiment was carried out on day seven after ligation.

Key findings

We found that the gene expression using microarray technology showed many differences in the border infarcted left ventricular area compared with the remote noninfarcted left ventricular area after administration of Guanxin No.2 decoction.

Conclusions

Guanxin No.2 decoction has a long history in treating ischaemic cardiomyopathy in China, but the molecular mechanism has been unclear. In this study we found that some important genes may have contributed to the cardioprotective effect of Guanxin No.2 decoction.

Sildenafil augments early protective transcriptional changes after ischemia in mouse myocardium

Recently, targeting cyclic-GMP specific phosphodiesterase-5 (PDE5) has attracted much interest in several cardiopulmonary diseases, in particular myocardial ischemia (MI). Although multiple mechanisms were postulated for these beneficial effects at cellular level, early transcriptional changes were unknown. The aim of present study was to examine gene expression profiles in response to MI after 24 h of ischemia in murine model and compare transcriptional modulation by sildenafil, a popular phosphodiesterase 5 (PDE5) inhibitor. Mice were divided into four groups: Control sham (C), Sildenafil sham (S), Control MI (CMI) and Sildenafil MI (SMI). Sildenafil was given at a dose of 0.7 mg/kg intraperitoneally 30 min before LAD occlusion. cDNA microarray analysis of peri-infarct tissue was done using a custom cloneset and employing a looped dye swap design. Replicate signals were median averaged and normalized using LOWESS algorithm. R/MAANOVA analysis was used and false discovery rate corrected permutation p-values <0.005 were employed as significance thresholds. 156 genes were identified as significantly regulated demonstrating fold difference >1.5 in at least one of the four groups. 52 genes were significantly upregulated in SMI compared to CMI. For a randomly chosen subset of genes (9), microarray data were confirmed through real time RT-PCR. The differentially expressed genes could be classified into following groups based on their function: phosphorylation/dephosphorylation, apoptosis, differentiation, ATP binding. Our results suggest that sildenafil treatment might regulate early genetic reprogramming strategy for preservation of the ischemic myocardium.

Designing heart performance by gene transfer

The birth of molecular cardiology can be traced to the development and implementation of high-fidelity genetic approaches for manipulating the heart. Recombinant viral vector-based technology offers a highly effective approach to genetically engineer cardiac muscle in vitro and in vivo. This review highlights discoveries made in cardiac muscle physiology through the use of targeted viral-mediated genetic modification. Here the history of cardiac gene transfer technology and the strengths and limitations of viral and nonviral vectors for gene delivery are reviewed. A comprehensive account is given of the application of gene transfer technology for studying key cardiac muscle targets including Ca(2+) handling, the sarcomere, the cytoskeleton, and signaling molecules and their posttranslational modifications. The primary objective of this review is to provide a thorough analysis of gene transfer studies for understanding cardiac physiology in health and disease. By comparing results obtained from gene transfer with those obtained from transgenesis and biophysical and biochemical methodologies, this review provides a global view of cardiac structure-function with an eye towards future areas of research. The data presented here serve as a basis for discovery of new therapeutic targets for remediation of acquired and inherited cardiac diseases.

Cytokine expression profiling of the myocardium reveals a role for CX3CL1 (fractalkine) in heart failure

Several lines of evidence suggest that inflammatory processes mediated by cytokines are involved in the pathogenesis of heart failure (HF). However, the regulation of cytokine expression and the role of cytokines during HF development are not well understood. To address this issue, we have examined alterations in gene expression during HF progression by microarray technology in non-infarcted left ventricular (LV) murine tissue at various time points after myocardial infarction (MI). The highest number of regulated genes was found five days after MI. In total, we identified 14 regulated genes encoding cytokines with no previous association to HF. The strongest up-regulation was found for the chemokine fractalkine (CX3CL1). In human failing hearts we detected a 3-fold increase in CX3CL1 protein production, and both cardiomyocytes and fibrous tissue revealed immunoreactivity for CX3CL1 and its specific receptor CX3CR1. We also found that the circulating level of CX3CL1 was increased in patients with chronic HF in accordance with disease severity (1.6-fold in NYHA II, 2.2-fold in NYHA III and 2.9-fold in NYHA IV). In vitro experiments demonstrated that CX3CL1 production could be induced by inflammatory cytokines known to be highly expressed in HF. CX3CL1 itself induced the expression of markers of cardiac hypertrophy and protein phosphatases in neonatal cardiomyocytes. Given the increased CX3CL1 production in both an experimental HF model and in patients with chronic HF as well as its direct effects on cardiomyocytes, we suggest a role for CX3CL1 and its receptor CX3CR1 in the pathogenesis of HF.

Integrating metabolomics and phenomics with systems models of cardiac hypoxia

Hypoxia is the major cause of necrotic cell death in myocardial infarction. Cellular energy supply and demand under hypoxic conditions is regulated by many interacting signaling and transcriptional networks, which complicates studies on individual proteins and pathways. We apply an integrated systems approach to understand the metabolic and functional response to hypoxia in muscle cells of the fruit fly Drosophila melanogaster. In addition to its utility as a hypoxia-tolerant model organism, Drosophila also offers advantages due to its small size, fecundity, and short life cycle. These traits, along with a large library of single-gene mutations, motivated us to develop new, computer-automated technology for gathering in vivo measurements of heart function under hypoxia for a large number of mutant strains. Phenotype data can be integrated with in silico cellular networks, metabolomic data, and microarrays to form qualitative and quantitative network models for prediction and hypothesis generation. Here we present a framework for a systems approach to hypoxia in the cardiac myocyte, starting from nuclear magnetic resonance (NMR) metabolomics, a constraint-based metabolic model, and phenotypic profiles.

Gene expression profiling by DNA microarray technology

Methods in molecular and genetic biology have provided important clues to elucidate the complex mechanisms of oral and craniofacial development and pathogenesis of diseases. It has become increasingly clear that a biological phenotype is a result of multiple factors involving a large number of regulatory genes, while a single nucleotide mutation can cause various degrees of oral and craniofacial abnormalities. These oral and craniofacial problems often present a challenge to the molecular screening process. Recent advances in microarray-based technologies allow for large-scale gene expression analysis in a single experiment, which have been applied to genome-wide assays, mutational analysis, drug discovery, developmental biology, and molecular analysis of various diseases. This review introduces the basic principle and some modifications of techniques and materials used in microarray technology, as well as currently available microarray data analysis strategies. Microarray technology can be applied to the soon-to-be-available human genome database and will be a powerful research tool for those inquiring into specific problems associated with oral and craniofacial biology.

Dynamic resolution of functionally related gene sets in response to acute heat stress

Background

Using a gene clustering strategy we determined intracellular pathway relationships within skeletal myotubes in response to an acute heat stress stimuli. Following heat shock, the transcriptome was analyzed by microarray in a temporal fashion to characterize the dynamic relationship of signaling pathways.

Results

Bioinformatics analyses exposed coordination of functionally-related gene sets, depicting mechanism-based responses to heat shock. Protein turnover-related pathways were significantly affected including protein folding, pre-mRNA processing, mRNA splicing, proteolysis and proteasome-related pathways. Many responses were transient, tending to normalize within 24 hours.

Conclusion

In summary, we show that the transcriptional response to acute cell stress is largely transient and proteosome-centric.

Regulation of cardiac Na+/Ca2+ exchanger by phospholemman

Phospholemman (PLM) is the first sequenced member of the FXYD family of regulators of ion transport. The mature protein has 72 amino acids and consists of an extracellular N terminus containing the signature FXYD motif, a single transmembrane (TM) domain, and a cytoplasmic C-terminal domain containing four potential sites for phosphorylation. PLM and other members of the FXYD family are known to regulate Na+-K+-ATPase. Using adenovirus-mediated gene transfer into adult rat cardiac myocytes, we showed that changes in contractility and intracellular Ca2+ homeostasis associated with PLM overexpression or downregulation are not consistent with the effects expected from inhibition of Na+-K+-ATPase by PLM. Additional studies with heterologous expression of PLM and cardiac Na+/Ca2+ exchanger 1 (NCX1) in HEK293 cells and cardiac myocytes isolated from PLM-deficient mice demonstrated by co-localization, co-immunoprecipitation, and electrophysiological and radioactive tracer uptake techniques that PLM associates with NCX1 in the sarcolemma and transverse tubules and that PLM inhibits NCX1, independent of its effects on Na+-K+-ATPase. Mutational analysis indicates that the cytoplasmic domain of PLM is required for its regulation of NCX1. In addition, experiments using phosphomimetic and phospho-deficient PLM mutants, as well as activators of protein kinases A and C, indicate that PLM phosphorylated at serine68 is the active form that inhibits NCX1. This is in sharp contrast to the finding that the unphosphorylated PLM form inhibits Na+-K+-ATPase. We conclude that PLM regulates cardiac contractility by modulating the activities of NCX and Na+-K+-ATPase.

Functional genomics by cDNA subtractive hybridization

The regulation of myocardial gene expression is highly sensitive to any extracellular or intracellular stimulus that affects contractile function. Subtractive suppression hybridization represents a large-scale, unbiased method for detecting transcriptionally and posttranscriptionally regulated genes, both known and unknown, independently of the prevalence of these transcripts. The strength of subtractive hybridization relies on its unbiased nature and its power to extract even low-abundance transcripts. Therefore, the subtraction experiments can reveal "unexpected" gene profiles and can represent a starting point for the cloning and characterization of novel genes. However, the procedure and the subsequent sequencing of the subtracted genes are labor intensive, and, because the method is purely qualitative, it also requires alternative methods of validation.

Multiplicity of expression of FXYD proteins in mammalian cells: dynamic exchange of phospholemman and gamma-subunit in response to stress

Functional properties of Na-K-ATPase can be modified by association with FXYD proteins, expressed in a tissue-specific manner. Here we show that expression of FXYDs in cell lines does not necessarily parallel the expression pattern of FXYDs in the tissue(s) from which the cells originate. While being expressed only in lacis cells in the juxtaglomerular apparatus and in blood vessels in kidney, FXYD1 was abundant in renal cell lines of proximal tubule origin (NRK-52E, LLC-PK1, and OK cells). Authenticity of FXYD1 as a part of Na-K-ATPase in NRK-52E cells was demonstrated by co-purification, co-immunoprecipitation, and co-localization. Induction of FXYD2 by hypertonicity (500 mosmol/kgH(2)O with NaCl for 48 h or adaptation to 700 mosmol/kgH(2)O) correlated with downregulation of FXYD1 at mRNA and protein levels. The response to hypertonicity was influenced by serum factors and entailed, first, dephosphorylation of FXYD1 at Ser(68) (1-5 h) and, second, induction of FXYD2a and a decrease in FXYD1 with longer exposure. FXYD1 was completely replaced with FXYD2a in cells adapted to 700 mosmol/kgH(2)O and showed a significantly decreased sodium affinity. Thus dephosphorylation of FXYD1 followed by exchange of regulatory subunits is utilized to make a smooth transition of properties of Na-K-ATPase. We also observed expression of mRNA for multiple FXYDs in various cell lines. The expression was dynamic and responsive to physiological stimuli. Moreover, we demonstrated expression of FXYD5 protein in HEK-293 and HeLa cells. The data imply that FXYDs are obligatory rather than auxiliary components of Na-K-ATPase, and their interchangeability underlies responses of Na-K-ATPase to cellular stress.

Earliest changes in the left ventricular transcriptome postmyocardial infarction

We report a genome-wide survey of early responses of the mouse heart transcriptome to acute myocardial infarction (AMI). For three regions of the left ventricle (LV), namely, ischemic/infarcted tissue (IF), the surviving LV free wall (FW), and the interventricular septum (IVS), 36,899 transcripts were assayed at six time points from 15 min to 48 h post-AMI in both AMI and sham surgery mice. For each transcript, temporal expression patterns were systematically compared between AMI and sham groups, which identified 515 AMI-responsive genes in IF tissue, 35 in the FW, 7 in the IVS, with three genes induced in all three regions. Using the literature, we assigned functional annotations to all 519 nonredundant AMI-induced genes and present two testable models for central signaling pathways induced early post-AMI. First, the early induction of 15 genes involved in assembly and activation of the activator protein-1 (AP-1) family of transcription factors implicates AP-1 as a dominant regulator of earliest post-ischemic molecular events. Second, dramatic increases in transcripts for arginase 1 (ARG1), the enzymes of polyamine biosynthesis, and protein inhibitor of nitric oxide synthase (NOS) activity indicate that NO production may be regulated, in part, by inhibition of NOS and coordinate depletion of the NOS substrate, L: -arginine. ARG1: was the single-most highly induced transcript in the database (121-fold in IF region) and its induction in heart has not been previously reported.

Genetic background of acute coronary syndromes

Acute coronary syndromes (ACS) are one of the major causes of mortality nowadays. Although much is known about factors involved in atherogenesis and acute coronary events, there are still many cases in which a lack of classical risk factors, together with family history, suggests the presence of an unrevealed genetic predisposition and molecular mechanisms. This paper reviews genetic predisposition to ACS. It also indicates which genes are linked to the processes of destabilization and rupture of atherosclerotic plaque and thus may be potential targets for more effective prophylaxis and treatment.

A multidimensional proteomic approach to identify hypertrophy-associated proteins

Left ventricular hypertrophy (LVH) is a leading cause of congestive heart failure. The exact mechanisms that control cardiac growth and regulate the transition to failure are not fully understood, in part due to the lack of a complete inventory of proteins associated with LVH. We investigated the proteomic basis of LVH using the transverse aortic constriction model of pressure overload in mice coupled with a multidimensional approach to identify known and novel proteins that may be relevant to the development and maintenance of LVH. We identified 123 proteins that were differentially expressed during LVH, including LIM proteins, thioredoxin, myoglobin, fatty acid binding protein 3, the abnormal spindle-like microcephaly protein (ASPM), and cytoskeletal proteins such as actin and myosin. In addition, proteins with unknown functions were identified, providing new directions for future research in this area. We also discuss common pitfalls and strategies to overcome the limitations of current proteomic technologies. Together, the multidimensional approach provides insight into the proteomic changes that occur in the LV during hypertrophy.

Cardiovascular genomics: a current overview of in vivo and in vitro studies

The cardiovascular system is the first system that is developed in the embryo. The cardiovascular development is a complex process involving the coordination, differentiation, and interaction of distinct cell lineages to form the heart and the diverse array of arteries, veins, and capillaries required to supply oxygen and nutrients to all tissues. Embryonic stem cells have been proposed as an interesting model system to investigate molecular and cellular mechanisms involved in mammalian development. The present review is focused on extrinsic soluble factors, intrinsic transcription factors, receptors, signal transduction pathways, and genes regulating the development of cardiovascular system in vivo and in vitro. Special emphasis has been given to cardiovascular genomics including gene expression studies on the cardiovascular system under developmental and pathophysiological conditions.

Regulation of neuronal type genes in congestive heart failure rats

AIM

After myocardial infarction (MI), complex changes in the heart occur during progression into congestive heart failure (CHF). This study sought to identify regulated genes that could have a functional role in some of the changes seen in CHF.

METHODS

Myocardial infarction was induced by ligation of the left anterior descending coronary artery (LAD) in Wistar rats. Gene expression changes in 1- and 7-day MI left ventricular myocardium was analysed using complementary DNA (cDNA) filter arrays. Regulated genes were identified by repeated measurements and a ranked ratio analysis method.

RESULTS

A total of 135 genes were identified as differentially expressed. A few genes were robustly regulated at 1-day MI. In 7-day CHF hearts, changes in the expression of neuronal type genes was prominent (32%, n = 28). Eleven of these genes with no described association with CHF were selected for validation. One gene failed the validation. In CHF hearts, the expression of the muscarinic m4 (Chrm4) and nicotinic alpha4 (Chrna4) acetylcholin receptors, the ATP receptor P2rx4, nerve growth factor receptor (Ngfr), discoidin domain receptor 1 (Ddr1), neuronal pentraxin receptor (Nptxr), peripheral myelin protein Pmp-22, leukocyte type 12-lipoxygenase (Alox15), cytochrome P450 4F5 (Cyp4F5) and cardiac Kcne1 were all increased (range 1.6-6.0-fold, P < 0.01 for all genes). The lack of significant regulation of these genes at 1-day post-MI, suggests that the induction of these genes at 7-day post-MI is not a short-term response induced by the infarct itself.

CONCLUSION

These neuronal type genes may participate in underlying processes that affect contractility, intracardiac nerve function and development of arrhythmias in CHF hearts.

New Paradigms in Cardiovascular Medicine

Considerable progress has been made in understanding the pathophysiology of perioperative stress responses and their impact on the cardiovascular system; however, researchers are just beginning to unravel genetic and molecular determinants that predispose to increased risk for postoperative cardiovascular adverse events. A new field, coined perioperative genomics, aims to apply functional genomic approaches to uncover the biological reasons why similar patients can have dramatically different clinical outcomes after surgery. For the perioperative physician, such findings may soon translate into prospective risk assessment incorporating genomic profiling of markers important in inflammatory, thrombotic, vascular, and neurologic responses to perioperative stress, with implications ranging from individualized additional pre-operative testing and physiological optimization, to perioperative decision-making, choice of monitoring strategies, and critical care resource utilization. We review current knowledge regarding genomic technologies in perioperative cardiovascular disease characterization and outcome prediction, as well as discuss future trends/challenges for translating integrated "omic" information into daily clinical management of the surgical patient.

Distinct QTLs are linked to cardiac left ventricular mass in a sex-specific manner in a normotensive inbred rat inter-cross

Genetic mapping of the progeny of an F(2) inter-cross between WKY and WKHA rats had previously allowed us to detect male-specific linkage between locus Cm 24 and left ventricular mass index (LVMI). By further expanding that analysis, we detected additional loci that were all linked to LVMI in a sex-specific manner despite their autosomal location. In males, we detected one additional locus (Lvm 8) on Chromosome 5 (LOD=3.4), the two loci Lvm 13 (LOD=4.5) and Lvm 9 (LOD=2.8) on Chromosome 17, and locus Lvm 10 (LOD=4.2) on Chromosome 12. The locus Lvm 13 had the same boundaries as locus Cm 26 previously reported by others using a different cross. None of these loci showed linkage to LVM in females. In contrast, we identified in females the novel locus Lvm 11 on Chromosome 15 (LOD=2.8) and locus Lvm 12 (LOD=2.7) that had the same boundaries on Chromosome 3 as locus Cm 25 detected previously by others using a cross of other normotensive strains. In prepubertal males, there were no differences in the width of cardiomyocytes from WKY and WKHA rats, but cardiomyocytes from WKHA became progressively wider than that of WKY as sexual maturation progressed. Altogether, these results provide evidence that distinct genes may influence LVMI of rats in a sex-dependent manner, maybe by involving sex-specific interactions of sex steroids with particular genes involved in the determination of LVMI and/or cardiomyocyte width.

Phospholemman overexpression inhibits Na+-K+-ATPase in adult rat cardiac myocytes: relevance to decreased Na+ pump activity in postinfarction myocytes

Messenger RNA levels of phospholemman (PLM), a member of the FXYD family of small single-span membrane proteins with putative ion-transport regulatory properties, were increased in postmyocardial infarction (MI) rat myocytes. We tested the hypothesis that the previously observed reduction in Na+-K+-ATPase activity in MI rat myocytes was due to PLM overexpression. In rat hearts harvested 3 and 7 days post-MI, PLM protein expression was increased by two- and fourfold, respectively. To simulate increased PLM expression post-MI, PLM was overexpressed in normal adult rat myocytes by adenovirus-mediated gene transfer. PLM overexpression did not affect the relative level of phosphorylation on serine68 of PLM. Na+-K+-ATPase activity was measured as ouabain-sensitive Na+-K+ pump current (Ip). Compared with control myocytes overexpressing green fluorescent protein alone, Ip measured in myocytes overexpressing PLM was significantly (P < 0.0001) lower at similar membrane voltages, pipette Na+ ([Na+]pip) and extracellular K+ ([K+]o) concentrations. From -70 to +60 mV, neither [Na+]pip nor [K+]o required to attain half-maximal Ip was significantly different between control and PLM myocytes. This phenotype of decreased V(max) without appreciable changes in K(m) for Na+ and K+ in PLM-overexpressed myocytes was similar to that observed in MI rat myocytes. Inhibition of Ip by PLM overexpression was not due to decreased Na+-K+-ATPase expression because there were no changes in either protein or messenger RNA levels of either alpha1- or alpha2-isoforms of Na+-K+-ATPase. In native rat cardiac myocytes, PLM coimmunoprecipitated with alpha-subunits of Na+-K+-ATPase. Inhibition of Na+-K+-ATPase by PLM overexpression, in addition to previously reported decrease in Na+-K+-ATPase expression, may explain altered V(max) but not K(m) of Na+-K+-ATPase in postinfarction rat myocytes.

Serine 68 phospholemman phosphorylation during forskolin-induced swine carotid artery relaxation

BACKGROUND

Phospholemman (PLM) is an abundant phosphoprotein in the plasma membrane of cardiac, skeletal and smooth muscle. It is a member of the FXYD family of proteins that bind to and regulate the Na,K-ATPase. Protein kinase A (PKA) is known to phosphorylate PLM on serine 68 (S68), although the functional effect of S68 PLM phosphorylation is unclear. We therefore evaluated S68 PLM phosphorylation in swine carotid arteries.

METHODS

Two anti-PLM antibodies, one to S68 phosphorylated PLM and one to unphosphorylated PLM, were made to PLM peptides in rabbits and tested with purified PLM and PKA-treated PLM. Swine carotid arteries were mounted isometrically, contracted, relaxed with forskolin and then homogenized. Proteins were separated on SDS gels and the intensity of immunoreactivity to the two PLM antibodies determined on immunoblots.

RESULTS

The antipeptide antibody 'C2' primarily reacted with unphosphorylated PLM, and the antipeptide antibody 'CP68' detected S68 PLM phosphorylation. Histamine stimulation of intact swine carotid artery induced a contraction, increased the CP68 PLM antibody signal and reduced the C2 PLM antibody signal. High extracellular [K(+)] depolarization induced a contraction without altering the C2 or CP68 PLM signal. Forskolin-induced relaxation of histamine or extracellular [K(+)] contracted arteries correlated with an increased CP68 signal. Nitroglycerin-induced relaxation was not associated with changes in the C2 or CP68 PLM signal.

CONCLUSIONS

These data suggest that a contractile agonist increased S68 PLM phosphorylation. Agents that increase [cAMP], but not agents that increase [cGMP], increased S68 PLM phosphorylation. S68 PLM phosphorylation may be involved in cAMP-dependent regulation of smooth muscle force.

Differential gene expression in coronary arteries from patients presenting with ischemic heart disease: further evidence for the inflammatory basis of atherosclerosis

BACKGROUND AND OBJECTIVE

The pathogenesis of human coronary artery disease (CAD) is likely to require the transcription of many different genes. We report here the differential gene expression profiling of human CAD using copy DNA (cDNA)/nylon array hybridization techniques.

METHODS AND RESULTS

Human coronary arteries were obtained at the time of cardiac transplantation. Ten patients were transplanted for ischemic heart disease (IHD) and 5 for dilated cardiomyopathy (DCM). We generated a customized cDNA array containing 9206 clones and after hybridization of patient samples, data reduction, and refinement, identified 515 sequence-verified, differentially expressed clones. These clones represented 361 genes that were differentially expressed at significant levels between IHD and DCM arteries (t test, P < .05). Of these clones, 70% were defined genes of known function and 30% were genes of unknown function. Of the differentially expressed genes, 53.6% were up-regulated and 46.4% were down-regulated. Hierarchical clustering was performed and several distinct functional clusters were identified, including a cluster of genes related to inflammatory mechanisms. Validation by real-time polymerase chain reaction was undertaken with 2 genes known to be up-regulated in atherosclerosis (interleukin 1beta [IL-1beta] and IL-8) and 2 novel genes identified by the array analysis (signal transducer and activator of transcription 6 [STAT6] and IL-1 receptor-associated kinase [IRAK]). Differential expression of IL-1beta, IL-8, and STAT6 were confirmed by this method. Immunohistochemistry of STAT6 demonstrated increased expression in vascular smooth muscle cells of IHD coronary arteries.

CONCLUSION

These data support the inflammatory basis of human atherosclerotic CAD and identify novel genes in atherosclerosis.

In vitro models to evaluate acute and chronic injury to the heart and vascular systems

Multiple in vitro model systems are currently available to evaluate structure and function relationships in the cardiovascular system as well as the system's response to injury. As the level of molecular sophistication continues to advance, so does the level of complexity of the analysis. One of the most daunting tasks faced by researchers interested in studying cardiovascular function and injury is the selection of the system or systems best suited to answer the particular question at hand. In order to successfully apply any given model system, the researcher must recognize the advantages and limitations in the system of choice. This review provides a listing of the historical and modern techniques used to study cardiovascular function and chemically-induced toxicity. With the growing number of new pharmaceuticals discovered each year, it is imperative to use experimental model systems that allow for identification of targets that participate in or mediate adverse outcomes. Clearly, in vitro analysis cannot replace in vivo experimentation, but the methods currently available allow for a reduction in the number of animals used for experimentation and a better understanding of the complexity associated with the injury response.

Differential cardiac gene expression during cardiopulmonary bypass: Ischemia-independent upregulation of proinflammatory genes

OBJECTIVE

Cardiac surgery with cardiopulmonary bypass induces both systemic and local inflammatory responses implicated in the pathogenesis of myocardial dysfunction. Multifactorial perioperative sources of myocardial injury complicate understanding of the molecular mechanisms involved. By using microarray technology, this study examines myocardial gene expression responses to cardiopulmonary bypass in the absence of cardioplegic arrest and ischemia-reperfusion injury.

METHODS

We used a unique rat model of cardiopulmonary bypass in which sternotomy, direct operations on the heart, aortic crossclamping, and cardioplegic arrest were not performed. Hearts from 6 animals randomized to either 90 minutes of cardiopulmonary bypass or sham control animals were used to perform cDNA microarray analyses of 2343 genes. Real-time quantitative polymerase chain reaction was used to confirm the microarray results for a subset of genes.

RESULTS

Compared with sham-operated control animals, myocardium from animals undergoing cardiopulmonary bypass revealed 42 differentially expressed genes. Upregulated genes include the transcription activator nuclear factor kappaB, adhesion molecules (vascular cell adhesion molecule 1 and P-selectin), and interleukin 6 receptor subunits; downregulated genes include transforming growth factor beta receptor 2, tissue inhibitor of metalloproteinase 3, and mitogen-activated protein kinase 1. Distinct proinflammatory gene cascades were confirmed by means of category overrepresentation analysis.

CONCLUSIONS

This study represents an initial report on the use of microarray technology to elucidate cardiac transcriptional programs in response to cardiopulmonary bypass-specific injury in vivo. These preliminary findings, combined with future functional genomic studies superimposing ischemia and reperfusion and other inflammatory stimuli, should improve our understanding of the molecular regulatory networks involved in myocardial responses to injury and aid in the development of novel cardioprotective and perfusion strategies.

Identification of an endogenous inhibitor of the cardiac Na+/Ca2+ exchanger, phospholemman

Rapid and precise control of Na(+)/Ca(2+) exchanger (NCX1) activity is essential in the maintenance of beat-to-beat Ca(2+) homeostasis in cardiac myocytes. Here, we show that phospholemman (PLM), a 15-kDa integral sarcolemmal phosphoprotein, is a novel endogenous protein inhibitor of cardiac NCX1. Using a heterologous expression system that is devoid of both endogenous PLM and NCX1, we first demonstrated by confocal immunofluorescence studies that both exogenous PLM and NCX1 co-localized at the plasma membrane. Reciprocal co-immunoprecipitation studies revealed specific protein-protein interaction between PLM and NCX1. The functional consequences of direct association of PLM with NCX1 was the inhibition of NCX1 activity, as demonstrated by whole-cell patch clamp studies to measure NCX1 current density and radiotracer flux assays to assess Na(+)-dependent (45)Ca(2+) uptake. Inhibition of NCX1 by PLM was specific, because a single mutation of serine 68 to alanine in PLM resulted in a complete loss of inhibition of NCX1 current, although association of the PLM mutant with NCX1 was unaltered. In native adult cardiac myocytes, PLM co-immunoprecipitated with NCX1. We conclude that PLM, a member of the FXYD family of small ion transport regulators known to modulate Na(+)-K(+)-ATPase, also regulates Na(+)/Ca(2+) exchange in the heart.

Prior exercise training improves the outcome of acute myocardial infarction in the rat

OBJECTIVES

The aim of this research was to investigate the structural, functional, and molecular features of the remodeling heart in prior swim-trained infarcted rats.

BACKGROUND

Physical exercise training is a known protective factor against cardiovascular morbidity and mortality. The structural and molecular aspects underlying this protection in the remodeling heart have not been investigated.

METHODS

After seven weeks of swimming exercise training, rats underwent surgical ligation of the left coronary artery followed by a four-week sedentary period. Untrained control rats underwent the same surgical protocol. Left ventricular function was assessed by echocardiography four weeks after infarction, and hearts were sampled for histological and molecular analysis. Ribonucleic acid from the surviving left ventricle was analyzed by complementary deoxyribonucleic acid arrays followed by Northern blotting or quantitative reverse transcription polymerase chain reaction of selected messenger ribonucleic acids (mRNAs).

RESULTS

Scar area was 1.6-fold smaller (p = 0.0002), arteriolar density was 1.7-fold higher (p = 0.0002), and left ventricular shortening fraction was 1.9-fold higher (p = 0.003) in the exercise-trained compared with sedentary hearts. Eleven genes whose expression level varied by at least +/-1.5-fold distinguished the prior exercised rats from their sedentary counterparts. Compared with sedentary, the exercised hearts displayed 9- and 2.4-times lower levels of atrial natriuretic peptide and aldolase mRNA (p = 0.03 and 0.04, respectively), and a 2.7- and 1.9-fold higher abundance of cytochrome c-oxidase and fatty acid binding protein, respectively (p < 0.03, each).

CONCLUSIONS

Swimming exercise training before acute myocardial infarction reduces scar size, increases arteriole density, and manifests adaptation of stress- and energy-metabolism-related genes that may contribute to the improved heart function observed during remodeling.

Serine 68 of phospholemman is critical in modulation of contractility, [Ca2+]i transients, and Na+/Ca2+ exchange in adult rat cardiac myocytes

Overexpression of phospholemman (PLM) in normal adult rat cardiac myocytes altered contractile function and cytosolic Ca2+ concentration ([Ca2+]i) homeostasis and inhibited Na+/Ca2+ exchanger (NCX1). In addition, PLM coimmunoprecipitated and colocalized with NCX1 in cardiac myocyte lysates. In this study, we evaluated whether the cytoplasmic domain of PLM is crucial in mediating its effects on contractility, [Ca2+]i transients, and NCX1 activity. Canine PLM or its derived mutants were overexpressed in adult rat myocytes by adenovirus-mediated gene transfer. Confocal immunofluorescence images using canine-specific PLM antibodies demonstrated that the exogenous PLM or its mutants were correctly targeted to sarcolemma, t-tubules, and intercalated discs, with little to none detected in intracellular compartments. Overexpression of canine PLM or its mutants did not affect expression of NCX1, sarco(endo)plasmic reticulum Ca(2+)-ATPase, Na(+)-K(+)-ATPase, and calsequestrin in adult rat myocytes. A COOH-terminal deletion mutant in which all four potential phosphorylation sites (Ser62, Ser63, Ser68, and Thr69) were deleted, a partial COOH-terminal deletion mutant in which Ser68 and Thr69 were deleted, and a mutant in which all four potential phosphorylation sites were changed to alanine all lost wild-type PLM's ability to modulate cardiac myocyte contractility. These observations suggest the importance of Ser68 or Thr69 in mediating PLM's effect on cardiac contractility. Focusing on Ser68, the Ser68 to Glu mutant was fully effective, the Ser63 to Ala (leaving Ser68 intact) mutant was partially effective, and the Ser68 to Ala mutant was completely ineffective in modulating cardiac contractility, [Ca2+]i transients, and NCX1 currents. Both the Ser63 to Ala and Ser68 to Ala mutants, as well as PLM, were able to coimmunoprecipitate NCX1. It is known that Ser68 in PLM is phosphorylated by both protein kinases A and C. We conclude that regulation of cardiac contractility, [Ca2+]i transients, and NCX1 activity by PLM is critically dependent on Ser68. We suggest that PLM phosphorylation at Ser68 may be involved in cAMP- and/or protein kinase C-dependent regulation of cardiac contractility.

Left-right asymmetric ventricular expression of CARP in the piglet heart: regional response to experimental heart failure

BACKGROUND AND AIM

Cardiac ankyrin repeat protein (CARP), whose expression is down-regulated in response to doxorubicin (Dox) in vitro, has been proposed to be a marker of experimentally-induced cardiac hypertrophy in rodent models. In piglets, the rapid hypertrophy rate of the left ventricle (LV) as compared to that of the right ventricle (RV) represents a natural model of asymmetric ventricular enlargement. We tested whether CARP expression correlates with postnatal ventricular hypertrophy and to what extent CARP can be sensitive to Dox treatment in vivo.

METHODS

CARP mRNA and protein levels were quantified (by Northern blot hybridization, semi-quantitative RT-PCR and Western blot) in the piglet heart, both during early postnatal development and upon Dox-induced cardiomyopathy (Dox-CM).

RESULTS

The study revealed: (1) significantly augmented CARP mRNA and protein levels in the LV compared to the RV resulting in left vs. right asymmetry in ventricular CARP expression throughout early postnatal development; (2) dose- and chamber-dependent CARP mRNA and protein enrichment in ventricular myocardium in response to Dox; and (3) abolishment of asymmetric patterns of ventricular CARP expression at heart failure resulting from Dox-CM.

CONCLUSIONS

(1) CARP is differentially regulated in the LV and RV during both postnatal development and disease; and (2) monitoring of ventricular CARP expression patterns can be used for further analysis of transition from compensated to overt heart failure.

Computational physiology and the Physiome Project

Bioengineering analyses of physiological systems use the computational solution of physical conservation laws on anatomically detailed geometric models to understand the physiological function of intact organs in terms of the properties and behaviour of the cells and tissues within the organ. By linking behaviour in a quantitative, mathematically defined sense across multiple scales of biological organization--from proteins to cells, tissues, organs and organ systems--these methods have the potential to link patient-specific knowledge at the two ends of these spatial scales. A genetic profile linked to cardiac ion channel mutations, for example, can be interpreted in relation to body surface ECG measurements via a mathematical model of the heart and torso, which includes the spatial distribution of cardiac ion channels throughout the myocardium and the individual kinetics for each of the approximately 50 types of ion channel, exchanger or pump known to be present in the heart. Similarly, linking molecular defects such as mutations of chloride ion channels in lung epithelial cells to the integrated function of the intact lung requires models that include the detailed anatomy of the lungs, the physics of air flow, blood flow and gas exchange, together with the large deformation mechanics of breathing. Organizing this large body of knowledge into a coherent framework for modelling requires the development of ontologies, markup languages for encoding models, and web-accessible distributed databases. In this article we review the state of the field at all the relevant levels, and the tools that are being developed to tackle such complexity. Integrative physiology is central to the interpretation of genomic and proteomic data, and is becoming a highly quantitative, computer-intensive discipline.

Dynamic changes of gene expression profiles during postnatal development of the heart in mice

OBJECTIVE

To study postnatal cardiac differentiation in the mouse.

HYPOTHESIS

There might be mechanisms or factors in cardiac differentiation that could be identified by systematic gene expression analysis during postnatal cardiac development.

METHODS

Expression of 6144 genes was examined in mouse heart, from the newborn period (day 0), through day 7 and day 14 day, to adulthood, using the cDNA microarray approach. Northern blotting and immunohistochemical techniques were used to confirm the microarray results.

RESULTS

Various cardiac development related genes involving the cell cycle (cyclin B1, proliferating cell nuclear antigen (PCNA), and Ki67), growth factors (IGF-II, pleiotrophin (PTN), and midkine (MK)), and transcriptional regulation, cytoskeleton, and detoxification enzymes were identified by microarray analysis. Some of these genes were also confirmed by Northern blotting and immunohistochemistry of their RNA and protein content. In vivo treatment with PTN (20 ng/g) increased bromodeoxyuridine incorporation (by 2.24-fold) and PCNA expression (by 1.71-fold) during day 7 to day 14, indicating that PTN induces cell proliferation in mouse heart.

CONCLUSIONS

Global gene expression analysis in the whole heart may be useful in understanding the orchestrated process of postnatal development or terminal differentiation in the cardiac environment. These data are likely to be helpful in studying developmental anomalies of the heart in neonates.