Proteomics of the heart

Mass spectrometry-based proteomics is a sophisticated identification tool specializing in portraying protein dynamics at a molecular level. Proteomics provides biologists with a snapshot of context-dependent protein and proteoform expression, structural conformations, dynamic turnover, and protein-protein interactions. Cardiac proteomics can offer a broader and deeper understanding of the molecular mechanisms that underscore cardiovascular disease, and it is foundational to the development of future therapeutic interventions. This review encapsulates the evolution, current technologies, and future perspectives of proteomic-based mass spectrometry as it applies to the study of the heart. Key technological advancements have allowed researchers to study proteomes at a single-cell level and employ robot-assisted automation systems for enhanced sample preparation techniques, and the increase in fidelity of the mass spectrometers has allowed for the unambiguous identification of numerous dynamic posttranslational modifications. Animal models of cardiovascular disease, ranging from early animal experiments to current sophisticated models of heart failure with preserved ejection fraction, have provided the tools to study a challenging organ in the laboratory. Further technological development will pave the way for the implementation of proteomics even closer within the clinical setting, allowing not only scientists but also patients to benefit from an understanding of protein interplay as it relates to cardiac disease physiology.

Heart proteomic profiling discovers MYH6 and COX5B as biomarkers for sudden unexplained death

Sudden unexplained death (SUD) is not uncommon in forensic pathology. Yet, diagnosis of SUD remains challenging due to lack of specific biomarkers. This study aimed to screen differentially expressed proteins (DEPs) and validate their usefulness as diagnostic biomarkers for SUD cases. We designed a three-phase investigation, where in the discovery phase, formalin-fixed paraffin-embedded (FFPE) heart specimens were screened through label-free proteomic analysis of cases dying from SUD, mechanical injury and carbon monoxide (CO) intoxication. A total of 26 proteins were identified to be DEPs for the SUD cases after rigorous criterion. Bioinformatics and Adaboost-recursive feature elimination (RFE) analysis further revealed that three of the 26 proteins (MYH6, COX5B and TNNT2) were potential discriminative biomarkers. In the training phase, MYH6 and COX5B were verified to be true DEPs in cardiac tissues from 29 independent SUD cases as compared with a serial of control cases (n = 42). Receiver operating characteristic (ROC) analysis illustrated that combination of MYH6 and COX5B achieved optimal diagnostic sensitivity (89.7 %) and specificity (84.4 %), with area under the curve (AUC) being 0.91. A diagnostic software based on the logistic regression formula derived from the training phase was then constructed. In the validation phase, the diagnostic software was applied to eight authentic SUD cases, seven (87.5 %) of which were accurately recognized. Our study provides a valid strategy towards practical diagnosis of SUD by integrating cardiac MYH6 and COX5B as dual diagnostic biomarkers.

N-Terminomic Identification of Intracellular MMP-2 Substrates in Cardiac Tissue

Proteases are enzymes that induce irreversible post-translational modifications by hydrolyzing amide bonds in proteins. One of these proteases is matrix metalloproteinase-2 (MMP-2), which has been shown to modulate extracellular matrix remodeling and intracellular proteolysis during myocardial injury. However, the substrates of MMP-2 in heart tissue are limited, and lesser known are the cleavage sites. Here, we used degradomics to investigate the substrates of intracellular MMP-2 in rat ventricular extracts. First, we designed a novel, constitutively active MMP-2 fusion protein (MMP-2-Fc) that we expressed and purified from mammalian cells. Using this protease, we proteolyzed ventricular extracts and used subtiligase-mediated N-terminomic labeling which identified 95 putative MMP-2-Fc proteolytic cleavage sites using mass spectrometry. The intracellular MMP-2 cleavage sites identified in heart tissue extracts were enriched for proteins primarily involved in metabolism, as well as the breakdown of fatty acids and amino acids. We further characterized the cleavage of three of these MMP-2-Fc substrates based on the gene ontology analysis. We first characterized the cleavage of sarco/endoplasmic reticulum calcium ATPase (SERCA2a), a known MMP-2 substrate in myocardial injury. We then characterized the cleavage of malate dehydrogenase (MDHM) and phosphoglycerate kinase 1 (PGK1), representing new cardiac tissue substrates. Our findings provide insights into the intracellular substrates of MMP-2 in cardiac cells, suggesting that MMP-2 activation plays a role in cardiac metabolism.

Data-Independent Acquisition Proteomics and N-Terminomics Methods Reveal Alterations in Mitochondrial Function and Metabolism in Ischemic-Reperfused Hearts

Myocardial ischemia-reperfusion (IR) (stunning) injury triggers changes in the proteome and degradome of the heart. Here, we utilize quantitative proteomics and comprehensive degradomics to investigate the molecular mechanisms of IR injury in isolated rat hearts. The control group underwent aerobic perfusion, while the IR injury group underwent 20 min of ischemia and 30 min of reperfusion to induce a stunning injury. As MMP-2 activation has been shown to contribute to myocardial injury, hearts also underwent IR injury with ARP-100, an MMP-2-preferring inhibitor, to dissect the contribution of MMP-2 to IR injury. Using data-independent acquisition (DIA) and mass spectroscopy, we quantified 4468 proteins in ventricular extracts, whereby 447 proteins showed significant alterations among the three groups. We then used subtiligase-mediated N-terminomic labeling to identify more than a hundred specific cleavage sites. Among these protease substrates, 15 were identified following IR injury. We identified alterations in numerous proteins involved in mitochondrial function and metabolism following IR injury. Our findings provide valuable insights into the biochemical mechanisms of myocardial IR injury, suggesting alterations in reactive oxygen/nitrogen species handling and generation, fatty acid metabolism, mitochondrial function and metabolism, and cardiomyocyte contraction.

Quantitative proteomic and phosphoproteomic profiling of ischemic myocardial stunning in swine

Despite decades of research on the pathophysiology of myocardial stunning, protein changes and/or phosphorylation status underlying alterations in cardiac function/structure remain inadequately understood. Here, we utilized comprehensive and quantitative proteomic and phosphoproteomic approaches to explore molecular mechanisms of myocardial stunning in swine. The closed-chest swine (n = 5 pigs) were subjected to a 10-min left anterior descending coronary artery (LAD) occlusion producing regional myocardial stunning. Tissues from the ischemic LAD region and a remote nonischemic area of the left ventricle were collected 1 h after reperfusion. Ion current-based proteomics (IonStar) and quantitative phosphoproteomics were employed in parallel to identify alterations in protein level and site-specific phosphorylation changes. A novel swine heart protein database exhibiting high accuracy and low redundancy was developed here to facilitate comprehensive study. Further informatic investigations identified potential protein-protein interactions in stunned myocardium. In total, we quantified 2,099 protein groups and 4,699 phosphorylation sites with only 0.4% missing values. Proteomic analyses revealed downregulation of contractile function and extracellular matrix remodeling. Meanwhile, alterations in phosphorylation linked with contractile dysfunction and apoptotic cell death were uncovered. NetworKIN/STRING analysis predicted regulatory kinases responsible for altered phosphosites, such as protein kinase C-mediated phosphorylation of cardiac troponin I-S199 and CaMKII-mediated phosphorylation of phospholamban-T17. In summary, the ion current-based proteomics and phosphoproteomics reliably identified novel alterations in protein content and phosphorylation contributing to contractile dysfunction, extracellular matrix (ECM) damage, and programmed cell death in stunned myocardium, which corroborate well with our physiological observations. Moreover, this work developed a comprehensive database of the swine heart proteome, a highly valuable resource for future translational research in porcine models with cardiovascular diseases.NEW & NOTEWORTHY We first used ion current-based proteomics and phosphoproteomics to reliably identify novel alterations in protein expression and phosphorylation contributing to contractile dysfunction, extracellular matrix (ECM) damage, and programmed cell death in stunned myocardium and developed a comprehensive swine heart-specific proteome database, which provides a valuable resource for future research in porcine models of cardiovascular diseases.

Tyrosine nitration of mitochondrial proteins during myocardial ischemia and reperfusion

Myocardial ischemia reperfusion is associated with mitochondrial dysfunction and increased formation of reactive oxygen/nitrogen species. The main purpose of this study was to assess the role of tyrosine nitration of mitochondrial proteins in postischemic contractile dysfunction known as myocardial stunning. Isolated Langendorff-perfused rat hearts were subjected to 20-min global ischemia followed by 30-min reperfusion. The reperfused hearts showed marked decline in left ventricular developed pressure, maximal rate of contraction (+dP/dt), and maximal rate of relaxation (-dP/dt). Immunofluorescence and ELISA assays demonstrated enhanced protein tyrosine nitration in reperfused hearts. Using two-dimensional gel electrophoresis and MALDI-TOF/TOF mass spectrometry, eight mitochondrial proteins were identified to be nitrated after ischemia reperfusion. These proteins are crucial in mitochondrial electron transport, fatty acid oxidation, tricarboxylic acid cycle, ATP synthesis, and control of high-energy phosphates. The proteome data also indicated reduced abundance in several of nitrated proteins. The results suggest that these changes may contribute to inhibition of aconitase activity but are unlikely to affect electron transport chain activity. Whether tyrosine nitration of mitochondrial proteins can be considered the contributing factor of postischemic contractile dysfunction remains to be explored.

Cardiac Disorders and Pathophysiology of Sarcomeric Proteins

The sarcomeric proteins represent the structural building blocks of heart muscle, which are essential for contraction and relaxation. During recent years, it has become evident that posttranslational modifications of sarcomeric proteins, in particular phosphorylation, tune cardiac pump function at rest and during exercise. This delicate, orchestrated interaction is also influenced by mutations, predominantly in sarcomeric proteins, which cause hypertrophic or dilated cardiomyopathy. In this review, we follow a bottom-up approach starting from a description of the basic components of cardiac muscle at the molecular level up to the various forms of cardiac disorders at the organ level. An overview is given of sarcomere changes in acquired and inherited forms of cardiac disease and the underlying disease mechanisms with particular reference to human tissue. A distinction will be made between the primary defect and maladaptive/adaptive secondary changes. Techniques used to unravel functional consequences of disease-induced protein changes are described, and an overview of current and future treatments targeted at sarcomeric proteins is given. The current evidence presented suggests that sarcomeres not only form the basis of cardiac muscle function but also represent a therapeutic target to combat cardiac disease.

Modulation of NFKB1/p50 by ROS leads to impaired ATP production during MI compared to cardiac hypertrophy

Pathological hypertrophy and myocardial infarction (MI) are two etiologically different cardiac disorders having differential molecular mechanisms of disease manifestation. However, no study has been conducted so far to analyze and compare the differential status of energy metabolism in these two disease forms. It was shown recently by our group that production of ATP is significantly impaired during MI along with inhibition of pyruvate dehydrogenase E1-β (PDHE1 B) by pyruvate dehydrogenase kinase 4 (PDK4). However, the ATP levels showed no significant change during pathological hypertrophy compared to control group. To seek a plausible explanation of this phenomenon, the peroxisome proliferator-activated receptor alpha (PPAR) pathway was studied in all the experimental groups which revealed that PGC1α- ERRα axis remains active in MI while the same remained inactive during pathological hypertrophy possibly by NF-κB that plays a significant role in deactivating this pathway during hypertrophy. At the same time, it was observed that reactive oxygen species (ROS) negatively regulates NF-κB activity during MI by oxidation of cysteine residues of p50- the DNA binding subunit of NF-κB. Thus, this study reports for the first time, a possible mechanism for the differential status of energy metabolism during two etiologically different cardiac pathophysiological conditions involving PGC1α-ERRα axis along with p50 subunit of NF-κB.

Role of Protein Carbonylation in Skeletal Muscle Mass Loss Associated with Chronic Conditions

Muscle dysfunction, characterized by a reductive remodeling of muscle fibers, is a common systemic manifestation in highly prevalent conditions such as chronic heart failure (CHF), chronic obstructive pulmonary disease (COPD), cancer cachexia, and critically ill patients. Skeletal muscle dysfunction and impaired muscle mass may predict morbidity and mortality in patients with chronic diseases, regardless of the underlying condition. High levels of oxidants may alter function and structure of key cellular molecules such as proteins, DNA, and lipids, leading to cellular injury and death. Protein oxidation including protein carbonylation was demonstrated to modify enzyme activity and DNA binding of transcription factors, while also rendering proteins more prone to proteolytic degradation. Given the relevance of protein oxidation in the pathophysiology of many chronic conditions and their comorbidities, the current review focuses on the analysis of different studies in which the biological and clinical significance of the modifications induced by reactive carbonyls on proteins have been explored so far in skeletal muscles of patients and animal models of chronic conditions such as COPD, disuse muscle atrophy, cancer cachexia, sepsis, and physiological aging. Future research will elucidate the specific impact and sites of reactive carbonyls on muscle protein content and function in human conditions.

Analysis of Mitochondrial Proteins in the Surviving Myocardium after Ischemia Identifies Mitochondrial Pyruvate Carrier Expression as Possible Mediator of Tissue Viability

The endogenous mechanisms contributing to tissue survival following myocardial infarction are not fully understood. We investigated the alterations in the mitochondrial proteome after ischemia-reperfusion (I/R) and its possible implications on cell survival. Mitochondrial proteomic analysis of cardiac tissue from an in vivo porcine I/R model found that surviving tissue in the peri-infarct border zone showed increased expression of several proteins. Notably, these included subunits of the mitochondrial pyruvate carrier (MPC), namely MPC1 and MPC2. Western blot, immunohistochemistry, and mRNA analysis corroborated the elevated expression of MPC in the surviving tissue. Furthermore, MPC1 and MPC2 protein levels were found to be markedly elevated in the myocardium of ischemic cardiomyopathy patients. These findings led to the hypothesis that increased MPC expression is cardioprotective due to enhancement of mitochondrial pyruvate uptake in the energy-starved heart following I/R. To test this, isolated mouse hearts perfused with a modified Krebs buffer (containing glucose, pyruvate, and octanoate as metabolic substrates) were subjected to I/R with or without the MPC transport inhibitor UK5099. UK5099 increased myocardial infarction and attenuated post-ischemic recovery of left ventricular end-diastolic pressure. However, aerobically perfused control hearts that were exposed to UK5099 did not modulate contractile function, although pyruvate uptake was blocked as evidenced by increased cytosolic lactate and pyruvate levels. Our findings indicate that increased expression of MPC leads to enhanced uptake and utilization of pyruvate during I/R. We propose this as a putative endogenous mechanism that promotes myocardial survival to limit infarct size.

Expression of heat shock protein 27 and troponin T and troponin I after naloxone-precipitated morphine withdrawal

Heat shock protein (Hsp27) renders cardioprotection from stress situations but little is known about its role in myofilaments. In this study we have evaluated the relationship between Hsp27 and troponin response after naloxone-induced morphine withdrawal. Rats were treated with two morphine (75 mg) pellets during six days. Precipitated withdrawal was induced by naloxone on day seven. Hsp27 expression, Hsp27 phosphorylated at serine 82 (Ser82), cardiac troponin T (cTnT), cardiac troponin I (cTnI) and µ-calpain were evaluated by immunoblotting in left ventricle. Hsp, cTnT and cTnI was also evaluated by immunofluorescence procedure. Our results show that enhancement in Hsp27 expression and phosphorylation induced by naloxone-precipitated morphine withdrawal occurs with concomitant increases of cTnT and µ-calpain expression, whereas cTnI was decreased. We also observed co-localization of Hsp27 with cTnT in cardiac tissues. These findings provide new information into the possible role of Hsp27 in the protection of cTnT degradation by µ-calpain (a protease mediating proteolysis of cTnT and cTnI) after morphine withdrawal.

Understanding different facets of cardiovascular diseases based on model systems to human studies: a proteomic and metabolomic perspective

Cardiovascular disease has remained as the largest cause of morbidity and mortality worldwide. From dissecting the disease aetiology to identifying prognostic markers for better management of the disease is still a challenge for researchers. In the post human genome sequencing era much of the thrust has been focussed towards application of advanced genomic tools along with evaluation of traditional risk factors. With the advancement of next generation proteomics and metabolomics approaches it has now become possible to understand the protein interaction network & metabolic rewiring which lead to the perturbations of the disease phenotype. Further, elucidating different post translational modifications using advanced mass spectrometry based methods have provided an impetus towards in depth understanding of the proteome. The past decade has observed a plethora of studies where proteomics has been applied successfully to identify potential prognostic and diagnostic markers as well as to understand the disease mechanisms for various types of cardiovascular diseases. In this review, we attempted to document relevant proteomics based studies that have been undertaken either to identify potential biomarkers or have elucidated newer mechanistic insights into understanding the patho-physiology of cardiovascular disease, primarily coronary artery disease, cardiomyopathy, and myocardial ischemia. We have also provided a perspective on the potential of proteomics in combating this deadly disease.

BIOLOGICAL SIGNIFICANCE

This review has catalogued recent studies on proteomics and metabolomics involved in understanding several cardiovascular diseases (CVDs). A holistic systems biology based approach, of which proteomics and metabolomics are two very important components, would help in delineating various pathways associated with complex disorders like CVD. This would ultimately provide better mechanistic understanding of the disease biology leading to development of prognostic biomarkers. This article is part of a Special Issue entitled: Proteomics in India.

Comparative Proteome Profiling during Cardiac Hypertrophy and Myocardial Infarction Reveals Altered Glucose Oxidation by Differential Activation of Pyruvate Dehydrogenase E1 Component Subunit β

Cardiac hypertrophy and myocardial infarction (MI) are two etiologically different disease forms with varied pathological characteristics. However, the precise molecular mechanisms and specific causal proteins associated with these diseases are obscure to date. In this study, a comparative cardiac proteome profiling was performed in Wistar rat models for diseased and control (sham) groups using two-dimensional difference gel electrophoresis followed by matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry. Proteins were identified using Protein Pilot™ software (version 4.0) and were subjected to stringent statistical analysis. Alteration of key proteins was validated by Western blot analysis. The differentially expressed protein sets identified in this study were associated with different functional groups, involving various metabolic pathways, stress responses, cytoskeletal organization, apoptotic signaling and other miscellaneous functions. It was further deciphered that altered energy metabolism during hypertrophy in comparison to MI may be predominantly attributed to induced glucose oxidation level, via reduced phosphorylation of pyruvate dehydrogenase E1 component subunit β (PDHE1-B) protein during hypertrophy. This study reports for the first time the global changes in rat cardiac proteome during two etiologically different cardiac diseases and identifies key signaling regulators modulating ontogeny of these two diseases culminating in heart failure. This study also pointed toward differential activation of PDHE1-B that accounts for upregulation of glucose oxidation during hypertrophy. Downstream analysis of altered proteome and the associated modulators would enhance our present knowledge regarding altered pathophysiology of these two etiologically different cardiac disease forms.

Protein carbonylation and muscle function in COPD and other conditions

Skeletal muscle, the most abundant tissue in mammals, is essential for any activity in life. Muscle dysfunction is a common systemic manifestation in highly prevalent conditions such as chronic obstructive pulmonary disease (COPD), cancer cachexia, and sepsis. It has a significant impact on exercise tolerance, thus worsening the patients' quality of life and survival. Among several factors, oxidative stress is a major player in the etiology of skeletal muscle dysfunction associated with those conditions. Whereas low levels of oxidants are absolutely required for normal cell adaptation, high levels of reactive oxygen species (ROS) alter the function and structure of molecules such as proteins, DNA, and lipids. Specifically, protein carbonylation, a common variety of protein oxidation, was shown to alter the function of key enzymes and structural proteins involved in muscle contractile performance. Moreover, increased levels of ROS may also activate proteolytic systems, thus leading to enhanced protein breakdown in several models. In the current review, the specific modifications induced by carbonylation in protein structure and function in muscles have been described. Furthermore, the potential role of ROS in the activation of proteolytic systems in skeletal muscles is also discussed. The review summarizes the effects of protein carbonylation on muscles in several models and conditions such as COPD, disuse muscle atrophy, cancer cachexia, sepsis, and aging. Future research should focus on the elucidation of the specific protein sites modified by ROS in these muscles using redox proteomics analyses and on the assessment of the consequent alterations in protein function and stability.

Exercise and cardiac preconditioning against ischemia reperfusion injury

Cardiovascular disease (CVD), including ischemia reperfusion (IR) injury, remains a major cause of morbidity and mortality in industrialized nations. Ongoing research is aimed at uncovering therapeutic interventions against IR injury. Regular exercise participation is recognized as an important lifestyle intervention in the prevention and treatment of CVD and IR injury. More recent understanding reveals that moderate intensity aerobic exercise is also an important experimental model for understanding the cellular mechanisms of cardioprotection against IR injury. An important discovery in this regard was the observation that one-to-several days of exercise will attenuate IR injury. This phenomenon has been observed in young and old hearts of both sexes. Due to the short time course of exercise induced protection, IR injury prevention must be mediated by acute biochemical alterations within the myocardium. Research over the last decade reveals that redundant mechanisms account for exercise induced cardioprotection against IR. While much is now known about exercise preconditioning against IR injury, many questions remain. Perhaps most pressing, is what mechanisms mediate cardioprotection in aged hearts and what sex-dependent differences exist. Given that that exercise preconditioning is a polygenic effect, it is likely that multiple mediators of exercise induced cardioprotection have yet to be uncovered. Also unknown, is whether post translational modifications due to exercise are responsible for IR injury prevention. This review will provide an overview the major mechanisms of IR injury and exercise preconditioning. The discussion highlights many promising avenues for further research and describes how exercise preconditioning may continue to be an important scientific paradigm in the translation of cardioprotection research to the clinic.

Synergistic protection of MLC 1 against cardiac ischemia/reperfusion-induced degradation: a novel therapeutic concept for the future

Cardiovascular diseases are a major burden to society and a leading cause of morbidity and mortality in the developed world. Despite clinical and scientific advances in understanding the molecular mechanisms and treatment of heart injury, novel therapeutic strategies are needed to prevent morbidity and mortality due to cardiac events. Growing evidence reported over the last decade has focused on the intracellular targets for proteolytic degradation by MMP-2. Of particular interest is the establishment of MMP-2-dependent degradation of cardiac contractile proteins in response to increased oxidative stress conditions, such as ischemia/reperfusion. The authors' laboratory has identified a promising preventive therapeutic target using the classical pharmacological concept of synergy to target MMP-2 activity and its proteolytic action on a cardiac contractile protein. This manuscript provides an overview of the body of evidence that supports the importance of cardiac contractile protein degradation in ischemia/reperfusion injury and the use of synergy to protect against it.

Proteomic analysis of right and left cardiac ventricles under aerobic conditions and after ischemia/reperfusion

Ischemia/reperfusion (I/R) injury is a major consequence of a cardiovascular intervention. The study of changes of the left and right ventricle proteomes from hearts subjected to I/R may be a key to revealing the pathological mechanisms underlying I/R-induced heart contractile dysfunction. Isolated rat hearts were perfused under aerobic conditions or subjected to 25 min global ischemia and 30 min reperfusion. At the end of perfusion, right and left ventricular homogenates were analyzed by 2DE. Contractile function and coronary flow were significantly reduced by I/R. 2DE followed by mass spectrometry identified ten protein spots whose levels were significantly different between aerobic left and right ventricles, eight protein spots whose levels were different between aerobic and I/R left ventricle, ten protein spots whose levels were different between aerobic and I/R right ventricle ten protein spots whose levels were different between the I/R groups. Among these protein spots were ATP synthase beta subunit, myosin light chain 2, myosin heavy chain fragments, peroxiredoxin-2, and heat shock proteins, previously associated with cardiovascular disease. These results reveal differences between proteomes of left and right ventricle both under aerobic conditions and in response to I/R that contribute to a better understanding of I/R injury.

Myofilament proteins: From cardiac disorders to proteomic changes

Myofilament proteins of the cardiac sarcomere house the molecular machinery responsible for generating tension and pressure. Release of intracellular Ca(2+) triggers myofilament tension generation and shortening, but the response to Ca(2+) is modulated by changes in key regulatory proteins. We review how these proteomic changes are essential to adaptive physiological regulation of cardiac output and become maladaptive in cardiac disorders. We also review the essentials of proteomic techniques used to study myofilament protein changes, including degradation, isoform expression, phosphorylation and oxidation. Selected proteomic studies illustrate the applications of these approaches.

Cardiac myofilaments: from proteome to pathophysiology

This review addresses the functional consequences of altered post-translational modifications of cardiac myofilament proteins in cardiac diseases such as heart failure and ischemia. The modifications of thick and thin filament proteins as well as titin are addressed. Understanding the functional consequences of altered protein modifications is an essential step in the development of targeted therapies for common cardiac diseases.

Mitochondria: A mirror into cellular dysfunction in heart disease

Cardiovascular (CV) disease is the single most significant cause of morbidity and mortality worldwide. The emerging global impact of CV disease means that the goals of early diagnosis and a wider range of treatment options are now increasingly pertinent. As such, there is a greater need to understand the molecular mechanisms involved and potential targets for intervention. Mitochondrial function is important for physiological maintenance of the cell, and when this function is altered, the cell can begin to suffer. Given the broad range and significant impacts of the cellular processes regulated by the mitochondria, it becomes important to understand the roles of the proteins associated with this organelle. Proteomic investigations of the mitochondria are hampered by the intrinsic properties of the organelle, including hydrophobic mitochondrial membranes; high proportion of basic proteins (pI greater than 8.0); and the relative dynamic range issues of the mitochondria. For these reasons, many proteomic studies investigate the mitochondria as a discrete subproteome. Once this has been achieved, the alterations that result in functional changes with CV disease can be observed. Those alterations that lead to changes in mitochondrial function, signaling and morphology, which have significant implications for the cardiomyocyte in the development of CV disease, are discussed.

Microarray and proteomic analysis of the cardioprotective effects of cold blood cardioplegia in the mature and aged male and female

Recently we have shown that the cardioprotection afforded by cardioplegia is modulated by age and gender and is significantly decreased in the aged female. In this report we use microarray and proteomic analyses to identify transcriptomic and proteomic alterations affecting cardioprotection using cold blood cardioplegia in the mature and aged male and female heart. Mature and aged male and female New Zealand White rabbits were used for in situ blood perfused cardiopulmonary bypass. Control hearts received 30 min sham ischemia and 120 min sham reperfusion. Global ischemia (GI) hearts received 30 min of GI achieved by cross-clamping of the aorta. Cardioplegia (CP) hearts received cold blood cardioplegia prior to GI. Following 30 min of GI the hearts were reperfused for 120 min and then used for RNA and protein isolation. Microarray and proteomic analyses were performed. Functional enrichment analysis showed that mitochondrial dysfunction, oxidative phosphorylation and calcium signaling pathways were significantly enriched in all experimental groups. Glycolysis/gluconeogenesis and the pentose phosphate pathway were significantly changed in the aged male only (P < 0.05), while glyoxylate/dicarboxylate metabolism was significant in the aged female only (P < 0.05). Our data show that specific pathways associated with the mitochondrion modulate cardioprotection with CP in the aged and specifically in the aged female. The alteration of these pathways significantly contributes to decreased myocardial functional recovery and myonecrosis following ischemia and may be modulated to allow for enhanced cardioprotection in the aged and specifically in the aged female.

High molecular mass proteomics analyses of left ventricle from rats subjected to differential swimming training

BACKGROUND

Regular exercises are commonly described as an important factor in health improvement, being directly related to contractile force development in cardiac cells.In order to evaluate the links between swimming exercise intensity and cardiac adaptation by using high molecular mass proteomics, isogenic Wistar rats were divided into four groups: one control (CG) and three training groups (TG's), with low, moderate and high intensity of exercises.In order to evaluate the links between swimming exercise intensity and cardiac adaptation by using high molecular mass proteomics, isogenic Wistar rats were divided into four groups: one control (CG) and three training groups (TG's), with low, moderate and high intensity of exercises.

RESULTS

Findings here reported demonstrated clear morphologic alterations, significant cellular injury and increased energy supplies at high exercise intensities. α-MyHC, as well proteins associated with mitochondrial oxidative metabolism were shown to be improved. α-MyHC expression increase 1.2 fold in high intensity training group when compared with control group. α-MyHC was also evaluated by real-time PCR showing a clear expression correlation with protein synthesis data increase in 8.48 fold in high intensity training group. Other myofibrillar protein, troponin , appear only in high intensity group, corroborating the cellular injury data. High molecular masses proteins such as MRS2 and NADH dehydrogenase, involved in metabolic pathways also demonstrate increase expression, respectily 1.5 and 1.3 fold, in response to high intensity exercise.

CONCLUSIONS

High intensity exercise demonstrated an increase expression in some high molecular masses myofibrilar proteins, α-MyHC and troponin. Furthermore this intensity also lead a significant increase of other high molecular masses proteins such as MRS2 and NADH dehydrogenase in comparison to low and moderate intensities. However, high intensity exercise also represented a significant degree of cellular injury, when compared with the individuals submitted to low and moderate intensities.

Proteomic analyses of transgenic LQT1 and LQT2 rabbit hearts elucidate an increase in expression and activity of energy producing enzymes

Various biochemical and genomic mechanisms are considered to be a hallmark of metabolic remodeling in the stressed heart, including the hypertrophied and failing heart. In this study, we used quantitative proteomic 2-D Fluorescence Difference In-Gel Electrophoresis (2-D DIGE) in conjunction with mass spectrometry to demonstrate differential protein expression in the hearts of transgenic rabbit models of Long QT Syndrome 1 (LQT1) and Long QT Syndrome 2 (LQT2) as compared to littermate controls (LMC). The results of our proteomic analysis revealed upregulation of key metabolic enzymes involved in all pathways associated with ATP generation, including creatine kinase in both LQT1 and LQT2 rabbit hearts. Additionally, the expression of lamin-A protein was increased in both LQT1 and LQT2 rabbit hearts as was the expression of mitochondrial aldehyde dehydrogenase and desmoplakin in LQT1 and LQT 2 rabbit hearts, respectively. Results of the proteomic analysis also demonstrated down regulation in the expression of protein disulfide-isomerase A3 precuorsor and dynamin-like 120 kDa protein (mitochondrial) in LQT1, and of alpha-actinin 2 in LQT2 rabbit hearts. Up regulation of the expression of the enzymes associated with ATP generation was substantiated by the results of selective enzyme assays in LQT1 and LQT2 hearts, as compared to LMC, which revealed increases in the activities of glycogen phosphorylase (+50%, +65%, respectively), lactate dehydrogenase (+25%, +25%) pyruvate dehydrogenase (+31%, +22%), and succinate dehydrogenase (+32%, +60%). The activity of cytochrome c-oxidase, a marker for the mitochondrial function was also found to be significantly elevated (+80%) in LQT1 rabbit hearts as compared with LMC. Western blot analysis in LQT1 and LQT2 hearts compared to LMC revealed an increase in the expression of very-long chain-specific acyl-CoA dehydrogenase (+35%, +33%), a rate-limiting enzymes in β-oxidation of fatty acids. Collectively, our results demonstrate similar increases in the expression and activities of key ATP-generating enzymes in LQT1 and LQT2 rabbit hearts, suggesting an increased demand, and in turn, increased energy supply across the entire metabolic pathway by virtue of the upregulation of enzymes involved in energy generation.

Proteomic analysis of metabolic, cytoskeletal and stress response proteins in human heart failure

Human heart failure is a complex syndrome and a primary cause of morbidity and mortality in the world. However, the molecular pathways involved in the remodelling process are poorly understood. In this study, we performed exhaustive global proteomic surveys of cardiac ventricle isolated from failing and non-failing human hearts, and determined the regulatory pathway to uncover the mechanism underlying heart failure. Two-dimensional gel electrophoresis (2-DE) coupled with tandem mass spectrometry was used to identify differentially expressed proteins in specimens from failing (n = 9) and non-failing (n = 6) human hearts. A total of 25 proteins with at least 1.5-fold change in the failing heart were identified; 15 proteins were up-regulated and 10 proteins were down-regulated. The altered proteins belong to three broad functional categories: (i) metabolic [e.g. NADH dehydrogenase (ubiquinone), dihydrolipoamide dehydrogenase, and the cytochrome c oxidase subunit]; (ii) cytoskeletal (e.g. myosin light chain proteins, troponin I type 3 and transthyretin) and (iii) stress response (e.g. αB-crystallin, HSP27 and HSP20). The marked differences in the expression of selected proteins, including HSP27 and HSP20, were further confirmed by Western blot. Thus, we carried out full-scale screening of the protein changes in human heart failure and profiled proteins that may be critical in cardiac dysfunction for future mapping.

Mitochondrial energy metabolism plays a critical role in the cardioprotection afforded by intermittent hypobaric hypoxia

Intermittent hypobaric hypoxia (IHH) is an effective protective strategy against myocardial ischaemia-reperfusion (I/R) injury, but the precise mechanisms are far from clear. To understand the overall effects of IHH on the myocardial proteins during I/R, we analysed functional performance and the protein expression profile in isolated hearts from normoxic rats and from rats adapted to IHH (5000 m, 4 h day(-1), 4 weeks) following I/R injury (30 min/45 min). Intermittent hypobaric hypoxia significantly improved the postischaemic recovery of left ventricular function compared with the recovery in time-matched normoxic control hearts. Two-dimensional electrophoresis with matrix-assisted laser desorption/ionization and time-of-flight mass spectrometric analysis was then used to assess protein alterations in left ventricles from normoxic and IHH groups, with or without I/R. The expressions of 16 proteins changed by over fivefold; nine of these proteins are involved in energy metabolism. Immunoblot and real-time PCR analysis confirmed the IHH-increased expressions of the ATP synthase subunit β, mitochondrial aldehyde dehydrogenase and heat shock protein 27 in left ventricles. Furthermore, IHH significantly attenuated the reduction of myocardial ATP content, mitochondrial ATP synthase activity, membrane potential and respiratory control ratios due to I/R. In addition, inhibition of mitochondrial ATP synthase by oligomycin (1 μmol l(-1)) abolished the IHH-induced improvements in three parameters: postischaemic recovery of left ventricular function, mitochondrial membrane potential and respiratory control ratios. These results suggest that an improvement in mitochondrial energy metabolism makes an important contribution to the cardioprotection afforded by IHH against postischaemic myocardial dysfunction.

Inactivation of thiol-dependent enzymes by hypothiocyanous acid: role of sulfenyl thiocyanate and sulfenic acid intermediates

Myeloperoxidase (MPO) forms reactive oxidants including hypochlorous and hypothiocyanous acids (HOCl and HOSCN) under inflammatory conditions. HOCl causes extensive tissue damage and plays a role in the progression of many inflammatory-based diseases. Although HOSCN is a major MPO oxidant, particularly in smokers, who have elevated plasma thiocyanate, the role of this oxidant in disease is poorly characterized. HOSCN induces cellular damage by targeting thiols. However, the specific targets and mechanisms involved in this process are not well defined. We show that exposure of macrophages to HOSCN results in the inactivation of intracellular enzymes, including creatine kinase (CK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). In each case, the active-site thiol residue is particularly sensitive to oxidation, with evidence for reversible inactivation and the formation of sulfenyl thiocyanate and sulfenic acid intermediates, on treatment with HOSCN (less than fivefold molar excess). Experiments with DAz-2, a cell-permeable chemical trap for sulfenic acids, demonstrate that these intermediates are formed on many cellular proteins, including GAPDH and CK, in macrophages exposed to HOSCN. This is the first direct evidence for the formation of protein sulfenic acids in HOSCN-treated cells and highlights the potential of this oxidant to perturb redox signaling processes.

Release of tissue-specific proteins into coronary perfusate as a model for biomarker discovery in myocardial ischemia/reperfusion injury

Diagnosis of acute coronary syndromes is based on protein biomarkers, such as the cardiac troponins (cTnI/cTnT) and creatine kinase (CK-MB) that are released into the circulation. Biomarker discovery is focused on identifying very low abundance tissue-derived analytes from within albumin-rich plasma, in which the wide dynamic range of the native protein complement hinders classical proteomic investigations. We employed an ex vivo rabbit model of myocardial ischemia/reperfusion (I/R) injury using Langendorff buffer perfusion. Nonrecirculating perfusate was collected over a temporal profile of 60 min reperfusion following brief, reversible ischemia (15 min; 15I/60R) for comparison with irreversible I/R (60I/60R). Perfusate proteins were separated using two-dimensional gel electrophoresis (2-DE) and identified by mass spectrometry (MS), revealing 26 tissue-specific proteins released during reperfusion post-15I. Proteins released during irreversible I/R (60I/60R) were profiled using gel-based (2-DE and one-dimensional gel electrophoresis coupled to liquid chromatography and tandem mass spectrometry; geLC-MS) and gel-free (LC-MS/MS) methods. A total of 192 tissue-specific proteins were identified during reperfusion post-60I. Identified proteins included those previously associated with I/R (myoglobin, CK-MB, cTnI, and cTnT), in addition to examples currently under investigation in large cohort studies (heart-type fatty acid binding protein; FABPH). The postischemic release profile of a novel cardiac-specific protein, cysteine and glycine-rich protein 3 (Csrp3; cardiac LIM domain protein) was validated by Western blot analysis. We also identified Csrp3 in serum from 6 of 8 patients postreperfusion following acute myocardial infarction. These studies indicate that animal modeling of biomarker release using ex vivo buffer perfused tissue to limit the presence of obfuscating plasma proteins may identify candidates for further study in humans.

Cigarette smoke-induced oxidative stress in skeletal muscles of mice

Cigarette smoke (CS)-induced oxidative stress may cause muscle alterations in chronic conditions such as chronic obstructive pulmonary disease (COPD). We sought to explore in AKR/J mice exposed to CS for 6 months and in control animals, levels of protein oxidation, oxidized proteins (immunoblotting, proteomics) and antioxidant mechanisms in both respiratory and limb muscles, body weight modifications, systemic inflammation, and lung structure. Compared to control mice, CS-exposed animals exhibited a reduction in body weight gain at 3 months and thereafter, showed lung emphysema, and exhibited increased oxidative stress levels in their diaphragms and gastrocnemius at 6 months. Proteins involved in glycolysis, ATP production and distribution, carbon dioxide hydration, and muscle contraction were carbonylated in respiratory and limb muscles. Blood tumor necrosis factor (TNF)-alpha levels were significantly greater in CS-exposed mice than in control animals. In AKR/J mice, chronic exposure to CS induces lung emphysema concomitantly with greater oxidative modifications on muscle proteins in both respiratory and limb muscles, and systemic inflammation.

The cellular and molecular origin of reactive oxygen species generation during myocardial ischemia and reperfusion

Myocardial ischemia-reperfusion injury is an important cause of impaired heart function in the early postoperative period subsequent to cardiac surgery. Reactive oxygen species (ROS) generation increases during both ischemia and reperfusion and it plays a central role in the pathophysiology of intraoperative myocardial injury. Unfortunately, the cellular source of these ROS during ischemia and reperfusion is often poorly defined. Similarly, individual ROS members tend to be grouped together as free radicals with a uniform reactivity towards biomolecules and with deleterious effects collectively ascribed under the vague umbrella of oxidative stress. This review aims to clarify the identity, origin, and progression of ROS during myocardial ischemia and reperfusion. Additionally, this review aims to describe the biochemical reactions and cellular processes that are initiated by specific ROS that work in concert to ultimately yield the clinical manifestations of myocardial ischemia-reperfusion. Lastly, this review provides an overview of several key cardioprotective strategies that target myocardial ischemia-reperfusion injury from the perspective of ROS generation. This overview is illustrated with example clinical studies that have attempted to translate these strategies to reduce the severity of ischemia-reperfusion injury during coronary artery bypass grafting surgery.

Cardiac proteomic responses to ischemia-reperfusion injury and ischemic preconditioning

Cardiac ischemia and ischemia-reperfusion (I/R) injury are major contributors to morbidity and mortality worldwide. Pathological mechanisms of I/R and the physiological mechanisms of ischemic preconditioning (IPC), which is an effective cardiac protective response, have been widely investigated in the last decade to search for means to prevent or treat this disease. Proteomics is a powerful analytical tool that has provided important information to identify target proteins and understand the underlying mechanisms of I/R and IPC. Here, we review the application of proteomics to I/R injury and IPC to discover target proteins. We analyze the functional meaning of the accumulated data on hundreds of proteins using various bioinformatics applications. In addition, we review exercise-induced proteomic alterations in the heart to understand the potential cardioprotective role of exercise against I/R injury. Further developments in the proteomic field that target specialized proteins will yield new insights for optimizing therapeutic targets and developing a wide range of therapeutic agents against ischemic heart disease.

Identification of targeting peptides for ischemic myocardium by in vivo phage display

Therapies selectively targeting ischemic myocardium could be applied by intravenous injection. Here, we report an approach for ischemic tissue-selective targeting based on in vivo screening of random peptide sequences using phage display. We performed in vivo biopanning using a phage library in a rat model of ischemia-reperfusion and identified three peptide motifs, CSTSMLKAC, CKPGTSSYC, and CPDRSVNNC, that exhibited preferential binding to ischemic heart tissue compared to normal heart as well as other control organs. The CSTSMLKAC sequence was capable of mediating selective homing of phage to ischemic heart tissue. The CSTSMLKAC peptide was then made as a fusion protein with Sumo-mCherry and injected intravenously in a mouse model of myocardial ischemia-reperfusion injury; subsequently, bio-distribution of Sumo-mCherry-CSTSMLKAC was measured with quantitative ELISA. The targeting peptide led to a significant increase in homing to ischemic left ventricle compared to tissues from non-ischemic left ventricle, the right ventricle, lung, liver, spleen, skeletal muscle, and brain (all p<0.001). These results indicate that the peptide sequence CSTSMLKAC represents a novel molecular tool that may be useful in targeting ischemic tissue and delivering bioengineered proteins into the injured myocardium by systemic intravenous administration.

Antioxidant network expression abrogates oxidative posttranslational modifications in mice

Antioxidant enzymatic pathways form a critical network that detoxifies ROS in response to myocardial stress or injury. Genetic alteration of the expression levels of individual enzymes has yielded mixed results with regard to attenuating in vivo myocardial ischemia-reperfusion injury, an extreme oxidative stress. We hypothesized that overexpression of an antioxidant network (AON) composed of SOD1, SOD3, and glutathione peroxidase (GSHPx)-1 would reduce myocardial ischemia-reperfusion injury by limiting ROS-mediated lipid peroxidation and oxidative posttranslational modification (OPTM) of proteins. Both ex vivo and in vivo myocardial ischemia models were used to evaluate the effect of AON expression. After ischemia-reperfusion injury, infarct size was significantly reduced both ex vivo and in vivo, ROS formation, measured by dihydroethidium staining, was markedly decreased, ROS-mediated lipid peroxidation, measured by malondialdehyde production, was significantly limited, and OPTM of total myocardial proteins, including fatty acid-binding protein and sarco(endo)plasmic reticulum Ca(²+)-ATPase (SERCA)2a, was markedly reduced in AON mice, which overexpress SOD1, SOD3, and GSHPx-1, compared with wild-type mice. These data demonstrate that concomitant SOD1, SOD3, and GSHPX-1 expression confers marked protection against myocardial ischemia-reperfusion injury, reducing ROS, ROS-mediated lipid peroxidation, and OPTM of critical cardiac proteins, including cardiac fatty acid-binding protein and SERCA2a.

Parallel proteomics to improve coverage and confidence in the partially annotated Oryctolagus cuniculus mitochondrial proteome

The ability to decipher the dynamic protein component of any system is determined by the inherent limitations of the technologies used, the complexity of the sample, and the existence of an annotated genome. In the absence of an annotated genome, large-scale proteomic investigations can be technically difficult. Yet the functional and biological species differences across animal models can lead to selection of partially or nonannotated organisms over those with an annotated genome. The outweighing of biology over technology leads us to investigate the degree to which a parallel approach can facilitate proteome coverage in the absence of complete genome annotation. When studying species without complete genome annotation, a particular challenge is how to ensure high proteome coverage while meeting the bioinformatic stringencies of high-throughput proteomics. A protein inventory of Oryctolagus cuniculus mitochondria was created by overlapping "protein-centric" and "peptide-centric" one-dimensional and two-dimensional liquid chromatography strategies; with additional partitioning into membrane-enriched and soluble fractions. With the use of these five parallel approaches, 2934 unique peptides were identified, corresponding to 558 nonredundant protein groups. 230 of these proteins (41%) were identified by only a single technical approach, confirming the need for parallel techniques to improve annotation. To determine the extent of coverage, a side-by-side comparison with human and mouse cardiomyocyte mitochondrial studies was performed. A nonredundant list of 995 discrete proteins was compiled, of which 244 (25%) were common across species. The current investigation identified 142 unique protein groups, the majority of which were detected here by only one technical approach, in particular peptide- and protein-centric two-dimensional liquid chromatography. Although no single approach achieved more than 40% coverage, the combination of three approaches (protein- and peptide-centric two-dimensional liquid chromatography and subfractionation) contributed 96% of all identifications. Parallel techniques ensured minimal false discovery, and reduced single peptide-based identifications while maximizing sequence coverage in the absence of the annotated rabbit proteome.

Functional proteomic analysis of experimental autoimmune myocarditis-induced chronic heart failure in the rat

Experimental autoimmune myocarditis (EAM)-induced heart failure in rats is used to study the pathogenesis of heart failure. Based on a proteomic analysis of soluble (S) and membranous (M) fractions extracted from ventricles of rats with a stable chronic form of EAM-induced heart failure, we assessed changes in protein levels and their correlation to heart functions to gain insights into the pathogenesis and to explore new targets for the treatment of heart failure. Proteins were separated by two-dimensional gel electrophoresis and silver stained spots were analyzed. In the S-fraction, 274+/-3 spots were detected in the normal (N)-group and 273+/-6 in the heart failure (HF)-group. In the HF-group, 26 of the spots were increased and 15 were decreased in intensity. In the M-fraction, 277+/-3 spots were detected in the N-group and 277+/-2 in the HF-group, with 20 spots increased and 10 decreased in intensity. We analyzed relationships between the expression of these proteins and 11 parameters of heart function, and found all the significantly changed spots to correlate with at least one of the parameters. We analyzed 49 spots that correlated with over 9 parameters of heart function using mass spectrometry, and identified 15 as proteins with increased expression including glucose regulated protein (GRP)78, an endoplasmic-stress related protein, and heat shock protein (HSP)90beta, a molecular chaperone, and 4 spots as proteins with decreased expression. It is suggested that in the heart failure model, GRP78 and HSP90beta play a role in the protection or deterioration of the heart and may be new targets for treatment.

Novel O-palmitolylated beta-E1 subunit of pyruvate dehydrogenase is phosphorylated during ischemia/reperfusion injury

BACKGROUND

During and following myocardial ischemia, glucose oxidation rates are low and fatty acids dominate as a source of oxidative metabolism. This metabolic phenotype is associated with contractile dysfunction during reperfusion. To determine the mechanism of this reliance on fatty acid oxidation as a source of ATP generation, a functional proteomics approach was utilized.

RESULTS

2-D gel electrophoresis of mitochondria from working rat hearts subjected to 25 minutes of global no flow ischemia followed by 40 minutes of aerobic reperfusion identified 32 changes in protein abundance compared to aerobic controls. Of the five proteins with the greatest change in abundance, two were increased (long chain acyl-coenzyme A dehydrogenase (48 +/- 1 versus 39 +/- 3 arbitrary units, n = 3, P < 0.05) and alpha subunit of ATP synthase (189 +/- 15 versus 113 +/- 23 arbitrary units, n = 3, P < 0.05)), while two were decreased (24 kDa subunit of NADH-ubiquinone oxidoreductase (94 +/- 7 versus 127 +/- 9 arbitrary units, n = 3, P < 0.05) and D subunit of ATP synthase (230 +/- 11 versus 368 +/- 47 arbitrary units, n = 3, P < 05)). Two forms of pyruvate dehydrogenase betaE1 subunit, the rate-limiting enzyme for glucose oxidation, were also identified. The protein level of the more acidic form of pyruvate dehydrogenase was reduced during reperfusion (37 +/- 4 versus 56 +/- 7 arbitrary units, n = 3, P < 05), while the more basic form remained unchanged. The more acidic isoform was found to be O-palmitoylated, while both isoforms exhibited ischemia/reperfusion-induced phosphorylation. In silico analysis identified the putative kinases as the insulin receptor kinase for the more basic form and protein kinase Czeta or protein kinase A for the more acidic form. These modifications of pyruvate dehydrogenase are associated with a 35% decrease in glucose oxidation during reperfusion.

CONCLUSIONS

Cardiac ischemia/reperfusion induces significant changes to a number of metabolic proteins of the mitochondrial proteome. In particular, ischemia/reperfusion induced the post-translational modification of pyruvate dehydrogenase, the rate-limiting step of glucose oxidation, which is associated with a 35% decrease in glucose oxidation during reperfusion. Therefore these post-translational modifications may have important implications in the regulation of myocardial energy metabolism.

Redox balance and carbonylated proteins in limb and heart muscles of cachectic rats

In fast- and slow-twitch limb and heart muscles of cachectic rats, redox balance and muscle structure were explored. The nature of the oxidatively modified proteins also was identified in these muscles. Reactive carbonyls, hydroxynonenal (HNE)- and malondialdehyde (MDA)-protein adducts, and antioxidant enzyme levels were determined in limb and heart muscles of cachectic (7 days after inoculation of Yoshida AH-130 ascites hepatoma) and control rats. Moreover, carbonylated proteins were identified (proteomics), and fiber-type composition evaluated (morphometry) in these muscles. In cachectic rats, compared with the controls: (a) HNE- and MDA-protein adducts levels were greater in gastrocnemius, tibialis anterior, soleus, and heart; (b) in the gastrocnemius, type II fiber size was reduced, and the intensity of carbonylated protein immunostaining was significantly greater in these fibers; and (c) proteins involved in glycolysis, ATP production and distribution, carbon dioxide hydration, muscle contraction, and mitochondrial metabolism were significantly more carbonylated in limb and heart muscles. Cancer cachexia alters redox balance in fast- and slow-twitch limb and heart muscles of rats, inducing increased oxidative modifications of key proteins involved in muscle structure and function. Additionally, it induces a reduction in type II fiber size in the gastrocnemius, which is associated with increased protein oxidation.

Proteomics analysis of the cardiac myofilament subproteome reveals dynamic alterations in phosphatase subunit distribution

Myofilament proteins are responsible for cardiac contraction. The myofilament subproteome, however, has not been comprehensively analyzed thus far. In the present study, cardiomyocytes were isolated from rodent hearts and stimulated with endothelin-1 and isoproterenol, potent inducers of myofilament protein phosphorylation. Subsequently, cardiomyocytes were “skinned,” and the myofilament subproteome was analyzed using a high mass accuracy ion trap tandem mass spectrometer (LTQ Orbitrap XL) equipped with electron transfer dissociation. As expected, a small number of myofilament proteins constituted the majority of the total protein mass with several known phosphorylation sites confirmed by electron transfer dissociation. More than 600 additional proteins were identified in the cardiac myofilament subproteome, including kinases and phosphatase subunits. The proteomic comparison of myofilaments from control and treated cardiomyocytes suggested that isoproterenol treatment altered the subcellular localization of protein phosphatase 2A regulatory subunit B56α. Immunoblot analysis of myocyte fractions confirmed that β-adrenergic stimulation by isoproterenol decreased the B56α content of the myofilament fraction in the absence of significant changes for the myosin phosphatase target subunit isoforms 1 and 2 (MYPT1 and MYPT2). Furthermore, immunolabeling and confocal microscopy revealed the spatial redistribution of these proteins with a loss of B56α from Z-disc and M-band regions but increased association of MYPT1/2 with A-band regions of the sarcomere following β-adrenergic stimulation. In summary, we present the first comprehensive proteomics data set of skinned cardiomyocytes and demonstrate the potential of proteomics to unravel dynamic changes in protein composition that may contribute to the neurohormonal regulation of myofilament contraction.

Differential protein expression profiling of myocardial tissue in a mouse model of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disorder caused by mutations in genes encoding sarcomere proteins. The mechanisms involved in the development of cardiac hypertrophy and heart failure remain poorly understood. Global proteomic profiling was used to study the cardiac proteome of mice predisposed to developing HCM. Hearts from three groups of mice (n=3 hearts per group) were studied: non-transgenic (NTG) and cardiac-specific transgenic models over-expressing either the normal (TnI(WT)) or a mutant cardiac troponin I gene (Gly203Ser; TnI(G203S)). Two-dimensional gel electrophoresis (2-DE) coupled with tandem mass spectrometry was used to identify proteins. Image analysis was performed using Progenesis SameSpots. A total of 34 proteins with at least a twofold change in the TnI(G203S) mouse model were identified. Alterations were detected in components involved in energy production, Ca(2+) handling, and cardiomyocyte structure. Expression level changes in cytoskeletal and contractile proteins were well represented in the study, including the intermediate filament protein desmin, which was further investigated in two additional physiological and pathological settings, i.e., exercise treatment, and severe heart failure in a novel double-mutant TnI-203/MHC-403 model of HCM. This study highlights the potential role of tissue proteomic profiling for mapping proteins, which may be critical in cardiac dysfunction and progression to heart failure in HCM.

Role of oxidative stress in ischemia-reperfusion-induced alterations in myofibrillar ATPase activities and gene expression in the heart

Ischemia-reperfusion (IR) in the heart has been shown to produce myofibrillar remodeling and depress Ca2+ sensitivity of myofilaments; however, the mechanisms for these alterations are not clearly understood. In view of the role of oxidative stress in cardiac dysfunction due to IR, isolated rat hearts were subjected to global ischemia for 30 min followed by a 30-minute period of reperfusion. IR was found to induce cardiac dysfunction, as reflected by depressed LVDP, +dP/dt, and -dP/dt, and elevated LVEDP, and to reduce myofibrillar Ca2+-stimulated ATPase activity. These changes were simulated by perfusing the hearts with a mixture of xanthine plus xanthine oxidase, which is known to generate oxyradicals. The alterations in cardiac function and myofibrillar Ca2+-stimulated ATPase in IR hearts were attenuated by pretreatment with antioxidants (superoxide dismutase plus catalase, and N-acetylcysteine) and leupeptin, an inhibitor of Ca2+-dependent protease. The levels of mRNA for myosin heavy chain isoforms (alpha-MHC and beta-MHC) and myosin light chain (MLC1) were depressed in IR hearts. These changes in gene expression due to IR were prevented upon perfusing the hearts with superoxide plus catalase, with N-acetylcysteine, or with leupeptin. The results suggest that oxidative stress due to IR injury and associated proteolysis play an important role in inducing changes in myofibrillar Ca2+-stimulated ATPase activity and gene expression in the heart.

Transcriptomic and proteomic analysis of global ischemia and cardioprotection in the rabbit heart

Cardioplegia is used to partially alleviate the effects of surgically induced global ischemia injury; however, the molecular mechanisms involved in this cardioprotection remain to be elucidated. To improve the understanding of the molecular processes modulating the effects of global ischemia and the cardioprotection afforded by cardioplegia, we constructed rabbit heart cDNA libraries and isolated, sequenced, and identified a compendium of nonredundant cDNAs for use in transcriptomic and proteomic analyses. New Zealand White rabbits were used to compare the effects of global ischemia and cardioplegia compared with control (nonischemic) hearts. The effects of RNA and protein synthesis on the cardioprotection afforded by cardioplegia were investigated separately by preperfusion with either alpha-amanitin or cycloheximide. Our results demonstrate that cardioplegia partially ameliorates the effects of global ischemia and that the cardioprotection is modulated by RNA- and protein-dependent mechanisms. Transcriptomic and proteomic enrichment analyses indicated that global ischemia downregulated genes/proteins associated with mitochondrial function and energy production, cofactor catabolism, and the generation of precursor metabolites of energy. In contrast, cardioplegia significantly increased differentially expressed genes/proteins associated with the mitochondrion and mitochondrial function and significantly upregulated the biological processes of muscle contraction, involuntary muscle contraction, carboxylic acid and fatty acid catabolic processes, fatty acid beta-oxidation, and fatty acid metabolic processes.

Alterations to the protein profile of bladder carcinoma cell lines induced by plant extract MINA-05 in vitro

Bladder cancer (BLCa) is a severe urological cancer of both men and women that commonly recurs and once invasive, is difficult to treat. MINA-05 (CK Life Sciences Int'l, Hong Kong) is a derivative of complex botanical extracts, shown to reduce cellular proliferation of bladder and prostate carcinomas. We tested the effects of MINA-05 against human BLCa cell sublines, B8, B8-RSP-GCK, B8-RSP-LN and C3, from a transitional cell carcinoma, grade IV, to determine the molecular targets of treatment by observing the cellular protein profile. Cells were acclimatised for 48 h then treated for 72 h with concentrations of MINA-05 reflecting 1/2 IC(50), IC(50) and 2 x IC(50) (n = 3) or with vehicle, (0.5% DMSO). Dose-dependant changes in protein abundance were detected and characterised using 2-dimensional electrophoresis and MS. We identified 10 proteins that underwent changes in abundance, pI and/or molecular mass in response to treatment. MINA-05 was shown to influence proteins across numerous functional classes including cytoskeletal proteins, energy metabolism proteins, protein degradation proteins and tumour suppressors, suggesting a global impact on these cell lines. This study implies that the ability of MINA-05 to retard cellular proliferation is attributed to its ability to alter cell cycling, metabolism, protein degradation and the cancer cell environment.

The effect of weight loss on protein profiles of gastrocnemius muscle in rabbits: a study using 1D electrophoresis and peptide mass fingerprinting

The study of physiological changes occurring during selection contributes to an improved understanding of relationships leading to efficiencies in animal production. To investigate the effects of food restriction in gastrocnemius muscle protein expression, 20% weight reduction was induced in New Zealand White (meat producing) and wild rabbits, using one-dimensional gel electrophoresis and peptide mass fingerprinting. Lower expression levels of myosin heavy chains were found in the Wild Rabbits Restricted Group, while myosin light chain and alpha-crystallin proteins were not detected in restricted groups. Glyceraldeyde-3-phosphate dehydrogenase and glycogen phosphorylase expression levels were similar for all experimental groups. Phosphopyruvate hydratase beta was not detected in the wild rabbit restricted diet group. Pyruvate kinase levels were 50% lower in the New Zealand Restricted group. LIM protein detection was absent in the control New Zealand group. Results also show relevance of actin in preserving muscle structure in depressed food availability, the sensitivity of both myosin light chain and alpha-crystallin protein to restricted feed and the role of PK in the resistance of New Zealand rabbits to food restriction.