Neutrophils Fuel Effective Immune Responses through Gluconeogenesis and Glycogenesis.

Neutrophils can function and survive in injured and infected tissues, where oxygen and metabolic substrates are limited. Using radioactive flux assays and LC-MS tracing with U-13C glucose, glutamine, and pyruvate, we observe that neutrophils require the generation of intracellular glycogen stores by gluconeogenesis and glycogenesis for effective survival and bacterial killing. These metabolic adaptations are dynamic, with net increases in glycogen stores observed following LPS challenge or altitude-induced hypoxia. Neutrophils from patients with chronic obstructive pulmonary disease have reduced glycogen cycling, resulting in impaired function. Metabolic specialization of neutrophils may therefore underpin disease pathology and allow selective therapeutic targeting.

Modification of the secretion pattern of proteases, inflammatory mediators, and extracellular matrix proteins by human aortic valve is key in severe aortic stenosis.

One of the major challenges in cardiovascular medicine is to identify candidate biomarker proteins. Secretome analysis is particularly relevant in this search as it focuses on a subset of proteins released by a cell or tissue under certain conditions. The sample can be considered as a plasma subproteome and it provides a more direct approximation to the in vivo situation. Degenerative aortic stenosis is the most common worldwide cause of valve replacement. Using a proteomic analysis of the secretome from aortic stenosis valves we could identify candidate markers related to this pathology, which may facilitate early diagnosis and treatment. For this purpose, we have designed a method to validate the origin of secreted proteins, demonstrating their synthesis and release by the tissue and ruling out blood origin. The nLC-MS/MS analysis showed the labeling of 61 proteins, 82% of which incorporated the label in only one group. Western blot and selective reaction monitoring differential analysis, revealed a notable role of the extracellular matrix. Variation in particular proteins such as PEDF, cystatin and clusterin emphasizes the link between aortic stenosis and atherosclerosis. In particular, certain proteins variation in secretome levels correlates well, not only with label incorporation trend (only labeled in aortic stenosis group) but, more importantly, with alterations found in plasma from an independent cohort of samples, pointing to specific candidate markers to follow up in diagnosis, prognosis, and therapeutic intervention.

Secretome of human aortic valves.

One of the major challenges in cardiovascular medicine is to identify candidate biomarker proteins. Between different proteomics studies, the secretome is a valuable tool in the search for biomarkers locally released by a studied tissue and remains particularly important while working with vascular tissues, since the secreted proteins would be probably shed to the blood. In this chapter, we described a method to validate the origin of secreted proteins in human aortic valves, demonstrating their synthesis and release by the tissue and ruling out blood origin.

A comparative study of immunodepletion and equalization methods for aortic stenosis human plasma.

Calcified aortic valve disease is a slowly progressive disorder that ranges from mild valve thickening with no obstruction of blood flow, known as aortic sclerosis, to severe calcification with impaired leaflet motion or aortic stenosis. Until now, aortic stenosis (AS) was thought to result from aging and "wear and tear" of the aortic valve, but nowadays, it is known that it presents the same risk factors as atherosclerosis and cardiovascular diseases.A proteomic analysis of plasma could permit to identify the changes in protein expression induced by AS in this biological sample. However, the characterization of human plasma proteome is a very complicated task, due to the wide dynamic range of concentration that separates the most abundant proteins and the less common ones (10-12 orders of magnitude). For this reason, plasma analysis requires pre-fractionation methods, and several such techniques are currently used to deplete albumin and other abundant plasma proteins.In this work we describe two different and optimized protocols to decrease the plasma proteome complexity for proteomic analysis. With this, comprehensive and systematic characterization of the plasma proteome in the healthy and diseased aortic stenosis (AS) state will greatly facilitate the development of "useful" biomarkers for early disease detection, clinical diagnosis, and therapy.

Multiple reaction monitoring (MRM) of plasma proteins in cardiovascular proteomics.

Different methodologies have been used through years to discover new potential biomarkers related with cardiovascular risk. The conventional proteomic strategy involves a discovery phase that requires the use of mass spectrometry (MS) and a validation phase, usually on an alternative platform such as immunoassays that can be further implemented in clinical practice. This approach is suitable for a single biomarker, but when large panels of biomarkers must be validated, the process becomes inefficient and costly. Therefore, it is essential to find an alternative methodology to perform the biomarker discovery, validation, and -quantification. The skills provided by quantitative MS turn it into an extremely attractive alternative to antibody-based technologies. Although it has been traditionally used for quantification of small molecules in clinical chemistry, MRM is now emerging as an alternative to traditional immunoassays for candidate protein biomarker validation.

Inside human aortic stenosis: a proteomic analysis of plasma.

Valvular aortic stenosis (AS) produces a slowly progressive obstruction in left ventricular outflow track. For this reason, aortic valve replacement is warranted when the valvular stenosis is hemodinamically significant, becoming the most common worldwide cause of aortic valve surgery. Recent epidemiologic studies have revealed an association between degenerative AS and cardiovascular risk factors for atherosclerosis, althought reducing the exposure to such factors and statin therapies both fail to delay or reverse the pathology. Hence, a deeper understanding of the pathophysiology of this disease is required to identify appropriate preventive measures. A proteomic analysis of plasma will permit to know and identify the changes in protein expression induced by AS in this tissue. Using two-dimensional difference gel electrophoresis (2D-DIGE) followed by mass spectrometry (MS), we compared the crude (not pre-fractioned) and pre-fractioned plasma from AS patients and control subjects. We sought to identify plasma proteins whose expression is modified in AS. In addition we investigated if crude plasma presented some alterations in the more abundant proteins since to date, has never been studied before. We also further investigated the link between this disease and atherosclerosis with a view to identifying new potential markers and therapeutic targets.

Secretome analysis of atherosclerotic and non-atherosclerotic arteries reveals dynamic extracellular remodeling during pathogenesis.

AIMS: Early detection of cardiovascular diseases and knowledge of underlying mechanisms is essential. Tissue secretome studies resemble more closely to the in vivo situation, showing a much narrower protein concentrations dynamic range than plasma. This study was aimed to the analysis of human arterial tissue secretome and to the quantitative comparison of healthy and atherosclerotic secretome to discover proteins with key roles in atherosclerosis development. METHODS AND RESULTS: Secretomes from three biological replicates of human atherosclerotic coronary arteries (APC), preatherosclerotic coronaries (PC) and mammaries (M) were analyzed by LC-MS/MS. The identified proteins were submitted to Ingenuity Pathway Analysis (IPA) tool. Label-free MS/MS based quantification was performed and validated by immunohistochemistry. 64 proteins were identified in the 3 replicates of at least one of the 3 groups and 15 secreted proteins have not been previously reported in plasma. Four proteins were significantly released in higher amounts by mammary tissue: gelsolin, vinculin, lamin A/C and phosphoglucomutase 5. CONCLUSION: The study of tissue secretome reveals key proteins involved in atherosclerosis which have not been previously reported in plasma. Novel proteins are here highlighted which could be potential therapeutic targets in clinical practice. This article is part of a Special Issue entitled: Proteomics: The clinical link.

Analysis of the plasma proteome associated with acute coronary syndrome: does a permanent protein signature exist in the plasma of ACS patients?

Acute coronary syndrome (ACS) is triggered by the occlusion of a coronary artery usually due to the thrombosis caused by an atherosclerotic plaque. The identification of proteins directly involved in the pathophysiological events underlying ACS will enable more precise diagnoses and a more accurate prognosis to be determined. Accordingly, we have performed a longitudinal study of the plasma proteome in ACS patients by 2-DE and DIGE. Plasma samples from patients, healthy controls, and stable coronary artery disease (CAD) patients were immunodepleted of the six most abundant proteins, and they were analyzed in parallel at four different times: 0 (on admission) and after 4, 60, and 180 days. From a total of 1400 spot proteins analyzed, 33 proteins were differentially expressed in ACS patients when compared with control subjects/stable patients. A small group of seven proteins that appear to be altered at admission remain affected for 6 months and also in the stable CAD patients. Interestingly, the maximum number of altered proteins was observed in the stable CAD patients. Some of the proteins identified had been previously associated with ACS whereas others (such as Alpha-1-B-glycoprotein, Hakata antigen, Tetranectin, Tropomyosin 4) constitute novel proteins that are altered in this pathology.

Valvular aortic stenosis: a proteomic insight.

UNLABELLED: Calcified aortic valve disease is a slowly progressive disorder that ranges from mild valve thickening with no obstruction of blood flow, known as aortic sclerosis, to severe calcification with impaired leaflet motion or aortic stenosis. In the present work we describe a rapid, reproducible and effective method to carry out proteomic analysis of stenotic human valves by conventional 2-DE and 2D-DIGE, minimizing the interference due to high calcium concentrations. Furthermore, the protocol permits the aortic stenosis proteome to be analysed, advancing our knowledge in this area. SUMMARY: Until recently, aortic stenosis (AS) was considered a passive process secondary to calcium deposition in the aortic valves. However, it has recently been highlighted that the risk factors associated with the development of calcified AS in the elderly are similar to those of coronary artery disease. Furthermore, degenerative AS shares histological characteristics with atherosclerotic plaques, leading to the suggestion that calcified aortic valve disease is a chronic inflammatory process similar to atherosclerosis. Nevertheless, certain data does not fit with this theory making it necessary to further study this pathology. The aim of this study is to develop an effective protein extraction protocol for aortic stenosis valves such that proteomic analyses can be performed on these structures. In the present work we have defined a rapid, reproducible and effective method to extract proteins and that is compatible with 2-DE, 2D-DIGE and MS techniques. Defining the protein profile of this tissue is an important and challenging task that will help to understand the mechanisms of physiological/pathological processes in aortic stenosis valves.

A novel methodology for the analysis of membrane and cytosolic sub-proteomes of erythrocytes by 2-DE.

With the aim of studying a wide cohort of erythrocyte samples in a clinical setting, we propose here a novel approach that allows the analysis of both human cytosolic and membrane sub-proteomes. Despite their simple structure, the high content of hemoglobin present in the red blood cells (RBCs) makes their proteome analysis enormously difficult. We investigate here different strategies for isolation of the membrane and cytosolic fractions from erythrocytes and their influence on proteome profiling by 2-DE, paying particular attention to hemoglobin removal. A simple, quick and satisfactory approach for hemoglobin depletion based on HemogloBind reagent was satisfactorily applied to erythrocyte cells, allowing the analysis of the cytosolic sub-proteome by 2-DE without major interference. For membrane proteome, a novel combined strategy based on hypotonic lysis isolation and further purification on minicolumns is described here, allowing detection of high molecular weight proteins (i.e. spectrin, ankyrin) and well-resolved 2-DE patterns. An aliquot of the membrane fraction was also in solution digested and analyzed by nano-LC coupled to an LTQ-Orbitrap mass spectrometer. A total of 188 unique proteins were identified by this approach. This study sets the basis for future clinical studies where the erythrocyte cell may be implicated.

Atorvastatin modifies the protein profile of circulating human monocytes after an acute coronary syndrome.

Aggressive treatment with high-dose atorvastatin reduces more effectively the incidence of cardiovascular events than moderate statin therapy. The mechanism of this benefit has not been fully elucidated. In order to know the potential effects of statin treatment on the protein expression of circulating monocytes in acute coronary syndrome (ACS) patients, a proteomic analysis of these cells was carried out by 2-DE and MS. Twenty-five patients with non-ST-elevation acute coronary syndrome (NSTEACS) were randomized, the fourth day after admission, to receive ATV 80 mg/dL (n = 14) or conventional treatment (CT) (n = 11), for two months. Blood was withdrawn at the end of the treatment, and monocytes were extracted for proteomic analysis and their protein expression patterns determined. Age, sex, total cholesterol, LDL, HDL, triglycerides, body mass index, presence of hypertension, diabetes, and smoking status were not significantly different between the two groups of patients. The expression of 20 proteins was modified by intensive ATV. Among the most relevant results stand out the normalization by intensive ATV treatment of the expression of proteins that modulate inflammation and thrombosis such as protein disulfide isomerase ER60 (PDI), Annexin I, and prohibitin, or that have other protective effects as HSP-70. Thus, this approach shed light at the molecular level of the beneficial mechanisms of anti-atherothrombotic drugs.

Circulating human monocytes in the acute coronary syndrome express a characteristic proteomic profile.

We examined the proteome of circulating monocytes of patients with acute coronary syndrome at different times in comparison to that of patients with stable coronary artery disease. On admission, the expression of 18 spot proteins was altered, 10 of which were totally absent. This pattern changed progressively, and at 6 months, there were no differences with the monocyte proteome of stable patients.

Characterization of the human atheroma plaque secretome by proteomic analysis.

Atherosclerosis is one of the most common causes of death in developed countries. Atherosclerosis is an inflammatory process that results in the development of complex lesions or plaques that protrude into the arterial lumen. Plaque rupture and thrombosis result in the acute clinical complications of myocardial infarction and stroke. Although certain risk factors (dyslipidemias, diabetes, hypertension) and humoral markers of plaque vulnerability (C-reactive protein, interleukin-6, -10 and -18, CD-40L) have been identified, a highly sensitive and specific biomarker or protein profile, which could provide information on the stability/vulnerability of atherosclerotic lesions, remains to be identified. Recently, we have described a novel strategy consisting in the proteomic analysis of proteins released by normal and atherosclerotic arterial walls in culture. This method enables harvesting of proteins that are only secreted by pathological or normal arterial walls. By focusing only on the secreted proteins found in the tissue culture media, there is an intended bias toward those molecules that would have a higher probability of later being found in plasma. Using this approach, we have shown that carotid atherosclerotic plaques cultured in vitro are able to secrete proteins, and also that a differential pattern of protein secretion of normal arteries vs pathological ones has been observed. In this chapter, the proteomic analysis of the human atheroma plaque secretome is described.

Characterization of circulating human monocytes by proteomic analysis.

We describe a simple method for isolation of human blood monocytes with the high purity required for proteomic analysis, which avoids contamination by other blood cells (platelets and lymphocytes) and the most abundant plasma proteins (albumin and immunoglobulins). Blood monocytes were purified by gradient centrifugation followed by positive selection with monoclonal antibodies coupled to paramagnetic beads. This method is compatible with flow cytometry, which was used to assess the purity of the cell population. After solubilization of monocytes, the proteins where analyzed by two-dimensional gel electrophoresis in several pH ranges. Image analysis of gels allowed the reproducible detection and quantification of the spots present in the gel. This method is useful for clinical studies of monocytes from a large number of patients, owing to its rapidity and reproducibility, which permits comparative analysis of normal vs pathological samples and allows follow up of the expressed proteins of monocytes from each patient.

Depletion of high-abundance proteins in plasma by immunoaffinity subtraction for two-dimensional difference gel electrophoresis analysis.

Blood plasma is believed the most complex human-derived proteome, containing other tissue proteome subsets. Almost all body cells communicate with the plasma, either directly or through tissues or biological fluids, and many of these cells release at least a part of their content into the plasma upon damage or death. A comprehensive, systematic characterization of the plasma proteome in the healthy and diseased states will greatly facilitate the development of biomarkers for early disease detection, clinical diagnosis, and therapy. However, the characterization of human plasma proteome is a very complicated task, owing to the wide dynamic range of concentration that separates the most abundant proteins and the less common ones (10-12 orders of magnitude). The removal of its predominant proteins by affinity chromatography using an FPLC system improves the presence of low-abundance proteins in two-dimensional gel electrophoresis (2DE). The "Multiple Affinity Removal System" (Agilent Technologies) retains albumin, IgG, IgA, haptoglobin, transferrin, and antitrypsin with high specificity and reproducibility. After depletion, we have independently analyzed the flow-through (low-abundance proteins), and the retained fractions, by 2DE (4.0-7.0 pH range). Image analysis of the stained gels revealed that more than 300 spots appeared in the retained fraction and about 1800 spots appeared in the nonretained fraction. This methodology is a valuable tool for clinical proteomics, because its reproducibility allows comparative studies and quantitative analysis by 2DE or two-dimensional differential gel electrophoresis of plasma or sera samples from subjects with different pathological or physiological conditions. In addition, the method allows the comparison of experimental results from different laboratories.

Vascular proteomics.

The characterization of patients with acute coronary syndromes (ACS) at the molecular and cellular levels provides a novel vision for understanding the pathological and clinical expression of the disease. Recent advances in proteomic technologies permit the evaluation of systematic changes in protein expression in many biological systems and have been extensively applied to cardiovascular diseases (CVD). The cardiovascular system is in permanent intimate contact with blood, making blood-based biomarker discovery a particularly worthwhile approach. Thus, proteomics can potentially yield novel biomarkers reflecting CVD, establish earlier detection strategies, and monitor response to therapy. Here we review the different proteomic strategies used in the study of atherosclerosis and the novel proteins differentially expressed and secreted by atherosclerotic lesions which constitute novel potential biomarkers (HSP-27, Cathepsin D). Special attention is paid to MS-Imaging of atheroma plaque and the generation, for the first time, of 2-D images of lipids, showing the distribution of these molecules in the different areas of the atherosclerotic lesions. In addition new potential biomarkers have been identified in plasma (amyloid A1α, transtherytin), circulating cells (protein profile in monocytes from ACS patients) and individual cells constituents of atheroma plaques (endothelial, VSMC, macrophages) which provide novel insights into vascular pathophysiology.

Quest for novel cardiovascular biomarkers by proteomic analysis.

Atherosclerosis, and the resulting coronary heart disease and stroke, is the most common cause of death in developed countries. Atherosclerosis is an inflammatory process that results in the development of complex lesions or plaques that protrude into the arterial lumen. Plaque rupture and thrombosis result in the acute clinical complications of myocardial infarction (MI) and stroke. Although certain risk factors (dyslipidemias, diabetes, hypertension) and humoral markers of plaque vulnerability (C-reactive protein, interleukin-6, 10 and 18, CD40L) have been identified, a highly sensitive and specific biomarker or protein profile, which could provide information on the stability/vulnerability of atherosclerotic lesions, remains to be identified. In this review, we report several proteomic approaches which have been applied to circulating or resident cells, atherosclerotic plaques or plasma, in the search for new proteins that could be used as cardiovascular biomarkers. First, an example using a differential proteomic approach (2-DE and MS) comparing the secretome from control mammary arteries and atherosclerotic plaques is displayed. Among the different proteins identified, we showed that low levels of HSP-27 could be a potential marker of atherosclerosis. Second, we have revised several studies performed in cells involved in the pathogenesis of atherosclerosis (foam cells and smooth muscle cells). Another approach consists of performing proteomic analysis on circulating cells or plasma, which will provide a global view of the whole body response to atherosclerotic aggression. Circulating cells can bear information reflecting directly an inflammatory or pro-coagulant state related to the pathology. As an illustration, we report that circulating monocytes and plasma in patients with acute coronary syndromes has disclosed that mature Cathepsin D is increased both in the plasma and monocytes of these patients. Finally, the problems of applying proteomic approach directly to plasma will be discussed. The purpose of this review is to provide the reader with an overview of different proteomic approaches that can be used to identify new biomarkers in vascular diseases.