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 HSP27 phosphorylation sites in human atherosclerotic plaque secretome.

Atherosclerosis is one of the main causes of death in developed countries. Atheroma plaque formation is promoted by the interaction between the cells conforming the arterial wall, smooth muscle cells, and endothelial cells, together with lipoproteins and inflammatory cells (mainly macrophages and T-lymphocytes). These interactions can be mediated by proteins secreted from these cells, which therefore exert an important role in the atherosclerotic process. We recently described a novel strategy for the characterization of the human atherosclerotic plaque secretome, combining two-dimensional gel electrophoresis and mass spectrometry (MS). Among the identified proteins, two isoforms of heat shock protein 27 (HSP27), a protein recently described as a potential biomarker of atherosclerosis, were detected. However, the putative mechanisms in which HSP27 isoforms could be involved in the atherosclerotic process are unknown. Thus, the role that phosphorylated HSP27 could play in the atherosclerotic process is actually under study. The present work shows the strategies employed to characterize the phosphorylation in the HSP27 secreted by atheroma plaque samples. The application of liquid chromatography tandem mass spectrometry (MS/MS), as well as the combination of immobilized metal affinity chromatography methodology with matrix-assisted laser desorption/ionization MS/MS are described.

The proteome of endothelial cells.

Endothelial cells form a continuous monolayer lining the inside face of all blood vessels, and present the ability to selectively control vascular permeability. The endothelium is involved in a wide variety of normal physiological and pathological processes. The endothelial dysfunction occurs under activation conditions, with the acquisition of many new functional, inflammatory, and immune properties, and as a consequence, endothelial cells display many different transcription profiles. We describe here the isolation and culture of the most useful model of human umbilical vein endothelial cells, and undertake the proteomic analysis under both basal quiescent condition and activated by stimulation with a proinflammatory cytokine. Series of two-dimensional electrophoresis have allowed us to detect a total of close to 600 polypeptide spots using 4.0-7.0 pH range in both culture conditions. We have selected 233 proteins by cross-matching the gels, and found that 70% showed an increase and 30% a decrease of expression levels in activated cells. Subsequent identification of 35 altered peptides is made by matrix-assisted laser desorption and ionization time-of-flight mass spectrometry, as well as a study of posttranslational modifications. These global findings may contribute to understand the effects of pathological stimuli and the mechanisms that regulate vascular diseases.

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.

Vascular protection of dual therapy (atorvastatin-amlodipine) in hypertensive patients.

Hypertension frequently coexists with other cardiovascular risk factors, such as hypercholesterolemia, and their combination is associated with a greater rate of cardiovascular events. Recent clinical data support that treatment of hypertensive patients with a combination of antihypertensive and lipid-lowering therapies leads to a higher reduction in the incidence of cardiovascular events. In the Anglo-Scandinavian Cardiac Outcomes Trial-Blood Pressure Lowering Arm (ASCOT-BPLA), an optimal prevention of cardiovascular events was reached in patients who were randomly assigned to atorvastatin and the amlodipine treatment. However, the potential underlying mechanisms of these vascular protective effects are not fully elucidated. Because experimental studies have shown that statins and calcium channel blockers have antiatherosclerotic effects, the effect of atorvastatin alone or in combination with amlodipine was analyzed in the protein secretion profile of atherosclerotic plaques that were cultured ex vivo. In this respect, the addition of atorvastatin and amlodipine to atherosclerotic plaques normalized the levels of the different released proteins to that obtained from healthy arteries. This review highlights recent clinical and experimental studies that support that a combined treatment of hypertensive patients with both statins and calcium channel blockers could promote a higher reduction in their global cardiovascular risk profile and associated mortality. As an example, the application of a proteomic approach to assess the modulation by atorvastatin alone or in combination with amlodipine on the proteins that are released by atherosclerotic plaques has allowed the identification of novel therapeutic targets by which these drugs could promote their additive/synergic effects.

Modulación mediante tratamiento con atorvastatina y/o amlodipino del perfil de proteínas liberadas por placas ateroscleróticas humanas / Modulation of the profile of proteins released by human atherosclerotic plaques through

Introducción. Entre las diversas estrategias seguidas para analizar la compleja estructura de la placa de ateroma, nuestro grupo se ha centrado en el estudio de las proteínas secretadas por la pared vascular, que podrían ser potenciales marcadores plasmáticos. Las estatinas o los agentes bloqueadores de los canales de calcio (BCC) pueden modular los valores de las proteínas circulantes en sujetos con diversas afecciones cardiovasculares. Métodos. La electroforesis bidimensional y la espectrometría de masas (EM) se han aplicado al estudio de proteínas diferencialmente secretadas por placas de ateroma incubadas ex vivo respecto a zonas fibrosas adyacentes. Asimismo, hemos estudiado el efecto modulador de la atorvastatina (10­5 M), el amlodipino (10­6 M) o la combinación de ambos fármacos. Resultados. De una media de 620 proteínas detectadas por gel, se identificaron en total 83 proteínas secretadas por las placas ateromatosas mediante EM: 34 proteínas incrementadas en los sobrenadantes de las placas cultivadas ex vivo respecto a las zonas control y 31 con valores de secreción inferiores en la zona ateromatosa. La adición in vitro de fármacos a las placas de ateroma produjo diferentes efectos en los valores de secreción proteicos, dependiendo del tipo de fármaco y de la proteína considerada, si bien la mayoría de las proteínas identificadas revertía a valores control independientemente del tratamiento. Conclusión. Mediante este análisis proteómico hemos caracterizado nuevas proteínas potencialmente involucradas en la formación e inestabilidad de la placa de ateroma. La modulación por distintos tratamientos farmacológicos de dichos marcadores puede ayudar a comprender nuevos mecanismos de acción de dichos fármacos (AU)

Introduction. Analysis of the complex structure of the atheroma plaque is a classical object of cardiovascular research. We studied proteins secreted by the vascular wall, which could be potential plasma markers. Statins or calcium channel blockers modulate the levels of different circulating proteins in patients with diverse cardiovascular diseases. Methods. Two-dimensional electrophoresis and mass spectrometry were applied to identify and characterize proteins differentially secreted by atheroma plaque samples incubated ex vivo versus adjacent fibrous segments considered as controls. We also analyzed the modulatory effect of atorvastatin (10­5 M), amlodipine (10­6 M) and the combination of both drugs. Results. From an average of 620 proteins detected per gel, a total of 83 proteins secreted by atheroma plaque samples were identified by mass spectrometry: 34 proteins were increased in atheroma plaque supernatants versus control segments while 31 showed decreased secretion levels in atheroma plaques. Different effects were detected after in vitro drug administration to complicated atheroma plaques, depending on the kind of drug and protein considered, although the majority of the proteins identified reverted to normal levels independently of the treatment administered. Conclusion. Proteomic analysis characterized a significant number of novel proteins potentially involved in the formation and instability of complicated atherosclerotic plaques. Modulation of these markers by different drugs may help us to understand new potential mechanisms through which these drugs exert their beneficial effects on atherothrombosis (AU)

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.

Identification by a differential proteomic approach of heat shock protein 27 as a potential marker of atherosclerosis.

BACKGROUND: We hypothesized that normal and pathological vessel walls display a differential pattern of secreted proteins. We have recently set up the conditions for comparing secretomes from carotid atherosclerotic plaques and control arteries using a proteomic approach to assess whether differentially secreted proteins could represent markers for atherosclerosis. METHODS AND RESULTS: Normal endartery segments and different regions of endarterectomy pieces (noncomplicated/complicated plaques) were incubated in protein-free medium, and the released proteins were analyzed by 2D electrophoresis (2-DE). Among the differently secreted proteins, we have identified heat shock protein-27 (HSP27). Surprisingly, compared with control arteries, HSP27 release was drastically decreased in atherosclerotic plaques and barely detectable in complicated plaque supernatants. HSP27 was expressed primarily by intact vascular cells of normal arteries and carotid plaques (immunohistochemistry). Plasma detection of soluble HSP27 showed that circulating HSP27 levels are significantly decreased in the blood of patients with carotid stenosis relative to healthy subjects (0.19 [0.1 to 1.95] versus 83 [71.8 to 87.8]) ng/mL, P<0.0001). CONCLUSIONS: HSP27 secretion is decreased in complicated atherosclerotic plaques, and sHSP27 plasma levels are decreased in atherosclerotic patients compared with healthy subjects. Plasma sHSP27 levels could be a potential index of atherosclerosis, although further validation is needed in large patient cohorts.

Isolation of circulating human monocytes with high purity for proteomic analysis.

We describe a simple method for isolation of human blood monocytes with the high purity (95-98%) 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 specific monoclonal antibodies coupled to paramagnetic beads. The elution conditions of the positive selection step were modified to avoid contamination with albumin. This method is compatible with flow cytometry which was used to assess the purity of the cell population. From 28 mL of blood, 10(7) monocytes with > 96% purity are routinely obtained. From the isolated monocytes 200-250 microg of protein could be recovered. The whole method can be performed in three hours. Similar results were obtained using a negative selection step but with lower purity (92%), increased cost and longer time. After solubilization of monocytes, the proteins were analyzed by two-dimensional gel electrophoresis (2-DE) in the 3-10, 4-7, 6-9 and 6-11 pH range. DNA was the main contaminant that interfered with the 2-DE and it was removed by treatment with DNAse. Image analysis of gels allowed the reproducible detection and quantification of 1500 spots in the 4-7 pH range and more than 2000 spots in total by combining (overlapping) 2-D gels in the 4-7, 6-9 and 6-11 pH range. This method is useful for clinical studies of monocytes from a large number of patients due to its rapidity and reproducibility, which permits comparative analysis of normal versus pathological samples and which allows follow up of the expressed proteins of monocytes from each patient.

Proteomic analysis of human vessels: application to atherosclerotic plaques.

Atherosclerosis is a chronic disease that affects medium and large arteries. This process originates from the interaction between cells of the arterial wall, lipoproteins and inflammatory cells, leading to the development of complex lesions or plaques that protrude into the arterial lumen. Plaque rupture and thrombosis result in acute clinical complications such as myocardial infarction and stroke. Owing to the heterogeneous cellular composition of the plaques, a proteomic analysis of the whole lesion is not appropriate. Therefore, we have studied the proteins secreted by human carotid atherosclerotic plaques, obtained by endarterectomy. Normal artery segments and different regions of the surgical pieces (noncomplicated plaque, complicated plaque with thrombus) were cultured in protein-free medium and the secreted proteins (supernatants) analyzed by two-dimensional gel electrophoresis. Normal artery segments secreted a moderate number of proteins (42 spots). However in the two-dimensional (2-D) gels (pH 3-10) of segments bearing a plaque, the number of spots increased markedly (154). The number of spots also increased (202) in the 2-D gels of artery segments with a ruptured plaque and thrombus. Thus, the more complicated the lesion, the higher the number of secreted proteins, suggesting the production of specific proteins relating to the complexity of the atherosclerotic lesion.