Lymphatic vessels are lined by lymphatic endothelial cells (LECs), and are critical for health. However, the role of metabolism in lymphatic development has not yet been elucidated. Here we report that in transgenic mouse models, LEC-specific loss of CPT1A, a rate-controlling enzyme in fatty acid β-oxidation, impairs lymphatic development. LECs use fatty acid β-oxidation to proliferate and for epigenetic regulation of lymphatic marker expression during LEC differentiation. Mechanistically, the transcription factor PROX1 upregulates CPT1A expression, which increases acetyl coenzyme A production dependent on fatty acid β-oxidation. Acetyl coenzyme A is used by the histone acetyltransferase p300 to acetylate histones at lymphangiogenic genes. PROX1-p300 interaction facilitates preferential histone acetylation at PROX1-target genes. Through this metabolism-dependent mechanism, PROX1 mediates epigenetic changes that promote lymphangiogenesis. Notably, blockade of CPT1 enzymes inhibits injury-induced lymphangiogenesis, and replenishing acetyl coenzyme A by supplementing acetate rescues this process in vivo.

Summary 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- 13 C 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.

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.

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.

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.

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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.

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. Molecular & Cellular Proteomics 12: