High-resolution two-dimensional gel electrophoresis analysis of atrial tissue proteome reveals down-regulation of fibulin-1 in atrial fibrillation

Pericardial Fluid Annexin A1 Is a Marker of Atrial Fibrillation in Aortic Stenosis: A Proteomics Analysis

Atrial fibrillation (AF) is the most common arrhythmia with adverse clinical outcomes. Pericardial fluid (PF) mirrors the heart’s pathophysiological status due to its proximity. This study aimed to characterise the PF proteome to identify new biomarkers of disease. Eighty-three patients submitted to aortic valve replacement surgery with severe aortic stenosis were selected, and their baseline echocardiographic and clinical variables were documented. Thirteen samples were selected blindly for proteome characterisation following a shotgun (GeLC–MS/MS) and a label-free quantification approach (LFQ). According to previous AF history, a partial least squares discriminant analysis (PLS-DA) was conducted, and the top 15 variables important in projection were identified. To inquire potential biomarkers, ROC curves were designed using LFQ data. Target proteins were further validated by ELISA, in both pericardial fluid and serum. Proteome analysis uncovered nine proteins up- and downregulated ≥2-fold. Annexin A1, annexin A2, and vimentin were among the top 15 most important variables for group discrimination in PLS-DA. Protein—protein interaction and gene ontology enrichment analysis presented functional interaction among identified proteins, which were all part of focal adhesion sites. Annexin A1 was increased in the pericardial fluid of AF patients but not in serum when quantified by ELISA. Annexin A1 is a novel pericardial fluid biomarker of AF in patients with severe aortic stenosis.

CD5L, Macrophage Apoptosis Inhibitor, Was Identified in Epicardial Fat-Secretome and Regulated by Isoproterenol From Patients With Heart Failure

Objectives

Neurohormonal dysfunction, which can regulate epicardial fat activity, is one of the main promoters of atrial fibrillation (AF) in patients with heart failure (HF). Our aim was to study the epicardial fat mediators for AF in patients with HF and its catecholaminergic regulation.

Methods

We have included 29 patients with HF who underwent cardiac surgery and were followed up for 5 years. Released proteins by epicardial adipose tissue (EAT) after isoproterenol treatment were identified by nano-high-performance liquid chromatography (HPLC) and triple time-of-flight (TOF) analysis. Common and differential identified proteins in groups of patients with AF before and after surgery were determined by the FunRich tool. Plasma and epicardial fat biopsy proteins were quantified by western blot.

Results

Our results identified 17 common released proteins by EAT, after isoproterenol treatment, from HF patients who suffered AF or developed new-onset AF during follow-up. Mostly, they were involved on inflammatory response and extracellular matrix. One of them was CD5L, a macrophage apoptosis inhibitor. Its secretion by isoproterenol treatment was validated on western blot. The CD5L levels on epicardial fat were also higher in the group of male patients who present or develop AF (0.44 ± 0.05 vs. 0.18 ± 0.15; p < 0.016). However, there were no differences regarding plasma levels.

Conclusion

Our results suggest the role of epicardial fat CD5L as a mediator of AF and its possible paracrine effect by catecholaminergic activity.

Weighted gene co‑expression network analysis to identify key modules and hub genes associated with atrial fibrillation

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia and significantly increases the risks of morbidity, mortality and health care expenditure; however, treatment for AF remains unsatisfactory due to the complicated and incompletely understood underlying mechanisms. In the present study, weighted gene co‑expression network analysis (WGCNA) was conducted to identify key modules and hub genes to determine their potential associations with AF. WGCNA was performed in an AF dataset GSE79768 obtained from the Gene Expression Omnibus, which contained data from paired left and right atria in cardiac patients with persistent AF or sinus rhythm. Differentially expressed gene (DEG) analysis was used to supplement and validate the results of WGCNA. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were also performed. Green and magenta modules were identified as the most critical modules associated with AF, from which 6 hub genes, acetyl‑CoA Acetyltransferase 1, death domain‑containing protein CRADD, gypsy retrotransposon integrase 1, FTX transcript, XIST regulator, transcription elongation factor A like 2 and minichromosome maintenance complex component 3 associated protein, were hypothesized to serve key roles in the pathophysiology of AF due to their increased intramodular connectivity. Functional enrichment analysis results demonstrated that the green module was associated with energy metabolism, and the magenta module may be associated with the Hippo pathway and contain multiple interactive pathways associated with apoptosis and inflammation. In addition, the blue module was identified to be an important regulatory module in AF with a higher specificity for the left atria, the genes of which were primarily correlated with complement, coagulation and extracellular matrix formation. These results suggest that may improve understanding of the underlying mechanisms of AF, and assist in identifying biomarkers and potential therapeutic targets for treating patients with AF.

Differences in atrial fibrillation‑associated proteins between the left and right atrial appendages from patients with rheumatic mitral valve disease: A comparative proteomic analysis

The majority of proteomic studies have focused on identifying atrial fibrillation (AF)-associated proteins in the right atrium (RA), thus potential differences in AF-associated proteins between the RA and left atrium (LA) remain unknown. The aim of the present study was to perform proteomic analysis to compare the potential differences in AF-associated proteins between the right atrial appendage (RAA) and left atrial appendage (LAA) in patients with rheumatic mitral valve disease (RMVD). RAA and LAA tissues were obtained from 18 patients with RMVD (10 with AF) during mitral valve replacement surgery. Two-dimensional fluorescence difference gel electrophoresis (2-D DIGE) proteomics analysis was performed using these tissues to identify AF-associated proteins in RAA and LAA. Subsequently, the proteomics data was validated using western blot analysis of nine selected proteins. In RAA, 32 AF-associated proteins were significantly dysregulated (15 upregulated and 17 downregulated). In LAA, 31 AF-associated proteins were significantly dysregulated (13 upregulated and 18 downregulated). Among these AF-associated proteins, 17 were AF-associated in both RAA and LAA, 15 were AF-associated only in RAA, and 14 were AF-associated only in LAA. Amongst the differentially expressed proteins, western blot analysis validated the results for 6 AF-associated proteins, and demonstrated similar distributions in RAA and LAA compared with the 2-D DIGE results. Of these proteins, 2 proteins were AF-associated in both RAA and LAA, 2 were AF-associated only in RAA, and 2 were AF-associated only in LAA. Additionally, the different distributions of AF-associated proteins in the RAA and LAA of patients with RMVD was analyzed, which may reflect the different regulatory mechanisms of the RA and LA in AF. These findings may provide new insights into the underlying molecular mechanisms of AF in patients with RMVD.

Fibulins and their role in cardiovascular biology and disease

Fibulins are a group of extracellular matrix proteins of which many are present in high amounts in the cardiovascular system. They share common biochemical properties and are often found in relation to basement membranes or elastic fibers. Observations in humans with specific mutations in fibulin genes, together with results from genetically engineered mice and data from human cardiovascular tissue suggest that the fibulin family of proteins play important functional roles in the cardiovascular system. Moreover, fibulin-1 circulates in high concentrations in plasma and may function as a cardiovascular disease marker.

Cardiac protein changes in ischaemic and dilated cardiomyopathy: a proteomic study of human left ventricular tissue

The development of heart failure (HF) is characterized by progressive alteration of left ventricle structure and function. Previous works on proteomic analysis in cardiac tissue from patients with HF remain scant. The purpose of our study was to use a proteomic approach to investigate variations in protein expression of left ventricle tissue from patients with ischaemic (ICM) and dilated cardiomyopathy (DCM). Twenty-four explanted human hearts, 12 from patients with ICM and 12 with DCM undergoing cardiac transplantation and six non-diseased donor hearts (CNT) were analysed by 2DE. Proteins of interest were identified by mass spectrometry and validated by Western blotting and immunofluorescence. We encountered 35 differentially regulated spots in the comparison CNT versus ICM, 33 in CNT versus DCM, and 34 in ICM versus DCM. We identified glyceraldehyde 3-phophate dehydrogenase up-regulation in both ICM and DCM, and alpha-crystallin B down-regulation in both ICM and DCM. Heat shock 70 protein 1 was up-regulated only in ICM. Ten of the eleven differentially regulated proteins common to both aetiologies are interconnected as a part of a same network. In summary, we have shown by proteomics analysis that HF is associated with changes in proteins involved in the cellular stress response, respiratory chain and cardiac metabolism. Although we found altered expression of eleven proteins common to both ischaemic and dilated aetiology, we also observed different proteins altered in both groups. Furthermore, we obtained that seven of these eleven proteins are involved in cell death and apoptosis processes, and therefore in HF progression.

Plasma concentrations of extracellular matrix protein fibulin-1 are related to cardiovascular risk markers in chronic kidney disease and diabetes

BACKGROUND

Fibulin-1 is one of a few extracellular matrix proteins present in blood in high concentrations. We aimed to define the relationship between plasma fibulin-1 levels and risk markers of cardiovascular disease.

METHODS

Plasma fibulin-1 was determined in subjects with chronic kidney disease (n = 32; median age 62.5, inter-quartile range 51 - 73 years) and 60 age-matched control subjects. Among kidney disease patients serological biomarkers related to cardiovascular disease (fibrinogen, interleukin 6, C-reactive protein) were measured. Arterial applanation tonometry was used to determine central hemodynamic and arterial stiffness indices.

RESULTS

We observed a positive correlation of fibulin-1 levels with age (r = 0.38; p = 0.033), glycated hemoglobin (r = 0.80; p = 0.003), creatinine (r = 0.35; p = 0.045), and fibrinogen (r = 0.39; p = 0.027). Glomerular filtration rate and fibulin-1 were inversely correlated (r = -0.57; p = 0.022). There was a positive correlation between fibulin-1 and central pulse pressure (r = 0.44; p = 0.011) and central augmentation pressure (r = 0.55; p = 0.001). In a multivariable regression model, diabetes, creatinine, fibrinogen and central augmentation pressure were independent predictors of plasma fibulin-1.

CONCLUSION

Increased plasma fibulin-1 levels were associated with diabetes and impaired kidney function. Furthermore, fibulin-1 levels were associated with hemodynamic cardiovascular risk markers. Fibulin-1 is a candidate in the pathogenesis of cardiovascular disease observed in chronic kidney disease and diabetes.

Plasma fibulin-1 is linked to restrictive filling of the left ventricle and to mortality in patients with aortic valve stenosis

BACKGROUND

Plasma fibulin-1 levels have been associated with N-terminal pro-B-type natriuretic peptide levels and left atrial size and shown to be predictive of mortality in patients with diabetes. The mechanisms behind these connections are not fully understood but are probably related to its roles as an extracellular matrix protein in cardiovascular tissues.

METHODS AND RESULTS

One hundred twenty-five patients with severe aortic stenosis who were scheduled for aortic valve replacement (AVR) were evaluated with preoperative echocardiography and their plasma fibulin-1 levels were determined with ELISA. The cohort was followed for a median of 4 years after AVR. Increased restrictive left ventricular (LV) filling pattern was observed with increased plasma fibulin-1 levels (2% versus 29% versus 24% in low, middle, and high plasma fibulin-1 tertile groups, P=0.004). Likewise, reduced longitudinal systolic LV function (6.6 ± 1.1 versus 6.1 ± 1.3 versus 5.7 ± 1.5 cm/s, P=0.05) and increased LV filling pressures was systolic velocity of the mitral annulus observed with increasing plasma fibulin-1 concentrations (ratio of early transmitral flow velocity to early diastolic flow velocity of the mitral annulus 13 ± 4 versus 15 ± 5 versus 16 ± 6 in the fibulin-1 tertile groups, P=0.04).

CONCLUSIONS

In patients with symptomatic severe aortic stenosis undergoing AVR, plasma fibulin-1 is associated with restrictive filling of the LV, decreased longitudinal systolic function of the LV, and increased LV filling pressures.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrial.gov with Identifier: NCT00294775.

Prevention of postoperative atrial fibrillation: novel and safe strategy based on the modulation of the antioxidant system

Postoperative atrial fibrillation (AF) is the most common arrhythmia following cardiac surgery with extracorporeal circulation. The pathogenesis of postoperative AF is multifactorial. Oxidative stress, caused by the unavoidable ischemia-reperfusion event occurring in this setting, is a major contributory factor. Reactive oxygen species (ROS)-derived effects could result in lipid peroxidation, protein carbonylation, or DNA oxidation of cardiac tissue, thus leading to functional and structural myocardial remodeling. The vulnerability of myocardial tissue to the oxidative challenge is also dependent on the activity of the antioxidant system. High ROS levels, overwhelming this system, should result in deleterious cellular effects, such as the induction of necrosis, apoptosis, or autophagy. Nevertheless, tissue exposure to low to moderate ROS levels could trigger a survival response with a trend to reinforce the antioxidant defense system. Administration of n-3 polyunsaturated fatty acids (PUFA), known to involve a moderate ROS production, is consistent with a diminished vulnerability to the development of postoperative AF. Accordingly, supplementation of n-3 PUFA successfully reduced the incidence of postoperative AF after coronary bypass grafting. This response is due to an up-regulation of antioxidant enzymes, as shown in experimental models. In turn, non-enzymatic antioxidant reinforcement through vitamin C administration prior to cardiac surgery has also reduced the postoperative AF incidence. Therefore, it should be expected that a mixed therapy result in an improvement of the cardioprotective effect by modulating both components of the antioxidant system. We present novel available evidence supporting the hypothesis of an effective prevention of postoperative AF including a two-step therapeutic strategy: n-3 PUFA followed by vitamin C supplementation to patients scheduled for cardiac surgery with extracorporeal circulation. The present study should encourage the design of clinical trials aimed to test the efficacy of this strategy to offer new therapeutic opportunities to patients challenged by ischemia-reperfusion events not solely in heart, but also in other organs such as kidney or liver in transplantation surgeries.

Heat shock proteins in oncology: diagnostic biomarkers or therapeutic targets?

Heat shock proteins (HSP) are a family of proteins induced in cells exposed to different insults. This induction of HSPs allows cells to survive stress conditions. Mammalian HSPs have been classified into six families according to their molecular size: HSP100, HSP90, HSP70, HSP60, HSP40 and small HSPs (15 to 30kDa) including HSP27. These proteins act as molecular chaperones either helping in the refolding of misfolded proteins or assisting in their elimination if they become irreversibly damaged. In recent years, proteomic studies have characterized several different HSPs in various tumor types which may be putative clinical biomarkers or molecular targets for cancer therapy. This has led to the development of a series of molecules capable of inhibiting HSPs. Numerous studies speculated that over-expression of HSP is in part responsible for resistance to many anti-tumor agents and chemotherapeutics. Hence, from a pharmacological point of view, the co-administration of HSP inhibitors together with other anti-tumor agents is of major importance in overcoming therapeutic resistance. In this review, we provide an overview of the current status of HSPs in autoimmune, cardiovascular, and neurodegenerative diseases with special emphasis on cancer.