Glycated albumin modulates platelet susceptibility to flow induced activation and aggregation

Post-translational modifications in kidney diseases and associated cardiovascular risk

Patients with chronic kidney disease (CKD) are at an increased cardiovascular risk compared with the general population, which is driven, at least in part, by mechanisms that are uniquely associated with kidney disease. In CKD, increased levels of oxidative stress and uraemic retention solutes, including urea and advanced glycation end products, enhance non-enzymatic post-translational modification events, such as protein oxidation, glycation, carbamylation and guanidinylation. Alterations in enzymatic post-translational modifications such as glycosylation, ubiquitination, acetylation and methylation are also detected in CKD. Post-translational modifications can alter the structure and function of proteins and lipoprotein particles, thereby affecting cellular processes. In CKD, evidence suggests that post-translationally modified proteins can contribute to inflammation, oxidative stress and fibrosis, and induce vascular damage or prothrombotic effects, which might contribute to CKD progression and/or increase cardiovascular risk in patients with CKD. Consequently, post-translational protein modifications prevalent in CKD might be useful as diagnostic biomarkers and indicators of disease activity that could be used to guide and evaluate therapeutic interventions, in addition to providing potential novel therapeutic targets.

Antiplatelet activity and toxicity profile of novel phosphonium salts derived from Michael reaction

In this work, five novel phosphonium salts derived from the Michael reaction were screened for their antiplatelet activity. Our findings revealed that compounds 2a, 2b, 2c, and 2d significantly inhibit platelet aggregation triggered by ADP or collagen (P < 0.001). Notably, compound 2c inhibited the arachidonic acid pathway (P < 0.001). Moreover, the selected compounds reduce CD62-P expression and inhibit GPIIb/IIIa activation. The interactions of the active compounds with their targets, ADP and collagen receptors, P2Y12 and GPVI respectively were investigated in silico using molecular docking studies. The results revealed a strong affinity of the active compounds for P2Y12 and GPVI. Additionally, cytotoxicity assays on platelets, erythrocytes, and human embryonic kidney HEK293 cells showed that compounds 2a, 2c and 2d were non-toxic even at high concentrations. In summary, our study shows that phosphonium salts can have strong antiplatelet power and suggests that compounds 2a, 2c and 2d could be promising antiplatelet agents for the management of cardiovascular diseases.

Platelet and endothelial cell responses under concurrent shear stress and tensile strain

Thrombosis can lead to significant mortality and morbidity. Both platelets and vascular endothelial cells play significant roles in thrombosis. Platelets' response to blood flow-induced shear stress can vary greatly depending on shear stress magnitude, pattern and shear exposure time. Endothelial cells are also sensitive to the biomechanical environment. Endothelial cell activation and dysfunction can occur under low oscillatory shear stress and low tensile strain. Platelet and endothelial cell interaction can also be affected by mechanical conditions. The goal of this study was to investigate how blood flow-induced shear stress, vascular wall tensile strain, platelet-endothelial cell stress history, and platelet-endothelial cell interaction affect platelet thrombogenicity. Platelets and human coronary artery endothelial cells were pretreated with physiological and pathological shear stress and/or tensile strain separately. The pretreated cells were then put together and exposed to pulsatile shear stress and cyclic tensile strain simultaneously in a shearing-stretching device. Following treatment, platelet thrombin generation rate, platelet and endothelial cell activation, and platelet adhesion to endothelial cells was measured. The results demonstrated that shear stress pretreatment of endothelial cells and platelets caused a significant increase in platelet thrombin generation rate, cell surface phosphatidylserine expression, and adhesion to endothelial cells. Shear stress pretreatment of platelets and endothelial cells attenuated endothelial cell ICAM-1 expression under stenosis conditions, as well as vWF expression under recirculation conditions. These results indicate that platelets are sensitized by prior shearing, while in comparison, the interaction with shear stress-pretreated platelets may reduce endothelial cell sensitivity to pathological shear stress and tensile strain.

Optimizing glycation control in diabetes: An integrated approach for inhibiting nonenzymatic glycation reactions of biological macromolecules

Diabetes is a multifactorial disorder that increases mortality and disability due to its complications. A key driver of these complications is nonenzymatic glycation, which generates advanced glycation end-products (AGEs) that impair tissue function. Therefore, effective nonenzymatic glycation prevention and control strategies are urgently needed. This review comprehensively describes the molecular mechanisms and pathological consequences of nonenzymatic glycation in diabetes and outlines various anti-glycation strategies, such as lowering plasma glucose, interfering with the glycation reaction, and degrading early and late glycation products. Diet, exercise, and hypoglycemic medications can reduce the onset of high glucose at the source. Glucose or amino acid analogs such as flavonoids, lysine and aminoguanidine competitively bind to proteins or glucose to block the initial nonenzymatic glycation reaction. In addition, deglycation enzymes such as amadoriase, fructosamine-3-kinase, parkinson's disease protein, glutamine amidotransferase-like class 1 domain-containing 3A and terminal FraB deglycase can eliminate existing nonenzymatic glycation products. These strategies involve nutritional, pharmacological, and enzymatic interventions that target different stages of nonenzymatic glycation. This review also emphasizes the therapeutic potential of anti-glycation drugs for preventing and treating diabetes complications.

Revisiting Methodologies for In Vitro Preparations of Advanced Glycation End Products

Chronic elevation of sugar and oxidative stress generally results in development of advanced glycation end products (AGEs) in diabetic individuals. Accumulation of AGEs in an individual can give rise to the activation of several pathways that will ultimately lead to various complications. Such AGEs can also be prepared in an in vitro environment. For an in vitro preparation of advanced glycation end products (AGEs), proteins, lipids, or nucleic acids are generally required to be incubated with reducing sugars at a physiological temperature or higher depending upon the protocol optimized for its preparation. Certain other factors are also optimized and added to the buffer to hasten its preparation or alter the properties of prepared AGEs. Through this review, we intend to highlight the various studies related to the experimental procedures for the preparation of different types of AGEs. In addition, we present the comparative study of methodologies optimized for the preparation of AGEs.

Prognostic implication of serum glycated albumin for patients with non-ST-segment elevation acute coronary syndrome undergoing percutaneous coronary intervention

BACKGROUND

It has been demonstrated that glycated albumin (GA) is significantly associated with diabetes complications and mortality. However, among patients diagnosed with non-ST-elevation acute coronary syndrome (NSTE-ACS) administered percutaneous coronary intervention (PCI), the predictive value of GA for poor prognosis is unclear.

METHODS

This study eventually included 2247 NSTE-ACS patients in Beijing Anzhen Hospital, Capital Medical University in January-December 2015 who received PCI. All patients were followed up until death or for 48 months post-discharge. The primary endpoint was major adverse cardio-cerebral events (MACCEs), including all-cause death, non-fatal myocardial infarction, ischemia-induced revascularization and non-fatal ischemic stroke.

RESULTS

In total, 547 (24.3%) MACCEs were recorded during the follow-up period. Upon adjusting for potential confounders, GA remained an important risk predictor of MACCEs (As nominal variate: hazard ratio [HR] 1.527, 95% confidence interval [CI] 1.236-1.886, P < 0.001; As continuous variate: HR 1.053, 95% CI 1.027-1.079, P < 0.001). GA addition significantly enhanced the predictive ability of the traditional risk model (Harrell's C-index, GA vs. Baseline model, 0.694 vs. 0.684, comparison P = 0.002; continuous net reclassification improvement (continuous-NRI) 0.085, P = 0.053; integrated discrimination improvement (IDI) 0.007, P = 0.020).

CONCLUSION

GA is highly correlated with poor prognosis in NSTE-ACS patients undergoing PCI, suggesting that it may be a major predictive factor of adverse events among these individuals.

Irreversible post-translational modifications - Emerging cardiovascular risk factors

Despite the introduction of lipid-lowering drugs, antihypertensives, antiplatelet and anticoagulation therapies for primary prevention of cardiovascular and heart diseases (CVD), it remains the number one cause of death globally, raising the question for novel/further essential factors besides traditional risk factors such as cholesterol, blood pressure and coagulation. With continuous identification and characterization of non-enzymatic post-translationally modified isoforms of proteins and lipoproteins, it is becoming increasingly clear that irreversible non-enzymatic post-translational modifications (nPTMs) alter the biological functions of native proteins and lipoproteins thereby transforming innate serum components into CVD mediators. In particular renal insufficiency and metabolic imbalance are major contributors to the systemically increased concentration of reactive metabolites and thus increased frequency of nPTMs, promoting multi-morbid disease development centering around cardiovascular disease. nPTMs are significantly involved in the onset and progression of cardiovascular disease and represent a significant and novel risk factor. These insights represent potentially new avenues for risk assessment, prevention and therapy. This review chapter summarizes all forms of nPTMs found in CKD and under metabolic imbalance and discusses the biochemical connections between molecular alterations and the pathological impact on increased cardiovascular risk, novel nPTM-associated non-traditional cardiovascular risk factors, and clinical implication of nPTM in cardiovascular disease.

Comprehensive overview of human serum albumin glycation in diabetes mellitus

The presence of excess glucose in blood is regarded as a sweet hurt for patients with diabetes. Human serum albumin (HSA) is the most abundant protein in human plasma, which undergoes severe non-enzymatic glycation with glucose in patients with diabetes; this modifies the structure and function of HSA. Furthermore, the advanced glycation end products produced by glycated HSA can cause pathological damage to the human body through various signaling pathways, eventually leading to complications of diabetes. Many potential glycation sites on HSA have different degrees of sensitivity to glucose concentration. This review provides a comprehensive assessment of the in vivo glycation sites of HSA; it also discusses the effects of glycation on the structure and function of HSA. Moreover, it addresses the relationship between HSA glycation and diabetes complications. Finally, it focuses on the value of non-enzymatic glycation of HSA in diabetes-related clinical applications.

Endothelial Dysfunction is Associated With Early-Onset Cryptogenic Ischemic Stroke in Men and With Increasing Age

Background

The aim of this study was to assess the association between endothelial function and early‐onset cryptogenic ischemic stroke (CIS), with subgroup analyses stratified by sex and age groups.

Methods and Results

We prospectively enrolled 136 consecutive patients aged 18 to 49 years (median age, 41 years; 44% women) with a recent CIS and 136 age‐ and sex‐matched (±5 years) stroke‐free controls. Endothelial function was measured with an EndoPAT 2000 device and analyzed as tertiles of natural logarithm of reactive hyperemia index with lower values reflecting dysfunction. We used conditional logistic regression adjusting for age, education, hypertension, diabetes mellitus, dyslipidemia, current smoking, heavy drinking, obesity, and diet score to assess the independent association between endothelial function and CIS. Patients in the lowest tertile of natural logarithm of reactive hyperemia index were more often men and they more frequently had a history of dyslipidemia; they were also more often obese, had a lower diet score, and lower high‐density lipoprotein cholesterol. In the entire cohort, we found no association in patients with endothelial function and CIS compared with stroke‐free controls. In sex‐ and age‐specific analyses, endothelial dysfunction was associated with CIS in men (adjusted odds ratio [OR], 3.50 for lowest versus highest natural logarithm of reactive hyperemia index tertile; 95% CI, 1.22–10.07) and in patients ≥41 years (OR, 5.78; 95% CI, 1.52–21.95). These associations remained significant when dyslipidemia was replaced with the ratio of total to high‐density lipoprotein cholesterol.

Conclusions

Endothelial dysfunction appears to be an independent player in early‐onset CIS in men and patients approaching middle age.

SARS-CoV-2 proteins regulate inflammatory, thrombotic and diabetic responses in human arterial fibroblasts

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for many pathological processes, including altered vascular disease development, dysfunctional thrombosis and a heightened inflammatory response. However, there is limited work to determine the underlying cellular responses induced by exposure to SARS-CoV-2 structural proteins. Thus, our objective was to investigate how human arterial adventitial fibroblasts inflammation, thrombosis and diabetic disease markers are altered in response to Spike, Nucleocapsid and Membrane-Envelope proteins. We hypothesized that after a short-term exposure to SARS-CoV-2 proteins, adventitial fibroblasts would have a higher expression of inflammatory, thrombotic and diabetic proteins, which would support a mechanism for altered vascular disease progression. After incubation, the expression of gC1qR, ICAM-1, tissue factor, RAGE and GLUT-4 was significantly up-regulated. In general, the extent of expression was different for each SARS-CoV-2 protein, suggesting that SARS-CoV-2 proteins interact with cells through different mechanisms. Thus, SARS-CoV-2 protein interaction with vascular cells may regulate vascular disease responses.

Nicotine: Regulatory roles and mechanisms in atherosclerosis progression

Smoking is an independent risk factor for atherosclerosis. The smoke produced by tobacco burning contains more than 7000 chemicals, among which nicotine is closely related to the occurrence and development of atherosclerosis. Nicotine, a selective cholinergic agonist, accelerates the formation of atherosclerosis by stimulating nicotinic acetylcholine receptors (nAChRs) located in neuronal and non-neuronal tissues. This review introduces the pathogenesis of atherosclerosis and the mechanisms involving nicotine and its receptors. Herein, we focus on the various roles of nicotine in atherosclerosis, such as upregulation of growth factors, inflammation, and the dysfunction of endothelial cells, vascular smooth muscle cells (VSMC) as well as macrophages. In addition, nicotine can stimulate the generation of reactive oxygen species, cause abnormal lipid metabolism, and activate immune cells leading to the onset and progression of atherosclerosis. Exosomes, are currently a research hotspot, due to their important connections with macrophages and the VSMC, and may represent a novel application into future preventive treatment to promote the prevention of smoking-related atherosclerosis. In this review, we will elaborate on the regulatory mechanism of nicotine on atherosclerosis, as well as the effects of interference with nicotine receptors and the use of exosomes to prevent atherosclerosis development.

Advanced glycation end products and their adverse effects: The role of autophagy

The critical roles played by advanced glycation endproducts (AGEs) accumulation in diabetes and diabetic complications have gained intense recognition. AGEs interfere with the normal functioning of almost every organ with multiple actions like apoptosis, inflammation, protein dysfunction, mitochondrial dysfunction, and oxidative stress. However, the development of a potential treatment strategy is yet to be established. Autophagy is an evolutionarily conserved cellular process that maintains cellular homeostasis with the degradation and recycling systems. AGEs can activate autophagy signaling, which could be targeted as a therapeutic strategy against AGEs induced problems. In this review, we have provided an overview of the adverse effects of AGEs, and we put forth the notion that autophagy could be a promising targetable strategy against AGEs.

High glycated albumin is an independent predictor of low response to clopidogrel in ACS patients: a cross-sectional study

BACKGROUND

Glycated albumin (GA) is a marker of short-term glycemic control and is strongly associated with the occurrence of diabetes. Previous studies have shown an association between GA and the effect of clopidogrel therapy on ischemic stroke. However, limited information is available regarding this relationship in acute coronary syndrome (ACS) patients. In this study, we evaluated the effect of GA on platelet P2Y12 inhibition by clopidogrel in patients with ACS.

METHODS

Consecutive Chinese patients with ACS who received loading or maintenance doses of clopidogrel in addition to aspirin were recruited. At least 12 h after the patient had taken the clopidogrel dose, thromboelastography (TEG) and light transmittance aggregometry (LTA) were used to calculate the quantitative platelet inhibition rate to determine clopidogrel-induced antiplatelet reactivity. A prespecified cutoff of the maximum amplitude of adenosine diphosphate (ADP)-induced platelet-fibrin clot strength > 47 mm plus an ADP-induced platelet inhibition rate < 50% assessed by TEG or ADP-induced platelet aggregation > 40% assessed by LTA to indicate low responsiveness to clopidogrel were applied for evaluation. Patients were categorized into two groups based on a GA level of 15.5%, the cutoff point indicating the development of early-phase diabetes. Multivariate linear regression analysis was used to assess the interaction of GA with clopidogrel antiplatelet therapy.

RESULTS

A total of 1021 participants were evaluated, and 28.3% of patients (289 of 1021) had low responsiveness to clopidogrel assessed by TEG. In patients with elevated GA levels, low responsiveness to clopidogrel assessed by TEG was observed in 33.7% (139 of 412) of patients, which was a significantly higher rate than that in the lower-GA-level group (24.6%, P = 0.002). According to multivariate linear regression analysis, a GA level > 15.5% was independently associated with low responsiveness to clopidogrel after adjustment for age, sex and other conventional confounding factors. This interaction was not mediated by a history of diabetes mellitus. A GA level ≤ 15.5% was associated with a high positive value [75.4%, 95% CI 73.0-77.6%] for predicting a normal responsiveness to clopidogrel.

CONCLUSIONS

GA could be a potential biomarker to predict the effects of clopidogrel antiplatelet therapy in ACS patients and might be a clinical biomarker to guide DAPT de-escalation.

Involvement of glycated albumin in adipose-derived-stem cell-mediated interleukin 17 secreting T helper cell activation

BACKGROUND

Advanced glycation end products (AGE) are a marker of various diseases including diabetes, in which they participate to vascular damages such as retinopathy, nephropathy and coronaropathy. Besides those vascular complications, AGE are involved in altered metabolism in many tissues, including adipose tissue (AT) where they contribute to reduced glucose uptake and attenuation of insulin sensitivity. AGE are known to contribute to type 1 diabetes (T1D) through promotion of interleukin (IL)-17 secreting T helper (Th17) cells.

AIM

To investigate whether lean adipose-derived stem cells (ASC) could be able to induce IL-17A secretion, with the help of AGE.

METHODS

As we have recently demonstrated that ASC are involved in Th17 cell promotion when they are harvested from obese AT, we used the same co-culture model to measure the impact of glycated human serum albumin (G-HSA) on human lean ASC interacting with blood mononuclear cells. IL-17A and pro-inflammatory cytokine secretion were measured by ELISA. Receptor of AGE (RAGE) together with intercellular adhesion molecule 1 (ICAM-1), human leukocyte Antigen (HLA)-DR, cluster of differentiation (CD) 41, and CD62P surface expressions were measured by cytofluorometry. Anti-RAGE specific monoclonal antibody was added to co-cultures in order to evaluate the role of RAGE in IL-17A production.

RESULTS

Results showed that whereas 1% G-HSA only weakly potentiated the production of IL-17A by T cells interacting with ASC harvested from obese subjects, it markedly increased IL-17A, but also interferon gamma and tumor necrosis factor alpha production in the presence of ASC harvested from lean individuals. This was associated with increased expression of RAGE and HLA-DR molecule by co-cultured cells. Moreover, RAGE blockade experiments demonstrated RAGE specific involvement in lean ASC-mediated Th-17 cell activation. Finally, platelet aggregation and ICAM-1, which are known to be induced by AGE, were not involved in these processes.

CONCLUSION

Thus, our results demonstrated that G-HSA potentiated lean ASC-mediated IL-17A production in AT, suggesting a new mechanism by which AGE could contribute to T1D pathophysiology.

Combined impact of body mass index and glycemic control on the efficacy of clopidogrel-aspirin therapy in patients with minor stroke or transient ischemic attack

Background: A single index of body mass index (BMI) may not fully address its impact on anti-platelet therapy. We aimed to elucidate the combined impact of BMI and dysglycemia expressed by glycated albumin (GA) on efficacy of clopidogrel-aspirin therapy among minor stroke (MS) or transient ischemic attack (TIA) patients.

Results: Patients with overweight/obesity and low GA levels still benefited from clopidogrel-aspirin therapy for stroke recurrence (Hazard ratio [HR]: 0.48, 95 % confidence interval [CI]: 0.28–0.82), so did those with high GA levels but low/normal weight (HR: 0.67, 95 % CI: 0.45–0.99). However, patients with both overweight/obesity and high GA levels did not benefit from clopidogrel-aspirin therapy (HR: 0.89, 95 % CI: 0.59–1.33).

Conclusions: Compared with aspirin alone, efficacy of clopidogrel-aspirin therapy for stroke still exists in overweight/obesity patients with normal glycemic control.

Methods: In Clopidogrel in High-Risk Patients with Acute Nondisabling Cerebrovascular Events trial, 3044 patients with available baseline GA were recruited. Low/normal weight and overweight/obesity were defined as BMI < 25 kg/m² and ≥ 25 kg/m², respectively. Elevated and low GA levels were defined as GA levels > 15.5 % and ≤ 15.5 %, respectively. The primary outcome was stroke recurrence during the 90-day follow-up.

Effect of advanced glycation end products on platelet activation and aggregation: a comparative study of the role of glyoxal and methylglyoxal

Advanced glycation end products (AGEs) arising from dietary intake have been associated with numerous chronic diseases including cardiovascular diseases. The interaction between platelets and AGEs has been proposed to play a role in the etiology of cardiovascular diseases. However, the effects of the interaction between platelets and Maillard reaction products generated from glyoxal (Gly) or methylglyoxal (MG) are poorly understood. In this work, the effects of AGEs generated by the reaction between Gly or MG with Lys or bovine serum albumin (BSA) on platelet activation and aggregation were assessed. AGEs were generated incubating Gly or MG with Lys or BSA during 5 hours or 14 days, respectively. AGEs generation were characterized by kinetic studies and by amino acid analysis. Human platelet-rich plasma (PRP) was incubated with different concentrations of AGEs from Lys-MG or Lys-Gly and BSA-MG or BSA-Gly. Platelet activation was determined quantifying the expression of CD62 (P-selectin) in PRP exposed to different AGEs concentrations. It was found that Lys-MG and Lys-Gly induced an increase in P-selectin expression (p < .05), being 33.9% higher for Lys-MG when compared to Lys-Gly. Platelets incubated in the presence of BSA-MG and BSA-Gly did not show an increase in the P-selectin expression. Platelet aggregation was significantly higher for the mixture Lys-MG (in all the range of concentrations evaluated), whereas for Lys-Gly it was only significant the highest concentration (Lys 168 µM/Gly 168 µM). It was observed a significant increase in platelet aggregation induced by ADP for samples BSA-Gly. AGEs formed with MG-Lys induce a higher activation and aggregation of platelets when compared to those formed from Gly-Lys.

Platelet-Activation Mechanisms and Vascular Remodeling

This overview article for the Comprehensive Physiology collection is focused on detailing platelets, how platelets respond to various stimuli, how platelets interact with their external biochemical environment, and the role of platelets in physiological and pathological processes. Specifically, we will discuss the four major functions of platelets: activation, adhesion, aggregation, and inflammation. We will extend this discussion to include various mechanisms that can induce these functional changes and a discussion of some of the salient receptors that are responsible for platelets interacting with their external environment. We will finish with a discussion of how platelets interact with their vascular environment, with a special focus on interactions with the extracellular matrix and endothelial cells, and finally how platelets can aid and possibly initiate the progression of various vascular diseases. Throughout this overview, we will highlight both the historical investigations into the role of platelets in health and disease as well as some of the more current work. Overall, the authors aim for the readers to gain an appreciation for the complexity of platelet functions and the multifaceted role of platelets in the vascular system. © 2017 American Physiological Society. Compr Physiol 8:1117-1156, 2018.

AGE-RAGE Stress, Stressors, and Antistressors in Health and Disease

Adverse effects of advanced glycation end-products (AGEs) on the tissues are through nonreceptor- and receptor-mediated mechanisms. In the receptor-mediated mechanism, interaction of AGEs with its cell-bound receptor of AGE (RAGE) increases generation of oxygen radicals, activates nuclear factor-kappa B, and increases expression and release of pro-inflammatory cytokines resulting in the cellular damage. The deleterious effects of AGE and AGE-RAGE interaction are coined as "AGE-RAGE stress." The body is equipped with defense mechanisms to counteract the adverse effects of AGE and RAGE through endogenous enzymatic (glyoxalase 1, glyoxalase 2) and AGE receptor-mediated (AGER1, AGER2) degradation of AGE, and through elevation of soluble receptor of AGE (sRAGE). Exogenous defense mechanisms include reduction in consumption of AGE, prevention of AGE formation, and downregulation of RAGE expression. We have coined AGE and RAGE as "stressors" and the defense mechanisms as "anti-stressors." AGE-RAGE stress is defined as a shift in the balance between stressors and antistressors in the favor of stressors. Measurements of stressors or antistressors alone would not assess AGE-RAGE stress. For true assessment of AGE-RAGE stress, the equation should include all the stressors and antistressors. The equation for AGE-RAGE stress, therefore, would be the ratio of AGE + RAGE/sRAGE + glyoxalase1 + glyoxalase 2 + AGER1 +AGER2. This is, however, not practical in patients. AGE-RAGE stress may be assessed simply by the ratio of AGE/sRAGE. A high ratio of AGE/sRAGE indicates a relative shift in stressors from antistressors, suggesting the presence of AGE-RAGE stress, resulting in tissue damage, initiation, and progression of the diseases and their complications.

How schistosomes alter the human serum proteome

Schistosomes are intravascular parasitic worms that cause the debilitating disease schistosomiasis. To better understand how these long-lived parasites may subvert host immune and hemostatic capabilities, we examine here the impact of adult Schistosoma mansoni worms on the human serum proteome. Normal human serum (150μl) was incubated at 37°C for one hour either in the presence or absence of adult worms (∼50 pairs). Thereafter parasites were removed, serum samples were labeled and their proteins resolved for comparative analysis by 2D-Differential in-Gel Electrophoresis (2D-DIGE). Several differences were noted between the two samples. Twenty protein spots were recovered and identified following trypsin digestion and mass spectroscopy. Strikingly, most of these (11/20) are associated with the complement system and include complement components C3, C4, factor B, complement factor H related protein 1 and clusterin. Western blot analysis confirms the impact of the worms on C3, C4 and factor B in serum. The data suggest that schistosomes engage complement but can rapidly degrade selected complement proteins which may help explain the worm's refractoriness towards complement-mediated attack. Other serum proteins identified as being impinged upon by schistosomes are alpha 2 macroglobulin, alpha 1 anti-chymotrypsin, actin cytoplasmic 2, serum amyloid A-4, protein DDX26B, hemoglobin subunit B and serum albumin. While the molecular nature of the interaction between these proteins and schistosomes is not known, possible roles for some of them in hemostasis, immune evasion and in the host response to serum stress are suggested.

Glycated albumin modifies platelet adhesion and aggregation responses

A diabetic vasculature is detrimental to cardiovascular health through the actions of advanced glycation end products (AGEs) on endothelial cells and platelets. Platelets activated by AGEs agonize endothelial responses promoting cardiovascular disease (CVD) development. While it has been established that AGEs can alter platelet functions, little is known about the specific platelet pathways that AGEs modify. Therefore, we evaluated the effects of AGEs on specific salient platelet pathways related to CVDs and whether the effects that AGEs elicit are dependent on glycation extent. To accomplish our objective, platelets were incubated with reversibly or irreversibly glycated albumin. A time course for adhesion and aggregation agonist receptor expression was assessed. Optical platelet aggregometry was used to confirm the functional activity of platelets after AGE exposure. In general, platelets subjected to glycated albumin had a significantly enhanced adhesion and aggregation potential. Furthermore, we observed an enhancement in dense body secretion and intracellular calcium concentration. This was especially prevalent for platelets exposed to irreversibly glycated albumin. Additionally, functional aggregation correlated well with receptor expression, suggesting that AGE-induced altered receptor sensitivity translated to altered platelet functions. Our findings indicate that under diabetic vascular conditions platelets become more susceptible to activation and aggregation due to an overall enhanced receptor expression, which may act to promote CVD development.

Platelet activation, adhesion, inflammation, and aggregation potential are altered in the presence of electronic cigarette extracts of variable nicotine concentrations

Tobacco smoke extracts prepared from both mainstream and sidestream smoking have been associated with heightened platelet activation, aggregation, adhesion, and inflammation. Conversely, it has been shown that pure nicotine inhibits similar platelet functions. In this work, we 1) evaluated the effects of e-cigarette extracts on platelet activities and 2) elucidated the differences between the nicotine-dependent and non-nicotine dependent (e.g. fine particulate matter or toxic compounds) effects of tobacco and e-cigarette products on platelet activities. To accomplish these goals, platelets from healthy volunteers (n = 50) were exposed to tobacco smoke extracts, e-cigarette vapor extracts, and pure nicotine and changes in platelet activation, adhesion, aggregation, and inflammation were evaluated, using optical aggregation, flow cytometry, and ELISA methods. Interestingly, the exposure of platelets to e-vapor extracts induced a significant up-regulation in the expression of the pro-inflammatory gC1qR and cC1qR and induced a marked increase in the deposition of C3b as compared with traditional tobacco smoke extracts. Similarly, platelet activation, as measured by a prothrombinase based assay, and platelet aggregation were also significantly enhanced after exposure to e-vapor extracts. Finally, platelet adhesion potential toward fibrinogen, von Willebrand factor, and other platelets was also enhanced after exposure to e-cigarette vapor extracts. In the presence of pure nicotine, platelet functions were observed to be inhibited, which further suggests that other constituents of tobacco smoke and electronic vapor can antagonize platelet functions, however, the presence of nicotine in extracts somewhat perpetuated the platelet functional changes in a dose-dependent manner.

Glycated albumin with loss of fatty acid binding capacity contributes to enhanced arachidonate oxygenation and platelet hyperactivity: relevance in patients with type 2 diabetes

High plasma concentrations of nonesterified fatty acids (NEFAs), transported bound to serum albumin, are associated with type 2 diabetes (T2D). The effects of albumin on platelet function were investigated in vitro. Modifications of albumin, such as those due to glycoxidation, were found in patients with T2D, and the consequences of these modifications on biological mechanisms related to NEFA handling were investigated. Mass spectrometry profiles of albumin from patients with T2D differed from those from healthy control subjects. Diabetic albumin showed impaired NEFA binding capacity, and both structural and functional alterations could be reproduced in vitro by incubating native albumin with glucose and methylglyoxal. Platelets incubated with albumin isolated from patients with T2D aggregated approximately twice as much as platelets incubated with albumin isolated from healthy control subjects. Accordingly, platelets incubated with modified albumin produced significantly higher amounts of arachidonate metabolites than did platelets incubated with control albumin. We concluded that higher amounts of free arachidonate are made available for the generation of active metabolites in platelets when the NEFA binding capacity of albumin is blunted by glycoxidation. This newly described mechanism, in addition to hypoalbuminemia, may contribute to platelet hyperactivity and increased thrombosis, known to occur in patients with T2D.

Combined incubation of platelets and endothelial cells with glycated albumin: Altered thrombogenic and inflammatory responses

Diabetes mellitus is a salient risk factor for the development of cardiovascular diseases (CVDs). Part of this risk is associated with the presence of advanced glycation end products (AGEs), which have been shown to up-regulate platelet or endothelial cell inflammatory and thrombogenic responses that are associated with CVDs. However, platelets perform mechanisms that alter endothelial cell inflammatory and thrombogenic responses, and endothelial cells perform similar mechanisms on platelets. Thus, our goal was to evaluate platelet and endothelial cell inflammatory and thrombogenic reactions that AGEs elicit during concurrent exposure. Endothelial cells were incubated with AGEs for 5 days, after which platelets were added. A time course for CVD inflammatory and thrombogenic responses was quantified as a function of extent of glycation. In general, the presence of platelets reduced AGE-induced endothelial cell responses associated with CVD progression and the presence of endothelial cells reduced platelet adhesion and activation responses, as compared with individual exposures. In general, the presence of irreversibly glycated albumin promoted CVD development to a greater extent than reversibly glycated albumin. This suggests that under diabetic conditions, platelets and endothelial cells can negatively feedback on each other, likely via enhanced adhesion, to elicit a reduced response associated with CVD progression.

Glycated albumin: an overview of the In Vitro models of an In Vivo potential disease marker

Glycation is a general spontaneous process in proteins which has significant impact on their physical and functional properties. These changes in protein properties could be related to several pathological consequences such as cataract, arteriosclerosis and Alzheimer's disease. Among the proteins, glycation of Human serum albumin (HSA) is of special interest. Human serum albumin is the most abundant protein in the plasma and because of its high sensitivity for glycation, undergoes structural and functional changes due to binding of reducing sugars in vitro. The glycation process occurs by plasma glucose in vivo which has great impacts on the three dimensional structure of protein. These changes are efficient and stable enough which makes the protein to be considered as a new special disease marker instead of HbA1C for diabetes. In some cases, glycated albumin was used as an alternative marker for glycemic control. Glycated albumin reacts with glucose ten times more rapidly than HbA1C and has shorter half-life which makes it more reliable for indicating glycemic states. In this review, glycation of Human Serum Albumin has been overviewed, starting from overall concepts of glycation, followed by some Examples of pathological consequences of protein glycation. The BSA aggregation was reviewed in terms of structural and biological impacts of glycation on the protein followed by reporting documents which indicate possibility of glycated albumin to be used as specific marker for diabetes. Finally, some of the studies related to the models of glycated albumin have been briefly described, with an emphasis on In vitro studies. It is interesting to note the relationship found between in vitro glycation experiments and the propensity of proteins to form amyloid structures, a point that could be further explored as to its significance in hyperglycemic states.

Role of multiligand/RAGE axis in platelet activation

In the context of plaque progression, platelet hyperactivity associated with hyperlipidemia contributes to the development of a pro-thrombotic state. In this context, it has been demonstrated that advanced glycation end products (AGEs) significantly increases platelet activation and receptor for AGEs (RAGE) expression at the platelet surface membrane. In addition to AGEs, other ligands (S100, HMGB1 and amyloid β, among others) of RAGE have raised particular attention in platelet activation. Therefore, in this article we describe platelet hyperactivity by AGEs via RAGE-independent and RAGE-dependent pathways.

Advanced glycation end products and diabetic complications

During long standing hyperglycaemic state in diabetes mellitus, glucose forms covalent adducts with the plasma proteins through a non-enzymatic process known as glycation. Protein glycation and formation of advanced glycation end products (AGEs) play an important role in the pathogenesis of diabetic complications like retinopathy, nephropathy, neuropathy, cardiomyopathy along with some other diseases such as rheumatoid arthritis, osteoporosis and aging. Glycation of proteins interferes with their normal functions by disrupting molecular conformation, altering enzymatic activity, and interfering with receptor functioning. AGEs form intra- and extracellular cross linking not only with proteins, but with some other endogenous key molecules including lipids and nucleic acids to contribute in the development of diabetic complications. Recent studies suggest that AGEs interact with plasma membrane localized receptors for AGEs (RAGE) to alter intracellular signaling, gene expression, release of pro-inflammatory molecules and free radicals. The present review discusses the glycation of plasma proteins such as albumin, fibrinogen, globulins and collagen to form different types of AGEs. Furthermore, the role of AGEs in the pathogenesis of diabetic complications including retinopathy, cataract, neuropathy, nephropathy and cardiomyopathy is also discussed.

Advanced glycation end products and diabetic complications

During long standing hyperglycaemic state in diabetes mellitus, glucose forms covalent adducts with the plasma proteins through a non-enzymatic process known as glycation. Protein glycation and formation of advanced glycation end products (AGEs) play an important role in the pathogenesis of diabetic complications like retinopathy, nephropathy, neuropathy, cardiomyopathy along with some other diseases such as rheumatoid arthritis, osteoporosis and aging. Glycation of proteins interferes with their normal functions by disrupting molecular conformation, altering enzymatic activity, and interfering with receptor functioning. AGEs form intra- and extracellular cross linking not only with proteins, but with some other endogenous key molecules including lipids and nucleic acids to contribute in the development of diabetic complications. Recent studies suggest that AGEs interact with plasma membrane localized receptors for AGEs (RAGE) to alter intracellular signaling, gene expression, release of pro-inflammatory molecules and free radicals. The present review discusses the glycation of plasma proteins such as albumin, fibrinogen, globulins and collagen to form different types of AGEs. Furthermore, the role of AGEs in the pathogenesis of diabetic complications including retinopathy, cataract, neuropathy, nephropathy and cardiomyopathy is also discussed.

Combined effects of physiologically relevant disturbed wall shear stress and glycated albumin on endothelial cell functions associated with inflammation, thrombosis and cytoskeletal dynamics

Aims/Introduction

Diabetes mellitus is a major risk factor in the development of cardiovascular diseases (CVDs). The presence of advanced glycation end‐products (AGEs) promotes CVDs by upregulating endothelial cell (EC) inflammatory and thrombotic responses, in a similar manner as disturbed shear stress. However, the combined effect of disturbed shear stress and AGEs on EC function has yet to be determined. Our goal was to evaluate these effects on EC responses.

Materials and Methods

ECs were incubated with AGEs for 5 days. ECs were then subjected to physiological or pathological shear stress. Cell metabolic activity, surface expression of intercellular adhesion molecule‐1, thrombomodulin, connexin‐43 and caveolin‐1, and cytoskeleton organization were quantified.

Results

The results show that irreversibly glycated albumin and pathological shear stress increased EC metabolic activity, and upregulated and downregulated the EC surface expression of intercellular adhesion molecule‐1 and thrombomodulin, respectively. Expression of connexin‐43, caveolin‐1 and cytoskeletal organization was independent of shear stress; however, the presence of irreversibly glycated AGEs markedly increased connexin‐43, and decreased caveolin‐1 expression and actin cytoskeletal connectivity.

Conclusions

Our data suggest that irreversibly glycated albumin and disturbed shear stress could promote CVD pathogenesis by enhancing EC inflammatory and thrombotic responses, and through the deterioration of the cytoskeletal organization.

Platelets express and release osteocalcin and co-localize in human calcified atherosclerotic plaques

BACKGROUND

Although vascular-calcification mechanisms are only partially understood, the role of circulating calcifying cells and non-collagenous bone matrix proteins in the bone-vascular axis is emerging. In spite of the fact that platelets represent a cellular interface between hemostasis, inflammation and atherosclerosis, and have a myeloid precursor, a possible involvement in the modulation of vascular calcification has rarely been investigated. We investigated if osteocalcin (OC) is released by platelets and described OC expression in patients with carotid artery occlusive disease.

METHODS

Expression and release of OC were determined by Western blot, immunofluorescence, fluorescence-activated cell sorting (FACS) and ELISA in human resting and activated platelets and megakaryocytes. Co-localization of platelet aggregates, macrophages, OC and calcifications was studied in carotid endarterectomy specimens and normal tissues.

RESULTS

Human platelets expressed OC and co-localized with CD63 in δ-granules. Upon activation with an endogenous mechanism, platelets released OC in the extracellular medium. Expression of OC in megakaryocytes suggested lineage specificity. The OC count in circulating platelets and the released amount were significantly higher in patients with carotid artery occlusive disease than in healthy controls (P < 0.0001) in spite of similar serum levels. In atherosclerotic plaques, OC strongly overlapped with CD41+ platelets in the early stage of calcification, but this was not seen in normal tissues. CD68+OC+ cells were present at the periphery of the calcified zone.

CONCLUSIONS

Given the active role played by platelets in the atherosclerotic process, the involvement of OC release from platelets in atherosclerotic lesions and the impact of genetic and cardiovascular risk factors in mediating bone-marrow preconditioning should be investigated further.

Differences between mainstream and sidestream tobacco smoke extracts and nicotine in the activation and aggregation of platelets subjected to cardiovascular conditions in diabetes

Mainstream and sidestream tobacco smoke extracts have been shown to increase platelet activation directly. Furthermore, advanced glycation end products, which are present in the diabetic vasculature, have also been shown to enhance platelet activity. However, the combined effects of these two risk factors on platelet functions remain unclear. Platelets were exposed to tobacco extracts concurrently with advanced glycation end products. Timed samples were removed to assess the extent of platelet activity. The presence of smoke extracts enhanced platelet activity as compared to control conditions, this was especially prevalent for sidestream extracts. With the addition of irreversibly glycated albumin, there was an additive effect, further enhancing platelet responses. This was at least partially regulated by α-granule release and CD41 expression. The combination of cardiovascular risk factors can significantly enhance platelet activation and aggregation, and therefore it is possible to accelerate cardiovascular diseases through the interactions of multiple cardiovascular risk factors.

Intraplatelet oxidative/nitrative stress: inductors, consequences, and control

This article provides an overview of the current knowledge on intraplatelet oxidative/nitrative stress, an abnormality associated with platelet activation and hyper-reactivity. The first issue discussed is related to induction of platelet endogenous stress by the molecules present within the circulating (extracellular) milieu that bathes these cells. The second issue concerns the intraplatelet oxidative/nitrative stress associated with specific pathologies or clinical procedures and action of particular molecules and platelet agonists as well as of the specialized intraplatelet milieu and its redox system; the biomarkers of endogenous oxidative/nitrative stress are also briefly outlined. Next, the association between intraplatelet oxidative/nitrative stress and the risk factors of the metabolic syndrome is presented. Then, the most recent strategies aimed at the control/regulation of platelet endogenous oxidative/nitrative stress, such as exploitation of circulating extracellular reactive oxygen species scavengers, manipulation of platelet molecules, and the use of antioxidants, are discussed. Finally, the results of studies on platelet-dependent redox mechanisms, which deserve immediate attention for potential clinical exploitation, are illustrated.

Spontaneous platelet aggregation evaluated by laser light scatter in patients with type 2 diabetes: effects of short-term improved glycemic control and adiponectin

Spontaneous platelet aggregation (SPA) is enhanced in patients with type 2 diabetes. Adiponectin may inhibit platelet aggregation. The aims of the current study were to identify factors associated with in vitro SPA measured by a laser light scattering method and to investigate the effects of short-term glycemic control and adiponectin on SPA. In study 1, we investigated platelet aggregation in 20 healthy control subjects and 82 patients with type 2 diabetes. In study 2, we evaluated the changes of SPA and serum high-molecular-weight (HMW) adiponectin after 2 weeks of improved glycemic control in 20 hospitalized diabetic patients. In study 3, using washed platelets from 10 healthy subjects, in vitro SPA was measured over 15 min in the absence or presence of recombinant adiponectin (20 μg/mL). Platelet aggregation was assessed with a laser light scatter aggregometer that measured the size of platelet aggregates. SPA was defined as formation of small aggregates under constant stirring in the absence of any agonists. The area under the curve was calculated for SPA and also for agonist-induced small, medium, and large aggregates. SPA was increased in diabetic patients compared with control subjects. In diabetic patients, SPA was correlated positively with plasma fibrinogen, fasting plasma glucose, glycated albumin, and high-sensitivity C-reactive protein. A stepwise multivariate analysis showed that plasma fibrinogen was the strongest independent determinant of SPA in diabetic patients. In 20 diabetic patients, SPA decreased significantly after 2 weeks of glycemic control. A significant negative correlation was found between changes of SPA and those of HMW adiponectin during treatment. The in vitro study showed that adiponectin inhibited the spontaneous aggregation of washed platelets. In conclusion, hyperfibrinogenemia and hyperglycemia are associated independently with SPA in patients with type 2 diabetes. SPA is reduced after even short-term improvement of glycemic control and adiponectin also inhibits SPA directly.

Glycated albumin modulates endothelial cell thrombogenic and inflammatory responses

BACKGROUND

It has become established that a diabetic vasculature promotes cardiovascular disease progression via changes to endothelial cells, platelets, and the interactions of these cells. It is believed that the majority of these changes are induced by the presence of advanced glycation end products (AGEs), which permanently alter various functions. Studies have shown that platelets perpetuate endothelial cell responses under these conditions. However, the role of changes in endothelial cell thrombogenicity and inflammatory responses, after subjected to AGEs, has not been characterized. Our objective was to evaluate the effects of AGEs on these functions.

METHODS

To accomplish this, albumin was chemically modified by exposure to glucose for up to 8 weeks, and endothelial cells were subjected to glycated albumin for up to 5 days in a cell culture system. A time course for changes in endothelial cell viability, density, morphology, and metabolic activity were investigated, along with the surface expression of intercellular adhesion molecule-1, thrombomodulin, tissue factor, connexin-43, and caveolin-1.

RESULTS

Endothelial cells exposed to irreversibly glycated albumin were less viable, proliferated slower, and had a lower metabolic activity as compared to cells exposed to nonglycated albumin. Endothelial cells that were exposed to any glycated albumin were procoagulant and proinflammatory as compared with all other conditions. There were no overall trends in the expression of connexin-43 or caveolin-1.

CONCLUSIONS

Our data suggest that the presence of irreversible glycated albumin is deleterious to endothelial cells, makes endothelial cells more procoagulant, and promotes inflammatory responses. It is therefore possible that endothelial cell activation may precede and promote platelet activation during diabetic conditions.

Thrombogenic potential of Innovia polymer valves versus Carpentier-Edwards Perimount Magna aortic bioprosthetic valves

Trileaflet polymeric prosthetic aortic valves (AVs) produce hemodynamic characteristics akin to the natural AV and may be most suitable for applications such as transcatheter implantation and mechanical circulatory support (MCS) devices. Their success has not yet been realized due to problems of calcification, durability, and thrombosis. We address the latter by comparing the platelet activation rates (PARs) of an improved polymer valve design (Innovia LLC) made from poly(styrene-block-isobutylene-block-styrene) (SIBS) with the commercially available Carpentier-Edwards Perimount Magna Aortic Bioprosthetic Valve. We used our modified prothrombinase platelet activity state (PAS) assay and flow cytometry methods to measure platelet activation of a pair of 19 mm valves mounted inside a pulsatile Berlin left ventricular assist device (LVAD). The PAR of the polymer valve measured with the PAS assay was fivefold lower than that of the tissue valve (p = 0.005) and fourfold lower with flow cytometry measurements (p = 0.007). In vitro hydrodynamic tests showed clinically similar performance of the Innovia and Magna valves. These results demonstrate a significant improvement in thrombogenic performance of the polymer valve compared with our previous study of the former valve design and encourage further development of SIBS for use in heart valve prostheses.

The glycation of albumin: structural and functional impacts

Oxidative stress and protein modifications are frequently observed in numerous disease states. Glucose constitutes a vital nutrient necessary to cellular oxygen metabolism. However, hyperglycemia-associated damage is an important factor in diabetes disorders. Albumin, the major circulating protein in blood, can undergo increased glycation in diabetes. From recent studies, it has become evident that protein glycation has important implications for protein activity, unfolding, and degradation, as well as for cell functioning. After giving a brief overview of the key role of albumin in overall antioxidant defense, this review examines its role as a target of glycation reactions. A synthesis of state of the art methods for measuring and characterizing albumin glycation is detailed. In light of recent data, we then report the impact of glycation on the structure of albumin and its various activities, especially its antioxidant and binding capacities. The biological impact of glycated albumin on cell physiology is also discussed, specifically the role of the protein as a biological marker of diabetes.

The combined effects of sidestream smoke extracts and glycated serum albumin on endothelial cells and platelets

Background

The purpose of this study was to test the hypothesis that sidestream tobacco smoke extracts would inhibit the culture of endothelial cells and enhance platelet aggregation under diabetic vascular conditions. Sidestream tobacco smoke and advanced glycation end products are known cardiovascular risk factors and we aimed to determine the combined interaction between these two risk factors to promote cardiovascular diseases associated with diabetes.

Methods

Human umbilical vein endothelial cells were cultured in the presence of sidestream tobacco smoke extracts (SHS) or nicotine and glycated albumin (AGE) or non-glycated albumin. After 3 days, endothelial cell viability and density were investigated. Platelets were also incubated with these compounds for up to 6 hours. Platelet aggregation and the surface expression of CD41 and CD62P were examined. In some experiments, platelets were added to the endothelial cell culture to determine if an interaction between platelets and endothelial cells occurs that can alter the responses to SHS or AGE.

Results

In general, the endothelial cell culture conditions were reduced in the presence of AGE and SHS. Nicotine, did not play a role in this reduction. Platelet aggregation proceeded faster in the presence of AGE and SHS. Interestingly, with the combined culture of endothelial cells and platelets, the endothelial cell culture conditions were improved and the platelet functional changes were diminished in the presence of SHS and AGE, as compared with the individual incubations.

Conclusions

Our data suggests that diabetics that are exposed to SHS may have a higher likelihood for cardiovascular disease development through a diminished endothelial cell viability and an increased platelet activity, which are partially mediated by CD41 and not CD62P. This study provides support for an increased cardiovascular risk for diabetic patients that are exposed to SHS. This study also provides a new experimental technique to monitor platelet-endothelial cell interactions.