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

Integrative Role of Albumin: Evolutionary, Biochemical and Pathophysiological Aspects

Being one of the main proteins in the human body and many animal species, albumin plays a crucial role in the transport of various ions, electrically neutral molecules and in maintaining the colloidal osmotic pressure of the blood. Albumin is able to bind almost all known drugs, many nutraceuticals and toxic substances, determining their pharmaco- and toxicokinetics. However, albumin is not only the passive but also the active participant of the pharmacokinetic and toxicokinetic processes possessing a number of enzymatic activities. Due to the thiol group of Cys34, albumin can serve as a trap for reactive oxygen and nitrogen species, thus participating in redox processes. The interaction of the protein with blood cells, blood vessels, and also with tissue cells outside the vascular bed is of great importance. The interaction of albumin with endothelial glycocalyx and vascular endothelial cells largely determines its integrative role. This review provides information of a historical nature, information on evolutionary changes, inflammatory and antioxidant properties of albumin, on its structural and functional modifications and their significance in the pathogenesis of some diseases.

Serum Albumin in Health and Disease: Esterase, Antioxidant, Transporting and Signaling Properties

Being one of the main proteins in the human body and many animal species, albumin plays a decisive role in the transport of various ions-electrically neutral and charged molecules-and in maintaining the colloidal osmotic pressure of the blood. Albumin is able to bind to almost all known drugs, as well as many nutraceuticals and toxic substances, largely determining their pharmaco- and toxicokinetics. Albumin of humans and respective representatives in cattle and rodents have their own structural features that determine species differences in functional properties. However, albumin is not only passive, but also an active participant of pharmacokinetic and toxicokinetic processes, possessing a number of enzymatic activities. Numerous experiments have shown esterase or pseudoesterase activity of albumin towards a number of endogeneous and exogeneous esters. Due to the free thiol group of Cys34, albumin can serve as a trap for reactive oxygen and nitrogen species, thus participating in redox processes. Glycated albumin makes a significant contribution to the pathogenesis of diabetes and other diseases. The interaction of albumin with blood cells, blood vessels and tissue cells outside the vascular bed is of great importance. Interactions with endothelial glycocalyx and vascular endothelial cells largely determine the integrative role of albumin. This review considers the esterase, antioxidant, transporting and signaling properties of albumin, as well as its structural and functional modifications and their significance in the pathogenesis of certain diseases.

Antithrombotic Treatment in Diabetes Mellitus: A Review of the Literature about Antiplatelet and Anticoagulation Strategies Used for Diabetic Patients in Primary and Secondary Prevention

Background:

Diabetes mellitus (DM) is on the rise globally. Its prevalence has nearly doubled during the last two decades and it is estimated to affect 8.8% of the global population. Cardiovascular disease (CVD) is the leading cause of death in diabetic population and despite modern anti-inflammatory and cardioprotective therapeutic strategies diabetic patients have at least a twice fold risk of cardiovascular events. Prothrombotic state in DM is associated with multiple determinants such as platelet alterations, oxidative stress, endothelial changes, circulating mediators. Thus, proper antithrombotic strategies to reduce the risk of CVD in this population is critical.

Methods:

This article reviews the current antiplatelet and anticoagulant agents in the aspect of primary and secondary prevention of CVD in the diabetic population.

Results:

The use of aspirin may be considered only at high-risk patients in the absence of contraindications. Cangrelor was not inferior to clopidogrel in preventing the composite outcome of CV death, myocardial infraction and revascularization without increasing major bleeding. Triple therapy in the subpopulation with DM significantly reduced the composite primary outcome of CV death, myocardial infraction or repeat target lesion revascularization. That was not the case for stent thrombosis, which was similar in both groups. Importantly, triple therapy did not result in increased bleeding complications, which were similar in both groups. However, cilostazol is linked to various adverse effects (e.g., headache, palpitations, and gastrointestinal disturbances) that drive many patients to withdrawal.

Conclusion:

In conclusion, DM is a rapidly growing disease that increases the risk of CVD, AF, and CV mortality. Proper antithrombotic strategies to reduce CVD risk in DM is a necessity. Also, new antithrombotic treatments and combination therapies may play a critical role to overcome antiplatelet resistance in DM patients and reduce morbidity and mortality attributed to CVD.

Impact of advanced glycation end products (AGEs) signaling in coronary artery disease

Coronary artery disease remains the leading cause of mortality in adult diabetic population with however, a high predominance also in non-diabetic subjects. In search of common molecular mechanisms and metabolic by-products with potential pathogenic role, increased advanced glycation end products (AGEs) present a critical biomarker for CAD development in both cases. Interaction of AGEs with their transmembrane cell receptor, RAGE in endothelial and smooth muscle cells as well as in platelets, activates intracellular signaling that leads to endothelial injury, modulation of vascular smooth muscle cell function and altered platelet activity. Furthermore, tissue accumulation of AGEs affects current treatment approaches being involved in stent restenosis. The present review provides an update of AGE-induced molecular mechanisms involved in CAD pathophysiology while it discusses emerging therapeutic interventions targeting AGE reduction and AGE-RAGE signaling with beneficial clinical outcome.

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.

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.

Altered platelets' morphological parameters in children with type 1 diabetes – a case-control study

BACKGROUND

Platelet hyperreactivity is a factor which contributes towards increased risk of cardiovascular events in adults with type 2 diabetes (T2DM). However, little is known about platelets' disturbances among children with type 1 diabetes (T1DM). The aim of the study was to investigate whether platelets' morphology or function are altered in children with type 1 diabetes, potentially predisposing them to cardiovascular events in the future.

METHODS

The study group consisted of 389 children with T1DM during the 2008-2010 period. Patients with acute diabetes complications and ongoing infections were excluded from the study. An equinumerous (N = 389), age and sex-matched control group was assembled from children undergoing routine, minor surgical procedures in the same hospital. Platelet: count (PLT), mean volume (MPV), distribution width (PDW) and platelet large cell ratio (P-LCR) as well as HbA1c levels were measured. For statistical analysis we used Chi-square tests, the student's t-test, one-way analysis of variance (ANOVA), the Pearson's correlation coefficient and linear regression models in order to adjust for covariates.

RESULTS

MPV, PDW and P-LCR were significantly higher among children with diabetes in comparison with the control group (MPV 10.47+/-0.85 fL vs 10.23+/-0.94 fL, p = 0.0007; PDW 12.09+/-1.80% vs 11.66+/-1.90%, p = 0.0032; P-LCR 28.21+/-6.15% vs 26.29+/-6.38%, p < 0.0001). PLT however, were shown to be similar (263.55+/-60.04 vs 268.77+/-65.78 10(3)/μl; p = 0.5637). In both cases and controls age was inversely correlated with platelet count (for study group: r = -0.30, p < 0.0001; for control group: r = -0.34, p < 0.0001), positively correlated with MPVs (r = 0.20, p < 0.0001; r = 0.26, p < 0.0001), PDW (r = 0.25, p < 0.0001 and r = 0.24, p < 0.0001) and P-LCR (r = 0.26, p < 0.0001; r = 0.26, p < 0.0001). After adjustment for confounding factors, higher platelet counts were associated with poorer metabolic control (beta = 0.20; 0.0001).

CONCLUSIONS

Platelets of paediatric patients with T1DM show morphological evidence of hyperreactivity (higher MPV, PDW and P-LCR), while poorer metabolic control increases their number potentially predisposing the patients to future cardiovascular events.