Plasma levels of platelet-derived microparticles in patients with obstructive sleep apnea syndrome

Obstructive Sleep Apnea, Platelet Aggregation, and Cardiovascular Risk

BACKGROUND

Although related, the precise mechanisms linking obstructive sleep apnea (OSA) and cardiovascular disease (CVD) are unclear. Platelets are mediators of CVD risk and thrombosis and prior studies suggested associations of OSA and platelet activity. The aim of this study is to assess the link between OSA, platelet activity, and CVD-related risk factors.

METHODS AND RESULTS

We studied the association of OSA-measures and platelet aggregation in participants dually enrolled in the SHHS (Sleep Heart and Health Study) and FHS (Framingham Heart Study). We applied linear regression models with adjustment for demographic and clinical covariates and explored interactions with OSA and CVD-related factors, including age, sex, body mass index, hypertension, OSA diagnosis (apnea-hypopnea index 4%≥5), and aspirin use. Our final sample was of 482 participants (60 years [14.00], 50.4% female). No associations were observed between apnea-hypopnea index 4% and platelet aggregation in the main sample. Stratified analysis revealed an association in aspirin users (n=65) for our primary exposure (apnea-hypopnea index 4%, β=0.523; P<0.001; n=65), and secondary exposures: hypoxic burden (β=0.358; P<0.001), minimum saturation (β=-0.519; P=0.026), and oxygen desaturation index 3% (β=74.672; P=0.002). No associations were detected in nonaspirin users (n=417).

CONCLUSIONS

No associations were detected between OSA and platelet aggregation in a community sample. Our finding that OSA associates with increased platelet aggregation in the aspirin group, most of whom use it for primary prevention of CVD, suggests that platelet aggregation may mediate the adverse impact of OSA on vascular health in individuals with existing CVD risk, supporting further investigation.

The Associations of Platelet Activation and Coagulation Parameters with Obstructive Sleep Apnoea: A Large-Scale Observational Study

OBJECTIVES

Obstructive sleep apnoea (OSA) is associated with an increased risk of cardiovascular disease, with alterations in coagulability suspected as the mediating factor. This study explored blood coagulability and breathing-related parameters during sleep in patients with OSA.

DESIGN

Cross-sectional observational study. Setting. Shanghai Sixth People's Hospital. Participants. 903 patients diagnosed by standard polysomnography. Main Outcome and Measures. The relationships between coagulation markers and OSA were evaluated using Pearson's correlation, binary logistic regression, and restricted cubic spline (RCS) analyses.

RESULTS

The platelet distribution width (PDW) and activated partial thromboplastin time (APTT) decreased significantly with increasing OSA severity (both p < 0.001). PDW was positively associated with the apnoea-hypopnea index (AHI), oxygen desaturation index (ODI), and microarousal index (MAI) (ß = 0.136, p < 0.001; ß = 0.155, p < 0.001; and ß = 0.091, p = 0.008, respectively). APTT was negatively correlated with AHI (ß = -0.128, p < 0.001) and ODI (ß = -0.123, p = 0.001). PDW was negatively correlated with percentage of sleep time with oxygen saturation below 90%(CT90) (ß = -0.092, p = 0.009). The minimum arterial oxygen saturation (SaO₂) correlated with PDW (ß = -0.098, p = 0.004), APTT (ß = 0.088, p = 0.013), and prothrombin time (PT) (ß = 0.106, p = 0.0003). ODI was risk factors for PDW abnormalities (odds ratio (OR) = 1.009, p = 0.009) after model adjustment. In the RCS, a nonlinear dose-effect relationship was demonstrated between OSA and the risk of PDW and APTT abnormalities.

CONCLUSION

Our study revealed nonlinear relationships between PDW and APTT, and AHI and ODI, in OSA, with AHI and ODI increasing the risk of an abnormal PDW and thus also the cardiovascular risk. This trial is registered with ChiCTR1900025714.

Association Between the Severity of Obstructive Sleep Apnea and the Risk Stratification of Acute Pulmonary Embolism

Obstructive sleep apnea (OSA) has been associated with the initiation and progression of cardiovascular disease. This study aimed to explore the relationship between the severity of OSA and the risk stratification of acute pulmonary embolism (PE). In this single-center cohort study, patients diagnosed with PE were evaluated for OSA via polygraphy monitoring. The simplified PE severity index (sPESI) and the number of patients requiring systemic thrombolysis were used to determine the severity of the disease. Echocardiography was performed on all participants. All patients were divided into 2 groups (OSA group and non-OSA group), and the patients in OSA group were then divided into 3 groups based on the severity of OSA. Patients with severe OSA had a significantly higher number of patients with sPESI ≥ 1 (P = .005). A higher proportion of patients with severe OSA require systemic thrombolysis (P = .010). Patients with apnea-hypopnea index (AHI) > 30/h had a much higher fibrinogen (P = .004) and D-dimer (P = .040) level than those in the non-OSA group. The levels of creatinine were significantly higher in patients with OSA (P = .040). Echocardiography showed a significant difference in left ventricular ejection fraction (LVEF) between patients in non-OSA and severe OSA groups (P = .035). And brain natriuretic peptide (BNP) also exhibited a progressive worsening related to the deepest desaturation and oxygen desaturation index. OSA, especially with AHI > 30/h, is correlated with the severity and prognosis of acute PE. This might be attributed to the prothrombotic effect, renal impairment, and cardiac dysfunction in patients with severe OSA.

Extracellular Vesicles and Hypertension

Hypertension implicates multiple organs and systems, accounting for the majority of cardiovascular diseases and cardiac death worldwide. Extracellular vesicles derived from various types of cells could transfer a variety of substances such as proteins, lipids, and nucleic acids from cells to cells, playing essential roles in both physiological and pathological processes. Extracellular vesicles are demonstrated to be closely associated with the development of essential hypertension by mediating the renin-angiotensin-aldosterone system and crosstalk between multiple vascular cells. Extracellular vesicles also participate in various kinds of pathogenesis of secondary hypertensions including acute kidney injury, renal parenchymal diseases, kidney transplantation, secretory diseases (primary aldosteronism, pheochromocytoma and paraganglioma, Cushing's syndrome), and obstructive sleep apnea. Extracellular vesicles have been proved to have the potential to be served as new biomarkers in the diagnosis, treatment, and prognosis assessment of hypertension. In the future, large multicenter cohorts are highly in demand for further verifying the sensitivity and specificity of extracellular vesicles as biomarkers.

Intermittent Hypoxia and Atherosclerosis: From Molecular Mechanisms to the Therapeutic Treatment

Intermittent hypoxia (IH) has a dual nature. On the one hand, chronic IH (CIH) is an important pathologic feature of obstructive sleep apnea (OSA) syndrome (OSAS), and many studies have confirmed that OSA-related CIH (OSA-CIH) has atherogenic effects involving complex and interacting mechanisms. Limited preventive and treatment methods are currently available for this condition. On the other hand, non-OSA-related IH has beneficial or detrimental effects on the body, depending on the degree, duration, and cyclic cycle of hypoxia. It includes two main states: intermittent hypoxia in a simulated plateau environment and intermittent hypoxia in a normobaric environment. In this paper, we compare the two types of IH and summarizes the pathologic mechanisms and research advances in the treatment of OSA-CIH-induced atherosclerosis (AS), to provide evidence for the systematic prevention and treatment of OSAS-related AS.

Blood Cell-Derived Microvesicles in Hematological Diseases and beyond

Microvesicles or ectosomes represent a major type of extracellular vesicles that are formed by outward budding of the plasma membrane. Typically, they are bigger than exosomes but smaller than apoptotic vesicles, although they may overlap with both in size and content. Their release by cells is a means to dispose redundant, damaged, or dangerous material; to repair membrane lesions; and, primarily, to mediate intercellular communication. By participating in these vital activities, microvesicles may impact a wide array of cell processes and, consequently, changes in their concentration or components have been associated with several pathologies. Of note, microvesicles released by leukocytes, red blood cells, and platelets, which constitute the vast majority of plasma microvesicles, change under a plethora of diseases affecting not only the hematological, but also the nervous, cardiovascular, and urinary systems, among others. In fact, there is evidence that microvesicles released by blood cells are significant contributors towards pathophysiological states, having inflammatory and/or coagulation and/or immunomodulatory arms, by either promoting or inhibiting the relative disease phenotypes. Consequently, even though microvesicles are typically considered to have adverse links with disease prognosis, progression, or outcomes, not infrequently, they exert protective roles in the affected cells. Based on these functional relations, microvesicles might represent promising disease biomarkers with diagnostic, monitoring, and therapeutic applications, equally to the more thoroughly studied exosomes. In the current review, we provide a summary of the features of microvesicles released by blood cells and their potential implication in hematological and non-hematological diseases.

Role of Circulating Microparticles in Type 2 Diabetes Mellitus: Implications for Pathological Clotting

Type 2 diabetes mellitus (T2DM) is a multifactorial chronic metabolic disease characterized by chronic hyperglycemia due to insulin resistance and a deficiency in insulin secretion. The global diabetes pandemic relates primarily to T2DM, which is the most prevalent form of diabetes, accounting for over 90% of all cases. Chronic low-grade inflammation, triggered by numerous risk factors, and the chronic activation of the immune system are prominent features of T2DM. Here we highlight the role of blood cells (platelets, and red and white blood cells) and vascular endothelial cells as drivers of systemic inflammation in T2DM. In addition, we discuss the role of microparticles (MPs) in systemic inflammation and hypercoagulation. Although once seen as inert by-products of cell activation or destruction, MPs are now considered to be a disseminated storage pool of bioactive effectors of thrombosis, inflammation, and vascular function. They have been identified to circulate at elevated levels in the bloodstream of individuals with increased risk of atherothrombosis or cardiovascular disease, two significant hallmark conditions of T2DM. There is also general evidence that MPs activate blood cells, express proinflammatory and coagulant effects, interact directly with cell receptors, and transfer biological material. MPs are considered major players in the pathogenesis of many systemic inflammatory diseases and may be potentially useful biomarkers of disease activity and may not only be of prognostic value but may act as novel therapeutic targets.

Coagulation and Fibrinolysis in Obstructive Sleep Apnoea

Obstructive sleep apnoea (OSA) is a common disease which is characterised by repetitive collapse of the upper airways during sleep resulting in chronic intermittent hypoxaemia and frequent microarousals, consequently leading to sympathetic overflow, enhanced oxidative stress, systemic inflammation, and metabolic disturbances. OSA is associated with increased risk for cardiovascular morbidity and mortality, and accelerated coagulation, platelet activation, and impaired fibrinolysis serve the link between OSA and cardiovascular disease. In this article we briefly describe physiological coagulation and fibrinolysis focusing on processes which could be altered in OSA. Then, we discuss how OSA-associated disturbances, such as hypoxaemia, sympathetic system activation, and systemic inflammation, affect these processes. Finally, we critically review the literature on OSA-related changes in markers of coagulation and fibrinolysis, discuss potential reasons for discrepancies, and comment on the clinical implications and future research needs.

Analysis of Circulating Microvesicles Levels and Effects of Associated Factors in Elderly Patients With Obstructive Sleep Apnea

Background: The incidence of obstructive sleep apnea (OSA) in the elderly is high, and the disorder is associated with a variety of chronic diseases. Microvesicles (MVs) are extracellular vesicles secreted by various cells during stimulation or apoptosis that play an important role in the pathogenesis of OSA. However, concentrations of circulating MVs in elderly patients with OSA remain unclear.

Methods: Patients aged >60 years old were recruited and underwent polysomnography. Circulating plasma MV concentrations, including annexin V⁺MVs, endothelial MVs (EMVs), platelet MVs (PMVs), and leukocyte MVs (LMVs) levels, were measured using a flow cytometer with different labeling methods. Potential factors affecting the concentration of circulating MVs in elderly patients with OSA were determined via Spearman's correlation and multiple linear regression analysis.

Results: Levels of circulating MVs, including both single- (annexin V⁺MVs, CD144⁺EMVs, CD41a⁺PMVs, and CD45⁺LMVs) and dual-labeled MVs (annexin V⁺CD144⁺EMVs), were elevated in elderly patients with OSA. Circulating MVs were positively correlated with OSA severity (AHI, ODI, and SPO_2min). To some extent, obesity affected the MV concentrations in elderly patients with OSA. In addition, age and comorbidities may be associated with MV levels, but the correlations between the MV levels and age or comorbidities were not significant.

Conclusion: Concentrations of circulating MVs in elderly patients with OSA are associated with the labeling method used, OSA severity, and obesity. The effects of age and comorbidities on circulating MV levels require further verification using a larger sample size.

Procoagulant State of Sleep Apnea Depends on Systemic Inflammation and Endothelial Damage

INTRODUCTION

Growing evidence shows a hypercoagulable state in obstructive sleep apnea (OSA) that could be a risk factor for thromboembolic disease.

OBJECTIVES

We aimed to elucidate mechanisms involved in the procoagulant profile observed in patients with OSA and to investigate the potential utility of global tests in its characterization.

METHODS

Thirty-eight patients with severe OSA without previous history of thrombosis and nineteen healthy age- and sex-matched controls were included. Kinetic of clot formation was determined using rotational thromboelastometry. Haemostatic capacity of plasma and microparticles was determined by Calibrated Automated Thrombinography. Platelet surface receptors, activation markers and formation of platelet/leukocytes aggregates were analyzed by flow cytometry.

RESULTS

Thromboelastometry showed a procoagulant state in patients with OSA that did not seem to be related to a basal activation of platelets but by the increased existence of platelet/leukocyte aggregates. Patients with OSA presented many signs of endothelial damage such as increased plasma levels of E-selectin and cfDNA and enhanced thrombin generation due to the presence of microparticles rich in tissue-factor, which is related to OSA severity.

CONCLUSIONS

OSA induces an enhancement in the dynamics of clot formation which appears to be caused by at least two pathological mechanisms. First, a greater formation of platelet-leukocyte aggregates; secondly, endothelial damage which provokes a greater procoagulant potential due to the increase in tissue factor-rich microparticles. Moreover, this study has identified thromboelastometry and thrombin generation assay as useful tools to evaluate the prothrombotic state in these patients.

Cardiovascular morbidities of obstructive sleep apnea and the role of circulating extracellular vesicles

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway collapse during sleep resulting in impaired blood gas exchange, namely intermittent hypoxia (IH) and hypercapnia, fragmented sleep (SF), increased oxidative stress and systemic inflammation. Among a myriad of potential associated morbidities, OSA has been particularly implicated as mechanistically contributing to the prevalence and severity of cardiovascular diseases (CVD). However, the benefits of continuous positive airway pressure (CPAP), which is generally employed in OSA treatment, to either prevent or improve CVD outcomes remain unconvincing, suggesting that the pathophysiological mechanisms underlying the incremental CVD risk associated with OSA are not clearly understood. One of the challenges in development of non-invasive diagnostic assays is the ability to identify clinically and mechanistically relevant biomarkers. Circulating extracellular vesicles (EVs) and their cargos reflect underlying changes in cellular homeostasis and can provide insights into how cells and systems cope with physiological perturbations by virtue of the identity and abundance of miRNAs, mRNAs, proteins, and lipids that are packaged in the EVs under normal as well as diseased states, such as OSA. EVs can not only provide unique insights into coordinated cellular responses at the organ or systemic level, but can also serve as reporters of the effects of OSA in CVD, either by their properties enabling regeneration and repair of injured vascular cells or by damaging them. Here, we highlight recent progress in the pathological CVD consequences of OSA, and explore the putative roles of EVs in OSA-associated CVD, along with emerging diagnostic and therapeutic opportunities.

The reviews of this paper are available via the supplemental material section.

The release of phosphorylated-HSP27 from activated platelets of obstructive sleep apnea syndrome (OSAS) patients

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is a well known risk of arterial thrombosis that results in cardiovascular morbidity. It has been reported that platelet aggregability is enhanced in patients with OSAS. In the present study, we investigated whether phosphorylated-HSP27 is released from the activated platelets of OSAS patients.

METHODS

Patients diagnosed with OSAS (n = 21) were recruited, and platelet-rich plasma (PRP) was stimulated by ADP, ristosetin, collagen, and thrombin receptor-activating peptide. Platelet aggregation was measured using an aggregometer with a laser-scattering system. The levels of protein phosphorylation and the released levels of phosphorylated-HSP27 were determined by Western blot analysis and an ELISA, respectively.

RESULTS

The phosphorylation of HSP27 in the platelets was induced by the stimulators. The released levels of phosphorylated-HSP27 was correlated with the levels of phosphorylated-HSP27 stimulated by ADP or collagen. The levels of ADP-induced phosphorylated-HSP27 were correlated with those of both phosphorylated-protein kinase B (Akt) and phosphorylatd-p38 mitogen-activated protein kinase; however, the levels of phosphorylated-HSP27 stimulated by collagen were correlated with phosphorylated-Akt levels only. The ED₅₀ value of ADP on the platelet aggregation in OSAS (1.067 ± 0.128 μM) was lower than that in healthy subjects (1.778 ± 0.122 μM) and was inversely correlated with both the value of minimum SpO₂ and the released level of phosphorylated-HSP27 stimulated by ADP.

CONCLUSION

The results strongly suggest that phosphorylated-HSP27 is released from the activated platelets of OSAS patients.

Cardiovascular Consequences of Obstructive Sleep Apnea

PURPOSE OF REVIEW

To review the clinical evidence for a relationship between obstructive sleep apnea and hypertension, arrhythmias, coronary artery disease, and congestive heart failure.

RECENT FINDINGS

Current data show that obstructive sleep apnea is a risk for cardiovascular disease. Studies have linked untreated moderate to severe obstructive sleep apnea to hypertension, cardiac arrhythmias, coronary artery disease, and congestive heart failure. However, uncertainty regarding benefits of treatment of obstructive sleep apnea to reduce the risk of cardiovascular disease still exists. The issue of poor compliance has been an on-going limitation of CPAP trials. Evidence shows obstructive sleep apnea is a risk factor for cardiovascular disease but trials have yet to clarify if cardiovascular disease morbidity and mortality decreases with treatment of the apnea. Future treatment trials are needed to address the question of whether treatment decreases cardiovascular risk in patients with obstructive sleep apnea.

Sleep Disordered Breathing and Cardiovascular Diseases

Sleep disordered breathing (SDB), which causes sleep deprivation, intermittent hypoxia, and negative intrathoracic pressure swings, can be accompanied by other harmful pathophysiologies relating to cardiovascular diseases (CVD), including sudden death, atrial fibrillation, stroke, and coronary artery disease leading to heart failure. Continuous positive airway pressure (CPAP) therapy for SDB has been reported to provide favorable effects such as lowered systemic blood pressure and improved endothelial function. However, in recent randomized controlled trials, CPAP has failed to demonstrate its beneficial prognostic impact on the primary or secondary setting of CVD. In this review article, we describe the characteristics of SDB complicated with CVD, the prognostic impacts of SDB in CVD, and the beneficial effects of CPAP on CVD.

Obstructive sleep apnoea and venous thromboembolism: pathophysiological links and clinical implications

Obstructive sleep apnoea (OSA) and pulmonary embolism (PE) remain major health issues worldwide. Data from pathophysiological studies suggest that both intermittent hypoxia and sleep fragmentation are associated with increased blood coagulability, endothelial dysfunction and venous stasis. There is growing evidence that OSA is potentially prevalent in and a risk factor for PE. Conversely, patients with acute PE have two to four times greater risk of moderate-to-severe OSA. The role of continuous positive airway pressure (CPAP) treatment in improving clinically meaningful outcomes in PE patients remains unclear, although some authors have suggested that CPAP could improve the hypercoagulability state and normalise circadian alterations in some of the coagulation molecules, as observed in patients with OSA. Emerging research highlights the complex interdependent relationships between OSA and PE, emphasising the need for rigorous, well-powered trials that address the impact of OSA and its treatment on the prevention and management of PE. Undoubtedly, these will require closer collaboration between the sleep medicine and clinical/venous thromboembolism communities.

Obstructive Sleep Apnea: From Intermittent Hypoxia to Cardiovascular Complications via Blood Platelets

Obstructive sleep apnea is a chronic condition characterized by recurrent episodes of apneas or hypopneas during sleep leading to intermittent hypoxemia and arousals. The prevalence of the sleep disordered breathing is estimated that almost 50% of men and 24% of women suffer from moderate to severe form of the disorder. Snoring, collapse of upper airways and intermittent hypoxia are main causes of smoldering systemic inflammation in patients suffering from obstructive sleep apnea. The systematic inflammation is considered one of the key mechanisms leading to significant cardiovascular complications. Blood platelets, formerly not even recognized as cells, are currently gaining attention as crucial players in the immune continuum. Platelet surface is endowed with receptors characteristic for cells classically belonging to the immune system, which enables them to recognize pathogens, immune complexes, and interact in a homo- and heterotypic aggregates. Platelets participate in the process of transcellular production of bioactive lipids by delivering both specific enzymes and substrate molecules. Despite their lack of nucleus, platelets synthetize proteins in a stimuli-dependent manner. Atherosclerosis and consequent cardiovascular complications result from disruption in homeostasis of both of the platelet roles: blood coagulation and inflammatory processes modulation. Platelet parameters, routinely evaluated as a part of complete blood count test, were proposed as markers of cardiovascular comorbidity in patients with obstructive sleep apnea. Platelets were found to be excessively activated in this group of patients, especially in obese subjects. Persistent activation results in enhanced spontaneous aggregability and change in cytokine production. Platelet-lymphocyte ratio was suggested as an independent marker for cardiovascular disease in obstructive sleep apnea syndrome and continuous positive air pressure therapy was found to have an impact on platelet parameters and phenotype. In this literature review we summarize the current knowledge on the subject of platelets involvement in obstructive sleep apnea syndrome and consider the possible pathways in which they contribute to cardiovascular comorbidity.

Extracellular Vesicle MicroRNA Transfer in Lung Diseases

MicroRNAs (miRNAs) are single-stranded, small non-coding RNAs that ate involved in the transcriptional and post-transcriptional regulation of gene expression. Recently, miRNAs were demonstrated to be effectively delivered to a target cell or tissue from a host cell via extracellular vesicles (EVs). These EVs can be detected in blood, urine, exhaled breath condensates, bronchoalveolar lavage fluid (BALF), and other fluids. miRNAs are generated by donor cells and then packaged into EVs and delivered with intact functionality. After being delivered to the target cells, they regulate the translation of their target genes and the function of the target cells. Thus, EV transported miRNAs have become a new method for intercellular communication. EV miRNA transfer is well-documented in various pulmonary diseases, such as chronic obstructive pulmonary disease (COPD), asthma, pulmonary hypertension, and acute lung injury (ALI). In this review, we summarize the novel findings of EV miRNA transfer, focusing on the roles of miR-210, miR-200, miR-17, miR-146a, miR-155, and other miRNAs that are transported from primary human bronchial epithelial cells (HBECs), BALF, mesenchymal stem cells, and dendritic cells.

[Membranous microparticles and respiratory disease]

Microparticles (MP) are plasmic membrane fragments released from cells after physiological stimulation or stress conditions like inflammation or infection. Their production is correlated to the rate of cell apoptosis. All types of cells can produce MP but they are produced mainly by platelets, endothelial cells, and leukocytes. They carry many bio-active molecules on their surface, specific to the parental cell, giving them the ability to be biomarkers and bio-effectors. MP are present in circulating blood, tissues and many biological fluids. Circulating MP levels can change during the course of many diseases. They have been the subject of many studies in the fields of cardiovascular disease and oncology. In the lungs, they are present in circulating blood and in the airways. They seem to have a role in pulmonary homeostasis in physiological situations and also in the expression of several disease processes. In this review of the literature, we were interested in the quantitative and qualitative variations in MP and their impact in airway diseases like chronic obstructive pulmonary disease (COPD) and asthma, pulmonary fibrosis and pulmonary hypertension.

Sustained apnea induces endothelial activation

BACKGROUND

Apnea diving has gained worldwide popularity, even though the pathophysiological consequences of this challenging sport on the human body are poorly investigated and understood. This study aims to assess the influence of sustained apnea in healthy volunteers on circulating microparticles (MPs) and microRNAs (miRs), which are established biomarkers reflecting vascular function.

HYPOTHESIS

Short intermittent hypoxia due to voluntary breath-holding affects circulating levels of endothelial cell-derived MPs (EMPs) and endothelial cell-derived miRs.

METHODS

Under dry laboratory conditions, 10 trained apneic divers performed maximal breath-hold. Venous blood samples were taken, once before and at 4 defined points in time after apnea. Samples were analyzed for circulating EMPs and endothelial miRs.

RESULTS

Average apnea time was 329 seconds (±103), and SpO₂ at the end of apnea was 79% (±12). Apnea was associated with a time-dependent increase of circulating endothelial cell-derived EMPs and endothelial miRs. Levels of circulating EMPs in the bloodstream reached a peak 4 hours after the apnea period and returned to baseline levels after 24 hours. Circulating miR-126 levels were elevated at all time points after a single voluntary maximal apnea, whereas miR-26 levels were elevated significantly only after 30 minutes and 4 hours. Also miR-21 and miR-92 levels increased, but did not reach the level of significance.

CONCLUSIONS

Even a single maximal breath-hold induces acute endothelial activation and should be performed with great caution by subjects with preexisting vascular diseases. Voluntary apnea might be used as a model to simulate changes in endothelial function caused by hypoxia in humans.

Antiplatelet activity of flavonoid and coumarin drugs

Polyphenols are used as phlebotonic drugs, but their mechanism of action remains unknown. Since platelet activity and platelet-endothelial cell interactions are involved in the pathogenesis of cardiovascular disease, this work examines whether different flavonoid and coumarin drugs are able to inhibit platelet aggregation. This specific case of coumarins, the antiplatelet effect is not linked with a possible interaction over blood coagulation since this effect only dicoumarols have it. The antiplatelet capacity of polyphenols was assayed using peripheral blood platelets from healthy controls. The distribution of the different platelets subsets was quantified by flow cytometry, using the calcium ionophore as a pro-aggregant. The number of GPIIb/IIIa receptors occupied by the drugs was assayed by flow cytometry using two CD61 surface fluorescein antibodies. All the polyphenols tested inhibited platelet aggregation. A percentage antiplatelet activity of 88.91±7.98% was recorded for naringin, 48.43±8.84% for naringenin, 53.83±7.87% for esculetin, 54.65±6.91% for fraxetin, and 25.75±4.12% for coumarin. Naringin showed significantly greater percentage occupation of GPIIb/IIIa receptors than did naringenin (14.82±0.81% vs. 3.90±0.55%), and esculetin returned significantly higher values than fraxetin and coumarin (12.47±0.97 vs. 7.53±0.49 and 7.90±0.69 respectively). All drugs show important antiplatelet activity. Naringin was the best antiplatelet compound, showing the greatest antiplatelet activity and the highest percentage binding of GPIIb/IIIa receptors. However, any of the compounds used could be used in the prevention of cardiovascular disease.

Obstructive Sleep Apnea in Acute Stroke: A Role for Systemic Inflammation

BACKGROUND AND PURPOSE

Sleep-disordered breathing is common among patients with stroke resulting in 4- to 6-fold higher prevalence of obstructive sleep apnea (OSA). We prospectively evaluated clinical characteristics and laboratory markers of inflammation and coagulability associated with OSA severity during the acute post stroke period.

METHODS

Consecutive patients admitted to the department of Neurology after an acute ischemic stroke were evaluated during the first 48 hours of symptom onset using Watch peripheral arterial tonometry, a wrist-worn ambulatory sleep study device that utilizes peripheral arterial tonometry. Morning blood samples of the patient were tested for tumor necrosis factor, interleukin-6, and plasminogen activator inhibitor-1 levels.

RESULTS

A total of 43 patients with acute stroke were admitted during the study period, 22 (51%) of which have been found to have moderate sleep apnea (apnea hypopnea index [AHI]≥15), AHI≥5 was found in 86% of the patients, and severe OSA (AHI≥30) in 32.5%. Patients with OSA (AHI≥15) did not differ from the rest in stroke severity or symptoms, yet they had higher prevalence of recurrent stroke and atrial fibrillation. All 3 biomarkers levels were higher among patients with AHI≥15: tumor necrosis factor (6.39 versus 3.57 pg/mL), interleukin-6 (6.64 versus 3.14 pg/mL), and plasminogen activator inhibitor-1 (176.64 versus 98.48 pg/mL). After the stratification of AHI into 3 groups (AHI<5, 5-14, and ≥15), the analysis showed that only the highest AHI group differed from the other 2 groups in biomarkers levels.

CONCLUSIONS

Use of bed-side somnography technology revealed that in an unselected sample of patients with acute ischemic stroke, almost 90% had sleep-disordered breathing with third having severe form of the disorder. Sleep-disordered breathing was associated with significantly increased levels of inflammatory biomarkers, providing possible pathophysiological explanation of OSA-associated stroke risk. These results warrant prospective screening of patients with stroke for the presence of sleep-disordered breathing and lay the rationale for an interventional trial.

Dynamic microvesicle release and clearance within the cardiovascular system: triggers and mechanisms

Interest in cell-derived microvesicles (or microparticles) within cardiovascular diagnostics and therapeutics is rapidly growing. Microvesicles are often measured in the circulation at a single time point. However, it is becoming clear that microvesicle levels both increase and decrease rapidly in response to certain stimuli such as hypoxia, acute cardiac stress, shear stress, hypertriglyceridaemia and inflammation. Consequently, the levels of circulating microvesicles will reflect the balance between dynamic mechanisms for release and clearance. The present review describes the range of triggers currently known to lead to microvesicle release from different cellular origins into the circulation. Specifically, the published data are used to summarize the dynamic impact of these triggers on the degree and rate of microvesicle release. Secondly, a summary of the current understanding of microvesicle clearance via different cellular systems, including the endothelial cell and macrophage, is presented, based on reported studies of clearance in experimental models and clinical scenarios, such as transfusion or cardiac stress. Together, this information can be used to provide insights into potential underlying biological mechanisms that might explain the increases or decreases in circulating microvesicle levels that have been reported and help to design future clinical studies.

Adenosine Diphosphate-Induced Platelets Aggregability in Polysomnographically Verified Obstructive Sleep Apnea

Obstructive sleep apnea syndrome (OSAS) is a risk factor for arterial thrombosis and cardiovascular morbidity. Activated platelets play key roles in the development of atherothrombosis, thus may be involved in these complications of OSAS. Herein, we evaluated the relationship between severity of OSAS and the degree of platelet aggregates as a marker of activated platelets in 64 patients with OSAS. Platelet aggregations were determined by means of optical aggregometry, using adenosine diphosphate (ADP) as an agonist. Compared with the control group, ADP-induced platelet aggregability was increased in patients with total OSAS, severe OSAS, and in mild to moderate OSAS. Moreover, ADP-induced platelet aggregation was correlated with the Epworth sleepiness scale (ESS) in patients with severe OSAS. Obstructive sleep apnea syndrome is associated with enhanced platelets aggregations, which may predispose the cardiovascular sequels. The ESS may be important in predicting platelet activation and thus atherothrombotic complications in those with OSAS.

Obstructive sleep apnea syndrome: coagulation anomalies and treatment with continuous positive airway pressure

INTRODUCTION

Obstructive sleep apnea syndrome (OSAS) is a highly prevalent sleep disorder associated with severe cardiovascular events, morbidity and mortality. Recent evidence has highlighted OSAS as an independent risk factor for an excessive platelet activation and arterial thrombosis, but the underlying mechanisms have not yet been determined. Studies in cell culture and animal models have significantly increased our understanding of the mechanisms of inflammation in OSAS. Hypoxia is a critical pathophysiological element that leads to an intense sympathetic activity, in association with systemic inflammation, oxidative stress and procoagulant activity. While platelet dysfunction and/or hypercoagulability play an important role in the pathogenesis of vascular disease, there are limited studies on the potential role of blood viscosity in the development of vascular disease in OSAS.

CONCLUSION

Further studies are required to determine the precise role of hypercoagulability in the cardiovascular pathogenesis of OSAS, particularly its interaction with oxidative stress, thrombotic tendency and endothelial dysfunction. Nasal continuous positive airway pressure (nCPAP), the gold standard treatment for OSAS, not only significantly reduced apnea-hypopnoea indices but also markers of hypercoagulability, thus representing a potential mechanisms by which CPAP reduces the rate of cardiovascular morbidity and mortality in OSAS patients.

Procoagulant and platelet-derived microvesicle absolute counts determined by flow cytometry correlates with a measurement of their functional capacity

BACKGROUND

Flow cytometry is the most commonly used technology to measure microvesicles (MVs). Despite reported limitations of this technique, MV levels obtained using conventional flow cytometry have yielded many clinically relevant findings, such as associations with disease severity and ability to predict clinical outcomes. This study aims to determine if MV enumeration by flow cytometry correlates with a measurement of their functional capacity, as this may explain how flow cytometry generates clinically relevant results.

METHODS

ONE HUNDRED SAMPLES FROM HEALTHY INDIVIDUALS AND PATIENTS WITH OBSTRUCTIVE SLEEP APNOEA WERE ANALYSED BY CONVENTIONAL FLOW CYTOMETRY (FACSCALIBUR) AND BY THREE FUNCTIONAL MV ASSAYS: Zymuphen MP-activity in which data were given as phosphatidylserine equivalent, STA(®) Phospholipid Procoag Assay expressed as clotting time and Endogenous Thrombin Potential (ETP) reflecting in vitro thrombin generation. Correlations were determined by Spearman correlation.

RESULTS

Absolute counts of lactadherin+ procoagulant MVs generated by flow cytometry weakly correlated with the results obtained from the Zymuphen MP-activity (r=0.5370, p<0.0001); correlated with ETP (r=0.7444, p<0.0001); negatively correlated with STA(®) Phospholipid Procoag Assay clotting time (-0.7872, p<0.0001), reflecting a positive correlation between clotting activity and flow cytometry. Levels of Annexin V+ procoagulant and platelet-derived MVs were also associated with functional assays. Absolute counts of MVs derived from other cell types were not correlated with the functional results.

CONCLUSIONS

Quantitative results of procoagulant and platelet-derived MVs from conventional flow cytometry are associated with the functional capability of the MVs, as defined by three functional MV assays. Flow cytometry is a valuable technique for the quantification of MVs from different cellular origins; however, a combination of several analytical techniques may give the most comprehensive information on the role of MVs in health and disease.

Impact of obstructive sleep apnea treatment by continuous positive airway pressure on cardiometabolic biomarkers: a systematic review from sham CPAP randomized controlled trials

Reducing cardiometabolic risk may represent an important target for effective obstructive sleep apnea (OSA) treatment. The impact of continuous positive airway pressure (CPAP), the first line therapy of OSA, on metabolic or inflammatory markers is still debated. A systematic literature search using several databases was performed. We provide a systematic analysis of randomized studies comparing therapeutic versus sham CPAP intervention and also include studies using a CPAP withdrawal design. We addressed the impact of CPAP on the following cardiometabolic biomarkers: 1) plasma and urine catecholamines and their metabolites that reflect sympathetic activity; 2) insulin resistance and lipid metabolism biomarkers; 3) oxidative stress, systemic and vascular inflammation biomarkers; 4) liver enzymes highlighting the association between OSA and nonalcoholic fatty liver disease (NAFLD); 5) coagulation biomarkers. The impact of CPAP on sympathetic activity is robust across studies and occurs rapidly. In contrast to sympathetic activity, the well-designed studies included in this review failed to demonstrate that CPAP alters metabolic or inflammatory markers in OSA. CPAP did not change glucose, lipids, insulin resistance levels or the ratio of patients with metabolic syndrome. In unselected OSA patients, it is not realistic to expect a clinically relevant decrease in cardiometabolic biomarkers with CPAP therapy.

The association between sleep characteristics and prothrombotic markers in a population-based sample: Chicago Area Sleep Study

BACKGROUND AND AIM

Short sleep duration and poor quality sleep are associated with coronary heart disease (CHD) mortality; however, the underlying pathophysiologic process remains unclear. Sleep apnea may confound the association because of its relationship with formation of thrombi, the vascular occlusive process in CHD. We tested whether sleep duration and quality were associated with prothrombotic biomarkers in adults with a low probability of apnea.

METHODS

We included adults aged 35-64 years recruited from the community and who had an apnea hypopnea index <15 after one night of screening (n=506). Sleep duration and maintenance were determined from 7 days of wrist actigraphy; daytime sleepiness was estimated using the Epworth Sleepiness Scale. Factor VIII (FVIII), von Willebrand factor (vWF), thrombin antithrombin (TAT) complexes, and plasminogen activator inhibitor-1 (PAI-1) were measured in fasting blood.

RESULTS

Sleep duration, maintenance, and daytime sleepiness were not associated with FVIII, vWf, or TAT. Sleep maintenance was modestly inversely associated with higher levels of log-transformed PAI-1 (β = -0.07, standard error (SE)=0.03 per 4.8%, p=0.04) following adjustment for demographic characteristics, cardiovascular risk factors, and body mass index (BMI).

CONCLUSIONS

Mild impairment in sleep was modestly associated with activation of coagulation; further study is needed to evaluate the role of fibrinolytic factors in sleep-mediated coronary thrombosis.

Clinical markers of the hypercoagulable state by rotational thrombelastometry in obese patients submitted to bariatric surgery

BACKGROUND

Metabolic and inflammatory disturbances associated with obesity are considered important trigger factors for venous thromboembolism (VTE). Identification of clinical markers indicating a hypercoagulability state could define a group of high-risk patients in the surgical setting. This study aimed to identify these markers using rotational thrombelastometry (ROTEM) analysis, an established method for hemostasis testing that can detect hyperfunctional stages of the clotting process.

METHODS

From June to December 2010, this study investigated 109 consecutive obese patients (28 women and 22 men, mean age 46 years, body mass index 46.6 ± 7 kg/m(2)) with no history of VTE who were candidates for bariatric surgery. Preoperative clinical and metabolic characteristics and ROTEM analysis were recorded. Hypercoagulable risk was defined when patients showed a clot strength (G) of ≥11 dynes/cm(2).

RESULTS

Of the 109 patients, 20 (18%) were hypercoagulable according to ROTEM analysis. Metabolic/inflammatory biomarkers such as leptin, C-reactive protein, fibrinogen levels, and platelet count were significantly higher in the high-risk patients. In the multivariate analysis, fibrinogen was an independent predictor of G ≥ 11 dynes/cm(2) [odds ratio (OR) 2.92, 95 % confidence interval (CI) 1.80-5.21, p = 0.023]. After adjustment to other data, only waist circumference affected the prediction [OR 4.42, 95 % CI 2.27-6.71, p = 0.009]. Receiver operating characteristic curve analysis showed that 3.95 g/l was the best cutoff point for fibrinogen predictability (sensitivity 100 %, specificity 41%).

CONCLUSION

A hypercoagulability state in obese patients is associated with central obesity and high fibrinogen levels, which should be considered clinical hallmarks of this state. More aggressive perioperative prophylaxis for VTE should be recommended when these hallmarks are present in obese patients.

Obstructive sleep apnea syndrome: blood viscosity, blood coagulation abnormalities, and early atherosclerosis

Obstructive sleep apnea syndrome (OSAS) is an independent risk factor for atherosclerosis and arterial thrombosis, which are associated with high cardiovascular (CV) morbidity and mortality. In studies performed in clinical populations with elevated CV event risk profiles, the occurrence of moderate to severe OSAS was very often accompanied by a worsened vascular function and increased prevalence of structural abnormalities. Recent investigations of atherosclerosis in OSAS have focused on thrombotic tendency and blood viscosity, providing new insight into mechanisms of the disease. Despite that knowledge about the mechanisms of development of CV disease in patients with OSAS is still incomplete, observations confirm a relationship between sleep-disordered breathing and the rheological properties (flow properties) of blood. While platelet dysfunction and hypercoagulability (PDMPs, PaI-1, and SF) play important roles in the pathogenesis of vascular disease, there are limited studies on the potential role of blood viscosity in the development of vascular disease in OSAS.