Sotiris Tsalamandris

The role of microRNAs in coronary artery disease: From pathophysiology to diagnosis and treatment

MicroRNAs (miRNAs) are tiny non-coding RNA molecules that regulate gene expression predominantly at the post-transcriptional level. Far from being simple intracellular regulators, miRNAs have recently been involved in intercellular communication and have been shown to circulate in the bloodstream in stable forms. In the past years specific miRNA expression patterns have been linked to the development of atherosclerosis and coronary artery disease, two closely related conditions. The study of miRNAs has promoted our understanding of the processes involved in the pathogenesis of atherosclerosis and innovative diagnostic and therapeutic approaches have emerged. In this review, we present the role of miRNAs in the development of atherosclerosis, on coronary artery disease progression and we assess their role as diagnostic biomarkers. Finally we evaluate the therapeutic and preventive opportunities that arise from the study of miRNAs in coronary artery disease and especially in myocardial infarction.

The Role of Endothelial Dysfunction in Aortic Aneurysms

Abdominal aortic aneurysm is a vascular disease which, despite the fact that it shares common risk factors with atherosclerosis, develops in parallel but as a partly independent process, through different pathogenic mechanisms. The pathogenic mechanisms involve metalloproteinase and collagenase activation, median and adventitial degradation, elastin lysis, vascular smooth cells transformation and apoptosis, collagen production and lysis imbalance combined with excessive inflammatory infiltration. Endothelial cells respond to a number of stimulating factors, including smoking, hypertension and AT1 receptor stimulation and non-uniform distribution of wall stress. Their ability to produce NO is crucial in order to adapt. Endothelial cells contribute to AAA development due to increased oxidative stress which is partly mediated by impaired NO bioavailability due to endothelial dysfunction and NADPH oxidase overexpression. In addition, they express several molecules among which adherence molecules, selectins, endothelin-1, regulating inflammatory infiltration and oxidative stress. Inflammatory cells consist of monocytes, polymorphonuclear neutrophils and lymphocytes and they are involved in the degrading process in the aortic wall by secreting proteolytic enzymes or by releasing interleukins which mediate the inflammation response. Endothelial dysfunction and arterial stiffness reflect on indices like FMD, carotid-femoral PWV and augmentation index, sometimes with controversial results. At present, surgical treatment is the only option provided in patients with large AAA, in particular. Focusing on the emerging role of endothelial cells in AAA pathology may contribute in creating new therapeutic options in a disease which has not yet a well-accepted, implemented pharmaceutical treatment.

Vascular function and ocular involvement in sarcoidosis.

Ocular involvement occurs in sarcoidosis (Sar) patients mainly in the form of uveitis. This study was designed to determine if uveitis in Sar patients is associated with vascular impairment. We enrolled 82 Sar patients and 77, age and sex matched, control subjects (Cl). Sar patients were divided into those with ocular sarcoidosis (OS) and those without ocular sarcoidosis (WOS). Endothelial function was evaluated by flow-mediated dilation (FMD). Pulse wave velocity (PWV) was measured as an index of aortic stiffness and augmentation index (AIx) as a measure of arterial wave reflections. Although there was no significant difference in sex, age and mean arterial pressure, patients with OS compared to WOS patients and Cl subjects had impaired FMD (p<0.001), increased AIx (p=0.02) and increased PWV (p=0.001). Interestingly, impaired FMD in Sar patients was independently, from possible covariates (age, sex, smoking habits, arterial hypertension, dyslipidemia), associated with increased odds of ocular involvement (odds ratio=1.69, p=0.001). More precisely ROC curve analysis revealed that FMD had a significant diagnostic ability for the detection of OS (AUC=0.77, p<0.001) with a sensitivity of 79% and a specificity of 68% for an FMD value below 6.00%. To conclude in the present study we have shown that ocular involvement in Sar patients is associated with impaired endothelial function and increased arterial stiffness. These results strengthen the vascular theory which considers uveitis a consequence of vascular dysfunction in Sar patients and reveals a possible clinical importance of the use of endothelial function tests.

Circulating Biomarkers Determining Inflammation in Atherosclerosis Progression.

Atherosclerosis is the main underlying pathology of cardiovascular disease and is precipitated by various hereditary and non-hereditary risk factors. Inflammation is considered an important step in the progression of atherosclerosis and involves numerous cells, mediators and cellular procedures. Therefore, a biomarker able to determine the vascular inflammatory status is imperative as the combination of inflammatory biomarkers with the classic risk factors might provide further information about atherosclerosis progression and cardiovascular risk. The identification of novel inflammatory molecules and the improvement in analytical methods allows the potential implementation of these tests in every day clinical practice. In the current article, we focus on the role of established and novel biomarkers in atherosclerosis progression and in the determination of cardiovascular risk. We also present recent data concerning the risk stratification of patients according to their inflammatory status and the possible anti-inflammatory treatment strategies.

Genotyping, Platelet Activation, and Cardiovascular Outcome in Patients after Percutaneous Coronary Intervention: Two Pieces of the Puzzle of Clopidogrel Resistance

Objectives: Individual platelet responses to antiplatelet therapy depend on genetic, cellular, and clinical factors. CYP2C19 and P2Y12 receptor polymorphisms are implicated in platelet responses to antiplatelet treatment. We aimed to evaluate the impact of CYP2C19 and C34T P2Y12 genotyping on platelet reactivity and cardiovascular outcome in patients after percutaneous coronary intervention (PCI) on clopidogrel treatment. Methods: We enrolled 408 patients with stable coronary artery disease (CAD) receiving aspirin and clopidogrel (75 mg/day) 1 month after PCI. High on-treatment platelet reactivity was evaluated using the VerifyNow Assay in a subset of patients. CYP2C19*2 and C34T P2Y12 genotyping was performed by real-time polymerase chain reaction. The primary end point was the composite of death or hospitalization for cardiovascular causes, and patients were followed for a median time of 13 months. Results: In the total study population, 37% were carriers of at least 1 CYP2C19*2 loss-of-function allele, and 53% were carriers of at least 1 C34T loss-of-function allele. Interestingly, homozygotes of the CYP2C19*2 loss-of-function allele had significantly increased P2Y12 reaction units (PRU) (p = 0.007). However, PRU did not differ between carriers and noncarriers of the C34T loss-of-function allele (p = 0.41). Moreover, carriers of CYP2C19*2 had an increased hazard ratio (HR) for the occurrence of the primary end point (for carriers HR = 1.96, 95% CI 1.05-3.66, p = 0.03), whereas the C34T polymorphism had no impact on the cardiovascular outcome (p = 0.17). Finally, PRU was associated with cardiovascular outcome even after adjustment for the presence of any reduced function allele polymorphism. Conclusions: We documented a different effect of CYP2C19 and P2Y12 receptor polymorphisms on platelet reactivity and cardiovascular outcome in CAD patients after PCI on clopidogrel treatment. Importantly, increased platelet reactivity adversely affects the cardiovascular outcome independently of the studied polymorphisms.

Effects of CYP2C19 Polymorphism on Endothelial Function, Arterial Stiffness and Inflammation in Coronary Artery Disease Patients Under Clopidogrel Treatment

BACKGROUND Clopidogrels ability to inhibit platelet function determined its clinical usefulness. The role of CYP2C19*2 genotype on antiplatelet treatment is recently under question. Arterial wall properties and inflammation are key players in atherosclerosis development. Hence, we evaluated the impact of CYP2C19*2 genetic polymorphism on endothelial function, arterial stiffness and inflammation in coronary artery disease (CAD) patients receiving clopidogrel treatment. METHODS AND RESULTS In this study we enrolled 408 consecutive patients with stable CAD under dual antiplatelet therapy (clopidogrel 75mg/day, aspirin 100mg/day), 30 days after percutaneous coronary intervention. Measurement of flow-mediated dilation (FMD) of the brachial artery was used to evaluate endothelial function. Carotid-femoral pulse wave velocity (PWV) and augmentation index (AIx) was measured to estimate arterial stiffness. Real time polymerase chain reaction was used for the genotyping of CYP2C19*2. Levels of tumor necrosis factor alpha (TNF-a) and interleukin 6 (IL-6) were measured with ELISA. We found no difference in basic clinical and demographic characteristics nor in FMD, PWV, AIx and inflammatory status (p=NS for all) between CYP2C19 homozygotes for the wild type; carriers of reduced function allele and homozygotes for the reduced function allele. CONCLUSION CYP2C19*2 loss of action polymorphism causes no impact on vascular function and inflammatory status in stable CAD patients receiving clopidogrel treatment.

Statins and Inflammation in Cardiovascular Disease

BACKGROUND Chronic inflammation and immune system activation underlie a variety of seemingly unrelated cardiac conditions including not only atherosclerosis and the subsequent coronary artery disease but also peripheral artery disease, hypertension with target organ damage and heart failure. The beneficial effects of HMG-CoA reductase inhibitors or statins are mainly attributed to their ability to inhibit hepatic cholesterol biosynthesis. Beyond their lipid lowering activity, ample evidence exists in support of their potent anti-inflammatory properties which initiate from the inhibition of GTPase isoprenylation, activating a cataract of secondary pathways and extend to the inhibition and blocking of immune cell activation and interaction. OBJECTIVE To summarize the anti-inflammatory mechanisms of statins in clinical and experimental settings in cardiovascular disease. METHODS A systematic search of PubMed and the Cochrane Database was conducted in order to identify the majority of trials, studies, current guidelines and novel articles related to the subject. RESULTS In vitro, statins have immuno-modulatory and anti-inflammatory effects, and they can exert anti-atherosclerotic effects independently of their hypolipidemic actions. In addition, positive results have emerged from mechanistic and experimental studies on the active role of HMG-CoA reductase inhibitors in HF. By extrapolating those data in clinical setting, we further understand how HMG-CoA reductase inhibitors can beneficially affect not only systolic but also diastolic HF. CONCLUSION In this review article, we present the basic pathophysiologic data supporting the anti-inflammatory actions of statins in clinical and experimental settings and we link these mechanisms with confirmatory clinical data on the potent non lipid lowering effects of HMG-CoA reductase inhibitors.

Redox State in Atrial Fibrillation Pathogenesis and Relevant Therapeutic Approaches

BACKGROUND Myocardial redox state is a critical determinant of atrial biology, regulating cardiomyocyte apoptosis, ion channel function, and cardiac hypertrophy/fibrosis and function. Nevertheless, it remains unclear whether the targeting of atrial redox state is a rational therapeutic strategy for atrial fibrillation prevention. OBJECTIVE To review the role of atrial redox state and anti-oxidant therapies in atrial fibrillation. METHOD Published literature in Medline was searched for experimental and clinical evidence linking myocardial redox state with atrial fibrillation pathogenesis as well as studies looking into the role of redoxtargeting therapies in the prevention of atrial fibrillation. RESULTS Data from animal models have shown that altered myocardial nitroso-redox balance and NADPH oxidases activity are causally involved in the pathogenesis of atrial fibrillation. Similarly experimental animal data supports that increased reactive oxygen / nitrogen species formation in the atrial tissue is associated with altered electrophysiological properties of atrial myocytes and electrical remodeling, favoring atrial fibrillation development. In humans, randomized clinical studies using redox-related therapeutic approaches (e.g. statins or antioxidant agents) have not documented any benefits in the prevention of atrial fibrillation development (mainly post-operative atrial fibrillation risk). CONCLUSION Despite strong experimental and translational data supporting the role of atrial redox state in atrial fibrillation pathogenesis, such mechanistic evidence has not been translated to clinical benefits in atrial fibrillation risk in randomized clinical studies using redox-related therapies.

Impact of C34T P2Y12 genotype on endothelial function and arterial stiffness in patients after percutaneous coronary intervention receiving clopidogrel

Impact of C34T P2Y12 genotype on endothelial function and arterial stiffness in patients after percutaneous coronary intervention receiving clopidogrel☆☆☆ Gerasimos Siasos , Stamatios Kioufis , Evangelos Oikonomou , Marina Zaromitidou , Manolis Vavuranakis , Konstantinos Maniatis , Nikolaos Papageorgiou , Konstantinos Mourouzis , Spyridon Papaioannou , Sotiris Tsalamandris , Athanasios G. Papavassiliou , Christodoulos Stefanadis , Dimitris Tousoulis a,⁎

Coronary microcirculation and the no-reflow phenomenon.

The no-reflow phenomenon refers to the post-percutaneous coronary intervention condition in which, despite re-establishing epicardial coronary vessel patency, the flow to the previously ischemic myocardium is markedly reduced. When it does occur, it attenuates the beneficial effect of reperfusion therapy and substantial regions of the myocardium fail to receive adequate perfusion. The pathophysiology of this phenomenon is not completely understood. The possible mechanisms could be related to alterations in the microvascular circulation. Various mechanisms such as activation of inflammatory pathways, vascular damage and hemorrhage, leukocyte infiltration, and cellular edema may be responsible. As the no-reflow phenomenon is associated with adverse clinical consequences, it is of great importance to identify exact responsible mechanisms and apply effective preventive and therapeutic strategies. In this review, we describe an updated overview of the pathophysiological mechanisms and the current preventive tools for no-reflow as well as therapeutic interventions in order to improve coronary blood flow and consequently the prognosis for these patients.