Current Topics in Medicinal Chemistry - Volume 13, Issue 2, 2013

Natriuretic neuropeptides (ANP, BNP, CNP) are produced primarily in the cardiac atria under normal conditions. The main stimulus for ANP and BNP peptide synthesis and secretion is cardiac wall stress. Cardiac ventricular myocytes constitute the major source of BNP-related peptides. Ventricular NT-proBNP production is upregulated in cardiac failure and locally in the area surrounding a myocardial infarct. NT-proBNP is cleared passively by organs with high rate of blood flow (muscle, liver, kidney). It has a longer half life than BNP and higher plasma concentration. BNP and NTproBNP tend to be higher in women and lower in obese individuals. They are also higher in elderly, in left ventricular tachycardia, right ventricular overload, myocardial ischemia, hypoxaemia, renal dysfunction, liver cirrhosis, sepsis and infection. NT-proBNP is useful both in the diagnosis and prognosis of heart failure and is considered to be a gold standard biomarker in heart failure similar to BNP. A cut-off point 300 pg/ml has 99% sensitivity, 60%specificity and NPV 98%for exclusion of acute heart failure. NT proBNP has also a strong prognostic value of death in acute and chronic heart failure and also predicts short and long term mortality in patient with suspected or confirmed unstable CVD. Natriuretic peptides are also prognostic markers for the RV (Right Ventricular) Dysfunction. Their release is due to myocardial stretch from right ventricular pressure overload.Finally, there are data supporting that NT-proBNP might be useful to put a time frame on atrial fibrillation of unknown onset.

Since its identification in 1988 and the recognition of its primary role as a potent vasoconstrictor, endothelin has been extensively studied and is now considered as a ubiquitous protein, involved in important aspects of human homeostasis as well as in several pathophysiological pathways, mostly associated with cardiovascular disease. From an evolutionary point of view, endothelin consists a primitive molecule with the rare characteristic of being exactly the same in all mammals, thus permitting scientists to perform experiments in animals and doing predictions for humans. The understanding of its contribution to the genesis, evolution and maintenance of disease through activation of special receptor subtypes has led to the development of both selective and unselective receptor antagonists. Despite the disappointing results of these antagonists in the field of heart failure, almost from the initial animal trials of bosentan, a dual endothelin receptor antagonist, in pulmonary arterial hypertension, it has been demonstrated that the drug leads at least to hemodynamic and clinical improvement of the patients, thus receiving official approval for the management of this rare but eventually lethal disease. Resistant hypertension is another area where endothelin receptor blockers might potentially play a role, while the pathophysiological role of endothelin in atherosclerotic coronary artery disease is well-established and the relative research goes on. The main goal of this review is to describe the endothelin system and mostly to enlighten its role in pathophysiologic pathways, as well to state the relative research in the various fields of cardiovascular disease and also highlight its prognostic significance wherever there exists one.

Myeloperoxidase (MPO), a heme protein released by leukocytes, is one of the most widely studied during the last decades molecule that plays a crucial role in inflammation and oxidative stress in the cellular level. It has become increasingly recognized that MPO performs a very important role as part of the innate immune system through the formation of microbicidal reactive oxidants, whilst it affects the arterial endothelium with a number of mechanisms that include modification of net cellular cholesterol flux and impairment of Nitric Oxide (NO)-induced vascular relaxation. In that way, MPO is implicated into both the formation and propagation of atheromatosis and there is substantial evidence that it also promotes ischemia through destabilization of the vulnerable plaque. Numerous studies have added information on the notion that MPO and its oxidant products are part of the inflammatory cascade initiated by endothelial injury and they are significantly overproduced at the site of arterial inflammation. Subsequent studies achieved quantification of this observation showing significant elevations of the systemic levels of MPO in a wide spectrum of cardiovascular disease scenarios with acute coronary syndromes and heart failure being the most studied. This review highlights key-aspects of MPO’s pathophysiological properties and summarizes the role of MPO as a diagnostic and prognostic tool for a number of cardiovascular pathologies.

Adiponectin, a newly discovered adipose-tissue secreting hormone, is a major regulator of a wide spectrum of physiological processes, such as energy metabolism, inflammation and vascular homeostasis. Emerging data suggest that adiponectin is the link between obesity and obesity-related disorders with cardiovascular disease. Adiponectin is a dominant insulin-sensitive adipokine and, in contrast to other adipose-tissue derived cytokines, it has major anti-diabetic, antiatherogenic and anti-inflammatory properties. Adiponectin has been extensively studied in the context of several aspects and risk factors of cardiovascular disease such as obesity, diabetes type I and II, coronary heart disease, hypertension, heart failure, cerebrovascular disease and smoking. The aim of this article is to summarize the acquired so far knowledge on adiponectin in relation to cardiovascular disease, to review its main biological and biochemical characteristics, to highlight the main mechanisms of adiponectin-driven beneficial effects on vasculature and briefly to refer to the basic correlations of adiponectin with the important aforementioned aspects of cardiovascular disease.

Cystatin C (cys-C) is a small protein molecule (120 amino acid peptide chain, approximately 13kDa) produced by virtually all nucleated cells in the human body. It belongs to the family of papain-like cysteine proteases and its main biological role is the extracellular inhibition of cathepsins. It’s near constant production rate, the fact that it is freely filtered from the glomerular membrane and then completely reabsorbed without being secreted from the proximal tubular cells, made it an almost perfect candidate for estimating renal function. The strong correlation between chronic kidney disease (CKD) and cardiovascular disease (CVD) along with the growing understanding of the role of cysteinyl cathepsins in the pathophysiology of CVD inspired researchers to explore the potential association of cys-C with CVD. Throughout the spectrum of CVD (peripheral arterial disease, stroke, abdominal aortic aneurysm, heart failure, coronary artery disease) adverse outcomes and risk stratification have been associated with high plasma levels of cys-C. The exact mechanisms behind the observed correlations have not been comprehensively clarified. Plausible links between high cys-C levels and poor cardiovascular outcome could be impaired renal function, atherogenesis and inflammatory mediators, remodeling of myocardial tissue and others (genetic factors, aging and social habits). The scope of the present article is to systematically review the current knowledge about cys-C biochemistry, metabolism, methods of detection and quantification and pathophysiological associations with different aspects of CVD.

Asymmetric Dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) production. ADMA is generated from methylation of arginine residues by protein arginine methyltransferases (PRMTs) and subsequent proteolysis, while its elimination is achieved mainly by degradation with dimethylarginine dimethylaminohydrolase (DDAH). Oxidative stress, endothelial nitric oxide synthase (eNOS) inhibition, eNOS uncoupling, inflammation and shear stress play a pivotal role in ADMA pathophysiology by managing PRMT/DDAH expression and NO synthesis and leading to a common result - endothelial dysfunction. Endothelial dysfunction seems to be the common finding in studies investigating the role of ADMA in cardiovascular disease (CVD). High-performance liquid chromatography (HPLC), mass spectrometry (MS) and enzyme-linked immunosorbent assay (ELISA) are the existing methods for ADMA quantification. However, none of them fulfils all the criteria to be characterized as “gold standard”. ADMA is significantly associated with risk factors for CVD and almost with every disease of the cardiovascular system; showing an independent, strong prognostic value for mortality and future cardiovascular events. This article aims to review the current knowledge about ADMA biology and metabolism, pathophysiological mechanisms implicating ADMA in CVD, methods for the determination of ADMA and its association with CVD risk factors and established CVDs.

Cardiovascular disease is the leading cause of death worldwide and coronary artery disease is its most prevalent manifestation, associated with high mortality and morbidity. In clinical practice cardiac troponins (cTn) are the cornerstone of the diagnosis, risk stratification and thus selection of the optimal treatment strategy in patients with acute coronary syndrome. According to the third update of the universal definition of myocardial infarction (MI) cTn is the preferred cardiac biomarker of myocardial necrosis in the setting of acute myocardial ischemia. Over the last years newer high sensitivity cardiac troponin (hs-cTn) assays have been developed that are more sensitive than conventional assays, have low limit of detection, low imprecision and low reference limits, but due to variability, the deployment of a standardization and harmonization method is required before their wide use in clinical practice. Recent studies have shown that their utilization seems to improve the diagnostic accuracy detecting MI in patients presenting with chest pain. However, the improved sensitivity comes along with a decreased specificity, though serial cTn measurements and the detection of early changes could improve the specificity and the overall diagnostic performance. Moreover, apart from their use in the diagnosis and risk stratification of MI and acute coronary syndromes, hs-cTn assays seem to have a key role in risk stratification and short and long-term prognosis in a variety of cardiovascular modalities such as stable coronary disease, heart failure and acute pulmonary embolism. In addition, studies have suggested that cTns may be used as a biomarker in the primary prevention of cardiovascular disease leading to the identification of high-risk populations or individuals with silent heart disease.

MicroRNAs are small RNA molecules and constitute a relatively novel class of gene expression regulators, found in the great majority of eukaryotic cells. Their role in human physiology and pathology is actively being researched with new exciting discoveries continuously coming to the forefront. MicroRNAs play a crucial role in the biogenesis and function of the cardiovascular system and act as important regulators of various metabolic and signaling pathways in cardiovascular disease. In this review there will be a summary on current knowledge about the expression, regulation and function of microRNAs in the most common diseases of the cardiovascular system as well as a presentation of and discussion about their promising future role as new biomarkers and therapeutic targets.

The introduction of biochemical biomarkers in the evaluation of patients with cardiovascular disease has led to practice-changing advancements in the way these patients are diagnosed and managed. Measurements of cardiac troponins or brain-type natriuretic peptide (BNP) and its precursor, N-terminal brain-type natriuretic peptide (NT-proBNP), have become indispensable in the evaluation of patients with acute coronary syndromes and heart failure, respectively, constituting an integral part of the diagnostic algorithm and risk stratification of these conditions. Copeptin, a glycopeptide, part of the prehormone molecule of the antidiuretic hormone – or arginine-vasopressin – has shown considerable promise in this field. There is evidence that copeptin might be useful as a diagnostic or prognostic biomarker and risk-stratifier in a range of cardiovascular disease conditions. The main clinical scenarios where copeptin has been studied as a biomarker are: early rule-out of myocardial infarction in patients with acute chest pain, diagnosis of heart failure in patients with acute dyspnea and determining the prognosis of destabilized or chronic stable heart failure. The present review is aimed at providing concise information about the molecular structure and biosynthesis of copeptin, the available medical chemistry methods of quantification, and the potential clinical uses of this molecule in patients with heart disease.