Current Vascular Pharmacology - Volume 8, Issue 4, 2010

The inflammatory pathogenesis of atherosclerosis is now well-established, owing to in vitro and in vivo studies and the application of high sensitivity assays for C-reactive protein (CRP) in the general population and specific groups at risk for cardiovascular disease (CVD). In view of the complexity of inflammation-induced atherosclerosis, the rationale for comparative studies of atherogenesis in rheumatic diseases with diverse inflammatory pathogenesis seems obvious; they are human in vivo models to study inflammatory mechanisms involved in atherosclerosis and the impact of treatment. Factors implicated in atherogenesis in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), familial Mediterranean fever (FMF) and Behcet's disease (BD) are discussed in this review. Evidence suggests that enhanced atherosclerosis causes premature cardiovascular events in the autoimmune disease, SLE, and the “high-grade” inflammatory rheumatic disease, RA. Preliminary data suggest that enhanced atherogenesis may accompany FMF in the absence of sufficient suppression of inflammation by colchicine. In the setting of BD, the role of atherosclerosis in the premature manifestation of coronary pathology has not been confirmed; coronary vasculitis and aneurysms appear to constitute the basis of myocardial infarction (MI) in BD. A variety of established and novel risk factors are believed to influence enhanced atherogenesis in rheumatic diseases. Antiphospholipid antibodies are thought to be intimately involved in atherogenesis in SLE and to a lesser extend in RA. CRP may play a more universal role in all rheumatic diseases. The application of high resolution ultrasound of peripheral arteries and other non-invasive techniques may allow targeted use of statins, ACE inhibitors, antiplatelet agents and other cardioprotective drugs in patients with rheumatic diseases, but this needs to be evaluated specifically in prospective studies.

Background: The management of the Metabolic Syndrome (MetS) includes lifestyle interventions (e.g. diet and exercise for weight reduction), as well as drug treatment to normalize blood pressure, high-density lipoprotein cholesterol, triglycerides and glucose values. Treatment of atherogenic dyslipidemia should comprise a primary therapeutic target since it is associated with an increased risk of cardiovascular disease. Objective: To review the efficacy of the drugs available for the management of the dyslipidemia associated with MetS. Methods: MEDLINE was searched up to May 10, 2009 for studies in English using the mesh-terms “metabolic syndrome”, “hypercholesterolemia”, “dyslipidemia”, “treatment”, “statins” and “cardiovascular disease” in various combinations to identify treatment strategies for the management of the dyslipidemia of the MetS. Results/Conclusions: Several drugs have been described for the management of the dyslipidemia of the MetS, namely statins, fibrates, ezetimibe, niacin, bile acid sequestrants, cholesteryl ester transfer protein inhibitors, as well as combined treatment regimes. Although each of these may deal to some extent with some aspect of the dyslipidemia of the MetS compared with placebo, a direct comparison of all these agents has not been carried out. A head-to-head comparison between the suggested regimes could identify the mono- or combination therapy for the optimal management of dyslipidemia associated with MetS.

Intracellular cAMP is an ubiquitous intracellular second messenger that regulates important cellular functions. Intracellular cAMP levels are regulated by the enzymes adenylyl cyclase and phosphodiesterases. The role of cAMP in atherosclerosis is not widely accepted and incompletely characterized. Several reports support a role of cAMP in atherogenesis by modulating the function of vascular endothelium, the production of reactive oxygen species, the recruitment of circulating monocytes to the artery wall and their differentiation into macrophages- foam cells, by controlling the expression of pro- and anti-inflammatory interleukins, and regulating serum levels of triglycerides and cholesterol. Previous reports suggested an important role of cAMP in the modulation of atherosclerotic plaque progression by removal of excess free cholesterol from macrophages by inducing the ABCA1 secretory pathway and reducing circulating levels of cholesterol. Studies suggested a crucial role of cAMP on the development of acute coronary syndromes [(ACS); unstable angina, and acute myocardial infarction] and stroke, by modulating platelet aggregation and thrombus formation and the expression of metalloproteinases. This review focuses on the identified mechanisms and roles of cAMP in the prevention of atherosclerosis, atherogenesis, and progression of atherosclerosis and the development of ACS. Finally, it provides evidence that showed the beneficial effects that may derive from the inhibition of phosphodiesterase III and activation of adenylyl cyclase and subsequent elevation of cAMP levels. Thus, cAMP may be a possible target for the prevention and treatment of atherosclerosis.

Hereditary Haemorrhagic Telangiectasia (HHT) or Rendu-Osler-Weber syndrome, is an autosomal dominant rare disease characterized by localized angiodysplasia. This is manifested as epistaxis, mucocutaneous and gastrointestinal telangiectases, and arteriovenous malformations in the pulmonary, cerebral or hepatic circulation. The prevalence is between 1 in 5,000 to 8,000, although it is higher in some regions. The most frequent clinical manifestation of HHT is epistaxis, normally from light to moderate from the 4th decade of life. However, many patients show severe epistaxis which may interfere with their quality of life. The epistaxis is due to telangiectasia on the nasal mucosa. These are focally dilated postcapilar venules, which in advanced phases show many layers of smooth muscle cells without elastic fibers, and very frequently directly connect with dilated arterioles. As a consequence of these vascular alterations, telangiectases are very sensitive to slight trauma and even to the friction with the air when breathing, which gives rise to nose bleeds. Unfortunately, there is no optimal pharmacological treatment for the epistaxis in HHT. The use of antifibrinolytic agents for the treatment of HHT has been studied recently by our group as an effective relief for nasal and gastric haemorrhages. This work represents a systematic review and the begining of a systematic laboratory work we are now conducting in our lab to screen for “orphan drugs” as therapeutic agents in HHT. In this context, the use of hormones, immunosuppresants and anti-angiogenic agents are under preclinical study in our laboratory.

It is well known that solid cancers are associated with thromboembolic complications, but recent studies have shown that the incidence of thrombosis may be as high (or even higher) in patients with malignant haematological disorders. However, this may be obscured by the significant morbidity and mortality due to other complications of haematological malignancies, such as bleeding and infections. The vast majority of patients with haematological neoplasias also have clinically silent haemostatic abnormalities, but some may show clinical manifestations, including venous thromboembolism, pulmonary embolism, disseminated intravascular coagulation and life-threatening thrombohaemorrhagic syndrome in acute leukaemias. The pathogenesis of thromboembolic disease in haematological malignancies is complex and multifactorial: tumour cell-derived procoagulant, fibrinolytic or proteolytic factors and inflammatory cytokines affect clotting activation, and chemotherapy and anti-angiogenic drugs increase thrombotic risk in patients with lymphoma, acute leukaemia and multiple myeloma. Infectious complications are another important factor: endotoxins from gramnegative bacteria induce the release of tissue factor (TF), tumour necrosis factor (TNF) and interleukin-1b (IL-1b), and gram-positive organisms can release bacterial mucopolysaccharides that directly activate factor XII. Leukaemic patients may be affected by other prothrombotic factors, including hyperleukocytosis, increased TF expression and activation, and the prothrombotic properties of therapeutic agents such as all-trans retinoic acid and L-asparaginase, which can induce thrombosis involving multiple organs. The very high risk of haemorrhage in these patients warrants prospective randomised trials evaluating optimal anti-thrombotic prophylaxis and treatment.

Atherosclerotic plaque destabilization is a major cause of unstable angina, myocardial infarction, and sudden cardiac death. Macrophages, which are an essential component of unstable plaques, play a pivotal role in the destabilization process, whereas smooth muscle cells contribute to plaque stability. Selective removal of macrophages is therefore an interesting pharmacological objective to stabilize vulnerable, rupture-prone lesions. Pharmacological agents such as clodronate, nitric oxide donors, mammalian target of rapamycin (mTOR) inhibitors, protein synthesis inhibitors, and statins, that are capable of selectively depleting macrophages in atherosclerotic plaques without affecting smooth muscle or endothelial cells, have recently been identified. This review focuses on the mechanism of action of these drugs as well as on the potential pitfalls of drug-induced macrophage depletion.

There is a growing interest focusing on the inflammatory response caused by essential hypertension. Inflammatory mechanisms play an important role in the pathogenesis and progression of cardiovascular disease. Recent studies have shown that tissue expression and plasma concentrations of several inflammatory markers and mediators are associated with increased risk of hypertension. These molecules include C-reactive protein, adhesion molecules, such as vascular cell adhesion molecule-1, intercellular adhesion molecule-1 and chemokines. The evaluation of these markers may influence the specific pharmacologic responses and the clinical outcome of the patients with essential hypertension. Moreover, therapeutic approaches targeted to lower blood pressure and suppress inflammatory response may have additional clinical benefits. However, further randomized studies are required to determine the potential favorable effects of suppression of inflammation in the management of arterial hypertension.

Chronic stress and probably the accompanying changes in personal behaviours can influence life expectancy. The role of adrenocorticotropic hormone (ACTH) and cortisol in atherosclerosis is not widely accepted and incompletely characterized. Several reports support a role of these hormones in atherogenesis by modulating the function of vascular endothelium, the recruitment of circulating monocytes to the artery wall and their differentiation into macrophages- foam cells, by controlling the expression of pro- and anti-inflammatory interleukins. Previous reports suggested an important role of ACTH and cortisol in the modulation of atherosclerotic plaque progression by removal of excess free cholesterol from macrophages. Studies suggested a crucial role of these hormones on the development of acute coronary syndromes [(ACS); unstable angina, and acute myocardial infarction] and stroke, by modulating platelet aggregation and thrombus formation. This review focuses on the identified mechanisms and roles of ACTH and cortisol in atherogenesis, progression of atherosclerosis and the development of ACS. Finally, it proposes experimental studies to evaluate the therapeutic potential of new glucocorticoid antagonists, the effects that may derive from the inhibition cortisol synthesis and the role of 11β-hydroxysteroid dehydrogenase type 1 inhibitors in atherogenesis, progression of atherosclerosis and the development of ACS. These hormones may be a possible additional target for the prevention and treatment of atherosclerosis.

The vascular manifestations associated with diabetes mellitus (DM) result from the dysfunction of several vascular physiology components mainly involving the endothelium, vascular smooth muscle and platelets. It is also known that hyperglycemia-induced oxidative stress plays a role in the development of this dysfunction. This review considers the basic physiology of the endothelium, especially related to the synthesis and function of nitric oxide. We also discuss the pathophysiology of vascular disease associated with DM. This includes the role of hyperglycemia in the induction of oxidative stress and the role of advanced glycation end-products. We also consider therapeutic strategies.

Arachidonic acid metabolism plays a key role in atherothrombotic events affecting the coronary or cerebrovascular territory, as reflected by experimental studies based on biochemical measurements of eicosanoid biosynthesis and the results of inhibitor trials in these settings. Two cyclooxygenase (COX)-isozymes exist, COX-1 and COX-2, that differ in terms of regulatory mechanisms of expression, tissue distribution, substrate specificity, and susceptibility to inhibition by drugs. Whereas the role of COX-1 expressed in platelets in acute coronary syndromes and ischemic stroke is definitely established through several large clinical studies with aspirin, the role of COX-2 activity in these settings is still unclear, because this enzyme was characterized only recently (1991) and its inhibitors (coxibs) only became available in 1998. In this review, we discuss the different expression profile of COX-2-related enzymes in the cells actively involved in atherothrombosis, the role of these enzymes as cause of plaque “instability”, and the clinical consequences of their inhibition. Recent studies suggest that variable expression of transmembrane and downstream receptors, as well as genetic mutations represent important determinants of the functional consequences of COX-2 expression and inhibition in different clinical settings.

Postoperative atrial fibrillation (POAF) is a common complication following cardiac surgery, occurring in 20% to 60% of patients. Advanced age, history of atrial fibrillation (AF), heart failure, peripheral arterial disease and chronic obstructive pulmonary disease are predictors of POAF. The pathogenesis of AF seems to be multifactorial, and includes electrical and structural remodeling as well as inflammation (a systemic response caused by cardiopulmonary bypass and cardiotomy). Numerous pharmacologic agents can decrease the incidence of POAF. It is also necessary to evaluate an agent's ability to decrease stroke, mortality, length of stay and hospital costs. Currently, the use of beta-blockers with adjunctive amiodarone has been shown to reduce POAF and several of its complications. Two therapeutic choices exist in patients with POAF: rate control and rhythm control. The decision which is more important to target should be based on the symptoms of the individual patient. Unlike in patients with chronic AF, POAF is generally transient, and the risks of anticoagulation may outweigh the benefits. Surgical ablation techniques and ablation devices have progressed considerably. This made the procedures quicker and simpler, and therefore feasible in virtually all clinical contexts. In turn, this has raised the issue of post-ablation arrhythmias. Although relapsing AF is generally addressed conservatively, it may require ablation, frequently transseptal. Further research is needed to identify the predictors of POAF and the most effective pharmacological and invasive methods for the prevention and treatment of POAF.

Patients classified as having a “poor lung function” in large populations studies are at increased risk of atherothrombosis, but potential mechanisms are unclear. A large proportion of these people are affected by chronic obstructive pulmonary disease (COPD), a recognized risk factor for vascular events. Systemic inflammation is the main atherothrombotic abnormality in COPD, but hypoxia-related platelet activation, pro-coagulant status and oxidative stress may play a role. Systemic inflammation is presumably a leading mechanism of atherothrombosis also in people who have a “restrictive” spirometric dysfunction, rather than the classic obstructive pattern of COPD. Many persons with “poor lung function” are affected by diabetes and their cardiovascular risk is therefore linked to the diabetic status. Patients affected by diabetes tend to have a “restrictive” dysfunction, rather than COPD. Recent studies show that restriction at spirometry precedes the onset of diabetes, thereby representing a marker of mechanisms involved in the pre-diabetic, insulin-resistant state. This is also proved by the fact that most patients with metabolic syndrome, a pre-diabetic condition, have a restrictive ventilatory pattern at spirometry. A significant proportion of people with “poor lung function” have visceral obesity, a cardiovascular risk factor. By hampering lung expansion, visceral obesity causes a restrictive ventilatory pattern. In conclusion, the term “poor lung function” includes various chronic illnesses with different mechanisms of atherothrombosis. Research is needed for better understanding why persons with lung dysfunctions have higher cardiovascular risk, and for identifying adequate preventive strategies.