Current Vascular Pharmacology - Volume 6, Issue 3, 2008

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Matrix metalloproteinases (MMPs) play a major role in extracellular matrix (ECM) turnover under both physiological and pathological conditions. Studies on venous tissues from experimental animals and humans identified several MMP subtypes, and showed significant changes in the expression and activity of specific MMPs during vein wall remodeling. Also, significant research has focused on the role of MMPs in chronic venous disease (CVD) and varicose vein formation in the lower extremities and their progression to thrombophlebitis and venous leg ulcer. Several hypotheses have been forwarded regarding the pathophysiological mechanisms underlying the relation between MMPs and the formation, progression and complications of varicose veins. The effects of MMPs on ECM degradation could result in significant venous tissue remodeling and degenerative and structural changes in the vein wall, leading to venous dilation and valve dysfunction. MMPs may also induce early changes in the endothelium and venous smooth muscle function in the absence of significant ECM degradation or structural changes in the vein wall. In addition, evidence suggests increased activity of MMPs in the advanced stages of chronic venous insufficiency (CVI) associated with skin changes and leg ulceration as well as in the wound fluid environment. Several pharmacological therapies and surgical strategies are being utilized in the management of varicose veins, with variable success and recurrence rates. Inhibition of MMPs may represent a novel therapeutic intervention to limit the progression of varicose veins to CVI and leg ulceration.

A broad spectrum of global haemostatic assays has recently been developed and modified in an attempt to overcome the drawbacks of classical screening tests used for evaluation of coagulation and fibrinolysis. The Overall Haemostasis Potential (OHP) assay is one of such assays. The assay is based on repeated spectrophotometric registration of fibrin-aggregation in citrated plasma, to which small amounts of exogenous thrombin, tissue type plasminogen activator and calcium chloride have been added. The area under the fibrin aggregation curve which then develops is calculated and is the laboratory parameter used for OHP determination. The Overall Coagulation Potential (OCP) and Overall Fibrinolytic Potential (OFP) are supplementary parameters of OHP, providing details of underlying changes in coagulation and/or fibrinolysis. The sensitivity of the assay for detecting hypercoagulation in normal pregnancy, in preeclampsia, some thrombophilias, coronary heart disease, diabetes, stroke and vascular surgery has been evaluated. Since the assay can monitor haemostasis balance in the sample, it may serve as a laboratory tool to determine hypocoagulation, especially in patients with haemophilia A or B. Preliminary findings also indicate that the OHP assay may be useful in the monitoring of anticoagulant treatments. Larger controlled clinical studies are, however, mandatory before a definite conclusion about the usefulness of the method can be drawn.

The pharmacology characteristics of dihydropyridine calcium channel blockers (CCB) make them an attractive antihypertensive medication for use in the perioperative setting of coronary artery bypass graft (CABG) surgery. They lack the negative inotropic, negative chronotropic, and negative bathmotropic effects of phenylalkylamine and benzothiazepine CCB that limit the use in patients with heart failure or patients with bradyarrythmias. With the aging population and significant rise in the prevalence of heart failure, the use of dihydropyridine CCB as antihypertensive medication after CABG surgery has become more common. Furthermore, intravenous dihydropyridine CCB are being used in the perioperative setting as vasodilatory agents after radial artery harvesting for total arterial coronary revascularization. We review the pharmacological effects of intravenous dihydropyridine CCB, analyze the literature, and comment on the consequences in modern clinical practice.

The formation and progression of atherosclerotic plaques followed by rupture, thrombus formation and vessel blockage leads to ischemic tissue damage and the clinical condition underlying most cardiovascular disease. Therapeutic agents for the prevention of atherosclerosis have all targeted epidemiologically-identified and relatively easily measured risk factors (e.g. lipids and blood pressure). This strategy has proven somewhat effective but is of less than optimal efficacy as rates of cardiovascular disease remain high. Treatment targeting the mechanisms of atherosclerosis in the vessel wall is a conceptually attractive proposition to complement the risk factor directed strategy. Vascular smooth muscle cells (VSMC) are the major cellular component of the vascular media and migration and proliferation leads to the formation of the neointima the development of which renders the vessels particularly sensitive to atherosclerosis. Numerous hormones and growth factors act on VSMC to cause migration, proliferation and the secretion of extracellular matrix and modulation or dysfunction of these processes is the most likely cause of atherosclerosis. Endothelin-1 (ET-1) is a 21 amino acid peptide that acts on 7 transmembrane G protein coupled receptors to elicit a plethora of responses that can modulate the behaviour of VSMCs and thus impact on the development of atherosclerosis. ET-1 is elevated in atherosclerotic plaques. People with diabetes have accelerated atherosclerosis and also show elevated plasma levels of ET-1. This review addresses the actions of ET-1 on VSMC and the signalling pathways through which it mediates its effects as the latter represent potential therapeutic targets for the prevention of atherosclerosis.

Oxidative stress has been linked to the origin and progression of cardiovascular diseases. Nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase is a multi-component, NADPH-dependent enzyme that generates superoxide anion in the presence of molecular oxygen. The enzyme has been identified and characterized in all 3 vascular wall cell types and represents the major source of reactive oxygen species (ROS) production in the vascular wall. Inhibition of NADPH oxidase activation appears to suppress the sequence of cellular events that leads to a variety of cardiovascular diseases, including atherosclerosis. The naturally occurring methoxyphenol apocynin has been found to inhibit NADPH oxidase upon activation by peroxidases (e.g. soybean peroxidase, myeloperoxidase) or ROS under mild reaction conditions. Upon peroxidase-catalyzed activation, the apocynin oxidation products act to block the assembly and activation of NADPH oxidase. Although the mechanism of inhibition of NADPH oxidase remains largely unknown, apocynin's high effectiveness and low toxicity makes it a promising lead compound in the development of new therapeutic agents for cardiovascular diseases.

In chronic inflammatory diseases such as rheumatoid arthritis (RA), systemic inflammation appears as an independent risk factor, contributing to increased cardiovascular mortality. This high cardiovascular mortality reveals the existence of accelerated atherosclerosis, the pathogenesis of which may be associated with traditional risk factors such as smoking, hypertension, dyslipidemia, deterioration of insulin sensitivity, and less traditional risk factors such as hyperhomocysteinemia, inflammatory conditions and endothelial dysfunction. Control of systemic inflammation theoretically provides a means of preventing this higher cardiovascular mortality among RA patients. In this review we address the question of the impact of anti-rheumatic drugs currently used in RA, such as non-steroidal anti-inflammatory drugs (e.g. non-selective or cyclooxygenase-2 selective inhibitors), steroidal anti-inflammatory drugs (glucocorticoids), traditional disease-modifying anti-rheumatic drugs (e.g. methotrexate) or biologics (e.g. anti-tumour necrosis factor alpha anti-tumour necrosis factor alpha) on cardiovascular diseases in RA patients. We also discuss the specific mechanisms involved in the differential cardiovascular effects of these therapeutic agents.

Potential hepatotoxicity related to amiodarone therapy is often a concern when deciding whether to initiate or continue treatment with this medication. While mostly associated with long-term oral administration of the drug, toxicity has also been reported early during intravenous administration and months after discontinuation of therapy. In the majority of patients, it is discovered incidentally during routine testing of liver biochemistry and rarely do the hepatic effects develop into symptomatic liver injury or failure. Despite the widespread use of amiodarone, prospective clinical studies have been sparse and there has been little consensus among experts in the field regarding optimum monitoring for adverse effects in patients receiving this drug. In order to examine the current state of knowledge surrounding the incidence, pathogenesis and mechanism of liver effects associated with amiodarone, the existing literature was reviewed, with particular emphasis on clinical recommendations for monitoring.