Reassessment of statins to retard the progression of aortic stenosis

The regulation of valvular and vascular sclerosis by osteogenic morphogens

Vascular calcification increasingly afflicts our aging, dysmetabolic population. Once considered only a passive process of dead and dying cells, vascular calcification has now emerged as a highly regulated form of biomineralization organized by collagenous and elastin extracellular matrices. During skeletal bone formation, paracrine epithelial-mesenchymal and endothelial-mesenchymal interactions control osteochondrocytic differentiation of multipotent mesenchymal progenitor cells. These paracrine osteogenic signals, mediated by potent morphogens of the bone morphogenetic protein and wingless-type MMTV integration site family member (Wnt) superfamilies, are also active in the programming of arterial osteoprogenitor cells during vascular and valve calcification. Inflammatory cytokines, reactive oxygen species, and oxylipids-increased in the clinical settings of atherosclerosis, diabetes, and uremia that promote arteriosclerotic calcification-elicit the ectopic vascular activation of osteogenic morphogens. Specific extracellular and intracellular inhibitors of bone morphogenetic protein-Wnt signaling have been identified as contributing to the regulation of osteogenic mineralization during development and disease. These inhibitory pathways and their regulators afford the development of novel therapeutic strategies to prevent and treat valve and vascular sclerosis.

Valvular heart disease: a primer for the clinical pharmacist

Valvular heart disease is a commonly encountered clinical condition that is not taught in most undergraduate and graduate pharmacy programs, leaving the practicing pharmacist without basic knowledge to expand on and subsequently apply to direct patient care. Unlike other areas of cardiology in which thousands of patients are recruited in many well-designed randomized clinical trials, data assessing treatments for valvular heart disease are limited and often consist of retrospective case series or observations. Our goal is to provide a basic overview of chronic valvular heart disease, with emphasis on describing the common conditions requiring surgery and the available options, as well as common pharmacologic therapies used in this patient population. Anomalies in valves can be broadly classified as stenosis and regurgitation. Depending on the valve and the type of anomaly, the impact on the cardiovascular system will vary. Understanding the hemodynamic consequences of aortic stenosis, aortic regurgitation, mitral stenosis, and mitral regurgitation is imperative to effectively counsel patients surrounding disease progression and self-monitoring, use of vasodilators, and prophylaxis for endocarditis and rheumatic fever. Further, patient characteristics factored into the choice of implanting either a bioprosthetic (tissue) or prosthetic (metal) valve encompass patient choice, life expectancy, and willingness or ability to accept lifelong anticoagulation therapy. The evolution of metal valves has resulted in newer generations under clinical study that have more laminar flow (minimizing interaction with blood products) and improved pyrolytic carbon (minimizing infection and interaction with blood products). Although antithrombotic therapy with warfarin is now mandatory in North America for all patients receiving metal valves, research is ongoing to assess the need with the most recent generation of valves.

Atherosclerotic inflammation triggers osteogenic bone transformation in calcified and stenotic human aortic valves: still a matter of debate

Sclerotic calcification of the aortic valve is a common disease in advanced age. However, pathophysiologic processes leading to valve calcifications are poorly understood. Transformation of atherosclerotic triggers to osteogenic differentiation is controversially discussed and is thought as a trigger of bone transformation in end stage disease. This study focuses on the transcriptional gene-profiling of severe calcified stenotic human aortic valves to clarify the molecular basis of the pathophysiological process. We collected severely calcified and stenotic human aortic valves (CSAV) with (CSAV+, n=10) and without (CSAV-, n=10) at least 4 weeks of statin pre-treatment prior to valve replacement and investigated transcriptional steady-state gene-profiling by using micro array technique and GAPDH-adjusted PCR for confirmation. Results were compared with findings in non-sclerotic aortic valves: C (n=6). Various parameters of inflammation were significantly up regulated as compared to C: eotaxin3, monokine induced by gamma-interferon, vascular adhesion protein-1 (VAP-1), peroxisome proliferative activated receptor-alpha or transforming growth factor beta 1 (TGF beta 1). Except for TGF beta 1 and VAP-1, statin pre-treatment neutralized altered gene expression. Genes of osteogenic bone transformation (tenascin C, bone sialoprotein, Cbfa1, Osteocalcin, Beta-catenin, Sox- and Cyclin-genes) were found unaltered in their expression in both, CSAV- or CSAV+ in comparison to C. This study shows continuing atherosclerotic inflammation on CSAV. Additionally, no evidence of initiated osteoblastic differentiation process was found. Pre-treatment of patients with statins partially neutralized the gene pattern of inflammation on the aortic valves. This suggests that there are potent benefits of statins on early development of inflammation on calcified aortic valves.

Dysregulation of antioxidant mechanisms contributes to increased oxidative stress in calcific aortic valvular stenosis in humans

OBJECTIVES

The aim of this study was to determine whether oxidative stress is increased in calcified, stenotic aortic valves and to examine mechanisms that might contribute to increased oxidative stress.

BACKGROUND

Oxidative stress is increased in atherosclerotic lesions and might play an important role in plaque progression and calcification. The role of oxidative stress in valve disease is not clear.

METHODS

Superoxide (dihydroethidium fluorescence and lucigenin-enhanced chemiluminescence), hydrogen peroxide H2O2 (dichlorofluorescein fluorescence), and expression and activity of pro- and anti-oxidant enzymes were measured in normal valves from hearts not suitable for transplantation and stenotic aortic valves that were removed during surgical replacement of the valve.

RESULTS

In normal valves, superoxide levels were relatively low and distributed homogeneously throughout the valve. In stenotic valves, superoxide levels were increased 2-fold near the calcified regions of the valve (p < 0.05); noncalcified regions did not differ significantly from normal valves. Hydrogen peroxide levels were also markedly elevated in calcified regions of stenotic valves. Nicotinamide adenine dinucleotide phosphate oxidase activity was not increased in calcified regions of stenotic valves. Superoxide levels in stenotic valves were significantly reduced by inhibition of nitric oxide synthases (NOS), which suggests uncoupling of the enzyme. Antioxidant mechanisms were reduced in calcified regions of the aortic valve, because total superoxide dismutase (SOD) activity and expression of all 3 SOD isoforms was significantly decreased. Catalase expression also was reduced in pericalcific regions.

CONCLUSIONS

This study provides the first evidence that oxidative stress is increased in calcified regions of stenotic aortic valves from humans. Increased oxidative stress is due at least in part to reduction in expression and activity of antioxidant enzymes and perhaps to uncoupled NOS activity. Thus, mechanisms of oxidative stress differ greatly between stenotic aortic valves and atherosclerotic arteries.