Vascular endothelium, hemodynamics, and the pathobiology of atherosclerosis

MicroRNAs as pharmacological targets in endothelial cell function and dysfunction

Endothelial cell dysfunction is a term which implies the dysregulation of normal endothelial cell functions, including impairment of the barrier functions, control of vascular tone, disturbance of proliferative, migratory and morphogenic capacities of endothelial cells, as well as control of leukocyte trafficking. MicroRNAs are short non-coding RNAs that have emerged as critical regulators of gene expression acting predominantly at the post-transcriptional level. This review summarizes the latest insights in the identification of endothelial-specific microRNAs and their targets, as well as their roles in controlling endothelial cell functions in both autocrine and paracrine manner. In addition, we discuss the therapeutic potential for the treatment of endothelial cell dysfunction and associated vascular pathophysiological conditions.

Vascular function during prolonged progression and regression of atherosclerosis in mice

OBJECTIVE

Endothelial dysfunction is associated with atherosclerosis in mice, but it is difficult to reduce cholesterol levels enough to study regression of atherosclerosis in genetically modified mice. The goal of this study was to examine vascular structure and function before and after reducing elevated plasma lipid levels with a genetic switch in Reversa mice, and identify novel mechanisms contributing to structural and functional improvements in the vasculature after reduction of blood lipids.

METHODS AND RESULTS

After 6 months of hypercholesterolemia, endothelial function (maximum relaxation to acetylcholine) in aorta was impaired and responses to nitric oxide were unaffected. Further impairment in endothelial function was observed after 12 months of hypercholesterolemia and was associated with reductions in sensitivity to nitric oxide. Expression of dihydrofolate reductase was reduced at 6 and 12 months, and addition of the tetrahydrobiopterin precursor sepiapterin significantly improved endothelial function. Reducing cholesterol levels at 6 months normalized dihydrofolate reductase expression and prevented further impairment in endothelial function. Similar functional changes were observed after 12 months of hypercholesterolemia followed by 2 months of lipid lowering.

CONCLUSIONS

Our data suggest that endothelial dysfunction after prolonged hypercholesterolemia is the result of both impairment of sensitivity to nitric oxide and reduced nitric oxide synthase cofactor bioavailability. Both of these changes can be prevented by normalizing blood lipids during moderately severe or advanced atherosclerosis.

The pathobiology of acute coronary syndromes: clinical implications and central role of the mitochondria

Ongoing investigation has provided new insights into the pathobiology of myocardial ischemic injury. These include an improved understanding of the roles of the major modes of cell injury and death, including oncosis, apoptosis, and unregulated autophagy, as well as the central role of the mitochondria in the progression of myocardial ischemic injury, reperfusion injury, and myocardial conditioning. This understanding is providing insights for developing new pathophysiologic, pharmacologic, and cell-based therapies, alone or in combination with percutaneous coronary interventions, for better preservation of myocardium and reduction of morbidity and mortality rates from ischemic heart disease.

Mechanisms of arterial remodeling: lessons from genetic diseases

Vascular disease is still the leading cause of morbidity and mortality in the Western world, and the primary cause of myocardial infarction, stroke, and ischemia. The biology of vascular disease is complex and still poorly understood in terms of causes and consequences. Vascular function is determined by structural and functional properties of the arterial vascular wall. Arterial stiffness, that is a pathological alteration of the vascular wall, ultimately results in target-organ damage and increased mortality. Arterial remodeling is accelerated under conditions that adversely affect the balance between arterial function and structure such as hypertension, atherosclerosis, diabetes mellitus, chronic kidney disease, inflammatory disease, lifestyle aspects (smoking), drugs (vitamin K antagonists), and genetic abnormalities [e.g., pseudoxanthoma elasticum (PXE), Marfan's disease]. The aim of this review is to provide an overview of the complex mechanisms and different factors that underlie arterial remodeling, learning from single gene defect diseases like PXE, and PXE-like, Marfan's disease and Keutel syndrome in vascular remodeling.