Current Vascular Pharmacology - Volume 13, Issue 3, 2015

Abdominal aortic aneurysms (AAA) are an important source of morbidity and mortality in the U.S. and worldwide. Treatment options are limited, with open surgery or endovascular repair remaining the only curative treatments. Classical cardiovascular medications have generally failed to prevent or significantly alter AAA formation or progression. Therefore, there is a tremendous need for better therapeutic approaches. With increasing knowledge of microRNA (miR) regulation in the context of cardiovascular disease, and with improving technical options permitting alteration of miRexpression levels in vitro and in vivo, we are offered a glimpse into the diagnostic and therapeutic possibilities of using miRs to treat vascular pathobiology. This review focuses on the role of miRs in aneurysmal disease of the abdominal aorta, summarizing recent publications regarding this topic, and outlining known effects of relevant miRs in AAA formation, including miR-21 and miR-29b. Despite there being only limited studies available, several other miRs also display clear potential for alteration of the disease process including miR-26a, the miR-17-92-cluster, miRs-221/222, miR-133 and miR-146a. While studies have shown that miRs can regulate the activity and interplay of vascular inflammatory cells, endothelial cells, smooth muscle cells and fibroblasts, all key elements leading to AAA formation, much work remains to be done.

Atherosclerosis (also known as arteriosclerotic vascular disease) is a chronic inflammatory disease of the arterial wall, characterized by the formation of lipid-laden lesions. The activation of endothelial cells at atherosclerotic lesion–prone sites in the arterial tree results in the up-regulation of cell adhesion molecules and chemokines, which mediate the recruitment of circulating monocytes. Accumulation of monocytes and monocyte-derived phagocytes in the wall of large arteries leads to chronic inflammation and the development and progression of atherosclerosis. The lesion experiences the following steps: foam cell formation, fatty streak accumulation, migration and proliferation of vascular smooth muscle cells, and fibrous cap formation. Finally, the rupture of the unstable fibrous cap causes thrombosis in complications of advanced lesions that leads to unstable coronary syndromes, myocardial infarction and stroke. MicroRNAs have recently emerged as a novel class of gene regulators at the post-transcriptional level. Several functions of vascular cells, such as cell differentiation, contraction, migration, proliferation and inflammation that are involved in angiogenesis, neointimal formation and lipid metabolism underlying various vascular diseases, have been found to be regulated by microRNAs and are described in the present review as well as their potential therapeutic application.

microRNAs (miRNAs), small non-coding RNA molecules that act as negative regulators of gene expression, are involved in a wide range of biological functions and control several cellular processes. This review illustrates miRNA regulation and function in tissue response to acute ischemia, focusing on miRNA role in acute myocardial infarction and describing a subset of miRNAs de-regulated upon cardiac ischemia. These miRNAs may represent “master ischemic” miRNAs, playing a pathogenetic role in one of the different components of tissue response to ischemia. Moreover, circulating miRNAs correlated to myocardial infarction and examples of miRNA involvement in ischemic diseases different from cardiac ischemia are also discussed. The identification of specific miRNAs as key regulators of cell biology has opened new clinical avenues, and may allow new diagnostic and/or prognostic tools development, as much as innovative therapeutic strategies. Two paradigmatic reports, in which miRNAs have been targeted to improve cardiac function in pre-clinical models of myocardial infarction, are described in detail and confirmed the efficacy of these strategies.

Peripheral artery disease (PAD) produces significant disability attributable to lower extremity ischemia. Limited treatment modalities exist to ameliorate clinical symptoms in patients with PAD. Growing evidence links microRNAs to key processes that govern disease expression in PAD including angiogenesis, endothelial function, inflammation, vascular regeneration, vascular smooth muscle cell function, restenosis, and mitochondrial function. MicroRNAs have been identified in circulation and may serve as novel biomarkers in PAD. This article reviews the potential contribution of microRNA to key pathways of disease development in PAD that may lead to microRNA-based diagnostic and therapeutic approaches.

Due to increased life expectancy in a growing world population, the impact of ageing on the pathophysiology of cardiovascular diseases will increase. Therefore, a better understanding of agerelated biological changes is important and necessary to combat cardiovascular diseases in the future. microRNAs (miRs) are small non coding RNAs emerging as key regulator in several vascular pathologies such as atherosclerosis or hypertension, which show a clear association with increasing age. This review discusses the involvement of miRs in several age-associated pathologies such as oxidative stress, vascular inflammation, vascular tension, endothelial cell senescence and impaired angiogenesis.

MicroRNAs have emerged as key players of gene regulation during development and disease states like cancer and cardiovascular diseases. Pulmonary arterial hypertension (PAH), a vascular disease characterized by pulmonary resistance and vessel occlusion, is not spared by microRNA implication. This is not surprising since PAH shares common aberrantly activated pathways with cancers that lead to proliferation and survival of pulmonary arterial smooth muscle cells, among others, within the artery wall and narrowing the lumen. Recent studies demonstrated the role of miR-204 and miR- 206 in pulmonary artery smooth muscle cell (PASMC) proliferation. Other microRNAs, such as miR-145, miR-21 and the miR17/92 cluster, have been associated with the disrupted BMPR2 pathway. During the last couple of years, the number of studies on the role of microRNA in PAH has broadened, defining it clearly as a HOT TOPIC. This current review presents an overview of the most recent knowledge as well as future possibilities. The use of microRNA therapies is still uncertain and poorly applied in the clinical setting yet. It is still critical to increase the knowledge and the translational potential of this HOT TOPIC to make it become a HOPE TOPIC.

MicroRNAs are negative regulators of gene expression that have been shown to be essential elements in the coordination of complex regulatory pathways. One of these short non-coding RNAs, microRNA-126, is highly enriched in the vascular endothelium and was shown to play distinct roles in angiogenesis, vasculogenesis and endothelial inflammation. Abrogation of this microRNA leads to severe complications in the response in vascular development as well as vital repair mechanisms carried out by endothelial cells. Interestingly, recent data suggest that the homeostatic role of microRNA-126 may reach far beyond its endothelial functions as this microRNA was also found to be present in cells of the hematopoietic system and in microvesicles or ‘free-form’ in the periphery. MicroRNA-126 is controlling the fate and/or function of a variety of cells differentiating from the hematopoietic lineage, including megakaryocytes and erythrocytes. Recent studies identified circulating microRNA-126 as a biomarker for myocardial injury and vascular damage in diabetes. Furthermore, reports have suggested a protective role of circulating microRNA-126 in murine models of organ ischemia. Here, we review current insights in the role of microRNA-126 in vascular homeostasis and conclude that this microRNA may serve to integrate and facilitate both local as well as systemic functions in vascular maintenance and repair.

Stroke is a leading cause of death and disability worldwide. Ischemic stroke is the dominant subtype of stroke and results from focal cerebral ischemia due to occlusion of major cerebral arteries. Thus, the restoration or improvement of reduced regional cerebral blood supply in a timely manner is very critical for improving stroke outcomes and poststroke functional recovery. The recovery from ischemic stroke largely relies on appropriate restoration of blood flow via angiogenesis. Newly formed vessels would allow increased cerebral blood flow, thus increasing the amount of oxygen and nutrients delivered to affected brain tissue. Angiogenesis is strictly controlled by many key angiogenic factors in the central nervous system, and these molecules have been well-documented to play an important role in the development of angiogenesis in response to various pathological conditions. Promoting angiogenesis via various approaches that target angiogenic factors appears to be a useful treatment for experimental ischemic stroke. Most recently, microRNAs (miRs) have been identified as negative regulators of gene expression in a post-transcriptional manner. Accumulating studies have demonstrated that miRs are essential determinants of vascular endothelial cell biology/angiogenesis as well as contributors to stroke pathogenesis. In this review, we summarize the knowledge of stroke-associated angiogenic modulators, as well as the role and molecular mechanisms of stroke-associated miRs with a focus on angiogenesis-regulating miRs. Moreover, we further discuss their potential impact on miR-based therapeutics in stroke through targeting and enhancing post-ischemic angiogenesis.

Several non-coding microRNAs (miRs) are implicated in the pathogenesis of obesity, metabolic syndrome, diabetes mellitus, atherosclerosis and cardiovascular disease. Some of these miRs are beneficial but others are hazardous. Silencing of the latter by antisense oligonucleotides has been attempted in animal models with promising results. However, the replacement of down-regulated beneficial miRs, by manufactured miR mimics, or increasing their expression is much more demanding and has several limitations. The treatment of cardiovascular diseases through miR manipulation shows potential, provided safety and cost effectiveness issues are considered carefully before implementation in humans.

Heart failure with preserved ejection fraction (HFpEF). Arterial hypertension (AH), arterial stiffness (AS), older age, and female gender are the main determinants of HFpEF, but several cardiac or extra-cardiac pathologies are also possible causes. The combined ventricular-vascular stiffening (abnormal left atrium-left ventricle coupling related to AS) is the main contributor of the increased prevalence of HFpEF in elderly persons, particularly elderly women, and in younger persons with AH. The hospitalization and mortality rates of HFpEF are similar to those of heart failure with reduced EF (HFrEF). However, although the prognosis of HFrEF has been substantially improved during the last 2 decades, the effective treatment of HFpEF remains an unmet need. Regimens effective in HFrEF have no substantial effect on HFpEF, because of different pathophysiologies of the 2 syndromes. Pipeline drugs seem promising, but it will take some years before they are commercially available. Aggressive treatment of noncardiac comorbidities seems to be the only option at hand. Treatment of anaemia, sleep disorders, chronic kidney disease (CKD), non-alcoholic fatty liver (NAFLD), atrial fibrillation, diabetes, and careful use of diuretics to reduce preload are effective to some degree. Statin treatment, despite the presence of dyslipidaemia, deserves special attention because it has been proven, mainly in small studies or post hoc analyses of trials, that it offers a substantial improvement in quality of life and a reduction in mortality rates. We need to urgently utilize these recourses to relieve a considerable part of the general population suffering from HFpEF, a deadly disease.

The current paradigm in attempting to treat metastatic renal cell carcinoma (mRCC) is a first line treatment with a vascular endothelial growth factor (VEGF) antagonist and second and subsequent treatments with either a vascular endothelial growth factor receptor (VEGFR) or an mTOR (mammalian Target of Rapamycin) inhibitor, while conventional chemotherapeutic and hormonal treatments do not play a role in the management of mRCC. Several drugs directed against VEGF and VEGFR have been developed in recent times. Phase III data validates sunitinib, pazopanib and sorafenib as the best-supported drugs in firstline therapy. Second-line treatment possibilities include axitinib, everolimus and sorafenib. Choosing the right combination of first and second line treatments, however, is difficult, because the success of treatment depends on the precondition of the patient. Hence, biomarkers indicating the best choice of therapy in individual patients are searched and newer trials are set to determine the role of surgery and vaccination together with anti-angiogenic drugs in the treatment of mRCC. In this review, current guidelines in mRCC management are summarized and possibilities of future personalized therapies are pointed out.

Levels of 25-hydroxy vitamin D [25(OH)D] are reported to be decreased in cardiovascular disease (CVD) and in other chronic immunopathologies. Vitamin D (vitD) has been shown to be significantly linked to mortality, and is thought to be a predictor of survival. Therefore, supplementation with vitD has been suggested as an option to improve clinical outcomes. In contrast to the causal assumption, we hypothesize that the decreased vitD levels, seen in patients with CVD and chronic immunopathologies is secondary to inflammation and not as pathophysiologically relevant as currently suggested. Under these conditions, low vitD might be mainly caused by oxidative stress that results from chronic, immune-mediated vascular and systemic inflammation seen in patients with CVD. The oxidative environment most likely causes biodegradation of vitD and interferes with key enzymes, disturbing the biosynthesis of 25(OH)D and 1,25(OH)D. Thus far, no clear evidence of a beneficial effect of vitD supplements exists, beyond treating vitD deficiency to improve skeletal health. Moreover, a prolonged and/or high dose vitD supplementation, unless needed to correct actual vitD deficiency [levels of 25(OH)D<20 ng/ml)] may even be immunologically harmful by downregulating Th1 immune responses and indirectly upregulating Th2 immune activation with potential detrimental metabolic and cardiovascular effects. Large randomized controlled studies of vitD with multiple outcomes (skeletal, metabolic, cardiovascular and mental) are urgently needed.

Cilostazol (CIL) is effective for the treatment of patients with peripheral arterial disease (PAD). CIL is an orally administered drug with multiple effects, including anti-platelets aggregation, favorable functions on plasmatic lipids and vasodilator ones, but how these effects might be related to improvement in patients walking affected by PAD is not fully understood. The latest data demonstrate that nitric oxide (NO) is induced by CIL through endothelial nitric oxide synthase (eNOS) activation via a cyclic-AMP (cAMP)/ protein kinase A (PKA)- and PI3K/Akt- dependent mechanism. This mechanism is also responsible for the vasodilatation dependent on endothelium which characterized patients receiving CIL. Other investigators have found that CIL notably reduces the exercise-induced host-inflammatory response in PAD patients, and consequently it improves lipid hydroperoxides and cell-adhesion molecule levels. We recently reported that CIL is able to cause neoangiogenesis in vivo by stimulating the production of proangiogenic proteins, such as vascular endothelial growth factor (VEGF), that increase levels of Endothelial progenitor cells (EPCs) and the formation of new blood vessels. The mechanisms of action of this drug are several and are not clear and established. The objective of the present review is to analyze the existing data about the therapeutic effects of CIL, with the purpose of providing practical indications about this topic for the management of subjects affected by ischemic disorders.

Aberrant proliferation of vascular smooth muscle cells [VSMCs] is implicated in the pathogenesis of vascular pathologies such as atherosclerosis and restenosis. Accumulating evidences have revealed that microRNAs are involved in cell proliferation in various pathological conditions. In the present study, we showed that miR-136 was up regulated in human coronary atherosclerotic plaques when compared with normal coronary artery tissues. Moreover, miR-136 levels were up regulated in proliferative vascular smooth muscle cells induced by platelet-derived growth factor [PDGF] or serum. In cultured VSMCs, over expression of miR-136 stimulated cell proliferation. PPP2R2A was proved to be the direct target gene of miR-136 and knockdown of PPP2R2A had a proliferative effect on VSMCs. miR-136-induced PPP2R2A down-regulation was accompanied by increased expression of ERK1/2 phosphorylation. Inhibition of ERK1/2 abolished the effect of miR-136 and knockdown of PPP2R2A on VSMCs proliferation. In summary, aberrant miR-136 up regulation in atherosclerosis contributes to abnormal VSMC proliferation through suppressing the ERK1/2 pathway by targeting PPP2R2A. Our study also suggested that specific modulation of miR-136 in human VSMCs may provide a potential approach for the treatment of atherosclerosis.

Essential hypertension is closely related to alterations of the microcirculation as evidenced by increased media-to-lumen ratio of small resistance arteries and capillary rarefaction. It has been proposed that microvasculature alterations can further deteriorate target organ damage under the influence of increased hemodynamic load in hypertension. More than a decade ago, small artery structure was found to be the most potent predictor of cardiovascular events in essential or secondary hypertension. Amelioration of resistance vessel structure by antihypertensive drugs showed a clear benefit when patients were treated with calcium antagonists and renin-angiotensin-aldosterone inhibitor regimens. Well-designed controlled studies are needed to address the important questions whether different antihypertensive agent combinations could be related to diverse microcirculatory “responses” in terms of structure and function.