Current Vascular Pharmacology - Volume 11, Issue 5, 2013

Hypoxia can induce functional and structural vascular remodeling by changing the expression of trophic factors to promote homeostasis. While most experimental approaches have been focused on functional remodeling, structural remodeling can reflect changes in the abundance and organization of vascular proteins that determine functional remodeling. Better understanding of age-dependent hypoxic macrovascular remodeling processes of the cerebral vasculature and its clinical implications require knowledge of the vasotrophic factors that influence arterial structure and function. Hypoxia can affect the expression of transcription factors, classical receptor tyrosine kinase factors, non-classical G-protein coupled factors, catecholamines, and purines. Hypoxia’s remodeling effects can be mediated by Hypoxia Inducible Factor (HIF) upregulation in most vascular beds, but alterations in the expression of growth factors can also be independent of HIF. PPARγ is another transcription factor involved in hypoxic remodeling. Expression of classical receptor tyrosine kinase ligands, including vascular endothelial growth factor, platelet derived growth factor, fibroblast growth factor and angiopoietins, can be altered by hypoxia which can act simultaneously to affect remodeling. Tyrosine kinase-independent factors, such as transforming growth factor, nitric oxide, endothelin, angiotensin II, catecholamines, and purines also participate in the remodeling process. This adaptation to hypoxic stress can fundamentally change with age, resulting in different responses between fetuses and adults. Overall, these mechanisms integrate to assure that blood flow and metabolic demand are closely matched in all vascular beds and emphasize the view that the vascular wall is a highly dynamic and heterogeneous tissue with multiple cell types undergoing regular phenotypic transformation.

This review discusses the importance of placental vascular development, as reflected by placental angiogenesis and placental blood flow, to placental function in normal pregnancies. We then summarize our current understanding of how maternal stress, including inadequate maternal nutrition as well as the application of assisted reproductive technologies (ART), leads to compromised placental angiogenesis and function and the subsequent effects on fetal and neonatal growth and development. Finally, we discuss several promising therapeutic approaches to ‘rescue’ placental vascular development and function in compromised pregnancies, leading to improved pregnancy and postnatal outcomes.

Endothelins are 21-amino acid peptides involved in vascular homeostasis. Three types of peptide have been identified, with endothelin-1 (ET-1) being the most potent vasoconstrictor currently known. Two endothelin receptor subtypes are found in various tissues, including the brain, heart, blood vessel, lung, and placenta. The ETA-receptor is associated with vasoconstriction in vascular smooth muscle. Conversely, the ETB-receptor can elicit a vasoconstrictor effect in vascular smooth muscle and a vasodilator effect via its action in endothelial cells. Both receptors play a key role in maintaining circulatory homeostasis and vascular function. Changes in ET-1 expression are found in various disease states, and overexpression of ET-1 is observed in hypertension and preeclampsia in pregnancy. Placental localization of ET-1 implies a key role in regulating the uteroplacental circulation. Additionally, ET-1 is important in the fetal circulation and is involved in the pulmonary circulation and closure of the ductus arteriosus after birth, as well as fetal growth constriction in utero. ET receptor antagonists and nitric oxide donors may provide therapeutic potential in treating conditions associated with overexpression of ET and hypertension.

Chymase is a chymotrypsin-like serine protease. It has been identified as a key angiotensin converting enzyme (ACE)-independent and endothelin converting enzyme (ECE)-independent converting enzyme that generates angiotensin II and endothelin-1 (ET-1). As an inflammatory protease, chymase participates in multiple inflammatory responses in the vasculature which drive cytokine production and adhesion molecule expression. Chymase is also involved in extracellular matrix remodeling in both vascular and non-vascular tissues. Consequently, chymase has been implicated in the pathogenesis of multiple cardiovascular, immune, and inflammatory diseases. Recent studies have shown that chymase expression and activity are increased in placental trophoblasts and in the maternal vascular endothelium in women diagnosed with preeclampsia, a hypertensive disorder in human pregnancy. The present review will address the potential roles of chymase-mediated placental and vascular dysfunction in preeclampsia. The effects of chymase on inflammatory responses associated with endothelial activation/dysfunction in preeclampsia are also discussed.

This review provides evidence that antenatal hypoxia, which represents a significant and worldwide problem, causes prenatal programming of the lung. A general overview of lung development is provided along with some background regarding transcriptional and signaling systems of the lung. The review illustrates that antenatal hypoxic stress can induce a continuum of responses depending on the species examined. Fetuses and newborns of certain species and specific human populations are well acclimated to antenatal hypoxia. However, antenatal hypoxia causes pulmonary vascular disease in fetuses and newborns of most mammalian species and humans. Disease can range from mild pulmonary hypertension, to severe vascular remodeling and dangerous elevations in pressure. The timing, length, and magnitude of the intrauterine hypoxic stress are important to disease development, however there is also a genetic-environmental relationship that is not yet completely understood. Determining the origins of pulmonary vascular remodeling and pulmonary hypertension and their associated effects is a challenging task, but is necessary in order to develop targeted therapies for pulmonary hypertension in the newborn due to antenatal hypoxia that can both treat the symptoms and curtail or reverse disease progression.

Maternal vascular adaptations, implantation of embryo, and placental growth and development are crucial for overall well-being of the fetus and are controlled by a range of signals, including growth factors and steroid hormones. The calcitonin (CT)/calcitonin gene-related peptide (CGRP) family peptides have been the focus of emerging studies, and these peptides appear to mediate some of the critical functions during pregnancy. Three peptides of the CT/CGRP family, CGRP, adrenomedullin, and intermedin, working through their overlapping receptor components, exert significant positive effects on vascular adaptations during pregnancy, uteroplacental vascular functions, and fetal growth. Many of the effects of these peptides are regulated by sex steroid hormones. Use of peptide antagonist in animals, together with genetic animal models, strongly implicates the importance of these 3 peptides in human pregnancy and related complications. However, insights into the underlying mechanisms of their actions on fetal-placental growth are limited by the lack of specificity of currently available antagonists. Future studies with specific knockdown of receptor components and/or peptides should be helpful for better understanding of these mechanisms and for the development of target-specific therapies to prevent pregnancy complications.

As compared to the adult, the developing fetus and newborn infant are at much greater risk for dysregulation of cerebral blood flow (CBF), with complications such as intraventricular and germinal matrix hemorrhage with resultant neurologic sequelae. To minimize this dysregulation and its consequences presents a major challenge. Although in many respects the fundamental signal transduction mechanisms that regulate relaxation and contraction pathways, and thus cerebrovascular tone and CBF in the immature organism are similar to those of the adult, the individual elements, pathways, and roles differ greatly. Here, we review aspects of these maturational changes of relaxation/contraction mechanisms in terms of both electro-mechanical and pharmaco-mechanical coupling, their biochemical pathways and signaling networks. In contrast to the adult cerebrovasculature, in addition to attenuated structure with differences in multiple cytoskeletal elements, developing cerebrovasculature of fetus and newborn differs in many respects, such as a strikingly increased sensitivity to [Ca2+]i and requirement for extracellular Ca2+ for contraction. In essence, the immature cerebrovasculature demonstrates both “hyper-relaxation” and “hypo-contraction”. A challenge is to unravel the manner in which these mechanisms are integrated, particularly in terms of both Ca2+-dependent and Ca2+-independent pathways to increase Ca2+ sensitivity. Gaining an appreciation of these significant age-related differences in signal mechanisms also will be critical to understanding more completely the vulnerability of the developing cerebral vasculature to hypoxia and other stresses. Of vital importance, a more complete understanding of these mechanisms promises hope for improved strategies for therapeutic intervention and clinical management of intensive care of the premature newborn.

The challenge of pregnancy to the mother requires that her own metabolic and endocrine needs be met while also taking on the literally growing demands of the unborn child. While all of the mother’s organs require continued support, the uterus and now added placenta must also develop substantially. One critical area of adaptation is thus the ability to provide added blood flow over and above that already serving the preexisting maternal organs. Previous reviews have covered in detail how this is achieved from an endocrine or indeed vascular physiology standpoint and we will not repeat that here. Suffice it to say in addition to new vessel growth, there is also the need to achieve reduced vascular resistance through maintenance of endothelial vasodilation, particularly through NO and PGI2 production in response to multiple agonists and their associated cell signaling systems. In this review, we continue our focus on pregnancy adaptive changes at the level of cell signaling, with a particular emphasis now on the developing story of the critical role of gap junctions. Remapping of cell signaling itself beyond changes in individual hormones and respective receptors brings about global changes in cell function, and recent studies have revealed that such post-receptor changes in cell signaling are equally if not more important in the process of pregnancy adaptation of endothelial function than the upregulated expression of vasodilator synthetic pathways themselves. The principle significance, however, of reviewing this aspect of pregnancy adaptation of endothelial cell function is that these same gap junction proteins that mediate pregnancy-adapted changes in vasodilatory signaling function may also be the focal point of failure in diseased pregnancy, and clues as to how and why are given by comparing studies of Cx43 functional suppression at wound sites with studies of preeclamptic pregnancy. If preeclamptic pregnancy is indeed a pregnancy misconstrued by the body in endocrine terms to be a wound, then the kinases so activated that correspondingly suppress Cx43 function in the vascular endothelium may also be valid pharmacologic targets for novel therapies in the near future.

Endothelial cells in the utero-placental circulation play an important physiological role in maintaining the fetoplacental vessels in a vasodilated state as these vessels are non-innervated. These endothelial cells produce both prostacyclin and nitric oxide which in addition to causing vasodilation also prevent platelet aggregation and adhesion of platelets to endothelial cells. Most investigators are of the opinion that energy metabolism of endothelial cells and ATP generation is mainly glycolytic. Glycolytic activity in endothelial cells is increased during proliferation to maintain ATP at normal levels by an increase in the expression of the glucose transporter. More recent studies have reported the existence of a functional F1F0 ATP synthase on the surface of HUVEC and it has been found to be enzymatically active in the synthesis of ATP. Additional studies utilizing very early passage HUVEC need to be carried out to ascertain the relative contribution of oxidative phosphorylation compared with the glycolytic pathway for ATP synthesis in normal pregnancy as well as in abnormal states like preeclampsia, diabetes, intrauterine injection as well as intrauterine growth restriction.

During a normal course of pregnancy, uterine vascular tone is significantly decreased resulting in a striking increase in uterine blood flow, which is essential for fetal development and fetal growth. Chronic hypoxia during gestation may adversely affect the normal adaptation of uterine vascular tone and increase the risk of preeclampsia and fetal intrauterine growth restriction. In this review, we present evidence that the regulation of K+ channels is an important mechanism in the adaptation of uterine vascular tone to pregnancy and hypoxia. There are four types of K+ channels identified in arterial smooth muscle cells: 1) voltage-dependent K+ (Kv) channels, 2) Ca2+-activated K+ (KCa) channels, 3) inward rectifier K+ (KIR) channels, and 4) ATP-sensitive K+ (KATP) channels. Pregnancy differentially augments the expression and activity of K+ channels via downregulation of protein kinase C signaling in uterine and other vascular beds, leading to decreased uterine vascular tone and increased uterine blood flow. Sex steroid hormones play an important role in the pregnancy- mediated alteration of K+ channels in the uterine vasculature. In addition, chronic hypoxia alters uterine vascular K+ channels expression and activities via modulation of steroid hormones/receptors-mediated signaling, resulting in increased uterine vascular tone during pregnancy.

Although blood flow in the placental vasculature is governed by the same physiological forces of shear, pressure and resistance as in other organs, it is also uniquely specialized on the maternal and fetal sides. At the materno-fetal interface, the independent uteroplacental and umbilicoplacental circulations must coordinate sufficiently to supply the fetus with the nutrients and substrates it needs to grow and develop. Uterine arterial flow must increase dramatically to accommodate the growing fetus. Recent evidence delineates the hormonal and endothelial mechanisms by which maternal vessels dilate and remodel during pregnancy. The umbilical circulation is established de novo during embryonic development but blood does not flow through the placenta until late in the first trimester. The umbilical circulation operates in the interest of maintaining fetal oxygenation over the course of pregnancy, and is affected differently by mechanical and chemical regulators of vascular tone compared to other organs. The processes that match placental vascular growth and fetal tissue growth are not understood, but studies of compromised pregnancies provide clues. The subtle changes that cause the failure of the normally regulated vascular processes during pregnancy have not been thoroughly identified. Likewise, practical and effective therapeutic strategies to reverse detrimental placental perfusion patterns have yet to be investigated.

Chronic kidney disease (CKD) is associated with high cardiovascular morbidity and mortality. The available data suggest that efforts to reduce mortality in the CKD population should be focused on treatment and prevention of, among others, coronary artery disease and congestive heart failure. Accelerated atherosclerosis present in CKD patients also leads to a decline in renal function. Definite data concerning the treatment of heart failure in CKD patients are lacking, because patients with significant renal impairment have mostly been excluded from randomized studies. Nevertheless, it seems that CKD patients should receive similar cardiovascular treatment to that used in patients with normal kidney function, but the doses of drugs ought to be titrated to achieve an optimal effect while avoiding adverse events. Several studies have also shown that despite the high risk, in patients with acute coronary syndrome (ACS), revascularization procedures in patients with CKD appear to be advantageous in the long run and are therefore justified. However, large clinical trials are needed to confirm the benefits and to identify possible disadvantages associated with various methods of treatment.

Arterial inflammation and remodeling, important sequellae of advancing age, are linked to the pathogenesis of age-associated arterial diseases e.g. hypertension, atherosclerosis, and metabolic disorders. Recently, high-throughput proteomic screening has identified milk fat globule epidermal growth factor VIII (MFG-E8) as a novel local biomarker for aging arterial walls. Additional studies have shown that MFG-E8 is also an element of the arterial inflammatory signaling network. The transcription, translation, and signaling levels of MFG-E8 are increased in aged, atherosclerotic, hypertensive, and diabetic arterial walls in vivo as well as activated vascular smooth muscle cells (VSMC) and a subset of macrophages in vitro. In VSMC, MFG-E8 increases proliferation and invasion as well as the secretion of inflammatory molecules. In endothelial cells (EC), MFG-E8 facilitates apoptosis. In addition, MFG-E8 has been found to be an essential component of the endothelial-derived microparticles that relay biosignals and modulate arterial wall phenotypes. This review mainly focuses upon the landscape of MFG-E8 expression and signaling in adverse arterial remodeling. Recent discoveries have suggested that MFG-E8 associated interventions are novel approaches for the retardation of the enhanced rates of VSMC proliferation and EC apoptosis that accompany arterial wall inflammation and remodeling during aging and age-associated arterial disease.

Background: Smoking adversely affects cardiovascular disease (CVD) morbidity and mortality; however the effect of long-term statin treatment in high risk smokers is not entirely clear. The primary endpoint of this post hoc analysis of the GREek Atorvastatin and Coronary Heart Disease Evaluation (GREACE) study (n=1,600 patients with established coronary heart disease, mean follow-up 3-years) was the incidence of major CVD events, a composite of death, myocardial infarction, revascularization, unstable angina, heart failure, and stroke in statin-treated patients (n=880) who continued to smoke (n=129) compared with ex-smokers (n=309) and never smokers (n=442) as well as on patients not treated with a statin (n=720) of all smoking categories. Secondary endpoints were the effect of smoking on chronic kidney disease (CKD) and on non-alcoholic fatty liver disease (NAFLD), two major and common independent CVD risk factors. Results: Among statin treated patients the hazard ratio (HR) for current smokers compared with never smokers was 1.86 [95% confidence interval-(CI) 1.19-2.10); similar was the HR for current smokers compared with ex-smokers. Absolute (16.3%) and relative (45.6%) CVD risk reduction was great in current smokers on statins compared with those not on a statin; however they still had the highest absolute CVD event incidence (19.4%). Low high density lipoprotein cholesterol and higher triglycerides may account, at least in part, for this. The highest risk of CVD events in any of the 6 groups was in the smokers not on a statin (35.7%). CKD and NAFLD were not negatively affected by smoking and they do not appear to be implicated in the adverse effect of smoking on CVD event rate in patients on a statin. Conclusions: Statins reduce CVD morbidity and mortality in current smokers with CVD, but these remain high in terms of absolute incidence compared with ex- and never smokers. CKD and NAFLD are not affected by smoking and do not seem to contribute to this high CVD event incidence. These make smoking cessation imperative in high risk patients even if they are on statins.

Introduction: Primary and secondary prevention of cardiovascular Disease (CVD) are major concerns and priorities. The best tools that we actually have to prevent CVD are the biomarkers. Numerous studies have shown that the presentation of cardiac disease in women is quite different from the presentation in men. Thus, one question arises “Are there any differences in biomarkers as well?” The answer to this question could open new avenues for a tailored management of cardiac diseases. Method and Results: We searched the PubMed and Medline databases for articles comparing differences between the 2 genders in terms of biomarker expression. Keywords used included “Cardiovascular biomarkers sex differences”. We reviewed the role of different biomarkers in the 2 genders in relation to cardiac events. Conclusions: Differences of expressions in biomarker levels were found between the 2 genders. Further investigation should be promoted.

Statins are well-established and effective drugs in the treatment of hyperlipidemias. However the effects of statins extend beyond lipid-lowering. The pleiotropic effects of statins have been shown to modify inflammatory cell signaling of the immune response to infection. Statins have emerged as potential immunomodulatory and antioxidant agents that might impact on sepsis outcomes. It was postulated that statins may be candidates for the treatment of sepsis. Recent animal and human data suggest that statin therapy might be beneficial in patients before the onset of sepsis or in its initial period, but should be used with care when patients are diagnosed with severe sepsis or septic shock. Some analyses also provide evidence for statins as an adjuvant therapy in sepsis. Because of the divergent results of studies, the potential benefit needs to be validated in randomized, controlled trials. In this review, we describe current evidence on the use of statins in the prevention and treatment of sepsis.