Search

Pharmacogenomics is a field aimed at understanding the genetic contribution to inter-patient variability in drug efficacy and toxicity. The promise of pharmacogenomics is that it will allow for individualized therapy based on a person's genetic makeup, allowing for the selection of the drug that is likely to be the most effective with minimal risk of toxicity. Pharmacogenomics can also be used to help guide the drug discovery process, although this is not discussed in this chapter. This chapter describes the various manners in which pharmacogenomics might be used in the treatment of cardiovascular disease, including those whose treatment is by trial-and-error (like hypertension), and those whose treatment is protocol-driven (like heart failure or myocardial infarction). The current literature on genetic associations with efficacy and toxicity of cardiovascular drug response is reviewed. The approaches to pharmacogenomics research are also reviewed, including a candidate gene-driven approach and genomic approaches. There is discussion of how the approaches to date, usually single-candidate gene, must become more sophisticated in order to better understand the genetic basis for variable drug response. There is also extensive discussion of the various laboratory approaches that are essential to pharmacogenomics, including a number of different polymorphism genotyping methods. Pharmacogenomics holds great promise for enhancing our understanding of cardiovascular drug response and allowing for individualized therapy. There will be substantial work in this field in the coming years, which will hopefully lead to the point of individualization of cardiovascular drug therapy in patients. [ABSTRACT FROM AUTHOR]

Genetic approaches such as gene targeting have been extensively used to gain a better understanding of the role of hormones and pathways involved in cardiovascular physiology. Given its pivotal role in cardiovascular homeostasis the renin-angiotensin system has been one of the most frequently targeted systems. Angiotensinogen (AGT), the only known precursor of the renin-angiotensin system, has received particular attention because genetic and molecular studies have shown that genetic variation at this locus impacts individual differences in blood pressure and the likelihood of developing essential hypertension. Knockout and overexpression of the AGT gene lead to adverse cardiovascular phenotypes. In this chapter we will review these data and detail a strategy using well-characterized cell-specific promoters to specifically target the AGT gene to defined cells and tissues. The development and characterization of these models has helped uncover the role and significance of local production of AGT in several tissues. [ABSTRACT FROM AUTHOR]

Dilated cardiomyopathy (DCM) without an established causative factor for the damage to the myocardium is termed "idiopathic DCM," and it is the cause of approximately one-fourth of the cases of congestive heart failure in the United States. Familial occurrence accounts for 20% or more of idiopathic DCM, and recently a considerable number of genes associated with DCM have been identified. This review will focus on 18 genes currently known as DCM response genes because of their pathological involvement in this disease. The incidence of DCM caused by each gene is relatively small; however, the study of these genes has led us to understand the specific disease pathways of DCM, which may ultimately lead to understanding the more common condition of heart failure. [ABSTRACT FROM AUTHOR]

Human embryonic stem (ES) cells are pluripotent cells isolated from the inner cell mass of blastocyst-stage embryos. These cells are capable of self-renewal and can differentiate into many cell types. In vivo, human ES cells injected into immune-deficient mice yield teratomas with ectodermal, mesodermal, and endodermal cell derivatives. In vitro, spontaneous aggregation of human ES cells results in the formation of embryoid bodies (EBs) comprised of differentiated cells from the three embryonic germ layers. The addition of growth factors can induce the differentiation of human ES cells into specific populations of cells, among them the cells of the cardiovascular system, cardiomyocytes, and endothelial cells. Functional cardiomyocytes caused the EBs to exhibit rhythmic contractions. The cells of the cardiovascular system were distinguished by molecular markers and by their structural and functional characteristics. Human ES cells may serve as a source of cells for cellular transplantation in different pathologies, among them cardiovascular diseases, and as a model to study the embryonic development of human beings. [ABSTRACT FROM AUTHOR]

Cell transplantation of noncontractile cells into ischemic or dilated cardiomyopathic hearts prevents progressive failure and improves cardiac function by incompletely understood mechanisms. Significant angiogenesis and extracellular matrix remodeling occur after cell transplantation, but these effects do not fully explain the improvement in systolic function of the heart. Recent provocative results suggest that cell transplantation may be able to induce neocardiomyogenesis, and may enhance regional systolic function by recruiting stem cells that differentiate into functioning cardiomyocytes. Enhancing these effects using a combined modality that includes transplantation of genetically modified cells may hold the key to future cardiac regeneration. [ABSTRACT FROM AUTHOR]

Therapeutic angiogenesis/vasculogenesis represents a new approach to treating patients with ischemic disease not curable with conventional treatment. Manipulation of the angiogenesis program and transplantation of progenitor cells is hoped to overcome endogenous liabilities that impede appropriate healing in atherosclerotic or diabetic patients. Viral vectors represent the usual means for delivering curative genes, but new nonviral methods are gaining importance for their safer profile. The number of angiogenic substances suitable for therapeutic purposes is rapidly growing, and combinatory strategies offer distinctive advantages. Combating endothelial death or interfering with vascular destabilization may prevent organ failure. Ex vivo engineered endothelial progenitor cells have been proposed for the treatment of peripheral and myocardial ischemia. The approach eliminates the drawback of immune response against viral vectors and makes repeating the therapeutic procedure in case of injury recurrence feasible. Genetic manipulation of stem cells opens new avenues for regenerative medicine. [ABSTRACT FROM AUTHOR]

Although there has been steady progress towards cardiovascular gene therapy in humans, gene therapy for cerebrovascular disorders is still in its infancy. Several major steps, including gene transfer to cerebral arteries and alteration of gene expression, have been taken. There are several promising targets for cerebrovascular gene therapy, such as prevention of cerebral vasospasm after subarachnoid hemorrhage, stimulation of formation of collateral vessels to ischemic brain, and treatment of atherosclerotic lesions in carotid arteries. Some major obstacles, however, must be overcome before cerebrovascular gene therapy can be clinically used in humans. A key to cerebrovascular gene therapy is the development of safe and effective vectors for gene/nucleotide delivery. In addition, advances in understanding the biology of diseases and vectors will be of great value. [ABSTRACT FROM AUTHOR]

The study describes the development of a vigilant vector for protection against myocardial ischemia. The concept is a vector that can be systemically injected that waits in the heart for an ischemic attack. The vector then switches on cardioprotective genes specifically in the heart to save the cells from apoptosis and maintain cardiac performance. Using the adenoassociated virus (AAV), we have developed a double vector system (a sensor and an effector vector), that has a gene switch responsive to hypoxia, and a myosin light chain 2 ventricular (MLC-2v) promoter so that expression only occurs in the heart. The gene switch causes expression of therapeutic genes, such as heme oxygenase 1 (HO-1) and super oxide dismutase (SOD), to provide cardioprotective effects. The sensor AAV contains an oxygen-dependent domain (ODD) of hypoxia-inducible factor-1 (HIF-1α). The vector is switched on by low oxygen (<1%) and switched off by normoxia. To amplify the cardioprotective effect, an amplification system is added to the gene switch. This system consists of the yeast gene, GAL4, together with the NFκβ protein P65. The MLC-2v promoter drives the expression of a fusion protein of GAL4/p65 exponentially with low oxygen. This fusion protein binds to the effector component of the amplification system in a second AAV or plasmid. The effector AAV has a GAL4 upstream sequence-binding site. Binding to this site by the fusion protein causes the expression of cardioprotective genes at a rate that increases exponentially as oxygen levels are reduced. This has been successfully tested in vitro in myocardial cells, including both embryonic prenatal and adult rat cardiomyocytes; and in vivo in mouse myocardial ischemic hearts. [ABSTRACT FROM AUTHOR]

This chapter reviews the use of viral gene transfer to disentangle the complexities of neurogenic hypertension. Viral gene manipulation allows lasting and controllable genetic manipulation in selected areas of the brain in different species and strains, including experiments in the spontaneously hypertensive rat, an established model of hypertension. Recent evidence indicates that, in contrast to pharmacological tools that may act on any cellular target within a given area of the brain, viral vectors deliver transgene in a nonuniform manner, and its concentration in different types of cells may vary greatly. This occurs as a result of both transductional tropism of a viral vector system and the transciptional activity of the promoter in different cellular types which are present in any brain nucleus. Properties of adenoviral and lentiviral vectors are compared and contrasted. Application of viral vectors for overexpression of biologically active molecules, expression of dominant negative proteins, pathway tracking, and other experiments to study central mechanisms of cardiovascular control are discussed. In summary, virally mediated gene delivery to the brain is a powerful research tool that can be used to address a wide range of questions related to mechanisms of human essential hypertension. [ABSTRACT FROM AUTHOR]

Traditional therapeutic approaches for the treatment and control of hypertension are effective in normalizing blood pressure (BP) in less than a third of patients with hypertension. These pharmacological approaches may have reached a plateau in their effectiveness and newer strategies need to be investigated to not only increase the number of patients achieving BP control, but to find ways to cure the disease instead of just manage it. Since completion of the Human Genome Project and the continuous advancement of gene delivery systems, it is now possible to investigate genetic means for the treatment and possible cure for hypertension. In this review, we discuss potential genetic targeting for treatment of hypertension. There are two generalized gene transfer approaches that have been used successfully for hypertension. One is an induction approach where genes that lower blood pressure are overexpressed. A second method is a reduction approach where products of genes that are known to increase blood pressure are decreased. There are a variety of methods that have been utilized to meet these objectives, such as "knockout" and " knock-in" animal models, and the use of sense and antisense (AS) technology. This review will focus on the sense and antisense applications, and how this technique is becoming more refined and precise through the targeting of specific tissues, the regulation and induction of components of the system, and use of other newer technologies, such as short interfering RNA (siRNA). Our lab has generally focused on the reduction approach, specifically in the genetic manipulation of components of the renin-angiotensin system (RAS). This system not only modulates BP, but has also been implicated in cardiac hypertrophy and morphology and in insulin resistance, which is highly correlated with hypertension. We will also discuss how new genes can be identified and subsequently serve as targets for the treatment of human hypertension. [ABSTRACT FROM AUTHOR]

Tissue kallikrein cleaves low-molecular-weight kininogen substrate to produce the potent vasodilator kinin peptide, which binds to kinin receptors and triggers a wide spectrum of biological effects. Tissue kallikrein levels are reduced in humans and animal models with hypertension and cardiovascular and renal disease. We investigated the role of the tissue kallikrein-kinin system in the cardiovascular, renal, and central nervous systems by systemic and local delivery of the human tissue kallikrein gene using a plasmid DNA or an adenovirus vector. Enhanced kallikrein/kinin levels following kallikrein gene transfer reduce blood pressure in several pressure- and volume-overload hypertensive animal models. Kallikrein gene transfer also exerts beneficial effects in protection against cardiac remodeling, renal fibrosis, restenosis, cerebral infarction, and neurological deficits. The improvement in cardiovascular, renal, and neurological function following kallikrein gene transfer is independent of kallikrein's ability to lower blood pressure. Kallikrein gene transfer has pleiotropic effects on apoptosis, inflammation, proliferation, hypertrophy, fibrosis, and angiogenesis in the heart, blood vessel, kidney, and brain. These effects are blocked by icatibant, a bradykinin B2 receptor antagonist, indicating a kinin-mediated event. Mechanistically, kallikrein gene transfer leads to increased nitric oxide (NO) levels and decreased oxidative stress and inflammatory response. These novel findings indicate that kallikrein/kinin, through NO formation, may act as an antioxidant and anti-inflammatory agent in protection against cardiovascular and renal disease in animal models, and may uncover new drug targets for the prevention and treatment of heart failure, end-stage renal disease, and stroke in humans. [ABSTRACT FROM AUTHOR]

The cardiovascular application of gene transfer and therapy has three overlapping goals. First, it can be seen as a molecular tool to probe pathways and mechanisms that are difficult to elucidate by other means. Second, it is widely used in preclinical studies and a variety of cardiovascular disease models to find the most efficient and safe clinical applications. Lastly, it is increasingly being used in clinical trial settings, for example to attenuate restenosis and vascular graft failure in coronary and peripheral vascular disease. We provide a critical overview of all three spheres of gene therapy-related strategies in cardiovascular disease research. [ABSTRACT FROM AUTHOR]

Heart failure associated with coronary artery disease is a major cause of morbidity and mortality. Recent developments in the understanding of the molecular mechanisms of heart failure have led to the identification of novel therapeutic targets which, combined with the availability of efficient gene delivery vectors, offer the opportunity for the design of gene therapies for protection of the myocardium. Viral and cell-based therapies have been developed to treat polygenic and complex diseases such as myocardial ischemia, hypertension, atherosclerosis, and restenosis. In addition, cell-based therapies may have potential application in neovascularization and regeneration of ischemic and infarcted myocardium. The recent isolation of regeneration-competent endothelial precursor cells from adult bone marrow provides a novel opportunity for repair of the failing heart using autologous cell transplantation. In this chapter we will focus on the latest advances in the field of gene- and cell-based therapies for treatment of heart failure, and their clinical applications. [ABSTRACT FROM AUTHOR]

Recent progress in molecular and cellular biology has developed numerous effective cardiovascular drugs. However, there are still number of diseases for which no known effective therapy exists, such as peripheral arterial disease, ischemic heart disease, restenosis after angioplasty, vascular bypass graft occlusion, and transplant coronary vasculopathy. Currently, gene therapy is emerging as a potential strategy for the treatment of cardiovascular disease to treat such diseases despite this limitation. The first human trial in cardiovascular disease started in 1994 to treat peripheral vascular disease, using vascular endothelial growth factor (VEGF). Since then, many different potent angiogenic growth factors have been clinically tested to treat peripheral arterial disease. In addition, therapeutic angiogenesis using VEGF gene was applied to treat ischemic heart disease from 1997. The results from these clinical trials appear to exceed expectations. Improvement of clinical symptoms in peripheral arterial disease and ischemic heart disease has been reported. Many different potent angiogenic growth factors have been tested in clinical trials to treat peripheral arterial disease or ischemic heart disease. In addition, another strategy for combating disease processes, to target to transcriptional process, has been tested in a human trial. Transfection of cis-element double-stranded (ds) oligodeoxynucleotides (ODN) (decoy) is an especially powerful tool in a new class of antigene strategies for gene therapy. Transfection of ds ODN, corresponding to the cis sequence, will result in the attenuation of authentic cis-trans interaction, leading to the removal of transfactors from the endogenous cis-elements with subsequent modulation of gene expression. Genetically modified vein grafts transfected with decoy against E2F, an essential transcription factor in cell cycle progression, revealed apparent long-term potency in human patients. This review focuses on the future potential of gene therapy for the treatment of cardiovascular disease. [ABSTRACT FROM AUTHOR]

Changes in blood pressure (BP) from low to high, are genetically controlled by many genes. Identifying genes that regulate BP is important for two major reasons: (1) for delineating the biochemical/physiological mechanisms for BP control; and (2) for utilizing this knowledge to improve clinical management strategies for maintenance of normal physiological BP, which is an important factor in reducing the risk for susceptibility to cardiovascular diseases. Genetic approaches to identify BP regulatory genes involve the use of rat models with elevated BP (hypertension). Typically, genetic linkage analyses and substitution mapping using congenic strains are performed. These studies are designed to enable the identification of BP regulatory genes primarily by virtue of their location on the rat genome. This chapter captures the current status of studies aimed at identifying BP causative genes using various congenic rat strains. [ABSTRACT FROM AUTHOR]

Coronary artery disease is among the leading causes of death worldwide. Clinical trials show a protective effect of statins against coronary artery disease. The mean risk reductions for subjects using statins compared with placebo found in these trials is about 30%. These are average reductions for all patients included in the trials. Important factors in interpreting the variability in outcome of drug therapy include the patient's health profile, prognosis, disease severity, quality of drug prescribing, compliance with prescribed pharmacotherapy, and the genetic profile of the patient. This chapter aims to give an overview of the known polymorphisms that have an influence on the effects of statins in the general population. The expectation is that in the future, a subject's genotype may determine whether he/she will be treated with statins or not. Determining the genotype will not deny therapy to a subject, but will help in the decision as to which therapy suits the patient best. [ABSTRACT FROM AUTHOR]

Hypertension is a serious risk factor for myocardial infarction, heart failure, vascular disease, stroke, and renal failure. Hypertension affects 50 million Americans with a prevalence rate of 25-30% in the adult Caucasian population. The incidence of hypertension and complications resulting from hypertension are even greater in the African-American population. The renin-angiotensin system plays an important role in the regulation of blood pressure, and previous studies have suggested that the angiotensinogen (AGT) gene locus is linked with human essential hypertension. Previous studies have suggested that a single nucleotide polymorphism that converts methionine to threonine at amino acid 235 is associated with hypertension in Caucasian population. This polymorphism is in linkage disequilibrium with A/G polymorphism at −6 position in the promoter of AGT gene. Reporter constructs containing variant A at −6 have increased promoter activity on transient transfection in human liver cells, suggesting that this variant may have increased transcriptional activity. However, this polymorphism is not associated with hypertension in the African-American and Chinese populations. We have found an A/G polymorphism at −217 of the human AGT gene promoter and have shown that frequency of allele A at −217 is significantly increased in the DNA of African-American hypertensive patients. We have also shown that: (a) reporter constructs containing AG gene promoter with nucleoside A at −217 have increased promoter activity on transient transfection; and (b) the C/EBP family of transcription factors and glucocorticoid receptor (GR) bind preferentially to this region of the promoter when nucleoside A is present at −217. In addition, variant −217A is always present with variants −532T, −793A, and −1074T in the human AGT gene promoter. We have also shown that liver enriched transcription factor HNF-3β binds more strongly when nucleoside T is present at −1074. Previous studies have shown that HNF-3β interacts with GR and plays an important role in liver-specific gene expression. These data suggest that AGT haplotype containing −217A, −532T, − 793A, and −1074T may be involved in increased expression of this gene, and may play a role in human hypertension. It will be important to confirm this observation in future human studies and to understand the role of this haplotype in transcriptional regulation using transgenic animals. [ABSTRACT FROM AUTHOR]

Molecular variants of individual components of the renin-angiotensin system have been thought to contribute to inherited predisposition toward essential hypertension. Angiotensin II type 1 receptor (AT-1) mediates the major pressor and trophic actions of angiotensin II (Ang II). Moreover, polymorphisms in genes of angiotensinogen and angiotensin-converting enzyme (ACE) have been associated with arterial hypertension and cardiovascular diseases, and some of them have been related to differential responses to antihypertensive drugs. So far, at least 25 different polymorphisms have been described in AT-1 gene (AT1R gene), both at the 3′ untranslated region and in its promoter region. Best evaluated with respect to the association with cardiovascular phenotypes is the +1166 A/C polymorphism. In particular, the C allele has been associated with the severe form of essential hypertension and in some studies an association was found between C allele in AT1R gene and D allele in ACE gene; but large discrepancies arise from ethnic variability. The role of AT1R A1166C polymorphism is ambiguous in pathologies related to high Ang II levels, such as deterioration of renal function (for example in diabetes), arterial stiffness, and hypertrophic cardiomyopathy. Recently, polymorphisms have also been described in angiotensin II type 2 receptor (AT-2) gene (AT2R gene), AT-2 being the mediator for vasodilatation, natriuresis, and apoptosis of smooth muscle cells. Associations were found between some of these polymorphisms and left ventricular structure, whereas the response to Ang II infusion did not differ across AT1R and AT2R genotypes. On the other hand, a relationship was suggested between AT1R A1166C polymorphism and the humoral and renal hemodynamic responses to losartan, an antihypertensive drug acting as an AT-1 blocker, as well as with enhanced Ang II vascular reactivity or sensitivity even when conflicting results were observed. The variability in the individual response to AT-1 antagonists could also result from variations in the pharmacokinetics of the drugs; in particular, losartan is essentially metabolized to its active form by cytochrome P450 2C9, which biotransforms many cardiovascular drugs but at different rates in function of both ethnic and individual genotypes. The other angiotensin II receptor, AT-2, should also be investigated because the different AT-1 antagonists do not share the same selectivity for both subtypes but all are able to increase Ang II levels, which enhances AT-2 related effects. Arterial hypertension is one of the main risk factors for stroke and coronary artery disease (CAD); however, no clear association was found between AT1R gene polymorphisms and the development of white matter lesions, stroke, CAD, or myocardial infarction, although some studies described relationships between AT1R A1166C polymorphism and hypercholesterolemia, or greater induced arterial vasoconstriction in CAD. Moreover, AT1R C allele, when associated with ACE D allele (of I/D polymorphism), could contribute to susceptibility to CAD and to interindividual differences in severity of cardiovascular disease. Further evaluation in adequately powered studies is necessary for final assessment of allelic markers in RAS component genes, namely AT1R and AT2R genes, as well as to determine predisposition to hypertension or related diseases, and to choose an antihypertensive drug for an individual and to develop more specifically targeted drugs. [ABSTRACT FROM AUTHOR]