Potential of gene therapy strategy for the treatment of hypertension

Future treatments in hypertension: Can we meet the unmet needs of patients?

The prevalence of arterial hypertension is approximately 47% in the United States and 55% in Europe. Multiple different medical therapies are used to treat hypertension including diuretics, beta blockers, calcium channel blockers, angiotensin receptor blockers, angiotensin converting enzyme inhibitors, alpha blockers, central acting alpha receptor agonists, neprilysin inhibitors and vasodilators. However, despite the numerous number of medications, the prevalence of hypertension is on the rise, a considerable proportion of the hypertensive population is resistant to these therapeutic modalities and a definitive cure is not possible with the current treatment approaches. Therefore, there is a need for novel therapeutic strategies to provide better treatment and control of hypertension. In this review, our aim is to describe the latest developments in the treatment of hypertension including novel medication classes, gene therapies and RNA-based modalities.

A gene therapy approach for long-term normalization of blood pressure in hypertensive mice by ANP-secreting human skin grafts

The use of bioengineered human skin as a bioreactor to deliver therapeutic factors has a number of advantages including accessibility that allows manipulation and monitoring of genetically modified cells. We demonstrate a skin gene therapy approach that can regulate blood pressure and treat systemic hypertension by expressing atrial natriuretic peptide (ANP), a hormone able to decrease blood pressure, in bioengineered human skin equivalents (HSE). Additionally, the expression of a selectable marker gene, multidrug resistance (MDR) type 1, is linked to ANP expression on a bicistronic vector and was coexpressed in the human keratinocytes and fibroblasts of the HSE that were grafted onto immunocompromised mice. Topical treatments of grafted HSE with the antimitotic agent colchicine select for keratinocyte progenitors that express both MDR and ANP. Significant plasma levels of human ANP were detected in mice grafted with HSE expressing ANP from either keratinocytes or fibroblasts, and topical selection of grafted HSE resulted in persistent high levels of ANP expression in vivo. Mice with elevated plasma levels of human ANP showed lower renin levels and, correspondingly, had lower systemic blood pressure than controls. Furthermore, mice with HSE grafts expressing human ANP did not develop elevated blood pressure when fed a high-salt diet. These findings illustrate the potential of this human skin gene therapy approach to deliver therapeutic molecules systemically for long-term treatment of diverse diseases.

Dopamine, kidney, and hypertension: studies in dopamine receptor knockout mice

Dopamine is important in the pathogenesis of hypertension because of abnormalities in receptor-mediated regulation of renal sodium transport. Dopamine receptors are classified into D(1)-like (D(1), D(5)) and D(2)-like (D(2), D(3), D(4)) subtypes, all of which are expressed in the kidney. Mice deficient in specific dopamine receptors have been generated to provide holistic assessment on the varying physiological roles of each receptor subtype. This review examines recent studies on these mutant mouse models and evaluates the impact of individual dopamine receptor subtypes on blood pressure regulation.

Genomic and proteomic approaches for targeting of angiotensin-converting enzyme2 for cardiovascular diseases

PURPOSE OF REVIEW

Our objective in this review is to summarize current understanding of the role of angiotensin-converting enzyme2 in cardiovascular pathophysiology. In addition, we will present recent advances and future directions in the use of genomic and proteomic approaches for the development of new therapeutic strategies that target angiotensin-converting enzyme2 for cardiovascular diseases.

RECENT FINDINGS

The angiotensin-converting enzyme homologue, angiotensin-converting enzyme2, plays a central role in counterbalancing the vasoconstrictive, proliferative, and hypertensive peptide, angiotensin II, by generating angiotensin-(1-7), which induces vasodilatory and antiproliferative actions in the cardiovascular system. Gene therapy is a strategy in which a vector is used to deliver beneficial genes systemically or directly into a specific organ. Recent observations suggest that angiotensin-converting enzyme2 overexpression by lentiviral vector-mediated gene delivery leads to an increased local angiotensin-converting enzyme2 expression and evokes protective mechanisms against hypertension and cardiovascular diseases. In addition, endogenous angiotensin-converting enzyme2 activation leads to cardiovascular protection.

SUMMARY

Prevalence of cardiovascular diseases continues to rise in spite of recent success in both the use of combination therapy and introduction of new pharmacotherapeutic agents. Thus, new and innovative approaches must be discovered in order to bring these diseases under control. Angiotensin-converting enzyme2 offers a new target in this regard and the use of state-of-the-art genomic and proteomic-based strategies to target this important member of the renin-angiotensin system holds potential for the development of improved therapeutics for cardiovascular diseases.

Natriuretic peptides: an update on bioactivity, potential therapeutic use, and implication in cardiovascular diseases

The natriuretic peptide system includes three known peptides: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). They contribute to the regulation of cardiovascular homeostasis through diuretic, natriuretic, and vasodilatory properties. Among them, ANP has received particular attention because of its effects on blood pressure regulation and cardiac function. Although the potential for its therapeutic application in the treatment of hypertension and heart failure has been evaluated in several experimental and clinical investigations, no pharmacological approach directly targeted at modulation of ANP levels has ever reached the stage of being incorporated into clinical practice. Recently, ANP has also received attention as being a possible cardiovascular risk factor, particularly in the context of hypertension, stroke, obesity, and metabolic syndrome. Abnormalities in either peptide levels or peptide structure are thought to underlie its implied role in mediating cardiovascular diseases. Meanwhile, BNP has emerged as a relevant marker of left ventricular (LV) dysfunction and as a useful predictor of future outcome in patients with heart failure. This review deals with the major relevant findings related to the cardiovascular and metabolic effects of natriuretic peptides, to their potential therapeutic use, and to their role in mediating cardiovascular diseases.

Inhibitory effect of D1-like and D3 dopamine receptors on norepinephrine-induced proliferation in vascular smooth muscle cells

The sympathetic nervous system plays an important role in the regulation of blood pressure. There is increasing evidence for positive and negative interactions between dopamine and adrenergic receptors; the activation of the alpha-adrenergic receptor induces vasoconstriction, whereas the activation of dopamine receptor induces vasorelaxation. We hypothesize that the D1-like receptor and/or D3 receptor also inhibit alpha1-adrenergic receptor-mediated proliferation in vascular smooth muscle cells (VSMCs). In this study, VSMC proliferation was determined by measuring [3H]thymidine incorporation, cell number, and uptake of 3-(4,5-dimethylthiazol-2-yl)-diphenyltetrazolium bromide (MTT). Norepinephrine increased VSMC number and MTT uptake, as well as [3H]thymidine incorporation via the alpha1-adrenergic receptor in aortic VSMCs from Sprague-Dawley rats. The proliferative effects of norepinephrine were attenuated by the activation of D1-like receptors or D3 receptors, although a D1-like receptor agonist, fenoldopam, and a D3 receptor agonist, PD-128907, by themselves, at low concentrations, had no effect on VSMC proliferation. Simultaneous stimulation of both D1-like and D3 receptors had an additive inhibitory effect. The inhibitory effect of D3 receptor was via protein kinase A, whereas the D1-like receptor effect was via protein kinase C-zeta. The interaction between alpha1-adrenergic and dopamine receptors, especially D1-like and D3 receptors in VSMCs, could be involved in the pathogenesis of hypertension.

Treatment with antisense oligonucleotide reduces the expression of type I collagen in a human-skin organ-wound model: implications for antifibrotic gene therapy

Increased collagen expression during wound healing causes scar formation, abnormal contracture, low tensile strength, functional impairment, and disfigurement. A novel ex vivo wound-injury model demonstrated that AS60, an antisense oligonucleotide (ASO) to type I collagen, reduced the mRNA and protein expression of type 1 collagen. Following a cutaneous wound injury in a human-skin organ culture, AS60 injection resulted in a 36% (P < 0.001) and 30% decrease (P < 0.001) in type 1 collagen mRNA and protein expression after 7 days. Similarly, transfection of cultured human fibroblasts with ASO resulted in a 36% decrease (P < 0.001) and a 31% decrease (P < 0.001) in type 1 collagen mRNA and protein expression. Immunofluorescence of human skin organ culture treated with ASO showed a specific reduction in collagen expression. Using AS60 to reduce collagen expression in human skin may have implications for its use as a gene therapy agent to reduce the formation of fibrotic scarring.

Cardiac overexpression of angiotensin converting enzyme 2 protects the heart from ischemia-induced pathophysiology

Angiotensin converting enzyme 2 (ACE2) has been linked to cardiac dysfunction and hypertension-induced cardiac pathophysiology. In this study, we used a gene overexpression approach to investigate the role of ACE2 in cardiac function and remodeling after myocardial infarction. Rats received an intracardiac injection of 4.5x10(8) lentivirus containing ACE2 cDNA, followed by permanent coronary artery ligation (CAL) of the left anterior descending artery. At 24 hours and 6 weeks after surgery, cardiac functions, viability, and pathophysiology were assessed by MRI) and by histological analysis. At 24 hours post-CAL, left ventricular (LV) anterior wall motion was stunted to the same extent in control CAL and lenti-ACE2-treated CAL rats. However lenti-ACE2-treated CAL rats showed a 60% reduction in delayed contrast-enhanced LV volume after gadodiamide injection, indicating early ischemic protection of myocardium by ACE2. At 6 weeks after CAL, lenti-ACE2 rats demonstrated a complete rescue of cardiac output, a 41% rescue of ejection fraction, a 44% rescue in contractility, a 37% rescue in motion, and a 53% rescue in LV anterior (infracted) wall thinning compared with control CAL rats. No changes were observed in the LV posterior (noninfarcted) wall other than an 81% rescue in motion produced by ACE2 in CAL rats. Finally, infarct size measured by 2,3,5-triphenyl-tetrazolium chloride staining was not significantly different between the ligated groups. These observations demonstrate that cardiac overexpression of ACE2 exerts protective influence on the heart during myocardial infarction by preserving cardiac functions, LV wall motion and contractility, and by attenuating LV wall thinning.

Dysregulation of dopamine-dependent mechanisms as a determinant of hypertension: studies in dopamine receptor knockout mice

Dopamine plays an important role in the pathogenesis of hypertension by regulating epithelial sodium transport and by interacting with vasoactive hormones/humoral factors, such as aldosterone, angiotensin, catecholamines, endothelin, oxytocin, prolactin pro-opiomelancortin, reactive oxygen species, renin, and vasopressin. Dopamine receptors are classified into D(1)-like (D(1) and D(5)) and D(2)-like (D(2), D(3), and D(4)) subtypes based on their structure and pharmacology. In recent years, mice deficient in one or more of the five dopamine receptor subtypes have been generated, leading to a better understanding of the physiological role of each of the dopamine receptor subtypes. This review summarizes the results from studies of various dopamine receptor mutant mice on the role of individual dopamine receptor subtypes and their interactions with other G protein-coupled receptors in the regulation of blood pressure.

Current Status of Cardiovascular Gene Therapy

Gene transfer for the therapeutic modulation of cardiovascular diseases is an expanding area of gene therapy. During the last decade several approaches have been designed for the treatment of hyperlipidemias, post-angioplasty restenosis, hypertension, and heart failure, and for protection of vascular by-pass grafts and promotion of therapeutic angiogenesis. Adenoviruses (Ads) and adeno-associated viruses (AAVs) are currently the most efficient vectors for delivering therapeutic genes into the cardiovascular system. Gene transfer using local gene delivery techniques have been shown to be superior to less-targeted intra-arterial or intra-venous applications. To date, no gene therapy drugs have been approved for clinical use in cardiovascular applications. In preclinical studies of therapeutic angiogenesis, various growth factors such as vascular endothelial growth factors (VEGFs) and fibroblast growth factors (FGFs), have shown positive results. Gene therapy also appears to have potential clinical applications in improving the patency of vascular grafts and in treating heart failure. Post-angioplasty restenosis, hypertension, and hyperlipidemias (excluding homozygotic familial hypercholesterolemia) can usually be managed satisfactorily by conventional approaches, and are therefore less favored areas for gene therapy. The development of technologies that can ensure long-term, targeted, and regulated gene transfer, and a careful selection of target patient populations, will be very important for the progress of cardiovascular gene therapy in clinical applications.

Endothelin-1 antisense oligonucleotide suppresses the proliferation of glomerular mesangial cells stimulated with angiotensin-II

Antisense oligonucleotide (AON) has been applied to modern molecular pharmacology. We have previously demonstrated that angiotensin-II (Ang-II) is an active stimulator of endothelin-1 (ET-1) production in glomerular mesangial cells. This study was designed to investigate the specific effect of ET-1 AON on inducing proliferation of cultured rat mesangial cells stimulated with Ang-II. ET-1 was measured by radioimmunoassays. The results were: (1) Ang-II enhanced ET-1 production of mesangial cells; (2) ET-1 production of mesangial cells was significantly suppressed by ET-1 AON, and this production was not affected by either ET-1 sense or scramble oligonucleotide in different concentrations; (3) Ang-II increased [3H]-thymidine uptake of mesangial cells, which was suppressed to 25% by ET-1 AON but not by ET-1 sense or scramble oligonucleotide. Our results indicate that ET-1 AON effectively suppresses the ET-1 production and the Ang-II-stimulated proliferation of mesangial cells, and therefore may offer treatment for proliferative glomerulonephritis.

Novel therapies blocking the renin-angiotensin-aldosterone system in the management of hypertension and related disorders

Although significant advances have been made in the therapeutic blockade of the renin-angiotensin-aldosterone system (RAAS) using angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers and non-selective aldosterone receptor antagonists, there is a clear need for both additional blocking strategies and enhancements of current therapeutic approaches. Vasopeptidase inhibition may still find a role despite the small incremental value of this approach and the obvious issue of kinin-mediated adverse effects still to be fully addressed. Blockade of the RAAS upstream using renin inhibitors as well as the greater selectivity of aldosterone blockade using selective aldosterone blockers such as eplerenone are also novel approaches. Not yet in clinical use but certainly an attractive therapeutic target is angiotensin II growth factor receptor transactivation, with selective inhibitors having been developed for various specific kinase pathways. Finally, ACE2 augmentation, antisense gene strategies, and vaccination against the renin-angiotensin system should still be considered experimental, but have significant appeal as additional approaches to the blockade of this system.

Overexpression of angiotensin-converting enzyme 2 in the rostral ventrolateral medulla causes long-term decrease in blood pressure in the spontaneously hypertensive rats

The rostral ventrolateral medulla (RVLM) is a relay point that provides supraspinal excitatory input to sympathetic preganglionic neurons in the regulation of blood pressure. The importance of the RVLM is further highlighted by observations that an increase of RVLM sensitivity to angiotensin II and enhanced sympathetic activity are associated with hypertension. Angiotensin-converting enzyme 2 (ACE2) has been shown to be central in maintaining the balance between vasoconstrictor activity of angiotensin II with vasoprotective action of angiotensin-(1-7) in the peripheral system. However, its role in central control of blood pressure in the RVLM is yet to be investigated. Thus, our objective in this study was to compare ACE2 expression in the RVLM of Wistar-Kyoto rats and spontaneously hypertensive rats and to determine whether RVLM ACE2 is involved in blood pressure control. ACE2 immunoreactivity was diffusely distributed in many cardiovascular regulatory neurons, including the RVLM. Western blot analysis revealed a 40% decrease in ACE2 in the RVLM of spontaneously hypertensive rat compared with Wistar-Kyoto rats. Lentiviral-mediated overexpression of ACE2 (lenti-ACE2) was used to determine whether a decrease in ACE2 in the RVLM is associated with hypertensive state. Bilateral injection of lenti-ACE2 resulted in a long-term expression of transgenic ACE2. This was associated with a decrease in mean arterial pressure exclusively in the spontaneously hypertensive rat (141+/-4 mm Hg in lenti-GFP versus 124+/-5 mm Hg in lenti-ACE2) and heart rate (304+/-7 bpm in lenti-GFP versus 285+/-5 bpm in lenti-ACE2). These observations demonstrate that overexpression of ACE2 overcomes its intrinsic decrease in the RVLM and decreases high blood pressure in the spontaneously hypertensive rat.

Beta-1 adrenergic receptor antisense-oligodeoxynucleotides ameliorates left ventricular remodeling in 2-Kidney, 1-Clip rats

Gene therapy has been applied to reduce blood pressure in rats. However, little is known about the effects of gene therapy on both blood pressure and left ventricular (LV) remodeling. This study was designed to compare the antihypertensive effect of ss(1) adrenergic receptor antisense oligodeoxynucleotides (ss(1)- AS-ODN) by delivery with the different charge ratios cationic liposomes DOTAP/DOPE and its impact on the LV remodeling in rats with 2-Kidney, 1-Clip (2K1C) Hypertension. Five charge ratios of liposome/ODN were tested in 2K1C rats. There was hypertension, cardiac dysfunction, LV hypertrophy and LV collagen deposition in 2K1C rats. On the basis of the magnitude and duration of hypotension, 2.0 was determined to be the optimal charge ratio, which decreased blood pressure by up to 39 mm Hg for 27 days. ss(1)-AS-ODN preserved cardiac function and inhibited LV mass and LV interstitial collagen deposition. In conclusion, cationic liposomes DOTAP/DOPE improve the antihypertensive effects of ss(1)-AS-ODN in renovascular hypertension and 2.0 were determined to be the optimal charge ratio. This study demonstrated that cardiac ss(1)-AR played a key role in LV remodeling and ss1-AS-ODN ameliorates cardiac dysfunction and LV remodeling.