Intravenous injection with antisense oligodeoxynucleotides against angiotensinogen decreases blood pressure in spontaneously hypertensive rats

Novel Pharmacological Approaches in the Treatment of Hypertension: A Focus on RNA-Based Therapeutics

Hypertension remains the leading cause of cardiovascular disease and premature death globally, affecting half of US adults. A high proportion of hypertensive patients exhibit uncontrolled blood pressure (BP), associated with poor adherence, linked to pill burden and adverse effects. Novel pharmacological strategies are urgently needed to improve BP control. Dysregulation of the renin-angiotensin system increases BP through its primary effector, Ang II (angiotensin II), which results in tissue remodeling and end-organ damage. Silencing liver angiotensinogen (the sole source of Ang II) has been achieved using novel RNA therapeutics, including the antisense oligonucleotide, IONIS-AGT (angiotensinogen)-LRX, and the small-interfering RNA, zilebesiran. Conjugation to N-acetylgalactosamine enables targeted delivery to hepatocytes, where endosomal storage, slow leakage, and small-interfering RNA recycling (for zilebesiran) result in knockdown over several months. Indeed, zilebesiran has an impressive and durable effect on systolic BP, reduced by up to 20 mm Hg and sustained for 6 months after a single administration, likely due to its very effective knockdown of angiotensinogen, without causing acute kidney injury or hyperkalemia. By contrast, IONIS-AGT-LRX caused less knockdown and marginal effects on BP. Future studies should evaluate any loss of efficacy relating to antidrug antibodies, safety issues associated with long-term angiotensinogen suppression, and broader benefits, especially in the context of common comorbidities such as type 2 diabetes and chronic kidney disease.

Angiotensinogen: More Than its Downstream Products: Evidence From Population Studies and Novel Therapeutics

The renin-angiotensin-aldosterone system (RAAS) is a well-defined pathway playing a key role in maintaining circulatory homeostasis. Abnormal activation of RAAS contributes to development of cardiovascular disease, including heart failure, cardiac hypertrophy, hypertension, and atherosclerosis. Although several key RAAS enzymes and peptide hormones have been thoroughly investigated, the role of angiotensinogen-the precursor substrate of the RAAS pathway-remains less understood. The study of angiotensinogen single-nucleotide polymorphisms (SNPs) has provided insight into associations between angiotensinogen and hypertension, congestive heart failure, and atherosclerotic cardiovascular disease. Targeted drug therapy of RAAS has dramatically improved clinical outcomes for patients with heart failure, myocardial infarction, and hypertension. However, all such therapeutics block RAAS components downstream of angiotensinogen and elicit compensatory pathways that limit their therapeutic efficacy as monotherapy. Upstream RAAS targeting by an angiotensinogen inhibitor has the potential to be more efficacious in patients with suboptimal RAAS inhibition and has a better safety profile than multiagent RAAS blockade. Newly developed therapeutics that target angiotensinogen through antisense oligonucleotides or silencer RNA technologies are providing a novel perspective into the pathobiology of angiotensinogen and show promise as the next frontier in the treatment of cardiovascular disease.

Therapeutic RNA-silencing oligonucleotides in metabolic diseases

Recent years have seen unprecedented activity in the development of RNA-silencing oligonucleotide therapeutics for metabolic diseases. Improved oligonucleotide design and optimization of synthetic nucleic acid chemistry, in combination with the development of highly selective and efficient conjugate delivery technology platforms, have established and validated oligonucleotides as a new class of drugs. To date, there are five marketed oligonucleotide therapies, with many more in clinical studies, for both rare and common liver-driven metabolic diseases. Here, we provide an overview of recent developments in the field of oligonucleotide therapeutics in metabolism, review past and current clinical trials, and discuss ongoing challenges and possible future developments.

CRISPR/Cas9 Mediated Deletion of the Angiotensinogen Gene Reduces Hypertension: A Potential for Cure?

[Figure: see text].

Targeting angiotensinogen with RNA-based therapeutics

PURPOSE OF REVIEW

To summarize all available data on targeting angiotensinogen with RNA-based therapeutics as a new tool to combat cardiovascular diseases.

RECENT FINDINGS

Liver-targeted, stable antisense oligonucleotides and small interfering RNA targeting angiotensinogen are now available, and may allow treatment with at most a few injections per year, thereby improving adherence. Promising results have been obtained in hypertensive animal models, as well as in rodent models of atherosclerosis, polycystic kidney disease and pulmonary fibrosis. The next step will be to evaluate the optimal degree of suppression, synergy with existing renin-angiotensin-aldosterone system blockers, and to determine harmful effects of suppressing angiotensinogen in the context of common comorbidities, such as heart failure and chronic kidney disease.

SUMMARY

Targeting angiotensinogen with RNA-based therapeutics is a promising new tool to treat hypertension and diseases beyond. Their long-lasting effects are particularly exciting, and if translated to a clinical application of at most a few administrations per year, may help to eliminate nonadherence.

Antisense oligonucleotides targeting angiotensinogen: insights from animal studies

Angiotensinogen (AGT) is the unique substrate of all angiotensin peptides. We review the recent preclinical research of AGT antisense oligonucleotides (ASOs), a rapidly evolving therapeutic approach. The scope of the research findings not only opens doors for potentially new therapeutics of hypertension and many other diseases, but also provides insights into understanding critical physiological and pathophysiological roles mediated by AGT.

Renin angiotensin aldosterone inhibition in the treatment of cardiovascular disease

A collective century of discoveries establishes the importance of the renin angiotensin aldosterone system in maintaining blood pressure, fluid volume and electrolyte homeostasis via autocrine, paracrine and endocrine signaling. While research continues to yield new functions of angiotensin II and angiotensin-(1-7), the gap between basic research and clinical application of these new findings is widening. As data accumulates on the efficacy of angiotensin converting enzyme inhibitors and angiotensin II receptor blockers as drugs of fundamental importance in the treatment of cardiovascular and renal disorders, it is becoming apparent that the achieved clinical benefits is suboptimal and surprisingly no different than what can be achieved with other therapeutic interventions. We discuss this issue and summarize new pathways and mechanisms effecting the synthesis and actions of angiotensin II. The presence of renin-independent non-canonical pathways for angiotensin II production are largely unaffected by agents inhibiting renin angiotensin system activity. Hence, new efforts should be directed to develop drugs that can effectively block the synthesis and/or action of intracellular angiotensin II. Improved drug penetration into cardiac or renal sites of disease, inhibiting chymase the primary angiotensin II forming enzyme in the human heart, and/or inhibiting angiotensinogen synthesis would all be more effective strategies to inhibit the system. Additionally, given the role of angiotensin II in the maintenance of renal homeostatic mechanisms, any new inhibitor should possess greater selectivity of targeting pathogenic angiotensin II signaling processes and thereby limit inappropriate inhibition.

Suppressing angiotensinogen synthesis attenuates kidney cyst formation in a Pkd1 mouse model

Activation of the intrarenal renin angiotensin system (RAS) is believed to play an important role in the development of hypertension and cystogenesis in autosomal dominant polycystic kidney disease (ADPKD). Results of clinical studies testing RAS inhibitors in slowing the progression of cystic disease in ADPKD are inconclusive, and we hypothesized that current RAS inhibitors do not adequately suppress intrarenal RAS. For this study, we compared a novel Gen 2 antisense oligonucleotide (ASO) that inhibits angiotensinogen (Agt) synthesis to lisinopril in adult conditional Pkd1 systemic-knockout mice, a model of ADPKD. Six weeks after Pkd1 global gene knockout, the mice were treated with Agt-ASO (66 mg/kg/wk), lisinopril (100 mg/kg/d), PBS (control), or scrambled ASO (66 mg/kg/wk) for 10 wk, followed by tissue collection. Agt ASO resulted in significant reduction in plasma, liver, and kidney Agt, and increased kidney renin compared with control treatments. Kidneys from Agt-ASO-treated mice were not as enlarged and showed reduced cystic volume compared with lisinopril or control treatments. Blood pressure was better controlled with lisinopril than with Agt-ASO. Agt-ASO suppressed cell proliferation in both cystic and noncystic cells compared with lisinopril and control treatments. However, Agt-ASO did not reduce cell proliferation in liver, which indicates that Agt-ASO targets cell signaling pathways that specifically suppresses cystogenesis in the kidney. These data suggest that Agt-ASO effectively attenuates intrarenal RAS and therefore can be a novel and effective agent for treating ADPKD.

Antisense-mediated angiotensinogen inhibition slows polycystic kidney disease in mice with a targeted mutation in Pkd2

Renal cyst enlargement is associated with the activation of both the circulating and intrarenal renin-angiotensin systems. Angiotensinogen (AGT) is the substrate for renin. The aim of the present study was to determine the effect of AGT inhibition on renal cyst enlargement. An AGT antisense oligonucleotide (ASO) that selectively inhibits AGT mRNA was injected once weekly in PKD2WS25 mice [an orthologous model of human autosmal dominant polycystic kidney disease (PKD) involving mutation of the Pkd2 gene] from 4 to 16 wk of age. The AGT ASO resulted in a 40% decrease in AGT RNA in the kidney, a 60% decrease in AGT RNA in the liver, and a significant decrease in AGT protein in the kidney and serum. The AGT ASO resulted in a significant decrease in kidney size, cyst volume density, and blood urea nitrogen. The AGT ASO resulted in a significant decrease in transforming growth factor-β and interstitial fibrosis in the kidney. Mice treated with the AGT ASO had a significant decrease in proinflammatory cytokines [chemokine (C-X-C motif) ligand (CXCL)1 and IL-12] in the kidney. Cluster of differentiation (CD)36 is a scavenger receptor found on tubular cells that can activate the renin-angiotensin system. Administration of a CD36 ASO had no effect on PKD and kidney function, suggesting that the effect of the AGT ASO is independent of CD36. In summary, AGT inhibition resulted in significant decreases in kidney size and cyst volume and an improvement in kidney function in PKD mice. The AGT ASO resulted in a decrease in transforming growth factor-β, interstitial fibrosis, and the proinflammatory cytokines CXCL1 and IL-12 in the kidney.

Therapeutic perspectives in hypertension: novel means for renin-angiotensin-aldosterone system modulation and emerging device-based approaches

The conventional antihypertensive therapies including renin–angiotensin–aldosterone system antagonists (converting enzyme inhibitors, receptor blockers, renin inhibitors, and mineralocorticoid receptor blockers), diuretics, β-blockers, and calcium channel blockers are variably successful in achieving the challenging target blood pressure values in hypertensive patients. Difficult to treat hypertension is still a commonly observed problem world-wide. A number of drugs are considered to be used as novel therapies for hypertension. Renalase supplementation, vasopeptidase inhibitors, endothelin antagonists, and especially aldosterone antagonists (aldosterone synthase inhibitors and novel selective mineralocorticoid receptor blockers) are considered an option in resistant hypertension. In addition, the aldosterone antagonists as well as (pro)renin receptor blockers or AT₂ receptor agonists might attenuate end-organ damage. This array of medications has now been complemented by a number of new approaches of non-pharmacological strategies including vaccination, genomic interference, controlled breathing, baroreflex activation, and probably most successfully renal denervation techniques. However, the progress on innovative therapies seems to be slow and the problem of resistant hypertension and proper blood pressure control appears to be still persisting. Therefore the regimens of currently available drugs are being fine-tuned, resulting in the establishment of several novel fixed-dose combinations including triple combinations with the aim to facilitate proper blood pressure control. It remains an exciting question which approach will confer the best blood pressure control and risk reduction in this tricky disease.

AT1 receptor antisense therapy transiently lowers blood pressure in Ren-2 transgenic rats

The effectiveness of antisense (AS) phosphorothioated oligodeoxynucleotides (AS-ODN) targeted to the angiotensin (ANG) type 1 (AT1) receptor, was studies in Ren-2 transgenic rats (TGR), whose ANG II-dependent hypertension can be attributed to the insertion of a single mouse renin gene. Our results show that a single intraarterial bolus injection of AT1-AS in 30-day-old rats results in a prolonged lowering of systolic blood pressure (SBP) for a period of 18 days with an average difference in SBP of 30 mm Hg between AS-treated and untreated TGR. No effect of AS therapy on SBP has been observed in control HanSD animals. However, at the end of the experiment, i.e. on day 100 of age, there were no differences in mean arterial pressure, proteinuria or cardiac hypertrophy between AS-treated and untreated TGR. Thus, no persistent effect of this therapy was observed after a single bolus injection. Collectively, the data show a prolonged antihypertensive effect of AT1 receptor antisense oligonucleotides during the developmental phase of hypertension in TGR when applied as a single treatment in prehypertensive animals which, however, does not persist up to the maintenance phase of hypertension in adulthood.

Suppression of complement regulatory proteins (CRPs) exacerbates experimental autoimmune anterior uveitis (EAAU)

This study was undertaken to explore the role of complement regulatory proteins (CRPs) in experimental autoimmune anterior uveitis (EAAU). We observed that the levels of CRPs, Crry and CD59, in the eyes of Lewis rats increased during EAAU and remained elevated when the disease resolved. The in vivo role of these CRPs in EAAU was explored using neutralizing mAbs, antisense oligodeoxynucleotides (AS-ODNs), and small interfering RNAs against rat Crry and CD59. Suppression of Crry in vivo at days 9, 14, or 19 by neutralizing mAb or AS-ODNs resulted in the early onset of disease, the exacerbation of intraocular inflammation, and delayed resolution. Suppression of CD59 was only effective when the Abs and ODNs were given before the onset of disease. The most profound effect on the disease was observed when a mixture of Crry and CD59 mAbs or AS-ODNs was administered. A similar effect was observed with a combination of Crry and CD59 small interfering RNA. There was no permanent histologic damage to ocular tissue after the inflammation cleared in these animals. Increased complement activation as determined by increased deposition of C3, C3 activation fragments, and membrane attack complex was observed in the eyes of Lewis rats when the function and/or expression of Crry and CD59 was suppressed. Thus, our results suggest that various ocular tissues up-regulate the expression of Crry and CD59 to avoid self-injury during autoimmune uveitis and that these CRPs play an active role in the resolution of EAAU by down-regulating complement activation in vivo.

Thyrotropin-releasing hormone in cardiovascular pathophysiology

Thyrotropin (TSH)-releasing hormone (TRH) also known as thyroliberin was the first of a number of peptides exerting several roles as a hormone and as a neuropeptide. Its ubiquitous distribution in the hypothalamus and in the extrahypothalamic regions and its diverse pharmacological and physiological effects are all features of its dual functions. For this reason, TRH has been the subject of much research throughout the past 20 years, work that has examined the structure, function, distribution, and regulation of the tripeptide and it has been extensively reviewed elsewhere [O'Leary R., O'Connor B. Thyrotropin-releasing hormone. J Neurochem. 1995;65:953-963.; Nillni E., Sevarino K. The biology of pro-thyrotropin-releasing hormone-derived peptides. Endocrine Reviews, 1999;20:599-664.]. After a brief overview of its distribution, hypothalamic and extrahypothalamic functions, and receptors involved, this review discusses efforts devoted to support TRH role in cardiovascular regulation with a main focus on hypertension pathophysiology in experimental models and humans.

Gene therapy for hypertension: the preclinical data

In spite of several drugs for the treatment of hypertension, there are many patients with poorly controlled high blood pressure. This is partly due to the fact that all available drugs are short-lasting (24 hr or less), have side effects, and are not highly specific. Gene therapy offers the possibility of producing longer-lasting effects with precise specificity from the genetic design. Preclinical studies on gene therapy for hypertension have taken two approaches. Chao et al. have carried out extensive studies on gene transfer to increase vasodilator proteins. They have transferred kallikrein, atrial natriuretic peptide, adrenomedullin, and endothelin nitric oxide synthase into different rat models. Their results show that blood pressure can be lowered for 3-12 weeks with the expression of these genes. The antisense approach, which we began by targeting angiotensinogen and the angiotensin type 1 receptor, has now been tested independently by several different groups in multiple models of hypertension. Other genes targeted include the beta 1-adrenoceptor, TRH, angiotensin gene activating elements, carboxypeptidase Y, c-fos, and CYP4A1. There have been two methods of delivery antisense; one is short oligodeoxynucleotides, and the other is full-length DNA in viral vectors. All the studies show a decrease in blood pressure lasting several days to weeks or months. Oligonucleotides are safe and nontoxic. The adeno-associated virus delivery antisense to AT1 receptors is systemic and in adult rodents decreases hypertension for up to 6 months. We conclude that there is sufficient preclinical data to give serious consideration to Phase I trials for testing the antisense ODNs, first and later the AAV.

Genetic targeting of the renin-angiotensin system for long-term control of hypertension

Although traditional approaches are effective for the treatment and control of hypertension, they have not succeeded in curing the disease, and have therefore reached a plateau. As a result of the completion of the Human Genome Project and the continuous advancement in gene delivery systems, it is now possible to investigate genetic means for the treatment and possible cure for hypertension. In this review we discuss the potential of genetic targeting of the renin-angiotensin system for the treatment of hypertension. We provide examples of various approaches that have used antisense technology with a high degree of success. We focus on our own research, which targets the use of antisense of the angiotensin type I receptor in various models of hypertension. Finally, we discuss the future of antisense technology in the treatment of human hypertension.

Tyrosine hydroxylase antisense gene therapy causes hypotensive effects in the spontaneously hypertensive rats

We investigated the effect of antisense oligodeoxynucleotides (AS ODN) against tyrosine hydroxylase (TH) on hypertension and sympathetic nervous system activity in spontaneously hypertensive rats (SHR). Systolic blood pressure (SBP) in SHR treated with TH AS ODN (50, 200 microg/rat, i.v.) was significantly lower than that of control SHR. Epinephrine and norepinephrine levels, TH activity, and TH protein levels in the adrenal medulla of SHR were reduced concomitant with TH AS ODN treatment-induced changes in SBP. In contrast, TH AS ODN (200 microg/rat) had no effect on SBP in Wistar-Kyoto rats (WKY), despite significantly decreased catecholamine levels, TH activity, and TH protein levels. These findings suggest that peripheral systemic injection of TH AS ODN may be effective as hypotensive therapy in SHR.

Gene therapy for hypertension: sense and antisense strategies

Gene therapy for hypertension is needed for the next generation of antihypertensive drugs. Current drugs, although effective, have poor compliance, are expensive and short-lasting (hours or one day). Gene therapy offers a way to produce long-lasting antihypertensive effects (weeks, months or years). We are currently using two strategies: antisense oligodeoxynucleotides (AS-ODN), an dantisense DNA delivered in viral vectors, to inhibit genes associated with vasoconstrictive properties. It is not necessary to know all the genes involved in hypertension, since many years of experience with drugs show which genes need to be controlled. AS-ODNs are short, single-stranded DNA that can be injected in naked form or in liposomes. AS-ODNs, targeted to AT1 receptors (AT1R), angiotensinogen (AGT), angiotensin converting enzyme (ACE) and beta 1-adrenergic receptors effectively reduce hypertension in rat models (SHR, 2K-1C and cold-induced) hypertension. The effects can last up to one month when delivered with liposomes. No side effects or toxic effects have been detected and repeated injections can be given. For the vector, adeno-associated virus (AAV) is used with a construct to include a CMV promoter, antisense DNA to AGT or AT1R and a reporter gene. Results in SHR demonstrate reduction and slowing of hypertension development with a single dose administration. Left ventricular hypertrophy is also reduced by AAV-AS-AGT treatment. Double transgenic mice (human renin plus human AGT) with high angiotensin II (Ang II) causing high blood pressure, treated with AAV-AT1R-AS, show a normalisation of blood pressure for over 6 months with a single injection of vector. We conclude that ODNs will probably be developed first because they can be treated like drugs for the treatment of hypertension with long-term effects. Viral vector delivery needs more engineering to be certain of its safety but one day may be used for a very prolonged control of blood pressure.

The potential role of antisense oligodeoxynucleotide therapy for cardiovascular disease

Current drugs used in the treatment of cardiovascular disease are effective but compliance is poor and they are short acting (hours or one day). Gene therapy offers a way to produce long-lasting effects (weeks, months or years). Antisense inhibition is being developed for the treatment of hypertension, myocardial ischaemia and improved allograft survival in human vascular bypass grafts. We are currently using 2 strategies: (i) antisense oligodeoxynucleotides (AS-ODNs) which are delivered nonvirally and (ii) antisense DNA delivered in viral vectors to inhibit genes associated with vasoconstrictive properties. It is not necessary to know all the genes involved in hypertension, since many years of experience with drugs show which genes need to be controlled. AS-ODN are short, single-stranded DNA that can be injected in naked form or in liposomes. AS-ODN targeted to angiotensin type 1 (AT1) receptors, angiotensinogen (ATG), angiotensin converting enzyme (ACE) and beta1 adrenoceptors effectively reduce hypertension in rat models. A single dose is effective for up to one month when delivered with liposomes. No adverse or toxic effects have been detected, and repeated injections are effective. For viral delivery, adeno-associated virus (AAV) is used with a construct to include a cytomegalovirus or tissue-specific promoter, antisense DNA to ATG, ACE or AT1 receptors and a reporter gene. Results in rats and transgenic mice show significant prolonged reduction of hypertension, with a single dose administration of AAV-AS. Left ventricular hypertrophy is also reduced by antisense treatment. AS-ODNs to AT1 receptors, ATG and beta1 adrenoceptors provide cardioprotection from the effects of myocardial ischaemia. The AT1 receptor is more protective than losartan and does not increase plasma angiotensin as losartan does.

Somatic gene therapy for hypertension

Gene therapy for hypertension is needed for the next generation of antihypertensive drugs. Current drugs, although effective, have poor compliance, are expensive and short-lasting (hours or one day). Gene therapy offers a way to produce long-lasting antihypertensive effects (weeks, months or years). We are currently using two strategies: a) antisense oligodeoxynucleotides (AS-ODN) and b) antisense DNA delivered in viral vectors to inhibit genes associated with vasoconstrictive properties. It is not necessary to know all the genes involved in hypertension, since many years of experience with drugs show which genes need to be controlled. AS-ODN are short, single-stranded DNA that can be injected in naked form or in liposomes. AS-ODN, targeted to angiotensin type 1 receptors (AT1-R), angiotensinogen (AGT), angiotensin converting enzyme, and ss1-adrenergic receptors effectively reduce hypertension in rat models (SHR, 2K-1C) and cold-induced hypertension. A single dose is effective up to one month when delivered with liposomes. No side effects or toxic effects have been detected, and repeated injections can be given. For the vector, adeno-associated virus (AAV) is used with a construct to include a CMV promoter, antisense DNA to AGT or AT1-R and a reporter gene. Results in SHR demonstrate reduction and slowing of development of hypertension, with a single dose administration. Left ventricular hypertrophy is also reduced by AAV-AGT-AS treatment. Double transgenic mice (human renin plus human AGT) with high angiotensin II causing high blood pressure, treated with AAV-AT1-R-AS, show a normalization of blood pressure for over six months with a single injection of vector. We conclude that ODNs will probably be developed first because they can be treated like drugs for the treatment of hypertension with long-term effects. Viral vector delivery needs more engineering to be certain of its safety, but one day may be used for a very prolonged control of blood pressure.

Reduction of plasma angiotensin II to normal levels by antisense oligodeoxynucleotides against liver angiotensinogen cannot completely attenuate vascular remodeling in spontaneously hypertensive rats

OBJECTIVE

The exact role of angiotensinogen (AGT) in vascular remodeling has yet to be determined. In the present study, we examined the effects of reducing plasma AGT by intravenous injections with antisense oligodeoxynucleotides (ODNs) against AGT targeted to the liver on vascular remodeling in spontaneously hypertensive rats (SHRs).

DESIGN AND METHODS

The ODNs against rat AGT were coupled to asialoglycoprotein (ASOR) carrier molecules, which serve as an important method for regulating liver gene expression. Male SHRs (n = 18) and age-matched male Wistar- Kyoto (WKY) rats (n = 4) were used for this study. All animals were fed a standard rat diet throughout the experiment At 10 weeks of age, the SHRs were divided into three groups (n = 6); systolic blood pressure (SBP) was similar in each group. The control group received saline, the sense group was injected with the sense ODN complex and the antisense group was injected with the antisense ODN complex. WKY rats were fed for the same period of time. The ASOR-poly(L)lysine-ODN complex was injected into the tail veins twice a week.

RESULTS

At the end of the treatment, a reduction in AGT mRNA levels in the liver and plasma AGT was observed only in the animals injected with antisense ODNs. Antisense ODNs significantly reduced the plasma angiotensin II (Ang II) concentrations to levels similar to those observed in WKY rats. Antisense ODNs significantly reduced the SBP (180.7 +/- 4.4 mmHg) and media cross-sectional areas of the aorta (1.11 +/- 0.02 mm2), which were still larger than those seen in WKY rats (140.3 +/- 2.1 mmHg, 0.84 +/- 0.02 mm2), compared with the SHRs injected with sense ODNs (225.2 +/- 4.4 mmHg, 1.24 +/- 0.02 mm2) and control SHRs (223.7 +/- 4.8 mmHg, 1.25 +/- 0.02 mm2). The aortic angiotensin-converting enzyme (ACE) activity and collagen concentrations, which were significantly higher than those seen in WKY rats, did not significantly change among the SHR groups. The aortic AGT, ACE, angiotensin II type 1 (AT1) receptor and angiotensin II type 2 (AT2) receptor mRNA also did not significantly change among the SHR groups.

CONCLUSION

On the basis of these findings, plasma AGT is thus considered to play a role in the development of hypertrophy of smooth muscle in the aorta of SHRs, it is thought to have only a slight effect, however, on the remodeling of the matrix tissue when the suppression of hypertension is insufficient.

Targeting of the renin-angiotensin system by antisense gene therapy: a possible strategy for the long-term control of hypertension

Traditional pharmacological agents have been successfully used for the treatment of hypertension for a number of decades. However, this therapeutic regimen has reached a conceptual plateau and a cure for the disease is far from appearing on the horizon. With this in mind, and recent advances in state of the art gene delivery system coupled with the anticipated completion of the human genome project, it is timely to think about the possibility of treating and/or curing hypertension using genetic means. In this review, we discuss the role of renin-angiotensin system (RAS) in hypertension; the current gene delivery/gene transfer systems and the RAS as a target for gene therapy to treat hypertension; the successful use of retroviral vectors to deliver antisense to the AT1 receptor (AT1-AS) to prevent the development of hypertension and cardiovascular pathophysiology; the potential use of the viral vectors for the reversal of hypertension; and the future of antisense gene therapy and potential advantages and limitations of this regimen in the treatment and/or control of hypertension.

Gene therapy of hypertensive vascular injury

Hypertension and vascular injury usually require prolonged treatment, and compliance is a key to efficacy for pharmacologically-based antihypertensive therapy. Gene therapy has the potential to be long lasting, with few side effects. Recent studies have provided promising results, in which hypertension can be treated by either augmentation of vasodilation or inhibition of vasoconstriction through gene transfer in experimental models. Gene transfer is also becoming useful for the study of mechanisms of physiologic and pathophysiologic conditions, including hypertension. In this mini-review, we summarize some recent studies in this area of research, and suggest some areas where progress is needed to advance the research toward gene therapy.

Intravenous angiotensinogen antisense in AAV-based vector decreases hypertension

Angiotensinogen (AGT) has been linked to hypertension. Because there are no direct inhibitors of AGT, we have developed antisense (AS) inhibition of AGT mRNA delivered in an adeno-associated virus (AAV)-based plasmid vector. This plasmid, driven by the cytomegalovirus promoter, contains a green fluorescent protein reporter gene and AS cDNA for rat AGT. Transfection of the plasmid into rat hepatoma cells brought a strong expression of the transgenes and a significant reduction in the level of AGT. In the in vivo study, naked plasmid DNA was intravenously injected into adult spontaneously hypertensive rats at different doses (0.6, 1.5, and 3 mg/kg). Expression of AGT AS mRNA was present in liver and heart, and it lasted longer in the liver. All three doses produced a significant decrease in blood pressure (BP). BP decreased for 2, 4, and 6 days, respectively. The lowest dose decreased BP by 12 +/- 3.0 mmHg, whereas the higher doses decreased BP by up to 22.5 +/- 5.2 mmHg compared with the control rats injected with saline (P < 0.01). The injection of the plasmid with liposomes produced a more profound and longer reduction (8 days) in BP. Consistent changes in plasma AGT level were observed. Sense plasmid had no effect. No liver toxicity was observed after injection of AS plasmid with or without liposomes. Our results suggest that the systemic delivery of AS against AGT mRNA by AAV-based plasmid vector, especially with liposomes, may have potential for gene therapy of hypertension and that further studies with the plasmid packaged into a recombinant AAV vector for a longer-lasting AS effect are warranted.

Angiotensinogen variants and human hypertension

The research on molecular genetics of human hypertension aims to identify the loci involved in the regulation of blood pressure, detect gene variants within the identified loci, associate them with intermediate phenotypes, and ultimately estimate their quantitative effects on blood pressure level and their interaction with main environmental factors. So far, the angiotensinogen (AGT) gene is one of the few candidate genes that has been investigated using these multiple statistical, clinical, and biochemical strategies. A highly polymorphic dinucleotide GT repeat (80% heterozygosity) has been used in several linkage studies. Other diallelic polymorphisms, located in the 5' regulatory region of the gene in intronic and exonic sequences, have been described, which were then used in association studies in different clinical settings. Positive associations between the M235T and the G-6A polymorphisms and plasma angiotensinogen levels indicates a pathway by which the AGT locus could be involved in essential hypertension.