New beta-blocker: prolonged reduction in high blood pressure with beta(1) antisense oligodeoxynucleotides

Antisense oligonucleotides for the arterial hypertension mechanisms study and therapy

Arterial hypertension is one of the most common chronic diseases in adults all over the world. This pathology can not only reduce patients’ life quality, but can also be accompanied by a number of complications. Despite the fact that there is a large group of antihypertensive drugs on the market, mainly representing different combinations of inhibitors of the renin-angiotensin system, adrenoreceptor blockers in combination with diuretics, there is no generally accepted “gold standard” for drugs that would not have side effects. The review discusses the main aspects of antisense oligonucleotides use in the context of arterial hypertension. It is well known that the medical implementation of antisense oligonucleotides aims to block the expression of particular genes involved in the pathology development, and a key advantage of this technique is a high selectivity of the effect. However, with the undoubted advantages of the method, there are difficulties in its application, related both to the properties of the oligonucleotides themselves (insufficient stability and poor penetration into cells), and to the variety of mechanisms of the origin of a particular pathology, arterial hypertension, in our case. The review provides a brief description of the main molecular targets for antisense treatment of hypertensive disease. The newest targets for therapy with oligonucleotides – microRNAs – are discussed. The main modifications of antisense nucleotides, designed to increase the duration of their effects and simplify the delivery of this type of drugs to the targets are discussed, in particular, combining antisense oligonucleotides with adenovirus-based expression vectors. Particular attention is given to antisense oligonucleotides in the complex with nanoparticles. The review discusses the results of the use of titanium dioxide (TiO2) containing antisense nanocomposites for the angiotensin converting enzyme in rats with stress induced arterial hypertension (ISIAH). It was shown that the use of antisense oligonucleotides continues to be a promising technique for studying the mechanisms of various forms of hypertensive disease and has a high potential for therapeutic use.

Specific beta1-adrenergic receptor silencing with small interfering RNA lowers high blood pressure and improves cardiac function in myocardial ischemia

OBJECTIVES

Beta-blockers are widely used and effective for treating hypertension, acute myocardial infarction (MI) and heart failure, but they present side-effects mainly due to antagonism of beta2-adrenergic receptor (AR). Currently available beta-blockers are at best selective but not specific for beta1 or beta2-AR.

METHODS

To specifically inhibit the expression of the beta1-AR, we developed a small interfering RNA (siRNA) targeted to beta1-AR. Three different sequences of beta1 siRNA were delivered into C6-2B cells with 90% efficiency.

RESULTS

One of the three sequences reduced the level of beta1-AR mRNA by 70%. The siRNA was highly specific for beta1-AR inhibition with no overlap with beta2-AR. To test this in vivo, systemic injection of beta1 siRNA complexed with liposomes resulted in efficient delivery into the heart, lung, kidney and liver, and effectively reduced beta1-AR expression in the heart without altering beta2-AR. beta1 siRNA significantly lowered blood pressure of spontaneously hypertensive rats (SHR) for at least 12 days and reduced cardiac hypertrophy following a single injection. Pretreatment with beta1 siRNA 3 days before induction of MI in Wistar rats significantly improved cardiac function, as demonstrated by dP/dt and electrocardiogram following the MI. The protective mechanism involved reduction of cardiomyocyte apoptosis in the beta1 siRNA-treated hearts.

CONCLUSIONS

The present study demonstrates the possibility of using siRNA for treating cardiovascular diseases and may represent a novel beta-blocker specific for beta1-AR.

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.

Gene-based therapy for hypertension--do preclinical data suggest a promising future?

Many experimental studies have obtained a prolonged control of blood pressure through gene treatment. This consists in the administration of genes coding for vasodilator proteins (the 'sense' approach), or of nucleotide sequences that are complementary to the mRNA of vasoconstrictor proteins, which are consequently synthesized in smaller amounts (the 'antisense' approach). Examples of the sense approach include the genes encoding endothelial nitric oxide synthase and kallikrein. Examples of the second type of approach are the antisense oligodeoxynucleotides to angiotensin-converting enzyme and endothelin-1. Also, RNA molecules, such as ribozymes and small interfering RNAs, are capable to inhibit RNA function. Whole sense genes are usually administered through viral vectors, while antisense oligonucleotides may be administered with plasmids or liposomes. Both viral and non-viral vectors have advantages and disadvantages. Despite the still persisting limitations, the possibility exists that in the future some forms of genetic treatment will be extended to the clinical setting, allowing a prolonged control of essential hypertension and its end-organ sequelae.

Genetic therapies for cardiovascular diseases

Recent advances in understanding the molecular and cellular basis of cardiovascular diseases, together with the availability of tools for genetic manipulation of the cardiovascular system, offer possibilities for new treatments. Gene therapies have demonstrated potential usefulness for treating complex cardiovascular diseases, such as hypertension, atherosclerosis and myocardial ischemia, in various animal models. Some of these experimental therapies are now undergoing clinical evaluation in patients with cardiovascular disease. However, the successful transition of these therapies into mainstream clinical practice awaits further improvements to vector platforms and delivery tools and the documentation of clinical feasibility, safety and efficacy through multi-center randomized trials.

Gene therapy for renal disorders: what are the benefits for the elderly?

Chronic renal failure is one of the major health problems for the elderly. Currently, about 50% of all patients receiving chronic dialysis for end-stage renal disease (ESRD) are aged 65 years or older. Their first-year mortality rate is as high as 30%. The leading causes of ESRD in the elderly are diabetic nephropathy, hypertension and large vessel diseases, and glomerulonephritis. The elderly are also prone to developing acute renal failure induced by ischaemic injury or nephrotoxic drugs. Gene transfer in experimental animals have been tested in all of these conditions, as well as in animal kidney transplantation models, with various degrees of success. However, there are many obstacles to be overcome before gene therapy can be tested clinically for renal disorders. In particular, the major challenges include determining how to prolong and control transgene expression or antisense inhibition and how to minimise the adverse effects of viral or nonviral vectors. Once these problems are solved, gene therapy will have a role in treating age-related renal impairment.

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.

Oligonucleotide lipoplexes: the influence of oligonucleotide composition on complexation

Despite extensive investigations into oligonucleotide lipoplexes, virtually no work has addressed whether the physicochemical properties of these assemblies vary as a function of the constituent oligonucleotide (ODN) sequence and/or composition. The present study was aimed at answering this question. To this end, we complexed N-(1-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTAP) liposomes, in dispersion, with either 18-mer phosphorothiote homo-oligonucleotides composed of either adenine, thymidine or cytosine; or one of three structurally related 18-mer phosphorothioate oligonucleotides (S-ODNs) (G3139, its reverse sequence and its two-base mismatch). After ODN addition to vesicles at different mole ratios, changes in pH and electrical surface potential at the lipid-water interface were analyzed by using the fluorophore heptadecyl-7-hydroxycoumarin while particle size distributions were analyzed by static-light scattering. The results indicate that each homo-oligonucleotide does indeed exhibit different complexation behavior. In particular, the maximal level of DOTAP neutralization by the polyadenine S-ODN is much lower than that for the two other homo-oligonucleotides and hence its lipoplex is much more positively charged. Much smaller electrostatic differences are also apparent between lipoplexes formed from each of the G3139-related ODNs. This paper identifies nucleotide base selection and sequence as a variable that can affect the physicochemical properties of oligonucleotide lipoplexes and hence probably their transfection competency.

Recent progress in gene delivery using non-viral transfer complexes

The delivery of genetic material into cells is a field that is expanding very rapidly. Non-viral delivery methods, especially ones that focus on the use of chemical agents complexed with genetic material, are the focus of this mini-review. More-recent uses of known transfection agents such as poly(ethylenimine), poly(L-lysine), and various liposomes are discussed, and some novel approaches (both chemical and methodical) are reviewed as well. A very brief look at how non-viral gene delivery research is being aimed at the clinic is also included.

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.