Reversal of hypertension by angiotensin II type 1 receptor antisense gene therapy in the adult SHR

Role of the central renin‑angiotensin system in hypertension (Review)

Present in more than one billion adults, hypertension is the most significant modifiable risk factor for mortality resulting from cardiovascular disease. Although its pathogenesis is not yet fully understood, the disruption of the renin-angiotensin system (RAS), consisting of the systemic and brain RAS, has been recognized as one of the primary reasons for several types of hypertension. Therefore, acquiring sound knowledge of the basic science of RAS and the under- lying mechanisms of the signaling pathways associated with RAS may facilitate the discovery of novel therapeutic targets with which to promote the management of patients with cardiovascular and kidney disease. In total, 4 types of angiotensin II receptors have been identified (AT1R-AT4R), of which AT1R plays the most important role in vasoconstriction and has been most extensively studied. It has been found in several regions of the brain, and its distribution is highly associated with that of angiotensin-like immunoreactivity in nerve terminals. The effect of AT1R involves the activation of multiple media and signaling pathways, among which the most important signaling pathways are considered to be AT1R/JAK/STAT and Ras/Raf/MAPK pathways. In addition, the regulation of the nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) and cyclic AMP response element-binding (CREB) pathways is also closely related to the effect of ATR1. Their mechanisms of action are related to pro-inflammatory and sympathetic excitatory effects. Central AT1R is involved in almost all types of hypertension, including spontaneous hypertension, salt-sensitive hypertension, obesity-induced hypertension, renovascular hypertension, diabetic hypertension, L-NAME-induced hypertension, stress-induced hypertension, angiotensin II-induced hyper- tension and aldosterone-induced hypertension. There are 2 types of central AT1R blockade, acute blockade and chronic blockade. The latter can be achieved by chemical blockade or genetic engineering. The present review article aimed to high- light the prevalence, functions, interactions and modulation means of central AT-1R in an effort to assist in the treatment of several pathological conditions. The identification of angiotensin-derived peptides and the development of AT-2R agonists may provide a wider perspective on RAS, as well as novel therapeutic strategies.

Analysis of Association of Angiotensin II Type 1 Receptor Gene A1166C Gene Polymorphism with Essential Hypertension

The A/C transversion at 1166 of the angiotensin II Type 1 Receptor (AT1R) gene per se does not characterize any functional diversity but has been associated with expression of the AT1R, consequently molecular variants of the gene may modulate the possible risk of essential hypertension. The present study was performed to determine the genotypic frequency of the A1166C polymorphism of the AT1R gene in essential hypertensive patients with the aim to assess the effect of variants of this polymorphism in hypertension. AT1R gene amplification was performed by PCR and A1166C polymorphism was determined by enzyme digestion methodologies in 224 consecutively enrolled essential hypertensive patients and 257 controls. Suitable descriptive statistics was used for different variables. Results revealed that genotype and allele distribution of the A1166C variant differed significantly in hypertensives and normotensives. Allele frequency at the A1166C position was 61%A and 39%C for control and 52%A and 48%C for patients. Observed frequencies were compatible with HWE expected frequencies in cases as well as in controls. rs5186 was found to be associated with hypertension (95% CI 1.1453-2.7932, p: 0.0106). The difference remained statistically significant after the multivariate adjustment (p < 0.05), with C/C variant conferring a risk of 1.74-fold of essential hypertension. This association was confirmed by inter-genotypic variations in the mean systolic and diastolic blood pressure in patients. In conclusion, genetic variation at the AT1R gene influences the risk of hypertension stratification and might serve as a predictive marker for the susceptibility to hypertension among affected families.

Association of angiotensin II type 1 receptor (A1166C) gene polymorphism and its increased expression in essential hypertension: a case-control study

OBJECTIVES

Hypertension is one of the major cardiovascular diseases. It affects nearly 1.56 billion people worldwide. The present study is about a particular genetic polymorphism (A1166C), gene expression and protein expression of the angiotensin II type I receptor (AT1R) (SNP ID: rs5186) and its association with essential hypertension in a Northern Indian population.

METHODS

We analyzed the A1166C polymorphism and expression of AT1R gene in 250 patients with essential hypertension and 250 normal healthy controls.

RESULTS

A significant association was found in the AT1R genotypes (AC+CC) with essential hypertension (χ2 = 22.48, p = 0.0001). Individuals with CC genotypes were at 2.4 times higher odds (p = 0.0001) to develop essential hypertension than individuals with AC and AA genotypes. The statistically significant intergenotypic variation in the systolic blood pressure was found higher in the patients with CC (169.4±36.3 mmHg) as compared to that of AA (143.5±28.1 mmHg) and AC (153.9±30.5 mmHg) genotypes (p = 0.0001). We found a significant difference in the average delta-CT value (p = 0.0001) wherein an upregulated gene expression (approximately 16 fold) was observed in case of patients as compared to controls. Furthermore, higher expression of AT1R gene was observed in patients with CC genotype than with AC and AA genotypes. A significant difference (p = 0.0001) in the protein expression of angiotensin II Type 1 receptor was also observed in the plasma of patients (1.49±0.27) as compared to controls (0.80±0.24).

CONCLUSION

Our findings suggest that C allele of A1166C polymorphism in the angiotensin II type 1 receptor gene is associated with essential hypertension and its upregulation could play an important role in essential hypertension.

Critical developmental periods in the pathogenesis of hypertension

Hypertension is one of the major risk factor of cardiovascular diseases, but after a century of clinical and basic research, the discrete etiology of this disease is still not fully understood. One reason is that blood pressure is a quantitative trait with multifactorial determination. Numerous genes, environmental factors as well as epigenetic factors should be considered. There is no doubt that although the full manifestation of hypertension and other cardiovascular diseases usually occurs predominantly in adulthood and/or senescence, the roots can be traced back to early ontogeny. The detailed knowledge of the ontogenetic changes occurring in the cardiovascular system of experimental animals during particular critical periods (developmental windows) could help to solve this problem in humans and might facilitate the age-specific prevention of human hypertension. We thus believe that this approach might contribute to the reduction of cardiovascular morbidity among susceptible individuals in the future.

Patterning of renal cGMP production by the natriuretic peptide receptor type A and blood pressure in spontaneously hypertensive rats

Although important advances have been made over past decades in studying the mechanisms of hypertension, the nature of cellular signaling patterns involved and their relationship remain unclear. High cGMP production rates in isolated renal glomeruli have been presented as a characteristic of spontaneously hypertensive rat (SHR) even before the development of hypertension, which suggests that this event might be a cause of the increase in blood pressure. Using cross-breeding between SHR and WKY parental strains to obtain F1 and F2 hybrids, we have investigated the patterning of high blood pressure and cGMP production rates. We have found that, in the F2 population, the mean blood pressure and both basal and ANP(1-28)-stimulated cGMP production are similar to the parental SHR. In addition, we have found a positive correlation between blood pressure and high cGMP production rates in the F2 population. The higher cGMP production was not a consequence of hypertension, since in DOCA-salt hypertensive rats cGMP production was similar to that observed in normotensive WKY rats. These observations suggest that high cGMP production is a characteristic linked to hypertension. Finally, reciprocal crosses between the SHR and WKY parental strains showed that in the F1 population blood pressure but not cGMP production are associated with the Y chromosome.

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.