Effect of the angiotensin II type 2-receptor gene (+1675 G/A) on left ventricular structure in humans

The rs1403543 Polymorphism of AGTR2, Which Encodes the Type-2 Angiotensin II Receptor, and Left Ventricular Mass in Polish Full-Term Newborns

BACKGROUND/OBJECTIVES

Left ventricular hypertrophy is a significant independent risk factor for increased cardiovascular morbidity and mortality. There are some reports indicating an association of rs1403543 (1675G>A) polymorphism in the AGTR2 gene, which encodes the type-2 angiotensin II receptor, with left ventricular hypertrophy or increased left ventricular mass (LVM) in adults. The aim of this study was to analyze the possible association of the AGTR2:rs1403543 polymorphism with LVM in full-term Polish healthy newborns.

METHODS

The study group comprised 207 consecutive, full-term, healthy newborns. LVM was assessed, on the 3rd day after birth, from the M-mode echocardiographic measurements of left ventricular dimensions using the Penn convention, with the Huwez et al.-modified equation mode. The AGTR2 polymorphism was identified by PCR-RFLP in genomic DNA extracted from cord blood leukocytes.

RESULTS

There were no significant differences in clinical and echocardiographic characteristics of male newborns in regard to the AGTR2:rs1403543 polymorphism. However, the LVM/body mass ratio in female newborns carrying at least one A allele (i.e., with genotype GA or AA) was significantly lower as compared to its value in reference (GG) homozygotes. In addition, in female newborns, the frequency of AGTR2 genotypes with at least one A allele was significantly higher in the lower tertile of LVM/body mass or LVM/body surface area (calculated using the Mosteller formula) ratios as compared with upper tertiles.

CONCLUSIONS

Our results suggest that the AGTR2:rs1403543 polymorphism may be associated with the physiological variability of cardiac mass in female newborns.

Genetic Variations Related to Angiotensin II Production and Risk for Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most prevalent human neoplasm, with constantly increasing annual incidence. Despite its slow growth, BCC is locally invasive and, if left untreated, can cause severe complications, including metastasis and death. The renin-angiotensin system (RAS) plays a key role in electrolyte balance, atrial pressure, tissue development, homeostasis, and inflammation, but also in cancer development. After binding to its type 1 receptor (AT1R), angiotensin II (ANGII), the system's principal hormonal effector, regulates cancer pathways spanning from the formation of the initial cancer cell to the construction and nutrition of the tumor microenvironment, angiogenesis, proliferation, and metastasis. Although the role of RAS in the development of skin pathologies has not been widely researched, RAS-targeting antihypertensive medications have been shown to have a chemoprotective effect against BCC. Based on those findings, our group conducted a series of genetic association studies to investigate the association between common functional variations in key genes related to ANGII production (AGT, ACE, ACE2, AT1R, AT2R, and CMA1) and the risk of BCC occurrence. This review provides a summary of the current understanding of the ANGII involvement in BCC development. The reliable and easily assessed pool of genetic biomarkers may be used for predictive testing and prevention purposes in high-risk individuals.

Correlation Between Angiotensin-Converting Enzyme Insertion/Deletion Gene Polymorphism and the Co-Occurrence of Left Ventricular Hypertrophy in Patients with Hypertension

The aim of this study was to explore the association between angiotensin-converting enzyme (ACE) gene insertion/deletion polymorphism in the 16th intron and the occurrence of left ventricular hypertrophy (LVH) in hypertensive individuals.This study included 269 patients with hypertension from Dushu Lake Hospital Affiliated to Soochow University who underwent echocardiographic examinations. Among them, 55 patients had hypertension combined with LVH, while 214 patients with hypertension did not have LVH, serving as the case and control groups, respectively. Polymerase chain reaction-restriction fragment length polymorphism was used to perform genetic testing for hypertension in all 269 patients. The Hardy-Weinberg equilibrium test was used to assess genetic equilibrium. The differences in genotype frequencies between the case and control groups were analyzed using the chi-square test. All statistical analyses were performed using SPSS software (version 27.0.1), with statistical significance set at P < 0.05.Genotype distribution in the case and control groups conformed to the Hardy-Weinberg equilibrium (P > 0.05). There was a significant difference in genotype distribution between the case and control groups.Conclusion: ACE gene polymorphism is associated with an increased risk of hypertension combined with LVH.

The Angiotensin AT2 Receptor: From a Binding Site to a Novel Therapeutic Target

Discovered more than 30 years ago, the angiotensin AT2 receptor (AT2R) has evolved from a binding site with unknown function to a firmly established major effector within the protective arm of the renin-angiotensin system (RAS) and a target for new drugs in development. The AT2R represents an endogenous protective mechanism that can be manipulated in the majority of preclinical models to alleviate lung, renal, cardiovascular, metabolic, cutaneous, and neural diseases as well as cancer. This article is a comprehensive review summarizing our current knowledge of the AT2R, from its discovery to its position within the RAS and its overall functions. This is followed by an in-depth look at the characteristics of the AT2R, including its structure, intracellular signaling, homo- and heterodimerization, and expression. AT2R-selective ligands, from endogenous peptides to synthetic peptides and nonpeptide molecules that are used as research tools, are discussed. Finally, we summarize the known physiological roles of the AT2R and its abundant protective effects in multiple experimental disease models and expound on AT2R ligands that are undergoing development for clinical use. The present review highlights the controversial aspects and gaps in our knowledge of this receptor and illuminates future perspectives for AT2R research. SIGNIFICANCE STATEMENT: The angiotensin AT2 receptor (AT2R) is now regarded as a fully functional and important component of the renin-angiotensin system, with the potential of exerting protective actions in a variety of diseases. This review provides an in-depth view of the AT2R, which has progressed from being an enigma to becoming a therapeutic target.

Renin Angiotensin Blockers and Cardiac Protection: From Basis to Clinical Trials

Despite a similar beneficial effect on blood pressure lowering observed with angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II type 1 receptor (AT1R) blocker (ARBs), several clinical trials and meta-analyses have reported higher cardiovascular mortality and lower protection against myocardial infarction with ARBs when compared with ACEIs. The European guidelines for the management of coronary syndromes and European guidelines on diabetes recommend using ARBs in patients who are intolerant to ACEIs. We reviewed the main pharmacological differences between ACEIs and ARBs, which could provide insights into the differences in the cardiac protection offered by these 2 drug classes. The effect of ACEIs on the tissue and plasma levels of bradykinin and on nitric oxide production and bioavailability is specific to the mechanism of action of ACEIs; it could account for the different effects of ACEIs and ARBs on endothelial function, atherogenesis, and fibrinolysis. Moreover, chronic blockade of AT1 receptors by ARBs induces a significant and permanent increase in plasma angiotensin II and an overstimulation of its still available receptors. In animal models, AT4 receptors have vasoconstrictive, proliferative, and inflammatory effects. Moreover, in models with kidney damage, atherosclerosis, and/or senescence, activation of AT2 receptors could have deleterious fibrotic, vasoconstrictive, and hypertrophic effects and seems prudent and reasonable to reserve the use of ARBs for patients who have presented intolerance to ACE inhibitors.

Association between polymorphisms of genes involved in the Renin-Angiotensin-Aldosterone System and the adaptive morphological and functional responses to essential hypertension

Hypertensive cardiac remodeling is illustrated by increased left ventricular (LV) mass index values and/or relative wall thickness (RWT) values >0.42, and functionally by isolated alteration of LV diastole (abnormal relaxation). The aim of the present study was to establish differentiated models of anatomical and functional adaptation to essential hypertension (EHT), in relation to the genetic variants of genes involved in the Renin-Angiotensin-Aldosterone System (RAAS). The M235T-AGT, I/D-ACE, A1166C-R1AngII, A3123C-R2AngII and G83A-REN genotypes were determined using PCR-Restriction Fragment Length Polymorphism in 139 hypertensive subjects. The relationship between the studied RAAS gene polymorphisms with morphological and functional cardiac remodeling was assessed by multiple logistic regression analysis. Patients carrying the C/C, A/C genotypes (A3123C-R2AngII polymorphism) had a 2.72-fold (P=0.033) increased risk of exhibiting an RWT value <0.42; in the multivariate model the risk was 4.02-fold higher (P=0.008). Analysis of LV diastolic dysfunction (LVDD) revealed that hypertensive patients carrying the T/T, M/T genotypes (M235T-AGT polymorphism) had a 2.24-fold (P=0.037) increased risk of developing LVDD and a 2.42-fold increased risk (P=0.039) after adjustment for confounders. Similarly, carriers of the G/G, A/G genotypes (G83A-REN) had a 2.32-fold (P=0.021) increased risk of developing LVDD, and this remained an independent risk factor based on the multivariate model (P=0.033). The results of the present study showed that no particular gene was associated with increased LV mass, but the A3123C-R2AngII polymorphism was associated with a non-concentric type of cardiac response in hypertensive patients. Conversely, the M235T-AGT and G83A-REN polymorphisms were found to be statistically significantly associated with LVDD when assessing abnormal relaxation.

Exploring AT2R and its polymorphism in different diseases: An approach to develop AT2R as a drug target beyond hypertension

The Angiotensin II type 2 receptor (AT2R) is one of the critical components of the renin-angiotensin system (RAS), which performs diverse functions like inhibiting cell differentiation, cell proliferation, vasodilatation, reduces oxidative stress and inflammation. AT2R is relatively less studied in comparison to other components of RAS despite its uniqueness (sex-linked) and diverse functions. The AT2R is differentially expressed in different tissues, and its gene polymorphisms are associated with several diseases. The molecular mechanism behind the association of AT2R and its gene polymorphisms with the diseases remains to be fully understood, which hinders the development of AT2R as a drug target. Single nucleotide polymorphisms (SNPs) in AT2R are found at different locations (exons, introns, promoter, and UTR regions) and were studied for association with different diseases. There may be different mechanisms behind these associations as some AT2R SNP variants were associated with differential expression, the SNPs (A1675G/A1332G) affect the alternate splicing of AT2R mRNA, A1332G genotype results in shortening of the AT2R mRNA and subsequently defective protein. Few SNPs were found to be associated with the diseases in either females (C4599A) or males (T1334C). Several other SNPs were expected to be associated with other similar/related diseases, but studies have not been done yet. The present review emphasizes on the significance of AT2R and its polymorphisms associated with the diseases to explore the precise role of AT2R in different diseases and the possibility to develop AT2R as a potential drug target.

Arterial Blood Pressure Variability and Other Vascular Factors Contribution to the Cognitive Decline in Parkinson's Disease

Dementia is one of the most disabling non-motor symptoms in Parkinson’s disease (PD). Unlike in Alzheimer’s disease, the vascular pathology in PD is less documented. Due to the uncertain role of commonly investigated metabolic or vascular factors, e.g., hypertension or diabetes, other factors corresponding to PD dementia have been proposed. Associated dysautonomia and dopaminergic treatment seem to have an impact on diurnal blood pressure (BP) variability, which may presumably contribute to white matter hyperintensities (WMH) development and cognitive decline. We aim to review possible vascular and metabolic factors: Renin-angiotensin-aldosterone system, vascular endothelial growth factor (VEGF), hyperhomocysteinemia (HHcy), as well as the dopaminergic treatment, in the etiopathogenesis of PD dementia. Additionally, we focus on the role of polymorphisms within the genes for catechol-O-methyltransferase (COMT), apolipoprotein E (APOE), vascular endothelial growth factor (VEGF), and for renin-angiotensin-aldosterone system components, and their contribution to cognitive decline in PD. Determining vascular risk factors and their contribution to the cognitive impairment in PD may result in screening, as well as preventive measures.

The Other Angiotensin II Receptor: AT2R as a Therapeutic Target

The active hormone of the renin-angiotensin system (RAS), angiotensin II (Ang II), is involved in several human diseases, driving the development and clinical use of several therapeutic drugs, mostly angiotensin I converting enzyme (ACE) inhibitors and angiotensin receptor type I (AT₁R) antagonists. However, angiotensin peptides can also bind to receptors different from AT₁R, in particular, angiotensin receptor type II (AT₂R), resulting in biological and physiological effects different, and sometimes antagonistic, of their binding to AT₁R. In the present Perspective, the components of the RAS and the therapeutic tools developed to control it will be reviewed. In particular, the characteristics of AT₂R and tools to modulate its functions will be discussed. Agonists or antagonists to AT₂R are potential therapeutics in cardiovascular diseases, for agonists, and in the control of pain, for antagonists, respectively. However, controlling their binding properties and their targeting to the target tissues must be optimized.

Association of renin-angiotensin system genetic polymorphisms and aneurysmal subarachnoid hemorrhage

OBJECTIVE

Renin-angiotensin system (RAS) genetic polymorphisms are thought to play a role in cerebral aneurysm formation and rupture. The Cerebral Aneurysm Renin-Angiotensin System (CARAS) study prospectively evaluated common RAS polymorphisms and their relation to aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

The CARAS study prospectively enrolled aSAH patients and controls at 2 academic centers in the United States. A blood sample was obtained from all patients for genetic evaluation and measurement of plasma angiotensin-converting enzyme (ACE) concentration. Common RAS polymorphisms were detected using 5′ exonuclease (TaqMan) genotyping assays and restriction fragment length polymorphism analysis.

RESULTS

Two hundred forty-eight patients were screened, and 149 aSAH patients and 50 controls were available for analysis. There was a recessive effect of the C allele of the angiotensinogen (AGT) C/T single-nucleotide polymorphism (SNP) (OR 1.94, 95% CI 0.912–4.12, p = 0.0853) and a dominant effect of the G allele of the angiotensin II receptor Type 2 (AT2) G/A SNP (OR 2.11, 95% CI 0.972–4.57, p = 0.0590) on aSAH that did not reach statistical significance after adjustment for potential confounders. The ACE level was significantly lower in aSAH patients with the II genotype (17.6 ± 8.0 U/L) as compared with the ID (22.5 ± 12.1 U/L) and DD genotypes (26.6 ± 14.2 U/L) (p = 0.0195).

CONCLUSIONS

The AGT C/T and AT2 G/A polymorphisms were not significantly associated with aSAH after controlling for potential confounders. However, a strong trend was identified for a dominant effect of the G allele of the AT2 G/A SNP. Downregulation of the local RAS may contribute to the formation of cerebral aneurysms and subsequent presentation with aSAH. Further studies are required to elucidate the relevant pathophysiology and its potential implication in treatment of patients with aSAH.

Blood pressure, arterial stiffness and endogenous lithium clearance in relation to AGTR1 A1166C and AGTR2 G1675A gene polymorphisms

Introduction:

Although recently a matter of epidemiologic controversy, sodium overload and its interaction with genetic factors predispose to hypertension and related target organ complications.

Methods:

In 131 (66 male) treated hypertensives, we measured peripheral and central arterial pressures and pulse wave augmentation indexes (AIx_P, AIx_C1, AIx_C2), pulse wave velocity (PWV), daily urinary sodium excretion and did genetic studies of AGTR1 A1166C and AGTR2 G1675A polymorphisms. Proximal (FE_Li) and distal (FDR_Na) sodium reabsorption measurements were performed using endogenous lithium clearance.

Results:

In men, we found interaction between FDR_Na and AGTR2 G1675A polymorphism with respect to AIx_C1 (p_INT=0.01), AIx_C2 (p_INT=0.05) and AIx_P (p_INT=0.006). Arterial stiffness increased with higher sodium reabsorption in the distal tubule, in the presence of AGTR2 G allele with the opposite tendency in A allele carriers. In the subgroup with FDR_Na below median, as compared to those with FDR_Na above median, the AIx_C1 (139.6±3.8 vs 159.1±5.7%; p=0.009), AIx_C2 (26.3±1.8 vs 33.3±1.7%; p=0.016) and AIx_P (83.4±2.5 vs 96.5±2.6%; p<0.0001) were lower, in the G allele carrying men and GG homozygous women.

Conclusions:

The relation between sodium reabsorption in the distal tubule and the development of arterial stiffness depends on the AGTR2 G1675A polymorphism in blood pressure independent fashion.

International Union of Basic and Clinical Pharmacology. XCIX. Angiotensin Receptors: Interpreters of Pathophysiological Angiotensinergic Stimuli [corrected]

The renin angiotensin system (RAS) produced hormone peptides regulate many vital body functions. Dysfunctional signaling by receptors for RAS peptides leads to pathologic states. Nearly half of humanity today would likely benefit from modern drugs targeting these receptors. The receptors for RAS peptides consist of three G-protein-coupled receptors—the angiotensin II type 1 receptor (AT1 receptor), the angiotensin II type 2 receptor (AT2 receptor), the MAS receptor—and a type II trans-membrane zinc protein—the candidate angiotensin IV receptor (AngIV binding site). The prorenin receptor is a relatively new contender for consideration, but is not included here because the role of prorenin receptor as an independent endocrine mediator is presently unclear. The full spectrum of biologic characteristics of these receptors is still evolving, but there is evidence establishing unique roles of each receptor in cardiovascular, hemodynamic, neurologic, renal, and endothelial functions, as well as in cell proliferation, survival, matrix-cell interaction, and inflammation. Therapeutic agents targeted to these receptors are either in active use in clinical intervention of major common diseases or under evaluation for repurposing in many other disorders. Broad-spectrum influence these receptors produce in complex pathophysiological context in our body highlights their role as precise interpreters of distinctive angiotensinergic peptide cues. This review article summarizes findings published in the last 15 years on the structure, pharmacology, signaling, physiology, and disease states related to angiotensin receptors. We also discuss the challenges the pharmacologist presently faces in formally accepting newer members as established angiotensin receptors and emphasize necessary future developments.

AT2R -1332 G:A polymorphism and diabetic nephropathy in type 2 diabetes mellitus patients

INTRODUCTION

The rennin-angiotensin system (RAS) plays a central role in the regulation of sodium metabolism, vascular tone, blood pressure, renal hemodynamics, and vascular modeling and is activated by hyperglycemiaObjectives: In the present study the influence of AT2R -1332 G:A polymorphism on the risk of T2DM and its complications in a population from Western Iran has been investigated.

PATIENTS AND METHODS

In a case-control study, 70 individuals with type 2 diabetes mellitus (T2DM) including normo-, micro- and macro-albuminuric patients and 112 healthy subjects from the Kermanshah province were studied to investigate the association between the angiotensin type 2 receptor (AT2R) -1332 G:A variants with the risk of T2DM and its complications. The genotypes of the AT2R were detected using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Analysis of AT2R -1332 G:A polymorphism indicated the absence of association between this polymorphism with T2DM and diabetic nephropathy.

RESULTS

Analysis of AT2R -1332 G:A polymorphism indicated the absence of association between this polymorphism with T2DM and diabetic nephropathy. In females with diabetic nephropathy a significantly higher frequency of AA genotype (50%) was detected compared to those without nephropathy (13.3%, p=0.015). The presence of A allele of AT2R was associated with significantly (p=0.029) increased risk of coronary artery disease (CAD) in diabetic patients without nephropathy.

CONCLUSION

Our study indicated an association between the AT2R -1332 G:A polymorphism and the risk of diabetic nephropathy in females only. Also, the A allele was associated with the risk of CAD in those diabetic patients without nephropathy.

Association of polymorphisms in angiotensin II receptor genes with aldosterone-producing adenoma

This study examined the association of polymorphisms in angiotensin II receptor genes (AT (1) R and AT (2) R) with the risk for aldosterone-producing adenoma (APA) in a Chinese Han population. Four polymorphisms including rs5182 (573T/C) in exon 4, rs5186 (1166A/C) in 3'-untranslated region (3'-UTR) in AT (1) R gene and rs5194 (2274G/A) in 3'-UTR, rs1403543 (1675G/A) in intron 1 in AT (2) R gene were detected in 148 APA patients and 192 normal subjects (serving as control) by using a MGB-Taqman probe. The distribution of genotypes of each locus was in accordance with Hardy-Weinberg Equilibrium (HWE) in the APA and control groups (P>0.05). The allele A frequency at rs5194 was significantly higher in the APA group (0.49) than in the control group (0.35) (χ (2)=12.08, P=0.001). Subjects with homozygotic genotype AA and heterozygotic genotype GA were at an increased risk for APA as compared to those with GG genotype (OR=2.66, 95% CI=1.45-4.87; OR=1.67, 95% CI=1.02-2.74). Furthermore, rs5194 single-nucleotide polymorphism (SNP) at AT (2) R gene was significantly associated with APA in additive (OR=1.64, 95% CI=1.21-2.20, P=0.001), dominant (OR=1.94, 95% CI=1.23-3.06, P=0.003), and recessive model (OR=2.01, 95% CI=1.17-3.45, P=0.01). It was concluded that rs5194 polymorphism at AT (2) R gene was associated with the risk for APA, which may constitute a genetic marker of APA.

Genetic variation in angiotensin II type 2 receptor gene influences extent of left ventricular hypertrophy in hypertrophic cardiomyopathy independent of blood pressure

Introduction. Hypertrophic cardiomyopathy (HCM), an inherited primary cardiac disorder mostly caused by defective sarcomeric proteins, serves as a model to investigate left ventricular hypertrophy (LVH). HCM manifests extreme variability in the degree and distribution of LVH, even in patients with the same causal mutation. Genes coding for renin—angiotensin—aldosterone system components have been studied as hypertrophy modifiers in HCM, with emphasis on the angiotensin (Ang) II type 1 receptor (AT1R). However, Ang II binding to Ang II type 2 receptors (AT2R) also has hypertrophy-modulating effects.

Methods. We investigated the effect of the functional +1675 G/A polymorphism (rs1403543) and additional single nucleotide polymorphisms in the 3’ untranslated region of the AT2R gene ( AGTR2) on a heritable composite hypertrophy score in an HCM family cohort in which HCM founder mutations segregate.

Results. We find significant association between rs1403543 and hypertrophy, with each A allele decreasing the average wall thickness by ~0.5 mm, independent of the effects of the primary HCM causal mutation, blood pressure and other hypertrophy covariates ( p = 0.020).

Conclusion. This study therefore confirms a hypertrophy-modulating effect for AT2R also in HCM and implies that +1675 G/A could potentially be used in a panel of markers that profile a genetic predisposition to LVH in HCM.

Angiotensin-converting enzyme and angiotensin II receptor subtype 2 genotypes in type 1 diabetes and severe hypoglycaemia requiring emergency treatment: a case cohort study

AIMS

In type 1 diabetes, individual susceptibility to severe hypoglycaemia is likely to be influenced by genetic factors. We have previously reported an association of the deletion (D-) allele of the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism and the A-allele of the angiotensin II receptor subtype 2 (AT2R) 1675 G>A polymorphism with risk of severe hypoglycaemia in such patients. The aim of this study was to test the hypothesis that these alleles are more frequent in patients suffering from the most severe episodes of hypoglycaemia requiring medical emergency treatment.

METHODS

The case cohort study consisted of 108 cases of type 1 diabetic patients with severe hypoglycaemia requiring medical emergency treatment during a 1-year period and 262 consecutive controls without such events. ACE I/D and AT2R 1675G>A genotype distributions were compared between cases and controls.

RESULTS

The proportion of D-allele carriers was higher amongst cases than controls (83 vs. 73%; P=0.032). In contrast, AT2R genotype distribution was similar in cases and controls. In a multiple regression analysis, D-allele carriage remained a significant risk factor for being a case [odds ratio: 1.9 (1.0-3.6)] together with male sex, impaired symptomatic awareness of hypoglycaemia and presence of nephropathy.

CONCLUSION

The D-allele of the ACE gene is associated with severe hypoglycaemia requiring emergency treatment in type 1 diabetic patients with preserved spontaneous ACE activity. This supports the association between high ACE activity and occurrence of severe hypoglycaemia.

The angiotensin II receptor type 2 polymorphism influences haemodynamic function and circulating RAS mediators in normotensive humans

BACKGROUND

The haemodynamic responses to angiotensin II type 1 (AT1) receptor blockade may be mediated in part by interactions between angiotensin II and the angiotensin II type 2 receptor (AT2R). An AT2R G1675A gene polymorphism has been described, but the functional effects of this polymorphism are unknown.

METHODS

Haemodynamic function, circulating renin-angiotensin system mediators and norepinephrine were measured in young healthy subjects at baseline and at 2 and 4 weeks after treatment with irbesartan. Subjects were divided into two groups on the basis of the AT2R G1675A gene polymorphism: GG subjects (n = 12) and AA/GA subjects (n = 22).

RESULTS

AA/AG subjects exhibited hypotensive and renal vasodilatory responses to irbesartan at 4 weeks, but GG subjects did not. In accord with haemodynamic effects, circulating aldosterone levels were suppressed in AA/AG, while circulating norepinephrine levels were augmented only in GG subjects. In contrast, increases in circulating renin, angiotensin II and plasma renin activity after irbesartan were exaggerated in AA/AG subjects.

CONCLUSIONS

The AT2R G1675A polymorphism is a determinant of haemodynamic responses to AT1 receptor blockade, an effect that may be due to influences on aldosterone escape.

Genetic polymorphism on type 2 receptor of angiotensin II, modifies cardiovascular risk and systemic inflammation in hypertensive males

BACKGROUND

Angiotensin type 2 receptor (AT2R), plays a crucial role in blood pressure regulation and atherogenesis. AT2R gene is located on chromosome X and the biological effect of polymorphism A1675G in this gene needs to be further specified. We examined the impact of A1675G on the risk and the severity of coronary artery disease (CAD), and the expression of proatherogenic inflammatory molecules in hypertensive patients.

METHODS

The study population consisted of 146 with CAD (102 with hypertension) and 266 age-matched individuals without CAD (114 with hypertension). The presence of A1675G polymorphism on AT2R gene was determined by PCR. Serum levels of C-reactive protein (CRP), fibrinogen, interleukin-6 (IL-6) and soluble vascular cell adhesion molecule-1 (sVCAM-1) were measured in all the participants.

RESULTS

The G allele was associated with decreased risk of CAD among hypertensives (odds ratio (OR) (95% confidence interval (CI))): 0.4 (0.2-0.9), P = 0.01) and less aggressive angiographic CAD (P < 0.001). The G allele was associated with lower IL-6 (median (25-75th percentile): 1.4 (0.6-3.8)), sVCAM-1 (621 (476-799)), CRP (1.2 (0.6-1.7)), and fibrinogen (369 (320-416)) vs. A allele (IL-6: 2.4 (1.1-4.5) P < 0.01, sVCAM-1: 702 (548-925) P < 0.05, CRP: 3.5 (2.0-6.1) P < 0.001, and fibrinogen: 407 (348-514) P < 0.01). The effect of A1675G on serum IL-6, sVCAM-1, and fibrinogen was driven by its effect among hypertensives (IL-6 3.1 (2.1-5.6 in A vs. 1.2 (0.3-3.4) in G P < 0.001, sVCAM-1: 890 (560-1000) in A vs. 556 (377-788) in G P < 0.01, and fibrinogen: 408 (354-510) in A vs. 369 (324-418) in G P < 0.001) whereas it had no effect among nonhypertensives.

CONCLUSIONS

Genetic polymorphism A1675G on AT2R gene affects cardiovascular risk and the severity of atherosclerosis by modifying systemic inflammation, especially in hypertensive males.

Angiotensin II type 2 receptor gene polymorphisms in cardiovascular disease

Considerable progress in our understanding of the role of the angiotensin II type 2 (AT(2)) receptor in the development of cardiac hypertrophy and coronary artery disease has been achieved using in vitro and in vivo animal models. Our understanding in humans, however, has been hindered by the lack of availability of specific AT(2) receptor agonists and antagonists suitable for human study. Nevertheless, an alternative approach involving genotyping humans for a functional polymorphism within the AT(2) receptor gene (-1332G/A) has been used in several association studies to elucidate the pathogenic role of the AT(2) receptor in cardiovascular disease. Both the A allele and the G allele have independently been associated with left ventricular remodelling. However, the methods of measuring left ventricular mass, sodium balance, age and degree of remodelling appear to influence the outcome. An association of carriers of the G allele and premature coronary artery disease has also been established, particularly in males presenting with stenotic atherosclerosis requiring revascularisation. At the molecular level, it remains unclear as to whether carriers of the G allele express more or fewer AT(2) receptors when compared to carriers of the A allele. Consequently, it is presently not possible to definitively interpret the role of the AT(2) receptor in human cardiovascular disease from these association studies.

Cellular mediators of renal vascular dysfunction in hypertension

The renal vasculature plays a major role in the regulation of renal blood flow and the ability of the kidney to control the plasma volume and blood pressure. Renal vascular dysfunction is associated with renal vasoconstriction, decreased renal blood flow, and consequent increase in plasma volume and has been demonstrated in several forms of hypertension (HTN), including genetic and salt-sensitive HTN. Several predisposing factors and cellular mediators have been implicated, but the relationship between their actions on the renal vasculature and the consequent effects on renal tubular function in the setting of HTN is not clearly defined. Gene mutations/defects in an ion channel, a membrane ion transporter, and/or a regulatory enzyme in the nephron and renal vasculature may be a primary cause of renal vascular dysfunction. Environmental risk factors, such as high dietary salt intake, vascular inflammation, and oxidative stress further promote renal vascular dysfunction. Renal endothelial cell dysfunction is manifested as a decrease in the release of vasodilatory mediators, such as nitric oxide, prostacyclin, and hyperpolarizing factors, and/or an increase in vasoconstrictive mediators, such as endothelin, angiotensin II, and thromboxane A(2). Also, an increase in the amount/activity of intracellular Ca(2+) concentration, protein kinase C, Rho kinase, and mitogen-activated protein kinase in vascular smooth muscle promotes renal vasoconstriction. Matrix metalloproteinases and their inhibitors could also modify the composition of the extracellular matrix and lead to renal vascular remodeling. Synergistic interactions between the genetic and environmental risk factors on the cellular mediators of renal vascular dysfunction cause persistent renal vasoconstriction, increased renal vascular resistance, and decreased renal blood flow, and, consequently, lead to a disturbance in the renal control mechanisms of water and electrolyte balance, increased plasma volume, and HTN. Targeting the underlying genetic defects, environmental risk factors, and the aberrant renal vascular mediators involved should provide complementary strategies in the management of HTN.

Association of angiotensin II type 2 receptor gene A1818T polymorphism with progression of immunoglobulin A nephropathy in Korean patients

We determined the relationship between the progression of immunoglobulin A nephropathy (IgAN) and the A1818T polymorphism in intron 2 of Angiotensin II type 2 receptor (AT2R) gene, which might play protective roles in the pathogenesis of IgAN. Patients with biopsy-proven IgAN were recruited from the registry of the Progressive REnal disease and Medical Informatics and gEnomics Research (PREMIER) which was sponsored by the Korean Society of Nephrology. A1818T polymorphism of AT2R gene was analyzed with PCR-RFLP method and the association with the progression of IgAN, which was defined as over 50% increase in baseline serum creatinine level, was analyzed with survival analysis. Among the 480 patients followed for more than 10 months, the group without T allele had significantly higher rates of progression of IgAN than the group with T allele (11.4% vs. 3.9%, p=0.024), although there were no significant differences in the baseline variables such as initial serum creatinine level, the degree of proteinuria, and blood pressure. In the Cox's proportional hazard model, the hazard ratio of disease progression in the patients with T allele was 0.221 (95% confidence interval for Exp(B): 0.052-0.940, p=0.041) compared to that of without T allele. In conclusion, A1818T polymorphism of AT2R gene was associated with the progression of IgAN.

AT2 receptors: functional relevance in cardiovascular disease

The renin angiotensin system (RAS) is intricately involved in normal cardiovascular homeostasis. Excessive stimulation by the octapeptide angiotensin II contributes to a range of cardiovascular pathologies and diseases via angiotensin type 1 receptor (AT1R) activation. On the other hand, tElsevier Inc.he angiotensin type 2 receptor (AT2R) is thought to counter-regulate AT1R function. In this review, we describe the enhanced expression and function of AT2R in various cardiovascular disease settings. In addition, we illustrate that the RAS consists of a family of angiotensin peptides that exert cardiovascular effects that are often distinct from those of Ang II. During cardiovascular disease, there is likely to be an increased functional importance of AT2R, stimulated by Ang II, or even shorter angiotensin peptide fragments, to limit AT1R-mediated overactivity and cardiovascular pathologies.

Genetics of the human renin angiotensin system

The genes coding for the renin angiotensin system have been extensively studied. During the last 15 years, informative markers and functional polymorphisms have been identified, and numerous linkage and association studies have been performed in cardiovascular diseases, especially human hypertension. This mini-review aims to summarize the main findings observed for each component of this enzymatic cascade taken alone or in combination, with an emphasis on the most recent or innovative studies.

Genetic variation and activity of the renin-angiotensin system and severe hypoglycemia in type 1 diabetes

BACKGROUND

The deletion-allele of the angiotensin-converting enzyme (ACE) gene and elevated ACE activity are associated with increased risk of severe hypoglycemia in type 1 diabetes. We explored whether genetic and phenotypic variations in other components of the renin-angiotensin system are similarly associated.

METHODS

Episodes of severe hypoglycemia were recorded in 171 consecutive type 1 diabetic outpatients during a 1-year follow-up. Participants were characterized at baseline by gene polymorphisms in angiotensinogen, ACE, angiotensin-II receptor types 1 (AT1R) and 2 (AT2R), and by plasma angiotensinogen concentration and serum ACE activity.

RESULTS

Three risk factors for severe hypoglycemia were identified: plasma angiotensinogen concentration in the upper quartile (relative rate [RR] vs. lower quartile 3.1, 95% confidence interval [CI,] 1.4-6.8), serum ACE activity in the upper quartile (RR vs. lower quartile 2.9, 95% CI, 1.3-6.2), and homo- or hemizygosity for the A-allele of the X chromosome-located AT2R 1675G/A polymorphism (RR vs. noncarriers 2.5, 95% CI, 1.4-5.0). The three risk factors contributed independently to prediction of severe hypoglycemia. A backward multiple regression analysis identified a high number of renin-angiotensin system-related risk factors and reduced ability to perceive hypoglycemic warning symptoms (impaired hypoglycemia awareness) as predictors of severe hypoglycemia.

CONCLUSIONS

High renin-angiotensin system activity and the A-allele of the AT2R 1675G/A polymorphism associate with high risk of severe hypoglycemia in type 1 diabetes. A potential preventive effect of renin-angiotensin system blocking drugs in patients with recurrent severe hypoglycemia merits further investigation.

High sodium intake modulates left ventricular mass in patients with G expression of +1675 G/A angiotensin II receptor type 2 gene

OBJECTIVES

In patients with hypertension left ventricular hypertrophy (LVH) is associated with genetic variations of the angiotensin type 2 receptor (AT2R). Hypertension and LVH are often aggravated by salt intake. Our objective was to assess the relationship between AT2R gene variation and salt intake and their impact on left ventricular mass (LVM).

METHODS AND RESULTS

In 205 subjects with normal or mildly elevated blood pressure, we assessed sodium intake and left ventricular structure and function by echocardiography. Intronic +1,675 G/A polymorphism of the AT2R gene was investigated. A-allele carriers had a greater LVM (P = 0.049) than G-allele carriers. Independent of diet, septal wall thickness was higher in A-allele carriers (P = 0.001). Fractional fibre shortening was greater in A-allele carriers (P = 0.034), and the velocity of circumferential fibre shortening tended to be greater in A-allele carriers (P = 0.057). When the two groups were stratified according to their salt intake, only G-allele carriers displayed a modulating effect of salt intake on LVM. Covariance analysis revealed that there was a trend towards a modulating effect of salt intake on LVM, even after taking blood pressure into account (P = 0.054).

CONCLUSION

Our data clearly support the notion that LVM is influenced by AT2R polymorphisms. Furthermore, G-allele carriers in particular appear to be susceptible to a modifying effect of increased salt intake on LVM.

X-linked angiotensin II type 2 receptor gene polymorphism -1332A/G in male patients with essential hypertension

BACKGROUND

The role of AT2R in regulation of blood pressure (BP) was mainly investigated in animal models. It is proposed to be a negative regulator of BP. X-linked AT2R -1332 A/G polymorphism has been denoted as functional. This polymorphism was associated with certain cardiovascular phenotypes in hypertensive patients, but it was poorly investigated in essential hypertension. The aim of our study was to evaluate possible association of -1332 A/G gene polymorphism with essential hypertension in males from Serbian population.

METHODS

The study group included 304 men of Caucasian origin, 190 normotensive (NT) and 114 hypertensive (HT), free of cardiovascular disorders. Genotyping was done by PCR RFLP method.

RESULTS

G/- genotype was in association with HT (OR 1.6, CI=1.0-2.6, p=0.04). Stratification by age (<40 years, mean 31.65+/-5.29 and >40 years, mean 51.36+/-8.32) pronounced significance only in older males (OR 2.4, CI=1.2-5.0, p=0.02). After adjustment for confounding factors the OR for hypertension remained unchanged and significant (adjusted OR 2.3, CI=1.0-5.4, p=0.04).

CONCLUSION

Hemizygosity for the G allele was found to be susceptibility factor for hypertension in males. Still, clarifying the role of AT2R in development of human hypertension requires further replication studies in larger and different populations.

Renin-angiotensin system and cardiovascular risk

The renin-angiotensin system is a major regulatory system of cardiovascular and renal function. Basic research has revealed exciting new aspects, which could lead to novel or modified therapeutic approaches. Renin-angiotensin system blockade exerts potent antiatherosclerotic effects, which are mediated by their antihypertensive, anti-inflammatory, antiproliferative, and oxidative stress lowering properties. Inhibitors of the system-ie, angiotensin converting enzyme inhibitors and angiotensin receptor blockers, are now first-line treatments for hypertensive target organ damage and progressive renal disease. Their effects are greater than expected by their ability to lower blood pressure alone. Angiotensin receptor blockers reduce the frequency of atrial fibrillation and stroke. Renin-angiotensin system blockade delays or avoids the onset of type 2 diabetes and prevents cardiovascular and renal events in diabetic patients. Thus, blockade of this system will remain a cornerstone of our strategies to reduce cardiovascular risk.

A comprehensive view of sex-specific issues related to cardiovascular disease

Cardiovascular disease (CVD) is the leading cause of mortality in women. In fact, CVD is responsible for a third of all deaths of women worldwide and half of all deaths of women over 50 years of age in developing countries. The prevalence of CVD risk factor precursors is increasing in children. Retrospective analyses suggest that there are some clinically relevant differences between women and men in terms of prevalence, presentation, management and outcomes of the disease, but little is known about why CVD affects women and men differently. For instance, women with diabetes have a significantly higher CVD mortality rate than men with diabetes. Similarly, women with atrial fibrillation are at greater risk of stroke than men with atrial fibrillation. Historically, women have been underrepresented in clinical trials. The lack of good trial evidence concerning sex-specific outcomes has led to assumptions about CVD treatment in women, which in turn may have resulted in inadequate diagnoses and suboptimal management, greatly affecting outcomes. This knowledge gap may also explain why cardiovascular health in women is not improving as fast as that of men. Over the last decades, mortality rates in men have steadily declined, while those in women remained stable. It is also becoming increasingly evident that gender differences in cultural, behavioural, psychosocial and socioeconomic status are responsible, to various degrees, for the observed differences between women and men. However, the interaction between sex-and gender-related factors and CVD outcomes in women remains largely unknown.

The AT2 gene may have a gender-specific effect on kidney function and pulse pressure in type I diabetic patients

Diabetic nephropathy shows a higher incidence in male subjects, which may in part be owing to genetic factors. The angiotensin II type 2 receptor (AT2), present in the renal glomerulus, may oppose the deleterious effects of the type I receptor (AT1) through vasodilatation and growth inhibition. We determined whether the functional intronic G1675A or A1818T polymorphism of the X-chromosomal AT2 gene is associated with blood pressure levels or with kidney function. We genotyped 996 (538 female/458 male subjects) Finnish patients with type I diabetes from the FinnDiane-study in a cross-sectional study. DNA samples were amplified using standard polymerase chain reaction protocol and the genotypes were determined by the minisequencing method. Male patients with the AA haplotype had a lower glomerular filtration rate (83 +/- 32 vs 94 +/- 34 ml min(-1) 1.73 m(-2), P = 0.008) and a higher pulse pressure (PP) (62 +/- 18 vs 57 +/- 15 mm Hg, P = 0.002; P < 0.05 after adjustment for age) than did those with the GT haplotype. No differences between the genotypes or haplotypes and these variables were evident in females. In males, the G1675A was also an independent variable in a linear regression analysis with PP (r(2) = 0.16, coefficient=3.64, s.e.m.=1.38, P < 0.01) as the dependent variable. These data suggest a gender-specific association between the AT2 gene and kidney function and premature aging of the arterial tree in patients with type I diabetes.

Angiotensin II type 2 receptor gene polymorphisms and cardioprotective role in essential hypertension

Angiotensin II type 2 receptor (AT2R) has been proved to be involved in a cardioprotective role, but only a few studies have addressed the association of AT2R-genotype with this role. Whether the AT2R genotype is associated with hypertension is controversial. The aim of the study was to explore the information of single-nucleotide polymorphisms (SNPs) of the AT2R gene in Cantonese, an essential subpopulation of Chinese, and study the association of SNPs in the AT2R gene with hypertension, and to detect the genotypes that indicate a cardioprotective role. Two hundred and sixty-two patients with essential hypertension and 75 normotensive subjects were enrolled for a case-control study. All of the subjects were Cantonese. Sixteen individuals were chosen to sequence the AT2R gene and 16 SNPs were acquired. G/T rs5193 and G/A rs5194 were two SNPs in the 3' untranslated region which were focused on the association of the AT2R-genotype and phonotype. Polymerase chain reaction was performed to amplify the fragment spanning the two SNPs. Genotype and haplotype were identified by dot blot hybridization. Four haplotypes in males (G-G, G-A, T-A, T-G) and eight haplotype combinations in females (G-G/G-G, G-A/G-A, G-G/G-A, G-G/T-A, G-G/T-G, T-A/T-A, T-G/T-G, and T-A/T-G) were detected. G-G and G-A haplotype were predominant, while T-A and T-G were rare in Cantonese. None of these was associated with hypertension. T-A carriers with essential hypertension indicated lower levels of left ventricular mass (LVM) and left ventricular hypertrophy index (LVHI). The levels of LVM and LVHI were still significantly lower in T-A carriers with hypertension adjusted for age or body mass index for men and women separately. No episodes of coronary heart disease and heart failure were detected in T-A carriers with hypertension. Haplotypes of G/T rs5193-G/A rs5194 are not associated with essential hypertension. Among these haplotypes, T-A may be implicated in a cardioprotective role to protect hypertense subjects from left ventricular hypertrophy.

Altered transmission of maternal angiotensin II receptor haplotypes in fetal growth restriction

Fetal growth restriction (FGR) predisposes to significant short- and long-term health problems. Epidemiological studies have suggested a role for inherited factors in its pathogenesis. The angiotensin II receptor genes, AGTR1 and AGTR2, are candidate genes because they mediate processes that are important for placentation. This study investigated AGTR1 and AGTR2 haplotypes and genotypes in FGR. A total of 107 families (father, mother, and baby) with FGR, and 101 families with normal pregnancies were genotyped at five sites in AGTR1 and six sites across AGTR2. All of the participants were white western Europeans. FGR was identified antenatally by ultrasound scans and confirmed postnatally by correcting the birth weight centile for gestation, infant sex, maternal height, weight, and parity. Fetal genes were investigated using transmission disequilibrium testing (TDT), and a case-control comparison of maternal haplotypes was conducted. FGR was associated with maternal (but not paternal) transmission of the AGTR1 haplotype (GenBank AF245699.1) g.4955T, g.5052T, g.5245C, g.5612A, and haplotype g.4955T, g.5052T, g.5245T, g.5612A. Haplotype g.4955A, g.5052G, g.5245T, g.5612G was undertransmitted (P = 0.002). TDT of the AGTR1 genotype showed undertransmission of maternal AGTR1 genotypes g.4955T>A (odds ratio (OR), 0.34 (95% confidence interval (CI), 0.14-0.86); P = 0.02), g.5052T>G (OR, 0.18 (0.06-0.48); P<0.001), and g.5612A>G (OR, 0.21 (0.08-0.55); P < 0.001) in FGR. There were no differences in maternal haplotype frequencies between normal pregnancy and FGR for AGTR1 or AGTR2 (P > 0.10). This is the first study to show distortion of transmission of maternal AGTR1 haplotypes in FGR, which suggests that this gene plays a role in FGR. In particular, maternal-fetal gene sharing may be an important factor.

Sodium excretion as a modulator of genetic associations with cardiovascular phenotypes in the European Project on Genes in Hypertension

Hypertension is a chronic age-related disorder, affecting nearly 20% of all adult Europeans. This disease entails debilitating cardiovascular complications and is the leading cause for drug prescriptions in Europeans older than 50 years. Intensive research over the past two decades has so far failed to identify common genetic polymorphisms with a major impact on blood pressure or associated cardiovascular phenotypes, suggesting that multiple genes each with a minor impact, along with gene-gene and gene-environment interactions, play a role. The European Project on Genes in Hypertension (EPOGH) is a large-scale, family-based study in which participants from seven different populations were phenotyped and genotyped according to standardized procedures. This review article summarizes the initial 5-year findings and puts these observations into perspective against other published studies. The EPOGH demonstrated that phenotype-genotype relations strongly depend on host factors such as gender and lifestyle, in particular salt intake as reflected by the 24-h urinary excretion of sodium. The EPOGH therefore highlights the concept that phenotype-genotype relations can only be studied within a defined ecogenetic context.

Intronic enhancement of angiotensin II type 2 receptor transgene expression in vitro and in vivo

The angiotensin II type 2 receptor (AT2R) can influence a variety of intracellular signaling molecules and cellular functions. However, its physiological functions and the roles of introns in the regulation of its expression have not been well determined. We first demonstrated that both intron 1 and intron 2 of AT2R could significantly enhance AT2R overexpression. Thus, we have provided some new prerequisites for further studies on the mechanisms that control AT2R gene expression. Next, we established a highly efficient method of delivering this receptor in vitro and in vivo using an AT2R recombinant adenoviral vector containing two introns of the AT2R. The vector may be useful in helping to uncover AT2R physiological functions and also for gene therapy related to AT2R. Moreover, we determined the important role of introns in gene expression cassettes and the inconsistency of expression between the targeted gene and the reporter gene.

Association of angiotensin-converting enzyme 2 (ACE2) gene polymorphisms with parameters of left ventricular hypertrophy in men. Results of the MONICA Augsburg echocardiographic substudy

Angiotensin-converting enzyme (ACE) activity is considered to be of major importance for the conversion of angiotensin (Ang) I to Ang II. Recently, a second ACE, named ACE2, has been identified. Experimental data provide evidence that ACE2 might be involved in modulating cardiac structure and function. In the present explorative study, we assessed whether polymorphisms in the ACE2 gene are related to echocardiographically determined parameters of left ventricular mass, structure or function in the general population. Five intronic single nucleotide polymorphisms (SNPs) were genotyped using the 5'-exonuclease activity (TaqMan) assay in the echocardiographic substudy of the third MONICA Augsburg survey. As ACE2 is located on the X chromosome, women and men were analysed separately. Four SNPs showed high pairwise linkage disequilibrium (rs4646156, rs879922, rs4240157 and rs233575). The minor alleles of these four SNPs were associated with higher left ventricular mass index (LVMI) and higher septal wall thickness (SWT) in men. Likewise, male carriers of a common haplotype (frequency 29.9%) consisting of the minor alleles of these four SNPs displayed higher values for LVMI and SWT than non-carriers (LVMI: TGGC 98.8+/-1.52 vs non-TGGC 94.8+/-0.99 g/m(2), p=0.027; SWT: TGGC 11.5+/-0.14 vs non-TGGC 11.1+/-0.09 mm, p=0.019). Furthermore, this haplotype was associated with an increased odds ratio (OR) for left ventricular hypertrophy (OR 3.10, p=0.006). In women, similar but less pronounced and consistent trends were observed. No association was observed between any of these SNPs and parameters of left ventricular systolic or diastolic function nor with blood pressure levels. This study provides evidence that genetic variants in the ACE2 gene may be associated with left ventricular mass, SWT and left ventricular hypertrophy in hemizygous men.

Intronic ANG II type 2 receptor gene polymorphism 1675 G/A modulates receptor protein expression but not mRNA splicing

The X-linked ANG II type 2 receptor (AT2) is supposed to be involved in cardiovascular disorders. Two studies associated the A allele of the AT2 gene polymorphism (PM) 1675 G/A with left ventricular hypertrophy in men and coronary ischemia in women. Because the PM is located in the short intron 1 of the AT2 gene within a sequence motif similar to the splice branch site consensus, we tested whether it might affect pre-mRNA splicing and/or modulate AT2 receptor expression. We first analyzed the AT2 mRNA splice pattern by RT-PCR in myocardial samples from 12 explanted human hearts and compared it with the respective genotypes. All 12 patients, 10 hemizygous males (7 A, 3 G allele carriers) and 2 homozygous females (2 G/G allele carriers), exhibited the same myocardial AT2 splice pattern with a relative abundance of transcript exon 1/2/3 compared with exon 1/3. Next, AT2 minigene constructs were cloned from both alleles, comprising the core promoter and the complete transcribed region up to the translation start codon, upstream of a luciferase reporter gene. These constructs were transfected into human (HT1080) and rat (PC12W) cell lines and rat vascular smooth muscle cells, and luciferase activities were assessed, as well as the splice patterns of the chimeric AT2/luciferase mRNAs. In all transfected cell types, the mRNA expressed from the AT2 constructs was spliced like the endogenous myocardial AT2 mRNA. However, luciferase activities driven by the G allele construct were significantly higher than those expressed from the A allele. Taken together, these data indicate that individuals carrying the G allele may express higher levels of AT2 receptor protein, which may be protective during the development of ventricular hypertrophy and coronary ischemia.

Angiotensin II type 2 receptor-mediated vasodilation. Focus on bradykinin, NO and endothelium-derived hyperpolarizing factor(s)

Angiotensin (Ang) II type 1 (AT(1)) receptors account for the majority of the cardiovascular effects Ang II, including vasoconstriction and growth stimulation. Recent evidence, mainly obtained in animals, suggests that Ang II type 2 (AT(2)) receptors counteract some or all of these effects. This review summarizes the current knowledge on the vasodilator effects induced by AT(2) receptors in humans and animals, focussing not only on the mediators of this effect, but also on the modulatory role of age, gender, and endothelial function. It is concluded that AT(2) receptor-mediated vasodilation most likely depends on the bradykinin-bradykinin type 2 (B(2)) receptor-NO-cGMP pathway, although evidence for a direct link between AT(2) and B(2) receptors is currently lacking. If indeed B(2) receptors are involved, this would imply that, in addition to NO, also the wide range of non-NO 'endothelium-derived hyperpolarizing factors' (EDHFs) that is released following B(2) receptor activation (e.g., K(+), cytochrome P450 products from arachidonic acid, H(2)O(2) and S-nitrososothiols), could contribute to AT(2) receptor-induced vasodilation.

Genetic polymorphisms and heart failure

Heart failure is a complex clinical syndrome. There is evidence for a genetic contribution to the pathophysiology of heart failure. Considering the fundamental role of neurohormonal factors in the pathophysiology and progression of cardiac dysfunction and hypertrophy, variants of genes involved in this system are logical candidate genes in heart failure. In this report, genetic polymorphisms of the major neurohormonal systems in heart failure will be discussed. Studies on polymorphisms of the renin-angiotensin-aldosterone system (RAAS), adrenergic receptor polymorphisms, endothelin (receptor) polymorphisms, and a group of miscellaneous polymorphisms that may be involved in the development or phenotypic expression of heart failure will be reviewed. Research on left ventricular hypertrophy is also included. The majority of genetic association studies focused on the ACE I/D polymorphism. Initial genetic associations have often been difficult to replicate, mainly due to problems in study design and lack of power. Promising results have been obtained with genetic polymorphisms of the RAAS and sympathetic system. Considering the evidence so far, a modifying role for these polymorphisms seems more likely than a role of these variants as susceptibility genes. Besides the need for larger studies to examine the effects of single nucleotide polymorphisms and haplotypes, future studies also need to focus on the complexity of these systems and study gene-gene interactions and gene-environment interactions.

The clinical significance of a common, functional, X-linked angiotensin II type 2-receptor gene polymorphism (-1332 G/A) in a cohort of 509 families with premature coronary artery disease

AIMS

To assess, in families with premature coronary artery disease (CAD), the possible association, with linkage, of the X-linked AT2 receptor (-1332 G/A) gene polymorphism and premature CAD.

METHODS AND RESULTS

We investigated 509 families with a history of premature CAD that consisted of one sibling affected with premature CAD and two unaffected siblings. Genotyping of subjects was performed using a restriction enzyme digestion of an initial 310 bp polymerase chain reaction fragment that included the AT2 (-1332 G/A) locus. The mean age of the 611 individuals affected by premature CAD at the time of event was 49.5 +/- 8.1 years. Conditional logistic regression analysis confirmed a significant predictive value of premature CAD for the covariates of hypertension, diabetes, dyslipidaemia, history of smoking, and male gender. The genetic data were analysed for these families using the X-linked sibling transmission/deletion test (XS-TDT) statistics program. In hemizygous men we observed evidence for association in the presence of linkage, for the AT2 (-1332 G/A) locus and premature CAD (P-exact value = 0.024) and also a trend towards association, in the presence of linkage, for this polymorphism and hypertension (P-exact value = 0.08).

CONCLUSIONS

We have observed evidence of association between the presence of linkage for the X-linked AT2 (-1332 G/A) polymorphism and premature CAD in hemizygous males.

Pharmacogenetics of antihypertensive drug response

Pharmacogenetics is a discipline of molecular medicine that investigates the genetic basis of individual variation of drug responses. Before the era of the human genome project and the subsequent progress in genomic research, this field was primarily restricted to the investigation of the genetics of drug-metabolizing enzymes as they account for individual differences in pharmacokinetics and tolerability of drugs. In the current genomic era, pharmacogenetic research is applied to all fields of drug treatment in clinical medicine, including hypertension research. In contrast to the traditional approach, however, the influence of individual genetic variation on the efficacy of a drug (ie, the pharmacodynamic response) is the major focus of pharmacogenetic research and its clinical applicability. Therefore, the identification of individual genetic variation influencing the blood pressure-lowering effect of an antihypertensive compound and the implementation of this knowledge into clinical practice is the major goal of pharmacogenetic research in the field of hypertension. In this article, some important, recent research work and progress on the pharmacogenetics of antihypertensive drug responses are reviewed and evaluated.

Left ventricular mass in relation to genetic variation in angiotensin II receptors, renin system genes, and sodium excretion

BACKGROUND

In the European Project On Genes in Hypertension (EPOGH), we investigated in 3 populations to what extent left ventricular mass (LVM) was associated with genetic variation in the angiotensin II receptors type 1 (AGTR1 A1166C) and type 2 (AGTR2 G1675A) while accounting for possible gene-gene interactions with the angiotensin-converting enzyme (ACE D/I) and angiotensinogen (AGT -532C/T) polymorphisms.

METHODS AND RESULTS

We randomly recruited 221 nuclear families (384 parents, 431 offspring) in Cracow (Poland), Novosibirsk (Russia), and Mirano (Italy). Echocardiographic LVM was indexed to body surface area, adjusted for covariates, and subjected to multivariate analyses using generalized estimating equations and quantitative transmission disequilibrium tests in a population-based and family-based approach, respectively. For AGTR1 and AGTR2, there was no heterogeneity in the phenotype-genotype relations across populations. LVM index was unrelated to the AGTR1 A1166C polymorphism. In men, in the population- and family-based analyses, the allelic effects of the AGTR2 polymorphism on LVM index differed (P=0.01) according to sodium excretion. In women, this gene-environment interaction did not reach statistical significance. In untreated men, LVM index (4.2 g/m2 per 100 mmol) and left ventricular internal diameter (0.73 mm/100 mmol) increased (P<0.02) with higher sodium excretion in the presence of the G allele with an opposite tendency in A allele carriers. The ACE D/I polymorphism, together with the ACE genotype-by-sodium interaction term, significantly and independently improved the models relating LVM index to the AGTR2 polymorphism and the AGTR2 genotype-by-sodium interaction.

CONCLUSIONS

The present findings support the hypothesis that in men the AGTR2 G1675A and the ACE D/I polymorphisms independently influence LVM and that salt intake modulates these genetic effects.