Functional and genetic studies of the angiotensin II type 1 receptor in pre-eclamptic and normotensive pregnant women

Cytokine-polymorphisms associated with Preeclampsia: A review

BACKGROUND

Preeclampsia (PE) is a syndromic disorder that affects 2% to 8% of pregnancies and is diagnosed principally when hypertension appears in the second-d half of pregnancy. WHO estimates the incidence of PE to be seven times higher in developing countries than in developed countries. Severe preeclampsia/eclampsia is one of the most important causes of maternal mortality, associated with 50,000 to 100,000 annual deaths globally as well as serious fetal and neonatal morbidity and mortality, especially in developing countries. Even though evidence from family-based studies suggest PE has a heritable component, its etiology, and specific genetic contributions remain unclear. Many studies examining the genetic factors contributing to PE have been conducted, most of them are focused on single nucleotide polymorphisms (SNPs). Given that PE has a very important inflammatory component, is mandatory to examine cytokine-SNPs for elucidating all mechanisms involved in this pathology. In this review, we describe the most important cytokine-polymorphisms associated with the onset and development of PE. We aim to provide current and relevant evidence in this regard.

METHODS

We searched English databases such as PubMed and the National Center for Biotechnology Information. The publication time of the papers was set from the establishment of the databases to February 2022. All studies about Th1/Th2/Th17 cytokines polymorphisms were included in our study.

RESULTS

SNPs in IFN-γ, TNF-α, IL-4, IL-6, IL-10, IL-17A, and IL-22 are associated with the development, early-onset and severity of PE, being the Th1/Th2/Th17 responses affected by the presence of these SNPs.

CONCLUSIONS

The changes in Th1/Th2/Th17 response modify processes such as placentation, control of inflammation, and vascular function. Nonetheless, association studies have shown different results depending on sample size, diagnostic, and population.

Responses of the renin-angiotensin-aldosterone system in pregnant chronic kidney disease patients with and without superimposed pre-eclampsia

Background

Women with chronic kidney disease (CKD) are at increased risk of superimposed pre-eclampsia (SPE). Accurate identification of SPE is challenging. We hypothesized that specific components of the renin-angiotensin-aldosterone system (RAAS) would discriminate between CKD and SPE. The aim of the study was to establish differences in circulating and intrarenal RAAS in women with CKD with and without SPE and compare these to normotensive controls (NCs) and women with pre-eclampsia (PE).

Methods

White European NC women (n = 20), women with PE (n = 9), normotensive CKD without SPE (n = 8) and with SPE (n = 11) were recruited in the third trimester. Plasma renin, plasma and urine total angiotensinogen (AGT) concentrations were quantified by enzyme-linked immunosorbent assay, urinary tetrahydroaldosterone (TH-aldo) concentration by gas chromatography-mass spectrometry and placental growth factor (PlGF) by immunoassay.

Results

Urinary TH-aldo:creatinine ratios were lower in women with PE or SPE compared with NC or women with CKD (P < 0.05 for all). The same group differences were observed for plasma active renin and PlGF concentrations (P < 0.05 for all). Urine total AGT was higher in women with PE compared with NC (P < 0.05) and urine TH-aldo:urine AGT was lower (P < 0.05). However, women with SPE had lower urinary AGT concentrations compared with women with PE (P < 0.05). No differences in plasma total AGT were observed between groups.

Conclusions

Women with SPE have a lower urinary TH-aldo:creatinine ratio, lower plasma active renin and lower PlGF concentrations than women with CKD, comparable to women with PE without pre-existing disease, suggestive of similar pathophysiology. These data suggest disruption of the RAAS pathway in SPE similar to PE. Exploration of the predictive value of RAAS components for adverse pregnancy events in women with CKD is required.

The Gene Variants of Maternal/Fetal Renin-Angiotensin System in Preeclampsia: A Hybrid Case-Parent/Mother-Control Study

Preeclampsia (PE) is a common pregnancy-related complication, and polymorphisms in angiotensinogen (AGT), angiotensin-converting enzyme (ACE), and angiotensin II type 1 receptor (AT1R) are believed to contribute to PE development. We implemented a hybrid study to investigate the influence of maternal and fetal ACE I/D, ACE G2350A, AGT M235T, AGT T174M, and AT1R A1166C polymorphisms on PE in Han Chinese women. Polymorphisms were genotyped in 1,488 subjects (256 patients experiencing PE, along with their fetuses and partners, and 360 normotensive controls with their fetuses). Transmission disequilibrium tests revealed that ACE I/D (P = 0.041), ACE G2350A (P = 0.035), and AT1R A1166C (P = 0.018) were associated with maternal PE. The log-linear analyses revealed that mothers whose offspring carried the MM genotype of AGT M235T had a higher risk of PE (OR = 1.54, P = 0.010), whereas mothers whose offspring carried the II genotype of ACE I/D or the GG genotype of ACE G2350A had a reduced risk (OR = 0.58, P = 0.039; OR = 0.47, P = 0.045, respectively). Our findings demonstrate that fetal ACE I/D, ACE G2350A, AGT M235T, and AT1R A1166C polymorphisms may play significant roles in PE development among pregnant Han Chinese women.

The effects of gene polymorphisms in angiotensin II receptors on pregnancy-induced hypertension and preeclampsia: a systematic review and meta-analysis

BACKGROUND

To assess whether the polymorphisms of angiotensin II type 1 and type 2 receptors (AT1R, AT2R) are associated with pregnancy-induced hypertension (PIH) and preeclampsia.

METHODS

Studies were searched from PubMed, ISI Web of Science and HuGE Navigator.

RESULTS

The A1166C polymorphism of AT1R, A1675G and C3123A polymorphisms of AT2R were analyzed. Significant association was found in recessive model (OR = 1.581, 95% confidence interval (CI): 1.054-2.371) and co-dominant (GG versus AG) model (OR = 1.900, 95%CI: 1.001-3.604) between the A1675G polymorphism and preeclampsia. No association was found between the other polymorphisms and PIH or preeclampsia.

CONCLUSIONS

The A1675G polymorphism might be associated with preeclampsia, but the A1166C and C3123A polymorphisms had no effect on PIH or preeclampsia.

The placental renin-angiotensin system and oxidative stress in pre-eclampsia

There is an inverse correlation between human birthweight and umbilical venous angiotensin II (AngII) concentrations. Oxidative stress and increased pro-renin receptor (PRR) both enhance the cleavage of angiotensin I from angiotensinogen (AGT). Pre-eclampsia, a hypertensive disorder of pregnancy, manifests as high blood pressure and proteinuria, and is a state of increased oxidative stress.

OBJECTIVES, STUDY DESIGN AND MAIN OUTCOME MEASURES

HYPOTHESIS

Pre-eclampsia will be associated with increased placental expression of components of the renin-angiotensin system, which could result in reduced infant birthweight. Biopsies were taken 1 cm from the placental edge from 27 normotensive controls and 23 pre-eclamptic White European women. Immunohistochemistry was performed for AGT, PRR, glutathione peroxidase 3 (GPx3) and the AT1R and AT2R AngII receptors. Protein expression was semi-quantitatively assessed (H-score).

RESULTS

AT1R expression was significantly increased in pre-eclamptic placentae, and negatively correlated with birthweight (r = -0.529, P = 0.009). AT1R expression was also negatively correlated with GPx3 expression overall (r = -0.647; P = 0.005). AT2R expression positively correlated with AGT (r = 0.615, P = 0.002) in the pre-eclamptic placentae only.

CONCLUSIONS

The raised AT1R expression in pre-eclampsia, together with inadequate antioxidant protection, possibly through lower GPx activity, might enhance the vasoconstrictor effect of locally-generated AngII, contributing to the restricted fetal growth characteristic of pre-eclampsia. Conversely, the AT2R:AGT association within the pre-eclamptic placenta may provide a compensatory mechanism.

Association of maternal AGTR1 polymorphisms and preeclampsia: a systematic review and meta-analysis

OBJECTIVE

Systematic review and meta-analysis to investigate the association between maternal AGTR1 gene single nucleotide polymorphisms (SNPs) and preeclampsia (PE).

METHODS

A systematic literature search was performed using PubMed, EMBASE, Scopus, and HuGE Literature Finder databases. The review was conducted according to PRISMA guidelines. Summary odds ratios (ORs) for the allelic and genotypic contrasts were calculated and compared to indicate the most appropriate genetic model for the polymorphism of interest. Among-study heterogeneity was assessed using the I(2) statistic and publication bias was evaluated visually using funnel plots.

RESULTS

Seven maternal SNPs investigated with PE were found, but only AGTR1 +1166A>C accumulated sufficient evidence for meta-analysis. Summary ORs calculated from eight studies (10 populations involving 845 PE cases and 1150 controls) did not reveal an association between the +1166A>C polymorphism and PE (allelic OR = 1.19, 95% CI: 0.96-1.47). No evidence of publication bias and among-study heterogeneity was detected.

CONCLUSIONS

meta-analysis findings did not support AGTR1 +1166A>C as a susceptibility locus for PE. Other AGTR1 SNPs require more study.

Identification of α1-antitrypsin as a positive acute phase protein in ayu (Plecoglossus altivelis) associated with Listonella anguillarum infection

α1-Antitrypsin (AAT) is implicated in the regulation of a variety of mammalian immune responses and was recently identified as a major serpin in blood plasma of some fish. However, AAT expression following bacterial infection in fish has not been well described. In this study, we cloned the full-length ayu (Plecoglossus altivelis) AAT gene cDNA. It contained a 1368-bp coding region, which encodes a 19-amino acids (aa) signal peptide and a 437-aa mature AAT containing the serpin's signature sequence ((427)LKFDRPFMMLV(437)). PNGase F digestion confirmed that the higher molecular mass of the serum AAT was caused by N-glycosylation. Phylogenetic analysis indicated that ayu AAT was closest to that of green spotted pufferfish. AAT transcripts were present in a variety of tissues, with the highest level in the liver. The real-time quantitative PCR data showed that AAT transcripts dramatically increased in various ayu tissues after Listonella anguillarum infection. Western blot analysis revealed that the serum AAT protein level significantly increased in response to inflammation, but displayed no significant changes after cadmium exposure or salinity challenge. This work represents the first report that identifies AAT as a positive acute-phase protein in ayu fish associated with bacterial infection, suggesting that it might play a role in fish innate immunity.

Association Study Between the Human Renin Gene and Preeclampsia

OBJECTIVE

We recently reported on a missense mutation in exon 9 of the human renin gene (G1051A) that may affect the functioning of this enzyme, and is associated with essential hypertension. The aim of the present study is to assess the association between the genotypes of this missense mutation in the renin gene and preeclampsia (PE) via a case-control study.

METHODS

DNA was extracted from peripheral blood leukocytes, and genotyping of G1051A was performed in 117 PE patients and in 171 non-PE controls.

RESULTS

The frequency of genotypes for G1051A was not significantly different between the two groups. The frequency of the A1051 allele was also not significantly different between PE patients (52.6%) and non-PE controls (50.6%).

CONCLUSIONS

The missense mutation G1051A in the human renin gene is not associated with PE.

Comparison between essential hypertension and pregnancy-induced hypertension: a genetic perspective

Essential hypertension (EH) accounts for 80-90% of hypertension, and pregnancy-induced hypertension (PIH) is responsible for hypertension during pregnancy. Both considered multifactorial disorders. While both have many features in common, conditions and causes of these diseases have yet to be clarified. Since both diseases are associated with hypertension, the genetic backgrounds may contain common features. The present study reviewed similarities and differences between women with EH and PIH, with a particular focus on their genetic backgrounds.

Genes and the preeclampsia syndrome

Preeclampsia is specific to pregnancy and is still a leading cause of maternal and perinatal mortality and morbidity, affecting about 3% of women, but the underlying pathogenetic mechanisms still remain unclear. Immune maladaptation, placental ischemia and increased oxidative stress represent the main components discussed to be of etiologic importance, and they all may have genetic implications. Since the familial nature of preeclampsia is known for many years, extensive research on the genetic contribution to the pathogenesis of this severe pregnancy disorder has been performed. In this review, we will overview the linkage and candidate gene studies carried out so far as well as summarize important historical notes on the genetic hypotheses generated in preeclampsia research. Moreover, the influence of maternal and fetal genes and their interaction as well as the role of genomic imprinting in preeclampsia will be discussed.

α1-Antitrypsin regulates CD14 expression and soluble CD14 levels in human monocytes in vitro

The recognition of bacterial lipopolysaccharide (LPS) is principally mediated by either membrane-bound or soluble form of the glycoprotein CD14 and CD14-associated signal transducer, toll-like receptor 4 (TLR4). Recent findings indicate that the serine protease inhibitor, alpha1-antitrypsin (AAT), may not only afford protection against proteolytic injury, but may also neutralize microbial activities and affect regulation of innate immunity. We postulated that AAT affects monocyte responses to LPS by regulating CD14 expression and soluble CD14 release. Here we show that a short-term (up to 2h) monocyte exposure to AAT alone or in combination with LPS leads to a remarkable induction of CD14 levels. In parallel, a short-term (2h) cell exposure to AAT/LPS significantly enhances LPS-induced NF kappaB (p50 and p65) activation in conjunction with increased TNFalpha, IL-1 beta and IL-8 release. In contrast, longer term incubation (18 h) of monocytes with combined AAT/LPS results in a significant reduction in expression of both CD14 and TLR4, inhibition of LPS-induced TNFalpha, IL-1 beta and IL-8 mRNA and protein expression. These findings provide evidence that AAT is an important regulator of CD14 expression and release in monocytes and suggest that AAT may be involved in LPS neutralization and prevention of over-activation of monocytes in vivo.

[Mutation screening in Angiotensin II receptors, AGTR1 and AGTR2, and evaluation of AGTR1 polymorphisms C573T and A1166C in patients with premature adrenarche]

Precocious pubarche is the appearance of pubic hair before the age of 8 years in girls and 9 years in boys. The most frequent etiology is idiopathic precocious adrenarche, suggested, after long-term follow-up, to be associated with metabolic syndrome. One of the factors involved in the genesis of precocious adrenarche is Angiotensin II (Ang II), which promotes cell proliferation and steroidogenesis through type 1 (AT1) and type 2 (AT2) receptors. In order to study Ang II receptors mutations, 50 children with idiopathic precocious adrenarche were evaluated and compared to a control group of normal individuals. Mutations were not detected in the AGTR1 and AGTR2 genes; however, two polymorphisms were identified in the AGTR1 gene: the C573T (exon 5) and the A1166C (3' untranslated region). The polymorphic allele T573 was found in 35% of the patients and 38% of controls. The polymorphic allele C1166 was present in 24% of the patients and 26% of controls. There was no statistical difference between groups. There was also no correlation between the polymorphisms and clinical and laboratory findings, as well as their family history of metabolic syndrome.

Genetic polymorphisms in vasoactive genes and preeclampsia: a meta-analysis

There are controversies in reports on the association of polymorphisms in endothelial nitric oxide synthase, angiotensinogen, angiotensin receptor type 1 and angiotensin-converting enzyme genes with an increased risk of developing preeclampsia. We performed a systematic search of published case-control studies through the PubMed database up to January 2006, and report the results of a meta-analysis of polymorphisms investigated in more than five studies: Glu298Asp in eNOS gene (9 analyses involving 1055 patients and 1788 controls), Met235Thr in AGT gene (13 analyses involving 1128 patients and 2278 controls), and intron 16 insertion-deletion polymorphism in ACE gene (10 analyses involving 1121 patients and 1361 controls). Statistically significant associations with preeclampsia were identified for the Met235Thr/AGT polymorphism: OR 1.65 (95% CI 1.19, 2.29) if the polymorphism is considered under the dominant genetic model, and OR 1.54 (95% CI 1.12, 2.11) under the recessive model. For insertion-deletion/ACE polymorphism, statistical significance was demonstrated when the polymorphism was considered under the recessive model: OR 1.51 (95% CI 1.17, 1.94). No single polymorphism was identified as having a major effect.

A1166C angiotensin II type 1 receptor gene polymorphism may predict hemodynamic response to losartan in patients with cirrhosis and portal hypertension

OBJECTIVE

Losartan, a dose of 25 mg/day, has been found to be effective in 50% of patients with portal hypertension without adverse effects. We evaluated the relationship between genetic polymorphisms of the renin-angiotensin system (A1166C angiotensin II type 1 receptor (AT1R), angiotensinogen T174M and M235T, and angiotensin-converting enzyme I/D) and the effects of losartan on portal and systemic hemodynamic in patients with cirrhosis and portal hypertension.

METHODS

We performed a longitudinal study that included 23 consecutive patients with cirrhosis and esophageal varices who received 25 mg/day of losartan during 12 wk. Hepatic venous pressure gradient (HVPG) and systemic hemodynamic were measured at baseline and after treatment. Genomic DNA was extracted from peripheral blood leukocytes; genetic polymorphisms of the renin-angiotensin system were investigated by polymerase chain reaction and restriction fragment length polymorphisms.

RESULTS

The homozygous patients for AT1R A allele showed higher pulmonary-wedged and free hepatic venous pressure on baseline. After treatment, they showed a higher decrease of HVPG (32.5%+/- 19.2) in comparison with patients with AC/CC genotype (2.4%+/-18.9), p < 0.01. Ten of 15 patients with AA genotype were responders, while only one of eight with AC/CC genotype (p < 0.002); genotype AA showed a positive predictive value of 66.6% and negative predictive value of 87.5%.

CONCLUSIONS

These results suggest that there is a relationship between the AT1R A1166C polymorphisms and the therapeutic response to losartan. The genetic testing may be used as a predictive factor of this response.

Haplotypes of the angiotensin II receptor genes AGTR1 and AGTR2 in women with normotensive pregnancy and women with preeclampsia

Angiotensin II (AII) acts as a growth factor in local systems, mediating diverse effects such as cellular proliferation and apoptosis. These effects are controlled through two main receptor subtypes: AGTR1 and AGTR2. We studied the haplotype frequencies of both receptor genes in women with preeclamptic pregnancies and normotensive pregnant women. We also looked for any association between AGTR1 genotype at sites in the 5' flanking region and binding of AII to platelets, which express AGTR1, in 58 normotensive pregnant women. There were nine common haplotypes of AGTR1, with no significant difference in haplotype frequency between the two groups of women. Platelet AII binding in normotensive pregnant women was associated with the genotype at g.5245C>T in the 5' flanking region of AGTR1 (GenBank AF245699.1), with CC homozygotes at g.5245 having the lowest levels, and g.5245 TT homozygotes having the highest levels (P=0.05). Two novel polymorphisms were identified in AGTR2 (GenBank AY324607.1) at nucleotides g.1701T>C and g.2184A>T. Variation of AGTR2 could be explained by the existence of four common haplotypes. There was evidence for a significant increase in the frequency of the haplotype TAATGC at nucleotides g.1701, g.2041, g.2184, g.4673, g.4679, and g.4975, respectively (P=0.004), in women with preeclampsia.

Hypertension-related gene polymorphisms in pre-eclampsia, eclampsia and gestational hypertension in Black South African women

OBJECTIVE

To examine whether polymorphisms in the renin-angiotensin system (RAS) are associated with pregnancy-related hypertensive disorders in a black South African population.

DESIGN

The angiotensin-converting enzyme (ACE) insertion/deletion, angiotensinogen M235T and angiotensin II receptor type 1 1166A<--C polymorphisms were assessed in study groups comprising 204 women with pre-eclampsia, 120 with eclampsia, 67 with early onset pre-eclampsia and 78 with gestational hypertension.

METHODS

Using chi analysis, results were compared with those obtained from 338 ethnically matched normotensive pregnant women following normal full term pregnancies. No significant differences in the distribution of any of these polymorphisms were found between patients with pre-eclampsia or eclampsia and the normal control subjects. Patients with gestational hypertension were less frequently homozygous for the ACE insertion polymorphism compared with controls (5 versus 13%, respectively; P = 0.049; odds ratio 0.36 [95% confidence interval (CI) 0.09-1.04]).

CONCLUSION

The commonly occurring RAS polymorphisms are not predictive of pre-eclampsia or eclampsia in the Black South African population.

Genetics of preeclampsia: what are the challenges?

Despite recent efforts to identify susceptibility genes of preeclampsia, the genetic determinants of the condition remain ill-defined, as is the situation for most disorders of complex inheritance patterns. The angiotensinogen, factor V, and methylenetetrahydrofolate reductase genes have been investigated in different populations, as have other genes involved in blood pressure, vascular volume control, thrombophilia, lipid metabolism, oxidative stress, and endothelial dysfunction. The study of the genetics of complex traits is faced with both methodological and genetic issues; these include adequate sample size to allow for the identification of modest genetic effects, of gene-gene and gene-environment interactions, the study of adequate quantitative traits and extreme phenotypes, haplotype analyses, statistical genetics, genome-wide (hypothesis-free) versus candidate-gene (hypothesis-driven) approaches, and the validation of positive associations. The use of genetically well-characterized populations showing a founder effect, such as the French-Canadian population of Quebec, in genetic association studies, may help to unravel the susceptibility genes of disorders showing complex inheritance, such as preeclampsia. It is necessary to better evaluate the role of the fetal genome in the resulting predisposition to preeclampsia and its complications. Eventually, we may be able to integrate genetic information to better identify the women at risk of developing preeclampsia, and to improve the management of those suffering from this condition.

Renin-angiotensin-aldosterone system loci and multilocus interactions in young-onset essential hypertension

OBJECTIVE

Renin-angiotensin-aldosterone system component genes have been associated to essential hypertension. Thus, we studied the association of singe locus or multilocus interactions with young-onset essential hypertension.

SETTING AND DESIGN

This is a case-control study based on a population sample of adolescent at an inner city.

PARTICIPANTS

We studied 54 adolescents with hypertension and 121 age-matched normotensives, recruited from a high-school student population of 934 interviewed individuals.

METHODS

Resting blood pressure was measured on three different days and normalized (Z-score) by sex and age. Genotypes of ACE (I/D) angiotensinogen (T174M and M235T), ATIR (A1166C), and CYP11B2 (C-344T) were determined by PCR/RFLP or ASO.

RESULTS

Although genotype frequencies were not different in both groups, we found a significant dominant effect of ACE D and angiotensinogen 235T alleles on normalized systolic arterial blood pressure in males. This effect was confirmed by sib-pair linkage analysis taking normalized blood pressure as a quantitative trait. We independently analyzed multilocus interactions in normotensive and hypertensive adolescents searching for multiple locus deviation from Hardy-Weinberg or linkage equilibrium. We found that from 63 multilocus combinations, 4 deviated significantly from equilibrium in hypertensive adolescents but none in the normotensives. Deviations from equilibrium may indicate that the combination of alleles at different loci affects susceptibility or resistance to the disease.

CONCLUSION

In addition to the angiotensin-converting enzyme (ACE) and angiotensinogen (AGT) gene variants, gene-gene interactions may be important causative factors in a complex disease such as young-onset essential hypertension.

Production of 8-epi prostaglandin F(2alpha) in human platelets during administration of organic nitrates

OBJECTIVES

The objective of this study was, using isolated platelets as a surrogate for vascular cells, to examine the effect of nonintermittent organic nitrate administration on 8-epi prostaglandin F(2alpha) (8-epi PGF(2alpha)) content and the effect of concurrent oral ascorbate administration.

BACKGROUND

The long-term efficacy of organic nitrates is hampered by hemodynamic tolerance, which develops during continuous administration. This has been associated with altered production of superoxide and nitric oxide, as well as oxidative stress. This effect may be ameliorated by the co-administration of antioxidants.

METHODS

Ten healthy male subjects received nitroglycerin (NTG) transdermally at a dosage of 0.4 mg/h for 3 days with ascorbate or lactose (1.2 g/day). After two weeks washout, the treatment was repeated with reversed ascorbate/lactose. Platelets were prepared by centrifugation and esterified 8-epi PGF(2alpha) measured at the start and finish of each treatment by immunoassay.

RESULTS

Nitroglycerin, in the absence of supplemental ascorbate, was associated with a significant increase in platelet-esterified 8-epi PGF(2alpha), from 32.9 (95% confidence interval [CI] 11.8 to 54.0) to 51.0 (95% CI 16.3 to 85.7) pg/mg protein (p < 0.05). Co-administration of ascorbate with NTG resulted in a significant decrease in 8-epi PGF(2alpha) production, from 38.8 (95% CI 24.9 to 52.7) to 19.0 (95% CI 13.5 to 24.5) pg/mg protein (p < 0.05).

CONCLUSIONS

Continuous NTG administration results in an increase in platelet-esterified 8-epi PGF(2alpha), a free radical and cyclooxygenase-dependent compound. This is reversed by co-administration of the free radical scavenger ascorbate. Whether this increase is merely a marker for increased oxidative stress or a mediator of oxidative injury contributing to the hemodynamic changes observed in nonintermittent organic nitrate treatment has yet to be resolved.

Angiotensin II type 1 receptor A1166C gene polymorphism is associated with an increased response to angiotensin II in human arteries

An adenine/cytosine (A/C) base substitution at position 1166 in the angiotensin II type 1 receptor (AT(1)R) gene is associated with the incidence of essential hypertension and increased coronary artery vasoconstriction. However, it is still unknown whether this polymorphism is associated with a difference in angiotensin II responsiveness. Therefore, we assessed whether the AT(1)R polymorphism is associated with different responses to angiotensin II in isolated human arteries. Furthermore, we evaluated whether inhibition of the renin-angiotensin system modifies the effect of the AT(1)R polymorphism. One hundred twelve patients who were undergoing coronary artery bypass graft surgery were prospectively randomized to receive an ACE inhibitor or a placebo for 1 week before surgery. Excess segments of the internal mammary artery were exposed to angiotensin II (0.1 nmol/L to 1 micromol/L) and KCl (60 mmol/L) in organ bath experiments. Patients homozygous for the C allele (n=17) had significantly greater angiotensin II responses (percentage of this maximal KCl-induced response) than did patients genotyped with AA+AC (n=95, P<0.05). Although ACE inhibition increased the response to angiotensin II, the difference in the response to angiotensin II, between CC and AA+AC patients remained intact in ACE inhibitor-treated patients. These results indicate increased responses to angiotensin II in patients with the CC genotype. The mechanism is preserved during ACE inhibition, which in itself also increased the response to angiotensin II. This reveals that the A1166C polymorphism may be in linkage disequilibrium with a functional mutation that alters angiotensin II responsiveness, which may explain the described relation between this polymorphism and cardiovascular abnormalities.

Hypertension in pregnancy: new recommendations for management

Hypertension in pregnancy is a frequent complication that has substantial adverse perinatal outcomes. Hypertension may be preexisting (chronic) essential or secondary hypertension; a second entity is pregnancy induced (gestational hypertension, preeclampsia). Recent advances have identified newer markers for pregnancy hypertension: several potential candidate genes may explain the apparent family inheritance of preeclampsia, and some thrombophilic markers have been associated with the condition. Management options for mild to moderate hypertension include a short hospital stay to exclude ongoing severe hypertension and to ascertain fetal well-being. Outpatient care with appropriate maternal and fetal surveillance, including umbilical artery doppler velocimetry, is recommended for better perinatal outcomes. Acute care for severe hypertension includes the use of magnesium sulfate to prevent eclampsia and antihypertensive medication. Expeditious delivery is recommended when the maternal or fetal states cannot be stabilized. Follow-up after delivery allows the uncovering of any other coexisting hypertensive or cardiovascular disorder.

New polymorphisms of the angiotensin II type 1 receptor gene and their associations with myocardial infarction and blood pressure: the ECTIM study. Etude Cas-Témoin de l'Infarctus du Myocarde

OBJECTIVE

In an earlier report, we suggested that a polymorphism located in the 3' untranslated region of the angiotensin II type 1 receptor gene (AT1R+1166 A/C) might interact with the angiotensin I converting enzyme (ACE) insertion/deletion (I/D) polymorphism to increase the risk of myocardial infarction. Since the AT1R+1166 A/C polymorphism does not appear to be functional, we postulated that it might be in linkage disequilibrium with an unidentified functional variant which would affect the regulation of the gene in response to angiotensin II. The present study was conducted to identify new polymorphisms of the AT1R gene that might be responsible for this interaction.

METHODS

The first four exons, which are untranslated, and 2.2 kb in the 5' flanking region of the AT1R gene were explored by polymerase chain reaction/single-strand conformation polymorphism. Seven polymorphisms were detected in the 5' region at positions -1424, -810, -713, -521, -214, -213 and -153 upstream from the start of transcription. The genotypes of the -810, -713, -214, -213 and -153 polymorphisms were completely concordant. One substitution was detected at the 55th nucleotide of exon 4. These polymorphisms, together with the +1166 A/C polymorphism and a previously described T/C substitution at the 573th nucleotide of exon 5, were genotyped in the Etude Cas-Témoin de l'Infarctus du Myocarde (ECTIM) study, a multicentre study comparing 651 patients who had survived a myocardial infarction and 728 controls from Belfast (United Kingdom) and Lille, Strasbourg and Toulouse (France).

RESULTS

The newly identified polymorphisms were not in linkage disequilibrium with the +1166 A/C polymorphism and therefore could not explain the interaction observed with ACE I/D. None of the polymorphisms was associated with blood pressure levels in control subjects. In the four populations, the A allele of the -810 polymorphism was associated with a lower risk of myocardial infarction (population-adjusted odds ratio of 0.80, confidence interval 0.65-0.97, P< 0.05).

CONCLUSIONS

None of the newly identified polymorphisms could account for the previously described interaction between the AT1R+1166 A/C and the ACE I/D polymorphisms affecting the risk of myocardial infarction. However, the present study suggests that AT1R-810 T/A, or other polymorphisms which are in complete association with it, might be associated with the risk of myocardial infarction. Further studies are required to confirm this finding and to identify the functional variants.

Distortion of maternal-fetal angiotensin II type 1 receptor allele transmission in pre-eclampsia

OBJECTIVE

To investigate the fetal angiotensin II type 1 receptor genotype in pre-eclampsia.

DESIGN

Case-control study.

POPULATION

Forty-one maternal-fetal pairs from pre-eclamptic pregnancies and 80 maternal-fetal pairs from normotensive pregnancies.

METHODS

Maternal and fetal DNA was genotyped at three diallelic polymorphisms, at nucleotides 573, 1062, and 1166, in the coding exon of the angiotensin II type 1 receptor gene, and at a dinucleotide repeat polymorphism in its 3' flanking region.

RESULTS

Allele and genotype frequencies at the four polymorphic regions investigated did not differ between pre-eclamptic and normotensive groups, in either fetal or maternal samples. Mothers heterozygous for the dinucleotide repeat allele designated A4 transmitted this allele to the fetus in 15 of 18 informative pre-eclamptic pregnancies and in eight of 26 normotensive pregnancies. This was greater than the expected probability in pre-eclamptic pregnancies (p=0.04) and less than expected in normotensive pregnancies (p<0.005). The 573T variant, which is in partial linkage disequilibrium with the A4 allele, showed a similar distortion of maternal-fetal transmission.

CONCLUSION

Angiotensin II type 1 receptor gene expression in the fetus may contribute to the aetiology of pre-eclampsia. It is unclear whether susceptibility is conferred by the fetal genotype acting alone, or by allele sharing by mother and fetus. Possible mechanisms for the effect of the angiotensin II type 1 receptor gene are suggested by the association of the 573T variant with low levels of surface receptor expression on platelets. If receptor expression is similarly genetically determined in the placenta, responsiveness to angiotensin II may be affected, with the potential to influence placentation or placental prostaglandin secretion.