Haplotype analysis of the prostacyclin synthase gene and essential hypertension

International Union of Basic and Clinical Pharmacology. CIX. Differences and Similarities between Human and Rodent Prostaglandin E2 Receptors (EP1-4) and Prostacyclin Receptor (IP): Specific Roles in Pathophysiologic Conditions

Prostaglandins are derived from arachidonic acid metabolism through cyclooxygenase activities. Among prostaglandins (PGs), prostacyclin (PGI2) and PGE2 are strongly involved in the regulation of homeostasis and main physiologic functions. In addition, the synthesis of these two prostaglandins is significantly increased during inflammation. PGI2 and PGE2 exert their biologic actions by binding to their respective receptors, namely prostacyclin receptor (IP) and prostaglandin E2 receptor (EP) 1-4, which belong to the family of G-protein-coupled receptors. IP and EP1-4 receptors are widely distributed in the body and thus play various physiologic and pathophysiologic roles. In this review, we discuss the recent advances in studies using pharmacological approaches, genetically modified animals, and genome-wide association studies regarding the roles of IP and EP1-4 receptors in the immune, cardiovascular, nervous, gastrointestinal, respiratory, genitourinary, and musculoskeletal systems. In particular, we highlight similarities and differences between human and rodents in terms of the specific roles of IP and EP1-4 receptors and their downstream signaling pathways, functions, and activities for each biologic system. We also highlight the potential novel therapeutic benefit of targeting IP and EP1-4 receptors in several diseases based on the scientific advances, animal models, and human studies. SIGNIFICANCE STATEMENT: In this review, we present an update of the pathophysiologic role of the prostacyclin receptor, prostaglandin E2 receptor (EP) 1, EP2, EP3, and EP4 receptors when activated by the two main prostaglandins, namely prostacyclin and prostaglandin E2, produced during inflammatory conditions in human and rodents. In addition, this comparison of the published results in each tissue and/or pathology should facilitate the choice of the most appropriate model for the future studies.

Altered Expression of Long Noncoding RNAs in Blood After Ischemic Stroke and Proximity to Putative Stroke Risk Loci

BACKGROUND AND PURPOSE

Although peripheral blood mRNA and micro-RNA change after ischemic stroke, any role for long noncoding RNA (lncRNA), which comprise most of the genome and have been implicated in various diseases, is unknown. Thus, we hypothesized that lncRNA expression also changes after stroke.

METHODS

lncRNA expression was assessed in 266 whole-blood RNA samples drawn once per individual from patients with ischemic stroke and matched with vascular risk factor controls. Differential lncRNA expression was assessed by ANCOVA (P<0.005; fold change>|1.2|), principal components analysis, and hierarchical clustering on a derivation set (n=176) and confirmed on a validation set (n=90). Poststroke temporal lncRNA expression changes were assessed using ANCOVA with confounding factor correction (P<0.005; partial correlation with time since event >|0.4|). Because sexual dimorphism exists in stroke, analyses were performed for each sex separately.

RESULTS

A total of 299 lncRNAs were differentially expressed between stroke and control males, whereas 97 lncRNAs were differentially expressed between stroke and control females. Significant changes of lncRNA expression with time after stroke were detected for 49 lncRNAs in men and 31 lncRNAs in women. Some differentially expressed lncRNAs mapped close to genomic locations of previously identified putative stroke-risk genes, including lipoprotein, lipoprotein(a)-like 2, ABO (transferase A, α1-3-N-acetylgalactosaminyltransferase; transferase B, α1-3-galactosyltransferase) blood group, prostaglandin 12 synthase, and α-adducins.

CONCLUSIONS

This study provides evidence of altered and sexually dimorphic lncRNA expression in peripheral blood of patients with stroke compared with that of controls and suggests that lncRNAs have potential for stroke biomarker development. Some regulated lncRNA could regulate some previously identified putative stroke-risk genes.

Haplotype Analysis of the CYP8A1 Gene Associated With Myocardial Infarction

Objective: The aim of this study was to assess the association between the human CYP8A1 gene and myocardial infarction (MI) in Chinese people. Methods: 210 MI patients and 206 age-matched controls were genotyped and constructed haplotypes for 3 SNPs [3982C>T (rs5602), C1117A (rs5629), C251T (rs454-98106)] of the human CYP8A1 gene. Results: The CC genotype of rs5629 was more frequently in MI patients than in control subjects (P = .030). The frequency of the A-C-T haplotype was significantly higher in MI patients than in control subjects (P =.001). The frequency of the C-T-T haplotype was significantly lower in MI patients than in control subjects (P= .011). Conclusions: The present results indicate that MI is associated with the CC genotype of rs5629 in the human CYP8A1 gene. The A-C-T haplotype appears to be a useful genetic marker and the C-T-T haplotype might be a protective factor of MI in Chinese people.

Association of polymorphisms of PTGS2 and CYP8A1 with myocardial infarction

: Cyclooxygenase-2 (COX-2) and prostacyclin synthase (PGIS) are enzymes involved in prostaglandin and prostacyclin synthesis, which have been linked to cardiovascular disease risk. We hypothesized that genetic variations altering the function of these enzymes would modify the risk of myocardial infarction (MI).

: In a Chinese case control study of MI patients (n=356) and healthy controls (n=350), we investigated the roles of polymorphisms in the PGIS gene (

: The CC genotype of

: The CC genotype of

Clin Chem Lab Med 2009;47:347–52.

Association study of aromatase gene (CYP19A1) in essential hypertension

BACKGROUND

As aromatase-deficient mice, which are deficient in estrogens, reportedly have reduced blood pressure, the aromatase gene (CYP19A1) is thought to be a susceptibility gene for essential hypertension (EH). The aim of the present study was to investigate the relationship between CYP19A1 and EH by examining single nucleotide polymorphisms (SNPs).

METHODS

Five SNPs in the human CYP19A1 gene (rs1870049, rs936306, rs700518, rs10046 and rs4646) were selected, and an association study was performed in 218 Japanese EH patients and 225 age-matched normotensive (NT) individuals.

RESULTS

There were significant differences between these groups in the distribution of genotypes rs700518 and rs10046 in male subjects, and genotypes rs700518, rs10046 and rs4646 in female subjects. On multiple logistic regression analysis, a significant association between rs700518 (p=0.023) and rs10046 (p=0.036) in male subjects and rs700518 in female subjects (p=0.018) was noted. Interestingly, the risk genotypes of rs700518 and rs10046 showed a sex-dependent inverse relationship. Both SBP and DBP levels were higher in total (cases and controls) male subjects with the G/G genotype with rs700518 or the T/T genotype with rs10046 than in male subjects without the G/G genotype or T/T genotype. SBP levels were lower in female subjects with the G/G genotype with rs700518 than in female subjects without G/G. The A-T haplotype constructed with rs1870049 and rs10046 was a susceptibility marker for EH.

CONCLUSIONS

We confirmed that rs700518 and rs10046, as well as a haplotype constructed with rs1870049 and rs10046, in the human CYP19A1 gene can be used as genetic markers for gender-specific EH.

A meta-analysis of association between C677T polymorphism in the methylenetetrahydrofolate reductase gene and hypertension

The C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene was implicated to be associated with hypertension due to its role in catalyzing the formation of 5-methylenetetrahydrofolate, a co-substrate for the conversion of homocysteine to methionine. Association studies were reported in different populations; however, a great number of subsequent studies have produced contrary results, possibly reflecting inadequate statistical power. With the cumulative data in recent years in both Caucasian and Asian populations, it was necessary to carry out a comprehensive analysis of previous findings. In this meta-analysis, we combined 26 English and Chinese studies in Caucasian and Asian populations published up to November 2006 to give a new picture of the role of the C677T polymorphism in the MTHFR gene. Evidence of significant association was detected between C677T polymorphism and hypertension in both populations. Additionally, the significant association between C677T polymorphism and hypertension/hypertension-in-pregnancy suggested that this polymorphism was one independent risk factor of hypertension.

Association study using single nucleotide polymorphisms in the estrogen receptor beta (ESR2) gene for preeclampsia

The pathophysiology of preeclampsia (PE) remains uncertain despite many research efforts. Actual hypotheses seek to explain the vascular damage that characterizes the disease. Recently, it was reported that the mouse disrupted estrogen receptor beta (ESR2) gene was associated with abnormal vascular function and hypertension. Moreover, some investigators have reported that subjects with a family history of hypertension have a statistically significant increased risk for PE. Thus, it is thought that the pathophysiology of PE overlaps that for hypertension. The aim of the present study was to investigate the relationships between single nucleotide polymorphisms (SNPs) in the human ESR2 gene and PE in Japanese subjects, and to assess the involvement of a family history of hypertension in these relationships. Based on a database search on the web site of the National Center of Biotechnology Information (NCBI), we chose four SNPs in the human ESR2 gene, and performed an association study in 84 PE patients and 160 age-matched non-PE subjects. The overall distribution in each SNP did not differ significantly between the two groups. However, after dividing the groups into subjects with and without a family history of hypertension, the allelic distribution of one of the SNPs (rs928554) revealed a positive association. Thus, a possible mutation linked to a SNP may prescribe a genetic predisposition for patients with a family history of hypertension in PE.

Haplotype-Based Case-Control Study Revealing an Association between the Adrenomedullin Gene and Proteinuria in Subjects with Essential Hypertension

Adrenomedullin (AM) has various physiological actions on the cardiovascular system, including vasodilatation, diuresis, natriuresis, inhibition of aldosterone secretion, and increases of the cardiac output, all of which cause hypotension. Since AM plays a role in the pathophysiology of vascular diseases, genes controlling AM might be involved in the development and etiology of essential hypertension (EH). However, there have been few studies examining the relationship between the AM gene and hypertension. The aims of this study were to genotype some of the genetic markers for the human AM gene in Japanese subjects, and via a haplotype-based case-control study, assess the association between and the AM gene and EH or its risk factors, such as hyperlipidemia, renal damage, and proteinuria. We genotyped 205 EH patients and 210 age-matched normotensive (NT) individuals for two single nucleotide polymorphisms of rs4399321, rs7944706 and a microsatellite polymorphism located approximately 5,400 base pairs downstream of the 3' end of the human AM gene. The overall distribution in each variant and haplotype did not significantly differ between the two groups. However, after dividing the groups into those subjects with and without proteinuria, the haplotype analysis revealed a positive association. In conclusion, a possible mutation linked to the haplotype may indicate a genetic predisposition for proteinuria in EH.

The microsatellite alleles on chromosome 1 associated with essential hypertension and blood pressure levels

Essential hypertension (EH) is thought to be a polygenic disease. Several candidate genes of this disease have been investigated in studies using polymorphic genetic markers, but some studies have failed to show any association of EH with these genes. In this experiment, we used microsatellite markers on chromosome 1, and performed an association study between EH and control subjects. Genomic DNA was amplified with fluorescently labelled primers from the Applied Biosystems PRISM linkage mapping set HD-5 comprising 63 highly polymorphic microsatellite markers with an average spacing of 4.5 cM. We isolated three loci showing significant differences: D1S507, D1S2713 and D1S2842. The P-values of the allele with the greatest post hoc contributions in D1S507, D1S2713 and D1S2842 were 0.0008, 0.0062 and 0.0084, respectively. All these values were significant after Bonferroni correction. Furthermore, we found that the three microsatellite alleles were associated with the levels of systolic blood pressure. These data suggest that there are at least the three susceptibility loci for EH on chromosome 1, and that a case-control study using microsatellite markers on genomewide basis is a useful method for isolating the susceptibility loci of multifactorial disorders.

The Methylentetrahydrofolate Reductase Gene Variant (C677T) as a Risk Factor for Essential Hypertension in Caucasians

Essential hypertension (EH) is a common, multifactorial disorder likely to be influenced by multiple genes of modest effect. The methylenetetrahydrofolate reductase (MTHFR) gene C677T mutation is functionally important, being strongly associated with reduced enzyme activity and increased plasma levels of homocysteine. Mild hyperhomocysteinemia is a known risk factor for cardiovascular disease (CVD) and hypothesised also to be involved in hypertension pathophysiology. The present study was performed to determine the prevalence of the 677T mutation in Australian Caucasian patients diagnosed with EH and to test whether the C677T variant is associated with the disorder. A case-control cohort, consisting of 250 EH patients and 250 age, sex and racially matched normotensive controls, were used for the association study. Comparison of C677T allele frequencies revealed a higher proportion of the mutant allele (T) in the EH group (40%) compared to unaffected controls (34%) (p=0.07). Furthermore, genotypic results indicated that the prevalence of the homozygous mutant genotype (T/T) in the affected group was higher than that of controls (14%:10%) (p=0.17). Interestingly, conditional logistic regression showed that the MTHFR C677T mutation conferred a mild, yet significant increase in risk of essential hypertension after adjusting for body mass index (odds ratio=1.57, 95% confidence interval: 1.04-2.37, p=0.03). These findings require further investigation in large independent samples, but suggest that essential hypertension, like CVD, may be mildly influenced by the MTHFR C677T variant.