Association study between a novel single nucleotide polymorphism of the promoter region of the prostacyclin synthase gene and essential hypertension

Genetic and Epigenetic Mechanisms Regulating Blood Pressure and Kidney Dysfunction

The pioneering work of Dr Lewis K. Dahl established a relationship between kidney, salt, and high blood pressure (BP), which led to the major genetic-based experimental model of hypertension. BP, a heritable quantitative trait affected by numerous biological and environmental stimuli, is a major cause of morbidity and mortality worldwide and is considered to be a primary modifiable factor in renal, cardiovascular, and cerebrovascular diseases. Genome-wide association studies have identified monogenic and polygenic variants affecting BP in humans. Single nucleotide polymorphisms identified in genome-wide association studies have quantified the heritability of BP and the effect of genetics on hypertensive phenotype. Changes in the transcriptional program of genes may represent consequential determinants of BP, so understanding the mechanisms of the disease process has become a priority in the field. At the molecular level, the onset of hypertension is associated with reprogramming of gene expression influenced by epigenomics. This review highlights the specific genetic variants, mutations, and epigenetic factors associated with high BP and how these mechanisms affect the regulation of hypertension and kidney dysfunction.

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.

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 between prostaglandin E2 receptor gene and essential hypertension

BACKGROUND

Essential hypertension (EH) is a complex multifactorial polygenic disorder that is thought to result from an interaction between an individual's genetic makeup and various environmental factors. In the kidney, prostaglandins (PGs) are important mediators of vascular tone and salt and water homeostasis, and are involved in the mediation and/or modulation of hormonal action. In previous studies, mice deficient in the prostaglandin E2 (PGE(2)) EP2 receptor had resting systolic blood pressure (BP) that was significantly lower than that of wild-type controls. The BP of those mice increased when they were put on a high-salt diet, suggesting that the EP2 receptor is involved in sodium handling by the kidney. In the present study, we investigated the association between EH and nucleotide polymorphisms in the gene encoding the prostaglandin E2 receptor subtype EP2 (PTGER2).

METHODS

We selected three single-nucleotide polymorphisms (SNP) in the human PTGER2 gene (rs1254601, rs2075797, and rs17197), and we performed a genetic association study of 266 EH patients and 253 age-matched normotensive (NT) controls.

RESULTS

There was no significant difference in overall distribution of genotypes or alleles of any of the SNP between the EH and NT groups. However, among men, the A/A type of the SNP rs17197 (rs17197, A/G in 3'UTR) was significantly more frequent in EH subjects than in NT subjects (P=0.041).

CONCLUSION

The present findings suggest that rs17197 is useful as a genetic marker of EH in men.

Genetic variations related to hypertension: a review

Hypertension is a complex multifactorial disorder with genetic, environmental and demographic factors contributing to its prevalence. The genetic element contribution to blood pressure variation ranges from 30 to 50%. Therefore, identifying hypertension susceptibility genes will help understanding the pathophysiology of the disease. In addition to the potential impact of genomic information in selecting antihypertensive drug therapy, it may also help in recognizing those at risk of developing the disease, which may lead to new preventive approaches. Several strategies and methods have been used to identify hypertension susceptibility genes. Currently, genetic analysis of such data produced complex results, which makes it difficult to draw final conclusion on the use of genomic data in management of hypertension. This review attempts to summarize present known genetic variations that may be implicated in the pathogenesis of hypertension and to discuss various research strategies used to identify them. It also highlights some of the opportunities and challenges, which may be encountered in interpreting the value of these genetic variations to improve management of hypertension.

The prostacyclin analogue beraprost sodium prevents development of arterial stiffness in elderly patients with cerebral infarction

Prostacyclin (PGI(2)) inhibits platelet aggregation, smooth muscle cell proliferation, and vasoconstriction. Arterial stiffness assessed by pulse wave velocity (PWV) predicts mortality in various cardiovascular diseases. To study the preventive effects of a prostacyclin analogue, beraprost sodium, on arterial PWV values in elderly patients with cerebral infarction. Forty-four patients with a history of cerebral infarction received beraprost sodium (120 microg/day p.o.) or no beraprost sodium (control) for 3 months. Arterial PWV and ankle brachial indices (ABI) were determined prior to starting the medication and after 3 months of medication. Initially, there were no differences in age, blood pressure, and body mass index. Further, PWV or ABI did not differ between the beraprost sodium group (n = 22) and the control group (n = 22). After 3 months, PWV in beraprost sodium group was significantly reduced (-123 +/- 282) when compared with the control group (147 +/- 274)(P = 0.006). ABI was not significantly different when comparing the two groups at 3 months. Long-term administration of beraprost sodium prevents the decline in arterial biomechanics in elderly patients with cerebral infarction.

Genome-wide linkage disequilibrium mapping of hypertension in Japan

Hypertension is a common, complex phenotype resulting from the interaction between genetic and environmental factors. To select candidate regions potentially responsible for hypertension, we are conducting a genome-wide linkage disequilibrium (LD) mapping of hypertension using dinucleotide repeat markers in 146 hypertensive and 136 normotensive subjects. Although the LD mapping is still underway, 19 alleles of 15 markers have already shown a nominally significant association (p<0.05), with odds ratios ranging from 0.08 to 5.12, suggesting the presence of many hypertension-related loci with weak effects in the human genome. These markers should be further assessed, adjusting for confounding factors and considering gene-gene and gene-environmental interactions in additional samples. In this report, we discuss our ongoing LD mapping project and describe the 15 markers thus far discovered. Among the 15 markers, D10S537 had a highly significant association with hypertension (p=5.3x10(-5); OR=3.80; 95% CI=1.98-7.27; where OR indicates the odds ratio and 95% CI indicates the 95% confidence interval). Further analysis in a large Japanese population showed that D10S537 was significantly associated with hypertension (p=0.044; OR=1.27; 95% CI=1.01-1.59). D10S537 was more significantly associated with hypertension in subjects with normotriglyceridemia in our population (p=0.007; OR=1.47; 95% CI=1.11-1.95).

Haplotype analysis of the prostacyclin synthase gene and essential hypertension

Previously, we discovered 3 polymorphisms in the prostacyclin synthase (PGIS) gene: 1) T-192G, in the 5-flanking region, a novel single-nucleotide polymorphism (SNP) that is not associated with essential hypertension (EH); 2) a variable number of tandem repeat (VNTR) polymorphism, 6 nucleotides upstream from the ATG start codon, that is associated with risk of cerebral infarction; and 3) C1117A, in exon 8, an SNP that does not cause an amino acid change in codon 373, and that is associated with risk of myocardial infarction (MI). The purpose of the present study was to establish haplotypes of the PGIS gene consisting of these 3 polymorphisms, and to assess the association between these haplotypes and EH. We detected 19 haplotypes. There was no significant difference in the overall distribution of haplotypes between EH and normotensive subjects. To summarize, we successfully identified haplotypes of the PGIS gene, and these haplotypes were not associated with EH.

A novel variable number of tandem repeat polymorphism of the renin gene and essential hypertension

The aims of the present study were to find new genetic markers of essential hypertension (EH) and to investigate relationships between EH and polymorphisms of the renin gene. Using single strand conformation polymorphism, we discovered a new variable number of tandem repeat (VNTR) polymorphism in intron 7 that is 18 bp upstream from the boundary with exon 8. Nucleotide sequencing revealed that this VNTR polymorphism is a tandem repeat of the 4-nucleotide sequence TCTG. There were 6 alleles of this VNTR polymorphism, ranging from 7 repeats to 12 repeats. We analyzed the association between EH and this VNTR polymorphism. There was no significant difference in the overall distribution of this VNTR polymorphism between the EH and normotensive subjects. In summary, we discovered a novel VNTR polymorphism in the renin gene, and this polymorphism was not associated with EH.

A novel missense mutation of exon 3 in the type A human natriuretic peptide receptor gene: possible association with essential hypertension

The natriuretic peptide (NP) family is involved in regulation of blood pressure and fluid volume. We recently characterized the exon/intron organization of the human type A NP receptor (hNPRA) gene. The aim of this study was to isolate the genetic markers according to the organization of this gene, and to study the association between this gene and essential hypertension. Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis, we identified a novel missense mutation, M3411, consisting of a methionine (ATG) to isoleucine (ATC) substitution at nucleotide 1023 in exon 3. Computer-aided three-dimensional structural analysis suggested that M341 exists in the loop between two alpha-helices, and that the mutation may influence receptor activities by altering the conformation of the alpha-helices. We performed an association study of the mutation in 210 essential hypertension (EH) patients and 210 normotensive controls. The overall distribution of alleles was not significantly different between the control and EH groups. However, the C/C homozygous genotype was found only in the EH group. The ratio of plasma brain natriuretic peptide (BNP)/mean blood pressure of the C/C genotype was significantly higher than that of the G/G genotype or the G/C genotype. We conclude that the significance of homozygous M3411 mutation in exon 3 is worth investigating for its possible association with EH.