Heterozygous disruption of CMA1 does not affect blood pressure

Association of polymorphisms in prolylcarboxypeptidase and chymase genes with essential hypertension in the Chinese Han population

INTRODUCTION

The prolylcarboxypeptidase (PRCP) gene encodes a membrane protein that acts on angiotensin II (Ang II) and kallikrein to release vasoactive peptides. The chymase (CMA1) gene is important for Ang II generation. Therefore, the two genes might be involved in the pathogenesis of essential hypertension (EH).

MATERIALS AND METHODS

Eleven tag single nucleotide polymorphisms (SNPs) in the PRCP gene and four tag SNPs and G-1903A (rs1800875) polymorphism in the CMA1 gene were genotyped in the Chinese Han population (n=1020) using a polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

In the PRCP gene, single site analyses indicated that the rs7104980 G allele was a susceptible factor for EH (adjusted odds ratio (OR)=1.98, 95% confidence interval (CI) 1.62-2.43, p=0.3×10(-10)). The protective effect of Hap3 GAGCACTAACA was observed without carrying the susceptible rs7104908 G allele (OR=0.67, 95% CI 0.56-0.81, p=0.3×10(-4)) by haplotype analyses. In the case of the CMA1 gene, no associations with EH were found through single site analyses. However, haplotype analyses showed that Hap16 TTTA significantly increased the risk of EH with OR=3.15 (p=0.0002) which may be driven by interaction with a nearby SNP combination.

CONCLUSIONS

The present results indicated PRCP rs7104980 can be considered as a marker for EH and Hap3 GAGCACTAACA (PRCP) and Hap16 TTTA (CMA1) might be associated with EH in Chinese Han population.

Accumulation of common polymorphisms is associated with development of hypertension: a 12-year follow-up from the Ohasama study

Hypertension is a complex multi-factorial and polygenic disorder. Nevertheless, most studies have focused on single-gene effects. Furthermore, a majority of these studies have been cross-sectional and diagnosed hypertension using conventional blood pressure (BP) measurements, which are known to be subject to biases, including the so-called white-coat effect. Thus, we performed a longitudinal association study to clarify the effects of polymorphism accumulation on the development of hypertension that is defined on the basis of self-measured BP at home (home BP). In 403 Japanese aged 40-79 years with home normotension (home BP <135/85 mm Hg, and not treated with antihypertensive medication at baseline), we examined the associations of 51 single-nucleotide polymorphisms (SNPs) classically nominated or reported to be associated with hypertension in the Japanese Millennium Genome Project for Hypertension with a 12-year risk of progression to home hypertension (home BP >or=135/85 mm Hg, or start of antihypertensive medication). Out of 51 SNPs, four significantly and independently predicted the risk of progression of home hypertension, even after adjustment for possible confounding factors, including baseline home BP value. These were rs3767489 near the regulator of G-protein signaling 2 (RGS2), rs4961 in adducin 1 (ADD1), rs2236957 in the calcium channel, voltage-dependent, alpha-2/delta-subunit 2 (CACNA2D2) and rs769214 in catalase (CAT). Accumulation of these SNPs significantly improved the predictive values for the development of home hypertension. In conclusion, this longitudinal study, which was based on home BP measurement, showed that accumulation of common polymorphisms reliably predicted the risk of future hypertension in the Japanese general population.

Genome-wide scan for blood pressure in Australian and Dutch subjects suggests linkage at 5P, 14Q, and 17P

Large-scale studies estimate the heritability of blood pressure at approximately 50%. We carried out a genome-wide linkage analysis to search for chromosomal loci that might explain this heritability using longitudinal, multiple measures of systolic and diastolic blood pressure obtained in sibling pairs and dizygotic twin pairs from 2 countries (a total of 286 pairs from Australia and 636 pairs from the Netherlands). These pairs and a large number of their parents were genotyped with microsatellite markers. Multivariate linkage analysis of the combined data of both countries, using a variance components approach, showed suggestive linkage for diastolic blood pressure on chromosomes 5p13.1 (logarithm of odds score: 2.48), 14q12 (logarithm of odds score: 2.40) and 17q24.3 (logarithm of odds score: 2.36). The highest logarithm of odds score of 1.21 for systolic blood pressure was observed on chromosome 13q34. These results replicate earlier findings and add to a slowly emerging picture of multiple loci contributing to quantitative blood pressure variation.

Chymase Gene (CMA1) Polymorphisms in Dutch and Japanese Sarcoidosis Patients

BACKGROUND

Chymase is released from mast cells following activation. Evidence suggests that chymase plays an important role in tissue injury and remodeling of the lungs, heart and skin.

OBJECTIVE

We postulated that chymase gene (CMA1) polymorphisms are associated with pulmonary fibrosis in Dutch and with cardiac and skin involvement in Japanese sarcoidosis patients.

PATIENTS AND METHODS

Dutch (n = 153) and Japanese (n = 122) sarcoidosis patients with controls (Dutch, n = 309; Japanese, n = 111) were studied. Pulmonary involvement in Dutch patients as well as clinical manifestations in Japanese patients was evaluated for association with five CMA1 polymorphisms.

RESULTS

The CMA1 polymorphisms were not associated with disease susceptibility in either population, or with radiographic evolution in the Dutch or with cardiac or skin involvement in the Japanese patients. The -526 T allele was associated with a lower iVC in Dutch patients.

CONCLUSIONS

The CMA1 polymorphisms studied do not contribute to disease susceptibility in Japanese or Dutch sarcoidosis patients. CMA1 polymorphisms do not influence radiographic evolution in Dutch sarcoidosis patients, nor do they predispose to cardiac or skin involvement in Japanese patients. However, the association between CMA1 -526 C/T and iVC in the Dutch patients suggests that chymase may modify the functional outcome of pulmonary sarcoidosis.

A Case of Gitelman's Syndrome with Decreased Angiotensin II-Forming Activity

Gitelman's syndrome (GS) is a variant of Bartter's syndrome (BS) characterized by hypokalemic alkalosis, hypomagnesemia, hypocalciuria and secondary aldosteronism without hypertension. A 31-year-old Japanese man who had suffered from mild hypokalemia for 10 years was admitted to our hospital. He had metabolic alkalosis, hypokalemia and hypocalciuria. Since he had two missense mutations (R261C and L623P) in the thiazide-sensitive Na-Cl cotransporter (TSC) gene (SLC12A3), he was diagnosed as having GS. He showed hyperreninism and a high angiotensin I (Ang I) level, whereas his angiotensin II (Ang II) and aldosterone levels were not elevated. His angiotensin converting enzyme (ACE) activities were normal, and administration of captopril inhibited the production of Ang II and aldosterone. We evaluated the Ang II-forming activity (AIIFA) of other enzymes in his lymphocytes. Interestingly, chymase-dependent AIIFA was not detected in the lymphocytes. Together, these results suggest that the lack of chymase activity resulted in the manifestation of GS without hyperaldosteronism.

Role of Chymase-Dependent Angiotensin II Formation in Regulating Blood Pressure in Spontaneously Hypertensive Rats

Vascular smooth muscle cells in spontaneously hypertensive rats (SHR) express angiotensin II-forming chymase (rat vascular chymase [RVCH]), which may contribute to blood pressure regulation. In this study, we studied whether chymase-dependent angiotensin II formation contributes to the regulation of blood pressure in SHR. The systolic blood pressure in 16-week-old Wistar-Kyoto (WKY) rats was 113 +/- 9 mmHg, compared to 172 +/- 3 mmHg in SHR. Using synthetic substrates for measuring angiotensin-converting enzyme (ACE) and chymase activities, it was found that both ACE and chymase activities in extracts from SHR aortas were significantly higher than in those from WKY rat aortas. Using angiotensin I as a substrate, angiotensin II formation in SHR was found to be significantly higher than that in WKY rats, and its formation was completely suppressed by an ACE inhibitor, but not by a chymase inhibitor. RVCH mRNA expression could not be detected in aorta extracts from either WKY rats or SHR. In carotid arteries isolated from WKY rats and SHR, angiotensin I-induced vasoconstriction was completely suppressed by an ACE inhibitor, but not by a chymase inhibitor. Angiotensin I-induced pressor responses in both WKY rats and SHR were also completely inhibited by an ACE inhibitor, but they were not affected by a chymase inhibitor. In SHR, an ACE inhibitor and an angiotensin II receptor blocker showed equipotent hypotensive effects, but a chymase inhibitor did not have a hypotensive effect. These results indicated that chymase-dependent angiotensin II did not regulate blood pressure in SHR in the present study.

Chymase as a novel target for the prevention of vascular diseases

In vascular tissues, chymase catalyzes the production of angiotensin II, which plays a crucial role in vascular diseases. Recent clinical studies and animal models of vascular proliferation and atherosclerosis have provided evidence that angiotensin II formed by chymase is involved in these processes. These observations suggest that chymase might promote the development of vascular proliferation and atherosclerosis. Chymase also activates matrix metalloproteinase 9, which promotes aortic aneurysm and angiogenesis, and thus chymase inhibitors might also prevent the progression of abdominal aortic aneurysm and angiogenesis. We propose that chymase is a novel target for preventing vascular diseases.