Aldosterone Synthase & Hypertension

描述(申请人提供)：高血压是心肌梗死、心力衰竭、血管疾病、中风和肾功能衰竭的严重危险因素。肾素-血管紧张素-醛固酮系统(RAAS)在血压调节中起着重要作用。不适当地增加醛固酮会导致与年龄相关的血压升高和其他心血管问题。醛固酮是在肾上腺皮质的ZG中合成的，而醛固酮合成酶是其生物合成的限速酶。醛固酮合成酶由Cyp11B2基因编码，其启动子-344处存在T/C多态。流行病学研究表明，Cyp11B2基因-344T变异与高血压和心肌肥厚有关。人类Cyp11B2基因启动子1kb有3个SNPs，几乎完全连锁不平衡。这些SNP分别是rs1799998(T/C at-344)、rs10087214(C/T at-470)、rs28659182(C/A at-663)。因此，变体-344T几乎总是与变体-470C、-663A(称为单体型-I)一起出现，而变体-344C几乎总是与变体-470T、-663T(称为单体型-II)一起出现。我们通过敲入hCyp11B2基因获得了转基因小鼠，hCyp11B2基因在HPRT基因座上包含单倍型-I或单倍型-II。与含有单倍型II的转基因小鼠相比，含有单倍型-I的转基因小鼠的肾上腺和肾脏中的hCyp11B2mRNA水平增加。此外，与携带hCyp11B2基因单倍型II的转基因动物相比，携带单倍型-I基因的雄性转基因动物血压升高。与单倍型-II相比，高盐(4%氯化钠饮食)和血管紧张素-II给药增加了hCyp11B2基因单倍型-I转基因小鼠的血压。因此，我们的假设是，与单倍型-II相比，转录因子与含有单倍型-I的hCyp11B2基因的核苷酸序列结合得更强，并增加其表达。这会增加含有单倍型-I的受试者的组织或血浆中的醛固酮水平。与-344C等位基因相比，携带-344T等位基因的受试者中，醛固酮生成调节改变的长期后果会导致血压和心血管并发症的增加。这些转基因小鼠将被用来了解这些单倍型对雄性和雌性动物血压调节的作用。转基因小鼠也可能被用来开发新的治疗试剂，以降低血压和心血管并发症。

DESCRIPTION (provided by applicant): Hypertension is a serious risk factor for myocardial infarction, heart failure, vascular disease, stroke, and renal failure. The renin-angiotensin-aldosterone system (RAAS) plays an important role in the regulation of blood pressure. Inappropriate increase of aldosterone causes age-related increase in blood pressure and other cardiovascular problems. Aldosterone is synthesized in the ZG of the adrenal cortex and aldosterone synthase is the rate limiting enzyme in its biosynthesis. Aldosterone synthase is coded by Cyp11B2 gene and the human gene has a T/C polymorphism located at -344 in its promoter. Epidemiological studies have suggested that variant -344T of Cyp11B2 gene is associated with hypertension and myocardial hypertrophy. Human Cyp11B2 gene has three SNPs in 1 Kb of its promoter that are in almost complete linkage dis-equilibrium. These SNPs are rs1799998 (T/C at -344), rs10087214 (C/T at -470), rs28659182 (C/A at -663). Thus variant -344T almost always occurs with variants -470C, -663A (named haplotype-I, and variant -344C almost always occurs with variants, - 470T, -663T (named haplotype-II). We have generated transgenic mice by knocking in hCyp11B2 gene containing either haplotype-I or haplotype-II at the HPRT locus. Transgenic mice containing haplotype-I have increased hCyp11B2 mRNA level in the adrenals and kidneys as compared to transgenic animals containing haplotype-II. In addition, male transgenic animals containing haplotype-I have increased blood pressure as compared to transgenic animals containing haplotype-II of hCyp11B2 gene. High salt (4% NaCl diet) and angiotensin-II administration increases blood pressure in transgenic mice containing haplotype-I of hCyp11B2 gene as compared to haplotype-II. Therefore, our hypothesis is that transcription factors bind strongly to the nucleotide sequence of hCyp11B2 gene containing haplotype-I as compared to haplotype-II, and increase its expression. This increases tissue or plasma aldosterone level in human subjects containing haplotype-I. The long term consequence of altered regulation of aldosterone production leads to an increase in blood pressure and cardiovascular complications in human subjects containing -344T allele as compared to -344C allele. These transgenic mice will be used to understand the role of these haplotypes on blood pressure regulation in male and female animals. Transgenic mice may also be used to develop new therapeutic reagents to reduce blood pressure and cardiovascular complications.