Contribution of Gstm1 to the severity of hypertension and chronic kidney disease

描述（由申请人提供）：高血压（HTN）是美国终末期肾病（ESRD）的主要原因。普遍认为氧化应激是HTN发展和慢性肾病（CKD）进展的共同因素。因此，影响处理氧化应激能力的遗传变异可能会影响HTN的严重程度和肾脏疾病的结果。我们已经确定了GSTM 1基因的无效变体，Nrf 2抗氧化途径的成员，作为高血压肾病进展的修饰剂。GSTM 1的基因产物是谷胱甘肽S-转移酶m-1或GSTM 1酶，其属于谷胱甘肽-S-转移酶的超家族，其代谢外源性物质和广泛的活性氧（ROS），以及作为脂质过氧化的终产物的高活性醛（RA）。大约30-50%的人完全缺乏GSTM 1酶，这是由于常见的GSTM 1无效等位基因GSTM 1（0）的纯合遗传。GSTM 1（0/0）基因型的人患HTN的风险增加。使用小鼠模型，我们先前发现Gstm 1是肾血管损伤易感性的强候选基因， 并且Gstm 1表达的减少导致血管平滑肌细胞（VSMC）增殖、迁移和氧化应激增加。在初步研究中，我们评估了GSTM 1（0）在非裔美国人肾脏病研究（AASK）试验队列中的作用。我们发现，肾小球滤过率（GFR）事件、透析或死亡时间的风险比（HR）在 有两个或一个无效等位基因的个体相对于有两个活跃等位基因的个体的平均遗传距离分别为2.15（p=0.005）和1.73（p=0.03）。我们的研究是第一个证明遗传变异与AASK试验参与者高血压肾病的临床结局之间的关联。尽管有强有力的证据表明GSTM 1的无效变体在人类疾病中的作用，但因果关系的直接证据和基因产物丢失导致疾病易感性的确切分子机制尚未建立。我们认为，遗传变异，即使是一个温和的递减变化，GSTM 1基因的表达提供了一个宽松的环境夸大氧化应激。我们假设GSTM 1通过其在RA代谢中的核心作用来改变HTN的严重程度和肾脏疾病的进展。为了验证这一假设，我们已经产生了Gstm 1-/-小鼠系，以确定Gstm 1的损失对高血压和CKD病程的贡献。目的1将使用三种HTN小鼠模型，确定Gstm 1缺失对高血压易感性和严重程度的影响。目的2将使用肾质量缺血性减少模型确定Gstm 1-Nrf 2通路在肾脏疾病严重程度和进展中的作用。目的3将确定GSTM 1对NRF 2表达和RA及其蛋白靶点的功能分子效应。还将确定GSTM 1的酶和功能性非酶结构域对VSMC增殖、迁移和氧化应激的相对贡献。

DESCRIPTION (provided by applicant): Hypertension (HTN) is a leading cause of end-stage renal disease (ESRD) in the U.S. There is general consensus that oxidative stress is a common factor in the development of HTN and progression of chronic kidney disease (CKD). Hence, genetic variants that affect the capacity to handle oxidative stress may influence the severity of HTN and the outcome of kidney disease. We have identified the null variant of the GSTM1 gene, a member of the Nrf2 antioxidant pathway, as a modifier of hypertensive kidney disease progression. The gene product of GSTM1 is glutathione S-transferase m-1, or GSTM1 enzyme, that belongs to a superfamily of glutathione-S-transferases that metabolize xenobiotics and a broad range of reactive oxygen species (ROS), and the highly reactive aldehydes (RAs) that are end products of lipid peroxidation. Approximately 30-50% of humans are completely deficient of GSTM1 enzyme due to homozygous inheritance of the common GSTM1 null allele, GSTM1(0). Those with the GSTM1(0/0) genotype have increased risks of HTN. Using a mouse model, we previously found that Gstm1 is a strong candidate gene for susceptibility to renal vascular injury, and that reduced expression of Gstm1 causes increased vascular smooth muscle cell (VSMC) proliferation, migration and oxidative stress. In preliminary studies, we assessed the effect of GSTM1(0) in the African American Study of Kidney Disease (AASK) Trial cohort. We found that the hazard ratios (HR) for the time to glomerular filtration rate (GFR) event, dialysis or death in those with two or one null alleles relative to those with two active alleles were 2.15 (p=0.005) and 1.73 (p=0.03), respectively. Our study is the first to demonstrate an association between a genetic variant and the clinical outcomes of the AASK Trial participants with hypertensive kidney disease. Despite the strong evidence implicating a role of the null variant of GSTM1 in human diseases, direct proof of causality and the exact molecular mechanism by which loss of the gene product causes disease susceptibility have not been established. We suggest that genetic variants that cause even a modest decremental change in the expression of GSTM1 gene provide a permissive environment of exaggerated oxidative stress. We hypothesize that GSTM1 acts to modify the severity of HTN and kidney disease progression through its central role in metabolizing RAs. To test this hypothesis, we have generated a Gstm1-/- mouse line to determine the contribution of loss of Gstm1 to hypertension and CKD course. Aim 1 will define the impact of Gstm1 deletion on the susceptibility to and severity of hypertension, using three mouse models of HTN. Aim 2 will determine the role of the Gstm1-Nrf2 pathway in kidney disease severity and progression, using the ischemic reduction of renal mass model. Aim 3 will define the functional molecular effects of GSTM1 on NRF2 expression and on RAs and their protein targets. The relative contribution of the enzymatic and functional non-enzymatic domains of GSTM1 on VSMC proliferation, migration and oxidative stress will also be determined.