A model of kidney stone disease using D. melanogaster

描述(申请人提供)：症状性肾结石可能是严重疼痛、感染和发病率的重要来源，影响多达12%的美国人，每年产生超过20亿美元的医疗费用。肾结石的形成过程仍然知之甚少，由于缺乏良好的肾结石形成模型，在开发药物或饮食干预以预防结石的发生或复发方面进展有限。在果蝇中，马氏管在功能上相当于人类的曲管，将离子和其他溶质从果蝇循环系统输送到排泄系统。此外，在苍蝇排泄系统中发现的一些基因在人类排泄系统中起着保守的作用。飞行小管产生含有钙、磷和其他离子与有机基质结合的结晶结节。这些结石似乎是由微小的球形结构形成的，这些结构与兰德尔斑块中看到的纳米颗粒(球晶)惊人地相似，兰德尔斑块是人类肾脏早期结石形成的核心。我们发现，这些苍蝇结石含有黄嘌呤和一种双膦酸盐结合物质，推测是羟基磷灰石和钙，这是早期人类结石的主要成分。我们还发现，抑制黄嘌呤脱氢酶(XDH)导致高蛋白饮食中的结石积累增加，这可以通过抑制维生素D受体同源基因来挽救。值得注意的是，这些基因和高蛋白饮食与人类结石病有关。鉴于其在肾小管生理学、排泄系统基因的保守性、结石形成的特点等方面与人类的相似之处，以及在果蝇中强大的遗传工具的可获得性，我们推测，黑腹隐翅虫可以作为一个有意义的模型来提高对肾结石疾病的理解和寻找新的治疗方法。拟议研究的目的是：(1)鉴定XDH基因敲除蝇早期结石形成和小管生理的特征；(2)鉴定调控早期苍蝇结石形成的遗传和药物操作；以及(2)开发黑腹毛虫作为研究肾结石的翻译模型的意义在于，它将为更好地了解人类肾结石形成的机制和发现肾结石疾病的新疗法提供机会。这一建议具有创新性，因为应用了寿命短、维护成本相对较低的无脊椎动物翻译模型，实现了为开发肾结石治疗药物而进行的大规模遗传和药物操作筛选。

DESCRIPTION (provided by applicant): Symptomatic kidney stones can be a significant source of severe pain, infection, and morbidity, affecting up to 12% of Americans and generating more than $2 billion in healthcare costs annually. The process of kidney stone formation remains poorly understood and there has been limited progress in developing medical or dietary interventions to prevent the occurrence or recurrence of stones due to paucity of good models for kidney stone formation. In Drosophila melanogaster (D. melanogaster), the Malpighian tubule is the functional equivalent of the human convoluted tubule and transports ions and other solutes from the fly circulatory system into the excretory system. Furthermore, a number of genes found in the fly excretory system play a conserved role in the human excretory system. The fly tubule produces crystalline concretions containing calcium, phosphorus, and other ions combined with an organic matrix. These concretions appear to be formed from small spherical structures that bear a striking resemblance to the nanoparticles (spherites) seen in Randall plaques, the nidus of early stone formation in human kidneys. We show that these fly stones contain xanthine and a bisphosphonate-binding substance, presumably hydroxyapatite and calcium, the primary component of early human stones. We have also found that inhibition of xanthine dehydrogenase (XDH) in D. melanogaster leads to increased accumulation of concretions on a high protein diet which can be rescued by inhibition of a Vitamin D receptor ortholog. Notably these genes and a high protein diet have been implicated in human stone disease. Given the similarities in tubule physiology, conservation of genes in the excretory system, and characteristics of stone formation between D. melanogaster and humans, and the availability of powerful genetic tools in the fly, we hypothesize that D. melanogaster can be utilized as a meaningful model to improve understanding of kidney stone disease and to identify novel therapeutics. The aims of the proposed study are: (1) Characterization of early stone formation and tubule physiology in the XDH knockdown fly; and (2) identification of genetic and pharmacologic manipulations that modulate early fly stone formation, The significance of developing D. melanogaster as a translational model for studying nephrolithiasis is that it would provide an opportunity to better understand the mechanism of human kidney stone formation and to discover novel therapeutics for kidney stone disease. This proposal is innovative because of the application of an invertebrate translational model characterized by a short lifespan and relatively low cost of maintenance, to achieve large scale screening of genetic and pharmacological manipulations for developing therapeutics for nephrolithiasis.