Leads and Target Validation for Vascular Calcification in Chronic Kidney Disease

描述（由申请人提供）：本申请涉及广泛的挑战领域（15）：“转化科学”和特定的挑战主题15-DK-103：“将NIDDK疾病发病机制中的新分子和途径的发现转化为潜在的治疗方法”。更具体地，本申请提出了验证治疗靶标并改善新型小分子化合物的生物利用度和药代动力学性质，用于预防和治疗动脉中层钙化，这是患有慢性肾病（CKD）、糖尿病、肥胖症和衰老的患者中常见的严重病症，其与心血管事件和死亡相关。迄今为止，还没有有效的药物治疗中膜钙化。我们实验室的研究表明，血管钙化通常被血管平滑肌产生的细胞外焦磷酸盐（PPi）抑制。血液透析患者血浆PPi浓度降低，与血管钙化呈负相关。我们已经表明，在尿毒症血管平滑肌中PPi的水平降低，并且通过注射PPi防止尿毒症大鼠和PPi缺乏的小鼠模型中的中膜钙化。细胞外PPi的关键调节因子是胞外酶组织非特异性碱性磷酸酶（TNAP），其水解PPi，从而破坏其抑制钙化的能力。我们还表明，在培养基中加入TNAP或通过病毒转导过度表达TNAP可导致培养的骨肉瘤钙化，而在表达I型胶原的组织中TNAP的转基因表达足以导致骨外钙化。我们还表明，TNAP是病理生理上调的网站中膜钙化的尿毒症arteriotas和小鼠模型的特发性婴儿动脉钙化，这表明假定的病理生理机制，连接PPi缺乏症中膜钙化的CKD患者。使用高通量筛选，我们已经确定了有效的TNAP抑制剂，完全防止钙化的血管在文化。我们推测，肾功能衰竭中的中膜血管钙化是由于血管系统中TNAP活性增加所致，这种异位钙化可以通过抑制TNAP的焦磷酸酶活性来预防。该RC 1提案集中于验证TNAP作为治疗靶点，并通过药物化学和结构-活性-关系研究改善新型TNAP抑制剂的生物利用度和药代动力学特性，以在CKD尿毒症大鼠模型中体内测试这种基于机制的治疗策略的有效性。中膜钙化的临床治疗一直局限于尽量减少与之有着千丝万缕联系的相关代谢性骨病的影响。这种间接方法在CKD中不是非常有效，并且不能解决糖尿病或衰老中发生的钙化。因此，需要更具体的治疗方法，直接解决中膜钙化的发病机制。TNAP的药理学抑制是解决该问题的新方法，其直接解决脉管系统中TNAP的上调和随后在肾衰竭中观察到的PPi缺乏。因为TNAP在正常条件下控制细胞外PPi水平，所以预期该疗法增加脉管系统中的局部PPi水平，从而抑制中膜钙化。- 与公共卫生的相关性脉管系统的中膜钙化在肾衰竭、糖尿病、肥胖症和衰老中常见，其通过损害动脉功能而导致发病率和死亡率。目前还没有针对这种流行病的治疗方法。我们的研究将验证中膜钙化的治疗靶点，并将优化新的铅化学品，以预防/治疗已建立的动物模型中的动脉钙化，从而满足这一未满足的临床需求。 公共卫生相关性：血管系统的中膜钙化在肾衰竭、糖尿病、肥胖和衰老中常见，其通过损害动脉功能而导致发病率和死亡率。目前还没有针对这种流行病的治疗方法。我们的研究将验证中膜钙化的治疗靶点，并将优化新的铅化学品，以预防/治疗已建立的动物模型中的动脉钙化，从而满足这一未满足的临床需求。

DESCRIPTION (provided by applicant): This application addresses broad Challenge Area (15): "Translational Science", and specific Challenge Topic, 15-DK-103: "Translate discovery of new molecules and pathways in pathogenesis of NIDDK diseases into potential therapies". More specifically, this application proposes to validate a therapeutic target and to improve the bioavailability and pharmacokinetic properties of novel small molecule compounds for the prevention and treatment of calcification of the medial layer of arteries, a common and severe condition in patients with chronic kidney disease (CKD), diabetes, obesity and aging that correlates with cardiovascular events and death. To-date there is no effective medical treatment for medial calcification. Research in our laboratories has demonstrated that vascular calcification is normally inhibited by extracellular pyrophosphate (PPi) produced by vascular smooth muscle. Plasma PPi concentrations are reduced in hemodialysis patients and are inversely correlated with vascular calcification. We have shown that levels of PPi are reduced in uremic vascular smooth muscle and that medial calcification in uremic rats and in mouse models of PPi-deficiency is prevented by injections of PPi. The key regulator of extracellular PPi is the ectoenzyme tissue-nonspecific alkaline phosphatase (TNAP) that hydrolyzes PPi, thus destroying its ability to suppress calcification. We have also shown that addition of TNAP to culture medium or overexpression of TNAP by viral transduction causes calcification in cultured aortas and transgenic expression of TNAP in tissues expressing type I collagen is sufficient to cause extraosseous calcification. We have also shown that TNAP is pathophysiologically upregulated at sites of medial calcification in uremic aortas and mouse models of idiopathic infantile arterial calcification, suggesting the putative pathophysiological mechanism that links PPi deficiency to medial calcification in patients with CKD. Using high throughput screening, we have identified potent inhibitors of TNAP that completely prevent calcification of aortas in culture. We hypothesize that medial vascular calcification in renal failure results from increased activity of TNAP in the vasculature and that this ectopic calcification can be prevented by inhibitors of TNAP's pyrophosphatase activity. This RC1 proposal focuses sharply on validating TNAP as a therapeutic target and in improving, via Medicinal Chemistry and structure-activity-relationship studies, the bioavailability and pharmacokinetic properties of novel TNAP inhibitors to enable in vivo testing of the effectiveness of this mechanism-based therapeutic strategy in a uremic rat model of CKD. The clinical management of medial calcification has been limited to minimizing the impact of the associated metabolic bone disease to which it is inextricably linked. This indirect approach has not been very effective in CKD and does not address the calcification that occurs in diabetes or with aging. Thus, there is a need for more specific therapies that directly address the pathogenesis of medial calcification. Pharmacological inhibition of TNAP is a novel approach to this problem that directly addresses the upregulation of TNAP in the vasculature and the ensuing PPi deficiency seen in renal failure. Because TNAP controls extracellular PPi levels under normal conditions this therapy is expected to increase local PPi levels in the vasculature thus inhibiting medial calcification. - Relevance to Public Health Medial calcification of the vasculature is of common occurrence in renal failure, diabetes, obesity and aging, where it contributes to morbidity and mortality through compromised arterial function. Currently there are no treatments for this prevalent condition. Our studies will validate a therapeutic target for medial calcification and will optimize new lead chemicals to prevent/treat arterial calcification in established animal models, thus filling this unmet clinical need. PUBLIC HEALTH RELEVANCE: Medial calcification of the vasculature is of common occurrence in renal failure, diabetes, obesity and aging, where it contributes to morbidity and mortality through compromised arterial function. Currently there are no treatments for this prevalent condition. Our studies will validate a therapeutic target for medial calcification and will optimize new lead chemicals to prevent/treat arterial calcification in established animal models, thus filling this unmet clinical need.