A Thioredoxin Mimetic for Radiocontrast Nephropathy

描述（由申请人提供）：我们正在开发一种新型小分子细胞保护药物，用于预防静脉注射放射性造影剂（CM）后的造影剂诱导肾病（CIN）。CIN主要由CM诱导的传入肾小动脉血管收缩介导，导致抗利尿和严重损害肾血流。随后的肾缺血诱导氧化和亚硝化应激，特别是在肾小管的细胞核内，其中发生DNA单链断裂。当这种基因组损伤然后被核DNA修复酶聚（ADP-核糖）聚合酶（“PARP”）识别时，NAD被切割以产生产物聚（ADP-核糖）。CM注射后PARP的超活化消耗NAD储存，导致氧化磷酸化的损失和ATP合成的干扰。为了解决这一未满足的需求，我们正在开发一种可渗透细胞的硫氧还蛋白模拟物（R-901），这是一种富含巯基的三肽，与天然硫氧还蛋白（TRX）基序非常相似。R-901表现出的体外效力分别是N-乙酰半胱氨酸（NAC）和抗坏血酸的450倍和50倍，并且体内效力基本上大于NAC。R-901的治疗性给药已在肺部炎症的小鼠模型中显示（由卵清蛋白致敏和再激发诱导）以减少组织学损伤、减少白细胞浸润、减弱组织氧化、阻断炎症前细胞因子表达和NF-κ B的核转位、减少抗炎细胞质蛋白IkB α的降解，并恢复还原型和氧化型谷胱甘肽的平衡。在由急性Cl 2气体吸入诱导的严重氧化还原应激的小鼠LD 100模型中，损伤后给予R-901使肺中性粒细胞浸润减少50%。基于其对氧化还原应激的超强催化作用以及氧化还原应激与CIN病理生理学的关键相关性，我们现在建议在脱水、前列腺素合成酶抑制和CM IV激发诱导的CIN大鼠模型中构建R-901的药效学特征。将假损伤组与在脱水或容量负荷条件下CM给药前开始的NAC或R-901（超过一个对数剂量范围）给药CM激发大鼠进行比较。在24小时时，将分析血浆中的肾功能以及肾损伤的生化、组织学和免疫组织化学参数。将比较R-901的肾脏和血浆浓度，以评估组织R-901摄取。我们预期R-901暴露水平将与组织保护程度相关，如肾坏死（组织学）、脂质过氧化、中性粒细胞浸润、细胞凋亡、坏死、过氧亚硝酸盐和聚（ADP-核糖）形成水平以及中性粒细胞明胶酶相关脂质运载蛋白的血清浓度所示。拟定的研究将为R-901的高级商业开发提供合理的基础，旨在使该产品作为接受CM注射的高风险患者的一线预防。 公共卫生相关性：放射性造影成像是一种非常有价值且经常使用的诊断方式，但其使用因随后发生肾损伤而变得复杂，通常达到需要透析的程度，特别是在风险最大的人群中，如老年人、糖尿病患者和先前存在肾损伤的人群。目前还没有批准的药物治疗来预防这种并发症。我们正在开发一种新的预防剂，通过直接保护肾细胞免受损伤来保护肾脏免受放射造影剂给药的影响。我们现在建议在临床相关的小动物模型中测试这种药剂， 放射造影剂导致的肾衰竭

DESCRIPTION (provided by applicant): We are developing a novel small molecule cytoprotective drug for the prevention of contrast-induced nephropathy (CIN) following intravenous radiocontrast media (CM) injection. CIN is mediated principally by CM-induced vasoconstriction of the afferent renal arteriololes, resulting in antidiuresis and severely compromised renal blood flow. The consequent renal ischemia induces oxidative and nitrosative stress, in particular within the nucleus of the renal tubules where DNA single strand breakage occurs. When this genomic injury is then recognized by the nuclear DNA repair enzyme poly (ADP-ribose) polymerase ("PARP"), NAD is cleaved to generate the product poly(ADP-ribose). Hyperactivation of PARP after CM injection depletes NAD stores, resulting in the loss of oxidative phosphorylation and interference with ATP synthesis. To address this unmet need, we are developing a cell-permeable thioredoxin mimetic (R-901), a thiol-rich tripeptide that is closely analogous to the native thioredoxin (TRX) motif. R-901 exhibits in vitro potency 450- and 50-fold > than N-acetylcysteine (NAC) and ascorbic acid, respectively, and in vivo potency substantially greater than NAC. Therapeutic administration of R-901 has been shown in a murine model of pulmonary inflammation (induced by ovalbumin sensitization and re-challenge) to reduce histologic injury, diminish leukocytic infiltration, attenuate tissue oxidation, block pr-inflammatory cytokine expression and nuclear translocation of NF-kB, diminish the degradation of the anti-inflammatory cytoplasmic protein IkBalpha, and restore the balance of reduced and oxidized forms of glutathione. In a murine LD100 model of severe redox stress induced by acute Cl2 gas inhalation, post-insult administration of R-901 reduced pulmonary neutrophil infiltration by 50%. Based on its ultrapotent catalysis of redox stress, and the critical relevance of redox stress to the pathophysiology of CIN, we now propose to construct a pharmacodynamic profile of R-901 in a rat model of CIN induced by dehydration, prostaglandin synthetase inhibition, and an IV challenge of CM. A sham injury group will be compared to treatment of CM-challenged rats with NAC or R-901 (over a one log dose range) initiated prior to CM administration under conditions of dehydration or volume loading. At 24 hours plasma will be analyzed for renal function and biochemical, histologic, and immunohistochemical parameters of renal injury. Renal and plasma concentrations of R-901 will be compared to assess tissue R-901 uptake. We expect that level of exposure to R-901 will correlate with the extent of tissue protection, as manifested by renal levels of necrosis (histology), lipid peroxidation, neutrophil infiltration, apoptosis, necrosis, peroxynitrite and poly(ADP- ribose) formation, and serum concentrations of neutrophil gelatinase-associated lipocalin. The proposed studies will provide a rational foundation for advanced commercial development of R-901, with the intent that this product will serve as first-line prophylaxis in high-risk patients undergoing CM injection. PUBLIC HEALTH RELEVANCE: Radiocontrast imaging is an invaluable and frequently used diagnostic modality for but its use is complicated by the subsequent development of kidney injury, often to the extent of requiring dialysis, particularly in populations at greatest risk, suh as the elderly, diabetic, and those with preexisting renal impairment. There are no approved pharmaceutical therapies to prevent this complication. We are developing a novel prophylactic agent that protects the kidney from radiocontrast administration by directly protecting kidney cells from injury. We now propose to test this agent in a clinically-relevant small animal model of radiocontrast-induced kidney failure.