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，用于静脉注射造影剂（CM）后预防造影剂引起的肾病（CIN）。CIN主要由cm诱导的肾小动脉血管收缩介导，导致抗利尿和肾血流严重受损。随之而来的肾缺血引起氧化和亚硝化应激，特别是在DNA单链断裂发生的肾小管核内。当这种基因组损伤被核DNA修复酶聚（adp -核糖）聚合酶（PARP）识别时，NAD被裂解产生产物聚（adp -核糖）。CM注射后PARP的过度激活会耗尽NAD的储存，导致氧化磷酸化的丧失和ATP合成的干扰。为了解决这一未满足的需求，我们正在开发一种细胞渗透性硫氧还蛋白模拟物（R-901），这是一种富含硫醇的三肽，与天然硫氧还蛋白（TRX）基元非常相似。R-901的体外效价分别是n -乙酰半胱氨酸（NAC）和抗坏血酸的450倍和50倍，体内效价明显高于NAC。在小鼠肺部炎症模型（由卵清蛋白致敏和再激发诱导）中，R-901治疗性管理已被证明可以减少组织学损伤，减少白细胞浸润，减轻组织氧化，阻断炎症前细胞因子表达和NF-kB的核易位，减少抗炎细胞质蛋白IkBalpha的降解，并恢复还原和谷胱甘肽氧化形式的平衡。在急性Cl2气体吸入引起的严重氧化还原应激小鼠LD100模型中，损伤后给予R-901可使肺中性粒细胞浸润减少50%。基于R-901对氧化还原应激的超强催化作用，以及氧化还原应激与CIN病理生理的重要相关性，我们现在提议构建R-901在脱水、前列腺素合成酶抑制和静脉注射CM诱导的大鼠CIN模型中的药效学谱。假性损伤组将与在CM给药前在脱水或体积负荷条件下开始NAC或R-901（超过1对数剂量范围）治疗CM挑战大鼠进行比较。24小时血浆分析肾功能及肾损伤的生化、组织学和免疫组织化学参数。将比较肾和血浆R-901浓度来评估组织R-901的摄取。我们预计，暴露于R-901的水平将与组织保护程度相关，表现为肾脏坏死水平（组织学）、脂质过氧化、中性粒细胞浸润、凋亡、坏死、过氧亚硝酸盐和聚（ADP-核糖）形成，以及中性粒细胞明胶酶相关脂钙蛋白的血清浓度。这些研究将为R-901的高级商业开发提供合理的基础，目的是使该产品成为高危患者CM注射的一线预防药物。

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.