Role of Ceramide-induced Kidney Cell Death in Acute Kidney Injury

描述（由申请人提供）：急性肾损伤（AKI）是一种死亡率很高的毁灭性疾病。凋亡和坏死在AKI中起主要作用，但对其诱导的调节因子缺乏基本的认识。这种差距的持续存在是一个重大问题，因为AKI具有高死亡率，而且很少有治疗干预措施来改变这种疾病的临床病程。长期目标是揭示AKI的机制，以开发新的治疗方法来保护肾脏。神经酰胺调节肾细胞凋亡和坏死，并在几种AKI模型中升高。在肾细胞凋亡和坏死过程中调节神经酰胺产生的因素以及神经酰胺是否导致肾细胞凋亡和坏死细胞死亡是完全未知的。同样，有许多不同的神经酰胺种类和特定神经酰胺种类在AKI中的作用尚未确定。该建议将回答这些问题，以实现开发神经酰胺作为治疗AKI的新治疗方法的目标。初步数据表明：(1)长链神经酰胺（C16 - C20-神经酰胺）在肾细胞凋亡过程中通过从头合成产生，阻断长链神经酰胺的生成可抑制细胞凋亡；（ii）促凋亡BCL-2蛋白BAK是肾细胞凋亡过程中神经酰胺合成酶（CerS）和长链神经酰胺生成的关键调控因子；（iii）酸性鞘磷脂酶（aSMase）在肾细胞坏死中产生超长链神经酰胺（c24 - c26 -神经酰胺）；（iv）肾皮质cer和酸性SMase被激活，特异性神经酰胺在AKI（顺素肾毒性和横纹肌溶解诱导的AKI）啮齿动物模型中升高数倍；(v)给予神经酰胺合成酶抑制剂的小鼠可免受顺铂诱导的AKI。这项不断扩大和发展的工作使我们提出以下假设：肾毒性刺激通过cer和smase介导的途径提高特定种类的肾神经酰胺，诱导肾细胞死亡并最终导致肾衰竭。这个假设将用三个例子来验证

DESCRIPTION (provided by applicant): Acute kidney injury (AKI) is a devastating disease with a high mortality rate. Apoptosis and necrosis play major roles in AKI, but there is a fundamental knowledge gap of the factors regulating their induction in AKI. Continued existence of this gap represents a significant problem as AKI has a high mortality rate and there are very few therapeutic interventions to alter the clinical course of this disease. The long-term goal is t uncover mechanisms involved in AKI for the development of novel therapeutics to protect the kidney. Ceramides regulate apoptosis and necrosis and are elevated in the kidney in several models of AKI. The factors that regulate production of ceramides during kidney apoptosis and necrosis and whether ceramides lead to apoptotic versus necrotic kidney cell death are completely unknown. Likewise, there are many different ceramide species and the roles for particular ceramide species in AKI have not been determined. This proposal will answer these questions to achieve the objective of developing ceramides as novel therapeutic approaches for the treatment of AKI. Preliminary data demonstrate that: (i) long-chain ceramides (C16 - C20- ceramides) are generated via de novo synthesis during kidney cell apoptosis and blocking their generation inhibits apoptosis; (ii) the pro-apoptotic BCL-2 protein BAK is a key regulator of ceramide synthases (CerS) and long-chain ceramide generation during kidney cell apoptosis; (iii) acid sphingomyelinase (aSMase) generated very long-chain ceramides (C24-C26-ceramides) occurs in kidney cell necrosis; (iv) kidney cortical CerS and acid SMase are activated and specific ceramides elevated several-fold in in vivo rodent models of AKI (cisplain nephrotoxicity and rhabdomyolysis-induced AKI); and (v) mice given inhibitors of enzymes responsible for ceramide synthesis are protected from cisplatin-induced AKI. This expanding and developing body of work has led us to propose the following hypothesis: nephrotoxic stimuli elevate specific species of kidney ceramides through CerS and SMase-mediated pathways, inducing kidney cell death and ultimately kidney failure. This hypothesis will be tested with three specific aims: (1) determine the mechanism by which BAK regulates CerS activity and generation of specific long-chain ceramides during kidney cell apoptosis; (2) determine the contribution of SMase-generated ceramide to kidney cell necrosis; and (3) determine the in vivo contribution of CerS and aSMase to cisplatin-induced AKI in mice. The approach is innovative because it will identify the mechanism by which BAK regulates ceramide synthases as well as the specific role of individual ceramide species in vivo in AKI. The proposed research is significant as it advances our current knowledge of mechanisms of kidney cell death AKI. Ultimately such knowledge has the potential to greatly improve the treatment of AKI.