Dietary targeting of dihydrolipoamide dehydrogenase for stroke tolerance

描述(申请人提供)：新发和复发的中风是美国第三大主要死亡原因和长期残疾的主要原因，但还没有定义有效的内源性目标来预防或减轻中风引起的脑损伤。我们发现线粒体二氢硫酰胺脱氢酶(DLDH)可能是卒中损伤的化学预适应的靶点。因此，该应用的目的是评价DLDH化学预适应的神经保护效果，并阐明其潜在的机制。我们的初步研究表明，当大鼠在4周的饮食中添加特异性和竞争性的DLDH抑制剂5-甲氧基吲哚-2-羧酸(MICA)时，短暂大脑中动脉闭塞(tMCAO，缺血1小时，再灌注24小时)后，脑梗塞体积减少了约60%。这一结果表明，MICA对DLDH的慢性抑制提供了强大的脑保护作用。对未发生卒中的MICA治疗大鼠的进一步研究表明，MICA治疗大鼠的DLDH活性低于对照组，而NAD(P)H：QO1活性显着增加。NQO1是一种可诱导的酶，其表达通过核转录因子E2相关因子2(NRF2)与抗氧化反应元件(ARE)的结合而激活。我们的初步研究还表明，4周的MICA饮食给药不会影响食物摄入量、体重增加、血糖浓度或线粒体呼吸复合体。这些初步结果支持我们的中心假设，即饮食抑制DLDH可诱导持续的脑保护，通过激活NRF2-ARE信号级联，促进缺血性卒中后认知和运动功能的恢复。这项拟议调查的理由是，确定无毒、可透过血脑屏障的化学制剂，对中风提供脑保护，并确定保护机制，将促进此类制剂的开发和临床应用，将人类中风受害者的死亡和残疾降至最低。我们计划检验我们的中心假说，从而通过解决以下三个具体目标来实现这一应用的目标：(1)确定MICA注射和tMCAO后Nrf2核定位和NQO1表达增加的程度，(2)衡量饮食预适应可以在多大程度上产生针对中风的持久神经保护，以及(3)评估MICA饮食和实验性中风对神经行为功能和作为CA1长期增强(LTP)衡量的海马区突触可塑性的影响。预计这项成功完成的研究将提供使用DLDH作为中风治疗靶点的新策略。

DESCRIPTION (provided by applicant): New and recurrent stroke is the third leading cause of death and the leading cause of long-term disability in the United States, yet no effective endogenous targets have been defined to prevent or attenuate stroke-induced brain injury. We have discovered that mitochondrial dihydrolipoamide dehydrogenase (DLDH) could be a target for chemical preconditioning against stroke injury. The objective of this application is thus to evaluate the neuroprotective efficacy of DLDH chemical preconditioning and delineate its underlying mechanisms. Our preliminary studies show that when rats were fed a 4-week diet supplemented with 5-methoxyindole-2- carboxylic acid (MICA), a specific and competitive DLDH inhibitor, brain infarction volume decreased by c. 60% after transient middle cerebral artery occlusion (tMCAO, 1 hr ischemia and 24 hr reperfusion). This result indicates that chronic DLDH inhibition by MICA affords robust cerebroprotection against stroke. Further studies of MICA-treated rats in the absence of stroke indicate that DLDH activity was lower than in control rats whilst NAD(P)H: quinone oxidoreductase-1 (NQO1) activity increased significantly in the MICA-treated rats. NQO1 is an inducible enzyme and its expression is activated by binding of the nuclear transcription factor E2-related factor 2 (Nrf2) to the antioxidant response element (ARE). Our preliminary studies also indicate that 4 weeks' MICA dietary administration did not affect food intake, body weight gain, blood glucose concentration, or mitochondrial respiratory complexes. These preliminary results support our central hypothesis that dietary inhibition of DLDH induces persistent cerebroprotection, affording enhanced recovery of cognitive and locomotor function after ischemic stroke, via activation of the Nrf2-ARE signaling cascade. The rationale for the proposed investigation is that identifying nontoxic, blood brain barrier-permeable chemical agents that afford brain protection from stroke, and defining the protective mechanisms, will foster development and clinical implementation of such agents to minimize death and disability in human victims of stroke. We plan to test our central hypothesis and, thereby, accomplish the objective of this application by addressing the following three Specific Aims: (1) To define the extent to which Nrf2 nuclear localization and NQO1 expression increase following MICA administration and tMCAO, (2) To measure the extent to which dietary preconditioning can produce persistent neuroprotection from stroke, and (3) To evaluate the effects of MICA diet and experimental stroke on neurobehavioral function and hippocampal synaptic plasticity measured as CA1 long-term potentiation (LTP). It is expected that the successfully completed study will provide novel strategies using DLDH as a target for stroke therapeutics.