Cerebral Vascular Redox Regulation in Stroke

摘要：与欧洲裔美国人相比，非洲裔美国人(AA)在缺血性中风方面存在差异， 中风患病率和死亡率高2倍，中年缺血性中风发病率高4倍，以及 更大的中风残疾，更多的中风后并发症，以及更慢的恢复。降低中风发病率和 死亡率和更好地治疗AA合并缺血性中风的先进治疗方法，这是我们对 需要调节氧化应激损伤和脑血流的基本途径。临床前和 临床证据表明，氧化还原失衡发生在缺血性卒中，氧化剂的形成增加和 抑制一氧化氮(NO)信号，这在AA人群中可能更受影响。然而， 导致再生障碍性贫血合并缺血性卒中氧化还原失衡的机制仍然是我们所知的一个主要空白。 我们已经确定在AA中存在细胞色素b5还原酶3(Cyb5R3)的高频变异。 人群(23%的次要等位基因频率)，而白人的这一比例不到1%。这个CyB5R3错义变体 将苏氨酸转变为丝氨酸氨基酸(T117S)，导致CyB5R3活性降低。要测试 这种变异在缺血性卒中后脑血管功能中的重要性，我们产生了一种新的CyB5R3 T117S小鼠模型。初步研究表明，CyB5R3 T117S小鼠发生显著更大的脑梗塞 体积，这表明CYB5R3 T117S小鼠更容易受到氧化应激的影响。从机械上讲，我们的飞行员 研究表明，CyB5R3 T117S是可溶性鸟苷酸环化酶(SGC)的氧化还原调节剂，sGC是一氧化氮 受体。基于这些初步数据，我们假设CyB5R3 T117S通过以下方式导致氧化还原失衡 SGC血红素氧化还原调节受损，导致脑血流不足和缺血性卒中加重。 提出了三个目标来检验这一假设：目标1)确定脑血管功能受损是否在 Cyb5R3 T117S和SMC Cyb5R3 KO小鼠导致更大的脑梗塞和恶化的中风预后，目的 2)确定NO-sGC-cGMP介导的脑血管损伤是否导致脑组织调节失调 Cyb5R3 T117S小鼠和SMC Cyb5R3 KO小鼠缺血性卒中后的动脉松弛 3)确定sGC激活剂和/或sGC刺激剂治疗是否减少了Cyb5R3 T117S的中风损伤 和SMC Cyb5R3 KO小鼠。这些研究的完成将填补我们对 CyB5R3 T117S在缺血性卒中发病机制中的作用，可能开发新的精确策略和 治疗大部分患有缺血性中风的再生障碍性贫血。

Abstract: African Americans (AA) show disparities in ischemic stroke when compared to Euro-Americans, with 2x higher stroke prevalence and mortality, 4x higher incidence of ischemic stroke during middle age, as well as greater stroke disability, more post-stroke complications, and slower recovery. To reduce stroke morbidity and mortality and advance therapies to better treat AA with ischemic stroke, an improvement in our understanding of the basic pathways that regulate oxidative stress damage and cerebral blood flow is needed. Preclinical and clinical evidence suggest that redox imbalance occurs in ischemic stroke, with increased oxidant formation and suppressed nitric oxide (NO) signaling, which may be more compromised in the AA population. However, the mechanisms that contribute to redox imbalance in AA with ischemic stroke remain a major gap in our knowledge. We have identified that a high frequency variant in cytochrome b5 reductase 3 (CYB5R3) exists in the AA population (23% minor allele frequency), compared to less than 1% in whites. This CYB5R3 missense variant confers a threonine to serine amino acid change (T117S) leading to reduced CYB5R3 activity. To test the importance of this variant in cerebral vascular function following ischemic stroke, we generated a novel CYB5R3 T117S murine model. Preliminary studies show that CYB5R3 T117S mice develop significantly greater infarct volume, suggesting that CYB5R3 T117S mice are more vulnerable to oxidative stress. Mechanistically, our pilot studies suggest CYB5R3 T117S serves as a redox regulator of soluble guanylyl cyclase (sGC), the nitric oxide receptor. Based on these preliminary data, we hypothesize that CYB5R3 T117S causes a redox imbalance by impairing sGC heme redox regulation leading to exacerbated cerebral blood flow deficiency and ischemic stroke. Three aims are proposed to test this hypothesis: Aim 1) define whether impaired cerebrovascular function in Cyb5R3 T117S and SMC Cyb5R3 KO mice causes greater brain infarct and worsened stroke outcomes, Aim 2) determine whether NO-sGC-cGMP-mediated cerebral blood vessel damage causes dysregulation of cerebral arterial relaxation in Cyb5R3 T117S mice and SMC Cyb5R3 KO mice after ischemic stroke, and Aim 3) determine whether sGC activator and/or sGC stimulator therapy reduces stroke damage in Cyb5R3 T117S and SMC Cyb5R3 KO mice. Completion of these studies will fill a major gap in our understanding of the role of CYB5R3 T117S in the pathogenesis of ischemic stroke, potentially developing new precision strategies and therapies for a large proportion of AA who suffer from ischemic stroke.