Cerebral Vascular Redox Regulation in Stroke

翻译后摘要：非洲裔美国人（AA）显示缺血性中风的差距相比，欧洲裔美国人， 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 更严重的中风残疾，更多的中风后并发症，和更慢的恢复。降低中风发病率， 死亡率和先进的治疗方法，以更好地治疗AA与缺血性卒中，提高我们的理解， 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，缺血性卒中中发生氧化还原失衡，氧化剂形成增加， 抑制一氧化氮（NO）信号，这可能是更妥协的AA人口。但 导致缺血性卒中AA患者氧化还原失衡的机制仍然是我们知识的一个主要空白。 我们已经确定了细胞色素b5还原酶3（CYB 5 R3）的一个高频变异存在于AA中， 少数群体（23%的次要等位基因频率），相比之下，白人中不到1%。CYB 5 R3错义变体 赋予苏氨酸至丝氨酸的氨基酸改变（T117 S），导致CYB 5 R3活性降低。测试 为了证实这种变异在缺血性卒中后脑血管功能中的重要性，我们构建了一种新的CYB 5 R3 T117 S鼠模型。初步研究表明CYB 5 R3 T117 S小鼠发生显著更大的梗死， 体积，表明CYB 5 R3 T117 S小鼠更容易受到氧化应激的影响。从机械学上讲，我们的飞行员 研究表明，CYB 5 R3 T117 S作为可溶性鸟苷酸环化酶（sGC）的氧化还原调节剂， 受体的基于这些初步数据，我们假设CYB 5 R3 T117 S通过以下途径引起氧化还原失衡： 损害sGC血红素氧化还原调节，导致恶化的脑血流缺乏和缺血性中风。 提出了三个目的来检验这一假设：目的1）确定是否受损的脑血管功能， Cyb 5 R3 T117 S和SMC Cyb 5 R3 KO小鼠导致更大的脑梗死和更严重的卒中结局，目的 2)确定NO-sGC-cGMP介导的脑血管损伤是否引起脑血管调节障碍， 缺血性卒中后Cyb 5 R3 T117 S小鼠和SMC Cyb 5 R3 KO小鼠的动脉舒张，以及Aim 3)确定sGC激活剂和/或sGC刺激剂治疗是否减少Cyb 5 R3 T117 S中的卒中损伤 和SMC Cyb 5 R3 KO小鼠。这些研究的完成将填补我们在理解 CYB 5 R3 T117 S在缺血性卒中发病机制中的作用，可能开发新的精确策略， 大部分患有缺血性中风的AA患者的治疗。

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.