Abstract：
The restoration of cerebral blood flow (CBF) to achieve brain tissue oxygenation (PbtO2) is the primary treatment for ischemic stroke, a significant cause of adult mortality and disability worldwide. Nitric oxide (NO) and its bioactive s-nitrosylated (SNO) reservoirs, such as s-nitrosoglutathione (GSNO), induce hypoxic vasodilation to enhance CBF during ischemia. The endogenous pool of SNOs/GSNO is enhanced via the activation of endothelial NO synthase (eNOS/NOS3) and by the suppression of class III alcohol dehydrogenase 5 (ADH5), also known as GSNO reductase (GSNOR). Remote ischemic conditioning (RIC), which augments NOS3 activity and SNO, is an emerging therapy in acute stroke. However, RIC has so far shown neutral effects in stroke clinical trials. As the majority of stroke patients are presented with endothelial dysfunctions and comorbidities, we tested the hypothesis that NOS3 dysfunction and diabetes will abolish the protective effects of RIC therapy in stroke, and the prior inhibition of GSNOR will turn RIC protective. Our data demonstrate that RIC during thrombotic stroke failed to enhance the CBF and the benefits of thrombolysis in NOS3 mutant (NOS3+/-) mice, a genetic model of NOS3 dysfunction. Interestingly, thrombotic stroke in diabetic mice enhanced the activity of GSNOR as early as 3 h post-stroke without decreasing the plasma nitrite (NO2-). In thrombotic stroke, neither a pharmacological inhibitor of GSNOR (GRI) nor RIC therapy alone was protective in diabetic mice. However, prior treatment with GRI followed by RIC enhanced the CBF and improved recovery. In a reperfused stroke model, the GRI-RIC combination therapy in diabetic mice augmented PbtO2, a translatory signature of successful microvascular reflow. In addition, RIC therapy unexpectedly increased the inflammatory markers at 6 h post-stroke in diabetic stroke that were downregulated in combination with GRI while improving the outcomes. Thus, we conclude that preexisting NOS3 dysfunctions due to comorbidities may neutralize the benefits of RIC in stroke, which can be turned protective in combination with GRI. Our findings may support the future clinical trial of RIC in comorbid stroke. Further studies are warranted to test and develop SNO reservoirs as the blood-associated biomarker to monitor the response and efficacy of RIC therapy in stroke.
摘要：
恢复脑血流量(CBF)以实现脑组织氧合(PbtO2)是缺血性脑卒中的主要治疗方法,全球成人死亡和残疾的重要原因。一氧化氮（NO）及其生物活性S-亚硝基化（SNO）储层，如s-亚硝基谷胱甘肽(GSNO)，在缺血期间诱导低氧血管舒张以增强CBF。通过激活内皮NO合酶（eNOS/NOS3）和抑制III类醇脱氢酶5（ADH5）来增强SNO/GSNO的内源性库，也称为GSNO还原酶（GSNOR）。远程缺血适应(RIC),这增加了NOS3活性和SNO，是急性中风的新兴疗法。然而,迄今为止，RIC在中风临床试验中显示出中性效果。由于大多数中风患者存在内皮功能障碍和合并症，我们检验了以下假设：NOS3功能障碍和糖尿病将消除RIC治疗在中风中的保护作用，和GSNOR的先前抑制将变成RIC保护。我们的数据表明，血栓性卒中期间的RIC未能增强NOS3突变（NOS3+/-）小鼠的CBF和溶栓益处，NOS3功能障碍的遗传模型。有趣的是,糖尿病小鼠的血栓性卒中早在卒中后3小时就增强了GSNOR的活性，而不降低血浆亚硝酸盐（NO2-）。在血栓性中风中，GSNOR(GRI)的药物抑制剂和单独的RIC治疗对糖尿病小鼠均无保护作用.然而,之前用GRI和RIC治疗可提高CBF并改善恢复.在再灌注笔划模型中，糖尿病小鼠的GRI-RIC联合治疗可增强PbtO2,这是成功的微血管复流的翻译特征.此外,RIC治疗出乎意料地增加了糖尿病卒中患者卒中后6小时的炎症标志物，这些标志物与GRI联合下调，同时改善了预后。因此，我们得出的结论是，由于合并症而预先存在的NOS3功能障碍可能会抵消RIC在卒中中的益处，可以与GRI结合使用。我们的发现可能支持RIC在合并症中风中的未来临床试验。需要进一步的研究来测试和开发SNO储库作为血液相关的生物标志物，以监测RIC治疗在中风中的反应和功效。
