Repurposing Metformin to Offset Stroke Risk and Injury in Comorbid Populations of Smokers

摘要：最近发表的体外和体内研究结果强烈表明血脑屏障（BBB） 烟草烟雾 (TS) 造成的损伤和中风风险增加很大程度上是由于常见的 关键调节剂，如氧化应激 (OS)、炎症和内源性抗氧化物质的改变 反应系统（ARE）受核因子红细胞2相关因子（Nrf2）调节。临床前研究 还表明尼古丁（电子烟中使用的电子液体的主要成分）也会导致操作系统， 加重脑缺血和继发性脑损伤。来自我们实验室的初步数据 向 TS 提供同样的证据；长期吸电子烟 (e-Cig) 会导致血脑屏障完整性丧失 和血管炎症，也是中风发作和术后病情恶化的危险因素。 缺血性脑损伤。此外，最近的报告表明，二甲双胍（MF）治疗前后 缺血性损伤可减轻应激并抑制炎症反应。本次赠款中提供的初步数据 表明 MF 促进 Nrf2 介导的反作用机制，从而大大降低 TS 毒性 在大脑和脑血管水平上，同时保护 BBB 完整性。我们提供额外的体内 有证据表明，MF 可以有效降低中风和炎症的氧化和炎症风险 减轻 TS 和电子烟引起的缺血后脑损伤。我们建议 MF 可以是 重新用于预防/减少 TS 和电子烟暴露造成的 BBB 损伤和随后的中风损伤 长期吸烟者/电子烟者。因此，我们的研究目标是： 1）评估和验证MF保护大脑微血管的分子机制 TS/e-Cig 的 BBB 包括缺血/再灌注 (IR) 损伤。我们将通过以下方式解开分子靶标 MF可对血脑屏障产生积极影响，减轻缺血性中风和脑血管负担 长期吸烟者和吸烟者的损害。 2) 评估体内预防性与治疗性（缺血后）给药的效果 二甲双胍可减少 TS/电子烟促进脑血管损伤和/或缺血后神经元损伤 损坏。体内研究将定义 MF 的 BBB 运输和中枢神经系统进入机制 主要缺血性损伤终点；包括梗塞和水肿体积、组织学终点和 中风后的行为恢复。最终，我们将描述 MF 的功效和治疗时间窗口 用于治疗暴露于 TS 或电子烟蒸汽的小鼠的中风。

Abstract: Recently published in vitro and in vivo findings strongly suggest that blood-brain barrier (BBB) impairment and increased risk for stroke by tobacco smoke (TS) develop largely in response to common key modulators such oxidative stress (OS), inflammation and alterations of the endogenous antioxidative response system (ARE) regulated by the nuclear factor erythroid 2-related factor (Nrf2). Preclinical studies have also shown that nicotine (the principal e-liquid's ingredient used in e-cigarettes) can also cause OS, exacerbation of cerebral ischemia and secondary brain injury. Preliminary data from our laboratories provides evidence that likewise to TS; chronic e-Cigarette (e-Cig) vaping can promote loss of BBB integrity and vascular inflammation as well as act as a risk factor for the onset of stroke and worsening of post- ischemic brain injury. In addition, recent reports have shown that metformin (MF) treatment before and after ischemic injury reduce stress and inhibit inflammatory responses. Preliminary data provided in this grant suggests that MF promotes Nrf2-mediated counteractive mechanisms which drastically reduce TS toxicity at the brain and cerebrovascular levels while protecting BBB integrity. We provide additional in vivo evidence showing that MF can effectively reduce the oxidative and inflammatory risk for stroke and attenuate post-ischemic brain injury promoted by TS and e-Cig vaping. We propose that MF could be repurposed to prevent/reduce BBB damage and subsequent stroke injury by TS and e-Cig exposure in chronic smokers/vapors. Thus, the objectives of our study are: 1) Assess and validate the brain microvascular molecular mechanisms by which MF can protect the BBB from TS/e-Cig including ischemic/reperfusion (IR) injury. We will unravel the molecular target through which MF can positively impact the BBB and reduce the burden of ischemic stroke and cerebrovascular impairments in chronic smokers and vapors. 2) Evaluate in vivo the effect of prophylactic versus therapeutic (post-ischemic) administration of metformin in reducing TS/e-Cig - promoted cerebrovascular impairment and/or post-ischemic neuronal damage. In vivo investigations will define a mechanism of BBB transport and CNS entry for MF along with major ischemic injury endpoints; including infarction and edema volume, histological endpoints and behavioral recovery after stroke. Ultimately, we will characterize MF's efficacy and therapeutic time window for stroke treatment in mice exposed to TS or e-Cig vapor.