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有力地表明血脑屏障(BBB) 烟草烟雾(TS)造成的损害和中风风险增加在很大程度上是由于常见的 氧化应激(OS)、炎症和内源性抗氧化剂变化等关键调节因子 反应系统(ARE)受核因子红系相关因子2(NRF2)的调节。临床前研究 还表明尼古丁(电子烟中使用的主要电子液体成分)也会导致OS， 加重脑缺血和继发性脑损伤。我们实验室的初步数据 提供的证据同样适用于TS；慢性电子烟(e-Cig)蒸发可促进BBB完整性的丧失 和血管炎症，并作为中风发病和后遗症恶化的危险因素 缺血性脑损伤。此外，最近的报道显示，二甲双胍(MF)治疗前后 缺血损伤可减轻应激，抑制炎症反应。本赠款中提供的初步数据 提示MF促进Nrf2介导的对抗机制，从而显著降低TS的毒性 在大脑和脑血管层面，同时保护血脑屏障的完整性。我们在体内提供了额外的 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e-Cig汽化促进的脑缺血后损伤。我们认为MF可能是 重新调整用途以预防/减少TS和e-Cig暴露造成的血脑屏障损害和随后的中风损伤 长期吸烟者/烟雾。因此，我们的研究目标是： 1)评估和验证MF保护脑微血管的分子机制 TS/e-Cig的血脑屏障包括缺血/再灌注(IR)损伤。我们将通过解开分子靶标 哪种MF能积极影响血脑屏障，减轻缺血性中风和脑血管疾病的负担 长期吸烟者和蒸气的损害。 2)体内评价预防性给药与治疗性给药(缺血后)的效果 二甲双胍减轻TS/e-Cig诱导的脑血管损伤和/或缺血后神经元的作用 损坏。体内研究将确定血脑屏障转运和中枢神经系统进入MF的机制，以及 主要缺血性损伤终点；包括梗塞和水肿量、组织学终点和 中风后的行为恢复。最终，我们将描述MF的疗效和治疗时间窗口 用于治疗暴露在TS或e-Cig蒸气中的小鼠的中风。

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.