Activation of the RXR/PPARγ axis improves long-term outcomes after ischemic stroke in aged mice

RXR/PPARγ 轴的激活可改善老年小鼠缺血性中风后的长期结果

• 批准号: 10364171
• 负责人: Jun Chen
• 金额: --
• 依托单位: VETERANS HEALTH ADMINISTRATION
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-01-01 至 2025-12-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10364171
• 关键词: Acute; Acute Brain Injuries; Adopted; Aging; Agonist; Animals; Anti-Inflammatory Agents; Antineoplastic Agents; Arbitration; Attenuated; Bexarotene; Biological; Body Size; Brain; Brain Ischemia; Caring; Cause of Death; Cells; Cerebral Ischemia; Cerebral cortex; Cerebrum; Chronic; Clinical Treatment; Clinical Trials; Cognitive; Data; Decision Trees; Development; Diagnosis; Disease; Distal; Dose; Elderly; Electrophysiology (science); Equilibrium; Evolution; Exhibits; FDA approved; Foundations; Funding; Future; Gatekeeping; Genetic Transcription; Goals; Guidelines; Histologic; Hyperactivity; Immune; Immune response; Immune system; Immunosuppression; Impairment; In Vitro; Inflammation; Inflammatory; Inflammatory Response; Injury; Ischemic Brain Injury; Ischemic Stroke; Knock-out; Left; Measurement; Metabolism; Microglia; Middle Cerebral Artery Occlusion; Modeling; Molecular; Mus; Nature; Nerve Fibers; Nervous System Physiology; Neuroglia; Neurologic Deficit; Neurological outcome; Neurons; Outcome; Oxidation-Reduction; PPAR gamma; Phagocytes; Phagocytosis; Pharmaceutical Preparations; Phenotype; Pilot Projects; Positioning Attribute; Primary Cell Cultures; Production; Proteins; RXR; Recovery; Recovery of Function; Research; Resolution; Role; Safety; Solid; Stroke; Survivors; Tamoxifen; Testing; Therapeutic; Time; Tissues; Veterans; aged; angiogenesis; behavior test; brain repair; central nervous system injury; clinical translation; clinically relevant; conditional knockout; disability; functional disability; functional outcomes; gray matter; healing; immune function; improved; in vitro testing; in vivo; insight; intraperitoneal; macrophage; mature animal; military men; military women; monocyte; neuroinflammation; neurological recovery; neuroprotection; new therapeutic target; novel; post stroke; pre-clinical; primary outcome; receptor binding; repaired; response; sex; stroke model; stroke outcome; stroke recovery; stroke therapy; tool; transcriptome; transcriptome sequencing; white matter; young adult

Ischemic stroke is a leading cause of death and long-term disability in elderly veterans. It is well established that post-stroke immune responses have a substantial impact on the progression of ischemic brain injury and brain recovery, but there are no clinical treatments that successfully harness the restorative power of the immune system while also tempering inflammation-induced secondary injuries. The reasons for this gap are multifactorial, but include a preclinical overemphasis on young adult animals, which simply do not display the same pathophysiological mechanisms underlying brain ischemia as the aged, including the dynamic inflammatory dialogue between glia and neurons. We propose to fill the critical gap in elderly veteran care by focusing on aged animals and repurposing an FDA-approved drug at low doses to correct hyperactive immune responses and tip the balance in favor of sustained tissue healing and long-term recovery of neurological functions. To commence this goal, we have conducted pilot studies on proteins that are highly enriched in microglia and brain-infiltrating macrophages (Mi/MΦ)—including the retinoid X receptor (RXR). RXR binds to peroxisome proliferator-activated receptor γ (PPARγ) to govern the transcription of genes critically involved in redox status, inflammation resolution, trophic factor production, and metabolism. Thus, RXR/PPARγ activation lies at the apex of a decision tree for arbitrating between polymorphic, often-opposing immune responses in Mi and MΦ. To engage this important biological target, we have chosen a selective RXR agonist, bexarotene, an FDA-approved antineoplastic agent lacking in pan-immunosuppressive effects and with excellent safety profiles. The scientific premise underlying the engagement of the RXR/PPARγ axis as a superior biological target for stroke is its ability to titrate immune balance toward anti-inflammatory/pro-repair phenotypes, while avoiding indiscriminate suppression of immune function in the vulnerable elderly. The premise of this proposal is also strengthened by our new preliminary discoveries: 1) Mi/MΦ-specific conditional knockout (mKO) of RXR or PPARγ worsens long-term outcomes after permanent distal middle cerebral artery occlusion (dMCAO) in mice. 2) RXR or PPARγ mKO mice exhibit impairments in post-stroke efferocytosis (Mi/MΦ phagocytosis of dying neurons) and resolution of neuroinflammation. 3) PPARγ mKO alters the Mi/MΦ transcriptome, with heightened proinflammatory responses and impaired phagocytosis according to RNA sequencing data. 4) Excitingly, intraperitoneal administration of low-dose bexarotene (10-20 times lower than in clinical trials) improves long-term outcomes after dMCAO in aged mice (20 months old). Accordingly, our research group is now in an excellent position to test the following core hypothesis: Activation of RXR improves long-term outcomes after ischemic stroke by promoting efferocytosis and inflammation-resolving, pro- repair microglial/macrophage responses. If funded, we will tackle three aims in a timely and efficient manner: Aim 1: Systematically test if bexarotene improves long-term histological and functional outcomes in aged (20 months old) stroke mice of both sexes. Aim 2: Test the subhypothesis that bexarotene promotes efferocytosis in Mi/MΦ and attenuates acute ischemic brain injury via activation of RXR. Aim 3: Test the subhypothesis that enhanced inflammation-resolving, pro-repair actions of Mi/MΦ contribute to bexarotene-afforded, RXR-dependent long-term beneficial effects against stroke. We will use aged subjects of both sexes and deploy state-of-the-art tools, such as cell-specific, conditional RXR knockout, electrophysiological measurements, stereological counting, and a battery of established behavior tests to gain novel mechanistic insights into the role of Mi/MΦ in stroke evolution. A rigorously confirmed beneficial effect of bexarotene on aged mice would facilitate its clinical translation into a potential stroke therapy for military men and women as well as elderly civilians.

众所周知，缺血性中风是老年退伍军人死亡和长期残疾的主要原因。 中风后免疫反应对缺血性脑损伤和脑损伤的进展有重大影响 恢复，但没有临床治疗方法可以成功利用免疫的恢复能力 系统同时也缓和炎症引起的继发性损伤 造成这种差距的原因是多因素的， 但包括对年​​轻成年动物的临床前过分强调，这些动物根本没有表现出相同的特征 老年脑缺血的病理生理机制，包括动态炎症 我们建议通过关注老年人来填补老年退伍军人护理的关键空白。 动物并重新利用 FDA 批准的低剂量药物来纠正过度活跃的免疫反应和提示 有利于组织持续愈合和神经功能长期恢复的平衡。 为了实现这一目标，我们对小胶质细胞中高度富集的蛋白质进行了初步研究 和脑浸润巨噬细胞 (Mi/MΦ)——包括与过氧化物酶体结合的视黄醇 X 受体 (RXR)。 增殖物激活受体γ（PPARγ）控制与氧化还原状态关键相关的基因的转录， 炎症消退、营养因子产生和代谢因此，RXR/PPARγ 激活位于顶点。 用于在 Mi 和 MΦ 中的多态性、经常相反的免疫反应之间进行仲裁的决策树。 为了参与这一重要的生物靶点，我们选择了一种选择性 RXR 激动剂贝沙罗汀，这是一种 FDA 批准的药物 缺乏泛免疫抑制作用且安全性优良的抗肿瘤药物。 RXR/PPARγ 轴作为中风的优越生物靶标的参与的前提是它的能力 向抗炎/促修复表型滴定免疫平衡，同时避免不加区别 抑制易受伤害的老年人的免疫功能。 我们新的初步发现也强化了该提议的前提：1）Mi/MΦ 特定 RXR 或 PPARγ 的条件性敲除 (mKO) 会导致永久性远端中段术后长期预后恶化 小鼠脑动脉闭塞 (dMCAO) 2) RXR 或 PPARγ mKO 小鼠在中风后表现出损伤。 胞吞作用（Mi/MΦ 吞噬濒临死亡的神经元）和神经炎症的消退 3) PPARγ mKO 改变。 Mi/MΦ 转录组，根据哮喘促炎症反应和吞噬作用受损 RNA 测序数据。令人兴奋的是，低剂量贝沙罗汀腹腔注射（低 10-20 倍） 比临床试验中的结果）改善了老年小鼠（20 个月大）的 dMCAO 后的长期结果。 研究小组现在处于测试以下核心假设的绝佳位置：RXR 的激活改善了 通过促进胞吞作用和炎症消退，促进缺血性中风后的长期结果 如果获得资助，我们将及时有效地实现三个目标： 目标 1：系统测试贝沙罗汀是否能改善老年人的长期组织学和功能结果 （20个月大）男女中风小鼠。 目标 2：检验贝沙罗汀促进 Mi/MΦ 中的胞吞作用并减弱急性胞吞作用的子假设 RXR 激活导致缺血性脑损伤。 目标 3：检验 Mi/MΦ 增强炎症消解和促修复作用的子假设 贝沙罗汀提供的、RXR 依赖性的抗中风长期有益作用。 我们将使用老年受试者，并部署最先进的工具，例如细胞特异性、条件性的 RXR 敲除、电生理测量、体视计数和一系列既定行为 测试以获得关于 Mi/MΦ 在中风演变中的作用的新机制见解。 贝沙罗汀对老年小鼠的有益作用将有助于其临床转化为潜在的中风疗法 适合军人和老年平民。