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: 10609791
• 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/10609791
• 关键词: Acute; Acute Brain Injuries; Adopted; Aging; Agonist; Animals; Anti-Inflammatory Agents; Antineoplastic Agents; Apical; Arbitration; Attenuated; Bexarotene; Biological; Brain; Brain Ischemia; Caring; Cause of Death; Cells; Cerebral Ischemia; Cerebral cortex; Cerebrum; Chronic; Clinical Treatment; Clinical Trials; Cognitive; Data; Decision Trees; Deterioration; Development; Diagnosis; Disease; Distal; Dose; Elderly; Electrophysiology (science); Equilibrium; Evolution; Exhibits; FDA approved; Foundations; Funding; Future; Gatekeeping; Genetic Transcription; Goals; Guidelines; Histologic; Hospitalization; Hyperactivity; Immune; Immune response; Immune system; Immunosuppression; Impairment; In Vitro; Infiltration; Inflammation; Inflammatory; Inflammatory Response; Injury; Ischemic Brain Injury; Ischemic Stroke; Knock-out; Knockout Mice; Left; Macrophage; 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; Tissues; Titrations; 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; long term recovery; mature animal; military men; military women; monocyte; neuroinflammation; 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.

缺血性中风是导致老年退伍军人死亡和长期残疾的主要原因。众所周知， 卒中后免疫反应对缺血性脑损伤和脑损伤的进展有重要影响 恢复，但还没有临床治疗方法能成功地利用免疫的恢复能力 系统，同时也缓和炎症引起的二次损伤。造成这种差距的原因是多方面的， 但包括对年轻成年动物的临床前过度强调，这一点并不相同 老年脑缺血的病理生理机制，包括动态炎症 神经胶质细胞和神经元之间的对话。我们建议将重点放在老年人身上，以填补老年退伍军人护理的关键空白 动物和改变FDA批准的低剂量药物的用途以纠正过度活跃的免疫反应和TIP 这种平衡有利于持续的组织愈合和神经功能的长期恢复。 为了实现这一目标，我们对小胶质细胞中高度浓缩的蛋白质进行了初步研究。 和脑浸润性巨噬细胞(Mi/MΦ)--包括维甲酸X受体(RxR)。RXR与过氧化物酶体结合 增殖物激活受体γ(PPARγ)调控与氧化还原状态密切相关的基因转录， 炎症消解、营养因子产生和新陈代谢。因此，RXR/PPARγ的激活处于顶端 用于在Mi和MΦ的多态、经常相反的免疫反应之间进行仲裁的决策树。至 为了达到这个重要的生物靶点，我们选择了一种选择性的RXR激动剂，贝沙罗汀，FDA批准的 抗肿瘤药物缺乏泛免疫抑制作用，具有良好的安全性。科学的 RXR/PPARγ轴作为中风的优越生物靶点的前提是它的能力 使免疫平衡向抗炎/促修复表型倾斜，同时避免不加区别地 脆弱老年人的免疫功能受到抑制。 我们的新初步发现也加强了这一建议的前提：1)特定于Mi/MΦ RXR或PPARγ的条件性敲除会恶化永久远中位术后的长期结果 小鼠脑动脉阻塞(DMCAO)模型。2)RXR或PPARγMKO小鼠在卒中后表现出损害 胞吐作用(死亡神经元的Mi/MΦ吞噬作用)和神经炎的消退。3)PPARγMKO改变 Mi/MΦ转录组，促炎症反应增强，吞噬功能受损，根据 RNA测序数据。4)令人兴奋的是，小剂量的贝沙罗汀(低10-20倍) 与临床试验相比)改善了老年小鼠(20个月大)dMCAO后的长期结果。因此，我们的 研究小组现在处于一个很好的位置来检验以下核心假设：激活RXR可以改善 通过促进泡腾和消炎，促进缺血性卒中后的长期预后 修复小胶质细胞/巨噬细胞反应。如果获得资金，我们将及时和有效地实现三个目标： 目的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个月龄)中风小鼠，雌雄不拘。 目的2：验证贝沙罗汀促进Mi/MΦ中的泡腾作用并减轻急性 通过激活RXR引起的缺血性脑损伤。 目的3：检验Mi/MΦ增强消炎、促修复作用的假设 贝克沙罗汀提供的、RXR依赖的对抗中风的长期有益效果。 我们将使用老年男女受试者，并部署最先进的工具，如细胞特异性、条件性 RXR基因敲除、电生理测量、体视学计数和一组已建立的行为 测试以获得对Mi/MΦ在中风进化中的作用的新的机械学见解。一个被严格证实的 贝沙罗汀对老龄小鼠的有益作用将促进其临床转化为潜在的中风治疗 适用于男女军人以及老年平民。