TLR4 antagonists as a therapeutic treatment for APOE-modulated neuroinflammation

描述（由申请人提供）：TLR4拮抗剂作为apoe调节的体内神经炎症的治疗性治疗，肽淀粉样蛋白（Abeta）水平升高，特别是可溶性低聚物Abeta42 (oAbeta)，被认为是阿尔茨海默病（AD）的近端原因。oAbeta可诱导直接神经毒性，oAbeta和含有Abeta42的不溶性斑块均可通过胶质细胞释放促炎细胞因子诱导间接神经毒性。此外，长时间的促炎反应可能导致胶质细胞对β的吞噬清除减少。Toll样受体4 （TLR4）是先天免疫的基础，由神经元和胶质细胞表达，被oAbeta激活，因此可能在AD的神经炎症特征中起重要作用。然而，关于抑制TLR4对AD发病是有利还是有害，体外和体内数据存在矛盾。总的关注集中在TLR4抑制是否会阻止a β诱导的神经炎症，降低或增加β水平和神经炎症。然而，目前还没有关于TLR4拮抗剂作为神经炎症治疗策略的疗效的数据。AD的主要遗传风险因素是载脂蛋白E （apoE）的APOE4基因的遗传，与APOE3相比，单等位基因或双等位基因的风险增加了大约4倍和15倍。APOE4可能通过涉及β积累和神经炎症的机制增加AD的风险，这两种机制都是由TLR4拮抗调节的。我们的初步数据表明，在体内和体外，与APOE3相比，APOE4增加了lps诱导的神经炎症。在体外，oAbeta对细胞因子分泌的诱导作用大于

DESCRIPTION (provided by applicant): TLR4 antagonists as a therapeutic treatment for APOE-modulated neuroinflammation in vivo Increased levels of the peptide amyloid beta (Abeta), particularly as soluble oligomeric Abeta42 (oAbeta), are considered the proximal cause of Alzheimer Disease (AD). oAbeta can induce direct neurotoxicity, and both oAbeta and insoluble plaques containing Abeta42 can induce indirect neurotoxicity via pro-inflammatory cytokine release from glia. In addition, a prolonged pro-inflammatory response may result in decreased phagocytic clearance of Abeta by glia. Toll like receptor 4 (TLR4) is fundamental for innate immunity, is expressed by neurons and glia, is activated by oAbeta, and therefore may a significant role in the neuroinflammation characteristic of AD. However, in vitro and in vivo data are conflicting as to whether inhibiting TLR4 is beneficial or detrimental for AD pathogenesis. Overall concern centers on whether TLR4 inhibition will prevent Aβ-induced neuroinflammation and reduce Abeta levels or increase Abeta levels and neuroinflammation. However, there currently are no data on the efficacy of TLR4 antagonists as a therapeutic strategy for neuroinflammation. The primary genetic risk factor for AD is inheritance of the APOE4 gene for apolipoprotein E (apoE), increasing the risk approximately 4- and 15-fold with a single or double allele, compared to APOE3. APOE4 may increase AD risk through mechanisms involving Abeta accumulation and neuroinflammation, both modulated by TLR4 antagonism. Our preliminary data demonstrate that LPS-induced neuroinflammation is increased with APOE4 compared to APOE3 in vivo and in vitro. In vitro, the induction of cytokine secretion by oAbeta is greater with apoE4 than apoE3, a response inhibited by TLR4-antagonism. However, the in vivo effects of TLR4 inhibition are unknown in a transgenic mouse model expressing familial AD mutations (FAD-Tg). In this proposal we will utilize novel TLR4 antagonists and identify the most efficacious candidate in vitro (Aim 1) to test in vivo (Aim 2). Because of the increased prevalence of APOE4 in AD patients and their differential response to therapeutic interventions compared to APOE3, it is critical to test therapeutics in FAD-Tg mice that also expresses human APOE. We have developed this new preclinical model, the novel EFAD-Tg mice, and demonstrate that compared to E3FAD, E4FAD mice have a greater cognitive impairment, decreased synaptic plasticity, and increased neuroinflammation and Abeta pathology, importantly, an increase in soluble oAbeta. Therefore, Aim 2 will test our hypothesis that TLR4 antagonists inhibit Abeta-meditated APOE-modulated neuroinflammation using EFAD mice treated with a TLR4 antagonist in both prevention (4-6 months) and treatment (6-7 months) paradigms, and compared to a TLR4 agonist. Overall this first study, will provide evidence for a novel mechanism (TLR4) underlying both Abeta-induced neuroinflammation and APOE4-induced AD risk. If TLR4 inhibition, which has not received sufficient attention for CNS conditions, is a valid target, the pharmacokinetic, pharmacodynamic, target engagement and efficacy read-outs identified both in vitro and in EFAD mice will enable future hit-finding or hit-o-lead TLR4 drug discovery projects for AD.