TLR4 antagonists as a therapeutic treatment for APOE-modulated neuroinflammation

描述(申请人提供)：TLR4拮抗剂作为治疗体内APOE调节的神经炎症的药物，多肽淀粉样β蛋白(Abeta)水平升高，特别是可溶性寡聚体Abeta42(OAbeta)，被认为是阿尔茨海默病(AD)的近端原因。OAbeta可以诱导直接的神经毒性，oAbeta和含有Abeta42的不溶性斑块都可以通过从胶质细胞释放促炎性细胞因子来诱导间接的神经毒性。此外，长期的促炎反应可能导致胶质细胞对Abeta的吞噬清除减少。Toll样受体4(Toll Like Receptor 4，TLR4)是先天免疫的基础，由神经元和神经胶质细胞表达，由oAbeta激活，可能在AD的神经炎症特征中起重要作用。然而，体外和体内数据对于抑制TLR4在AD发病中是有益还是有害的数据是相互矛盾的。总体来说，人们关注的焦点是抑制TLR4是否能预防A-�引起的神经炎症，降低Aβ水平，还是增加Aβ水平和神经炎症。然而，目前还没有关于TLR4拮抗剂作为神经炎治疗策略的疗效的数据。阿尔茨海默病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约4倍和15倍。ApoE4可能通过参与Abeta蓄积和神经炎症的机制增加AD的风险，这两种机制都由TLR4拮抗剂调节。我们的初步数据表明，在体内和体外，与APOE3相比，APOE4增加了内毒素诱导的神经炎症。在体外，oAβ对细胞因子分泌的诱导作用更强 载脂蛋白E4而不是载脂蛋白E3，这一反应被TLR4拮抗剂抑制。然而，在表达家族性AD突变的转基因小鼠模型(FAD-TG)中，TLR4抑制的体内效应尚不清楚。在这项建议中，我们将利用新的TLR4拮抗剂，并在体外确定最有效的候选药物(目标1)进行体内试验(目标2)。由于AD患者中APOE4的患病率增加，以及与APOE3相比，他们对治疗干预的不同反应，在也表达人APOE的FAD-TG小鼠中测试治疗方法至关重要。我们开发了这种新的临床前模型，即新型EFAD-TG小鼠，并证明与E3FAD相比，E4FAD小鼠有更大的认知障碍，突触可塑性降低，神经炎症和Abeta病理增加，重要的是，可溶性oAbeta增加。因此，Aim 2将验证我们的假设，即TLR4拮抗剂在预防(4-6个月)和治疗(6-7个月)的范例中使用TLR4拮抗剂治疗EFAD小鼠，抑制Abeta-冥想的APOE调节的神经炎症，并与TLR4激动剂进行比较。总体而言，这第一项研究将为Abeta诱导的神经炎症和APOE4诱导的AD风险背后的新机制(TLR4)提供证据。如果TLR4抑制是一个有效的靶点，那么在体外和EFAD小鼠中确定的药代动力学、药效学、靶点参与和疗效读出将使未来发现或Hit-o-Lead治疗AD的TLR4药物发现项目成为可能。

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 A�-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.