PSMC5基因调控海马神经元-小胶质细胞网络干预阿尔茨海默病的作用环节研究

Microglia activation is one of the causative factors for neuroinflammation, which is associated with the pathophysiology of Alzheimer's disease (AD). Epidemiological studies suggest that inhibition of microglial activation attenuates the severity of neurotoxicity. Inhibition of activated microglia is therefore an important therapeutic target for AD. Our previous study has shown that Luteolin significantly inhibited the expression of iNOS and COX-2 in LPS-induced BV2 microglia. Moreover, the compound down-regulated the proinflammatory cytokines (TNF-α and IL-1β) as well as the production of NO and PGE2 in these cells. when hippocampal neurons were co-cultured with LPS-stimulated BV2 microglia, the administration of 20 μM luteolin increased the neurons viability and reduced the number of apoptotic neurons. However, the mechanism by which luteolin inhibits microglial inflammation is not completely understood. An important signaling system that is affected by the activation of microglia is the nuclear factor κB (NF-κB) pathway. Reports demonstrated that after microglial activation, most NF-κB was bound to an isoform of Inhibitors-of-kappaB, IκBα, which resulted in near complete inhibition of the nuclear localization. The synthesis and degradation rates of IκBα are critical parameters in controlling the signaling of the entire NF-κB module. Therefore, proteolytic destruction of IκBα by the ubiquitin-proteasome system (UPS), a major eukaryotic pathway for regulated protein degradation, plays a key role in the immediate elimination of IκBα from the NF-κB pathway. A key component of the UPS is the multi-subunit enzyme complex, 26S proteasome, which is a major cellular non-liposomal protease. Modulation of the ubiquitin-26S proteasome system (UPS) with proteasome inhibitors has indicated possible efficacy for the treatment of neuro-inflammatory disorders. We used 2-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS) to identify proteins affected by Luteolin in activated microglia. We uncovered that the expression of 26S protease regulatory subunit 8 (PSMC5) was reduced. PSMC5 encodes one of the ATPase subunits, a member of the triple-A family of ATPases which have a chaperone-like activity. PSMC5 is an important regulatory subunit of the ubiquitin - proteasome pathway , and can activate the expression of inflammatory genes, but its molecular mechanisms remain elusive. According to the pre-experimental results, we speculate that the regulation of the expression of PSMC5 may become a potential target for prevention and treatment of AD. Taken together, we clarify that the regulation of the expression of PSMC5 induced the inhibition of nuclear factor-kappa B activation by vitro and in vivo experiments which can lead to a lower level of pro-inflammatory cytokines, and this molecular mechanisms play an important role in the AD. Thus, we provide new perspective and target of the prevention and treatment of AD.

脑内小胶质细胞的过度活化引起的神经炎症是阿尔茨海默病（AD）的重要发病机制之一。通过抑制/减轻神经炎症反应,维持海马神经元-小胶质细胞神经网络的平衡成为防治AD的一个有效新策略。我们前期研究发现：木犀草素可通过抑制TLR-4介导的NF-κB通路的激活，减轻神经炎症从而实现对海马神经元的保护。我们进一步运用蛋白质组学技术研究发现：木犀草素可抑制PSMC5的表达，PSMC5是泛素-蛋白酶体途径重要的调节亚基，可启动相关炎症基因的表达，但其作用的分子机制尚未清楚。结合预实验结果我们提出假说：调控PSMC5基因可能是干预AD的一个潜在治疗靶点。因此，我们拟通过体内、外实验，阐明通过抑制PSMC5的表达，抑制NF-κB的活化后可抑制小胶质细胞的活化，从而调控海马神经元-小胶质细胞神经网络的平衡，改善和阻断AD疾病的进展。这将为AD的防治提供全新的靶点并为研发天然、安全的抗AD药物提供重要的理论基础。

脑内小胶质细胞的过度活化引起的神经炎症是阿尔茨海默病（AD）的重要发病机制之一。通过抑制/减轻神经炎症反应,维持海马神经元-小胶质细胞神经网络的平衡成为防治AD的一个有效新策略。体外实验，证实下调PSMC5的表达通过抑制TLR-4介导的MyD 88依赖的泛素化的IκBα的降解来调控NF-κB的活化，从而减少LPS诱导BV2小胶质细胞炎症细胞因子的释放，进而减轻神经炎症反应。体内实验，证实下调PSMC5的表达可以抑制由LPS诱导的小鼠学习记忆损伤，并减少其引起的促炎因子的释放，增加其抑炎因子的释放。其机制可能是通过作用于TLR-4介导的信号通路的激活。阐明抑制PSMC5的表达，可调控海马神经元-小胶质细胞神经网络的平衡，改善和阻断AD疾病的进展。这将为AD的防治提供全新的靶点并为研发天然、安全的抗AD药物提供重要的理论基础。