Zhang Heng, Jia Longfei, Jia Jianping
Innovation Center for Neurological Disorders and Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing, China.
Beijing Key Laboratory of Geriatric Cognitive Disorders, Beijing, China.
Front Neurol. 2020 Jul 17;11:623. doi: 10.3389/fneur.2020.00623. eCollection 2020.
Alzheimer's disease (AD) is characterized by amyloid beta (Aβ) accumulation in the brain, which triggers the activation of microglia; in turn, microglia release neuroinflammatory factors capable of damaging neurons. Thus, a therapeutic approach targeting this sustained microglia-induced inflammatory response deserves investigation. Here, we examined whether oxiracetam (ORC), a nootropic of the racetam family, can indirectly prevent Aβ-induced neurotoxicity by attenuating microglial activation. Aβ42 oligomers were used to stimulate BV2 microglial cells, and the morphological changes and phagocytic capacity of BV2 cells were evaluated using fluorescence microscopy. We used quantitative reverse transcription polymerase chain reaction to assess the inhibitory effects of ORC on Aβ-induced mRNA levels of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α); enzyme-linked immunosorbent assay was used to examine the productions of these cytokines. We also assessed the mRNA level of inducible nitric oxide synthase and the production of nitric oxide (NO). The conditioned medium from BV2 cells was used to culture hippocampal HT22 cells to assess indirect toxicity using the MTT assay. ORC prevented the Aβ-induced activation of BV2 cells, as reflected by reduced morphological changes and phagocytic ability. In addition, ORC downregulated the expression of Aβ-induced cytokines (IL-1β, IL-6, and TNF-α) and the production of NO in BV2 cells. Furthermore, ORC protected HT22 cells from indirect damage evoked by Aβ-treated BV2 cell-conditioned medium, but not from direct Aβ-induced toxicity. ORC suppressed the activation of BV2 cells, decreased the production of Aβ-induced inflammatory molecules and NO in BV2 cells, and protected HT22 cells against indirect toxicity mediated by Aβ-treated BV2 cell-conditioned medium. Thus, ORC may exert a protective role in AD through attenuating the damage caused by inflammation and oxidative stress.
阿尔茨海默病（AD）的特征是大脑中β淀粉样蛋白（Aβ）的积累，这会触发小胶质细胞的激活；反过来，小胶质细胞会释放能够损害神经元的神经炎症因子。因此，针对这种由小胶质细胞持续诱导的炎症反应的治疗方法值得研究。在这里，我们研究了吡拉西坦家族的益智药奥拉西坦（ORC）是否可以通过减弱小胶质细胞的激活来间接预防Aβ诱导的神经毒性。使用Aβ42寡聚体刺激BV2小胶质细胞，并通过荧光显微镜评估BV2细胞的形态变化和吞噬能力。我们使用定量逆转录聚合酶链反应来评估ORC对Aβ诱导的白细胞介素-1β（IL-1β）、IL-6和肿瘤坏死因子-α（TNF-α）mRNA水平的抑制作用；酶联免疫吸附测定法用于检测这些细胞因子的产生。我们还评估了诱导型一氧化氮合酶的mRNA水平和一氧化氮（NO）的产生。使用BV2细胞的条件培养基培养海马HT22细胞，以通过MTT测定法评估间接毒性。ORC可预防Aβ诱导的BV2细胞激活，这表现为形态变化和吞噬能力降低。此外，ORC下调了Aβ诱导的细胞因子（IL-1β、IL-6和TNF-α）的表达以及BV2细胞中NO的产生。此外，ORC保护HT22细胞免受Aβ处理的BV2细胞条件培养基引起的间接损伤，但不能保护其免受直接Aβ诱导的毒性。ORC抑制BV2细胞的激活，降低BV2细胞中Aβ诱导的炎症分子和NO的产生，并保护HT22细胞免受Aβ处理的BV2细胞条件培养基介导的间接毒性。因此，ORC可能通过减轻炎症和氧化应激造成的损伤在AD中发挥保护作用。
