Department of Biochemistry, University of Allahabad, Allahabad, 211002, India.
Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA.
Mol Neurobiol. 2017 Oct;54(8):5815-5828. doi: 10.1007/s12035-016-0129-3. Epub 2016 Sep 22.
Autophagy is a catabolic process involved in the continuous removal of toxic protein aggregates and cellular organelles to maintain the homeostasis and functional integrity of cells. The mechanistic understanding of autophagy mediated neuroprotection during the development of neurodegenerative disorders remains elusive. Here, we investigated the potential role of rapamycin-induced activation of autophagy and PI3K/Akt1/mTOR/CREB pathway(s) in the neuroprotection of amyloid-beta (Aβ1-42)-insulted hippocampal neurons in rat model of Alzheimer's disease (AD) like phenotypes. A single intra-hippocampal injection of Aβ1-42 impaired redox balance and markedly induced synaptic dysfunction, neurotransmission dysfunction, and cognitive deficit, and suppressed pro-survival signaling in the adult rats. Rapamycin administration caused a significant reduction of mTOR complex 1 phosphorylation at Ser2481 and a significant increase in levels of autophagy markers such as microtubule-associated protein-1 light chain-3 (LC3), beclin-1, sequestosome-1/p62, unc-51-like kinase 1 (ULK1). In addition, rapamycin induced the activation of autophagy that further activated p-PI3K, p-Akt1 (Ser473), and p-CREB (Ser183) expression in Aβ1-42-treated rats. The activated autophagy markedly reversed Aβ1-42-induced impaired redox homeostasis by decreasing the levels of prooxidants-ROS generation, intracellular Ca flux and LPO, and increasing the levels of antioxidants-SOD, catalase, and GSH. The activated autophagy also provided significant neuroprotection against Aβ1-42-induced synaptic dysfunction by increasing the expression of synapsin-I, synaptophysin, and PSD95; and neurotransmission dysfunction by increasing the levels of CHRM2, DAD2 receptor, NMDA receptor, and AMPA receptor; and ultimately improved cognitive ability in rats. Wortmannin administration significantly reduced the expression of autophagy markers, p-PI3K, p-Akt1, and p-CREB, as well as the autophagy mediated neuroprotective effect. Our study demonstrate that autophagy can be an integrated part of pro-survival (PI3K/Akt1/mTOR/CREB) signaling and autophagic activation restores the oxidative defense mechanism(s), neurodegenerative damages, and maintains the integrity of synapse and neurotransmission in rat model of AD.
自噬是一种参与持续清除有毒蛋白聚集体和细胞细胞器的分解代谢过程，以维持细胞的内稳态和功能完整性。在神经退行性疾病发展过程中，自噬介导的神经保护的机制理解仍然难以捉摸。在这里，我们研究了雷帕霉素诱导的自噬激活和 PI3K/Akt1/mTOR/CREB 通路在阿尔茨海默病（AD）样表型大鼠模型中海马神经元中对淀粉样β（Aβ1-42）损伤的神经保护中的潜在作用。单次海马内注射 Aβ1-42 会破坏氧化还原平衡，并显著诱导突触功能障碍、神经传递功能障碍和认知缺陷，并抑制成年大鼠中的促生存信号。雷帕霉素给药导致 mTOR 复合物 1 在 Ser2481 处的磷酸化显著减少，并且自噬标记物（例如微管相关蛋白 1 轻链 3（LC3）、beclin-1、自噬相关蛋白 1/62（p62）、UNC-51 样激酶 1（ULK1））的水平显著增加。此外，雷帕霉素诱导的自噬激活进一步激活了 Aβ1-42 处理大鼠中的 p-PI3K、p-Akt1（Ser473）和 p-CREB（Ser183）的表达。激活的自噬通过降低促氧化剂-ROS 生成、细胞内 Ca 流和 LPO 的水平，以及增加抗氧化剂-SOD、过氧化氢酶和 GSH 的水平，显著逆转了 Aβ1-42 诱导的氧化还原稳态受损。激活的自噬还通过增加突触素-I、突触小泡蛋白和 PSD95 的表达提供了对 Aβ1-42 诱导的突触功能障碍的显著神经保护作用；通过增加 CHRM2、DAD2 受体、NMDA 受体和 AMPA 受体的水平，提供了对神经传递功能障碍的神经保护作用；并最终改善了大鼠的认知能力。渥曼青霉素给药显著降低了自噬标记物、p-PI3K、p-Akt1 和 p-CREB 的表达，以及自噬介导的神经保护作用。我们的研究表明，自噬可以是促生存（PI3K/Akt1/mTOR/CREB）信号的一个综合部分，自噬的激活恢复了氧化防御机制，减轻了神经退行性损伤，并维持了 AD 大鼠模型中突触和神经传递的完整性。
