Excessive light exposure is a detrimental environmental factor that plays a critical role in the pathogenesis of retinal degeneration. However, the mechanism of light-induced death of retina/photoreceptor cells remains unclear. The mammalian/mechanistic target of rapamycin (mTOR) and Poly (ADP-ribose) polymerase-1 (PARP-1) have become the primary targets for treating many neurodegenerative disorders. The aim of this study was to elucidate the mechanisms underlying light-induced photoreceptor cell death and whether the neuroprotective effects of mTOR and PARP-1 inhibition against death are mediated through apoptosis-inducing factor (AIF). Propidium iodide (PI)/Hoechst staining, lentiviral-mediated short hairpin RNA (shRNA), Western blot analysis, cellular fraction separation, plasmid transient transfection, laser confocal microscopy, a mice model, electroretinography (ERG), and hematoxylin-eosin (H & E) staining were employed to explore the mechanisms by which rapamycin/3-Aminobenzamide (3AB) exert neuroprotective effects of mTOR/PARP-1 inhibition in light-injured retinas. A parthanatos-like death mechanism was evaluated in light-injured 661 W cells that are an immortalized photoreceptor-like cell line that exhibit cellular and biochemical feature characteristics of cone photoreceptor cells. The death process featured over-activation of PARP-1 and AIF nuclear translocation. Either PARP-1 or AIF knockdown played a significantly protective role for light-damaged photoreceptors. More importantly, crosstalk was observed between mTOR and PARP-1 signaling and mTOR could have regulated parthanatos via the intermediate factor sirtuin 1 (SIRT1). The parthanatos-like injury was also verified in vivo, wherein either PARP-1 or mTOR inhibition provided significant neuroprotection against light-induced injury, which is evinced by both structural and functional retinal analysis. Overall, these results elucidate the mTOR-regulated parthanatos death mechanism in light-injured photoreceptors/retinas and may facilitate the development of novel neuroprotective therapies for retinal degeneration diseases. Our results demonstrate that inhibition of the mTOR/PARP-1 axis exerts protective effects on photoreceptors against visible-light–induced parthanatos. These protective effects are conducted by regulating the downstream factors of AIF, while mTOR possibly interacts with PARP-1 via SIRT1 to regulate parthanatos. Schematic diagram of mTOR interacting with PARP-1 to regulate visible light-induced parthanatos. Increased ROS caused by light exposure penetrates the nuclear membrane and causes nuclear DNA strand breaks. PARP-1 detects DNA breaks and synthesizes PAR polymers to initiate the DNA repair system that consumes a large amount of cellular NAD+. Over-production of PAR polymers prompts the release of AIF from the mitochondria and translocation to the nucleus, which leads to parthanatos. Activated mTOR may interact with PARP-1 via SIRT1 to regulate visible light-induced parthanatos.

中文翻译：

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mTOR 可能与 PARP-1 相互作用来调节光感受器中可见光诱导的 parthanatos。

过度光照是一种有害的环境因素，在视网膜变性的发病机制中起着至关重要的作用。然而，光诱导视网膜/感光细胞死亡的机制仍不清楚。雷帕霉素（mTOR）和聚（ADP-核糖）聚合酶-1（PARP-1）的哺乳动物/机械靶标已成为治疗许多神经退行性疾病的主要靶标。本研究的目的是阐明光诱导感光细胞死亡的机制，以及 mTOR 和 PARP-1 抑制死亡的神经保护作用是否是通过凋亡诱导因子 (AIF) 介导的。碘化丙啶 (PI)/Hoechst 染色、慢病毒介导的短发夹 RNA (shRNA)、蛋白质印迹分析、细胞级分分离、质粒瞬时转染、激光共聚焦显微镜、小鼠模型、视网膜电图 (ERG) 和苏木精-伊红 (H & E) 染色用于探索雷帕霉素/3-氨基苯甲酰胺 (3AB) 在光损伤视网膜中发挥 mTOR/PARP-1 抑制的神经保护作用的机制。在光损伤的 661 W 细胞中评估了类似 parthanatos 的死亡机制，661 W 细胞是一种永生化的光感受器样细胞系，表现出视锥细胞的细胞和生化特征。死亡过程的特点是 PARP-1 和 AIF 核易位的过度激活。PARP-1 或 AIF 敲低对光损伤的光感受器具有显着的保护作用。更重要的是，观察到 mTOR 和 PARP-1 信号之间的串扰，并且 mTOR 可能通过中间因子 Sirtuin 1 (SIRT1) 调节 parthanatos。类似parthanatos的损伤也在体内得到了验证，其中PARP-1或mTOR抑制提供了针对光诱导损伤的显着神经保护作用，这通过视网膜结构和功能分析得到了证实。总体而言，这些结果阐明了光损伤的光感受器/视网膜中 mTOR 调节的 parthanatos 死亡机制，并可能促进针对视网膜变性疾病的新型神经保护疗法的开发。我们的结果表明，抑制 mTOR/PARP-1 轴对光感受器发挥保护作用，防止可见光诱导的 parthanatos。这些保护作用是通过调节AIF的下游因子来实现的，而mTOR可能通过SIRT1与PARP-1相互作用来调节parthanatos。mTOR 与 PARP-1 相互作用调节可见光诱导的 parthanatos 的示意图。光照引起的 ROS 增加会穿透核膜并导致核 DNA 链断裂。PARP-1检测DNA断裂并合成PAR聚合物以启动消耗大量细胞NAD+的DNA修复系统。PAR 聚合物的过量产生促使 AIF 从线粒体释放并易位到细胞核，从而导致 parthanatos。