Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive degeneration of dopaminergic neurons in the substantia nigra. Oxidative stress has been reported to be closely related to the pathogenesis and worsening of symptoms of PD. One therapeutic strategy is to alleviate neuronal injuries caused by oxidative stress. In this study, we investigated protective effects of royal jelly (RJ) fatty acids and their derivatives on oxidative stress-induced cell death using human neuroblastoma SH-SY5Y cells. 4-Hydroperoxy-2-decenoic acid ethyl ester (HPO-DAEE), a synthesized RJ fatty acid derivative, markedly induced antioxidant enzymes such as heme oxygenase-1 (HO-1). Pretreatment with HPO-DAEE protected against 6-hydroxydopamine (6-OHDA)-induced cell death. NF-E2-related factor 2 (Nrf2), a master regulator of antioxidative responses, plays a key role in the acquisition of resistance to oxidative stress. HPO-DAEE elicited nuclear accumulation of Nrf2 and activated antioxidant response element (ARE), a cis-activating regulatory element, indicating that HPO-DAEE induced expression of antioxidant genes through Nrf2-ARE signaling. Recently, the activating transcription factor-4 (ATF4) has been shown to cooperate with Nrf2 and modulate antioxidant gene expression. We also found that HPO-DAEE promoted phosphorylation of eukaryotic initiation factor 2α (eIF2α), which is an upstream effector of ATF4, and subsequent nuclear accumulation of ATF4. The eIF2α phosphatase inhibitor, salubrinal, augmented HPO-DAEE-induced HO-1 expression and protection against 6-OHDA-induced cell death. These results indicate that HPO-DAEE activates both the Nrf2-ARE and eIF2α-ATF4 pathways. Moreover, ROS generation occurred upon treatment of SH-SY5Y cells with HPO-DAEE, and the antioxidants N-acetylcysteine and glutathione suppressed HPO-DAEE-induced activation of the Nrf2-ARE and eIF2α-ATF4 pathways. Therefore, sublethal oxidative stress caused by HPO-DAEE is likely to activate both these pathways. Taken together, we conclude that HPO-DAEE elicits adaptive responses to oxidative stress through cooperative activation of the Nrf2-ARE and eIF2α-ATF4 pathways.

帕金森氏病（PD）是一种神经退行性疾病，其特征是黑质中多巴胺能神经元的进行性退化。据报道氧化应激与PD的发病机理和PD症状的恶化密切相关。一种治疗策略是减轻由氧化应激引起的神经元损伤。在这项研究中，我们调查了使用人神经母细胞瘤SH-SY5Y细胞的蜂王浆（RJ）脂肪酸及其衍生物对氧化应激诱导的细胞死亡的保护作用。合成的RJ脂肪酸衍生物4-羟基氧-2-癸烯酸乙酯（HPO-DAEE）可以明显诱导抗氧化酶，如血红素加氧酶-1（HO-1）。用HPO-DAEE进行预处理可防止6-羟基多巴胺（6-OHDA）诱导的细胞死亡。NF-E2相关因子2（Nrf2），抗氧化反应的主要调节剂，在获得对氧化应激的抗性中起关键作用。HPO-DAEE引起Nrf2的核积累和活化的抗氧化剂反应元件（ARE），顺式-激活调节元件，表明HPO-DAEE通过Nrf2-ARE信号传导诱导抗氧化剂基因的表达。最近，激活转录因子4（ATF4）已显示与Nrf2协同调节抗氧化基因的表达。我们还发现，HPO-DAEE促进了ATF4的上游效应物-真核起始因子2α（eIF2α）的磷酸化，并促进了ATF4的核积累。eIF2α磷酸酶抑制剂salalbrinal增强了HPO-DAEE诱导的HO-1表达，并保护了6-OHDA诱导的细胞死亡。这些结果表明，HPO-DAEE激活Nrf2-ARE和eIF2α-ATF4途径。此外，在使用HPO-DAEE处理SH-SY5Y细胞后，就会产生ROS生成，抗氧化剂N-乙酰半胱氨酸和谷胱甘肽抑制HPO-DAEE诱导的Nrf2-ARE和eIF2α-ATF4途径的激活。因此，由HPO-DAEE引起的亚致死氧化应激可能会激活这两个途径。两者合计，我们得出结论，HPO-DAEE通过Nrf2-ARE和eIF2α-ATF4途径的协同激活引起对氧化应激的适应性反应。