Department of Bio-Analytical Chemistry, Faculty of Pharmacy, Musashino University, Nishitokyo-shi, Tokyo, Japan.
Department of Pharmacokinetics and Biopharmaceutics, Institute of Biomedical Sciences, Tokushima University, Tokushima, Japan.
Toxicol Sci. 2019 May 1;169(1):293-302. doi: 10.1093/toxsci/kfz043.
Zinc (Zn) plays an important role in many organisms in various physiological functions such as cell division, immune mechanisms and protein synthesis. However, excessive Zn release is induced in pathological situations and causes neuronal cell death. Previously, we reported that Cu ions (Cu2+) markedly exacerbates Zn2+-induced neuronal cell death by potentiating oxidative stress and the endoplasmic reticulum stress response. In contrast, the stress-activated protein kinase/c-Jun amino-terminal kinase (SAPK/JNK) signaling pathway is important in neuronal cell death. Thus, in this study, we focused on the SAPK/JNK signaling pathway and examined its involvement in Cu2+/Zn2+-induced neurotoxicity. Initially, we examined expression of factors involved in the SAPK/JNK signaling pathway. Accordingly, we found that phosphorylated (ie, active) forms of SAPK/JNK (p46 and p54) are increased by CuCl2 and ZnCl2 co-treatment in hypothalamic neuronal mouse cells (GT1-7 cells). Downstream factors of SAPK/JNK, phospho-c-Jun, and phospho-activating transcription factor 2 are also induced by CuCl2 and ZnCl2 co-treatment. Moreover, an inhibitor of the SAPK/JNK signaling pathway, SP600125, significantly suppressed neuronal cell death and activation of the SAPK/JNK signaling pathway induced by CuCl2 and ZnCl2 cotreatment. Finally, we examined involvement of oxidative stress in activation of the SAPK/JNK signaling pathway, and found that human serum albumin-thioredoxin fusion protein, an antioxidative protein, suppresses activation of the SAPK/JNK signaling pathway. On the basis of these results, our findings suggest that activation of ZnCl2-dependent SAPK/JNK signaling pathway is important in neuronal cell death, and CuCl2-induced oxidative stress triggers the activation of this pathway.
锌（Zn）在多种生理功能中发挥着重要作用，例如细胞分裂、免疫机制和蛋白质合成。然而，在病理情况下会诱导过量的 Zn 释放，从而导致神经元细胞死亡。先前，我们报道 Cu 离子（Cu2+）通过增强氧化应激和内质网应激反应显著加剧 Zn2+-诱导的神经元细胞死亡。相比之下，应激激活的蛋白激酶/c-Jun 氨基末端激酶（SAPK/JNK）信号通路在神经元细胞死亡中很重要。因此，在本研究中，我们重点研究了 SAPK/JNK 信号通路，并研究了其在 Cu2+/Zn2+-诱导的神经毒性中的作用。最初，我们检查了参与 SAPK/JNK 信号通路的因子的表达。因此，我们发现 CuCl2 和 ZnCl2 共同处理会增加下丘脑神经元小鼠细胞（GT1-7 细胞）中 SAPK/JNK（p46 和 p54）的磷酸化（即活性）形式。SAPK/JNK 的下游因子磷酸化 c-Jun 和磷酸化激活转录因子 2 也被 CuCl2 和 ZnCl2 共同处理诱导。此外，SAPK/JNK 信号通路抑制剂 SP600125 显著抑制了 CuCl2 和 ZnCl2 共同处理诱导的神经元细胞死亡和 SAPK/JNK 信号通路的激活。最后，我们研究了氧化应激在 SAPK/JNK 信号通路激活中的作用，发现抗氧化蛋白人血清白蛋白-硫氧还蛋白融合蛋白抑制了 SAPK/JNK 信号通路的激活。基于这些结果，我们的发现表明 ZnCl2 依赖性 SAPK/JNK 信号通路的激活在神经元细胞死亡中很重要，CuCl2 诱导的氧化应激触发了该通路的激活。
