Xu Quan-Hua, Song Bing-Jun, Liu Dan, Chen Yu-Hua, Zhou Yuan, Liu Wen-Bo, Li Hua, Long Tian-Lin, Zhang Rui, Liu Wei
Department of Neurosurgery, Bijie First People's Hospital, Bijie, Guizhou 551700, China.
Basic Medical Sciences Research Center, Shaanxi Fourth People's Hospital, Xi'an, Shaanxi 710043, China.
Brain Res. 2018 Jul 15;1691:1-8. doi: 10.1016/j.brainres.2018.04.012. Epub 2018 Apr 21.
JNK, a member of the mitogen activated protein kinases (MAPKs) superfamily, plays a key role in cell death in many neurological disorders, but systemic inhibition of JNK has detrimental side effects. JNK can be regulated by two direct upstream kinases: MAPK kinase 4 (MKK4) and MAPK kinase 7 (MKK7). Here, we investigated the effect of GADD45β-I, a recently designed cell-permeable inhibitor peptide for MKK7, on endoplasmic reticulum (ER) stress-induced cytotoxicity in neuronal HT22 cells. We found that treatment with the ER stress inducer tunicamycin (TM) increased the phosphorylation of JNK and MKK7 in HT22 cells, which was nullified by GADD45β-I. GADD45β-I significantly attenuated TM-induced toxicity via inhibiting apoptotic cell death, as evidenced by decreased number of TUNEL-positive cells and reduced caspase-3 activity. GADD45β-I treatment also decreased expression of ER stress associated pro-apoptotic proteins and prevented morphological changes of the ER after TM exposure. In addition, inhibition of mitochondrial oxidative stress and preservation of intracellular ATP levels were observed in GADD45β-I-treated cells. The experiments using siRNA transfection and Topflash reporter assay revealed a possible involvement of Wnt/β-catenin pathway in GADD45β-I-induced protection in HT22 cells. In summary, our results demonstrated that GADD45β-I exerted protective effects against TM-induced cytotoxicity via regulating JNK-Wnt pathway. Targeting MKK7 could represent a new therapeutic strategy for the treatment of neurological diseases where ER stress associated neuronal injury are involved.
JNK是丝裂原活化蛋白激酶（MAPK）超家族的成员之一，在许多神经疾病的细胞死亡过程中起关键作用，但对JNK的全身抑制具有有害的副作用。JNK可由两种直接上游激酶调节：丝裂原活化蛋白激酶激酶4（MKK4）和丝裂原活化蛋白激酶激酶7（MKK7）。在此，我们研究了GADD45β - I（一种最近设计的针对MKK7的细胞可渗透抑制肽）对神经元HT22细胞内质网（ER）应激诱导的细胞毒性的影响。我们发现，用ER应激诱导剂衣霉素（TM）处理可增加HT22细胞中JNK和MKK7的磷酸化，而GADD45β - I可使其磷酸化水平恢复正常。GADD45β - I通过抑制凋亡细胞死亡显著减轻了TM诱导的毒性，TUNEL阳性细胞数量减少和caspase - 3活性降低证明了这一点。GADD45β - I处理还降低了ER应激相关促凋亡蛋白的表达，并防止了TM暴露后ER的形态变化。此外，在经GADD45β - I处理的细胞中观察到线粒体氧化应激受到抑制且细胞内ATP水平得以维持。使用siRNA转染和Topflash报告基因检测的实验揭示了Wnt/β - 连环蛋白信号通路可能参与了GADD45β - I对HT22细胞的保护作用。总之，我们的结果表明，GADD45β - I通过调节JNK - Wnt信号通路对TM诱导的细胞毒性发挥保护作用。靶向MKK7可能代表了一种治疗涉及ER应激相关神经元损伤的神经疾病的新治疗策略。
