Antiapoptotic and cytotoxic properties of delta opioid peptide [D-Ala2,D-Leu5]enkephalin in PC12 cells
Antiapoptotic and cytotoxic properties of delta opioid peptide [D-Ala2,D-Leu5]enkephalin in PC12 cells
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作者：
Hayashi, T;Tsao, LI;Su, TP
δ阿片肽[D-Ala（2），D-Leu（5）]脑啡肽（DADLE）已被证明可促进器官存活并防止甲基苯丙胺诱导的神经变性。然而，DADLE的这些作用的细胞机制并不完全清楚。我们研究了DADLE在血清剥夺的嗜铬细胞瘤细胞（PC 12）中的作用，发现DADLE在这些细胞中保护细胞死亡。然而，DADLE的保护作用的剂量-反应曲线是U形的判断由三个生化或形态学检测：LDH释放，DNA梯状，和凋亡细胞核。发现飞摩尔至皮摩尔浓度的DADLE是抗凋亡的，而微摩尔浓度的DADLE在PC 12细胞中是细胞毒性的。选择性δ 2阿片受体拮抗剂可减弱DADLE的保护作用，选择性μ阿片受体拮抗剂可降低DADLE的细胞毒作用。用ERK激酶（MEK）的选择性抑制剂PD 98059处理细胞或用显性干扰形式的MEK（MEK-KA 97）转染细胞阻断DADLE的保护作用和DADLE诱导的ERK磷酸化。细胞毒性浓度的DADLE，另一方面，引起增加的Fas-配体（FasL）在PC 12细胞中的选择性μ拮抗剂衰减。因此，我们的研究结果表明，内源性阿片肽，在低浓度下，可能通过MEK-ERK途径，可能通过δ 2阿片受体，促进细胞存活，而他们可能会杀死细胞在高浓度下通过激活FasL通过一个迄今未知的机制，涉及μ阿片受体。(C)2001 Wiley-Liss，Inc.（匕首）。
The delta opioid peptide [D-Ala(2),D-Leu(5)]enkephalin (DADLE) has been shown to promote organ survival and to protect against methamphetamine-induced neurodegeneration. However, the cellular mechanisms of these actions of DADLE are not totally clear. We examined the action of DADLE in serum-deprived pheochromocytoma cells (PC12) and found that DADLE protected against cell death in those cells. However, the dose-response curves of the protective effects of DADLE are U-shaped as judged by three biochemical or morphological assays: the LDH release, the DNA laddering, and the apoptotic nuclei. It was found that femtomolar to picomolar concentrations of DADLE are antiapoptotic, whereas micormolar concentrations of DADLE are cytotoxic in PC12 cells. The protective effect of DADLE could be attenuated by a selective delta2 opioid antagonist and the cytotoxic action of DADLE was reduced by a selective mu opioid receptor antagonist. The treatment of cells with PD98059, a selective inhibitor of ERK kinase (MEK), or the transfection of cells with a dominant interfering form of MEK (MEK-KA97) blocked both the protective effect of DADLE and the ERK phosphorylation induced by DADLE. Cytotoxic concentrations of DADLE, on the other hand, caused an increase of Fas-ligand (FasL) in PC12 cells that was attenuated by a selective mu antagonist. Our results suggest, therefore, that endogenous opioid peptides may, at low concentrations, promote cell survival via the MEK-ERK pathway perhaps through delta2 opioid receptors, whereas they may kill cells at high concentrations via the activation of FasL through an as-yet unknown mechanism involving mu opioid receptors. (C) 2001 Wiley-Liss, Inc.(dagger).