Ceramide metabolism regulates autophagy and apoptotic cell death induced by melatonin in liver cancer cells.
Ceramide metabolism regulates autophagy and apoptotic cell death induced by melatonin in liver cancer cells.
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DOI：
10.1111/jpi.12249
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发表时间：
2015-09
影响因子：
10.3
通讯作者：
González-Gallego J
中科院分区：
文献类型：
--
作者：
Ordoñez R;Fernández A;Prieto-Domínguez N;Martínez L;García-Ruiz C;Fernández-Checa JC;Mauriz JL;González-Gallego J
自噬是一个在压力下维持体内平衡的过程，尽管在特定情况下它也有助于细胞死亡。神经酰胺已成为调控细胞自噬的重要效应因子，介导细胞凋亡与细胞自噬的相互作用。褪黑素诱导癌细胞凋亡；然而，其在自噬和神经酰胺代谢中的作用尚未清楚阐明。本研究旨在探讨褪黑素对肝癌细胞自噬和神经酰胺代谢的影响及其与褪黑素诱导的凋亡细胞死亡的可能联系。褪黑素（2 mM）通过JNK磷酸化诱导HepG2细胞瞬时自噬，其特征是Beclin1表达增加，p62降解，LC3II和LAMP2共定位，导致细胞活力下降。此外，atg5沉默使HepG2细胞对褪黑素诱导的凋亡敏感，提示自噬在细胞死亡中的双重作用。褪黑素通过从头合成和刺激酸性鞘磷脂酶（ASMase）来提高神经酰胺水平。肉豆蔻素抑制丝氨酸棕榈酰转移酶（SPT）可阻止褪黑素诱导的自噬，而丙咪嗪抑制ASMase可损害自噬通量。然而，ASMase抑制部分保护HepG2细胞对抗褪黑素，而SPT抑制显著增强细胞死亡。研究结果表明，spt介导的神经酰胺生成和自噬之间的相互作用可以防止褪黑激素的产生，而asmase诱导的特定神经酰胺生成参与褪黑激素介导的细胞死亡。因此，双重阻断SPT和自噬成为增强褪黑素在肝癌细胞中凋亡作用的潜在策略。
Autophagy is a process that maintains homeostasis during stress, although it also contributes to cell death under specific contexts. Ceramides have emerged as important effectors in the regulation of autophagy, mediating the crosstalk with apoptosis. Melatonin induces apoptosis of cancer cells; however, its role in autophagy and ceramide metabolism has yet to be clearly elucidated. This study was aimed to evaluate the effect of melatonin administration on autophagy and ceramide metabolism and its possible link with melatonin-induced apoptotic cell death in hepatocarcinoma (HCC) cells. Melatonin (2 mM) transiently induced autophagy in HepG2 cells through JNK phosphorylation, characterized by increased Beclin1 expression, p62 degradation and LC3II and LAMP2 colocalization, which translated in decreased cell viability. Moreover, ATG5-silencing sensitized HepG2 cells to melatonin induced-apoptosis, suggesting a dual role of autophagy in cell death. Melatonin enhanced ceramide levels through both de novo synthesis and acid sphingomyelinase (ASMase) stimulation. Serine palmitoyl transferase (SPT) inhibition with myriocin prevented melatonin induced autophagy and ASMase inhibition with imipramine impaired autophagy flux. However, ASMase inhibition partially protected HepG2 cells against melatonin while SPT inhibition significantly enhanced cell death. Findings suggest a cross-talk between SPT-mediated ceramide generation and autophagy in protecting against melatonin, while specific ASMase-induced ceramide production participates in melatonin-mediated cell death. Thus, dual blocking of SPT and autophagy emerge as a potential strategy to potentiate the apoptotic effects of melatonin in liver cancer cells.