Roles for C16-ceramide and sphingosine 1-phosphate in regulating hepatocyte apoptosis in response to tumor necrosis factor-α
Roles for C16-ceramide and sphingosine 1-phosphate in regulating hepatocyte apoptosis in response to tumor necrosis factor-α
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DOI：
10.1074/jbc.m503002200
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发表时间：
2005-07-29
影响因子：
4.8
通讯作者：
Brenner, DA
中科院分区：
文献类型：
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作者：
Osawa, Y;Uchinami, H;Brenner, DA
肿瘤坏死因子-α信号转导细胞死亡，同时诱导神经酰胺的产生，神经酰胺通过神经酰胺酶(CDase)和鞘氨醇激酶代谢为鞘氨醇和1-磷酸鞘氨醇(S1P)。由于细胞内神经酰胺和S1P(神经酰胺/S1P变阻器)水平之间的动态平衡可能决定细胞的存活，我们研究了这些神经鞘脂信号通路在肿瘤坏死因子-α诱导的原代肝细胞凋亡中的作用。在肿瘤坏死因子-α诱导大鼠和小鼠原代肝细胞凋亡过程中，内源性C-16-神经酰胺均升高。酸性鞘磷脂酶(ASMase)抑制剂丙咪嗪可抑制肿瘤坏死因子-α诱导的细胞凋亡和C16-神经酰胺的增加，ASMase的敲除也是如此。中性CDase(NCDase)过表达可抑制肿瘤坏死因子-α诱导的大鼠原代肝细胞C16-神经酰胺增加和细胞凋亡。此外，NCDase还能抑制D-氨基半乳糖加肿瘤坏死因子-α诱导的小鼠肝损伤和肝细胞凋亡。这种保护作用被鞘氨醇激酶抑制剂N，N-脱甲基鞘氨醇所消除，这表明NCDase的存活效应不仅是由于C-16-神经酰胺的减少，而且是S1P的形成。给予S1P或过表达NCDase可激活促生存蛋白激酶AKT，而显性负性AKT过表达则阻断NCDase的生存效应。总之，ASMase的激活和C16-神经酰胺的产生参与了肿瘤坏死因子-α诱导的肝细胞凋亡。NCDase通过减少C16-神经酰胺和通过S1P的形成激活AKT来阻止细胞凋亡。因此，鞘磷脂和AKT途径之间的相互作用可能决定了肿瘤坏死因子-α诱导的肝细胞凋亡。
Tumor necrosis factor (TNF)-alpha signals cell death and simultaneously induces the generation of ceramide, which is metabolized to sphingosine and sphingosine 1-phosphate (S1P) by ceramidase ( CDase) and sphingosine kinase. Because the dynamic balance between the intracellular levels of ceramide and S1P ( the "ceramide/ S1P rheostat") may determine cell survival, we investigated these sphingolipid signaling pathways in TNF-alpha-induced apoptosis of primary hepatocytes. Endogenous C-16-ceramide was elevated during TNF-alpha-induced apoptosis in both rat and mouse primary hepatocytes. The putative acid sphingomyelinase (ASMase) inhibitor imipramine inhibited TNF-alpha-induced apoptosis and C16-ceramide increase as did the knock out of ASMase. Overexpression of neutral CDase (NCDase) inhibited the TNF-alpha-induced increase of C16-ceramide and apoptosis in rat primary hepatocytes. Moreover, NCDase inhibited liver injury and hepatocyte apoptosis in mice treated with D- galactosamine plus TNF-alpha. This protective effect was abrogated by the sphingosine kinase inhibitor N,N-demethylsphingosine, suggesting that the survival effect of NCDase is due to not only C-16- ceramide reduction but also S1P formation. Administration of S1P or overexpression of NCDase activated the pro-survival kinase AKT, and overexpression of dominant negative AKT blocked the survival effect of NCDase. In conclusion, activation of ASMase and generation of C16- ceramide contributed to TNF-alpha-induced hepatocyte apoptosis. NCDase prevented apoptosis both by reducing C16- ceramide and by activation of AKT through S1P formation. Therefore, the cross-talk between sphingolipids and AKT pathway may determine hepatocyte apoptosis by TNF-alpha.