Mechanisms of lysophosphatidylcholine-induced hepatocyte lipoapoptosis
Mechanisms of lysophosphatidylcholine-induced hepatocyte lipoapoptosis
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DOI：
10.1152/ajpgi.00301.2011
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发表时间：
2012-01-01
影响因子：
4.5
通讯作者：
Gores, Gregory J.
中科院分区：
文献类型：
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作者：
Kakisaka, Keisuke;Cazanave, Sophie C.;Gores, Gregory J.
Kakisaka K, Cazanave SC, Fingas CD, Guicciardi ME, Bronk SF, Werneburg NW, Mott JL, Gores GJ。溶血磷脂胆碱诱导肝细胞脂质凋亡的机制。[J] .中国生物医学工程学报，2012,31(2):557 - 557。首次发表于2011年10月13日；doi: 10.1152 / ajpgi.00301.2011。-在饱和游离脂肪酸（FFA）如棕榈酸酯（PA）处理下，分离的肝细胞会发生脂肪凋亡，这是肝脂肪毒性的一个特征。然而，棕榈酸酯是直接对肝细胞有毒性，还是通过产生溶血磷脂酰胆碱（LPC）等脂质代谢物间接产生毒性，目前尚不清楚。pa介导的肝细胞脂质凋亡与内质网（ER）应激、c-Jun nh2末端激酶（JNK）激活以及JNK依赖性强效促凋亡的BH3-only蛋白PUMA （p53上调的凋亡调节剂）的上调有关。我们的目的是确定哪些脂毒性机制是由pa衍生的LPC激活的。我们使用Huh-7细胞和分离的小鼠和人原代肝细胞。细胞内LPC浓度随外源性、细胞外PA、硬脂酸盐或LPC浓度线性增加。Huh-7细胞或原代肝细胞与LPC孵育诱导细胞凋亡呈浓度依赖性。用LPC代替PA导致caspase依赖性细胞死亡，同时伴随着c-Jun磷酸化激活JNK磷酸化和PUMA表达增加。LPC还通过eIF2 α磷酸化和CAAT/增强子结合同源蛋白（CHOP）诱导诱导内质网应激。通过JNK或糖原合成酶激酶-3 （GSK-3）的药理抑制，LPC细胞毒性减弱。同样，短发夹RNA （shRNA）靶向敲低CHOP可保护Huh-7细胞免受lpc诱导的毒性。lpc诱导的PUMA上调可通过JNK抑制或shrna靶向敲低CHOP来阻止。最后，PUMA基因缺失使小鼠肝细胞对lpc诱导的细胞凋亡产生抗性。我们的结论是，lpc诱导的脂肪凋亡依赖于与PA在很大程度上难以区分的机制。这些数据表明，ffa介导的细胞毒性是通过产生有毒代谢物LPC间接产生的。
Kakisaka K, Cazanave SC, Fingas CD, Guicciardi ME, Bronk SF, Werneburg NW, Mott JL, Gores GJ. Mechanisms of lysophosphatidylcholine-induced hepatocyte lipoapoptosis. Am J Physiol Gastrointest Liver Physiol 302: G77-G84, 2012. First published October 13, 2011; doi:10.1152/ajpgi.00301.2011.-Isolated hepatocytes undergo lipoapoptosis, a feature of hepatic lipotoxicity, on treatment with saturated free fatty acids (FFA) such as palmitate (PA). However, it is unknown if palmitate is directly toxic to hepatocytes or if its toxicity is indirect via the generation of lipid metabolites such as lysophosphatidylcholine (LPC). PA-mediated hepatocyte lipoapoptosis is associated with endoplasmic reticulum (ER) stress, c-Jun NH2-terminal kinase (JNK) activation, and a JNK-dependent upregulation of the potent proapoptotic BH3-only protein PUMA (p53 upregulated modulator of apoptosis). Our aim was to determine which of these mechanisms of lipotoxicity are activated by PA-derived LPC. We employed Huh-7 cells and isolated murine and human primary hepatocytes. Intracellular LPC concentrations increase linearly as a function of the exogenous, extracellular PA, stearate, or LPC concentration. Incubation of Huh-7 cells or primary hepatocytes with LPC induced cell death by apoptosis in a concentration-dependent manner. Substituting LPC for PA resulted in caspase-dependent cell death that was accompanied by activating phosphorylation of JNK with c-Jun phosphorylation and an increase in PUMA expression. LPC also induced ER stress as manifest by eIF2 alpha phosphorylation and CAAT/enhancer binding homologous protein (CHOP) induction. LPC cytotoxicity was attenuated by pharmacological inhibition of JNK or glycogen synthase kinase-3 (GSK-3). Similarly, short-hairpin RNA (shRNA)-targeted knockdown of CHOP protected Huh-7 cells against LPC-induced toxicity. The LPC-induced PUMA upregulation was prevented by JNK inhibition or shRNA-targeted knockdown of CHOP. Finally, genetic deficiency of PUMA rendered murine hepatocytes resistant to LPC-induced apoptosis. We concluded that LPC-induced lipoapoptosis is dependent on mechanisms largely indistinguishable from PA. These data suggest that FFA-mediated cytotoxicity is indirect via the generation of the toxic metabolite, LPC.