Department of Food Science and Human Nutrition, Colorado State University, Gifford 234, Fort Collins, CO, 80523-1571, USA.
Mol Cell Biochem. 2009 Nov;331(1-2):31-40. doi: 10.1007/s11010-009-0142-1. Epub 2009 May 15.
Chronic exposure to elevated free fatty acids, in particular long chain saturated fatty acids, provokes endoplasmic reticulum (ER) stress and cell death in a number of cell types. The perturbations to the ER that instigate ER stress and activation of the unfolded protein in response to fatty acids in hepatocytes have not been identified. The present study employed H4IIE liver cells and primary rat hepatocytes to examine the hypothesis that saturated fatty acids induce ER stress via effects on ER luminal calcium stores. Exposure of H4IIE liver cells and primary hepatocytes to palmitate and stearate reduced thapsigargin-sensitive calcium stores and increased biochemical markers of ER stress over similar time courses (6 h). These changes preceded cell death, which was only observed at later time points (16 h). Co-incubation with oleate prevented the reduction in calcium stores, induction of ER stress markers and cell death observed in response to palmitate. Inclusion of calcium chelators, BAPTA-AM or EGTA, reduced palmitate- and stearate-mediated enrichment of cytochrome c in post-mitochondrial supernatant fractions and cell death. These data suggest that redistribution of ER luminal calcium contributes to long chain saturated fatty acid-mediated ER stress and cell death.
慢性暴露于升高的游离脂肪酸中，特别是长链饱和脂肪酸，会引起内质网（ER）应激和许多细胞类型的细胞死亡。在肝细胞中，引发 ER 应激和对脂肪酸的未折叠蛋白反应的 ER 扰动尚未确定。本研究采用 H4IIE 肝细胞和原代大鼠肝细胞，检验饱和脂肪酸是否通过影响 ER 腔钙库来诱导 ER 应激的假设。棕榈酸酯和硬脂酸酯暴露于 H4IIE 肝细胞和原代肝细胞中，在相似的时间过程中（6 h）减少了 thapsigargin 敏感的钙库，并增加了 ER 应激生物标志物。这些变化先于细胞死亡，只有在稍后的时间点（16 h）才观察到细胞死亡。与油酸共孵育可防止观察到的棕榈酸酯诱导的钙库减少、ER 应激标志物诱导和细胞死亡。包含钙螯合剂 BAPTA-AM 或 EGTA 可减少棕榈酸酯和硬脂酸酯介导的细胞色素 c 在线粒体后上清液部分和细胞死亡中的富集。这些数据表明，内质网腔钙的再分布导致长链饱和脂肪酸介导的 ER 应激和细胞死亡。
