Reduced endoplasmic reticulum luminal calcium links saturated fatty acid-mediated endoplasmic reticulum stress and cell death in liver cells

  • Yuren Wei
  • Dong Wang
  • Christopher L. Gentile
  • Michael J. Pagliassotti
Article

Abstract

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.

Keywords

Lipoapoptosis Unfolded protein response Hepatocyte Non-alcoholic fatty liver disease 

Notes

Acknowledgments

This work was supported by grants DK47416 and DK072017 from the National Institutes of Health and the Lillian Fountain Smith Foundation Endowment.

Supplementary material

11010_2009_142_MOESM1_ESM.eps (706 kb)
Supplemental Fig. 1 (A) Caspase-3 activity in H4IIE liver cells or primary hepatocytes incubated for 6 or 16 h in control media (LG), or control media supplemented with thapsigargin (Thap, 450 nM), oleate (O, 250 μM), or palmitate (P, 250 μM). (B) Caspase-3 activity in H4IIE liver cells or primary rat hepatocytes incubated for 16 h in control media (LG), or control media supplemented with palmitate (P, 250 μM) or palmitate (P, 250 μM) + oleate (O, 125 μM). (C) Caspase-3 activity in H4IIE liver cells or primary rat hepatocytes incubated for 16 h in control media (LG), or control media supplemented with oleate (O, 250 μM), linoleate (L, 250 μM), palmitate (P, 250 μM) or stearate (S, 250 μM) in the absence (no additions) or presence of BAPTA-AM (20 μM) or EGTA (1 mM). Data are reported as the mean ± SD for triplicate samples from 4 to 6 independent experiments. *Significantly (P < 0.05) different from LG−. +Significantly (P < 0.05) different from no additions of the same treatment group
11010_2009_142_MOESM2_ESM.eps (495 kb)
Supplemental Fig. 2(A) Real time PCR analysis of CHOP, GADD34, ATF4 mRNA in H4IIE liver cells and primary hepatocytes following 16 h incubations in control media (LG), or control media supplemented with oleate (O, 250 μM), linoleate (L, 250 μM), palmitate (P, 250 μM) or stearate (S, 250 μM) in the absence (no additions) or presence of BAPTA-AM (20 μM) or EGTA (1 mM). LG with no additions was set to 1. (B) MTT cell viability assay following 16 h incubations. Data are expressed as the mean ± SD for 4–6 independent experiments

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Copyright information

© Springer Science+Business Media, LLC. 2009

Authors and Affiliations

  • Yuren Wei
    • 1
  • Dong Wang
    • 1
  • Christopher L. Gentile
    • 1
  • Michael J. Pagliassotti
    • 1
  1. 1.Department of Food Science and Human NutritionColorado State UniversityFort CollinsUSA

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