Free fatty acids sensitise hepatocytes to TRAIL mediated cytotoxicity

Harmeet M Malhi, Fernando J. Barreyro, Hajime Isomoto, Steven F. Bronk, Gregory James Gores

Research output: Contribution to journalArticle

155 Citations (Scopus)

Abstract

Background: Elevated circulating free fatty acids (FFA) contribute to the development of hepatic steatosis and promote hepatocyte apoptosis by incompletely defined mechanisms. Although the death ligand TRAIL has been implicated in a variety of pathological liver diseases, the role of TRAIL in mediating apoptosis of FFA induced steatotic hepatocytes is unknown. Aim: We examined TRAIL cytotoxicity in an in vitro model of hepatocyte steatosis induced by FFA. Methods: Hepatocytes (Huh 7 cells, HepG2 cells, and primary rat hepatocytes) were rendered steatotic by incubation with oleic acid. Apoptosis was assessed morphologically and biochemically by caspase activity. TRAIL receptor regulation was examined using immunoblot analysis and siRNA for targeted knockdown. c-jun N-terminal kinase (JNK) inhibition was attained with SP600125. Results: Oleic acid sensitised the cells to TRAIL but not TNF-α cytotoxicity. FFA sensitisation to TRAIL occurred at much lower concentrations than required for FFA mediated sensitisation to Fas, or FFA induced lipoapoptosis. Oleic acid treatment led to upregulation of the cognate TRAIL receptor death receptor 5 (DR5) but not death receptor 4 (DR4). The upregulation of DR5 was JNK dependent. siRNA targeted knockdown of either DR5 or DR4 demonstrated that DR5 was responsible for FFA sensitisation to TRAIL killing. DR5 expression was enhanced in steatotic human liver samples. Conclusion: Our results suggest that FFA induced hepatocyte steatosis sensitises to TRAIL by a DR5 mediated JNK dependent mechanism.

Original languageEnglish (US)
Pages (from-to)1124-1131
Number of pages8
JournalGut
Volume56
Issue number8
DOIs
StatePublished - Aug 2007

Fingerprint

TNF-Related Apoptosis-Inducing Ligand Receptors
Nonesterified Fatty Acids
Hepatocytes
JNK Mitogen-Activated Protein Kinases
Oleic Acid
Apoptosis
Small Interfering RNA
Up-Regulation
Liver
Hep G2 Cells
Caspases
Liver Diseases

ASJC Scopus subject areas

  • Gastroenterology

Cite this

Free fatty acids sensitise hepatocytes to TRAIL mediated cytotoxicity. / Malhi, Harmeet M; Barreyro, Fernando J.; Isomoto, Hajime; Bronk, Steven F.; Gores, Gregory James.

In: Gut, Vol. 56, No. 8, 08.2007, p. 1124-1131.

Research output: Contribution to journalArticle

Malhi, Harmeet M ; Barreyro, Fernando J. ; Isomoto, Hajime ; Bronk, Steven F. ; Gores, Gregory James. / Free fatty acids sensitise hepatocytes to TRAIL mediated cytotoxicity. In: Gut. 2007 ; Vol. 56, No. 8. pp. 1124-1131.
@article{7c734b9bd8394adfaa80c8e71d1024a7,
title = "Free fatty acids sensitise hepatocytes to TRAIL mediated cytotoxicity",
abstract = "Background: Elevated circulating free fatty acids (FFA) contribute to the development of hepatic steatosis and promote hepatocyte apoptosis by incompletely defined mechanisms. Although the death ligand TRAIL has been implicated in a variety of pathological liver diseases, the role of TRAIL in mediating apoptosis of FFA induced steatotic hepatocytes is unknown. Aim: We examined TRAIL cytotoxicity in an in vitro model of hepatocyte steatosis induced by FFA. Methods: Hepatocytes (Huh 7 cells, HepG2 cells, and primary rat hepatocytes) were rendered steatotic by incubation with oleic acid. Apoptosis was assessed morphologically and biochemically by caspase activity. TRAIL receptor regulation was examined using immunoblot analysis and siRNA for targeted knockdown. c-jun N-terminal kinase (JNK) inhibition was attained with SP600125. Results: Oleic acid sensitised the cells to TRAIL but not TNF-α cytotoxicity. FFA sensitisation to TRAIL occurred at much lower concentrations than required for FFA mediated sensitisation to Fas, or FFA induced lipoapoptosis. Oleic acid treatment led to upregulation of the cognate TRAIL receptor death receptor 5 (DR5) but not death receptor 4 (DR4). The upregulation of DR5 was JNK dependent. siRNA targeted knockdown of either DR5 or DR4 demonstrated that DR5 was responsible for FFA sensitisation to TRAIL killing. DR5 expression was enhanced in steatotic human liver samples. Conclusion: Our results suggest that FFA induced hepatocyte steatosis sensitises to TRAIL by a DR5 mediated JNK dependent mechanism.",
author = "Malhi, {Harmeet M} and Barreyro, {Fernando J.} and Hajime Isomoto and Bronk, {Steven F.} and Gores, {Gregory James}",
year = "2007",
month = "8",
doi = "10.1136/gut.2006.118059",
language = "English (US)",
volume = "56",
pages = "1124--1131",
journal = "Gut",
issn = "0017-5749",
publisher = "BMJ Publishing Group",
number = "8",

}

TY - JOUR

T1 - Free fatty acids sensitise hepatocytes to TRAIL mediated cytotoxicity

AU - Malhi, Harmeet M

AU - Barreyro, Fernando J.

AU - Isomoto, Hajime

AU - Bronk, Steven F.

AU - Gores, Gregory James

PY - 2007/8

Y1 - 2007/8

N2 - Background: Elevated circulating free fatty acids (FFA) contribute to the development of hepatic steatosis and promote hepatocyte apoptosis by incompletely defined mechanisms. Although the death ligand TRAIL has been implicated in a variety of pathological liver diseases, the role of TRAIL in mediating apoptosis of FFA induced steatotic hepatocytes is unknown. Aim: We examined TRAIL cytotoxicity in an in vitro model of hepatocyte steatosis induced by FFA. Methods: Hepatocytes (Huh 7 cells, HepG2 cells, and primary rat hepatocytes) were rendered steatotic by incubation with oleic acid. Apoptosis was assessed morphologically and biochemically by caspase activity. TRAIL receptor regulation was examined using immunoblot analysis and siRNA for targeted knockdown. c-jun N-terminal kinase (JNK) inhibition was attained with SP600125. Results: Oleic acid sensitised the cells to TRAIL but not TNF-α cytotoxicity. FFA sensitisation to TRAIL occurred at much lower concentrations than required for FFA mediated sensitisation to Fas, or FFA induced lipoapoptosis. Oleic acid treatment led to upregulation of the cognate TRAIL receptor death receptor 5 (DR5) but not death receptor 4 (DR4). The upregulation of DR5 was JNK dependent. siRNA targeted knockdown of either DR5 or DR4 demonstrated that DR5 was responsible for FFA sensitisation to TRAIL killing. DR5 expression was enhanced in steatotic human liver samples. Conclusion: Our results suggest that FFA induced hepatocyte steatosis sensitises to TRAIL by a DR5 mediated JNK dependent mechanism.

AB - Background: Elevated circulating free fatty acids (FFA) contribute to the development of hepatic steatosis and promote hepatocyte apoptosis by incompletely defined mechanisms. Although the death ligand TRAIL has been implicated in a variety of pathological liver diseases, the role of TRAIL in mediating apoptosis of FFA induced steatotic hepatocytes is unknown. Aim: We examined TRAIL cytotoxicity in an in vitro model of hepatocyte steatosis induced by FFA. Methods: Hepatocytes (Huh 7 cells, HepG2 cells, and primary rat hepatocytes) were rendered steatotic by incubation with oleic acid. Apoptosis was assessed morphologically and biochemically by caspase activity. TRAIL receptor regulation was examined using immunoblot analysis and siRNA for targeted knockdown. c-jun N-terminal kinase (JNK) inhibition was attained with SP600125. Results: Oleic acid sensitised the cells to TRAIL but not TNF-α cytotoxicity. FFA sensitisation to TRAIL occurred at much lower concentrations than required for FFA mediated sensitisation to Fas, or FFA induced lipoapoptosis. Oleic acid treatment led to upregulation of the cognate TRAIL receptor death receptor 5 (DR5) but not death receptor 4 (DR4). The upregulation of DR5 was JNK dependent. siRNA targeted knockdown of either DR5 or DR4 demonstrated that DR5 was responsible for FFA sensitisation to TRAIL killing. DR5 expression was enhanced in steatotic human liver samples. Conclusion: Our results suggest that FFA induced hepatocyte steatosis sensitises to TRAIL by a DR5 mediated JNK dependent mechanism.

UR - http://www.scopus.com/inward/record.url?scp=34547193134&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34547193134&partnerID=8YFLogxK

U2 - 10.1136/gut.2006.118059

DO - 10.1136/gut.2006.118059

M3 - Article

C2 - 17470478

AN - SCOPUS:34547193134

VL - 56

SP - 1124

EP - 1131

JO - Gut

JF - Gut

SN - 0017-5749

IS - 8

ER -