The bile acid glycochenodeoxycholate induces trail-receptor 2/DR5 expression and apoptosis.
Toxic bile salts induce hepatocyte apoptosis by both Fas-dependent and -independent mechanisms. In this study, we examined the cellular mechanisms responsible for Fas-independent, bile acid-mediated apoptosis. HuH-7 cells, which are known to be Fas deficient, were stably transfected with the sodium-dependent bile acid transporting polypeptide. The toxic bile acid glycochenodeoxycholate (GCDC)-induced apoptosis in these cells in a time- and concentration-dependent manner. Apoptosis and mitochondrial cytochrome c release were inhibited by transfection with dominant negative FADD, CrmA transfection, or treatment with the selective caspase 8 inhibitor IETD-CHO. These observations suggested the Fas-independent apoptosis was also death receptor mediated. Reverse transcriptase-polymerase chain reaction demonstrated tumor necrosis factor-R1, tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-R1/DR4, -R2/DR5, and TRAIL, but not tumor necrosis factor-alpha expression by these cells. GCDC treatment increased expression of TRAIL-R2/DR5 mRNA and protein 10-fold while expression of TRAIL-R1 was unchanged. Furthermore, aggregation of TRAIL-R2/DR5, but not TRAIL-R1/DR4 was observed following GCDC treatment of the cells. Induction of TRAIL-R2/DR5 expression and apoptosis by bile acids provides new insights into the mechanisms of hepatocyte apoptosis and the regulation of TRAIL-R2/DR5 expression.
Higuchi
H
H
Division of Gastroenterology and Hepatology, Mayo Medical School, Clinic, and Foundation, Rochester, Minnesota 55905, USA.
Bronk
S F
SF
Takikawa
Y
Y
Werneburg
N
N
Takimoto
R
R
El-Deiry
W
W
Gores
G J
GJ
D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D003574:Cytochrome c Group / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005799:Genes, Dominant; D017930:Genes, Reporter; D005999:Glycochenodeoxycholic Acid / Q000378:metabolism* / Q000502:physiology*; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008024:Ligands; D008156:Luciferases / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D008957:Models, Genetic; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013347:Subcellular Fractions; D053221:TNF-Related Apoptosis-Inducing Ligand; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation
D051017:Apoptosis Regulatory Proteins; D061945:Caspase Inhibitors; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D008024:Ligands; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C505639:TNFRSF10B protein, human; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D005999:Glycochenodeoxycholic Acid; D008156:Luciferases; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9