Abstract
Extracellular adenosine disrupted mitochondrial membrane potentials in HuH-7 cells, a Fas-deficient human hepatoma cell line, and the effect was inhibited by the adenosine transporter inhibitor dipyridamole or by overexpressing Bcl-X(L). Adenosine downregulated the expression of mRNAs and proteins for Bcl-X(L) and inhibitor of apoptosis protein 2 (IAP2) to directly inhibit caspase-3, -7, and -9, but it otherwise upregulated the expression of mRNA and protein for DIABLO, an inhibitor of IAPs. Those adenosine effects were attenuated by dipyridamole. Caspase-3 and -8 were implicated in adenosine-induced HuH-7 cell death, and adenosine actually activated caspase-3 without caspase-9 activation. The caspase-3 activation was inhibited by overexpressing Bcl-X(L) or IAP2. Taken together, the results of the present study indicate that intracellularly transported adenosine activates caspase-3 by neutralizing caspase-3 inhibition due to IAP as a result of decreased IAP2 expression and reduced IAP activity in response to increased DIABLO expression and perhaps DIABLO release from damaged mitochondria, in addition to caspase-8 activation. This represents further insight into adenosine-induced HuH-7 cell apoptotic pathway.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine / pharmacology*
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Apoptosis Regulatory Proteins
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Baculoviral IAP Repeat-Containing 3 Protein
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Biological Transport / drug effects
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Blotting, Western
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Carcinoma, Hepatocellular / enzymology*
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Carcinoma, Hepatocellular / genetics
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Caspase 3 / metabolism*
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Caspase 9 / metabolism
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Cell Line, Tumor
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Down-Regulation / drug effects
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Enzyme Activation / drug effects
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Gene Expression Regulation, Neoplastic / drug effects
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Humans
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Inhibitor of Apoptosis Proteins / genetics
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Inhibitor of Apoptosis Proteins / metabolism*
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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Intracellular Space / drug effects
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Intracellular Space / metabolism
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Liver Neoplasms / enzymology*
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Liver Neoplasms / genetics
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Membrane Potential, Mitochondrial / drug effects
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Mitochondrial Proteins / genetics
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Mitochondrial Proteins / metabolism*
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Protease Inhibitors / pharmacology
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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Signal Transduction / drug effects
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Ubiquitin-Protein Ligases
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Up-Regulation / drug effects
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bcl-X Protein / genetics
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bcl-X Protein / metabolism*
Substances
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Apoptosis Regulatory Proteins
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DIABLO protein, human
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Inhibitor of Apoptosis Proteins
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Intracellular Signaling Peptides and Proteins
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Mitochondrial Proteins
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Protease Inhibitors
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RNA, Messenger
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bcl-X Protein
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BIRC3 protein, human
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Baculoviral IAP Repeat-Containing 3 Protein
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Ubiquitin-Protein Ligases
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Caspase 3
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Caspase 9
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Adenosine