1. Adenosine-induced caspase-3 activation by tuning Bcl-XL/DIABLO/IAP expression in HuH-7 human hepatoma cells.
- Author
-
Yang D, Yaguchi T, Nakano T, and Nishizaki T
- Subjects
- Apoptosis Regulatory Proteins, Baculoviral IAP Repeat-Containing 3 Protein, Biological Transport drug effects, Blotting, Western, Carcinoma, Hepatocellular genetics, Caspase 9 metabolism, Cell Line, Tumor, Down-Regulation drug effects, Enzyme Activation drug effects, Gene Expression Regulation, Neoplastic drug effects, Humans, Inhibitor of Apoptosis Proteins genetics, Intracellular Signaling Peptides and Proteins genetics, Intracellular Space drug effects, Intracellular Space metabolism, Liver Neoplasms genetics, Membrane Potential, Mitochondrial drug effects, Mitochondrial Proteins genetics, Protease Inhibitors pharmacology, RNA, Messenger genetics, RNA, Messenger metabolism, Reverse Transcriptase Polymerase Chain Reaction, Signal Transduction drug effects, Ubiquitin-Protein Ligases, Up-Regulation drug effects, bcl-X Protein genetics, Adenosine pharmacology, Carcinoma, Hepatocellular enzymology, Caspase 3 metabolism, Inhibitor of Apoptosis Proteins metabolism, Intracellular Signaling Peptides and Proteins metabolism, Liver Neoplasms enzymology, Mitochondrial Proteins metabolism, bcl-X Protein metabolism
- 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.
- Published
- 2010
- Full Text
- View/download PDF