title: Adenosine-induced caspase-3 activation by tuning Bcl-XL/DIABLO/IAP expression in HuH-7 human hepatoma cells.
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.
authors.affiliation: Division of Bioinformation, Department of Physiology, Hyogo College of Medicine, Nishinomiya, Japan.
authors.forename: Dongqin
authors.initials: D
authors.lastname: Yang
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yaguchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Nishizaki
mesh_terms: D000241:Adenosine / Q000494:pharmacology*; D051017:Apoptosis Regulatory Proteins; D000075747:Baculoviral IAP Repeat-Containing 3 Protein; D001692:Biological Transport / Q000187:drug effects; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000201:enzymology* / Q000235:genetics; D053148:Caspase 3 / Q000378:metabolism*; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008113:Liver Neoplasms / Q000201:enzymology* / Q000235:genetics; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D044767:Ubiquitin-Protein Ligases; D015854:Up-Regulation / Q000187:drug effects; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D051034:Inhibitor of Apoptosis Proteins; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D011480:Protease Inhibitors; D012333:RNA, Messenger; D051020:bcl-X Protein; C494832:BIRC3 protein, human; D000075747:Baculoviral IAP Repeat-Containing 3 Protein; D044767:Ubiquitin-Protein Ligases; D053148:Caspase 3; D053453:Caspase 9; D000241:Adenosine