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Adenosine‐dependent activation of hypoxia‐inducible factor‐1 induces late preconditioning in liver cells
Author(s) -
Alchera Elisa,
Tacchini Lorenza,
Imarisio Chiara,
Dal Ponte Caterina,
De Ponti Cristina,
Gammella Elena,
Cairo Gaetano,
Albano Emanuele,
Carini Rita
Publication year - 2008
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.22249
Subject(s) - ischemic preconditioning , adenosine , wortmannin , chelerythrine , hypoxia (environmental) , hepatocyte , endocrinology , medicine , small interfering rna , protein kinase c , intracellular , chemistry , pharmacology , biology , ischemia , kinase , microbiology and biotechnology , biochemistry , phosphatidylinositol , transfection , in vitro , organic chemistry , oxygen , gene
The cellular mechanisms by which ischemic preconditioning increases liver tolerance to ischemia/reperfusion injury are still poorly understood. This study investigated the role of the hypoxia‐inducible factor‐1 (HIF‐1) in the protection associated with the late phase of liver preconditioning. Late preconditioning was induced in primary cultured rat hepatocytes by a transient (10 minute) hypoxic stress or by 15 minutes incubation with the adenosine A 2A receptors agonist CGS21680 24 hours before exposure to 90 minutes of hypoxia in a serum‐free medium. Late preconditioning induced the nuclear translocation of HIF‐1 and the expression of carbonic anhydrase IX (CAIX), a HIF‐1–regulated transmembrane enzyme that catalyzes bicarbonate production. Such effects were associated with prevention of hepatocyte killing by hypoxia and the amelioration of intracellular acidosis and Na + accumulation. The inhibition of PKC‐mediated and PI3‐kinase–mediated signals with, respectively, chelerythrine and wortmannin abolished HIF‐1 activation and blocked both CAIX expression and the protective action of late preconditioning. CAIX expression was also prevented by interfering with the transcriptional activity of HIF‐1 using a dominant negative HIF‐1β subunit. The inhibition of CAIX with acetazolamide or the block of bicarbonate influx with disodium‐4‐acetamido‐4′‐isothiocyanato‐stilben‐2,2′‐disulfonate also reverted the protective effects of late preconditioning on intracellular acidosis and Na + accumulation. Conclusion: The stimulation of adenosine A 2A receptors induced late preconditioning in liver cells through the activation of HIF‐1. HIF‐1–induced expression of CAIX increases hepatocyte tolerance to ischemia by maintaining intracellular Na + homeostasis. These observations along with the importance of HIF‐1 in regulating cell survival indicates HIF‐1 activation as a possible key event in liver protection by late preconditioning. (H EPATOLOGY 2008.)