Inhibition of glucocorticoid-induced apoptosis with 5-aminoimidazole-4-carboxamide ribonucleoside, a cell-permeable activator of AMP-activated protein kinase.
The AMP-activated protein kinase (AMPK) is related to a growing family of protein kinases that are believed to protect cells against environmental and nutritional stress. In the present study the hypothesis of a protective role for AMPK against thymocyte apoptosis has been tested. It is shown that AMPK is expressed in rat thymocytes that contain the transcript for the a1 isoform of the AMPK catalytic subunit and can be activated by treatment with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), a well-established activator of AMPK. AICAR is not toxic and prevents glucocorticoid-induced apoptosis in the same concentration range used to activate AMPK. At concentrations higher than 1 mM, AICAR fully restores cell viability and inhibits DNA laddering in dexamethasone-treated thymocytes. Furthermore, AICAR blocks the dexamethasone-induced activation of caspase 3-like enzymes, which are believed to play a pivotal role in apoptotic cell death. Activation of AMPK by oligomycin, which depletes thymocytes of ATP, is also correlated to inhibition of caspase 3-like activity in dexamethasone-treated cells. However, AICAR and oligomycin do not exert any protective action when apoptosis is induced by staurosporine. These results indicate that AICAR is a powerful inhibitor of glucocorticoid-induced apoptosis and suggest that AMPK activation may interfere with a step in the apoptotic cascade triggered by dexamethasone.
Stefanelli
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C
Department of Biochemistry G. Moruzzi, University of Bologna, Italy. cstefan@biocfarm.unibo.it
Stanic
I
I
Bonavita
F
F
Flamigni
F
F
Pignatti
C
C
Guarnieri
C
C
Caldarera
C M
CM
D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases; D002470:Cell Survival; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008297:Male; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D012313:RNA / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D012265:Ribonucleotides / Q000494:pharmacology*; D013950:Thymus Gland / Q000166:cytology* / Q000201:enzymology
D005938:Glucocorticoids; D007527:Isoenzymes; D009097:Multienzyme Complexes; D012265:Ribonucleotides; D000620:Aminoimidazole Carboxamide; D012313:RNA; D003907:Dexamethasone; D004247:DNA; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; C031143:AICA ribonucleotide