Tyrosine phosphorylation of insulin receptor substrates during ischemia/reperfusion-induced apoptosis in rat liver.
BACKGROUND
Phosphoregulation of signal transduction pathways is a complex series of reactions that may modulate the cellular response to ischemia-reperfusion (I-R). The aim of this study was to evaluate the effect of normothermic liver I/R-induced apoptosis on phosphorylation and activation of signal proteins in tyrosine kinase pathways.


METHODS
In rats, a segmental normothermic ischemia of the liver was induced for 120 min. Liver apoptosis was determined using terminal deoxynucleotide-transferase-mediated deoxyuridine triphosphate nick end labeling assay, and activity of caspases-3 and -7 was determined by fluorescence. Liver tyrosine phosphorylation of proteins was examined by Western blot analysis.


RESULTS
Normothermic I-R resulted in increased in vivo caspases-3 and -7 activity and in liver apoptosis. Shc tyrosine phosphorylation and activation of ERK1/2 were increased after reperfusion, while tyrosine phosphorylation of IRS-1 and activation of PKB/Akt were decreased.


CONCLUSIONS
Normothermic liver I-R leads to increased apoptosis and to modifications in protein tyrosine phosphorylation pathways.
Cursio
Raffaele
R
Laboratoire de Recherches Chirurgicales, IFR 50, Faculté de Médecine, Université de Nice Sophia Antipolis, Nice, France. cursio@unice.fr
Miele
Claudia
C
Filippa
Nathalie
N
Colosetti
Pascal
P
Auberger
Patrick
P
Van Obberghen
Emmanuel
E
Gugenheim
Jean
J
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism*; D008099:Liver / Q000098:blood supply* / Q000473:pathology; D008297:Male; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew; D011972:Receptor, Insulin / Q000378:metabolism; D015427:Reperfusion Injury / Q000503:physiopathology*; D015398:Signal Transduction / Q000502:physiology*
D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D053148:Caspase 3; D053179:Caspase 7