Insulin inhibits caspase-3 activity in human renal tubular epithelial cells via the PI3-kinase/Akt pathway.
Apoptotic mechanisms in proximal renal tubular epithelial cells (PTEC) are crucial in the pathogenesis of acute kidney injury. We investigated whether insulin alters anti-apoptotic signalling in human PTEC. Cells were deprived of insulin for 0, 24 or 48 h and then stimulated with insulin for 0 or 5 min. Apoptosis was induced by camptothecin incubation. Insulin receptor kinase (IR-kinase) activity, phosphorylation of insulin receptor substrate-1 (IRS-1), IRS-1-associated PI3-kinase (p85), Ser(273)-phosphorylation of Akt and caspase-3 activity (C3-activity) were determined. Insulin stimulation increased the activity of IR-kinase, IRS-1 phosphorylation, p85 association with IRS-1 and Ser(273)-phosphorylation of Akt by at least 250%, respectively and decreased the C3-activity by 45% (p < 0.01, respectively). Deprivation of insulin for 24 and 48 h reduced basal and insulin-stimulated IR-kinase activity, IRS-1 phosphorylation, p85 association with IRS-1 and Ser(273)-phosphorylation of Akt by 30-40% and increased C3-activity by 15-20% (p < 0.01, respectively). Incubation with camptothecin increased C3-activity by 250-300% (p < 0.001). Subsequent insulin stimulation reversed the camptothecin induced increase of C3-activity. Our data indicate that apoptosis in PTEC is regulated by the insulin dependent PI3-kinase/Akt pathway. The enhancement of tubular-specific cell survival signals might represent a potential therapeutic tool for the protection of renal function in acute kidney injury.
Meier
Markus
M
Department of Internal Medicine I, University of Lubeck, Germany. markus.meier@uni-luebeck.de
Nitschke
Martin
M
Hocke
Caroline
C
Kramer
Jan
J
Jabs
Wolfram
W
Steinhoff
Jurgen
J
Schutt
Morten
M
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology; D002166:Camptothecin / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism*; D061945:Caspase Inhibitors; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D007684:Kidney Tubules / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D000077191:Wortmannin
D048868:Adaptor Proteins, Signal Transducing; D000730:Androstadienes; D002166:Camptothecin; D053148:Caspase 3; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D000077191:Wortmannin; C526292:IRS1 protein, human