Inhibition of Na,K-ATPase Activates PI3 Kinase and Inhibits Apoptosis in LLC-PK1 Cells

• DOI: 10.1006/bbrc.2001.5126
• Publication Date: 2002-09-16T13:50:03Z
• Authors: Xiaoming Zhou; Guisen Jiang; Aiping Zhao; Tzvetanka Bondeva; Przemyslaw Hirszel; Tamas Balla
• Keywords: Wortmannin; LY294002; Phosphoinositide 3-kinase

In the present study we used LLC-PK1 cells, a porcine renal proximal tubular cell line, to investigate whether PI3 kinase activation was involved in the anti-apoptotic effect of ouabain, a specific inhibitor of Na,K-ATPase. Apoptosis was induced by actinomycin D (Act D, 5 microM) and assessed by appearance of hypodiploid nuclei and DNA fragmentation. Ouabain attenuated Act D-induced apoptotic response in a dose-dependent manner. Incubation in a low K(+) medium (0.1 mM) which is another way to decrease Na,K-ATPase activity also had anti-apoptotic effect. Both ouabain and low K(+) medium increased the PI3 kinase activity in p85 immunoprecipitates. Ouabain, as well as incubation in the low K(+) medium, also increased the phosphorylation of Akt. Inhibition of PI3 kinase by either wortmannin or LY294002 reversed the cytoprotective effect of ouabain. These data together indicate that inhibition of Na,K-ATPase activates PI3 kinase in LLC-PK1 cells which could then exert the cytoprotective effect.