The Phytostilbene Resveratrol Induces Apoptosis in INS-1E Rat Insulinoma Cells
We investigated the effect of resveratrol on proliferation and induction of apoptosis of INS-1E rat insulinoma cells by cell counting, crystal violet staining, flow cytometry and immunoblotting. Resveratrol treatment of INS-1E cells at concentrations ≥50 μM resulted in a dose-dependent inhibition of cell proliferation, accumulation of the cells in the S and G0/G1 phase and a significant increase of the percentage of apoptotic cells. This was paralleled by an increase of cell granularity, apoptotic volume decrease (AVD), exposure of phosphatidylserine at the outer leaflet of the plasma membrane, an increase of the 7-AAD signal and caspase activation. The AMP-kinase (AMPK) inhibitor compound C (10 μM) significantly inhibited cell proliferation and induced caspase activation within 48 hours but this effect was not modified by resveratrol suggesting that AMPK is not a major target involved in mediating the proapoptotic effect of resveratrol in INS-1E cells. Immunoblotting revealed a significant inhibition of Akt (PKB) phosphorylation by 100 μM resveratrol within 1 hour. Addition of insulin (10 μM) to the culture medium strongly enhanced basal Akt phosphorylation. This enhancement was significantly attenuated by 50 and 100 μM resveratrol. We conclude that the antiproliferative/proapoptotic effect of resveratrol on INS-1E cells is due to negative interference with Akt signaling and most likely disruption of auto/paracrine insulin signaling.