Survivin-mediated protective effect of insulin on the doxorubicin-induced cardiac cell death.

After pretreatment with the indicated inhibitors for 1 h (A, B), or transfection with either survivin siRNA or Sp1 siRNA for 24 h (B), cells were left untreated or treated with insulin (Ins) for 1 h, followed by doxorubicin (Doxo) for 24 h. (A) Whole cell lysates were immunoblotted with anti-survivin antibodies. Numbers represent the mean ±S.D. of the normalized densitometric analyses of survivin protein levels (n = 4). (B) Cell viability was assessed by the MTT assay (n = 3 performed in triplicates). Values are mean ±S.D. (*p < 0.05; **p < 0.01; ***p < 0.001). (C) Schematic diagram of insulin-induced cardiac myocytes protection against doxorubicin toxicity. Pro-apoptotic signaling cascades induced by doxorubicin are shown as black lines and pro-survival (or anti-apoptotic) signaling pathways induced by insulin are shown as red lines. (+) indicates positive transcriptional regulator (e.g. activator); (-) indicates negative transcriptional regulator (e.g. repressor).