Blockage of SPD-induced HO-1 protein expression by aminoguanidine, NAC, or PI3K/Akt inhibitor. Cells were pre-treated with aminoguanidine (a), NAC (b), or LY 294002 (PI3K/Akt inhibitor) (c) 1 h prior to the treatment of SPD. After 24 h incubation, cell lysates were prepared, and 20 μ g samples of proteins were subjected to Western blotting, using anti-HO-1 antibody and anti-GAPDH.