Spermidine induced autophagy in HeLa cells. HeLa cells were treated with 0.5 mM spermidine for 8 h. The formation of autophagic vacuole was observed under TEM (A). The nucleus is marked with letter N, letter M indicates intact mitochondria. autophagic vacuole is labeled as A1, A2. Cells were treated with 0.5 mM spermidine for 2, 4, 6, 8, 10 h or starved for 5 h. The expression of LC3 protein was assessed by western blotting and followed by grey scale analysis (B). Alternatively, the cells were treated with indicated concentrations of spermidine for 8 h and followed by western blotting of p62 (C). *p < 0.05, compared with control.