omponents showed a significant increase in the number of SKI-II site autophagosomes at 13 h after OGD. When the autophagosomes fused with the lysosomes, their inner membranes disappeared, and the autophagosomes became single-membrane autophagic vacuoles at 612 h after OGD. The mitochondria displayed swelling, dilation and cristae disruption, and the number of intact mitochondria was drastically decreased in a time-dependent manner. The lysosomal staining was darkened, and the number of lysosomes was obviously increased at 6 h after OGD, indicating the activation of lysosomes. Moreover, morphological features of apoptosis and necrosis, such as cell shrinkage, chromatin condensation and damaged organelles with deteriorated membranes, were also observed at 12 h after OGD. Propofol Reduced the OGD-induced Cell Death To determine the influence of propofol on OGD-induced cell injury, PC12 cells were treated with propofol or 3-MA during OGD. A concentration of 2050 mmol/L of propofol or 20 mmol/L of 3-MA effectively blocked the activation of autophagy, as evidenced by the inhibition of LC3-II production. Lactate dehydrogenase leakage was measured as an indicator of OGD-induced injury in PC12 cells. The results showed that LDH leakage was markedly increased at 6 h after OGD. Propofol treatment resulted in a small but significant decrease in LDH leakage in a dose-dependent manner. Bafilomycin A1 is a selective inhibitor of vacuolar HATPase and therefore inhibits the maturation of autophagosomes. The results of the present study showed that the PC12 cell viability was decreased sharply 6 h after OGD. Propofol treatment significantly increased the cell viability of PC12 cells in a dosedependent manner. The Effect of Propofol on the Expression of Autophagyrelated Proteins in PC12 Cells Following OGD Autophagy is primarily regulated by one central pathway: the class III PI3K-Beclin-1-Bcl-2-dependent mechanism. To explore how propofol regulates OGD-induced autophagy, we analyzed the expression of several autophagy-related proteins involved in this pathway in the OGD-injured PC12 cells. OGD injury resulted in a significant increase of Beclin-1 and LC3-II expression as compared with the control group. In addition, class III PI3K, which positively mediates autophagy, was greatly upregulated in the OGD-injured PC12 cells. However, treatment with propofol and/or LY294002 significantly decreased Beclin-1 and class III PI3K expression in PC12 cells, suggesting that OGD-induced autophagic cell death is dependent ” on the formation of the class III PI3K sub-complex containing Beclin-1. To further confirm the influence of propofol on the response of the class III PI3K-Beclin-1-Bcl-2 interaction to OGD-induced autophagy in the presence 
of propofol, the cells were transiently transfected with small interference RNA against Beclin1 for 072 h, which is a principal regulator in the formation of autophagosomes and the initiation of autophagy through the class III PI3K pathway or the inhibition of autophagy through the Bcl-2 pathway. We observed a significantly increased interaction between Beclin-1 and class III PI3K, leading to Beclin1-dependent autophagic cell death, while the administration of propofol promoted Bcl-2 protein expression and significantly decreased class III PI3K protein expression in the ” OGD-injured PC12 cells. These observations suggest that the decreased expression of Beclin-1 and class III PI3K or the increased Bcl-2 expression by propofol in the OGDinjured