To mimic ischemic condition in vitro, primary neurons or PC12 cells were exposed to OGD as described previously (Liu et al., 2012). In brief, neurons or PC12 cells were subjected to OGD by replacing the normal growth medium with glucose free medium (DMEM without glucose) pre-equilibrated with 95% N2 and 5% CO2. The cells were then incubated in a humidified airtight chamber (Biospherix Ltd., Lacona, NY, USA) for 1 h, 3 h, or 6 h. Control cultures were incubated with normal DMEM medium without FBS at 37°C in 5% CO2/95% air. OGD was terminated by removing cells from the hypoxic chamber and the cells were collected separately for further measurement.