Experimental protocol diagram. (a) Searching a suitable curcumin concentration. The cells were divided into 5 groups, including the normal cultured control group, oxygen glucose 3 h OGD plus 24 reoxygenation treatment group (OGD/R), and 3 concentrations of curcumin treatment groups. After the treatments, cell viability and LDH release were assessed. (b) Observing curcumin-induced effect on SOD2 protein expression. The cells were divided into 4 groups, including normal cultured control group and 3 concentrations of curcumin treatment groups; after 3 h treatment, SOD2 expression was assessed by using western blot analysis. (c) Evaluating interfering effect of SOD2-siRNA. The cells were divided into 3 groups, including control group, SOD2-siRNA treatment group, and scrambled (SC)-siRNA treatment group. After the treatments, SOD2 protein expression was evaluated by using western blot analysis. (d) Exploring the role of SOD2 in curcumin-induced protection in HT22 cells. The cells were divided into 5 groups, including control, OGD/R treatment group, Cur + OGD/R group, SOD2-siRNA + Cur + OGD/R group, and SC-siRNA + Cur + OGD/R group; after the treatments, cell injury, apoptosis, SOD2 expression, cell morphology, intracellular ROS, mitochondrial functions, and superoxide were assessed.