LDLs exposure activates the apoptotic signaling pathway. At 48 hours after exposure to 100 μg/ml of LDLs, the cells cultured on the coverslips were fixed and subjected to immunocytochemistry with the first antibody against rabbit active caspase-3 and the second rabbit IgG conjugated with Alexa fluor 568. Representative images are shown. Bar, 25 μm (Figure 2 a ). Whole cell lysates were prepared at 0, 12, 24, 48 and 72 hours after the exposure to the 100 μg/ml of LDLs, and subjected to Western blot analysis using antibodies against p53 and actin. The representative images are shown in Figure 2c. The quantitative results are shown in Figure 3 b and d. The p53 levels were normalized by the actin levels in Western blotting. The changes under the LDLs exposure are expressed as relative changes of the level at 0 time point. Mean ± SD (n = 3). *, #: p < 0.05 vs. the 0 point.