PKCζ activation and ERK5 expression in the ApoE^−/− mouse. Aortas from 12-week-old ApoE^−/− mice were harvested for qualitative analysis of PKCζ activation (A-D red) and ERK5 expression (E-H red). The differential PKCζ activation or ERK5 expression is evident in the images of the whole aortic mount (4× lens; A,E), in the en face analysis of the aortic arch (20× lens; B,F), and specifically in the athero-prone (C,G; 60× lens) and athero-protected (D, H; 60× lens) areas of the aortic arch. EC morphology was changed in the early atherosclerosis regions (B,F; arrowheads) where ECs are stretched and may have lost PECAM-1 staining (green) at some cell junctions. Bar = 10 μm.