ERK5 deficiency in platelets decreases platelet accumulation in hyperlipidemic and oxidant stress conditions. Bone marrow from ERK5^flox/flox or ERK5^flox/PF4-cre⁺ mice was transplanted to 8- to 12-week-old apoE null recipient mice. Recipient mice were fed a Western HFD or CD for 5 weeks before performing in vivo thrombosis experiments. (A) Representative video images of carotid artery thrombi formation after 7.5% FeCl₃ treatment. Platelets were labeled by direct jugular vein injection of rhodamine 6G (0.5 mg/mL, 100 μL) and arteries were observed in real time using fluorescent intravital microscopy. The last image in each row indicates time to flow cessation. (B) Accumulating data showing blood flow cessation time. CD, chow diet; HFD, high-fat diet. (C) Representative video images of platelet accumulation in collagen-mediated thrombosis. (D-E) Quantification of platelet accumulation. For FeCl₃-mediated thrombosis experiments, P value was determined by Mann-Whitney rank sum test. For collagen-mediated thrombosis experiments, P value was determined by 2-way ANOVA with Tukey post hoc analysis. Data represented as mean ± SEM.