MEF2 transcription factor is one downstream target of ERK5, and ERK5 was required for laminar flow-induced expression of KLF2 in HUVECs13. To ask whether ERK5 are involved in TA-induced KLF2 expression, HCAECs were treated with TA and then the levels of ERK5 phosphorylation and total ERK5 were examined. As shown in Fig. 3B–D, TA induced ERK5-phosphorylation in a time-dependent manner without affecting total ERK5 expression. These results suggest that the ERK5-MEF2 dependent pathway is likely to mediate TA-induced upregulation of KLF2 in ECs.