P22phox promotes Ang-II-induced vascular smooth muscle cell phenotypic switch by regulating KLF4 expression

Abstract

NADPH oxidase (Nox) is the main source of reactive oxygen species in vascular diseases, which have been implicated in promoting VSMCs phenotypic switch. P22phox, the indispensable component of the complex Nox, is required for their activity and stability. Krüppel-like factor 4 (KLF4) is an important transcriptional regulator of VSMCs phenotypic switch. Both KLF4 and p22phox are involved in the proliferation, migration and differentiation of VSMC. This study aims to determine whether and how p22phox regulates KLF4 expression in phenotypic switching of VSMCs. In cultured primary rat VSMCs, we noticed that the expression of P22phox was significantly increased in combination with VSMCs phenotypic switch and up-regulated KLF4 expression in Ang-II-treated cells. Ang-II-induced VSMC dedifferentiation, proliferation, migration, KLF4 expression, H2O2 production and the phosphorylation of AKT, ERK1/2 were all inhibited by knockdown of P22phox. Furthermore, H2O2 treatment effectively enhanced the phosphorylation of AKT, ERK1/2 and the expression of KLF4, whereas LY294002 (a specific inhibitor of PI3K), U0126 (a specific inhibitor of ERK1/2) significantly attenuated the H2O2-induced up-regulation of KLF4. In conclusion, these results demonstrated that p22phox promotes Ang-II-induced VSMC phenotypic switch via the H2O2-ERK1/2/AKT-KLF4 signaling pathway.