Deletion of Krüppel‐Like Factor 4 in Endothelial and Hematopoietic Cells Enhances Neointimal Formation Following Vascular Injury

Abstract

BackgroundKrüppel‐like factor 4 (Klf4) is involved in a variety of cellular functions by activating or repressing the transcription of multiple genes. Results of previous studies showed that tamoxifen‐inducible global deletion of the Klf4 gene in mice accelerated neointimal formation following vascular injury, in part via enhanced proliferation of smooth muscle cells (SMCs). Because Klf4 is also expressed in non‐SMCs including endothelial cells (ECs), we determined if Tie2 promoter‐dependent deletion of Klf4 in ECs and hematopoietic cells affected injury‐induced neointimal formation.Methods and ResultsKlf4 conditional knockout (cKO) mice were generated by breeding Tie2‐Cre mice and Klf4 floxed mice, and their phenotype was analyzed after carotid ligation injury. Results showed that injury‐induced repression of SMC differentiation markers was unaffected by Tie2 promoter‐dependent Klf4 deletion. However, of interest, neointimal formation was significantly enhanced in Klf4‐cKO mice 21 days following carotid injury. Moreover, Klf4‐cKO mice exhibited an augmented proliferation rate, enhanced accumulation of macrophages and T lymphocytes, and elevated expression of cell adhesion molecules including vascular cell adhesion molecule–1 (Vcam1) and E‐selectin in injured arteries. Mechanistic analyses in cultured ECs revealed that Klf4 inhibited tumor necrosis factor‐α–induced expression of Vcam1 through blocking the binding of nuclear factor‐κB to the Vcam1 promoter.ConclusionsThese results provide evidence that Klf4 in non‐SMCs such as ECs regulates neointimal formation by repressing arterial inflammation following vascular injury.

Endothelial Krüppel-Like Factor 4 Mediates the Protective Effect of Statins against Ischemic AKI

“…27,28 Second, we previously reported that the number of neutrophils, lymphocytes, and monocytes in the blood did not differ between the Klf4 cKO and control mice. 11 In this study we showed that the accumulation of neutrophils and lymphocytes was enhanced in the kidneys at 24 hours after I/R injury in Klf4 cKO mice compared with that in control mice. However, these inflammatory cells do not express endogenous Klf4 in either Klf4 cKO or control mice.…”

“…11 Coimmunoprecipitation assays demonstrated that KLF4 and p65 physically interacted with each other. 11,33 In addition, we showed that TNFmediated increases in p65 binding to the VCAM1 promoter were attenuated in the presence of KLF4, as determined by chromatin immunoprecipitation assays.…”

“…11 Coimmunoprecipitation assays demonstrated that KLF4 and p65 physically interacted with each other. 11,33 In addition, we showed that TNFmediated increases in p65 binding to the VCAM1 promoter were attenuated in the presence of KLF4, as determined by chromatin immunoprecipitation assays. 11 The inhibitory action of KLF4 against p65 occurred in the nucleus rather than in the cytoplasm because phosphorylation and nuclear translocation of p65 were unaffected by KLF4 overexpression.…”

“…[23][24][25] Moreover, we previously showed that KLF4 inhibited TNF-induced expression of VCAM1 through blocking the binding of NF-kB to the VCAM1 promoter in cultured ECs. 11 To clarify the molecular mechanisms whereby statins attenuated renal I/R injury in control mice, but not in Klf4 cKO mice, we examined whether KLF4 contributed to the suppressive effect of statins on TNF-induced VCAM1 expression in HUVECs.…”

“…10 Moreover, we have previously reported that Tek promoter-dependent Klf4 deletion in ECs resulted in enhancement of injuryinduced neointimal formation, in part through overexpression of cell adhesion molecules and augmented infiltration of inflammatory cells into injured carotid arteries. 11 As such, the results of prior studies provide evidence that Klf4 is a critical factor regulating the development and progression of multiple vascular diseases through its effect on endothelial inflammation.…”