Department of Surgery (M.S., W.F.J., A.W., N.H.P., G.S., G.R.U., G.A.) and The Robert M. Berne Cardiovascular Research Center (G.R.U., G.K.O., G.A.), University of Virginia School of Medicine, Charlottesville, VA.
Circulation. 2013 Sep 10;128(11 Suppl 1):S163-74. doi: 10.1161/CIRCULATIONAHA.112.000238.
KLF4 mediates inflammatory responses after vascular injury/disease; however, the role of KLF4 in abdominal aortic aneurysms (AAAs) remains unknown. The goals of the present study were to (1) determine the role of KLF4 in experimental AAA; and (2) determine the effect of KLF4 on smooth muscle (SM) cells in AAAs.
KLF4 expression progressively increased at days 3, 7, and 14 after aortic elastase perfusion in C57BL/6 mice. Separately, loss of a KLF4 allele conferred AAA protection using ERTCre+ KLF4 flx/wt mice in the elastase AAA model. In a third set of experiments, SM-specific loss of 1 and 2 KLF4 alleles resulted in progressively greater protection using novel transgenic mice (MYHCre+ flx/flx, flx/wt, and wt/wt) in the elastase AAA model compared with control. Elastin degradation, MAC2, and cytokine production (MCP1, tumor necrosis factor-α, and interleukin-23) were significantly attenuated, whereas α-actin staining was increased in KLF4 knockout mice versus controls. Results were verified in global KLF4 and SM-specific knockout mice using an angiotensin II model of aneurysm formation. KLF4 inhibition with siRNA attenuated downregulation of SM gene expression in vitro, whereas in vivo studies demonstrated that KLF4 binds to promoters of SM genes by chromatin immunoprecipitation analysis. Finally, human aortic aneurysms demonstrated significantly higher KLF4 expression that was localized to SM cells.
KLF4 plays a critical role in aortic aneurysm formation via effects on SM cells. These results suggest that KLF4 regulates SM cell phenotypic switching and could be a potential therapeutic target for AAA disease.
KLF4 介导血管损伤/疾病后的炎症反应；然而，KLF4 在腹主动脉瘤（AAA）中的作用尚不清楚。本研究的目的是：（1）确定 KLF4 在实验性 AAA 中的作用；（2）确定 KLF4 对 AAA 中平滑肌（SM）细胞的影响。
在 C57BL/6 小鼠弹性蛋白酶灌注后第 3、7 和 14 天，KLF4 表达逐渐增加。另外，使用 ERTCre+ KLF4 flx/wt 小鼠在弹性蛋白酶 AAA 模型中，缺失一个 KLF4 等位基因可提供 AAA 保护。在第三组实验中，使用新型转基因小鼠（MYHCre+ flx/flx、flx/wt 和 wt/wt）在弹性蛋白酶 AAA 模型中，与对照组相比，SM 特异性缺失 1 和 2 个 KLF4 等位基因可提供逐渐更大的保护。弹性蛋白降解、MAC2 和细胞因子产生（MCP1、肿瘤坏死因子-α和白细胞介素-23）明显减弱，而 KLF4 敲除小鼠的α-肌动蛋白染色增加。在使用血管紧张素 II 形成动脉瘤模型的全局 KLF4 和 SM 特异性敲除小鼠中验证了这些结果。用 siRNA 抑制 KLF4 可减弱体外 SM 基因表达的下调，而体内研究表明 KLF4 通过染色质免疫沉淀分析与 SM 基因的启动子结合。最后，人主动脉瘤的 KLF4 表达明显升高，并且定位于 SM 细胞。
KLF4 通过对 SM 细胞的影响在主动脉瘤形成中起关键作用。这些结果表明，KLF4 调节 SM 细胞表型转换，可能成为 AAA 疾病的潜在治疗靶点。
