2-Methoxyestradiol prevents monocyte adhesion to vascular endothelial cells via downregulation of VCAM-1 expression

Abstract

2-Methoxyestradiol (2-ME) reduces atherosclerotic lesion formation. However, the underlying mechanisms remain largely unknown. In this work, we investigated the effect of 2-ME on monocyte adhesion to vascular endothelial cells. Lipopolysaccharides (LPS) greatly increased the attachment of monocyte onto cultured human umbilical vascular endothelial cells (HUVECs), which was inhibited by 2-ME in a dose- and time-dependent manner, or by the vascular cell adhesion protein-1 (VCAM-1) neutralizing antibody, suggesting that a functional releationship between 2-ME and VCAM-1 may exist. In accordance with this, treatment with 2-ME (10⁻⁷–10⁻⁵ M) for 6–48 h downregulated VCAM-1 protein expression. Meanwhile, the nuclear factor κB (NF-κB) p65 subunit activity and its nuclear translocation was inhibited by 2-ME in HUVECs. The PI3K inhibitor wortmannin or the specific Akt siRNA both inhibited the effects of 2-ME, suggesting that 2-ME inhibited p65 activity via PI3K/Akt signaling. In conclusion, 2-ME inhibits VCAM-1 expression and thus prevents monocyte adhesion to vascular endothelial cells via regulation of PI3K/Akt and NF-κB signaling. These findings will be helpful for better understanding the mechanisms through which 2-ME improves endothelial function.

Chinese abstract

2-甲氧雌二醇（2-ME）是能够减轻动脉粥样硬化病损的发生，但是其作用机制大部分都还不为人所知。在这项工作中，我们研究了2-ME对单核细胞在血管内皮细胞的粘附中所起的作用。脂多糖类（LPS）能够明显地促进单核细胞对培养人脐血管内皮细胞（HUVECs）的粘附，而这种促进作用能够为2-ME所抑制，该抑制作用呈现时间或剂量依赖模式；或者通过抗体中和血管细胞粘附分子-1（VCAM-1）来抑制，提示2-ME和VCAM-1之间可能存在一定的相关性。与之相应的是，运用2-ME（10⁷–10⁵ M）治疗6-48小时能够降调VCAM-1的表达。同时，2-ME能够抑制人脐血管内皮细胞核因子活化B细胞κ轻链增强子（NF-κB）P65亚单位的活性以及核转运。而P13K抑制素渥曼霉素或特异性抑制Akt 的siRNA都可以抑制2-ME的作用，提示2-ME通过P13K/Akt信号通路发挥作用。综上所述，2-ME通过调节PI3K/Akt 和 NF- κB 信号通路抑制VCAM-1的表达，从而抑制单核细胞对血管内皮的粘附。这些发现可以更好地帮助我们理解2-ME改善内皮功能的机制。

• 2-Methoxyestradiol
• monocyte adhesion
• nuclear factor κB
• vascular cell adhesion molecule-1
• vascular endothelial cells