2-methoxyestradiol induces vasodilation by stimulating NO release via PPARγ/PI3K/Akt pathway.

Weiyu Chen,Jinghe Huang,Tommaso Simoncini,Yongfu Zhang,Ping Li,Shuhui Zheng,Xiaodong Fu,Yuhong Cui,Raju Reddy

doi:10.1371/journal.pone.0118902

Abstract

The endogenous estradiol metabolite 2-methoxyestradiol (2-ME) reduces atherosclerotic lesion formation, while the underlying mechanisms remain obscure. In this work, we investigated the vasodilatory effect of 2-ME and the role of nitric oxide (NO) involved. In vivo studies using noninvasive tail-cuff methods showed that 2-ME decreased blood pressure in Sprague Dawley rats. Furthermore, in vitro studies showed that cumulative addition of 2-ME to the aorta caused a dose- and endothelium-dependent vasodilation. This effect was unaffected by the pretreatment with the pure estrogen receptor antagonist ICI 182,780, but was largely impaired by endothelial nitric oxide synthase (eNOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME) or by phosphoinositide 3-kinase (PI3K) inhibitor wortmannin (WM). Moreover, 2-ME（10−7 ∼10−5 M）enhanced phosphorylation of Akt and eNOS and promoted NO release from cultured human umbilical endothelial cells (HUVECs). These effects were blocked by PI3K inhibitor WM, or by the transfection with Akt specific siRNA, indicating that endothelial Akt/eNOS/NO cascade plays a crucial role in 2-ME-induced vasodilation. The peroxisome proliferator-activated receptor γ (PPARγ) mRNA and protein expression were detected in HUVECs and the antagonist GW9662 or the transfection with specific PPARγ siRNA inhibited 2-ME-induced eNOS and Akt phosphorylation, leading to the impairment of NO production and vasodilation. In conclusion, 2-ME induces vasodilation by stimulating NO release. These actions may be mediated by PPARγ and the subsequent activation of Akt/eNOS cascade in vascular endothelial cells.

Highlights

Cardiovascular disease is the most common cause of death in women
Estrogen replacement therapy is highly effective in the prevention of chronic diseases such as atherosclerosis and osteoporosis, while it increases the risk of developing breast and endometrial cancers [13]
2-ME is a major endogenous metabolite of E2. It is formed via the sequential conversion of E2 to 2-hydroxyestradiol by cytochrome P450s (CYP450s) and to 2-ME by catechol-Omethyltransferase (COMT) [2]

Summary

Introduction

Cardiovascular disease is the most common cause of death in women. Estrogen is believed to provide cardiovascular protective effects. In addition to its potent anticarcinogenic properties, 2-ME shares similar actions as E2 in the cardiovascular system It attenuates hypertension and coronary vascular remodeling [4], reduces atherosclerotic lesion formation [5] and inhibits neointima formation [6]. These cardiovascular effects are mainly attributed to the actions of 2-ME on vascular smooth muscle cells (VSMCs) [7], while the actions of 2-ME on vascular endothelial cells remain obscure. Endothelial dysfunction is the first step towards cardiovascular disease such as atherosclerosis [8] It is characterized by impaired vasodilation, pro-thrombosis, pro-coagulation, etc [9]. We explored the role of peroxisome proliferator-activated receptor γ (PPARγ) in regulating these signaling pathways in vascular endothelial cells

Results

Discussion

Findings

Materials and Methods