2-Methoxyestradiol, an Estradiol Metabolite, Inhibits Neointima Formation and Smooth Muscle Cell Growth via Double Blockade of the Cell Cycle

Abstract

2-Methoxyestradiol (2-ME), an endogenous metabolite of estradiol with no affinity for estrogen receptors, is a potent anticarcinogenic agent (in phase II clinical trials) and mediates the inhibitory effects of estradiol on smooth muscle cell (SMC) growth. Here we studied the intracellular mechanisms by which 2-ME inhibits SMC growth and whether 2-ME prevents injury-induced neointima formation. 2-ME concentrations that inhibit proliferation of cycling human aortic SMCs by >or=50% blocked cell-cycle progression in G(0)/G(1) and in G(2)/M phase, as determined by flow cytometry. Consistent with the cell-cycle effects, at a molecular level (Western blots), 2-ME inhibited cyclin D(1) and cyclin B(1) expression; cyclin-dependent kinase (cdk)-1 and cdk-2 activity; and retinoblastoma protein (pRb), extracellular signal-regulated kinase (ERK) 1/2, and Akt phosphorylation. 2-ME also upregulated the Cdk inhibitor p27 and interfered with tubulin polymerization. Moreover, 2-ME augmented COX-2 expression, suggesting that it may also inhibit SMC growth via prostaglandin formation. In rats, treatment with 2-ME abrogated injury-induced neointima formation; decreased proliferating SMCs; downregulated expression of proliferating-cell nuclear antigen (PCNA), c-myc, cyclin D(1), cyclin B(1), phosphorylated Akt, phosphorylated ERK1/2, p21, and pRb; inhibited cdk-1 and cdk-4 activity; and upregulated expression of cyclooxygenase (COX)-2 and p27. Caspase-3 cleavage assay and fluorescence-activated cell-sorting (FACS) analysis showed no evidence of apoptosis in 2-ME-treated SMCs, and TUNEL staining in carotid segments showed no evidence of 2-ME-induced apoptosis in vivo. The antimitotic effects of 2-ME on SMCs are mediated by the inhibition of key cell-cycle regulatory proteins and effects on tubulin polymerization and COX-2 upregulation. These effects of 2-ME most likely contribute to the antivasoocclusive actions of this endogenous compound.

Complexities of oestradiol pharmacology in pulmonary arterial hypertension

“…To explore the role of oestrogens in PAH, we observed the effect of endogenous and exogenous E 2 (17b-oestradiol) in rats with monocrotaline (MCT)-induced pulmonary hypertension (PH) [1]. Our results suggested similar protective roles of endogenous and exogenous E 2 in pulmonary vascular remodelling and right ventricular hypertrophy in MCT-induced PH rats, which is similar to the effect of E 2 reported in the study of UMAR et al [6]. E 2 therapy has been shown to rescue both pulmonary vasculopathy and right ventricle function in rats with PH.…”

“…Furthermore, 2ME is decisively more potent than E 2 in increasing prostacyclin synthesis and release, in inhibiting endothelin synthesis in endothelial cells, in stimulating nitric oxide release from endothelium, and in inhibiting growth of systemic and pulmonary vascular smooth muscle cells [2]. Similar to the effects of E 2 in the YUAN et al [1] study, inhibition of vascular remodelling by 2ME is also associated with down regulated expression of phosphorylated Akt and up regulated expression of cyclooxygenase-2 [6]. Thus, at least in part, the beneficial effects of oestradiol in MCT-PAH are mediated by 2ME.…”

Cytochrome P450 1B1 Is Critical for Neointimal Growth in Wire‐Injured Carotid Artery of Male Mice

“…However, CYP1B1 is known to metabolize 17β‐estradiol into 2‐hydroxyestradiol, and that is subsequently metabolized into 2‐methoxyestradiol, which minimizes Ang II–induced hypertension and oxidative stress in female mice55; both estradiol and 2‐methoxyestradiol reduce neointimal growth in response to balloon angioplasty 56, 57. Therefore, it would be important to determine if Cyp1b1 gene disruption or 2,3′,4,5′‐tetramethoxystilbene treatment enhances neointimal growth and associated pathophysiological changes in response to vascular injury by increasing oxidative stress in female mice.…”

Effect of formulation parameters on 2-methoxyestradiol release from injectable cylindrical poly(dl-lactide-co-glycolide) implants

“…To maintain the sink conditions, the release medium (3 L) was replaced everyday up to 27 days. At predetermined time intervals (1,3,7,14,21, and 28 days), three dialysis bags were taken out and implants were freeze-dried immediately. Freeze-dried implants were digested in acetonitrile, suitably diluted with acetonitrile and analyzed by HPLC.…”

“…2-Methoxyestradiol (2-ME), a metabolite of 17-β-estradiol, inhibits tumor growth, neovascularization, and growth of cancer cells (angiosarcoma, gastric, cervical, colorectal, hepatocellular, prostate, lung, pancreatic, breast, neuroblastoma, leukemia, multiple myeloma) [1][2][3][4][5][6]. In addition to inhibiting the proliferation of cancer cells, 2-ME also possesses antiangiogenic properties [7].…”