Abstract

2-Methoxyestradiol (2-ME; estradiol metabolite) inhibits vascular smooth muscle cell (VSMC) growth and protects against atherosclerosis and vascular injury; however, the mechanisms by which 2-ME induces these actions remain obscure. To assess the impact of 2-ME on biochemical pathways regulating VSMC biology, we used high-density oligonucleotide microarrays to identify differentially expressed genes in cultured human female aortic VSMCs treated with 2-ME acutely (4 hours) or long term (30 hours). Both single gene analysis and Gene Set Enrichment Analysis revealed 2-ME-induced downregulation of genes involved in mitotic spindle assembly and function in VSMCs. Also, Gene Set Enrichment Analysis identified effects of 2-ME on genes regulating cell-cycle progression, cell migration/adhesion, vasorelaxation, inflammation, and cholesterol metabolism. Transcriptional changes were associated with changes in protein expression, including inhibition of cyclin D1, cyclin B1, cyclin-dependent kinase 6, cyclin-dependent kinase 4, tubulin polymerization, cholesterol and steroid synthesis, and upregulation of cyclooxygenase 2 and matrix metalloproteinase 1. Microarray data suggested that 2-ME may activate peroxisome proliferator-activated receptors (PPARs) in VSMCs, and 2-ME has structural similarities with rosiglitazone (PPARγ agonist). However, our finding of weak activation and lack of binding of 2-ME to PPARs suggests that 2-ME may modulate PPAR-associated genes via indirect mechanisms, potentially involving cyclooxygenase 2. Indeed, the antimitogenic effects of 2-ME at concentrations that do not inhibit tubulin polymerization were blocked by the PPAR antagonist GW9662 and the cyclooxygenase 2 inhibitor NS398. Finally, we demonstrated that 2-ME inhibited hypoxia-inducible factor 1α. Identification of candidate genes that are positively or negatively regulated by 2-ME provides important leads to investigate and better understand the mechanisms by which 2-ME induces its vasoprotective actions.