Methoxyestradiol (2-ME), an endogenous metabolite of estradiol, not only exerts cytotoxic effects on cancer cells but also protects against multiple proliferative disorders, including atherosclerosis and injury-induced intimal thickening. However, the molecular mechanisms by which 2-ME induces its anti-vasoocclusive actions are largely unknown. Given that abnormal growth and excessive proliferation of smooth muscle cells (SMCs) importantly
contribute to the vascular remodeling process associated with hypertension and atherosclerosis, the aims of this study were to assess the impact of 2-ME on pathophysiological pathways regulating SMC growth using transcriptional profiling. High-density oligonucleotide microarrays (Affymetrix Human Genome U_133 Plus 2.0 GeneChips) were used to identify differentially expressed genes in cultured human aortic SMCs treated with 2-ME (acutely, for 4 hrs, n=3; and chronically, for 48 hrs, n=3) and vehicle-treated time-matched controls (n=3 for each time point). Both single gene analysis (performed using Significance Analysis of Microarrays) as well as Gene Set Enrichment Analysis (GSEA, a computational method that determines whether an a priori defined set of genes shows statistically significant, concordant differences between two biological states) indicated downregulation of genes critically involved in mitotic spindle assembly and function in SMCs chronically treated with 2-ME when compared to control cultures. GSEA analysis identified significant effects of 2-ME on cell cycle progression, cell migration/adhesion, vasorelaxation, apoptosis, the inflammatory response, and cholesterol homeostasis/metabolism. Major changes were also observed in genes regulating the respiratory chain and redox pathways. 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 and antivasoocclusive actions.