Estrogen Receptor‐Alpha (+/− Ligands) Modulates MMP‐13 Promoter Activity

Abstract

Objective Females are at increased risk for joint injuries/diseases, and the response of joint tissues to the hormonal milieu has been implicated. While the presence of ER-α has been well established in connective tissues, its functional role & potential for contributing to this risk is largely unknown. Matrix metalloproteinase 13 (MMP-13) is well recognized for its role in connective tissue repair and remodeling. The present studies were aimed at understanding the possible influence on the MMP-13 promoter by ER-α +/− specific ligands. Methods A rabbit synoviocyte cell line (HIG-82) was transiently transfected with expression constructs for ER-α + a series of MMP-13 promoter constructs (deletions, specific mutations), & the transfected cells were either untreated or were treated with ligands (17-β Estradiol, Tamoxifen, Raloxifene; 10−6 to 10−14 M). MMP-13 promoter activity was determined via luciferase assays. Results Preliminary studies showed that HIG-82 cells were negative for ER-α prior to transfection. The expression of MMP-13 promoter constructs was positively influenced by co-transfection with ER-α & the AP-1 regulatory site in the MMP-13 promoter was vital for its regulation. Addition of 17-β estradiol led to a dose-dependent decrease in the enhancement of promoter expression by ER-α, while other agonists/antagonists of ER-α exhibited differential affects on the activity of the MMP-13 promoter. Conclusions ER-α influences MMP-13 promoter activity differently in the presence or absence of specific agonists/ antagonists. These findings may have relevance to the functioning of tissues in joints such as the knee during the menstrual cycle or following menopause.