Norethisterone acetate alters coagulation gene expression in vitro in human cell culture

Both oestrogen and progestin and the route of administration have been implicated in cardiovascular and thromboembolic risk in post menopausal hormone users. Transdermal preparations have been reported as safer indicating that liver derived metabolites of oestrogen may be important. The aim of our study was to investigate the in vitro effects of 17β-estradiol, its metabolites, and norethisterone acetate (NETA) on the expression of coagulation genes in cultured human cells.

Human hepatocytes and human umbilical vein endothelial cells(HUVECS) were treated with 17β-estradiol, estrone, 2-hydroxyestradiol (2-OH), NETA and NETA/17β-estradiol (10nM) for 24hours. Fibrinogen, factor VII, prothrombin and plasminogen activator inhibitor -1 (PAI-1) mRNA expression was determined in hepatocyte cultures using TaqMan PCR. Tissue factor (TF), tissue factor pathway inhibitor (TFPI), tissue plasminogen activator (tPA) and PAI-1 expression was determined in HUVECS. Expression of estrogen receptors was also determined.

Fibrinogen and factor VII mRNA expression was upregulated 2-4 fold by estradiol and estrone. Addition of NETA downregulated fibrinogen and prothrombin. PAI-1 expression in hepatocytes was upregulated by estrone, 2-OH, NETA and NETA/17β-estradiol. In HUVECS, TF, TFPI and PAI-1 expression was upregulated by estrone but not by 17β-estradiol. NETA upregulated TF, TFPI and tPA expression. Estrogen receptor status was unaffected by the addition of NETA.

This data suggests a role for progestins in modifying the effects of oestrogen and its metabolites on coagulation gene expression which may contribute to the reduced thrombotic risk associated with transdermal preparations.