Schatz Frederick, Kuczynski Edward, Kloosterboer Helenius J, Buchwalder Lynn, Tang Caroline, Krikun Graciela, Lockwood Charles J
Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8063, USA.
Steroids. 2005 Nov;70(12):840-5. doi: 10.1016/j.steroids.2005.04.010.
Tibolone is a highly effective postmenopausal hormone treatment that has its biological activity dependent on metabolism to 3alpha- and 3beta-OH tibolone, which bind solely to the estrogen receptor. Despite the high levels of estrogen receptor-binding metabolites in the circulation, the endometrium becomes atrophic, suggesting inactivation of the estrogen response in this tissue which may be due to the progestogenic activity of tibolone and the Delta-4 tibolone metabolite. We evaluated the effects of tibolone and its metabolites on tissue factor (TF) and plasminogen activator inhibitor type 1 (PAI-1) expression in human endometrial stromal cells (HESCs). Since TF and PAI-1 exhibit long-term in vivo and in vitro up-regulation by progestin they serve as endpoints for assessing chronic effects of progestin exposure. Confluent HESCs were primed in serum-containing medium with vehicle control, 10(-8)mol/L estradiol, 10(-7)mol/L medroxyprogesterone acetate, or 10(-8) to 10(-6)mol/L tibolone or its metabolites, then switched to a defined medium with corresponding vehicle or steroids. After 24h, ELISAs indicated that the progestin elevated TF (6.2-fold +/-3.0; p<0.05) and PAI-1 (eight-fold +/-2.1; p<0.05) levels, whereas the cells were refractory to estradiol exposure. Tibolone and Delta-4 tibolone (10(-8) to 10(-6)mol/L) were as effective as 10(-7)mol/L medroxyprogesterone acetate in enhancing TF and PAI-1 output (p<0.05). Unexpectedly, at the higher concentrations 3alpha- and 3beta-OH tibolone also elevated TF and PAI-1 expression (p<0.05). Western blotting confirmed the ELISA results. Our findings suggest that HESCs metabolize 3alpha- and 3beta-OH tibolone to tibolone and subsequently to Delta-4 tibolone, which can both stimulate the progesterone receptor. Since TF and PAI-1 promote hemostasis by complementary mechanisms, our findings account for the reduced occurrence of abnormal uterine bleeding associated with tibolone therapy.
替勃龙是一种高效的绝经后激素治疗药物，其生物活性依赖于代谢为3α-和3β-羟基替勃龙，这两种代谢产物仅与雌激素受体结合。尽管循环中雌激素受体结合代谢产物水平很高，但子宫内膜会萎缩，这表明该组织中雌激素反应失活，这可能是由于替勃龙及其Δ-4代谢产物的孕激素活性所致。我们评估了替勃龙及其代谢产物对人子宫内膜基质细胞（HESC）中组织因子（TF）和纤溶酶原激活物抑制剂1型（PAI-1）表达的影响。由于TF和PAI-1在体内和体外长期受到孕激素的上调，它们可作为评估孕激素暴露慢性影响的终点指标。将汇合的HESC在含血清的培养基中用溶剂对照、10⁻⁸mol/L雌二醇、10⁻⁷mol/L醋酸甲羟孕酮或10⁻⁸至10⁻⁶mol/L替勃龙或其代谢产物进行预处理，然后切换至含有相应溶剂或类固醇的限定培养基中。24小时后，酶联免疫吸附测定（ELISA）表明，孕激素使TF（6.2倍±3.0；p<0.05）和PAI-1（8倍±2.1；p<0.05）水平升高，而细胞对雌二醇暴露无反应。替勃龙和Δ-4替勃龙（10⁻⁸至10⁻⁶mol/L）在增强TF和PAI-1输出方面与10⁻⁷mol/L醋酸甲羟孕酮一样有效（p<0.05）。出乎意料的是，在较高浓度下，3α-和3β-羟基替勃龙也会升高TF和PAI-1的表达（p<0.05）。蛋白质印迹法证实了ELISA结果。我们的研究结果表明，HESC将3α-和3β-羟基替勃龙代谢为替勃龙，随后再代谢为Δ-4替勃龙，这两种代谢产物均可刺激孕激素受体。由于TF和PAI-1通过互补机制促进止血，我们的研究结果解释了与替勃龙治疗相关的异常子宫出血发生率降低 的原因。
