Abstract. The present study was undertaken to investigate whether withdrawal of estrogen and progesterone (EP-withdrawal) stimulates prostaglandin F2α (PGF2α) production through oxygen radical (ROS)-induced NF-κB activation in human endometrial stromal cells (ESC). To study the EPwithdrawal, ESC that had been treated with estradiol (E, 10 -8 M) and medroxyprogesterone acetate (MPA, 10 -6 M) for 12 days were then incubated with or without E+MPA for a further 11 days. PGF2α concentrations in the medium and cyclooxygenase-2 (COX-2) mRNA levels were significantly increased after EP-withdrawal, while they were unchanged by the continuous treatment with E+MPA. When ESC were incubated with N-acetyl-L-cysteine (Nac, 50 mM), an antioxidant, during EP-withdrawal, Nac blocked the increases in PGF2α production and COX-2 mRNA expression caused by EPwithdrawal. Next, we examined whether ROS generated in response to EP-withdrawal acted through NF-κB activation. Electrophoretic mobility shift assay revealed that EP-withdrawal caused marked increases in NF-κB DNA binding activity, which was completely suppressed by Nac. Furthermore, when ESC were incubated with MG132 (3 µM), which inhibits NF-κB activation, during EPwithdrawal, MG132 blocked the increases in PGF2α production and COX-2 mRNA expression caused by EP-withdrawal. In conclusion, EP-withdrawal stimulates COX-2 expression and PGF2α production through ROS-induced NF-κB activation, suggesting a possible mechanism for menstruation. Key words: Endometrial stromal cell, Prostaglandin F2α, NF-κB, Superoxide dismutase, Superoxide radical (J. Reprod. Dev. 50: [215][216][217][218][219][220][221][222][223][224][225] 2004) eactive oxygen species (ROS), including superoxide radicals, cause cell damage, whereas superoxide dismutase (SOD) is an enzyme specific to scavenging superoxide radicals and protects cells from oxygen radical cytotoxicity. Oxidative stress and its defense system have been reported to play important roles in the regulation of reproductive function [1][2][3][4][5][6][7]. In the human endometrium, SOD activities decrease and ROS levels increase in the late secretory phase, just before menstruation, suggesting that these changes in SOD and ROS may be involved in endometrial breakdown [8]. Recently, much attention has been focused on the reports that ROS act as second messengers in the regulation of cellular function [9-

Immunohistochemistry for vascular endothelial growth factor (VEGF) and its receptors, fms-like tyrosine kinase (flt-1) and kinase insert domain-containing region (KDR), was performed on human endometrium obtained from patients with normal menstrual cycles, patients given oestrogen and progesterone, and women in early pregnancy. Intense immunostaining of VEGF was observed in both glandular epithelial and stromal cells during the mid-secretory phase; the immunostaining intensity was increased by administration of oestrogen plus progesterone and strong immunostaining was observed in decidual cells of early pregnancy. In addition to the immunostaining in vascular endothelial cells, strong KDR immunostaining was observed in glandular epithelial cells and in decidualized stromal cells induced by administration of oestrogen plus progesterone, whereas flt-1 immunostaining was negligible. Strong immunostaining for flt-1 and KDR was found in both vascular endothelial cells and decidual cells in early pregnancy. Endometrial stromal cells isolated from proliferative phase endometrium were incubated with oestrogen (10(-8) mol l-1) and medroxyprogesterone acetate (MPA; 10(-6) mol l-1) for 18 days to study the regulation of VEGF, flt-1 and KDR in endometrial stromal cells by oestrogen and progesterone. Expression of VEGF and KDR mRNAs was increased significantly by oestrogen and MPA, accompanied by decidualization, whereas flt-1 mRNA expression was not affected. In conclusion, VEGF and its receptors may play important roles in implantation and maintenance of pregnancy.

Apoptosis contributes to luteal regression in many species. In the postpartum rat, there are two different types of corpora lutea (CL) in the ovary: CL of pregnancy (CLP) and newly formed CL (NCL). To investigate the regulation of apoptosis in the two different types of CL during luteal regression, apoptosis and caspase-3 activity were examined in the CL obtained on Days 7, 15, and 21 of pregnancy and Days 0, 1, 3, 5, 7, and 9 postpartum. Furthermore, the effect of lactation on apoptosis in the CL was examined in two groups of postpartum rats: lactating rats that nurse more than 10 pups, and nonlactating rats that nurse no pups. Apoptotic cells were detected after Day 21 of pregnancy. In the CLP, remarkable increases in the number of apoptotic cells on Days 5 and 9 postpartum were observed in nonlactating rats (P < 0.01), but not in lactating rats. Changes in caspase-3 activity in the CLP were not consistent with those in number of apoptotic cells. In the NCL, an increase in apoptosis was found only on Day 5 postpartum in nonlactating rats (P < 0.01), but not in lactating rats. Changes in caspase-3 activity in the NCL were consistent with those in number of apoptotic cells. In conclusion, apoptosis is, at least in part, involved in luteal regression after parturition, and lactation appears to inhibit apoptosis. This study also suggests the presence of a caspase-3-independent mechanism for apoptosis in CLP regression in the rat.

Reactive oxygen species stimulate PGF2 alpha production in ESC, suggesting that they might influence endometrial function by regulating PGF2 alpha production.

The present study was undertaken to investigate the role of estrogen and progesterone in the expression of copper-zinc superoxide dismutase (Cu,Zn-SOD) and manganese SOD (Mn-SOD) in human endometrial stromal cells (ESC). ESC were incubated with estradiol (10(-8) mol/l), medroxyprogesterone acetate (MPA, 10(-6) mol/l), or estradiol + MPA for 18 days. MPA significantly increased Cu,Zn-SOD and Mn-SOD mRNA levels and enzyme activities as well as the mRNA level of insulin-like growth factor-binding protein-1 (IGFBP-1), a marker for decidualization. Estradiol only augmented the effects of MPA on Cu,Zn-SOD activity and IGFBP-1 mRNA level, and estradiol alone had no effect. To study the withdrawal of estrogen and progesterone (EP withdrawal), ESC that had been treated with estradiol + MPA for 12 days were washed and then incubated with or without estradiol + MPA for a further 11 days. Cu,Zn-SOD mRNA levels and activities declined after EP withdrawal, while they were gradually increased by the continuous treatment with estradiol + MPA. In contrast, Mn-SOD mRNA levels and activities were not affected by EP withdrawal. IGFBP-1 mRNA levels were significantly increased 4 days after EP withdrawal and decreased thereafter, whereas they were gradually increased by the continuous treatment with estradiol + MPA. In conclusion, Cu,Zn-SOD, Mn-SOD and IGFBP-1 are differently regulated by estrogen and progesterone in human ESC. The decrease in Cu,Zn-SOD after the ovarian steroid withdrawal may be involved in endometrial breakdown.