Michel A. Fortier

Expression of Cyclooxygenases 1 and 2 and Prostaglandin E Synthase in Bovine Endometrial Tissue During the Estrous Cycle

Abstract In ruminants, endometrial prostaglandin F2α (PGF2α) is responsible for luteolysis and prostaglandin E2 (PGE2) is thought to be involved in maternal recognition of pregnancy. In the present study, healthy uteri were collected from cows at the abattoir, and days of the estrous cycle were determined macroscopically. The uteri were classified into seven groups as Days 1–3, 4–6, 7–9, 10–12, 13–15, 16–18, and 19–21 of the estrous cycle. Endometrial scrapings were collected. The expression of cyclooxygenase (COX)-1 and COX-2 mRNAs and proteins and PGE synthase (PGES) mRNA was analyzed by Northern and Western blot. There was no expression of COX-1, either mRNA or protein, on any day of the estrous cycle. In contrast, COX-2 mRNA and protein were expressed at low and high levels on Days 1–12 and 13–21 of the estrous cycle, respectively. The level of expression of PGES was moderate, low, and high on Days 1–3, 4–12, and 13–21 of the estrous cycle, respectively. There were significant correlations between COX-2 mRNA and protein levels and between COX-2 and PGES mRNA levels. COX-1 mRNA and protein are not expressed on any day of the estrous cycle, whereas COX-2 mRNA and protein and PGES mRNA are differentially expressed and regulated in bovine endometrium during the estrous cycle. COX-2, rather than COX-1, is the primary isoenzyme involved in the endometrial production of prostaglandins, and the COX-2 and PGES pathway is responsible for the endometrial production of PGE2 in the bovine endometrium during the estrous cycle.

An Aldose Reductase with 20α-Hydroxysteroid Dehydrogenase Activity Is Most Likely the Enzyme Responsible for the Production of Prostaglandin F2α in the Bovine Endometrium

Prostaglandins are important regulators of reproductive function. In particular, prostaglandin F2α (PGF2α) is involved in labor and is the functional mediator of luteolysis to initiate a new estrous cycle in many species. These actions have been extensively studied in ruminants, but the enzymes involved are not clearly identified. Our objective was to identify which prostaglandin F synthase is involved and to study its regulation in the endometrium and in endometrial primary cell cultures. The expression of all previously known prostaglandin F synthases (PGFSs), two newly discovered PGFS-like genes, and a 20α-hydroxysteroid dehydrogenase was studied by Northern blot and reverse transcription PCR. These analyses revealed that none of the known PGFS or the PGFS-like genes were significantly expressed in the endometrium. On the other hand, the 20α-hydroxysteroid dehydrogenase gene was strongly expressed in the endometrium at the time of luteolysis. The corresponding recombinant enzyme has aK m of 7 μm for PGH2 and a PGFS activity higher than the lung PGFS. This enzyme has two different activities with the ability to terminate the estrous cycle; it metabolizes progesterone and synthesizes PGF2α. Taken together, these data point to this newly identified enzyme as the functional endometrial PGFS.

Effect of intravaginal dehydroepiandrosterone (Prasterone) on libido and sexual dysfunction in postmenopausal women

Objective: The objective of this study was to provide evidence that the transformation of DHEA into both androgens and/or estrogens locally in cells of the three layers of the vagina (epithelium, lamina propria, and muscularis) would have effects of greater impact, including effects on sexual function, than only effects on superficial epithelial cells as achieved with estrogens. Methods: This prospective, randomized, double-blind, and placebo-controlled phase III clinical trial has evaluated the effect of daily local intravaginal application of Prasterone (dehydroepiandrosterone; DHEA) for 12 weeks on the domains of sexual dysfunction, namely, desire/interest, arousal, orgasm, and pain at sexual activity, in 216 postmenopausal women with moderate to severe symptoms of vaginal atrophy. Results: A time- and dose-dependent improvement of the four domains of sexual function was observed. At the 12-week time interval, the 1.0% DHEA dose led, compared with placebo, to 49% (P = 0.0061) and 23% (P = 0.0257) improvements of the desire domains in the Menopause Specific Quality of Life and Abbreviated Sex Function questionnaires, respectively. Compared with placebo, the Abbreviated Sex Function arousal/sensation domain was improved by 68% (P = 0.006), the arousal/lubrication domain by 39% (P = 0.0014), orgasm by 75% (P = 0.047), and dryness during intercourse by 57% (P = 0.0001). Conclusions: By a local action in the vagina, DHEA applied daily at doses at which serum steroids remain well within normal postmenopausal values exerts relatively potent beneficial effects on all four aspects of sexual dysfunction. Such data indicate that combined androgenic/estrogenic stimulation in the three layers of the vagina exerts important beneficial effects on sexual function in women without systemic action on the brain and other extravaginal tissues.

Intravaginal dehydroepiandrosterone (Prasterone), a physiological and highly efficient treatment of vaginal atrophy

Objective: Because the secretion of dehydroepiandrosterone (DHEA), the exclusive source of sex steroids in postmenopausal women, is already decreased by 60% and continues to decline at the time of menopause, the objective of this study was to examine the effect of intravaginal DHEA on the symptoms and signs of vaginal atrophy. Methods: This prospective, randomized, double-blind and placebo-controlled phase III clinical trial studied the effect of Prasterone (DHEA) applied locally in the vagina on the signs and symptoms of vaginal atrophy in 216 postmenopausal women. Results: All three doses (0.25%, 0.5%, and 1.0%) of DHEA ovules applied daily intravaginally induced a highly significant beneficial change in the percentage of vaginal parabasal and superficial cells and pH as well as in the most bothersome symptom at 2 weeks. At the standard 12-week time interval, 0.5% DHEA caused a 45.9 ± 5.31 (P < 0.0001 vs placebo) decrease in the percentage of parabasal cells, a 6.8 ± 1.29% (P < 0.0001) increase in superficial cells, a 1.3 ± 0.13 unit (P < 0.0001) decrease in vaginal pH, and a 1.5 ± 0.14 score unit (P < 0.0001) decrease in the severity of the most bothersome symptom. Similar changes were seen on vaginal secretions, color, epithelial surface thickness, and epithelial integrity. Comparable effects were observed at the 0.25% and 1.0% DHEA doses. Conclusions: Local Prasterone, through local androgen and estrogen formation, causes a rapid and efficient reversal of all the symptoms and signs of vaginal atrophy with no or minimal changes in serum steroids, which remain well within the normal postmenopausal range. This approach avoids the fear of systemic effects common to all presently available estrogen formulations and adds a novel physiological androgenic component to therapy.

Cellular Mechanisms Involved during Oxytocin-Induced Prostaglandin F2α Production in Endometrial Epithelial Cells in Vitro: Role of Cyclooxygenase-21

PGs are important regulators of reproductive processes. At the time ofluteolysis in vivo, PGF2alpha is produced by endometrial cells, in response to oxytocin (OT). The mechanism by which OT induces the release of PGF2alpha remains to be defined. We have used 13 different cultures of bovine epithelial endometrial cells to study the effect of OT on the regulation of PGF2alpha and to identify the possible involvement of cyclooxygenases (COXs). OT induced a dose-dependent increase of both inositol phosphates (IPs) and [Ca2+]i concentration in epithelial cells labeled with [3H]-myoinositol or loaded with fura-2 (using a fluorescent microscope imaging system), respectively. OT induced a dose-dependent increase of both PGF2alpha production and COX-2 gene expression (as demonstrated by RT-PCR and Northern blots). PGF2alpha production was increased from 13.3 +/- 2.0 to 166.8 +/- 22.5 ng/ml (P < 0.0001). On the other hand, COX-2/beta-actin mRNA gene expression (as determined by densitometric analysis) was increased 5.1 +/- 0.7-fold (P < 0.001) with OT (10[-7] M) treatment, compared with control. Addition of indomethacin (1 microM) and a specific COX-2 inhibitor (NS-398, 1 microM) blocked the OT-induced PGF2alpha production. COX-1 and phospholipase A2 mRNA were expressed at steady-state levels, but no effect of OT was detected on their regulation. Combined to OT, 10 microq/ml of recombinant ovine interferon-tau (roIFN-tau) was able to decrease significantly (P < 0.0001) the dose-dependent increase of PGF2alpha production. Furthermore, partial bovine COX-1 (777 pb) and COX-2 (449 bp) cDNAs were cloned and sequenced. An homology of 83% and 97% was found in relation with rat and sheep, for COX-1, respectively. COX-2 was found to bear 84%, 86%, and 87% of homology in relation to rat, guinea pig, and human, respectively. Collectively, these results demonstrate, for the first time, that COX-2 is involved in the mechanism by which OT regulates PGF2alpha production in the endometrium.

Expression of Cyclooxygenase-2 and Granulocyte-Macrophage Colony-Stimulating Factor in the Endometrial Epithelium of the Cow Is Up-Regulated During Early Pregnancy and in Response to Intrauterine Infusions of Interferon-τ

Abstract On the basis of results obtained in vitro, we previously proposed a model in which signals from the conceptus, namely interferon-tau (IFN-τ) and prostaglandin E2, increase the expression of cyclooxygenase (COX)-2 or granulocyte-macrophage colony-stimulating factor (GM-CSF) in immune and nonimmune cells of the bovine endometrium. Two experiments were conducted to verify the validity of this hypothesis in vivo. In experiment 1, the in vivo expression of COX-2 and GM-CSF during early pregnancy was monitored. Uteri from heifers were collected at different days (d) of the estrous cycle and pregnancy (P). In experiment 2, the effects of intrauterine infusions of IFN-τ on the expression of COX-2 and GM-CSF were analyzed. Immunohistochemistry was performed on uterine sections, and image analysis was used to evaluate the staining intensity in the conceptus, the luminal epithelium (LE), and the subepithelial stroma. In experiment 1, staining for COX-2 was maximal between d18P and d24P, both in the LE and in the conceptus, whereas staining for GM-CSF reached a plateau between d18P and d30P in the LE. In experiment 2, in response to IFN-τ, COX-2 was up-regulated in the LE of the ipsilateral horn, whereas GM-CSF was enhanced in both uterine horns. The current report supports the view that the conceptus, through its secretion of IFN-τ, stimulates maternal epithelial expression of COX-2 and GM-CSF during the peri-attachment period in the cow.

IFN-τ increases PGE2 production and COX-2 gene expression in the bovine endometrium in vitro

Prostaglandins (PGs) are well known for their role in reproductive processes. At the time of pregnancy recognition, PGF2alpha is luteolytic and PGE2 may be antiluteolytic and luteotropic. During the preimplantation period, interferon-tau (IFN-tau) is produced by the conceptus and plays a crucial role in maternal recognition of pregnancy in domestic ruminants. We have demonstrated previously that recombinant bovine and ovine interferon-tau (rbIFN-tau and roIFN-tau) stimulate PGE2 production in epithelial cells, changing the primary PG produced by these cells from F2alpha to E2. In stromal cells, where PGE2 is the major PG produced, roIFN-tau induced an increase of both types of PGs. The aim of this paper is to identify the possible involvement of cyclooxygenases (COXs) in the modulation of PG production by trophoblastic interferons. Epithelial and stromal cells cultured in vitro were isolated from bovine endometrium and stimulated with increasing doses (1, 10 and 20 microg/ml) of roIFN-tau. PG levels in the culture media were measured by enzyme immunoassays (EIA) and total RNA was extracted from the cells. Northern blot analysis was performed to quantify cyclooxygenase COX-1 (constitutive), COX-2 (inducible) and phospholipase A2 (PLA2) messenger RNA (mRNA) production in response to treatment. The results indicate that roIFN-tau treatment did not affect COX-1 and PLA2 mRNA production in either cell type, whereas COX-2 expression was upregulated in both. The up-regulation of COX-2 transcript was greater in stromal than in epithelial cells. The increase in COX-2 mRNA levels was concurrent with increased production of PGE2 and PGF2alpha in stromal cells and principally PGE2 in epithelial cells. Furthermore, addition of indomethacin (1 microM) and a specific COX-2 inhibitor (NS-398, 1 microM) blocked the roIFN-tau-stimulation of PG production in both cell types. The mechanism whereby elevated COX-2 expression results in a selective increase of PGE2 in epithelial cells remains to be elucidated. In stromal cells, an increase in COX-2 mRNA levels may explain increased PG production. The overall effect of roIFN-tau in the two cell types is a net increase in PGE2 output.

Fat Depot‐specific Impact of Visceral Obesity on Adipocyte Adiponectin Release in Women

Our objective was to examine omental and subcutaneous adipocyte adiponectin release in women. We tested the hypothesis that adiponectin release would be reduced to a greater extent in omental than in subcutaneous adipocytes of women with visceral obesity. Omental and subcutaneous adipose tissue samples were obtained from 52 women undergoing abdominal hysterectomies (age: 47.1 ± 4.8 years; BMI: 26.7 ± 4.7 kg/m2). Adipocytes were isolated and their adiponectin release in the medium was measured over 2 h. Measures of body fat accumulation and distribution were obtained using dual‐energy X‐ray absorptiometry and computed tomography, respectively. Adiponectin release by omental and subcutaneous adipocytes was similar in lean individuals; however, in subsamples of obese or visceral obese women, adiponectin release by omental adipocytes was significantly reduced while that of subcutaneous adipocytes was not affected. Omental adipocyte adiponectin release was significantly and negatively correlated with total body fat mass (r = −0.47, P < 0.01), visceral adipose tissue area (r = −0.50, P < 0.01), omental adipocyte diameter (r = −0.43, P < 0.01), triglyceride levels (r = −0.32, P ≤ 0.05), cholesterol/high‐density lipoprotein (HDL)‐cholesterol (r = −0.31, P ≤ 0.05), fasting glucose (r = −0.39, P ≤ 0.01), fasting insulin (r = −0.36, P ≤ 0.05), homeostasis model assessment index (r = −0.39, P ≤ 0.01), and positively associated with HDL‐cholesterol concentrations (r = 0.33, P ≤ 0.05). Adiponectin release from subcutaneous cells was not associated with any measure of adiposity, lipid profile, or glucose homeostasis. In conclusion, compared to subcutaneous adipocyte adiponectin release, omental adipocyte adiponectin release is reduced to a greater extent in visceral obese women and better predicts obesity‐associated metabolic abnormalities.

Detection and Regulation of the Messenger for a Putative Bovine Endometrial 9-Keto-Prostaglandin E2 Reductase: Effect of Oxytocin and Interferon-Tau

Abstract During reproductive processes, prostaglandin (PG) E2 (PGE2) and PGF2α play important roles in which they often exert opposite effects. At the time of recognition of pregnancy in vivo, PGF2α is recognized as the luteolytic factor in ruminants and in most species including human, whereas PGE2 may exert a luteoprotective action. We have previously demonstrated that recombinant interferon-tau (rIFN-τ), the embryonic signal responsible for recognition of pregnancy in ruminants, stimulated in vitro the production of PGE2 and prostaglandin-endoperoxide synthase 2 (Ptgs2; also called cyclooxygenase-2) gene expression in both epithelial and stromal endometrial cells. Since PGE2 is the major prostaglandin produced by stromal cells, the effect on Ptgs2 could explain the increase in PGE2 output. At high concentrations, however, recombinant ovine (ro) IFN-τ acts on epithelial cells by changing the primary PG produced from PGF2α to PGE2. This change in the primary PG produced could be explained by a decrease in PGF synthase (PGFS) activity or an increase in PGE synthase activity, or by modulation of a putative PGE2–9-ketoreductase, which converts PGE2 into PGF2α. Therefore, we have investigated the regulation of the mRNAs for PGFS and PGE2-9-ketoreductase (9K-PGR), two enzymes that lead to the production of PGF2α. Others have described 9K-PGR activity in uterus, ovaries, kidney, and liver of different species and have established that this enzyme could possess both 9K-PGR and 20α-hydroxysteroid dehydrogenase (20α-HSD) activity. Some have concluded that 9K-PGR and 20α-HSD are identical enzymes. Using primers sequences chosen from homologous nucleotide sequences of published rabbit 20α-HSD/9K-PGR and rat 20α-HSD cDNAs, a 317-base pair (bp) fragment was amplified by reverse transcription-polymerase chain reaction (RT-PCR), cloned, and sequenced. Homologies of 83% and 78% were found with rabbit and rat 20α-HSD, respectively. The presence of 20α-HSD/9K-PGR and prostaglandin F synthase (PGFS) mRNA expression was studied semiquantitatively in cultured epithelial cells using RT-PCR. Stimulation of cells with roIFN-t resulted in a biphasic response, an inhibition of PGF2α production at low dose (1 ng/ml) and a stimulation of PGE2 at high dose (10 μg/ml). The increase of PGE2 was accompanied by reduced 9K-PGR and PGFS mRNA gene expression. The effect of oxytocin (OT) was also studied, and the presence of OT had no effect on either 9K-PGR or PGFS gene expression. The 20α-HSD/9K-PGR transcript was also detected in other bovine tissues at different intensity (liver > kidney > testis > ovaries). We believe that the 9K-PGR and PGFS can be key enzymes in the regulation of specific PGs in the endometrium during the periimplantation period.

Serum steroid levels during 12-week intravaginal dehydroepiandrosterone administration.

Objective: Because a previous 1-week study has shown no or minimal changes in the serum levels of dehydroepiandrosterone (DHEA) and its metabolites after up to daily 1.8% (23.4 mg) intravaginal DHEA, the objective of the present study was to investigate the serum steroid levels during a 12-week daily intravaginal administration of 0%, 0.25%, 0.5%, and 1.0% DHEA (Prasterone) 1.3 mL ovules. Methods: In a double-blind, placebo-controlled phase III study, 218 postmenopausal women (age range, 42-74 y) were randomized to receive daily one of four DHEA concentrations intravaginally. Serum steroids were measured by a Good Laboratory Practice-validated mass spectrometry technology in samples obtained at time of visit. Results: The serum levels of DHEA and 11 of its metabolites measured at screening, day 1, and weeks 2, 4, 8, and 12 in women showed no or minimal changes during the whole observation period, with all values remaining well within the limits of normal postmenopausal women. No accumulation of the steroid metabolites nor change in DHEA bioavailability was detected. Conclusions: The present data show that local daily intravaginal DHEA administration at DHEA doses of 3.25-13 mg was able to rapidly and efficiently achieve correction of all the signs and symptoms of vaginal atrophy and improve sexual function and caused no or minimal changes in serum sex steroid levels, which all remain within the normal postmenopausal range, thus avoiding the risks of all estrogen formulations.