Expression and localization of the 20α-hydroxysteroid dehydrogenase (HSD) enzyme in the reproductive tissues of the cynomolgus monkey Macaca fascicularis

The immunology of the macaque placenta: A detailed analysis and critical comparison with the human placenta

The cynomolgus monkey is increasingly considered in toxicological research as the most appropriate model for humans due to the species' close physiological contiguity, including reproductive physiology. Here, literature on the cynomolgus monkey placenta is reviewed in regards to its similarity to the human placenta and particularly for its immunological role, which is not entirely mirrored in humans. Pertinent original data are included in this article. The cynomolgus monkey placenta is evaluated based on three aspects: first, morphological development; second, the spatial and temporal appearance of maternal and fetal immune cells and certain immune cell products of the innate and adaptive immune systems; and third, the expression of relevant immune tolerance-related molecules including the homologs of anti-human leucocyte antigen, indoleamine 2,3-dioxygenase, FAS/FAS-L, annexin II, and progesterone. Parameters relevant to the immunological role of the placenta are evaluated from the immunologically immature stage of gestational day (GD) 50 until more mature stages close to birth. Selected comparisons are drawn with human and other laboratory animal placentas. In conclusion, the cynomolgus monkey placenta has a high degree of morphological and physiological similarity to the human placenta. However, there are differences in the topographical distribution of cell types and immune tolerance-related molecules. Three basic features are recognized: (1) the immunological capacity of the placenta changes throughout the lifetime of the organ; (2) these immunological changes include multiple parameters such as morphological adaptations, cell type involvement, and changes in immune-relevant molecule expression; and (3) the immune systems of two genetically disparate individuals (mother and child) are functionally intertwined at the maternal-fetal interface.

Characterization of transgenic mice expressing EGFP under the control of the monkey 20α-hydroxysteroid dehydrogenase promoter

To directly assess the molecular function of the monkey 20α-hydroxysteroid dehydrogenase (20α-HSD) promoter, we generated transgenic mice (tg) expressing enhanced green fluorescent protein (EGFP) under control of this promoter. We demonstrated that prostaglandin F₂α induced 20α-HSD promoter activity in CHO cells in a dose-dependent manner. Furthermore, forskolin treatment markedly reduced 20α-HSD promoter activity, and prolactin exhibited weak inhibitory activity. The transgenic mouse obtained one positive founder male. The transgene was propagated in 10 successive generations without any notable defects to the progeny. EGFP and 20α-HSD in the tg mice were colocalized in the luteal cells of the ovary during late pregnancy. Strong EGFP and 20α-HSD protein signals were also detected in the adult testis. Immunohistochemical analysis revealed high EGFP levels in the seminiferous epithelium, whereas 20α-HSD was expressed in the seminiferous tubules. Our data suggest that the ovaries in monkey and mouse exhibit similar expression patterns of 20α-HSD during pregnancy. However, the expression pattern of EGFP in tg mice testis slightly differed from that of the endogenous 20α-HSD. Further investigation is required to elucidate the functional mechanisms underlying regulation of the monkey 20α-HSD promoter in the tg mice.

Novel contraceptive targets to inhibit ovulation: the prostaglandin E2 pathway

BACKGROUND

Prostaglandin E2 (PGE2) is an essential intrafollicular regulator of ovulation. In contrast with the one-gene, one-protein concept for synthesis of peptide signaling molecules, production and metabolism of bioactive PGE2 requires controlled expression of many proteins, correct subcellular localization of enzymes, coordinated PGE2 synthesis and metabolism, and prostaglandin transport in and out of cells to facilitate PGE2 action and degradation. Elevated intrafollicular PGE2 is required for successful ovulation, so disruption of PGE2 synthesis, metabolism or transport may yield effective contraceptive strategies.

METHODS

This review summarizes case reports and studies on ovulation inhibition in women and macaques treated with cyclooxygenase inhibitors published from 1987 to 2014. These findings are discussed in the context of studies describing levels of mRNA, protein, and activity of prostaglandin synthesis and metabolic enzymes as well as prostaglandin transporters in ovarian cells.

RESULTS

The ovulatory surge of LH regulates the expression of each component of the PGE2 synthesis-metabolism-transport pathway within the ovulatory follicle. Data from primary ovarian cells and cancer cell lines suggest that enzymes and transporters can cooperate to optimize bioactive PGE2 levels. Elevated intrafollicular PGE2 mediates key ovulatory events including cumulus expansion, follicle rupture and oocyte release. Inhibitors of the prostaglandin-endoperoxide synthase 2 (PTGS2) enzyme (also known as cyclooxygenase-2 or COX2) reduce ovulation rates in women. Studies in macaques show that PTGS2 inhibitors can reduce the rates of cumulus expansion, oocyte release, follicle rupture, oocyte nuclear maturation and fertilization. A PTGS2 inhibitor reduced pregnancy rates in breeding macaques when administered to simulate emergency contraception. However, PTGS2 inhibition did not prevent pregnancy in monkeys when administered to simulate monthly contraceptive use.

CONCLUSION

PTGS2 inhibitors alone may be suitable for use as emergency contraceptives. However, drugs of this class are unlikely to be effective as monthly contraceptives. Inhibitors of additional PGE2 synthesis enzymes or modulation of PGE2 metabolism or transport also hold potential for reducing follicular PGE2 and preventing ovulation. Approaches which target multiple components of the PGE2 synthesis-metabolism-transport pathway may be required to effectively block ovulation and lead to the development of novel contraceptive options for women. Therapies which target PGE2 may also impact disorders of the uterus and could also have benefits for women's health in addition to contraception.

The transcription factor Ap-1 regulates monkey 20α-hydroxysteroid dehydrogenase promoter activity in CHO cells

Background

Monkey 20α-hydroxysteroid dehydrogenase (20α-HSD) is a catabolic enzyme responsible for converting progesterone into biologically inactive 20α-hydroxyprogesterone, thereby playing a key role in the estrous cycle or pregnancy and allowing ovulation and parturition to occur in most mammalian animals. Monkey 20α-HSD was highly abundant in ovarian and placental tissues during the pre-ovulation and pre-parturition phase and was primarily localized in the syncytiotrophoblast of the placenta. In this study, we focused on the molecular characterization of the monkey 20α-HSD promoter region by conducting reporter assays in Chinese hamster ovary (CHO) K1 cells.

Results

A reporter assay using constructs of various lengths of the 5′-flanking region (-890-Luc, -513-Luc, -306-Luc, -273-Luc, and -70-Luc) revealed that a region corresponding to the activator protein 1 (Ap-1) located between -281 and -274 bp was essential for the transcriptional activity. Absence of the Ap-1 site in -273-Luc dramatically decreased the transcription levels to the control levels. When the reporter constructs were co-transfected with Ap-1 (Jun) and specificity protein (Sp-1) genes, the transcription activities of the constructs increased with the exception of -273 and -70, while that of the double construct was reduced compared to that of Ap-1 alone. Furthermore, mutational analysis demonstrated that a putative Ap-1 site played an important role in the expression of the reporter gene. These findings were confirmed by EMSA examining the interactions of the protein Ap-1 in a nuclear extract from CHO-K1 cells and the expression levels of the Ap-1 transcription factor in pre-parturition placenta and CHO-K1 cells. Although mut-1 and mut-2 of Ap-1 bound with nuclear extracts from CHO-K1 cells, the transcriptional activity of mut-3 was almost completely suppressed.

Conclusions

Our results indicate that the Ap-1 site (-281 → -274) (5′-TGTCTCAT-3′) plays a crucial role in the activation of the monkey 20α-HSD gene. Thus, we demonstrated that monkey 20α-HSD promoter activity is regulated by the transcription factor Ap-1 in CHO-K1 cells.

Gene expression and localization of 20α-hydroxysteroid dehydrogenase (HSD) in reproductive tissues during early pregnancy of cattle

The enzyme 20α-hydroxysteroid dehydrogenase (20α-HSD) catalyzes the conversion of progesterone to its inactive form, 20α-hydroxyprogesterone, and this enzyme has an important role in the regulation of luteal function in mammals. It has previously been determined that the 20α-HSD gene is primarily expressed by large luteal cells during the late stage of the estrous cycle. In the present study, the amounts of mRNA were determined in cultured cells of the corpus luteum (CL) cells. The localization of 20α-HSD was also determined in ovaries, placenta, and endometrium during early pregnancy. The amount of 20α-HSD mRNA in cultured luteal cells increased with time and by treatment with the luteolysis agent prostaglandin F2α (PGF2α). Immunofluorescence assays detected increased protein in cultured luteal cells. The 20α-HSD mRNA and protein were present in the ovaries, placenta, and endometrium on Days 30, 60, and 90 of pregnancy. In particular, gene expression was much greater in the ovary than in the placenta and endometrium. Immuno-histochemical analysis indicated that bovine 20α-HSD was primarily localized in ovarian large luteal cells, placental cytotrophoblast villus, and glandular epithelial cells of the endometrium during early pregnancy. Furthermore, in situ analyses demonstrated colocalization of 20α-HSD mRNA and protein. Taken together, results of the present study indicate that 20α-HSD mRNA and protein are co-localized in large luteal cells, the placenta, and the endometrium during early pregnancy, suggesting that 20α-HSD regulates mechanisms involved in the maintenance of early pregnancy.

Flutamide influences placental aldo-keto reductase family 1 member C1 (AKR1C1) expression in pigs

Aldo-keto reductase family 1 member C1 (AKR1C1) catalyses the conversion of progesterone into inactive 20α-dihydroxyprogesterone. It is suggested that AKR1C1 expression in the placenta prevents from the cytotoxic effect of progesterone on foetuses during late pregnancy. The aim of the study was to determine whether the anti-androgen flutamide administered during late pregnancy (83-89 days of gestation) or before parturition (101-107 days of gestation) influences AKR1C1 expression in the porcine placenta. AKR1C1 mRNA and protein levels were measured using real-time PCR and western blotting, respectively. Immunolocalization of AKR1C1 within placentas was also performed. Flutamide significantly increased AKR1C1 mRNA (p = 0.008) and protein (p = 0.019) expression only during the pre-parturient period in pigs. AKR1C1 protein was immunolocalized in the epithelial and stromal cells of foetal and maternal part of placenta at both stages of gestation. Following flutamide treatment, the intensity of staining was higher (p = 0.045) on day 108 of gestation. In conclusion, porcine placental AKR1C1 expression seems to be regulated by an androgen signalling pathway and may be involved in foetal survival by preventing the detrimental effect of progesterone.

Ovarian and placental expression of 20α-hydroxysteroid dehydrogenase during pregnancy in deer

The enzyme 20α-hydroxysteroid dehydrogenase (20α-HSD) catalyzes the conversion of progesterone to its inactive form, 20α-hydroxyprogesterone. This enzyme has been shown to play a critical role in the regulation of luteal function in experimental animals. In this study, we cloned and expressed the gene encoding elk deer 20α-HSD from reproductive placental and ovarian tissues. PCR, 3'- and 5'-RACE, and northern blot analysis were performed for the cloning and characterization of deer 20α-HSD gene. We expressed recombinant deer 20α-HSD protein and used western blot analysis to determine protein expression levels in the placenta and ovary during pregnancy. The full cDNA sequence of 20α-HSD was used to clone an open reading frame encoding 323 amino acids and consisting of 1142 bp. The nucleotide sequence of deer 20α-HSD showed high homology with the sequences of the bovine (96%), goat (96%), and human (83%) 20α-HSD genes. 20α-HSD mRNA was strongly expressed in the placenta on days 30, 60, and 70 of pregnancy. A high level of the protein was also detected in the placenta but not in fetal skin tissue. The recombinant 20α-HSD protein produced in mammalian cells and bacterial systems had a molecular weight of approximately 37-kDa. The deer 20α-HSD protein signal was specifically localized in the basal part of the primary chorionic villi and chorionic stem villus of the placenta during early pregnancy. The 20α-HSD protein was also intensively localized in the larger luteal cells of the corpus luteum during pregnancy.

Role of aldo-keto reductase enzymes in mediating the timing of parturition

A better understanding of the mechanisms underlying parturition would provide an important step toward improving therapies for the prevention of preterm labor. Aldo–keto reductases (AKR) from the 1D, 1C, and 1B subfamilies likely contribute to determining the timing of parturition through metabolism of progesterone and prostaglandins. Placental AKR1D1 (human 5β reductase) likely contributes to the maintenance of pregnancy through the formation of 5β-dihydroprogesterone (DHP). AKR1C1, AKR1C2, and AKR1C3 catalyze the 20-ketosteroid and 3-ketosteroid reduction of progestins. They could therefore eliminate tocolytic progestins at term. Activation of the F prostanoid receptor by its ligands also plays a critical role in initiation of labor. AKR1C3 and AKR1B1 have prostaglandin (PG) F synthase activities that likely contribute to the initiation of labor. AKR1C3 converts PGH₂ to PGF_2α and PGD₂ to 9α,11β-PGF₂. AKR1B1 also reduces PGH₂ to PGF_2α, but does not form 9α,11β-PGF₂. Consistent with the potential role for AKR1C3 in the initiation of parturition, indomethacin, which is a potent and isoform selective inhibitor of AKR1C3, has long been used for tocolysis.