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

Placental Proteomics Reveals an Elevated Level of Aldo-Keto Reductase 1-B1, Highlighting Its Potential Role in Spontaneous Preterm Birth

Preterm birth (PTB) refers to the delivery of a baby before the completion of 37 weeks of gestation. It is a significant global health issue with implications for both mothers and neonates. The placenta is a transient organ crucial in the sustenance of pregnancy until parturition; its dysfunction is associated with different adverse pregnancy outcomes, including PTB. We conducted a nested case-control study of 40 placental tissue samples from preterm and term deliveries to study their comparative protein profiles. Label-free quantitation (LFQ) revealed 23 differentially expressed proteins (DEPs). Aldo-keto reductase-B1 (AKR1B1) protein expression profile exhibited a declining trajectory with an increasing period of gestation (POG). Immunoblotting and immunohistochemistry analyses of placental samples also revealed elevated protein levels in extreme preterm samples. AKR1B1 is a functional Prostaglandin F synthase responsible for the synthesis of Prostaglandin-F2α, a prostanoid that is elevated during parturition and involved in cervical ripening, membrane rupture, myometrial contraction, and inflammation. Hence, our finding supports the idea that elevated AKR1B1 levels play a significant role in the pathology of preterm birth by amplifying Prostaglandin-F2α synthesis in the placental milieu and can be further explored as a potential predictor of this condition. Data are available via ProteomeXchange with the identifier PXD043480.

Physiologically based pharmacokinetic modeling of long-acting extended-release naltrexone in pregnant women with opioid use disorder

Opioid use disorders (OUD) are a major issue in the U.S. Current treatments for pregnant women, like methadone and buprenorphine require daily dosing and have adverse effects. Monthly injectable naltrexone (XR-NTX) mitigates these adverse effects but is not recommended during pregnancy due to limited pharmacokinetic and safety data. This study developed a physiologically based pharmacokinetic (PBPK) model to describe XR-NTX pharmacokinetics during pregnancy, and to predict dosing recommendations. Model predictions were successfully validated with observed data. Maternal plasma XR-NTX profiles were simulated for 400 non-pregnant virtual females at the approved dose of 380 mg, then randomized to continue with either 380, 285, 190, or 95 mg during pregnancy. The non-pregnant virtual females had a mean predicted Cmax, AUC0-7days, and AUC0-28days of 23.3 ng/mL, 142 ng·d/mL, and 148 ng·d/mL, respectively. Maternal XR-NTX exposure (AUC0-28days) were predicted to increase by 1.37, 1.43, and 1.72 times during the first, second, and third trimester of pregnancy. However, the fetal-to-maternal exposure (AUC0-28days) was lower in the first (15%), second (7%), and third (9%) trimesters. A dose of 285 mg of XR-NTX in pregnancy during the first/second trimester and dose of 190 mg in the third trimester were predicted to provide maternal exposures that were comparable to non-pregnant levels at the standard dose. This study provides crucial insights into XR-NTX pharmacokinetics and proposes a dosing strategy during pregnancy, potentially aiding further clinical investigations and decision making regarding XR-NTX use during pregnancy.

Placental production of progestins is fully effective in villous cytotrophoblasts and increases with the syncytiotrophoblast formation

Placental syncytiotrophoblast (ST) is considered as the main placental endocrine tissue secreting progesterone, a steroid essential for maintenance of pregnancy. However, each step of progestins production has been poorly investigated in villous cytotrophoblast (VCT) regarding ST formation. We aimed to characterize progestins production during human differentiation of VCT into ST. VCTs were isolated from term placenta and cultivated, with or without forskolin (FSK), to stimulate trophoblast differentiation. Secreted progestins concentrations were determined by immuno-assay and Gas Chromatography-tandem mass spectrometry. Intracellular expression of cholesterol transporter and enzymes involved in steroidogenesis were studied by immunofluorescence, western-blot, and RT-qPCR. Progesterone and pregnenolone are produced by VCT and their secretion increases with VCT differentiation while 17-hydroxyprogesterone concentration remains undetectable. HSD3B1 enzyme expression increases whereas MLN64, the cholesterol placental mitochondrial transporter and P450SCC expressions do not. FSK induces progestins production. Progestins placental synthesis is effective since VCT and increases with ST formation thanks to mitochondria.

The Biosynthesis of Enzymatically Oxidized Lipids

Enzymatically oxidized lipids are a specific group of biomolecules that function as key signaling mediators and hormones, regulating various cellular and physiological processes from metabolism and cell death to inflammation and the immune response. They are broadly categorized as either polyunsaturated fatty acid (PUFA) containing (free acid oxygenated PUFA "oxylipins", endocannabinoids, oxidized phospholipids) or cholesterol derivatives (oxysterols, steroid hormones, and bile acids). Their biosynthesis is accomplished by families of enzymes that include lipoxygenases (LOX), cyclooxygenases (COX), cytochrome P450s (CYP), and aldo-keto reductases (AKR). In contrast, non-enzymatically oxidized lipids are produced by uncontrolled oxidation and are broadly considered to be harmful. Here, we provide an overview of the biochemistry and enzymology of LOXs, COXs, CYPs, and AKRs in humans. Next, we present biosynthetic pathways for oxylipins, oxidized phospholipids, oxysterols, bile acids and steroid hormones. Last, we address gaps in knowledge and suggest directions for future work.

Obesity during pregnancy affects sex steroid concentrations depending on fetal gender

BACKGROUND/OBJECTIVE

It is not clear whether maternal obesity along with fetal gender affect sex steroid metabolism during pregnancy. Therefore, we compared sex steroid concentrations and placental expression of steroidogenic enzymes between non-obese and obese pregnant women with non-pathological pregnancies, and investigated the influence of fetal gender on these parameters.

METHODS

In 35 normal weight (body mass index (BMI) 20-24.9 kg m^-2) (controls) and 36 obese women (BMI 30-36 kg m^-2) (obese), a fasting blood sample was obtained at first and at third trimester of gestation to measure progesterone, dehydroepiandrosterone (DHEA), DHEA sulfate, androstenedione, testosterone and estradiol by liquid chromatography-tandem mass spectrometry and estrone by radioimmunoassay. In a subset of women, placental mRNA and protein expression of steroidogenic enzymes was measured by quantitative PCR and western blot, respectively. The comparisons were primarily made between controls and obese, and then separately according to fetal gender.

RESULTS

At first and third trimesters of gestation serum progesterone was lower whereas testosterone was higher in obese women (P<0.05, respectively). Upon analyzing according to fetal gender, lower progesterone levels were present in obese pregnant women with male fetuses at first trimester and with female fetuses at third trimester (P<0.05, respectively). Testosterone was higher in obese women with male fetuses compared to control women with male fetuses (P<0.05). The placental protein expression of P450scc was higher in obese women compared to controls (P<0.05). P450 aromatase was higher in obese women with female fetuses (P=0.009), whereas in obese women with male fetuses P450 aromatase was lower compared to control women (P=0.026).

CONCLUSIONS

Obesity in non-pathological pregnancies alters the maternal serum progesterone and testosterone concentrations depending on fetal gender. These changes can be attributed to gender-related placental adaptations, as the expression of P450 aromatase is different in placentas from females compared to males.

Administration of Progesterone Throughout Pregnancy Increases Maternal Steroids Without Adverse Effect on Mature Oligodendrocyte Immunostaining in the Guinea Pig

Progesterone is administered to pregnant women at risk of premature labor, despite systematic reviews showing conflicting outcomes regarding its use, highlighting doubt over the effectiveness of the therapy. Progesterone can be rapidly metabolized into a number of steroids, but to date, there has been a lack of investigation into the fetal steroid profiles following administration and whether this impacts fetal neurodevelopment. The objective of this study was to determine the effect of progesterone treatment on allopregnanolone and cortisol levels in the fetus and on a marker of myelination in the fetal brain. We used a guinea pig model where pregnant dams were administered vehicle (β-cyclodextrin) or progesterone orally throughout pregnancy (GA29-61). Maternal and fetal fluids and tissues were collected at both preterm (GA61) and term (GA68) ages. Maternal and fetal progesterone and cortisol were analyzed by enzyme immunoassay and allopregnanolone by radioimmunoassay. Measurement of myelination of fetal brains (hippocampus, cingulum, and subcortical white matter) at preterm and term ages was performed by immunohistochemistry staining for myelin basic protein. We found that dams receiving progesterone had significantly elevated progesterone and cortisol concentrations, but there was no effect on allopregnanolone. Interestingly, the increased cortisol concentrations were not reflected in the fetuses, and there was no effect of progesterone treatment on myelination. Therefore, we conclude that in our guinea pig model, maternal administration of progesterone has no effect on cortisol levels or markers of mature oligodendrocytes in the fetus and suggest this is potentially due to the protective cortisol barrier in the placenta.

Induction of PGF2α synthesis by cortisol through GR dependent induction of CBR1 in human amnion fibroblasts

Abundant evidence indicates a pivotal role of prostaglandin F2α (PGF2α) in human parturition. Both the fetal and maternal sides of the fetal membranes synthesize PGF2α. In addition to the synthesis of PGF2α from PGH2 by PGF synthase (PGFS), PGF2α can also be converted from PGE2 by carbonyl reductase 1 (CBR1). Here, we showed that there was concurrent increased production of cortisol and PGF2α in association with the elevation of CBR1 in human amnion obtained at term with labor versus term without labor. In cultured primary human amnion fibroblasts, cortisol (0.01-1μM) increased PGF2α production in a concentration-dependent manner, in parallel with elevation of CBR1 levels. Either siRNA-mediated knockdown of glucocorticoid receptor (GR) expression or GR antagonist RU486 attenuated the induction of CBR1 by cortisol. Chromatin immunoprecipitation (ChIP) showed an increased enrichment of both GR and RNA polymerase II to CBR1 promoter. Knockdown of CBR1 expression with siRNA or inhibition of CBR1 activity with rutin decreased both basal and cortisol-stimulated PGF2α production in human amnion fibroblasts. In conclusion, CBR1 may play a critical role in PGF2α synthesis in human amnion fibroblasts, and cortisol promotes the conversion of PGE2 into PGF2α via GR-mediated induction of CBR1 in human amnion fibroblasts. This stimulatory effect of cortisol on CBR1 expression may partly explain the concurrent increases of cortisol and PGF2α in human amnion tissue with labor, and these findings may account for the increased production of PGF2α in the fetal membranes prior to the onset of labor.

Steroid Metabolome in the Umbilical Cord: Is It Necessary To Differentiate Between Arterial and Venous Blood?

Steroids are important markers in pregnancy. Although estimating their levels separately in umbilical arterial (UA) and venous blood (UV) enable more precise insights into the functioning fetoplacental unit compared to using mixed umbilical blood (UM), selective aspiration of UA and UV is technically more demanding than collecting UM. We measured the levels of 67 unconjugated steroids and steroid polar conjugates in UA and UV using GC-MS in 80 women giving birth within weeks 28 to 42 of gestation. The samples were sorted into three groups: women entering labor within weeks 28-32 (group A, n=19), weeks 33-37 (group B, n=19), and weeks 38-42 (group C, n=42) of gestation, respectively. The preterm labors were due to pathologies unrelated to steroid status. Most unconjugated steroids exhibited pronounced arteriovenous differences (AVD). The AVD were less distinct in more stable steroid conjugates. Most steroids positively correlate with gestational age, but unconjugated 5β-reduced pregnanes show negative correlations, as do testosterone and androstenediol, substrates for the placental synthesis of estrogens. Tight correlations between steroids in UA and UV indicate that steroid measurements in UA, UV and UM can be accurately derived from each other, which is important for the diagnostics of steroid related diseases in newborns.