Induction of Amnion Epithelial Apoptosis by Cortisol via tPA/Plasmin System

The dual role of glucocorticoid regeneration in inflammation at parturition

Introduction

Fetal membrane inflammation is an integral event of parturition. However, excessive pro-inflammatory cytokines can impose threats to the fetus. Coincidentally, the fetal membranes express abundant 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1), which generates biologically active cortisol to promote labor through induction of prostaglandin synthesis. Given the well-recognized anti-inflammatory actions of glucocorticoids, we hypothesized that cortisol regenerated in the fetal membranes might be engaged in restraining fetus-hazardous pro-inflammatory cytokine production for the safety of the fetus, while reserving pro-labor effect on prostaglandin synthesis to ensure safe delivery of the fetus.

Methods

The hypothesis was examined in human amnion tissue and cultured primary human amnion fibroblasts as well as a mouse model.

Results

11β-HSD1 was significantly increased in the human amnion in infection-induced preterm birth. Studies in human amnion fibroblasts showed that lipopolysaccharide (LPS) induced 11β-HSD1 expression synergistically with cortisol. Cortisol completely blocked NF-κB-mediated pro-inflammatory cytokine expression by LPS, but STAT3-mediated cyclooxygenase 2 expression, a crucial prostaglandin synthetic enzyme, remained. Further studies in pregnant mice showed that corticosterone did not delay LPS-induced preterm birth, but alleviated LPS-induced fetal organ damages, along with increased 11β-HSD1, cyclooxygenase 2, and decreased pro-inflammatory cytokine in the fetal membranes.

Discussion

There is a feed-forward cortisol regeneration in the fetal membranes in infection, and cortisol regenerated restrains pro-inflammatory cytokine expression, while reserves pro-labor effect on prostaglandin synthesis. This dual role of cortisol regeneration can prevent excessive pro-inflammatory cytokine production, while ensure in-time delivery for the safety of the fetus.

Role and action mechanisms of tPA in CRH-induced apoptosis of mouse oviductal epithelial and mural granulosa cells

Understanding how stress hormones induce apoptosis in oviductal epithelial cells (OECs) and mural granulosa cells (MGCs) can reveal the mechanisms by which female stress impairs embryonic development and oocyte competence. A recent study showed that tissue plasminogen activator (tPA) ameliorates corticosterone-induced apoptosis in MGCs and OECs by acting on its receptors low-density lipoprotein receptor-related protein 1 (LRP1) and Annexin A2 (ANXA2), respectively. However, whether tPA is involved in corticotropin-releasing hormone (CRH)-induced apoptosis and whether it uses the same or different receptors to inhibit apoptosis induced by different hormones in the same cell type remains unknown. This study showed that CRH triggered apoptosis in both OECs and MGCs and significantly downregulated tPA expression. Moreover, tPA inhibits CRH-induced apoptosis by acting on ANXA2 in both OECs and MGCs. While ANXA2 inhibits apoptosis via phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling, LRP1 reduces apoptosis via mitogen-activated protein kinase (MAPK) signaling. Thus, tPA used the same receptor to inhibit CRH-induced apoptosis in both OECs and MGCs, however used different receptors to inhibit corticosterone-induced apoptosis in MGCs and OECs. These data helps understand the mechanism by which female stress impairs embryo/oocyte competence and proapoptotic factors trigger apoptosis in different cell types.

Glucocorticoids and Their Receptor Isoforms: Roles in Female Reproduction, Pregnancy, and Foetal Development

Alterations in the hypothalamic-pituitary-adrenal (HPA) axis and associated changes in circulating levels of glucocorticoids are integral to an organism's response to stressful stimuli. Glucocorticoids acting via glucocorticoid receptors (GRs) play a role in fertility, reproduction, placental function, and foetal development. GRs are ubiquitously expressed throughout the female reproductive system and regulate normal reproductive function. Stress-induced glucocorticoids have been shown to inhibit reproduction and affect female gonadal function by suppressing the hypothalamic-pituitary-gonadal (HPG) axis at each level. Furthermore, during pregnancy, a mother's exposure to prenatal stress or external glucocorticoids can result in long-lasting alterations to the foetal HPA and neuroendocrine function. Several GR isoforms generated via alternative splicing or translation initiation from the GR gene have been identified in the mammalian ovary and uterus. The GR isoforms identified include the splice variants, GRα and GRβ, and GRγ and GR-P. Glucocorticoids can exert both stimulatory and inhibitory effects and both pro- and anti-inflammatory functions in the ovary, in vitro. In the placenta, thirteen GR isoforms have been identified in humans, guinea pigs, sheep, rats, and mice, indicating they are conserved across species and may be important in mediating a differential response to stress. Distinctive responses to glucocorticoids, differential birth outcomes in pregnancy complications, and sex-based variations in the response to stress could all potentially be dependent on a particular GR expression pattern. This comprehensive review provides an overview of the structure and function of the GR in relation to female fertility and reproduction and discusses the changes in the GR and glucocorticoid signalling during pregnancy. To generate this overview, an extensive non-systematic literature search was conducted across multiple databases, including PubMed, Web of Science, and Google Scholar, with a focus on original research articles, meta-analyses, and previous review papers addressing the subject. This review integrates the current understanding of GR variants and their roles in glucocorticoid signalling, reproduction, placental function, and foetal growth.

Paradoxical Induction of ALOX15/15B by Cortisol in Human Amnion Fibroblasts: Implications for Inflammatory Responses of the Fetal Membranes at Parturition

Inflammation of the fetal membranes is an indispensable event of parturition, with increasing prostaglandin E2 (PGE2) synthesis as one of the ultimate products that prime labor onset. In addition to PGE2, the fetal membranes also boast a large capacity for cortisol regeneration. It is intriguing how increased PGE2 synthesis is achieved in the presence of increasing amounts of classical anti-inflammatory glucocorticoids in the fetal membranes at parturition. 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE) synthesized by lipoxygenase 15/15B (ALOX15/15B) has been shown to enhance inflammation-induced PGE2 synthesis in amnion fibroblasts. Here, we examined whether glucocorticoids could induce ALOX15/15B expression and 15(S)-HETE production to promote PGE2 synthesis in amnion fibroblasts at parturition. We found that cortisol and 15(S)-HETE abundance increased parallelly in the amnion at parturition. Cortisol induced ALOX15/15B expression and 15(S)-HETE production paradoxically in amnion fibroblasts. Mechanism study revealed that this paradoxical induction was mediated by p300-mediated histone acetylation and interaction of glucocorticoid receptor with transcription factors CREB and STAT3. Conclusively, cortisol regenerated in the fetal membranes can paradoxically induce ALOX15/15B expression and 15(S)-HETE production in human amnion fibroblasts, which may further assist in the induction of PGE2 synthesis in the inflammatory responses of the fetal membranes for parturition.

Role of tPA in Corticosterone-Induced Apoptosis of Mouse Mural Granulosa and Oviductal Epithelial Cells

Although studies indicate that female stress-increased secretion of glucocorticoids impairs oocyte competence and embryo development, by inducing apoptosis of ovarian and oviductal cells, respectively, the mechanisms by which glucocorticoids induce apoptosis of ovarian and oviductal cells are largely unclear. Tissue plasminogen activator (tPA) has been involved in apoptosis of different cell types. However, while some studies indicate that tPA is proapoptotic, others demonstrate its antiapoptotic effects. This study has explored the role and action mechanisms of tPA in corticosterone-induced apoptosis of mouse mural granulosa cells (MGCs) and oviductal epithelial cells (OECs). The results demonstrate that culture with corticosterone significantly increased apoptosis, while decreasing levels of tPA (Plat) mRNA and tPA protein in both MGCs and OECs. Culture with tPA ameliorated corticosterone-induced apoptosis of MGCs and OECs. Furthermore, while tPA protected MGCs from corticosterone-induced apoptosis by interacting with low-density lipoprotein receptor-related protein 1 (LRP1), it protected OECs from the apoptosis by acting on Annexin 2 (ANXA2). In conclusion, tPA is antiapoptotic in both MGCs and OECs, and it protects MGCs and OECs from corticosterone-induced apoptosis by interacting with LRP1 and ANXA2, respectively, suggesting that tPA may use different receptors to inhibit apoptosis in different cell types.

Single cell transcriptomic analysis of human amnion identifies cell-specific signatures associated with membrane rupture and parturition

Background

The human amnion is an intrauterine tissue which is involved in the initiation of parturition. In-depth understanding of gene expression signatures of individual cell types in the amnion with respect to membrane rupture at parturition may help identify crucial initiators of parturition for the development of specific strategies to prevent preterm birth, a leading cause of perinatal mortality.

Results

Six major cell types were revealed in human amnion including epithelial cells, fibroblasts and immunocytes as well as three other cell types expressing dual cell markers including epithelial/fibroblast, immune/epithelial and immune/fibroblast markers. The existence of cell types expressing these dual cell markers indicates the presence of epithelial-mesenchymal (EMT), epithelial-immune (EIT) and mesenchymal-immune (MIT) transitions in amnion at parturition. We found that the rupture zone of amnion exhibited some specific increases in subcluster proportions of immune and EMT cells related to extracellular matrix remodeling and inflammation in labor. The non-rupture zone exhibited some common changes in subcluster compositions of epithelial and fibroblast cells with the rupture zone in labor, particularly those related to oxidative stress and apoptosis in epithelial cells and zinc ion transport in fibroblasts. Moreover, we identified that C–C motif chemokine ligand 20 (CCL20) was among the top up-regulated genes in amnion epithelial cells, fibroblasts and immunocytes in the rupture zone at parturition. Studies in pregnant mice showed that administration of CCL20 induced immunocytes infiltration to tissues at the maternal–fetal interface and led to preterm birth.

Conclusions

Apart from the conventional epithelial, fibroblast and immunocytes, human amnion cells may undergo EMT, EIT and FIT in preparation for parturition. Intense inflammation and ECM remodeling are present in the rupture zone, while enhanced apoptosis and oxidative stress in epithelial cells and zinc ion transport in fibroblasts are present in amnion regardless of the rupture zones at parturition. CCL20 derived from the major cell types of the amnion participates in labor onset.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00797-4.

C/EBPδ drives key endocrine signals in the human amnion at parturition

Amnion-derived prostaglandin E2 (PGE2) and cortisol are key to labor onset. Identification of a common transcription factor driving the expression of both cyclooxygenase-2 (COX-2) and 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1), the key enzymes in their production, may hold the key to the treatment of pre-term labor. Here, we have found that the CCAAT enhancer binding protein δ (C/EBPδ) is such a transcription factor which underlies the feed-forward induction of COX-2 and 11β-HSD1 expression by their own products PGE2 and cortisol in human amnion fibroblasts so that their production would be ensured in the amnion for the onset of labor. Moreover, the abundance of C/EBPδ in the amnion increases along with COX-2 and 11β-HSD1 at term and further increases at parturition. Knockout of C/EBPδ in mice delays the onset of labor further supporting the concept. In conclusion, C/EBPδ pathway may be speculated to serve as a potential pharmaceutical target in the amnion for treatment of pre-term labor.

Cortisol Regeneration in the Fetal Membranes, A Coincidental or Requisite Event in Human Parturition?

The fetal membranes are equipped with high capacity of cortisol regeneration through the reductase activity of 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1). The expression of 11β-HSD1 in the fetal membranes is under the feedforward induction by cortisol, which is potentiated by proinflammatory cytokines. As a result, the abundance of 11β-HSD1 increases with gestational age and furthermore at parturition with an escalation of cortisol concentration in the fetal membranes. Accumulated cortisol takes parts in a number of crucial events pertinent to the onset of labor in the fetal membranes, including extracellular matrix (ECM) remodeling and stimulation of prostaglandin output. Cortisol remodels the ECM through multiple approaches including induction of collagen I, III, and IV degradation, as well as inhibition of their cross-linking. These effects of cortisol are executed through activation of the autophagy, proteasome, and matrix metalloprotease 7 pathways, as well as inhibition of the expression of cross-linking enzyme lysyl oxidase in mesenchymal cells of the membranes. With regard to prostaglandin output, cortisol not only increases prostaglandin E2 and F2α syntheses through induction of their synthesizing enzymes such as cytosolic phospholipase A2, cyclooxygenase 2, and carbonyl reductase 1 in the amnion, but also decreases their degradation through inhibition of their metabolizing enzyme 15-hydroxyprostaglandin dehydrogenase in the chorion. Taking all together, data accumulated so far denote that the feedforward cortisol regeneration by 11β-HSD1 in the fetal membranes is a requisite event in the onset of parturition, and the effects of cortisol on prostaglandin synthesis and ECM remodeling may be enhanced by proinflammatory cytokines in chorioamnionitis.

Enhancement of cortisol-induced SAA1 transcription by SAA1 in the human amnion

Our previous studies have demonstrated that human fetal membranes are capable of de novo synthesis of serum amyloid A1 (SAA1), an acute phase protein of inflammation, wherein SAA1 may participate in parturition by inducing a number of inflammation mediators including interleukine-1β, interleukine-6 and prostaglandin E2. However, the regulation of SAA1 expression in the fetal membranes remains largely unknown. In the current study, we examined the regulation of SAA1 expression by cortisol, a crucial steroid produced locally in the fetal membranes at parturition, and the interaction between cortisol and SAA1 in the feed-forward induction of SAA1 expression in human amnion fibroblasts. Results showed that cortisol-induced SAA1 expression in a concentration-dependent manner, which was greatly enhanced by SAA1 despite modest induction of SAA1 expression by itself. Mechanism studies revealed that the induction of SAA1 expression by cortisol and SAA1 was blocked by either the transcription factor STAT3 antagonist AZD0530 or siRNA-mediated knockdown of STAT3. Furthermore, cortisol- and SAA1-induced STAT3 phosphorylation in a sequential order with the induction by SAA1 preceding the induction by cortisol. However, combination of cortisol and SAA1 failed to further intensify the phosphorylation of STAT3. Consistently, cortisol and SAA1 increased the enrichment of STAT3 at the SAA1 promoter. Taking together, this study has demonstrated that cortisol and SAA1 can reinforce each other in the induction of SAA1 expression through sequential phosphorylation of STAT3. The enhancement of cortisol-induced SAA1 expression by SAA1 may lead to excessive SAA1 accumulation resulting in parturition-associated inflammation in the fetal membranes.

Involvement of serum amyloid A1 in the rupture of fetal membranes through induction of collagen I degradation

The de novo synthesis of serum amyloid A1 (SAA1) is augmented in human fetal membranes at parturition. However, its role in parturition remains largely unknown. Here, we investigated whether SAA1 was involved in the rupture of fetal membranes, a crucial event in parturition accompanied with extensive degradation of collagens. Results showed that SAA1 decreased both intracellular and extracellular COL1A1 and COL1A2 abundance, the two subunits of collagen I, without affecting their mRNA levels in human amnion fibroblasts. These reductions were completely blocked only with inhibition of both matrix metalloproteases (MMPs) and autophagy. Consistently, SAA1 increased MMP-2/9 abundance and the markers for autophagic activation including autophagy related (ATG) 7 (ATG7) and the microtubule-associated protein light chain 3 β (LC3B) II/I ratio with the formation of LC3 punctas and autophagic vacuoles in the fibroblasts. Moreover, the autophagic degradation of COL1A1/COL1A2 and activation of MMP-2/9 by SAA1 were blocked by inhibitors for the toll-like receptors 2/4 (TLR2/4) or NF-κB. Finally, reciprocal corresponding changes of SAA1 and collagen I were observed in the amnion following spontaneous rupture of membranes (ROM) at parturition. Conclusively, SAA1 may participate in membrane rupture at parturition by degradating collagen I via both autophagic and MMP pathways. These effects of SAA1 appear to be mediated by the TLR2/4 receptors and the NF-κB pathway.

Extracellular matrix remodeling effects of serum amyloid A1 in the human amnion: Implications for fetal membrane rupture

PROBLEM

Rupture of fetal membranes is a crucial event at parturition, which is preceded by extensive extracellular matrix (ECM) remodeling. Our recent studies have demonstrated that the human fetal membranes are capable of de novo synthesis of serum amyloid A1 (SAA1), an acute phase protein, and the abundance of SAA1 in the amnion was increased at parturition. However, the exact role of SAA1 in human parturition remains to be established.

METHOD OF STUDY

The effects of SAA1 on the abundance of collagenases and lysyl oxidase, the enzyme that cross-links collagens, were investigated in culture primary human amnion fibroblasts and tissue explants with an aim to examine the involvement of SAA1 in the ECM remodeling in the amnion.

RESULTS

Serum amyloid A1 (SAA1) time- and dose-dependently increased the abundance of collagenases MMP-1, MMP-8, and MMP-13, while decreased the abundance of lysyl oxidase-like 1 (LOXL1). These effects of SAA1 were attenuated by siRNA-mediated knockdown of the Toll-like receptor (TLR) 4 and its antagonist CLI-095, but not by siRNA-mediated knockdown of TLR2. Furthermore, the inhibitors for NF-κB (JSH-23) and mitogen-activated protein kinases (MAPKs) p38 (SB203580) and JNK (SP600125) could also attenuate the effects of SAA1, while the inhibitor for MAPK ERK1/2 (PD 98059) could block the effects of SAA1 only on MMP-1, MMP-8, and LOXL1 but not on MMP-13.

CONCLUSION

These data highlight a possible role for SAA1 in ECM remodeling preceding membrane rupture by regulating the expression of collagenases MMP-1, MMP-8, MMP-13, and LOXL1 through TLR4-mediated activation of the NF-κB and MAPK pathways in amnion fibroblasts.

Protein 53 (P53) Expressions and Apoptotic Index of Amniotic Membrane Cells in the Premature Rupture of Membranes

BACKGROUND:

The premature rupture of membranes (PROM) represents an obstetric issue causing significant maternal and neonatal morbidity and mortality. Although protein 53 (p53), one of the proapoptotic proteins suspected of causing PROM at the molecular level is closely correlated with the occurrence of PROM, the exact mechanism remains still unclear.

AIM:

This study aims to investigate the hypothesis that p53 expression and the apoptotic index play a role in the PROM mechanism.

METHODS:

Placentas from 20 pregnancies (37–42 weeks gestation) and 20 pregnancies complicated by PROM were collected at delivery. The independent variable is represented by pregnant mothers with a single live fetus experiencing PROM (followed by labour and birth) while without PROM mothers represent the control. The research material was taken from the amnion tissue in the placenta. Also, p53 and apoptotic index (TUNEL) immunohistochemical examination were conducted at the Integrated Biomedical Laboratory, Medical Faculty of Udayana University, Bali. The correlation between the apoptotic index and p53 expression of the PROM group was tested using a McNemar Test.

RESULTS:

No statistically significant differences were found between the two groups (p > 0.05). There was a significant difference in p53 expression in PROM cases compared to those without PROM (11.15 + 5.59% vs. 0.95 + 2.52%) with χ² = 19.538 and p = 0.001. The apoptotic index in PROM cases was higher than in those without PROM (19.10 + 5.63% vs. 1.15 + 2.46%) with χ² = 32.40 and p = 0.001. There was a strong correlation between p53 expression and PROM with PR = 3.449 (95% CI = 1.801-6.605; p = 0.001). There was a strong correlation between the apoptotic index and PROM with PR = 19 (95% CI = 2.81-128.69; p = 0.001).

CONCLUSION:

p53 expression and the apoptotic index of amniotic membrane cells in cases of PROM was higher than in those without PROM, there was a strong correlation between p53 expression and apoptotic index with the occurrence of PROM.

Progestins Inhibit Tumor Necrosis Factor α-Induced Matrix Metalloproteinase 9 Activity via the Glucocorticoid Receptor in Primary Amnion Epithelial Cells

Progestins have been recommended for preterm birth prevention in high-risk women; however, their mechanism of action still remains an area of debate. Medroxyprogesterone acetate (MPA) has previously been shown to significantly inhibit tumor necrosis factor α (TNFα)-induced matrix metalloproteinase 9 (MMP9) messenger RNA (mRNA) expression and activity in primary amnion epithelial cells, a process that may lead to preterm premature rupture of membranes. A mechanism that explains MPA's inhibition of TNFα-induced MMP9 mRNA expression and activity in primary amnion epithelial cells is unclear since these cells lack the classic nuclear progesterone receptor but express a membrane-associated progesterone receptor-progesterone receptor membrane component 1 (PGRMC1) along with the glucocorticoid receptor (GR). Primary amnion epithelial cells harvested from healthy term pregnant women at cesarean section were treated with PGRMC1 (to knockdown PGRMC1 expression), GR (to knockdown GR expression), or control small interfering RNA (siRNA; 10 nm) for 72 hours, pretreated with ethanol or MPA (10^-6 M) for 6 hours, and then stimulated with or without TNFα 10 ng/mL for 24 hours. Real-time quantitative polymerase chain reaction and gelatin zymography were used to quantify MMP9 mRNA expression and activity, respectively. Experimental groups were compared using 1-way analysis of variance. Both TNFα-induced MMP9 mRNA expression and activity were significantly inhibited by pretreatment with MPA; however, only the inhibition of TNFα-induced MMP9 activity was partially reversed with PGRMC1 siRNA. However, GR siRNA reversed both the inhibition of TNFα-induced MMP9 mRNA expression and activity by MPA. This study demonstrates that MPA mediates its anti-inflammatory effects primarily through GR and partially through PGRMC1 in primary amnion epithelial cells.

Drastic induction of MMP-7 by cortisol in the human amnion: implications for membrane rupture at parturition

Preterm premature rupture of fetal membranes precedes 30-40% of preterm births. Activation of matrix metalloproteases (MMPs) is the one of the major causes of extracellular matrix (ECM) degradation in membrane rupture. Increased cortisol, regenerated by 11β-hydroxysteroid dehydrogenase 1 in the amnion at parturition, is known to participate in a number of parturition-pertinent events. However, whether cortisol has a role in the regulation of MMPs in the membranes is not known. Here, we addressed this issue using human amnion tissue, the most tensile layer of the membranes. RNA-sequencing revealed that cortisol induced MMP7 expression dramatically in amnion fibroblasts, which was confirmed by real-time quantitative RT-PCR and Western blotting analysis in cortisol-treated amnion explants and fibroblasts. Measurement of collagen IV α5 chain (COL4A5), a substrate for MMP-7, showed that cortisol reduced its extracellular abundance, which was blocked by an antibody against MMP-7. Moreover, increased MMP-7 but decreased COL4A5 abundance was observed in the amnion tissue following labor-initiated spontaneous rupture of membranes. Mechanistic studies showed that cortisol increased the phosphorylation of c-Jun and the expression of c-Fos, the 2 major components of activated protein 1 (AP-1), respectively. The knocking down of c-Fos or c-Jun significantly attenuated the induction of MMP7 expression by cortisol. Chromatin immunoprecipitation assays showed that cortisol stimulated the enrichment of c-Fos and c-Jun at the AP-1 binding site in the MMP7 promoter. The data suggest that induction of MMP7 by cortisol via AP-1 may be a contributing factor to ECM degradation in membrane rupture at parturition.-Wang, L.-Y., Wang, W.-S., Wang, Y.-W., Lu, J.-W., Lu, Y., Zhang, C.-Y., Li, W.-J., Sun, K., Ying, H. Drastic induction of MMP-7 by cortisol in the human amnion: implications for membrane rupture at parturition.

11β-HSD1 in Human Fetal Membranes as a Potential Therapeutic Target for Preterm Birth

Human parturition is a complex process involving interactions between the myometrium and signals derived from the placenta, fetal membranes, and fetus. Signals originating from fetal membranes are crucial components that trigger parturition, which is clearly illustrated by the labor-initiating consequence of membrane rupture. It has been recognized for a long time that among fetal tissues in late gestation the fetal membranes possess the highest capacity for cortisol regeneration by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). However, the exact role of this unique feature remains a mystery. Accumulating evidence indicates that this extra-adrenal source of cortisol may serve as an upstream signal for critical events in human parturition, including enhanced prostaglandin and estrogen synthesis as well as extracellular matrix remodeling. This may explain why such high capacity for cortisol regeneration develops in human fetal membranes at late gestation. Therefore, inhibition of 11β-HSD1 may provide a potential therapeutic target for prevention of preterm birth. This review summarizes the current understanding of the functional role of cortisol regeneration by 11β-HSD1 in human fetal membranes.

Proteasome-mediated degradation of collagen III by cortisol in amnion fibroblasts

Rupture of fetal membranes (ROM) can initiate parturition at both term and preterm. Collagen III in the compact layer of the amnion contributes to the tensile strength of fetal membranes. However, the upstream signals triggering collagen III degradation remain mostly elusive. In this study, we investigated the role of cortisol regenerated by 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) in collagen III degradation in human amnion fibroblasts with an aim to seek novel targets for the prevention of preterm premature ROM (pPROM)-elicited preterm birth. Human amnion tissue and cultured amnion tissue explants and amnion fibroblasts were used to study the regulation of collagen III, which is composed of three identical 3α 1 chains (COL3A1), by cortisol. Cortisol decreased COL3A1 protein but not mRNA abundance in a concentration-dependent manner. Cortisone also decreased COL3A1 protein, which was blocked by 11β-HSD1 inhibition. The reduction in COL3A1 protein by cortisol was not affected by a transcription inhibitor but was further enhanced by a translation inhibitor. Autophagic pathway inhibitor chloroquine or siRNA-mediated knock-down of ATG7, an essential protein for autophagy, failed to block cortisol-induced reduction in COL3A1 protein abundance, whereas proteasome pathway inhibitors MG132 and bortezomib significantly attenuated cortisol-induced reduction in COL3A1 protein abundance. Moreover, cortisol increased COL3A1 ubiquitination and the reduction of COL3A1 protein by cortisol was blocked by PYR-41, a ubiquitin-activating enzyme inhibitor. Conclusively, cortisol regenerated in amnion fibroblasts may be associated with ROM at parturition by reducing collagen III protein abundance through a ubiquitin-proteasome pathway.

AKAP95-mediated nuclear anchoring of PKA mediates cortisol-induced PTGS2 expression in human amnion fibroblasts

Phosphorylation of the transcription factors cyclic adenosine monophosphate response element-binding protein (CREB) and signal transducer and activator of transcription 3 (STAT3) by protein kinase A (PKA) is required for the cortisol-induced production of cyclooxygenase-2 (COX-2) and prostaglandin E₂ (PGE₂) in human amnion fibroblasts, which critically mediates human parturition (labor). We found that PKA was confined in the nucleus by A-kinase-anchoring protein 95 (AKAP95) in amnion fibroblasts and that this localization was key to the cortisol-induced expression of PTGS2, the gene encoding COX-2. Cortisol increased the abundance of nuclear PKA by stimulating the expression of the gene encoding AKAP95. Knockdown of AKAP95 not only reduced the amounts of nuclear PKA and phosphorylated CREB but also attenuated the induction of PTGS2 expression in primary human amnion fibroblasts treated with cortisol, whereas the phosphorylation of STAT3 in response to cortisol was not affected. The abundances of AKAP95, phosphorylated CREB, and COX-2 were markedly increased in human amnion tissue after labor compared to those in amnion tissues from cesarean sections without labor. These results highlight an essential role for PKA that is anchored in the nucleus by AKAP95 in the phosphorylation of CREB and the consequent induction of COX-2 expression by cortisol in amnion fibroblasts, which may be important in human parturition.

Stress and the HPA Axis: Balancing Homeostasis and Fertility

An organism’s reproductive fitness is sensitive to the environment, integrating cues of resource availability, ecological factors, and hazards within its habitat. Events that challenge the environment of an organism activate the central stress response system, which is primarily mediated by the hypothalamic–pituitary–adrenal (HPA) axis. The regulatory functions of the HPA axis govern the cardiovascular and metabolic system, immune functions, behavior, and reproduction. Activation of the HPA axis by various stressors primarily inhibits reproductive function and is able to alter fetal development, imparting a biological record of stress experienced in utero. Clinical studies and experimental data indicate that stress signaling can mediate these effects through direct actions in the brain, gonads, and embryonic tissues. This review focuses on the mechanisms by which stress activation of the HPA axis impacts fertility and fetal development.

Glucocorticoids and Reproduction: Traffic Control on the Road to Reproduction

Glucocorticoids are steroid hormones that regulate diverse cellular functions and are essential to facilitate normal physiology. However, stress-induced levels of glucocorticoids result in several pathologies including profound reproductive dysfunction. Compelling new evidence indicates that glucocorticoids are crucial to the establishment and maintenance of reproductive function. The fertility-promoting or -inhibiting activity of glucocorticoids depends on timing, dose, and glucocorticoid responsiveness within a given tissue, which is mediated by the glucocorticoid receptor (GR). The GR gene and protein are subject to cellular processing, contributing to signaling diversity and providing a mechanism by which both physiological and stress-induced levels of glucocorticoids function in a cell-specific manner. Understanding how glucocorticoids regulate fertility and infertility may lead to novel approaches to the regulation of reproductive function.

Induction of pro-inflammatory genes by serum amyloid A1 in human amnion fibroblasts

Serum amyloid A1 (SAA1) is an acute response protein, which is mainly produced by the liver, during infection. However, it remains unknown whether SAA1 can be produced in human fetal membranes where it is able to elicit events pertinent to labor initiation. We demonstrated that SAA1 was expressed in the fibroblasts and epithelium of the amnion and the trophoblasts of the chorion. Further study in human amnion fibroblasts showed that SAA1 production was augmented by interleukin-1β (IL-1β) and cortisol alone and synergistically, and SAA1 in turn induced the expression of IL-1β, interleukin-6 (IL-6), cyclooxygenase-2 (COX-2) and PGE2 production. These effects of SAA1 were mediated through activation of the NF-κB, p38 and ERK1/2 pathways via the toll-like receptor 4 (TLR4). Inhibition of TLR4 attenuated not only SAA1-induced activation of NF-κB, p38 and ERK1/2 but also increases in IL-1β, IL-6 and COX-2 expression. Moreover, SAA1 expression was increased in human amnion tissue following spontaneous labor. In conclusion, this study has demonstrated for the first time that SAA1 can be produced in human fetal membranes, which can be greatly induced in the presence of proinflammatory cytokines and glucocorticoids thereby producing effects associated with parturition.

Autophagic Degradation of Collagen 1A1 by Cortisol in Human Amnion Fibroblasts

Rupture of fetal membranes can initiate parturition at both term and preterm. Collagen is the crucial factor determining the tensile strength of the membranes. Toward the end of gestation, a feed-forward regeneration of cortisol via 11β-hydroxysteroid dehydrogenase 1 exists in fetal membranes. It remains undetermined whether cortisol contributes to collagen reduction in fetal membranes. In this study, we have examined whether cortisol accumulation is a causative factor for collagen reduction in human amnion fibroblasts, the major source of collagens in the membranes. Cortisol had no effect on collagen 1A1 (COL1A1) and 1A2 (COL1A2) messenger RNA (mRNA) abundance but decreased their protein abundance. The latter effect was affected by neither mRNA transcription inhibitor nor protein translation inhibitor. Mechanistic studies revealed that the reduction in COL1A1 but not COL1A2 protein by cortisol was blocked by lysosome inhibitor chloroquine or small interfering RNA (siRNA)-mediated knockdown of autophagy-related protein 7, an essential protein for autophagy, whereas the proteasome inhibitors MG132 and bortezomib were ineffective. Further analysis showed that cortisol dose dependently increased the ratio of LC3II/LC3I, a marker of lysosome activation, an effect blocked by the glucocorticoid receptor (GR) antagonist RU486 and siRNA-mediated knockdown of GR. Consistently, cortisol decreased COL1A1 and COL1A2 protein abundance in amnion tissue explants, and decreased COL1A1 and COL1A2 protein abundance was observed at parturition in the amnion tissue. Conclusively, cortisol regeneration in fetal membranes may contribute to rupture of fetal membranes at parturition by reducing collagen protein abundance. Lysosome-mediated autophagy accounts for the reduction in COL1A1 by cortisol, but the mechanism underlying the reduction in COL1A2 awaits further investigation.