Prokineticin-1 (PROK1) modulates interleukin (IL)-11 expression via prokineticin receptor 1 (PROKR1) and the calcineurin/NFAT signalling pathway

Physical TRPV1-PKR2 interaction modulates PKR2 localization, activation and β-arrestin-2 recruitment

Transient Receptor Potential Vanilloid 1 (TRPV1) plays a central role in nociception and inflammation-induced hyperalgesia. Prokineticin receptors (PKR1 and PKR2) are G protein-coupled receptors (GPCRs) that are expressed both centrally and peripherally and induce various signalling pathways through the binding of their endogenous ligands, the prokineticins. The activation of PKRs is modulated by interaction with accessory proteins such as snapin and β-arrestin-2. The prokineticin system is involved in the mechanisms of pain perception by triggering a strong hyperalgesia that lowers the thresholds for thermal and mechanical stimuli. PKR1 and PKR2 are both expressed in dorsal root ganglia (DRG) neurons where they colocalise with TRPV1. In this work, we have identified the regions that mediate the physical interaction between TRPV1 and PKR2. We demonstrated that in the presence of the accessory protein snapin, the strength of binding between TRPV1 and PKR2 is increased. TRPV1 proves to be a physiological regulator of PKR2, modulating its activation, localisation and β-arrestin binding as well as PK2-induced mechanical allodynia. The results obtained show for the first time that TRPV1 regulates PKR2 signalling, suggesting a bidirectional interaction between the two systems.

Oxytocin ameliorates lipopolysaccharide-induced acute orchitis model: interplay of oxidative stress and inflammatory pathways

Introduction

Lipopolysaccharide (LPS), a constituent of the outer membrane of Gram-negative bacteria, is a powerful inducer of systemic inflammation and has been extensively utilized in experimental models to simulate inflammatory responses and septic disorders. Recent research indicates that oxytocin (OXY), a neuropeptide typically linked to social bonding and reproductive functions, may influence inflammatory processes. This work examines the impact of OXY on LPS-induced testicular damage, aiming to elucidate its therapeutic potential in addressing inflammatory disorders and broadening the comprehension of its functions beyond conventional neuroendocrine roles.

Methods

Eighteen male albino rats were divided into three groups; the control group received no treatment; the LPS group received 0.5 mL of saline solution containing 5 mg/kg LPS intraperitoneally (orchitis model); and the LPS + OXY group received LPS and OXY (0.1 mg/kg) intraperitoneally every 12 h for 72 h.

Results and discussion

Animals subjected to LPS were found to have severe orchitis, as evidenced by increased oxidative stress and surging inflammatory mediators (TNF-α, IL-1β, and IL-6), with declined IL-10 levels. Besides, LPS increased the malondialdehyde (MDA) and decreased the glutathione (GSH) levels, inducing an oxidative stress cascade. In addition, there are dramatic increases in the TLR4, MyD88, NF-κB, and PK2/PKR1 protein expression levels. All these events could alter the sperm count, morphology, and testicular architecture.

Conclusion

Interestingly, OXY could mitigate LPS-induced oxidative damage and inflammation in testicular tissue alongside restoring the disrupted sperm count, motility, and morphology. This therapeutic potential of OXY might be accounted for by its anti-inflammatory, antioxidant, and antiapoptotic activities.

MRAP2a Binds and Modulates Activity and Localisation of Prokineticin Receptor 1 in Zebrafish

The prokineticin system plays a role in hypothalamic neurons in the control of energy homeostasis. Prokineticin receptors (PKR1 and PKR2), like other G-protein-coupled receptors (GPCRs) are involved in the regulation of energy intake and expenditure and are modulated by the accessory membrane protein 2 of the melanocortin receptor (MRAP2). The aim of this work is to characterise the interaction and regulation of the non-melanocortin receptor PKR1 by MRAP2a in zebrafish (zMRAP2a) in order to use zebrafish as a model for the development of drugs targeting accessory proteins that can alter the localisation and activity of GPCRs. To this end, we first showed that zebrafish PKR1 (zPKR1) is able to interact with both zMRAP2a and human MRAP2 (hMRAP2). This interaction occurs between the N-terminal region of zPKR1 and the C-terminal domain of zMRAP2a, which shows high sequence identity with hMRAP2 and a similar propensity for dimer formation. Moreover, we demonstrated that in Chinese hamster ovary (CHO) cells, zMRAP2a or hMRAP2 are able to modulate zPKR1 activation induced by zebrafish PK2 (zPK2) resulting in an impaired ERK and STAT3 activation.

Novel Insights into Prokineticin 1 Role in Pregnancy-related Diseases

Prokineticin 1 (PROK1) is a secreted protein involved in a range of physiological activities such as cell proliferation, migration, angiogenesis, and neuronal cell proliferation. Emerging evidences show that PROK1/PROK receptors (PROKRs) are expressed by trophoblasts, and decidual stroma cells at the maternal-fetal interface. PROK1 plays a critical role in successful pregnancy establishment by regulating the decidualization, implantation and placental development. Dysregulation of prokineticin signaling has been described in certain pathological states associated with pregnancy, including pre-eclampsia, recurrent miscarriage and fetal growth restriction. In this review, the expression and pleiotropic roles of PROK1 under physiological and pathological pregnancy conditions are discussed.

Gαq-PKD/PKCμ signal regulating the nuclear export of HDAC5 to induce the IκB expression and limit the NF-κB-mediated inflammatory response essential for early pregnancy

Decidualization, denoting the transformation of endometrial stromal cells into specialized decidual cells, is a prerequisite for normal embryo implantation and a successful pregnancy in human. Here, we demonstrated that knockout of Gαq lead to an aberrantly enhanced inflammatory state during decidualization. Furthermore, we showed that deficiency of Gαq resulted in over-activation of nuclear factor (NF)-κB signaling, due to the decreased expression of NFκBIA, which encode the IκB protein and is the negative regulator for NF-κB. Mechanistically, Gαq deficiency decreased the Protein kinase D (PKD, also called PKCμ) phosphorylation levels, leading to attenuated HDAC5 phosphorylation and thus its nuclear export. Aberrantly high level of nuclear HDAC5 retarded histone acetylation to inhibit the induced NFκBIA transcription during decidualization. Consistently, pharmacological activation of the PKD/PKCμ or inhibition of the HDAC5 restored the inflammatory state and proper decidual response. Finally, we disclosed that over-active inflammatory state in Gαq-deficient decidua deferred the blastocyst hatching and adhesion in vitro, and the decidual expression of Gαq was significantly lower in women with recurrent pregnancy loss compared with normal pregnancy. In brief, we showed here that Gαq as a key regulator of the inflammatory cytokine's expression and decidual homeostasis in response to differentiation cues, which is required for successful implantation and early pregnancy.

Losartan impairs HTR-8/SVneo trophoblast migration through inhibition of angiotensin II-induced pro-inflammatory profile in human endometrial stromal cells

A deep interaction between the endometrium and the invading trophoblast occurs during implantation in humans, with the acquisition of uterine receptivity to the invading embryo promoted by an elevation of pro-inflammatory cytokines in the endometrium, and the invasiveness of decidualizing endometrial stromal cells, augmented by trophoblast-derived signals. Considering that usage of angiotensin II type 1 (AT1) receptor blockers, among other renin-angiotensin system (RAS) antagonists, is associated with adverse pregnancy outcomes, here we aim to analyse the involvement of AT1 receptor in the reciprocal dialogue occurring between endometrial stroma and trophoblast cells. In human endometrial stromal cells (T-HESC) pre-incubated with a decidualization cocktail, angiotensin (Ang) II increased protein expression of prolactin and FOXO1, markers of endometrial decidualization, while promoting nuclear translocation of FOXO1. In addition, Ang II treatment increased CXCL8, and matrix metalloprotease (MMP)-2 levels in T-HESC. Incubation with the AT1 receptor blocker losartan or with an NFAT signalling inhibitor, decreased Ang II-induced secretion of prolactin, CXCL8, and MMP-2 in T-HESC. In a wound healing assay, conditioned medium (CM) obtained from Ang II-treated T-HESC, but not CM from losartan-pre-incubated T-HESC, increased migration of HTR-8/SVneo trophoblasts, effect that was inhibited in the presence of a CXCL8-neutralizing antibody. An increased secretion of CXCL8 and MMP-2 was observed after treatment of T-HESC with CM obtained from HTR-8/SVneo cells, which was not observed in T-HESC pre-incubated with losartan or with the NFAT inhibitor. This study evidenced a reciprocal RAS-coded messaging between trophoblast and ESC which is affected by the AT1 receptor blocker losartan.

PROKR1 delivery by cell-derived vesicles restores the myogenic potential of Prokr1-deficient C2C12 myoblasts

Cell-derived vesicles (CDVs) have been investigated as an alternative to exosomes. Here, we generated CDVs from Prokineticin receptor 1 (PROKR1) overexpressing HEK293T cells using micro-extrusion. More than 60 billion PROKR1-enriched CDV (PROKR1^Tg CDVs) particles with canonical exosome properties were recovered from 10⁷ cells. With 25 μg/mL of PROKR1^Tg CDVs, we observed delivery of PROKR1, significant reduction of apoptosis, and myotube formation in C2C12^Prokr1-/- myoblasts that have lost their myogenic potential but underwent apoptosis following myogenic commitment. Expression levels of early and late myogenic marker genes and glucose uptake capacity were restored to equivalent levels with wild-type control. Furthermore, PROKR1^Tg CDVs were accumulated in soleus muscle comparable to the liver without significant differences. Therefore, CDVs obtained from genetically engineered cells appear to be an effective method of PROKR1 protein delivery and offer promise as an alternative therapy for muscular dystrophy.

Analysis of role of aromatic residues in extracellular loop 2 of Prokineticin receptor 2 in ligand binding probed with genetically encoded photo-crosslinkers

Prokineticin 2 (PK2) and Prokineticin 2 beta (PK2β), products of alternative splicing of pk2 gene, are chemokine-like proteins. While PK2 mediates its biological activities by signaling with the same efficiency through two homologous G protein coupled receptors, prokineticin receptor 1 (PKR1) and prokineticin receptor 2 (PKR2), PK2β is able to bind specifically PKR1. Extracellular loop 2 (ECL2) of chemokine receptors is a part of a transmembrane (TM) ligand binding site. In the ECL2 of PKR2 is present, as well as in all chemokine receptors, an aromatic residue cluster, involving tryptophan 212 localized four residues after an ECL2 conserved cysteine, and Phenylalanine 198 located in the top of TM 4. In this work, the photoactivatable unnatural amino acid p-benzoyl-L-phenylalanine is incorporated by amber codon suppression technology into PKR2 in position 212. Experiments of photoactivatable cross-linking demonstrated the role of tryptophan in position 212 for binding the ligand contacting Tryptophan in position 24. We also analyzed the role of Phenylalanine 198 in the specificity of PKRs binding. The comparison of TM-bundle binding sites between PKR1 and PKR2 revealed that they are completely conserved except for one residue: valine 207 in human PKR1, which is phenylalanine 198 in human PKR2. The F198V mutation in PKR2 permits to obtain a receptor able to bind more efficiently PK2β, a ligand highly specific for PKR1.

Cytokine imbalance at materno-embryonic interface as a potential immune mechanism for recurrent pregnancy loss

Recurrent pregnancy loss (RPL) is a prominent reproductive disease that distresses about 2%-5% of couples. RPL is the loss of two or more successive spontaneous pregnancies prior to the 20th week of embryo development. The commencement of pregnancy necessitates implantation of the embryo into responsive maternal decidua synchronized with the process of placentation, decidual and myometrial trophoblast incursion as well as refashioning of spiral blood arteries of uterus. The collapse of any of the processes fundamental for pregnancy success may result into an array of pregnancy problems including spontaneous pregnancy loss. Endometrium of human female manufactures an extensive range of cytokines during the proliferative and secretory stage of the menstrual cycle. These endometrial cytokines are thought as major players for making the uterus ready for embryo implantation and placental development during pregnancy. Decidual cytokines regulate the invasion of trophoblast and remodeling of spiral arteries as well as take part in immune suppression to accomplish the pregnancy. Deterrence of maternal rejection of embryo needs a regulated milieu, which takes place essentially at the embryo-maternal interface and the tissues of the uterus. The reasons of RPL remain anonymous in a large number of cases that lead to difficulties in management and severe trauma in couples. Cytokine modulatory therapies have been shown promising for preventing RPL. Further study of novel factors is wanted to establish more effective RPL treatment protocols. The present study aims to review the outcome of cytokine breach at materno-embryonic interface and the efficacy of cytokine modulatory therapies in RPL.

Pleiotropic role of prokineticin 1 in the porcine endometrium during pregnancy establishment and embryo implantation †

Acquisition of endometrial receptivity for embryo implantation is one of the crucial processes during pregnancy and is induced mainly by progesterone and enhanced by conceptus signals. Prokineticin 1 (PROK1) is characterized as a secretory protein with diverse functions in various tissues, including the reproductive tract. PROK1, with its receptor PROKR1, are up-regulated in the porcine endometrium during implantation and in women's receptive endometrium and decidua. However, the function of PROK1 in embryo-maternal communication has still not been fully elucidated. Hence, we hypothesize that PROK1 is involved in endometrial receptivity development and implantation in pigs. In this study, using the porcine in vivo model of intrauterine infusions of estradiol-17β (E2) and prostaglandin E2 (PGE2), we revealed that these hormones elevated endometrial expression of PROK1 and PROKR1 mRNA, respectively. Moreover, E2, acting synergistically with PGE2, increased PROKR1 protein expression. We also evidenced that PROK1-PROKR1 signaling induced expression of following genes and/or proteins CCN2, CDH13, FGF2, NFATC2, ANGPT1, ANGPT2, CDH1, MUC4, SPP1, IFNG, IL6, LIF, LIFR, TNF, TGFB3, and FGF9, as well as phosphorylation of PTK2 and secretion of IL6 and IL11 by endometrial explants in vitro. Ingenuity pathway analysis revealed that functions associated with the PROK1-regulated genes/proteins include cell-to-cell contact, cell attachment, migration and viability, differentiation of epithelial tissue, leukocyte migration, inflammatory response, angiogenesis, and vasculogenesis. Summarizing, our study suggests that PROK1 acts pleiotropically as an embryonic signal mediator that regulates endometrial receptivity by increasing the expression of the genes and proteins involved in implantation and pregnancy establishment in pigs.

Trypanosoma cruzi trans-sialidase induces STAT3 and ERK activation by prokineticin receptor 2 binding

Tc85, as other members of trans-sialidase family, is involved in Trypanosoma cruzi parasite adhesion to mammalian cells. Particularly, Tc85 acts through specific interactions with prokineticin receptor 2, a G-protein coupled receptor involved in diverse physiological and pathological processes. In this manuscript, through biochemical analyses, we demonstrated that LamG, a Tc85 domain, physically interacts with the prokineticin receptor 2. Moreover, expressing prokineticin receptor 1 and 2 we demonstrated that LamG specifically activates prokineticin receptor 2 through a strong coupling with G_αi or G_αq proteins in yeast strains and inducing ERK and NFAT phosphorylation in CHO mammalian cells. To demonstrate a Tc85 physiological role in T. cruzi infection of the nervous system, we evidenced a strong STAT3 and ERK activation by LamG in mice Dorsal Root Ganglia. L173R is the most common prokineticin receptor 2 mutation reported in Kallmann syndrome and it is a founder mutation. Our results demonstrated that in cells co-expressing prokineticin receptor 2 mutant (L173R) and wild-type, LamG is unable to induce signal transduction. The L173R mutation in heterozygosity may allow for a selective advantage due to increased protection from T. cruzi infection. SIGNIFICANCE OF THE STUDY: The Chagas' disease affecting millions of people worldwide is caused by an eukaryotic microorganism called T. cruzi. Pharmacological treatment for patients with Chagas' disease is still limited. Indeed, the small number of drugs available shows important side effects that can be debilitating for patient health. In order to replicate and produce new parasites T. cruzi uses a complex of different proteins produced by both the parasite and the human host cells. So, understanding the molecular details used by T. cruzi to be internalised by different types of human cells is an important step towards the development of new drugs for this disease. Prokineticin receptors are relevant for host-parasite interaction. To characterise the signal transduction cascade induced by their activation may help to understand the molecular details of cell infection, leading to novel therapeutic alternative for this debilitating disease.

The Prokineticins: Neuromodulators and Mediators of Inflammation and Myeloid Cell-Dependent Angiogenesis

The mammalian prokineticins family comprises two conserved proteins, EG-VEGF/PROK1 and Bv8/PROK2, and their two highly related G protein-coupled receptors, PKR1 and PKR2. This signaling system has been linked to several important biological functions, including gastrointestinal tract motility, regulation of circadian rhythms, neurogenesis, angiogenesis and cancer progression, hematopoiesis, and nociception. Mutations in PKR2 or Bv8/PROK2 have been associated with Kallmann syndrome, a developmental disorder characterized by defective olfactory bulb neurogenesis, impaired development of gonadotropin-releasing hormone neurons, and infertility. Also, Bv8/PROK2 is strongly upregulated in neutrophils and other inflammatory cells in response to granulocyte-colony stimulating factor or other myeloid growth factors and functions as a pronociceptive mediator in inflamed tissues as well as a regulator of myeloid cell-dependent tumor angiogenesis. Bv8/PROK2 has been also implicated in neuropathic pain. Anti-Bv8/PROK2 antibodies or small molecule PKR inhibitors ameliorate pain arising from tissue injury and inhibit angiogenesis and inflammation associated with tumors or some autoimmune disorders.

Prokineticin 1 is up-regulated by insulin in decidualizing human endometrial stromal cells

Prokineticin 1 (PROK1), a hypoxia‐regulated angiogenic factor, has emerged as a crucial regulator of embryo implantation and placentation. Dysregulation of PROK1 has been linked to recurrent pregnancy loss, pre‐eclampsia, foetal growth restriction and preterm birth. These pregnancy complications are common in women with obesity and polycystic ovary syndrome, i.e. conditions associated with insulin resistance and compensatory hyperinsulinaemia. We investigated the effect of insulin on PROK1 expression during in vitro decidualization. Endometrial stromal cells were isolated from six healthy, regularly menstruating women and decidualized in vitro. Insulin induced a significant dose‐dependent up‐regulation of PROK1 on both mRNA and protein level in decidualizing endometrial stromal cells. This up‐regulation was mediated by hypoxia‐inducible factor 1‐alpha (HIF1α) via the phosphatidylinositol 3‐kinase (PI3K) pathway. Furthermore, we demonstrated that PROK1 did not affect the viability, but significantly inhibited the migration of endometrial stromal cells and the migratory and invasive capacity of trophoblast cell lines. This in vitro study provides new insights into the regulation of PROK1 by insulin in human decidualizing endometrial stromal cells, the action of PROK1 on migration of endometrial stromal cells, as well as migration and invasion of trophoblasts. We speculate that hyperinsulinaemia may be involved in the mechanisms by which PROK1 is linked to placenta‐related pregnancy complications.

Involvement of Prokineticin 2 and Prokineticin Receptor 1 in Lipopolysaccharide-Induced Testitis in Rats

Prokineticin 2, a newly discovered proinflammatory peptide, has been amply evidenced to be involved in the occurrence and progress of local and systematical inflammation. Although the presence of Prokineticn 2 in mammal testis has been documented clearly, research targeting the involvement of prokineticin 2 in testicular pathology, especially testitis, is rather scarce. Employing a lipopolysaccharide-induced testitis rat model, we for the first time demonstrated the expression and upregulation of prokineticin 2 in orchitis at several levels. Our effort also addressed the differential expression patterns of prokineticin 2 and interleukin-1β, a key inflammation indicator, during testitis suggesting Prokineticn 2 serves more than a proinflammatory factor in the context of testitis. Given one of the cognate receptors of prokineticin 2, prokineticin receptor 1 (PKR1) was also significantly upregulated in orchitis as discussed in the current study, it is very likely that PK2/PKR1 signaling contribute to the development of inflammation-related testicular diseases.

Micro-RNA Feedback Loops Modulating the Calcineurin/NFAT Signaling Pathway

Nuclear factor of activated T cells (NFAT) is a family of transcription factors important for innate and adaptive immune responses. NFAT activation is tightly regulated through the calcineurin/NFAT signaling pathway. There is increasing evidence on non-coding RNAs such as miRNAs playing a crucial role in regulating transcription factors and signaling pathways. However, not much is known about microRNAs (miRNAs) targeting the calcineurin/NFAT signaling pathway involved in immune response in human. In this study, a comprehensive pathway level analysis has been carried out to identify miRNAs regulating the calcineurin/NFAT signaling pathway. Firstly, by incorporating experimental data and computational predictions, 191 unique miRNAs were identified to be targeting the calcineurin/NFAT signaling pathway in humans. Secondly, combining miRNA expression data from activated T cells and computational predictions, 32 miRNAs were observed to be induced by NFAT transcription factors. Finally, 11 miRNAs were identified to be involved in a feedback loop to modulate the calcineurin/NFAT signaling pathway activity. This data demonstrate the potential role of miRNAs as regulators of the calcineurin/NFAT signaling pathway. The present study thus emphasizes the importance of pathway level analysis to identify miRNAs and understands their role in modulating signaling pathways and transcription factor activity.

Human Decidual Stromal Cells as a Component of the Implantation Niche and a Modulator of Maternal Immunity

The human decidua is a specialized tissue characterized by embryo-receptive properties. It is formed during the secretory phase of menstrual cycle from uterine mucosa termed endometrium. The decidua is composed of glands, immune cells, blood and lymph vessels, and decidual stromal cells (DSCs). In the process of decidualization, which is controlled by oestrogen and progesterone, DSCs acquire specific functions related to recognition, selection, and acceptance of the allogeneic embryo, as well as to development of maternal immune tolerance. In this review we discuss the relationship between the decidualization of DSCs and pathological obstetrical and gynaecological conditions. Moreover, the critical influence of DSCs on local immune cells populations as well as their relationship to the onset and maintenance of immune tolerance is described.

Prokineticin receptor variants (PKR1-I379V and PKR2-V331M) are protective genotypes in human early pregnancy

Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) and its receptor genes (PROKR1(PKR1) andPROKR2(PKR2)) play an important role in human early pregnancy. We have previously shown thatPROKR1andPROKR2are associated with recurrent miscarriage (RM) using the tag-SNP method. In this study, we aimed to identifyPROKR1andPROKR2variants in idiopathic RM patients by genotyping of the entire coding regions. Peripheral blood DNA samples of 100 RM women and 100 controls were subjected to sequence the entire exons ofPROKR1andPROKR2. Significant non-synonymous variant genotypes present in the original 200 samples were further confirmed in the extended samples of 144 RM patients and 153 controls. Genetic variants that were over- or under-represented in the patients were ectopically expressed in HEK293 and JAR cells to investigate their effects on intracellular calcium influx, cell proliferation, cell invasion, cell–cell adhesion, and tube organization. We found that the allele and genotype frequencies ofPROKR1(I379V) andPROKR2(V331M) were significantly increased in the normal control groups compared with idiopathic RM women (P<0.05).PROKR1(I379V) andPROKR2(V331M) decreased intracellular calcium influx but increased cell invasiveness (P<0.05), whereas cell proliferation, cell–cell adhesion, and tube organization were not significantly affected. In conclusion,PROKR1(I379V) andPROKR2(V331M) variants conferred lower risk for RM and may play protective roles in early pregnancy by altering calcium signaling and facilitating cell invasiveness.

EG-VEGF: a key endocrine factor in placental development

Endocrine gland-derived vascular endothelial growth factor (EG-VEGF), also named prokineticin 1, is the canonical member of the prokineticin family. Numerous reports suggest a direct involvement of this peptide in normal and pathological reproductive processes. Recent advances propose EG-VEGF as a key endocrine factor that controls many aspects of placental development and suggest its involvement in the development of preeclampsia (PE), the most threatening pathology of human pregnancy. This review describes the finely tuned action and regulation of EG-VEGF throughout human pregnancy, argues for its clinical relevance as a potential diagnostic marker of the onset of PE, and discusses future research directions for therapeutic targeting of EG-VEGF.

Transcription factor NFATc2 controls the emergence of colon cancer associated with IL-6-dependent colitis

NFAT transcription factors control T-cell activation and function. Specifically, the transcription factor NFATc2 affects the regulation of cell differentiation and growth and plays a critical role in the development of colonic inflammation. Here, we used an experimental model of colitis-associated colorectal carcinoma to investigate the contribution of NFATc2 to the promotion of colonic tumors. Compared with wild-type animals that readily presented with multiple colon tumors, NFATc2-deficient mice were protected from tumor development. This observed decrease in colonic tumor progression was associated with reduced endoscopic inflammation, increased apoptosis of lamina propria T lymphocytes, and significantly reduced levels of the critical proinflammatory cytokines interleukin (IL)-21 and IL-6. Administration of hyper IL-6 abrogated protection from tumor progression in NFATc2-knockout mice and restored tumor incidence to control levels. Taken together, our findings highlight a pivotal role for NFATc2 in the establishment of inflammation-associated colorectal tumors mediated by control of IL-6 expression.

Angiotensin II activates the calcineurin/NFAT signaling pathway and induces cyclooxygenase-2 expression in rat endometrial stromal cells

Cyclooxygenase (COX)-2, the inducible isoform of cyclooxygenase, plays a role in the process of uterine decidualization and blastocyst attachment. On the other hand, overexpression of COX-2 is involved in the proliferation of the endometrial tissue during endometriosis. Deregulation of the renin-angiotensin-system plays a role in the pathophysiology of endometriosis and pre-eclampsia. Angiotensin II increases intracellular Ca(2+) concentration by targeting phospholypase C-gamma in endometrial stromal cells (ESC). A key element of the cellular response to Ca(2+) signals is the activity of the Ca(2+)- and calmodulin-dependent phosphatase calcineurin. Our first aim was to study whether angiotensin II stimulated Cox-2 gene expression in rat ESC and to analyze whether calcineurin activity was involved. In cells isolated from non-pregnant uteri, COX-2 expression--both mRNA and protein--was induced by co-stimulation with phorbol ester and calcium ionophore (PIo), as well as by angiotensin II. Pretreatment with the calcineurin inhibitor cyclosporin A inhibited this induction. We further analyzed the role of the calcineurin/NFAT signaling pathway in the induction of Cox-2 gene expression in non-pregnant rat ESC. Cyclosporin A abolished NFATc1 dephosphorylation and translocation to the nucleus. Cyclosporin A also inhibited the transcriptional activity driven by the Cox-2 promoter. Exogenous expression of the peptide VIVIT -specific inhibitor of calcineurin/NFAT binding- blocked the activation of Cox-2 promoter and the up-regulation of COX-2 protein in these cells. Finally we analyzed Cox-2 gene expression in ESC of early-pregnant rats. COX-2 expression--both mRNA and protein--was induced by stimulation with PIo as well as by angiotensin II. This induction appears to be calcineurin independent, since it was not abrogated by cyclosporin A. In conclusion, angiotensin II induced Cox-2 gene expression by activating the calcineurin/NFAT signaling pathway in endometrial stromal cells of non-pregnant but not of early-pregnant rats. These results might be related to differential roles that COX-2 plays in the endometrium.

Prokineticin 1 induces inflammatory response in human myometrium: a potential role in initiating term and preterm parturition

The infiltration of human myometrium and cervix with leukocytes and the formation of a pro-inflammatory environment within the uterus have been associated with the initiation of both term and preterm parturition. The mechanism regulating the onset of this pro-inflammatory cascade is not fully elucidated. We demonstrate that prokineticin 1 (PROK1) is up-regulated in human myometrium and placenta during labor. The expression of PROK1 receptor remains unchanged during labor and is abundantly expressed in the myometrium. Gene array analysis identified 65 genes up-regulated by PROK1 in human myometrium, mainly cytokines and chemokines, including IL-1β, chemokine C-C motif ligand 3, and colony-stimulating factor 3. In addition, we demonstrate that PROK1 increases the expression of chemokine C-C motif ligand 20, IL-6, IL-8, prostaglandin synthase 2, and prostaglandin E(2) and F(2α) secretion. The treatment of myometrial explants with 100 ng/mL of lipopolysaccharide up-regulates the expression of PROK1, PROK1 receptor, and inflammatory mediators. The infection of myometrial explants with lentiviral microRNA targeting PROK1, preceding treatment with lipopolysaccharide, reduces the expression of inflammatory genes. We propose that PROK1 is a novel inflammatory mediator that can contribute to the onset of human parturition at term and partially mediate premature onset of inflammatory pathways during bacterial infection.

Prokineticin 1 induces Dickkopf 1 expression and regulates cell proliferation and decidualization in the human endometrium

Prokineticin 1 (PROK1) signalling via prokineticin receptor 1 (PROKR1) regulates the expression of several genes with important roles in endometrial receptivity and implantation. This study investigated PROK1 regulation of Dickkopf 1 (DKK1) expression, a negative regulator of canonical Wnt signalling, and its function in the non-pregnant endometrium and first trimester decidua. DKK1 mRNA expression is elevated during the mid-secretory phase of the menstrual cycle and expression increases further in first trimester decidua. DKK1 protein expression is localized to glandular epithelial and stromal cells during the proliferative, early- and mid-secretory phases, whereas expression is confined to the stroma in the late-secretory phase and first trimester decidua. PROK1 induces the expression of DKK1 in endometrial epithelial cells stably expressing PROKR1 and in first trimester decidua explants, via a Gq-calcium-calcineurin-nuclear factor of activated T-cells-mediated pathway. Endometrial epithelial cell proliferation is negatively regulated by PROK1-PROKR1 signalling. We demonstrate that this effect on cell proliferation occurs via DKK1 expression, as siRNA targeted against DKK1 reduces the PROK1-induced decrease in proliferation. Furthermore, decidualization of primary human endometrial stromal cells with progesterone and cyclic adenosine monophosphate is inhibited by miRNA knock down of PROK1 or DKK1. These data demonstrate important roles for PROK1 and DKK1 during endometrial receptivity and early pregnancy, which include regulation of endometrial cell proliferation and decidualization.

The role of the prokineticin 2 pathway in human reproduction: evidence from the study of human and murine gene mutations

A widely dispersed network of hypothalamic GnRH neurons controls the reproductive axis in mammals. Genetic investigation of the human disease model of isolated GnRH deficiency has revealed several key genes crucial for GnRH neuronal ontogeny and GnRH secretion. Among these genes, prokineticin 2 (PROK2), and PROK2 receptor (PROKR2) have recently emerged as critical regulators of reproduction in both mice and humans. Both prok2- and prokr2-deficient mice recapitulate the human Kallmann syndrome phenotype. Additionally, PROK2 and PROKR2 mutations are seen in humans with Kallmann syndrome, thus implicating this pathway in GnRH neuronal migration. However, PROK2/PROKR2 mutations are also seen in normosmic GnRH deficiency, suggesting a role for the prokineticin signaling system in GnRH biology that is beyond neuronal migration. This observation is particularly surprising because mature GnRH neurons do not express PROKR2. Moreover, mutations in both PROK2 and PROKR2 are predominantly detected in the heterozygous state with incomplete penetrance or variable expressivity frequently seen within and across pedigrees. In some of these pedigrees, a "second hit" or oligogenicity has been documented. Besides reproduction, a pleiotropic physiological role for PROK2 is now recognized, including regulation of pain perception, circadian rhythms, hematopoiesis, and immune response. Therefore, further detailed clinical studies of patients with PROK2/PROKR2 mutations will help to map the broader biological role of the PROK2/PROKR2 pathway and identify other interacting genes/proteins that mediate its molecular effects in humans.

Bioinformatic detection of E47, E2F1 and SREBP1 transcription factors as potential regulators of genes associated to acquisition of endometrial receptivity

BACKGROUND

The endometrium is a dynamic tissue whose changes are driven by the ovarian steroidal hormones. Its main function is to provide an adequate substrate for embryo implantation. Using microarray technology, several reports have provided the gene expression patterns of human endometrial tissue during the window of implantation. However it is required that biological connections be made across these genomic datasets to take full advantage of them. The objective of this work was to perform a research synthesis of available gene expression profiles related to acquisition of endometrial receptivity for embryo implantation, in order to gain insights into its molecular basis and regulation.

METHODS

Gene expression datasets were intersected to determine a consensus endometrial receptivity transcript list (CERTL). For this cluster of genes we determined their functional annotations using available web-based databases. In addition, promoter sequences were analyzed to identify putative transcription factor binding sites using bioinformatics tools and determined over-represented features.

RESULTS

We found 40 up- and 21 down-regulated transcripts in the CERTL. Those more consistently increased were C4BPA, SPP1, APOD, CD55, CFD, CLDN4, DKK1, ID4, IL15 and MAP3K5 whereas the more consistently decreased were OLFM1, CCNB1, CRABP2, EDN3, FGFR1, MSX1 and MSX2. Functional annotation of CERTL showed it was enriched with transcripts related to the immune response, complement activation and cell cycle regulation. Promoter sequence analysis of genes revealed that DNA binding sites for E47, E2F1 and SREBP1 transcription factors were the most consistently over-represented and in both up- and down-regulated genes during the window of implantation.

CONCLUSIONS

Our research synthesis allowed organizing and mining high throughput data to explore endometrial receptivity and focus future research efforts on specific genes and pathways. The discovery of possible new transcription factors orchestrating the CERTL opens new alternatives for understanding gene expression regulation in uterine function.

CTGF expression is up-regulated by PROK1 in early pregnancy and influences HTR-8/Svneo cell adhesion and network formation

BACKGROUND

Prokineticin-1 (PROK1) and connective tissue growth factor (CTGF) are expressed in human endometrium and first-trimester decidua and have individually been proposed to have roles in implantation and placentation. We have recently demonstrated that CTGF may be a target gene for PROK1 in gene array analysis of a prokineticin receptor-1 stably transfected Ishikawa endometrial epithelial cell line (PROKR1-Ishikawa). The first aim of the study was to determine the effect of PROK1 on CTGF expression in PROKR1-Ishikawa cells and first-trimester decidua samples. Secondly, the effect of CTGF on trophoblast-derived HTR-8/SVneo cell adhesion and network formation was investigated.

METHODS AND RESULTS

Real-time qPCR showed that CTGF expression is elevated in first-trimester decidua compared with non-pregnant endometrium. In decidua, CTGF co-localized with PROKR1 to the glandular epithelium and a subset of stromal cells. PROK1 increased CTGF mRNA and protein expression in PROKR1-Ishikawa cells and first-trimester human decidua (8–12 weeks gestation). Knock down of endogenous PROK1 using micro RNA constructs targeted at PROK1, resulted in decreased expression of CTGF mRNA and protein in decidua. Inhibitors of specific cell signalling molecules demonstrated that PROK1 regulates CTGF expression via the Gq, phospholipase C (PLC), cSrc, epidermal growth factor receptor (EGFR), mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) kinase pathway activation. Treatment of trophoblast-derived HTR-8/Svneo cells with 1 µg/ml CTGF significantly increased adhesion to collagen IV, and differentiation of the cells into tube-like structures in matrigel.

CONCLUSIONS

CTGF expression in early pregnancy decidua is regulated by PROK1, via activation of the Gq, PLC, cSrc, EGFR, MAPK/ERK kinase pathway. CTGF in turn may contribute to the regulation of trophoblast conversion of maternal spiral arteries.