Kisspeptin-10, a KiSS-1/metastin-derived decapeptide, is a physiological invasion inhibitor of primary human trophoblasts

Association of kisspeptin-10 levels with abortus imminens: a preliminary study

PURPOSE

To investigate the association between kisspeptin 10 (Kp-10) levels and early pregnancy bleeding and perinatal outcome.

METHODS

A total of 20 pregnant women with the complaint of vaginal bleeding during 7-18 gestational weeks and 20 healthy gestational week matched pregnant women were included in the study. Maternal plasma Kp-10 levels were measured with the enzyme immunoassay method. Adverse pregnancy outcomes like intrauterine growth restriction, preterm delivery, preeclampsia and low birth weight were evaluated in both groups.

RESULTS

Maternal plasma Kp-10 levels (p = 0.01) and birth weight (p = 0.06) were found to be lower in women with bleeding. Intrauterine growth restriction, preterm delivery and intrauterine exitus were noted more commonly in women with bleeding (10 vs. 0%, 25 vs. 15% and 20 vs. 0%, p = 0.08). Preeclampsia were developed in 5% of both groups. Kp-10 levels showed positive correlation with gestational week (p = 0.02) and ALT levels (p = 0.02).

CONCLUSION

[corrected] Kp-10 levels were found lower in women with early pregnancy bleeding.

Comparative expression profiles for KiSS-1 and REN genes in preeclamptic and healthy placental tissues

OBJECTIVE

The aim of the present work was to look at differences in the placental tissue expression of KiSS-1 and REN genes from preeclamptic and healthy pregnant women, that could account for a possible synergistic function for both genes in the pathogenesis of preeclampsia.

STUDY DESIGN

This case-control study involved 27 preeclamptic women and 27 normoevolutive pregnant women. cDNA was obtained from placental tissue to carry out qPCR for both KiSS-1 and REN genes in order to compare mRNA expression levels in the studied groups. Statistical analysis showed expression differences that correlate with clinical and/or biochemical variables.

RESULTS

Higher expression for KiSS-1 in PEE vs. control woman (p=0.001) was observed, whereas no difference was observed for REN expression (p=0.300) when all the subjects were included. However, REN expression was significant higher when the samples were stratified according to preeclampsia severity. For 18 mild preeclamptic patients the p-value was p=0.001 compared to their controls, while for the remaining nine with severe preeclampsia the expression became significant (p=0.001).

CONCLUSION

Our results suggest that the high KiSS-1 expression seen in preeclamptic patients is in accordance with its role as an inhibitor of trophoblast invasiveness and maintained until the end of gestation. On the other hand, aggressive therapeutic management and/or severity status of patients have a direct effect on placental REN expression levels, masking the natural high expression of this gene on preeclamptic placental tissue. Therefore it was not possible to establish a real concordant expression profile for KiSS-1 and REN genes.

Preeclampsia leads to dysregulation of various signaling pathways in placenta

OBJECTIVES

To compare gene expression profiles of placentas from preeclamptic and normal pregnancies.

STUDY DESIGN

We performed microarray experiments to analyze genome-wide expression profiling for 10 placentas from pregnant women with preeclampsia and 10 placentas from women who experienced noncomplicated pregnancies (CON), and to identify dysregulated signaling pathways as well as genes in preeclampsia. RT-PCR, real-time RT-PCR and/or immunofluorescence analyses were performed to validate the data obtained from microarray experiments.

RESULTS

Unsupervised hierarchical clustering showed heterogeneity of preeclampsia at the molecular levels, whereas expression profiles of preeclampsia are distinctly different from those of CON. A list of genes which are differentially expressed between preeclampsia and CON included well known preeclampsia markers, such as Flt-1, leptin, HTRA1 and SIGLEC6. Gene Set Enrichment Analysis, a pathway-oriented analysis method for expression profiles, provided evidence that a number of biological activities including pathways that regulate actin cytoskeleton, TGFβ signaling, oxidative phosphorylation, and proteasome activity were aberrantly either up-regulated or down-regulated in preeclampsia. RT-PCR and real-time-RT-PCR for genes contributing these biological pathways (gene sets) enriched in either CON or preeclampsia reinforced that these biological processes were systemically dysregulated in preeclampsia.

CONCLUSIONS

Genome-wide expression profiles of preeclampsia showed heterogeneous characteristics of preeclampsia at the molecular levels. Dysregulation of genes and biological pathways could contribute to abnormal behavior of preeclmapsia. Our results will help further understand underlying mechanisms by which preeclampsia affects placental physiology.

Mechanism of maternal vascular remodeling during human pregnancy

Remodeling of maternal spiral arteries by invasion of extravillous trophoblast (EVT) is crucial for an adequate blood supply to the fetus. EVT cells that migrate through the decidual tissue destroy the arterial muscular lining from the outside (interstitial invasion), and those that migrate along the arterial lumen displace the endothelium from the inside (endovascular invasion). Numerous factors including cytokines/growth factors, chemokines, cell adhesion molecules, extracellular matrix-degrading enzymes, and environmental oxygen have been proposed to stimulate or inhibit the differentiation/invasion of EVT. Nevertheless, it is still difficult to depict overall pictures of the mechanism controlling perivascular and endovascular invasion. Potential factors that direct interstitial trophoblast towards maternal spiral artery are relatively high oxygen tension in the spiral artery, maternal platelets, vascular smooth muscle cells, and Eph/ephrin system. On the other hand, very little is understood about endovascular invasion except for the involvement of endothelial apoptosis in this process. Only small numbers of molecules such as polysialylated neural cell adhesion molecules and CCR1 have been suggested as specific markers for the endovascular trophoblast. Therefore, an initial step to approach the mechanisms for endovascular invasion could be more detailed molecular characterization of the endovascular trophoblast.

International Union of Basic and Clinical Pharmacology. LXXVII. Kisspeptin receptor nomenclature, distribution, and function

Kisspeptins are members of the Arg-Phe amide family of peptides, which have been identified as endogenous ligands for a G-protein-coupled receptor encoded by a gene originally called GPR54 (also known as AXOR12 or hOT7T175). After this pairing, the gene has been renamed KISS1R. The International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification recommends that the official name for the receptor is the kisspeptin receptor to follow the convention of naming the receptor protein after the endogenous ligand. The endogenous ligand was initially called metastin, after its role as a metastasis suppressor, and is now referred to as kisspeptin-54 (KP-54), a C-terminally amidated 54-amino acid peptide cleaved from the 145-amino acid gene product. Shorter C-terminal cleavage fragments [KP-14, KP-13 and KP-10 (the smallest active fragment)] are also biologically active. Both receptor and peptide are widely expressed in human, rat, and mouse; the receptor sequence shares more than 80% homology in these species. Activation of the kisspeptin receptor by kisspeptin is via coupling to G(q/11) and the phospholipase C pathway, causing Ca(2+) mobilization. Mutations in the KISS1R gene result in hypogonadotropic hypogonadotropism, and targeted disruption of Kiss1r in mice reproduces this phenotype, which led to the discovery of the remarkable ability of the kisspeptin receptor to act as a molecular switch for puberty. In addition to regulating the reproductive axis, the kisspeptin receptor is also implicated in cancer, placentation, diabetes, and the cardiovascular system.

The effects of kisspeptin-54 on blood pressure in humans and plasma kisspeptin concentrations in hypertensive diseases of pregnancy

AIMS

To investigate (i) if kisspeptin administration alters heart rate (HR) or blood pressure (BP) in healthy male and female volunteers, (ii) whether circulating plasma kisspeptin concentrations in healthy pregnant women and women with hypertensive diseases of pregnancy correlate with BP and (iii) whether women with hypertensive diseases of pregnancy have altered plasma kisspeptin concentrations.

METHODS

We have previously reported the effects of administration of kisspeptin-54 on gonadotrophin secretion in healthy male and female volunteers. In these studies, cardiovascular parameters were not a primary endpoint. However, data were also collected on BP and HR for 4h post administration of kisspeptin-54. Blood samples were taken from 105 women in the third trimester of pregnancy (27 women with hypertensive diseases of pregnancy and 78 controls). Samples were assayed for plasma kisspeptin immunoreactivity (IR).

RESULTS

Administration of kisspeptin was not associated with significant changes in HR or BP in healthy men or women. There was no significant correlation between plasma kisspeptin concentration and BP in healthy pregnant women or in those with hypertensive diseases of pregnancy. No significant differences in plasma kisspeptin-IR concentrations were observed between women with hypertensive diseases of pregnancy and normotensive pregnant controls, plasma kisspeptin concentrations ±SE: controls 2878 ± 157pmol l(-1) ; pregnancy-induced hypertension 2696 ± 299pmoll(-1) (95% CI vs. controls -514, 878pmoll(-1) ); pre-eclampsia 3519 ± 357 (95% CI vs. controls -1644, 362pmoll(-1) ).

CONCLUSIONS

Elevation of plasma kisspeptin-IR is not associated with an alteration in BP in humans.

The vasoactive potential of kisspeptin-10 in the peripheral vasculature

Splice products of the Kiss1 protein (kisspeptins) have been shown to be involved in a diverse range of functions, including puberty, metastasis and vasoconstriction in large human arteries. Circulating Kisspeptin-10 (Kp-10) plasma levels are low in normal individuals but are elevated during various disease states as well as pregnancy. Here, we investigated the potential of Kp-10, the shortest biologically active kisspeptin, to influence microvascular effects, concentrating on the cutaneous vasculature. Kp-10 caused a dose-dependent increase in oedema formation (0.3-10 nmol/injection site), assessed by Evans Blue albumin dye extravasation, in the dorsal skin of CD1 mice. Oedema formation was shown to be inhibited by the histamine H(1) receptor antagonist mepyramine. The response was characterised by a ring of pallor at the injection site in keeping with vasoconstrictor activity. Therefore, changes in dorsal skin blood flow were assessed by clearance of intradermally injected (99m)technetium. Kp-10 was found to significantly reduce clearance, in keeping with decreased blood flow and providing further evidence for vasoconstrictor activity. The decreased clearance was partially inhibited by co-treatment with the cyclo-oxygenase inhibitor indomethacin. Finally evidence for the kisspeptin receptor gene (Kiss1R), but not the kisspeptin peptide gene (Kiss1), mRNA expression was observed in heart, aorta and kidney samples from normal and angiotensin II induced hypertensive mice, with similar mRNA levels observed in each. We have evidence for two peripheral vasoactive roles for kisspeptin-10. Firstly, plasma extravasation indicative of ability to induce oedema formation and secondly decreased peripheral blood flow, indicating microvascular constriction. Thus Kp-10 has vasoactive properties in the peripheral microvasculature.

Lack of KISS1R expression is associated with rapid progression of conventional renal cell carcinomas

The mortality of patients with conventional renal cell carcinomas (RCC) correlates directly with the development of metastasis, which cannot be reliably predicted simply by TNM classification. The aim of this study was to identify genes associated with the tumour progression. We have analysed the global gene expression in conventional RCCs, including those with and without progression by Affymetrix GeneChip and selected the genes by gene set enrichment analysis. The expression and function of KISS1R was validated by RT-PCR, western blotting and immunohistochemistry and by in vitro experiments. An immunohistochemical and clinical follow-up study showed that lack of KISS1R expression is associated with rapid progression of tumours. In vitro studies showed that activation of KISS1/KISS1R signalling by kisspeptin treatment decreases the motility and invasive capacity of tumour cells. The kisspeptin treatment also induces the expression of KISS1R in tumour cells in vitro and activates signalling in cases without constitutional expression of the receptor. Expression of the KISS1R protein can be used for estimating the prognosis of conventional RCCs. Confirming the activation of KISS1R signalling in vivo may open a way for kisspeptin treatment of patients with conventional RCCs.

Calcium signaling in placenta

The placenta sustains the developing fetus throughout gestation and its major functions include nutrition, gas and waste exchange via a variety of passive or active mechanisms. Up to 30 g of calcium (Ca(2+)) actively crosses the trophoblast layer during human pregnancy. The Ca(2+) ion not only plays an important role for skeletal development but is also an essential second messenger. This review is intended to highlight the implications of Ca(2+) signaling during reproduction and specifically placentation. Initially, a Ca(2+) wave induces fertilization of the oocyte. The intracellular Ca(2+) concentration is key for the blastocyst implantation, proper placental development and function. Current knowledge of many proteins involved in placental Ca(2+) regulation and their function in pathologic conditions is largely limited. Recent studies, however, point to alterations in Ca(2+) homeostasis in placental pathologies such as pre-eclampsia (PE) and intrauterine growth restriction (IUGR). A broader understanding of the role of Ca(2+) signaling during human reproduction may offer insight into impaired pregnancy outcomes.

The VEGF-regulated transcription factor HLX controls the expression of guidance cues and negatively regulates sprouting of endothelial cells

The HLX gene encoding a diverged homeobox transcription factor has been found to be up-regulated by vascular endothelial growth factor-A (VEGF-A) in endothelial cells. We have now investigated the gene repertoire induced by HLX and its potential biologic function. HLX strongly increased the transcripts for several repulsive cell-guidance proteins including UNC5B, plexin-A1, and semaphorin-3G. In addition, genes for transcriptional repressors such as HES-1 were up-regulated. In line with these findings, adenoviral overexpression of HLX inhibited endothelial cell migration, sprouting, and vessel formation in vitro and in vivo, whereas proliferation was unaffected. This inhibition of sprouting was caused to a significant part by HLX-mediated up-regulation of UNC5B as shown by short hairpin RNA (shRNA)-mediated down-modulation of the respective mRNA. VEGF-A stimulation of endothelial cells induced elevated levels of HLX over longer time periods resulting in especially high up-regulation of UNC5B mRNA as well as an increase in cells displaying UNC5B at their surface. However, induction of HLX was strongly reduced and UNC5B up-regulation completely abrogated when cells were exposed to hypoxic conditions. These data suggest that HLX may function to balance attractive with repulsive vessel guidance by up-regulating UNC5B and to down-modulate sprouting under normoxic conditions.

Gonadotropin-releasing hormone (GnRH) neuron migration: initiation, maintenance and cessation as critical steps to ensure normal reproductive function

GnRH neurons follow a carefully orchestrated journey from their birth in the olfactory placode area. Initially, they migrate along with the vomeronasal nerve into the brain at the cribriform plate, then progress caudally to sites within the hypothalamus where they halt and send projections to the median eminence to activate pituitary gonadotropes. Many factors controlling this precise journey have been elucidated by the silencing or over-expression of candidate genes in mouse models. Importantly, a number of these factors may not only play a role in normal physiology of the hypothalamic-pituitary-gonadal axis but also be mis-expressed to cause human disorders of GnRH deficiency, presenting as a failure to undergo normal pubertal development. This review outlines the current cadre of candidates thought to modulate GnRH neuronal migration. The further elucidation and characterization of these factors that impact GnRH neuron development may shed new light on human reproductive disorders and provide potential targets to develop new pro-fertility or contraceptive agents.

Kisspeptin-10 inhibits angiogenesis in human placental vessels ex vivo and endothelial cells in vitro

Recent studies suggest that kisspeptin (a neuropeptide central to the regulation of gonadotrophin secretion) has diverse roles in human physiology, including a putative role in implantation and placental function. Kisspeptin and its receptor are present in human blood vessels, where they mediate vasoconstriction, and kisspeptin is known to inhibit tumor metastasis and trophoblast invasion, both processes involving angiogenesis. We hypothesized that kisspeptin contributes to the regulation of angiogenesis in the reproductive system. The presence of the kisspeptin receptor was confirmed in human placental blood vessels and human umbilical vein endothelial cells (HUVEC) using immunochemistry. The ability of kisspeptin-10 (KP-10) (a shorter biologically active processed peptide) to inhibit angiogenesis was tested in explanted human placental arteries and HUVEC using complementary ex vivo and in vitro assays. KP-10 inhibited new vessel sprouting from placental arteries embedded in Matrigel and tube-like structure formation by HUVEC, in a concentration-dependent manner. KP-10 had no effect on HUVEC viability or apoptosis but induced concentration-dependent inhibition of proliferation and migration. In conclusion, KP-10 has antiangiogenic effects and, given its high expression in the placenta, may contribute to the regulation of angiogenesis in this tissue.

Molecular characterization, tissue distribution, and mRNA expression profiles of two Kiss genes in the adult male and female chub mackerel (Scomber japonicus) during different gonadal stages

Kisspeptins, encoded by the Kiss1 gene, have emerged as key modulators of reproduction in mammals. In contrast to the placental mammals, some teleosts express two Kiss genes, Kiss1 and Kiss2. In the present study, full-length cDNAs of Kiss1 and Kiss2 in the chub mackerel were cloned and sequenced. Chub mackerel Kiss1 and Kiss2 cDNAs encode 105 and 123 amino acids, respectively. A comparison of the deduced amino acid sequences of chub mackerel Kiss1 and Kiss2 with those of other vertebrate species showed a high degree of conservation only in the kisspeptin-10 region (Kp-10). The Kp-10 of chub mackerel Kiss1 (YNFNSFGLRY) and Kiss2 (FNFNPFGLRF) showed variations at three amino acids. Tissue distribution analysis using quantitative real-time PCR (qRT-PCR) revealed that the Kiss1 and Kiss2 transcripts were expressed in different tissues of adult chub mackerel. In addition, their levels in the adipose tissue exhibited sexually dimorphic expression. Further, to have a basic understanding on the involvement of Kiss1 and Kiss2 in the seasonal gonadal development, their relative mRNA expression profiles in the brain, pituitary, and gonads at different gonadal stages were analyzed using qRT-PCR. Kiss1 and Kiss2 levels in the brain showed a differential expression profile between male and female fish. In males, Kiss1 and Kiss2 levels gradually decreased from the immature stage to spermiation and reached a minimal level during the post-spawning period. In contrast, Kiss1 levels in the brain of females did not vary significantly among the different gonadal stages. However, Kiss2 levels fluctuated as that of males, gradually declining from the immature stage to the post-spawning period. The pituitary Kiss1 levels did not show significant fluctuations. However, Kiss1 levels in the gonads were highly elevated during spermiation and late vitellogenesis compared to the immature and post-spawning period. These results suggest the possible involvement of two Kiss genes in the brain and Kiss1 in the gonads of chub mackerel during seasonal gonadal development.

Expression of kisspeptins and kisspeptin receptor in the kidney of chronic renal failure rats

Kisspeptins are biologically active cleavage peptides of the KiSS-1 gene products with important roles in the suppression of tumor metastasis and in the reproduction. The aim of the present study is to clarify changes of the expression of kisspeptins and kisspeptin receptor in the kidney with and without chronic renal impairment. 5/6 nephrectomized rats were used as the rat model of chronic renal failure. Competitive quantitative RT-PCR showed that kisspeptin mRNA levels were decreased in the kidney of 5/6 nephrectomized rats at 56 days compared with sham-operated rats. In contrast, immunoreactive kisspeptin concentrations were increased in the kidney of 5/6 nephrectomized rats at 56 days. On the other hand, kisspeptin receptor mRNA levels were increased in the kidney of 5/6 nephrectomized rats at 14 and 56 days compared with sham-operated rats. Immunocytochemistry showed that kisspeptins and kisspeptin receptor were expressed in renal tubular cells, collecting duct cells, vascular smooth muscle cells in both rats. The intensity of kisspeptin receptor immunostaining was lower in 5/6 nephrectomized rats than in sham-operated rats. Western blot analysis confirmed that kisspeptin receptor protein levels were significantly decreased in the remnant kidney of 5/6 nephrectomized rats (about 23% of sham-operated rats), which is a good contrast to the kisspeptin receptor mRNA expression. The present study has shown that expression of kisspeptins and kisspeptin receptor are altered in the kidney tissues of chronic renal impairment, raising the possibility of their pathophysiological roles in chronic renal failure.

Kisspeptin-10 inhibits bone-directed migration of GPR54-positive breast cancer cells: Evidence for a dose-window effect

OBJECTIVES

The KiSS-1 gene product is absent or expressed at low level in metastatic breast cancer compared with their nonmetastatic counterparts. A deca-peptide derived from the KiSS-1 gene product, designated kisspeptin-10 (Kp-10), activates a receptor coupled to Gαq subunits (GPR54 or KiSS-1R). In this study we have analyzed whether Kp-10 treatment affects bone-directed migration of GPR54-positive breast cancer cells.

METHODS

GPR54 expression was analyzed using immune cytochemistry. Bone-directed breast cancer cell invasion was measured by assessment of the breast cancer cell migration rate through an artificial basement membrane. Chemokine receptor CXCR4 and stromal cell-derived factor-1 (SDF-1) mRNA expression was quantified using semi-quantitative RT-PCR. CXCR4 protein expression and SDF-1 protein secretion were measured using the western blot technique.

RESULTS

Breast cancer cell invasion was increased when cocultured with MG63 osteoblast-like cells. Treatment with KP-10 reduced the ability to invade a reconstituted basement membrane and to migrate in response to the cellular stimulus. This effect was significant in a dose-window of 10⁻⁹ M to 10⁻¹¹ M. Searching for the molecular mechanisms we found that KP-10 treatment significantly reduces expression of the chemokine receptor CXCR4 by the breast cancer cells. In addition, expression and secretion of its ligand SDF-1 by the MG63 cells were significantly reduced. Furthermore, SDF-1-induced CXCR4 signaling was down-regulated.

CONCLUSIONS

These data represent the first report that KP-10 inhibits bone-directed migration of GPR54-positive breast cancer cells. In addition, we found evidence for a KP-10 dose-window effect. Furthermore, the SDF-1/CXCR4 system seems to be involved in the anti-migratory action of KP-10.

The role of kisspeptin signalling in the regulation of the GnRH-gonadotrophin ovarian axis in mice

Kisspeptins are a series of overlapping peptides encoded by the Kiss1 gene that are required for central activation of the hypothalamic-pituitary-ovarian axis at puberty. Mutations that interfere with kisspeptin signalling prevent normal pubertal development in humans and mice. Mutations in the kisspeptin receptor GPR54, cause infertility and hypogonadotrophic hypogonadism in humans. The failure of the Gpr54 and Kiss1 mutant mice to ovulate has led to the suggestion that kisspeptin signalling may be required for the preovulatory luteinizing hormone (LH) surge. Although kisspeptin signalling has been shown to have an important central role in regulating the physiology of the ovary, the expression profile of Kiss1 and Gpr54 suggests that they may also have direct functions in the ovary and the placenta.

Critical growth factors and signalling pathways controlling human trophoblast invasion

Invasion of placental trophoblasts into uterine tissue and vessels is an essential process of human pregnancy and fetal development. Due to their remarkable plasticity invasive trophoblasts fulfil numerous functions, i.e. anchorage of the placenta, secretion of hormones, modulation of decidual angiogenesis/lymphangiogenesis and remodelling of maternal spiral arteries. The latter is required to increase blood flow to the placenta, thereby ensuring appropriate transfer of nutrients and oxygen to the developing fetus. Since failures in vascular changes of the placental bed are associated with pregnancy diseases such as preeclampsia or intrauterine growth restriction, basic research in this particular field focuses on molecular mechanisms controlling trophoblast invasion under physiological and pathological conditions. Throughout the years, an increasing number of growth factors, cytokines and angiogenic molecules controlling trophoblast motility have been identified. These factors are secreted from numerous cells such as trophoblast, maternal epithelial and stromal cells, as well as uterine NK cells and macrophages, suggesting that a complex network of cell types, mediators and signalling pathways regulates trophoblast invasiveness. Whereas essential features of the invasive trophoblast such as expression of critical proteases and adhesion molecules have been well characterised, the interplay between different cell types and growth factors and the cross-talk between distinct signalling cascades remain largely elusive. Similarly, key-regulatory transcription factors committing and differentiating invasive trophoblasts are mostly unknown. This review will summarise our current understanding of growth factors and signal transduction pathways regulating human trophoblast invasion/migration, as well as give insights into novel mechanisms involved in the particular differentiation process.

Microarray analysis identifies distinct gene expression profiles associated with histological subtype in human osteosarcoma

Osteosarcoma is the most common primary malignant bone tumour. Currently osteosarcoma classification is based on histological appearance. It was the aim of this study to use a more systematic approach to osteosarcoma classification based on gene expression analysis and to identify subtype specific differentially expressed genes. We analysed the global gene expression profiles of ten osteosarcoma samples using Affymetrix U133A arrays (five osteoblastic and five non-osteoblastic osteosarcoma patients). Differential gene expression analysis yielded 75 genes up-regulated and 97 genes down-regulated in osteoblastic versus non-osteoblastic osteosarcoma samples, respectively. These included genes involved in cell growth, chemotherapy resistance, angiogenesis, steroid- and neuropeptide hormone receptor activity, acute-phase response and serotonin receptor activity and members of the Wnt/ß-catenin pathway and many others. Furthermore, we validated the highly differential expression of six genes including angiopoietin 1, IGFBP3, ferredoxin 1, BMP, decorin, and fibulin 1 in osteoblastic osteosarcoma relative to non-osteoblastic osteosarcoma. Our results show the utility of gene expression analysis to study osteosarcoma subtypes, and we identified several genes that may play a role as potential therapeutic targets in the future.

A kisspeptin-10 analog with greater in vivo bioactivity than kisspeptin-10

The kisspeptins are neuropeptides that stimulate the hypothalamo-pituitary-gonadal (HPG) axis. The smallest endogenous kisspeptin, kisspeptin-10 (KP-10), binds to the receptor KISS1R with a similar affinity to the full-length peptide, kisspeptin-54 (KP-54), but is less effective in vivo, possibly because of increased enzymatic breakdown or clearance. The kisspeptin system may have therapeutic potential in the treatment of reproductive disorders and endocrine cancers. We have rationally modified the structure of KP-10 and tested the binding affinity of these analogs for the KISS1R. Those analogs that bound with relatively high affinity to KISS1R were tested for ability to stimulate ERK1/2 phosphorylation in vitro and for their ability to stimulate the HPG axis in vivo. One analog, [dY](1)KP-10, bound to KISS1R with lower affinity to KP-10 and exhibited similar bioactivity in vitro. However, in vivo peripheral administration of [dY](1)KP-10 increased plasma LH and testosterone more potently than KP-10 itself at 20 min postinjection in mice. In addition, 60 min postinjection, 0.15 nmol [dY](1)KP-10 significantly increased total testosterone levels in mice whereas the same dose of KP-10 had no significant effect. Should manipulation of the kisspeptin/KISS1R signaling system prove therapeutically useful, long-lasting analogs such as [dY](1)KP-10 may have greater therapeutic potential than endogenous forms of kisspeptin.

Goldfish kisspeptin: molecular cloning, tissue distribution of transcript expression, and stimulatory effects on prolactin, growth hormone and luteinizing hormone secretion and gene expression via direct actions at the pituitary level

Kisspeptin, the product of Kiss1 gene, is a novel regulator of the gonadotropic axis. In mammals, its stimulatory effect on gonadotropin secretion is well documented and mediated mainly by hypothalamic release of gonadotropin-releasing hormone. Although the pituitary actions of kisspeptin have been reported, the effects of kisspeptin on gonadotropin release via direct action on pituitary cells are still controversial. Using goldfish as a model, here we examined the direct actions of kisspeptin on pituitary functions in modern-day bony fish. As a first step, the structural identity of goldfish Kiss1 was established by 5'/3'RACE and Kiss1 transcript was shown to be widely expressed in various tissues in goldfish. At the pituitary level, Kiss1 receptor (Kiss1r) expression was detected in immuno-identified gonadotrophs, lactotrophs, and somatotrophs. Kiss1 transcript was also located in goldfish somatotrophs but not in lactotrophs or gonadotrophs. In parallel studies, goldfish kisspeptin-10 was synthesized and used to test the pituitary actions of kisspeptin in vitro. In goldfish pituitary cell cultures, 30-min incubation with kisspeptin-10 increased basal release of luteinizing hormone (LH), prolactin (PRL), and growth hormone (GH). Transcript expression of LH, PRL, and GH were also elevated by prolonging kisspeptin-10 treatment to 24h. These results taken together suggest that kisspeptin via Kiss1r activation can act directly at the pituitary level to trigger LH, PRL, and GH secretion and gene expression in goldfish. Our finding of Kiss1 expression in somatotrophs also rises the possibility that kisspeptin may be produced locally in the fish pituitary and serve as an autocrine/paracrine regulator.

KiSS1 suppresses TNFalpha-induced breast cancer cell invasion via an inhibition of RhoA-mediated NF-kappaB activation

Tumor necrosis factor-alpha (TNFalpha) induces cancer development and metastasis, which is prominently achieved by nuclear factor-kappa B (NF-kappaB) activation. TNFalpha-induced NF-kappaB activation enhances cellular mechanisms including proliferation, migration, and invasion. KiSS1, a key regulator of puberty, was initially discovered as a tumor metastasis suppressor. The expression of KiSS1 was lost or down-regulated in different metastatic tumors. However, it is unclear whether KiSS1 regulates TNFalpha-induced NF-kappaB activation and further tumor cell migration. In this study, we demonstrate that KiSS1 suppresses the migration of breast cancer cells by inhibiting TNFalpha-induced NF-kappaB pathway and RhoA activation. Both KiSS1 overexpression and KP10 (kisspeptin-10) stimulation inhibited TNFalpha-induced NF-kappaB activity, suppressed TNFalpha-induced cell migration and cell attachment to fibronectin in breast cancer cells while KP10 has little effect on cancer cell proliferation. Furthermore, KP10 inhibited TNFalpha-induced cell migration and RhoA GTPase activation. Therefore, our data demonstrate that KiSS1 inhibits TNFalpha-induced NF-kappaB activation via downregulation of RhoA activation and suppression of breast cancer cell migration and invasion.

The cytokine gene CXCL14 restricts human trophoblast cell invasion by suppressing gelatinase activity

Well-controlled trophoblast invasion into uterine decidua is a critical process for the normal development of placenta, which is tightly regulated by various factors produced within the trophoblast-endometrial microenvironment. CXCL14 is involved in tumor growth and metastasis, and its expression in placenta is temporally regulated during pregnancy. However, the role of CXCL14 in trophoblast function during human pregnancy is not clear. In this study, by using RT-PCR through human pregnancy, we found that CXCL14 was selectively expressed at early but not late pregnancy. Immunostaining revealed that CXCL14 proteins were strongly expressed in villous cytotrophoblasts and moderately in decidualized stromal cells but very weakly in syncytiotrophoblasts and extravillous trophoblasts. The effect of CXCL14 on trophoblast invasion were examined by using human villous explants cultured on Matrigel and further proved by invasion and migration assay of primary trophoblast cells and trophoblast cell line HTR-8/SVneo. Our data showed that CXCL14 significantly inhibited outgrowth of villous explant in vitro; this effect is due to suppression of trophoblast invasion and migration through regulating matrix metalloproteinases activities, whereas the trophoblast proliferation was not affected. Moreover, because a receptor for CXCL14 has not been identified, we performed further cell-specific CXCL14 binding activities with regard to different cell types within the maternal-fetal interface. Our data revealed that CXCL14 could specifically bind to trophoblast cells but not decidual cells from the maternal-fetal interface. These results suggest that CXCL14 plays an important role in regulating trophoblast invasion through an autocrine/paracrine manner during early pregnancy.

The VEGF-induced transcriptional response comprises gene clusters at the crossroad of angiogenesis and inflammation

VEGF-A is the major trigger of vasculogenesis and physiologic angiogenesis. We have investigated to which extent the gene repertoire induced by VEGF-A in endothelial cells is distinct from that of other growth factors and inflammatory cytokines. Genes upregulated in human umbilical vein endothelial cells treated with VEGF, EGF or IL-1 were compared by microarray analysis and clusters characteristic for individual or combinations of inducers were defined. VEGF-A upregulated in comparison to EGF a five-fold larger gene repertoire, which surprisingly overlapped to 60% with the inflammatory repertoire of IL-1. As shown by real-time RT-PCR for selected genes, VEGF-induction was mostly mediated by VEGF receptor-2 and the capacity of VEGF-A to induce genes in common with IL-1 largely depended on activation of the calcineurin/NFAT pathway, since cyclosporin A inhibited this induction. Another angiogenic growth factor, bFGF, did not share a comparable induction of inflammatory genes, but partially induced a small group of genes in common with VEGF-A, which were not regulated by EGF. Thus, the data display that VEGF-A induces a distinct gene repertoire, which, contrasting with other growth factors such as EGF or bFGF, includes an inherent inflammatory component possibly contributing to the cross-regulation of angiogenesis and inflammation as further indicated by the VEGF-mediated induction of leukocyte adhesion. Furthermore, a small group of genes selectively induced by VEGF-A with potential importance for angiogenesis is defined.

Histidine 379 of human laeverin/aminopeptidase Q, a nonconserved residue within the exopeptidase motif, defines its distinctive enzymatic properties

Human laeverin/aminopeptidase Q (LVRN/APQ) is a novel member of the M1 family of zinc aminopeptidases and is specifically expressed on the cell surface of human extravillous trophoblasts. Multiple sequence alignment of human M1 aminopeptidase revealed that the first Gly residue within the conserved exopeptidase motif of the M1 family, GXMEN motif, is uniquely substituted for His in human LVRN/APQ. In this study, we evaluated the roles of nonconserved His(379), comprising the exopeptidase motif in the enzymatic properties of human LVRN/APQ. We revealed that the substitution of His(379) with Gly caused significant changes in substrate specificity both toward fluorogenic substrates and natural peptide hormones. In addition, the susceptibilities of bestatin, a sensitive inhibitor for human LVRN/APQ, and natural inhibitory peptides were decreased in the H379G mutant. A molecular model suggested a conformational difference between wild-type and H379G human LVRN/APQs. These results indicate that His(379) of the enzyme plays essential roles in its distinctive enzymatic properties and contributes to maintaining the appropriate structure of the catalytic cavity of the enzyme. Our data may bring new insight into the biological significance of the unique exopeptidase motif of LVRN/APQ obtained during the evolution of primates.

Kisspeptin-10, a KISS1-derived decapeptide, inhibits tumor angiogenesis by suppressing Sp1-mediated VEGF expression and FAK/Rho GTPase activation

Kisspeptin-10 (Kp-10), a decapeptide derived from the primary translation product of KISS1 gene, has been reported previously to be a key hormone for puberty and an inhibitor for tumor metastasis via the activation of G protein-coupled receptor 54. However, whether Kp-10 inhibits angiogenesis, which is critical for tumor growth and metastasis and other human diseases, is still unknown. Here we show that Kp-10 significantly inhibits human umbilical vein endothelial cell (HUVEC) migration, invasion, and tube formation, key processes in angiogenesis. Using chicken chorioallantoic membrane assay and vascular endothelial growth factor (VEGF)-induced mouse corneal micropocket assay, we show that Kp-10 inhibits angiogenesis in vivo. Furthermore, Kp-10 inhibits tumor growth in severe combined immunodeficient mice xenografted with human prostate cancer cells (PC-3) through inhibiting tumor angiogenesis, whereas Kp-10 has little effect on the proliferation of HUVECs and human prostate cancer cells. In deciphering the underlying molecular mechanisms, we show that Kp-10 suppresses VEGF expression by inhibiting the binding of specificity protein 1 to VEGF promoter and by blocking the activation of c-Src/focal adhesion kinase and Rac/Cdc42 signaling pathways in HUVECs, leading to the inhibition of tumor angiogenesis.

A strategy for identifying circulating placental RNA markers for fetal growth assessment

OBJECTIVE

To evaluate whether circulating placental mRNAs in maternal plasma could serve as markers for the assessment of fetal growth or intrauterine growth restriction (IUGR).

METHODS

From a panel of placental transcripts detectable in maternal plasma identified by microarray previously, we chose growth-related transcripts, namely CSH1, GH2, KISS1, and ADAM12, as potential growth markers. Relationships between the maternal plasma mRNA concentrations with several fetal growth indicators were studied. Maternal plasma mRNA concentrations from IUGR pregnancies with or without pre-eclampsia (PET) were compared with gestational age matched controls cross-sectionally and longitudinally. The four transcripts were quantified by one-step real-time RT-PCR.

RESULTS

Maternal plasma GH2 mRNA significantly correlated with birth weight and fetal biometric measurements. Maternal plasma ADAM12 mRNA concentration was significantly higher in IUGR with PET than normal pregnancies in the cross-sectional comparison. No significant difference was observed for all markers between IUGR without PET and controls in both the cross-sectional and longitudinal comparisons.

CONCLUSION

This study presents a potential strategy in identifying surrogate markers for the study of fetal growth. Circulating GH2 mRNA in maternal plasma appeared to be associated with fetal growth. The utility of this strategy and the currently assessed markers could be explored in further studies.

Differential ovarian expression of KiSS-1 and GPR-54 during the estrous cycle and photoperiod induced recrudescence in Siberian hamsters (Phodopus sungorus)

Kisspeptins, coded by the KiSS-1 gene, regulate aspects of the reproductive axis by stimulating GnRH release via the G protein coupled receptor, GPR54. Recent reports show that KiSS/GPR54 may be key mediators in photoperiod-controlled reproduction in seasonal breeders, and that KiSS-1/GPR54 are expressed in the hypothalamus, ovaries, placenta, and pancreas. This study examined the expression of KiSS-1/GPR54 mRNA and protein in ovaries of Siberian hamsters (Phodopus sungorus). Ovaries from cycling hamsters were collected during proestrus (P), estrus (E), diestrus I (DI), and diestrus II (DII). To examine KiSS-1/GPR54 during stimulated recrudescence, additional hamsters were maintained either in long day (LD 16L:8D, control) or short day (SD 8L:16D) for 14 weeks and then transferred to LD for 0-8 weeks. Staining of KiSS-1/GPR54 protein was detected by immunohistochemistry in steroidogenic cells of pre-antral and antral follicles, and corpora lutea. Immunostaining peaked in P and E, but decreased in the diestrus stages (P < 0.05). In recrudescing ovaries, KiSS-1/GPR54 immunostaining was low after 14 weeks of SD exposure (post-transfer [PT] week 0), and increased during the early weeks of recrudescence. Expression of KiSS-1/GPR54 mRNA was low with short day exposure, but increased during recrudescence and was higher at PT week 8 as compared to PT weeks 0 and 2 (P < 0.05). The elevated KiSS-1/GPR54 expression during P and E suggests a potential role in ovulation in Siberian hamsters. Transient increases in KiSS-1/GPR54 expression following LD stimulation are also suggestive of possible involvement in ovulation and/or restoration of ovarian function.

A role for kisspeptins in pregnancy: facts and speculations

Kisspeptin is a neuropeptide that was originally discovered in 1996 from a metastasis tumour suppressor gene,KISS1and was appropriately named metastin. More recently, the discovery of inactivating mutations in the receptor for kisspeptin, a G protein-coupled receptor, GPR54 (KISS1R), have been shown to result in a failure to progress through puberty in man. These findings have led to the kisspeptin/KISS1R system being described as an essential gatekeeper of reproductive function. Recent studies have suggested additional roles of kisspeptin, other than in the central control of the gonadotropic axis including placentation and pregnancy, energy homeostasis and cardiovascular function. Therefore, kisspeptin–KISS1R signalling potentially plays diverse roles in human physiology. Here, we review the literature regarding the role and physiological significance of kisspeptin in pregnancy and highlight some of the key questions that require addressing.

Discovery of potent kisspeptin antagonists delineate physiological mechanisms of gonadotropin regulation

Neurons that produce gonadotropin-releasing hormone (GnRH) are the final common pathway by which the brain regulates reproduction. GnRH neurons are regulated by an afferent network of kisspeptin-producing neurons. Kisspeptin binds to its cognate receptor on GnRH neurons and stimulates their activity, which in turn provides an obligatory signal for GnRH secretion, thus gating down-stream events supporting reproduction. We have developed kisspeptin antagonists to facilitate the direct determination of the role of kisspeptin neurons in the neuroendocrine regulation of reproduction. In vitro and in vivo studies of analogues of kisspeptin-10 with amino substitutions have identified several potent and specific antagonists. A selected antagonist was shown to inhibit the firing of GnRH neurons in the brain of the mouse and to reduce pulsatile GnRH secretion in female pubertal monkeys; the later supporting a key role of kisspeptin in puberty onset. This analog also inhibited the kisspeptin-induced release of luteinizing hormone (LH) in rats and mice and blocked the postcastration rise in LH in sheep, rats, and mice, suggesting that kisspeptin neurons mediate the negative feedback effect of sex steroids on gonadotropin secretion in mammals. The development of kisspeptin antagonists provides a valuable tool for investigating the physiological and pathophysiological roles of kisspeptin in the regulation of reproduction and could offer a unique therapeutic agent for treating hormone-dependent disorders of reproduction, including precocious puberty, endometriosis, and metastatic prostate cancer.

Activation of Rho and Rho-associated kinase by GPR54 and KiSS1 metastasis suppressor gene product induces changes of cell morphology and contributes to apoptosis

The mechanism of action of the metastasis suppressor KiSS1 and its receptor GPR54 is still incompletely characterized. Although the loss of KiSS1 expression by tumor cells has been associated with a metastatic phenotype, the nature of the cellular target of the secreted kisspeptins is unknown. Although an autocrine model of action has been generally assumed, metastasis suppression by KiSS1 has also been shown in cells that do not express GPR54, suggesting a paracrine mechanism in which kisspeptins affect cells in the metastatic niche. Activation of GPR54 was shown to inhibit cell motility and invasion of tumor cells, induce the formation of stress fibers, and reduce the expression of matrix metalloproteinase 9. We showed previously that the activation of GPR54 by kisspeptin-10 suppressed CXCR4-mediated chemotaxis in response to stromal cell-derived factor 1/CXCL12 and abolished the phosphorylation of Akt by CXCR4. We also demonstrated that activation of GPR54 inhibited Akt phosphorylation after the activation of epidermal growth factor receptor and the insulin receptor and triggered apoptosis in epithelial and lymphoid cell lines through a mechanism involving extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase. We show here that the activation of GPR54 induced immediate and profound changes of cell morphology, including cytoplasmic condensation and formation of unpolarized plasma membrane protrusions. These events were dependent on Rho and Rho-Associated Kinase (ROCK) activation. The activation of ROCK also contributed to GPR54-mediated apoptosis in 293 cells, and its effect was additive to and independent of ERK activation. These results suggest that RhoA and ROCK are additional key components of the antimetastatic effect of kisspeptins.

KiSS-1 in the mammalian ovary: distribution of kisspeptin in human and marmoset and alterations in KiSS-1 mRNA levels in a rat model of ovulatory dysfunction

Kisspeptins, the products of the KiSS-1 gene acting via G protein-coupled receptor 54 (GPR54), have recently emerged as pivotal signals in the hypothalamic network triggering the preovulatory surge of gonadotropins and, hence, ovulation. Additional actions of kisspeptins at other levels of the hypothalamic-pituitary-ovarian axis have been suggested but remain to date scarcely studied. We report herein the pattern of expression of KiSS-1 and GPR54 in the human and nonhuman primate ovary and evaluate changes in ovarian KiSS-1 expression in a rat model of ovulatory dysfunction. KiSS-1 and GPR54 mRNAs were detected in human ovarian tissue and cultured granulosa-lutein cells. In good agreement, kisspeptin immunoreactivity was observed in cyclic human and marmoset ovaries, with prominent signals in the theca layer of growing follicles, corpora lutea, interstitial gland, and ovarian surface epithelium. GPR54 immunoreactivity was also found in human theca and luteal cells. Administration of indomethacin to cyclic female rats disturbed ovulation and resulted in a dramatic drop in ovarian KiSS-1, but not GPR54, cyclooxygenase-2 (COX-2), or progesterone receptor, mRNA levels at the time of ovulation; an effect mimicked by the selective COX-2 inhibitor NS398 and rescued by coadministration of PGE(2). Likewise, the stimulatory effect of human choriogonadotropin on ovarian KiSS-1 expression was partially blunted by indomethacin. In contrast, KiSS-1 mRNA levels remained unaltered in another model of ovulatory failure, i.e., the RU486-treated rat. In summary, we document for the first time the expression of KiSS-1/kisspeptin and GPR54 in the human and nonhuman primate ovary. In addition, we provide evidence for the ability of inhibitors of COX-2, known to disturb follicular rupture and ovulation, to selectively alter the expression of KiSS-1 gene in rat ovary. Altogether, our results are suggestive of a conserved role of local KiSS-1 in the direct control of ovarian functions in mammals.

Changes of placental Kiss-1 mRNA expression and maternal/cord kisspeptin levels at preterm delivery

Kisspeptin, a placental polypeptide secreted throughout pregnancy, is suggested to play a role at parturition. Here we evaluated whether its placental mRNA expression and maternal/fetal plasma levels change at term and preterm delivery, and its effect on oxytocin secretion from placental explants. Samples were collected from 40 women with singleton pregnancies who underwent elective cesarean section at term (TNL), term vaginal delivery (TD), and preterm vaginal delivery (PTD). Plasma Kisspeptin and oxytocin levels were assessed by ELISA; placental mRNA expression by Real-time quantitative RT-PCR analysis. Placental expression was significantly (P < 0.0001) higher in PTD than TNL and TD and significantly (P < 0.001) higher in TD than TNL. Maternal/fetal plasma concentrations did not differ among the groups, and maternal were significantly higher than fetal levels (P < 0.05). In placental explants increasing doses of kisspeptin did not modify oxytocin secretion. In conclusion, labor is associated with increased placental KiSS-1 expression without changes in maternal/fetal circulation.

Identification of novel trophoblast invasion-related genes: heme oxygenase-1 controls motility via peroxisome proliferator-activated receptor gamma

Invasion of cytotrophoblasts (CTBs) into uterine tissues is essential for placental development. To identify molecules regulating trophoblast invasion, mRNA signatures of purified villous (CTB, poor invasiveness) and extravillous trophoblasts (EVTs) (high invasiveness) isolated from first trimester human placentae and villous explant cultures, respectively, were compared using GeneChip analyses yielding 991 invasion/migration-related transcripts. Several genes involved in physiological and pathological cell invasion, including A disintegrin and metalloprotease-12, -19, -28, as well as Spondin-2, were up-regulated in EVTs. Pathway prediction analyses identified several functional modules associated with either the invasive or noninvasive trophoblast phenotype. One of the genes that was down-regulated in the invasive mRNA pool, heme oxygenase-1 (HO-1), was selected for functional analyses. Real-time PCR analyses, Western blotting, and immunofluorescence of first trimester placentae and differentiating villous explant cultures demonstrated down-regulation of HO-1 in invasive EVTs as compared with CTBs. Modulation of HO-1 expression in loss-of as well as gain-of function cell models (BeWo and HTR8/SVneo, respectively) demonstrated an inverse relationship of HO-1 expression with trophoblast migration in transwell and wound healing assays. Importantly, HO-1 expression led to an increase in protein levels and activity of the nuclear hormone receptor peroxisome proliferator activated receptor (PPAR) gamma. Pharmacological inhibition of PPARgamma abrogated the inhibitory effects of HO-1 on trophoblast migration. Collectively, our results demonstrate that gene expression profiling of EVTs and CTBs can be used to unravel novel regulators of cell invasion. Accordingly, we identify HO-1 as a negative regulator of trophoblast motility acting via up-regulation of PPARgamma.

Alterations in hypothalamic KiSS-1 system in experimental diabetes: early changes and functional consequences

Using long-term streptozotocin (STZ)-treated male rats, we recently proposed that defective function of hypothalamic KiSS-1 system is mechanistically relevant for central hypogonadotropism of uncontrolled diabetes. However, the temporal pattern of such defects and its potential contribution to disturbed gonadotropin secretion in the diabetic female remain so far unexplored. To cover these issues, expression analyses and hormonal tests were conducted in diabetic male (1 wk after STZ; short term) and female (4 wk after STZ; long term) rats. Short-term diabetic males had lower basal testosterone levels and decreased gonadotropin responses to orchidectomy (ORX), which associated with significantly attenuated post-ORX rises of hypothalamic KiSS-1 mRNA. Yet kisspeptin administration to diabetic males was able to acutely elicit supramaximal LH and testosterone responses and normalize post-ORX gonadotropin secretion. Long-term diabetic females showed persistent anestrus and significantly decreased basal gonadotropin levels as well as blunted LH responses to ovariectomy; changes that were linked to lowering of basal and postovariectomy expression of hypothalamic KiSS-1 mRNA. Moreover, despite prevailing gonadotropin suppression, LH responses to acute kisspeptin administration were fully preserved, and even enhanced after its repeated injection, in diabetic females. In sum, our present findings further define the temporal course and mechanistic relevance of altered hypothalamic KiSS-1 system in the hypogonadotropic state of uncontrolled diabetes. Furthermore, our data provide the basis for the potential therapeutic intervention of the KiSS-1 system as adjuvant in the management of disturbed gonadotropin secretion of type 1 diabetes in the female.

Kisspeptin-54 at high doses acutely induces testicular degeneration in adult male rats via central mechanisms

BACKGROUND AND PURPOSE

The kisspeptins are critical regulators of reproduction and a therapeutic target for reproductive disease. Intracerebroventricular (i.c.v.) or peripheral injection of kisspeptin potently stimulates the hypothalamic-pituitary gonadal (HPG) axis via gonadotrophin-releasing hormone (GnRH). However, little is known regarding the effects of kisspeptin administration on testicular function. We investigated the mechanism(s) of kisspeptin-induced testicular degeneration in the rat.

EXPERIMENTAL APPROACH

Kisspeptin-54 (50 nmol.day(-1)) was continuously administered subcutaneously (6 h to 3 days) to male Wistar rats and reproductive hormones and testicular histology analysed. We also investigated the effects of a single subcutaneous injection of 0.5, 5 or 50 nmol kisspeptin-54. In order to determine whether the testicular degeneration observed is peripherally or centrally mediated, we investigated effects of i.c.v. injections of 5 nmol kisspeptin-54 and pre-administered a GnRH-receptor antagonist (cetrorelix) to rats peripherally treated with kisspeptin-54.

KEY RESULTS

Continuous subcutaneous administration of kisspeptin-54 caused testicular degeneration after only 12 h, when gonadotrophins were still markedly raised, suggesting that the degeneration is independent of the desensitization of the HPG axis to kisspeptin-54. Furthermore, a single subcutaneous injection of kisspeptin-54 caused dose-dependent testicular degeneration. Continuous kisspeptin-54 administration is thus not required to cause testicular degeneration. Pretreatment with cetrorelix blocked kisspeptin-induced testicular degeneration, and a single i.c.v. injection of kisspeptin-54 caused testicular degeneration, suggesting it is GnRH-mediated.

CONCLUSIONS AND IMPLICATIONS

Kisspeptin-induced testicular degeneration appears to be centrally mediated, and result from acute hyper-stimulation of the HPG axis. Doses must be carefully considered if kisspeptin is to be used therapeutically.

Prognostic value of metastin expression in human pancreatic cancer

BACKGROUND

KiSS-1 was identified as a metastasis-suppressing gene in melanoma cells. The KiSS-1 gene product (metastin) was isolated from human placenta as the ligand of GPR54, a G-protein-coupled receptor. The role of metastin and GPR54 in tumor progression is not fully understood.

METHODS

We investigated the clinical significance of metastin and GPR54 expression in pancreatic cancer. We evaluated immunohistochemical expression of metastin and GPR54 in pancreatic ductal adenocarcinoma tissues obtained from 53 consecutive patients who underwent resection between July 2003 and May 2007 at Kyoto University Hospital. In 23 consecutive patients, the plasma metastin level was measured before surgery by enzyme immunoassay.

RESULTS

Strong immunohistochemical expression of metastin was detected in 13 tumors (24.5%), while strong expression of GPR54 was detected in 30 tumors (56.6%). Tumors that were negative for both metastin and GPR54 expression were significantly larger than tumors that were positive for either metastin or GPR54 (p = 0.047). Recurrence was less frequent in patients who had metastin-positive tumors compared with those who had metastin-negative tumors (38.5% versus 70.0%, p = 0.04). Strong expression of metastin and GPR54 was significantly correlated with longer survival (p = 0.02). Metastin expression by pancreatic cancer was an independent prognostic factor for longer survival (hazard ratio, 2.1; 95% confidence interval, 1.1-4.7; p = 0.03), and the patients with a high plasma metastin level (n = 6) did not die after surgical resection.

CONCLUSION

Strong expression of metastin and GPR54 by pancreatic cancer is associated with longer survival. Metastin expression is an independent prognostic factor for the survival of pancreatic cancer patients. The plasma metastin level could become a noninvasive prognostic factor for the assessment of pancreatic cancer.

From KISS1 to kisspeptins: An historical perspective and suggested nomenclature

The cancer suppressor gene, KISS1, was initially described as having an important role in inhibiting cancer metastasis. Since then, KISS1 and its receptor, KISS1R, have been shown to play a key role in controlling the onset of puberty of reproductive physiology in the human and other species. Recent studies have also linked KISS1/kisspeptin/KISS1R to other processes, such as vasoconstriction, aging, adipocyte physiology, and perhaps as a molecular conduit linking metabolism and reproduction. This article highlights the history of KISS1/kisspeptin/KISS1R biology and proposes a consensus for nomenclature of the key molecules in this signaling pathway.

Reproductive functions of kisspeptin and Gpr54 across the life cycle of mice and men

The reproductive phenotypes of nearly two dozen patients with mutations in GPR54 have been reported, as have the phenotypes of four mouse lines mutant for Gpr54 and two lines mutant for Kiss1. These phenotypes demonstrate that kisspeptin/Gpr54 function is required at all phases of the life cycle when the secretion of gonadotropin-releasing hormone (GnRH) is robust. Furthermore, there is phenotypic variability ranging from severe hypogonadism to partial sexual development. Collectively, these findings suggest that kisspeptin and Gpr54 serve as an essential conduit for relaying developmental information to the GnRH neuron.

Kisspeptins and the control of gonadotropin secretion in humans

The kisspeptin hormones are a family of peptides encoded by the KiSS-1 gene, which bind to the G-protein coupled receptor-54 (GPR54). Interactions between kisspeptin and GPR54 are thought to play a critical role in reproduction. In agreement with animal data, kisspeptin-54 administration acutely stimulates the release of gonadotrophins in both male and female healthy subjects, with no observed adverse effects. Furthermore, its potency is comparable to those of other gonadotrophin secretagogues studied. The kisspeptin-GPR54 system thus offers a novel means of therapeutically manipulating the hypothalamo-pituitary-gonadal (HPG) axis in humans. This article aims to provide a focused review of the experimental data which inform us how kisspeptin influences the HPG axis in humans.

The role of kisspeptin and GPR54 in the hippocampus

The granule cells of the dentate gyrus form the input stage of the hippocampal trisynaptic circuit and their function is strongly influenced by peptidergic systems. GPR54 is highly and discretely expressed in these cells. We have found that activation of GPR54 with kisspeptin-10 causes a rapid and large increase in the amplitude of excitatory synaptic responses in granule cells, without changing membrane properties. The effect was suppressed by the G-protein inhibitor GDP-beta-S and the calcium chelator BAPTA, and analysis of miniature EPSCs revealed an increase in mean amplitude but not event frequency, indicating that GPR54 and the mechanisms for enhancing EPSCs are postsynaptic, possibly involving changes in AMPA receptor number or conductance. The kisspeptin-induced synaptic potentiation was abolished by inhibitors of ERK1/2, tyrosine kinase, and CaMKII. RT-PCR experiments showed that KiSS-1 is expressed in the dentate gyrus. KiSS-1 mRNA was significantly increased by seizure activity in rats and when neuronal activity in organotypic hippocampal slice cultures was enhanced by kainate or picrotoxin, while mRNA for GPR54 remained essentially unchanged. These results suggest that kisspeptin may be locally synthesized and act as an autocrine factor. In separate experiments, hippocampal KiSS-1 mRNA in male rats was increased after gonadectomy. In summary, kisspeptin is a novel endogenous factor which is dynamically regulated by neuronal activity and which, in marked distinction from other neuropeptides, increases synaptic transmission in dentate granule cells through signaling cascades possibly linked to the MAP kinase system. This novel peptide system may play a role in cognition and in the pathogenesis of epilepsy.

Human diseases associated with GPR54 mutations

G protein-coupled receptor 54 (GPR54) was first described as an orphan receptor in the rat brain one decade ago. At that time, all we knew about this receptor was that it had a high homology with other G protein-coupled receptors, like galanin receptors. Later, its endogenous ligand, kisspeptin, was identified and the kisspeptin-GPR54 system became one of the most important excitatory neuroendocrine regulators of puberty initiation. Several loss-of-function mutations in GPR54 gene were described to be associated with sporadic and familial normosmic isolated hypogonadotropic hypogonadism phenotype in humans. Consistent with this fact, knockout mice for gpr54(-/-) recapitulated the human phenotype of the lack of reproductive maturation. On the other hand, a unique activating mutation (R386P) was recently described in this receptor in a girl with central precocious puberty. This missense mutation located at carboxy-terminal tail of the GPR54 leads to prolonged activation of intracellular signaling pathways in response to kisspeptin, suggesting an uncommon model of G protein-coupled receptor activation. This chapter will describe the kisspeptin-GPR54 complex physiology and its current role in human diseases.

Regulation of KiSS1 gene expression

Kisspeptins are the protein products encoded by KiSS1 gene, an important tumor metastatic suppressor and pivotal master hormone of puberty. Although KiSS1 gene is expressed in both central and peripheral tissues, the molecular mechanisms that determine the temporal and spatial expression of KiSS1 gene are not well understood. This review provides an update on the latest studies and ideas about the expression of KiSS1 gene as a puberty gatekeeper and a metastasis suppressor, with special emphasis on the molecular mechanisms for the transcriptional regulation of KiSS1 gene expression.

Identification of two isoforms of the Kisspeptin-1 receptor (kiss1r) generated by alternative splicing in a modern teleost, the Senegalese sole (Solea senegalensis)

The KISSPEPTIN-1 receptor (KISS1R) and its ligands (KISSPEPTINS) are implicated in the regulation of the onset of puberty. We report the coding region and genomic structure of the kiss1r gene of a modern teleost, the Senegalese sole (Ss). Ss kiss1r cDNA contained an opening frame of 1137 bp, which results in a predicted 378 amino acid protein. Searching genomic databases allowed the identification of kiss1r orthologues in six new species belonging to three vertebrate groups and established the evolutionary relationships of all KISS1R sequences available to date. Analysis of Ss kiss1r revealed for the first time in any vertebrate KISS1R gene the presence of features that are characteristic of a mechanism of alternative splicing. This was confirmed by the identification of two transcripts, Ss kiss1r_v1 and Ss kiss1r_v2. The latter, arising from intron III retention, contained a 27 codons insert in transmembrane region 4 with two stop codons, suggesting it may lead to a truncated protein. The mRNA of the two variants was differently expressed in several tissues. In the brain, levels of the Ss kiss1r_v1 were higher than those of Ss kiss1r_v2. In the gonads, the opposite was observed. Both isoforms exhibited changes depending on sex and maturity stage. The presence of two variants may help to explain some discrepancies observed in past studies regarding KISS1R expression during puberty. Thus, the existence of alternative splicing for the KISS1R gene may contribute to our understanding of the many physiological functions suspected to be mediated by KISSPEPTIN-KISS1R signaling.