Kisspeptin-10

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Kisspeptin-10 is a peptide hormone capable of increasing circulating follicle-stimulating hormone, luteinizing hormone and testosterone levels in humans. Clinically, these effects suggest its use as a treatment for infertility. However, its testosterone-increasing effect indicates potential misuse in sports. As such, it is included in the 2024 World Anti-Doping Agency Prohibited List. This work describes the successful validation of an initial testing procedure (screening) and a confirmation procedure for kisspeptin-10 in urine using liquid chromatography-mass spectrometry. Additionally, kisspeptin-10 was incubated in human serum to mimic endogenous metabolism to improve method sensitivity, as previous research had demonstrated a rapid elimination time of only 30 min after injection (in rats). Four metabolites, corresponding to peptide fragments y9, y8, y7 and y5, were found and added to the ITP in full scan mode. A degradation product discovered during early experimentation was found to probably be caused by oxidation of the tryptophan residue into a kynurenine residue. Further research should elucidate the kinetic parameters of the reaction to improve product stability. Using the validated confirmation procedure, a black-market vial of kisspeptin-10 was analysed. The product contained no unexpected impurities, although it appeared to have undergone more degradation than the purchased reference standard.

Kisspeptin-10 Prevents the Development of Cerebral Aneurysms by Reducing the Expression of Egr-1.

Cerebral aneurysms (CAs) are a prevalent brain condition with poorly understood pathological features. The Kisspeptin-10 (KP-10)/G protein-coupled receptor 54 (GPR54) system is a vital neuroendocrine pathway primarily implicated in the regulation of reproductive functions and energy metabolism. This research explores the role of the KP-10/GPR54 system in CAs. Serum levels of KP-10 in CA patients and animal models were assessed using commercial ELISA kits. Mice were divided into five groups: WT, GPR54-/-, CA, CA + KP-10, and CA + GPR54-/- + KP-10. The CA profiles were evaluated using Verhoeff-van Gieson staining. Human brain microvascular endothelial cells (HBMVECs) were stimulated with Ang II (10-7 mol/L) with or without KP-10 (50, 100 nM). Angiogenic tube formation was then assessed. We found that KP-10 levels were reduced in both CA patients and mouse models. In CA mice, Gpr54 expression in the Circle of Willis (COW) was also decreased. KP-10 reduced CA size in wild-type mice, but not in Gpr54 knockout mice. It also reduced matrix metalloproteinase-9 (MMP-9), macrophage infiltration, and vascular endothelial growth factor-A (VEGF-A) expression, effects that were absent in Gpr54 knockout mice. In vitro, KP-10 inhibited Ang II-induced proliferation, angiogenic tube formation, and VEGF-A expression in HBMVECs by reducing early growth response-1 (Egr-1). These effects were abolished when Gpr54 was knocked down, indicating that KP-10's action is dependent on Gpr54. This study shows that KP-10 binding to Gpr54 inhibits Egr-1 expression, thereby suppressing MMP-9 and VEGF-A, reducing macrophage infiltration and angiogenesis, and preventing cerebral aneurysm development. Thus, the KP-10/Gpr54 system is a key therapeutic target for the treatment of cerebral aneurysms.

Kisspeptin isoforms: versatile players in reproduction and beyond.

Kisspeptin and its cognate G-protein-coupled receptor (GPCR), the kisspeptin-1 receptor (KISS-1R), are central to mammalian reproduction, regulating the hypothalamic-pituitary-gonadal axis. They are upstream regulators of gonadotropin-releasing hormone (GnRH) secretion, a hallmark of the onset of puberty, subsequently tuning luteinizing hormone and follicle-stimulating hormone levels and bringing about steroid hormone production. In mammals, kisspeptin (Kp) is synthesized as a 145-mer pre-pro-polypeptide by the KISS1 gene, which further undergoes cleavage to form four kisspeptin isoforms: Kp-54, Kp-14, Kp-13 and Kp-10. They all share a common decapeptide sequence (Kp-10), followed by an RF-amide in their C-terminal end. Kp-10, the smallest isoform, is reported to activate KISS-1R to its full functional potential. The reproductive roles of Kp-54 and Kp-10 have been studied extensively by in vivo and clinical studies owing to their longer terminal half-life and commercial bargain, respectively. This comprehensive review aims to collate the multitude of functions displayed by all naturally occurring kisspeptin isoforms and other kisspeptin-like peptides in reproduction and beyond, including metabolic regulation and therapeutic potential. The structural architecture of kisspeptin isoforms reported using alanine scan substitution studies and secondary structure using circular dichroism and nuclear magnetic resonance spectroscopy studies have also been highlighted. Several kisspeptin agonists and antagonists have been developed for ovulation induction in assisted reproduction and management of pubertal disorders. This review summarizes the diverse roles and structural insights of kisspeptin isoforms to help in the identification of new horizons and thematic areas for basic and translational research, culminating in potential therapeutic applications.

Kisspeptins inhibit human airway smooth muscle proliferation.

Sex and gender disparity in asthma is recognized and suggests a modulatory role for sex steroids, particularly estrogen. However, there is a dichotomous role for estrogen in airway remodeling, making it unclear whether sex hormones are protective or detrimental in asthma and suggesting a need to explore mechanisms upstream or independent of estrogen. We hypothesize that kisspeptin (Kp)/KISS1R signaling serves this role. Airway smooth muscle (ASM) is a key structural cell type that contributes to remodeling in asthma. We explored the role of Kp/KISS1R in regulating ASM proliferation. We report potentially novel data indicating that Kp and KISS1R are expressed in human airways, especially ASM, with lower expression in ASM from women compared with men and lower in patients with asthma compared with people without asthma. Proliferation studies showed that cleaved forms of Kp, particularly Kp-10, mitigated PDGF-induced ASM proliferation. Pharmacological inhibition and shRNA knockdown of KISS1R increased basal ASM proliferation, which was further amplified by PDGF. The antiproliferative effect of Kp-10 in ASM was mediated by inhibition of MAPK/ERK/Akt pathways, with altered expression of PCNA, C/EBP-α, Ki-67, cyclin D1, and cyclin E leading to cell cycle arrest at G0/G1 phase. Overall, we demonstrate the importance of Kp/KISS1R signaling in regulating ASM proliferation and a potential therapeutic avenue to blunt remodeling in asthma.

Kisspeptin-10 binding to Gpr54 in osteoclasts prevents bone loss by activating Dusp18-mediated dephosphorylation of Src.

Osteoclasts are over-activated as we age, which results in bone loss. Src deficiency in mice leads to severe osteopetrosis due to a functional defect in osteoclasts, indicating that Src function is essential in osteoclasts. G-protein-coupled receptors (GPCRs) are the targets for ∼35% of approved drugs but it is still unclear how GPCRs regulate Src kinase activity. Here, we reveal that GPR54 activation by its natural ligand Kisspeptin-10 (Kp-10) causes Dusp18 to dephosphorylate Src at Tyr 416. Mechanistically, Gpr54 recruits both active Src and the Dusp18 phosphatase at its proline/arginine-rich motif in its C terminus. We show that Kp-10 binding to Gpr54 leads to the up-regulation of Dusp18. Kiss1, Gpr54 and Dusp18 knockout mice all exhibit osteoclast hyperactivation and bone loss, and Kp-10 abrogated bone loss by suppressing osteoclast activity in vivo. Therefore, Kp-10/Gpr54 is a promising therapeutic target to abrogate bone resorption by Dusp18-mediated Src dephosphorylation.

Roles of the kisspeptin/GPR54 system in pathomechanisms of atherosclerosis.

Kisspeptin-10 (KP-10), a potent vasoconstrictor and inhibitor of angiogenesis, and its receptor, GPR54, have currently received much attention with respect to atherosclerosis, since both KP-10 and GPR54 are expressed at high levels in atheromatous plaques and restenotic lesions after wire-injury. The present review introduces the emerging roles of the KP-10/GPR54 system in atherosclerosis. KP-10 suppresses migration and proliferation of human umbilical vein endothelial cells (HUVECs), and induces senescence in HUVECs. KP-10 increases adhesion of human monocytes to HUVECs. KP-10 also stimulates expression of interleukin-6, tumor necrosis factor-α, monocyte chemotactic protein-1, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin genes in HUVECs. KP-10 enhances oxidized low-density lipoprotein-induced foam cell formation associated with upregulation of CD36 and acyl-coenzyme A: cholesterol acyltransferase-1 in human monocyte-derived macrophages. In human aortic smooth muscle cells, KP-10 suppresses angiotensin II-induced migration and proliferation, however, it enhances apoptosis and activities of matrix metalloproteinase (MMP)-2 and MMP-9 by upregulation of extracellular signal-regulated kinase 1/2, p38, Bax, and caspase-3. Four-week-infusion of KP-10 into Apoe-/- mice accelerates development of aortic atherosclerotic lesions with increased monocyte/macrophage infiltration and vascular inflammation, also, it decreases intraplaque vascular smooth muscle cell content. Proatherosclerotic effects of endogenous and exogenous KP-10 were completely attenuated upon infusion of P234, a GPR54 antagonist, in Apoe-/- mice. These findings suggest that KP-10 may contribute to acceleration of progression and to the instability of atheromatous plaques, leading to rupture of plaques. This GPR54 antagonist may be useful for the prevention and treatment of atherosclerosis. Thus, the KP-10/GPR54 system may serve as a novel therapeutic target for atherosclerotic diseases.

GPR54 and kisspeptin in reproduction.

Kisspeptins, the peptide products of the KiSS-1 gene, were identified in 2001 as natural ligands of the previously orphan G protein-coupled receptor, GPR54. They include, among others, metastin and kisspeptin-10. The known biological functions of kisspeptins were initially restricted to their ability to suppress tumour metastasis, hence the name of metastin. However, in late 2003, two groups independently reported that loss-of-function mutations of the GPR54 gene are linked to absence of puberty onset and hypogonadotrophic hypogonadism in humans--a phenotype that was reproduced in GPR54-null mice. Those seminal observations revealed a totally unexpected, fundamental role of the KiSS-1/GPR54 system in control of puberty and reproductive function and boosted an extraordinary interest for the characterization of these novel facets of kisspeptin physiology. Indeed, in the last 2 years, metastin and kisspeptin-10 have been demonstrated as very potent stimulators of the gonadotrophic axis, in a number of species and through different routes of administration. In addition, the hypothalamic KiSS-1/GPR54 system has been proven as an essential gatekeeper of GnRH neurons, involved in their activation at puberty and their regulation by gonadal steroids and (probably) metabolic factors. This review comprehensively examines the experimental evidence obtained to date supporting a pivotal role of kisspeptins and GPR54 in the control of reproduction.

Safety Evaluation of KP-10 (Metastin 45-54) Following once Daily Intravenous Administration for 14 Days in Dog.

Kisspeptin-10 (previously referred as metastin 45-54), an active fragment of the endogenous full-length kisspeptin-145, is a potential therapeutic agent for reproductive disorders such as infertility, amenorrhea, and pubertal delay. A safety evaluation of KP-10 was conducted in dogs at the doses of 30, 100, and 1,000 μg/kg, given once daily intravenously for 14 days with a 14-day recovery period. There were no overt signs of drug-related toxicity observed in clinical signs, body weights, food consumption, clinical pathology, histopathology, urinalysis, electrocardiogram, or respiratory rate. Due to very rapid clearance of the peptide, luteinizing hormone (LH) levels were measured as a surrogate marker to demonstrate KP-10 exposure. The LH response reached a maximum concentration at 5 minutes post-dose and remained relatively unchanged for at least 30 minutes after dosing with no gender effect. LH concentrations on Day 1 were generally greater than on day 14. Vaginal cytology results indicated all dogs were in anestrous throughout the dosing period. There were also no KP-10-related findings observed in recovery animals on Day 29. In conclusion, KP-10 demonstrated favorable safety profile in dog where 1,000 μg/kg dose was considered as a no-observed-adverse-effect level dose when administered IV once daily for 14 days.

Kisspeptin-10 Protects Against TNF-α-Induced Chondrocyte Senescence via the SIRT1/p53/p21 Signaling.

In Osteoarthritis (OA), the senescence of chondrocytes plays a pivotal role, contributing to cartilage degradation and impairing tissue repair mechanisms. (Kp-10), a peptide hormone, exerts diverse biological functions across multiple cell types and tissues via its receptor Gpr54. However, its role in chondrocytes and OA has been understudied. This study investigates the role of Kp-10 in mitigating TNF-α- induced senescence in primary chondrocytes, a hallmark of OA pathogenesis. Gpr54 expression was confirmed in both primary chondrocytes and the ATDC5 chondrogenic cell line, with TNF-α treatment leading to a dose-dependent decrease in Gpr54 expression. Kp-10 treatment at concentrations of 50 and 100 nM effectively ameliorated TNF-α-induced senescence, as evidenced by diminished senescence-associated β-galactosidase staining and enhanced telomerase activity. Moreover, Kisspeptin-10 modulated the expression of key regulators involved in cellular aging, including hTERT and TERF2, and suppressed the activation of the p53/p21 pathway. Notably, Kp-10 restored SIRT1 expression, which was downregulated by TNF-α. Silencing SIRT1 abolished the protective effects of Kp-10, highlighting the essential role of SIRT1 in its anti-senescence action. These findings suggest that Kp-10 may be a promising therapeutic strategy for OA by mitigating chondrocyte senescence and improving cellular function by modulating the SIRT1 and p53/p21 pathways.

Kisspeptin/KISS1R Signaling Modulates Human Airway Smooth Muscle Cell Migration.

Airway remodeling is a cardinal feature of asthma, associated with increased airway smooth muscle (ASM) cell mass and upregulation of extracellular matrix deposition. Exaggerated ASM cell migration contributes to excessive ASM mass. Previously, we demonstrated the alleviating role of Kp (kisspeptin) receptor (KISS1R) activation by Kp-10 in mitogen (PDGF [platelet-derived growth factor])-induced human ASM cell proliferation in vitro and airway remodeling in vivo in a mouse model of asthma. Here, we examined the mechanisms by which KISS1R activation regulates mitogen-induced ASM cell migration. KISS1R activation using Kp-10 significantly inhibited PDGF-induced ASM cell migration, further confirmed using KISS1R shRNA. Furthermore, KISS1R activation modulated F/G actin dynamics and the expression of promigration proteins like CDC42 (cell division control protein 42) and cofilin. Mechanistically, we observed reduced ASM RhoA-GTPAse with KISS1R activation. The antimigratory effect of KISS1R was abolished by PKA (protein kinase A)-inhibitory peptide. Conversely, KISS1R activation significantly increased cAMP and phosphorylation of CREB (cAMP-response element binding protein) in PDGF-exposed ASM cells. Overall, these results highlight the alleviating properties of Kp-10 in the context of airway remodeling.

KISS1 in breast cancer progression and autophagy.

Tumor suppressors are cellular proteins typically expressed in normal (non-cancer) cells that not only regulate such cellular functions as proliferation, migration and adhesion, but can also be secreted into extracellular space and serve as biomarkers for pathological conditions or tumor progression. KISS1, a precursor for several shorter peptides, known as metastin (Kisspeptin-54), Kisspeptin-14, Kisspeptin-13 and Kisspeptin-10, is one of those metastasis suppressor proteins, whose expression is commonly downregulated in the metastatic tumors of various origins. The commonly accepted role of KISS1 in metastatic tumor progression mechanism is the ability of this protein to suppress colonization of disseminated cancer cells in distant organs critical for the formation of the secondary tumor foci. Besides, recent evidence suggests involvement of KISS1 in the mechanisms of tumor angiogenesis, autophagy and apoptosis regulation, suggesting a possible role in both restricting and promoting cancer cell invasion. Here, we discuss the role of KISS1 in regulating metastases, the link between KISS1 expression and the autophagy-related biology of cancer cells and the perspectives of using KISS1 as a potential diagnostic marker for cancer progression as well as a new anti-cancer therapeutics.

Kisspeptin modulates fertilization capacity of mouse spermatozoa.

Kisspeptin acts as an upstream regulator of the hypothalamus-pituitary-gonad axis, which is one of the main regulatory systems for mammalian reproduction. Kiss1 and its receptor Kiss1r (also known as G protein-coupled receptor 54 (Gpr54)) are expressed in various organs, but their functions are not well understood. The purpose of this study was to investigate the expression profiles and functions of kisspeptin and KISS1R in the reproductive tissues of imprinting control region mice. To identify the expression pattern and location of kisspeptin and KISS1R in gonads, testes and ovarian tissues were examined by immunohistochemical or immunofluorescent staining. Kisspeptin and KISS1R were expressed primarily in Leydig cells and seminiferous tubules respectively. KISS1R was specifically localized in the acrosomal region of spermatids and mature spermatozoa. Kisspeptin, but not KISS1R, was expressed in the cumulus-oocyte complex and oviductal epithelium of ovarian and oviductal tissues. The sperm intracellular calcium concentrations significantly increased in response to treatment with kisspeptin 10 in Fluo-4-loaded sperm. The IVF rates decreased after treatment of sperm with the kisspeptin antagonist peptide 234. These results suggest that kisspeptin and KISS1R might be involved in the fertilization process in the female reproductive tract. In summary, this study indicates that kisspeptin and KISS1R are expressed in female and male gametes, respectively, and in mouse reproductive tissues. These data strongly suggest that the kisspeptin system could regulate mammalian fertilization and reproduction.

Endocrine-metabolic effects of kisspeptin in mammals.

Kisspeptins (Kp) play crucial roles in regulating reproductive functions. In recent decades, new effects of Kp on other systems, such as the cardiovascular, respiratory, and musculoskeletal systems, and its possible therapeutic effects on gestational hypothyroidism, diabetes mellitus, and neoplasms have been identified. Additionally, Kp signaling has been investigated in endocrine-metabolic regulation; nonetheless, there are few reviews on this subject. This study aims to provide a comprehensive overview of the effects of Kp on endocrine-metabolic physiology in mammals. Kp modulates the release of hormones from various endocrine organs, including the hypothalamus, pituitary, gonadal, adrenal, and pancreatic glands. The metabolic effects of Kp exhibit significant sexual dimorphism, manifesting as an increase in metabolic activity, a decrease in body weight in females, and an increase in weight gain in males. Further research is necessary to investigate the effects of Kp on a wide variety of systems, which will help in advancing knowledge in this field. Further sex-specific studies are needed to investigate the therapeutic potential of Kp.

Does kisspeptin exert a local modulatory effect on bovine ovarian steroidogenesis?

Kisspeptin, a hypothalamic neuropeptide encoded by the KISS1 gene, has a pivotal role in promoting GnRH secretion in mammals. Kisspeptin and its receptor (KISS1R) are also expressed in certain peripheral tissues including gonads, suggesting intra-gonadal roles. Such actions at the level of the bovine ovary have not been explored previously. The current aims were to determine whether KISS1 and its receptor (KISS1R) are expressed in the bovine ovary and whether kisspeptin or a kisspeptin antagonist can modulate ovarian steroid production by cultured ovarian cells. Granulosa (GC) and theca interna (TC) were collected from antral follicles (3-18 mm) categorized into five class sizes. Early, mid and regressing corpora lutea (CL) were also collected for RT-qPCR analysis of KISS1 and KISS1R expression. Bovine TC and GC cultured under both non-luteinizing (serum-free) and luteinizing (serum-supplemented) conditions were treated for 4 days with kisspeptin-10 (10-10-10-6M) or kisspeptin antagonist (p234; 10-10-10-6M), alone and in combination with either FSH (GC), LH (TC) or forskolin (luteinized GC/TC). Steroid secretion (GC: oestradiol, progesterone; TC: androstenedione, progesterone; luteinized GC/TC: progesterone) was measured by ELISA and viable cell number determined by neutral red uptake assay. KISS1 and KISS1R transcripts were detected in TC, GC and CL with significant differences between follicle categories and CL stages. However, neither kisspeptin-10 nor kisspeptin antagonist affected steroid secretion or viable cell number in any of the four ovarian cell culture models. As such, the hypothesis that kisspeptin has a direct intra-ovarian role to modulate follicular or luteal steroidogenesis, or cell proliferation/survival, is not supported.

Kisspeptin-10 inhibits OHSS by suppressing VEGF secretion.

The aim of the present study was to elucidate the effects of kisspeptin-10 (Kp-10) on ovarian hyperstimulation syndrome (OHSS) and its related mechanism in OHSS rat models, human umbilical vein endothelial cells (HUVECs) and human luteinized granulosa cells. OHSS is a systemic disorder with high vascular permeability (VP) and ovarian enlargement. KISS1R (KISS1 receptor) is the specific receptor of kisspeptin. The kisspeptin/KISS1R system inhibits the expression of vascular endothelial growth factor (VEGF), which is the main regulator of VP. In our study, decreased expression of Kiss1r was observed in both ovaries and lung tissue of OHSS rats. Injection of exogenous Kp-10 inhibited the increase of VP and VEGF while promoting the expression of Kiss1r in both the ovarian and lung tissue of OHSS rats. Using HUVECs, we revealed that a high level of 17-β estradiol (E2), a feature of OHSS, suppressed the expression of KISS1R and increased VEGF and nitric oxide (NO) through estrogen receptors (ESR2). Furthermore, KISS1R mRNA also decreased in the luteinized human granulosa cells of high-risk OHSS patients, and was consistent with the results in rat models and HUVECs. In conclusion, Kp-10 prevents the increased VP of OHSS by the activation of KISS1R and the inhibition of VEGF.

Comprehensive Analysis of Kisspeptin Signaling: Effects on Cellular Dynamics in Cervical Cancer.

Kisspeptin, a key neuropeptide derived from the KISS1R gene, is renowned for its critical role in regulating the hypothalamic-pituitary-gonadal axis and reproductive hormone secretion. Beyond its primary function in reproductive biology, emerging research has illuminated its influence in various cancers, mediating significant effects through its interaction with the G protein-coupled receptor, kisspeptin receptor. This interaction has been implicated in modulating cellular processes such as proliferation and metastasis, making it a potential target for therapeutic intervention. Our study initially screened ten kisspeptin-10 analogs through cytotoxic effects of kisspeptin-10 (KP10) and its analogs in several cancer types, including cervical, prostate, breast, and gastric cancers, with a particular focus on cervical cancer, where the most profound effects were observed. Further exploration using kinase array assays revealed that these analogs specifically alter key kinases involved in cancer progression. Migration assays demonstrated a substantial decrease in cell motility, and Bioluminescence Resonance Energy Transfer assays confirmed these analogs' strong interactions with the kisspeptin receptor. Overall, our results indicate that these KP10 analogs not only hinder cervical cancer cell proliferation but also curtail migration through targeted modulation of kinase signaling, suggesting their potential as therapeutic agents in managing cervical cancer progression. This comprehensive approach underscores the therapeutic promise of exploiting kisspeptin signaling in cancer treatment strategies.

Kisspeptin regulates steroidogenesis and spermiation in anuran amphibian.

Kisspeptin (Kp) system has a recognized role in the control of gonadotropic axis, at multiple levels. Recently, a major focus of research has been to assess any direct activity of this system on testis physiology. Using the amphibian anuran, Pelophylax esculentus, as animal model, we demonstrate - for the first time in non-mammalian vertebrate - that testis expresses both Kiss-1 and Gpr54 proteins during the annual sexual cycle and that ex vivo 17B-estradiol (E2, 10-6 M) increases both proteins over control group. Since the interstitium is the main site of localization of both ligand and receptor, its possible involvement in the regulation of steroidogenesis has been evaluated by ex vivo treatment of testis pieces with increasing doses of Kp-10 (10-9-10-6 M). Treatments have been carried out in February - when a new wave of spermatogenesis occurs - and affect the expression of key enzymes of steroidogenesis inducing opposite effects on testosterone and estradiol intratesticular levels. Morphological analysis of Kp-treated testes reveals higher number of tubules with spermatozoa detached from Sertoli cells than control group and the expression of connexin 43, the main junctional protein in testis, is deeply affected by the treatment. In spite of the effects on spermatozoa observed ex vivo, in vivo administration of Kp-10 has been unable to induce sperm release in cloacal fluid. In conclusion, we demonstrate Kp-10 effects on steroidogenesis with possible involvement in the balance between testosterone and estradiol levels, and report new Kp-10 activities on spermatozoa-Sertoli cell interaction.

Author Correction: Kisspeptin-10 binding to Gpr54 in osteoclasts prevents bone loss by activating Dusp18-mediated dephosphorylation of Src.

Kisspeptin-10 Mitigates α-Synuclein-Mediated Mitochondrial Apoptosis in SH-SY5Y-Derived Neurons via a Kisspeptin Receptor-Independent Manner.

The hypothalamic neurohormone kisspeptin-10 (KP-10) was inherently implicated in cholinergic pathologies when aberrant fluctuations of expression patterns and receptor densities were discerned in neurodegenerative micromilieus. That said, despite variable degrees of functional redundancy, KP-10, which is biologically governed by its cognate G-protein-coupled receptor, GPR54, attenuated the progressive demise of α-synuclein (α-syn)-rich cholinergic-like neurons. Under explicitly modeled environments, in silico algorithms further rationalized the surface complementarities between KP-10 and α-syn when KP-10 was unambiguously accommodated in the C-terminal binding pockets of α-syn. Indeed, the neuroprotective relevance of KP-10's binding mechanisms can be insinuated in the amelioration of α-syn-mediated neurotoxicity; yet it is obscure whether these extenuative circumstances are contingent upon prior GPR54 activation. Herein, choline acetyltransferase (ChAT)-positive SH-SY5Y neurons were engineered ad hoc to transiently overexpress human wild-type or E46K mutant α-syn while the mitigation of α-syn-induced neuronal death was ascertained via flow cytometric and immunocytochemical quantification. Recapitulating the specificity observed on cell viability, exogenously administered KP-10 (0.1 µM) substantially suppressed wild-type and E46K mutant α-syn-mediated apoptosis and mitochondrial depolarization in cholinergic differentiated neurons. In particular, co-administrations with a GPR54 antagonist, kisspeptin-234 (KP-234), failed to abrogate the robust neuroprotection elicited by KP-10, thereby signifying a GPR54 dispensable mechanism of action. Consistent with these observations, KP-10 treatment further diminished α-syn and ChAT immunoreactivity in neurons overexpressing wild-type and E46K mutant α-syn. Overall, these findings lend additional credence to the previous notion that KP-10's binding zone may harness efficacious moieties of neuroprotective intent.

Adult Neurogenesis Is Regulated by the Endocannabinoid and Kisspeptin Systems.

Neurogenesis is considered the most robust form of plasticity in the adult brain. To better decipher this process, we evaluated the potential crosstalk of Kisspeptin and Endocannabinoid Systems (KPS and ECS, respectively) on hippocampal neurogenesis. Male adolescent rats were exposed to kisspeptin-10 (KP10) and the endocannabinoid anandamide (AEA) administered alone or in combination with the type 1 cannabinoid receptor (CB1R) antagonist SR141716A. The expression of Kiss1 and Kisspeptin receptor (Kiss1R) has been characterized for the first time in rat hippocampus together with the expression of the CB1R and the Transient Receptor Potential Vanilloid 1 ion channel receptor (TRPV1). Results show that both systems inhibit neurogenesis by reducing the extracellular signal-regulated kinase (ERK) signaling. Despite little differences in the expression of Kiss1R and CB1R, TRPV1 is enhanced by both KP10 and AEA treatments, suggesting TRPV1 as a common thread. KP10 administration reduces CB1R expression in the dentate gyrus, while AEA does not. KPS, unlike ECS, promotes the expression of estrogen receptor α (ER-α) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), also upregulating sirtuin 1 (SIRT1), brain-derived-neurotrophic factor (BDNF), and c-Jun. These findings suggest that the interaction between ECS and KPS could be involved in the fine-tuning of neurogenesis, highlighting a novel role for KPS.

New Insights in Bovine Follicular Cysts.

The aim of the present study was to understand the involved factors in follicular cysts in dairy cows. The study consisted of an in vivo and in vitro approach. The in vivo part, hormonal evaluation (Kisspeptin-10 [Kp-10], Gonadotropin inhibiting hormone [GnIH], Luteinizing hormone [LH], Oestrogens [E2] and cortisol) was performed in sera of both healthy (H) and cows with follicular cysts (FC). The in vitro part was concentrated on estimating the distribution of GPR54 (Kp-10 receptor) and GPR147 (GnIH receptor) on cystic and preovulatory follicles. Serum concentrations of Kp-10, GnIH, LH, E2 and cortisol were significantly higher in Group FC compared with Group H. Gene expression analysis showed a reduction in GPR54 mRNA levels in FC compared to preovulatory follicles, while no expression of the GPR147 receptor was detected. The lower presence of GPR54 in FC compared to the preovulatory follicle can be determined by a down-receptor regulation induced by elevated serum concentrations of Kp-10 in cows with ovarian FC. Endocrine imbalances of the hypothalamic-pituitary-ovarian axis, characterising FC, may reflect altered patterns of Kp-10 and GnIH secretion.

Role of Kisspeptin and NKB in Puberty in Nonhuman Primates: Sex Differences.

To understand the roles of kisspeptin and neurokinin B (NKB) in puberty and sex differences in their involvement, we conducted a series of experiments measuring the release of gonadotropin-releasing hormone (GnRH) and kisspeptin in the median eminence of the hypothalamus in male and female monkeys throughout sexual development. Results indicate that kisspeptin-10 and the NKB agonist, senktide, stimulated GnRH release in males and females at the prepubertal and pubertal stages, but females are much more sensitive to kisspeptin signaling than males. Moreover, throughout the progress of puberty, major remodeling of kisspeptin and NKB signaling pathways for the regulation of GnRH release takes place. In females during puberty, reciprocal pathways (i.e., kisspeptin signaling mediated through NKB neurons and NKB signaling mediated through kisspeptin neurons) are established, to provide powerful and flexible mechanisms for GnRH neurosecretory activity necessary for complex female reproductive function in adulthood. By contrast, during puberty in males, reciprocal pathways are consolidated to a simpler kisspeptin-dominant signaling pathway. Nevertheless, in primates, both kisspeptin and NKB signaling are contributing factors for the pubertal increase in GnRH release, rather than initiating puberty.

Kisspeptin-10 increases collagen content in the myocardium by focal adhesion kinase activity.

The aim of the study was to evaluate the role of kisspeptin-10 (KiSS-10) in the regulation of collagen content in cardiac fibroblasts. An attempt was also made to describe the mechanism of the effect of KiSS-10 on collagen metabolism. The studies indicate that kisspeptin-10 significantly increases the content of intracellular collagen in the myocardium. KiSS-10 also elevates the level of phosphorylated focal adhesion kinase (FAK) in human cardiac fibroblasts. The inhibition of FAK negates the stimulatory effect of KiSS-10 on collagen deposition in vitro. These changes correlate with an increase in the level of propeptides of procollagen type I (PICP) and III (PIIICP) in fibroblast culture medium and mouse PIIICP in serum. Moreover, this hormone inhibits the release of metalloproteinases (MMP-1,-2,-9) and elevates the secretion of their tissue inhibitors (TIMP-1,-2,-4). KiSS-10 also enhances the expression of α1 chains of procollagen type I and III in vitro. Thus, KiSS-10 is involved in the regulation of collagen metabolism and cardiac fibrosis. Augmentation of collagen deposition by KiSS-10 is dependent on the protein synthesis elevation, inhibition of MMPs activity (increase of TIMPs release) or decrease of MMPs concentration. The profibrotic activity of KiSS-10 is mediated by FAK and is not dependent on TGF-β1.

Kisspeptin-10 and gonadotropin inhibiting hormone during pregnancy in dairy cows.

Recently, two different molecules have been discovered to play an important role in reproduction: kisspeptin (Kp) and gonadotropin inhibiting hormone (GnIH). The aim of this study was to establish the trend of kisspeptin 10 (Kp‑10) and GnIH concentrations, during all phases of pregnancy in cattle, in order to understand their possible role in the physiology of pregnancy. To examine the correlation between these hormones and steroid hormones, cortisol and oestradiol 17β (E2) were also analyzed. Eighty pregnant cows were enrolled and the pregnancy was divided into 8 periods of 30 days each (from 30‑60 days to 240‑270 days). Blood samples were collected from all cows, once only for cow. Kp‑10, GnIH, cortisol and E2 were measured in sera. After an initial plateau, Kp‑10 concentrations increased at 90‑120 days and then decreased until 180‑210 days, undergoing a further increase until 240‑270 days. GnIH concentrations decreased until 90‑120 days, then increased until the end of gestation. These trends were opposing until 180‑210 days, whereat concentrations of both increased until the end of gestation. Cortisol concentrations were homogenous at all times, except at the final period, in which they were higher. E2 showed two peaks, at 90‑120 days and 240‑270 days. The trends in Kp‑10 and GnIH concentrations suggest that these two hormones might act to maintain the delicate endocrine equilibrium of pregnancy.

Kisspeptin-10/basal LH ratio improves differentiation of central precocious puberty and premature thelarche.

Distinguishing idiopathic central precocious puberty (ICPP) from premature thelarche (PT) remains a clinical challenge and often necessitates GnRH stimulation testing. Kisspeptin-10 (Kp-10), Neurokinin B (NKB), and Neuropeptide Y (NPY) are key regulators of GnRH secretion and may serve as surrogate biomarkers. We evaluated whether these neuropeptides, alone or in combination with basal gonadotropins, could provide clinically useful discrimination of ICPP and PT. In this prospective study, Indian girls aged 6-9&#xa0;years were enrolled as controls (n&#xa0;=&#xa0;40), ICPP (n&#xa0;=&#xa0;33), and PT (n&#xa0;=&#xa0;23). Anthropometry, basal LH, FSH, estradiol, pelvic ultrasonography, and plasma Kp-10, NKB, and NPY levels were assessed. Diagnostic performance was evaluated using receiver operating characteristic (ROC) analysis. Logistic regression models assessed incremental predictive value: Model 1 included the Kp-10/basal LH ratio; Model 2 added bone age advancement (BA-CA); and Model 3 further included basal estradiol. Clinical utility was examined using decision curve analysis (DCA). Anthropometric parameters did not differ between ICPP and PT. Kp-10 and NKB levels were higher in both early-puberty groups than controls, but neither marker alone discriminated ICPP from PT. The composite Kp-10/basal LH ratio showed superior performance, with an ROC-derived cut-off <4.07&#xa0;ng/mIU (sensitivity 72.7%, specificity 87.0%, accuracy 78%). All three models showed similar discrimination (AUC 0.78-0.79), with no meaningful improvement after adding BA-CA or estradiol. DCA demonstrated a higher net benefit for the Kp-10/basal LH ratio compared with treat-all or treat-none strategies across clinically relevant thresholds. The Kp-10/basal LH ratio provides robust discrimination and meaningful clinical utility in differentiating ICPP from PT and may reduce reliance on GnRH stimulation testing.

The kisspeptin (KiSS-1)/GPR54 system in cancer biology.

Kisspeptin (KiSS-1) gene, initially described as a melanoma metastasis suppressor gene, encodes a number of peptides (kp-54, kp-14, kp-13, kp-10), which are endogenous ligands to a G protein-coupled receptor, referred as hOT7T175 or AXOR12 or GPR54. So far intensive investigation has provided substantiate evidence supporting the role of KiSS-1/GPR54 system in cancer biology as well as in the regulation of the reproductive function and trophoblast invasion. The precise mechanism by which KiSS-1/GPR54 system is affecting cancer cell growth and metastasis includes complex endocrine, paracrine and autocrine actions. Nevertheless, the detail mechanism of such actions is still under intensive investigation. Herein we review the evidence which support the role of KiSS-1/GPR54 system in cancer biology.

Neuroendocrine Regulation of Stress-Induced T Cell Dysfunction during Lung Cancer Immunosurveillance via the Kisspeptin/GPR54 Signaling Pathway.

Emerging evidence suggests that physiological distress is highly correlated with cancer incidence and mortality. However, the mechanisms underlying psychological challenges-mediated tumor immune evasion are not systematically explored. Here, it is demonstrated that acute restraint (AR) increases the level of the plasma neuropeptide hormones, kisspeptin, and the expression levels of its receptor, Gpr54, in the hypothalamus, splenic and tumor-infiltrating T cells, suggesting a correlation between the neuroendocrine system and tumor microenvironment. Accordingly, administration of kisspeptin-10 significantly impairs T cell function, whereas knockout of Gpr54 in T cells inhibits lung tumor progression by suppressing T cell dysfunction and exhaustion with or without AR. In addition, Gpr54 defective OT-1 T cells show superior antitumor activity against OVA peptide-positive tumors. Mechanistically, ERK5-mediated NR4A1 activation is found to be essential for kisspeptin/GPR54-facilitated T cell dysfunction. Meanwhile, pharmacological inhibition of ERK5 signaling by XMD8-92 significantly reduces the tumor growth by enhancing CD8+ T cell antitumor function. Furthermore, depletion of GPR54 or ERK5 by CRISPR/Cas9 in CAR T cells intensifies the antitumor responses to both PSMA+ and CD19+ tumor cells, while eliminating T cell exhaustion. Taken together, these results indicate that kisspeptin/GPR54 signaling plays a nonredundant role in the stress-induced tumor immune evasion.

Kisspeptin-10 (KP-10) stimulates osteoblast differentiation through GPR54-mediated regulation of BMP2 expression and activation.

Kisspeptin-10 (KP-10) acts as a tumor metastasis suppressor via its receptor, G-protein-coupled receptor 54 (GPR54). The KP-10-GPR54 system plays an important role in embryonic kidney development. However, its function in osteoblast differentiation is unknown. Osteoblast differentiation is controlled by a range of hormones and cytokines, such as bone morphogenetic protein (BMPs), and multiple transcription factors, such as Runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), and Distal-less homeobox 5 (Dlx5). In the present study, KP-10-treatment significantly increased the expression of osteogenic genes, including mRNA and protein levels of BMP2, in C3H10T1/2 cells. Moreover, KP-10 induced BMP2-luc activity and increased phosphorylation of Smad1/5/9. In addition, NFATc4 specifically mediated KP-10-induced BMP2 gene expression. However, KP-10 treatment did not induce expression of the BMP2 and Runx2 genes in GPR54-/- cells. To examine whether KP-10 induced secretion of BMP2 to the culture medium, we used the conditioned-medium (C.M) of KP-10 treated medium on C3H10T1/2 cells. Dlx5 and Runx2 expressions were higher in GPR54-/- cells treated with C.M than in those treated with KP-10. These results demonstrate that BMP2 protein has an autocrine effect upon KP-10 treatment. Taken together, these findings suggest that KP-10/GPR54 signaling induces osteoblast differentiation via NFATc4-mediated BMP2 expression.

The antidepressant-like effects of kisspeptin-10 are reversed by kisspeptin antagonist peptide 234 in male rats.

Kisspeptins are reported to be the most potent activators of the hypothalamus-pituitary-gonadal (HPG) axis known to date. Kisspeptin potently elicits gonadotropin-releasing hormone (GnRH) release and luteinizing hormone (LH) secretion, even in the pre-pubertal period. Beyond the hypothalamus, kisspeptin is also expressed in limbic and paralimbic brain regions, which are areas of the neurobiological network primarily implicated in emotional behaviors alongside sexual functions. Therefore, an increasing body of studies has implicated kisspeptin as having many influences on emotional behaviors. The study was set out to explore if the kisspeptin/GPR54 signaling system is required for the anti-depressant-like effect of kisspeptin-10 (KP-10), besides the regulation of the HPG axis. To test this concept, peptide 234 (P234), a kisspeptin antagonist, was given to the male rats, and its modulatory effect on the anti-depressant-like effects of kisspeptin was investigated by using a forced swimming test (FST). The study has also sought to know whether kisspeptin can exert its effects through adrenergic and serotonergic receptors. To investigate this, the agents yohimbine (Yoh), an alpha-2 adrenergic receptor antagonist, and cyproheptadine (Cry), a non-selective 5-HT2 serotonergic receptor antagonist, were administered in the experiments. Our results indicate that, in rats, the anti-depressant-like effects of KP-10 in a modified rat FST are mediated by GPR54 receptors, since the kisspeptin antagonist peptide 234 reversed kisspeptin-induced anti-depressant-like effects. Our data also demonstrate that the anti-depressant-like effects of kisspeptin, at least in part, are mediated by an interaction of the alpha-2 adrenergic and 5-HT2 serotonergic receptors.

Kisspeptin-10 Promotes Progesterone Synthesis in Bovine Ovarian Granulosa Cells via Downregulation of microRNA-1246.

The objective of this study was to clarify the effect of kisspeptin-10 (kp-10) on the synthesis of progesterone (P4) in bovine granulosa cells (BGCs) and its mechanisms via microRNA 1246 (miR-1246). According to the results, we found that treating with kp-10 for 24 h could increase P4 level, the mRNA expression of the steroidogenesis-related gene steroidogenic acute regulatory protein (StAR), free cholesterol content, and decrease miR-1246 expression in BGCs. Overexpression of miR-1246 significantly inhibited P4 synthesis, StAR mRNA expression, and free cholesterol content in BGCs, whereas underexpression of miR-1246 significantly reversed this effect in BGCs. Additionally, overexpression of miR-1246 counteracted the accelerative effect of kp-10 on P4 synthesis, StAR mRNA expression, and free cholesterol content in BGCs. Conversely, underexpression of miR-1246 enhanced the accelerative effect of kp-10 on P4 synthesis, StAR mRNA expression, and free cholesterol content in BGCs. Meanwhile, results of dual-luciferase reporter assays indicated that miR-1246 targeted the 3'UTR of StAR in BGCs. These results demonstrated that kp-10 induced P4 synthesis in BGCs by promoting free cholesterol transport via regulating expression of miR-1246/StAR.

Kisspeptin-10 Preserves the Blood-Brain Barrier's Integrity Post-Stroke by Augmenting Claudin-10 Expression.

The integrity of the Blood-Brain Barrier (BBB) is crucial in the pathophysiological progression of acute ischemic stroke (AIS). However, the potential of Kisspeptin-10 (Kp-10), with its antioxidant and anti-inflammatory properties, has not been explored experimentally in the context of stroke management. This study aimed to investigate the neurovascular protective effects of Kp-10 following cerebral ischemia using both in&#xa0;vivo and in&#xa0;vitro models. A middle cerebral artery occlusion (MCAO) model was established in C57BL/6 mice, followed by Kp-10 administration. Neurological deficits (Longa score), infarct volume (TTC staining), BBB permeability (14C-Sucrose), and Claudin-10 expression (qRT-PCR and immunohistochemistry) were assessed to evaluate the therapeutic effects of Kp-10. Human brain microvascular endothelial cells (HBMVECs) were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) to mimic ischemic conditions. Endothelial permeability, oxidative stress (OS), and nuclear factor erythroid 2-related factor 2 (Nrf2) levels were evaluated. Nrf2 silencing was performed to validate its role in Kp-10-mediated protection. Initially, we observed a significant reduction in Kp-10 expression within the cortical tissue of mice subjected to MCAO. Subsequent administration of Kp-10 not only alleviated neurological deficits but also significantly mitigated blood-brain barrier (BBB) dysfunction following stroke induction, as evidenced by reduced 14C-sucrose leakage. Furthermore, Kp-10 treatment led to an upregulation of Claudin-10 expression in the post-stroke cortical region. In our in&#xa0;vitro experiments, we employed HBMVECs exposed to OGD/R to simulate ischemic conditions. We found that Kp-10 effectively reduced OGD/R-induced endothelial permeability by enhancing Claudin-10 expression. Additionally, Kp-10 exhibited antioxidant capabilities by decreasing mitochondrial reactive oxygen species (ROS) levels, increasing superoxide dismutase (SOD) activity, and upregulating nuclear factor erythroid 2-related factor 2 (Nrf2) expression. Notably, when Nrf2 was knocked down in HBMVECs, the protective effects of Kp-10 on endothelial permeability and Claudin-10 expression were abolished, indicating that the beneficial actions of Kp-10 are mediated through the Nrf2 pathway. In conclusion, our findings suggest that Kp-10 holds promise as a therapeutic strategy to preserve BBB integrity and promote neuroprotection following stroke, acting primarily via the Nrf2 signalling pathway. These findings suggest that Kp-10 may represent a promising therapeutic strategy for preserving BBB integrity following ischemic stroke.

Kisspeptin-10 Improves Gestational Diabetes Mellitus Symptoms in Rats by Suppressing Insulin Resistance in Placental Trophoblast Cells by Activating the Cyclic AMP/Protein Kinase A Pathway.

Gestational diabetes mellitus (GDM) is a common pregnancy complication that leads to insulin resistance (IR) and adversely affects both maternal and fetal health. Kisspeptin-10 (Kp-10), a peptide acting via G Protein-Coupled Receptor 54 (Gpr54), has shown potential in modulating insulin secretion, but its role in GDM remains unclear. This study explores Kp-10's therapeutic effects on GDM by targeting IR in placental tissues. We used GDM rat models (induced by a high-fat diet and streptozotocin) and high-glucose-treated HTR8/SVneo trophoblast cells to investigate Kp-10's effects on glucose metabolism, insulin signaling, and the cAMP/PKA pathway. Our results show that Gpr54 expression was significantly downregulated in the placental tissues of GDM rats, which was associated with impaired glucose uptake and IR. Kp-10 treatment improved fasting blood glucose (FBG) levels, insulin sensitivity, and fetal outcomes, including increased fetal weight and decreased fetal blood glucose. Moreover, Kp-10 restored the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway and enhanced glucose uptake by upregulating Glut-4, Insr, and Irs1 expression in both placental tissues and HTR8/SVneo cells. The effects of Kp-10 were reversed by the cAMP inhibitor SQ22536, confirming the involvement of the cAMP/PKA pathway in its anti-IR effects. Our findings suggest that Kp-10 has the potential as a therapeutic agent for alleviating IR in GDM and improving maternal-fetal outcomes.

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.

Kisspeptin-10 Rescues Cholinergic Differentiated SHSY-5Y Cells from &#x3b1;-Synuclein-Induced Toxicity In Vitro.

The neuropathological substrate of dementia with Lewy bodies (DLB) is defined by the inextricable cross-seeding accretion of amyloid-&#x3b2; (A&#x3b2;) and &#x3b1;-synuclein (&#x3b1;-syn)-laden deposits in cholinergic neurons. The recent revelation that neuropeptide kisspeptin-10 (KP-10) is able to mitigate A&#x3b2; toxicity via an extracellular binding mechanism may provide a new horizon for innovative drug design endeavors. Considering the sequence similarities between &#x3b1;-syn's non-amyloid-&#x3b2; component (NAC) and A&#x3b2;'s C-terminus, we hypothesized that KP-10 would enhance cholinergic neuronal resistance against &#x3b1;-syn's deleterious consequences through preferential binding. Here, human cholinergic SH-SY5Y cells were transiently transformed to upsurge the mRNA expression of &#x3b1;-syn while &#x3b1;-syn-mediated cholinergic toxicity was quantified utilizing a standardized viability-based assay. Remarkably, the E46K mutant &#x3b1;-syn displayed elevated &#x3b1;-syn mRNA levels, which subsequently induced more cellular toxicity compared with the wild-type &#x3b1;-syn in choline acetyltransferase (ChAT)-positive cholinergic neurons. Treatment with a high concentration of KP-10 (10 &#xb5;M) further decreased cholinergic cell viability, while low concentrations of KP-10 (0.01-1 &#xb5;M) substantially suppressed wild-type and E46K mutant &#x3b1;-syn-mediated toxicity. Correlating with the in vitro observations are approximations from in silico algorithms, which inferred that KP-10 binds favorably to the C-terminal residues of wild-type and E46K mutant &#x3b1;-syn with CDOCKER energy scores of -118.049 kcal/mol and -114.869 kcal/mol, respectively. Over the course of 50 ns simulation time, explicit-solvent molecular dynamics conjointly revealed that the docked complexes were relatively stable despite small-scale fluctuations upon assembly. Taken together, our findings insinuate that KP-10 may serve as a novel therapeutic scaffold with far-reaching implications for the conceptualization of &#x3b1;-syn-based treatments.

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.

An increase in kisspeptin-54 release occurs with the pubertal increase in luteinizing hormone-releasing hormone-1 release in the stalk-median eminence of female rhesus monkeys in vivo.

The G-protein coupled receptor GPR54 and its ligand, KiSS-1-derived peptide kisspeptin-54, appear to play an important role in the mechanism of puberty. This study measures the release of kisspeptin-54 in the stalk-median eminence (S-ME) during puberty and examines its potential role in the pubertal increase in LHRH-1 release in female rhesus monkeys. First, developmental changes in release of kisspeptin-54 and LHRH-1 were assessed in push-pull perfusate samples obtained from the S-ME of prepubertal, early pubertal, and midpubertal female rhesus monkeys. Whereas LHRH-1 levels in 10-min intervals had been measured previously for other experiments, kisspeptin-54 levels in 40-min pooled samples were newly measured by RIA. The results indicate that a significant increase in kisspeptin-54 release occurred in association with the pubertal increase in LHRH-1 release and that a nocturnal increase in kisspeptin-54 release was already observed in prepubertal monkeys and continued through the pubertal period. Second, we measured kisspeptin-54 release in the S-ME of midpubertal monkeys at 10-min intervals using a microdialysis method. Kisspeptin-54 release in the S-ME was clearly pulsatile with an interpulse interval of about 60 min, and approximately 75% of kisspeptin-54 pulses were correlated with LHRH-1 pulses. Finally, the effect of kisspeptin-10 on LHRH-1 release was examined with the microdialysis method. Kisspeptin-10 infusion through a microdialysis probe significantly stimulated LHRH-1 release in a dose-dependent manner. Collectively, the results are consistent with the hypothesis that kisspeptin plays a role in puberty.

The KiSS-1/GPR54 system: Essential roles in physiological homeostasis and cancer biology.

KiSS-1, first identified as an anti-metastasis gene in melanoma, encodes C-terminally amidated peptide products, including kisspeptin-145, kisspeptin-54, kisspeptin-14, kisspeptin-13 and kisspeptin-10. These products are endogenous ligands coupled to G protein-coupled receptor 54 (GPR54)/hOT7T175/AXOR12. To date, the regulatory activities of the KiSS-1/GPR54 system, such as puberty initiation, antitumor metastasis, fertility in adulthood, hypothalamic-pituitary-gonadal axis (HPG axis) feedback, and trophoblast invasion, have been investigated intensively. Accumulating evidence has demonstrated that KiSS-1 played a key role in reproduction and served as a promising biomarker relative to the diagnosis, identification of therapeutic targets and prognosis in various carcinomas, while few studies have systematically summarized its subjective factors and concluded the functions of KiSS-1/GPR54 signaling in physiology homeostasis and cancer biology. In this review, we retrospectively summarized the regulators of the KiSS-1/GPR54 system in different animal models and reviewed its functions according to physiological homeostasis regulations and above all, cancer biology, which provided us with a profound understanding of applying the KiSS-1/GPR54 system into medical applications.

Synthesis and characterisation of DOTA-kisspeptin-10 as a potential gallium-68/lutetium-177 pan-tumour radiopharmaceutical.

Kisspeptin (KISS1) and its cognate receptor (KISS1R) are implicated in the progression of various cancers. A gallium-68 labelled kisspeptin-10 (KP10), the minimal biologically active structure, has potential as a pan-tumour radiopharmaceutical for the detection of cancers. Furthermore, a lutetium-177 labelled KP10 could find therapeutic application in treating oncological diseases. DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) was attached to the NH2-terminus of KP10 as we posited from our previous publications that this modification would not impair biological activity. Here, we showed that the biological activity, as monitored by stimulation of inositol phosphate accumulation in HEK293 transfected with the KISS1R gene, was indeed similar for KP10 and DOTA-KP10. The optimisation of radiolabelling with gallium-68 and lutetium-177 is described. Stability in serum, plasma and whole blood was also investigated. Pharmacokinetics and biodistribution were established with micro-PET/CT (positron emission tomography/computerised tomography) and ex vivo measurements. Dynamic studies with micro-PET/CT demonstrated that background clearance for the radiopharmaceutical was rapid with a blood half-life of 18&#x2009;&#xb1;&#x2009;3&#x2009;min. DOTA-KP10 demonstrated preserved functionality at KISS1R and good blood clearance. These results lay the foundation for the further development of DOTA-KP10 analogues that have high binding affinity along with proteolytic resistance.

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

Trophoblast invasion of the uterine extracellular matrix, a critical process of human implantation and essential for fetal development, is a striking example of controlled invasiveness. To identify molecules that regulate trophoblast invasion, mRNA signatures of trophoblast cells isolated from first trimester (high invasiveness) and term placentae (no/low invasiveness) were compared using U95A GeneChip microarrays yielding 220 invasion/migration-related genes. In this 'invasion cluster', KiSS-1 and its G-protein-coupled receptor KiSS-1R were expressed at higher levels in first trimester trophoblasts than at term of gestation. Receptor and ligand mRNA and protein were localized to the trophoblast compartment. In contrast to KiSS-1, which is only expressed in the villous trophoblast, KiSS-1R was also found in the extravillous trophoblast, suggesting endocrine/paracrine activation mechanisms. The primary translation product of KiSS-1 is a 145 amino acid polypeptide (Kp-145), but shorter kisspeptins (Kp) with 10, 13, 14 or 54 amino acid residues may be produced. We identified Kp-10, a dekapeptide derived from the primary translation product, in conditioned medium of first trimester human trophoblast. Kp-10, but not other kisspeptins, increased intracellular Ca(2+) levels in isolated first trimester trophoblasts. Kp-10 inhibited trophoblast migration in an explant as well as transwell assay without affecting proliferation. Suppressed motility was paralleled with suppressed gelatinolytic activity of isolated trophoblasts. These results identified Kp-10 as a novel paracrine/endocrine regulator in fine-tuning trophoblast invasion generated by the trophoblast itself.

Kisspeptin regulates airway hyperresponsiveness and remodeling in a mouse model of asthma.

Asthma is a multifactorial disease of origin characterized by airway hyperresponsiveness (AHR) and airway remodeling. Several pieces of evidence from other pathologies suggest that Kisspeptins (Kp) regulate cell proliferation, migration, and invasion, mechanisms that are highly relevant to asthma. Our recent in vitro studies show Kp-10 (active peptide of Kp), via its receptor, KISS1R, inhibits human airway smooth muscle cell proliferation. Here, we hypothesize a crucial role for Kp-10 in regulating AHR and airway remodeling in vivo. Utilizing C57BL/6J mice, we assessed the effect of chronic intranasal Kp-10 exposure on mixed allergen (MA)-induced mouse model of asthma. MA-challenged mice showed significant deterioration of lung function compared to those exposed to vehicle (DPBS); Kp-10 treatment significantly improved the MA-altered lung functions. Mice treated with Kp-10 alone did not show any notable changes in lung functions. MA-exposed mice showed a significant reduction in KISS1R expression as compared to vehicle alone. MA-challenged mice showed significant alterations in immune cell infiltration in the airways and remodeling changes. Proinflammatory cytokines were significantly increased upon MA exposure, an effect abrogated by Kp-10 treatment. Furthermore, biochemical and histological studies showed Kp-10 exposure significantly reduced MA-induced smooth muscle mass and soluble collagen in the lung. Overall, our findings highlight the effect of chronic Kp-10 exposure in regulating MA-induced AHR and remodeling. &#xa9; 2023 The Pathological Society of Great Britain and Ireland.