Growth hormone-releasing hormone antagonist MIA-602 inhibits inflammation induced by SARS-CoV-2 spike protein and bacterial lipopolysaccharide synergism in macrophages and human peripheral blood mononuclear cells.

COVID-19 is characterized by an excessive inflammatory response and macrophage hyperactivation, leading, in severe cases, to alveolar epithelial injury and acute respiratory distress syndrome. Recent studies have reported that SARS-CoV-2 spike (S) protein interacts with bacterial lipopolysaccharide (LPS) to boost inflammatory responses in vitro, in macrophages and peripheral blood mononuclear cells (PBMCs), and in vivo. The hypothalamic hormone growth hormone-releasing hormone (GHRH), in addition to promoting pituitary GH release, exerts many peripheral functions, acting as a growth factor in both malignant and non-malignant cells. GHRH antagonists, in turn, display potent antitumor effects and antinflammatory activities in different cell types, including lung and endothelial cells. However, to date, the antinflammatory role of GHRH antagonists in COVID-19 remains unexplored. Here, we examined the ability of GHRH antagonist MIA-602 to reduce inflammation in human THP-1-derived macrophages and PBMCs stimulated with S protein and LPS combination. Western blot and immunofluorescence analysis revealed the presence of GHRH receptor and its splice variant SV1 in both THP-1 cells and PBMCs. Exposure of THP-1 cells to S protein and LPS combination increased the mRNA levels and protein secretion of TNF-α and IL-1ß, as well as IL-8 and MCP-1 gene expression, an effect hampered by MIA-602. Similarly, MIA-602 hindered TNF-α and IL-1ß secretion in PBMCs and reduced MCP-1 mRNA levels. Mechanistically, MIA-602 blunted the S protein and LPS-induced activation of inflammatory pathways in THP-1 cells, such as NF-κB, STAT3, MAPK ERK1/2 and JNK. MIA-602 also attenuated oxidative stress in PBMCs, by decreasing ROS production, iNOS and COX-2 protein levels, and MMP9 activity. Finally, MIA-602 prevented the effect of S protein and LPS synergism on NF-кB nuclear translocation and activity. Overall, these findings demonstrate a novel antinflammatory role for GHRH antagonists of MIA class and suggest their potential development for the treatment of inflammatory diseases, such as COVID-19 and related comorbidities.

Antagonist of Growth Hormone-Releasing Hormone Potentiates the Antitumor Effect of Pemetrexed and Cisplatin in Pleural Mesothelioma.

Pleural mesothelioma (PM) is an aggressive cancer with poor prognosis and no effective therapies, mainly caused by exposure to asbestos. Antagonists of growth hormone-releasing hormone (GHRH) display strong antitumor effects in many experimental cancers, including lung cancer and mesothelioma. Here, we aimed to determine whether GHRH antagonist MIA-690 potentiates the antitumor effect of cisplatin and pemetrexed in PM. In vitro, MIA-690, in combination with cisplatin and pemetrexed, synergistically reduced cell viability, restrained cell proliferation and enhanced apoptosis, compared with drugs alone. In vivo, the same combination resulted in a strong growth inhibition of MSTO-211H xenografts, decreased tumor cell proliferation and increased apoptosis. Mechanistically, MIA-690, particularly with chemotherapeutic drugs, inhibited proliferative and oncogenic pathways, such as MAPK ERK1/2 and cMyc, and downregulated cyclin D1 and B1 mRNAs. Inflammatory pathways such as NF-kB and STAT3 were also reduced, as well as oxidative, angiogenic and tumorigenic markers (iNOS, COX-2, MMP2, MMP9 and HMGB1) and growth factors (VEGF and IGF-1). Overall, these findings strongly suggest that GHRH antagonists of MIA class, such as MIA-690, could increase the efficacy of standard therapy in PM.

Thermomagnetic Resonance Effect of the Extremely Low Frequency Electromagnetic Field on Three-Dimensional Cancer Models.

In our recent studies, we have developed a thermodynamic biochemical model able to select the resonant frequency of an extremely low frequency electromagnetic field (ELF-EMF) specifically affecting different types of cancer, and we have demonstrated its effects in vitro. In this work, we investigate the cellular response to the ELF electromagnetic wave in three-dimensional (3D) culture models, which mimic the features of tumors in vivo. Cell membrane was modelled as a resistor-capacitor circuit and the specific thermal resonant frequency was calculated and tested on two-dimensional (2D) and three-dimensional (3D) cell cultures of human pancreatic cancer, glioblastoma and breast cancer. Cell proliferation and the transcription of respiratory chain and adenosine triphosphate synthase subunits, as well as uncoupling proteins, were assessed. For the first time, we demonstrate that an ELF-EMF hampers growth and potentiates both the coupled and uncoupled respiration of all analyzed models. Interestingly, the metabolic shift was evident even in the 3D aggregates, making this approach particularly valuable and promising for future application in vivo, in aggressive cancer tissues characterized by resistance to treatments.

Antagonist of growth hormone-releasing hormone MIA-690 attenuates the progression and inhibits growth of colorectal cancer in mice.

Colorectal cancer (CRC) is an aggressive tumor in which new treatment options deliver negative results on cure rates and long-term survival. The anticancer effects of growth hormone-releasing hormone (GHRH) antagonists have been reported in various experimental tumors, but their activity in CRC is unknown. In the present study, we demonstrated that chronic treatment with GHRH antagonist of MIAMI class, MIA-690, promoted survival and gradually blunted tumor progression in experimentally induced colitis-associated cancer in mice, paralleled by reduced inflammation in colon tissue. In particular, MIA-690 improved disease activity index score, and reduced loss of weight and mortality, by improving the survival rates, compared with vehicle-treated group. MIA-690 was also found to reduce various inflammatory and oxidative markers, such as serotonin, prostaglandin (PG)E2 and 8-iso-PGF2α levels, as well as COX-2, iNOS, TNF-α, IL-6 and NF-kB gene expression. Moreover, MIA-690 inhibited the protein expression of c-Myc, P-AKT and Bcl-2 and upregulated p53 protein expression. In conclusion, we showed that MIA-690 suppresses CRC progression and growth by reducing inflammatory and oxidative markers and modulating apoptotic and oncogenic pathways. Further investigations are required for translating these findings into the clinics.

Antagonists of Growth Hormone-Releasing Hormone Inhibit the Growth of Pituitary Adenoma Cells by Hampering Oncogenic Pathways and Promoting Apoptotic Signaling.

Pituitary adenomas (PAs) are intracranial tumors, often associated with excessive hormonal secretion and severe comorbidities. Some patients are resistant to medical therapies; therefore, novel treatment options are needed. Antagonists of growth hormone-releasing hormone (GHRH) exert potent anticancer effects, and early GHRH antagonists were found to inhibit GHRH-induced secretion of pituitary GH in vitro and in vivo. However, the antitumor role of GHRH antagonists in PAs is largely unknown. Here, we show that the GHRH antagonists of MIAMI class, MIA-602 and MIA-690, inhibited cell viability and growth and promoted apoptosis in GH/prolactin-secreting GH3 PA cells transfected with human GHRH receptor (GH3-GHRHR), and in adrenocorticotropic hormone ACTH-secreting AtT20 PA cells. GHRH antagonists also reduced the expression of proteins involved in tumorigenesis and cancer progression, upregulated proapoptotic molecules, and lowered GHRH receptor levels. The combination of MIA-690 with temozolomide synergistically blunted the viability of GH3-GHRHR and AtT20 cells. Moreover, MIA-690 reduced both basal and GHRH-induced secretion of GH and intracellular cAMP levels. Finally, GHRH antagonists inhibited cell viability in human primary GH- and ACTH-PA cell cultures. Overall, our results suggest that GHRH antagonists, either alone or in combination with pharmacological treatments, may be considered for further development as therapy for PAs.

Protective effects of growth hormone-releasing hormone analogs in DSS-induced colitis in mice.

Besides its metabolic and endocrine effects, growth hormone (GH)-releasing hormone (GHRH) is involved in the modulation of inflammation. Recently synthetized GHRH antagonist MIA-690 and MR-409, GHRH agonist, developed by us have shown potent pharmacological effects in various experimental paradigms. However, whether their administration modify resistance to chronic inflammatory stimuli in colon is still unknown. Ex vivo results demonstrated that MIA-690 and MR-409 inhibited production of pro-inflammatory and oxidative markers induced by lipopolysaccharide on isolated mouse colon specimens. In vivo, both MIA-690 and MR-409 have also been able to decrease the responsiveness to nociceptive stimulus, in hot plate test. Additionally, both peptides also induced a decreased sensitivity to acute and persistent inflammatory stimuli in male mice, in formalin test and dextran sodium sulfate (DSS)-induced colitis model, respectively. MIA-690 and MR-409 attenuate DSS-induced colitis with particular regard to clinical manifestations, histopathological damage and release of pro-inflammatory and oxidative markers in colon specimens. Respect to MR-409, MIA-690 showed higher efficacy in inhibiting prostaglandin (PG)E2, 8-iso-PGF2α and serotonin (5-HT) levels, as well as tumor necrosis factor (TNF)-α, interleukin (IL)-6 and nitric oxide synthase gene expression in colon specimens of DSS-induced colitis. Furthermore, MIA-690 decreased serum insulin-like growth factor (IGF)-1 levels in mice DSS-treated, respect to MR-409. Thus, our findings highlight the protective effects of MIA-690 and MR-409 on inflammation stimuli. The higher antinflammatory and antioxidant activities observed with MIA-690 could be related to decreased serum IGF-1 levels.

Calcitriol Inhibits Viability and Proliferation in Human Malignant Pleural Mesothelioma Cells.

Malignant pleural mesothelioma (MPM) is a rare and aggressive tumor, often associated with exposure to asbestos and characterized by poor prognosis and limited treatment options. The biologically active form of vitamin D, calcitriol, exerts anticancer effects in many cell types, both alone and in combination with chemotherapy drugs, through binding to vitamin D receptor (VDR); however, the role of calcitriol in MPM is still unknown. This study aimed to determine the potential antitumor role of calcitriol in MPM. The results showed that calcitriol reduces cell viability and proliferation in human MPM cells lines, which express both cytoplasmic and nuclear VDR; furthermore, calcitriol potentiated the inhibitory activity of the chemotherapy drug PEM. These effects were paralleled by cell cycle arrest and inhibition in expression of c-Myc and cyclins involved in cell cycle progression. Exposure of MPM cells to calcitriol also produced an alteration in mitochondrial function and inhibition in the expression of respiratory chain complex subunits. Finally, the inhibitory effects of calcitriol were also observed on viability of human primary MPM cells. Collectively, these results indicate a novel anticancer role for calcitriol in MPM, suggesting potential for vitamin D derivatives, alone or in combination with chemotherapy, in the treatment of this malignancy.

Statins Directly Regulate Pituitary Cell Function and Exert Antitumor Effects in Pituitary Tumors.

INTRODUCTION: Pituitary neuroendocrine tumors (PitNETs), the most abundant of all intracranial tumors, entail severe comorbidities. First-line therapy is transsphenoidal surgery, but subsequent pharmacological therapy is often required. Unfortunately, many patients are/become unresponsive to available drugs (somatostatin analogues [SSAs]/dopamine agonists), underscoring the need for new therapies. Statins are well-known drugs commonly prescribed to treat hyperlipidemia/cardiovascular diseases, but can convey additional beneficial effects, including antitumor actions. The direct effects of statins on normal human pituitary or PitNETs are poorly known. Thus, we aimed to explore the direct effects of statins, especially simvastatin, on key functional parameters in normal and tumoral pituitary cells, and to evaluate the combined effects of simvastatin with metformin (MF) or SSAs. METHODS: Effects of statins in cell proliferation/viability, hormone secretion, and signaling pathways were evaluated in normal pituitary cells from a primate model (Papio anubis), tumor cells from corticotropinomas, somatotropinomas, nonfunctioning pituitary tumors, and PitNET cell-lines (AtT20/GH3-cells). RESULTS: All statins decreased AtT20-cell proliferation, simvastatin showing stronger effects. Indeed, simvastatin reduced cell viability and/or hormone secretion in all PitNETs subtypes and cell-lines, and ACTH/GH/PRL/FSH/LH secretion (but not expression), in primate cell cultures, by modulating MAPK/PI3K/mTOR pathways and expression of key receptors (GH-releasing hormone-receptor/ghrelin-R/Kiss1-R) regulating pituitary function. Addition of MF or SSAs did not enhance simvastatin antitumor effects. CONCLUSION: Our data reveal direct antitumor effects of simvastatin on PitNET-cells, paving the way to explore these compounds as a possible tool to treat PitNETs.

Antinflammatory, antioxidant, and behavioral effects induced by administration of growth hormone-releasing hormone analogs in mice.

Growth hormone-releasing hormone (GHRH) antagonist MIA-690 and GHRH agonist MR-409, previously synthesized and developed by us have demonstrated potent antitumor effects. However, little is known about the effects of these analogs on brain functions. We investigated the potential antinflammatory and antioxidant effects of GHRH antagonist MIA-690 and GHRH agonist MR-409, on isolated mouse prefrontal cortex specimens treated with lipopolysaccharide (LPS). Additionally, we studied their effects on emotional behavior after chronic in vivo treatment. Ex vivo, MIA-690 and MR-409 inhibited LPS-induced inflammatory and pro-oxidative markers. In vivo, both MIA-690 and MR-409 induced anxiolytic and antidepressant-like effects, increased norepinephrine and serotonin levels and decreased nuclear factor-kB, tumor necrosis factor-α and interleukin-6 gene expression in prefrontal cortex. Increased nuclear factor erythroid 2-related factor 2 expression was also found in mice treated with MIA-690 and MR-409. MIA-690 showed higher efficacy in inhibiting all tested inflammatory and oxidative markers. In addition, MR-409 induced a down regulation of the gene and protein expression of pituitary-type GHRH-receptor in prefrontal cortex of mice after 4 weeks of treatment at 5 µg/day. In conclusion, our results demonstrate anxiolytic and antidepressant-like effects of GHRH analogs that could involve modulatory effects on monoaminergic signaling, inflammatory and oxidative status.

The extremely low frequency electromagnetic stimulation selective for cancer cells elicits growth arrest through a metabolic shift.

The efficacy of the very low frequency electromagnetic field in cancer treatment remains elusive due to a lack of explanatory mechanisms for its effect. We developed a novel thermodynamic model that calculates for every cell type the frequency capable of inhibiting proliferation. When this frequency was applied to two human cancer cell lines, it reduced their growth while not affecting healthy cells. The effect was abolished by the inhibition of calcium fluxes. We found evidences of an enhanced respiratory activity due to the increased expression of the elements of the respiratory chain and oxidative phosphorylation, both at the mRNA and protein level. The respiratory burst potentiated the production of reactive oxygen species but was not associated to increased levels of ATP, leading to the conclusion that the energy was readily spent in the adaptive response to the electromagnetic field. Taken together, our data demonstrate that, regardless of individual molecular defects, it is possible to control cancer cells with a specific irradiation that imposes a mitochondrial metabolic switch, regulating calcium fluxes and deleterious to cancer growth. This approach lays the foundations for a personalized cancer medicine.

Actions and Potential Therapeutic Applications of Growth Hormone-Releasing Hormone Agonists.

In this article, we briefly review the identification of GHRH, provide an abridged overview of GHRH antagonists, and focus on studies with GHRH agonists. Potent GHRH agonists of JI and MR class were synthesized and evaluated biologically. Besides the induction of the release of pituitary GH, GHRH analogs promote cell proliferation and exert stimulatory effects on various tissues, which express GHRH receptors (GHRH-Rs). A large body of work shows that GHRH agonists, such as MR-409, improve pancreatic ß-cell proliferation and metabolic functions and facilitate engraftment of islets after transplantation in rodents. Accordingly, GHRH agonists offer a new therapeutic approach to treating diabetes. Various studies demonstrate that GHRH agonists promote repair of cardiac tissue, producing improvement of ejection fraction and reduction of infarct size in rats, reduction of infarct scar in swine, and attenuation of cardiac hypertrophy in mice, suggesting clinical applications. The presence of GHRH-Rs in ocular tissues and neuroprotective effects of GHRH analogs in experimental diabetic retinopathy indicates their possible therapeutic applications for eye diseases. Other effects of GHRH agonists, include acceleration of wound healing, activation of immune cells, and action on the central nervous system. As GHRH might function as a growth factor, we examined effects of GHRH agonists on tumors. In vitro, GHRH agonists stimulate growth of human cancer cells and upregulate GHRH-Rs. However, in vivo, GHRH agonists inhibit growth of human cancers xenografted into nude mice and downregulate pituitary and tumoral GHRH-Rs. Therapeutic applications of GHRH analogs are discussed. The development of GHRH analogs should lead to their clinical use.

Proton pump inhibitors promote the growth of androgen-sensitive prostate cancer cells through ErbB2, ERK1/2, PI3K/Akt, GSK-3ß signaling and inhibition of cellular prostatic acid phosphatase.

Prostate cancer (PCa) is one of the most common cancer in men. Although hormone-sensitive PCa responds to androgen-deprivation, there are no effective therapies for castration-resistant PCa. It has been recently suggested that proton pump inhibitors (PPIs) may increase the risk of certain cancers; however, association with PCa remains elusive. Here, we evaluated the tumorigenic activities of PPIs in vitro, in PCa cell lines and epithelial cells from benign prostatic hyperplasia (BPH) and in vivo, in PCa mice xenografts. PPIs increased survival and proliferation, and inhibited apoptosis in LNCaP cells. These effects were attenuated or absent in androgen-insensitive DU-145 and PC3 cells, respectively. Specifically, omeprazole (OME) promoted cell cycle progression, increased c-Myc expression, ErbB2 activity and PSA secretion. Furthermore, OME induced the phosphorylation of MAPK-ERK1/2, PI3K/Akt and GSK-3ß, and blunted the expression and activity of cellular prostatic acid phosphatase. OME also increased survival, proliferation and PSA levels in BPH cells. In vivo, OME promoted tumor growth in mice bearing LNCaP xenografts. Our results indicate that PPIs display tumorigenic activities in PCa cells, suggesting that their long-term administration in patients should be carefully monitored.

Antagonists of growth hormone-releasing hormone (GHRH) inhibit the growth of human malignant pleural mesothelioma.

Malignant pleural mesothelioma (MPM) is an aggressive malignancy associated with exposure to asbestos, with poor prognosis and no effective therapies. The strong inhibitory activities of growth hormone-releasing hormone (GHRH) antagonists have been demonstrated in different experimental human cancers, including lung cancer; however, their role in MPM remains unknown. We assessed the effects of the GHRH antagonists MIA-602 and MIA-690 in vitro in MPM cell lines and in primary MPM cells, and in vivo in MPM xenografts. GHRH, GHRH receptor, and its main splice variant SV1 were found in all the MPM cell types examined. In vitro, MIA-602 and MIA-690 reduced survival and proliferation in both MPM cell lines and primary cells and showed synergistic inhibitory activity with the chemotherapy drug pemetrexed. In MPM cells, GHRH antagonists also regulated activity and expression of apoptotic molecules, inhibited cell migration, and reduced the expression of matrix metalloproteinases. These effects were accompanied by impairment of mitochondrial activity and increased production of reactive oxygen species. In vivo, s.c. administration of MIA-602 and MIA-690 at the dose of 5 µg/d for 4 wk strongly inhibited the growth of MPM xenografts in mice, along with reduction of tumor insulin-like growth factor-I and vascular endothelial growth factor. Overall, these results suggest that treatment with GHRH antagonists, alone or in association with chemotherapy, may offer an approach for the treatment of MPM.

A Linear Fragment of Unacylated Ghrelin (UAG6-13) Protects Against Myocardial Ischemia/Reperfusion Injury in Mice in a Growth Hormone Secretagogue Receptor-Independent Manner.

Unacylated ghrelin (UAG), the most abundant form of ghrelin in circulation, has been shown to exert cardioprotective effect in experimental cardiopathies. The present study aimed to investigate the cardioprotective effect of a linear bioactive fragment of UAG against myocardial ischemia-induced injury and dysfunction in C57BL/6 wild type mice and the mechanisms involved. Treatments were administered at doses of 100 (UAG), 1,000 and 3,000 (UAG6-13) nmol/kg at 12 h interval during 14 days prior to 30 min left coronary artery ligation and reperfusion for a period of 6 or 48 h. The infarct area was decreased in a dose-dependent manner at 48 h of reperfusion, with a reduction of 54% at the highest dose of UAG6-13 tested. Myocardial hemodynamics were improved as demonstrated by an increase in cardiac output, maximum first derivative of left ventricular pressure, and preload recruitable stroke work, a load-independent contractility index. Six hours after reperfusion, circulating levels of IL-6 and TNF-α pro-inflammatory cytokines were reduced, and the effect was maintained at 48 h for TNF-α. 5' AMP-activated protein kinase (AMPK) was activated, while acetyl-CoA carboxylase (ACC) activity was inhibited, along with a decrease in apoptotic protein levels. In isolated hearts, the effect of UAG6-13 was unaffected by the presence of D-Lys3-GHRP-6, a ghrelin receptor (GHSR1a) antagonist, suggesting that the peptide acted through a GHSR1a-independent pathway. The results support the therapeutic application of UAG bioactive peptide fragments against myocardial ischemia/reperfusion injury.

Growth hormone-releasing hormone attenuates cardiac hypertrophy and improves heart function in pressure overload-induced heart failure.

It has been shown that growth hormone-releasing hormone (GHRH) reduces cardiomyocyte (CM) apoptosis, prevents ischemia/reperfusion injury, and improves cardiac function in ischemic rat hearts. However, it is still not known whether GHRH would be beneficial for life-threatening pathological conditions, like cardiac hypertrophy and heart failure (HF). Thus, we tested the myocardial therapeutic potential of GHRH stimulation in vitro and in vivo, using GHRH or its agonistic analog MR-409. We show that in vitro, GHRH(1-44)NH2 attenuates phenylephrine-induced hypertrophy in H9c2 cardiac cells, adult rat ventricular myocytes, and human induced pluripotent stem cell-derived CMs, decreasing expression of hypertrophic genes and regulating hypertrophic pathways. Underlying mechanisms included blockade of Gq signaling and its downstream components phospholipase Cß, protein kinase Cε, calcineurin, and phospholamban. The receptor-dependent effects of GHRH also involved activation of Gαs and cAMP/PKA, and inhibition of increase in exchange protein directly activated by cAMP1 (Epac1). In vivo, MR-409 mitigated cardiac hypertrophy in mice subjected to transverse aortic constriction and improved cardiac function. Moreover, CMs isolated from transverse aortic constriction mice treated with MR-409 showed improved contractility and reversal of sarcolemmal structure. Overall, these results identify GHRH as an antihypertrophic regulator, underlying its therapeutic potential for HF, and suggest possible beneficial use of its analogs for treatment of pathological cardiac hypertrophy.

Role of Melatonin, Galanin, and RFamide Neuropeptides QRFP26 and QRFP43 in the Neuroendocrine Control of Pancreatic ß-Cell Function.

Glucose homeostasis is finely regulated by a number of hormones and peptides released mainly from the brain, gastrointestinal tract, and muscle, regulating pancreatic secretion through cellular receptors and their signal transduction cascades. The endocrine function of the pancreas is controlled by islets within the exocrine pancreatic tissue that release hormones like insulin, glucagon, somatostatin, pancreatic polypeptide, and ghrelin. Moreover, both exocrine and endocrine pancreatic functions are regulated by a variety of hormonal and neural mechanisms, such as ghrelin, glucagon-like peptide, glucose-dependent insulinotropic polypeptide, or the inhibitory peptide somatostatin. In this review, we describe the role of neurohormones that have been less characterized compared to others, on the regulation of insulin secretion. In particular, we will focus on melatonin, galanin, and RFamide neuropeptides QRFP26 and QRFP43, which display either insulinotropic or insulinostatic effects. In fact, in addition to other hormones, amino acids, cytokines, and a variety of proteins, brain-derived hormones are now considered as key regulators of glucose homeostasis, representing potential therapeutic targets for the treatment of diabetes and obesity.

Obestatin regulates cardiovascular function and promotes cardioprotection through the nitric oxide pathway.

Patients with ischaemic heart disease or chronic heart failure show altered levels of obestatin, suggesting a role for this peptide in human heart function. We have previously demonstrated that GH secretagogues and the ghrelin gene-derived peptides, including obestatin, exert cardiovascular effects by modulating cardiac inotropism and vascular tone, and reducing cell death and contractile dysfunction in hearts subjected to ischaemia/reperfusion (I/R), through the Akt/nitric oxide (NO) pathway. However, the mechanisms underlying the cardiac actions of obestatin remain largely unknown. Thus, we suggested that obestatin-induced activation of PI3K/Akt/NO and PKG signalling is implicated in protection of the myocardium when challenged by adrenergic, endothelinergic or I/R stress. We show that obestatin exerts an inhibitory tone on the performance of rat papillary muscle in both basal conditions and under ß-adrenergic overstimulation, through endothelial-dependent NO/cGMP/PKG signalling. This pathway was also involved in the vasodilator effect of the peptide, used both alone and under stress induced by endothelin-1. Moreover, when infused during early reperfusion, obestatin reduced infarct size in isolated I/R rat hearts, through an NO/PKG pathway, comprising ROS/PKC signalling, and converging on mitochondrial ATP-sensitive potassium [mitoK(ATP)] channels. Overall, our results suggest that obestatin regulates cardiovascular function in stress conditions and induces cardioprotection by mechanisms dependent on activation of an NO/soluble guanylate cyclase (sGC)/PKG pathway. In fact, obestatin counteracts exaggerated ß-adrenergic and endothelin-1 activity, relevant factors in heart failure, suggesting multiple positive effects of the peptide, including the lowering of cardiac afterload, thus representing a potential candidate in pharmacological post-conditioning.

The Arg-Phe-amide peptide 26RFa/glutamine RF-amide peptide and its receptor: IUPHAR Review 24.

The RFamide neuropeptide 26RFa was first isolated from the brain of the European green frog on the basis of cross-reactivity with antibodies raised against bovine neuropeptide FF (NPFF). 26RFa and its N-terminally extended form glutamine RF-amide peptide (QRFP) have been identified as cognate ligands of the former orphan receptor GPR103, now renamed glutamine RF-amide peptide receptor (QRFP receptor). The 26RFa/QRFP precursor has been characterized in various mammalian and non-mammalian species. In the brain of mammals, including humans, 26RFa/QRFP mRNA is almost exclusively expressed in hypothalamic nuclei. The 26RFa/QRFP transcript is also present in various organs especially in endocrine glands. While humans express only one QRFP receptor, two isoforms are present in rodents. The QRFP receptor genes are widely expressed in the CNS and in peripheral tissues, notably in bone, heart, kidney, pancreas and testis. Structure-activity relationship studies have led to the identification of low MW peptidergic agonists and antagonists of QRFP receptor. Concurrently, several selective non-peptidic antagonists have been designed from high-throughput screening hit optimization. Consistent with the widespread distribution of QRFP receptor mRNA and 26RFa binding sites, 26RFa/QRFP exerts a large range of biological activities, notably in the control of energy homeostasis, bone formation and nociception that are mediated by QRFP receptor or NPFF2. The present report reviews the current knowledge concerning the 26RFa/QRFP-QRFP receptor system and discusses the potential use of selective QRFP receptor ligands for therapeutic applications.

Obestatin promotes proliferation and survival of adult hippocampal progenitors and reduces amyloid-ß-induced toxicity.

The ghrelin gene-derived peptide obestatin promotes survival in different cell types through a yet undefined receptor; however, its potential neuroprotective activities are still unknown. Here, obestatin effects were investigated on proliferation and survival of adult rat hippocampal progenitor cells (AHPs). Obestatin immunoreactivity was found in AHPs; moreover, obestatin binding to AHPs was displaced by the GLP-1R agonist Ex-4 and antagonist Ex-9. Furthermore, obestatin increased cell proliferation and survival in growth factor deprived medium and inhibited apoptosis; these effects were blocked by Ex-9. The underlying mechanisms involved Gαs/cAMP/PKA/CREB signaling, phosphorylation of ERK1/2 and PI3K/Akt, and the PI3K targets GSK-3ß/ß-catenin and mTOR. Obestatin also counteracted Aß1-42-induced detrimental effects through inhibition of GSK-3ß activity and Tau hyperphosphorylation, main hallmarks of neuronal death in Alzheimer's disease. These findings indicate a novel protective role for obestatin in AHPs and candidate this peptide as potential therapeutic target for increasing neurogenesis and for approaching neurodegenerative disorders.