Publications by authors named "Laurence Desrues"

23 Publications

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Stabilization Strategies for Linear Minigastrin Analogues: Further Improvements the Inclusion of Proline into the Peptide Sequence.

J Med Chem 2020 12 23;63(23):14668-14679. Epub 2020 Nov 23.

Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria.

Minigastrin (MG) analogues, known for their high potential to target cholecystokinin-2 receptor (CCK2R) expressing tumors, have limited clinical applicability due to low enzymatic stability. By introducing site-specific substitutions within the C-terminal receptor-binding sequence, reduced metabolization and improved tumor targeting can be achieved. In this work, the influence of additional modification within the N-terminal sequence has been explored. Three novel 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated CCK2R ligands with proline substitution at different positions were synthesized. Substitution did not affect CCK2R affinity, and the conjugates labeled with indium-111 and lutetium-177 showed a high enzymatic stability in different incubation media as well as (57-79% intact radiopeptide in blood of BALB/c mice at 1 h p.i.) combined with enhanced tumor uptake (29-46% IA/g at 4 h in xenografted BALB/c nude mice). The inclusion of Pro contributes significantly to the development of CCK2R ligands with optimal targeting properties for application in targeted radiotherapy.
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http://dx.doi.org/10.1021/acs.jmedchem.0c01233DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7734625PMC
December 2020

Development of Novel -In-Labelled DOTA Urotensin II Analogues for Targeting the UT Receptor Overexpressed in Solid Tumours.

Biomolecules 2020 03 19;10(3). Epub 2020 Mar 19.

Institute for Research and Innovation in Biomedicine (IRIB), University of Rouen Normandy, INSERM U1239, DC2N, Rouen, France, 76000 Rouen, France.

Overexpression of G protein-coupled receptors (GPCRs) in tumours is widely used to develop GPCR-targeting radioligands for solid tumour imaging in the context of diagnosis and even treatment. The human vasoactive neuropeptide urotensin II (hUII), which shares structural analogies with somatostatin, interacts with a single high affinity GPCR named UT. High expression of UT has been reported in several types of human solid tumours from lung, gut, prostate, or breast, suggesting that UT is a valuable novel target to design radiolabelled hUII analogues for cancer diagnosis. In this study, two original urotensinergic analogues were first conjugated to a DOTA chelator via an aminohexanoic acid (Ahx) hydrocarbon linker and then -hUII and DOTA-urantide, complexed to the radioactive metal indium isotope to successfully lead to radiolabelled DOTA-Ahx-hUII and DOTA-Ahx-urantide. The In-DOTA-hUII in human plasma revealed that only 30% of the radioligand was degraded after a 3-h period. DOTA-hUII and DOTA-urantide exhibited similar binding affinities as native peptides and relayed calcium mobilization in HEK293 cells expressing recombinant human UT. DOTA-hUII, not DOTA-urantide, was able to promote UT internalization in UT-expressing HEK293 cells, thus indicating that radiolabelled In-DOTA-hUII would allow sufficient retention of radioactivity within tumour cells or radiolabelled DOTA-urantide may lead to a persistent binding on UT at the plasma membrane. The potential of these radioligands as candidates to target UT was investigated in adenocarcinoma. We showed that hUII stimulated the migration and proliferation of both human lung A549 and colorectal DLD-1 adenocarcinoma cell lines endogenously expressing UT. In vivo intravenous injection of In-DOTA-hUII in C57BL/6 mice revealed modest organ signals, with important retention in kidney. In-DOTA-hUII or In-DOTA-urantide were also injected in nude mice bearing heterotopic xenografts of lung A549 cells or colorectal DLD-1 cells both expressing UT. The observed significant renal uptake and low tumour/muscle ratio (around 2.5) suggest fast tracer clearance from the organism. Together, DOTA-hUII and DOTA-urantide were successfully radiolabelled with Indium, the first one functioning as a UT agonist and the second one as a UT-biased ligand/antagonist. To allow tumour-specific targeting and prolong body distribution in preclinical models bearing some solid tumours, these radiolabelled urotensinergic analogues should be optimized for being used as potential molecular tools for diagnosis imaging or even treatment tools.
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http://dx.doi.org/10.3390/biom10030471DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7175314PMC
March 2020

Urantide Improves Cardiac Function, Modulates Systemic Cytokine Response, and Increases Survival in A Murine Model of Endotoxic Shock.

Shock 2020 10;54(4):574-582

Department of Anesthesiology and Critical Care, Rouen University Hospital, Rouen, France.

Introduction: Urotensin II is a potent vasoactive peptide activating the the G protein-coupled urotensin II receptor UT, and is involved in systemic inflammation and cardiovascular functions. The aim of our work was to study the impact of the UT antagonist urantide on survival, systemic inflammation, and cardiac function during endotoxic shock.

Methods: C57Bl/6 mice were intraperitoneally injected with lipopolysaccharide (LPS) and then randomized to be injected either by urantide or NaCl 0.9% 3, 6, and 9 h (H3, H6, H9) after LPS. The effect of urantide on the survival rate, the levels of cytokines in plasma at H6, H9, H12, the expression level of nuclear factor-kappa B (NF-κB-p65) in liver and kidney (at H12), and the cardiac function by trans-thoracic echocardiography from H0 to H9 was evaluated.

Results: Urantide treatment improved survival (88.9% vs. 30% on day 6, P < 0.05). This was associated with changes in cytokine expression: a decrease in IL-6 (2,485 [2,280-2,751] pg/mL vs. 3,330 [3,119-3,680] pg/mL, P < 0.01) at H6, in IL-3 (1.0 [0.40-2.0] pg/mL vs. 5.8 [3.0-7.7] pg/mL, P < 0.01), and IL-1β (651 [491-1,135] pg/mL vs. 1,601 [906-3,010] pg/mL, P < 0.05) at H12 after LPS administration. Urantide decreased the proportion of cytosolic NF-κB-p65 in liver (1.3 [0.9-1.9] vs. 3.2 [2.3-4], P < 0.01) and kidney (0.3 [0.3-0.4] vs. 0.6 [0.5-1.1], P < 0.01). Urantide improved cardiac function (left ventricular fractional shortening: 24.8 [21.5-38.9] vs. 12.0 [8.7-17.6] %, P < 0.01 and cardiac output: 30.3 [25.9-39.8] vs. 15.1 [13.0-16.9] mL/min, P < 0.0001).

Conclusion: These results show a beneficial curative role of UT antagonism on cytokine response (especially IL-3), cardiac dysfunction, and survival during endotoxic shock in mice, highlighting a potential new therapeutic target for septic patients.
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http://dx.doi.org/10.1097/SHK.0000000000001448DOI Listing
October 2020

Association between vasoactive peptide urotensin II in plasma and cerebral vasospasm after aneurysmal subarachnoid hemorrhage: a potential therapeutic target.

J Neurosurg 2018 Oct 1:1-11. Epub 2018 Oct 1.

1Normandie Université, UNIROUEN, INSERM, DC2N.

OBJECTIVECerebral vasospasm (VS) is a severe complication of aneurysmal subarachnoid hemorrhage (SAH). Urotensin II (UII) is a potent vasoactive peptide activating the urotensin (UT) receptor, potentially involved in brain vascular pathologies. The authors hypothesized that UII/UT system antagonism with the UT receptor antagonist/biased ligand urantide may be associated with post-SAH VS. The objectives of this study were 2-fold: 1) to leverage an experimental mouse model of SAH with VS in order to study the effect of urotensinergic system antagonism on neurological outcome, and 2) to investigate the association between plasma UII level and symptomatic VS after SAH in human patients.METHODSA mouse model of SAH was used to study the impacts of UII and the UT receptor antagonist/biased ligand urantide on VS and neurological outcome. Then a clinical study was conducted in the setting of a neurosurgical intensive care unit. Plasma UII levels were measured in SAH patients daily for 9 days, starting on the 1st day of hospitalization, and were compared with plasma UII levels in healthy volunteers.RESULTSIn the mouse model, urantide prevented VS as well as SAH-related fine motor coordination impairment. Seventeen patients with SAH and external ventricular drainage were included in the clinical study. The median plasma UII level was 43 pg/ml (IQR 14-80 pg/ml). There was no significant variation in the daily median plasma UII level (median value for the 17 patients) from day 0 to day 8. The median level of plasma UII during the 9 first days post-SAH was higher in patients with symptomatic VS than in patients without VS (77 pg/ml [IQR 33.5-111.5 pg/ml] vs 37 pg/ml [IQR 21-46 pg/ml], p < 0.05). Concerning daily measures of plasma UII levels in VS, non-VS patients, and healthy volunteers, we found a significant difference between SAH patients with VS (median 66 pg/ml [IQR 30-110 pg/ml]) and SAH patients without VS (27 pg/ml [IQR 15-46 pg/ml], p < 0.001) but no significant difference between VS patients and healthy volunteers (44 pg/ml [IQR 27-51 pg/ml]) or between non-VS patients and healthy volunteers.CONCLUSIONSThe results of this study suggest that UT receptor antagonism with urantide prevents VS and improves neurological outcome after SAH in mice and that an increase in plasma UII is associated with cerebral VS subsequent to SAH in humans. The causality link between circulating UII and VS after SAH remains to be established, but according to our data the UT receptor is a potential therapeutic target in SAH.
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http://dx.doi.org/10.3171/2018.4.JNS172313DOI Listing
October 2018

Sexual Disorders of Patients With Metastatic Renal Cell Carcinoma (mRCC) Treated With Antiangiogenic Therapies.

Clin Genitourin Cancer 2018 10 21;16(5):369-375.e1. Epub 2018 May 21.

U1086 INSERM-UCBN "Cancers & Préventions", Normandie Université, Caen, France; Departments of Clinical Research Unit, Centre François Baclesse, Caen, France; Department of Medical Oncology, Centre François Baclesse, Caen, France. Electronic address:

Background: Targeted therapies, in particular antiangiogenic therapies (AATs), have become the standard of treatment for metastatic renal cell carcinoma (mRCC). Although common adverse effects like fatigue have been well-established, sexual disorders induced by these treatments, although often reported, have been poorly evaluated. The aim of this study was to evaluate the impact of AATs on the sexual life of patients with mRCC and the relationships with quality of life (QoL), fatigue, and biologic parameters.

Patients And Methods: This longitudinal study included patients with mRCC on first- or second-line AATs. Sexuality was evaluated by the French version of Changes in Sexual Functioning Questionnaire short-Form (CSFQ); QoL and fatigue were measured by the Functional Assessment of Cancer Therapy General (FACT-G) and the Multidimensional Fatigue Inventory (MFI-20), respectively. Biologic parameters were also assessed.

Results: Among 75 patients included in the study, 39 agreed to respond to the sexual functioning questionnaire (CSFQ). At baseline, all patients had at least 1 sexual dysfunction. No relationship with QoL, fatigue, and biologic parameters was shown. After 3 months of treatment, a decrease in at least 1 sexual dimension was observed in 69% of patients. The most affected sexual dimensions were pleasure (34%) and desire/interest (38%). No significant relationship between sexual dysfunctions and biologic parameters was found. The percentage of non-participants (50%) and the absence of a control arm are the main limitations.

Discussion: Patients with mRCC exhibit sexual dysfunction that could be increased by AATs independently of the impact on fatigue and QoL. Further studies aiming to define the role of biologic parameters like inflammatory markers and thyroid parameters are warranted.

Conclusion: Sexual disorders induced or degraded by AAT are an independent side effect that should be taken into account in oncology supportive care departments.
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http://dx.doi.org/10.1016/j.clgc.2018.05.013DOI Listing
October 2018

Prospective Evaluation of the Impact of Antiangiogenic Treatment on Cognitive Functions in Metastatic Renal Cancer.

Eur Urol Focus 2016 Dec 17;2(6):642-649. Epub 2016 May 17.

Department of Medical Oncology, Institut Gustave Roussy, Villejuif, France.

Background: Little is known about the cognitive effects of antiangiogenic therapies (AATs) in metastatic renal cell carcinoma (mRCC) and their relation with fatigue.

Objective: To evaluate the impact of AATs on cognition and its connection with fatigue and quality of life (QoL) in patients with mRCC.

Design, Setting, And Participants: This prospective study enrolled 75 patients starting AAT as first or second line for mRCC and assessed them at 3 mo (n=58) and 6 mo (n=50).

Outcome Measurements And Statistical Analysis: We assessed objective cognitive decline with a neuropsychological battery of tests and cognitive complaint, fatigue, and QoL with validated self-reported questionnaires using the Fisher exact test, Wilcoxon test, and Spearman correlation coefficient.

Results And Limitations: A decline of cognitive functions was observed in 18 patients (31%) including 13 without cognitive impairment at baseline. The score of fatigue was increased in all patients except one. A relationship between cognitive complaints and fatigue was observed (p<0.05) but not with objective cognitive decline. Cognitive complaints and fatigue had a significant impact on most of the domains of QoL (p<0.01). A positive correlation was found between fatigue and inflammatory markers but not with cognition. The main limitation of this study is the absence of a control group.

Conclusions: AAT induced cognitive decline in patients with mRCC independently of fatigue. These side effects affecting QoL should be better assessed in clinical trials and taken into account in routine practice.

Patient Summary: Fatigue is a well-known effect of antiangiogenic therapies (AATs) of cancer. The study performed in patients with treated metastatic renal cancer shows a decline of cognitive functions induced by AATs, such as information-processing speed or working memory, in a third of patients, independently of fatigue. Patients on AATs should be informed of these possible adverse effects.
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http://dx.doi.org/10.1016/j.euf.2016.04.009DOI Listing
December 2016

The G Protein-Coupled Receptor UT of the Neuropeptide Urotensin II Displays Structural and Functional Chemokine Features.

Front Endocrinol (Lausanne) 2017 25;8:76. Epub 2017 Apr 25.

Normandie University, UNIROUEN, INSERM, DC2N, Rouen, France.

The urotensinergic system was previously considered as being linked to numerous physiopathological states, including atherosclerosis, heart failure, hypertension, pre-eclampsia, diabetes, renal disease, as well as brain vascular lesions. Thus, it turns out that the actions of the urotensin II (UII)/G protein-coupled receptor UT system in animal models are currently not predictive enough in regard to their effects in human clinical trials and that UII analogs, established to target UT, were not as beneficial as expected in pathological situations. Thus, many questions remain regarding the overall signaling profiles of UT leading to complex involvement in cardiovascular and inflammatory responses as well as cancer. We address the potential UT chemotactic structural and functional definition under an evolutionary angle, by the existence of a common conserved structural feature among chemokine receptorsopioïdergic receptors and UT, i.e., a specific proline position in the transmembrane domain-2 TM2 (P2.58) likely responsible for a kink helical structure that would play a key role in chemokine functions. Even if the last decade was devoted to the elucidation of the cardiovascular control by the urotensinergic system, we also attempt here to discuss the role of UII on inflammation and migration, likely providing a peptide chemokine status for UII. Indeed, our recent work established that activation of UT by a gradient concentration of UII recruits Gαi/o and Gα13 couplings in a spatiotemporal way, controlling key signaling events leading to chemotaxis. We think that this new vision of the urotensinergic system should help considering UT as a chemotactic therapeutic target in pathological situations involving cell chemoattraction.
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http://dx.doi.org/10.3389/fendo.2017.00076DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5403833PMC
April 2017

Chemotactic G protein-coupled receptors control cell migration by repressing autophagosome biogenesis.

Autophagy 2016 12 7;12(12):2344-2362. Epub 2016 Oct 7.

a Normandie Univ, UNIROUEN, INSERM, DC2N , Rouen , France.

Chemotactic migration is a fundamental behavior of cells and its regulation is particularly relevant in physiological processes such as organogenesis and angiogenesis, as well as in pathological processes such as tumor metastasis. The majority of chemotactic stimuli activate cell surface receptors that belong to the G protein-coupled receptor (GPCR) superfamily. Although the autophagy machinery has been shown to play a role in cell migration, its mode of regulation by chemotactic GPCRs remains largely unexplored. We found that ligand-induced activation of 2 chemotactic GPCRs, the chemokine receptor CXCR4 and the urotensin 2 receptor UTS2R, triggers a marked reduction in the biogenesis of autophagosomes, in both HEK-293 and U87 glioblastoma cells. Chemotactic GPCRs exert their anti-autophagic effects through the activation of CAPNs, which prevent the formation of pre-autophagosomal vesicles from the plasma membrane. We further demonstrated that CXCR4- or UTS2R-induced inhibition of autophagy favors the formation of adhesion complexes to the extracellular matrix and is required for chemotactic migration. Altogether, our data reveal a new link between GPCR signaling and the autophagy machinery, and may help to envisage therapeutic strategies in pathological processes such as cancer cell invasion.
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http://dx.doi.org/10.1080/15548627.2016.1235125DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5173274PMC
December 2016

Impact of meriolins, a new class of cyclin-dependent kinase inhibitors, on malignant glioma proliferation and neo-angiogenesis.

Neuro Oncol 2014 Nov 2;16(11):1484-98. Epub 2014 Jun 2.

Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), PRES Normandy, TC2N network, University of Rouen, Mont-Saint-Aignan, France (M.J., C.L., L.D., M.-T.S., V.L., P.G., H.C.); Neuro-oncology department, Hospices Civils de Lyon, Hôpital Neurologique, Bron, France (C.M., J.H.); Lyon Neuroscience Research Center INSERM U1028/CNRS UMR 5292, Lyon, France (C.M., J.H.); University of Claude Bernard - Lyon 1, Villeurbanne, France (C.M., J.H.); Institut de Chimie et Biochimie Moléculaires et Supramoléculaires UMR 5246, University of Claude Bernard - Lyon 1, Villeurbanne, France (F.L., G.L., B.J., N.L.); Protein Phosphorylation & Human Disease Group & USR3151, Station Biologique, Roscoff, France (N.L., L.M.); ManRos Therapeutics, Roscoff, France (L.M.).

Background: Glioblastomas are the most frequent and most aggressive primary brain tumors in adults. The median overall survival is limited to a few months despite surgery, radiotherapy, and chemotherapy. It is now clearly established that hyperactivity of cyclin-dependent kinases (CDKs) is one of the processes underlying hyperproliferation and tumoral growth. The marine natural products meridianins and variolins, characterized as CDK inhibitors, display a kinase-inhibitory activity associated with cytotoxic effects. In order to improve selectivity and efficiency of these CDK inhibitors, a series of hybrid compounds called meriolins have been synthesized.

Methods: The potential antitumoral activity of meriolins was investigated in vitro on glioma cell lines (SW1088 and U87), native neural cells, and a human endothelial cell line (HUV-EC-C). The impact of intraperitoneal or intratumoral administrations of meriolin 15 was evaluated in vivo on 2 different nude mice-xenografted glioma models.

Results: Meriolins 3, 5, and 15 exhibited antiproliferative properties with nanomolar IC50 and induced cell-cycle arrest and CDK inhibition associated with apoptotic events in human glioma cell lines. These meriolins blocked the proliferation rate of HUV-EC-C through cell cycle arrest and apoptosis. In vivo, meriolin 15 provoked a robust reduction in tumor volume in spite of toxicity for highest doses, associated with inhibition of cell division, activation of caspase 3, reduction of CD133 cells, and modifications of the vascular architecture.

Conclusion: Meriolins, and meriolin 15 in particular, exhibit antiproliferative and proapoptotic activities on both glioma and intratumoral endothelial cells, constituting key promising therapeutic lead compounds for the treatment of glioblastoma.
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http://dx.doi.org/10.1093/neuonc/nou102DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4201071PMC
November 2014

The octadecaneuropeptide ODN prevents 6-hydroxydopamine-induced apoptosis of cerebellar granule neurons through a PKC-MAPK-dependent pathway.

J Neurochem 2013 May 19;125(4):620-33. Epub 2013 Feb 19.

Laboratory of Functional Neurophysiology and Pathology, Research Unit, UR/11ES09, Department of Biological Sciences, Faculty of Science of Tunis, University Tunis El Manar, Tunis, Tunisia.

Oxidative stress, induced by various neurodegenerative diseases, initiates a cascade of events leading to apoptosis, and thus plays a critical role in neuronal injury. In this study, we have investigated the potential neuroprotective effect of the octadecaneuropeptide (ODN) on 6-hydroxydopamine (6-OHDA)-induced oxidative stress and apoptosis in cerebellar granule neurons (CGN). ODN, which is produced by astrocytes, is an endogenous ligand for both central-type benzodiazepine receptors (CBR) and a metabotropic receptor. Incubation of neurons with subnanomolar concentrations of ODN (10⁻¹⁸ to 10⁻¹² M) inhibited 6-OHDA-evoked cell death in a concentration-dependent manner. The effect of ODN on neuronal survival was abrogated by the metabotropic receptor antagonist, cyclo₁₋₈ [DLeu⁵]OP, but not by a CBR antagonist. ODN stimulated polyphosphoinositide turnover and ERK phosphorylation in CGN. The protective effect of ODN against 6-OHDA toxicity involved the phospholipase C/ERK MAPK transduction cascade. 6-OHDA treatment induced an accumulation of reactive oxygen species, an increase of the expression of the pro-apoptotic gene Bax, a drop of the mitochondrial membrane potential and a stimulation of caspase-3 activity. Exposure of 6-OHDA-treated cells to ODN blocked all the deleterious effects of the toxin. Taken together, these data demonstrate for the first time that ODN is a neuroprotective agent that prevents 6-OHDA-induced oxidative stress and apoptotic cell death.
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http://dx.doi.org/10.1111/jnc.12140DOI Listing
May 2013

Down-regulation of GABA(A) receptor via promiscuity with the vasoactive peptide urotensin II receptor. Potential involvement in astrocyte plasticity.

PLoS One 2012 1;7(5):e36319. Epub 2012 May 1.

Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, Astrocyte and Vascular Niche, University of Rouen, Mont-Saint-Aignan, France.

GABA(A) receptor (GABA(A)R) expression level is inversely correlated with the proliferation rate of astrocytes after stroke or during malignancy of astrocytoma, leading to the hypothesis that GABA(A)R expression/activation may work as a cell proliferation repressor. A number of vasoactive peptides exhibit the potential to modulate astrocyte proliferation, and the question whether these mechanisms may imply alteration in GABA(A)R-mediated functions and/or plasma membrane densities is open. The peptide urotensin II (UII) activates a G protein-coupled receptor named UT, and mediates potent vasoconstriction or vasodilation in mammalian vasculature. We have previously demonstrated that UII activates a PLC/PIPs/Ca(2+) transduction pathway, via both G(q) and G(i/o) proteins and stimulates astrocyte proliferation in culture. It was also shown that UT/G(q)/IP(3) coupling is regulated by the GABA(A)R in rat cultured astrocytes. Here we report that UT and GABA(A)R are co-expressed in cerebellar glial cells from rat brain slices, in human native astrocytes and in glioma cell line, and that UII inhibited the GABAergic activity in rat cultured astrocytes. In CHO cell line co-expressing human UT and combinations of GABA(A)R subunits, UII markedly depressed the GABA current (β(3)γ(2)>α(2)β(3)γ(2)>α(2)β(1)γ(2)). This effect, characterized by a fast short-term inhibition followed by drastic and irreversible run-down, is not relayed by G proteins. The run-down partially involves Ca(2+) and phosphorylation processes, requires dynamin, and results from GABA(A)R internalization. Thus, activation of the vasoactive G protein-coupled receptor UT triggers functional inhibition and endocytosis of GABA(A)R in CHO and human astrocytes, via its receptor C-terminus. This UII-induced disappearance of the repressor activity of GABA(A)R, may play a key role in the initiation of astrocyte proliferation.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0036319PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3341351PMC
September 2012

Analysis of the melanotrope cell neuroendocrine interface in two amphibian species, Rana ridibunda and Xenopus laevis: a celebration of 35 years of collaborative research.

Gen Comp Endocrinol 2011 Jan 1;170(1):57-67. Epub 2010 Oct 1.

Department of Cellular Animal Physiology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands.

This review gives an overview of the functioning of the hypothalamo-hypophyseal neuroendocrine interface in the pituitary neurointermediate lobe, as it relates to melanotrope cell function in two amphibian species, Rana ridibunda and Xenopus laevis. It primarily but not exclusively concerns the work of two collaborating laboratories, the Laboratory for Molecular and Cellular Neuroendocrinology (University of Rouen, France) and the Department of Cellular Animal Physiology (Radboud University Nijmegen, The Netherlands). In the course of this review it will become apparent that Rana and Xenopus have, for the most part, developed the same or similar strategies to regulate the release of α-melanophore-stimulating hormone (α-MSH). The review concludes by highlighting the molecular and cellular mechanisms utilized by thyrotropin-releasing hormone (TRH) to activate Rana melanotrope cells and the function of autocrine brain-derived neurotrophic factor (BDNF) in the regulation of Xenopus melanotrope cell function.
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http://dx.doi.org/10.1016/j.ygcen.2010.09.022DOI Listing
January 2011

The vasoactive peptides urotensin II and urotensin II-related peptide regulate astrocyte activity through common and distinct mechanisms: involvement in cell proliferation.

Biochem J 2010 Apr 28;428(1):113-24. Epub 2010 Apr 28.

EA4310, Inserm U982, DC2N, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, Astrocyte and Vascular Niche, European Institute for Peptide Research (IFRMP 23), University of Rouen, Mont-Saint-Aignan, Normandy, France.

UII (urotensin II) and its paralogue URP (UII-related peptide) are two vasoactive neuropeptides whose respective central actions are currently unknown. In the present study, we have compared the mechanism of action of URP and UII on cultured astrocytes. Competition experiments performed with [125I]UII showed the presence of very-high- and high-affinity binding sites for UII, and a single high-affinity site for URP. Both UII and URP provoked a membrane depolarization accompanied by a decrease in input resistance, stimulated the release of endozepines, neuropeptides specifically produced by astroglial cells, and generated an increase in [Ca2+]c (cytosolic Ca2+ concentration). The UII/URP-induced [Ca2+]c elevation was PTX (pertussis toxin)-insensitive, and was blocked by the PLC (phospholipase C) inhibitor U73122 or the InsP3 channel blocker 2-APB (2-aminoethoxydiphenylborane). The addition of the Ca2+ chelator EGTA reduced the peak and abolished the plateau phase, whereas the T-type Ca2+ channel blocker mibefradil totally inhibited the Ca2+ response evoked by both peptides. However, URP and UII induced a mono- and bi-phasic dose-dependent increase in [Ca2+]c and provoked short- and long-lasting Ca2+ mobilization respectively. Similar mono- and bi-phasic dose-dependent increases in [3H]inositol incorporation into polyphosphoinositides in astrocytes was obtained, but the effect of UII was significantly reduced by PTX, although BRET (bioluminescence resonance energy transfer) experiments revealed that both UII and URP recruited Galphao-protein. Finally, UII, but not URP, exerted a dose-dependent mitogenic activity on astrocytes. Therefore we described that URP and UII exert not only similar, but also divergent actions on astrocyte activity, with UII exhibiting a broader range of activities at physiological peptide concentrations.
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http://dx.doi.org/10.1042/BJ20090867DOI Listing
April 2010

Paradoxical effect of ethanol on potassium channel currents and cell survival in cerebellar granule neurons.

J Neurochem 2009 Aug 31;110(3):976-89. Epub 2009 May 31.

Laboratory of Neuroendocrine and Neuronal Cell Differentiation and Communication, European Institute for Peptide Research, University of Rouen, Mont-Saint-Aignan, France.

Transient exposure to ethanol (EtOH) results in a massive neurodegeneration in the developing brain leading to behavioral and cognitive deficits observed in fetal alcohol syndrome. There is now compelling evidence that K+ channels play an important role in the control of programmed cell death. The aim of the present work was to investigate the involvement of K+ channels in the EtOH-induced cerebellar granule cell death and/or survival. At low and high concentrations, EtOH evoked membrane depolarization and hyperpolarization, respectively. Bath perfusion of EtOH (10 mM) depressed the I(A) (transient K+ current) potassium current whereas EtOH (400 mM) provoked a marked potentiation of the specific I(K) (delayed rectifier K+ current) current. Pipette dialysis with GTPgammaS or GDPbetaS did not modify the effects of EtOH (400 mM) on both membrane potential and I(K) current. In contrast, the reversible depolarization and slowly recovering inhibition of I(A) induced by EtOH (10 mM) became irreversible in the presence of GTPgammaS. EtOH (400 mM) induced prodeath responses whereas EtOH (10 mM) and K+ channel blockers promoted cell survival. Altogether, these results indicate that in cerebellar granule cells, EtOH mediates a dual effect on K+ currents partly involved in the control of granule cell death.
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http://dx.doi.org/10.1111/j.1471-4159.2009.06197.xDOI Listing
August 2009

Beta-amyloid peptide stimulates endozepine release in cultured rat astrocytes through activation of N-formyl peptide receptors.

Glia 2008 Oct;56(13):1380-9

INSERM U413, Laboratory of Cellular and Molecular Neuroendocrinology, University of Rouen, Mont-Saint-Aignan, France.

Astroglial cells synthesize and release endozepines, a family of neuropeptides derived from diazepam-binding inhibitor (DBI). The authors have recently shown that beta-amyloid peptide (Abeta) stimulates DBI gene expression and endozepine release. The purpose of this study was to determine the mechanism of action of Abeta in cultured rat astrocytes. Abeta(25-35) and the N-formyl peptide receptor (FPR) agonist N-formyl-Met-Leu-Phe (fMLF) increased the secretion of endozepines in a dose-dependent manner with EC(50) value of approximately 2 microM. The stimulatory effects of Abeta(25-35) and the FPR agonists fMLF and N-formyl-Met-Met-Met (fMMM) on endozepine release were abrogated by the FPR antagonist N-t-Boc-Phe-Leu-Phe-Leu-Phe. In contrast, Abeta(25-35) increased DBI mRNA expression through a FPR-independent mechanism. Abeta(25-35) induced a transient stimulation of cAMP formation and a sustained activation of polyphosphoinositide turnover. The stimulatory effect of Abeta(25-35) on endozepine release was blocked by the adenylyl cyclase inhibitor somatostatin, the protein kinase A (PKA) inhibitor H89, the phospholipase C inhibitor U73122, the protein kinase C (PKC) inhibitor chelerythrine and the ATP binding cassette transporter blocker glyburide. Taken together, these data demonstrate for the first time that Abeta(25-35) stimulates endozepine release from rat astrocytes through a FPR receptor positively coupled to PKA and PKC.
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http://dx.doi.org/10.1002/glia.20705DOI Listing
October 2008

Effect of GABA A receptor activation on UT-coupled signaling pathways in rat cortical astrocytes.

Peptides 2008 May 15;29(5):727-34. Epub 2008 Feb 15.

INSERM U413, Laboratory of Cellular and Molecular Neuroendocrinology, 76821 Mont-Saint-Aignan, France.

Cultured rat cortical astrocytes express two types of urotensin II (UII) binding sites: a high affinity site corresponding to the UT (GPR14) receptor and a low affinity site that has not been fully characterized. Activation of the high affinity site in astroglial cells stimulates polyphosphoinositide (PIP) turnover and provokes an increase in intracellular calcium concentration. We have hypothesized that the existence of distinct affinity sites for UII in rat cortical astrocytes could be accounted for by a possible cross-talk between UT and the ligand-gated ion channel GABA(A) receptor (GABA A R). Exposure of cultured astrocytes to UII provoked a bell-shaped increase in cAMP production, with an EC50 stimulating value of 0.83+/-0.04 pM, that was totally blocked in the presence of the adenylyl cyclase inhibitor SQ 22,536. In contrast, UII was found to inhibit forskolin-induced cAMP formation. In the presence of the specific PKA inhibitor H89, UII provoked a sustained stimulation of cAMP formation. Inhibition of PKA by H89 strongly reduced the stimulatory effect of UII on PIP metabolism. GABA and the GABA A R agonist isoguvacine provoked a marked inhibition of UII-induced cAMP synthesis and a significant reduction of UII-evoked PIP turnover. These data suggest that functional interaction between UT and GABA(A)R negatively regulates coupling of UT to the classical PLC/IP(3) signaling cascade as well as to the adenylyl cyclase/PKA pathway.
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http://dx.doi.org/10.1016/j.peptides.2008.01.024DOI Listing
May 2008

[Orn5]URP acts as a pure antagonist of urotensinergic receptors in rat cortical astrocytes.

Peptides 2008 May 6;29(5):813-9. Epub 2007 Nov 6.

INSERM U413, Laboratory of Cellular and Molecular Neuroendocrinology, Mont-Saint-Aignan, France.

Cultured rat astrocytes, which express functional urotensin II (UII)/UII-related peptide (URP) receptors (UT), represent a very suitable model to investigate the pharmacological profile of UII and URP analogs towards native UT. We have recently designed three URP analogs [D-Trp4]URP, [Orn5]URP and [D-Tyr6]URP, that act as UT antagonists in the rat aortic ring bioassay. However, it has been previously reported that UII/URP analogs capable of inhibiting the contractile activity of UII possess agonistic activity on UT-transfected cells. In the present study, we have compared the ability of URP analogs to compete for [125 I]URP binding and to modulate cytosolic calcium concentration ([Ca2+]c) in cultured rat astrocytes. All three analogs displaced radioligand binding: [D-Trp4]URP and [D-Tyr6]URP interacted with high- and low-affinity sites whereas [Orn5]URP only bound high-affinity sites. [D-Trp4]URP and [D-Tyr6]URP both induced a robust increase in [Ca2+]c in astrocytes while [Orn5]URP was totally devoid of activity. [Orn5]URP provoked a concentration-dependent inhibition of URP- and UII-evoked [Ca2+]c increase and a rightward shift of the URP and UII dose-response curves. The present data indicate that [D-Trp4]URP and [D-Tyr6]URP, which act as UII antagonists in the rat aortic ring assay, behave as agonists in the [Ca2+]c mobilization assay in cultured astrocytes, whereas [Orn5]URP is a pure selective antagonist in both rat aortic ring contraction and astrocyte [Ca2+]c mobilization assays.
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http://dx.doi.org/10.1016/j.peptides.2007.10.023DOI Listing
May 2008

Biochemical and functional characterization of high-affinity urotensin II receptors in rat cortical astrocytes.

J Neurochem 2006 Oct 29;99(2):582-95. Epub 2006 Aug 29.

INSERM, Laboratory of Cellular and Molecular Neuroendocrinology, European Institute for Peptide Research, University of Rouen, Mont-Saint-Aignan, France.

The urotensin II (UII) gene is primarily expressed in the central nervous system, but the functions of UII in the brain remain elusive. Here, we show that cultured rat astrocytes constitutively express the UII receptor (UT). Saturation and competition experiments performed with iodinated rat UII ([(125)I]rUII) revealed the presence of high- and low-affinity binding sites on astrocytes. Human UII (hUII) and the two highly active agonists hUII(4-11) and [3-iodo-Tyr9]hUII(4-11) were also very potent in displacing [(125)I]rUII from its binding sites, whereas the non-cyclic analogue [Ser5,10]hUII(4-11) and somatostatin-14 could only displace [(125)I]rUII binding at micromolar concentrations. Reciprocally, rUII failed to compete with [(125)I-Tyr0,D-Trp8]somatostatin-14 binding on astrocytes. Exposure of cultured astrocytes to rUII stimulated [(3)H]inositol incorporation and increased intracellular Ca(2+) concentration in a dose-dependent manner. The stimulatory effect of rUII on polyphosphoinositide turnover was abolished by the phospholipase C inhibitor U73122, but only reduced by 56% by pertussis toxin. The GTP analogue Gpp(NH)p caused its own biphasic displacement of [(125)I]rUII binding and provoked an affinity shift of the competition curve of rUII. Pertussis toxin shifted the competition curve towards a single lower affinity state. Taken together, these data demonstrate that rat astrocytes express high- and low-affinity UII binding sites coupled to G proteins, the high-affinity receptor exhibiting the same pharmacological and functional characteristics as UT.
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http://dx.doi.org/10.1111/j.1471-4159.2006.04130.xDOI Listing
October 2006

The delayed rectifier channel current IK plays a key role in the control of programmed cell death by PACAP and ethanol in cerebellar granule neurons.

Ann N Y Acad Sci 2006 Jul;1070:173-9

INSERM U413, Laboratory of Cellular and Molecular Neuroendocrinology, European Institute for Peptide Research (IFRMP 23), University of Rouen, 76821 Mont-Saint-Aignan, France.

Alcohol exposure during development causes severe brain malformations, and thus, identification of molecules that can counteract the neurotoxicity of ethanol deserves high priority. Since activation of potassium (K+) currents has been shown to play a critical role in the control of programmed cell death, we have investigated the effects of ethanol and PACAP on K+ currents in cultured cerebellar granule cells using the patch-clamp technique in the whole cell configuration. In the presence of the fast-inactivating IA current blocker 4-AP, a focal application of ethanol (200 mM) in the vicinity of granule cells provoked a robust hyperpolarization and a marked increase of the delayed rectifier IK current. Addition of PACAP (0.1 microM) in the bath solution prevented ethanol-induced membrane hyperpolarization and suppressed the stimulatory effect of ethanol on IK current. These data suggest that ethanol alters neuronal survival, at least in part, through activation of IK, and that PACAP abolishes ethanol-induced cerebellar granule cell death via inhibition of IK..
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http://dx.doi.org/10.1196/annals.1317.008DOI Listing
July 2006

The regulation of alpha-MSH release by GABA is mediated by a chloride-dependent [Ca2+]c increase in frog melanotrope cells.

Peptides 2005 Oct;26(10):1936-43

European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, University of Rouen, 76821 Mont-Saint-Aignan, France.

In frog melanotrope cells, gamma-aminobutyric acid (GABA) induces a biphasic effect, i.e. a transient stimulation followed by a more sustained inhibition of alpha-MSH release, and both phases of the GABA effect are mediated by GABAA receptors. We have previously shown that the stimulatory phase evoked by GABAA receptor agonists can be accounted for by calcium entry. In the present study, we have investigated the involvement of the chloride flux on GABA-induced [Ca2+]c increase and alpha-MSH release. We show that GABA evokes a concentration-dependent [Ca2+]c rise through specific activation of the GABAA receptor. The GABA-induced [Ca2+]c increase results from opening of voltage-activated L- and N-type calcium channels, and sodium channels. Variations of the extracellular Cl- concentration revealed that GABA-induced [Ca2+]c rise and alpha-MSH release both depend on the Cl- flux direction and driving force. These observations suggest for the first time that GABA-gated Cl- efflux provokes an increase in [Ca2+]c increase that is responsible for hormone secretion.
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http://dx.doi.org/10.1016/j.peptides.2004.11.022DOI Listing
October 2005

Signal transduction in Rana melanotrope cells: mechanism of action of neurotensin on secretory and electrical activities.

Ann N Y Acad Sci 2005 Apr;1040:131-6

European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, University of Rouen, Mont-Saint-Aignan, France.

The pars intermedia of the frog (Rana esculenta) pituitary, which is composed of a single population of endocrine cells, the melanotrophs, is a very suitable model to study the mode of action of hypophysiotropic neuropeptides. We have recently characterized neurotensin (NT) in Rana esculenta and found that synthetic frog NT (fNT) stimulates the electrical and secretory activities of melanotrophs. By combining biochemical, pharmacological, microfluorimetric, and electrophysiological approaches, we observed that NT stimulates inositol-trisphosphate production that provokes Ca(2+) release from intracellular stores. The resulting increase in cytosolic Ca(2+) concentration ([Ca(2+)](c)) activates the secretion of alpha-melanocyte-stimulating hormone (alpha-MSH), stimulates Ca(2+)-dependent protein kinase (PKC) activity, and provokes a depolarizing chloride efflux. PKC reduces the amplitude, whereas membrane depolarization increases the frequency of L- and N-type Ca(2+) currents underlain by the action potential discharge. The complex regulatory processes exerted by NT on Ca(2+) signaling likely generate discrete variations in the [Ca(2+)](c) at various distances from secretory vesicles, contributing to the fine-tuning of alpha-MSH secretion.
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http://dx.doi.org/10.1196/annals.1327.016DOI Listing
April 2005

Neurotensin stimulates both calcium mobilization from inositol trisphosphate-sensitive intracellular stores and calcium influx through membrane channels in frog pituitary melanotrophs.

Endocrinology 2003 Dec 18;144(12):5556-67. Epub 2003 Sep 18.

European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, Institut National de la Santé et de la Recherche Médicale, Unité-413, University of Rouen, 76821 Mont-Saint-Aignan, France.

Neurotensin (NT) is a potent stimulator of electrical and secretory activities in frog pituitary melanotrophs. The aim of the present study was to characterize the transduction pathways associated with activation of NT receptors in frog melanotrophs. Application of synthetic frog NT (fNT) increased the cytosolic calcium concentration ([Ca2+]c) and stimulated the formation of inositol trisphosphate (IP3). The phospholipase C inhibitor U-73122 blocked the electrophysiological and secretory effects of fNT. Intracellular application of the IP3 receptor antagonist heparin abolished fNT-induced electrical activity. Suppression of Ca2+ in the incubation medium markedly reduced the effect of NT on [Ca2+]c, firing rate, and alpha-melanocyte-stimulating hormone (alphaMSH) secretion. Similarly, the inhibitor of IP3-induced Ca2+ release and store-operated Ca2+ channels, 2-Aminoethoxydiphenylborane, and the nonselective Ca2+ channel blockers GdCl3 and NiCl2, attenuated the [Ca2+]c increase and the electrical and secretory responses evoked by fNT. Coapplication of the L- and N-type Ca2+ channel blockers nifedipine and omega-CgTx GVIA reduced the effects of fNT on action potential discharge, [Ca2+]c increase, and alphaMSH release. The protein kinase C (PKC) inhibitors, PKC-(19-31) and chelerythrine, reduced the electrophysiological and secretory responses induced by iterative applications of fNT. Collectively, these results demonstrate that, in frog melanotrophs, NT stimulates the phospholipase C/PKC pathway and increases [Ca2+]c. Both Ca2+ release from intracellular stores and Ca2+ influx through L- and N-type Ca2+ channels are involved in fNT-induced alphaMSH secretion. In addition, the present data indicate that PKC plays a crucial role in maintenance of the responsiveness of melanotrophs to NT.
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http://dx.doi.org/10.1210/en.2003-0176DOI Listing
December 2003

Isolation, characterization, and distribution of a novel neuropeptide, Rana RFamide (R-RFa), in the brain of the European green frog Rana esculenta.

J Comp Neurol 2002 Jun;448(2):111-27

European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U-413, UA CNRS, University of Rouen, 76821 Mont- Saint-Aignan, France.

A novel neuropeptide of the RFamide peptide family was isolated in pure form from a frog (Rana esculenta) brain extract by using reversed-phase high performance liquid chromatography in combination with a radioimmunoassay for mammalian neuropeptide FF (NPFF). The primary structure of the peptide was established as Ser-Leu-Lys- Pro-Ala-Ala-Asn-Leu-Pro-Leu- Arg-Phe-NH(2). The sequence of this neuropeptide, designated Rana RFamide (R-RFa), exhibits substantial similarities with those of avian LPLRFamide, gonadotropin-inhibitory hormone, and human RFRP-1. The distribution of R-RFa was investigated in the frog central nervous system by using an antiserum directed against bovine NPFF. In the brain, immunoreactive cell bodies were primarily located in the hypothalamus, i.e., the anterior preoptic area, the suprachiasmatic nucleus, and the dorsal and ventral hypothalamic nuclei. The most abundant population of R-RFa-containing neurons was found in the periependymal region of the suprachiasmatic nucleus. R-RFa- containing fibers were widely distributed throughout the brain from the olfactory bulb to the brainstem, and were particularly abundant in the external layer of the median eminence. In the spinal cord, scattered immunoreactive neurons were found in the gray matter. R-RFa-positive processes were found in all regions of the spinal cord, but they were more abundant in the dorsal horn. This study provides the first characterization of a member of the RFamide peptide family in amphibians. The occurrence of this novel neuropeptide in the hypothalamus and median eminence and in the dorsal region of the spinal cord suggests that, in frog, R-RFa may exert neuroendocrine activities and/or may be involved in the transmission of nociceptive stimuli.
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http://dx.doi.org/10.1002/cne.10253DOI Listing
June 2002