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Messi E, Pimpinelli F, Andrè V, Rigobello C, Gotti C, Maggi R. The alpha-7 nicotinic acetylcholine receptor is involved in a direct inhibitory effect of nicotine on GnRH release: In vitro studies. Mol Cell Endocrinol 2018; 460:209-218. [PMID: 28754351 DOI: 10.1016/j.mce.2017.07.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 07/04/2017] [Accepted: 07/24/2017] [Indexed: 12/28/2022]
Abstract
The activation of nicotinic cholinergic receptors (nAChR) inhibits the reproductive axis; however, it is not clear whether nicotine may directly modulate the release of hypothalamic gonadotropin-releasing hormone (GnRH). Experiments carried out in GT1-1 immortalized GnRH neurons reveal the presence of a single class of high affinity α4β2 and α7 nAchR subtypes. The exposure of GT1-1 cells to nicotine does not modify the basal accumulation of GnRH. However, nicotine was found to modify GnRH pulsatility in perifusion experiments and inhibits, the release of GnRH induced by prostaglandin E1 or by K+-induced cell depolarization; these effects were reversed by D-tubocurarine and α-bungarotoxin. In conclusion, the results reported here indicate that: functional nAChRs are present on GT1-1 cells, the activation of the α-bungarotoxin-sensitive subclass (α7) produces an inhibitory effect on the release of GnRH and that the direct action of nicotine on GnRH neurons may be involved in reducing fertility of smokers.
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Affiliation(s)
- Elio Messi
- Dept. of Pharmacological and Biomedical Sciences, Università Degli Studi di Milano, Milan, Italy
| | - Federica Pimpinelli
- Dept. of Pharmacological and Biomedical Sciences, Università Degli Studi di Milano, Milan, Italy
| | - Valentina Andrè
- Dept. of Pharmacological and Biomedical Sciences, Università Degli Studi di Milano, Milan, Italy
| | - Chiara Rigobello
- Dept. of Pharmacological and Biomedical Sciences, Università Degli Studi di Milano, Milan, Italy
| | - Cecilia Gotti
- CNR, Neuroscience Institute-Milano, Biometra University of Milan, Milan, Italy
| | - Roberto Maggi
- Dept. of Pharmacological and Biomedical Sciences, Università Degli Studi di Milano, Milan, Italy.
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Fujioka H, Kakehashi C, Funabashi T, Akema T. Immunohistochemical evidence for the relationship between microglia and GnRH neurons in the preoptic area of ovariectomized rats with and without steroid replacement. Endocr J 2013; 60:191-6. [PMID: 23090753 DOI: 10.1507/endocrj.ej12-0280] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Prostaglandins (PGs), whose synthesis is catalyzed by the rate-limiting enzyme cyclooxygenase (COX) including COX-1 and COX-2, are among the important mediators involved in the regulation of gonadotropin-releasing hormone (GnRH) secretion. However, the cellular origin of PGs remains obscure in terms of its relationship to GnRH neurons. The present study was therefore aimed to clarify the anatomical relationship between COX-1-producing microglia and GnRH neurons in the preoptic area (POA), and to examine possible influence of ovarian steroids. We performed a triple labeled immunofluorescent histochemistry of COX-1, CD11b (a specific marker for microglia) and GnRH in the POA of ovarian steroid-primed and non-primed ovariectomized rats. The result confirmed our previous study suggesting COX-1 immunoreactivity in the vicinity of, but not within, GnRH neurons in the POA. COX-1 around GnRH cells was entirely (100%) localized in cells containing CD11b regardless of steroid replacement in ovariectomized rats. These CD11b-immunoreactive cells had small cell bodies and highly branched fibers characteristic of ramified microglia. Three-dimensional reconstruction of confocal images revealed close proximity of some COX-1-containing microglia and GnRH neurons. These results showed selective and constitutive expression of COX-1 in ramified microglia in the vicinity of GnRH neurons, providing evidence for intercellular communication, mediated by PGs, from microglia to GnRH cells.
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Affiliation(s)
- Hitomi Fujioka
- Department of Physiology, St. Marianna University School of Medicine, Kawasaki 216-8511, Japan
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Toni M, Spisni E, Griffoni C, Santi S, Riccio M, Lenaz P, Tomasi V. Cellular prion protein and caveolin-1 interaction in a neuronal cell line precedes Fyn/Erk 1/2 signal transduction. J Biomed Biotechnol 2010; 2006:69469. [PMID: 17489019 PMCID: PMC1559926 DOI: 10.1155/jbb/2006/69469] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
It has been reported that cellular prion protein (PrPc) is enriched in caveolae or caveolae-like domains with caveolin-1 (Cav-1)
participating to signal transduction events by Fyn kinase recruitment. By using the Glutathione-S-transferase (GST)-fusion proteins
assay, we observed that PrPc strongly interacts in vitro with Cav-1. Thus, we ascertained the PrPc caveolar localization in a
hypothalamic neuronal cell line (GN11), by confocal microscopy analysis, flotation on density gradient, and coimmunoprecipitation
experiments. Following the anti-PrPc antibody-mediated stimulation of live GN11 cells, we observed that PrPc clustered on
plasma membrane domains rich in Cav-1 in which Fyn kinase converged to be activated. After these events, a signaling cascade
through p42/44 MAP kinase (Erk 1/2) was triggered, suggesting that following translocations from rafts to caveolae or caveolaelike
domains PrPc could interact with Cav-1 and induce signal transduction events.
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Affiliation(s)
- Mattia Toni
- Department of Experimental Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy
| | - Enzo Spisni
- Department of Experimental Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy
| | - Cristiana Griffoni
- Department of Experimental Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy
| | - Spartaco Santi
- National Research Council, Institute of Cytomorphology, 40136 Bologna, Italy
| | - Massimo Riccio
- National Research Council, Institute of Cytomorphology, 40136 Bologna, Italy
| | - Patrizia Lenaz
- Department of Experimental Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy
| | - Vittorio Tomasi
- Department of Experimental Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy
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Toni M, Massimino ML, Griffoni C, Salvato B, Tomasi V, Spisni E. Extracellular copper ions regulate cellular prion protein (PrPC) expression and metabolism in neuronal cells. FEBS Lett 2005; 579:741-4. [PMID: 15670838 DOI: 10.1016/j.febslet.2004.12.053] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Revised: 12/22/2004] [Accepted: 12/22/2004] [Indexed: 11/20/2022]
Abstract
The physiological functions of cellular prion protein (PrP(C)) remain unclear. It has been demonstrated that PrP(C) is a copper binding protein and proposed that its functions could be strictly linked to copper metabolism and neuroprotection. The aim of this study was to clarify how extracellular copper modifies PrP(C) expression and metabolism in cultured neurones. We reported here that copper delivered at physiological concentrations significantly decreases PrP(C) mRNA expression in GN11 neurones. Moreover, copper increases the release of PrP(C) into the culture medium. These results indicate that extracellular copper strongly affects the amount of cellular PrP and might represent an interesting strategy to decrease the expression of PrP(C) in neurones and its conversion in the pathological isoform PrP(Sc).
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Affiliation(s)
- Mattia Toni
- Department of Experimental Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy
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Pimpinelli F, Redaelli E, Restano-Cassulini R, Curia G, Giacobini P, Cariboni A, Wanke E, Bondiolotti GP, Piva F, Maggi R. Depolarization differentially affects the secretory and migratory properties of two cell lines of immortalized luteinizing hormone-releasing hormone (LHRH) neurons. Eur J Neurosci 2003; 18:1410-8. [PMID: 14511321 DOI: 10.1046/j.1460-9568.2003.02866.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In this report we studied and compared the biochemical and the electrophysiological characteristics of two cell lines (GT1-7 and GN11) of immortalized mouse LHRH-expressing neurons and the correlation with their maturational stage and migratory activity. In fact, previous results indicated that GN11, but not GT1-7, cells exhibit an elevated motility in vitro. The results show that the two cell lines differ in terms of immunoreactivity for tyrosine hydroxylase and nestin as well as of production and release of 3,4-dihydroxyphenylalanine (DOPA) and of intracellular distribution and release of the LHRH. Patch-clamp recordings in GN11 cells, reveal the presence of a single inward rectifier K+ current indicative of an immature neuronal phenotype (neither firing nor electrical activity). In contrast, as known from previous studies, GT1-7 cells show the characteristics of mature LHRH neurons with a high electrical activity characterized by spontaneous firing and excitatory postsynaptic potentials. K+-induced depolarization induces in GT1-7 cells, but not in GN11 cells, a strong increase in the release of LHRH in the culture medium. However, depolarization of GN11 cells significantly decreases their chemomigratory response. In conclusion, these results indicate that GT1-7 and GN11 cells show different biochemical and electrophysiological characteristics and are representative of mature and immature LHRH neurons, respectively. The early stage of maturation of GN11 cells, as well as the low electrical activity detected in these cells, appears to correlate with their migratory activity in vitro.
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Affiliation(s)
- Federica Pimpinelli
- Laboratory of Developmental Neuroendocrinology, Department of Endocrinology, Center of Excellence on Neurodegenerative Diseases, University of Milano, Via G. Balzaretti, 9, 20133 Milan, Italy
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Maggi R, Pimpinelli F, Molteni L, Milani M, Martini L, Piva F. Immortalized luteinizing hormone-releasing hormone neurons show a different migratory activity in vitro. Endocrinology 2000; 141:2105-12. [PMID: 10830297 DOI: 10.1210/endo.141.6.7494] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The development of two cell lines (GT1 and GN) of immortalized LHRH neurons has allowed an accurate study of the mechanisms controlling the synthesis and the secretion of LHRH. These cell lines, obtained in mice by genetic targeted tumorigenesis, retain many of the phenotypic characteristics of LHRH neurons. Of interest, GT1 cells derive from an hypothalamic tumor, whereas GN cells were obtained from a tumor localized in the olfactory bulb. The different origin of these cell lines lead to hypothesize that they might represent hypothalamic postmigratory neurons (GT1 cells), or LHRH neurons blocked at an early stage of their migration (GN cells). Using different experimental procedures, we found that the two cell subclones GT1-7 and GN11 express a different morphology and migratory behavior in vitro. In particular, we found that GN11 cells, but not GT1-7 cells, show the morphological shape of migrating neurons. When analyzing the spontaneous motility we found that only GN11 cells express a high capacity of migrating in a matrix of collagen gel. Moreover, in a chemomigratory assay GN11 cells did show a significant response to the chemotactic stimulus represented by the FBS. On the contrary, GT1-7 cells show very low spontaneous motility and appear insensitive to the FBS stimulus. These results suggest that the simultaneous use of the GT1-7/GN11 cells may represent an experimental tool for screening the factors possibly involved in the control of the migratory processes of LHRH neurons in normal and in pathological conditions, such as those due to their impaired migration, like it happens in Kallmann's syndrome.
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Affiliation(s)
- R Maggi
- Department of Endocrinology, University of Milano, Italy.
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Harris TG, Battaglia DF, Brown ME, Brown MB, Carlson NE, Viguié C, Williams CY, Karsch FJ. Prostaglandins mediate the endotoxin-induced suppression of pulsatile gonadotropin-releasing hormone and luteinizing hormone secretion in the ewe. Endocrinology 2000; 141:1050-8. [PMID: 10698181 DOI: 10.1210/endo.141.3.7393] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Five experiments were conducted to test the hypothesis that PGs mediate the endotoxin-induced inhibition of pulsatile GnRH and LH secretion in the ewe. Our approach was to test whether the PG synthesis inhibitor, flurbiprofen, could reverse the inhibitory effects of endotoxin on pulsatile LH and GnRH secretion in ovariectomized ewes. Exp 1-4 were cross-over experiments in which ewes received either flurbiprofen or vehicle 2 weeks apart. Jugular blood samples were taken for LH analysis throughout a 9-h experimental period. Depending on the specific purpose of the experiment, flurbiprofen or vehicle was administered after 3.5 h, followed by endotoxin, vehicle, or ovarian steroids (estradiol plus progesterone) at 4 h. In Exp 1, flurbiprofen reversed the endotoxin-induced suppression of mean serum LH concentrations and the elevation of body temperature. In Exp 2, flurbiprofen prevented the endotoxin-induced inhibition of pulsatile LH secretion and stimulation of fever, reduced the stimulation of plasma cortisol and progesterone, but did not affect the rise in circulating tumor necrosis factor-alpha. In Exp 3, flurbiprofen in the absence of endotoxin had no effect on pulsatile LH secretion. In Exp 4, flurbiprofen failed to prevent suppression of pulsatile LH secretion induced by luteal phase levels of the ovarian steroids progesterone and estradiol, which produce a nonimmune suppression of gonadotropin secretion. In Exp 5, flurbiprofen prevented the endotoxin-induced inhibition of pulsatile GnRH release into pituitary portal blood. Our finding that this PG synthesis inhibitor reverses the inhibitory effect of endotoxin leads to the conclusion that PGs mediate the suppressive effects of this immune/inflammatory challenge on pulsatile GnRH and LH secretion.
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Affiliation(s)
- T G Harris
- Department of Physiology, University of Michigan, Ann Arbor 48109-0404, USA
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