http://http://dspace.unitus.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Sun, 19 May 2013 23:02:49 GMT 2013-05-19T23:02:49Z http://hdl.handle.net/2067/1442 Title: Localization and function of GABA transporter 1 in the retina Authors: Casini, Giovanni Abstract: Plasma membrane transporters, located in the presynaptic terminal and/or surrounding glial cells, terminate synaptic transmission by operating rapid, high affinity uptake of the neurotransmitter from the synaptic cleft. Pharmacological blockade of transporters increases extracellular neurotransmitter levels and prolongs transmitter exposure to the receptors. GABA transporters (GATs) belong to the Na+ and Cl--dependent transporter family. Four GATs have been isolated and cloned in mammals. Of them, GAT-1 and GAT-3 are expressed in the retina. GAT-1 has a widespread distribution to different retinal cell types, but it is prominently expressed in amacrine cells of all vertebrate species studied to date. There are some species differences in the expression patterns of GAT-1 in the retina. It is expressed by horizontal cells in non-mammalian but not in mammalian retinas, and it is expressed in Müller glial cells of rats and guinea pigs, but not of rabbits and primates. Functionally, GAT-1, together with GAT-3, regulates the extracellular GABA levels in the retina, thereby determining the level of inhibitory interactions and affecting visual processing in the retinal pathways. GAT-1 may interact with GABAC receptors on bipolar cell terminals and influence ganglion cell responses. It may also interact with GABAB receptors in the regulation of retinal waves of spontaneous activity which are known to play critical roles during development of the visual system. Other important functional actions are exerted by GAT-1 through reversed GABA transport. These include GABA release by cholinergic/GABAergic starburst amacrine cells and GABA release during early retinal development. Mon, 31 Dec 2007 23:00:00 GMT http://hdl.handle.net/2067/1442 2007-12-31T23:00:00Z http://hdl.handle.net/2067/1429 Title: Expression, localization and functional coupling of the somatostatin receptor subtype 2 in a mouse model of oxygen-induced retinopathy Authors: Dal Monte, Massimo; Ristori, Chiara; Videau, Catherine; Loudes, Catherine; Martini, Davide; Casini, Giovanni; Epelbaum, Jacques; Bagnoli, Paola Abstract: PURPOSE. In the mouse model of oxygen-induced retinopathy (OIR) somatostatin (SRIF) acting at the SRIF receptor subtype 2 (sst2) inhibits angiogenic responses to hypoxia through a downregulation of vascular endothelial growth factor. Information on the sites where SRIF-sst2 interactions take place is lacking, and downstream effectors mediating SRIF-sst2 antiangiogenic actions are unknown. METHODS. In the OIR model, retinal expression of SRIF was evaluated with RT-PCR and RIA. The bindings of [125I]LTT-SRIF-28 and [125I]Tyr3-octreotide were measured in coronal sections of the eye. With Western blot we evaluated the levels of sst2A as well as the expression and the activity of the Signal Transducer and Activator of Transcription (STAT)3. The analysis of STAT3 was performed in hypoxic mice treated with the sst2 agonist octreotide or with the sst2 antagonist D-Tyr8 cyanamid 154806 (CYN). Retinal localization of sst2A was assessed by single and double immunohistochemistry with an endothelial cell marker. RESULTS. In the hypoxic retina, both SRIF and sst2 levels as well as [125I]Tyr3-octreotide binding were downregulated. In addition, sst2A immunostaining was decreased in the neuroretina, but was increased in capillaries. Hypoxia increased both expression and activity of STAT3. This increase was inhibited by octreotide, while was strengthened by CYN. CONCLUSIONS. These data suggest that i. sst2 expressed by capillaries may be responsible of the antiangiogenic effects of SRIF and ii. downstream effectors in this action include the transcription factor STAT3. These results support the possibility of using sst2- selective ligands in the treatment of proliferative retinopathies and indicate STAT3 as an additional target for novel therapeutic approach. Description: L'articolo è disponibile sul sito dell'editore http://www.arvo.org/eweb/StartPage.aspx?Site=arvo2 Thu, 31 Dec 2009 23:00:00 GMT http://hdl.handle.net/2067/1429 2009-12-31T23:00:00Z http://hdl.handle.net/2067/1439 Title: Localization patterns of fibroblast growth factor 1 and its receptors FGFR1 and FGFR2 in postnatal mouse retina Authors: Catalani, Elisabetta; Tomassini, Silvia; Bosco, Luigi; Casini, Giovanni Abstract: Fibroblast growth factors (FGFs) exert basic functions both during embryonic development and in the adult. In mammalian retinas, expression of FGFs and their receptors has been reported, however information on the organization of the FGF system is still incomplete. Here, we report detailed double label immunohistochemical investigations of the localization patterns of FGF1 and of its receptors FGFR1 and FGFR2 in adult and in early postnatal mouse retinas. In adult retinas, FGF1 is localized to ganglion cells, horizontal cells and photoreceptor inner and outer segments. FGFR1 is in ganglion cells and in Müller cells, while FGFR2 is primarily localized to ganglion cells and to the nuclei of Müller cells, in addition to glycine containing amacrine cells. During postnatal development, the patterns of FGF1, FGFR1 or FGFR2 immunostainings are similar to those in the adult, but transient FGF1 expressing cells are detected in the proximal inl before eye opening. These patterns are consistent with an important involvement of FGF1, FGFR1 and FGFR2 in ganglion cell maturation (during development) and survival (in the adult). In addition, FGF1 may affect amacrine cell development, while Müller cells appear to receive important regulation from both FGFR1 and FGFR2 throughout postnatal life. Finally, in immature retinas, large numbers of amacrine cells, including calbindin and glycine containing amacrine cells, display both FGF1 and FGFR2 immunoreactivities in their nuclei, suggesting an action of FGF1 on FGFR2 receptors during a restricted period of postnatal development for the maturation of these amacrine cells. Description: L'articolo è disponibile sul sito dell'editore http://www.springerlink.com Wed, 31 Dec 2008 23:00:00 GMT http://hdl.handle.net/2067/1439 2008-12-31T23:00:00Z http://hdl.handle.net/2067/1448 Title: Adenylyl cyclase/cAMP system involvement in the antiangiogenic effect of somatostatin in the retina. Results from transgenic mice. Authors: Ristori, Chiara; Ferretti, Maria Enrica; Pavan, Barbara; Cervellati, Franco; Casini, Giovanni; Catalani, Elisabetta; Dal Monte, Massimo; Biondi, Carla Abstract: Neoangiogenesis is a response to retinal hypoxia that is inhibited by somatostatin (SRIF) through its subtype 2 receptor (sst2). Using a mouse model of hypoxia-induced retinopathy, we investigated the possibility that inhibition of adenylyl cyclase (AC) is involved in SRIF anti-angiogenic actions. Hypoxia increased AC responsiveness in wild type (WT) retinas and in retinas lacking sst2, but not in sst2-overexpressing retinas. Hypoxia also altered AC isoform expression, but with different patterns depending on sst2 expression level. Among the nine AC isoforms, AC VII isoform mRNA and protein resulted the most affected. Indeed, in hypoxia AC VII expression was significantly enhanced in WT retinas and it was further increased in sst2-lacking retinas, but not in retinas overexpressing sst2. These data suggest an involvement of AC/cAMP in mediating both hypoxia-evoked retinal neoangiogenesis and SRIF protective actions. The AC VII isoform is a candidate to a main role in these mechanisms. Description: L'articolo è disponibile sul sito dell'editore http://www.springerlink.com/ Mon, 31 Dec 2007 23:00:00 GMT http://hdl.handle.net/2067/1448 2007-12-31T23:00:00Z http://hdl.handle.net/2067/1479 Title: Changes in neuronal response to ischemia in retinas with genetic alterations of somatostatin receptor expression Authors: Catalani, Elisabetta; Cervia, Davide; Martini, Davide; Bagnoli, Paola; Simonetti, Elisa; Timperio, Anna Maria; Casini, Giovanni Abstract: Ischemia is a primary cause of neuronal death in retinal diseases. The repertoire of expressed transmitter receptors would determine the neurons’ responses to ischemic damage, and peptidergic receptors may be involved. With a new in vitro model of the ischemic mouse retina, we investigated whether an altered expression of somatostatin receptors could modulate retinal responses to ischemia. We used retinas of somatostatin receptor 1 (sst1) knock out (KO) mice, where sst2 are over-expressed and over-functional, and of sst2 KO mice. TUNEL analysis of ischemic retinas showed a marked reduction of cell death in sst1 KO retinas, while there were no differences between wild-type (WT) and sst2 KO retinas. In addition, caspase-3 mRNA expression was also reduced in sst1 KO as compared to WT retinas. An immunohistochemical analysis demonstrated that different cell populations responded differently to the ischemic insult, and that the persistence of some immunohistochemical markers was greater in sst1 KO than in WT or in sst2 KO retinas. In particular, rod bipolar cell survival was markedly improved in sst1 KO retinas, while it was dramatically decreased in sst2 KO retinas. Furthermore, consistent with a role of glutamate excitotoxicity in ischemia-induced neuronal death, retinal glutamate release was observed to increase under ischemic conditions, but this increase was significantly reduced in sst1 KO retinas. These observations demonstrate that an increased presence of functional sst2 protects against retinal ischemia, thus implementing the background for the use of sst2 analogs in therapies of retinal diseases such as glaucoma or diabetic retinopathy. Description: L'articolo è disponibile sul sito dell'editore http://onlinelibrary.wiley.com/ Sun, 31 Dec 2006 23:00:00 GMT http://hdl.handle.net/2067/1479 2006-12-31T23:00:00Z http://hdl.handle.net/2067/1484 Title: Physiology and pathology of somatostatin in the mammalian retina: a current view Authors: Cervia, Davide; Casini, Giovanni; Bagnoli, Paola Abstract: In the retina, peptidergic signalling participates in multiple circuits of visual information processing. The neuropeptide somatostatin (SRIF) is localised to amacrine cells and, in some instances, in a subset of ganglion cells. The variegated expression patterns of SRIF receptors (sst1-sst5) and the variety of signalling mechanisms activated by retinal SRIF suggest that this peptide may exert multiple actions on retinal neurons and on retinal physiology, although our current understanding reflects a rather complicated picture. SRIF, mostly through sst2, may act as a positive factor in the retina by regulating retinal homeostasis and protecting neurons against damage. In this respect, SRIF analogues seem to constitute a promising therapeutic arsenal to cure different retinal diseases, as for instance ischemic and diabetic retinopathies. However, further investigations are needed not only to fully understand the functional role of the SRIF system in the retina but also to exploit new chemical space for drug-like molecules. Description: L'articolo è disponibile sul sito dell'editore http://www.sciencedirect.com/ Mon, 31 Dec 2007 23:00:00 GMT http://hdl.handle.net/2067/1484 2007-12-31T23:00:00Z http://hdl.handle.net/2067/1488 Title: Modulation of the neuronal response to ischemia by somatostatin analogues in wild-type and knock-out mouse retinas Authors: Cervia, Davide; Martini, Davide; Ristori, Davide; Catalani, Elisabetta; Timperio, Anna Maria; Bagnoli, Paola; Casini, Giovanni Abstract: Somatostatin acts at five G protein-coupled receptors, sst1-sst5. In mouse ischemic retinas, the overexpression of sst2 (as in sst1 knock-out mice) results in reduction of cell death and glutamate release. Here, we reported that, in wild-type retinas, somatostatin, the multireceptor ligand pasireotide and the sst2 agonist octreotide decreased ischemia-induced cell death and that octreotide also decreased glutamate release. In contrast, cell death was increased by blocking sst2 with cyanamide. In sst2 over-expressing ischemic retinas, somatostatin analogues increased cell death, and octreotide also increased glutamate release. To explain this reversal of the anti-ischemic effect of somatostatin agonists in the presence of sst2 over-expression, we tested sst2 desensitisation due to internalisation or altered receptor function. We observed that: i) sst2 was not internalised, ii) among G protein-coupled receptor kinases (GRKs) and regulators of G protein signalling (RGSs), GRK1 and RGS1 expression increased following ischemia, iii) both GRK1 and RGS1 were downregulated by octreotide in wild-type ischemic retinas, iv) octreotide down-regulated GRK1 but not RGS1 in sst2 over-expressing ischemic retinas. These results demonstrate that sst2 activation protects against retinal ischemia. However, in the presence of sst2 over-expression sst2 is functionally desensitised by agonists, possibly due to sustained RGS1 levels. Description: L'articolo è disponibile sul sito dell'editore http://onlinelibrary.wiley.com/ Mon, 31 Dec 2007 23:00:00 GMT http://hdl.handle.net/2067/1488 2007-12-31T23:00:00Z http://hdl.handle.net/2067/1481 Title: Long-term effects of nicotine on rat fungiform taste buds Authors: Tomassini, Silvia; Cuoghi, Valeria; Catalani, Elisabetta; Casini, Giovanni; Bigiani, Albertino Abstract: Nicotine, an alkaloid found in tobacco smoke, has been recognized as capable of inducing changes in taste functionality in conditions of chronic exposure. The mechanisms underlying these sensory alterations, however, are currently unknown. We addressed this issue by studying the long-term effects of nicotine on the anatomical features of taste buds, the peripheral end-organs of taste, in rat fungiform papillae. Nicotine was administered to rats via drinking water over a period of 3 weeks, which represents a standard method to achieve chronic drug exposure in laboratory animals. We found that prolonged administration of nicotine induced a significant reduction in the size of fungiform taste buds, without affecting their total number on the rat tongue. Morphometric measurements as well as evaluations of taste cell membrane capacitance suggested that the reduced size of taste organs was determined by a decrease in the number of cells per taste bud. In addition, chronic treatment with nicotine caused an increase in the relative density of cells expressing gustducin, a specific G protein _-subunit found in some taste cells and involved in bitter/sweet transduction. Interestingly, changes in the expression pattern of gustducin turned out to be more pronounced in periadolescent/adolescent than in adult rats. As a whole, our data indicate that long-term nicotine administration induces significant changes in the anatomical properties of taste buds in rat fungiform papillae. These changes could have a profound impact on the sensory information relayed to the brain; therefore, they may be responsible, at least in part, for the alterations in taste functionality observed during chronic nicotine exposure, a condition found in regular smokers. Description: L'articolo è disponibile sul sito dell'editore http://www.sciencedirect.com/ Sun, 31 Dec 2006 23:00:00 GMT http://hdl.handle.net/2067/1481 2006-12-31T23:00:00Z http://hdl.handle.net/2067/1483 Title: Antiangiogenic role of somatostatin receptor 2 in a model of hypoxia-induced neovascularization in the retina: Results from transgenic mice Authors: Dal Monte, Massimo; Cammalleri, Maurizio; Martini, Davide; Casini, Giovanni; Bagnoli, Paola Abstract: PURPOSE. To determine whether the somatostatin receptor 2 (sst2) influences angiogenesis and its associated factors in a model of hypoxia-induced retinal neovascularization. METHODS. sst1-knockout (KO) mice, in which sst2 is overexpressed and overfunctional, and sst2-KO mice were used. Angiogenesis was evaluated in fluorescein-perfused retinas. Angiogenesis- associated factors were determined by RT-PCR and immunohistochemistry. RESULTS. Retinal neovascularization was increased in sst2-KO mice, but remained unchanged in sst1-KO compared with wild-type (WT) mice. Retinal levels of sst2 mRNA were not affected by hypoxia. Normoxic levels of angiogenesis regulators were similar in WT and KO retinas except for mRNA levels of IGF-1, Ang-2, and its receptor Tie-2. In WT, hypoxia induced an increase in mRNA levels of (1) VEGF and its receptors, (2) IGF-1R, and (3) Ang-2 and Tie-2. The increase in VEGF and IGF-1R mRNAs was more pronounced after sst2 loss, but was less pronounced when sst2 was overexpressed. In addition, in hypoxic retinas, sst2 loss increased IGF-1 mRNA, whereas it decreased Ang-1, Tie-1, and Tie-2 mRNA levels. Moreover, Tie-1 mRNA increased when sst2 was overexpressed. Immunohistochemistry confirmed the results in hypoxic retinas on increased expression of VEGF, IGF-1, and their receptors after sst2 loss. It also allowed the localization of these factors to specific retinal cells. In this respect, VEGFR-2, IGF-1, and IGF-1R were localized to Mu¨ller cells. CONCLUSIONS. These results suggest that sst2 may be protective against angiogenesis. The immediate clinical importance lies in the establishment of a potential pharmacological target based on sst2 pharmacology. Description: L'articolo è disponibile sul sito dell'editore http://www.arvo.org/eweb/StartPage.aspx?Site=arvo2 Sun, 31 Dec 2006 23:00:00 GMT http://hdl.handle.net/2067/1483 2006-12-31T23:00:00Z http://hdl.handle.net/2067/1485 Title: Involvement of the cAMP-dependent pathway in the reduction of epileptiform bursting caused by somatostatin in the mouse hippocampus Authors: Ristori, Chiara; Cammalleri, Maurizio; Martini, Davide; Pavan, Barbara; Liu, Yanqiang; Casini, Giovanni; Dal Monte, Massimo; Bagnoli, Paola Abstract: The cAMP pathway is major signal transduction system involved in hippocampal neurotransmission. Recently, the peptide somatostatin-14 (SRIF) has emerged as a key signal that, by activating its receptors, inhibits epileptiform bursting in the mouse hippocampus. Little is known on transduction mechanisms which may mediate SRIF function in native cell/tissues. Using a well established model of epileptiform activity induced by Mg2+-free medium with 4-aminopyridine (0 Mg2+⁄4-AP) in mouse hippocampal slices, we demonstrated that PKA-related signaling is upregulated by hippocampal bursting and that treatment with SRIF normalizes this upregulation. We also demonstrated that the SRIF-induced inhibition of PKA impairs phosphorylation of the NMDA receptor subunit NR1. Extracellular recordings of the 0 Mg2+⁄4-AP-induced hippocampal discharge from the CA3 region demonstrated that treating slices with compounds which interfere with PKA activity prevent SRIF inhibition of epileptiform bursting. Our results suggest that SRIF modulation of hippocampal activity may involve PKA-related signaling. Description: L'articolo è disponibile sul sito dell'editore http://www.springerlink.com Mon, 31 Dec 2007 23:00:00 GMT http://hdl.handle.net/2067/1485 2007-12-31T23:00:00Z http://hdl.handle.net/2067/1486 Title: The cyclooxygenase-2/prostaglandin E2 pathway is involved in the somatostatin-induced decrease of epileptiform bursting in the mouse hippocampus Authors: Ristori, Chiara; Cammalleri, Maurizio; Martini, Davide; Pavan, Barbara; Casini, Giovanni; Cervia, Davide; Bagnoli, Paola Abstract: The neuromodulatory peptide somatostatin-14 (SRIF) plays an important inhibitory role in epilepsy, but little is known on the signalling mechanisms coupled to this effect of SRIF. We have previously demonstrated that SRIF induces reduction of epileptiform bursting in a model of interictal-like activity in mouse hippocampal slices. In this same model, we investigated whether the cyclooxygenase 2 (COX-2)/prostaglandin E2 (PGE2) pathway is part of those signalling mechanisms mediating SRIF anti-epileptic actions. Both the expression of COX-2 (mRNA and protein) and the endogenous release of PGE2 increased in concomitance with epileptiform bursting. In particular, COX-2 protein increased in CA1/CA3 pyramidal layer and in the granular layer of the dentate gyrus. In addition, the selective inhibition of COX-2 by NS-398 markedly decreased endogenous PGE2 release induced by epileptiform bursting and the epileptiform bursting itself. Similar effects on epileptiform bursting were obtained with another COX-2 inhibitor, i.e., meloxicam. SRIF application counteracted the increase of both COX-2 expression and PGE2 release which occurred in concomitance with epileptiform bursting. Interestingly, SRIF and NS-398 comparably reduced epileptiform bursting in a non-additive manner and PGE2 abolished the inhibitory effect of SRIF on epileptiform bursting. These results demonstrate that: i) the COX-2/PGE2 pathway facilitates epileptiform bursting; and ii) SRIF exerts an anti-epileptic role by coupling to the COX-2/PGE2 pathway. In conclusion, we have identified a key set of signalling events that underlie anti-convulsant effects of SRIF in a mouse model of hippocampal bursting, thus providing useful data not only to identify alternative intervention points for the modulation of SRIF function, but also to exploit new chemical space for drug-like molecules. Description: L'articolo è disponibile sul sito dell'editore http://www.sciencedirect.com/ Mon, 31 Dec 2007 23:00:00 GMT http://hdl.handle.net/2067/1486 2007-12-31T23:00:00Z http://hdl.handle.net/2067/1470 Title: Modulation of the neuronal response to ischemia by somatostatin analogues in wild-type and knock-out mouse retinas Authors: Cervia, Davide; Martini, Davide; Ristori, Chiara; Catalani, Elisabetta; Timperio, Anna Maria; Bagnoli, Paola; Casini, Giovanni Abstract: Somatostatin acts at five G protein-coupled receptors, sst1-sst5. In mouse ischemic retinas, the over-expression of sst2 (as in sst1 knock-out mice) results in reduction of cell death and glutamate release. Here, we reported that, in wild-type retinas, somatostatin, the multireceptor ligand pasireotide and the sst2 agonist octreotide decreased ischemia-induced cell death and that octreotide also decreased glutamate release. In contrast, cell death was increased by blocking sst2 with cyanamide. In sst2 over-expressing ischemic retinas, somatostatin analogues increased cell death, and octreotide also increased glutamate release. To explain this reversal of the anti-ischemic effect of somatostatin agonists in the presence of sst2 over-expression, we tested sst2 desensitisation due to internalisation or altered receptor function. We observed that: i) sst2 was not internalised, ii) among G protein-coupled receptor kinases (GRKs) and regulators of G protein signalling (RGSs), GRK1 and RGS1 expression increased following ischemia, iii) both GRK1 and RGS1 were down-regulated by octreotide in wild-type ischemic retinas, iv) octreotide down-regulated GRK1 but not RGS1 in sst2 over-expressing ischemic retinas. These results demonstrate that sst2 activation protects against retinal ischemia. However, in the presence of sst2 over-expression sst2 is functionally desensitised by agonists, possibly due to sustained RGS1 levels. Description: L'articolo è disponibile sul sito dell'editore http://onlinelibrary.wiley.com/ Mon, 31 Dec 2007 23:00:00 GMT http://hdl.handle.net/2067/1470 2007-12-31T23:00:00Z http://hdl.handle.net/2067/1477 Title: Peptidergic receptors Authors: Casini, Giovanni; Cervia, Davide Abstract: The term neuropeptides refers to a relatively large number of biologically active molecules localized to discrete cell populations of nervous system, including autonomic ganglion neurons and their effector cells. Different combinations of transmitters and peptides are found in ganglionic cells of the autonomic system which comprise a functional “chemical code” for neurons subserving specific actions. Generally, peptidergic receptors are G-protein coupled receptors acting through multiple transduction pathways which reflect the pleiotropic actions of peptides. This section represents a current view of the most important actions of peptides and their receptors in the autonomic nervous system and in peripheral organs. Description: L'articolo è disponibile sul sito dell'editore http://www.sciencedirect.com/ Wed, 31 Dec 2008 23:00:00 GMT http://hdl.handle.net/2067/1477 2008-12-31T23:00:00Z