The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. http://http://dspace.unitus.it:80 2013-05-24T17:48:03Z 2013-05-24T17:48:03Z Dal Monte, Massimo Ristori, Chiara Videau, Catherine Loudes, Catherine Martini, Davide Casini, Giovanni Epelbaum, Jacques Bagnoli, Paola http://hdl.handle.net/2067/1429 2011-06-28T10:47:12Z 2009-12-31T23:00:00Z

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

2009-12-31T23:00:00Z Catalani, Elisabetta Cervia, Davide Martini, Davide Bagnoli, Paola Simonetti, Elisa Timperio, Anna Maria Casini, Giovanni http://hdl.handle.net/2067/1479 2011-06-28T08:35:40Z 2006-12-31T23:00:00Z

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/

2006-12-31T23:00:00Z Ristori, Chiara Cammalleri, Maurizio Martini, Davide Pavan, Barbara Casini, Giovanni Cervia, Davide Bagnoli, Paola http://hdl.handle.net/2067/1486 2011-06-27T12:10:19Z 2007-12-31T23:00:00Z

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/

2007-12-31T23:00:00Z Cervia, Davide Martini, Davide Ristori, Davide Catalani, Elisabetta Timperio, Anna Maria Bagnoli, Paola Casini, Giovanni http://hdl.handle.net/2067/1488 2011-06-28T14:16:27Z 2007-12-31T23:00:00Z

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/

2007-12-31T23:00:00Z Dal Monte, Massimo Cammalleri, Maurizio Martini, Davide Casini, Giovanni Bagnoli, Paola http://hdl.handle.net/2067/1483 2011-08-08T23:05:04Z 2006-12-31T23:00:00Z

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

2006-12-31T23:00:00Z Ristori, Chiara Cammalleri, Maurizio Martini, Davide Pavan, Barbara Liu, Yanqiang Casini, Giovanni Dal Monte, Massimo Bagnoli, Paola http://hdl.handle.net/2067/1485 2011-06-28T14:05:00Z 2007-12-31T23:00:00Z

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

2007-12-31T23:00:00Z Cammalleri, Maurizio Martini, Davide Timperio, Anna Maria Bagnoli, Paola http://hdl.handle.net/2067/1845 2011-07-04T19:20:26Z 2008-12-31T23:00:00Z

Title: Functional effect of somatostatin receptor 1 activation on synaptic transmission in the mouse hyppocampus Authors: Cammalleri, Maurizio; Martini, Davide; Timperio, Anna Maria; Bagnoli, Paola Abstract: Somatostatin-14 (SRIF) co-localizes with GABA in the hippocampus and regulates neuronal excitability. A role of SRIF in the control of hippocampal activity has been proposed, although the exact contribution of each SRIF receptor (sst1– sst5) in mediating SRIF action requires some clarification. We used hippocampal slices of wild-type and sst1 knockout (KO) mice and selective pharmacological tools to provide conclusive evidence for a role of sst1 in mediating SRIF inhibition of synaptic transmission. With single- and double-label immunohistochemistry, we determined the distribution of sst1 in hippocampal slices and we quantified sst1 colocalization with SRIF. With electrophysiology, we found that sst1 activation with CH-275 inhibited both the NMDA- and the a-amino- 3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-mediated responses. Results from sst1 KO slices confirmed the specificity of CH-275 effects; sst1 activation did not affect the inhibitory transmission which was in contrast increased by sst4 activation with L-803,087 in both wild-type and sst1 KO slices. The AMPA-mediated responses were increased by L-803,087. Functional interaction between sst1 and sst4 is suggested by the finding that their combined activation prevented the CH-275-induced inhibition of AMPA transmission. The involvement of pre-synaptic mechanisms in mediating inhibitory effects of sst1 on excitatory transmission was demonstrated by the finding that CH-275 (i) increased the paired-pulse facilitation ratio, (ii) did not influence the AMPA depolarization in the presence of tetrodotoxin, and (iii) inhibited glutamate release induced by epileptiform treatment. We conclude that SRIF control of excitatory transmission through an action at sst1 may represent an important contribution to the regulation of hippocampal activity. Description: L'articolo è disponibile sul sito dell'editore http://onlinelibrary.wiley.com/

2008-12-31T23:00:00Z Cammalleri, Maurizio Cervia, Davide Dal Monte, Massimo Martini, Davide Langenegger, Daniel Fehlmann, Dominique Feuerbach, Dominik Pavan, Barbara Hoyer, Daniel Bagnoli, Paola http://hdl.handle.net/2067/1460 2011-06-28T10:33:18Z 2005-12-31T23:00:00Z

Title: Compensatory changes in the hippocampus of somatostatin knockout mice: upregulation of somatostatin receptor 2 and its function in the control of bursting activity and synaptic transmission Authors: Cammalleri, Maurizio; Cervia, Davide; Dal Monte, Massimo; Martini, Davide; Langenegger, Daniel; Fehlmann, Dominique; Feuerbach, Dominik; Pavan, Barbara; Hoyer, Daniel; Bagnoli, Paola Abstract: Somatostatin-14 (SRIF) colocalizes with GABA in the hippocampus and regulates neuronal excitability. A role of SRIF in the control of seizures has been proposed although its exact contribution requires some clarification. In particular, SRIF knock out (KO) mice do not exhibit spontaneous seizures, indicating that compensatory changes may occur in KO. In the KO hippocampus, we examined whether specific SRIF receptors and/or the cognate peptide cortistatin-14 (CST) compensate for SRIF’s absence. We found increased levels of both sst2 receptors (sst2) and CST and we explored the functional consequences of sst2 compensation on bursting activity and synaptic responses in hippocampal slices. Bursting was decreased by SRIF in wild type (WT) mice, but it was not affected by either CST or sst2 agonist and antagonist. sst4 agonist increased bursting frequency in either WT or KO. In WT, but not in KO, its effects were blocked by agonizing or antagonizing sst2, suggesting that sst2 and sst4 are functionally coupled in the WT hippocampus. Bursting was reduced in KO as compared to WT and was increased upon application of sst2 antagonist while SRIF, CST and sst2 agonist had no effect. At the synaptic level, we observed that in WT, SRIF decreased excitatory postsynaptic potentials which were, in contrast, increased by sst2 antagonist in KO. We conclude that sst2 compensates for SRIF absence and that its upregulation is responsible for reduced bursting and decreased excitatory transmission in KO mice. We suggest that a critical density of sst2 is needed to control hippocampal activity. Description: L'articolo è disponibile sul sito dell'editore http://onlinelibrary.wiley.com/

2005-12-31T23:00:00Z Cervia, Davide Martini, Davide Garcia-Gil, Mercedes Di Giuseppe, Graziano Guella, Graziano Dini, Fernando Bagnoli, Paola http://hdl.handle.net/2067/1459 2011-06-07T17:17:55Z 2005-12-31T23:00:00Z

Title: Cytotoxic effects and apoptotic signalling mechanisms of the sesquiterpenoid euplotin C, a secondary metabolite of the marine ciliate Euplotes crassus, in tumour cells Authors: Cervia, Davide; Martini, Davide; Garcia-Gil, Mercedes; Di Giuseppe, Graziano; Guella, Graziano; Dini, Fernando; Bagnoli, Paola Abstract: Most antitumour agents with cytotoxic properties induce apoptosis. The lipophilic compound euplotin C, isolated from the ciliate Euplotes crassus, is toxic to a number of different opportunistic or pathogenic microorganisms, although its mechanism of action is currently unknown. We report here that euplotin C is a powerful cytotoxic and pro-apoptotic agent in mouse AtT-20 and rat PC12 tumour-derived cell lines. In addition, we provide evidence that euplotin C treatment results in rapid activation of ryanodine receptors, depletion of Ca2+ stores in the endoplasmic reticulum (ER), the release of cytochrome c from the mitochondria, activation of caspase-12, and activation of caspase-3, leading to apoptosis. Intracellular Ca2+ overload is an early event which induces apoptosis and is parallelled by ER stress and the release of cytochrome c, whereas caspase-12 may be activated by euplotin C at a later stage in the apoptosis pathway. These events, either independently or concomitantly, lead to the activation of the caspase-3 and its downstream effectors, triggering the cell to undergo apoptosis. These results demonstrate that euplotin C may be considered for the design of cytotoxic and pro-apoptotic new drugs. Description: L'articolo è disponibile sul sito dell'editore http://www.springerlink.com/

2005-12-31T23:00:00Z Cervia, Davide Martini, Davide Ristori, Chiara Catalani, Elisabetta Timperio, Anna Maria Bagnoli, Paola Casini, Giovanni http://hdl.handle.net/2067/1470 2011-06-28T14:15:27Z 2007-12-31T23:00:00Z

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/

2007-12-31T23:00:00Z Cervia, Davide Di Giuseppe, Graziano Ristori, Chiara Martini, Davide Gambellini, Gabriella Bagnoli, Paola Dini, Fernando http://hdl.handle.net/2067/1474 2011-06-27T13:05:33Z 2008-12-31T23:00:00Z

Title: The secondary metabolite euplotin c induces apoptosis-like death in the marine ciliated protist euplotes vannus Authors: Cervia, Davide; Di Giuseppe, Graziano; Ristori, Chiara; Martini, Davide; Gambellini, Gabriella; Bagnoli, Paola; Dini, Fernando Abstract: The sesquiterpenoid euplotin C is a secondary metabolite produced by the ciliated protist Euplotes crassus and provides a mechanism for damping populations of potential competitors. Indeed, E. crassus is virtually resistant to its own product while different non-producer species representing an unbiased sample of the marine, interstitial, ciliate diversity are sensitive. For instance, euplotin C exerts a marked disruption of different homeostatic mechanisms in Euplotes vannus. We demonstrate by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay that euplotin C quickly decreases viability and mitochondrial function of E. vannus with a very high efficacy and at micromolar potency. In addition, euplotin C induces apoptosis in E. vannus as 4,6-diamino-2-phenylindole and Terminal Transferase dUTP Nick End Labeling staining show the rapid condensation and fragmentation of nuclear material in cells treated with euplotin C. These effects occur without detectable permeabilisation or rupture of cell membranes and with no major changes in the overall morphology, although some traits, such as vacuolisation and disorganised microtubules, can be observed by transmission electron microscopy. In particular, E. vannus show profound changes of the mitochondrial ultrastructure. Finally, we also show that caspase activity in E. vannus is increased by euplotin C. These data elucidate the pro-apoptotic role of euplotin C and suggest a mechanism for its impact on natural selection. Description: L'articolo è disponibile sul sito dell'editore http://onlinelibrary.wiley.com/

2008-12-31T23:00:00Z