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V Bruno

Publications and source records attributed to V Bruno.

At least 37 records · Page 2Linked to original sources
PubMed1999

Group-I metabotropic glutamate receptors: hypotheses to explain their dual role in neurotoxicity and neuroprotection.

The role of group-I metabotropic glutamate receptors (mGlu1 and 5) in neurodegeneration is still controversial. While antagonists of these receptors are consistently neuroprotective, agonists have been found to either amplify or attenuate excitotoxic neuronal death. At least three variables affect responses to agonists: (i) the presence of the NR2C subunit in the NMDA receptor complex; (ii) the existence of an activity-dependent functional switch of group-I mGlu receptors, similar to that described for the regulation of glutamate release; and (iii) the presence of astrocytes expressing mGlu5 receptors. Thus, a number of factors, including the heteromeric composition of NMDA receptors, the exposure time to drugs or to ambient glutamate, and the function of astrocytes clearing extracellular glutamate and producing neurotoxic or neuroprotective factors, must be taken into account when examining the role of group-I mGlu receptors in neurodegeneration/neuroprotection.

Animals↗
PubMed1999

Neuroprotective actions of novel and potent ligands of group I and group II metabotropic glutamate receptors.

The role of group I metabotropic glutamate (mGlu) receptors in neurodegeneration is controversial because of the contradictory effects of mGlu1/5 agonists in in vitro models of neuronal cell death. In this study, novel and selective antagonists of mGlu1 and mGlu5: LY367385 and LY367366 were found to show consistent neuroprotective effects against N-methyl-D-aspartate (NMDA)-induced excitotoxicity in vitro and in vivo. Furthermore, intraventricular administration of LY367385 reduced hippocampal cell death in gerbils subjected to transient global ischemia. Previous studies have also shown that activation of group II mGlu receptors may contribute to neuroprotective mechanisms in vitro and in vivo. Three potent group II mGlu agonists--LY354740, LY379268 and LY389795--were found to attenuate both NMDA excitotoxicity and staurosporine-induced neuronal cell death. LY354740 and LY379268 were protective against transient global ischemia in gerbils when dosed intraperitoneally. These results support the view that antagonists of mGlu1 and mGlu5 and agonists of group II mGlu receptors may be useful agents in the therapeutic treatment of neurodegenerative disease.

Animals↗
PubMed1999

(R,S)-4-phosphonophenylglycine, a potent and selective group III metabotropic glutamate receptor agonist, is anticonvulsive and neuroprotective in vivo.

Group III metabotropic glutamate receptors (mGluRs) are thought to modulate neurotoxicity of excitatory amino acids, via mechanisms of presynaptic inhibition, such as regulation of neurotransmitter release. Here, we describe (R,S)-4-phosphonophenylglycine (PPG) as a novel, potent, and selective agonist for group III mGluRs. In recombinant cell lines expressing the human receptors hmGluR4a, hmGluR6, hmGluR7b, or hmGluR8a, EC50 values for (R,S)-PPG of 5.2 +/- 0.7 microM, 4.7 +/- 0.9 microM, 185 +/- 42 microM, and 0.2 +/- 0.1 microM, respectively, were measured. The compound showed EC50 and IC50 values of >/=200 microM at group I and II hmGluRs and was inactive at cloned human N-methyl-D-aspartate, alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate, and kainate receptors (>300 microM). On the other hand, it showed micromolar affinity for a Ca2+/Cl--dependent L-glutamate binding site in rat brain, similar to other phosphono-substituted amino acids like L-2-amino-4-phosphonobutyrate. In cultured cortical neurons, (R, S)-PPG provided protection against a toxic pulse of N-methyl-D-aspartate (EC50 = 12 microM), which was reversed by the group III mGluR antagonist (R,S)-alpha-methylserine-O-phosphate but not by the group II antagonist (2S)-alpha-ethylglutamate. Moreover, (R,S)-PPG protected against N-methyl-D-aspartate- and quinolinic acid-induced striatal lesions in rats and was anticonvulsive in the maximal electroshock model in mice. In contrast to the group III mGluR agonists L-2-amino-4-phosphonobutyrate and L-serine-O-phosphate, (R,S)-PPG showed no proconvulsive effects (2200 nmol i.c.v.). These data provide novel in vivo evidence for group III mGluRs as attractive targets for neuroprotective and anticonvulsive therapy. Also, (R,S)-PPG represents an attractive tool to analyze the roles of group III mGluRs in nervous system physiology and pathology.

Animals↗
PubMed1999

Activation of A(1) adenosine or mGlu3 metabotropic glutamate receptors enhances the release of nerve growth factor and S-100beta protein from cultured astrocytes.

Pharmacological activation of A(1) adenosine receptor with 2-chloro-N6-cyclopentyladenosine (CCPA) or mGlu3 metabotropic glutamate receptors with (2S,2'R,3'R)-2-(2', 3'-dicarboxycyclopropyl)glycine (DCG-IV) or aminopyrrolidine-2R, 4R-dicarboxylate (2R,4R-APDC) enhanced the release of nerve growth factor (NGF) or S-100beta protein from rat cultured astrocytes. Stimulation of release by CCPA and DCG-IV or 2R,4R-APDC was inhibited by the A(1) adenosine receptor antagonist 8-cyclopentyl-1, 3-dipropylxanthine and by the mGlu2/3 receptor antagonist (2S,1'S, 2'S,3'R)-2-(2'-carboxy-3'-phenylcyclopropyl)glycine (PCCG-4), respectively. Time-course studies revealed a profound difference between the release of S-100beta protein and the release of NGF in response to extracellular signals. Stimulation of S-100beta protein exhibited rapid kinetics, peaking after 1 h of drug treatment, whereas the enhancement of NGF release was much slower, requiring at least 6 h of A(1) adenosine or mGlu3 receptor activation. In addition, stimulation of NGF but not S-100beta release was substantially reduced in cultures treated with the protein synthesis inhibitor cycloheximide. In addition, a 6-8 h treatment of cultured astrocytes with A(1) or mGlu3 receptor agonists increased the levels of both NGF mRNA and NGF-like immunoreactive proteins, including NGF prohormone. We conclude that activation of A(1) adenosine or mGlu3 receptors produces pleiotropic effects in astrocytes, stimulating the synthesis and/or the release of protein factors. Astrocytes may therefore become targets for drugs that stimulate the local production of neurotrophic factors in the CNS, and this may provide the basis for a novel therapeutic strategy in chronic neurodegenerative disorders.

Adenosine↗
PubMed1998

Neuroprotection by glial metabotropic glutamate receptors is mediated by transforming growth factor-beta.

The medium collected from cultured astrocytes transiently exposed to the group-II metabotropic glutamate (mGlu) receptor agonists (2S,1'R, 2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV) or (S)-4-carboxy-3-hydroxyphenylglycine (4C3HPG) is neuroprotective when transferred to mixed cortical cultures challenged with NMDA (). The following data indicate that this particular form of neuroprotection is mediated by transforming growth factor-beta (TGFbeta). (1) TGFbeta1 and -beta2 were highly neuroprotective against NMDA toxicity, and their action was less than additive with that produced by the medium collected from astrocytes treated with DCG-IV or 4C3HPG (GM/DCG-IV or GM/4C3HPG); (2) antibodies that specifically neutralized the actions of TGFbeta1 or -beta2 prevented the neuroprotective activity of DCG-IV or 4C3HPG, as well as the activity of GM/DCG-IV or GM/4C3HPG; and (3) a transient exposure of cultured astrocytes to either DCG-IV or 4C3HPG led to a delayed increase in both intracellular and extracellular levels of TGFbeta. We therefore conclude that a transient activation of group-II mGlu receptors (presumably mGlu3 receptors) in astrocytes leads to an increased formation and release of TGFbeta, which in turn protects neighbor neurons against excitotoxic death. These results offer a new strategy for increasing the local production of neuroprotective factors in the CNS.

Animals↗
PubMed1998

Selective activation of group-II metabotropic glutamate receptors is protective against excitotoxic neuronal death.

Aminopyrrolidine-2R,4R-dicarboxylated (2R,4R-APDC) has recently been introduced as a potent and highly selective agonist of metabotropic glutamate (mGlu) receptor subtypes mGlu2 and -3. In murine cortical cultures containing both neurons and astrocytes, 2R,4R-APDC attenuated the delayed neuronal degeneration induced by a 10-min pulse of N-methyl-D-aspartate (NMDA). 2R,4R-APDC was maximally neuroprotective in a range of concentrations (0.1-1 microM) comparable to that reported for the activation of mGlu2 or -3 receptors in heterologous expression systems. The action of 2R,4R-APDC was sensitive to the mGlu2/3 receptor antagonists, (2S)-alpha-ethylglutamate and (2S,1S',2S',3R')-2-(2'-carboxy-3'-phenylcyclopropyl)glycine. These results indicate that activation of mGlu2 and/or -3 receptors is sufficient per se to protect neurons against excitotoxic degeneration, and encourage the search for potent, selective and systemically active mGlu2/3 receptor agonists as neuroprotective drugs.

Animals↗
PubMed1998

A role for phospholipase D (Pld1p) in growth, secretion, and regulation of membrane lipid synthesis in yeast.

The SEC14 gene encodes a phosphatidylinositol/phosphatidylcholine transfer protein essential for secretion and growth in yeast (1). Mutations (cki1, cct1, and cpt1) in the CDP-choline pathway for phosphatidylcholine synthesis suppress the sec14 growth defect (2), permitting sec14(ts) cki1, sec14(ts) cct1, and sec14(ts) cpt1 strains to grow at the sec14(ts) restrictive temperature. Previously, we reported that these double mutant strains also excrete the phospholipid metabolites, choline and inositol (3). We now report that these choline and inositol excretion phenotypes are eliminated when the SPO14 (PLD1) gene encoding phospholipase D1 is deleted. In contrast to sec14(ts) cki1 strains, sec14(ts) cki1 pld1 strains are not viable at the sec14(ts) restrictive temperature and exhibit a pattern of invertase secretion comparable with sec14(ts) strains. Thus, the PLD1 gene product appears to play an essential role in the suppression of the sec14(ts) defect by CDP-choline pathway mutations, indicating a role for phospholipase D1 in growth and secretion. Furthermore, sec14(ts) strains exhibit elevated Ca2+-independent, phophatidylinositol 4,5-bisphosphate-stimulated phospholipase D activity. We also propose that phospholipase D1-mediated phosphatidylcholine turnover generates a signal that activates transcription of INO1, the structural gene for inositol 1-phosphate synthase.

Cytidine Diphosphate Choline↗
PubMed1998

Neuroprotective activity of N-acetylaspartylglutamate in cultured cortical cells.

The endogenous dipeptide, alpha-N-acetylaspartylglutamate behaves as a partial agonist of N-methyl-D-aspartate receptors, but can also activate metabotropic glutamate receptors, with a high degree of selectivity for the metabotropic glutamate receptor 3 subtype. Knowing that agonists of group-II metabotropic glutamate receptors (i.e. of mGlu2 and -3 receptors) are neuroprotective, we have examined the neuroprotective activity of alpha-N-acetylaspartylglutamate in mixed cultures of mouse cortical cells exposed to a toxic pulse with N-methyl-D-aspartate. Alpha-N-acetylaspartylglutamate co-applied with N-methyl-D-aspartate was neuroprotective, but its action was insensitive to the selective group-II metabotropic glutamate receptor antagonist, ethylglutamate. Protection was instead antagonized by ethylglutamate when alpha-N-acetylaspartylglutamate was applied to the cultures immediately after the N-methyl-D-aspartate pulse, a condition in which there was no direct competition between alpha-N-acetylaspartylglutamate and N-methyl-D-aspartate at the level of N-methyl-D-aspartate receptors. alpha-N-acetylaspartylglutamate was highly neuroprotective when transiently applied to pure cultures of cortical astrocytes and the conditioned medium, collected 20 h later, was transferred to sister mixed cultures challenged with N-methyl-D-aspartate. This particular form of neuroprotection was attenuated or abolished when astrocytes where exposed to alpha-N-acetylaspartylglutamate in the presence of the group-II metabotropic glutamate receptor antagonists ethylglutamate or (2S, 1'S,2'S,3'R)-2-(2'-carboxy-3'-phenylcyclopropyl)glycine, but not in the presence of the N-methyl-D-aspartate receptor antagonist, D-2-amino-5-phosphonopentanoate. These results indicate that alpha-N-acetylaspartylglutamate induces neuroprotective effects in culture, which are mediated, at least in part, by the activation of glial metabotropic glutamate receptor 3 receptors.

2-Amino-5-phosphonovalerate↗
PubMed1998

The metabotropic glutamate receptor mGlu5 controls the onset of developmental apoptosis in cultured cerebellar neurons.

Cultured cerebellar granule cells grown in medium containing 10 mM K+ undergo apoptosis after 4-5 days in vitro (DIV), and, at that time, the activity of metabotropic glutamate (mGlu) receptors coupled to polyphosphoinositide (PI) hydrolysis begins to decline. In granule cells at 4 DIV, the mGlu receptor subtype mGlu5 was expressed at high levels. The expression of another PI-coupled mGlu receptor, the mGlu1a, was low at 4 DIV but increased during the following days. In cultures at 4-5 DIV, the few cells that already showed an apoptotic phenotype were devoid of mGlu5 receptors, but they all expressed mGlu1a receptors. The development of apoptosis was accelerated after treating the cultures with: (i) mGlu5 antisense oligonucleotides; (ii) the mixed mGlu receptor antagonist, (+)-alpha-methyl-4-carboxyphenylglycine; or (iii) the glutamate depleting enzyme, alanine aminotransferase. In contrast, an induced overexpression of mGlu5 receptors protected cultured granule cells against apoptotic death. We suggest that the activity of mGlu5 receptors supports cell survival, and a decline in the expression of mGlu5 receptors gives access to programmed cell death in cerebellar granule cells developing in primary cultures.

Animals↗
PubMed1997

Metabotropic glutamate receptor agonists stimulate polyphosphoinositide hydrolysis in primary cultures of rat hepatocytes.

The metabotropic glutamate (mGlu) receptor agonists, quisqualate and (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), but not (RS)-3,5-dihydroxyphenylglycine or (2S,3S,4S)-alpha-(carboxycyclopropyl)glycine, stimulated [3H]inositolmonophosphate ([3H]InsP) formation in primary cultures of rat hepatocytes. 1S,3R-ACPD-stimulated [3H]InsP formation was inhibited by alpha-methyl-4-carboxyphenylglycine, indicating that cultured hepatocytes express functional mGlu receptors coupled to polyphosphoinositide hydrolysis. The identity of these receptors is not similar to that of any of the known mGlu receptor subtypes characterized in heterologous expression systems.

Animals↗
PubMed1997

Role of the yeast phosphatidylinositol/phosphatidylcholine transfer protein (Sec14p) in phosphatidylcholine turnover and INO1 regulation.

In yeast, mutations in the CDP-choline pathway for phosphatidylcholine biosynthesis permit the cell to grow even when the SEC14 gene is completely deleted (Cleves, A., McGee, T., Whitters, E., Champion, K., Aitken, J., Dowhan, W., Goebl, M., and Bankaitis, V. (1991) Cell 64, 789-800). We report that strains carrying mutations in the CDP-choline pathway, such as cki1, exhibit a choline excretion phenotype due to production of choline during normal turnover of phosphatidylcholine. Cells carrying cki1 in combination with sec14(ts), a temperature-sensitive allele in the gene encoding the phosphatidylinositol/phosphatidylcholine transporter, have a dramatically increased choline excretion phenotype when grown at the sec14(ts)-restrictive temperature. We show that the increased choline excretion in sec14(ts) cki1 cells is due to increased turnover of phosphatidylcholine via a mechanism consistent with phospholipase D-mediated turnover. We propose that the elevated rate of phosphatidylcholine turnover in sec14(ts) cki1 cells provides the metabolic condition that permits the secretory pathway to function when Sec14p is inactivated. As phosphatidylcholine turnover increases in sec14(ts) cki1 cells shifted to the restrictive temperature, the INO1 gene (encoding inositol-1-phosphate synthase) is also derepressed, leading to an inositol excretion phenotype (Opi-). Misregulation of the INO1 gene has been observed in many strains with altered phospholipid metabolism, and the relationship between phosphatidylcholine turnover and regulation of INO1 and other co-regulated genes of phospholipid biosynthesis is discussed.

Carrier Proteins↗
PubMed1997

The neuroprotective activity of group-II metabotropic glutamate receptors requires new protein synthesis and involves a glial-neuronal signaling.

The group-II metabotropic glutamate (mGlu) receptor agonists (2S,1'R, 2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV), S-4-carboxy-3-hydroxyphenylglycine (4C3HPG), and (2S,1'S, 2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I) protected mouse cortical neurons grown in mixed cultures against excitotoxic degeneration induced by a 10 min pulse with NMDA. Protection was observed not only when agonists were added in combination with NMDA but also when they were transiently applied to cultures 6-20 hr before the NMDA pulse. In both cases, neuroprotection was reduced by the group-II mGlu receptor antagonist (2S,1'S,2'S,3'R)-2-(2'-carboxy-3'-phenylcyclopropyl)glycine (PCCG-IV), as well as by the protein synthesis inhibitor cycloheximide (CHX). Both neurons and astrocytes in mixed cultures were immunostained with an antibody that recognized mGlu2 and mGlu3 receptors in recombinant cells. To determine whether astrocytes played any role in the neuroprotection mediated by group-II mGlu receptors, we exposed pure cultures of cortical astrocytes to DCG-IV, 4C3HPG, or L-CCG-I for 10 min. The astrocyte medium collected 2-20 hr after the exposure to any of these drugs was highly neuroprotective when transferred to mixed cultures treated with NMDA. This protective activity was reduced when CHX was applied to astrocyte cultures immediately after the transient exposure to group-II mGlu receptor agonists. We conclude that neuroprotection mediated by group-II mGlu receptors in cultured cortical cells requires new protein synthesis and involves an interaction between neurons and astrocytes.

Animals↗
PubMed1997

"Mad" or "bad"? Evaluating the decision to hospitalize SED youth using qualitative data.

This study examines variables associated with positive and negative hospitalization outcomes of seriously emotionally disturbed (SED) youth, and proposes that the context of the decision-making process that takes place before hospitalization plays a role in determining outcomes. Qualitative data from 13 case histories were analyzed to determine the effects of hospitalization after a 2-year follow-up period. Several indicators that have predicted negative outcomes in earlier studies are supported here, including bizarre symptom patterns, educational impairment, and additional hospitalization during the follow-up period. There was agreement in fewer than half of the cases among research clinicians, the subject, or the subject's family regarding the outcome. Findings demonstrate the advantages of qualitative methods in determining the manner in which definitions of mental health influence hospitalization outcomes, suggesting that mental health categories are not a priori categories in the subjects' or families' minds. The social context of the decision to hospitalize is found to be a contributing factor in hospitalization outcomes.

Adolescent↗
PubMed1996

Activation of group III metabotropic glutamate receptors is neuroprotective in cortical cultures.

(RS)-alpha-Methyl-4-phosphonophenylglycine (MPPG) and (S)-alpha-methyl-3-carboxyphenylalanine (M3CPA), two novel preferential antagonists of group III metabotropic glutamate (mGlu) receptors, antagonized the neuroprotective activity of L-2-amino-4-phosphono-butanoate (L-AP4) or L-serine-O-phosphate in mice cultured cortical cells exposed to a toxic pulse of N-methyl-D-aspartate. In contrast, MPPG did not influence the neuroprotective activity of the selective group II mGlu receptor agonist, (2S,1'R,2'R,3'R)-2-(2,3-dicarboxy-cyclopropyl) glycine (DCG-IV). These results indicate that activation of group III mGu receptors exerts neuroprotective activity against excitotoxic neuronal death. At least one of the two major group III mGlu receptor subtypes, i.e. mGlu4 receptor, is expressed by cultured cortical neurons, as shown by immunocytochemical analysis with specific polyclonal antibodies.

Alanine↗
PubMed1996

Growth conditions influence DNA methylation in cultured cerebellar granule cells.

Growth conditions influenced DNA methylation in cultured cerebellar granule cells, as indicated by immunocytochemical analysis with monoclonal antibodies raised against 5-methylcytidine. In cultures grown under suboptimal conditions, i.e. in medium containing 10 instead of 25 mM K+, a substantial reduction in both the number of immunopositive cells and the intensity of immunostaining occurred at 4 days in vitro (DIV), a time which preceded the appearance of the morphological features of apoptosis. These results suggest that a reduction in DNA methylation is one of the biochemical events associated with the 'condemned phase' of apoptosis, in which granule cells grown under suboptimal conditions become committed to death.

Animals↗
PubMed1996

Metabotropic glutamate receptors: a new target for the therapy of neurodegenerative disorders?

Metabotropic glutamate (mGlu) receptors are a large, heterogeneous family of G-protein coupled receptors, which modulate excitatory synaptic transmission through various transduction pathways. Evidence is now accumulating that individual mGlu-receptor subtypes mediate distinct, facilitatory (group I subtypes) or inhibitory (group II and group III subtypes), actions on neurodegenerative processes. Drugs interacting with mGlu receptors are expected to influence both the induction and progression of neuronal degeneration without hampering the efficiency of fast excitatory synaptic transmission. For these reasons, mGlu receptors can be considered as promising drug targets in the experimental therapy of acute or chronic neurodegenerative diseases.

Animals↗
PubMed1996

(2S,1'S,2'S,3'R)-2-(2'-carboxy-3'-phenylcyclopropyl)glycine, a potent and selective antagonist of type 2 metabotropic glutamate receptors.

The pharmacological profile of (2S,1'S,2'S,3'R)-2-(2'-Carboxy-3'-phenylcyclopropyl)glycine (PCCG-IV) at metabotropic glutamate receptor (mGluR) subtypes mGluR1a, mGluR2, mGluR4a, and mGluR5 was examined. PCCG-IV potently antagonized glutamate-induced inhibition of forskolin-stimulated cAMP formation in baby hamster kidney cells expressing mGluR2 in a competitive manner (KB = 8.2 +/- 0.4 microM). PCCG-IV was a weak agonist at mGluR4a but inactive at the cloned phosphoinositide-coupled mGluRs (mGluR1a and mGluR5a). PCCG-IV was significantly more potent and selective as an antagonist at mGluR2 compared with previously described mGluR2 antagonists, including alpha-methyl-4-carboxyphenylglycine. In mice cortical neurons, PCCG-IV antagonized the neuroprotective effects of a selective mGluR2 agonist, (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine, at low doses (0.2-20 microM), whereas a higher dose of PCCG-IV (80 microM) was similarly neuroprotective to L-2-amino-4-phosphonobutanoate. The neuroprotective effect of PCCG-IV was blocked by an antagonist of mGluR4a, alpha-methyl-4-phosphonophenylglycine. Thus, PCCG-IV is a novel and useful tool for delineating the physiological roles of group II mGluRs in the central nervous system.

Animals↗