Biomedical subjects

F Nicoletti

Publications and source records attributed to F Nicoletti.

At least 181 records · Page 10Linked to original sources

PubMed1995

Activation of metabotropic glutamate receptors protects cultured neurons against apoptosis induced by beta-amyloid peptide.

Prolonged exposure of cultured cortical cells or cultured cerebellar granule cells to the residue 25-35 fragment of beta-amyloid peptide (beta AP), beta AP(25-35), induced neuronal apoptosis, as revealed by morphological analysis, fluorescent chromatin staining, and immunodetection of oligonucleosomes released from the nucleus into the cytoplasm. beta AP(25-35)-induced apoptosis was insensitive to ionotropic glutamate receptor antagonists but was substantially attenuated by the metabotropic glutamate receptor (mGluR) agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid. The neuroprotective action of (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid was antagonized by (RS)-alpha-methyl-4-carboxyphenylglycine and was mimicked by (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (a selective agonist of mGluR2 and -3 subtypes) and by L-2-amino-4-phosphobutanoate and L-serine-O-phosphate (selective agonists of mGluR4, -6, and -7 subtypes). However, whereas all of these drugs behaved as neuroprotectants in cultured cortical cells, only L-2-amino-4-phosphobutanoate and L-serine-O-phosphate [and not (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine] reduced beta AP(25-35)-induced apoptosis in cultured cerebellar granule cells. The neuroprotective activity of mGluR agonists may be related to their ability to inhibit membrane Ca2+ conductance, because drugs that block voltage-sensitive Ca2+ channels, such as nimodipine or Co2+, could also attenuate beta AP(25-35)-induced apoptosis.

Aminobutyrates↗

PubMed1994

Sulfolobus acidocaldarius terminal oxidase. A kinetic investigation and its structural interpretation.

The thermoacidophilic archaebacterium Sulfolobus acidocaldarius possesses a very unusual terminal oxidase. We report original kinetic experiments on membranes of this microorganism carried out by stopped flow, using time-resolved optical spectroscopy combined with singular value decomposition analysis. The reduced-oxidized kinetic difference spectrum of the Sulfolobus membranes is characterized by three significant peaks in the visible region at 605, 586, and 560 nm. The 605-nm peak and part of the 586-nm peak (cytochrome aa3-type quinol oxidase) are reduced synchronously by both ascorbate plus N,N,N',N'-tetramethyl-p-phenylendiamine (TMPD) and dithionite, and they are very rapidly oxidized by molecular oxygen. A second pool of cytochromes seems to contribute to the 586-nm peak which is not reduced by ascorbate plus TMPD and reacts very slowly with dithionite. The b-type cytochromes (560 nm peak) are reduced by both reductants and are essentially "non-autoxidizable" at room temperature. Only one CO binding site with spectral features, kinetic properties, and ligand affinity not very dissimilar from those of mammalian cytochrome oxidase can be detected in the ascorbate-reduced membranes. On the contrary, a second CO binding site having unusual properties for aa3 terminal oxidases can be detected in the dithionite-reduced membranes.

Ascorbic Acid↗

PubMed1994

(2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl) glycine positively modulates metabotropic glutamate receptors coupled to polyphosphoinositide hydrolysis in rat hippocampal slices.

In rat hippocampal slices, the novel metabotropic glutamate receptor (mGluR) ligand, (1S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV) enhanced the stimulation of polyphosphoinositide (PPI) hydrolysis elicited by quisqualate or by submaximal concentrations of ibotenate or (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD). The enhancing effect of DCG-IV was (i) specific for mGluR agonists, (ii) restricted to hippocampal slice preparation, (iii) reversible, and (iv) not subject to homologous desensitization, in addition, DCG-IV did not interact with L-2-amino-4-phosphonobutanoate (AP4), a noncompetitive antagonist of mGluRs coupled to PPI hydrolysis in brain slices [32]. The action of DCG-IV on quisqualate-stimulated PPI hydrolysis was insensitive to antagonists of ionotropic glutamate receptors and did not appear to be a consequence of a reduction in the intracellular levels of cAMP [14]. When the stimulation of PPI hydrolysis was measured as a function of the incubation time, DCG-IV potentiated quisqualate-stimulated PPI hydrolysis after 60 min of incubation, when quisqualate had already reached its maximal effect. Knowing that activation of protein kinase C (PKC) limits the extent of mGluR agonist-stimulated PPI hydrolysis over time, we have studied the enhancing effect of DCG-IV in the presence of the PKC activator, 12-O-tetradecanoylphorbol-13-acetate (TPA). As expected [9], TPA reduced quisqualate-stimulated PPI hydrolysis in control slices, but was inactive in slices incubated in the presence of DCG-IV. Taken collectively, these results suggest that DCG-IV positively modulates the activity of mGluRs coupled to PPI hydrolysis through a mechanism, which involves PKC-mediated phosphorylation processes.

Animals↗

PubMed1994

Protective action of idebenone against excitotoxic degeneration in cultured cortical neurons.

The novel free radical scavenger and electron-trapping agent, idebenone, protects cultured cortical neurons against necrotic degeneration induced by either a brief exposure to N-methyl-D-aspartate (NMDA) or a prolonged exposure to kainate. As opposed to the NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]- cyclohepten-5,10-imine hydrogen maleate (MK801), idebenone rescued cortical neurons even when applied 30 min after the NMDA pulse, suggesting that the drug interferes with the chain of toxic reactions triggered by an excessive stimulation of excitatory amino acid receptors.

Animals↗

PubMed1994

Electron transfer and ligand binding in terminal oxidases. Impact of recent structural information.

A consensus structure for the active site of terminal oxidases has been recently proposed by Hosler et al. [(1993) J. Bioenerg. Biomem. 25, 121-135]. We exploit the novel structural information to propose a hypothesis for the large difference in the rate of internal electron transfer found when experiments are started either with the reduced or with the oxidized enzyme. This rationale also allows us to discuss the oxidation state of the prevailing oxygen reacting species with reference to the concentration of the two substrates (oxygen and cytochrome c) and to the structural state of the oxidase.

Amino Acid Sequence↗

PubMed1994

Interaction between metabotropic receptors and purinergic transmission in rat hippocampal slices.

Inhibition of forskolin-stimulated cAMP formation by (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) in rat hippocampal slices was partially obliterated by the adenosine-depleting enzyme, adenosine deaminase, or by the adenosine receptor agonist, 5'-(N-ethylcarboxamido)-adenosine, suggesting that activation of metabotropic glutamate receptors (mGluRs) modulates the release of endogenous adenosine. Consistent with this hypothesis, forskolin stimulated the release of purines from rat hippocampal slices, and this effect was reduced by 1S,3R-ACPD. To establish which transduction pathway is involved in the modulation of forskolin-stimulated purine release, we have tested the novel mGluR2 agonist, (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV), which reduced forskolin-stimulated cAMP formation but, as opposed to 1S,3R-ACPD, did not stimulate polyphosphoinositide hydrolysis. DCG-IV was highly potent and more efficacious than 1S,3R-ACPD in inhibiting forskolin-stimulated purine release. Neither DCG-IV nor 1S,3R-ACPD reduced the release of purines stimulated by depolarizing concentrations of K+, suggesting that their effect was stimulus-specific. These results indicate that, in rat hippocampal slices, activation of mGluR2 receptors attenuates the release of purines induced by forskolin, a process that amplifies the final effect of forskolin on cAMP formation as a result of A2 purinergic receptor activation. Thus, the final effect of mGluR agonists on forskolin-stimulated cAMP formation in hippocampal slices depends on both a direct inhibition of adenylyl cyclase and the inhibition of adenosine release.

Adenosine↗

PubMed1994

Protective effect of the metabotropic glutamate receptor agonist, DCG-IV, against excitotoxic neuronal death.

(2S,1'R,2'R,3'R)-2-(2,3-Dicarboxycyclopropyl)glycine (DCG-IV), a potent agonist of subtypes 2 and 3 of metabotropic glutamate receptors (mGluR2 or 3), protected cultured cortical neurons against excitotoxicity induced either by a brief exposure to N-methyl-D-aspartate (NMDA) or a prolonged exposure to kainate. As a neuroprotective agent, DCG-IV was much more potent than the mixed agonists 1S,3R-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) or (2S,1'S,2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I), suggesting a neuroprotective role for mGluR2 or 3 against excitotoxic neuronal death.

1-Methyl-3-isobutylxanthine↗

PubMed1994

Protection from experimental autoimmune diabetes in the non-obese diabetic mouse with soluble interleukin-1 receptor.

We have evaluated the effects of a treatment with soluble interleukin-1 receptor (sIL-1R) in the accelerated model of autoimmune diabetes induced by cyclophosphamide (CY) in the non-obese diabetic (NOD) mouse. Prior to the CY challenge (350 mgkg body weight), female euglycemic NOD mice were randomly divided into three groups (A-C). Groups B and C were treated daily from 1 day before to 13 days after the CY challenge with sIL-1R at doses of 0.2 and 2 mg/kg body weight. Group A was treated with PBS. By 2 weeks after CY administration, an acute form of autoimmune diabetes with glycosuria, hyperglycemia and severe insulitis occurred in the majority (13/20, 65%) of the control mice (group A). In contrast, repeated injections with sIL-1R protected NOD mice from insulin-dependent diabetes mellitus (IDDM) development in a dose-dependent fashion; the incidence of IDDM was 53.3% (8/15) in the mice treated with 0.2 mg/kg and only 6.7% (1/15) in those treated with 2 mg/kg. However, none of the doses of the sIL-1R reduced the extent of insulitis in NOD mice. Importantly, the anti-diabetogenic property of sIL-1R may not involve major T cell function impairment; accordingly, in parallel experiments, splenic lymphoid cells from NOD mice not challenged with CY, but treated with 2 mg/kg sIL-1R for 5 consecutive days showed a normal distribution of mononuclear cell subsets and maintained their capacity to secrete interferon-gamma and IL-2 and to proliferate in response to polyclonal mitogenic stimulation with concanavalin A.

Animals↗

PubMed1994

Protection from experimental autoimmune thyroiditis in CBA mice with the novel immunosuppressant deoxyspergualin.

The effects of the novel immunosuppressant Deoxyspergualin (DSP) on the development of experimental autoimmune thyroiditis (EAT) in CBA mice were studied. For EAT induction, the mice were immunized with 100 micrograms of porcine thyroglobulin (p Tg) emulsified in CFA on day 0 and in IFA, for boosting, on day 14. Twenty-eight days after primary immunization, histological and serological signs of EAT occurred in control mice treated with PBS which showed marked lymphoid infiltration of the thyroid glands along with increased serum titres of anti-pTg antibodies. Development of both these EAT features was significantly suppressed when the mice were treated with 2.5 mg/kg body weight DSP, given daily, five times a week, from day -2 to day +28 after immunization. The effect appeared to be dose-dependent and DSP was ineffective when given under the same experimental conditions at the dose of 0.5 mg/kg body weight. No DSP-toxic effects could be observed during the experiment. These results provide further evidence for the powerful immunosuppressive properties of DSP and suggest that this drug may be used in the treatment of autoimmune thyroid diseases and other T-cell mediated autoimmune disorders in humans.

Animals↗

PubMed1994

The effects of thymopentin on the development of SLE-like syndrome in the MRL/lpr-lpr mouse.

Thymopentin (TP-5) is a synthetic pentapeptide that corresponds to the active 32-36 amino acid sequence of the thymic hormone thymopoietin, of which it retains all the immunomodulatory properties. In this study, we have evaluated the effects of long term prophylactic treatment with TP-5 on the clinical, immunological and histological parameters of the SLE-like syndrome that spontaneously occurs in MRL/lpr-lpr (MRL-lpr) mice. TP-5, administered (s.c.) to these mice at the doses of 1, 10 and 100 mg/kg, was given daily, five times a week, from the 9th to the 26th weeks of life. The prophylactic treatment with TP-5 prolonged in a clear dose-dependent fashion the lifespan of MRL-lpr mice as compared with PBS-treated control mice, and the effect reached statistical significance at the doses of 10 and 100 mg/kg. In parallel ex vivo studies, this clinical effect was associated with multiple profound modifications of the immune system including: (i) the reduction of the spontaneous and Con A-induced release of interleukin-4 (IL-4); (ii) the increased secretion of interferon-gamma (IFN-gamma) and IL-6 upon polyclonal mitogenic stimulation, and (iii) the amelioration of the defective Con A-induced lymphoproliferative response. In contrast, although the drug diminished the severity of proteinuria in MRL-lpr mice, it neither reduced histological signs of lupus nephritis nor diminished the serum titres of anti-native DNA and anti-histone autoantibodies. These results indicate that TP-5 displayed powerful immunodulatory activities in a well known model of human SLE.

Amino Acid Sequence↗

PubMed1994

Chronic L-alpha-glyceryl-phosphoryl-choline increases inositol phosphate formation in brain slices and neuronal cultures.

Repeated, but not single injections of L-alpha-glyceryl-phosphorylcholine (alpha GPC) significantly increased basal [3H]inositol monophosphate (InsP) formation in hippocampal, cortical, and striatal slices of male rats. The effect was dose-dependent and was accompanied by an increased incorporation of [3H]inositol into the phospholipid fraction. Incubation of brain slices with different neurotransmitter antagonists, such as atropine, prazosin, or L-2-amino-4-phosphonobutanoate (L-AP4) did not modify the increase in [3H]InsP formation produced by alpha GPC, suggesting that the effect is not mediated by an increased availability of a specific neurotransmitter. Similar results were obtained in cerebellar and cortico-striatal neurones in primary culture exposed to daily addition of alpha GPC since the second day of maturation in vitro. We suggest that alpha GPC treatment may result in an increased rate of phospholipid synthesis, including the phosphoinositides available for signal transduction at central nervous system level.

Animals↗

PubMed1994

Reduction of spontaneous autoimmune diabetes in diabetes-prone BB rats with the novel immunosuppressant fusidic acid. Effect on T-cell proliferation and production of interferon-gamma.

Diabetes-prone (DP) BB rats spontaneously develop a hyperglycaemic condition which closely resembles human insulin-dependent diabetes mellitus (IDDM), both in terms of clinical and histological features. The incidence of IDDM was significantly reduced when these animals were treated with 2 or 4 mg fusidic acid (FA)/day i.m. from day 30 to day 120 of age. In addition, the mean insulitis score was significantly diminished in the animals treated with FA compared to both vehicle-treated and untreated controls. Finally, 2 mg/day of FA i.m. prevented cell proliferation and interferon-gamma secretion from peripheral blood mononuclear cells upon ex vivo stimulation with concanavalin A. The capacity of FA to substantially reduce the incidence of autoimmune diabetes in a well-known animal model of human IDDM supports previous observations regarding the immunosuppressive properties of FA and its potential use in the treatment of human autoimmune diabetes.

Age Factors↗

PubMed1993

Characterization of metabotropic glutamate receptors negatively linked to adenylyl cyclase in brain slices.

We have characterized the pharmacological profile of activation of metabotropic glutamate receptors negatively linked to adenylyl cyclase (mGluR decreases cAMP) in brain slices. Among the putative mGluR agonists, (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV) and (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), were the most potent inhibitors of forskolin-stimulated cAMP formation in hippocampal slices, followed by ibotenate, L-2-amino-3-phosphonopropionate (AP3), quisqualate, L-glutamate and beta-N-methylamino-L-alanine (BMAA). Inhibition of forskolin-stimulated cAMP formation by DL-2-amino-4-phosphonobutanoate (AP4) was biphasic, suggesting that the drug interacts with more than one mGluR decreases cAMP subtype. Both L-AP4 and L-serine-O-phosphate (a restricted analogue of AP4) were much more effective in inhibiting forskolin-stimulated cAMP formation than their D-isomers, indicating that interaction of these drugs with the mGluR decreases cAMP is stereoselective. Despite the fact that DCG-IV and ibotenate behave as NMDA receptor agonists, their effect was insensitive to MK-801. The regional pattern of expression of mGluR decreases cAMPS, as estimated by using 1S,3R-ACPD as an agonist, did not correlate with the steady-state levels of mGluR2 mRNA. Thus, 1S,3R-ACPD inhibited forskolin-stimulated cAMP in slices from hippocampus, cerebral cortex, corpus striatum, olfactory tubercle or hypothalamus, but not in slices from olfactory bulb or cerebellum; in contrast, mGluR2 mRNA levels were high in the olfactory bulb and very low in the corpus striatum. 1S,3R-ACPD also inhibited forskolin-stimulated cAMP formation in cortical membranes, excluding the involvement of trans-synaptic mechanisms in the activity of mGluR decreases cAMPS.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗

PubMed1993

(2s,1'R,2'R,3'R)-2-(2,3-Dicarboxycyclopropyl) glycine enhances quisqualate-stimulated inositol phospholipid hydrolysis in hippocampal slices.

In adult rat hippocampal slices, (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV) did not affect the basal hydrolysis of polyphosphoinositides but dramatically enhanced (EC50 value = 30 nM) the stimulation of [3H]inositol monophosphate (InsP) formation by quisqualate, without substantially affecting the stimulation produced by maximal concentrations of 1S,3R-amino-cyclopentane-1,3-dicarboxylic acid (ACPD) or carbamylcholine. alpha-Amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) was virtually devoid of activity on [3H]InsP formation, either in the absence or presence of DCG-IV. These results suggest that DCG-IV acts, directly or indirectly, as a positive modulator of metabotropic glutamate receptors in the rat hippocampus.

Animals↗

PubMed1993

Amyloid beta protein does not interact with tachykinin receptors coupled to inositol phospholipid hydrolysis in human astrocytoma cells.

We have tested the interaction between amyloid beta protein (A beta P) and tachykinin receptors in cultured UC-11MG astrocytoma cells, which express high affinity substance P receptors and respond to substance P with an unusually large stimulation of polyphosphoinositide hydrolysis. Both the full-length A beta P (A beta P1-40) and the fragment 25-35 (A beta P25-35) did not affect the stimulation of [3H]inositolmonophosphate (InsP) formation by substance P. A beta P25-35 was also inactive when applied to the cultures 18 or 72 h prior to the assay. In addition, A beta P25-35 did not displace specifically bound [3H]SarMet substance P from its recognition sites in intact UC-11MG cells. These results suggest that, at least in this specific cell type, amyloid peptides do not interact with substance P receptors.

Amyloid beta-Peptides↗

PubMed1993

The effects of a monoclonal antibody to interferon-gamma on experimental autoimmune thyroiditis (EAT): prevention of disease and decrease of EAT-specific T cells.

CBA/J mice immunized with thyroglobulin (Tg) develop an experimental autoimmune thyroiditis (EAT) with lymphocytic infiltration of the thyroid glands, autoantibodies to Tg and occurrence of EAT-specific T cells. When these mice were treated for 4 weeks after immunization with 1 mg/week of a monoclonal antibody (mAb) that neutralizes the activity of interferon-gamma (IFN) a beneficial effect on the onset of EAT was observed. Characteristic features of EAT were significantly reduced, including the lymphocytic infiltrations of the thyroid glands and the serum levels of autoantibodies to Tg. Moreover, in lymphoid organs, mAb to IFN-gamma significantly reduced the percentages of Tg-specific CD8+ cells, labeled by the anti-clonotypic mAb AG7. These Tg-specific T cells seem responsible for thyroid damages and disease development, since EAT was simultaneously abrogated. These results show that IFN-gamma plays an essential role in the pathophysiology of EAT and suggest the possibility to treat autoimmune thyroid diseases with mAb to IFN-gamma or drugs able to antagonize the production and/or the action of this cytokine.

Animals↗

PubMed1993

Pharmacological characterization of metabotropic glutamate receptors in cultured cerebellar granule cells.

A detailed pharmacological characterization of metabotropic glutamate receptors (mGluR) was performed in primary cultures of cerebellar granule cells at 6 days in vitro (DIV). The rank order of agonists induced polyphosphoinositide (PPI) hydrolysis (after correcting for the ionotropic component in the response) was as follows: in terms of efficiency, Glu > quisqualate (quis) = ibotenate (ibo) > (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid (ACPD) > beta-methyl-amino-L-alanine (BMAA) and in terms of potency, quis > ACPD > Glu > ibo = BMAA. Ionotropic excitatory amino acid (EAA) receptor agonists, such as alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) were relatively inactive (in the presence of Mg2+). Quis and ACPD-induced PPI hydrolysis was unaffected by ionotropic Glu receptor antagonists, but was inhibited, in part by L-2-amino-3-phosphonopropionate (AP3). In contrast, Glu-or ibo- induced PPI hydrolysis was reduced, in part, by both AP3 and NMDA receptor antagonists. Characteristic interactions involving different transmitter receptors were noted. PPI hydrolysis evoked by quis and 1S,3R-ACPD was not additive. In contrast, PPI hydrolysis stimulated by quis/ACPD and carbamylcholine was additive (indicating different receptors/transduction pathways). In the presence of Mg2+, the metabotropic response to quis/AMPA and NMDA was synergistic (this being consistent with AMPA receptor-induced depolarization activating NMDA receptor). On the other hand, in Mg(2+)-free buffer the effects of quis and NMDA, at concentrations causing maximal PPI hydrolysis, were additive (indicating that PPI hydrolysis was effected by two different mechanisms).(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗

PubMed1993

Oxytocin reduces the activity of N-methyl-D-aspartate receptors in cultured neurons.

N-Methyl-D-Aspartate(NMDA)-sensitive glutamate receptors, are critically involved in the induction of the learning process. Activation of NMDA receptors by glutamate lead to massive influx of extracellular Ca2+, with ensuing activation of a variety of Ca(2+)-dependent enzymes, including protein kinase C. This triggers a cascade of intracellular reactions which is essential for memory formation. In culture neurons, high concentrations of oxytocin (> 1 microM) attenuate the stimulation of 45Ca2+ influx promoted by glutamate through the activation NMDA receptors. In addition, the hormone reduces glutamate-stimulated [3H]4-beta-phorbol 12,13-dibutyrate (PdBu) binding in intact cells, a parameter that reflects the translocation of protein kinase C from the cytosol to the cell membrane. Taken collectively, these results indicate that oxytocin reduces the activity of NMDA receptors, thus impairing one of the major substrates for the induction of learning and memory.

Animals↗