Biomedical subjects

F Nicoletti

Publications and source records attributed to F Nicoletti.

At least 37 records · Page 2Linked to original sources

PubMed2004

Protective effects of estradiol on TRAIL-induced apoptosis in a human oligodendrocytic cell line: evidence for multiple sites of interactions.

Demyelinating diseases are high impact neurological disorders. Steroids are regarded as protective molecules in the susceptibility to these diseases. Here, we studied the interactions between tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), a potent proapoptotic molecule toxic to oligodendrocytes, and 17-beta-estradiol (E-17-beta), in human oligodendrocytic MO3.13 cells. Exposure of cells to TRAIL resulted in the upregulation of both death receptors DR4 and DR5 and apoptosis, as well as the activation of caspase-8 and -3, increased phosphorylation of Jun-N-terminal kinase and p38 kinase, and the reduction of bcl-2 and bcl-xL proteins. TRAIL-mediated MO3.13 cell apoptosis was abrogated by the dominant-negative form of the adaptor protein FADD and by caspase inhibitors. Preincubation with E-17-beta completely prevented both TRAIL-induced DR4 and DR5 upregulation and apoptosis. Estrogen-induced cytoprotection was time and concentration dependent and reverted by antiestrogens. Estrogen treatment per se reduced kinase phosphorylation, and upregulated bcl-2 and bcl-xL proteins. In conclusion, our data show that the detrimental role of TRAIL on oligodendrocytes can be effectively counteracted by estrogens, thus suggesting that the underlying molecular interactions can be of potential relevance in characterizing novel targets for therapy of demyelinating disorders.

Apoptosis↗

PubMed2004

Testosterone amplifies excitotoxic damage of cultured oligodendrocytes.

An overactivation of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/kainate receptors has been implicated in the pathophysiology of oligodendrocyte damage in demyelinating disorders of the CNS. We decided to examine the effect of testosterone on excitotoxic death of oligodendrocytes because a gender difference exists in the incidence and disease course of multiple sclerosis. Short-term pure cultures of oligodendrocytes (4 days in vitro) were exposed to a brief pulse with kainate or AMPA + cyclothiazide for the induction of excitotoxicity. Exposure to testosterone enantate was slightly toxic per se and amplified both AMPA and kainate toxicity. Testosterone treatment induced all gene targets of p53, and amplified the induction of these genes induced by kainate. The effect of testosterone was mediated by the activation of androgen receptors and was resistant to the aromatase inhibitors, dl-aminoglutethimide and 4-hydroxyandrost-4-ene-3,17-dione. Testosterone treatment also potentiated the stimulation of 45Ca2+ influx induced by AMPA + cyclothiazide or kainate without changing the expression of the glutamate receptor (GluR) 1, -2/3, and -4 subunits of AMPA receptors or the GluR6/7 subunits of kainate receptors. We conclude that testosterone amplifies excitotoxic damage of oligodendrocytes acting at an early step of the death cascade triggered by AMPA/kainate receptors.

Animals↗

PubMed2004

Regulation of mGlu4 metabotropic glutamate receptor signaling by type-2 G-protein coupled receptor kinase (GRK2).

We examined the role of G-protein coupled receptor kinase-2 (GRK2) in the homologous desensitization of mGlu4 metabotropic glutamate receptors transiently expressed in human embryonic kidney (HEK) 293 cells. Receptor activation with the agonist l-2-amino-4-phosphonobutanoate (l-AP4) stimulated at least two distinct signaling pathways: inhibition of cAMP formation and activation of the mitogen-activated protein kinase (MAPK) pathway [assessed by Western blot analysis of phosphorylated extracellular signal-regulated kinase (ERK) 1 and 2]. Activation of both pathways was attenuated by pertussis toxin. Overexpression of GRK2 (but not GRK4) largely attenuated the stimulation of the MAPK pathway by l-AP4, whereas it slightly potentiated the inhibition of FSK-stimulated cAMP formation. Transfection with a kinase-dead mutant of GRK2 (GRK2-K220R) or with the C-terminal fragment of GRK2 also reduced the mGlu4-mediated stimulation of MAPK, suggesting that GRK2 binds to the Gbetagamma subunits to inhibit signal propagation toward the MAPK pathway. This was confirmed by the evidence that GRK2 coimmunoprecipitated with Gbetagamma subunits in an agonist-dependent manner. Finally, neither GRK2 nor its kinase-dead mutant had any effect on agonist-induced mGlu4 receptor internalization in HEK293 cells transiently transfected with GFP-tagged receptors. Agonist-dependent internalization was instead abolished by a negative-dominant mutant of dynamin, which also reduced the stimulation of MAPK pathway by l-AP4. We speculate that GRK2 acts as a "switch molecule" by inhibiting the mGlu4 receptor-mediated stimulation of MAPK and therefore directing the signal propagation toward the inhibition of adenylyl cyclase.

Cell Line↗

PubMed2004

Similarities between methamphetamine toxicity and proteasome inhibition.

The monoamine neurotoxin methamphetamine (METH) is commonly used as an experimental model for Parkinson's disease (PD). In fact, METH-induced striatal dopamine (DA) loss is accompanied by damage to striatal nerve endings arising from the substantia nigra. On the other hand, PD is characterized by neuronal inclusions within nigral DA neurons. These inclusions contain alpha-synuclein, ubiquitin, and various components of a metabolic pathway named the ubiquitin-proteasome (UP) system, while mutation of genes coding for various components of the UP system is responsible for inherited forms of PD. In this presentation we demonstrate for the first time the occurrence of neuronal inclusions in vivo in the nigrostriatal system of the mouse following administration of METH. We analyzed, in vivo and in vitro, the shape and the fine structure of these neuronal bodies by using transmission electron microscopy. Immunocytochemical investigation showed that these METH-induced cytosolic inclusions stain for ubiquitin, alpha-synuclein, and UP-related molecules, thus sharing similar components with Lewy bodies occurring in PD, with an emphasis on enzymes belonging to the UP system. In line with this, blockade of this multicatalytic pathway by the selective inhibitor epoxomycin produced cell inclusions with similar features. Moreover, using a multifaceted pharmacological approach, we could demonstrate the need for endogenous DA in order to form neuronal inclusions.

Animals↗

PubMed2004

Metabotropic receptors as targets for drugs of potential use in the treatment of neuropathic pain.

Glutamate is the major neurotransmitter in the mammalian central nervous system and plays a pivotal role in both acute and chronic pain. The actions of glutamate are mediated by two receptor families: ionotropic glutamate receptors (iGluRs), and metabotropic glutamate receptors (mGluRs). Activation of glutamate receptor can elicit both hyperalgesic and analgesic effects. Eight mGluRs subtypes (mGluR1-mGluR8) have been identified and classified into three groups. Among these, group I mGluRs (mGlu1 and -5) have been implicated in the processes of central sensitization and persistent nociception, whereas activation of group II mGluRs (mGlu2/3) is effective against neuropathic or inflammatory pain. In this review we focus on the role of mGlu2/3 in the modulation of persistent pain, and on their potential use as drug targets in pain management.

Acetylcarnitine↗

PubMed2003

An increased expression of the mGlu5 receptor protein following LTP induction at the perforant path-dentate gyrus synapse in freely moving rats.

The involvement of metabotropic glutamate (mGlu) receptors in the induction of long-term potentiation (LTP) in vivo has been consistently documented. We have investigated whether LTP induction in the dentate gyrus of rats leads to changes in expression of mGlu2/3 or -5 receptor subtypes in the hippocampus. LTP was induced at the medial perforant path-dentate gyrus synapses, and mGlu receptor expression was examined by Western blot or in situ hybridization. An up-regulation of mGlu5 receptors was observed in the hippocampus both 24 and 48 h following LTP induction. This effect was restricted to the dentate gyrus and CA1 region, whereas no changes in mGlu5 receptor protein (but an increase in mRNA levels) were observed in the CA3 region. The increased expression of mGlu5 receptors was directly related to the induction of LTP, because it was not observed when tetanic stimulation was carried out in animals treated with the NMDA receptor antagonist, 2-amino-5-phosphonopentanoate (AP5). Western blot analysis also showed a reduced expression of mGlu2/3 receptors in the whole hippocampus 24 h after LTP induction, indicating that the increased expression of mGlu5 receptors was specific. These data suggest that an up-regulation of mGlu5 receptors is a component of the plastic changes that follow the induction of LTP at the perforant path-dentate gyrus synapse.

2-Amino-5-phosphonovalerate↗

PubMed2003

Endogenous activation of group-II metabotropic glutamate receptors inhibits the hypothalamic-pituitary-adrenocortical axis.

Systemic injection of the mGlu2/3 receptor antagonist, LY341495 (1 mg/kg, i.p.), increased plasma corticosterone in mice to an extent similar to that induced by the despair test. Treatment with the mGlu2/3 receptor agonist, LY379268 (1 mg/kg, i.p.), or the non-competitive mGlu5 receptor antagonist, MPEP (5 mg/kg, i.p.), failed to induce significant changes in corticosterone levels. Searching for a site of action of LY341495, we examined the expression of mGlu receptor subtypes in the various anatomical regions of the mouse hypothalamic-pituitary-adrenal (HPA) axis. Only mGlu5 and -7 receptor mRNAs were detected in the adrenal gland by RT-PCR, whereas mGlu -1, -3, -4, -5, -7 and -8 receptor mRNAs were detected in the anterior pituitary. All transcripts (with the exception of mGlu5 and mGlu6 receptor mRNAs) were detected in the hypothalamus. However, Western blot analysis showed the presence of mGlu2/3 receptor proteins only in the hypothalamus and not in the anterior pituitary. This was consistent with functional data showing that LY341495 (0.1 and 1 microM) failed to affect ACTH secretion from isolated mouse anterior pituitaries. Moving from these observations, we examined whether LY341495 could activate the HPA axis by inhibiting mGlu2/3 receptors at hypothalamic level. We measured the release of corticotropin releasing hormone (CRH) in isolated mouse hypothalami incubated in the presence of subtype-selective mGlu receptor agonists or antagonists. Among all the drugs we have tested, only LY341495 was able to increase CRH secretion. With high concentrations of LY341495 (1 microM) this increase was similar to that induced by 50 mM K(+). The action of LY341495 was prevented by the combined application of the mGlu2/3 receptor agonist, LY379268. We conclude that group-II mGlu receptors tonically regulate the HPA axis by controlling CRH secretion at hypothalamic level.

Adrenal Glands↗

PubMed2003

(-)-PHCCC, a positive allosteric modulator of mGluR4: characterization, mechanism of action, and neuroprotection.

Group-III metabotropic glutamate receptors (mGluR4, -6, -7, and -8) modulate neurotoxicity of excitatory amino acids and beta-amyloid-peptide (betaAP), as well as epileptic convulsions, most likely via presynaptic inhibition of glutamatergic neurotransmission. Due to the lack of subtype-selective ligands for group-III receptors, we previously utilized knock-out mice to identify mGluR4 as the primary receptor mediating neuroprotection of unselective group-III agonists such as L-AP(4) or (+)-PPG, whereas mGluR7 is critical for anticonvulsive effects. In a recent effort to find group-III subtype-selective drugs we identified (+/-)-PHCCC as a positive allosteric modulator for mGluR4. This compound increases agonist potency and markedly enhances maximum efficacy and, at higher concentrations, directly activates mGluR4 with low efficacy. All the activity of (+/-)-PHCCC resides in the (-)-enantiomer, which is inactive at mGluR2, -3, -5a, -6, -7b and -8a, but shows partial antagonist activity at mGluR1b (30% maximum antagonist efficacy). Chimeric receptor studies showed that the binding site of (-)-PHCCC is localized in the transmembrane region.Finally, (-)-PHCCC showed neuroprotection against betaAP- and NMDA-toxicity in mixed cultures of mouse cortical neurons. This neuroprotection was additive to that induced by the highly efficacious mGluR1 antagonist CPCCOEt and was blocked by MSOP, a group-III mGluR antagonist. Our data provide evidence for a novel pharmacological site on mGluR4, which may be used as a target-site for therapeutics.

Amyloid beta-Peptides↗

PubMed2003

Reduced activity of hippocampal group-I metabotropic glutamate receptors in learning-prone rats.

Following the hypothesis of the "signal-to-noise" ratio we examined whether changes in the activity of group-I metabotropic glutamate (mGlu) receptors in the hippocampus are associated with a condition that specifically enhances the learning capacity in rats. As a model, we used rats that had been nursed by mothers drinking a solution of corticosterone (13.5 mg of daily intake of corticosterone hemisuccinate) during the lactation period. These rats were prone to learn, as indicated by a better performance in a passive avoidance test. Stimulation of polyphosphoinositide (PI) hydrolysis by the mGlu receptor agonist, 1S,3R-1-amino-cyclopentan-1,3-dicarboxylic acid (1S,3R-ACPD), was attenuated in hippocampal slices prepared from corticosterone-nursed male and female rats at 30 or 60 days of postnatal life, an age at which an increased learning capacity could be demonstrated. This effect was specific because the PI response to carbamylcholine was unchanged. A reduced PI hydrolysis in corticosterone-nursed rats was also observed when group-I mGlu receptors (i.e. mGlu1 and -5 receptors) were selectively activated using 3,5-dihydroxyphenylglycine or 1S,3R-APCD combined with the selective group-II mGlu receptor antagonist, 2S-2-amino-2-(1S,2S-2-carboxycyclopropan-1-yl)-3-(xanth-9-yl)propionate. Western blot analysis showed a selective reduction in the expression of mGlu1a receptor protein in the hippocampus of corticosterone-nursed rats, whereas expression of mGlu5 and mGlu2/3 receptors was unchanged. The reduction in mGlu-receptor mediated PI hydrolysis in the hippocampus may contribute to the greater learning capacity of corticosterone-nursed rats by reducing the background noise over which a specific signal must be superimposed during learning. This hypothesis was supported by the evidence that mGlu-receptor stimulated PI hydrolysis was amplified in hippocampal slices from rats subjected to a passive avoidance learning paradigm, and that this amplification was greater in slices from corticosterone-nursed rats of both sexes.

Animals↗

PubMed2003

Relationship between learning, stress and hippocampal brain-derived neurotrophic factor.

Brain-derived neurotrophic factor (BDNF) expression in the hippocampus is reduced in response to acute, as well as repeated immobilization stress. This effect might be mediated by corticosterone, because corticosterone administration is known to reduce hippocampal BDNF. However, rats subjected to a learning paradigm showed an increased BDNF expression in the hippocampus despite the high corticosterone levels found during the test. To dissect the relative contributions of learning and stress to the overall changes in BDNF levels we set up an experimental model in which two groups of rats received the same amount of stress, but only one group had the possibility to learn how to avoid it. Using this model, we now report that learning and stress exert an opposite modulation on BDNF levels in the hippocampus, and that the increasing effect of learning predominates over the decreasing effect of stress.

Animals↗

PubMed2002

Serum concentrations of the interferon-gamma-inducible chemokine IP-10/CXCL10 are augmented in both newly diagnosed Type I diabetes mellitus patients and subjects at risk of developing the disease.

AIMS/HYPOTHESIS: Chemokines are chemotactic cytokines controlling the recruitment of leukocytes from the blood by regulating integrin adhesiveness. It has been shown that the migration of CD4+Th1 and CD4+Th2 cells is governed by specific chemokines. Increasing evidence suggests that the CD4+Th1 cheomoattractant chemokine CXCL10, also termed Interferon (IFN)-gamma -inducible protein (IP)-10 is pathogenetically involved in several immunoinflammatory and autoimmune diseases. METHODS: IFN-gamma and IP-10 were quantified by solid-phase ELISA in sera of patients with either newly diagnosed or long-term Type I (insulin-dependent) diabetes mellitus, and in sera of their healthy first degree relatives. The latter were subdivided into "low" and "high" risk prediabetic subjects depending on whether they were negative or positive for the anti-beta-cell autoantibodies ICA and GAD. RESULTS: Compared with healthy control subjects (18%, 9/50), those with a low risk of disease (21%, 5/24) and the group of patients with long-term Type I diabetes (24%, 12/50), IP-10 was found more frequently and at increased concentrations in both newly diagnosed Type I diabetic patients (84%, 42/50) and in those with a high risk of disease (73%, 16/22); in the latter, the IP-10 concentrations correlated with those of IFN-gamma. CONCLUSION/INTERPRETATION: Circulating IP-10 concentrations is increased in patients with Type I diabetes, but only during the early and subclinical stage of the disease.

Adult↗

PubMed2002

Continuous subcutaneous infusion of apomorphine rescues nigro-striatal dopaminergic terminals following MPTP injection in mice.

Apomorphine has been introduced in the treatment of late-stage Parkinson's Disease (PD). The disadvantage of a short half-life of apomorphine is now overcome by the use of a continuous subcutaneous (s.c.) self-delivering system. We examined whether continuous s.c. infusion of apomorphine rescues nigro-striatal dopaminergic neurons from toxicity induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice. Apomorphine was continuously infused in mice by means of a s.c. minipump that delivered the drug at a rate of 0.5 or 3.15 mg/kg/day. MPTP induced a >80% reduction in striatal dopamine (DA) after one day. DA levels were still substantially reduced one month following MPTP injection, in spite of a partial recovery. Similarly, striatal immunoreactivity for tyrosine hydroxylase and dopamine transporter was markedly reduced at this time interval. Continuous s.c. infusion of apomorphine starting 40 h following MPTP injection rescued striatal dopaminergic terminals, as assessed by measurements of DA and its metabolites, as well as TH and DAT immunostaining after one month. The neurorescuing effect was more remarkable at a delivery rate of 3.15 mg/kg/day of apomorphine. In contrast, no rescue was observed when apomorphine was administered as a single daily s.c. bolus of 1 or 5mg/kg starting 40 h following MPTP. We conclude that apomorphine is able to rescue nigro-striatal dopaminergic neurons when continuously delivered at doses that are comparable to those delivered by minipumps in PD patients. These results suggest that continuous s.c. infusion of apomorphine not only relieves the symptoms, but also reduce the ongoing degeneration of nigro-striatal dopaminergic neurons in PD patients.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed2002

Imipramine treatment up-regulates the expression and function of mGlu2/3 metabotropic glutamate receptors in the rat hippocampus.

We examined the effect of a chronic imipramine treatment (10 mg/kg, i.p., once daily for 21 days) on the expression and function of metabotropic glutamate (mGlu) receptors in discrete regions of the rat brain. Chronic imipiramine treatment up-regulated the expression of mGlu2/3 receptor proteins in the hippocampus, nucleus accumbens, cerebral cortex and corpus striatum. Expression of mGlu1a receptor protein was increased exclusively in the hippocampus, whereas no changes in the expression of mGlu4 and mGlu5 receptors or Homer-1a protein were detected. Using hippocampal slices, we examined the stimulation of polyphosphoinositide (PI) hydrolysis induced by mGlu receptor agonists in control and imipramine-treated rats. Imipramine treatment amplified the PI response to the non subtype-selective mGlu receptor agonist, 1S,3R-aminocyclopentane-1,3-dicarboxylated (1S,3R-ACPD) in both hippocampal and cortical slices, but failed to affect the response to the selective mGlu1/5 receptor agonist, S-3,5-dihydroxyphenylglycine (DHPG). Amplification was restored when DHPG was combined with the selective mGlu2/3 receptor agonist, LY379268. In addition, 1S,3R-ACPD-stimulated PI hydrolysis was no longer enhanced in imipramine-treated rats when the mGlu2/3 component of the PI response was abrogated by the antagonist, LY341495. In contrast, the ability of LY379268 to inhibit forskolin-stimulated cAMP formation was reduced in hippocampal slices of rats chronically treated with imipramine. Taken together, these results suggest that neuroadaptive changes in the expression and function of mGlu2/3 receptors occur in response to chronic antidepressants.

Adrenergic Uptake Inhibitors↗

PubMed2002