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Biomedical subjects

F Moroni

Publications and source records attributed to F Moroni.

At least 73 records · Page 4Linked to original sources
PubMed1994

Glutamate receptor antagonists protect against ischemia-induced retinal damage.

The effects of intravitreal injections of excitatory amino acid receptor antagonists have been studied on the ischemic neuronal damage induced by photochemical occlusion of the retinal vessels. Rats were systemically injected with rose bengal fluorescein dye and one of their eyes was exposed to bright light. The activities of the enzymes, choline-acetyltransferase and glutamate decarboxylase, were measured as an index of neuronal loss in the lesioned tissue. Lesioned retinas had a 75 +/- 5% reduction in choline-acetyltransferase activity and a 72 +/- 8% reduction in glutamate-decarboxylase activity, suggesting that the lesion causes a massive loss of retinal neurons, which use acetylcholine or gamma-aminobutyric acid (GABA) as neurotransmitter. A single intravitreal injection of excitatory amino acid receptor antagonists, performed immediately after the lesion, significantly reduced this loss. Both alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-D-aspartate) (NMDA) types of ionotropic glutamate receptor antagonists were active in a dose-dependent manner. Almost complete protection was also obtained with relatively large doses of thiokynurenic acid (400 nmol), a non-selective antagonist of both AMPA and NMDA glutamate receptors, while 7-Cl-thiokynurenic acid, a potent and selective glycine receptor antagonist, was not active up to 200 nmol. These results strongly suggest that excitotoxic mechanisms are involved in ischemia-induced neuronal death in the retina and that appropriate treatments with antagonists of both AMPA and NMDA receptor types may significantly reduce this damage.

2-Amino-5-phosphonovalerate↗
PubMed1994

Modulation of human lymphoblastoid interferon activity by melatonin in metastatic renal cell carcinoma. A phase II study.

BACKGROUND: Numerous attempts to identify active cytotoxic agents for the treatment of metastatic renal cell carcinoma (RCC) have proved disappointing. However, several recent developments in biologic therapy of neoplastic disease have substantially improved the prospects for the treatment of advanced RCC. Melatonin (MLT), a hormone regulated by the pineal gland, has been shown to act on the immune system by causing the release of cytokines from activated T-cell populations. METHODS: A series of 22 patients with documented progressing RCC entered a trial in which the authors studied the effect of a long term regimen (12 months) with human lymphoblastoid interferon (IFN), 3 mega units (MU) intramuscularly 3 times per week, and MLT, 10 mg orally every day. RESULTS: Twenty-one patients were evaluable for response and toxicity. There were seven remissions (33%): three complete, involving lung and soft tissue and four partial, with a median duration at the time of this writing of 16 months. Nine patients achieved stable disease, and five progressed. General toxicity was mild. Fever, chills, arthralgias, and myalgias occurred rarely. Leukopenia and hepatic enzyme elevation were modest and always reversible. CONCLUSIONS: Response rate and toxic effects observed during this study warrant additional randomized studies to define the role of MLT's concomitant administration in the clinical response to IFN in metastatic RCC.

Adult↗
PubMed1994

Modulation of the kynurenine pathway in search for new neuroprotective agents. Synthesis and preliminary evaluation of (m-nitrobenzoyl)alanine, a potent inhibitor of kynurenine-3-hydroxylase.

The synthesis of (o-nitrobenzoyl)-, (m-nitrobenzoyl)-, and (p-nitrobenzoyl)alanine (o-, m-, and p-NBA), three new kynurenine analogues, and their evaluation as inhibitors of kynureninase and kynurenine-3-hydroxylase are reported. The most potent of these compounds, m-NBA, has an IC50 of 0.9 +/- 0.1 microM as an inhibitor of kynurenine-3-hydroxylase and of 100 +/- 12 microM as an inhibitor of kynureninase. When administered to rats, m-NBA significantly increases the concentration of kynurenine and kynurenic acid in the brain as well as in blood and in the liver. m-NBA has also been shown to increase the concentration of kynurenic acid in hippocampal extracellular fluid. This increase is associated with sedative and anticonvulsant activities, thus confirming the possibility of antagonizing L-glutamate-mediated effects by modulating the kynurenine pathway of L-tryptophan metabolism.

Alanine↗
PubMed1994

Sulfate esters of hydroxy amino acids as stereospecific glutamate receptor agonists.

Enantiomerically pure sulfate esters of the hydroxy amino acids homoserine, hydroxyproline and 4-hydroxypipecolic acid were synthesized and tested on alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors present in the mice cortical wedge preparation and on NMDA receptors present in the myenteric plexus of the guinea pig with the aim of finding new possible endogenous ligands (either agonists or antagonists) for excitatory amino acid receptors. The linear and flexible compound S-homoserine sulfate caused a depolarization of both AMPA and NMDA receptors. In the cortex its agonist action had an EC50 of 150 microM for NMDA and 300 microM for AMPA receptors and in the myenteric plexus its EC50 was 600 microM. The stereoisomer R-homoserine sulfate did not depolarize the cortical wedges and failed to cause ileal contraction up to a concentration of 500 microM. Among the four possible stereoisomers of 4-hydroxyproline sulfate, which are rigid structures and may be regarded as cyclization forms of homoserine sulfate, t-S-hydroxyproline sulfate was a selective AMPA receptor agonist with an EC50 of 70 microM in the cortex. The other three isomers were not active as agonists up to 500 microM and none of them had antagonist activity. Finally, t-4-hydroxy-S-pipecolic acid-4-sulfate, a superior homologue of t-S-hydroxyproline sulfate, was found to be one of the most potent and selective NMDA receptor agonists so far described with an EC50 of 0.7 microM in the cortex and 250 microM in the myenteric plexus.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1994

Ammonium acetate inhibits ionotropic receptors and differentially affects metabotropic receptors for glutamate.

The effects of ammonium salts in concentration similar to those found in plasma in course of hepatic encephalopathy (2-4 mM) were studied in brain slices in order to clarify how glutamate synapses are affected by this pathological situation. Electrophysiological (mice cortical wedge preparations) and biochemical techniques (inositol phosphates and cyclic AMP measurements) were used so that the function of both the ionotropic and metabotropic glutamate receptors was evaluated. Ammonium acetate (2-4 mM), but not sodium acetate reduced the degree of depolarization of cortical wedges induced by different concentrations of N-methyl-D-aspartic acid (NMDA) or (S)-alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). This reduction was non-competitive in nature and did not reverse during the experimental period (90 min). In a similar manner, ammonium acetate reduced the formation of inositol phosphates induced by (1S,3R)-1-amynocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) (100 microM), the prototype agonist of metabotropic glutamate receptors. When the metabotropic glutamate receptors negatively linked to the forskolin-stimulated cyclic AMP formation were evaluated, ammonium acetate significantly hampered forskolin effects and its actions were additive with those of the metabotropic glutamate receptor agonist 1S,3R-ACPD. In conclusion, our results suggest that toxic concentrations of ammonium impair the function of glutamate receptors of NMDA and AMPA type and of the metabotropic glutamate receptors linked to inositol phosphate formation while they functionally potentiate the action of glutamate agonists on the receptors negatively linked to adenylyl cyclase.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Melatonin: a peroxyl radical scavenger more effective than vitamin E.

We have compared the peroxyl radical scavenger ability to melatonin with that of vitamin E, vitamin C and reduced glutathione (GSH). In the assay system, beta-phycoerythrin (beta-PE) was used as fluorescent indicator protein, 2-2'-azo-bis(2-amidinopropane)dihydrochloride as a peroxyl radical generator and the water soluble vitamin E analogue. Trolox, as reference standard. Results are expressed as oxygen radical absorbing capacity (ORAC(perox)) units, where 1 ORAC unit equals the net protection produced by 1 microM Trolox. A linear correlation of ORAC values with concentration (0.5-4 microM) of all the substances tested has been observed. However, on molar basis, the relative ORAC(perox) of Trolox, vitamin C, GSH and melatonin was 1:1.12:0:68:2.04, respectively. Thus, melatonin, which is a lipid-soluble compound, was twice more active than vitamin E, believed to be the most effective lipophilic antioxidant.

Amidines↗
PubMed1994

The depolarization-induced outflow of D-[3H]aspartate from rat brain slices is modulated by metabotropic glutamate receptors.

Rat brain slices were used to study the effects of different metabotropic glutamate receptor ligands on (i) the depolarization (30 mM KCl)-induced outflow of previously taken up D-[3H]aspartate; (ii) the inhibition of forskolin (30 microM)-induced cyclic AMP accumulation; and (iii) the hydrolysis of phosphoinositides. In addition, the localization of mRNAs coding for different metabotropic glutamate receptor subtypes was detected using in situ hybridization. (1S-3R)-1-Aminocyclopentane-1,3-dicarboxylic acid (30-300 microM), a non selective metabotropic glutamate receptor agonist, significantly increased the KCl-induced output of radioactivity from cortical slices, whereas it inhibited the output from striatal slices. Conversely, (1S,3S,4S)-carboxycyclopropylglycine (0.1-1 microM), a relatively selective agonist of the mGluR2 metabotropic glutamate receptor subtype, had an inhibitory effect on the output of D-[3H]aspartate from both cortical and striatal slices and proved to be the most potent metabotropic glutamate receptor agonist in inhibiting cyclic AMP accumulation, but not in stimulating phosphoinositide hydrolysis. Since 2-amino-4-phosphonobutyrate (a mGluR4, mGluR6 and mGluR7 agonist) was not active in any of the assays tested, we hypothesized that the mGluR2 subtype could be involved in these events. Accordingly, mGluR2 mRNA expression was abundant in cortical neurons projecting to the striatum. Our experiments suggest that the stimulation of metabotropic glutamate receptors may either decrease or increase transmitter release depending on the subtype that prevails in the region under study.

Animals↗
PubMed1994

Inhibitors of kynurenine hydroxylase and kynureninase increase cerebral formation of kynurenate and have sedative and anticonvulsant activities.

Kynurenate is an endogenous antagonist of the ionotropic glutamate receptors. It is synthesized from kynurenine, a tryptophan metabolite, and a significant increase in its brain concentration could be useful in pathological situations. We attempted to increase its neosynthesis by modifying kynurenine catabolism. Several kynurenine analogues were synthesized and tested as inhibitors of kynurenine hydroxylase (E.C.1.14.13.9) and of kynureninase (E.C.3.7.1.3), the two enzymes which catalyse the conversion of kynurenine to excitotoxin quinolinate. Among these analogues we observed that nicotinylalanine, a compound whose pharmacological properties have previously been reported, had an IC50 of 900 +/- 180 microM as inhibitor of kynurenine hydroxylase and of 800 +/- 120 microM as inhibitor of kynureninase. In the search for more potent molecules we noticed that meta-nitrobenzoylalanine had an IC50 of 0.9 +/- 0.1 microM as inhibitor of kynurenine hydroxylase and of 100 +/- 12 microM as inhibitor of kynureninase. When administered to rats meta-nitrobenzoylalanine (400 mg/kg) significantly increased the concentration of kynurenine (up to 10 times) and kynurenate (up to five times) in the brain. Similar results were obtained in the blood and in the liver. Furthermore meta-nitrobenzoylalanine increased in a dose dependent, long lasting (up to 13 times and up to 4 h) manner the concentration of kynurenate in the hippocampal extracellular fluid, as evaluated with a microdialysis technique. This increase was associated with a decrease in the locomotor activity and with protection from maximal electroshock-induced seizures in rats or from audiogenic seizures in DBA/2 mice. The conclusions drawn from the present study are: (i) meta-nitrobenzoylalanine is a potent inhibitor of kynurenine hydroxylase also affecting kynureninase; (ii) the inhibition of these enzymes causes a significant increase in the brain extracellular concentration of kynurenate; (iii) this increase is associated with sedative and anticonvulsant actions, suggesting a functional antagonism of the excitatory amino acid receptors.

Alanine↗
PubMed1994

The glycine antagonist and free radical scavenger 7-Cl-thio-kynurenate reduces CA1 ischemic damage in the gerbil.

We examined whether 7-Cl-thio-kynurenate, a potent antagonist at the glycine site of the N-methyl-D-aspartate receptor which also inhibits lipid peroxidation, protected CA1 pyramidal cells following transient forebrain ischemia. Global ischemia was produced in anesthetized gerbils by 5 min bilateral carotid artery occlusion; hippocampal injury was assessed seven days later. 7-Cl-thio-kynurenate (100 mg/kg, i.p. x 5) dramatically attenuated ischemia-induced CA1 cell loss (from 95 +/- 1 to 7 +/- 3%): the protection was associated with a delayed and marked reduction in the animals' temperature. However, when the gerbils were maintained normothermic for at least 360 min, 7-Cl-thio-kynurenate still provided partial (54 +/- 11%) but significant protection. No protection was observed when a reduction in temperature with a time course similar to that caused by 7-Cl-thio-kynurenate was experimentally induced in saline-treated ischemic animals. In situ hybridization revealed that expression of NMDA-R1, a subunit of the N-methyl-D-aspartate receptor, was selectively reduced in CA1 seven days following global ischemia. In ischemic gerbils treated with 7-Cl-thio-kynurenate, protected CA1 cells were still able to express normal amounts of NMDA-R1 messenger RNA. Our results demonstrate that 7-Cl-thio-kynurenate, a glutamate receptor blocker possessing radical scavenger properties, is effective in reducing CA1 hippocampal damage following global ischemia in the gerbil. Since there is growing evidence that a positive feedback interaction between activation of glutamate receptors and free radical formation may be responsible for the generation of ischemic brain damage, drugs capable of interfering with both pathogenic mechanisms may be useful in preventing post-ischemic neuronal death.

Animals↗
PubMed1993

Age-dependent modifications of mitochondrial trans-membrane potential and mass in rat splenic lymphocytes during proliferation.

The specific fluorescent probes, Rhodamine 123 (Rh-123) and Nonyl-Acridine Orange (NAO) were, respectively, used to monitor the changes in membrane potential and mass of lymphocyte mitochondria during aging and proliferation. An age-dependent increase of the uptake of both fluorochromes was observed in resting cells; however, NAO fluorescence increased to a greater extent when compared with the Rh-123 probe. This resulted in a lower respiratory activity per unit of mitochondrial mass in old cells than in the young ones. Following mitogenic stimulation, most of the lymphocytes from young rats showed an increase in their membrane potential and mass. On the contrary about 50% of cells from old rats had depolarized mitochondria after 72 h from the stimulation. Present data support that mitochondria of lymphocytes from old rats are extremely sensitive to the stressing conditions resulting from mitogenic stimulation.

Aging↗
PubMed1993

Bretylium differentiates between distinct signal transducing pathways in human lymphocytes.

The selection of signal transducing pathways of T cells depends on the type of triggers. Antigens, antibodies or lectins induce the T cell receptor-CD3 operated pathway, and IL-2 transmits its activation signal via the IL-2 receptor. It has been demonstrated that bretylium, a quaternary ammonium ion, can significantly inhibit the first pathway at the same dose range that stimulates cell activation through the IL-2 receptor system. In the light of the different complexity of the two pathways at the plasma membrane level, and the non-toxic and reversible behavior of the drug, it is suggested that the bretylium induced sustained membrane hyperpolarization is responsible for the observation. This finding may open new possibilities in studying the mechanism of different signal transducing pathways.

Blotting, Northern↗
PubMed1993

Photochemically-induced lesion of the rat retina: a quantitative model for the evaluation of ischemia-induced retinal damage.

The effects of ischemia-induced retinal damage were quantitatively evaluated in rats with the aim of obtaining a suitable model to study the pathogenesis of the loss of retinal neurons after ischemic episodes. Anaesthetized rats were injected with 80 mg/kg i.v. of the fluorescein rose bengal dye and one eye was exposed to cold light for different periods (from 5 to 30 min). The animals were sacrificed at different times (1 and 4 hr; 2 and 7 days) after the lesion and the photochemically-induced damage was evaluated. The damaged retinae appeared thicker, numerous neurons of the inner nuclear layers showed swelling of the perinuclear cytoplasm and the retinal vessels were enlarged. The activity of choline acetyltransferase (ChAT) and glutamic acid decarboxylase (GAD), two marker enzymes of the GABAergic and cholinergic neurons, significantly decreased, indicating a degeneration of GABAergic and cholinergic amacrine cells.

Animals↗
PubMed1993

Vitamin E deficiency impairs the modifications of mitochondrial membrane potential and mass in rat splenocytes stimulated to proliferate.

This study was designed to evaluate the time-dependent changes of mitochondrial membrane potential and mass during Con-A-induced proliferation of splenic lymphocytes from rat fed a normal or a vitamin E deficient diet. Rhodamine 123 and Nonyl Acridine Orange were used as specific probes to monitor the membrane potential and mass of mitochondria, respectively, by means of flow cytometry. The results demonstrate that the increase of Rh-123 and NAO uptake observed in cells from normally fed rats was prevented by vitamin E deficiency, at any time considered. After 72 h from Con A stimulation, 62% of cells from controls, as against 16% of cells from vitamin E deficient rats, showed hyperpolarized mitochondria. At the same time, in this last group, 60% of cells had depolarized organelles. The same pattern was observed considering the changes of mitochondrial mass, measured using NAO as a probe. These data support that mitogenic stimulation induced an increase of the respiratory activity of mitochondria with subsequent production of superoxide radicals. This resulted in depolarization and loss of mass of the organelles if the intracellular level of vitamin E is not adequate.

Acridine Orange↗
PubMed1993

Definition of a pharmacophore for the metabotropic glutamate receptors negatively linked to adenylyl cyclase.

(2S,3S,4S)-alpha-Carboxycyclopropylglycine (L-CCG I) and trans-1-amino-(1S,3R)-cyclopentanedicarboxylic acid ((1S,3R)-ACPD), partially constrained L-glutamate analogs known to be agonists at the metabotropic glutamate receptors (mGluRs) adenylyl cyclase coupled, have been submitted to conformational analysis and the data obtained utilized to define a pharmacophore which takes into account the location of hydrogen bonding donating sites of the receptor. This pharmacophore has been utilized to define the agonist mGluRs decreases cAMP bioactive conformation of L-Glu.

Adenylyl Cyclase Inhibitors↗
PubMed1993

Pharmacological characterization of the metabotropic glutamate receptor inhibiting D-[3H]-aspartate output in rat striatum.

1. The effects of several agonists of the metabotropic glutamate receptor (mGluR) were studied in adult rat striatal slices by measuring (i) KCl (30 mM)-induced output of previously taken up D-[3H]-aspartate (Asp), (ii) forskolin (30 microM)-induced adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation and (iii) phophoinositide (PI) hydrolysis. 2. K(+)-induced efflux of D-[3H]-Asp was inhibited by the following mGluR agonists: (1S,3S,4S)-(carboxycyclopropyl)glycine (L-CCG-I), (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) and quisqualic acid (Quis). 2-Amino-4-phosphonobutyrate (L-AP4) was inactive up to 300 microM. The maximal inhibition of D-[3H]-Asp output was 60 +/- 8%. The EC50s of mGluR agonists were: 0.5 microM for L-CCG-I, 100 microM for 1S,3R-ACPD and 100 microM for Quis. 3. Forskolin-induced cyclic AMP accumulation was also inhibited by mGluR agonists. The maximal inhibition was 50 +/- 4% and was obtained at a concentration of 10 microM for L-CCG-I and 100 microM for 1S,3R-ACPD. The EC50s for this inhibition were: 0.9 microM for L-CCG-I and 20 microM for 1S,3R-ACPD. Quis (300 microM) inhibited cyclic AMP accumulation by approximately 20%. L-AP4 slightly potentiated cyclic AMP accumulation. 4. PI hydrolysis was stimulated by mGluR agonists. The most potent compound was Quis (100 microM), which increased inositol phosphate formation up to 2.2 fold over control values. Its EC50 was 15 microM. L-CCG-I and 1S,3R-ACPD increased inositol phosphate formation by approximately 1.8 fold and their EC50 values were 30 and 25 microM, respectively. L-AP4 did not affect PI hydrolysis. 5. In conclusion, mGluR agonists that reduce D-[3H]-Asp output have a pharmacological profile similar to that of mGluR agonists inhibiting cyclic AMP accumulation. L-CCG-I appears to be a relatively selective agonist for the mGluR receptor which inhibits D-[3H]-Asp efflux and cyclic AMP accumulation,while Quis appears to act preferentially on the mGluR receptor linked to the metabolism of PIs.

Amino Acids, Dicarboxylic↗
PubMed1993

A study of the dose dependency of a glycine receptor antagonist in focal ischemia.

N-methyl-D-aspartate receptor antagonists are potent neuroprotectants in experimental focal cerebral ischemia, but behavioral and neuropathologic changes seen with these drugs in rodent models may limit the clinical utility of these compounds. Glycine's modulation of N-methyl-D-aspartate channel function offers another pharmacologic approach to excitotoxicity in ischemia. The potent glycine antagonist 7 Chlorothiokynurenic acid (7-Cl-Thio-Kyna) was studied in a permanent middle cerebral artery occlusion stroke model in the rat. The compound was effective, in a dose-dependent manner, in attenuating infarct size when administered before or after permanent middle cerebral artery occlusion. Its activity was mainly due to glycine antagonism inasmuch as 5 Chlorothiokynurenic acid, a compound having other pharmacological activities in common with 7-CI-Thio-Kyna (for instance the radical scavenger action), was inactive in this model. 7-Cl-Thio-Kyna did not produce cytological changes similar to MK 801.

Animals↗