Biomedical subjects

Gloria Lazzeri

Publications and source records attributed to Gloria Lazzeri.

17 recordsLinked to original sources

PubMed2006

Fine ultrastructure and biochemistry of PC12 cells: a comparative approach to understand neurotoxicity.

The PC12 cell line is commonly used as a tool to understand the biochemical mechanisms underlying the physiology and degeneration of central dopamine neurons. Despite the broad use of this cell line, there are a number of points differing between PC12 cells and dopamine neurons in vivo which are missed out when translating in vitro data into in vivo systems. This led us to compare the PC12 cells with central dopamine neurons, aiming at those features which are predictors of in vivo physiology and degeneration of central dopamine neurons. We carried out this comparison, either in baseline conditions, following releasing or neurotoxic stimuli (i.e. acute or chronic methamphetamine), to end up with therapeutic agents which are suspected to produce neurotoxicity (l-DOPA). Although the neurotransmitter pattern of PC12 cells is close to dopamine neurons, ultrastructural morphometry demonstrates that, in baseline conditions, PC12 cells possess very low vesicles density, which parallels low catecholamine levels. Again, compartmentalization of secretory elements in PC12 cells is already pronounced in baseline conditions, while it is only slightly affected following catecholamine-releasing stimuli. This low flexibility is caused by the low ability of PC12 cells to compensate for sustained catecholamine release, due both to non-sufficient dopamine synthesis and poor dopamine storage mechanisms. This contrasts markedly with dopamine-containing neurons in vivo lending substance to opposite findings between these compartments concerning the sensitivity to a number of neurotoxins.

Adrenal Medulla↗

PubMed2006

Convergent roles of alpha-synuclein, DA metabolism, and the ubiquitin-proteasome system in nigrostriatal toxicity.

Recent studies disclosed the relevance of specific molecules for the onset of Parkinson's disease (PD) and for the composition of neuronal inclusions. The scenario which is now emerging leads to identify a potential common pathway named the ubiquitin-proteasome (UP) system. In line with this, striatal or systemic inhibiton of the UP system causes experimental Parkinsonism characterized by the formation of neuronal inclusions. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which is also a complex I inhibitor, has been used for decades to produce experimental Parkinsonism with no evidence for neuronal inclusions in rodents. This leaves open the question whether neuronal inclusions need an alternative mechanism or the inhibition of complex I needs to be carried out continuously to build up inclusions. In the present article, we administered continuously MPTP. In these experimental conditions we compared the neurological consequence of intermittent versus continuous MPTP. In both cases we observed a severe dopamine (DA) denervation and cell loss. However, when MPTP was delivered continuously, spared DA nigral neurons develop ubiquitin, parkin, and alpha-synuclein positive inclusions, which are not detectable after intermittent dosing. The onset of Parkinsonism is associated with inhibition of the UP system. We compared these results with those obtained with amphetamine derivative in vivo and in vitro in which occurrence of neuronal inclusions was associated with inhibition of the UP system and we evaluated the role of DA metabolism in inducing these effects.

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

PubMed2006

In PC12 cells neurotoxicity induced by methamphetamine is related to proteasome inhibition.

Neurodegenerative disorders are featured by a variety of pathological hallmarks, and very often they are characterized by neuronal inclusions in specific brain nuclei. Occurrence of neuronal inclusions has been often related to the onset of cell death. Recent studies demonstrated that amphetamine derivatives produce intracellular inclusions, which are reminiscent of those occurring in degenerative disorders. In the present article, we analyzed the correlation between neuronal inclusions and cell death using methamphetamine (METH) in PC12 cell cultures. We found that the dose necessary to induce cell death is higher compared with that required to induce inclusions formation. Our results demonstrate a dissociation between formation of inclusion bodies and cell death suggesting that neuronal inclusions do not necessarily lead to cell death. The conclusions of the present article suggest that the onset of inclusion bodies represents a slight consequence of toxicity, which requires a prolonged cell viability to take place.

Animals↗

PubMed2006

Inclusion dynamics in PC12 is comparable between amphetamines and MPTP.

In previous studies it was demonstrated that amphetamine derivatives and 1-methyl article-4-phenylpyridinium produce neuronal cell bodies. In the present work, we compared the fine ultrastructure of the intracellular inclusions induced by these different neurotoxic treatments. In particular, we compared the dynamical changes occurring when a mild toxic stimulus acts for different time intervals. For this purpose, we exposed catecholamine-synthesizing PC12 cells to different amphetamine derivatives (methamphetamine and 3,4-methylenedioxymethamphetamine), or 1-methyl-4-phenylpyridinium ion, which represents the active metabolite of the neurotoxin 1-methyl-4-phenyl-1,3,4,6-tetrahydropyridine. Despite inclusions that are elicited by different mechanisms depending on the specific neurotoxin, their ultrastructural features are similar and there is a high parallelism in their temporal evolution. This suggests that formation of inclusions is a multi-step process that might be elicited by different stimuli and, once triggered, leads to the same final effect.

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

PubMed2006

MDMA and seizures: a dangerous liaison?

In the past decades, there was a massive increase in the abuse of methylenedioxymethamphetamine (MDMA) in the Western countries. Seizure onset after MDMA is considered to be related mainly to its acute systemic effects (e.g., hyponatremia and hyperthermia). However, additional mechanisms might concur to it as well. Experiments aimed at disclosing the basis for such an acute effect have the advantage of profiting of controlled conditions and the "pure" compounds, as opposed to the limits of clinical data which are biased by several confounding factors. Amphetamines exert profound effect on different monoaminergic systems, which might participate to lowering of seizure threshold. Chronic effects of MDMA abuse on seizure threshold have not been explored in detail so far. Recent data showed that in mice receiving small, repeated doses of MDMA, a persisting pro-convulsant effect toward limbic seizures and metabolic hyperexcitability can be observed. In the present article, we reviewed these studies and we report our preliminary experimental data documenting the lack of mossy fiber sprouting at short time intervals following MDMA, when seizure susceptibility is already present.

Acute Disease↗

PubMed2005

Lansoprazole prevents experimental gastric injury induced by non-steroidal anti-inflammatory drugs through a reduction of mucosal oxidative damage.

AIM: This study investigated the mechanisms of protection afforded by the proton pump inhibitor lansoprazole against gastric injury induced by different non-steroidal anti-inflammatory drugs (NSAIDs) in rats. METHODS: Male Sprague-Dawley rats were orally treated with indomethacin (100 micromol/kg), diclofenac (60 micromol/kg), piroxicam (150 micromol/kg) or ketoprofen (150 micromol/kg). Thirty minutes before NSAIDs, animals were orally treated with lansoprazole 18 or 90 micromol/kg. Four hours after the end of treatments, the following parameters were assessed: gastric mucosal PGE2, malondialdehyde (MDA), myeloperoxidase (MPO) or non-proteic sulfhydryl compounds (GSH) levels; reverse transcription-polymerase chain reaction (RT-PCR) of mucosal COX-2 mRNA; gastric acid secretion in pylorus-ligated animals; in vitro effects of lansoprazole (1-300 micromol/L) on the oxidation of low density lipoproteins (LDLs) induced by copper sulphate. RESULTS: All NSAIDs elicited mucosal necrotic lesions which were associated with neutrophil infiltration and reduction of PGE2 levels. Increments of MPO and MDA contents, as well as a decrease in GSH levels were detected in the gastric mucosa of indomethacin- or piroxicam-treated animals. Indomethacin enhanced mucosal cyclooxygenase-2 expression, while not affecting cyclooxygenase-1. At the oral dose of 18 micromol/kg lansoprazole partly counteracted diclofenac-induced mucosal damage, whereas at 90 micromol/kg it markedly prevented injuries evoked by all test NSAIDs. Lansoprazole at 90 micromol/kg reversed also the effects of NSAIDs on MPO, MDA and GSH mucosal contents, without interfering with the decrease in PGE2 levels or indomethacin-induced cyclooxygenase-2 expression. However, both lansoprazole doses markedly inhibited acid secretion in pylorus-ligated rats. Lansoprazole concentration-dependently reduced the oxidation of LDLs in vitro. CONCLUSION: These results suggest that, besides the inhibition of acid secretion, lansoprazole protection against NSAID-induced gastric damage depends on a reduction in mucosal oxidative injury, which is also responsible for an increment of sulfhydryl radical bioavailability. It is also suggested that lansoprazole does not influence the down-regulation of gastric prostaglandin production associated with NSAID treatment.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2005

Occurrence of neuronal inclusions combined with increased nigral expression of alpha-synuclein within dopaminergic neurons following treatment with amphetamine derivatives in mice.

In recent years several clinical and research findings have demonstrated the involvement of the presynaptic protein alpha-synuclein in a variety of neurodegenerative disorders which are known as synucleinopathies. Although the function of this protein in the physiology of the cell remains unknown, it is evident that both genetic alterations or a mere overexpression of the native molecule produces a degeneration of nigral dopamine-containing neurons leading to movement disorders, as demonstrated in inherited Parkinson's disease. In the present study, we investigated whether widely abused drugs such as methamphetamine and methylenedioxymethamphetamine (ecstasy), which are known to damage the nigrostriatal dopamine pathway of mice, increase the expression of alpha-synuclein within dopamine neurons of the substantia nigra pars compacta. The results of this study demonstrate that nigrostriatal dopamine denervation and occurrence of intracellular inclusions in nigral neurons produced by amphetamine derivatives are related to increased expression of alpha-synuclein within dopamine neurons of the substantia nigra. This lends substance to the hypothesis that increased amounts of native alpha-synuclein may be per se a detrimental factor for the dopamine neurons.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2005

Neuronal inclusions in degenerative disorders Do they represent static features or a key to understand the dynamics of the disease?

This brief paper analyzes a few degenerative diseases expressing as movement disorders and featuring at sub-cellular level the presence of neuronal inclusions in selective brain regions. We will first draw a short draft of representative neurological diseases featuring inclusion bodies by describing the type of inclusions occurring in various disorders and analyzing both common features and distinctive aspects. As a further step, we move from the bed to the bench side discussing recent developments obtained from experimental models of these disorders which shed new light into the cause and progression of neuronal inclusions, thus helping to understand the pathophysiology of neuronal degeneration underlying movement disorders. In line with this, we will focus on recent studies which led to reproduce neuronal inclusions in vivo and in vitro by manipulating selective cellular structures/enzymatic pathways. In this way, we will try to encompass the dynamics of inclusion formation based on their fine ultrastructure and the analysis of the molecular components as well as their subcellular compartmentalization trying to relate the dynamics of inclusion formation and the pathophysiology of the disease process. An emphasis will be made on the ubiquitin proteasome system and Parkinson's disease where the analysis of neuronal inclusions enlightened potential therapeutic strategies to occlude the progression of this neuronal degeneration featured by movement disorders.

Animals↗

PubMed2005

Parkinson-like syndrome induced by continuous MPTP infusion: convergent roles of the ubiquitin-proteasome system and alpha-synuclein.

In animals, sporadic injections of the mitochondrial toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) selectively damage dopaminergic neurons but do not fully reproduce the features of human Parkinson's disease. We have now developed a mouse Parkinson's disease model that is based on continuous MPTP administration with an osmotic minipump and mimics many features of the human disease. Although both sporadic and continuous MPTP administration led to severe striatal dopamine depletion and nigral cell loss, we find that only continuous administration of MPTP produced progressive behavioral changes and triggered formation of nigral inclusions immunoreactive for ubiquitin and alpha-synuclein. Moreover, only continuous MPTP infusions caused long-lasting activation of glucose uptake and inhibition of the ubiquitin-proteasome system. In mice lacking alpha-synuclein, continuous MPTP delivery still induced metabolic activation, but induction of behavioral symptoms and neuronal cell death were almost completely alleviated. Furthermore, the inhibition of the ubiquitinproteasome system and the production of inclusion bodies were reduced. These data suggest that continuous low-level exposure of mice to MPTP causes a Parkinson-like syndrome in an alpha-synuclein-dependent manner.

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

PubMed2004

Loud noise enhances nigrostriatal dopamine toxicity induced by MDMA in mice.

The neurotoxicity of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) has been intensely investigated due to the widespread abuse of this drug and its neurotoxic effects. In mice, MDMA neurotoxicity has been demonstrated for striatal dopamine (DA) terminals. However, the current literature has reported great variability in the effects induced by MDMA; this is partially due to changes in environmental conditions. For instance, elevated temperature and a crowded noisy environment markedly increase the neurotoxic effects induced by MDMA. The environmental factor loud noise is often present during ecstasy intake; however, only a few studies have analysed the consequence of a concomitant exposure to loud noise and ecstasy intake. In the present experimental work, we investigated whether nigrostriatal DA toxicity occurring after MDMA administration was potentiated in the presence of loud noise (100 dBA). We administered MDMA to C57/Black mice using a "binging" pattern for two durations of white noise exposure. We found a marked enhancement of MDMA toxicity (7.5 mg/Kg x4, 2 hours apart, i.p.) in the presence of white noise exposure lasting for at least 6 hours. The striatal damage was assessed by assaying DA levels as well as the loss of tyrosine hydroxylase (TH) and the increase in striatal glial fibrillary acidic protein (GFAP) immunohistochemistry. Since loud noise often accompanies ecstasy intake, the present findings call for more in-depth studies aimed at disclosing the fine mechanisms underlying this enhancement.

Animals↗

PubMed2004

Mechanisms of gastroprotection by lansoprazole pretreatment against experimentally induced injury in rats: role of mucosal oxidative damage and sulfhydryl compounds.

This study investigated the mechanisms involved in the protective actions exerted by lansoprazole against experimental gastric injury. Following the intraluminal injection of ethanol-HCl, the histomorphometric analysis of rat gastric sections demonstrated a pattern of mucosal lesions associated with a significant increase in the mucosal contents of malondialdehyde and 8-iso-prostaglandin F(2alpha) (indices of lipid peroxidation), as well as a decrease in the levels of mucosal sulfhydryl compounds, assayed as reduced glutathione (GSH). Pretreatment with lansoprazole 90 micromol/kg, given intraduodenally as single dose or once daily by intragastric route for 8 days, significantly prevented ethanol-HCl-induced gastric damage. The concomitant changes in the mucosal levels of malondialdehyde, 8-iso-prostaglandin F(2alpha) and GSH elicited by ethanol-HCl were also counteracted by lansoprazole. In separate experiments, performed on animals undergoing 2-h pylorus ligation, lansoprazole did not enhance the concentration of prostaglandin E(2), bicyclo-prostaglandin E(2), or nitric oxide (NO) metabolites into gastric juice. Western blot analysis revealed the expression of both type 1 and 2 cyclooxygenase (COX) isoforms in the gastric mucosa of pylorus-ligated rats. These expression patterns were not significantly modified by single-dose or repeated treatment with lansoprazole. Lansoprazole also exhibited direct antioxidant properties by reducing 8-iso-prostaglandin F(2alpha) generation in an in vitro system where human native low-density lipoproteins were subjected to oxidation upon exposure to CuSO(4). The present results suggest that the protective effects of lansoprazole can be ascribed to a reduction of gastric oxidative injury, resulting in an increased bioavailability of mucosal sulfhydryl compounds. It is also proposed that lansoprazole does not exert modulator effects on the gastric expression of COX isoforms as well as on the activity of NO pathways.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2004

Methamphetamine produces neuronal inclusions in the nigrostriatal system and in PC12 cells.

Mice treated with the psychostimulant methamphetamine (MA) showed the appearance of intracellular inclusions in the nucleus of medium sized striatal neurones and cytoplasm of neurones of the substantia nigra pars compacta but not in the frontal cortex. All inclusions contained ubiquitin, the ubiquitin activating enzyme (E1), the ubiquitin protein ligase (E3-like, parkin), low and high molecular weight heat shock proteins (HSP 40 and HSP 70). Inclusions found in nigral neurones stained for alpha-synuclein, a proteic hallmark of Lewy bodies that are frequently observed in Parkinson's disease and other degenerative disorders. However, differing from classic Lewy bodies, MA-induced neuronal inclusions appeared as multilamellar bodies resembling autophagic granules. Methamphetamine reproduced this effect in cultured PC12 cells, which offered the advantage of a simple cellular model for the study of the molecular determinants of neuronal inclusions. PC12 inclusions, similar to those observed in nigral neurones, were exclusively localized in the cytoplasm and stained for alpha-synuclein. Time-dependent experiments showed that inclusions underwent a progressive fusion of the external membranes and developed an electrodense core. Inhibition of dopamine synthesis by alpha-methyl-p-tyrosine (alphaMpT), or administering the antioxidant S-apomorphine largely attenuated the formation of inclusions in PC12 cells exposed to MA. Inclusions were again observed when alphaMpT-treated cells were loaded with l-DOPA, which restored intracellular dopamine levels.

Animals↗

PubMed2003

Fine structure and biochemical mechanisms underlying nigrostriatal inclusions and cell death after proteasome inhibition.

Mutation of genes encoding for various components of a metabolic pathway named the ubiquitin-proteasome system (UP) leads to inherited forms of Parkinson's disease (PD), whereas various components of the UP are constantly present within neuronal inclusions, Lewy bodies, that characterize most genetic and sporadic forms of PD. It has been hypothesized that impairment of this metabolic pathway might be a common mechanism for the onset of PD, and a recent study demonstrated a dysfunction of the UP system within the substantia nigra of patients affected by sporadic PD. In search for the mechanisms underlying the selective toxicity for nigral neurons after inhibition of the UP system, we explored the selective effects after striatal microinfusions of lactacystin or epoxomycin and potential retrograde changes within the ipsilateral substantia nigra. We found that neurotoxicity was selective for striatal dopamine (DA) components and led to retrograde apoptosis within nigral DA cells, which developed neuronal inclusions staining for antigens of the UP system. We found the same ultrastructural features characterizing inclusions obtained in vivo and in vitro after UP inhibition. In vivo, lactacystin-epoxomycin-induced toxicity was suppressed by inhibiting DA synthesis. Similarly, in vitro inclusions and apoptosis were prevented by reducing endogenous DA. On the other hand, toxicity of proteasome inhibition was enhanced by drugs augmenting DA availability: l-3,4-dihydroxyphenylalanine, monoamine oxidase blockers, and DA beta-hydroxylase blockers. These findings demonstrate that impairment of the UP system produces cell death and neuronal inclusions selectively for DA-containing neurons that depend on the occurrence of endogenous DA.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2003

A damage to locus coeruleus neurons converts sporadic seizures into self-sustaining limbic status epilepticus.

Various studies demonstrated that the neurotransmitter norepinephrine (NE) plays a relevant role in modulating seizures; in particular, a powerful effect consists in delaying the kindling of limbic areas such as the amygdala and hippocampus. Given the rich NE innervation of limbic regions, we selected a sensitive trigger area, the anterior piriform cortex, to test whether previous loss of noradrenergic terminals modifies sporadic seizures in rats. The damage to locus coeruleus terminals was produced by using the selective neurotoxin N-(-2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4, 60 mg/kg i.p.). In intact rats, bicuculline (a GABA-A antagonist, 118 pmol) microinfused into this area produced sporadic seizures, while in rats previously injected with DSP-4, bicuculline determined long-lasting self-sustaining status epilepticus. In intact rats, sporadic seizures were accompanied by a marked increase in norepinephrine release in the contralateral piriform cortex, while in locus coeruleus-lesioned rats this phenomenon was attenuated. While bicuculline-induced sporadic seizures were prevented by the focal infusion of amino-7-phosphonoheptanoic acid (AP-7, a selective NMDA antagonist), or 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulphonamide (NBQX, a selective non-NMDA antagonist), status epilepticus obtained in norepinephrine-lesioned rats was insensitive to AP-7 but was still inhibited by NBQX. By using fluorescent staining for damaged (Fluoro-Jade B) and intact (DAPI) neurons, as well as cresyl violet, we found that rats undergoing status epilepticus developed neuronal loss in various limbic regions. This study demonstrates a powerful effect of noradrenergic terminals in regulating the onset of limbic status epilepticus and its sensitivity to specific glutamate antagonists.

Animals↗

PubMed2003

DNA damage associated with ultrastructural alterations in rat myocardium after loud noise exposure.

Noise exposure causes changes at different levels in human organs, particularly the cardiovascular system, where it is responsible for increasing heart rate, peripheral vascular resistance, and blood pressure. In this study, we evaluated the effect of noise exposure on DNA integrity and ultrastructure of rat cardiomyocytes. The exposure to loud noise (100 dBA) for 12 hr caused a significant increase of DNA damage, accompanied by swelling of mitochondrial membranes, dilution of the matrix, and cristolysis. These alterations were concomitant with increased in situ noradrenaline levels and utilization. Genetic and ultrastructural alterations did not decrease 24 hr after the cessation of the stimulus. An elevated oxyradical generation, possibly related to altered sympathetic innervation, is hypothesized as responsible for the induction and persistence of noise-induced cellular damage.

Animals↗

PubMed2002

Improved tonsillar disposition of azithromycin following a 3-day oral treatment with 20 mg kg(-1) in paediatric patients.

The present study was performed in order to compare azithromycin concentrations in tonsils of paediatric patients treated with different dose regimens of this antibiotic. Sixty-four children, scheduled to undergo surgical removal of tonsils, were treated with azithromycin 10 or 20 mgkg(-1) daily as oral suspension for 3 days. Samples of blood and tonsil were collected during surgery at days 0.5, 2.5, 4.5, 6.5 or 8.5 after the last dose. Azithromycin concentrations were measured by reversed phase high-performance liquid chromatography. In patients treated with 10 mgkg(-1), the highest concentrations of azithromycin were detected in plasma and tonsils at day 0.5 and 2.5, respectively. Consistent drug levels could be measured in tonsils up to 8.5 days. After administration of 20 mgkg(-1), azithromycin tonsillar concentrations were higher than those obtained with 10 mgkg(-1) up to day 6.5, whereas plasma levels did not differ significantly. The present results indicate that an improved tonsillar distribution of azithromycin can be achieved when this antibiotic is administered for 3 days at doses higher than 10 mgkg(-1) daily. These findings give pharmacokinetic support to the suggestion that increments of azithromycin dosing might ensure enhanced therapeutic levels at infective sites of the upper respiratory tract.

Administration, Oral↗

PubMedDate not supplied

Is there a role for uridine and pyrimidine nucleosides in the treatment of vascular dementia?

In the 70s, the discovery of a constant loss of acetylcholine (Ach) in the brains of people suffering from dementia led to the development, in order to improve cognitive functions, of drugs that increased Ach levels. The possibility that loss of a given neurotransmitter might be associated with the onset of a specific neurological syndrome led to suggestions that, as had already been found in Parkinson's disease, replacement therapy might drastically improve the course of the syndrome. We are now aware of the limits of this therapeutic approach. In this review, we analyse potential factors contributing to the partial failure of Ach replacement therapy, contrasting common beliefs regarding the Ach synapse with the difficulties in restoring its activity through replacement drugs. Considering the search for alternative strategies, in the second part of the review, we overview progress of research into pyrimidine compounds, now emerging as a new modulatory system acting through specific pyrimidino-receptors involved in various steps of cell signalling. Pyrimidine nucleosides might be useful in the chronic treatment of cognitive deficits resulting from vascular dementia.

Acetylcholine↗