Biomedical subjects

Antonio Paparelli

Publications and source records attributed to Antonio Paparelli.

At least 19 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

Overexpression of alpha-synuclein following methamphetamine: is it good or bad?

alpha-Synuclein is a presynaptic protein involved in various degenerative disorders now defined as synucleinopathies. These include neurological diseases that share a few pathological features consisting of aggregates of both normal and altered alpha-synuclein within specific neuronal populations and/or glial cells. The prototype of synucleinopathies is represented by Parkinson's disease (PD) in which alpha-synuclein is identified as a constant component of neuronal pale eosinophilic inclusions: "the Lewy Bodies." In the present article, we discuss the potential significance of amphetamine-induced overexpression of alpha-synuclein in light of clinical findings showing neurodegeneration following overexpression of alpha-synuclein and recent experimental studies that measured increased expression of alpha-synuclein following amphetamine derivatives.

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↗

PubMed2006

MDMA induces caspase-3 activation in the limbic system but not in striatum.

Several studies, carried out in chronic (+/-) 3,4-methylenedioxymethamphetamine (MDMA) abusers, have shown memory loss and cognitive impairment, as well as persistent electroencephalographic changes. This suggests that, at least in humans, forebrain areas, including the limbic system, might be altered by MDMA. Consistently, recent experimental evidences suggest that, in rodents, MDMA, besides effects on the basal ganglia, produces alterations in the hippocampus. Therefore, the aim of the present article was to investigate whether treatment with MDMA produces activation of the caspase-3 enzyme, which is part of an enzymatic pathway involved in cell death, within limbic areas (i.e., hippocampus, amygdala, and piriform cortex) and striatum. A marked induction of caspase-3 activity was demonstrated in the amygdala and hippocampus, although MDMA did not affect caspase-3 activity neither in the striatum nor in the frontal cortex. These data indicate that limbic structures possess a high sensitivity to MDMA with respect to the activation of at least one step in the apoptotic pathway. Potential implications and pitfalls of such an experimental observation are reported.

Animals↗

PubMed2006

Comparison between heroin and heroin-cocaine polyabusers: a psychopathological study.

The concomitant use of cocaine by heroin-dependent subjects, or by patients on methadone maintenance treatment, is a relevant phenomenon that determines the negative consequences on health, social adjustment, and outcome of opioid addiction treatment. Little is known about the patterns of co-use of these two substances and the pathophysiological alterations following this condition. Only a few studies have evaluated the neurochemical effects in subjects carrying this specific pattern of abuse. Similarly, the impact of cocaine abuse on psychiatric and social function in subjects already affected by opioid addiction is still poorly understood and further studies are necessary to investigate this specific area that could profoundly affect methadone maintenance treatment. The aim of this article is to investigate the psychopathological symptoms of heroin-cocaine abuse in a group of heroin addicts applying for treatment. Results show a direct relationship between cocaine abuse and a higher rate of psychiatric disorders, but a negative correlation with the severity of self-rated psychopathology.

Adult↗

PubMed2006

The comet assay as a method of assessment of neurotoxicity: usefulness for drugs of abuse.

Comet assay is a quick and versatile method for assessing DNA damage in individual cells. It allows the detection of single and double DNA strand breaks, as well as the presence of alkali labile sites. DNA breaks may represent the direct effect of some damaging agent, or they may be intermediates in cellular repair. DNA strand breaks may also come from the action of free radicals generated by oxidative stress processes. The present article summarizes some data from our and other groups underlining the suitability of the Comet assay in assessing neurotoxicity and its potential in evaluating drugs of abuse-related genotoxicity.

Brain↗

PubMed2006

Morphological evidence that xenon neuroprotects against N-methyl-DL-aspartic acid-induced damage in the rat arcuate nucleus: a time-dependent study.

The hyperactivation of glutamate receptors, especially those of the N-methyl-d-aspartate subtype (NMDA), can induce excess calcium entry into cells, leading to neuronal death. Since the anesthetic gas xenon behaves as an NMDA antagonist, the present article investigated, by distinct morphological approaches and after different times, the possible neuroprotectant effects of this gas in a model of neuronal damage induced by N-methyl-dl-aspartic acid (NMA) on rat arcuate nucleus. Rats were assigned to the following groups: controls; xenon exposure; NMA treatment; or xenon exposure + NMA treatment. Animals were placed in an experimental cage and after 10 min a mixture of xenon (or nitrogen) 70% and oxygen 30% was delivered. After 3 h, 1, 2, 5, or 7 days from gas exposure, rats were euthanized and the whole brain was removed and processed for either transmission electron microscopy or light microscopy. In the arcuate nucleus from NMA-treated animals only 40-60% of cell population survived in all times with several degenerating neurons giving the typical appearance of a "bull's eye." At ultrastructural level, chromatin margination, nuclear shrinkage, mitochondria with matrix dilution, dilated endoplasmic cisternae, and electrondense cytoplasm were detected. Xenon alone did not induce changes, but reduced of about 50% NMA-induced cell loss as well as degenerating neurons, with the maximal neuroprotection at 7 days. These results confirm that in the rat arcuate nucleus NMA can induce a severe neuronal damage that is already marked after 3 h. Xenon significantly reduced the neuronal damage at all times and can be then regarded as a promising neuroprotectant agent.

Animals↗

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

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↗

PubMed2004

Effects of loud noise exposure on DNA integrity in rat adrenal gland.

Loud noise is generally considered an environmental stressor causing negative effects on acoustic, cardiovascular, nervous, and endocrine systems. In this study, we investigated the effects of noise exposure on DNA integrity in rat adrenal gland evaluated by the comet assay. The exposure to loud noise (100 dBA) for 12 hr caused a significant increase of DNA damage in the adrenal gland. Genetic alterations did not decrease 24 hr after the cessation of the stimulus. We hypothesize that an imbalance of redox cell status is responsible for the induction and persistence of noise-induced cellular damage.

Adrenal Glands↗

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

Protective role of group-II metabotropic glutamate receptors against nigro-striatal degeneration induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in mice.

To examine how mGlu2/3 metabotropic glutamate receptors affect nigro-striatal degeneration, we used the agonist, LY379268, and the antagonist, LY341495, in mice challenged with the nigro-striatal toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In control mice, high doses of MPTP (20 mg/kg, i.p., injected four times with 2 h of interval) induced a nearly total degeneration of the nigro-striatal pathway, as shown by measurements of striatal dopamine (DA) levels and by immunohistochemical analysis of tyrosine hydroxylase, high affinity dopamine transporter, and glial fibrillary acidic protein in the corpus striatum and substantia nigra. Lower cumulative doses of MPTP (30 mg/kg, i.p., injected only once) produced a partial lesion of the nigro-striatal pathway (about 50% reduction of striatal DA content). Systemic injection of LY379268 (1 mg/kg, i.p., 30 min prior to each injection of MPTP) partially reduced the extent of nigro-striatal degeneration induced by high doses of MPTP. Similar results were obtained by continuously delivering LY379268 (1 mg/kg/d for 7 d) by means of a subcutaneous osmotic minipump. The protective effect of LY379268 was antagonized by LY341495 (also delivered by the osmotic minipump). In mice challenged with the lower cumulative dose of MPTP, injection of LY379268 did not produce a significant neuroprotective effect. In contrast, the lesion was amplified by the antagonist, LY341495. Neither LY379268 nor LY341495 influenced the central bioavailability and the local half-life of MPTP, as shown by measurements of the toxin and its active metabolite, MPP(+), in the striatum. We conclude that mGlu2/3 receptors play a protective role against MPTP toxicity, and that the efficacy of the agonist, LY379268, critically depends on the extent of the nigro-striatal lesion.

Amino Acids↗

PubMed2002

Effects of loud noise exposure on mouse myocardium: a comparison with the rat.

Loud noise is an environmental stressor of everyday life, which affects different organs and apparati, in particular the cardiovascular system. We have already reported that noise exposure produces significant alterations in the rat myocardium, consisting of mitochondrial damage, which is evident as lysis of the cristae and dilution of the matrix. Since there are high similarities between mouse and human species, the aim of our study was to investigate the effects of acute noise exposure on the mouse heart. We found that noise exposure affects mouse myocardium at similar subcellular sites to those already described in the rat; nonetheless, quantitative analysis of the percentage of altered mitochondria in both species disclosed a clear difference between mouse and rat myocardium, which strongly suggests a different sensitivity to noise stimulus. We hypothesize that the species differences on the extent of myocardial alterations here observed might be due to the zonal pattern of cardiac noradrenergic receptors, which should be the final effectors for noise-induced myocardial changes.

Acoustic Stimulation↗