The potential effects of nutrients and light on autophagy-mediated visual function and clearance of retinal aggregates

Increasing findings indicate that a dysfunction in the autophagy machinery is common during retinal degeneration. The present article provides evidence showing that an autophagy defect in the outer retinal layers is commonly described at the onset of retinal degeneration. These findings involve a number of structures placed at the border between the inner choroid and the outer retina encompassing the choriocapillaris, the Bruch's membrane, photoreceptors and Mueller cells. At the center of these anatomical substrates are placed cells forming the retinal pigment epithelium (RPE), where autophagy seems to play most of its effects. In fact, a failure of the autophagy flux is mostly severe at the level of RPE. Among various retinal degenerative disorders, age-related macular degeneration (AMD) is mostly affected by a damage to RPE, which can be reproduced by inhibiting the autophagy machinery and it can be counteracted by the activation of the autophagy pathway. In the present manuscript evidence is provided that such a severe impairment of retinal autophagy may be counteracted by administration of a number of phytochemicals, which possess a strong stimulatory activity on autophagy. Likewise, natural light stimulation administered in the form of pulsatile specific wavelengths is capable of inducing autophagy within the retina. This dual approach to stimulate autophagy is further strengthened by the interaction of light with phytochemicals which is shown to activate the chemical properties of these natural molecules in sustaining retinal integrity. The beneficial effects of photo-biomodulation combined with phytochemicals is based on the removal of toxic lipid, sugar and protein species along with the stimulation of mitochondrial turn-over. Additional effects of autophagy stimulation under the combined effects of nutraceuticals and light pulses are discussed concerning stimulation of retinal stem cells which partly correspond to a subpopulation of RPE cells.

Biological determinants of blood-based cytokines in the Alzheimer's Disease clinical continuum

Converging translational and clinical research strongly indicates that altered immune and inflammatory homeostasis (neuroinflammation) plays a critical pathophysiological role in Alzheimer's disease (AD), across the clinical continuum. A dualistic role of neuroinflammation may account for a complex biological phenomenon, representing a potential pharmacological target. Emerging blood-based pathophysiological biomarkers, such as cytokines (Cyt) and interleukins (ILs) have been studied as indicators of neuroinflammation in AD. However, inconsistent results have been reported, probably due to lack of standardization of assays with methodological and analytical differences. We used machine-learning and a cross-validation-based statical workflow to explore and analyze the potential impact of key biological factors, such as age, sex, apolipoproteinE (APOE) genotype (the major genetic risk factor for late-onset AD) on Cyt. A set of Cyt was selected based on previous literature, and we investigated any potential association in a pooled cohort of cognitively healthy, mild cognitive impairment (MCI), and AD-like dementia patients. We also performed explorative analyses to extrapolate preliminary clinical insights. We found a robust sex effect on IL12 and an APOE-related difference in IL10, with the latter being also related to the presence of advanced cognitive decline. IL1β was the variable most significantly associated with MCI-to-dementia conversion over a 2.5 year-clinical follow-up. Albeit preliminary, our data support further clinical research to understand whether plasma Cyt may represent reliable and non-invasive tools serving the investigation of neuroimmune and inflammatory dynamics in AD and to foster biomarker-guided pathway-based therapeutic approaches, within the precision medicine development framework.

Locus Coeruleus magnetic resonance imaging: a comparison between native-space and template-space approach

Locus Coeruleus (LC) is the main noradrenergic nucleus of the brain, which is involved in many physiological functions including cognition; its impairment may be crucial in the neurobiology of a variety of brain diseases. Locus Coeruleus-Magnetic Resonance Imaging (LC-MRI) allows to identify in vivo LC in humans. Thus, a variety of research teams have been using LC-MRI to estimate LC integrity in normal aging and in patients affected by neurodegenerative disorders, where LC integrity my work as a biomarker. A number of variations between LC-MRI studies exist, concerning post-acquisition analysis and whether this had been performed within MRI native space or in ad hoc-built MRI template space. Moreover, the reproducibility and reliability of this tool is still to be explored. Therefore, in the present study, we analyzed a group of neurologically healthy, cognitively intact elderly subjects, using both a native space- and a template space-based LC-MRI analysis. We found a good inter-method agreement, particularly considering the LC Contrast Ratio. The template space-based approach provided a higher spatial resolution, lower operator-dependency, and allowed the analysis of LC topography. Our ad hoc-developed LC template showed LC morphological data that were in line with templates published very recently. Remarkably, present data significantly overlapped with a recently published LC "metaMask", that had been obtained by averaging the results of a variety of previous LC-MRI studies. Thus, such a template space-based approach may pave the way to a standardized LC-MRI analysis and to be used in future clinic-anatomical correlations.

Retinal Degeneration Following Chronic Administration of the Parkinsonism-Inducing Neurotoxin MPTP

During late stages, retinal degenerative disorders affecting photoreceptors progress independently from the specific disease trigger. In fact, a number of detrimental consequences occur downstream of photoreceptors, which are triggered by the loss of photoreceptors themselves. Such downstream anatomical alterations were originally thought to be compensatory events aimed to restore retinal function. At present, these phenomena are deciphered as detrimental effects and the term retinal degeneration is used to indicate the loss of cells and architecture within the inner retina as a consequence of damage to photoreceptors. In the process of testing a photoreceptor-dependent downstream spreading of neurodegeneration we applied a neurotoxin mimicking Parkinson's disease (PD), 1-methyl, 4-phenyl, 1,2,3,6-tetrahydropyridine (MPTP). Chronic MPTP administration produces degeneration within the mouse retina. This is evident by apoptosis quite circumscribed to photoreceptors, which is reminiscent of most phenotypes of retinal degeneration. Retinal pathology following plain HE histochemistry is more widespread with delamination and loss of neuronal packaging in the inner retina. The retinal damage is characterized by a marked synucleinopathy mostly within retinal ganglion cells. In contrast, dopamine-containing structures are intact while norepinephrine is significantly reduced. Despite the involvement of the retina in PD is documented, no study so far analyzed the onset of a synucleinopathy and a degenerative process mimicking what is now recognized in typical retinal degeneration. The present data provide a novel vista on the reciprocal role of the retina in neurodegenerative disorders.

Exosomes and alpha-synuclein within retina from autophagy to protein spreading in neurodegeneration

In the course of age-related macular degeneration (AMD) as well as in multiple retinal disorders protein aggregates are described at various levels in the retina. In AMD this fills the space between retinal pigment epithelium (RPE) in the form of drusen, which contains amyloid and other protein aggregates along with lipids. Nonetheless, in very advanced stages of AMD, as well as in other retinal pathologies and early on in retinitis pigmentosa, a number of neuronal inclusions, which stain for α-synuclein spreads all over the retinal layers. Thus, an early or later defect in the clearance of α-synuclein may represent a final common pathway to these phenomena. The physiological clearance of α-synuclein is provided by the autophagy machinery starting at the level of the RPE and occurring throughout the retina. Such a process is also involved in the clearance of melanin-dependent toxic metabolites under the effects of different wavelengths and the stimulatory activity of the sympathetic nervous system. In search for the occurrence of these culprits, here we report the presence of α-synuclein in the retina combined with exosomal detection to document the presence of a α-synuclein spreading apparatus. This was correlated with the occurrence of autophagy markers throughout retinal layers, along with sympathetic innervation, which in turn was related to melanin content.

The bacterial quorum sensing molecule, 2-heptyl-3-hydroxy-4-quinolone (PQS), inhibits signal transduction mechanisms in brain tissue and is behaviorally active in mice

Interkingdom communication between bacteria and host organisms is one of the most interesting research topics in biology. Quorum sensing molecules produced by Gram-negative bacteria, such as acylated homoserine lactones and quinolones, have been shown to interact with host cell receptors, stimulating innate immunity and bacterial clearance. To our knowledge, there is no evidence that these molecules influence CNS function. Here, we have found that low micromolar concentrations of the Pseudomonas aeruginosa quorum sensing autoinducer, 2-heptyl-3-hydroxy-4-quinolone (PQS), inhibited polyphosphoinositide hydrolysis in mouse brain slices, whereas four selected acylated homoserine lactones were inactive. PQS also inhibited forskolin-stimulated cAMP formation in brain slices. We therefore focused on PQS in our study. Biochemical effects of PQS were not mediated by the bitter taste receptors, T2R4 and T2R16. Interestingly, submicromolar concentrations of PQS could be detected in the serum and brain tissue of adult mice under normal conditions. Levels increased in five selected brain regions after single i.p. injection of PQS (10 mg/kg), peaked after 15 min, and returned back to normal between 1 and 4 h. Systemically administered PQS reduced spontaneous locomotor activity, increased the immobility time in the forced swim test, and largely attenuated motor response to the psychostimulant, methamphetamine. These findings offer the first demonstration that a quorum sensing molecule specifically produced by Pseudomonas aeruginosa is centrally active and influences cell signaling and behavior. Quorum sensing autoinducers might represent new interkingdom signaling molecules between ecological communities of commensal, symbiotic, and pathogenic microorganisms and the host CNS.

Measurement of drusen and their correlation with visual symptoms in patients affected by age-related macular degeneration

Age-related macular degeneration (AMD) is a common retinal disorder, which became more and more prevalent in the last decades. AMD is now the most prevalent cause of blindness in the western world. The disorder is classified into two phenotypes named dry and wet AMD. This is based on the recruitment of novel blood vessels and inflammatory exudates in wet AMD. In both phenotypes, the pathological hallmark is the presence of proteinaceous aggregates called drusen, which mostly accumulate between the choroid and the retinal pigment. Drusen in dry AMD represent the evident pathological finding although they are present, though less defined, in wet AMD. In AMD drusen are supposed to be a pathogenic trigger of the disorder. In fact, drusen may mechanically alter retinal function. A novel hypothesis exists, suggesting that a metabolic defect (systemic or focal within the retinal pigment epithelium) may be the real determinant of visual impairment, while causing the concomitant accumulation of proteinaceous debris and lipids forming the drusen. Here we face such an issue by analyzing the retinal anatomy to correlate visual impairment with the occurrence of drusen number, size and the extent of a drusenoid area in the foveal region. A comparison is made with wet AMD where new vessels and retinal exudates prevail. The study is carried out in 120 patients affected by dry or wet AMD and 21 patients where paradoxical findings are described. The main question consists in inferring whether the occurrence of visual impairment is due, in fact, to a drusen-dependent mechanical damage or drusen just occurs as an independent consequence of an upstream metabolic alteration, which concomitantly impairs the visual process. The present data indicate that, despite a significant difference in visual function between mild and severe AMD patients in the amount of drusen exists, a strong correlation between drusen and visual impairment does not occur. This suggests that drusen and visual deterioration develop as a consequence of similar upstream biochemical alterations but it is likely that drusen do not produce visual deterioration. This is strengthened here by extreme clinical conditions, where visual impairment is severe with a slight alteration in the planar pattern of the retina or, vice versa an extended drusenoid area occurs concomitantly with fair visual acuity, contrast sensitivity and lack of metamorphopsia. A biochemical analysis of key areas in the function of specific domains in the pigment epithelium as described in the accompanying manuscript should help to better disclose the real morpho-functional deficit, which takes place in AMD.

Step by step procedure for stereological counts of catecholamine neurons in the mouse brainstem

This work represents a detailed methodological description of automated stereology dedicated to all brainstem catecholamine nuclei. Each tyrosine-hydroxylase-containing nucleus was analyzed to count the following features: i) nuclear volume; ii) neuron number per nucleus; iii) neuron area per each nucleus.A number of reports described catecholamine-containing neurons within brainstem of a variety of animal species. In a recently published work, we reported a simultaneous quantitative analysis of tyrosine hydroxylase-positive neurons in the whole brainstem. Here we report the detailed step by step stereological procedure which allowed to perform a morphometric assessment of each catecholamine nucleus. This protocol provides the method chance to analyze simultaneously various morphological features in the same experimental setting to avoid variability when single nuclei are analyzed in different experiments. This improves the reliability of comparisons between brainstem catecholamine nuclei within the reticular formation to increase our insight about the key functional roles played by these cells in the mammalian brain. In fact, despite being a discrete number of neurons scattered in a small brain area, these cells provide remarkable axonal collateralization which allows the modulation of neuronal activity in the entire CNS. The step by step description of brainstem stereology provided here is reported in order to share these methods and enhance quantitative studies about these fascinating nuclei. At the same time we aim to provide a tool to be used routinely when analyzing the morphology and physiology of brainstem catecholamine cells.

The nature of catecholamine-containing neurons in the enteric nervous system in relationship with organogenesis, normal human anatomy and neurodegeneration

The gastrointestinal tract is provided with extrinsic and intrinsic innervation. The extrinsic innervation includes the classic vagal parasympathetic and sympathetic components, with afferent sensitive and efferent secretomotor fibers. The intrinsic innervations is represented by the enteric nervous system (ENS), which is recognized as a complex neural network controlling a variety of cell populations, including smooth muscle cells, mucosal secretory cells, endocrine cells, microvasculature, immune and inflammatory cells. This is finalized to regulate gastrointestinal secretion, absorption and motility. In particular, this network is organized in several plexuses each one providing quite autonomous control of gastrointestinal functions (hence the definition of "second brain"). The similarity between ENS and CNS is further substantiated by the presence of local sensitive pseudo- unipolar ganglionic neurons with both peripheral and central branching which terminate in the enteric wall. A large variety of neurons and neurotransmitters takes part in the ENS. However, the nature of these neurons and their role in the regulation of gastrointestinal functions is debatable. In particular, the available literature reporting the specific nature of catecholamine- containing neurons provides conflicting evidence. This is critical both for understanding the specific role of each catecholamine in the gut and, mostly, to characterize specifically the enteric neuropathology occurring in a variety of diseases. An emphasis is posed on neurodegenerative disorders, such as Parkinson's disease, which is associated with the loss of catecholamine neurons. In this respect, the recognition of the nature of such neurons within the ENS would contribute to elucidate the pathological mechanisms which produce both CNS and ENS degeneration and to achieve more effective therapeutic approaches. Despite a great emphasis is posed on the role of noradrenaline to regulate enteric activities only a few reports are available on the anatomy and physiology of enteric dopamine neurons. Remarkably, this review limits the presence of enteric noradrenaline (and adrenaline) only within extrinsic sympathetic nerve terminals. This is based on careful morphological studies showing that the only catecholamine-containing neurons within ENS would be dopaminergic. This means that enteric pathology of catecholamine neurons should be conceived as axon pathology for noradrenaline neurons and whole cell pathology for dopamine neurons which would be the sole catecholamine cell within intrinsic circuitries affecting gut motility and secretions.The gastrointestinal tract is provided with extrinsic and intrinsic innervation. The extrinsic innervation includes the classic vagal parasympathetic and sympathetic components, with afferent sensitive and efferent secretomotor fibers. The intrinsic innervations is represented by the enteric nervous system (ENS), which is recognized as a complex neural network  controlling a variety of cell populations, including smooth muscle cells, mucosal secretory cells, endocrine cells, microvasculature, immune and inflammatory cells. This is finalized to regulate gastrointestinal secretion, absorption and motility. In particular, this network is organized in several plexuses each one providing quite autonomous control of gastrointestinal functions (hence the definition of "second brain"). The similarity between ENS and CNS is further substantiated by the presence of local sensitive pseudounipolar ganglionic neurons with both peripheral and central branching which terminate in the enteric wall. A large variety of neurons and neurotransmitters takes part in the ENS. However, the nature of these neurons and their role in the regulation of gastrointestinal functions is debatable. In particular, the available literature reporting the specific nature of catecholamine-containing neurons provides conflicting evidence. This is critical both for understanding the specific role of each catecholamine in the gut and, mostly, to characterize specifically the enteric neuropathology occurring in a variety of diseases. An emphasis is posed on neurodegenerative disorders, such as including Parkinson's disease, which is associated with the loss of catecholamine neurons. In this respect, the recognition of the nature of such neurons within the ENS would contribute to elucidate the pathological mechanisms which produce both CNS and ENS degeneration and to achieve more effective therapeutic approaches. Despite a great emphasis is posed on the role of noradrenaline to regulate enteric activities only a few reports are available on the anatomy and physiology of enteric dopamine neurons. Remarkably, this review limits the presence of enteric noradrenaline (and adrenaline) only within extrinsic sympathetic nerve terminals. This is based on careful morphological studies showing that the only catecholamine-containing neurons within ENS would be dopaminergic. This means that enteric pathology of catecholamine neurons should be conceived as axon pathology for noradrenaline neurons and whole cell pathology for dopamine neurons which would be the sole catecholamine cell within intrinsic circuitries affecting gut motility and secretions.

A small dose of apomorphine counteracts the deleterious effects of middle cerebral artery occlusion in different models

The present manuscript investigates in two animal species by using two different experimental models of middle cerebral artery occlusion (permanent and transient), the neuroprotective effects of the dopamine receptor agonist apomorphine. These effects were evaluated by measuring the infarct volume and by counting muscle strength at different time points following the ischemic insult. Apomorphine at the dose of 3 mg/Kg when adminsitered at two hours following the occlusion of the middle cerebral artery was able to reduce significantly the infarct volume in the cortex of mice and the ischemic volume of the basal ganglia perfused by the perforant branches of the middle cerebral artery in the rat. In this latter case the behavioral evaluation (i.e. muscle strength) was preserved most effectively in the contralateral side at 24 and 72 hours. The present findings contribute to foster the concept that DA agonists might be useful in the treatment of cerebral ischemia. At the same time the behavioral improvement induced by DA administration following basal ganglia ischemia may be interpreted as the effects of an authentic disease modifying effect rather than a simple symtomatic relief due to a potential loss of DA containing axons in the basal ganglia. These data add on previous evidence showing analogous effects induced by the DA precursor L-DOPA. Apart from providing an evidence of a neuroprotective effect induced by increased DA stimulation the present data call for further studies aimed at comparing the effects of apomorphine with other DA agonists. In fact the quinoline moiety of apomorphine was claimed to protect neurons from a variety of insults independently from a DA agonist activity. The induction of protein clearing pathways appears to be potentially relevant for these effects.

Methamphetamine increases Prion Protein and induces dopamine-dependent expression of protease resistant PrPsc

The cellular prion protein (PrPc) is physiologically expressed within selective brain areas of mammals. Alterations in the secondary structure of this protein lead to scrapie-like prion protein (PrPsc), which precipitates in the cell. PrPsc has been detected in infectious, inherited or sporadic neurodegenerative disorders. Prion protein metabolism is dependent on autophagy and ubiquitin proteasome. Despite not being fully elucidated, the physiological role of prion protein relates to chaperones which rescue cells under stressful conditions.Methamphetamine (METH) is a widely abused drug which produces oxidative stress in various brain areas causing mitochondrial alterations and protein misfolding. These effects produce a compensatory increase of chaperones while clogging cell clearing pathways. In the present study, we explored whether METH administration modifies the amount of PrPc. Since high levels of PrPc when the clearing systems are clogged may lead to its misfolding into PrPsc, we further tested whether METH exposure triggers the appearance of PrPsc. We analysed the effects of METH and dopamine administration in PC12 and striatal cells by using SDS-PAGE Coomassie blue, immune- histochemistry and immune-gold electron microscopy. To analyze whether METH administration produces PrPsc aggregates we used antibodies directed against PrP following exposure to proteinase K or sarkosyl which digest folded PrPc but misfolded PrPsc. We fond that METH triggers PrPsc aggregates in DA-containing cells while METH is not effective in primary striatal neurons which do not produce DA. In the latter cells exogenous DA is needed to trigger PrPsc accumulation similarly to what happens in DA containing cells under the effects of METH. The present findings, while fostering novel molecular mechanisms involving prion proteins, indicate that, cell pathology similar to prion disorders can be mimicked via a DA-dependent mechanism by a drug of abuse.

A subcellular analysis of genetic modulation of PINK1 on mitochondrial alterations, autophagy and cell death

Mutations in the PTEN-induced putative kinase1 (PINK1) represent the second most frequent cause of autosomal recessive Parkinson's disease. The PINK1 protein mainly localizes to mitochondria and interacts with a variety of proteins, including the pro-autophagy protein beclin1 and the ubiquitin-ligase parkin. Upon stress conditions, PINK1 is known to recruit parkin at the surface of dysfunctional mitochondria and to activate the mitophagy cascade. Aim of this study was to use a simple and highly reproducible catecholamine cell model and transmission electron microscopy to characterize whether PINK1 could affect mitochondrial homeostasis, the recruitment of specific proteins at mitochondria, mitophagy and apoptosis. Samples were analyzed both in baseline conditions and following treatment with methamphetamine (METH), a neurotoxic compound which strongly activates autophagy and produces mitochondrial damage. Our data provide robust sub-cellular evidence that the modulation of PINK1 levels dramatically affects the morphology and number of mitochondria and the amount of cell death. In particular, especially upon METH exposure, PINK1 is able to increase the total number of mitochondria, concurrently recruit beclin1, parkin and ubiquitin and enhance the clearance of damaged mitochondria. In the absence of functional PINK1 and upon autophagy stress, we observe a failure of the autophagy system at large, with marked accumulation of dysfunctional mitochondria and dramatic increase of apoptotic cell death. These findings highlight the strong neuroprotective role of PINK1 as a key protein in the surveillance and regulation of mitochondrial homeostasis.

Methamphetamine induces ectopic expression of tyrosine hydroxylase and increases noradrenaline levels within the cerebellar cortex

Methamphetamine produces locomotor activation and typical stereotyped motor patterns, which are commonly related with increased catecholamine activity within the basal ganglia, including the dorsal and ventral striatum. Since the cerebellum is critical for movement control, and for learning of motor patterns, we hypothesized that cerebellar catecholamines might be a target of methamphetamine. To test this experimental hypothesis we injected methamphetamine into C57 Black mice at the doses of 5 mg/kg two or three times, 2 h apart. This dosing regimen is known to be toxic for striatal dopamine terminals. However, we found that in the cerebellum, methamphetamine increased the expression of the primary transcript of the tyrosine hydroxylase (TH) gene, followed by an increased expression of the TH protein. Increased TH was localized within Purkinje cells, where methamphetamine increased the number of TH-immunogold particles, and produced a change in the distribution of the enzyme by increasing the cytoplasmic percentage. Increased TH expression was accompanied by a slight increase in noradrenaline content. This effect was highly site-specific for the cortex of posterior vermal lobules, while only slight effects were detectable in the hemispheres. The present data indicate that the cerebellum does represent a target of methamphetamine, which produces specific and fine alterations of the catecholamine system involving synthesis, amount, and compartmentalization of TH as well as increased noradrenaline levels. This may be relevant for motor alterations induced by methamphetamine. In line with this, inherited cerebellar movement disorders in various animal species including humans are associated with increased TH immunoreactivity within intrinsic neurons of the same lobules of the cerebellar cortex.

Endogenous activation of metabotropic glutamate receptors supports the proliferation and survival of neural progenitor cells

The use of neural progenitor cells (NPCs) is limited by the incomplete knowledge of the extracellular signals regulating their proliferation and survival. We report that cultured mouse NPCs express functional mGlu3 and mGlu5 metabotropic glutamate receptors. Pharmacological blockade of both receptors reduced NPC proliferation and survival, whereas activation of mGlu5 receptors substantially enhanced cell proliferation. Adult mice lacking mGlu5 receptors or treated with mGlu5 or mGlu3 receptor antagonists showed a dramatic reduction in the number of dividing neuroprogenitors present in the subventricular zone and in the dentate gyrus of the hippocampus. These data disclose a novel function of mGlu receptors and offer new potential strategies for the optimization of cell replacement therapy in neurodegenerative disorders.

Previous exposure to (±) 3,4-methylenedioxymethamphetamine produces long-lasting alteration in limbic brain excitability measured by electroencephalogram spectrum analysis, brain metabolism and seizure susceptibility

Seizures represent the most common neurological emergency in ecstasy abusers; however, no study addressed whether (+/-) 3,4-methylenedioxymethamphetamine ("ecstasy") per se might produce long-lasting alterations in brain excitability related to a pro-convulsant effect. C57 Black mice were treated with three regimens of (+/-) 3,4-methylenedioxymethamphetamine (5mg/kg x 2 for 1, 2 or three consecutive days). Following the last dose of (+/-) 3,4-methylenedioxymethamphetamine, during a time interval of 8 weeks, the following procedures were carried out: 1) cortical electroencephalographic recordings, including power-spectrum analysis; 2) administration of sub-threshold doses of kainate; 3) measurement of regional [(14)C]2-deoxyglucose uptake; 4) monoamine assay. We demonstrate that all mice pre-treated with (+/-) 3,4-methylenedioxymethamphetamine showed long-lasting encephalographic changes with frequencies peaking at 3-4.5 Hz at the power-spectrum analysis. This is concomitant with latent brain hyperexcitability within selected limbic brain regions, as shown by seizure facilitation and long-lasting latent metabolic hyperactivity which can be unraveled by phasic glutamate stimulation. This study sheds new light into the brain targets of (+/-) 3,4-methylenedioxymethamphetamine and discloses the occurrence of (+/-) 3,4-methylenedioxymethamphetamine-induced latent hyperexcitability within limbic areas, while it might provide a model to study in controlled experimental conditions limbic seizures and status epilepticus in C57 Black mice. Persistent changes produced by (+/-) 3,4-methylenedioxymethamphetamine in limbic brain excitability might be responsible for seizures and limbic-related disorders in chronic (+/-) 3,4-methylenedioxymethamphetamine abusers.

Morphological and biochemical evidence that apomorphine rescues striatal dopamine terminals and prevents methamphetamine toxicity

Apomorphine, given by a single injection, repeated injections, or by continuous infusion, was tested for neuroprotective effects in mice administered methamphetamine or N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in order to induce striatal dopamine (DA) depletion. In the first part of the study, the DA agonist (R)-apomorphine was administered at various doses (1, 5, and 10 mg/kg), 15 min before methamphetamine (5 mg/kg x 3, 2 h apart). Mice were sacrificed 5 days later. In the second part, apomorphine was administered either continuously by subcutaneous minipump (cumulative daily dose of 0.5, 1, and 3.15 mg/kg), or as single, repeated daily injections (up to 5 mg/kg) starting 40 h after an acute administration of MPTP (30 mg/kg). Mice were sacrificed at different time intervals (up to 1 month) following MPTP injection. In all the animals, the integrity of striatal DA terminals was evaluated by measuring striatal DA levels and TH immunohistochemistry. Apomorphine dose-dependently prevented methamphetamine toxicity. These effects were neither due to a decrease in the amount of striatal methamphetamine nor to the hypothermia, and they were not reversed by the DA antagonist haloperidol. Moreover, chronic, continuous (but not pulsatile) administration of apomorphine rescued damaged striatal dopaminergic terminals. These findings confirm a protective effect of apomorphine that also consists of a neurorescue of damaged striatal DA terminals. This suggests a new hypothesis about the long-term benefits observed during continuous apomorphine administration in Parkinson's disease patients.

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.

The antioxidant drug dipyridamole spares the vitamin E and thiols in red blood cells after oxidative stress

OBJECTIVE

To test the antioxidant effect of therapeutic doses of dipyridamole on cellular membranes, human erythrocytes were chosen as an appropriate model to study oxidative stress induced by cumene hydroperoxide because of their high content in heme-Fe(2+).

METHODS

The oxidative stress was induced by incubation with 160 micromoll(-1) cumene hydroperoxide and expressed by three main factors: lipid peroxidation by means of kinetics of decrease in fluorescence emission of the probe incorporated in the cell membranes, vitamin E oxidation and intracellular thiol content. The concentrations of dipyridamole tested (2-20 micromoll(-1)) did not exceed pharmacological doses.

RESULTS

After 7 min of incubation at 25 degrees C with the oxidant and 20 micromoll(-1) dipyridamole thiol content was 50.1%+/-2.6 compared with 31.5%+/-2.4 in the absence of the drug. After 12 min vitamin E content was 88.3%+/-2.3 compared with 64.7%+/-3.4 of untreated cells in the absence of dipyridamole. Dipyridamole added 5 min after the oxidation reaction suppressed the fluorescence decrease for a time proportional to the drug concentration.

CONCLUSIONS

Thus, at clinically realistic doses dipyridamole shows a concentration-dependent antioxidant effect. It protects membranes from oxidation and spares the antioxidant power of erythrocytes.