Student insights towards animal welfare science and law. Survey results from Sassari University, Italy

In this paper, we describe the results of an online survey consisting of 23 questions created to evaluate the knowledge and interest on animal welfare by students attending 15 different scientific, medical, and biomedical courses at University of Sassari, Italy. The survey collected students' demographic data, level of knowledge both on animal welfare and 3Rs, as well as their opinions on animal experimentation. The majority of the cohort was female and over 24 years of age. About a third of the students responded that their graduate programme included subjects that taught science, ethics, and animal welfare legislation. Just 21.2% of respondents had heard about the concept of 3Rs. About a quarter of the students believed that animal models can be replaced by in vitro and in silico methods while half believed that both are needed. However, 70% of the participants did not know the existence of an Ethics and Animal Welfare Committee. The result showed the importance of an Animal Welfare Course for the professional future of a larger number of students and underlined the key role of veterinary medicine in promoting ethics and animal experimentation.

Early combination treatment with existing HIV antivirals: an effective treatment for COVID-19?

OBJECTIVE

Since no effective therapy exists, we aimed to test existing HIV antivirals for combination treatment of Coronavirus disease 19 (COVID-19).

MATERIALS AND METHODS

The crystal structures of SARS-CoV-2 main protein (Mpro) (PDB ID: 6Y2F) and SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) (PDB ID: 7BV2) both available from Protein Data Bank were used in the study. Automated Docking by using blind and standard method both on Mpro and RdRp bound to the modified template-primer RNA was performed with AutoDock 4.2.6 program suite. Lamarckian genetic algorithm (LGA) was used for structures docking. All inhibitors were docked with all bonds completely free to rotate.

RESULTS

Our molecular docking findings suggest that lopinavir, ritonavir, darunavir, and atazanavir activated interactions with the key binding sites of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) protease with a better inhibition constant (Ki) for lopinavir, ritonavir, and darunavir. Furthermore, we evidenced the ability of remdesivir, tenofovir, emtricitabine, and lamivudine to be incorporated in SARS-CoV-2 RdRp in the same protein pocket where poses the corresponding natural nucleoside substrates with comparable Ki and activating similar interactions. In principle, the four antiviral nucleotides might be used effectively against SARS-CoV-2.

CONCLUSIONS

The combination of a protease inhibitor and two nucleoside analogues, drugs widely used to treat HIV infection, could be evaluated in clinical trials for the treatment of COVID-19.

Underserved populations and bacterial and protozoal sexually transmitted infections: a lost health-care opportunity

OBJECTIVE

The purpose of our review is an update about the burden of sexually transmitted infections (STIs) among various types of underserved populations, such as migrants, substance abusers, homeless and incarcerated inmates. First-line test and treatment based on the latest available evidence according to the revised guidelines of Centers for Disease Control and Prevention have also been considered.

MATERIALS AND METHODS

We performed a comprehensive research using scientific databases such as Medline and Pubmed, followed by a review of citations and reference list. A consultation with other experts in the management of the various subpopulations was also conducted.

RESULTS

Health-care is often influenced by social determinants, which play a vital role in the diffusion of STIs. The consequence is a socio-economical and ethnic disparity in the rate of STIs. Early screening and treatment of STIs should be implemented in clinical practice, starting from marginalized social groups, which are the most affected by this health problem.

CONCLUSIONS

In the literature, there are very few papers containing information on STIs prevalence in various types of underserved populations, such as migrants, substance abusers, homeless and incarcerated inmates. The availability of more accurate epidemiological data is needed. In these groups, the most relevant barrier is the lower perception of health-care need, with an underestimation of risk and symptoms of STIs, causing a retard of diagnosis and health-care provision and use. For these populations, targeted interventions are needed, particularly on unaware people, responsible for most STIs transmissions.

The burden of HIV-associated neurocognitive disorder (HAND) in post-HAART era: a multidisciplinary review of the literature

OBJECTIVE

The purpose of the present multidisciplinary review is to give an updated insight into the most recent findings regarding the pathophysiology, diagnosis and therapeutics of HIV-associated neurocognitive disorder (HAND).

MATERIALS AND METHODS

We performed a comprehensive search, through electronic databases (Pubmed - MEDLINE) and search engines (Google Scholar), of peer-reviewed publications (articles and reviews) and conferences proceedings on HAND pathophysiology, diagnosis, and therapy, from 1999 to 2016.

RESULTS

It seems to be increasingly clear that neurodegeneration in HIV-1 affected patients is a multi-faceted disease involving numerous factors, from chronic inflammation to central nervous system (CNS) compartmentalization of HIV. Diagnosis of HAND may benefit from both laboratory analysis and advanced specific neuroimaging techniques. As regards HAND therapy, modified HAART combinations and simplification strategies have been tested, while novel exciting frontiers seem to involve the use of nanoparticles with the ability to cross the Blood-Brain Barrier (BBB).

CONCLUSIONS

Albeit highly active antiretroviral therapy (HAART) allowed a major decrease in morbidity and mortality for AIDS patients, CNS involvement still represents a challenge in HIV patients even today, affecting up to 50% of patients with access to combination antiretroviral therapy (cART). Future studies will have to focus on CNS compartmentalization, drugs' ability to penetrate and suppress viral replication in this compartment, and on new approaches to reduce HIV-associated neuroinflammation.

Low electro-synthesis potentials improve permselectivity of polymerized natural phenols in biosensor applications

First-generation amperometric biosensors are often based on the electro-oxidation of oxidase-generated H₂O₂. At the applied potential used in most studies, other molecules such as ascorbic acid or dopamine can be oxidized. Phenylenediamines are commonly used to avoid this problem: when these compounds are electro-deposited onto the transducer surface in the form of poly-phenylenediamine, a highly selective membrane is formed. Although there is no evidence of toxicity of the resulting polymer, phenylenediamine monomers are considered carcinogenic. An aim of this work was to evaluate the suitability of natural phenols as non-toxic alternatives to the ortho isomer of phenylenediamine. Electrosynthesis over Pt-Ir electrodes of 2-methoxy phenols (guaiacol, eugenol and isoeugenol), and hydroxylated biphenyls (dehydrodieugenol and magnolol) was achieved. The potentials used in the present study are significantly lower than values commonly applied during electro-polymerization. Polymers were obtained by means of constant potential amperometry, instead of cyclic voltammetry, in order to achieve multiple polymerizations, hence decreasing the time of realization and variability. Permselective properties of natural phenols were significantly improved at low polymerization potentials. Among the tested compounds, isoeugenol and magnolol, polymerized respectively at +25mV and +170mV against Ag/AgCl reference electrode, proved as permselective as poly-ortho-phenylenediamine and may be considered as effective polymeric alternatives. The natural phenol-coated electrodes were stable and responsive throughout 14 days. A biosensor prototype based on acetylcholine esterase and choline oxidase was electro-coated with poly-magnolol in order to evaluate the interference-rejecting properties of the electrosynthesized film in an amperometric biosensor; a moderate decrease in ascorbic acid rejection was observed during in vitro calibration of biosensors.

Electropolymerized phenol derivatives as permselective polymers for biosensor applications

Amperometric biosensors are often coated with a polymeric permselective film to avoid electroactive interference by reducing agents present in the target medium. Phenylenediamine and phenol monomers are commonly used to form these permselective films in the design of microsensors and biosensors. This paper aims to evaluate the permselectivity, stability and lifetime of polymers electrosynthesized using either constant potential amperometry (CPA) or cyclic voltammetry (CV) from naturally occurring phenylpropanoids in monomeric and dimeric forms (eugenol, isoeugenol, dehydrodieugenol and magnolol). Sensors were characterized by scanning electron microscopy and permselectivity analysis. Magnolol formed an electro-deposited polymer with a more defined three-dimensional texture in comparison with the other films. The phenol-derived films showed different permselectivity towards H2O2 over ascorbic acid and dopamine, likely to be related to the thickness and compactness of the polymer. The CV-derived films had a better permselectivity compared to the CPA-corresponding polymers. Based on these results, the permselectivity, stability and lifetime of a biosensor for glucose were studied when a magnolol coating was electro-deposited. The structural principles governing the permselectivity of the magnolol-derived film are suggested to be mainly related to the conformational flexibility of this monomer. Newly designed biosensors, coated with electropolymerized natural phenol derivatives, may represent promising analytical devices for different application fields.

Ceftriaxone blocks the polymerization of α-synuclein and exerts neuroprotective effects in vitro

The β-lactam antibiotic ceftriaxone was suggested as a therapeutic agent in several neurodegenerative disorders, either for its ability to counteract glutamate-mediated toxicity, as in cerebral ischemia, or for its ability to enhance the degradation of misfolded proteins, as in Alexander's disease. Recently, the efficacy of ceftriaxone in neuroprotection of dopaminergic neurons in a rat model of Parkinson's disease was documented. However, which characteristics of ceftriaxone mediate its therapeutic effects remains unclear. Since, at the molecular level, neuronal α-synuclein inclusions and pathological α-synuclein transmission play a leading role in initiation of Parkinson-like neurodegeneration, we thought of investigating, by circular dichroism spectroscopy, the capability of ceftriaxone to interact with α-synuclein. We found that ceftriaxone binds with good affinity to α-synuclein and blocks its in vitro polymerization. Considering this finding, we also documented that ceftriaxone exerts neuroprotective action in an in vitro model of Parkinson's disease. Our data, in addition to the findings on neuroprotective activity of ceftriaxone on Parkinson-like neurodegeneration in vivo, indicates ceftriaxone as a potential agent in treatment of Parkinson's disease.

Simultaneous telemetric monitoring of brain glucose and lactate and motion in freely moving rats

A new telemetry system for simultaneous detection of extracellular brain glucose and lactate and motion is presented. The device consists of dual-channel, single-supply miniature potentiostat-I/V converter, a microcontroller unit, a signal transmitter, and a miniaturized microvibration sensor. Although based on simple and inexpensive components, the biotelemetry device has been used for accurate transduction of the anodic oxidation currents generated on the surface of implanted glucose and lactate biosensors and animal microvibrations. The device was characterized and validated in vitro before in vivo experiments. The biosensors were implanted in the striatum of freely moving animals and the biotelemetric device was fixed to the animal's head. Physiological and pharmacological stimulations were given in order to induce striatal neural activation and to modify the motor behavior in awake, untethered animals.

Do on- and off-pump coronary bypass surgery differently affect perioperative peripheral tissue metabolism?

BACKGROUND

Microdialysis allows the in-vivo assessment of interstitial fluids. We studied the metabolic status of peripheral tissues (skeletal muscle) in patients undergoing coronary artery bypass surgery on- (CABG) or off-pump (OPCAB).

METHODS

Twenty patients candidates to elective coronary bypass surgery were randomly assigned to undergo CABG or OPCAB. A microdialysis catheter was inserted in the left deltoid muscle before surgery and left in place for 24 hours, and metabolic markers of peripheral tissue perfusion (glucose, lactate, pyruvate, glycerol and lactate/pyruvate (L/P) ratio) were assessed before, at the end, and 24 hours after surgery.

RESULTS

Preoperative clinical features were similar in both groups. Interstitial levels of glucose and lactate increased over time, being in both groups significantly higher than baseline 24 hours after surgery, whereas glycerol levels did not change over time and between groups. In addition, there was an increase over time of pyruvate levels which were significantly higher in CABG after surgery, whereas L/P ratio was significantly higher in OPCAB 24 hours after surgery.

CONCLUSION

Metabolic changes after coronary bypass surgery occur with some differences related to CPB use. Overall, these changes suggest that, after coronary surgery, a certain degree of hypermetabolic state ensues, lasting up to 24 hours after surgery; the postoperative increase in pyruvate levels in CABG patients, together with the changes in L/P ratio occurring only in OPCAB patients implies an higher risk of tissue hypoperfusion/ischemia for patients submitted to OPCAB, although this does not lead to permanent cellular damage, as the markers of this complication (e.g., glycerol) do not change over time.

Combining nitric oxide release with anti-inflammatory activity preserves nigrostriatal dopaminergic innervation and prevents motor impairment in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of Parkinson's disease

Background

Current evidence suggests a role of neuroinflammation in the pathogenesis of Parkinson's disease (PD) and in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of basal ganglia injury. Reportedly, nonsteroidal anti-inflammatory drugs (NSAIDs) mitigate DAergic neurotoxicity in rodent models of PD. Consistent with these findings, epidemiological analysis indicated that certain NSAIDs may prevent or delay the progression of PD. However, a serious impediment of chronic NSAID therapy, particularly in the elderly, is gastric, renal and cardiac toxicity. Nitric oxide (NO)-donating NSAIDs, have a safer profile while maintaining anti-inflammatory activity of parent compounds. We have investigated the oral activity of the NO-donating derivative of flurbiprofen, [2-fluoro-α-methyl (1,1'-biphenyl)-4-acetic-4-(nitrooxy)butyl ester], HCT1026 (30 mg kg^-1 daily in rodent chow) in mice exposed to the parkinsonian neurotoxin MPTP.

Methods

Ageing mice were fed with a control, flurbiprofen, or HCT1026 diet starting ten days before MPTP administration and continuing for all the experimental period. Striatal high affinity synaptosomial dopamine up-take, motor coordination assessed with the rotarod, tyrosine hydroxylase (TH)- and dopamine transporter (DAT) fiber staining, stereological cell counts, immunoblotting and gene expression analyses were used to assess MPTP-induced nigrostriatal DAergic toxicity and glial activation 1-40 days post-MPTP.

Results

HCT1026 was well tolerated and did not cause any measurable toxic effect, whereas flurbiprofen fed mice showed severe gastrointestinal side-effects. HCT1026 efficiently counteracted motor impairment and reversed MPTP-induced decreased synaptosomal [³H]dopamine uptake, TH- and DAT-stained fibers in striatum and TH⁺ neuron loss in subtantia nigra pars compacta (SNpc), as opposed to age-matched mice fed with a control diet. These effects were associated to a significant decrease in reactive macrophage antigen-1 (Mac-1)-positive microglial cells within the striatum and ventral midbrain, decreased expression of iNOS, Mac-1 and NADPH oxidase (PHOX), and downregulation of 3-Nitrotyrosine, a peroxynitrite finger print, in SNpc DAergic neurons.

Conclusions

Oral treatment with HCT1026 has a safe profile and a significant efficacy in counteracting MPTP-induced dopaminergic (DAergic) neurotoxicity, motor impairment and microglia activation in ageing mice. HCT1026 provides a novel promising approach towards the development of effective pharmacological neuroprotective strategies against PD.

Reactive astrocytes and Wnt/β-catenin signaling link nigrostriatal injury to repair in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of Parkinson's disease

Emerging evidence points to reactive glia as a pivotal factor in Parkinson's disease (PD) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mouse model of basal ganglia injury, but whether astrocytes and microglia activation may exacerbate dopaminergic (DAergic) neuron demise and/or contribute to DAergic repair is presently the subject of much debate. Here, we have correlated the loss and recovery of the nigrostriatal DAergic functionality upon acute MPTP exposure with extensive gene expression analysis at the level of the ventral midbrain (VM) and striata (Str) and found a major upregulation of pro-inflammatory chemokines and wingless-type MMTV integration site1 (Wnt1), a key transcript involved in midbrain DAergic neurodevelopment. Wnt signaling components (including Frizzled-1 [Fzd-1] and β-catenin) were dynamically regulated during MPTP-induced DAergic degeneration and reactive glial activation. Activated astrocytes of the ventral midbrain were identified as candidate source of Wnt1 by in situ hybridization and real-time PCR in vitro. Blocking Wnt/Fzd signaling with Dickkopf-1 (Dkk1) counteracted astrocyte-induced neuroprotection against MPP(+) toxicity in primary mesencephalic astrocyte-neuron cultures, in vitro. Moreover, astroglial-derived factors, including Wnt1, promoted neurogenesis and DAergic neurogenesis from adult midbrain stem/neuroprogenitor cells, in vitro. Conversely, lack of Wnt1 transcription in response to MPTP in middle-aged mice and failure of DAergic neurons to recover were reversed by pharmacological activation of Wnt/β-catenin signaling, in vivo, thus suggesting MPTP-reactive astrocytes in situ and Wnt1 as candidate components of neuroprotective/neurorescue pathways in MPTP-induced nigrostriatal DAergic plasticity.

Real-time monitoring of brain tissue oxygen using a miniaturized biotelemetric device implanted in freely moving rats

A miniaturized biotelemetric device for the amperometric detection of brain tissue oxygen is presented. The new system, derived from a previous design, has been coupled with a carbon microsensor for the real-time detection of dissolved O(2) in the striatum of freely moving rats. The implantable device consists of a single-supply sensor driver, a current-to-voltage converter, a microcontroller, and a miniaturized data transmitter. The oxygen current is converted to a digital value by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC). The digital data is sent to a personal computer using a six-byte packet protocol by means of a miniaturized 434 MHz amplitude modulation (AM) transmitter. The receiver unit is connected to a personal computer (PC) via a universal serial bus. Custom developed software allows the PC to store and plot received data. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption, and good linear response in the nanoampere current range. The in vivo results confirmed previously published observations on oxygen dynamics in the striatum of freely moving rats. The system serves as a rapid and reliable model for studying the effects of different drugs on brain oxygen and brain blood flow and it is suited to work with direct-reduction sensors or O(2)-consuming biosensors.

Contributions by a novel edge effect to the permselectivity of an electrosynthesized polymer for microbiosensor applications

Pt electrodes of different sizes (2 x 10(-5)-2 x 10(-2) cm(2)) and geometries (disks and cylinders) were coated with the ultrathin non-conducting form of poly(o-phenylenediamine), PPD, using amperometric electrosynthesis. Analysis of the ascorbic acid (AA) and H(2)O(2) apparent permeabilities for these Pt/PPD sensors revealed that the PPD deposited near the electrode insulation (Teflon or glass edge) was not as effective as the bulk surface PPD for blocking AA access to the Pt substrate. This discovery impacts on the design of implantable biosensors where electrodeposited polymers, such as PPD, are commonly used as the permselective barrier to block electroactive interference by reducing agents present in the target medium. The undesirable "edge effect" was particularly marked for small disk electrodes which have a high edge density (ratio of PPD-insulation edge length to electrode area), but was essentially absent for cylinder electrodes with a length of >0.2 mm. Sample biosensors, with a configuration based on these findings (25 microm diameter Pt fiber cylinders) and designed for brain neurotransmitter L-glutamate, behaved well in vitro in terms of Glu sensitivity and AA blocking.

Biotelemetric monitoring of brain neurochemistry in conscious rats using microsensors and biosensors

In this study we present the real-time monitoring of three key brain neurochemical species in conscious rats using implantable amperometric electrodes interfaced to a biotelemetric device. The new system, derived from a previous design, was coupled with carbon-based microsensors and a platinum-based biosensor for the detection of ascorbic acid (AA), O₂ and glucose in the striatum of untethered, freely-moving rats. The miniaturized device consisted of a single-supply sensor driver, a current-to-voltage converter, a microcontroller and a miniaturized data transmitter. The redox currents were digitized to digital values by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC), and sent to a personal computer by means of a miniaturized AM transmitter. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption and good linear response in the nanoampere current range. The in-vivo results confirmed previously published observations on striatal AA, oxygen and glucose dynamics recorded in tethered rats. This approach, based on simple and inexpensive components, could be used as a rapid and reliable model for studying the effects of different drugs on brain neurochemical systems.

Novel integrated microdialysis-amperometric system for in vitro detection of dopamine secreted from PC12 cells: design, construction, and validation

A novel dual channel in vitro apparatus, derived from a previously described design, has been coupled with dopamine (DA) microsensors for the flow-through detection of DA secreted from PC12 cells. The device, including two independent microdialysis capillaries, was loaded with a solution containing PC12 cells while a constant phosphate-buffered saline (PBS) medium perfusion was carried out using a dual channel miniaturized peristaltic pump. One capillary was perfused with normal PBS, whereas extracellular calcium was removed from extracellular fluid of the second capillary. After a first period of stabilization and DA baseline recording, KCl (75 mM) was added to the perfusion fluid of both capillaries. In this manner, a simultaneous "treatment-control" experimental design was performed to detect K+-evoked calcium-dependent DA secretion. For this purpose, self-referencing DA microsensors were developed, and procedures for making, testing, and calibrating them are described in detail. The electronic circuitry was derived from previously published schematics and optimized for dual sensor constant potential amperometry applications. The microdialysis system was tested and validated in vitro under different experimental conditions, and DA secretion was confirmed by high-performance liquid chromatography with electrochemical detection (HPLC-EC). PC12 cell viability was quantified before and after each experiment. The proposed apparatus serves as a reliable model for studying the effects of different drugs on DA secretion through the direct comparison of extracellular DA increase in treatment-control experiments performed on the same initial PC12 cell population.

Control of the oxygen dependence of an implantable polymer/enzyme composite biosensor for glutamate

Biosensors for glutamate (Glu) were fabricated from Teflon-coated Pt wire (cylinders and disks), modified with the enzyme glutamate oxidase (GluOx) and electrosynthesized polymer PPD, poly(o-phenylenediamine). The polymer/enzyme layer was deposited in two configurations: enzyme before polymer (GluOx/PPD) and enzyme after polymer (PPD/GluOx). These four biosensor designs were characterized in terms of response time, limit of detection, Michaelis-Menten parameters for Glu (J max and K(M)(Glu)), sensitivity to Glu in the linear response region, and dependence on oxygen concentration, K(M)(O2). Analysis showed that the two polymer/enzyme configurations behaved similarly on both cylinders and disks. Although the two geometries showed different behaviors, these differences could be explained in terms of higher enzyme loading density on the disks; in many analyses, the four designs behaved like a single population with a range of GluOx loading. Enzyme loading was the key to controlling the K(M)(O2) values of these first generation biosensors. The counterintuitive, and beneficial, behavior that biosensors with higher GluOx loading displayed a lower oxygen dependence was explained in terms of the effects of enzyme loading on the affinity of GluOx for its anionic substrate. Some differences between the properties of surface immobilized GluOx and glucose oxidase are highlighted.

Oxygen tolerance of an implantable polymer/enzyme composite glutamate biosensor displaying polycation-enhanced substrate sensitivity

Biosensors were fabricated at neutral pH by sequentially depositing the polycation polyethyleneimine (PEI), the stereoselective enzyme L-glutamate oxidase (GluOx) and the permselective barrier poly-ortho-phenylenediamine (PPD) onto 125-microm diameter Pt wire electrodes (Pt/PEI/GluOx/PPD). These devices were calibrated amperometrically at 0.7 V versus SCE to determine the Michaelis-Menten parameters for enzyme substrate, l-glutamate (Glu) and co-substrate, dioxygen. The presence of PEI produced a 10-fold enhancement in the detection limit for Glu (approximately 20 nM) compared with the corresponding PEI-free configurations (Pt/GluOx/PPD), without undermining their fast response time (approximately 2 s). Most remarkable was the finding that, although some designs of PEI-containing biosensors showed a 10-fold increase in linear region sensitivity to Glu, their oxygen dependence remained low.

The efficiency of immobilised glutamate oxidase decreases with surface enzyme loading: an electrostatic effect, and reversal by a polycation significantly enhances biosensor sensitivity

The apparent Michaelis constant, K(M), for glutamate oxidase (GluOx) immobilised on Pt electrodes increased systematically with enzyme loading. The effect was due, at least in part, to electrostatic repulsion between neighbouring oxidase molecules and the anionic substrate, glutamate (Glu). This understanding has allowed us to increase the Glu sensitivity of GluOx-based amperometric biosensors in the linear response region (100+/-11 nA cm(-2)microM(-1) at pH 7.4; SD, n=23) by incorporating a polycation (polyethyleneimine, PEI) to counterbalance the polyanionic protein. Differences in the behaviour of glucose biosensors of a similar configuration highlight a limitation of using glucose oxidase as a model enzyme in biosensor design.

Estrogen, neuroinflammation and neuroprotection in Parkinson's disease: glia dictates resistance versus vulnerability to neurodegeneration

Post-menopausal estrogen deficiency is recognized to play a pivotal role in the pathogenesis of a number of age-related diseases in women, such as osteoporosis, coronary heart disease and Alzheimer's disease. There are also sexual differences in the progression of diseases associated with the nigrostriatal dopaminergic system, such as Parkinson's disease, a chronic progressive degenerative disorder characterized by the selective degeneration of mesencephalic dopaminergic neurons in the substancia nigra pars compacta. The mechanism(s) responsible for dopaminergic neuron degeneration in Parkinson's disease are still unknown, but oxidative stress and neuroinflammation are believed to play a key role in nigrostriatal dopaminergic neuron demise. Estrogen neuroprotective effects have been widely reported in a number of neuronal cell systems including the nigrostriatal dopaminergic neurons, via both genomic and non-genomic effects, however, little is known on estrogen modulation of astrocyte and microglia function in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of Parkinson's disease. We here highlight estrogen modulation of glial neuroinflammatory reaction in the protection of mesencephalic dopaminergic neurons and emphasize the cardinal role of glia-neuron crosstalk in directing neuroprotection vs neurodegeneration. In particular, the specific role of astroglia and its pro-/anti-inflammatory mechanisms in estrogen neuroprotection are presented. This study shows that astrocyte and microglia response to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine injury vary according to the estrogenic status with direct consequences for dopaminergic neuron survival, recovery and repair. These findings provide a new insight into the protective action of estrogen that may possibly contribute to the development of novel therapeutic treatment strategies for Parkinson's disease.

Glutathione deficiency potentiates manganese-induced increases in compounds associated with high-energy phosphate degradation in discrete brain areas of young and aged rats

Aging is a factor known to increase neuronal vulnerability to oxidative stress, which is widely accepted as a mechanism of manganese-induced neuronal damage. We previously showed that subchronic exposure to manganese induced greater energy impairment (as revealed by increases in hypoxanthine, xanthine and uric acid levels) in the striatum and brainstem of aged rats vs young rats. This study shows that inhibition of glutathione (GSH) synthesis, by means of buthionine (SR) sulfoximine, decreased GSH levels and increased the ascorbic acid oxidation status in the striatum and limbic forebrain of both young and aged rats. In addition, inhibition of GSH synthesis greatly potentiated the manganese-induced increase in inosine, hypoxanthine, xanthine and uric acid levels in both regions of aged rats; moreover, inhibition of GSH synthesis significantly increased inosine, hypoxanthine, xanthine and uric acid levels in both regions of young rats, compared with the manganese-treated group. These results suggest that an impairment in the neuronal antioxidant system renders young rats susceptible to manganese-induced energetic impairment, and further support the hypothesis that an impairment in this system plays a permissive role in the increase of neuronal vulnerability that occurs with aging.

Glutamate and catabolites of high-energy phosphates in the striatum and brainstem of young and aged rats subchronically exposed to manganese

The degradation of high-energy phosphates was recently shown to precede manganese-induced cellular death. We evaluated hypoxanthine, xanthine, uric acid and glutamate levels in the striatum and brainstem of 3- and 20-month-old rats after subchronic oral exposure to manganese (MnCl2, 200 mg/kg/day in young rats, and 50-100 or 200 mg/kg/day in aged rats). Aged rats had higher basal levels of hypoxanthine, xanthine, and glutamate both in the striatum and brainstem than young rats; conversely, basal uric acid levels were lower in the striatum, but higher in the brainstem. Manganese induced a significantly greater increase in hypoxanthine, xanthine, uric acid and glutamate levels in aged rats than in young rats in both brain regions. These findings depict a greater manganese-induced energetic impairment (increases in hypoxanthine and xanthine levels), xanthine oxidase-induced free radical generation (increases in xanthine and uric acid levels), and excitotoxic status (increases in glutamate levels) in aged rats than in young rats. In addition, these findings may also account for a greater manganese toxicity to the nigro-striatal dopaminergic system in aged than in young rats, as shown in a previous work.

On the mechanism of d-amphetamine-induced changes in glutamate, ascorbic acid and uric acid release in the striatum of freely moving rats

1. The effects of systemic, intrastriatal or intranigral administration of d-amphetamine on glutamate, aspartate, ascorbic acid (AA), uric acid, dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) concentrations in dialysates from the striatum of freely-moving rats were evaluated using microdialysis. 2. d-Amphetamine (2 mg kg-1) given subcutaneously (s.c.) increased DA, AA and uric acid and decreased DOPAC + HVA, glutamate and aspartate dialysate concentrations over a 3 h period after d-amphetamine. 5-HIAA concentrations were unaffected. Individual changes in glutamate and AA dialysate concentrations were negatively correlated. 3. d-Amphetamine (0.2 mM), given intrastriatally, increased DA and decreased DOPAC + HVA and aspartate dialysate concentrations, but failed to change those of glutamate, AA uric acid or 5-HIAA, over a 2 h period after d-amphetamine. Haloperidol (0.1 mM), given intrastriatally, increased aspartate concentrations without affecting those of glutamate or AA. 4. d-Amphetamine (0.2 mM), given intranigrally, increased AA and uric acid dialysate concentrations and decreased those of glutamate, aspartate and DA; DOPAC + HVA and 5-HIAA concentrations were unaffected. 5. These results suggest that d-amphetamine-induced increases in AA and uric acid and decreases in glutamate concentrations are triggered at nigral sites. The changes in aspartate levels may be evoked by at least two mechanisms: striatal (mediated by inhibitory dopaminergic receptors) and nigral (activation of amino acid carrier-mediated uptake).

Enhancing effect of manganese on L-DOPA-induced apoptosis in PC12 cells: role of oxidative stress

L-DOPA and manganese both induce oxidative stress-mediated apoptosis in catecholaminergic PC12 cells. In this study, exposure of PC12 cells to 0.2 mM MnCl2 or 10-20 microM L-DOPA neither affected cell viability, determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, nor induced apoptosis, tested by flow cytometry, fluorescence microscopy, and the TUNEL technique. L-DOPA (50 microM) induced decreases in both cell viability and apoptosis. When 0.2 mM MnCl2 was associated with 10, 20, or 50 microM L-DOPA, a concentration-dependent decrease in cell viability was observed. Apoptotic cell death also occurred. In addition, manganese inhibited L-DOPA effects on dopamine (DA) metabolism (i.e., increases in DA and its acidic metabolite levels in both cell lysate and incubation medium). The antioxidant N-acetyl-L-cysteine significantly inhibited decreases in cell viability, apoptosis, and changes in DA metabolism induced by the manganese association with L-DOPA. An increase in autoxidation of L-DOPA and of newly formed DA is suggested as a mechanism of manganese action. These data show that agents that induce oxidative stress-mediated apoptosis in catecholaminergic cells may act synergistically.

Effects of allopurinol on striatal dopamine, ascorbate and uric acid during an acute morphine challenge: ex vivo and in vivo studies

In the present study in vivo and ex vivo experiments were combined to evaluate the effects of allopurinol on the neurochemical changes induced by an acute morphine challenge (2 mg kg-1, s.c.). In samples from rat striatum, levels of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 3-methoxytyramine (3-MT), ascorbate (AA), dehydroascorbate (DHAA), hypoxanthine, xanthine and uric acid (UA) were measured. Brain microdialysis experiments were carried out in freely moving rats. Striatal dialysate levels were assayed for DA, DOPAC + HVA, AA and UA using liquid chromatography followed by electrochemical detection. Morphine administration increased the striatal levels of DA metabolites, UA and DHAA and the extracellular concentrations of DA, DOPAC + HVA, UA and AA. Allopurinol (50 mg kg-1 by gavage), an inhibitor of xanthine oxidase which catalyses oxidation of xanthine to UA, decreased basal UA and AA concentrations and the morphine-induced increase in DA metabolites and AA oxidation. Since oxidation of DA and xanthines generates reactive oxygen species (ROS) and AA and UA are the main cellular antioxidants, these findings suggest that: (a) single morphine administration increases DA and xanthine oxidative metabolism with a consequent increase in ROS production, which may account for changes in concentrations of extracellular AA and tissue DHAA; (b) allopurinol decreases morphine-induced DA and xanthine oxidation; (c) UA and AA may act in concert to regulate levels of ROS in the brain.