Prevention of dopaminergic neurotoxicity by targeting nitric oxide and peroxynitrite: implications for the prevention of methamphetamine-induced neurotoxic damage

Neurotoxicity of methamphetamine: Main effects and mechanisms

Methamphetamine (METH) is an illicit psychostimulant that is abused throughout the world. METH addiction is also a major public health concern and the abuse of large doses of the drug is often associated with serious neuropsychiatric consequences that may include agitation, anxiety, hallucinations, paranoia, and psychosis. Some human methamphetamine users can also suffer from attention, memory, and executive deficits. METH-associated neurological and psychiatric complications might be related, in part, to METH-induced neurotoxic effects. Those include altered dopaminergic and serotonergic functions, neuronal apoptosis, astrocytosis, and microgliosis. Here we have endeavored to discuss some of the main effects of the drug and have presented the evidence supporting certain of the molecular and cellular bases of METH neurotoxicity. The accumulated evidence suggests the involvement of transcription factors, activation of dealth pathways that emanate from mitochondria and endoplasmic reticulum (ER), and a role for neuroinflammatory mechanisms. Understanding the molecular processes involved in METH induced neurotoxicity should help in developing better therapeutic approaches that might also serve to attenuate or block the biological consequences of use of large doses of the drug by some humans who meet criteria for METH use disorder.

Psychoactive Drugs-From Chemical Structure to Oxidative Stress Related to Dopaminergic Neurotransmission. A Review

Nowadays, more and more young people want to experience illegal, psychoactive substances, without knowing the risks of exposure. Besides affecting social life, psychoactive substances also have an important effect on consumer health. We summarized and analyzed the published literature data with reference to the mechanism of free radical generation and the link between chemical structure and oxidative stress related to dopaminergic neurotransmission. This review presents data on the physicochemical properties, on the ability to cross the blood brain barrier, the chemical structure activity relationship (SAR), and possible mechanisms by which neuronal injuries occur due to oxidative stress as a result of drug abuse such as "bath salts", amphetamines, or cocaine. The mechanisms of action of ingested compounds or their metabolites involve intermediate steps in which free radicals are generated. The brain is strongly affected by the consumption of such substances, facilitating the induction of neurodegenerative diseases. It can be concluded that neurotoxicity is associated with drug abuse. Dependence and oxidative stress are linked to inhibition of neurogenesis and the onset of neuronal death. Understanding the pathological mechanisms following oxidative attack can be a starting point in the development of new therapeutic targets.

The Main Molecular Mechanisms Underlying Methamphetamine- Induced Neurotoxicity and Implications for Pharmacological Treatment

Methamphetamine (METH) is a popular new-type psychostimulant drug with complicated neurotoxicity. In spite of mounting evidence on METH-induced damage of neural cell, the accurate mechanism of toxic effect of the drug on central nervous system (CNS) has not yet been completely deciphered. Besides, effective treatment strategies toward METH neurotoxicity remain scarce and more efficacious drugs are to be developed. In this review, we summarize cellular and molecular bases that might contribute to METH-elicited neurotoxicity, which mainly include oxidative stress, excitotoxicity, and neuroinflammation. We also discuss some drugs that protect neural cells suffering from METH-induced neurotoxic consequences. We hope more in-depth investigations of exact details that how METH produces toxicity in CNS could be carried out in future and the development of new drugs as natural compounds and immunotherapies, including clinic trials, are expected.

Iron Oxide Nanoparticles Induce Dopaminergic Damage: In vitro Pathways and In Vivo Imaging Reveals Mechanism of Neuronal Damage

Various iron-oxide nanoparticles have been in use for a long time as therapeutic and imaging agents and for supplemental delivery in cases of iron-deficiency. While all of these products have a specified size range of ∼ 40 nm and above, efforts are underway to produce smaller particles, down to ∼ 1 nm. Here, we show that after a 24-h exposure of SHSY-5Y human neuroblastoma cells to 10 μg/ml of 10 and 30 nm ferric oxide nanoparticles (Fe-NPs), cellular dopamine content was depleted by 68 and 52 %, respectively. Increases in activated tyrosine kinase c-Abl, a molecular switch induced by oxidative stress, and neuronal α-synuclein expression, a protein marker associated with neuronal injury, were also observed (55 and 38 % percent increases, respectively). Inhibition of cell-proliferation, significant reductions in the number of active mitochondria, and a dose-dependent increase in reactive oxygen species (ROS) were observed in neuronal cells. Additionally, using a rat in vitro blood-brain barrier (BBB) model, a dose-dependent increase in ROS accompanied by increased fluorescein efflux demonstrated compromised BBB integrity. To assess translational implications, in vivo Fe-NP-induced neurotoxicity was determined using in vivo MRI and post-mortem neurochemical and neuropathological correlates in adult male rats after exposure to 50 mg/kg of 10 nm Fe-NPs. Significant decrease in T 2 values was observed. Dynamic observations suggested transfer and retention of Fe-NPs from brain vasculature into brain ventricles. A significant decrease in striatal dopamine and its metabolites was also observed, and neuropathological correlates provided additional evidence of significant nerve cell body and dopaminergic terminal damage as well as damage to neuronal vasculature after exposure to 10 nm Fe-NPs. These data demonstrate a neurotoxic potential of very small size iron nanoparticles and suggest that use of these ferric oxide nanoparticles may result in neurotoxicity, thereby limiting their clinical application.

Nucleus accumbens invulnerability to methamphetamine neurotoxicity

Methamphetamine (Meth) is a neurotoxic drug of abuse that damages neurons and nerve endings throughout the central nervous system. Emerging studies of human Meth addicts using both postmortem analyses of brain tissue and noninvasive imaging studies of intact brains have confirmed that Meth causes persistent structural abnormalities. Animal and human studies have also defined a number of significant functional problems and comorbid psychiatric disorders associated with long-term Meth abuse. This review summarizes the salient features of Meth-induced neurotoxicity with a focus on the dopamine (DA) neuronal system. DA nerve endings in the caudate-putamen (CPu) are damaged by Meth in a highly delimited manner. Even within the CPu, damage is remarkably heterogeneous, with ventral and lateral aspects showing the greatest deficits. The nucleus accumbens (NAc) is largely spared the damage that accompanies binge Meth intoxication, but relatively subtle changes in the disposition of DA in its nerve endings can lead to dramatic increases in Meth-induced toxicity in the CPu and overcome the normal resistance of the NAc to damage. In contrast to the CPu, where DA neuronal deficiencies are persistent, alterations in the NAc show a partial recovery. Animal models have been indispensable in studies of the causes and consequences of Meth neurotoxicity and in the development of new therapies. This research has shown that increases in cytoplasmic DA dramatically broaden the neurotoxic profile of Meth to include brain structures not normally targeted for damage. The resistance of the NAc to Meth-induced neurotoxicity and its ability to recover reveal a fundamentally different neuroplasticity by comparison to the CPu. Recruitment of the NAc as a target of Meth neurotoxicity by alterations in DA homeostasis is significant in light of the numerous important roles played by this brain structure.

Formation and Implications of Alpha-Synuclein Radical in Maneb- and Paraquat-Induced Models of Parkinson's Disease

Parkinson's disease (PD) is a debilitating, progressive, neurodegenerative disorder characterized by progressive loss of dopaminergic neurons and motor deficits. Alpha-synuclein-containing aggregates represent a feature of a variety of neurodegenerative disorders, including PD; however, the mechanism that initiates and promotes intraneuronal alpha-synuclein aggregation remains unknown. We hypothesized protein radical formation as an initiating mechanism for alpha-synuclein aggregation. Therefore, we used the highly sensitive immuno-spin trapping technique to investigate protein radical formation as a possible mechanism of alpha-synuclein aggregation as well as to investigate the source of protein radical formation in the midbrains of Maneb- and paraquat-coexposed mice. Coexposure to Maneb and paraquat for 6 weeks resulted in active microgliosis, NADPH oxidase activation, and inducible nitric oxide synthase (iNOS) induction, which culminated in protein radical formation in the midbrains of mice. Results obtained with immuno-spin trapping and immunoprecipitation experiments confirmed formation of alpha-synuclein radicals in dopaminergic neurons of exposed mice. Free radical formation requires NADPH oxidase and iNOS, as indicated by decreased protein radical formation in knockout mice (P47phox(-/-) and iNOS(-/-)) and in mice treated with inhibitors such as FeTPPS (a peroxynitrite decomposition catalyst), 1400 W (an iNOS inhibitor), or apocynin (a NADPH oxidase inhibitor). Concurrence of protein radical formation with dopaminergic neuronal death indicated a link between protein radicals and disease progression. Taken together, these results show for the first time the formation and detection of the alpha-synuclein radical and suggest that NADPH oxidase and iNOS play roles in peroxynitrite-mediated protein radical formation and subsequent neuronal death in the midbrains of Maneb- and paraquat-coexposed mice.

Protective Effects of Propofol Against Methamphetamine-induced Neurotoxicity

CONTEXT

Methamphetamine (METH) is widely abused in worldwide. METH use could damage the dopaminergic system and induce neurotoxicity via oxidative stress and mitochondrial dysfunction. Propofol, a sedative-hypnotic agent, is known for its antioxidant properties. In this study, we used propofol for attenuating of METH-induced neurotoxicity in rats.

SUBJECTS AND METHODS

We used Wistar rats that the groups (six rats each group) were as follows: Control, METH (5 mg/kg IP), and propofol (5, 10 and 20 mg/kg, IP) was administered 30 min before METH. After 24 h, animals were killed, brain tissue was separated and the mitochondrial fraction was isolated, and oxidative stress markers were measured.

RESULTS

Our results showed that METH significantly increased oxidative stress markers such as lipid peroxidation, reactive oxygen species formation and glutathione oxidation in the brain, and isolated mitochondria. Propofol significantly inhibited METH-induced oxidative stress in the brain and isolated mitochondria. Mitochondrial function decreased dramatically after METH administration that propofol pretreatment significantly improved mitochondrial function. Mitochondrial swelling and catalase activity also increased after METH exposure but was significantly decreased with propofol pretreatment.

CONCLUSIONS

These results suggest that propofol prevented METH-induced oxidative stress and mitochondrial dysfunction and subsequently METH-induced neurotoxicity. Therefore, the effectiveness of this antioxidant should be evaluated for the treatment of METH toxicity and neurodegenerative disease.

Is there a role for nitric oxide in methamphetamine-induced dopamine terminal degeneration?

Methamphetamine (METH) abuse results in long-term damage to the dopaminergic system, manifesting as decreases in dopamine (DA) tissue content, DA transporter binding, as well as tyrosine hydroxylase and vesicular monoamine transporter immunostaining. However, the exact cascade of events that ultimately result in this damage has not been clearly elucidated. One factor that has been heavily implicated in METH-induced DA terminal degeneration is the production of nitric oxide (NO). Unfortunately, many of the studies attempting to clarify the role of NO in METH-induced neurotoxicity have been confounded by issues such as the disruption of METH-induced hyperthermia, preventing the formation of strong conclusions. As a result, there is a body of work suggesting that NO is sufficient for METH-induced neurotoxicity, while other studies suggest that NO does not play a role in METH-induced degeneration of DA nerve terminals. This review summarizes the existing studies investigating the role of NO in METH-induced neurotoxicity, and argues that while NO may be necessary for METH-induced neurotoxicity, it is not sufficient. Finally, important areas of future investigation are highlighted and discussed.

Neurotoxicity of methamphetamine and 3,4-methylenedioxymethamphetamine

Amphetamines are a class of psychostimulant drugs that are widely abused for their stimulant, euphoric, empathogenic and hallucinogenic properties. Many of these effects result from acute increases in dopamine and serotonin neurotransmission. Subsequent to these acute effects, methamphetamine and 3,4 methylenedioxymethamphetamine (MDMA) produce persistent damage to dopamine and serotonin nerve terminals. This review summarizes the numerous interdependent mechanisms including excitotoxicity, mitochondrial damage and oxidative stress that have been demonstrated to contribute to this damage. Emerging non-neuronal mechanisms by which the drugs may contribute to monoaminergic terminal damage, as well as the neuropsychiatric consequences of this terminal damage are also presented. Methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) have similar chemical structures and pharmacologic properties compared to other abused substances including cathinone (khat), as well as a relatively new class of novel synthetic amphetamines known as 'bath salts' that have gained popularity among drug abusers.

Counteraction by nitric oxide synthase inhibitor of neurochemical alterations of dopaminergic system in 6-OHDA-lesioned rats under L-DOPA treatment

Nitric oxide synthase inhibitors reduce L-3, (Del-Bel et al., Cell Mol Neurobiol 25(2):371-392, 2005) 4-dihydroxyphenylalanine (L-DOPA)-induced abnormal motor effects subsequent to depletion of dopaminergic neurons in rodents and non-human primates. The present study used quantitative high-performance liquid chromatography to analyze, for the first time, dopamine metabolism in striatum of rats in order to elucidate the mechanism of action of the nitric oxide synthase inhibitors. Adult male Wistar rats received unilateral microinjection of saline (sham) or 6-hydroxydopamine (6-OHDA-lesioned) in the medial forebrain bundle. Past 3 weeks, rats were treated during 21 days with L-DOPA/benserazide (30 mg/kg/7.5 mg/kg, respectively, daily). On the 22nd day rats received an intraperitoneal (i.p.) injection of either vehicle or 7-nitroindazole, a preferential neuronal nitric oxide synthase inhibitor before L-DOPA. Abnormal involuntary movements and rotarod test were assessed as behavioral correlate of motor responses. Lesion intensity was evaluated through tyrosine hydroxylase immunohystochemical reaction. Dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), and an extent of dopamine striatal tissue levels/dopamine metabolism were measured in the striatum. Lesion with 6-OHDA decreased dopamine, DOPAC, and DOPAC/dopamine ratio in the lesioned striatum. L-DOPA treatment induced abnormal involuntary movements and increased DOPAC/dopamine ratio (nearly five times) in the lesioned striatum. L-DOPA-induced dyskinesia was mitigated by 7-nitroindazole, which also decreased dopamine turnover, dopamine and DOPAC levels. Our results revealed an almost two times increase in dopamine content in the non-lesioned striatum of 6-OHDA-lesioned rats. Reduction of striatal DOPAC/dopamine ratio in dyskinetic rats may suggest an increase in the dopamine availability. Our data confirm contribution of nitrergic transmission in the pathogenesis of L-DOPA-induced dyskinesia with potential utilization of nitric oxide synthase inhibitors for treatment.

Expression and activity of nitric oxide synthase isoforms in methamphetamine-induced striatal dopamine toxicity

Nitric oxide is implicated in methamphetamine (METH)-induced neurotoxicity; however, the source of the nitric oxide has not been identified. Previous work has also revealed that animals with partial dopamine loss induced by a neurotoxic regimen of methamphetamine fail to exhibit further decreases in striatal dopamine when re-exposed to methamphetamine 7-30 days later. The current study examined nitric oxide synthase expression and activity and protein nitration in striata of animals administered saline or neurotoxic regimens of methamphetamine at postnatal days 60 and/or 90, resulting in four treatment groups: Saline:Saline, METH:Saline, Saline:METH, and METH:METH. Acute administration of methamphetamine on postnatal day 90 (Saline:METH and METH:METH) increased nitric oxide production, as evidenced by increased protein nitration. Methamphetamine did not, however, change the expression of endothelial or inducible isoforms of nitric oxide synthase, nor did it change the number of cells positive for neuronal nitric oxide synthase mRNA expression or the amount of neuronal nitric oxide synthase mRNA per cell. However, nitric oxide synthase activity in striatal interneurons was increased in the Saline:METH and METH:METH animals. These data suggest that increased nitric oxide production after a neurotoxic regimen of methamphetamine results from increased nitric oxide synthase activity, rather than an induction of mRNA, and that constitutively expressed neuronal nitric oxide synthase is the most likely source of nitric oxide after methamphetamine administration. Of interest, animals rendered resistant to further methamphetamine-induced dopamine depletions still show equivalent degrees of methamphetamine-induced nitric oxide production, suggesting that nitric oxide production alone in response to methamphetamine is not sufficient to induce acute neurotoxic injury.

Methamphetamine-induced nitric oxide promotes vesicular transport in blood-brain barrier endothelial cells

Methamphetamine's (METH) neurotoxicity is thought to be in part due to its ability to induce blood-brain barrier (BBB) dysfunction. Here, we investigated the effect of METH on barrier properties of cultured rat primary brain microvascular endothelial cells (BMVECs). Transendothelial flux doubled in response to METH, irrespective of the size of tracer used. At the same time, transendothelial electrical resistance was unchanged as was the ultrastructural appearance of inter-endothelial junctions and the distribution of key junction proteins, suggesting that METH promoted vesicular but not junctional transport. Indeed, METH significantly increased uptake of horseradish peroxidase into vesicular structures. METH also enhanced transendothelial migration of lymphocytes indicating that the endothelial barrier against both molecules and cells was compromised. Barrier breakdown was only observed in response to METH at low micromolar concentrations, with enhanced vesicular uptake peaking at 1 μM METH. The BMVEC response to METH also involved rapid activation of endothelial nitric oxide synthase and its inhibition abrogated METH-induced permeability and lymphocyte migration, indicating that nitric oxide was a key mediator of BBB disruption in response to METH. This study underlines the key role of nitric oxide in BBB function and describes a novel mechanism of drug-induced fluid-phase transcytosis at the BBB.

INO-4885 [5,10,15,20-tetra[N-(benzyl-4'-carboxylate)-2-pyridinium]-21H,23H-porphine iron(III) chloride], a peroxynitrite decomposition catalyst, protects the heart against reperfusion injury in mice

Oxidative/nitrative stress caused by peroxynitrite, the reaction product of superoxide (O2(.-)) and nitric oxide (NO), is the primary cause of myocardial ischemia/reperfusion injury. The present study determined whether INO-4885 [5,10,15,20-tetra[N-(benzyl-4'-carboxylate)-2-pyridinium]-21H,23H-porphine iron(III) chloride], a new peroxynitrite decomposition catalyst, may provide cellular protection and protect heart from myocardial ischemia/reperfusion injury. Adult male mice were subjected to 30 min of ischemia and 3 or 24 h of reperfusion. Mice were randomized to receive vehicle, INO-4885 without catalytic moiety, or INO-4885 (3-300 microg/kg i.p.) 10 min before reperfusion. Infarct size, apoptosis, nitrotyrosine content, NO/O2(.-) production, and inducible nitric-oxide synthase (iNOS)/NADPH oxidase expression were determined. INO-4885 treatment reduced ischemia/reperfusion-induced protein nitration and caspase 3 activation in a dose-dependent fashion in the range of 3 to 100 microg/kg. However, doses exceeding 100 microg/kg produced nonspecific effects and attenuated its protective ability. At the optimal dose (30 microg/kg), INO-4885 significantly reduced infarct size (p < 0.01), decreased apoptosis (p < 0.01), and reduced tissue nitrotyrosine content (p < 0.01). As expected, INO-4885 had no effect on ischemia/reperfusion-induced iNOS expression and NO overproduction. To our surprise, this compound significantly reduced superoxide production and partially blocked NADPH oxidase overexpression in the ischemic/reperfused cardiac tissue. Additional experiments demonstrated that INO-4885 provided better cardioprotection than N-(3-(aminomethyl)benzyl)acetamidine (1400W, a selective iNOS inhibitor), apocynin (an NADPH oxidase inhibitor), or Tiron (a cell-permeable superoxide scavenger). Taken together, our data demonstrated that INO-4885 is a cardioprotective molecule that attenuates myocardial reperfusion injury by facilitating peroxynitrite decomposition and inhibiting NADPH oxidase-derived O2(.-) production.

Minocycline restores striatal tyrosine hydroxylase in GDNF heterozygous mice but not in methamphetamine-treated mice

Inflammation, phospho-p38 MAPK activation, and a reduction in glial cell line-derived neurotrophic factor (GDNF) occur in Parkinson's disease. Microglial activation in the substantia nigra and a tyrosine hydroxylase deficit in the striatum of 3-month-old GDNF heterozygous (GDNF(+/-)) mice were previously reported and both were exacerbated by a toxic methamphetamine binge. The current study assessed the effects of minocycline on these methamphetamine-induced effects. Minocycline (45 mg/kg, i.p.x 14 days post-methamphetamine or saline injections) reduced microglial activation and phospho-p38 MAPK in the substantia nigra of saline-treated GDNF(+/-) mice and in methamphetamine-treated wildtype and GDNF(+/-) mice. Although minocycline increased tyrosine hydroxylase-immunoreactivity in GDNF(+/-) mice, it did not attenuate the methamphetamine-induced reduction of tyrosine hydroxylase. The results suggest that neuroinflammation is deleterious to the dopamine system of GDNF(+/-) mice but is not the primary cause of methamphetamine-induced damage to the dopamine system in either GDNF(+/-) or wildtype mice.

Targeting oxidative/nitrergic stress ameliorates motor impairment, and attenuates synaptic mitochondrial dysfunction and lipid peroxidation in two models of Huntington's disease

In this study, we reproduced two toxic models resembling some motor/kinetic deficits of Huntington's disease induced by bilateral intrastriatal injections of either quinolinic acid (QUIN, 120 nmol/microl per side) or 3-nitropropionic acid (3-NP, 250 nmol/microl per side) to rats. Motor skills (including total distance walked/traveled and total horizontal and vertical activities) were evaluated in a box-field system at 1 and 7 days post-lesion. In order to investigate whether these alterations were associated with the oxidative/nitrergic stress evoked by the nitrogen reactive species peroxynitrite (ONOO(-)) in the striatum, some rats were pretreated with the ONOO(-) decomposition catalyst iron porphyrinate (Fe(TPPS), 10 mg/kg, i.p.) 120 min prior to toxins infusion. With the aim to further characterize some possible mechanisms by which motor tasks were affected and/or preserved, biochemical analysis of peroxidative damage to lipids and mitochondrial dysfunction were both assessed in synaptic membranes isolated from the striata of QUIN-, 3-NP- and/or Fe(TPPS)-treated animals. Our results show that targeting oxidative/nitrergic stress by Fe(TPPS) in these toxic models results in amelioration of motor deficits linked to inhibition of peroxidative damage and recovery of mitochondrial function in synaptic membranes. Based on these findings, we hypothesize that the protection exerted by Fe(TPPS) on the biochemical markers analyzed reflects the possible preservation of the functional status of the nerve tissue by limiting the deleterious actions of ONOO(-), further accounting for partial recovery of integrative motor functions.

The role of oxidative stress, metabolic compromise, and inflammation in neuronal injury produced by amphetamine-related drugs of abuse

Methamphetamine (METH) and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) are amphetamine derivatives with high abuse liability. These amphetamine-related drugs of abuse mediate their effects through the acute activation of both dopaminergic and serotonergic neurons. Long-term abuse of these amphetamine derivatives, however, results in damage to both dopaminergic and serotonergic terminals throughout the brain. This toxicity is mediated in part by oxidative stress, metabolic compromise, and inflammation. The overall objective of this review is to highlight experimental evidence that METH and MDMA increase oxidative stress, produce mitochondrial dysfunction, and increase inflammation that converge and culminate in the long-term toxicity to dopaminergic and serotonergic neurons.

Iron porphyrinate Fe(TPPS) reduces brain cell damage in rats intrastriatally lesioned by quinolinate

It has been recently demonstrated that the reactive nitrogen species (RNS) peroxynitrite (ONOO(-)) is involved in the neurotoxic pattern produced by quinolinic acid in the rat brain [V. Pérez-De La Cruz, C. González-Cortés, S. Galván-Arzate, O.N. Medina-Campos, F. Pérez-Severiano, S.F. Ali, J. Pedraza-Chaverrí, A. Santamaría, Excitotoxic brain damage involves early peroxynitrite formation in a model of Huntington's disease in rats: protective role of iron porphyrinate 5,10,15,20-tetrakis (4-sulfonatophenyl)porphyrinate iron (III), Neuroscience 135 (2005) 463-474.]. The aim of this work was to investigate whether ONOO(-) can also be responsible for morphological alterations and inflammatory events in the same paradigm. For this purpose, we evaluated the effect of a pre-treatment with the iron porphyrinate Fe(TPPS), a well-known ONOO(-) decomposition catalyst (10 mg/kg, i.p., 120 min before lesion), on the quinolinate-induced striatal cell damage and immunoreactivities to glial-fibrilar acidic protein (GFAP), interleukin 6 (IL-6) and inducible nitric oxide synthase (iNOS), one and seven days after the intrastriatal infusion of quinolinate (240 nmol/microl) to rats. The striatal tissue from animals lesioned by quinolinate showed a significant degree of damage and enhanced immunoreactivities to GFAP, IL-6 and iNOS, both at 1 and 7 days post-lesion. Pre-treatment of rats with Fe(TPPS) significantly attenuated or prevented all these markers at both post-lesion times tested, except for GFAP immunoreactivity at 7 days post-lesion and iNOS immunoreactivity at 1 day post-lesion. Altogether, our results suggest that ONOO(-) is actively participating in triggering inflammatory events and morphological alterations in the toxic model produced by quinolinate, since the use of agents affecting its formation, such as Fe(TPPS), are effective experimental tools to reduce the brain lesions associated to excitotoxic and oxidative damage.

Methamphetamine induces autophagy and apoptosis in a mesencephalic dopaminergic neuronal culture model: role of cathepsin-D in methamphetamine-induced apoptotic cell death

Autophagy is a phylogenetically conserved process that plays a critical role in the degradation of oxidatively damaged proteins and organelle turnover. The role of oxidative stress and apoptosis in methamphetamine (METH)-induced neurotoxicity is well known; however, the potential contribution of autophagy to METH-induced oxidative damage in dopaminergic neuronal systems remains unclear. The goals of the present article were twofold: (a) to develop an in vitro dopaminergic cell culture model to study cellular and molecular mechanisms underlying METH-induced autophagy and apoptosis, and (b) to determine whether lysosomal protease cathepsin-D activation, resulting from the loss of lysosomal membrane integrity, contributes to METH-induced apoptosis. To accomplish these goals, we characterized morphological and biochemical changes in an immortalized mesencephalic dopaminergic neuronal cell line (N27 cells) following treatment with METH. Exposure of METH (2 mM) to N27 cells resulted in the appearance of cytoplasmic vacuolar structures reminiscent of autophagic vacuoles within 3 h. In order to ascertain the identity of the vacuolar structures that are formed following METH exposure, immunohistochemical staining for markers of autophagy were performed. LAMP 2, a classical marker of autophagolysosomes, revealed an extensive punctuate pattern of distribution on the vacuolar membrane surface, with exclusive localization in the cytoplasm. Additionally, using DNA fragmentation analysis we showed a dose-dependent increase in fragmented DNA in METH treated N27 cells. Since METH-induced autophagy preceded DNA fragmentation, we tested whether dysfunction of the autophagolysosomal system contributes to nuclear damage. Immunofluorescence studies with cathepsin-d demonstrated a granular pattern of staining in untreated cells, whereas an increased cathepsin- D immunoreactivity with a globular pattern of staining was observed in METH-treated cells. Nevertheless, blockade of cathepsin-D activation by pepstatin-A, cathepsin-D inhibitor, failed to alter METH-induced DNA fragmentation. Collectively, these results demonstrate that N27 dopaminergic neuronal cell model may serve as an excellent in vitro model to study the mechanisms of METH-induced autophagy and apoptosis. Furthermore, it is less likely that cathepsin-D may serve as a trigger for the induction of apoptosis subsequent to exposure of N27 dopaminergic neuronal cells to METH.

A role for nitric oxide-mediated peroxynitrite formation in a model of endotoxin-induced shock

The aim of the present study was to assess the relative contributions of peroxynitrite formation following induction of nitric-oxide synthase (iNOS) in the pathophysiology of endotoxin-induced shock in the rat. To this end, we used a selective inhibitor of iNOS, N-(3-(aminomethyl)benzyl)acetamidine (1400W), and a peroxynitrite decomposition catalyst, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato iron III chloride (FeTTPs). Intravenous (i.v.) administration of Escherichia coli lipopolysaccharide (LPS; 4 mg/kg) elicited a time-dependent fall in mean arterial pressure as well as liver, renal, and pancreatic tissue damage. 1400W (3-10 mg/kg i.v.) administered 30 min before LPS delayed the development of hypotension but did not improve survival. On the other hand, FeTTPs administered (10-100 mg/kg i.v.) inhibited in a dose-dependent manner LPS-induced hypotension, tissue injury, and improved mortality rate. In separate experiments, rats were treated with LPS (4 mg/kg) or saline for control, and their aortas were isolated and placed in organ baths 2 h later. Tissues from LPS-treated rats had significant inhibition of contractile activity to phenylephrine as well as a significantly impaired relaxation response to acetylcholine. FeTPPs, when administered (100 mg/kg i.v.) 1 h before LPS, prevented the LPS-induced aortic contractile and endothelial dysfunction. These results demonstrate that nitric oxide-derived peroxynitrite formation plays an important role in this model of endotoxemia. Our results also suggest that use of an iNOS inhibitor in this setting has little beneficial effect in part because, in the presence of a failing eNOS system, some NO is needed to maintain adequate organ function.

Protective effect of the radical scavenger edaravone against methamphetamine-induced dopaminergic neurotoxicity in mouse striatum

The administration of high doses of methamphetamine causes the degeneration of striatal dopaminergic fibers in the brains of rodents, and oxidative stress appears to be one of the main factors of neurotoxicity. This study examined whether edaravone, a radical scavenger, protects against methamphetamine-induced neurotoxicity in mice. Methamphetamine treatment (4 mg/kg, s.c. x 4 with 2 h intervals) showed striatal dopaminergic degeneration as observed by decreases in dopamine levels and tyrosine hydroxylase immunoreactivity in the striatum. The neurotoxicity was reduced by edaravone (3 mg/kg, i.p.), when it was administered four times 30 min before methamphetamine at 2 h intervals and additionally four times after methamphetamine at 12 h intervals. An immunohistochemical study showed that methamphetamine increased 3-nitrotyrosine immunoreactivity, an in vivo marker of peroxynitrite production, and activated microglia and astrocytes in the striatum. Edaravone blocked the increase in 3-nitrotyrosine immunoreactivity and the activation of astrocytes, but it did not affect the activation of microglia. Edaravone did not affect methamphetamine-induced hyperthermia and striatal dopamine release. These results suggest that edaravone protects against methamphetamine-induced neurotoxicity in the striatum by blocking peroxynitrite production. This study also suggests that methamphetamine activates microglia in a radical-independent mechanism.

Nitric Oxide and Oxidative Stress in the Brain of Rats Exposed In Utero to Cocaine

The role of nitric oxide (NO) and lipid peroxidation (LPO) processes in the physiological deficits induced by in utero cocaine exposure was examined in rats. NO generation in the hippocampus and cortex was detected using the electron paramagnetic resonance and LPO products were measured as thiobarbituric acid reactive species (TBARS). Pregnant Sprague-Dawley rats received a daily intraperitoneal injection of 20 mg/kg cocaine (IUC) or saline solution for control dams (IUV) between E17-E20. NO level was lower in the brain of IUC rats at postnatal day 1 and 2, but not 4, as compared with IUV rats. TBARS content was increased at day 1-4. Animals were used for behavioral testing at 25 days of age. Both NO and TBARS were elevated in the hippocampus of IUC rats as compared with IUV rats. Juvenile IUC rats developed significant learning impairments in the water-maze, as revealed by probe test retrieval deficits. Behavioral sessions resulted in a significant increase of TBARS levels only in IUV animals. Therefore, IUC rats showed a significant oxidative stress in basal conditions that may be related to their impaired learning ability. We did not find direct correlation between the changes in NO generation and intensity of LPO processes. It may probably mean that changes in intensity of LPO processes observed during prenatal cocaine exposure are not directly linked to NO pathway activation.

Excitotoxic brain damage involves early peroxynitrite formation in a model of Huntington’s disease in rats: Protective role of iron porphyrinate 5,10,15,20-tetrakis (4-sulfonatophenyl)porphyrinate iron (III)

Oxidative/nitrosative stress is involved in NMDA receptor-mediated excitotoxic brain damage produced by the glutamate analog quinolinic acid. The purpose of this work was to study a possible role of peroxynitrite, a reactive oxygen/nitrogen species, in the course of excitotoxic events evoked by quinolinic acid in the brain. The effects of Fe(TPPS) (5,10,15,20-tetrakis (4-sulfonatophenyl)porphyrinate iron (III)), an iron porphyrinate and putative peroxynitrite decomposition catalyst, were tested on lipid peroxidation and mitochondrial function in brain synaptic vesicles exposed to quinolinic acid, as well as on peroxynitrite formation, nitric oxide synthase and superoxide dismutase activities, lipid peroxidation, caspase-3-like activation, DNA fragmentation, and GABA levels in striatal tissue from rats lesioned by quinolinic acid. Circling behavior was also evaluated. Increasing concentrations of Fe(TPPS) reduced lipid peroxidation and mitochondrial dysfunction induced by quinolinic acid (100 microM) in synaptic vesicles in a concentration-dependent manner (10-800 microM). In addition, Fe(TPPS) (10 mg/kg, i.p.) administered 2 h before the striatal lesions, prevented the formation of peroxynitrite, the increased nitric oxide synthase activity, the decreased superoxide dismutase activity and the increased lipid peroxidation induced by quinolinic acid (240 nmol/microl) 120 min after the toxin infusion. Enhanced caspase-3-like activity and DNA fragmentation were also reduced by the porphyrinate 24 h after the injection of the excitotoxin. Circling behavior from quinolinic acid-treated rats was abolished by Fe(TPPS) six days after quinolinic acid injection, while the striatal levels of GABA, measured one day later, were partially recovered. The protective effects that Fe(TPPS) exerted on quinolinic acid-induced lipid peroxidation and mitochondrial dysfunction in synaptic vesicles suggest a primary action of the porphyrinate as an antioxidant molecule. In vivo findings suggest that the early production of peroxynitrite, altogether with the enhanced risk of superoxide anion (O2*-) and nitric oxide formation (its precursors) induced by quinolinic acid in the striatum, are attenuated by Fe(TPPS) through a recovery in the basal activities of nitric oxide synthase and superoxide dismutase. The porphyrinate-mediated reduction in DNA fragmentation simultaneous to the decrease in caspase-3-like activation from quinolinic acid-lesioned rats suggests a prevention in the risk of peroxynitrite-mediated apoptotic events during the course of excitotoxic damage in the striatum. In summary, the protective effects that Fe(TPPS) exhibited both under in vitro and in vivo conditions support an active role of peroxynitrite and its precursors in the pattern of brain damage elicited by excitotoxic events in the experimental model of Huntington's disease. The neuroprotective mechanisms of Fe(TPPS) are discussed.

Comparative Effects of NO-Synthase Inhibitor and NMDA Antagonist on Generation of Nitric Oxide and Release of Amino Acids and Acetylcholine in the Rat Brain Elicited by Amphetamine Neurotoxicity

The aim of this study was to clarify the role of nitric oxide (NO) and lipid peroxidation (LPO) processes as well as the contribution of various neurotransmitters in pathophysiological mechanisms of neurotoxicity induced by amphetamine (AMPH). NO level was determined directly in brain tissues using electron paramagnetic resonance spectroscopy technique. The content of the products of lipid peroxidation (LPO) was measured spectrophotometrically as thiobarbituric acid reactive species (TBARS). The output of neurotransmitter amino acids (glutamate, aspartate, and GABA) and acetylcholine (ACH) was monitored in nucleus accumbens (NAc) by push-pull technique with HPLC detection. Repeated, systemic application of AMPH elevated striatal and cortical NO generation and LPO production. Moreover, administration of AMPH led to a marked and long-lasting increase of ACH release. Surprisingly, while glutamate output was not affected, aspartate release was enhanced 30 to 50 min after each AMPH injection. The release rate of GABA was also elevated. The selective NO-synthase inhibitor 7-nitroindazole (7-NI) was highly effective in abating the rise in the neurotransmitter release induced by the AMPH. The NOS inhibitor also abolished the increase of NO generation produced by AMPH, but did not influence the intensity of LPO elicited by the AMPH administration. Pretreatment with the noncompetitive NMDA receptor antagonist dizocilpine (MK-801) completely prevented increase of NO generation and TBARS formation induced by multiple doses of AMPH. Dizocilpine also abolished the effect of the psychostimulant drug on the release of neurotransmitters ACH, glutamate, aspartate, and GABA in the NAc. Our findings suggest a key role of NO in AMPH-induced transmitter release, but not in the formation of LPO products. It appears that AMPH enhances release of ACH and neurotransmitter amino acids through increased NO synthesis and induces neurotoxicity via NO and also by NO-independent LPO.

Peroxynitrite decomposition catalyst ameliorates renal damage and protein nitration in cisplatin-induced nephrotoxicity in rats

Background

Oxidative stress is involved in cisplatin-nephrotoxicity. However, it has not completely established if reactive nitrogen species and nitrosative stress are involved in this experimental model. The purpose of this work was to study the role of peroxynitrite, a reactive nitrogen specie, in cisplatin-nephrotoxicity using the compound 5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrinato iron (III) (FeTPPS), a soluble complex able to metabolize peroxynitrite.

Results

In rats treated with cisplatin (a single intraperitoneal dose of 7.5 mg/kg body weight), renal nitrosative stress was made evident by the increase in 3-nitrotyrosine on day 3. In addition, cisplatin-induced nephrotoxicity was evident by the histological damage of proximal tubular cells and by the increase in (a) serum creatinine, (b) blood urea nitrogen, and (c) urinary excretion of N-acetyl-β-D-glucosaminidase and total protein. Cisplatin-induced nitrosative stress and nephrotoxicity were attenuated by FeTPPS-treatment (15 mg/kg body weight, intraperitoneally, every 12 hours for 3 days).

Conclusions

Nitrosative stress is involved in cisplatin-induced nephrotoxicity in rats. Our data suggest that peroxynitrite is involved, at least in part, in cisplatin-induced nephrotoxicity and protein nitration.

The nNOS inhibitor, AR-R17477AR, prevents the loss of NF68 immunoreactivity induced by methamphetamine in the mouse striatum

The present study examined the time-course and regionally-selective changes in the levels of the neurofilament protein NF68 in the mouse brain induced by methamphetamine (METH). The ability of low ambient temperature, or of the specific neuronal nitric oxide synthase (nNOS) inhibitor AR-R17477AR, to protect against both long-term striatal NF68 and dopamine loss induced by METH (3 mg/kg, i.p.) was also studied. Seven days after METH administration (3, 6 and 9 mg/kg, i.p., three times at 3 h intervals), mice showed a reduction of about 40% in immunoreactivity for NF68 in the striatum. This effect was not produced in cortex after METH administration at the dose of 3 mg/kg. No difference from controls was observed when measurements were carried out 1 h and 24 h after the last METH injection at the dose of 3 mg/kg. The loss of NF68 immunoreactivity seems to be associated with the long-term dopamine depletion induced by METH, since no change in serotonin concentration is observed in either the striatum or cortex 7 days after dosing. Animals kept at a room temperature of 4 degrees C showed a loss of NF68 similar to those treated at 22 degrees C but an attenuation of dopamine depletion in the striatum. Pre-treatment with AR-R17477AR (5 mg/kg, s.c.) 30 min before each of the three METH (3 mg/kg, i.p.) injections provided complete protection against METH-induced loss of NF68 immunoreactivity and attenuated the decrease in striatal dopamine and HVA concentrations by about 50%. These data indicate that both the reduction of NF68 immunoreactivity and the loss of dopamine concentration are due to an oxidative stress process mediated by reactive nitrogen species, and are not due to changes in body temperature.

Methamphetamine activates DNA binding of specific redox-responsive transcription factors in mouse brain

Cellular oxidative stress and alterations in redox status can be implicated in methamphetamine (METH)-induced neurotoxicity. To elucidate the molecular signaling pathways of METH-induced neurotoxicity, we investigated the effects of a single intraperitoneal injection of METH (1.0, 10, or 20 mg/kg) on DNA-binding activity of specific redox-sensitive transcription factors in mouse brain. Transcription factors studied included activator protein-1 (AP-1), nuclear factor-kappaB (NF-kappaB), cAMP-responsive element-binding protein (CREB), SP-1, and signal transducers and activators of transcription (STAT1 and STAT3). Significant and dose-dependent inductions of AP-1 and CREB DNA-binding activities were observed in four different regions (striatum, frontal cortex, hippocampus, and cerebellum) isolated from the brains of mice injected with METH. However, injections with METH did not affect DNA binding activities of NF-kappaB, SP-1, STAT1, and STAT3. These results suggest that METH-induced oxidative stress may trigger the molecular signaling pathways via specific and selective activation of AP-1 and CREB.

Nitric oxide scavenger carboxy-PTIO potentiates the inhibition of dopamine uptake by nitric oxide donors

2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO) has been increasingly used as nitric oxide (NO) scavenger. Carboxy-PTIO reacts with NO to form nitric dioxide and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl (carboxy-PTI). In rat C6 glioma cells expressing human dopamine transporter, carboxy-PTIO paradoxically potentiated the inhibition of [(3)H]dopamine uptake by two NO donors, diethylamine/NO and (Z)-1-[N-(3-ammoniopropyl)-N-(n-propyl)-amino]/NO. Further examinations revealed that carboxy-PTI concentration-dependently reduced dopamine uptake, indicating that the formation of carboxy-PTI may account for the failure of carboxy-PTIO to abolish NO elicited effects. These results suggest that caution should be taken in interpreting data obtained using carboxy-PTIO and probably other NO scavengers.

Reduced nicotinamide nucleotides prevent nitration of tyrosine hydroxylase by peroxynitrite

Tyrosine hydroxylase (TH) is the initial and rate-limiting enzyme in the biosynthesis of the neurotransmitter dopamine (DA). TH activity is inhibited by peroxynitrite (ONOO(-)) by a mechanism that involves nitration of tyrosine residues and oxidation of cysteine residues in the enzyme. Reduced forms of the nicotinamide adenine dinucleotide cofactors, NADH and NADPH, protect TH from inhibition by ONOO(-) and prevent nitration of tyrosine residues. NAD, the oxidized form of the cofactors, neither protects TH from ONOO(-)-induced inhibition nor prevents the nitration of tyrosine residues in the enzyme. These results suggest that the redox status of the nicotinamide nucleotide cofactors could influence the ability of ONOO(-) to modify proteins that are important to the function of DA neurons.

Induction of the immediate early genes egr-1 and c-fos by methamphetamine in mouse brain

Methamphetamine (METH) is one of the most commonly abused psychostimulant, and is known to induce dopaminergic neurotoxicity by generating oxidative stress and free radicals. In the present study we investigated the effects of METH on egr-1 and c-fos immediate early gene induction in different regions of mouse brain, at different doses and different time courses. We also measured the tissue levels of monoamines in order to correlate their changes with gene expression. A single injection of METH (40 mg/kg) significantly increased egr-1 and c-fos mRNA expression within 30 min in frontal cortex, nucleus accumbens, caudate putamen, septum and CA1 region of hippocampus. Time course studies showed that in most cases, both genes were expressed within 30 min and decreased after 60 min. METH produced a significant decrease in striatal dopamine level, reaching a very low level after 24 h. Striatal serotonin level significantly increased and returned to control levels after 2 h. These data show that METH induced egr-1 and c-fos mRNA expression in selective brain areas, which correlated with an alteration in monoamines.

Aging increases the susceptiblity to methamphetamine-induced dopaminergic neurotoxicity in rats: correlation with peroxynitrite production and hyperthermia

Methamphetamine (METH) produces dopaminergic neurotoxicity by the production of reactive oxygen (ROS) and nitrogen (RNS) species. The role of free radicals has also been implicated in the process of aging. The present study was designed to evaluate whether METH-induced dopaminergic neurotoxicity and hyperthermia is a result of peroxynitrite production and if these effects correlate with age. One-, six- and 12-month-old male rats (n = 8) were administered a single dose of METH (0, 5, 10, 20, and 40 mg/kg, intraperitoneally). The formation of 3-nitrotyrosine (3-NT) as a marker of peroxynitrite production as well as dopamine and its metabolites DOPAC and HVA were measured in the striatum 4-h after METH-administration. Rectal temperature was monitored every 30 min after METH administration until 4 h. At 40 mg/kg METH, a 100% mortality in 12-month-old animals was observed, whereas no deaths occurred in 1- or 6-month-old rats. An age-dependent increase in hyperthermia was observed after METH-administration. A similar pattern of dose-dependent increase in the formation of 3-NT and in the depletion of dopamine and its metabolites with age was observed in the striatum. Furthermore, no effect was observed at 5 mg/kg METH in 1-month-old animals, whereas the effect was significant in 6- and 12-month-old animals. These data suggest that aging increases the susceptibility of the animals toward METH-induced peroxynitrite generation and striatal dopaminergic neurotoxicity.

Methamphetamine-induced dopaminergic neurotoxicity: role of peroxynitrite and neuroprotective role of antioxidants and peroxynitrite decomposition catalysts

Oxidative stress, reactive oxygen (ROS), and nitrogen (RNS) species have been known to be involved in a multitude of neurodegenerative disorders such as Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS). Both ROS and RNS have very short half-lives, thereby making their identification very difficult as a specific cause of neurodegeneration. Recently, we have developed a high performance liquid chromatography/electrochemical detection (HPLC/EC) method to identify 3-nitrotyrosine (3-NT), an in vitro and in vivo biomarker of peroxynitrite production, in cell cultures and brain to evaluate if an agent-driven neurotoxicity is produced by the generation of peroxynitrite. We show that a single or multiple injections of methamphetamine (METH) produced a significant increase in the formation of 3-NT in the striatum. This formation of 3-NT correlated with the striatal dopamine depletion caused by METH administration. We also show that PC12 cells treated with METH has significantly increased formation of 3-NT and dopamine depletion. Furthermore, we report that pretreatment with antioxidants such as selenium and melatonin can completely protect against the formation of 3-NT and depletion of striatal dopamine. We also report that pretreatment with peroxynitrite decomposition catalysts such as 5, 10,15,20-tetrakis(N-methyl-4'-pyridyl)porphyrinato iron III (FeTMPyP) and 5, 10, 15, 20-tetrakis (2,4,6-trimethyl-3,5-sulfonatophenyl) porphinato iron III (FETPPS) significantly protect against METH-induced 3-NT formation and striatal dopamine depletion. We used two different approaches, pharmacological manipulation and transgenic animal models, in order to further investigate the role of peroxynitrite. We show that a selective neuronal nitric oxide synthase (nNOS) inhibitor, 7-nitroindazole (7-NI), significantly protect against the formation of 3-NT as well as striatal dopamine depletion. Similar results were observed with nNOS knockout and copper zinc superoxide dismutase (CuZnSOD)-overexpressed transgenic mice models. Finally, using the protein data bank crystal structure of tyrosine hydroxylase, we postulate the possible nitration of specific tyrosine moiety in the enzyme that can be responsible for dopaminergic neurotoxicity. Together, these data clearly support the hypothesis that the reactive nitrogen species, peroxynitrite, plays a major role in METH-induced dopaminergic neurotoxicity and that selective antioxidants and peroxynitrite decomposition catalysts can protect against METH-induced neurotoxicity. These antioxidants and decomposition catalysts may have therapeutic potential in the treatment of psychostimulant addictions.