Protective action of neuronal nitric oxide synthase inhibitor in the MPTP mouse model of Parkinson's disease

Positron Emission Tomography with [18F]ROStrace Reveals Progressive Elevations in Oxidative Stress in a Mouse Model of Alpha-Synucleinopathy

The synucleinopathies are a diverse group of neurodegenerative disorders characterized by the accumulation of aggregated alpha-synuclein (aSyn) in vulnerable populations of brain cells. Oxidative stress is both a cause and a consequence of aSyn aggregation in the synucleinopathies; however, noninvasive methods for detecting oxidative stress in living animals have proven elusive. In this study, we used the reactive oxygen species (ROS)-sensitive positron emission tomography (PET) radiotracer [18F]ROStrace to detect increases in oxidative stress in the widely-used A53T mouse model of synucleinopathy. A53T-specific elevations in [18F]ROStrace signal emerged at a relatively early age (6-8 months) and became more widespread within the brain over time, a pattern which paralleled the progressive development of aSyn pathology and oxidative damage in A53T brain tissue. Systemic administration of lipopolysaccharide (LPS) also caused rapid and long-lasting elevations in [18F]ROStrace signal in A53T mice, suggesting that chronic, aSyn-associated oxidative stress may render these animals more vulnerable to further inflammatory insult. Collectively, these results provide novel evidence that oxidative stress is an early and chronic process during the development of synucleinopathy and suggest that PET imaging with [18F]ROStrace holds promise as a means of detecting aSyn-associated oxidative stress noninvasively.

Nitrosative stress in Parkinson's disease

Parkinson’s Disease (PD) is a neurodegenerative disorder characterized, in part, by the loss of dopaminergic neurons within the nigral-striatal pathway. Multiple lines of evidence support a role for reactive nitrogen species (RNS) in degeneration of this pathway, specifically nitric oxide (NO). This review will focus on how RNS leads to loss of dopaminergic neurons in PD and whether RNS accumulation represents a central signal in the degenerative cascade. Herein, we provide an overview of how RNS accumulates in PD by considering the various cellular sources of RNS including nNOS, iNOS, nitrate, and nitrite reduction and describe evidence that these sources are upregulating RNS in PD. We document that over 1/3 of the proteins that deposit in Lewy Bodies, are post-translationally modified (S-nitrosylated) by RNS and provide a broad description of how this elicits deleterious effects in neurons. In doing so, we identify specific proteins that are modified by RNS in neurons which are implicated in PD pathogenesis, with an emphasis on exacerbation of synucleinopathy. How nitration of alpha-synuclein (aSyn) leads to aSyn misfolding and toxicity in PD models is outlined. Furthermore, we delineate how RNS modulates known PD-related phenotypes including axo-dendritic-, mitochondrial-, and dopamine-dysfunctions. Finally, we discuss successful outcomes of therapeutics that target S-nitrosylation of proteins in Parkinson’s Disease related clinical trials. In conclusion, we argue that targeting RNS may be of therapeutic benefit for people in early clinical stages of PD.

Coriandrum sativum attenuates microglia mediated neuroinflammation and MPTP-induced behavioral and oxidative changes in Parkinson's disease mouse model

Coriandrum sativum Linn. (family: Umbelliferae; C. sativum), is a potential herb widely used as a spice and traditional medicine. In the present work, the effects of C. sativum fruit extract (CSE), against lipopolysaccharide (LPS)-stimulated BV-2 microglia-mediated neuroinflammation in vitro and 1-methyl-4 phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) animal model in vivo was investigated. LPS-stimulated increase in nitric oxide (NO), inducible NO synthase, cyclooxygenase-2, interleukin-6 and tumor necrosis factor-alpha were significantly (p < 0.05 ~ p < 0.001) inhibited by CSE (25, 50 and 100 μg/mL) in BV-2 microglial cells. Further, CSE inhibited the LPS-induced nuclear factor of kappa-beta activation and IκB-α phosphorylation in BV-2 microglia. In vivo studies, CSE (100, 200 and 300 mg/kg) ameliorated the MPTP (25 mg/kg, i.p.)-induced changes in locomotor, cognitive and behavior functions evaluated by rotarod, passive avoidance and open field test significantly (p < 0.05 ~ p < 0.001). The MPTP-induced changes in brain oxidative enzyme levels such as superoxide dismutase, catalase, and lipid peroxidation were significantly (p < 0.01 and p < 0.001 at 200 and 300 mg/kg, respectively) restored with CSE treatment. High-performance thin-layer chromatography fingerprinting analysis of CSE exhibited several distinctive peaks with quercetin and kaempferol-3O-glucoside as identifiable compounds. In conclusion, our study indicated that CSE attenuated neuroinflammatory processes in LPS-stimulated microglia in vitro and restored the MPTP-induced behavioral deficits and brain oxidative enzyme status in vivo proving its therapeutic potential in the treatment of neuroinflammatory and oxidative stress-mediated neurodegeneration seen in PD.

Calmodulin and Its Binding Proteins in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disorder that manifests with rest tremor, muscle rigidity and movement disturbances. At the microscopic level it is characterized by formation of specific intraneuronal inclusions, called Lewy bodies (LBs), and by a progressive loss of dopaminergic neurons in the striatum and substantia nigra. All living cells, among them neurons, rely on Ca²⁺ as a universal carrier of extracellular and intracellular signals that can initiate and control various cellular processes. Disturbances in Ca²⁺ homeostasis and dysfunction of Ca²⁺ signaling pathways may have serious consequences on cells and even result in cell death. Dopaminergic neurons are particularly sensitive to any changes in intracellular Ca²⁺ level. The best known and studied Ca²⁺ sensor in eukaryotic cells is calmodulin. Calmodulin binds Ca²⁺ with high affinity and regulates the activity of a plethora of proteins. In the brain, calmodulin and its binding proteins play a crucial role in regulation of the activity of synaptic proteins and in the maintenance of neuronal plasticity. Thus, any changes in activity of these proteins might be linked to the development and progression of neurodegenerative disorders including PD. This review aims to summarize published results regarding the role of calmodulin and its binding proteins in pathology and pathogenesis of PD.

Neuroprotective effects of the gliopeptide ODN in an in vivo model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by a progressive loss of dopamine (DA) neurons through apoptotic, inflammatory and oxidative stress mechanisms. The octadecaneuropeptide (ODN) is a diazepam-binding inhibitor (DBI)-derived peptide, expressed by astrocytes, which protects neurons against oxidative cell damages and apoptosis in an in vitro model of PD. The present study reveals that a single intracerebroventricular injection of 10 ng ODN 1 h after the last administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) prevented the degeneration of DA neurons induced by the toxin in the substantia nigra pars compacta of mice, 7 days after treatment. ODN-mediated neuroprotection was associated with a reduction of the number of glial fibrillary acidic protein-positive reactive astrocytes and a strong inhibition of the expression of pro-inflammatory genes such as interleukins 1β and 6, and tumor necrosis factor-α. Moreover, ODN blocked the inhibition of the anti-apoptotic gene Bcl-2, and the stimulation of the pro-apoptotic genes Bax and caspase-3, induced by MPTP in the substantia nigra pars compacta. ODN also decreased or even in some cases abolished MPTP-induced oxidative damages, overproduction of reactive oxygen species and accumulation of lipid oxidation products in DA neurons. Furthermore, DBI knockout mice appeared to be more vulnerable than wild-type animals to MPTP neurotoxicity. Taken together, these results show that the gliopeptide ODN exerts a potent neuroprotective effect against MPTP-induced degeneration of nigrostriatal DA neurons in mice, through mechanisms involving downregulation of neuroinflammatory, oxidative and apoptotic processes. ODN may, thus, reduce neuronal damages in PD and other cerebral injuries involving oxidative neurodegeneration.

Progressive loss of nigrostriatal dopaminergic neurons induced by inflammatory responses to fipronil

Inflammatory responses are involved in mechanisms of neuronal cell damage in the pathogenesis of neurodegenerative diseases such as Parkinson's disease (PD). We investigated the mechanisms whereby inflammatory responses contribute to loss of dopaminergic neurons in fipronil (FPN)-treated rats. After stereotaxic injection of FPN in the substantia nigra (SN), the number of tyrosine hydroxylase (TH)-positive neurons and the levels of TH expression in the SN decreased at 7days, and a significant decrease was observed at 14days with a subsequent reduction in striatal TH expression. Decreases in dopamine (DA) levels, however, began at 3days post-injection, preceding the changes in TH expression. In contrast, glial fibrillary acidic protein (GFAP) expression was significantly increased at 3days and persisted for up to 14days post-lesion; these changes in GFAP expression appeared to be inversely correlated with TH expression. Furthermore, we found that FPN administration induced an inflammatory response characterized by increased levels of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and tumor necrosis factor-α (TNF-α), which was mediated by activated microglia following infusion of FPN unilaterally into the SN. Intranigral injection of FPN underwent an inflammatory response with a resultant ongoing loss of dopaminergic neurons, indicating that pesticides may have important implication for the study of PD.

Medicinal plant Combretum leprosum mart ameliorates motor, biochemical and molecular alterations in a Parkinson's disease model induced by MPTP

ETHNOPHARMACOLOGICAL RELEVANCE

Combretum leprosum is a popular medicinal plant distributed in north and northeastern regions of Brazil. Many different parts of this plant are used in traditional medicine to treat several inflammatory diseases. Parkinson's disease (PD) is a disorder associated with inflammatory toxic factors and the treatments available provide merely a delay of the neurodegeneration.

AIM OF THE STUDY

We investigated the potential neuroprotective properties of the C. leprosum ethanolic extract (C.l.EE) in a murine model of PD using the toxin 1-methyl-4 phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP).

MATERIALS AND METHODS

The mice were split into four groups: V/S (vehicle/saline), E/S (extract/saline), V/M (vehicle/MPTP) and E/M (extract/ MPTP). Mice received MPTP (30mg/kg, i.p.) or vehicle (10ml/kg, i.p.) once a day for 5 consecutive days and vehicle (10ml/kg) or C.l.EE (100mg/kg) orally by intra-gastric gavage (i.g.) during a 14-d period, starting 3 days before the first MPTP injection. All groups were assessed for behavioural impairments (amphetamine-induced locomotor activity and muscle strength), dopamine content in striatum using high performance liquid chromatography (HPLC), tyrosine hydroxylase (TH) and dopamine transporter (DAT) gene expressions using qPCR.

RESULTS

Animals were injected with d-amphetamine (2mg/kg) and the activity was recorded. Amphetamine-induced hyperlocomotion was observed in all groups; however animals treated with MPTP showed exacerbated hyperlocomotion (approximately 3 fold increase compared to control groups). By contrast, mice treated with MPTP that received C.l.EE exhibited attenuation of the hyperlocomotion and did not differ from control groups. Muscle strength test pointed that C.l.EE strongly avoided muscular deficits caused by MPTP (approximately 2 fold increase compared to V/M group). Dopamine and its metabolites were measured in the striatum. The V/M group presented a dopamine reduction of 80%. On the other hand, the E/M group exhibited an increase in dopamine and its metabolites levels (approximately 3 fold increase compared to V/M group). Tyrosine hydroxylase (TH) and dopamine transporter (DAT) gene expressions were significantly reduced in the V/M group (60%). Conversely, C.l.EE treatment was able to increase the mRNA levels of those genes in the E/M group (approximately 2 fold for TH and DAT).

CONCLUSIONS

These data show, for the first time, that C. leprosum ethanolic extract prevented motor and molecular changes induced by MPTP, and partially reverted dopamine deficit. Thus, our results demonstrate that C.l.EE has potential for the treatment and prevention of PD.

The preferential nNOS inhibitor 7-nitroindazole and the non-selective one N(G)-nitro-L-arginine methyl ester administered alone or jointly with L-DOPA differentially affect motor behavior and monoamine metabolism in sham-operated and 6-OHDA-lesioned rats

Reciprocal interactions between nitrergic and dopaminergic systems play a key role in the control of motor behavior. In the present study, we performed a comparative analysis of motor behavior (locomotor activity, catalepsy, rotational behavior) and monoamine metabolism in the striatum and substantia nigra of unilaterally sham-operated and 6-OHDA-lesioned rats treated with the preferential neuronal nitric oxide synthase (nNOS) inhibitor 7-nitroindazole (7-NI) or the non-selective one N(G)-nitro-L-arginine methyl ester (L-NAME), alone or in combination with L-DOPA. Each NOS inhibitor given alone (50mg/kg) induced a distinct catalepsy 30 min after injection but only 7-NI impaired spontaneous locomotion after 10 min. In 6-OHDA-lesioned rats, chronic L-DOPA (25mg/kg) induced 2.5-h long contralateral rotations. 7-NI (30 and 50mg/kg) markedly reduced the intensity of L-DOPA-induced contralateral rotations while extending their duration until 4.5h whereas L-NAME (50 and 100mg/kg) only tended to attenuate their intensity without affecting the duration. 7-NI but not L-NAME significantly increased endogenous tissue DA levels in the nigrostriatal system of both sham-operated and 6-OHDA-lesioned rats. In L-DOPA-treated group, 7-NI significantly enhanced the L-DOPA-derived tissue DA content in this system and decreased the level of the intracellular DA metabolite DOPAC produced by monoamine oxidase (MAO). In contrast to 7-NI, L-NAME decreased markedly DA content and did not affect DOPAC level in the ipsilateral striatum. It means that the differences in 7-NI and L-NAME-mediated modulation of L-DOPA-induced behavioral and biochemical effects resulted not only from the inhibition of NOS activity but also from differences in their ability to inhibit MAO.

Phenyl Ether- and Aniline-Containing 2-Aminoquinolines as Potent and Selective Inhibitors of Neuronal Nitric Oxide Synthase

Excess nitric oxide (NO) produced by neuronal nitric oxide synthase (nNOS) is implicated in neurodegenerative disorders. As a result, inhibition of nNOS and reduction of NO levels is desirable therapeutically, but many nNOS inhibitors are poorly bioavailable. Promising members of our previously reported 2-aminoquinoline class of nNOS inhibitors, although orally bioavailable and brain-penetrant, suffer from unfavorable off-target binding to other CNS receptors, and they resemble known promiscuous binders. Rearranged phenyl ether- and aniline-linked 2-aminoquinoline derivatives were therefore designed to (a) disrupt the promiscuous binding pharmacophore and diminish off-target interactions and (b) preserve potency, isoform selectivity, and cell permeability. A series of these compounds was synthesized and tested against purified nNOS, endothelial NOS (eNOS), and inducible NOS (iNOS) enzymes. One compound, 20, displayed high potency, selectivity, and good human nNOS inhibition, and retained some permeability in a Caco-2 assay. Most promisingly, CNS receptor counterscreening revealed that this rearranged scaffold significantly reduces off-target binding.

Mitochondria: A Therapeutic Target for Parkinson's Disease?

Parkinson’s disease (PD) is one of the most common neurodegenerative disorders. The exact causes of neuronal damage are unknown, but mounting evidence indicates that mitochondrial-mediated pathways contribute to the underlying mechanisms of dopaminergic neuronal cell death both in PD patients and in PD animal models. Mitochondria are organized in a highly dynamic tubular network that is continuously reshaped by opposing processes of fusion and fission. Defects in either fusion or fission, leading to mitochondrial fragmentation, limit mitochondrial motility, decrease energy production and increase oxidative stress, thereby promoting cell dysfunction and death. Thus, the regulation of mitochondrial dynamics processes, such as fusion, fission and mitophagy, represents important mechanisms controlling neuronal cell fate. In this review, we summarize some of the recent evidence supporting that impairment of mitochondrial dynamics, mitophagy and mitochondrial import occurs in cellular and animal PD models and disruption of these processes is a contributing mechanism to cell death in dopaminergic neurons. We also summarize mitochondria-targeting therapeutics in models of PD, proposing that modulation of mitochondrial impairment might be beneficial for drug development toward treatment of PD.

Near infrared radiation protects against oxygen-glucose deprivation-induced neurotoxicity by down-regulating neuronal nitric oxide synthase (nNOS) activity in vitro

Near infrared radiation (NIR) has been shown to be neuroprotective against neurological diseases including stroke and brain trauma, but the underlying mechanisms remain poorly understood. In the current study we aimed to investigate the hypothesis that NIR may protect neurons by attenuating oxygen-glucose deprivation (OGD)-induced nitric oxide (NO) production and modulating cell survival/death signaling. Primary mouse cortical neurons were subjected to 4 h OGD and NIR was applied at 2 h reoxygenation. OGD significantly increased NO level in primary neurons compared to normal control, which was significantly ameliorated by NIR at 5 and 30 min post-NIR. Neither OGD nor NIR significantly changed neuronal nitric oxide synthase (nNOS) mRNA or total protein levels compared to control groups. However, OGD significantly increased nNOS activity compared to normal control, and this effect was significantly diminished by NIR. Moreover, NIR significantly ameliorated the neuronal death induced by S-Nitroso-N-acetyl-DL-penicillamine (SNAP), a NO donor. Finally, NIR significantly rescued OGD-induced suppression of p-Akt and Bcl-2 expression, and attenuated OGD-induced upregulation of Bax, BAD and caspase-3 activation. These results suggest NIR may protect against OGD at least partially through reducing NO production by down-regulating nNOS activity, and modulating cell survival/death signaling.

α-Asarone attenuates microglia-mediated neuroinflammation by inhibiting NF kappa B activation and mitigates MPTP-induced behavioral deficits in a mouse model of Parkinson's disease

The selective loss of dopaminergic neurons in Parkinson's disease (PD) is associated with microglial activation. Therefore, the importance of early therapeutic intervention to inhibit microglial activation would be an effective strategy to alleviate the progression of PD. α-Asarone, an active compound found in Araceae and Annonaceae plant species has been used to improve various disease conditions including central nervous system disorders. In the present study the in vitro and in vivo therapeutic effects of α-asarone isolated from the rhizome of Acorus gramineus Solander was evaluated on microglia-mediated neuroinflammation and neuroprotection. Lipopolysaccharide (LPS)-stimulated BV-2 microglial cells were used to evaluate in vitro effects. 1-methyl-4 phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mouse model of PD was developed to study the neuroprotective effects of α-asarone in vivo. The results indicated that α-asarone significantly attenuated the LPS-stimulated increase in neuroinflammatory responses and suppressed pro-inflammatory cytokine production in BV-2 cells. Mechanistic study revealed that α-asarone inhibited the LPS-stimulated activation via regulation of nuclear factor kappa-B by blocking degradation of inhibitor kappa B-alpha signaling in BV-2 microglial cells. In in vivo studies, MPTP intoxication to mice resulted in brain microglial activation and significant behavioral deficits. Prophylactic treatment with α-asarone suppressed microglial activation and attenuated PD-like behavioral impairments as assessed by the Y-maze and pole tests. Taken together, these data demonstrate that α-asarone is a promising neuroprotective agent that should be further evaluated and developed for future prevention and treatment of microglia-mediated neuroinflammatory conditions including PD.

Apoptotic cell death and altered calcium homeostasis caused by frataxin depletion in dorsal root ganglia neurons can be prevented by BH4 domain of Bcl-xL protein

Friedreich ataxia (FRDA) is a neurodegenerative disease characterized by a decreased expression of the mitochondrial protein frataxin. Major neurological symptoms of the disease are due to degeneration of dorsal root ganglion (DRG) sensory neurons. In this study we have explored the neurodegenerative events occurring by frataxin depletion on primary cultures of neurons obtained from rat DRGs. Reduction of 80% of frataxin levels in these cells was achieved by transduction with lentivirus containing shRNA silencing sequences. Frataxin depletion caused mitochondrial membrane potential decrease, neurite degeneration and apoptotic cell death. A marked increase of free intracellular Ca(2+) levels and alteration in Ca(2+)-mediated signaling pathways was also observed, thus suggesting that altered calcium homeostasis can play a pivotal role in neurodegeneration caused by frataxin deficiency. These deleterious effects were reverted by the addition of a cell-penetrant TAT peptide coupled to the BH4, the anti-apoptotic domain of Bcl-x(L). Treatment of cultured frataxin-depleted neurons with TAT-BH4 was able to restore the free intracellular Ca(2+) levels and protect the neurons from degeneration. These observations open the possibility of new therapies of FRDA based on modulating the Ca(2+) signaling and prevent apoptotic process to protect DRG neurons from neurodegeneration.

α-Synuclein and mitochondrial bioenergetics regulate tetrahydrobiopterin levels in a human dopaminergic model of Parkinson disease

Parkinson disease (PD) is a multifactorial disease resulting in preferential death of the dopaminergic neurons in the substantia nigra. Studies of PD-linked genes and toxin-induced models of PD have implicated mitochondrial dysfunction, oxidative stress, and the misfolding and aggregation of α-synuclein (α-syn) as key factors in disease initiation and progression. Many of these features of PD may be modeled in cells or animal models using the neurotoxin 1-methyl-4-phenylpyridinium (MPP(+)). Reducing oxidative stress and nitric oxide synthase (NOS) activity has been shown to be protective in cell or animal models of MPP(+) toxicity. We have previously demonstrated that siRNA-mediated knockdown of α-syn lowers the activity of both dopamine transporter and NOS activity and protects dopaminergic neuron-like cells from MPP(+) toxicity. Here, we demonstrate that α-syn knockdown and modulators of oxidative stress/NOS activation protect cells from MPP(+)-induced toxicity via postmitochondrial mechanisms rather than by a rescue of the decrease in mitochondrial oxidative phosphorylation caused by MPP(+) exposure. We demonstrate that MPP(+) significantly decreases the synthesis of the antioxidant and obligate cofactor of NOS and TH tetrahydrobiopterin (BH4) through decreased cellular GTP/ATP levels. Furthermore, we demonstrate that RNAi knockdown of α-syn results in a nearly twofold increase in GTP cyclohydrolase I activity and a concomitant increase in basal BH4 levels. Together, these results demonstrate that both mitochondrial activity and α-syn play roles in modulating cellular BH4 levels.

Molsidomine, a nitric oxide donor, modulates rotational behavior and monoamine metabolism in 6-OHDA lesioned rats treated chronically with L-DOPA

Some biochemical and histological studies of Parkinson's disease patients' brains and 6-OHDA-lesioned rats suggest that dopaminergic dennervation of the striatum leads to the nitrergic system hypofunction in this structure. Hence, recently the modulation of nitric oxide (NO)- soluble guanylyl cyclase-cyclic GMP signaling is considered to be a new target for the treatment of Parkinson's disease. The aim of our study was to examine the impact of chronic combined treatment with low doses of the NO donor molsidomine (2 and 4mg/kg) and L-DOPA (12.5 and 25mg/kg) on rotational behavior and monoamine metabolism in the striatum (STR) and substantia nigra (SN) of unilaterally 6-OHDA-lesioned rats. Chronic administration of molsidomine at a dose of 2mg/kg jointly with 25mg/kg of L-DOPA significantly decreased the number of contralateral rotations when compared to L-DOPA alone. Other combinations of the examined drug doses were less effective. The tissue DA levels in the ipsilateral STR and SN after the last chronic doses of molsidomine (2mg/kg) and L-DOPA (12.5 or 25mg/kg), were significantly higher than after L-DOPA alone. Chronic L-DOPA treatment alone or jointly with a lower dose of molsidomine decreased 5-HT levels and accelerated its catabolism in the examined structures. However, combination of a higher dose of molsidomine with L-DOPA (25mg/kg) did not reduce 5-HT content while its catabolism was less intensive. The obtained results show that low doses of molsidomine can modulate rotational behavior and tissue DA and 5-HT concentrations in the STR and SN of 6-OHDA-lesioned rats treated chronically with L-DOPA.

Functions of S100 proteins

The S100 protein family consists of 24 members functionally distributed into three main subgroups: those that only exert intracellular regulatory effects, those with intracellular and extracellular functions and those which mainly exert extracellular regulatory effects. S100 proteins are only expressed in vertebrates and show cell-specific expression patterns. In some instances, a particular S100 protein can be induced in pathological circumstances in a cell type that does not express it in normal physiological conditions. Within cells, S100 proteins are involved in aspects of regulation of proliferation, differentiation, apoptosis, Ca2+ homeostasis, energy metabolism, inflammation and migration/invasion through interactions with a variety of target proteins including enzymes, cytoskeletal subunits, receptors, transcription factors and nucleic acids. Some S100 proteins are secreted or released and regulate cell functions in an autocrine and paracrine manner via activation of surface receptors (e.g. the receptor for advanced glycation end-products and toll-like receptor 4), G-protein-coupled receptors, scavenger receptors, or heparan sulfate proteoglycans and N-glycans. Extracellular S100A4 and S100B also interact with epidermal growth factor and basic fibroblast growth factor, respectively, thereby enhancing the activity of the corresponding receptors. Thus, extracellular S100 proteins exert regulatory activities on monocytes/macrophages/microglia, neutrophils, lymphocytes, mast cells, articular chondrocytes, endothelial and vascular smooth muscle cells, neurons, astrocytes, Schwann cells, epithelial cells, myoblasts and cardiomyocytes, thereby participating in innate and adaptive immune responses, cell migration and chemotaxis, tissue development and repair, and leukocyte and tumor cell invasion.

Nitric oxide synthase inhibitors protect against rotenone-induced, oxidative stress mediated parkinsonism in rats

Rotenone is known to cause progressive dopaminergic neuronal loss in rodents, but it remains unclear how this mitochondrial complex-I inhibitor mediates neurodegeneration specific to substantia nigra pars compacta (SNpc). One of the proposed mechanisms is increased free radical generation owing to mitochondrial electron transport chain dysfunction following complex-I inhibition. The present study examined the role of nitric oxide (NO) and hydroxyl radicals (OH) in mediating rotenone-induced dopaminergic neurotoxicity. Indications of NO involvement are evidenced by inducible nitric oxide synthase (NOS) over-expression, and increased NADPH-diaphorase staining in SNpc neurons 96h following rotenone administration. Treatment of these animals with specific neuronal NOS inhibitor, 7-nitroindazole (7-NI) and non-specific NOS inhibitor, N-ω-nitro-l-argenine methyl ester (l-NAME) caused reversal of rotenone-induced striatal dopamine depletion, and attenuation of the neurotoxin-induced decrease in the number of tyrosine hydroxylase immunoreactive neurons in SNpc, as well as in apomorphine and amphetamine-induced unilateral rotations. Interestingly, the study also demonstrated the contribution of OH in mediating rotenone nigral toxicity since there appeared a significant generation of the reactive oxygen species in vivo 24h following rotenone administration, a copious loss of reduced and oxidized glutathione, and increased superoxide dismutase and catalase activities in the cytosolic fractions of the ipsilateral SNpc area on the 5th day. An OH scavenging capacity of 7-NI and l-NAME in a Fenton-like reaction, as well as complete reversal of the rotenone-induced increases in the antioxidant enzyme activities, and the loss in reduced and oxidized glutathione contents in the SNpc supported OH involvement in rotenone-induced dopaminergic neurotoxicity. While these results strongly suggest the contribution of both OH and NO, resulting in acute oxidative stress culminating in dopaminergic neurodegeneration caused by rotenone, the course of events indicated generation of OH as the primary event in the neurotoxic processes.

Development of the human corpus striatum and the presence of nNOS and 5-HT2A receptors

This study focussed on the development of the corpus striatum in the fetus, using silver impregnation and immunohistochemistry. For the latter, we looked for nNOS positive cells and 5-HT(2A) receptors positive cells in the corpus striatum during development. During the initial formation of the corpus striatum, there was migration cells of the ganglionic eminence toward the putamen by 15-17 weeks of gestation. Process formation in the neurons started by week 17 and became very complex before term (31/32 weeks of gestation). By 25-27 gestational weeks, the globus pallidus already had two parts and the corpus striatum was similar to the adult in configuration. The nNOS positive cells appeared early (21-23 weeks in gestation) while 5-HT(2A) receptors positive cells were not observed until 31/32 weeks gestation. The number of positive cells in both groups was relatively small. It is anticipated that further developmental changes would occur in the postnatal/neonatal phases.

Nitric oxide and DOPAC-induced cell death: from GSH depletion to mitochondrial energy crisis

The molecular mechanisms inherent to cell death associated with Parkinson's disease are not clearly understood. Diverse pathways, sequence of events and models have been explored in several studies. Recently, we have proposed an integrative mechanism, encompassing the interaction of nitric oxide (•NO) and a major dopamine metabolite, dihydroxyphenylacetic (DOPAC), leading to a synergistic mitochondrial dysfunction and cell death that may be operative in PD. In this study, we have studied the sequence of events underlying the mechanisms of cell death in PC12 cells exposed to •NO and DOPAC in terms of: a) free radical production; b) modulation by glutathione (GSH); c) energetic status and d) outer membrane mitochondria permeability. Using Electron Paramagnetic Resonance (EPR) it is shown the early production of oxygen free radicals followed by a depletion of GSH reflected by an increase of GSSG/GSH ratio in the cells treated with the mixture of •NO/DOPAC, as compared with the cells individually exposed to each of the stimulus. Glutathione ethyl ester (GSH-EE) and N-acetylcysteine (NAC) may rescue cells from death, increasing GSH content and preventing ATP loss in cells treated with the mixture DOPAC/•NO but failed to exert similar effects in the cells challenged only with •NO. The depletion of GSH is accompanied by a decreased activity of mitochondrial complex I. At a later stage, the concerted action of DOPAC and •NO include a rise in the ratio Bax/Bcl-2, an observation not evident when cells were exposed only to •NO. The results support a free radical-induced pathway leading to cell death involving the concerted action of DOPAC and •NO and the critical role of GSH in maintaining a functional mitochondria.

Targeting oxidative stress, mitochondrial dysfunction and neuroinflammatory signaling by selective cyclooxygenase (COX)-2 inhibitors mitigates MPTP-induced neurotoxicity in mice

Several studies have pointed towards the role of oxidative stress, mitochondrial dysfunction and neuroinflammation in Parkinson's disease (PD). The present study was focused on the possible neuroprotective effect of selective cyclooxygenase (COX)-2-inhibitors: valdecoxib and NS-398 in 1-methyl-4-phenyl-1,2,3,6-tertahydropyridine (MPTP)-induced neurotoxicity in mice. MPTP administration in dose of 40 mg/kg, i.p (four injections of 10mg/kg, i.p. at an interval of 1h each) significantly induced the Parkinson-like symptoms in mice as indicated by change in locomotor activity, inability to correct posture (bar test), and oxidative stress (increased levels of lipid peroxidation, nitrite concentration, and depletion of antioxidant enzyme). MPTP administration significantly impaired mitochondrial complex-I activity and redox activity, upregulated the caspase-3 and NF-κB levels as compared to vehicle group. Treatment with valdecoxib (5 or 10 mg/kg, p.o.) or NS-398 (5 or 10mg/kg, p.o.) for 7 days significantly reversed behavioral, biochemical, mitochondrial complex alterations as well as attenuated the induction of proinflammatory mediators in MPTP-treated groups. The findings of the present study substantiate the neuroprotective role of selective COX-2 inhibitors in ameliorating MPTP-induced neurodegeneration in mice and suggest the possible therapeutic potential of these drugs in the management of PD.

Care for child development: basic science rationale and effects of interventions

The past few years have witnessed increasing interest in devising programs to enhance early childhood development. We review current understandings of brain development, recent advances in this field, and their implications for clinical interventions. An expanding body of basic science laboratory data demonstrates that several interventions, including environmental enrichment, level of parental interaction, erythropoietin, antidepressants, transcranial magnetic stimulation, transcranial direct current stimulation, hypothermia, nutritional supplements, and stem cells, can enhance cerebral plasticity. Emerging clinical data, using functional magnetic resonance imaging and clinical evaluations, also support the hypothesis that clinical interventions can increase the developmental potential of children, rather than merely allowing the child to achieve an already predetermined potential. Such interventions include early developmental enrichment programs, which have improved cognitive function; high-energy and high-protein diets, which have increased brain growth in infants with perinatal brain damage; constraint-induced movement therapy, which has improved motor function in patients with stroke, cerebral palsy, and cerebral hemispherectomy; and transcranial magnetic stimulation, which has improved motor function in stroke patients.

Hexokinase II gene transfer protects against neurodegeneration in the rotenone and MPTP mouse models of Parkinson's disease

A typical feature of Parkinson's disease is the progressive loss of dopaminergic neurons in the substantia nigra, in which inhibition of mitochondrial complex I activity may play an important role. Rotenone or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) inhibit the mitochondrial complex I and they cause the death of substantia nigra dopaminergic neurons, thereby providing acute murine models of Parkinson's disease. We have found that increasing mitochondrial hexokinase II activity can prevent cell death in neuronal cultures treated with rotenone. As a result, we have studied the effects of hexokinase II gene transfer in vivo using a herpes simplex virus type 1 (HSV-1) amplicon vector. The placHK2 amplicon vector was injected into substantia nigra of mice that were subsequently administered rotenone or MPTP. Overexpression of hexokinase II prevented both rotenone and MPTP-induced dopaminergic neuronal cell death, as well as reducing the associated motor defects. Our results provide the first proof-of-principle that hexokinase II protects against dopaminergic neurodegeneration in vivo, emphasizing the role of this enzyme in promoting neuronal survival. Thus, the increase of hexokinase II expression by gene transfer or other means represents a promising approach to treat Parkinson's and other neurodegenerative diseases.

Dual motor response to l-dopa and nociceptin/orphanin FQ receptor antagonists in 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) treated mice: Paradoxical inhibition is relieved by D(2)/D(3) receptor blockade

Motor activity of mice acutely treated with the parkinsonian toxin 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) was monitored for 6 days using behavioral tests which provide complementary information on motor function: the bar, reaction time, drag, stair climbing, grip, rotarod and footprinting tests. These tests consistently disclosed a prolonged motor impairment characterized by akinesia, bradykinesia, speed reduction, loss of coordination and gait patterns. This impairment was associated with approximately 60% loss of striatal dopamine terminals, as revealed by tyrosine hydroxylase immunohistochemistry, and was attenuated by dopaminergic drugs. Indeed, the dopamine precursor, l-dopa (1-10 mg/kg), and the D(3)/D(2) receptor agonist pramipexole (0.0001-0.001 mg/kg) promoted stepping activity in the drag test (a test for akinesia/bradykinesia). The novel nociceptin/orphanin FQ receptor (NOP) antagonist 1-[1-(cyclooctylmethyl)-1,2,3,6-tetrahydro-5-(hydroxymethyl)-4-pyridinyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (Trap-101, 0.001-0.1 mg/kg), an analogue of 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (J-113397), also promoted stepping and synergistically or additively (depending on test) attenuated parkinsonism when combined to dopamine agonists. High doses of l-dopa (100 mg/kg), pramipexole (0.1 mg/kg), Trap-101 and J-113397 (1 mg/kg), however, failed to modulate stepping, worsening immobility time and/or rotarod performance. Low doses of amisulpride (0.1 mg/kg) reversed motor inhibition induced by l-dopa and J-113397, suggesting involvement of D(2)/D(3) receptors. This study brings further evidence for a dopamine-dependent motor phenotype in MPTP-treated mice reinforcing the view that this model can be predictive of symptomatic antiparkinsonian activity provided the appropriate test is used. Moreover, it offers mechanistic interpretation to clinical reports of paradoxical worsening of parkinsonism following l-dopa. Finally, it confirms that NOP receptor antagonists may be proven effective in reversing parkinsonism when administered alone or in combination with dopamine agonists.

Biochemical alterations of the striatum in an MPTP-treated mouse model of Parkinson's disease

We investigated the biochemical alterations of the striatum of mice subjected to seven experimental schedules with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP) treatment. The mice were treated intraperitoneally (i.p.) with MPTP (20 mg/kg in saline) four times a day at 2-hr intervals showed severe and persistent depletions of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striatum, as compared with those (1) treated with MPTP (15 mg/kg in saline, i.p.) once a day for 14 consecutive days; (2)MPTP (30 mg/kg in saline, i.p.) twice a day for 5 consecutive days; (3) MPTP (10 mg/kg in saline, i.p.) four times a day at 1-hr intervals for 2 consecutive days; (4) MPTP (20 mg/kg in saline, i.p.) once a day for 4 consecutive days; (5) MPTP (20 mg/kg in saline, i.p.) twice a day for 2 consecutive days; (6) MPTP (20 mg/kg in saline, i.p.) twice a day for 4 consecutive days. In our Western blot analysis, furthermore, the mice that received MPTP (20 mg/kg in saline) four times a day at 2-hr intervals showed a severe decrease of the striatal tyrosine hydroxylase (TH) protein levels and a significant increase of the striatal glial fibrillary acidic protein (GFAP) levels. These results demonstrate that the model with acute MPTP treatment can cause severe neuronal damage in the mouse striatum, as compared to the model with continuous treatment with MPTP. Thus our findings may support the validity of acute MPTP treatment model for unraveling in the neurodegenerative processes in PD.

Effect of N-methyl-D-aspartate (NMDA) receptor antagonists on alpha-synuclein-evoked neuronal nitric oxide synthase activation in the rat brain

alpha-Synuclein (ASN), a small presynaptic protein that is abundant in the brain, is implicated in the pathogenesis of neurodegenerative disorders including Parkinson's and Alzheimer's disease. The central domain of alpha-synuclein, the non-amyloid beta component of the Alzheimer's disease amyloid (NAC) is probably responsible for its toxicity. However, the molecular mechanism of alpha-synuclein action remains largely elusive. The present study examined the effect of alpha-synuclein and the NAC peptide on nitric oxide synthase (NOS) activity in rat brain cortical and hippocampal slices using a radiochemical technique. Moreover, nitrite levels in brain slices incubated in the presence of alpha-synuclein were measured using the Griess reaction. ASN and the NAC stimulated NOS activity by about 70% and 40%, respectively. beta-Synuclein, a homologous protein of ASN that lacks the NAC domain, had no effect on NOS activity. Under the same experimental conditions, alpha-synuclein increased nitrite levels by 27%. alpha-Synuclein and the NAC affected the activity of constitutive neuronal isoform of NOS, but had no impact on the endothelial or inducible NOS isoforms. The effect of alpha-synuclein and the NAC peptide on NOS activity was inhibited by MK-801 and APV, antagonists of the NMDA receptor. These results indicate that the NMDA receptor plays an important role in alpha-synuclein-evoked nitric oxide synthesis. We suggest that nitric oxide liberated by the over-activated neuronal isoform of NOS could react with superoxide to form peroxynitrite, which modulates the function of a variety of biomolecules including proteins, lipids, and DNA.

Neuroprotective and anti-inflammatory activities of ketogenic diet on MPTP-induced neurotoxicity

Ketogenic diet (KD) is a high-fat, low-protein and low-carbohydrate diet. It is reported that KD can provide the neuroprotection for the neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease (PD) and amyotrophic lateral sclerosis. The main clinical symptom of PD is motor dysfunction derived from the loss of dopaminergic neurons in the substantia nigra (SN) and dopamine content in the striatum subsequently. It is well known that treatments with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice produce motor dysfunction, biochemical, and neurochemical changes remarkably similar to idiopathic PD patients. In this study, we investigated the neuroprotective and anti-inflammatory effects of KD in MPTP-treated mice. The data showed that pretreatment with KD alleviated the motor dysfunction induced by MPTP. The decrease of Nissl-staining and tyrosine hydroxylase (TH)-positive neurons induced by MPTP was inhibited in the SN. The change of dopamine was very similar to dopaminergic neurons in the SN. KD inhibited the activation of microglia induced by MPTP in the SN. The levels of proinflammatory cytokines (interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha) in the SN were also decreased and induced by MPTP. So, we concluded that KD was neuroprotective and anti-inflammatory against MPTP-neurotoxicity.

Gender differences on MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) neurotoxicity in C57BL/6 mice

The aim of this study was to investigate the impact of gender difference in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated animal model of Parkinson's disease (PD). In the present study, we investigated the time-dependent alterations of dopamine and its metabolites, striatal tyrosine hydroxylase (TH) protein, dopamine transporter (DAT) protein, glial fibrillary acidic protein (GFAP) protein and midbrain TH protein and motor function in male and female mice 5h and 1, 3 and 7 days after four administrations of MPTP (20mg/kg) at 2-h intervals. The present study showed that the decrease of dopamine, DOPAC (3,4-dihydroxyphenylacetic acid) and HVA (homovanillic acid) content in female mice was more pronounced than that in male animals 1, 3 and 7 days after MPTP treatment. Our Western blot analysis study also demonstrated that the decrease of both striatal and midbrain TH protein levels in female mice was more pronounced than that in male animals from 1 to 7 days after MPTP treatment. As compared to male mice, in contrast, the increase of striatal GFAP protein levels in female mice was observed from 5h to 7 days after MPTP treatment. Furthermore, the present study showed that motor deficits were found in both male and female mice 1 and 7 days after MPTP treatment. In the present study, moreover, the decrease of striatal DAT protein levels in female mice was more pronounced than that in male animals 1, 3 and 7 days after MPTP treatment. These results demonstrate that our administrations of MPTP at 2-h intervals can cause more severe damage in female mice as compared with male animals. The gender difference may be due to the decrease of DAT expression caused by MPTP. Thus our findings provide further valuable information for the pathogenesis of PD.

Developmental alterations of DHPG-induced long-term depression of corticostriatal synaptic transmission: switch from NMDA receptor-dependent towards CB1 receptor-dependent plasticity

In animal models of early Parkinson's disease (PD), motor deficits are accompanied by excessive striatal glutamate release. Blockade of group I metabotropic glutamate receptors (mGluRs), endocannabinoid degradation and nitric oxide (NO) synthesis combats PD symptoms. Activation of group I mGluRs with the specific agonist 3,5-dihydroxyphenylglycine (DHPG) induces long-term depression of corticostriatal transmission (LTD(DHPG)) in the adult mouse striatum requiring NO synthesis downstream to cannabinoid CB1 receptor (CB1R) activation suggesting a dual role for LTD(DHPG): neuroprotective by down-regulation of glutamatergic transmission and, under certain circumstances, neurotoxic by release of NO. We report now that LTD(DHPG) undergoes a developmental switch from N-methyl-D-aspartate (NMDA)-receptor-dependent/CB1R-independent to NMDA receptor-independent/CB1R-dependent plasticity with NO playing an essential role for LTD(DHPG) at all developmental stages. The gain in function of CB1R is explained by their developmental up-regulation evaluated with real-time reverse transcription-polymerase chain reaction. These findings are relevant for the pathophysiology and therapy of PD as they link the activation of group I mGluRs, endocannabinoid release, and striatal NO production.

Protective effect of cyclooxygenase (COX)-inhibitors against drug-induced catatonia and MPTP-induced striatal lesions in rats

The present study explored the involvement of cyclooxygenase (COX) in the pathophysiology of Parkinson's disease (PD). Further, the protective effect of COX-inhibitors against perphenazine-induced catatonia and 1-methyl-4-phenyl-1, 2, 3, 6-tertahydropyridine (MPTP)-induced striatal lesions in rats was evaluated. Administration of perphenazine (5 mg/kg., i.p.) produced severe catatonia (rigid behavior) in rats; the maximum score reached at 4 h (estimated as 100% AUC) and declined within 24 h. An intrastriatal injection of MPTP produced hypolocomotor activity in rats. Both perphenazine and MPTP produced oxidative stress as demonstrated by increased levels of lipid peroxides, nitrite and decreased antioxidant defense system in the whole brain and striatal region, in particular. Pretreatment with various COX-inhibitors viz. rofecoxib, celecoxib, nimesulide or naproxen offered protection against perphenazine-induced catatonia, the effect was more pronounced with rofecoxib. Rofecoxib and celecoxib (both selective COX-2 inhibitors) also reversed the perphenazine-induced oxidative stress. Further, prior treatment with rofecoxib (8 mg/kg, p.o.) reversed both the behavioral and biochemical changes induced by MPTP. These results suggest that COX-inhibitors particularly, rofecoxib offers protection against drug-induced catatonia and MPTP-induced striatal lesions possibly by modulating dopaminergic neurotransmission and/or oxidative stress.

Systemic administration of proteasome inhibitor protects against MPTP neurotoxicity in mice

Dysfunction of the proteasome has been suggested to contribute in the degeneration of nigrostriatal dopaminergic neurons. Here, we investigated to determine whether systematic administration of proteasome inhibitor, carbobenzoxy-L: -gamma-t-butyl-L: -glutamyl-L: -alanyl-L: -leucinal (PSI) protects against MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) neurotoxicity in mice. Three administrations of MPTP at 1-h intervals to mice reduced significantly the concentration of dopamine, DOPAC (3,4-dihydroxyphenylacetic acid) and HVA (homovanillic acid) in the striatum after 5 days. In contrast, PSI (0.3 and 1.0 mg/kg) prevented a significant decrease in dopamine, DOPAC and HVA contents of the striatum 5 days after MPTP treatment. In our Western blot analysis study, PSI at a dose of 1.0 mg/kg prevented a significant decrease in TH (tyrosine hydroxylase) protein and a significant increase in glial fibrillary acidic protein 5 days after MPTP treatment. Furthermore, our immunohistochemical study showed that PSI at a dose of 1.0 mg/kg prevented a significant loss in TH immunopositive neurons in the striatum and substantia nigra 5 days after MPTP treatment. In contrast, PSI caused a significant increase in the number of intense ubiquitin immunopositive cells in the striatum and substantia nigra 5 days after MPTP treatment. These results indicate that proteasome inhibitors can protect against MPTP neurotoxicity in mice. The neuroprotective effect of PSI against dopaminergic cell damage may be mediated by the elevation of ubiquitination. Thus, our findings provide further valuable information for the pathogenesis of Parkinson's disease.

Rotenone and paraquat do not directly activate microglia or induce inflammatory cytokine release

Both epidemiological and pathological data suggest an inflammatory response including microglia activation and neuro-inflammation in the Parkinsonian brain. Treatments with lipopolysaccharide (LPS), rotenone and paraquat have been used as models for Parkinson's disease, as they cause dopaminergic neuron degeneration in culture and in animals. Recent studies have suggested that rotenone and paraquat induce neuro-inflammation, however, it is not known if they can directly activate microglia. Here, we use primary cultured microglia to address this question. Microglia activation was analyzed by morphological changes and release of nitric oxide and inflammatory cytokines. Treatment with LPS was used as a positive control. While LPS induced morphological changes characteristic of microglial activation and release of nitric oxide and inflammatory cytokines, rotenone and paraquat did not. Our results suggest that paraquat and rotenone do not act directly on microglia and that neuro-inflammation and microglial activation in animals treated with these agents are likely non-cell autonomous, and may occur as a result of dopaminergic neuron damage or factors released by neurons and other cells.

MPTP intoxication in mice: a useful model of Leigh syndrome to study mitochondrial diseases in childhood

The basal ganglia, which are interconnected in the striato-nigral dopaminergic network, are affected in several childhood diseases including Leigh syndrome (LS). LS is the most common mitochondrial disorder affecting children and usually arise from inhibition of the respiratory chain. This vulnerability is attributed to a particular susceptibility to energetic stress, with mitochondrial inhibition as a common pathogenic pathway. In this study we developed a LS model for neuroprotection trials in mice by using the complex I inhibitor MPTP. We first verified that MPTP significantly inhibits the mitochondrial complex I in the brain (p = 0.018). This model also reproduced the biochemical and pathological features of LS: MPTP increased plasmatic lactate levels (p = 0.023) and triggered basal ganglia degeneration, as evaluated through dopamine transporter (DAT) autoradiography, tyrosine hydroxylase (TH) immunohistochemistry, and dopamine dosage. Striatal DAT levels were markedly decreased after MPTP treatment (p = 0.003). TH immunoreactivity was reduced in the striatum and substantia nigra (p = 0.005), and striatal dopamine was significantly reduced (p < 0.01). Taken together, these results confirm that acute MPTP intoxication in young mice provides a reproducible pharmacological paradigm of LS, thus opening new avenues for neuroprotection research.

Neuronal nitric oxide synthase: structure, subcellular localization, regulation, and clinical implications

Nitric oxide (NO), a free gaseous signaling molecule, is involved in the regulation of the cardiovascular, nervous and immune system. The neurotransmitter function of nitric oxide is dependent on dynamic regulation of its biosynthetic enzyme, nitric oxide synthase (NOS). There are three types of NOS, neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS). Of the three NOS, we focus on nNOS in the present review. Brain nNOS exists in particulate and soluble forms and the differential subcellular localization of nNOS may contribute to its diverse functions. Proteins bearing PDZ domains can interact directly with the PDZ domain of nNOS, influencing the subcellular distribution and/or activity of the enzyme. During the past several years, an increasing number of reports have demonstrated the importance of nNOS in a variety of synaptic signaling events. nNOS has been implicated in modulating physiological functions such as learning, memory, and neurogenesis, as well as being involved in a number of human diseases. In this review we concentrate on recent findings regarding the structural features, subcellular localization and factors regulating nNOS function. In particular, we conclude with a section discussing the role of nNOS in a wide range of physiological and pathological conditions.

Age- and sex-differences in the nitric oxide synthase expression and dopamine concentration in the murine model of Parkinson's disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

Parkinson's disease (PD) is an age- and sex-related neurodegenerative disorder of unknown aetiology. The involvement of nitric oxide synthase (NOS) in the etiopathogenesis of PD is quite well documented. We decided to examine changes in dopamine (DA) levels as well as iNOS, nNOS, eNOS mRNA and protein expression in the striatum of C57BL male and female (2- and 12-month old) mice in the course of PD-related neurodegeneration induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The significantly decreased level of DA was previously observed in male than in female, irrespective of age. In young mice the recovery of DA was significantly greater in female compared to male mice. On the contrary, both in male and female old animals the low concentration of DA was extended up to 21 days post MPTP injection. The increases in iNOS protein expression post MPTP intoxication occurred more rapidly in male (young and old) than in female mice. The pattern of changes in iNOS protein expression was also different in young versus aged mice. nNOS protein expression increased earlier in young male than young female mice. No changes were observed in eNOS expression. In conclusion, our results support the hypothesis of the involvement of iNOS and nNOS, but not eNOS in neurodegenerative processes. Our findings suggest that age- and sex-differences in DA concentration and iNOS expression as well as sex-differences of nNOS expression after intoxication may depend on the increased susceptibility of males as well as older animals to toxic effect of MPTP and aggravated process of recovery in old brains.

Effects of estrogens on striatal damage after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in male and female mice

Emerging evidence shows a beneficial effect of estrogens for Parkinson's disease, yet the exact potency of these compounds implicated remain obscured. In this study, we investigated the neuroprotective effect of 17beta-estradiol and estrone against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced striatal toxicity in mice. The neuroprotective effects of both compounds were evaluated by HPLC and Western blot analyses 5 days after the last of 4 consecutive injections of MPTP at 1-h intervals to mice. Subacute treatment (10 days) with estrone or 17beta-estradiol at low doses (0.05 and 0.2mg/kg) showed no significant changes against MPTP-induced damage of striatal dopamine terminals in mice. Furthermore, acute treatment with estrone at high doses (0.5 and 2.0mg/kg) showed no significant alterations against MPTP-induced damage of striatal dopamine terminals in mice. In contrast, acute treatment with 17beta-estradiol at high doses exhibited a neuroprotective effect against the damage of striatal dopamine terminals in both male and female mice after MPTP treatments. The results demonstrate that estrogen therapy with high doses may have a neuroprotective effect on the damage of striatal dopamine terminals in the MPTP-induced mice. These findings may lead to be development of estrogen therapy for the prevention and treatment of Parkinson's disease.

Comparative pharmacological study of free radical scavenger, nitric oxide synthase inhibitor, nitric oxide synthase activator and cyclooxygenase inhibitor against MPTP neurotoxicity in mice

The biochemical and cellular changes that occur following the administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) are remarkably similar to that seen in idiopathic Parkinson's disease(PD). There is growing evidence indicating that reactive oxygen species (ROS), reactive nitrogen species (RNS) and inflammation are a major contributor to the pathogenesis and progression of PD. Hence, we investigated whether 7-nitroindazole [neuronal nitric oxide synthase (nNOS) inhibitor], edaravone (free radical scavenger), minocycline [inducible NOS (iNOS) inhibitor], fluvastatin [endothelial NOS (eNOS) activator], pitavastatin (eNOS activator), etodolac [cyclooxygenase-2 (COX-2) inhibitor] and indomethacin (COX inhibitor) can protect against MPTP neurotoxicity in mice under the same conditions. For the evaluation of each drug, the levels of dopamine, DOPAC and HVA were quantified using HPLC with an electrochemical detector. Four administrations of MPTP at 1-h intervals to mice produced marked depletion of dopamine, DOPAC (3,4-dihydroxyphenylacetic acid) and HVA (homovanilic acid) in the striatum after 5 days. 7-Nitroindazole prevented dose-dependently a significant reduction in dopamine contents of the striatum 5 days after MPTP treatment. In contrast, edaravone, minocycline, fluvastatin, pitavastatin, etodolac and indomethacin did not show the neuroprotective effect on MPTP-induced striatal dopamine, DOPAC and HVA depletions after 5 days. The present study demonstrates that the overexpression of nNOS may play a major role in the neurotoxic processes of MPTP, as compared with the production of ROS, the overexpression of iNOS, the modulation of eNOS and the involvement of inflammatory response. Thus our pharmacological findings provide further information for progressive neurodegeneration of the nigrostriatal dopaminergic neuronal pathway.

Nociceptin/orphanin FQ receptor blockade attenuates MPTP-induced parkinsonism

Endogenous nociceptin/orphanin FQ (N/OFQ) inhibits the activity of dopamine neurons in the substantia nigra and affects motor behavior. In this study we investigated whether a N/OFQ receptor (NOP) antagonist, J-113397, can modify movement in naive mice and nonhuman primates and attenuate motor deficits in MPTP-treated parkinsonian animals. J-113397 facilitated motor activity in naïve mice at low doses (0.1-1 mg/kg) and inhibited it at higher ones (10 mg/kg). Likewise, in MPTP-treated mice, J-113397 reversed motor deficit at 0.01 mg/kg but worsened hypokinesia at higher doses (1 mg/kg). In naïve nonhuman primates, J-113397, ineffective up to 1 mg/kg, produced inconsistent motor improvements at 3 mg/kg. Conversely, in parkinsonian primates J-113397 (0.01 mg/kg) reversed parkinsonism, being most effective against hypokinesia. We conclude that endogenous N/OFQ modulates motor activity in mice and nonhuman primates and contributes to parkinsonian symptoms in MPTP-treated animals. NOP receptor antagonists may represent a novel approach to Parkinson's disease.