Fenretinide Beneficial Effects on Amyotrophic Lateral Sclerosis-associated SOD1G93A Mutant Protein Toxicity: In Vitro and In Vivo Evidences.

Amyotrophic lateral sclerosis (ALS) is the most frequent motor neuron disease for which effective treatment options are still lacking. ALS occurs in sporadic and familial forms which are clinically indistinguishable; about 20% of familial ALS cases are linked to mutations of the superoxide dismutase 1 (SOD1) gene. Fenretinide (FEN), a cancer chemopreventive and antiproliferative agent currently used in several clinical trials, is a multi-target drug which also exhibits redox regulation activities. We analyzed the effects of FEN on mutant SOD1 (mSOD1) toxicity in motoneuronal (NSC34) and a muscle (C2C12) cell lines and evaluated the impacts of chronic administration of a new nanomicellar fenretinide formulation (NanoMFen) on ALS disease progression in the SOD1G93A mouse model. The results showed that FEN significantly prevents the toxicity of mSOD1 expression in NSC34 motor neuron; furthermore, FEN is able to partially overcome the toxic effect of mSOD1 on the myogenic program of C2C12 muscle cells. Administration of NanoMFen ameliorates the disease progression and increases median survival of mSOD1G93A ALS mice, even when given after disease onset; beneficial effects in ALS mice, however, is restricted to female sex. Our data support the therapeutic potential of FEN against ALS-associated SOD1G93A mutant protein toxicity and promote further studies to elucidate specific cellular targets of the drug in ALS. Furthermore, the sex-related efficacy of NanoMFen in mSOD1G93A ALS mice strengthens the importance, in the perspective of a precision medicine approach, of gender pharmacology in ALS research.

Adenosine A2A receptor inhibition reduces synaptic and cognitive hippocampal alterations in Fmr1 KO mice.

In fragile X syndrome (FXS) the lack of the fragile X mental retardation protein (FMRP) leads to exacerbated signaling through the metabotropic glutamate receptors 5 (mGlu5Rs). The adenosine A2A receptors (A2ARs), modulators of neuronal damage, could play a role in FXS. A synaptic colocalization and a strong permissive interaction between A2A and mGlu5 receptors in the hippocampus have been previously reported, suggesting that blocking A2ARs might normalize the mGlu5R-mediated effects of FXS. To study the cross-talk between A2A and mGlu5 receptors in the absence of FMRP, we performed extracellular electrophysiology experiments in hippocampal slices of Fmr1 KO mouse. The depression of field excitatory postsynaptic potential (fEPSPs) slope induced by the mGlu5R agonist CHPG was completely blocked by the A2AR antagonist ZM241385 and strongly potentiated by the A2AR agonist CGS21680, suggesting that the functional synergistic coupling between the two receptors could be increased in FXS. To verify if chronic A2AR blockade could reverse the FXS phenotypes, we treated the Fmr1 KO mice with istradefylline, an A2AR antagonist. We found that hippocampal DHPG-induced long-term depression (LTD), which is abnormally increased in FXS mice, was restored to the WT level. Furthermore, istradefylline corrected aberrant dendritic spine density, specific behavioral alterations, and overactive mTOR, TrkB, and STEP signaling in Fmr1 KO mice. Finally, we identified A2AR mRNA as a target of FMRP. Our results show that the pharmacological blockade of A2ARs partially restores some of the phenotypes of Fmr1 KO mice, both by reducing mGlu5R functioning and by acting on other A2AR-related downstream targets.

Beneficial Effects of Fingolimod on Social Interaction, CNS and Peripheral Immune Response in the BTBR Mouse Model of Autism.

Autism Spectrum Disorders (ASD) are neurodevelopmental disorders characterized by social communication deficits and repetitive/stereotyped behaviours. We evaluated the effects of a chronic treatment with the immunomodulator drug Fingolimod (FTY720 - a non-selective Sphingosine 1-Phosphate Receptor ligand) in an ASD model, the BTBR T+tf/J (BTBR) mouse strain. In adult BTBR males, chronic FTY720 treatment (4 weeks) increased social and vocal response during a male-female interaction and hippocampal expression of BDNF and Neuregulin 1, two trophic factors reduced in BTBR when compared to control C57 mice. FTY720 also re-established the expression of IL-1ß and MnSOD in the hippocampus, whereas it did not modify IL-6 mRNA content. In addition to its central effect, FTY720 modulated the activation state of peripheral macrophages in the BTBR model, both in basal conditions and after stimulation with an immune challenge. Furthermore, IL-6 mRNA colonic content of BTBR mice, reduced when compared with C57 mice, was normalized by chronic treatment with FTY720. Our study, while indicating FTY720 as a tool to attenuate relevant alterations of the BTBR neurobehavioural phenotype, emphasizes the importance of gut mucosal immune evaluation as an additional target that deserve to be investigated in preclinical studies of anti-inflammatory therapeutic approaches in ASD.

Modulating P1 Adenosine Receptors in Disease Progression of SOD1G93A Mutant Mice.

Amyotrophic lateral sclerosis (ALS) is a fatal progressing neurodegenerative disease; to date, despite the intense research effort, only two therapeutic options, with very limited effects, are available. The purinergic system has been indicated as a possible new therapeutic target for ALS, but the results are often contradictory and generally confused. The present study was designed to determine whether P1 adenosine receptor ligands affected disease progression in a transgenic model of ALS. SOD1G93A mice were chronically treated, from presymptomatic stage, with a selective adenosine A2A receptor agonist (CGS21680), antagonist (KW6002) or the A1 receptor antagonist DPCPX. Body weight, motor performance and survival time were evaluated. The results showed that neither the stimulation nor the blockade of adenosine A2A receptors modified the progressive loss of motor skills or survival of mSOD1G93A mice. Conversely, blockade of adenosine A1 receptors from the presymptomatic stage significantly attenuated motor disease progression and induced a non-significant increase of median survival in ALS mice. Our data confirm that the modulation of adenosine receptors can elicit very different (and even opposite) effects during the progression of ALS course, thus strengthens the importance of further studies to elucidated their real therapeutic potential in this pathology.

Neuronal adenosine A2A receptor overexpression is neuroprotective towards 3-nitropropionic acid-induced striatal toxicity: a rat model of Huntington's disease.

The A2A adenosine receptor (A2AR) is widely distributed on different cellular types in the brain, where it exerts a broad spectrum of pathophysiological functions, and for which a role in different neurodegenerative diseases has been hypothesized or demonstrated. To investigate the role of neuronal A2ARs in neurodegeneration, we evaluated in vitro and in vivo the effect of the neurotoxin 3-nitropropionic acid (3-NP) in a transgenic rat strain overexpressing A2ARs under the control of the neural-specific enolase promoter (NSEA2A rats). We recorded extracellular field potentials (FP) in corticostriatal slice and found that the synaptotoxic effect of 3-NP was significantly reduced in NSEA2A rats compared with wild-type animals (WT). In addition, after exposing corticostriatal slices to 3-NP 10 mM for 2 h, we found that striatal cell viability was significantly higher in NSEA2A rats compared to control rats. These in vitro results were confirmed by in vivo experiments: daily treatment of female rats with 3-NP 10 mg/kg for 8 days induced a selective bilateral lesion in the striatum, which was significantly reduced in NSEA2A compared to WT rats. These results demonstrate that the overexpression of the A2AR selectively at the neuronal level reduced 3-NP-induced neurodegeneration, and suggest an important function of the neuronal A2AR in the modulation of neurodegeneration.

The adenosine A2A receptor agonist T1-11 ameliorates neurovisceral symptoms and extends the lifespan of a mouse model of Niemann-Pick type C disease.

Niemann-Pick C is a fatal neurovisceral disorder caused, in 95% of cases, by mutation of NPC1 gene. Therapeutic options are extremely limited and new "druggable" targets are highly warranted. We previously demonstrated that the stimulation of the adenosine A2A receptor (A2AR) normalized the pathological phenotype of cellular models of NPC1. Since the validation of A2ARs as a therapeutic target for NPC1 can be obtained only conducting studies in in vivo models of the disease, in the present paper, the effects of two agonists of A2ARs were evaluated in the mouse model Balb/c Npc1nih, hereafter indicated as NPC1-/-. The agonists CGS21680 (2.5 and 5mg/kg/day by intraperitoneal injection) and T1-11 (50mg/kg/day in drinking water) were administered at a presymptomatic stage of the disease of NPC1-/- mice (PN28 and PN30, respectively); the experimental groups were the following: vehicle-treated WT mice (N=16 for both CGS and T1-11 treatments); vehicle-treated NPC1-/- mice (N=14 for CGS and 12 for T1-11 treatment); CGS-treated NPC1-/- mice (N=7) and T1-11-treated NPC1-/- mice (N=11). The efficacy of the treatments was evaluated by comparing vehicle-treated and CGS or T1-11-treated NPC1-/- mice for their motor deficits (analyzed by both rotarod and footprint tests), hippocampal cognitive impairment (by Novel Object Recognition (NOR) test), cerebellar neurodegeneration (Purkinje neurons counting), and cholesterol and sphingomyelin accumulation in spleen and liver. Finally, the effect of both agonists on survival was evaluated by applying a humane late endpoint (weight loss >30% of peak weight, punched posture and reduced activity in the cage). The results demonstrated that, while CGS21680 only slightly attenuated cognitive deficits, T1-11 ameliorated motor coordination, significantly improved cognitive impairments, increased the survival of Purkinje neurons and reduced sphingomyelin accumulation in the liver. More importantly, it significantly prolonged the lifespan of NPC1-/- mice. In vitro experiments conducted in a neuronal model of NPC1 demonstrated that the ability of T1-11 to normalize cell phenotype was mediated by the selective activation of A2ARs and modulation of intracellular calcium levels. In conclusion, our results fully confirm the validity of A2ARs as a new target for NPC1 treatment. As soon as new ligands with improved pharmacokinetic characteristics (i.e. orally active, with brain bioavailability and metabolic stability) will be obtained, A2AR agonists could represent a breakthrough in the treatment of NPC.

Aberrant self-grooming as early marker of motor dysfunction in a rat model of Huntington's disease.

In the study of neurodegenerative diseases, rodent models provide experimentally accessible systems to study multiple pathogenetic aspects. The identification of early and robust behavioural changes is crucial to monitoring disease progression and testing potential therapeutic strategies in animals. Consistent experimental data support the translational value of rodent self-grooming as index of disturbed motor functions and perseverative behaviour patterns in different rodent models of brain disorders. Huntington's disease (HD) is a progressive neurodegenerative disorder, characterized by severe degeneration of basal ganglia, cognitive and psychiatric impairments and motor abnormalities. In the rat species, intrastriatal injection of the excitotoxin quinolinic acid (QA) mimics some of the neuroanatomical and behavioural changes found in HD, including the loss of GABAergic neurons and the appearance of motor and cognitive deficits. We show here that striatal damage induced by unilateral QA injection in dorsal striatum of rats triggers aberrant grooming behaviour as early as three weeks post-lesion in absence of other motor impairments: specifically, both quantitative (frequency and duration) and qualitative (the sequential pattern of movements) features of self-grooming behaviour were significantly altered in QA-lesioned rats placed in either the elevated plus-maze and the open-field. The consistent abnormalities in self-grooming recorded in two different experimental contexts support the use of this behavioural marker in rodent models of striatal damage such as HD, to assess the potential effects of drug and cell replacement therapy in the early stage of disease.

Fingolimod: A Disease-Modifier Drug in a Mouse Model of Amyotrophic Lateral Sclerosis.

Fingolimod phosphate (FTY720), the first approved oral therapy for multiple sclerosis, primarily acts as an immunomodulator. Its concomitant effects in the central nervous system, however, indicate a potentially broader spectrum of activity in neurodegenerative diseases. In the present study, we investigated the possible effects of fingolimod in a mouse model of amyotrophic lateral sclerosis (ALS), a neurodegenerative disease characterized by a strong neuroinflammatory component. Fingolimod (0.1 and 1 mg/kg i.p.) was administered to mSOD1G93A mice, a well-characterized mouse model of ALS, starting from the onset of motor symptoms to the end stage of the disease. The drug was able to improve the neurological phenotype (p < 0.05) and to extend the survival (p < 0.01) of ALS mice. The beneficial effect of fingolimod administration was associated with a significant modulation of neuroinflammatory and protective genes (CD11b, Foxp3, iNOS, Il1ß, Il10, Arg1, and Bdnf) in motor cortex and spinal cord of animals. Our data show, for the first time, that fingolimod is protective in ALS mice and that its beneficial effects are accompanied by a modulation of microglial activation and innate immunity. Considering that the treatment was started in already symptomatic mice, our data strongly support fingolimod as a potential new therapeutic approach to ALS.

Striatal adenosine-cannabinoid receptor interactions in rats over-expressing adenosine A2A receptors.

Adenosine A2A receptors (A2 A Rs) and cannabinoid CB1 receptors (CB1 Rs) are highly expressed in the striatum, where they functionally interact and form A2A /CB1 heteroreceptor complexes. We investigated the effects of CB1 R stimulation in a transgenic rat strain over-expressing A2 A Rs under the control of the neural-specific enolase promoter (NSEA2A rats) and in age-matched wild-type (WT) animals. The effects of the CB1 R agonist WIN 55,212-2 (WIN) were significantly lower in NSEA2A rats than in WT animals, as demonstrated by i) electrophysiological recordings of synaptic transmission in corticostriatal slices; ii) the measurement of glutamate outflow from striatal synaptosomes and iii) in vivo experiments on locomotor activity. Moreover, while the effects of WIN were modulated by both A2 A R agonist (CGS 21680) and antagonists (ZM 241385, KW-6002 and SCH-442416) in WT animals, the A2 A R antagonists failed to influence WIN-mediated effects in NSEA2A rats. The present results demonstrate that in rats with genetic neuronal over-expression of A2 A Rs, the effects mediated by CB1 R activation in the striatum are significantly reduced, suggesting a change in the stoichiometry of A2A and CB1 receptors and providing a strategy to dissect the involvement of A2 A R forming or not forming heteromers in the modulation of striatal functions. These findings add additional evidence for the existence of an interaction between striatal A2 A Rs and CB1 Rs, playing a fundamental role in the regulation of striatal functions. We studied A2A -CB1 receptor interaction in transgenic rats over-expressing adenosine A2A receptors under the control of the neuron-specific enolase promoter (NSEA2A ). In these rats, we demonstrated a reduced effect of the CB1 receptor agonist WIN 55,212-2 in the modulation of corticostriatal synaptic transmission and locomotor activity, while CB1 receptor expression level did not change with respect to WT rats. A reduction in the expression of A2A -CB1 receptor heteromers is postulated.

Effects of chronic caffeine intake in a mouse model of amyotrophic lateral sclerosis.

Caffeine is a nonselective adenosine receptor antagonist; chronic consumption has proved protective toward neurodegenerative diseases such as Parkinson's and Alzheimer's diseases. The present study was designed to determine whether caffeine intake affected survival and/or motor performance in a transgenic model of amyotrophic lateral sclerosis (ALS). SOD1(G93A) mice received caffeine through drinking water from 70 days of age until death. Body weight, motor performance and survival were evaluated. Furthermore, the expression of adenosine A(2A) receptors (A(2A) Rs), glial glutamate transporter (GLT1), and glial fibrillar acidic protein (GFAP) were evaluated by Western blotting. The results showed that caffeine intake significantly shortened the survival of SOD1(G93A) mice (log rank test, P = 0.01) and induced a nonsignificant advancing of disease onset. The expression of A(2A) R, GLT1, and GFAP was altered in the spinal cords of ALS mice, but caffeine did not influence their expression in either wild-type or SOD1(G93) mice. These data indicate that adenosine receptors may play an important role in ALS.

Influence of CGS 21680, a selective adenosine A(2A) receptor agonist, on NMDA receptor function and expression in the brain of Huntington's disease mice.

The effect of chronic treatment with the selective adenosine A(2A) receptor agonist CGS 21680 on N-Methyl-d-Aspartate (NMDA) receptor function and expression has been studied in the striatum and cortex of R6/2 mice, a genetic mouse model of Huntington's disease (HD). Starting from 8weeks of age, R6/2 and wild type (WT) mice were treated daily with CGS 21680 (0.5mg/kg i.p.) for 3weeks and the expression levels of NMDA receptor subunits were then evaluated. In addition, to study CGS 21680-induced changes in NMDA receptor function, NMDA-induced toxicity in corticostriatal slices from both R6/2 and WT mice was investigated. We found that CGS 21680 increased NR2A subunit expression and the NR2A/NR2B ratio in the cortex of R6/2 mice, having no effect in WT mice. In the striatum, CGS 21680 reduced NR1 expression in both R6/2 and WT mice while the effect on NR2A and NR2/NR2B expression was genotype-dependent, reducing and increasing their expression in WT and R6/2 mice, respectively. On the contrary, NMDA-induced toxicity in corticostriatal slices was not modified by the treatment in WT or HD mice. These results demonstrate that in vivo activation of A(2A) receptors modulates the subunit composition of NMDA receptors in the brain of HD mice.

Striatal 6-OHDA lesion in mice: Investigating early neurochemical changes underlying Parkinson's disease.

Early phases of Parkinson's disease (PD) are characterized by a mild reduction of dopamine (DA) in striatum and by emergence of psychiatric disturbances that precede overt motor symptoms. In order to characterize the neurochemical re-arrangements induced by such striatal impairment, we used a mouse model in which a low dose of 6-hydroxydopamine (6-OHDA) was bilaterally injected into the dorsal striatum. These mice showed a DA reduction of about 40% that remained stable up to 12 weeks after injection. This reduction was accompanied by changes in DA metabolite levels, such as HVA, transiently reduced at 4 weeks, and DOPAC, decreased at 12 weeks. No change in the 5-hydroxytryptamine (5-HT) levels was found but the 5-hydroxyindoleacetic acid (5-HIAA)/5-HT ratio was increased at 4 weeks. In addition, at the same time-point, the levels of 15-F(2t)-IsoP, an index of oxidative stress, and of PGE(2), a major product of cyclooxygenase-2, were decreased in different brain areas while BDNF levels were increased. These neurochemical changes were accompanied by altered behavioral responses concerning the emotional reactivity. Overall, the present findings suggest that a change of 5-HT metabolism and a modification of oxidative stress levels may play a role in the early PD degeneration phases.

Remodeling of striatal NMDA receptors by chronic A(2A) receptor blockade in Huntington's disease mice.

Excitotoxicity plays a major role in the pathogenesis of Huntington disease (HD), a fatal neurodegenerative disorder. Adenosine A(2A) receptors (A(2A)Rs) modulate excitotoxicity and have been suggested to play a pathogenetic role in HD. The main aim of this study was to evaluate the effect of A(2A)R blockade on the expression and functions of NMDA receptors in the striatum of HD mice (R6/2). We found that 3 weeks' treatment with SCH 58261 (0.01 mg/kg/day i.p. from the 8th week of age) modified NR1 and NR2A/NR2B expression in the striatum of R6/2 (Western blotting) while had no effect on NMDA-induced toxicity in corticostriatal slices (electrophysiological experiments). In conclusion, in vivo A(2A)R blockade induced a remodeling of NMDA receptors in the striatum of HD mice. Even though the functional relevance of the above effect remains to be fully elucidated, these results add further evidence to the modulatory role of A(2A)Rs in HD.

A role for oxidized DNA precursors in Huntington's disease-like striatal neurodegeneration.

Several human neurodegenerative disorders are characterized by the accumulation of 8-oxo-7,8-dihydroguanine (8-oxodG) in the DNA of affected neurons. This can occur either through direct oxidation of DNA guanine or via incorporation of the oxidized nucleotide during replication. Hydrolases that degrade oxidized purine nucleoside triphosphates normally minimize this incorporation. hMTH1 is the major human hydrolase. It degrades both 8-oxodGTP and 8-oxoGTP to the corresponding monophosphates. To investigate whether the incorporation of oxidized nucleic acid precursors contributes to neurodegeneration, we constructed a transgenic mouse in which the human hMTH1 8-oxodGTPase is expressed. hMTH1 expression protected embryonic fibroblasts and mouse tissues against the effects of oxidants. Wild-type mice exposed to 3-nitropropionic acid develop neuropathological and behavioural symptoms that resemble those of Huntington's disease. hMTH1 transgene expression conferred a dramatic protection against these Huntington's disease-like symptoms, including weight loss, dystonia and gait abnormalities, striatal degeneration, and death. In a complementary approach, an in vitro genetic model for Huntington's disease was also used. hMTH1 expression protected progenitor striatal cells containing an expanded CAG repeat of the huntingtin gene from toxicity associated with expression of the mutant huntingtin. The findings implicate oxidized nucleic acid precursors in the neuropathological features of Huntington's disease and identify the utilization of oxidized nucleoside triphosphates by striatal cells as a significant contributor to the pathogenesis of this disorder.

Nonmotor symptoms in Parkinson's disease: investigating early-phase onset of behavioral dysfunction in the 6-hydroxydopamine-lesioned rat model.

To investigate the psychiatric symptoms accompanying the early phases of Parkinson's disease (PD), we injected adult rats with 10.5 microg 6-hydroxydopamine (6-OHDA) bilaterally into the dorsal striatum. The resulting neurodegeneration led, 12 weeks after injection, to a mild (36%) reduction of striatal dopamine. We tested the behavioral response of sham and 6-OHDA-lesioned animals at different time points after injection to evaluate the onset and progression of behavioral abnormalities. The results showed that such a mild reduction of dopamine levels was associated with a decrease in anxiety-like behavior, an increase in "depression"-like behavior, and a marked change in social behavior. Learning and memory abilities were not affected. Overall, the PD rat model used here displays behavioral alterations having face validity with psychiatric symptoms of the pathology and thus appears to be a valuable tool for investigating the neural bases of the early phases of PD.

Behavioural and neurochemical characterization of the adenosine A2A receptor antagonist ST1535.

ST1535 (2-butyl-9-methyl-8-(2H-1,2,3-triazol 2-yl)-9 H-purin-6-ylamine) is a novel compound showing a preferential adenosine A(2A) receptor antagonist profile. To explore the potential neuroprotective profile of this compound, we evaluated whether ST1535 prevented quinolinic acid (QA)-induced glutamate outflow in the rat striatum (a reliable index of neuroprotective activity in vivo). Microdialysis experiments were performed in naive Wistar rats. In these experiments, a behaviourally active and inactive doses of ST1535 were used. Both doses significantly prevented QA-induced glutamate outflow in the striatum. These results show that ST1535 protects towards striatal excitotoxicity, even though its reduced A(2A)/A(1) selectivity might limit its actual neuroprotective potential.

Neuroprotective effects of thymosin beta4 in experimental models of excitotoxicity.

The aim of this study was to evaluate the possible neuroprotective effects of thymosin beta(4) in different models of excitotoxicity. The application of thymosin beta(4) significantly attenuated glutamate-induced toxicity both in primary cultures of cortical neurons and in rat hippocampal slices. In in vivo experiments, the intracerebroventricular administration of thymosin beta(4) significantly reduced hippocampal neuronal loss induced by kainic acid. These results show that thymosin beta(4) induced a protective effect in models of excitotoxicity. The mechanisms underlying such an effect, as well as the real neuroprotective potential of thymosin beta(4), are worthy of further investigations.

Effects of the adenosine A2A receptor antagonist SCH 58621 on cyclooxygenase-2 expression, glial activation, and brain-derived neurotrophic factor availability in a rat model of striatal neurodegeneration.

Inhibition of adenosine A2A receptors (A2ARs) is neuroprotective in several experimental models of striatal diseases. However, the mechanisms elicited by A2AR blockade are only partially known, and critical aspects about the potential beneficial effects of A2AR antagonism in models of neurodegeneration still await elucidation. In the present study, we analyzed the influence of the selective A2AR antagonist SCH 58261 in a rat model of striatal excitotoxicity obtained by unilateral intrastriatal injection of quinolinic acid (QA). We found that SCH 58261 differently affected the expression of cyclooxygenase-2 (COX-2) induced by QA in cortex and striatum. The antagonist enhanced COX-2 expression in cortical neurons and prevented it in striatal microglia-like cells. Similarly, SCH 58261 differently regulated astrogliosis and microglial activation in the 2 brain regions. In addition, the A2AR antagonist prevented the QA-induced increase in striatal brain-derived neurotrophic factor levels. Because COX-2 activity has been linked to excitotoxic processes and because brain-derived neurotrophic factor depletion has been observed in mouse models as well as in patients with Huntington disease, we suggest that the final outcome of A2AR blockade (namely neuroprotection vs neurodegeneration) is likely to depend on the balance among its various and region-specific effects.

Adenosine A2A receptor blockade before striatal excitotoxic lesions prevents long term behavioural disturbances in the quinolinic rat model of Huntington's disease.

Huntington's disease (HD) is a progressive neurodegenerative disorder, characterised by severe degeneration of basal ganglia, motor abnormalities, impaired cognitive function and emotional disturbances. Many of the distinct neuropathological features of HD are reproduced in rats by intrastriatal injections of the excitotoxin quinolinic acid (QA), and QA-induced excitotoxicity is partially prevented by administration of the A(2A) receptor antagonist prior to the QA injection. In this study, we assessed the neuroprotective effects of the adenosine A(2A) receptor antagonist SCH 58261 on the progressive behavioural alterations reported in the QA rat model of Huntington's disease. Male rats received i.p. SCH 58261 (0.01mg/kg) or vehicle 20min before a bilateral injection of quinolinic acid (QA, 300nmol/1mul) or its vehicle in the dorsal striatum. Motor activity and anxiety levels were analyzed in an open-field arena and in an elevated plus-maze at 2 weeks, 2 months and 6 months post-lesion. In QA-lesioned rats SCH 58261 prevented alterations of wall rearing behaviour starting from 2 weeks post-lesion while emotional changes (reduced anxiety) were back to control levels by 6 months post-lesion. These findings extend to the behavioural parameters the protective effects of SCH 58261 in the QA model of Huntington's disease.

Quinolinic acid modulates the activity of src family kinases in rat striatum: in vivo and in vitro studies.

Quinolinic acid (QA) has been shown to evoke neurotoxic events via NMDA receptor (NMDAR) overactivation and oxidative stress. NMDARs are particularly vulnerable to free radicals, which can modulate protein tyrosine kinase (PTK) and phosphotyrosine phosphatase (PTP) activities. The src family of tyrosine kinases are associated with the NMDAR complex and regulate NMDA channel function. Because QA is an NMDAR agonist as well as a pro-oxidant agent, we investigated whether it may affect the activity of PTKs and PTPs in vivo and in vitro. In synaptosomes prepared from striata dissected 15 min, 30 min or 15 days after bilateral injection of QA we observed modulation of the phosphotyrosine pattern; a significant decrease in PTP activity; and a sustained increase in c-src and lyn activity at 15 and 30 min after treatment with QA, followed by a decrease 2 weeks later. Striatal synaptosomes treated in vitro with QA showed time- and dose-dependent modulation of c-src and lyn kinase activities. Moreover, the nitric oxide synthase inhibitor NG-nitro-L-arginine-methyl ester, the NMDAR antagonist d-2-amino-5-phosphonovaleric acid and pyruvate suppressed the QA-induced modulation of c-src activity. These findings suggest a novel feature of QA in regulating src kinase activity through the formation of reactive radical species and/or NMDAR overactivation.