Quinolinic Acid Administration Research Articles

Exploring the neuroprotective effects of montelukast on brain inflammation and metabolism in a rat model of quinolinic acid-induced striatal neurotoxicity

BackgroundOne intrastriatal administration of quinolinic acid (QA) in rats induces a lesion with features resembling those observed in Huntington’s disease. Our aim is to evaluate the effects of the cysteinyl leukotriene receptor antagonist montelukast (MLK), which exhibited neuroprotection in different preclinical models of neurodegeneration, on QA-induced neuroinflammation and regional metabolic functions.MethodsThe right and left striatum of Sprague Dawley and athymic nude rats were injected with QA and vehicle (VEH), respectively. Starting from the day before QA injection, animals were treated with 1 or 10 mg/kg of MLK or VEH for 14 days. At 14 and 30 days post-lesion, animals were monitored with magnetic resonance imaging (MRI) and positron emission tomography (PET) using [18F]-VC701, a translocator protein (TSPO)-specific radiotracer. Striatal neuroinflammatory response was measured post-mortem in rats treated with 1 mg/kg of MLK by immunofluorescence. Rats treated with 10 mg/kg of MLK also underwent a [18F]-FDG PET study at baseline and 4 months after lesion. [18F]-FDG PET data were then used to assess metabolic connectivity between brain regions by applying a covariance analysis method.ResultsMLK treatment was not able to reduce the QA-induced increase in striatal TSPO PET signal and MRI lesion volume, where we only detected a trend towards reduction in animals treated with 10 mg/kg of MLK. Post-mortem immunofluorescence analysis revealed that MLK attenuated the increase in striatal markers of astrogliosis and activated microglia in the lesioned hemisphere. We also found a significant increase in a marker of anti-inflammatory activity (MannR) and a trend towards reduction in a marker of pro-inflammatory activity (iNOS) in the lesioned striatum of MLK—compared to VEH-treated rats. [18F]-FDG uptake was significantly reduced in the striatum and ipsilesional cortical regions of VEH-treated rats at 4 months after lesion. MLK administration preserved glucose metabolism in these cortical regions, but not in the striatum. Finally, MLK was able to counteract changes in metabolic connectivity and measures of network topology induced by QA, in both lesioned and non-lesioned hemispheres.ConclusionsOverall, MLK treatment produced a significant neuroprotective effect by reducing neuroinflammation assessed by immunofluorescence and preserving regional brain metabolism and metabolic connectivity from QA-induced neurotoxicity in cortical and subcortical regions.

Plumbagin Alleviates Intracerebroventricular-Quinolinic Acid Induced Depression-like Behavior and Memory Deficits in Wistar Rats.

Plumbagin, a hydroxy-1,4-naphthoquinone, confers neuroprotection via antioxidant and anti-inflammatory properties. The present study aimed to assess the effect of plumbagin on behavioral and memory deficits induced by intrahippocampal administration of Quinolinic acid (QA) in male Wistar rats and reveal the associated mechanisms. QA (300 nM/4 μL in Normal saline) was administered i.c.v. in the hippocampus. QA administration caused depression-like behavior (forced swim test and tail suspension tests), anxiety-like behavior (open field test and elevated plus maze), and elevated anhedonia behavior (sucrose preference test). Furthermore, oxidative–nitrosative stress (increased nitrite content and lipid peroxidation with reduction of GSH), inflammation (increased IL-1β), cholinergic dysfunction, and mitochondrial complex (I, II, and IV) dysfunction were observed in the hippocampus region of QA-treated rats as compared to normal controls. Plumbagin (10 and 20 mg/kg; p.o.) treatment for 21 days significantly ameliorated behavioral and memory deficits in QA-administered rats. Moreover, plumbagin treatment restored the GSH level and reduced the MDA and nitrite level in the hippocampus. Furthermore, QA-induced cholinergic dysfunction and mitochondrial impairment were found to be ameliorated by plumbagin treatment. In conclusion, our results suggested that plumbagin offers a neuroprotective potential that could serve as a promising pharmacological approach to mitigate neurobehavioral changes associated with neurodegeneration.

Mast cells and histamine are involved in the neuronal damage observed in a quinolinic acid-induced model of Huntington's disease.

Huntington´s disease (HD) is a pathological condition that can be studied in mice by the administration of quinolinic acid (QUIN), an agonist of the N-methyl-d-aspartate receptor (NMDAR) that induces NMDAR-mediated cytotoxicity and neuroinflammation. Mast cells (MCs) participate in numerous inflammatory processes through the release of important amounts of histamine (HA). In this study, we aimed to characterize the participation of MCs and HA in the establishment of neural and oxidative damage in the QUIN-induced model of HD. C57BL6/J mice (WT), MC-deficient c-KitW-sh/W-sh (Wsh) mice and Wsh mice reconstituted by intracerebroventricular (i.c.v.) injection of 5×105 bone marrow-derived mast cells (BMMCs), or i.c.v. administered with HA (5µg) were used. All groups of animals were intrastriatally injected with 1µL QUIN (30nmol/µL) and 3days later, apomorphine-induced circling behavior, striatal GABA levels and the number of Fluoro-Jade positive cells, as indicators of neuronal damage, were determined. Also, lipid peroxidation (LP) and reactive oxygen species production (ROS), as markers of oxidative damage, were analyzed. Wsh mice showed less QUIN-induced neuronal and oxidative damage than WT and Wsh-MC reconstituted animals. Histamine administration restored the QUIN-induced neuronal and oxidative damage in the non-reconstituted Wsh mice to levels equivalent or superior to those observed in WT mice. Our results demonstrate that MCs and HA participate in the neuronal and oxidative damages observed in mice subjected to the QUIN -induced model of Huntington's disease.

The CNS-penetrant soluble guanylate cyclase stimulator CYR119 attenuates markers of inflammation in the central nervous system

BackgroundInflammation in the central nervous system (CNS) is observed in many neurological disorders. Nitric oxide-soluble guanylate cyclase-cyclic guanosine monophosphate (NO–sGC–cGMP) signaling plays an essential role in modulating neuroinflammation. CYR119 is a CNS-penetrant sGC stimulator that amplifies endogenous NO–sGC–cGMP signaling. We evaluated target engagement and the effects of CYR119 on markers of neuroinflammation in vitro in mouse microglial cells and in vivo in quinolinic acid (QA)-induced and high-fat diet-induced rodent neuroinflammation models.MethodsTarget engagement was verified in human embryonic kidney (HEK) cells, rat primary neurons, mouse SIM-A9 cells, and in rats by measuring changes in cGMP and downstream targets of sGC signaling [phosphorylated vasodilator-stimulated phosphoprotein (pVASP), phosphorylated cAMP-response element binding (pCREB)]. In SIM-A9 cells stimulated with lipopolysaccharides (LPS), markers of inflammation were measured when cells were treated with or without CYR119. In rats, microinjections of QA and vehicle were administered into the right and left hemispheres of striatum, respectively, and then rats were dosed daily with either CYR119 (10 mg/kg) or vehicle for 7 days. The activation of microglia [ionized calcium binding adaptor molecule 1 (Iba1)] and astrocytes [glial fibrillary acidic protein (GFAP)] was measured by immunohistochemistry. Diet-induced obese (DIO) mice were treated daily with CYR119 (10 mg/kg) for 6 weeks, after which inflammatory genetic markers were analyzed in the prefrontal cortex.ResultsIn vitro, CYR119 synergized with exogenous NO to increase the production of cGMP in HEK cells and in primary rat neuronal cell cultures. In primary neurons, CYR119 stimulated sGC, resulting in accumulation of cGMP and phosphorylation of CREB, likely through the activation of protein kinase G (PKG). CYR119 attenuated LPS-induced elevation of interleukin 6 (IL-6) and tumor necrosis factor (TNF) in mouse microglial cells. Following oral dosing in rats, CYR119 crossed the blood–brain barrier (BBB) and stimulated an increase in cGMP levels in the cerebral spinal fluid (CSF). In addition, levels of proinflammatory markers associated with QA administration or high-fat diet feeding were lower in rodents treated with CYR119 than in those treated with vehicle.ConclusionsThese data suggest that sGC stimulation could provide neuroprotective effects by attenuating inflammatory responses in nonclinical models of neuroinflammation.

Intrastriatal Quinolinic Acid Administration Impairs Redox Homeostasis and Induces Inflammatory Changes: Prevention by Kynurenic Acid

Kynurenic acid (KYNA) and quinolinic acid (QUIN) are metabolites formed in the degradation of tryptophan (Trp). QUIN is a selective NMDA receptor antagonist and may exert neurotoxic effects, whereas KYNA is an agonist of glutamatergic and cholinergic receptors and presents antioxidant properties. KYNA/QUIN ratio is decreased in several central nervous system disorders, but the mechanisms involved are not well elucidated. In the present study, we try to determine the neuroprotective capacity of KYNA on the QUIN effects in redox homeostasis changes (H2DCF oxidation, superoxide dismutase/catalase (SOD/CAT) ratio, glutathione peroxidase (GPx) activity, sulfhydryl content, and nitrite levels), as well as on inflammatory parameters (levels of TNF-α, IL-1β, and IL-6). KYNA and QUIN effects on the activities of Na+,K+-ATPase and acetylcholinesterase (AChE) were also evaluated. Thirty-day-old male Wistar rats underwent stereotactic surgery and received intrastriatal injections as follows: group 1-control (PBS-injected), group 2-KYNA (100μM), group 3-QUIN (150nM), and group 4-KYNA + QUIN (KYNA-injected followed QUIN-injected). Results demonstrated that the KYNA administration was able to prevent the increase in reactive oxygen species, SOD/CAT ratio, and pro-inflammatory cytokines (IL-1β and IL-6) and the decrease in GPx activity, sulfhydryl content, and nitrite levels caused by QUIN. KYNA was also able to partially prevent the decrease in Na+,K+-ATPase activity and the increase in AChE activity caused by QUIN. This study may help in the elucidation of neuroprotective effects of KYNA against oxidative and inflammatory insults caused by QUIN in the striatum of young male Wistar rats.

Mangiferin ameliorates intracerebroventricular-quinolinic acid-induced cognitive deficits, oxidative stress, and neuroinflammation in Wistar rats.

INTRODUCTION:Mangiferin (MGF), a xanthonoid polyphenol, confers neuroprotection via combating oxidative stress and inflammation. The current investigation aimed to assess the neuroprotective potential of MGF on behavioral and neurochemical anomalies evoked by administration of quinolinic acid (QA) through intrastriatal injection in male Wistar rats and to reveal the associated mechanisms.MATERIALS AND METHODS:QA (300 nm/4 μl saline) was administered intracerebroventricular in the striatum (unilaterally) once. Thereafter, MGF 20 and 40 mg/kg (peroral) was administered to the animals for 21 days.RESULTS:QA administration caused marked alteration in motor activity (rotatod), footprint analysis, and cognitive function (Morris water maze test, and novel object recognition test). Furthermore, oxido-nitrosative stress (increased nitrite content, lipid peroxidation, with reduction of GSH), cholinergic dysfunction, and mitochondrial complex (I, II, and IV) dysfunction were observed in hippocampus and striatal region of QA-treated rats in comparison to normal control. Pro inflammatory mediators (tumor necrosis factor-alpha TNF-α and interleukin-1β) were noted to increase in the hippocampus and striatum of QA-treated rats. In addition, we observed BDNF depletion in both the hippocampus and striatum of QA-treated animals. MGF treatment significantly ameliorated memory and motor deficits in QA-administered rats. Moreover, MGF treatment (40 mg/kg) restored the GSH level and reduced the MDA, nitrite level, and pro-inflammatory cytokines in striatum and hippocampus. Furthermore, QA-induced cholinergic dysfunction (AChE), BDNF depletion and mitochondrial impairment were found to be ameliorated by MGF treatment.CONCLUSION:The results suggest that MGF offers the neuroprotective potential that may be a promising pharmacological approach to ameliorate cognitive deficits associated with neurodegeneration.

Adenosine and NMDA Receptors Modulate Neuroprotection-Induced NMDA Preconditioning in Mice.

The severity score of quinolinic acid (QA)-induced seizures was investigated after N-methyl-D-aspartate (NMDA) preconditioning associated with adenosine receptors. Also, the levels of adenosine A1 and A2A receptors and subunits of NMDA receptors in the hippocampi of mice were determined to define components of the resistance mechanism. Adult CF-1 mice were treated intraperitoneally with saline or NMDA (75mg/kg), and some mice were treated intracerebroventricularly (i.c.v.) with 0.1pmol of adenosine receptor antagonists 8-cyclopentyltheophylline (CPT; receptor A1) or ZM241385 (receptor A2A) 0, 1, or 6h after NMDA administration. These adenosine receptor antagonists were administered to block NMDA's protective effect. Seizures and their severity scores were evaluated during convulsions induced by QA (36.8nmol) that was administered i.c.v. 24h after NMDA. The cell viability and content of subunits of the NMDA receptors were analyzed 24h after QA administration. NMDA preconditioning reduced the maximal severity 6 displayed in QA-administered mice, inducing protection in 47.6% of mice after QA-induced seizures. CPT increased the latency of seizures when administered 0 or 6h, and ZM241385 generated the same effect when administered 6h after NMDA administration. The GluN1 content was lower in the hippocampi of the QA mice and the NMDA-preconditioned animals without seizures. GluN2A content was unaltered in all groups. The results demonstrated the components of resistance evoked by NMDA, in which adenosine receptors participate in a time-dependent mode. Similarly, the reduction on GluN1 expression in the hippocampus may contribute to this effect during the preconditioning period.

Role of Phosphatidylinositol-3 Kinase Pathway in NMDA Preconditioning: Different Mechanisms for Seizures and Hippocampal Neuronal Degeneration Induced by Quinolinic Acid

N-methyl D-aspartate (NMDA) preconditioning is evoked by the administration of a subtoxic dose of NMDA and is protective against neuronal excitotoxicity. This effect may involve a diversity of targets and cell signaling cascades associated to neuroprotection. Phosphatidylinositol-3 kinase/protein kinase B (PI3K/Akt) and mitogen-activated protein kinases (MAPKs) such as extracellular regulated protein kinase 1/2 (ERK1/2) and p38MAPK pathways play a major role in neuroprotective mechanisms. However, their involvement in NMDA preconditioning was not yet fully investigated. The present study aimed to evaluate the effect of NMDA preconditioning on PI3K/Akt, ERK1/2, and p38MAPK pathways in the hippocampus of mice and characterize the involvement of PI3K on NMDA preconditioning-evoked prevention of seizures and hippocampal cell damage induced by quinolinic acid (QA). Thus, mice received wortmannin (a PI3K inhibitor) and 15min later a subconvulsant dose of NMDA (preconditioning) or saline. After 24h of this treatment, an intracerebroventricular QA infusion was administered. Phosphorylation levels and total content of Akt, glycogen synthase protein kinase-3β (GSK-3β), ERK1/2, and p38MAPK were not altered after 24h of NMDA preconditioning with or without wortmmanin pretreatment. Moreover, after QA administration, behavioral seizures, hippocampal neuronal degeneration, and Akt activation were evaluated. Inhibition of PI3K pathway was effective in abolishing the protective effect of NMDA preconditioning against QA-induced seizures, but did not modify neuronal protection promoted by preconditioning as evaluated by Fluoro-Jade B staining. The study confirms that PI3K participates in the mechanism of protection induced by NMDA preconditioning against QA-induced seizures. Conversely, NMDA preconditioning-evoked protection against neuronal degeneration is not altered by PI3K signaling pathway inhibition. These results point to differential mechanisms regarding protection against a behavioral and cellular manifestation of neural damage.

Bilateral quinolinic acid-induced lipid peroxidation, decreased striatal monoamine levels and neurobehavioral deficits are ameliorated by GIP receptor agonist D-Ala2GIP in rat model of Huntington's disease

Huntington's disease (HD) is an inherited complex progressive neurodegenerative disorder with an established etiopathology linked to neuronal oxidative stress and corticostriatal excitotoxicity. Present study explores the effects of glucose-dependent insulinotropic polypeptide (GIP) receptor agonist on the neurobehavioral sequelae of quinolinic acid-induced phenotype of Huntington's disease in rats. Bilateral administration of quinolinic acid (300 nmol/4 μl) to the rat striatum led to characteristic deficits in, locomotor activity, motor coordination, neuromuscular coordination and short-term episodic memory. Therapeutic treatment for 14 days with a stable and brain penetrating GIP receptor agonist, D-Ala2GIP (100 nmol/kg, i.p.), attenuated the neurobehavioral deficits due to quinolinic acid (QA) administration. Protective actions of D-Ala2GIP were sensitive to blockade with a GIP receptor antagonist, (Pro3)GIP (50 nmol/kg, i.p.), indicating specific involvement of GIP receptor signaling pathway. Stimulation of GIP receptor with D-Ala2GIP attenuated lipid peroxidation, evidenced by reduced levels of brain malondialdehyde (MDA), and restoration of reduced glutathione (GSH) levels in brain. Quinolinic acid administration led to significant loss of striatal monoamines, e.g., norepinephrine, epinephrine, serotonin, dopamine, and metabolites, 3,4-Dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-Hydroxyindoleacetic acid (5-HIAA). D-Ala2GIP attenuated the QA-induced depletion of striatal monoamines, without affecting the monoamine degradation pathways. Thus, observed effects with D-Ala2GIP in the QA-induced Huntington's disease model could be attributable to reduction in lipid peroxidation, restoration of endogenous antioxidants and decreased striatal monoamine levels. These findings together suggest that stimulation of GIP receptor signaling pathway in brain could be a potential therapeutic strategy in the symptomatic management of Huntington's disease.

Induction of Neuroinflammatory Response and Histopathological Alterations Caused by Quinolinic Acid Administration in the Striatum of Glutaryl-CoA Dehydrogenase Deficient Mice.

Glutaric acidemia type I (GA I) is an inherited neurometabolic disorder caused by a severe deficiency of the mitochondrial glutaryl-CoA dehydrogenase (GCDH) activity. Patients usually present progressive cortical leukodystrophy and commonly develop acute bilateral striatal degeneration mainly during infections that markedly worse their prognosis. A role for quinolinic acid (QA), a key metabolite of the kynurenine pathway, which is activated during inflammatory processes, on the pathogenesis of the acute striatum degeneration occurring in GA I was proposed but so far has not yet been evaluated. Therefore, we investigated whether an acute intrastriatal administration of quinolinic acid (QA) could induce histopathological alterations in the striatum of 30-day-old wild-type (WT) and GCDH knockout (Gcdh-/-) mice. Striatum morphology was evaluated by hematoxylin and eosin, T lymphocyte presence (CD3), and glial activation (GFAP and S100β) by immunohistochemistry and 3-nitrotyrosine (YNO2) by immunofluorescence. QA provoked extensive vacuolation, edema, and especially lymphocyte infiltration in the striatum of Gcdh-/-. QA also enhanced CD3 staining and the number of YNO2 positive cells in Gcdh-/- mice, relatively to WT, indicating T lymphocyte infiltration and nitrosative stress, respectively. QA-treated WT mice also showed an increase of GFAP and S100β staining, which is indicative of reactive astrogliosis, whereas the levels of these astrocytic proteins were not changed in Gcdh-/- QA-injected mice. The present data indicate that QA significantly contributes to the histopathological changes observed in the striatum of Gcdh-/- mice.

Neuroprotective effects of intrastriatal injection of rapamycin in a mouse model of excitotoxicity induced by quinolinic acid

BackgroundThe mammalian target of rapamycin (mTOR) is a kinase involved in a variety of physiological and pathological functions. However, the exact role of mTOR in excitotoxicity is poorly understood. Here, we investigated the effects of mTOR inhibition with rapamycin against neurodegeneration, and motor impairment, as well as inflammatory profile caused by an excitotoxic stimulus.MethodsA single and unilateral striatal injection of quinolinic acid (QA) was used to induce excitotoxicity in mice. Rapamycin (250 nL of 0.2, 2, or 20 μM; intrastriatal route) was administered 15 min before QA injection. Forty-eight hours after QA administration, rotarod test was performed to evaluate motor coordination and balance. Fluoro-Jade C, Iba-1, and GFAP staining were used to evaluate neuronal cell death, microglia morphology, and astrocytes density, respectively, at this time point. Levels of cytokines and neurotrophic factors were measured by ELISA and Cytometric Bead Array 8 h after QA injection. Striatal synaptosomes were used to evaluate the release of glutamate.ResultsWe first demonstrated that rapamycin prevented the motor impairment induced by QA. Moreover, mTOR inhibition also reduced the neurodegeneration and the production of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α induced by excitotoxic stimulus. The lowest dose of rapamycin also increased the production of IL-10 and prevented the reduction of astrocyte density induced by QA. By using an in vitro approach, we demonstrated that rapamycin differently alters the release of glutamate from striatal synaptosomes induced by QA, reducing or enhancing the release of this neurotransmitter at low or high concentrations, respectively.ConclusionTaken together, these data demonstrated a protective effect of rapamycin against an excitotoxic stimulus. Therefore, this study provides new evidence of the detrimental role of mTOR in neurodegeneration, which might represent an important target for the treatment of neurodegenerative diseases.

Absence of aryl hydrocarbon receptors increases endogenous kynurenic acid levels and protects mouse brain against excitotoxic insult and oxidative stress.

L-kynurenine (Kyn) is a key element of tryptophan metabolism; it is enzymatically converted by kynurenine aminotransferase II (KAT II) to kynurenic acid (KYNA), which acts as an antagonist to the NMDA receptor-glycine site. Kyn is also an endogenous ligand of the aryl hydrocarbon receptor (AhR), a transcription factor that regulates the expression of a diverse set of genes. KYNA levels are reduced in several regions of the brain of Huntington's disease (HD) patients. The present work uses an AhR-null mouse and age-matched wild-type mice to determine the effect of the absence of AhR on KYNA availability. We found that, in AhR-null mice, there is an increase of KYNA levels in specific brain areas associated with higher expression of KAT II. Moreover, we induced an excitotoxic insult by intrastriatal administration of quinolinic acid, a biochemical model of HD, in both AhR-null and wild-type mice to evaluate the neurological damage as well as the oxidative stress caused by the lesion. The present work demonstrates that, in specific brain regions of AhR-null mice, the levels of KYNA are increased and that this induces a neuroprotective effect against neurotoxic insults. Moreover, AhR-null mice also show improved motor performance in the rotarod test, indicating a constitutive protection of striatal tissue.

Improvement of mitochondrial NAD+/FAD+-linked state-3 respiration by caffeine attenuates quinolinic acid induced motor impairment in rats: Implications in Huntington's disease

BackgroundChronic quinolinic acid (QA) lesions in rats closely resemble Huntington's disease like conditions. Oxidative stress and mitochondrial dysfunction have long been implicated in the neurotoxic effects of QA acting through N-methyl-d-aspartate (NMDA) receptors. Reports suggest that inhibition of adenosine A2A receptor function elicits neuroprotective effect in QA induced neurotoxicity in rats. Caffeine, a preferential A2A receptor antagonist imitates antioxidant like actions and exerts neuroprotective effects in various neurodegenerative conditions. Thus, the present study was designed to evaluate the neuroprotective effects of caffeine against QA induced neurotoxicity in rats. MethodsIn the present study, QA (200nmol/2μl saline) has been administered bilaterally to the striatum of rats followed by chronic caffeine (10, 20 and 40mg/kg) administration for 21 days. Motor performance of the animals was evaluated in weekly intervals and subsequently after 21 days, the animals were sacrificed and measurement of mitochondrial complexes activity, respiration rate and endogenous antioxidant levels were carried out in the striatal region. ResultsSingle intrastriatal QA administration resulted in drastic reduction in body weight, marked motor impairment (decreased total locomotor activity in actophotometer and impaired grip strength in rotarod), increased oxidative stress, impaired mitochondrial complexes activities and decreased state 3 respiration (NAD+/FAD+-linked) in rats. However, chronic treatment of caffeine for 21 days significantly attenuated the QA induced behavioural, biochemical and mitochondrial alterations displaying neuroprotective efficacy. ConclusionThe study highlights the possible involvement of A2A receptor antagonism in the neuroprotective effect of caffeine against QA induced mitochondrial dysfunction and oxidative stress in rats.

Rosiglitazone Synergizes the Neuroprotective Effects of Valproic Acid Against Quinolinic Acid-Induced Neurotoxicity in Rats: Targeting PPARγ and HDAC Pathways

Huntington's disease (HD) is an autosomal dominant progressive neurodegenerative disorder which affects medium spiny GABAergic neurons mainly in the striatum. Oxidative damage, neuro-inflammation, apoptosis, protein aggregation, and signaling of neurotrophic factors are some of the common cellular pathways involved in HD. Quinolinic acid (QA) causes excitotoxicity by stimulating N-methyl-D-aspartate receptors via calcium overload leading to neurodegeneration. Neuroprotective potential of peroxisome proliferator activated receptor-γ (PPARγ) agonists and histone deacetylase (HDAC) inhibitors have been well documented in experimental models of neurodegenerative disorders; however, their exact mechanisms are not clear. Therefore, present study has been designed to explore possible neuroprotective mechanism of valproic acid (VPA) and its interaction with rosiglitazone against QA induced HD-like symptoms in rats. Single bilateral intrastriatal QA (200 nmol/2 μl saline) administration significantly caused motor incoordination, memory impairment, oxidative damage, mitochondrial dysfunction (complex I, II, II and IV), cellular alterations [tumor necrosis factor-alpha (TNF-α), caspase-3, brain derived neurotrophic factor, acetylcholinesterase], and striatal neurodegeneration as compared to sham group. Treatment with rosiglitazone (5, 10 mg/kg) and VPA (100, 200 mg/kg) for 21 days significantly attenuated these behavioral, biochemical, and cellular alterations as compared to control (QA 200 nmol) group. However, VPA (100 mg/kg) treatment in combination with rosiglitazone (5 mg/kg) for 21 days synergized their neuroprotective effect, which was significant as compared to their effects per se in QA-treated animals. The present study provides an evidence of possible interplay of PPARγ agonists and HDAC inhibitors as a novel therapeutic strategy in the management of HD.

Minocycline modulates neuroprotective effect of hesperidin against quinolinic acid induced Huntington's disease like symptoms in rats: Behavioral, biochemical, cellular and histological evidences

Emerging evidences indicate hesperidin, a citrus flavanone, attenuates neurodegenerative processes and related complications. Besides its anti-oxidant properties, the other probable mechanisms which underpin its neuroprotective potential are still not clear. In light of emerging role of flavonoids in modulating oxidative stress and neuro-inflammation, the study has been designed to explore the possible neuroprotective effect of hesperidin and its combination with minocycline (microglial inhibitor), against quinolinic acid (QA) induced Huntington's disease (HD) like symptoms in rats. Unilateral intrastriatal administration of QA (300nmol/4µl) significantly reduced body weight, impaired behavior (locomotor activity, beam balance and memory performance), caused oxidative damage (increased lipid peroxidation, nitrite concentration, depleted super oxide dismutase and reduced glutathione), demonstrated mitochondrial dysfunction (decreased Complex-I, II, III, and IV activities), increased striatal lesion volume and altered the levels of TNF-α, caspase-3 as well as BDNF expression, as compared to sham group. Meanwhile, chronic hesperidin (100mg/kg, p.o.) and minocycline (25mg/kg, p.o.) treatment for 21 days significantly attenuated the behavioral, biochemical and cellular alterations as compared to QA treated (control) animals, whereas hesperidin (50mg/kg, p.o.) treatment was found to be non-significant. However, treatment of hesperidin (50mg/kg) in combination with minocycline (25mg/kg) potentiated their neuroprotective effect, which was significant as compared to their effects per se in QA treated animals. Taken altogether, the results of the present study suggest a possible interplay of microglial modulation and anti-oxidant effect in neuroprotective potential of hesperidin against QA induced HD like symptoms in rats.

JAK2 inhibition is neuroprotective and reduces astrogliosis after quinolinic acid striatal lesion in adult mice

Quinolinic acid (QA) striatal lesion in rodents induces neuronal death, astrogliosis and migration of neuroblasts from subventricular zone to damaged striatum. These phenomena occur in some human neurodegenerative illnesses, but the underlying mechanisms are unknown. We investigated the effect of AG490, a Janus-kinase 2 (JAK2) inhibitor, on astrogliosis, neuronal loss and neurogenesis in the striatum of adult mice after unilateral infusion of QA (30nmol). Animals were given subcutaneous injections of AG490 (10mg/kg) or vehicle immediately after lesion and then once daily for six days. Brain sections were used for neuronal stereological quantification, immunohistochemical and Western Blotting analyses for GFAP and doublecortin, markers of astrocytes and neuroblasts, respectively. The total area of doublecortin-positive cells (ADPC) and the number of neurons (NN) in the lesioned (L) and contralateral (CL) sides were evaluated. Neurogenesis index (NI=ADPC(L)/ADPC(CL)) and neuronal ratio (NR=NN(L)/NN(CL)) were calculated. After QA administration, blotting for GFAP showed an ipsilateral decrease of 19% in AG490- vs vehicle-treated animals. NR was 25% higher in mice given AG490 vs controls given vehicle. NI showed a decrease of 21% in AG490- vs vehicle-treated mice. Our results indicate that JAK2 inhibition reduces QA lesion and suggest that astrogliosis may impair neuronal survival in this model.

Protective Effect of Safranal, a Constituent of Crocus sativus, on Quinolinic Acid-induced Oxidative Damage in Rat Hippocampus.

Quinolinic acid (QA)-mediated excitotoxicity has been widely used as a model for studying neurodegenerative disorders. Recent studies suggested that saffron (Crocus sativus) or its active metabolite, i.e. safranal, exerts pharmacological actions on central nervous system including anxiolytic, anticonvulsant, and neuroprotective properties. The present study aimed to investigate the effect safranal pretreatment on QA-induced oxidative damage in rat hippocampus. Under anesthesia, a guide cannula was stereotaxically inserted into left ventral hippocampus of rats. The rats were then given either saline or safranal (72.75, 145.5, and 291 mg/kg, IP) 30 min before administration of QA (300 nmol, intrahippocampal injection). The markers of oxidative stress including thiobarbituric acid reactive substances (TBARS, as an index of lipid preoxidation), total sulfhydryl groups, antioxidant capacity of hippocampus (using FRAP assay), and oxidative DNA damage (%tail DNA, using comet assay) were measured in hippocampus. The QA induced a significant increase in TBARS levels and %tail DNA and remarkable decrease in antioxidant power (FRAP value) and total sulfhydryl content of hippocampus, in comparison with control animals. Systemic administration of safranal (291 mg/kg, IP), effectively and dose-dependently decreased the QA-induced lipid peroxidation (P<0.001) and oxidative DNA damage (P<0.001). Safranal also prevented the decrease of hippocampal thiol redox and antioxidant status (P<0.001) produced by QA. Safranal have protective effects on different markers of oxidative damage in hippocampal tissue following QA administration. Our findings might raise a possibility of potential therapeutic application of safranal for preventing and treating neurodegenerative disorders such as Alzheimer's disease.

Targeting Neuro-Inflammatory Cytokines and Oxidative Stress by Minocycline Attenuates Quinolinic-Acid-Induced Huntington’s Disease-Like Symptoms in Rats

Recent experimental and clinical reports support the fact that the minocycline exhibits significant neuroprotective activity in neurodegenerative diseases. However, its mechanism of neuroprotection is still far from our understanding. Besides, minocycline does not always produce neuroprotective effect. Therefore, this study has been designed to explore the possible mechanism of minocycline in experimental model of HD in rats. Intrastriatal administration of quinolinic acid caused a significant reduction in body weight, motor dysfunction (impaired locomotor activity, rotarod performance, and beam walk test), oxidative damage (as evidenced by increase in lipid peroxidation, nitrite concentration, and depletion of super oxide dismutase and catalase), increased TNF-α and IL-6 levels as compared to the sham-treated animals. Minocycline (25, 50, and 100mg/kg) treatment (for 21days) significantly improved body weight, locomotor activity, rotarod performance, balance beam walk performance, oxidative defense, attenuated TNF-α and IL-6 levels as compared to quinolinic-acid (QA)-treated animals. This study provides evidence that minocycline might have neuroprotective effect against QA-induced Huntington-like behavioral, biochemical alterations, and neuroinflammation in rats.

Intracerebroventricular administration of inosine is anticonvulsant against quinolinic acid-induced seizures in mice: An effect independent of benzodiazepine and adenosine receptors

Inosine (INO) has an anticonvulsant effect against seizures induced by antagonists of GABAergic system. Quinolinic acid (QA) is an agonist NMDA receptors implicated in the neurobiology of seizures. In the present study, we investigated the anticonvulsant effect of intracerebroventricular (i.c.v.) INO administration against QA-induced seizures in adult mice. We also investigated whether the benzodiazepines (BZ) or adenosine (ADO) receptors were involved in the INO effects. Animals were pretreated with an i.c.v. injection of either vehicle or INO before an i.c.v. administration of 4μl QA (36.8nmol). All animals pretreated with vehicle followed by QA presented seizures. INO protected against QA-induced seizures in a time and dose dependent manner (up to 60% at 400nmol, 5min before QA injection). Diazepam (DZ) and ADO (i.c.v.) also exhibited anticonvulsant effect against QA induced seizures. Additionally, i.p. administration of either flumazenil, a BZ receptor antagonist, or caffeine, an ADO receptor antagonist, did not change the anticonvulsant potency of INO i.c.v. injection, but completely abolished the DZ and ADO anticonvulsant effects, respectively. In conclusion, this study demonstrated that INO exert anticonvulsant effect against hyperactivity of the glutamatergic system independently of BZ or ADO receptors activation.

Evaluation of a multiple system atrophy model in rats using multitracer microPET

A double toxin-double lesion strategy is appropriate for mimicking of striatonigral degeneration. Because knowledge of human pathology is limited, animal models must be well characterized prior to testing of therapeutic approaches to treat multiple system atrophy. In double-toxin animal models, however, reduced contralateral rotation after apomorphine injection is restored within a few weeks via an unknown mechanism; the animals thus revert to PD status. We assessed this phenomenon using multitracer microPET and tissue staining. Five adult male Wistar rats received injections of 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle (MFB), followed 3 weeks later by injections of quinolinic acid (QA) into the ipsilateral striatum. Apomorphine-induced rotation tests were performed 1 week after each injection, and 6 and 10 weeks after QA injection. Rotarod tests were performed weekly after 6-OHDA injection. MSA-p status was characterized by microPET 5 and 10 weeks after QA injection using the tracers 2-deoxy-2-[(18)F]-fluoro-D-glucose ([(18)F]-FDG) and [(18)F]-N-(3-fluoropropyl)-2-carbomethoxy-3-(4-iodophenyl)nortropane ([(18)F]-FP-CIT). Histological changes were evaluated by tyrosine hydroxylase (TH) and cresyl violet staining. The numbers of apomorphine-induced rotations increased contralaterally after 6-OHDA lesions were created, but decreased significantly after QA administration (p = 0.007). Five weeks after QA injection, however, contralateral rotation again increased and persisted for 1 month. Rotarod rotation differed significantly between the intact and PD states (p < 0.05), but not between the PD and MSA-p states. MicroPET revealed glucose hypometabolism and dopamine transporter (DAT) impairment on the lesioned side of the striatum 1 and 2 months after QA lesion surgery. Loss of nigral cells was confirmed by TH immunostaining, and striatal atrophy was observed upon cresyl violet staining. Pathological changes consistent with MSA-p can be generated by the double toxin-double lesion method and persist during follow-up. Behavioral tests, such as drug-induced rotation and rotarod tests, are not appropriate for long-term follow-up in the MSA-p model, suggesting the need for development of more appropriate behavioral tests.