Anti-inflammatory effects of ellagic acid and vanillic acid against quinolinic acid-induced rat model of Huntington's disease by targeting IKK-NF-κB pathway.

Huntington disease (HD), an autosomal dominant neurodegenerative disorder characterized by involuntary choreatic movements with cognitive and behavioral disturbances. HD striatum has increased conversion of kynurenine to quinolinic acid (QA) which activates NMDA receptors leading to activation of microglia and increased levels of nuclear factor kappa B (NF-κB) leading to elevated transcription of inducible nitric oxide synthase (iNOS) and various cytokines causing neuronal death via neuroinflammation, oxidative stress, mitochondrial dysfunction and apoptosis. Therefore, inhibiting IKK-NF-κB pathway induced excitotoxicity, oxidative stress and neuroinflammation could be a potential intervention in slowing down the disease progression. QA injection intrastriatally (IS-QA) produce damage mimicking HD where neuroinflammation, oxidative stress and mitochondrial dysfunction play crucial role. Ellagic acid (EA) and vanillic acid (VA) are well reported to possess antioxidant and NF-κB inhibiting effect. Hence, in present study, rats administered IS-QA were treated with EA and VA for 21 days to explore their neuroprotective effects. Behavioral studies, biochemical estimations for oxidative stress and acetylcholinesterase assay were performed. Mitochondrial function was determined by estimating mitochondrial enzyme complexes; inflammatory markers like TNF-α, IL-6, NF-κB by ELISA and apoptosis by caspase-3 levels. Brain damage was determined by histopathology which revealed their neuroprotective effects. Various doses of EA and VA produced improved motor and cognitive functions, oxidative stress and neuroinflammation were also reduced and mitochondrial functioning was improved. In a nutshell, these results signify improved motor and cognitive functions by EA and VA in QA model of HD, along with declined oxidative stress, mitochondrial dysfunction and neuroinflammation.

Modelagem celular in vitro da Doença de Huntington com ácido 3-nitropropiônico e ácido quinolínico & Avaliação das funções neuroprotetoras da adenosina / In vitro cell modeling of Huntington's Disease with 3-nitropropionic acid and quinolinic acid and evaluation of the neuroprotective functions of adenosine

A Doença de Huntington (Huntington's disease - HD) trata-se de uma patologia neurodegenerativa hereditária caracteriza por meio da expressão das proteínas huntingtinas mutantes (mHtt), das mortes dos neurônios espinhais médios (medium spiny neurons MSNs) GABAérgicos D2-positivos do striatum e da hipercinesia. Uma hipótese se refere à função das mHtts de potencializarem os efeitos excitotóxicos das estimulações dos receptores de NMDA (NMDAR) por meio da inibição da succinato desidrogenase, resultando em desequilibrio das [Ca2+]i, estresse oxidativo e apoptose. A adenosina agonista dos receptores purinérgicos P1 tem sido descrita por conta das suas funções neuroprotetoras e neuromodulatórias. Assim, estabelecemos dois modelos in vitro da HD fundamentados nas neurodiferenciações das linhagens murinas de célula-tronco embrionárias E14-TG2a e progenitoras neurais do hipocampo HT-22; seguidas pelos tratamentos com ácido quinolínico (QA) agonista seletivo dos NMDARs , na ausência e na presença do ácido 3-nitropropiônico (3-NP) inibidor irreversível da succinato desidrogenase. Estes modelos foram utilizados nas avaliações das funções neuroprotetoras da adenosina. Os neurônios pós-mitóticos das culturas de E14-TG2a diferenciadas foram caracterizados conforme os MSNs GABAérgicos do striatum; enquanto os neurônios HT-22 diferenciados foram caracterizados de modo inespecífico. Metodologia: imunofluorescência (microscopia e citometria); PCR em tempo real; análise das variações dos potenciais das membranas plasmáticas e das variações transientes das [Ca2+]i por microfluorimetria; e quantificações das reduções do AlamarBlue® (% de sobrevida celular) e das atividades extracelulares de LDH (U/L) (necrose) por espectrometria. Avaliamos a capacidade do 3-NP de potencializar os efeitos excitotóxicos do QA comparando dois grupos de neurônios HT-22 diferenciados: QA 8mM (EC50) (controle); e 3-NP 5mM/QA 8mM. Avaliarmos o potencial neuroprotetor da adenosina comparando quatro grupos de neurônios HT-22 diferenciados: QA 8mM; adenosina 250µM/QA 8mM; 3-NP 5mM/QA 8mM; 3-NP 5mM/adenosina 250µM/QA 8mM. Os neurônios pós-mitóticos derivados das E14TG2a foram classificados como MSNsGABAérgicos do striatum integrantes de uma cultura neuronal heterogênea semelhante às conexões nigroestriatais, corticoestriatais, striatonigral e striatopallidal. Os neurônios HT-22 diferenciados perfaziam uma cultura neuronal heterogênea, não totalmente madura, composta por neurônios glutamatérgicos, dopaminérgicos, colinérgicos e GABAérgicos. Os neurônios HT-22 diferenciados 3-NP 5mM apresentaram menores % de sobrevida celular após os tratamentos com QA 8mM por 24h (p<0.05); e maiores amplitudes das variações das [Ca2+]i dependentes do QA 8mM (p<0.05) (cinética 6 minutos). Por outro lado, os neurônios HT-22 diferenciados pré- tratados com 3-NP 5mM apresentaram menores atividades extracelulares de LDH após o tratamento com QA 8mM por 24h menor proporção de necrose. Os pré-tratamentos com adenosina 250µM indicaram uma tendência dos efeitos neuroprotetores (p>0.05) maiores % de sobrevida celular; menores atividades extracelulares de LDH; e menores amplitudes das variações transientes das [Ca2+]i. Em conjunto, nossos resultados indicam que a inibição da succinato desidrogenase potencializa os efeitos excitotóxicos dos NMDARs por meio da alteração das [Ca2+]i e, provavelmente, dos mecanismos de morte celular; enquanto a adenosina apenas tendeu à neuroproteção

Huntington's disease (HD) is a hereditary neurodegenerative pathology characterized by mutant huntingtin proteins (mHtt) expression, striatum D2-positive GABAergic medium spiny neurons (MSNs) cell death and hyperkinetic motor symptoms development. One hypothesis refers to the principle that mHtt potentiates the excitotoxic effects of NMDA receptor (NMDAR) stimulation by the inhibition of mitochondrial succinate dehydrogenase, resulting in [Ca2+]i imbalance, oxidative stress and apoptosis. Adenosine P1 purinergic receptor agonist is related to neuroprotective and neuromodulatory functions. Thus, we established two in vitro HD models based on the neurodifferentiation of murine embryonic stem cell lines E14-TG2a and hippocampal neuroprogenitor cell line HT-22 followed by treatment with quinolinic acid (QA) selective agonist of NMDARs , in the absence and in the presence of 3-nitropropionic acid (3-NP) irreversible inhibitor of succinate dehydrogenase. These models were used to assess the neuroprotective functions of adenosine. Post-mitotic neurons from differentiated E14-TG2a cultures were characterized according to striatum's GABAergic MSNs; while the differentiated HT-22 neurons were characterized in a non-specific way. Methodology included immunofluorescence (microscopy and cytometry); real-time PCR; analysis of variations in the plasma membrane potentials and of transient variations in the [Ca2+]i by microfluorimetry; and quantification of AlamarBlue® reductions (% cell survival) and of extracellular LDH activity (U/L) (necrosis) by spectrometry. We evaluated the ability of 3-NP to potentiate the excitotoxic effects of QA by comparing two groups of differentiated HT-22 neurons: 8mM QA (control); and 5mM 3-NP/8mM QA. We evaluated the neuroprotective potential of adenosine comparing four groups of differentiated HT-22 neurons: QA 8mM; 250µM adenosine/8mM QA; 5mM 3-NP/8mM QA; 5mM 3-NP/250µM adenosine/8mM QA. Postmitotic neurons derived from E14TG2a were classified as striatums GABAergic MSNs that are part of a heterogeneous neuronal culture similar to nigrostriatal, corticostriatal, striatonigral, and striatopallidal connections. Differentiated HT-22 neurons consisted of a heterogeneous neuronal culture and not fully mature glutamatergic,dopaminergic, cholinergic and GABAergic neurons. Differentiated HT-22 neurons following 5mM 3-NP treatment showed lower % cell survival after treatments with 8mM QA for 24h (p<0.05); and higher amplitudes of the variations of [Ca2+]i induced by 8mM QA (p<0.05) (kinetics 6 minutes). On the other hand, differentiated HT-22 neurons 5mM 3-NP showed lower extracellular LDH activities after treatment with 8mM QA for 24h indicating a lower proportion of necrotic cells. Pretreatments with 250µM adenosine indicated a trend towards neuroprotective effects, such as higher percentages of cell survival; lower extracellular LDH activities; and lower amplitudes of transient variations of [Ca2+]i. Taken together, our results indicate that succinate dehydrogenase inhibition potentiated the excitotoxic effects of NMDARs by altering [Ca2+]i and, probably, cell death mechanisms, while adenosine only to neuroprotection

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.

The kynurenine pathway and quinolinic acid: pivotal roles in HIV associated neurocognitive disorders.

This brief review will first consider HIV associated neurocognitive disorder followed by the current understanding of its neuropathogenesis. Against this background the role of the kynurenine pathway will be detailed. Evidence both direct and indirect will be discussed for involvement of the kynurenine pathway at each step in the neuropathogenesis of HIV associated neurocognitive disorder.

Role of the medial and lateral caudate-putamen in mediating an auditory conditional response association.

Rats with quinolinic acid lesions of the medial or lateral caudate-putamen (CPu) and controls were tested for performance of a previously learned auditory conditional response association task. The task involved the selection of two possible responses when presented with one of two different tones. Results indicated that lesions of either the medial or the lateral CPu produced a sustained deficit in the auditory conditional response association task. Only the lateral CPu lesioned rats exhibited transient motor problems immediately following surgery, but these problems did not interfere with the execution of the appropriate responses. It is suggested that both the medial and the lateral CPu are involved in response selection and response separation within egocentric space.

[Behavior characterization of a model of Huntington's disease in rats, induced by quinolinic acid]. / Caracterización conductual de un modelo de enfermedad de Huntington en ratas inducido por ácido quinolínico.

INTRODUCTION: Huntington's disease (HD) is a progressive neurodegenerative disorder, characterized by severe degeneration of basal ganglia neurons. Behavioral symptoms of HD include abnormal, uncontrollable and constant choreiform movements, impaired cognitive function and emotional disturbance. OBJECTIVE: In order to explore the changes of cognitive and motor functions induced by quinolinate lesion we realized this experiment. MATERIALS AND METHODS: We studied the behavior of rats with unilateral quinolinate induced lesions of the medial striatum. Intact 3 months old male rats (n = 23) were trained in the Morris Water Maze during three consecutive days, eight trials/day (acquisition), and before surgery they were randomly assigned either to intact or lesion groups. Fifteen days after the lesion the rats were tested using retention test (one day/four trials, with the escape platform in the same position as in acquisition test), on the next three days the rats were tested in the transfer test (three days/eight trials-day, with the platform in the new position). The Paw reaching test and the asymmetrical rotational behavior test in respond to amphetamine were also tested in these rats. RESULTS: Lesioned animals exhibited deficient retrieval of stored memories of visuospatial skills and impaired transfer of learning. In relation with motor activity the lesioned rats showed a profound impairment in the skill of the left forelimb for reaching food compared with its right forelimb as well as with the forelimb abilities of intact rats. The lesioned animals showed significant rotational behavior induced by amphetamine agonist, ipsilateral to the lesioned striatum. CONCLUSIONS: These results are consistent with the notion that the striatal degeneration could sufficiently account for the cognitive abnormalities associated with HD, and with the key role played by basal ganglia in enabling voluntary and postural adjustment of the movements.

Time-course analysis and comparison of acute and chronic intrastriatal quinolinic acid administration on forelimb reaching deficits in the rat.

Rats were trained to use a single forelimb for a food pellet retrieval task. During baseline testing all rats exhibited > 90% use of a preferred limb for the task. Following baseline, rats were subjected to chronic administration (18 day) or acute injection of quinolinic acid (QUIN) or vehicle to the striatum contralateral to the preferred limb. Rats were tested 48 h after insertion of chronic delivery probes or after acute injection and retested every 48 h over an 18-day period. Compared to vehicle, rats receiving chronic QUIN (7.6 nmol/h) exhibited an increase in the number of reach attempts required to meet task criteria. Chronic QUIN did not produce a significant change in latency to initiate the task or an increase in latency to complete the task. No rats exposed to chronic QUIN exhibited a switch in limb preference for the task. Unlike animals exposed to chronic QUIN, a significant number of animals receiving acute QUIN injections switched to exclusive use of the ipsilateral (nonpreferred) limb for the task. Quantitative histological analysis revealed no significant difference in lesion volume between acute and chronic lesion animals. These findings suggest that behavioral manifestations of histopathologically similar lesions may be vastly different depending on the methods used to produce these lesions. More specifically, the acute injection model resulted primarily in forelimb disuse, whereas the chronic model resulted in continued abnormal use of the affected limb. Understanding adaptive strategies used in these models may be particularly important when testing newly developed transgenic models of neurodegenerative diseases and the therapeutic potential of newly developed neuroprotectants.

Effects of severity of host striatal damage on the morphological development of intrastriatal transplants in a rodent model of Huntington's disease: implications for timing of surgical intervention.

OBJECT: The goal of this study was to investigate the effect of the severity of host neural damage on the morphological development of intrastriatal transplants in a rodent model of Huntington's disease. METHODS: Sprague-Dawley rats were subjected to unilateral striatal lesioning induced by administration of quinolinic acid (20 nM, 40 nM, or 90 nM). Seven days postlesioning, intrastriatal cell suspension grafts were placed in the right striatum in some of these animals. Grafts were also placed in the right striatum of additional animals that had not been subjected to lesioning. The rats were killed and processed for morphological analysis 8 weeks after grafting. The results indicate that striatal grafts survive and grow much better when implanted into a lesioned striatum rather than into an intact striatum, as measured both by the volume and the numbers of medium-sized spiny neurons within the graft. Only a small or modest lesion is necessary to produce this effect. By some measures (such as graft volume) grafts survive less well when the lesion is more extensive. The presence of a graft reduced the extent of striatal atrophy induced by the lesions, but this effect was not caused by differences in the numbers of surviving neurons per se. CONCLUSIONS: These results have significant implications for the timing of surgical intervention and patient selection with respect to current and future clinical trials of striatal transplantation in the treatment of Huntington's disease.

Histological and behavioral protection by (-)-nicotine against quinolinic acid-induced neurodegeneration in the hippocampus.

Injections of quinolinic acid (60, 180, and 600 nmol) in the dorsal hippocampus induced significant neurotoxicity that was evident 1 day after the injection. By day 3, pyramidal as well as granular cells were affected even at the lowest dose of quinolinic acid, an effect that persisted up to 20 days. Consistent with the histological findings, animals with bilateral injections in the dorsal hippocampus were cognitively impaired during acquisition and retention of spatial information in the water maze. A subacute treatment with (-)-nicotine (62 micromol/kg/day) delivered by subcutaneous minipumps prevented the histological and cognitive deficits induced by the bilateral quinolinic acid (60 nmol) injections. These data indicate that quinolinic acid can induce degeneration of both pyramidal as well as granule cells in the hippocampus, leading to cognitive impairments in the rat, and that activation of neuronal nicotinic acetylcholine receptors can prevent the neurodegenerative process induced by quinolinic acid.