Striatal Damage Research Articles

Neuroprotective effects of pifithrin-\u03b1 against traumatic brain injury in the striatum through suppression of neuroinflammation, oxidative stress, autophagy, and apoptosis

Cortical and hippocampal neuronal damages caused by traumatic brain injury (TBI) are associated with motor and cognitive impairments; however, only little attention paid to the striatal damage. It is known that the p53 tumor-suppressor transcription factor participated in TBI-induced secondary brain damage. We investigated how the p53 inactivator pifithrin (PFT)-α affected TBI-induced striatal neuronal damage at 24 h post-injury. Sprague-Dawley rats subjected to a controlled cortical impact were used as TBI models. We observed that p53 mRNA significantly increased, whereas p53 protein expression was distributed predominantly in neurons but not in glia cells in striatum after TBI. PFT-α improved motor deficit following TBI. PFT-α suppressed TBI-induced striatal glial activation and expression of proinflammatory cytokines. PFT-α alleviated TBI-induced oxidative damage TBI induced autophagy was evidenced by increased protein expression of Beclin-1 and shift of microtubule-associated light chain (LC)3-I to LC3-II, and decreased p62. These effects were reduced by PFT-α. Post-injury PFT-α treatment reduced the number of degenerating (FJC-positive) and apoptotic neurons. Our results suggest that PFT-α may provide neuroprotective effects via p53-dependent or -independent mechanisms depending on the cell type and timing after the TBI and can possibly be developed into a novel therapy to ameliorate TBI-induced neuronal damage.

Motor Assessment in Huntington's Disease Mice.

Motor deficits are a characteristic consequence of striatal damage, whether induced by experimental lesions, or in genetic models of Huntington's disease involving polyglutamine expansion in the huntingtin protein. With the growing power of genetic models and genetic tools for analysis, mice are increasingly the animal model of choice, and objective quantitative measures of motor performance are in demand for experimental analysis of disease pathophysiology, progression, and treatment. We present methodological protocols for six of the most common tests of motor function-ranging from spontaneous activity, locomotor coordination, balance, and skilled limb use-that are simple, effective, efficient, and widely used for motor assessment in Huntington's disease research in experimental mice.

Pathway-Specific Control of Striatal Neuron Vulnerability by Corticostriatal Cannabinoid CB1 Receptors.

The vast majority of neurons within the striatum are GABAergic medium spiny neurons (MSNs), which receive glutamatergic input from the cortex and thalamus, and form two major efferent pathways: the direct pathway, expressing dopamine D1 receptor (D1R-MSNs), and the indirect pathway, expressing dopamine D2 receptor (D2R-MSNs). While molecular mechanisms of MSN degeneration have been identified in animal models of striatal damage, the molecular factors that dictate a selective vulnerability of D1R-MSNs or D2R-MSNs remain unknown. Here, we combined genetic, chemogenetic, and pharmacological strategies with behavioral and neurochemical analyses, and show that the pool of cannabinoid CB1 receptor (CB1R) located on corticostriatal terminals efficiently safeguards D1R-MSNs, but not D2R-MSNs, from different insults. This cell-specific response relies on the regulation of glutamatergic signaling, and is independent from the CB1R-dependent control of astroglial activity in the striatum. These findings define cortical CB1R as a pivotal synaptic player in dictating a differential vulnerability of D1R-MSNs versus D2R-MSNs, and increase our understanding of the role of coordinated cannabinergic-glutamatergic signaling in establishing corticostriatal circuits and its dysregulation in neurodegenerative diseases.

Neurological Changes in Vulnerable Brain Areas of Chronic Cerebral Hypoperfusion Mice

Background: Chronic cerebral hypoperfusion (CCH) is associated with neurological changes and cognitive decline. It is a major cause of vascular dementia and a contributing factor in Alzheimer disease. Animal models are useful in helping to elucidate the mechanisms of these diseases while demonstrating differences in pathological onset and severity. Furthermore, different mouse strains show differences in their susceptibility to neurological damage resulting in different cognitive outcomes. Purpose: This study investigated the effect of CCH induced by permanent unilateral common carotid artery occlusion (UCO) on neurological damage in vulnerable brain regions such as hippocampus, striatum, and white matter areas from 2 to 8 weeks following CCH induction. Methods: Thirty-six male Institute of Cancer Research (ICR) mice were randomly divided into 2 main experimental groups, Sham and UCO. These 2 main groups were further divided into 3 observation periods of 2, 4, and 8 weeks following CCH. Histological study was then employed using 0.1% cresyl violet and luxol fast blue staining to assess neurological damage. Results: We found equal levels of neurological damage induced by CCH between ipsi- and contralateral hemispheres. Hippocampus and striatum damage were slightly increased from 2 to 8 weeks rising to significance at 8 weeks in both areas, while the white matter densities of the corpus callosum, internal capsule, optic tract and striatum fiber did not change. Conclusion: CCH induced by UCO in ICR mice induces hippocampal and striatal damage at 8 weeks while leaving white matter undamaged.

Purinergic Antagonism Prevents Mitochondrial Dysfunction and Behavioral Deficits Associated with Dopaminergic Toxicity Induced by 6-OHDA in Rats.

Purinoceptors are present in neurons, microglia and oligodendrocytes and regulate dopamine (DA) release, striatal-related function and striatal neuronal and DA cells damage. Therefore, purinoceptors may be involved in the pathology of Parkinson's disease (PD) and purinergic antagonism may show neuroprotective effect. The study investigated the role of the non-selective purinergic receptor antagonist pyridoxalphosphate-6-azophenyl-2', 4'-disulfonic acid (PPADS) and a selective purinergic receptor P2X7 receptor antagonist Brilliant Blue G (BBG) against 6-OHDA induced dopaminergic neurotoxicity in rats; while adenosine triphosphate (ATP) was used as a P2X receptor agonist. Behavioral parameters like spontaneous motor activity, narrow beam walk, footprint, bar catalepsy, grip strength and rotarod tests were performed to evaluate motor deficits in PD. Striatal DA contents were estimated as neurochemical measures of PD. Mitochondrial studies and oxidative status were assessed to investigate the mechanism of purinergic system antagonists. Involvement of purinergic receptors in apoptosis was assessed by expressing cytochrome-C, caspase-9 and caspase-3. Both the antagonists not only attenuated 6-OHDA induced motor deficits but also protected against 6-OHDA induced DA depletion in the striatum. Oxidative stress, mitochondrial integrity and dysfunction were attenuated by purinergic antagonists. Further, they attenuated mitochondrial-linked apoptosis as observed by a decrease in expression of cytochrome-C, caspase-9 and caspase-3. Therefore, purinoceptor antagonism shows neuroprotective effect in 6-OHDA induced dopamine toxicity through preservation of mitochondrial bioenergetics and anti-apoptotic activities.

Safe and Efficient Silencing with a Pol II, but Not a Pol lII, Promoter Expressing an Artificial miRNA Targeting Human Huntingtin.

Huntington’s disease is a devastating, incurable neurodegenerative disease affecting up to 12 per 100,000 patients worldwide. The disease is caused by a mutation in the Huntingtin (Htt) gene. There is interest in reducing mutant Huntingtin by targeting it at the mRNA level, but the maximum tolerable dose and long-term effects of such a treatment are unknown. Using a self-complementary AAV9 vector, we delivered a mir-155-based artificial miRNA under the control of the chicken β-actin or human U6 promoter. In mouse brain, the artificial miRNA reduced the human huntingtin mRNA by 50%. The U6, but not the CβA promoter, produced the artificial miRNA at supraphysiologic levels. Embedding the antisense strand in a U6-mir-30 scaffold reduced expression of the antisense strand but increased the sense strand. In mice treated with scAAV9-U6-mir-155-HTT or scAAV9-CβA-mir-155-HTT, activated microglia were present around the injection site 1 month post-injection. Six months post-injection, mice treated with scAAV9-CβA-mir-155-HTT were indistinguishable from controls. Those that received scAAV9-U6-mir-155-HTT showed behavioral abnormalities and striatal damage. In conclusion, miRNA backbone and promoter can be used together to modulate expression levels and strand selection of artificial miRNAs, and in brain, the CβA promoter can provide an effective and safe dose of a human huntingtin miRNA.

Caffeine alleviates progressive motor deficits in a transgenic mouse model of spinocerebellar ataxia.

Machado-Joseph disease (MJD) is a neurodegenerative spinocerebellar ataxia (SCA) associated with an expanded polyglutamine tract within ataxin-3 for which there is currently no available therapy. We previously showed that caffeine, a nonselective adenosine receptor antagonist, delays the appearance of striatal damage resulting from expression of full-length mutant ataxin-3. Here we investigated the ability of caffeine to alleviate behavioral deficits and cerebellar neuropathology in transgenic mice with a severe ataxia resulting from expression of a truncated fragment of polyglutamine-expanded ataxin-3 in Purkinje cells. Control and transgenic c57Bl6 mice expressing in the mouse cerebella a truncated form of human ataxin-3 with 69 glutamine repeats were allowed to freely drink water or caffeinated water (1g/L). Treatments began at 7 weeks of age, when motor and ataxic phenotype emerges in MJD mice, and lasted up to 20 weeks. Mice were tested in a panel of locomotor behavioral paradigms, namely rotarod, beam balance and walking, pole, and water maze cued-platform version tests, and then sacrificed for cerebellar histology. Caffeine consumption attenuated the progressive loss of general and fine-tuned motor function, balance, and grip strength, in parallel with preservation of cerebellar morphology through decreasing the loss of Purkinje neurons and the thinning of the molecular layer in different folia. Caffeine also rescued the putative striatal-dependent executive and cognitive deficiencies in MJD mice. Our findings provide the first in vivo demonstration that caffeine intake alleviates behavioral disabilities in a severely impaired animal model of SCA. Ann Neurol 2017;81:407-418.

Effect of rutin against a mitochondrial toxin, 3-nitropropionicacid induced biochemical, behavioral and histological alterations-a pilot study on Huntington's disease model in rats.

Dietary compounds like flavonoids may offer protection against neurodegeneration. Huntington's disease (HD) is a neurodegenerative disorder characterized by symptoms like chorea and dementia. 3-Nitropropionic acid (3-NP), a Succinate dehydrogenase (SDH) inhibitor produces behavioral, biochemical and histological changes in the striatum, mimics HD in animals and humans. The present study was designed to examine the protective activity of Rutin (RT), a primary flavonoid from citrus fruits, green tea on 3-NP induced experimental model of HD in rats. Rats were pretreated with Rutin, a potent antioxidant (25 and 50mg/kg b.w.) orally prior to the intraperitoneally (i.p.) administration of 3-NP (10mg/kg b.w.) for 14days. Behavioral assessments were carried out on 5th, 10th and 15th day after 3-NP treatment. Body weight, biochemical and histological studies were analyzed on 15th day. Systemic administration of 3-NP significantly reduced the body weight, locomotor activities (Rota rod, Open field test), memory (Morris water maze) and antioxidants such as Glutathione (GSH) levels, activities of Superoxide dismutase (SOD), Catalase (CAT), Glutathione peroxidase (GPx), Glutathione-S-transferase (GST), Glutathione reductase (GR). 3-NP also produces striatal damage by increased the levels of lipid peroxides, nitrite, Glial Fibrillary Acidic Protein (GFAP) and activity of Acetylcholine esterase (AchE). Thus, Rutin treatment of 25 and 50mg/kg b.w. has significantly restored all the biochemical, behavioral and histological alterations caused by the 3-NP through its antioxidant activity. The findings of our study indicates that Rutin may have an important role in protecting the striatum from oxidative/nitrosative insults caused by 3-NP. These results suggest that RT might be a drug of choice to treat HD.

MPP+-Lesioned Mice: an Experimental Model of Motor, Emotional, Memory/Learning, and Striatal Neurochemical Dysfunctions.

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces motor and nonmotor dysfunctions resembling Parkinson's disease (PD); however, studies investigating the effects of 1-methyl-4-phenylpyridinium (MPP+), an active oxidative product of MPTP, are scarce. This study investigated the behavioral and striatal neurochemical changes (related to oxidative damage, glial markers, and neurotrophic factors) 24h after intracerebroventricular administration of MPP+ (1.8-18μg/mouse) in C57BL6 mice. MPP+ administration at high dose (18μg/mouse) altered motor parameters, since it increased the latency to leave the first quadrant and reduced crossing, rearing, and grooming responses in the open-field test and decreased rotarod latency time. MPP+ administration at low dose (1.8μg/mouse) caused specific nonmotor dysfunctions as it produced a depressive-like effect in the forced swim test and tail suspension test, loss of motivational and self-care behavior in the splash test, anxiety-like effect in the elevated plus maze test, and short-term memory deficit in the step-down inhibitory avoidance task, without altering ambulation. MPP+ at doses of 1.8-18μg/mouse increased tyrosine hydroxylase (TH) immunocontent and at 18μg/mouse increased α-synuclein and decreased parkin immunocontent. The astrocytic calcium-binding protein S100B and glial fibrillary acidic protein (GFAP)/S100B ratio was decreased following MPP+ administration (18μg/mouse). At this highest dose, MPP+ increased the ionized calcium-binding adapter molecule 1 (Iba-1) immunocontent, suggesting microglial activation. Also, MPP+ at a dose of 18μg/mouse increased thiobarbituric acid reactive substances (TBARS) and glutathione (GSH) levels and increased glutathione peroxidase (GPx) and hemeoxygenase-1 (HO-1) immunocontent, suggesting a significant role for oxidative stress in the MPP+-induced striatal damage. MPP+ (18μg/mouse) also increased striatal fibroblast growth factor 2 (FGF-2) and brain-derived neurotrophic factor (BDNF) levels. Moreover, MPP+ decreased tropomyosin receptor kinase B (TrkB) immunocontent. Finally, MPP+ (1.8-18μg/mouse) increased serum corticosterone levels and did not alter acetylcholinesterase (AChE) activity in the striatum but increased it in cerebral cortex and hippocampus. Collectively, these results indicate that MPP+ administration at low doses may be used as a model of emotional and memory/learning behavioral deficit related to PD and that MPP+ administration at high dose could be useful for analysis of striatal dysfunctions associated with motor deficits in PD.

Insights into the epigenetic mechanisms involving histone lysine methylation and demethylation in ischemia induced damage and repair has therapeutic implication

Cerebral ischemic stroke is one of the leading causes of death and disability worldwide. Therapeutic interventions to minimize ischemia-induced neural damage are limited due to poor understanding of molecular mechanisms mediating complex pathophysiology in stroke. Recently, epigenetic mechanisms mostly histone lysine (K) acetylation and deacetylation have been implicated in ischemic brain damage and have expanded the dimensions of potential therapeutic intervention to the systemic/local administration of histone deacetylase inhibitors. However, the role of other epigenetic mechanisms such as histone lysine methylation and demethylation in stroke-induced damage and subsequent recovery process is elusive. Here, we established an Internal Carotid Artery Occlusion (ICAO) model in CD1 mouse that resulted in mild to moderate level of ischemic damage to the striatum, as suggested by magnetic resonance imaging (MRI), TUNEL and histopathological staining along with an evaluation of neurological deficit score (NDS), grip strength and rotarod performance. The molecular investigations show dysregulation of a number of histone lysine methylases (KMTs) and few of histone lysine demethylases (KDMs) post-ICAO with significant global attenuation in the transcriptionally repressive epigenetic mark H3K9me2 in the striatum. Administration of Dimethyloxalylglycine (DMOG), an inhibitor of KDM4 or JMJD2 class of histone lysine demethylases, significantly ameliorated stroke-induced NDS by restoring perturbed H3K9me2 levels in the ischemia-affected striatum. Overall, these results highlight the novel role of epigenetic regulatory mechanisms controlling the epigenetic mark H3K9me2 in mediating the stroke-induced striatal damage and subsequent repair following mild to moderate cerebral ischemia.

Antioxidant-Rich Fraction of Urtica dioica Mediated Rescue of Striatal Mito-Oxidative Damage in MPTP-Induced Behavioral, Cellular, and Neurochemical Alterations in Rats.

Parkinson's disease (PD) having a complex and multi-factorial neuropathology includes mainly the degeneration of the dopaminergic nigrostriatal pathway, which is a cumulative effect of depleted endogenous antioxidant enzymes, increased oxidative DNA damage, mitochondrial dysfunction, excitotoxicity, and neuroinflammation. The present study was designed to investigate the neuroprotective effect of a potent antioxidant from Urtica dioica in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of parkinsonism. MPTP was administered intranigrally for the induction of PD in male Wistar rats. Behavioral alterations were assessed in between the study period. Animals were sacrificed immediately after behavioral session, and different biochemical, cellular, and neurochemical parameters were measured. Intranigrally repeated administration of MPTP showed significant impairment of motor co-ordination and marked increase of mito-oxidative damage and neuroinflammation in rats. Intranigral MPTP significantly decreases the dopamine and its metabolites with impairment of dopaminergic cell density in rat brain. However, post-treatment with the potent antioxidant fraction of Urtica dioica Linn. (UD) (20, 40, 80mg/kg) improved the motor function, mito-oxidative defense alteration significantly and dose dependently in MPTP-treated rats. In addition, the potent antioxidant fraction of UD attenuated the pro-inflammatory cytokines (TNF-α and IL-β) and restored the level of dopamine and its metabolites in MPTP-induced PD in rats. Moreover, minocycline (30mg/kg) with lower dose of UD (20mg/kg) had significantly potentiated the protective effect of minocycline as compared to its effect with other individual drug-treated groups. In conclusion, Urtica dioica protected the dopaminergic neurons probably by reducing mito-oxidative damage, neuroinflammation, and cellular alteration along with enhanced neurotrophic potential. The above results revealed that the antioxidant rich fraction of UD contain flavonoids and phenolic compounds, which have a promising approach in therapeutics of PD.

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.

Fragment C Domain of Tetanus Toxin Mitigates Methamphetamine Neurotoxicity and Its Motor Consequences in Mice.

Background:The C-terminal domain of the heavy chain of tetanus toxin (Hc-TeTx) is a nontoxic peptide with demonstrated in vitro and in vivo neuroprotective effects against striatal dopaminergic damage induced by 1-methyl-4-phenylpyridinium and 6-hydoxydopamine, suggesting its possible therapeutic potential in Parkinson’s disease. Methamphetamine, a widely abused psychostimulant, has selective dopaminergic neurotoxicity in rodents, monkeys, and humans. This study was undertaken to determine whether Hc-TeTx might also protect against methamphetamine-induced dopaminergic neurotoxicity and the consequent motor impairment.Methods:For this purpose, we treated mice with a toxic regimen of methamphetamine (4mg/kg, 3 consecutive i.p. injections, 3 hours apart) followed by 3 injections of 40 ug/kg of Hc-TeTx into grastrocnemius muscle at 1, 24, and 48 hours post methamphetamine treatment.Results:We found that Hc-TeTx significantly reduced the loss of dopaminergic markers tyrosine hydroxylase and dopamine transporter and the increases in silver staining (a well stablished degeneration marker) induced by methamphetamine in the striatum. Moreover, Hc-TeTx prevented the increase of neuronal nitric oxide synthase but did not affect microglia activation induced by methamphetamine. Stereological neuronal count in the substantia nigra indicated loss of tyrosine hydroxylase-positive neurons after methamphetamine that was partially prevented by Hc-TeTx. Importantly, impairment in motor behaviors post methamphetamine treatment were significantly reduced by Hc-TeTx.Conclusions:Here we demonstrate that Hc-TeTx can provide significant protection against acute methamphetamine-induced neurotoxicity and motor impairment, suggesting its therapeutic potential in methamphetamine abusers.

Essential fatty acid-rich diets protect against striatal oxidative damage induced by quinolinic acid in rats

Essential fatty acids have an important effect on oxidative stress-related diseases. The Huntington's disease (HD) is a hereditary neurologic disorder in which oxidative stress caused by free radicals is an important damage mechanism. The HD experimental model induced by quinolinic acid (QUIN) has been widely used to evaluate therapeutic effects of antioxidant compounds. The aim of this study was to test whether the fatty acid content in olive- or fish-oil-rich diet prevents against QUIN-related oxidative damage in rats. Rats were fed during 20 days with an olive- or a fish-oil-rich diet (15% w/w). Posterior to diet period, rats were striatally microinjected with QUIN (240 nmol/µl) or saline solution. Then, we evaluated the neurological damage, oxidative status, and gamma isoform of the peroxisome proliferator-activated receptor (PPARγ) expression. Results showed that fatty acid-rich diet, mainly by fish oil, reduced circling behavior, prevented the fall in GABA levels, increased PPARγ expression, and prevented oxidative damage in striatal tissue. In addition none of the enriched diets exerted changes neither on triglycerides or cholesterol blood levels, nor or hepatic function. This study suggests that olive- and fish-oil-rich diets exert neuroprotective effects.

Cortical regulation of striatal projection neurons and interneurons in a Parkinson's disease rat model.

Striatal neurons can be either projection neurons or interneurons, with each type exhibiting distinct susceptibility to various types of brain damage. In this study, 6-hydroxydopamine was injected into the right medial forebrain bundle to induce dopamine depletion, and/or ibotenic acid was injected into the M1 cortex to induce motor cortex lesions. Immunohistochemistry and western blot assay showed that dopaminergic depletion results in significant loss of striatal projection neurons marked by dopamine- and cyclic adenosine monophosphate-regulated phosphoprotein, molecular weight 32 kDa, calbindin, and μ-opioid receptor, while cortical lesions reversed these pathological changes. After dopaminergic deletion, the number of neuropeptide Y-positive striatal interneurons markedly increased, which was also inhibited by cortical lesioning. No noticeable change in the number of parvalbumin-positive interneurons was found in 6-hydroxydopamine-treated rats. Striatal projection neurons and interneurons show different susceptibility to dopaminergic depletion. Further, cortical lesions inhibit striatal dysfunction and damage induced by 6-hydroxydopamine, which provides a new possibility for clinical treatment of Parkinson's disease.

Neuroprotective effect of caffeic acid phenethyl ester in 3-nitropropionic acid-induced striatal neurotoxicity

Caffeic acid phenethyl ester (CAPE), derived from honeybee hives, is a bioactive compound with strong antioxidant activity. This study was designed to test the neuroprotective effect of CAPE in 3-nitropropionic acid (3NP)-induced striatal neurotoxicity, a chemical model of Huntington's disease (HD). Initially, to test CAPE's antioxidant activity, a 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) antioxidant assay was employed, and CAPE showed a strong direct radical-scavenging eff ect. In addition, CAPE provided protection from 3NP-induced neuronal cell death in cultured striatal neurons. Based on these observations, the in vivo therapeutic potential of CAPE in 3NP-induced HD was tested. For this purpose, male C57BL/6 mice were repeatedly given 3NP to induce HD-like pathogenesis, and 30 mg/kg of CAPE or vehicle (5% dimethyl sulfoxide and 95% peanut oil) was administered daily. CAPE did not cause changes in body weight, but it reduced mortality by 29%. In addition, compared to the vehicle-treated group, robustly reduced striatal damage was observed in the CAPE-treated animals, and the 3NP-induced behavioral defi cits on the rotarod test were signifi cantly rescued after the CAPE treatment. Furthermore, immunohistochemical data showed that immunoreactivity to glial fibrillary acidic protein (GFAP) and CD45, markers for astrocyte and microglia activation, respectively, were strikingly reduced. Combined, these data unequivocally indicate that CAPE has a strong antioxidant eff ect and can be used as a potential therapeutic agent against HD.

Effect of embelin against 3-nitropropionic acid-induced Huntington's disease in rats.

3-Nitropropionic acid (3-NP) causes severe neurotoxicity in animals, which depicts Huntington's disease (HD) in humans. Embelin, the main active constituent of Embelia ribes, has been reported to possess various pharmacological actions, mainly anti-inflammatory, antioxidant, anticonvulsant and neuroprotective. The aim of the present study was to evaluate the neuroprotective effect of embelin against 3-NP induced experimental HD in rats. Adult Wistar rats were pretreated with vehicle/embelin (10 and 20mg/kg p.o.) for 7 days. From 8th day onwards, embelin was co-treated with 3-NP (15mg/kg, i.p.) for 7 days. At the end of the treatment schedule, animals were evaluated for behavioral alterations and brain homogenates were used for estimation of oxidative stress parameters (lipid peroxidation, reduced glutathione, catalase and glutathione-S-transferase). 2,3,5-Triphenyl tetrazolium chloride (TTC) stained brain slices were used for lesion size measurement. Administration of 3-NP significantly altered the behavioral and neuronal antioxidant status and caused significant neuronal damage in striatal region. Embelin, at both the tested doses, caused a significant reversal of behavioral and antioxidant status alterations and reversed the striatal neuronal damage induced by 3-NP. These findings suggest the neuroprotective effect of embelin against HD. The observed protective effect might be attributed to the antioxidant properties of embelin.

HMGB1 Promotes Mitochondrial Dysfunction-Triggered Striatal Neurodegeneration via Autophagy and Apoptosis Activation.

Impairments in mitochondrial energy metabolism are thought to be involved in many neurodegenerative diseases. The mitochondrial inhibitor 3-nitropropionic acid (3-NP) induces striatal pathology mimicking neurodegeneration in vivo. Previous studies showed that 3-NP also triggered autophagy activation and apoptosis. In this study, we focused on the high-mobility group box 1 (HMGB1) protein, which is important in oxidative stress signaling as well as in autophagy and apoptosis, to explore whether the mechanisms of autophagy and apoptosis in neurodegenerative diseases are associated with metabolic impairment. To elucidate the role of HMGB1 in striatal degeneration, we investigated the impact of HMGB1 on autophagy activation and cell death induced by 3-NP. We intoxicated rat striata with 3-NP by stereotaxic injection and analyzed changes in expression HMGB1, proapoptotic proteins caspase-3 and phospho-c-Jun amino-terminal kinases (p-JNK). 3-NP–induced elevations in p-JNK, cleaved caspase-3, and autophagic marker LC3-II as well as reduction in SQSTM1 (p62), were significantly reduced by the HMGB1 inhibitor glycyrrhizin. Glycyrrhizin also significantly inhibited 3-NP–induced striatal damage. Neuronal death was replicated by exposing primary striatal neurons in culture to 3-NP. It was clear that HMGB1 was important for basal autophagy which was shown by rescue of cells through HMGB1 targeting shRNA approach.3-NP also induced the expression of HMGB1, p-JNK, and LC3-II in striatal neurons, and p-JNK expression was significantly reduced by shRNA knockdown of HMGB1, an effect that was reversed by exogenously increased expression of HMGB1. These results suggest that HMGB1 plays important roles in signaling for both autophagy and apoptosis in neurodegeneration induced by mitochondrial dysfunction.

VGF and striatal cell damage in in vitro and in vivo models of Huntington's disease

Huntington’s disease (HD) is an inherited genetic disorder, characterized by cognitive dysfunction and abnormal body movements, and at present there is no effective treatment for HD. Therapeutic options for HD are limited to symptomatic treatment approaches and there is no cure for this devastating disease. Here, we examined whether SUN N8075, (2S)-1-(4-amino-2,3,5-trimethylphenoxy)-3-{4-[4-(4-fluorobenzyl)phenyl]-1-piperazinyl}-2-propanol dimethanesulfonate, which exerts neuroprotective effects by antioxidant effects and induction of VGF nerve growth factor inducible (VGF), has beneficial effects in STHdh cells derived from striatum of knock-in HD mice and R6/2 HD mice. In an in vitro study, SUN N8075 inhibited the cell death caused by mutant huntingtin (mHtt) and upregulated the VGF mRNA level via the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). Furthermore, 30 amino acid of VGF C-terminal peptide, AQEE-30 inhibited the cell death and the aggregation of mHtt. In an in vivo study, SUN N8075 improved the survival and the clasping response in the R6/2 mice. Furthermore, SUN N8075 increased the number of surviving neurons in the striatum of the R6/2 mice. These findings suggest that SUN N8075 may be an effective candidate for HD treatments.

The CB₁ cannabinoid receptor signals striatal neuroprotection via a PI3K/Akt/mTORC1/BDNF pathway.

The CB1 cannabinoid receptor, the main molecular target of endocannabinoids and cannabis active components, is the most abundant G protein-coupled receptor in the mammalian brain. In particular, the CB1 receptor is highly expressed in the basal ganglia, mostly on terminals of medium-sized spiny neurons, where it plays a key neuromodulatory function. The CB1 receptor also confers neuroprotection in various experimental models of striatal damage. However, the assessment of the physiological relevance and therapeutic potential of the CB1 receptor in basal ganglia-related diseases is hampered, at least in part, by the lack of knowledge of the precise mechanism of CB1 receptor neuroprotective activity. Here, by using an array of pharmacological, genetic and pharmacogenetic (designer receptor exclusively activated by designer drug) approaches, we show that (1) CB1 receptor engagement protects striatal cells from excitotoxic death via the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin complex 1 pathway, which, in turn, (2) induces brain-derived neurotrophic factor (BDNF) expression through the selective activation of BDNF gene promoter IV, an effect that is mediated by multiple transcription factors. To assess the possible functional impact of the CB1/BDNF axis in a neurodegenerative-disease context in vivo, we conducted experiments in the R6/2 mouse, a well-established model of Huntington's disease, in which the CB1 receptor and BDNF are known to be severely downregulated in the dorsolateral striatum. Adeno-associated viral vector-enforced re-expression of the CB1 receptor in the dorsolateral striatum of R6/2 mice allowed the re-expression of BDNF and the concerted rescue of the neuropathological deficits in these animals. Collectively, these findings unravel a molecular link between CB1 receptor activation and BDNF expression, and support the relevance of the CB1/BDNF axis in promoting striatal neuron survival.