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Quinolinic acid (QA)-induced neurotoxicity involves a cascade of events such as increased calcium concentration in cytoplasm, exhaustive ATP depletion, oxidative stress, as well as selective GABAergic, dopaminergic, and cholinergic neuronal death. Clinical data hint towards the connection between signalling of dopaminergic system and efficient amelioration of chorea following a tetrabenazine administration in Huntington's disease patients. Therefore, the present study has been designed to explore the neuroprotective potential of paliperidone, an active metabolite of risperidone (a dopaminergic antagonist) against QA-induced neurotoxicity and related complications in rats. QA (200 nmol) was administered bilaterally to the striatum over a period of 2 min by means of a 28-gauge stainless steel needle attached to a Hamilton syringe. The study protocol involves seven treatment groups (n = 12): naïve, sham, control (QA), paliperidone (0.5, 1 and 2 mg/kg) and paliperidone (2) per se. Single bilateral intrastriatal injection of QA (200 nmol/2 μl saline) significantly caused motor incordination, memory impairment, oxidative damage, decrease in biogenic amines levels, cellular alterations (TNF-α, IL-6, PGE2, PGF2α, caspase-3, BDNF, mitochondrial function) and damage of striatal neurons compared to the sham treatment. Treatment with paliperidone (0.5, 1 and 2 mg/kg) for 21 days significantly attenuated the QA-induced behavioural (motor and memory function), neurochemical (antioxidant enzymes and biogenic amines) and cellular alterations, as well as striatal neurodegeneration. The study indicated that modulation of dopaminergic pathway by paliperidone treatment could be a useful approach in the management of motor and memory abnormality in HD patients.

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]