L-deprenyl attenuates the rotenone-induced dopaminergic neurotoxicity: experimental evidences in rats

Parkinson disease (PD) is progressive neurological disorder because of massive degeneration of nigrostriatal dopaminergic neurons. The pathogenesis of PD is unknown, but considerable evidence suggests multifactorial factors including genetic, mitochondrial dysfunction, oxidative stress, excitotoxicity, calcium cytotoxicity, environmental factors and apoptosis. We investigated the role of oxidative damage produced by intranigral infusion of a potent mitochondrial complex-I inhibitor, rotenone and studied the neuroprotective effects with a well-known antiparkinsonian drug L-deprenyl in rats. Unilateral stereotaxic intranigral infusion of rotenone 6 lg caused significant decrease in dopamine levels. L-deprenyl (10 mg/kg) treatment significantly attenuated the DA depletion caused by rotenone. Parallely, a significant decrease in the concentration of GSH was also observed in the SN was reverted by L-deprenyl treatment. L-deprenyl significantly attenuated the rotenone-induced decrease in tyrosine hydroxylase immunoreactivity in striatum. The results suggest that L-deprenyl can rescue the dopaminergic neurons from the rotenone mediated neurodegeneration in this experimental animal model

Neuro-nutraceuticals: Further insights into their promise for brain health

In this Special Issue on “Nutraceuticals: Molecular and Functional Insights into how Natural Products Nourish the Brain”, the editors bring together contributions from experts in nutraceutical research to provide a contemporary overview of how select chemically identified molecules from natural products can beneficially affect brain function at the molecular level. Other contributions address key emergent issues such as bioavailability, neuronal health, inflammation and the holistic benefit of multi-targeted actions that impact upon how nutraceuticals ultimately leverage the brain to function better. In terms of the benefit of nutraceuticals it is clear that some naturally occurring molecules can be advantageous to both the young and aged brain, and that they have actions that ultimately can be directed to aid either in the improvement of cognition or in the management of debilitating neurodegenerative and neuropsychiatric condition

Chronic, low-dose rotenone reproduces Lewy neurites found in early stages of Parkinson's disease, reduces mitochondrial movement and slowly kills differentiated SH-SY5Y neural cells

<p>Abstract</p> <p>Background</p> <p>Parkinson's disease, the most common adult neurodegenerative movement disorder, demonstrates a brain-wide pathology that begins pre-clinically with alpha-synuclein aggregates ("Lewy neurites") in processes of gut enteric and vagal motor neurons. Rostral progression into substantia nigra with death of dopamine neurons produces the motor impairment phenotype that yields a clinical diagnosis. The vast majority of Parkinson's disease occurs sporadically, and current models of sporadic Parkinson's disease (sPD) can utilize directly infused or systemic neurotoxins.</p> <p>Results</p> <p>We developed a differentiation protocol for human SH-SY5Y neuroblastoma that yielded non-dividing dopaminergic neural cells with long processes that we then exposed to 50 nM rotenone, a complex I inhibitor used in Parkinson's disease models. After 21 days of rotenone, ~60% of cells died. Their processes retracted and accumulated ASYN-(+) and UB-(+) aggregates that blocked organelle transport. Mitochondrial movement velocities were reduced by 8 days of rotenone and continued to decline over time. No cytoplasmic inclusions resembling Lewy bodies were observed. Gene microarray analyses showed that the majority of genes were under-expressed. qPCR analyses of 11 mtDNA-encoded and 10 nDNA-encoded mitochondrial electron transport chain RNAs' relative expressions revealed small increases in mtDNA-encoded genes and lesser regulation of nDNA-encoded ETC genes.</p> <p>Conclusion</p> <p>Subacute rotenone treatment of differentiated SH-SY5Y neuroblastoma cells causes process retraction and partial death over several weeks, slowed mitochondrial movement in processes and appears to reproduce the Lewy neuritic changes of early Parkinson's disease pathology but does not cause Lewy body inclusions. The overall pattern of transcriptional regulation is gene under-expression with minimal regulation of ETC genes in spite of rotenone's being a complex I toxin. This rotenone-SH-SY5Y model in a differentiated human neural cell mimics changes of early Parkinson's disease and may be useful for screening therapeutics for neuroprotection in that disease stage.</p

Lesion of the Cerebellar Noradrenergic Innervation Enhances the Harmaline-Induced Tremor in Rats

Abnormal synchronous activation of the glutamatergic olivo-cerebellar pathway has been suggested to be crucial for the harmaline-induced tremor. The cerebellum receives two catecholaminergic pathways: the dopaminergic pathway arising from the ventral tegmental area/substantia nigra pars compacta, and the noradrenergic one from the locus coeruleus. The aim of the present study was to examine a contribution of the cerebellar catecholaminergic innervations to the harmaline-induced tremor in rats. Rats were injected bilaterally into the cerebellar vermis with 6-hydroxydopamine (6-OHDA; 8 μg/0.5 μl) either alone or this treatment was preceded (30 min earlier) by desipramine (15 mg/kg ip). Harmaline was administered to animals in doses of 7.5 or 15 mg/kg ip. Tremor of forelimbs was measured as a number of episodes during a 90-min observation. Rats were killed by decapitation 30 or 120 min after harmaline treatment. The levels of dopamine, noradrenaline, serotonin, and their metabolites were measured by HPLC in the cerebellum, substantia nigra, caudate–putamen, and frontal cortex. 6-OHDA injected alone enhanced the harmaline-induced tremor. Furthermore, it decreased the noradrenaline level by ca. 40–80% in the cerebellum and increased the levels of serotonin and 5-HIAA in the caudate–putamen and frontal cortex in untreated and/or harmaline-treated animals. When 6-OHDA treatment was preceded by desipramine, it decreased dopaminergic transmission in some regions of the cerebellum while inducing its compensatory activation in others. The latter lesion did not markedly influence the tremor induced by harmaline. The present study indicates that noradrenergic innervation of the cerebellum interacts with cerebral serotonergic systems and plays an inhibitory role in the harmaline-induced tremor

Stereotaxical Infusion of Rotenone: A Reliable Rodent Model for Parkinson's Disease

A clinically-related animal model of Parkinson's disease (PD) may enable the elucidation of the etiology of the disease and assist the development of medications. However, none of the current neurotoxin-based models recapitulates the main clinical features of the disease or the pathological hallmarks, such as dopamine (DA) neuron specificity of degeneration and Lewy body formation, which limits the use of these models in PD research. To overcome these limitations, we developed a rat model by stereotaxically (ST) infusing small doses of the mitochondrial complex-I inhibitor, rotenone, into two brain sites: the right ventral tegmental area and the substantia nigra. Four weeks after ST rotenone administration, tyrosine hydroxylase (TH) immunoreactivity in the infusion side decreased by 43.7%, in contrast to a 75.8% decrease observed in rats treated systemically with rotenone (SYS). The rotenone infusion also reduced the DA content, the glutathione and superoxide dismutase activities, and induced alpha-synuclein expression, when compared to the contralateral side. This ST model displays neither peripheral toxicity or mortality and has a high success rate. This rotenone-based ST model thus recapitulates the slow and specific loss of DA neurons and better mimics the clinical features of idiopathic PD, representing a reliable and more clinically-related model for PD research

Synergistic actions of melatonin in combination with anti-parkinsonian drugs in experimental model of Parkinson’s disease

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by progressive degeneration and loss of nigrostriatal dopaminergic neurons in the midbrain, A9 substantia nigra neurons leading to severe striatal dopamine (DA) depletion resulting in tremor, rigidity and hypokinesia (Carlsson, 2002). PD is named after James Parkinson who first described the disease as “Shaking Palsy” (Paralysis Agitans) in his classic monograph “An essay on the Shaking Palsy” (Parkinson, 1817). This debilitating disorder has no cure existing, and recent epidemiological studies suggest an increasing trend in its incidents; predicting an alarming 2-fold increase in affected population by 2030 in several countries (Dorsey et al., 2007). Currently used drugs for PD provides symptomatic relief, and are based on increasing the striatal levels of DA, or controlling the DA transmission. However, these drugs are generally short acting, and with time develop serious side effects. There are cases when the drugs need to be discontinued due to exacerbation of DA-mediated effects. At this juncture, there is a great need of alternative therapies, or designs that would effectively reduce the dose of drugs that causes ‘on-off’ effects, dyskinesias, other undesirable motor effects, non-motor complications, and slower the progression of the disease. One of such effective therapy is using a peripheral aromatic amino acid decarboxylase inhibitor, carbidopa along with L-3,4-dihydroxyphenylalanine (L-DOPA). The present study mainly addressed such alternative approaches so as to find better therapeutic agents that may synergize with the existing PD drugs

Early-life Treatment of Antiserotonin Antibodies Alters Sensitivity to Serotonin Receptors, Nociceptive Stimulus and Serotonin Metabolism in Adult Rats

A single systemic administration of serotonin (5-HT) antibodies on day-1 of the life of rat has been investigated for neurotransmitter contents in nucleus raphe, and several discrete brain regions, as well as for serotoninergic syndromes and nociceptive responses in adult animals. 5-HT antiserum raised in rabbits were purified and characterized prior to subcutaneous administration in neonatal rats. Control animals received normal rabbit serum. Antibodies tagged with radioactive iodine were traced in the brains of rat pups treated subcutaneously. These animals at adulthood, exhibited an increase in body weight, increased sensitivity to serotonin agonist 5-methoxy-N-N-dimethyl tryptamine, and to nociceptive stimulus to subcutaneously administered formalin. Animals neonatally treated with 5-HT antiserum once on day 1 of life, exhibited significant decrease in the contents of serotonin and its metabolite as compared to normal serum treated animals specifically in nucleus raphe dorsalis, but not in substantia gresia centralis, nucleus accumbens, nucleus caudatus putamen, substantia nigra or tuberculum olfactorium during the study period of seven days to four months. The contents of dopamine or norepinephrine were not consistently altered in any of the nuclei studied. Since 5-HT is known to act as a trophic factor for its own development and its target areas, exposure to 5-HT antibodies during birth might have adversely affected the development of the serotoninergic system and resulted in long-lasting changes in behavior and 5-HT levels in the brain. These results have strong implications for the treatment of childhood developmental disorders such as autism where hyperserotoninemia is associated with the disease syndromes

Neuroprotection by Bromocriptine Against 1-methyl-4- phenyl-1,2,3,6-tetrahydropyridine-induced Neurotoxicity in Micel

Mice were treated with 1-methyl-4- phenyl-1,2,3,6-tetrahydropyridine (MPTP; 30 mg/kg i.p. twice, 16 h apart). This resulted in changes in motor performance and toxic insult of nigral neurons as evidenced by dopamine depletion in nucleus caudatus putamen. In vitro and in vivo treatment of MPTP caused the generation of hydroxyl radicals (•OH) as measured by a sensitive salicylate hydroxylation procedure. A dopamine agonist, bromocriptine (10 mM and 10 mg/kg i.p.), blocked •OH formation caused by MPTP in vitro (20 mM) and in vivo (30 mg/kg i.p.). An MPTP-induced increase in the activity of catalase and superoxide dismutase in substantia nigra on the seventh day was reduced by bromocriptine pretreatment. Bromocriptine blocked MPTP-induced behavioral dysfunction as well as glutathione and dopamine depletion, indicating its potent neuroprotective action. This study suggests that bromocriptine stimulates antioxidant mechanisms in the brain and acts as a free radical scavenger in addition to its action at dopamine receptors, thus indicating its strength as a valuable neuroprotectant. —Muralikrishnan, D., Mohanakumar, K. P. Neuroprotection by bromocriptine against 1- methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity in mice

Melatonin protects against oxidative stress caused by 1-methyl- 4-phenyl-1,2,3,6-tetrahydropyridine in the mouse nigrostriatum

We tested the hypothesis that melatonin acts as a powerful hydroxyl radical (•OH) scavenger in vivo in the brain, and interferes with oxidative stress caused by the parkinsonian neurotoxin, 1-methyl- 4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We investigated the e.ect of melatonin on in vitro •OH production employing a Fenton-like reaction in test tubes, and ex vivo •OH generation in isolated mitochondria induced by 1-methyl-4-phenyl pyridinium (MPP+), as well as on in vivo •OH formation in the mouse striatum following systemic administration of MPTP. We also measured reduced glutathione (GSH) levels, and superoxide dismutase (SOD) activity in the nucleus caudatus putamen (NCP) and substantia nigra (SN), 7 days following MPTP and/or melatonin administration. Melatonin caused a signi.cant and dose-dependent inhibition of the production of •OH in the in vitro, ex vivo and in vivo experimental conditions.Melatonin caused no changes in monoamine oxidase-B activity, in vitro in mitochondrial P2 fractions or in vivo following systemic administration. MPTP treatment in mice caused a signi.cant depletion of GSH, and increased the speci.c activity of SOD both in SN and NCP on the seventh day. MPTP-induced GSH depletion was dose-dependently blocked in SN and NCP by melatonin. Higher doses of melatonin exhibited a synergistic e.ect on MPTP-induced increase in the SOD activity in the SN. These results suggest that while GSH inhibition is a direct consequence of •OH generation following neurotoxin administration, the increase in SOD activity is a compensatory mechanism for removing superoxide radicals generated as the result of MPTP. Our results not only point to the potency of melatonin in blocking the primary insults caused by MPTP, but also provide evidence for triggering secondary neuroprotective mechanisms, suggesting its use as a therapeutic agent in neurodegenerative disorders, such as Parkinson’s disease