Bio-synthesized selenium nanoparticles ameliorate Brain oxidative stress in Parkinson disease rat models

AIM

Parkinson disease (PD) is a prevalent central nervous system degenerative condition that impacts elderly people. Recent clinical and experimental study findings have established oxidative stress as one of the main pathogeneses of PD. Selenium, a trace metals with antioxidant effects, might reverse the neurobehavioral impairments and oxidative stress in rats. Thus, the goal of this study was to ascertain if Selenium Nano Particles (SeNPs) are also effective to protect brain cells from oxidative stress or not.

MAIN METHODS

SeNPs were synthesized utilizing Ascorbic acid and chitosan as a reducing and stabilizing agent. Next, eight groups (N: 6) of male Wistar rats were randomly assigned and injected by different dosage (0.1, 0,2, and 0.3 mg/kg) of Se and SeNP. Finally, to ascertain the protective benefits of SeNP on PD rats, behavioral evaluation, clinical symptoms, antioxidant activity, and oxidant levels were examined.

KEY FINDINGS

According to the findings, PD rats' motor functions had developed by SeNP injection. Higher MDA levels and inhibited antioxidant activities (SOD, CAT, and GPX) in lesion group are highlighting the significant role of oxidative stress in dopaminergic neuron death and neurobehavioral abnormalities. SeNP also protect against oxidative stress as compared to the lesion group. The levels of MDA had greatly reduced while the activities of enzymes, TAC, and SeNP both had significantly increased.

SIGNIFICANCE

By enhancing antioxidant activity, administration of SeNP can reduce the hazardous consequences of oxidative stress.

COVID-19 and Parkinson's Disease: Shared Inflammatory Pathways Under Oxidative Stress

The current coronavirus pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in a serious global health crisis. It is a major concern for individuals living with chronic disorders such as Parkinson’s disease (PD). Increasing evidence suggests an involvement of oxidative stress and contribution of NFκB in the development of both COVID-19 and PD. Although, it is early to identify if SARS-CoV-2 led infection enhances PD complications, it is likely that oxidative stress may exacerbate PD progression in COVID-19 affected individuals and/or vice versa. In the current study, we sought to investigate whether NFκB-associated inflammatory pathways following oxidative stress in SARS-CoV-2 and PD patients are correlated. Toward this goal, we have integrated bioinformatics analysis obtained from Basic Local Alignment Search Tool of Protein Database (BLASTP) search for similarities of SARS-CoV-2 proteins against human proteome, literature review, and laboratory data obtained in a human cell model of PD. A Parkinson’s like state was created in 6-hydroxydopamine (6OHDA)-induced differentiated dopamine-containing neurons (dDCNs) obtained from an immortalized human neural progenitor cell line derived from the ventral mesencephalon region of the brain (ReNVM). The results indicated that SARS-CoV-2 infection and 6OHDA-induced toxicity triggered stimulation of caspases-2, -3 and -8 via the NFκB pathway resulting in the death of dDCNs. Furthermore, specific inhibitors for NFκB and studied caspases reduced the death of stressed dDCNs. The findings suggest that knowledge of the selective inhibition of caspases and NFκB activation may contribute to the development of potential therapeutic approaches for the treatment of COVID-19 and PD.

Proaggregant nuclear factor(s) trigger rapid formation of α-synuclein aggregates in apoptotic neurons

Cell-to-cell transmission of α-synuclein (αS) aggregates has been proposed to be responsible for progressive αS pathology in Parkinson disease (PD) and related disorders, including dementia with Lewy bodies. In support of this concept, a growing body of in vitro and in vivo experimental evidence shows that exogenously introduced αS aggregates can spread into surrounding cells and trigger PD-like pathology. It remains to be determined what factor(s) lead to initiation of αS aggregation that is capable of seeding subsequent propagation. In this study we demonstrate that filamentous αS aggregates form in neurons in response to apoptosis induced by staurosporine or other toxins-6-hydroxy-dopamine and 1-methyl-4-phenylpyridinium (MPP+). Interaction between αS and proaggregant nuclear factor(s) is associated with disruption of nuclear envelope integrity. Knocking down a key nuclear envelop constituent protein, lamin B1, enhances αS aggregation. Moreover, in vitro and in vivo experimental models demonstrate that aggregates released upon cell breakdown can be taken up by surrounding cells. Accordingly, we suggest that at least some αS aggregation might be related to neuronal apoptosis or loss of nuclear membrane integrity, exposing cytosolic α-synuclein to proaggregant nuclear factors. These findings provide new clues to the pathogenesis of PD and related disorders that can lead to novel treatments of these disorders. Specifically, finding ways to limit the effects of apoptosis on αS aggregation, deposition, local uptake and subsequent propagation might significantly impact progression of disease.

Indirubin-3-Oxime Effectively Prevents 6OHDA-Induced Neurotoxicity in PC12 Cells via Activating MEF2D Through the Inhibition of GSK3β

Indirubin-3-oxime (I3O), a synthetic derivative of indirubin, was originally designed as potent inhibitors of cyclin-dependent kinases (CDKs) and glycogen synthase kinase 3β (GSK3β) for leukemia therapy. In the current study, we have shown, for the first time, that I3O prevented 6-hydroxydopamine (6OHDA)-induced neuronal apoptosis and intracellular reactive oxygen species accumulation in PC12 cells in a concentration-dependent manner. GSK3β inhibitors but not CDK5 inhibitors reduced the neurotoxicity induced by 6OHDA. Moreover, the activation of GSK3β was observed after 6OHDA treatment. Furthermore, 6OHDA substantially decreased the transcriptional activity of myocyte enhancer factor 2D (MEF2D), a transcription factor that plays an important role in dopaminergic neuron survival, and reduced nuclear localized MEF2D expression. Interestingly, indirubin-3-oxime and GSK3β inhibitors prevented 6OHDA-induced dysregulation of MEF2D. In addition, short hairpin RNA-mediated decrease of MEF2D expression significantly abolished the neuroprotective effects of indirubin-3-oxime. Collectively, our results strongly suggested that indirubin-3-oxime prevented 6OHDA-induced neurotoxicity via activating MEF2D, possibly through the inhibition of GSK3β. In view of the capability of indirubin-3-oxime to cross the blood-brain barrier, our findings further indicated that indirubin-3-oxime might be a novel drug candidate for neurodegenerative disorders, including Parkinson's disease in particular.

The degeneration of dopaminergic synapses in Parkinson's disease: A selective animal model

Available evidence increasingly suggests that the degeneration of dopamine neurons in Parkinson's disease starts in the striatal axons and synaptic terminals. A selective procedure is described here to study the mechanisms involved in the striatal denervation of dopaminergic terminals. This procedure can also be used to analyze mechanisms involved in the dopaminergic re-innervation of the striatum, and the role of astrocytes and microglia in both processes. Adult Sprague-Dawley rats were injected in the lateral ventricles with increasing doses of 6-hydroxydopamine (12-50 μg), which generated a dose-dependent loss of dopaminergic synapses and axons in the striatum, followed by an axonal sprouting (weeks later) and by a progressive recovery of striatal dopaminergic synapses (months later). Both the degeneration and regeneration of the dopaminergic terminals were accompanied by astrogliosis. Because the experimental manipulations did not induce unspecific damage in the striatal tissue, this method could be particularly suitable to study the basic mechanisms involved in the distal degeneration and regeneration of dopaminergic nigrostriatal neurons, and the possible role of astrocytes and microglia in the dynamics of both processes.

Partial depletion of striatal dopamine enhances penetrance of cognitive deficits in a transgenic mouse model of Alzheimer's disease

Parkinson's disease and Alzheimer's disease (AD) are recognized to coexist on a spectrum of neurodegeneration, and it has been proposed that molecular interactions among pathogenic proteins are a basis for the overlap between these two diseases. We instead hypothesized that degeneration of the nigrostriatal dopaminergic system enhances the clinical penetrance of early-stage AD. To determine the effect of striatal dopamine (DA) on the pathological effects in an experimental model of AD, APPSWE /PS1ΔE9 mice received striatal injections of the neurotoxin 6-hydroxydopamine (6OHDA). Animals were tested in a Barnes maze protocol and in a water T-maze protocol at different ages to determine the onset of cognitive impairment. APPSWE /PS1ΔE9 mice that received 6OHDA injections showed significant impairment in Barnes maze performance at an earlier age than controls. Additionally, at 12 months of age, APPswe /PS1ΔE9 + 6OHDA mice demonstrated worse behavioral flexibility than other groups in a task-switch phase of the water T-maze. To determine the neuroprotective effects of dopaminergic neurotransmission against amyloid-β42 (Aβ42 ) toxicity, neuronal branch order and dendrite length were quantified in primary medium spiny neuron (MSN) cultures pretreated with increasing doses of the D1 and D2 receptor agonists before being exposed to oligomerized Aβ42 . Although there were no differences in Aβ peptide levels or plaque burden among the groups, in murine MSN culture dopaminergic agonists prevented a toxic response to Aβ42. Depletion of DA in the striatum exacerbated the cognitive impairment seen in a mouse model of early-stage AD; this may be due to a protective effect of dopaminergic innervation against Aβ striatal neurotoxicity.

Prefrontal D1 dopamine signaling is necessary for temporal expectation during reaction time performance

Responses during a simple reaction time task are influenced by temporal expectation, or the ability to anticipate when a stimulus occurs in time. Here, we test the hypothesis that prefrontal D1 dopamine signaling is necessary for temporal expectation during simple reaction time task performance. We depleted dopamine projections to the medial prefrontal circuits by infusing 6-hydroxidopamine, a selective neurotoxin, into the ventral tegmental area (VTA) of rats, and studied their performance on a simple reaction time task with two delays. VTA dopamine depletion did not change movements or learning of the reaction time task. However, VTA dopamine-depleted animals did not develop delay-dependent speeding of reaction times, suggesting that mesocortical dopamine signaling is required for temporal expectation. Next, we manipulated dopamine signaling within the medial prefrontal cortex using local pharmacology. We found that SCH23390, a D1-type dopamine receptor antagonist, specifically attenuated delay-dependent speeding, while sulpiride, a D2-type receptor antagonist, did not. These data suggest that prefrontal D1 dopamine signaling is necessary for temporal expectation during performance of a simple reaction time task. Our findings provide insight into temporal processing of the prefrontal cortex, and how dopamine signaling influences prefrontal circuits that guide goal-directed behavior.