Mitochondrial Dysfunction and Parkinson's Disease: Pathogenesis and Therapeutic Strategies

Parkinson's disease (PD) is a common age-related neurodegenerative disorder whose pathogenesis is not completely understood. Mitochondrial dysfunction and increased oxidative stress have been considered as major causes and central events responsible for the progressive degeneration of dopaminergic (DA) neurons in PD. Therefore, investigating mitochondrial disorders plays a role in understanding the pathogenesis of PD and can be an important therapeutic target for this disease. This study discusses the effect of environmental, genetic and biological factors on mitochondrial dysfunction and also focuses on the mitochondrial molecular mechanisms underlying neurodegeneration, and its possible therapeutic targets in PD, including reactive oxygen species generation, calcium overload, inflammasome activation, apoptosis, mitophagy, mitochondrial biogenesis, and mitochondrial dynamics. Other potential therapeutic strategies such as mitochondrial transfer/transplantation, targeting microRNAs, using stem cells, photobiomodulation, diet, and exercise were also discussed in this review, which may provide valuable insights into clinical aspects. A better understanding of the roles of mitochondria in the pathophysiology of PD may provide a rationale for designing novel therapeutic interventions in our fight against PD.

Addressing the Neuroprotective Actions of Coffee in Parkinson’s Disease: An Emerging Nutrigenomic Analysis

Caffeine is one of the predominant dietary components and psychostimulants present in coffee, a widely appreciated beverage. Corroborating epidemiological and laboratory evidence have suggested an inverse association between the dietary intakes of coffee and the risk of Parkinson’s Disease (PD). Growing attention has been paid to the impact of coffee consumption and genetic susceptibility to PD pathogenesis. Coffee is believed to play prominent roles in mediating the gene makeup and influencing the onset and progression of PD. The current review documents a current discovery of the coffee × gene interaction for the protective management of PD. The evidence underlying its potent impacts on the adenosine receptors (A2AR), estrogen receptors (ESR), heme oxygenase (HO), toxicant responsive genes, nitric oxide synthase (NOS), cytochrome oxidase (Cox), familial parkinsonism genetic susceptibility loci, bone marrow stromal cell antigen 1 (BST1), glutamate receptor gene and apolipoprotein E (APOE) genotype expressions is outlined. Furthermore, the neuroprotective mechanisms of coffee for the amelioration of PD are elucidated.

Association between statin use and Parkinson's disease in Korean patients with hyperlipidemia

INTRODUCTION

Findings on the association between statin therapy and Parkinson's disease (PD) occurrence have been inconsistent. This study aimed to identify the association between statin use and PD in participants with a history of hyperlipidemia or blood cholesterol >200 in a Korean population to exclude nonstatin users owing to normal lipid values.

METHODS

We conducted a nested case-control analysis using the Korean National Health Insurance Service-National Sample Cohort assessed between 2002 and 2015. We identified 3026 PD cases. A total of 12,104 controls were then individually matched by age, sex, income, and region of residence at a ratio of 1:4. Potential confounders comprised basic demographic factors, lifestyle factors, various medical conditions and comorbidities. A conditional/unconditional logistic regression method was applied.

RESULTS

Compared with statin use for <6 months, adjusted odds ratios (aORs) with 95% confidence intervals (CIs) for 6-12 months of statin use and ≥12 months of statin use were 1.03 (0.92-1.15) and 1.61 (1.35-1.93) after adjustment for confounders, respectively (P = 0.664 and P < 0.001). In analyses according to statin solubility, only the association between lipophilic statin use for ≥12 months and PD maintained statistical significance, with an aOR of 1.64 (95% CI = 1.34-2.01, P < 0.001). These relations were consistent in subgroup analyses by covariates.

CONCLUSIONS

Statin use for more than 12 months was associated with a higher probability of PD in the Korean population with hyperlipidemia. This probability was significant for lipophilic statins but not hydrophilic statins.

Opposite Roles of Co-enzyme Q10 and Formaldehyde in Neurodegenerative Diseases

Most of neurodegenerative diseases (NDD) have no cure. The common etiology of neurodegenerations is unclear. Air pollutant-gaseous formaldehyde is notoriously known to induce demyelination and cognitive impairments. Unexpectedly, an amount of formaldehyde has been detected in the brains. Multiple factors can induce the generation and accumulation of endogenous formaldehyde. Excessive formaldehyde can induce oxidative stress to generate H2O2; in turn, H2O2 promote formaldehyde production. Clinical investigations have shown that an abnormal high level of formaldehyde but low level of coenzyme Q10 (coQ10) was observed in patients with NDD. Further studies have proven that excessive formaldehyde directly inactivates coQ10, reduces the ATP generation, enhances oxidative stress, initiates inflammation storm, induces demyelination; subsequently, it results in neurodegeneration. Although the low water solubility of coQ10 limits its clinical application, nanomicellar water-soluble coQ10 exhibits positive therapeutical effects. Hence, nanopackage of coQ10 may be a promising strategy for treating NDD.

Systemic mitochondrial disruption is a key event in the toxicity of bacterial pore-forming toxins to Caenorhabditis elegans

Pore-forming toxins (PFTs) are important weapons of multiple bacterial pathogens to establish their infections. PFTs generally form pores in the plasma membrane of target cells; however, the intracellular pathogenic processes triggered after pore-formation remain poorly understood. Using Caenorhabditis elegans as a model and Bacillus thuringiensis nematicidal Cry PFTs, we show here that the localized PFT attack causes a systemic mitochondrial damage, important for the PFT toxicity. We find that PFTs punch pores only in gut cells of nematodes, but unexpectedly mitochondrial disruption is able to occur in distal unperforated regions, such as the head and muscle tissues. We demonstrate that PFTs affect the activity of the mitochondrial respiratory chain (MRC) complex I resulting in the loss of mitochondrial membrane potential (ΔΨ_m ), which causes further mitochondrial fragmentation and the reduction of total mitochondrial content. Worms with decreased ΔΨ_m or inhibited MRC activity show higher sensitivity to PFTs. The inhibition of mitochondrial fission or the increase of mitochondrial content markedly improves the survival of animals treated with PFTs. These findings suggest that mitochondrial changes underpin PFT-mediated toxicity against nematodes and that systemic mitochondrial disruption caused by localized pore-formation represents a conserved key intracellular event in the mode of action of PFTs.

Can Nutritional Adequacy Help Evade Neurodegeneration in Older Age? A Review

There is an increase in susceptibility to chronic and debilitating diseases with aging. The reason for the underlying neuronal degeneration and normal aging of the brain remains elusive. Different research studies have been conducted to discover how the brain degenerates and the importance of vitamins' role in the neurocognitive decline. Comprehensive literature research was conducted using all relevant data available from PubMed and Google scholar for this article. There has been evidence linking the consumption of essential nutrients to preventing the disease conditions that result in cognitive decline. This article provides the latest scientific advances specific to how dietary nutrients and non-nutrient may affect cognitive aging. An adequate supply of nutrients like vitamin B2 (riboflavin), vitamin B12, vitamin E, essential fatty acid (omega-3 fatty acid), and flavonoids play a vital role in ensuring healthy aging, enhancing memory, and strengthening neuroprotection. These nutrients help in neurodegenerative diseases like Alzheimer's disease and Parkinson's. We recommend more research studies to determine the underlying mechanism of how these essential nutrients work in the prevention of cognitive decline. These studies will help provide the evidence needed for new dietary recommendations for combating these diseases that often affect aging patients.

Melatonin regulates mitochondrial dynamics and alleviates neuron damage in prion diseases

Prion diseases are neurodegenerative diseases associated with neuron damage and behavioral disorders in animals and humans. Melatonin is a potent antioxidant and is used to treat a variety of diseases. We investigated the neuroprotective effect of melatonin on prion-induced damage in N2a cells. N2a cells were pretreated with 10 μM melatonin for 1 hour followed by incubation with 100 μM PrP^106-126 for 24 hours. Melatonin markedly alleviated PrP^106-126-induced apoptosis of N2a cells, and inhibited PrP^106-126-induced mitochondrial abnormality and dysfunction, including mitochondrial fragmentation and overproduction of reactive oxygen species (ROS), suppression of ATP, reduced mitochondrial membrane potential (MMP), and altered mitochondrial dynamic proteins dynamin-related protein 1 (DRP1) and optic atrophy protein 1 (OPA1). Our findings identify that pretreatment with melatonin prevents the deleterious effects of PrPSc on mitochondrial function and dynamics, protects synapses and alleviates neuron damage. Melatonin could be a novel and effective medication in the therapy of prion diseases.

Microfluidic system for Caenorhabditis elegans culture and oxygen consumption rate measurements

Mitochondrial respiration is a key signature for the assessment of mitochondrial functioning and mitochondrial dysfunction is related to many diseases including metabolic syndrome and aging-associated conditions. Here, we present a microfluidic Caenorhabditis elegans culture system with integrated luminescence-based oxygen sensing. The material used for the fabrication of the microfluidic chip is off-stoichiometry dual-cure thiol-ene-epoxy (OSTE+), which is well-suited for reliably recording on-chip oxygen consumption rates (OCR) due to its low gas permeability. With our microfluidic approach, it was possible to confine a single nematode in a culture chamber, starting from the L4 stage and studying it over a time span of up to 6 days. An automated protocol for successive worm feeding and OCR measurements during worm development was applied. We found an increase of OCR values from the L4 larval stage to adulthood, and a continuous decrease as the worm further ages. In addition, we performed a C. elegans metabolic assay in which exposure to the mitochondrial uncoupling agent FCCP increased the OCR by a factor of about two compared to basal respiration rates. Subsequent treatment with sodium azide inhibited completely mitochondrial respiration.

Enhanced mitochondrial inhibition by 3,4-dihydroxyphenyl-acetaldehyde (DOPAL)-oligomerized α-synuclein

Oligomeric forms of α-synuclein are believed to cause mitochondrial injury, which may contribute to neurotoxicity in Parkinson's disease (PD). Here oligomers of α-synuclein were prepared using the dopamine metabolite, DOPAL (3,4-dihydroxyphenyl-acetaldehyde), in the presence of guanidinium hydrochloride. Electron microscopy, mass spectrometry, and Western blotting studies revealed enhanced and stable oligomerization with DOPAL compared with dopamine or CuCl₂ /H₂ O₂ . Using isolated mouse brain mitochondria, DOPAL-oligomerized α-synuclein (DOS) significantly inhibited oxygen consumption rates compared with untreated, control-fibrillated, and dopamine-fibrillated synuclein, or with monomeric α-synuclein. Inhibition was greater in the presence of malate plus pyruvate than with succinate, suggesting the involvement of mitochondrial complex I. Mitochondrial membrane potential studies using fluorescent probes, JC-1, and Safranin O also detected enhanced inhibition by DOS compared with the other aggregated forms of α-synuclein. Testing a small customized chemical library, four compounds were identified that rescued membrane potential from DOS injury. While diverse in chemical structure and mechanism, each compound has been reported to interact with mitochondrial complex I. Western blotting studies revealed that none of the four compounds disrupted the oligomeric banding pattern of DOS, suggesting their protection involved direct mitochondrial interaction. The remaining set of chemicals also did not disrupt oligomeric banding, attesting to the high structural stability of this α-synuclein proteoform. DOPAL and α-synuclein are both found in dopaminergic neurons, where their levels are elevated in PD and in animal models exposed to chemical toxicants, including agricultural pesticides. The current study provides further evidence of α-synuclein-induced mitochondrial injury and a likely role in PD neuropathology.

Sulfuretin protects hepatic cells through regulation of ROS levels and autophagic flux

Palmitate (PA) exposure induces stress conditions featuring ROS accumulation and upregulation of p62 expression, resulting in autophagic flux blockage and cell apoptosis. Sulfuretin (Sul) is a natural product isolated from Rhus verniciflua Stokes; the cytoprotective effect of Sul on human hepatic L02 cells and mouse primary hepatocytes under PA-induced stress conditions was investigated in this study. Sul induced mitophagy by activation of p-TBK1 and LC3 and produced a concomitant decline in p62 expression. Autophagosome formation and mitophagy were assessed by the sensitive dual fluorescence reporter mCherry-EGFP-LC3B, and mitochondrial fragmentation was analyzed using MitoTracker Deep Red FM. A preliminary structure-activity relationship (SAR) for Sul was also investigated, and the phenolic hydroxyl group was found to be pivotal for maintaining the cytoprotective bioactivity of Sul. Furthermore, experiments using flow cytometry and western blots revealed that Sul reversed the cytotoxic effect stimulated by the autophagy inhibitors 3-methyladenine (3-MA) and chloroquine (CQ), and its cytoprotective effect was almost eliminated when the autophagy-related 5 (Atg5) gene was knocked down. These studies suggest that, in addition to its antioxidative effects, Sul stimulates mitophagy and restores impaired autophagic flux, thus protecting hepatic cells from apoptosis, and that Sul has potential future medical applications for hepatoprotection.

Comparative analysis of three different protocols for cholinergic neuron differentiation in vitro using mesenchymal stem cells from human dental pulp

A decrease in the activity of choline acetyltransferase, the enzyme responsible for acetylcholine synthesis in the cholinergic neurons cause neurological disorders involving a decline in cognitive abilities, such as Alzheimer's disease. Mesenchymal stem cells (MSCs) can be used as an efficient therapeutic agents due to their neuronal differentiation potential. Different source derived MSCs may have different differentiation potential under different inductions. Various in vitro protocols have been developed to differentiate MSCs into specific neurons but the comparative effect of different protocols utilizing same source derived MSCs, is not known. To address this issue, dental pulp derived MSCs (DPSCs) were differentiated into cholinergic neurons using three different protocols. In protocol I, DPSCs were pre-induced with serum-free ADMEM containing 1 mM of β-mercaptoethanol for 24 h and then incubated with 100 ng/ml nerve growth factor (NGF) for 6 days. Under protocol II, DPSCs were cultured in serum-free ADMEM containing 15 µg/ml of D609 (tricyclodecan-9-yl-xanthogenate) for 4 days. Under protocol III, the DPSCs were cultured in serum-free ADMEM containing 10 ng/ml of basic fibroblast growth factor (bFGF), 50 µM of forskolin, 250 ng/ml of sonic hedgehog (SHH), and 0.5 µM of retinoic acid (RA) for 7 days. The DPSCs were successfully trans-differentiated under all the protocols, exhibited neuron-like morphologies with upregulated cholinergic neuron-specific markers such as ChAT, HB9, ISL1, BETA-3, and MAP2 both at mRNA and protein levels in comparison to untreated cells. However, protocol III-induced cells showed the highest expression of the cholinergic markers and secreted the highest level of acetylcholine.

Stem Cell Transplantation and Physical Exercise in Parkinson's Disease, a Literature Review of Human and Animal Studies

The absence of effective and satisfactory treatments that contribute to repairing the dopaminergic damage caused by Parkinson's Disease (PD) and the limited recovery capacity of the nervous system are troubling issues and the focus of many research and clinical domains. Recent advances in the treatment of PD through stem cell (SC) therapy have recognized their promising restorative and neuroprotective effects that are implicated in the potentiation of endogenous mechanisms of repair and contribute to functional locomotor improvement. Physical exercise (PE) has been considered an adjuvant intervention that by itself induces beneficial effects in patients and animal models with Parkinsonism. In this sense, the combination of both therapies could provide synergic or superior effects for motor recovery, in contrast with their individual use. This review aims to provide an update on recent progress and the potential effectiveness of SC transplantation and PE for the treatment of locomotor deficits in PD. It has reviewed the neuropathological pathways involved in the classical motor symptoms of this condition and the mechanisms of action described in experimental studies that are associated with locomotor enhancement through exercise, cellular transplantation, and their union in some neurodegenerative conditions.

Diet and longevity: The effects of traditional eating habits on human lifespan extension

Since the dawn of time human beings have been trying to improve the quality of the existence and extend their lifespan. Genetic, environmental, behavioral and dietary factors influence the pathways that regulate aging and life expectancy, thus rendering longevity a very complex phenomenon. Although a long-lived elixir has not yet been found, physicians and scientists agree that nutrition has a major impact on the overall mortality and morbidity, hence becoming the subject of a widespread scientific research. This review describes, analyzes and compares the effects of different types of diets in reducing the onset of typical Western countries non-communicable diseases (NCDs) (cardiovascular diseases, tumors, chronic respiratory diseases, diabetes, etc.), thus increasing the average lifespan. It will first depict the most relevant characteristics, nutraceutical properties and effects on the populations of the Mediterranean, Japanese, Vegetarian and New Nordic Diet. Finally, it will describe the impact of different dietary restrictions in modulating the genetic pathways that regulate metabolism and aging. Overall, this work reinforces the evidence that specific eating habits, in addition to healthy and active lifestyles, are crucial to increase people’s health span and to achieve an optimal longevity.

Proteasome-targeted nanobodies alleviate pathology and functional decline in an α-synuclein-based Parkinson's disease model

Therapeutics designed to target α-synuclein (α-syn) aggregation may be critical in halting the progression of pathology in Parkinson's disease (PD) patients. Nanobodies are single-domain antibody fragments that bind with antibody specificity, but allow readier genetic engineering and delivery. When expressed intracellularly as intrabodies, anti-α-syn nanobodies fused to a proteasome-targeting proline, aspartate or glutamate, serine, and threonine (PEST) motif can modulate monomeric concentrations of target proteins. Here we aimed to validate and compare the in vivo therapeutic potential of gene therapy delivery of two proteasome-directed nanobodies selectively targeting α-syn in a synuclein overexpression-based PD model: VH14*PEST (non-amyloid component region) and NbSyn87*PEST (C-terminal region). Stereotaxic injections of adeno-associated viral 5-α-syn (AAV5-α-syn) into the substantia nigra (SN) were performed in Sprague-Dawley rats that were sorted into three cohorts based on pre-operative behavioral testing. Rats were treated with unilateral SN injections of vectors for VH14*PEST, NbSyn87*PEST, or injected with saline 3 weeks post lesion. Post-mortem assessments of the SN showed that both nanobodies markedly reduced the level of phosphorylated Serine-129 α-syn labeling relative to saline-treated animals. VH14*PEST showed considerable maintenance of striatal dopaminergic tone in comparison to saline-treated and NbSyn87*PEST-treated animals as measured by tyrosine hydroxylase immunoreactivity (optical density), DAT immunoreactivity (optical density), and dopamine concentration (high-performance liquid chromatography). Microglial accumulation and inflammatory response, assessed by stereological counts of Iba-1-labeled cells, was modestly increased in NbSyn87*PEST-injected rats but not in VH14*PEST-treated or saline-treated animals. Modest behavioral rescue was also observed, although there was pronounced variability among individual animals. These data validate in vivo therapeutic efficacy of vector-delivered intracellular nanobodies targeting α-syn misfolding and aggregation in synucleinopathies such as PD.

High expression of the HMGB1-TLR4 axis and its downstream signaling factors in patients with Parkinson's disease and the relationship of pathological staging

Objective

To detect the expression of high-mobility group box protein 1 (HMGB1) and toll-like receptor 4 (TLR4) and their downstream signaling factors-myeloid differentiation factor 88 (MyD88), nuclear factor kappa B (NF-κB), and tumor necrosis factor alpha (TNF-α)-in the sera of patients with Parkinson's disease (PD) in order to evaluate the relationship of the HMGB1-TLR4 axis with PD development and progression.

Methods

The serum HMGB1 and TLR4 protein levels of 120 patients with PD and 100 healthy volunteers were measured using double-antibody sandwich ELISA, and their correlations with PD staging, disease duration, drug treatment effectiveness, and clinical classification were analyzed. In addition, their correlations with the key downstream factors of the HMGB1-TLR4 axis (MyD88, NF-κB, and TNF-α) were analyzed.

Results

HMGB1 and TLR4 expressions were higher in the peripheral blood of patients with PD than in healthy volunteers. PD patients with poor drug treatment outcomes had significantly higher HMGB1 and TLR4 expressions than PD patients with stable drug treatment outcomes. Higher HMGB1 and TLR4 expressions were found in patients at higher PD stages, and patients with >4-year disease duration had significantly higher HMGB1 and TLR4 expressions than patients with <4-year disease duration. No significant difference in HMGB1 and TLR4 expressions was found among patients with tremor-dominant, akinetic-rigid, and mixed subtypes of PD. NF-κB and TNF-α expressions were positively correlated with high expression of the HMGB1-TLR4 axis.

Conclusion

High expression of the HMGB1-TLR4 axis is closely associated with PD development, progression, drug treatment effectiveness, staging, and disease duration and has great significance for PD diagnosis and treatment.

Autoimmune rheumatic diseases and the risk of Parkinson disease: a nationwide population-based cohort study in Taiwan

BACKGROUNDS

In autoimmune rheumatic diseases (ARDs), the levels of inflammatory mediators are increased and microglia may be activated, resulting in an inflammatory state and the degeneration of dopaminergic neurons. We investigated the association between ARDs and Parkinson disease (PD).

METHODS

We identified ARD patients through the Taiwan National Health Insurance Research Database from 2001 to 2012. From the general population, we randomly selected a comparison cohort that was frequency-matched by age (in 5-year increments), sex and index year. We analysed the risk of PD, stratified by sex, age and comorbidities, by using a Cox regression model.

RESULTS

The risk of PD was 1.37 times greater in ARD patients than in controls after adjustment for age, sex, and comorbidities. ARD subgroups, such as the rheumatoid arthritis and Sjogren syndrome (SS) cohorts, were associated with a significantly higher risk of PD (adjusted hazard ratio [HR], 1.14; 95% confidence interval [CI], 1.03-1.2 and adjusted HR, 1.56; 95% CI, 1.35-1.79, respectively). Furthermore, primary and secondary SS patients had significantly higher risks of PD (adjusted HR, 1.58; 95% CI, 1.32-1.88 and adjusted HR, 1.53, 95% CI, 1.23-1.90, respectively).

CONCLUSIONS

The risk of PD was significantly higher in the ARD patients. Prospective studies are needed to confirm whether ARDs indeed increase the risk of PD.

The effectiveness of external sensory cues in improving functional performance in individuals with Parkinson's disease: a systematic review with meta-analysis

A systematic review with meta-analysis was performed to investigate the effect external sensory cued therapy on activities of daily living (ADL) performance that include walking and daily tasks such as dressing for individuals with Parkinson's disease (PD). A detailed computer-aided search of the literature was applied to MEDLINE, Cumulative Index to Nursing and Allied Health Literature, EMBASE and PubMed. Studies investigating the effects of external sensory cued therapy on ADL performance for individuals with PD in all stages of disease progression were collected. Relevant articles were critically reviewed and study results were synthesized by two independent researchers. A data-analysis method was used to extract data from selected articles. A meta-analysis was carried out for all randomized-controlled trials. Six studies with 243 individuals with PD were included in this review. All six studies yielded positive findings in favour of external sensory cues. The meta-analysis showed that external sensory cued therapy improved statistically after treatment (P=0.011) and at follow-up (P<0.001) for ADL performance. The results of this review provided evidence of an improvement in ADL performance in general in individuals with PD. It is recommended that clinicians incorporate external sensory into a training programme focused on improving daily task performance.

Cell viability and dopamine secretion of 6-hydroxydopamine-treated PC12 cells co-cultured with bone marrow-derived mesenchymal stem cells

In the present study, PC12 cells induced by 6-hydroxydopamine as a model of Parkinson's Disease, were used to investigate the protective effects of bone marrow-derived mesenchymal stem cells bone marrow-derived mesenchymal stem cells against 6-hydroxydopamine-induced neurotoxicity and to verify whether the mechanism of action relates to abnormal α-synuclein accumulation in cells. Results showed that co-culture with bone marrow-derived mesenchymal stem cells enhanced PC12 cell viability and dopamine secretion in a cell dose-dependent manner. MitoLight staining was used to confirm that PC12 cells co-cultured with bone marrow-derived mesenchymal stem cells demonstrate reduced levels of cell apoptosis. Immunocytochemistry and western blot analysis found the quantity of α-synuclein accumulation was significantly reduced in PC12 cell and bone marrow-derived mesenchymal stem cell co-cultures. These results indicate that bone marrow-derived mesenchymal stem cells can attenuate 6-hydroxydopamine-induced cytotoxicity by reducing abnormal α-synuclein accumulation in PC12 cells.

Protective effects of the thioredoxin and glutaredoxin systems in dopamine-induced cell death

Although the etiology of sporadic Parkinson disease (PD) is unknown, it is well established that oxidative stress plays an important role in the pathogenic mechanism. The thioredoxin (Trx) and glutaredoxin (Grx) systems are two central systems upholding the sulfhydryl homeostasis by reducing disulfides and mixed disulfides within the cell and thereby protecting against oxidative stress. By examining the expression of redox proteins in human postmortem PD brains, we found the levels of Trx1 and thioredoxin reductase 1 (TrxR1) to be significantly decreased. The human neuroblastoma cell line SH-SY5Y and the nematode Caenorhabditis elegans were used as model systems to explore the potential protective effects of the redox proteins against 6-hydroxydopamine (6-OHDA)-induced cytotoxicity. 6-OHDA is highly prone to oxidation, resulting in the formation of the quinone of 6-OHDA, a highly reactive species and powerful neurotoxin. Treatment of human cells with 6-OHDA resulted in an increased expression of Trx1, TrxR1, Grx1, and Grx2, and small interfering RNA for these genes significantly increased the cytotoxic effects exerted by the 6-OHDA neurotoxin. Evaluation of the dopaminergic neurons in C. elegans revealed that nematodes lacking trxr-1 were significantly more sensitive to 6-OHDA, with significantly increased neuronal degradation. Importantly, both the Trx and the Grx systems were also found to directly mediate reduction of the 6-OHDA-quinone in vitro and thus render its cytotoxic effects. In conclusion, our results suggest that the two redox systems are important for neuronal survival in dopamine-induced cell death.

The impact of reactive oxygen species and genetic mitochondrial mutations in Parkinson's disease

The exact pathogenesis of Parkinson's disease (PD) is still unknown and proper mechanisms that correspond to the disease remain unidentified. It is understood that PD is age-related; as age increases, the chance of onset responds accordingly. Although there are no current means of curing PD, the understanding of reactive oxygen species (ROS) provides significant insight to possible treatments. Complex I deficiencies of the respiratory chain account for the majority of unfavorable neural apoptosis generation in PD. Dopaminergic neurons are severely damaged as a result of the deficiency. Symptoms such as inhibited cognitive ability and loss of smooth motor function are the results of such impairment. The genetic mutations of Parkinson's related proteins such as PINK1 and LRRK2 contribute to mitochondrial dysfunction which precedes ROS formation. Various pathways are inhibited by these mutations, and inevitably causing neural cell damage. Antioxidants are known to negate the damaging effects of free radical overexpression. This paper expands on the specific impact of mitochondrial genetic change and production of free radicals as well as its correlation to the neurodegeneration in Parkinson's disease.

Cholinergic Neuron-Like Cells Derived from Bone Marrow Stromal Cells Induced by Tricyclodecane-9-yl-Xanthogenate Promote Functional Recovery and Neural Protection after Spinal Cord Injury

The rate of neuronal differentiation of bone marrow stromal cells (BMSCs) in vivo is very low; therefore, it is necessary to elevate the number of BMSC-derived neurons to cure neurodegenerative diseases. We previously reported that tricyclodecane-9-yl-xanthogenate (D609), an inhibitor of phosphatidylcholine-specific phospholipase C (PC-PLC), induced BMSCs to differentiate into neuron-like cells in vitro. However, the neuronal type is not clear, and it is still unknown whether these neuron-like cells possess physiological properties of functional neurons and whether they can contribute to the recovery of neuron dysfunction. To answer these questions, we investigated their characteristics by detecting neuronal function-related neurotransmitters and calcium image. The results showed that these cells exhibited functional cholinergic neurons in vitro. Transplantation of these cholinergic neuron-like cells promoted the recovery of spinal cord-injured mice, and they were more effective than BMSCs. The number of cholinergic neurons was increased after injection with BMSC-derived cholinergic neuron-like cells, indicating their high differentiation rate in vivo. Moreover, the proportion of cholinergic neurons in host cells and secretion of acetylcholine were increased, and preservation of neurofilament was also observed in the lesion of mice implanted with BMSC-derived neurons, suggesting the neuronal protection of BMSC-derived neurons. Our findings provide both a simple method to induce the differentiation of BMSCs into cholinergic neuron-like cells and a putative strategy for the therapy of spinal cord injuries.

Omega-3 fatty acids in neurodegenerative diseases: focus on mitochondria

Mitochondrial dysfunction represents a common early pathological event in brain aging and in neurodegenerative diseases, e.g., in Alzheimer's (AD), Parkinson's (PD), and Huntington's disease (HD), as well as in ischemic stroke. In vivo and ex vivo experiments using animal models of aging and AD, PD, and HD mainly showed improvement of mitochondrial function after treatment with polyunsaturated fatty acids (PUFA) such as docosahexaenoic acid (DHA). Thereby, PUFA are particular beneficial in animals treated with mitochondria targeting toxins. However, DHA showed adverse effects in a transgenic PD mouse model and it is not clear if a diet high or low in PUFA might provide neuroprotective effects in PD. Post-treatment with PUFA revealed conflicting results in ischemic animal models, but intravenous administered DHA provided neuroprotective efficacy after acute occlusion of the middle cerebral artery. In summary, the majority of preclinical data indicate beneficial effects of n-3 PUFA in neurodegenerative diseases, whereas most controlled clinical trials did not meet the expectations. Because of the high half-life of DHA in the human brain clinical studies may have to be initiated much earlier and have to last much longer to be more efficacious.

Mitochondrial respiration in human viable platelets--methodology and influence of gender, age and storage

Studying whole cell preparations with intact mitochondria and respiratory complexes has a clear benefit compared to isolated or disrupted mitochondria due to the dynamic interplay between mitochondria and other cellular compartments. Platelet mitochondria have a potential to serve as a source of human viable mitochondria when studying mitochondrial physiology and pathogenic mechanisms, as well as for the diagnostics of mitochondrial diseases. The objective of the present study was to perform a detailed evaluation of platelet mitochondrial respiration using high-resolution respirometry. Further, we aimed to explore the limits of sample size and the impact of storage as well as to establish a wide range of reference data from different pediatric and adult cohorts. Our results indicate that platelet mitochondria are well suited for ex-vivo analysis with the need for minute sample amounts and excellent reproducibility and stability.

Assessing mitochondrial dysfunction in cells

Assessing mitochondrial dysfunction requires definition of the dysfunction to be investigated. Usually, it is the ability of the mitochondria to make ATP appropriately in response to energy demands. Where other functions are of interest, tailored solutions are required. Dysfunction can be assessed in isolated mitochondria, in cells or in vivo, with different balances between precise experimental control and physiological relevance. There are many methods to measure mitochondrial function and dysfunction in these systems. Generally, measurements of fluxes give more information about the ability to make ATP than do measurements of intermediates and potentials. For isolated mitochondria, the best assay is mitochondrial respiratory control: the increase in respiration rate in response to ADP. For intact cells, the best assay is the equivalent measurement of cell respiratory control, which reports the rate of ATP production, the proton leak rate, the coupling efficiency, the maximum respiratory rate, the respiratory control ratio and the spare respiratory capacity. Measurements of membrane potential provide useful additional information. Measurement of both respiration and potential during appropriate titrations enables the identification of the primary sites of effectors and the distribution of control, allowing deeper quantitative analyses. Many other measurements in current use can be more problematic, as discussed in the present review.

Mitochondrial therapeutics in Alzheimer's disease and Parkinson's disease

In neurons, mitochondria serve a wide variety of processes that are integral to their function and survival. It is, therefore, not surprising that evidence of mitochondrial dysfunction is observed across numerous neurodegenerative diseases. Alzheimer's disease and Parkinson's disease are two such diseases in which aberrant mitochondrial activity is proposed to contribute to pathogenesis. Current therapies for each disease target various mechanisms, but few, if any, directly target improved mitochondrial function. Recent discoveries pertaining to mitochondrial dynamics reveal that regulation of mitochondrial fission and fusion may play a key role in the pathogenesis of these diseases and consequently could be novel future therapeutic targets.