Coenzyme Q induces nigral mitochondrial uncoupling and prevents dopamine cell loss in a primate model of Parkinson's disease

Mitochondrial UCP1: Potential thermogenic mechanistic switch for the treatment of obesity and neurodegenerative diseases using natural and epigenetic drug candidates

BACKGROUND

Brown fat is known to provide non-shivering thermogenesis through mitochondrial uncoupling mediated by uncoupling protein 1 (UCP1). Non-shivering is not dependent on UCP2, UCP4, and BMCP1/UCP5 genes, which are distinct from UCP1 in a way that they are not constitutive uncouplers. Although they are susceptible to free fatty acid and free radical activation, their functioning has a significant impact on the performance of neurons.

METHODOLOGY

Using subject-specific keywords (Adipose tissue; Adipocytes; Mitochondria; Obesity; Thermogenesis; UCP's in Neurodegeneration; Alzheimer's disease; Parkinson's disease), research articles and reviews were retrieved from Web of Science, ScienceDirect, Google Scholar, and PubMed. This article includespublications published between 2018 and 2023. The drugs that upregulate UCP1 are included in the study while the drugs that do not impact UCP1 are were not included.

RESULTS

Neuronal UCPs have a direct impact on synaptic plasticity, neurodegenerative processes, and neurotransmission, by modulating calcium flux, mitochondrial biogenesis, local temperature, and free radical generation. Numerous significant advances in the study of neuronal UCPs and neuroprotection are still to be made. Identification of the tissue-dependent effects of UCPs is essential first. Pharmacologically targeting neuronal UCPs is a key strategy for preventing both neurodegenerative diseases and physiological aging. Given that UCP2 has activities that are tissue-specific, it will be essential to develop treatments without harmful side effects. The triggering of UCPs by CoQ, an essential cofactor, produces nigral mitochondrial uncoupling, reduces MPTP-induced toxicity, and may even decrease the course of Parkinson's disease, according to early indications.

CONCLUSION

Herein, we explore the potential of UCP1 as a therapeutic target for treating obesity, neurodegenerative diseases as well as a potential activator of both synthetic and natural drugs. A deeper knowledge of synaptic signaling and neurodegeneration may pave the way to new discoveries regarding the functioning and controlling of these genes.

Reactive oxygen species, toxicity, oxidative stress, and antioxidants: chronic diseases and aging

A physiological level of oxygen/nitrogen free radicals and non-radical reactive species (collectively known as ROS/RNS) is termed oxidative eustress or "good stress" and is characterized by low to mild levels of oxidants involved in the regulation of various biochemical transformations such as carboxylation, hydroxylation, peroxidation, or modulation of signal transduction pathways such as Nuclear factor-κB (NF-κB), Mitogen-activated protein kinase (MAPK) cascade, phosphoinositide-3-kinase, nuclear factor erythroid 2-related factor 2 (Nrf2) and other processes. Increased levels of ROS/RNS, generated from both endogenous (mitochondria, NADPH oxidases) and/or exogenous sources (radiation, certain drugs, foods, cigarette smoking, pollution) result in a harmful condition termed oxidative stress ("bad stress"). Although it is widely accepted, that many chronic diseases are multifactorial in origin, they share oxidative stress as a common denominator. Here we review the importance of oxidative stress and the mechanisms through which oxidative stress contributes to the pathological states of an organism. Attention is focused on the chemistry of ROS and RNS (e.g. superoxide radical, hydrogen peroxide, hydroxyl radicals, peroxyl radicals, nitric oxide, peroxynitrite), and their role in oxidative damage of DNA, proteins, and membrane lipids. Quantitative and qualitative assessment of oxidative stress biomarkers is also discussed. Oxidative stress contributes to the pathology of cancer, cardiovascular diseases, diabetes, neurological disorders (Alzheimer's and Parkinson's diseases, Down syndrome), psychiatric diseases (depression, schizophrenia, bipolar disorder), renal disease, lung disease (chronic pulmonary obstruction, lung cancer), and aging. The concerted action of antioxidants to ameliorate the harmful effect of oxidative stress is achieved by antioxidant enzymes (Superoxide dismutases-SODs, catalase, glutathione peroxidase-GPx), and small molecular weight antioxidants (vitamins C and E, flavonoids, carotenoids, melatonin, ergothioneine, and others). Perhaps one of the most effective low molecular weight antioxidants is vitamin E, the first line of defense against the peroxidation of lipids. A promising approach appears to be the use of certain antioxidants (e.g. flavonoids), showing weak prooxidant properties that may boost cellular antioxidant systems and thus act as preventive anticancer agents. Redox metal-based enzyme mimetic compounds as potential pharmaceutical interventions and sirtuins as promising therapeutic targets for age-related diseases and anti-aging strategies are discussed.

Age-associated sex difference in the expression of mitochondria-based redox sensitive proteins and effect of pioglitazone in nonhuman primate brain

BACKGROUND

Paraoxonase 2 (PON2) and neuronal uncoupling proteins (UCP4 and UCP5) possess antioxidant, anti-apoptotic activities and minimize accumulation of reactive oxygen species in mitochondria. While age and sex are risk factors for several disorders that are linked with oxidative stress, no study has explored the age- and sex-dependent expression of PON2 isoforms, UCP4 and UCP5 in primate brain or identified a drug to activate UCP4 and UCP5 in vivo. Preclinical studies suggest that the peroxisome proliferator-activated receptor gamma agonist, pioglitazone (PIO), can be neuroprotective, although the mechanism responsible is unclear. Our previous studies demonstrated that pioglitazone activates PON2 in primate brain and we hypothesized that pioglitazone also induces UCP4/5. This study was designed to elucidate the age- and sex-dependent expression of PON2 isoforms, UCP4 and UCP5, in addition to examining the impact of systemic PIO treatment on UCP4 and UCP5 expression in primate brain.

METHODS

Western blot technique was used to determine the age- and sex-dependent expression of UCP4 and UCP5 in substantia nigra and striatum of African green monkeys. In addition, we tested the impact of daily oral pioglitazone (5 mg/kg/day) or vehicle for 1 or 3 weeks on expression of UCP4 and UCP5 in substantia nigra and striatum in adult male monkeys. PIO levels in plasma and cerebrospinal fluid (CSF) were determined using LC-MS.

RESULTS

We found no sex-based difference in the expression of PON2 isoforms, UCP4 and UCP5 in striatum and substantia nigra of young monkeys. However, we discovered that adult female monkeys exhibit greater expression of PON2 isoforms than males in substantia nigra and striatum. Our data also revealed that adult male monkeys exhibit greater expression of UCP4 and UCP5 than females in substantia nigra but not in striatum. PIO increased UCP4 and UCP5 expression in substantia nigra and striatum at 1 week, but after 3 weeks of treatment this activation had subsided.

CONCLUSIONS

Our findings demonstrate a sex-, age- and region-dependent profile to the expression of PON2, UCP4 and UCP5. These data establish a biochemical link between PPARγ, PON2, UCP4 and UCP5 in primate brain and demonstrate that PON2, UCP4 and UCP5 can be pharmacologically stimulated in vivo, revealing a novel mechanism for observed pioglitazone-induced neuroprotection. We anticipate that these outcomes will contribute to the development of novel neuroprotective treatments for Parkinson's disease and other CNS disorders.

Mitochondria and Brain Disease: A Comprehensive Review of Pathological Mechanisms and Therapeutic Opportunities

Mitochondria play a vital role in maintaining cellular energy homeostasis, regulating apoptosis, and controlling redox signaling. Dysfunction of mitochondria has been implicated in the pathogenesis of various brain diseases, including neurodegenerative disorders, stroke, and psychiatric illnesses. This review paper provides a comprehensive overview of the intricate relationship between mitochondria and brain disease, focusing on the underlying pathological mechanisms and exploring potential therapeutic opportunities. The review covers key topics such as mitochondrial DNA mutations, impaired oxidative phosphorylation, mitochondrial dynamics, calcium dysregulation, and reactive oxygen species generation in the context of brain disease. Additionally, it discusses emerging strategies targeting mitochondrial dysfunction, including mitochondrial protective agents, metabolic modulators, and gene therapy approaches. By critically analysing the existing literature and recent advancements, this review aims to enhance our understanding of the multifaceted role of mitochondria in brain disease and shed light on novel therapeutic interventions.

Alpha synuclein post translational modifications: potential targets for Parkinson's disease therapy?

Parkinson's disease (PD) is the most common neurodegenerative disorder with motor symptoms. The neuropathological alterations characterizing the brain of patients with PD include the loss of dopaminergic neurons of the nigrostriatal system and the presence of Lewy bodies (LB), intraneuronal inclusions that are mainly composed of alpha-synuclein (α-Syn) fibrils. The accumulation of α-Syn in insoluble aggregates is a main neuropathological feature in PD and in other neurodegenerative diseases, including LB dementia (LBD) and multiple system atrophy (MSA), which are therefore defined as synucleinopathies. Compelling evidence supports that α-Syn post translational modifications (PTMs) such as phosphorylation, nitration, acetylation, O-GlcNAcylation, glycation, SUMOylation, ubiquitination and C-terminal cleavage, play important roles in the modulation α-Syn aggregation, solubility, turnover and membrane binding. In particular, PTMs can impact on α-Syn conformational state, thus supporting that their modulation can in turn affect α-Syn aggregation and its ability to seed further soluble α-Syn fibrillation. This review focuses on the importance of α-Syn PTMs in PD pathophysiology but also aims at highlighting their general relevance as possible biomarkers and, more importantly, as innovative therapeutic targets for synucleinopathies. In addition, we call attention to the multiple challenges that we still need to face to enable the development of novel therapeutic approaches modulating α-Syn PTMs.

Anti-Seizure and Neuronal Protective Effects of Irisin in Kainic Acid-Induced Chronic Epilepsy Model with Spontaneous Seizures

An increased level of reactive oxygen species is a key factor in neuronal apoptosis and epileptic seizures. Irisin reportedly attenuates the apoptosis and injury induced by oxidative stress. Therefore, we evaluated the effects of exogenous irisin in a kainic acid (KA)-induced chronic spontaneous epilepsy rat model. The results indicated that exogenous irisin significantly attenuated the KA-induced neuronal injury, learning and memory defects, and seizures. Irisin treatment also increased the levels of brain-derived neurotrophic factor (BDNF) and uncoupling protein 2 (UCP2), which were initially reduced following KA administration. Furthermore, the specific inhibitor of UCP2 (genipin) was administered to evaluate the possible protective mechanism of irisin. The reduced apoptosis, neurodegeneration, and spontaneous seizures in rats treated with irisin were significantly reversed by genipin administration. Our findings indicated that neuronal injury in KA-induced chronic epilepsy might be related to reduced levels of BDNF and UCP2. Moreover, our results confirmed the inhibition of neuronal injury and epileptic seizures by exogenous irisin. The protective effects of irisin may be mediated through the BDNF-mediated UCP2 level. Our results thus highlight irisin as a valuable therapeutic strategy against neuronal injury and epileptic seizures.

Evidence for Oxidative Pathways in the Pathogenesis of PD: Are Antioxidants Candidate Drugs to Ameliorate Disease Progression?

Parkinson’s disease (PD) is a progressive neurodegenerative disorder that arises due to a complex and variable interplay between elements including age, genetic, and environmental risk factors that manifest as the loss of dopaminergic neurons. Contemporary treatments for PD do not prevent or reverse the extent of neurodegeneration that is characteristic of this disorder and accordingly, there is a strong need to develop new approaches which address the underlying disease process and provide benefit to patients with this debilitating disorder. Mitochondrial dysfunction, oxidative damage, and inflammation have been implicated as pathophysiological mechanisms underlying the selective loss of dopaminergic neurons seen in PD. However, results of studies aiming to inhibit these pathways have shown variable success, and outcomes from large-scale clinical trials are not available or report varying success for the interventions studied. Overall, the available data suggest that further development and testing of novel therapies are required to identify new potential therapies for combating PD. Herein, this review reports on the most recent development of antioxidant and anti-inflammatory approaches that have shown positive benefit in cell and animal models of disease with a focus on supplementation with natural product therapies and selected synthetic drugs.

Coenzyme Q10 and Parkinsonian Syndromes: A Systematic Review

Coenzyme Q₁₀ (CoQ₁₀) has an important role as an antioxidant. Being that oxidative stress is one of the mechanisms involved in the pathogenesis of Parkinson’s disease (PD) and other neurodegenerative diseases, several studies addressed the concentrations of CoQ₁₀ in the different tissues of patients with PD and other parkinsonian syndromes (PS), trying to elucidate their value as a marker of these diseases. Other studies addressed the potential therapeutic role of CoQ₁₀ in PD and PS. We underwent a systematic review and a meta-analysis of studies measuring tissue CoQ₁₀ concentrations which shows that, compared with controls, PD patients have decreased CoQ₁₀ levels in the cerebellar cortex, platelets, and lymphocytes, increased total and oxidized CoQ₁₀ levels in the cerebrospinal fluid and a non-significant trend toward decreased serum/plasma CoQ₁₀ levels. Patients with multiple system atrophy (MSA) showed decreased CoQ₁₀ levels in the cerebellar cortex, serum/plasma, cerebrospinal fluid, and skin fibroblasts. Patients with Lewy body dementia (LBD) showed decreased cerebellar cortex CoQ₁₀, and those with progressive supranuclear palsy (PSP) had decreased CoQ₁₀ levels in the cerebrospinal fluid. A previous meta-analysis of studies addressing the therapeutic effects of CoQ₁₀ in PD showed a lack of improvement in patients with early PD. Results of the treatment with CoQ₁₀ in PSP should be considered preliminary. The potential role of CoQ₁₀ therapy in the MSA and selected groups of PD patients deserves future studies.

Uncoupling Proteins as Therapeutic Targets for Neurodegenerative Diseases

Most of the major retinal degenerative diseases are associated with significant levels of oxidative stress. One of the major sources contributing to the overall level of stress is the reactive oxygen species (ROS) generated by mitochondria. The driving force for ROS production is the proton gradient across the inner mitochondrial membrane. This gradient can be modulated by members of the uncoupling protein family, particularly the widely expressed UCP2. The overexpression and knockout studies of UCP2 in mice have established the ability of this protein to provide neuroprotection in a number of animal models of neurological disease, including retinal diseases. The expression and activity of UCP2 are controlled at the transcriptional, translational and post-translational levels, making it an ideal candidate for therapeutic intervention. In addition to regulation by a number of growth factors, including the neuroprotective factors LIF and PEDF, small molecule activators of UCP2 have been found to reduce mitochondrial ROS production and protect against cell death both in culture and animal models of retinal degeneration. Such studies point to the development of new therapeutics to combat a range of blinding retinal degenerative diseases and possibly other diseases in which oxidative stress plays a key role.

Contributions and Limitations of Mitochondria-Targeted and Non-Targeted Antioxidants in the Treatment of Parkinsonism: an Updated Review

As conventional therapeutics can only treat the symptoms of Parkinson's disease (PD), major focus of research in recent times is to slow down or prevent the progression of neuronal degeneration in PD. Non-targeted antioxidants have been an integral part of the conventional therapeutics regimen; however, their importance have lessened over time because of their controversial outcomes in clinical PD trials. Inability to permeate and localize within the mitochondria remains the main drawback on the part of non-targeted antioxidants inspite of possessing free radical scavenging properties. In contrast, mitochondrial-targeted antioxidants (MTAs), a special class of compounds have emerged having high advantages over non-targeted antioxidants by virtue of efficient pharmacokinetics and better absorption rate with capability to localize many fold inside the mitochondrial matrix. Preclinical experimentations indicate that MTAs have the potential to act as better alternatives compared to conventional non-targeted antioxidants in treating PD; however, sufficient clinical trials have not been conducted to investigate the efficacies of MTAs in treating PD. Controversial clinical outcomes on the part of non-targeted antioxidants and lack of clinical trials involving MTAs have made it difficult to go ahead with a direct comparison and in turn have slowed down the progress of development of safer and better alternate strategies in treating PD. This review provides an insight on the roles MTAs and non-targeted antioxidants have played in the treatment of PD till date in preclinical and clinical settings and discusses about the limitations of mitochondria-targeted and non-targeted antioxidants that can be resolved for developing effective strategies in treating Parkinsonism.

Exploring multifunctional antioxidants as potential agents for management of neurological disorders

Free radical or oxidative stress may be a fundamental mechanism underlying several human neurologic diseases. Therapy using free radical scavengers (antioxidants) has the potential to prevent, delay, or ameliorate many neurologic disorders. However, the biochemistry of oxidative pathobiology is complex, and optimum antioxidant therapeutic options may vary and need to be tailored to individual diseases. In vitro and animal model studies support the potential beneficial role of various antioxidant compounds in neurological disease. Antioxidants generally play an important role in reducing or preventing the cell damage and other changes which occur in the cells like mitochondrial dysfunction, DNA mutations, and lipid peroxidation in the cell membrane. Based on their mechanism of action, antioxidants can be used to treat various neurological disorders like Huntington's disease, Alzheimer's disease, and Parkinson's disease. Vitamin E has a scavenging action for reactive oxygen species (ROS) and also prevents the lipid peroxidation. Creatine generally reduces the mitochondrial dysfunction in Parkinson's disease (PD) patients. Various metal chelators are used in PD for the prevention of accumulation of the metals. Superoxidase dismutase (SOD), lipases, and proteases act as repair enzymes in patients with AD. Accordingly, the antioxidant defense system is found to be most useful for treating various neurological disorders.

Neuroprotection of retinal cells by Caffeic Acid Phenylethyl Ester（CAPE) is mediated by mitochondrial uncoupling protein UCP2

Oxidative stress due to mitochondrial produced reactive oxygen species is a major cause of damage seen in many retinal degenerative diseases. Caffeic acid phenylethyl ester （CAPE） is protective agent in multiple tissues and is reported to have anti-oxidant properties. Systemically applied CAPE protected retinal ganglion cells from ischemic injury induced by increased intraocular pressure. CAPE provided complete protection for ARPE19 retinal pigment epithelial cells against tert-butyl hydrogen peroxide and reduced both basal and LPS-stimulated ROS production. The major effect of CAPE was mediated by the mitochondrial uncoupling protein UCP2 since both pharmacological inhibition of UCP2 and siRNA-induced knockdown removed the ability of CAPE to block ROS production. Based on common structural features, CAPE may be acting as a mimetic of the natural UCP2 homeostatic regulator 4-hydroxy-2-nonenal. CAPE may provide a valuable tool to treat oxidative stress-related damage in retinal and other degenerative diseases.

Are ion channels potential therapeutic targets for Parkinson's disease?

Parkinson's disease (PD) is primarily associated with the progressive neurodegeneration of the dopaminergic neurons in the substantia nigra region of the brain. The resulting motor symptoms are managed with the help of dopamine replacement therapies. However, these therapeutics do not prevent the neurodegeneration underlying the disease and therefore lose their effectiveness in managing disease symptoms over time. Thus, there is an urgent need to develop newer therapeutics for the benefit of patients. The release of dopamine and the firing activity of substantia nigra neurons is regulated by several ion channels that act in concert. Dysregulations of these channels cause the aberrant movement of various ions in the intracellular milieu. This eventually leads to disruption of intracellular signalling cascades, alterations in cellular homeostasis, and bioenergetic deficits. Therefore, ion channels play a central role in driving the high vulnerability of dopaminergic neurons to degenerate during PD. Targeting ion channels offers an attractive mechanistic strategy to combat the process of neurodegeneration. In this review, we highlight the evidence pointing to the role of various ion channels in driving the PD processes. In addition, we also discuss the various drugs or compounds that target the ion channels and have shown neuroprotective potential in the in-vitro and in-vivo models of PD. We also discuss the current clinical status of various drugs targeting the ion channels in the context of PD.

Targeting cellular batteries for the therapy of neurological diseases

The mitochondria, apart from being known as the cell's "powerhouse," are crucial in the viability of nerve cells. Any damage to these cellular organelles can result in their cellular level dysfunction which includes rapidly multiplying reactive oxygen species (ROS) from the mitochondrial membrane, impaired calcium ion homeostasis, and disturbed mitochondrial dynamics by the formation of permeability transition pore in mitochondria. All these impaired biochemical changes lead to various neurological disorders such as progressive supranuclear palsy (PSP), Parkinson's disease (PD), and Alzheimer's disease (AD). Moreover, impaired mitochondrial functions are particularly prone to damage owing to prolonged lifespan and stretched length of the neurons. At the same time, neurons are highly dependent on ATP, and thus, the mitochondria play a central role in the pathogenesis pertaining to neuronal disorders. Dysfunction in the mitochondria is an early pathological hallmark of neurological disorders, and its early detection with the help of suitable biomarkers can lead to promising treatment in this area. Thus, the drugs which are targeting mitochondrial dysfunctions are the emerging area of research in connection with neurological disorders. This can be evidenced by the great opportunities for mitigation, diagnosis, and treatment of numerous human disorders that entail mitochondrial dysfunction at the nexus of their pathogenesis. Here, we throw light at the mitochondrial pathologies and indications of dysfunctional mitochondria in PD, AD, and PSP. There is also an insight into the possible therapeutic strategies highlighting the need for mitochondria-based medicine and made an attempt for claiming the prerequisite for the therapy of neurological diseases.

Improvement of Oxidative Stress and Mitochondrial Dysfunction by β-Caryophyllene: A Focus on the Nervous System

Mitochondrial dysfunction results in a series of defective cellular events, including decreased adenosine triphosphate (ATP) production, enhanced reactive oxygen species (ROS) output, and altered proteastasis and cellular quality control. An enhanced output of ROS may damage mitochondrial components, such as mitochondrial DNA and elements of the electron transport chain, resulting in the loss of proper electrochemical gradient across the mitochondrial inner membrane and an ensuing shutdown of mitochondrial energy production. Neurons have an increased demand for ATP and oxygen, and thus are more prone to damage induced by mitochondrial dysfunction. Mitochondrial dysfunction, damaged electron transport chains, altered membrane permeability and Ca²⁺ homeostasis, and impaired mitochondrial defense systems induced by oxidative stress, are pathological changes involved in neurodegenerative disorders. A growing body of evidence suggests that the use of antioxidants could stabilize mitochondria and thus may be suitable for preventing neuronal loss. Numerous natural products exhibit the potential to counter oxidative stress and mitochondrial dysfunction; however, science is still looking for a breakthrough in the treatment of neurodegenerative disorders. β-caryophyllene is a bicyclic sesquiterpene, and an active principle of essential oils derived from a large number of spices and food plants. As a selective cannabinoid receptor 2 (CB2) agonist, several studies have reported it as possessing numerous pharmacological activities such as antibacterial (e.g., Helicobacter pylori), antioxidant, anti-inflammatory, analgesic (e.g., neuropathic pain), anti-neurodegenerative and anticancer properties. The present review mainly focuses on the potential of β-caryophyllene in reducing oxidative stress and mitochondrial dysfunction, and its possible links with neuroprotection.

Antioxidant Therapeutics in Parkinson's Disease: Current Challenges and Opportunities

Oxidative stress is considered one of the pathological mechanisms that cause Parkinson’s disease (PD), which has led to the investigation of several antioxidants molecules as a potential therapeutic treatment against the disease. Although preclinical studies have demonstrated the efficacy of these compounds to maintain neuronal survival and activity in PD models, these results have not been reflected in clinical trials, antioxidants have not been able to act as disease modifiers in terms of clinical symptoms. Translational medicine currently faces the challenge of redesigning clinical trials to standardize criteria when testing molecules to reduce responses’ variability. Herein, we discuss current challenges and opportunities regarding several non-enzymatic antioxidants’ therapeutic molecules for PD patients’ potential treatment.

Oxidative Stress in Parkinson's Disease: Potential Benefits of Antioxidant Supplementation

Parkinson's disease (PD) occurs in approximately 1% of the population over 65 years of age and has become increasingly more common with advances in age. The number of individuals older than 60 years has been increasing in modern societies, as well as life expectancy in developing countries; therefore, PD may pose an impact on the economic, social, and health structures of these countries. Oxidative stress is highlighted as an important factor in the genesis of PD, involving several enzymes and signaling molecules in the underlying mechanisms of the disease. This review presents updated data on the involvement of oxidative stress in the disease, as well as the use of antioxidant supplements in its therapy.

Potassium channels and their emerging role in parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder, which is associated with a selective loss of dopaminergic neurons in the substantia nigra (SN) and a reduction of dopamine in the striatum. Recently, ion channel dysfunction has been considered a reason for the pathogenesis of PD. Potassium (K⁺) channels are widespread in the central nervous system, and play key roles in modulating cellular excitability, synaptic transmission, and neurotransmitter release. Based on recent studies and data, we propose that K⁺ channels may be new therapeutic targets for PD that slow the progressive loss of dopaminergic neurons and attenuate motor and non-motor symptoms. In this review, we mainly focus on: delayed rectifier, inwardly rectifying, and double-pore K⁺ channels. We summarize the expression and function of these channels in PD-related brain regions. We also discuss the effects of pharmacological blockade or activation of K⁺ channels in the progression and treatment of PD.

Mitophagy could fight Parkinson's disease through antioxidant action

During aging, the process of mitophagy, a system that allows the removal of dysfunctional mitochondria through lysosomal degradation, starts to malfunction. Because of this defect, damaged mitochondria are not removed correctly, and their decomposing components accumulate inside the cells. Dysfunctional mitochondria that are not removed by mitophagy produce high amounts of reactive oxygen species (ROS) and, thus, cause oxidative stress. Oxidative stress, in turn, is very harmful for the cells, neuronal cells, in particular. Consequently, the process of mitophagy plays a crucial role in mitochondria-related disease. Mitochondrial dysfunctions and oxidative stress are well-established factors contributing to Parkinson's disease (PD), one of the most common neurodegenerative disorders. In this review, we report various known antioxidants for PD treatments and describe the stimulation of mitophagy process as a novel and exciting method for reducing oxidative stress in PD patients. We describe the different mechanisms responsible for mitochondria removal through the mitophagy process. In addition, we review the functional connection between mitophagy induction and reduction of oxidative stress in several in vitro models of PD and also agents (drugs and natural compounds) already known to be antioxidants and to be able to activate mitophagy. Finally, we propose that there is an urgent need to test the use of mitophagy-inducing antioxidants in order to fight PD.

The Role of PGC-1α/UCP2 Signaling in the Beneficial Effects of Physical Exercise on the Brain

In understanding the pathology of neurological diseases, the role played by brain energy metabolism is gaining prominence. Animal models have demonstrated that regular physical exercise improves brain energy metabolism while also providing antidepressant, anxiolytic, antioxidant and neuroprotective functions. This review summarizes the latest evidence on the roles played by peroxisome proliferator-activated receptor gamma (PPAR-γ) coactivator 1-alpha (PGC-1α) and mitochondrial uncoupling protein (UCP) in this scenario. The beneficial effects of exercise seem to depend on crosstalk between muscles and nervous tissue through the increased release of muscle irisin during exercise.

Idebenone Alleviates Neuroinflammation and Modulates Microglial Polarization in LPS-Stimulated BV2 Cells and MPTP-Induced Parkinson's Disease Mice

Background: Idebenone is an antioxidant and a coenzyme Q10 analog that has been used to treat neurodegeneration disease. Some studies show idebenone exerts anti-inflammatory effects. However, whether idebenone can be used to reduce the neuroinflammation in Parkinson’s disease (PD) has been little studied.

Methods: The study investigated the potential anti-inflammatory effects of idebenone in vitro and in vivo, using cell models of Lipopolysaccharide (LPS)-simulated BV2 cells and animal models of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD with or without idebenone. To verify how idebenone exerts its effects on the BV2 cell activation and PD model, we performed the mechanistic studies in vitro and in vivo.

Results:In vitro study showed that pretreatment with idebenone could attenuate the production of pro-inflammatory factors in LPS-stimulated BV2 cells and promoted a phenotypic switch from the M1 state to the M2 state. Mechanistically, idebenone reduced the activation of the MAPK and NF-κB signaling pathway upon LPS stimulation. Furthermore, in vivo experiments confirmed that pretreatment with idebenone could ameliorate MPTP-induced neurodegeneration and modulate microglia phenotypes through inhibition of the MAPK and NF-κB signaling pathway in the SN.

Conclusion: These results suggest that idebenone ameliorates the neurological deficits related to PD and this effect is partly mediated by inhibiting the neuroinflammation and modulating microglia phenotypes.

Crosstalk between mitochondrial dysfunction, oxidative stress, and age related neurodegenerative disease: Etiologies and therapeutic strategies

Mitochondrial function is vital for normal cellular processes. Mitochondrial damage and oxidative stress have been greatly implicated in the progression of aging, along with the pathogenesis of age-related neurodegenerative diseases (NDs), such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Although antioxidant therapy has been proposed for the prevention and treatment of age-related NDs, unraveling the molecular mechanisms of mitochondrial dysfunction can lead to significant progress in the development of effective treatments against such diseases. Aging is associated with the generation and accumulation of reactive oxygen species (ROS) that are the major contributors to oxidative stress. Oxidative stress is caused because of the imbalance between the production of ROS and their oxidation, which can affect the mitochondrial respiratory chain function, thereby altering the membrane permeability and calcium homeostasis, along with increasing the heteroplasmic mtDNA and weakening the mitochondrial defense systems. Mitochondrial dysfunction mainly affects mitochondrial biogenesis and dynamics that are prominent in several age-related NDs. Mitochondrial dysfunction has a crucial role in the pathophysiology of age-related NDs. Several mitochondria targeted strategies, such as enhancing the antioxidant bioavailability via novel delivery systems, identifying unique mitochondrial proteins as specific drug targets, investigating the signaling pathways of mitochondrial biogenesis and dynamics, and identifying effective natural products are potentially effective to counteract mitochondrial dysfunction-related NDs.

The Role of Irisin in Alzheimer's Disease

Alzheimer’s disease (AD) is characterized by progressive memory dysfunction, oxidative stress, and presence of senile plaques formed by amyloid beta (Aβ) accumulation in the brain. AD is one of the most important causes of morbidity and mortality worldwide. AD has a variety of risk factors, including environmental factors, metabolic dysfunction, and genetic background. Recent research has highlighted the relationship between AD and systemic metabolic changes such as glucose and lipid imbalance and insulin resistance. Irisin, a myokine closely linked to exercise, has been associated with glucose metabolism, insulin sensitivity, and fat browning. Recent studies have suggested that irisin is involved in the process in central nervous system (CNS) such as neurogenesis and has reported the effects of irisin on AD as one of the neurodegenerative disease. Here, we review the roles of irisin with respect to AD and suggest that irisin highlight therapeutic important roles in AD. Thus, we propose that irisin could be a potential future target for ameliorating AD pathology and preventing AD onset.

Deletion of Kir6.2/SUR1 potassium channels rescues diminishing of DA neurons via decreasing iron accumulation in PD

ATP-sensitive potassium (K-ATP) channels express in the central nervous system extensively which coupling cell metabolism and cellular electrical activity. K-ATP channels in mature substantia nigra (SN) dopaminergic (DA) neurons are composed of inwardly rectifying potassium channel (Kir) subunit 6.2 and sulfonylurea receptor 1 (SUR1). Our previous study revealed that regulating K-ATP channel exerts the protective effect on DA neurons in a mouse model of Parkinson's disease (PD). However, the detailed mechanism underlying the role of Kir6.2/K-ATP remains unclear. In the present study, we found the deletion of Kir6.2 dramatically alleviated PD-like motor dysfunction of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) PD model. We further found that Kir6.2 knockout selectively restored the reduction of both DA neuronal number and dopamine transmitter level in the nigrostriatal of MPTP-treated PD mice. To gain some understanding on the molecular basis of this effect, we focused on the regulation of Kir6.2 deletion on iron metabolism which is tightly associated with DA neuron damage. We found that Kir6.2 knockout suppressed the excessive iron accumulation in MPTP-treated mouse midbrain and inhibited the upregulation of ferritin light chain (FTL), which is a main intracellular iron storage protein. We probed further and found out that the deletion of Kir6.2 inhibited the excessive production of FTL via IRP-IRE regulatory system, and thereby protecting SN DA neurons against MPTP challenge. Our findings suggest that Kir6.2 plays a crucial role in the pathogenesis of PD and regulating Kir6.2/K-ATP channel may be a promising strategy for PD treatment.

A glance at the therapeutic potential of irisin against diseases involving inflammation, oxidative stress, and apoptosis: An introductory review

Irisin is a hormone-like molecule mainly released by skeletal muscles in response to exercise. Irisin induces browning of the white adipose tissue and has been shown to regulate glucose and lipid homeostasis. Keeping its energy expenditure and metabolic properties in view, numerous studies have focused on its therapeutic potential for the treatment of metabolic disorders like obesity and type 2 diabetes. Recently, the anti-inflammatory, anti-apoptotic and anti-oxidative properties of irisin have received a great deal of attention of the scientific society. These pathogenic processes are often associated with initiation, progression, and prognosis of numerous diseases like myocardial infarction, kidney diseases, cancer, lung injury, inflammatory bowel diseases, atherosclerosis, liver diseases, obesity and type 2 diabetes. In the current review, we present evidence regarding the anti-inflammatory, anti-apoptotic and anti-oxidative potential of irisin pertaining to various pathological conditions. Here, we explore multiple molecular pathways targeted by irisin therapy. Given the promising effects of irisin, many diseases with evident oxidative stress, inflammation and apoptosis can be targeted by irisin.

Anti-Oxidants in Parkinson's Disease Therapy: A Critical Point of View

Parkinson’s disease (PD) is a degenerative neurological syndrome, which is characterized by the preferential death of dopaminergic (DAergic) neurons in the Substantia Nigra. The pathogenesis of this disorder remains poorly understood and PD is still incurable. Current drug treatments are aimed primarily for the treatment of symptoms to improve the quality of life. Therefore, there is a need to find out new therapeutic strategies that not only provide symptomatic relief but also halt or reverse the neuronal damage hampering PD progression. Oxidative stress has been identified as one of the major contributors for the nigral loss in both sporadic and genetic forms of PD. In this review we first evaluate the current literature that links oxidative stress and mitochondrial dysfunction to PD. We then consider the results obtained through the treatment of animal models or PD patients with molecules that prevent oxidative stress or reduce mitochondrial dysfunction.

The emerging neuroprotective role of mitochondrial uncoupling protein-2 in traumatic brain injury

Traumatic brain injury (TBI) is a multifaceted disease with intrinsically complex heterogeneity and remains a significant clinical challenge to manage. TBI model systems have demonstrated many mechanisms that contribute to brain parenchymal cell death, including glutamate and calcium toxicity, oxidative stress, inflammation, and mitochondrial dysfunction. Mitochondria are critically regulated by uncoupling proteins (UCP), which allow protons to leak back into the matrix and thus reduce the mitochondrial membrane potential by dissipating the proton motive force. This uncoupling of oxidative phosphorylation from adenosine triphosphate (ATP) synthesis is potentially critical for protection against cellular injury as a result of TBI and stroke. A greater understanding of the underlying mechanism or mechanisms by which uncoupling protein-2 (UCP2) functions to maintain or optimize mitochondrial function, and the conditions which precipitate the failure of these mechanisms, would inform future research and treatment strategies. We posit that UCP2-mediated function underlies the physiological response to neuronal stress associated with traumatic and ischemic injury and that clinical development of UCP2-targeted treatment would significantly impact these patient populations. With a focus on clinical relevance in TBI, we synthesize current knowledge concerning UCP2 and its potential neuroprotective role and apply this body of knowledge to current and potential treatment modalities.

Perspectives on mitochondrial uncoupling proteins-mediated neuroprotection

The integrity of mitochondrial function is essential to cell life. It follows that disturbances of mitochondrial function will lead to disruption of cell function, expressed as disease or even death. Considering that neuronal uncoupling proteins (UCPs) decrease reactive oxygen species (ROS) production at the expense of energy production, it is important to understand the underlying mechanisms by which UCPs control the balance between the production of adenosine triphosphate (ATP) and ROS in the context of normal physiological activity and in pathological conditions. Here we review the current understanding of neuronal UCPs-mediated respiratory uncoupling process by performing a survey in their physiology and regulation. The latest findings regarding neuronal UCPs physiological roles and their involvement and interest as potential targets for therapeutic intervention in brain diseases will also be exploited.

The centrality of mitochondria in the pathogenesis and treatment of Parkinson's disease

Parkinson's disease (PD) is an incurable neurodegenerative disorder leading to progressive motor impairment and for which there is no cure. From the first postmortem account describing a lack of mitochondrial complex I in the substantia nigra of PD sufferers, the direct association between mitochondrial dysfunction and death of dopaminergic neurons has ever since been consistently corroborated. In this review, we outline common pathways shared by both sporadic and familial PD that remarkably and consistently converge at the level of mitochondrial integrity. Furthermore, such knowledge has incontrovertibly established mitochondria as a valid therapeutic target in neurodegeneration. We discuss several mitochondria-directed therapies that promote the preservation, rescue, or restoration of dopaminergic neurons and which have been identified in the laboratory and in preclinical studies. Some of these have progressed to clinical trials, albeit the identification of an unequivocal disease-modifying neurotherapeutic is still elusive. The challenge is therefore to improve further, not least by more research on the molecular mechanisms and pathophysiological consequences of mitochondrial dysfunction in PD.

Transcriptomic meta-analysis of multiple sclerosis and its experimental models

Background

Multiple microarray analyses of multiple sclerosis (MS) and its experimental models have been published in the last years.

Objective

Meta-analyses integrate the information from multiple studies and are suggested to be a powerful approach in detecting highly relevant and commonly affected pathways.

Data sources

ArrayExpress, Gene Expression Omnibus and PubMed databases were screened for microarray gene expression profiling studies of MS and its experimental animal models.

Study eligibility criteria

Studies comparing central nervous system (CNS) samples of diseased versus healthy individuals with n >1 per group and publically available raw data were selected.

Material and Methods

Included conditions for re-analysis of differentially expressed genes (DEGs) were MS, myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (EAE) in rats, proteolipid protein-induced EAE in mice, Theiler’s murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD), and a transgenic tumor necrosis factor-overexpressing mouse model (TNFtg). Since solely a single MS raw data set fulfilled the inclusion criteria, a merged list containing the DEGs from two MS-studies was additionally included. Cross-study analysis was performed employing list comparisons of DEGs and alternatively Gene Set Enrichment Analysis (GSEA).

Results

The intersection of DEGs in MS, EAE, TMEV-IDD, and TNFtg contained 12 genes related to macrophage functions. The intersection of EAE, TMEV-IDD and TNFtg comprised 40 DEGs, functionally related to positive regulation of immune response. Over and above, GSEA identified substantially more differentially regulated pathways including coagulation and JAK/STAT-signaling.

Conclusion

A meta-analysis based on a simple comparison of DEGs is over-conservative. In contrast, the more experimental GSEA approach identified both, a priori anticipated as well as promising new candidate pathways.

Mitochondrial enhancement for neurodegenerative movement disorders: a systematic review of trials involving creatine, coenzyme Q10, idebenone and mitoquinone

BACKGROUND

Neurodegenerative movement disorders mainly include Parkinson's disease (PD), atypical parkinsonisms, Huntington's disease (HD), and Friedreich's ataxia (FA). With mitochondrial dysfunction observed in these diseases, mitochondrial enhancement such as creatine, coenzyme Q10 (CoQ10) and its analogues (idebenone and mitoquinone) has been regarded as a potential treatment.

AIM

In this paper, we systematically analysed and summarized the efficacy of mitochondrial enhancement in improving motor and other symptoms in neurodegenerative movement disorders.

METHODS

We searched the electronic databases PubMed, EMBASE, CINAHL, Cochrane Library and China National Knowledge Infrastructure until September 2013 for eligible randomized controlled trials (RCTs), as well as unpublished and ongoing trials. We calculated the mean differences for continuous data with 95% confidence intervals and pooled the results using a fixed-effect model, if no significant statistical heterogeneity was found (I(2) < 50%).

RESULTS

We included 16 studies with 1,557 randomized patients, which compared creatine, CoQ10 or its analogues with placebo in motor and other symptoms. No significant improvements were found in the motor symptoms of PD, atypical parkinsonisms or HD patients, while only the high dose of idebenone seems to be promising for motor improvement in FA. Certain benefits are found in other symptoms.

CONCLUSIONS

There is insufficient evidence to support the use of mitochondrial enhancement in patients with neurodegenerative movement disorders. More well-designed RCTs with large samples are required for further confirmation.

Autophagy as an essential cellular antioxidant pathway in neurodegenerative disease

Oxidative stress including DNA damage, increased lipid and protein oxidation, are important features of aging and neurodegeneration suggesting that endogenous antioxidant protective pathways are inadequate or overwhelmed. Importantly, oxidative protein damage contributes to age-dependent accumulation of dysfunctional mitochondria or protein aggregates. In addition, environmental toxins such as rotenone and paraquat, which are risk factors for the pathogenesis of neurodegenerative diseases, also promote protein oxidation. The obvious approach of supplementing the primary antioxidant systems designed to suppress the initiation of oxidative stress has been tested in animal models and positive results were obtained. However, these findings have not been effectively translated to treating human patients, and clinical trials for antioxidant therapies using radical scavenging molecules such as α-tocopherol, ascorbate and coenzyme Q have met with limited success, highlighting several limitations to this approach. These could include: (1) radical scavenging antioxidants cannot reverse established damage to proteins and organelles; (2) radical scavenging antioxidants are oxidant specific, and can only be effective if the specific mechanism for neurodegeneration involves the reactive species to which they are targeted and (3) since reactive species play an important role in physiological signaling, suppression of endogenous oxidants maybe deleterious. Therefore, alternative approaches that can circumvent these limitations are needed. While not previously considered an antioxidant system we propose that the autophagy-lysosomal activities, may serve this essential function in neurodegenerative diseases by removing damaged or dysfunctional proteins and organelles.

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Significant oxidative damage occurs in neurodegenerative disease brains.

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Effective in animal models with single toxins, antioxidants are ineffective in clinical trials.

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The failure of antioxidant therapy maybe due to propagation of cellular damage.

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Autophagic clearance of diverse damaged molecules may provide antioxidant mechanisms.

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Further mechanistic and translational studies on autophagy therapy are needed.

Chronic alcohol consumption increases the expression of uncoupling protein-2 and -4 in the brain

BACKGROUND

Chronic alcohol consumption leads to oxidative stress in a variety of cells, especially in brain cells because they have a reduced oxidative metabolism of alcohol. Uncoupling proteins (UCPs) are anion channels of the inner mitochondrial membrane, which can decouple internal respiration. "Mild uncoupling" of the mitochondrial respiratory chain leads to a reduced production of free radicals (reactive oxygen species) and a reduction in oxidative cell stress. The extent to which chronic alcohol consumption regulates UCP-2 and -4 in the brain is still unknown.

METHODS

We examined the effects of a 12-week 5% alcohol diet in the brain of male Wistar rats (n = 34). Cerebral gene and protein expression of UCP-2, -4, as well as Bcl-2, and the release of cytochrome c out of the mitochondria were detected by real-time polymerase chain reaction and Western blot analysis. The percentage of degenerated cells was determined by Fluoro-Jade B staining of brain slices.

RESULTS

Brains of rats with a chronic alcohol diet showed an increased gene and protein expression of UCP-2 and -4. The expression of the antiapoptotic protein Bcl-2 in the brain of the alcohol-treated animals was decreased significantly, whereas cytochrome c release from mitochondria was increased. In addition increased neurodegeneration could be demonstrated in the alcohol-treated animals.

CONCLUSIONS

Chronic alcohol consumption leads to a cerebral induction of UCP-2 and -4 with a simultaneous decrease in the antiapoptotic protein Bcl-2, cytochrome c release from mitochondria and increased neurodegeneration. This study reveals a compensatory effect of UCP-2 and -4 in the brain during chronic alcohol consumption.

Coenzyme Q10 depletion in medical and neuropsychiatric disorders: potential repercussions and therapeutic implications

Coenzyme Q10 (CoQ10) is an antioxidant, a membrane stabilizer, and a vital cofactor in the mitochondrial electron transport chain, enabling the generation of adenosine triphosphate. It additionally regulates gene expression and apoptosis; is an essential cofactor of uncoupling proteins; and has anti-inflammatory, redox modulatory, and neuroprotective effects. This paper reviews the known physiological role of CoQ10 in cellular metabolism, cell death, differentiation and gene regulation, and examines the potential repercussions of CoQ10 depletion including its role in illnesses such as Parkinson's disease, depression, myalgic encephalomyelitis/chronic fatigue syndrome, and fibromyalgia. CoQ10 depletion may play a role in the pathophysiology of these disorders by modulating cellular processes including hydrogen peroxide formation, gene regulation, cytoprotection, bioenegetic performance, and regulation of cellular metabolism. CoQ10 treatment improves quality of life in patients with Parkinson's disease and may play a role in delaying the progression of that disorder. Administration of CoQ10 has antidepressive effects. CoQ10 treatment significantly reduces fatigue and improves ergonomic performance during exercise and thus may have potential in alleviating the exercise intolerance and exhaustion displayed by people with myalgic encepholamyletis/chronic fatigue syndrome. Administration of CoQ10 improves hyperalgesia and quality of life in patients with fibromyalgia. The evidence base for the effectiveness of treatment with CoQ10 may be explained via its ability to ameliorate oxidative stress and protect mitochondria.

WITHDRAWN: Coenzyme Q10 for Parkinson's disease

BACKGROUND

A number of preclinical studies in both in vitro and in vivo models of Parkinson's disease have demonstrated that coenzyme Q10 can protect the nigrostriatal dopaminergic system. Some clinical trials have looked at the neuroprotective effects of coenzyme Q10 in patients with early and midstage Parkinson's disease.

OBJECTIVES

To assess the evidence from randomized controlled trials on the efficacy and safety of treatment with coenzyme Q10 compared to placebo in patients with early and midstage Parkinson's disease.

SEARCH METHODS

We searched the Cochrane Movment Disorders Group Trials Register, CENTRAL (The Cochrane Library 2009, Issue 4), MEDLINE (January 1966 to March 2011), and EMBASE (January 1985 to March 2011). We handsearched the references quoted in the identified trials, congress reports from the most important neurological association and movement disorder societies in Europe and America (March 2011), checked reference lists of relevant studies and contacted other researchers.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared coenzyme Q10 to placebo for patients who suffered early and midstage primary Parkinson's disease. Studies in which the method of randomization or concealment were unknown were included. Cross-over studies were excluded.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. All disagreements were resolved by consensus between authors and were explained. We attempted to contact the authors of studies for further details if any data were missing and to establish the characteristics of unpublished trials through correspondence with the trial coordinator or principal investigator. Adverse effects information was collected from the trials.

MAIN RESULTS

Four randomized, double-blind, placebo-controlled trials with a total of 452 patients met the inclusion criteria and were included in the review. In overall, there were improvements in activities of daily living (ADL) UPDRS (WMD -3.12, 95% CI -5.88 to -0.36) and Schwab and England (WMD 4.43, 95% CI 0.05 to 8.81) for coenzyme Q10 at 1200 mg/d for 16 months versus placebo.In safety outcomes, only the risk ratios (RR) of pharyngitis (RR 1.04, 95% CI 0.18 to 5.89) and diarrhea (RR 1.39, 95% CI 0.62 to 3.16) are mild elevated between coenzyme Q10 therapy and placebo and there were no differences in the number of withdrawals due to adverse effects (RR 0.61, 95% CI 0.23 to 1.62).

AUTHORS' CONCLUSIONS

Coenzyme Q10 therapy with 1200 mg/d for 16 months was well tolerated by patients with Parkinson's disease. The improvements in ADL UPDRS and Schwab and England were positive, but it need to be further confirmed by larger sample. For total and other subscores of UPDRS, the effects of coenzyme Q10 seemed to be less clear.

Coenzyme Q10 decreases amyloid pathology and improves behavior in a transgenic mouse model of Alzheimer's disease

Increased oxidative stress is implicated in the pathogenesis of Alzheimer's disease (AD). A large body of evidence suggests that mitochondrial dysfunction and increased reactive oxygen species occur prior to amyloid-β (Aβ) deposition. Coenzyme Q10 (CoQ10), a component of the mitochondrial electron transport chain, is well characterized as a neuroprotective antioxidant in animal models and human trials of Huntington's disease and Parkinson's disease, and reduces plaque burden in AβPP/PS1 mice. We now show that CoQ10 reduces oxidative stress and amyloid pathology and improves behavioral performance in the Tg19959 mouse model of AD. CoQ10 treatment decreased brain levels of protein carbonyls, a marker of oxidative stress. CoQ10 treatment resulted in decreased plaque area and number in hippocampus and in overlying cortex immunostained with an Aβ42-specific antibody. Brain Aβ42 levels were also decreased by CoQ10 supplementation. Levels of amyloid-β protein precursor (AβPP) β-carboxyterminal fragments were decreased. Importantly, CoQ10-treated mice showed improved cognitive performance during Morris water maze testing. Our results show decreased pathology and improved behavior in transgenic AD mice treated with the naturally occurring antioxidant compound CoQ10. CoQ10 is well tolerated in humans and may be promising for therapeutic trials in AD.

Susceptibility to a parkinsonian toxin varies during primate development

Symptoms of Parkinson's disease typically emerge later in life when loss of nigrostriatal dopamine neuron function exceeds the threshold of compensatory mechanisms in the basal ganglia. Although nigrostriatal dopamine neurons are lost during aging, in Parkinson's disease other detrimental factors must play a role to produce greater than normal loss of these neurons. Early development has been hypothesized to be a potentially vulnerable period when environmental or genetic abnormalities may compromise central dopamine neurons. This study uses a specific parkinsonian neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), to probe the relative vulnerability of nigrostriatal dopamine neurons at different stages of primate development. Measures of dopamine, homovanillic acid, 1-methyl-pyridinium concentrations and tyrosine hydroxylase immunoreactive neurons indicated that at mid-gestation dopamine neurons are relatively vulnerable to MPTP, whereas later in development or in the young primate these neurons are resistant to the neurotoxin. These studies highlight a potentially greater risk to the fetus of exposure during mid-gestation to environmental agents that cause oxidative stress. In addition, the data suggest that uncoupling protein-2 may be a target for retarding the progressive loss of nigrostriatal dopamine neurons that occurs in Parkinson's disease and aging.

Coenzyme Q10 for Parkinson's disease

BACKGROUND

A number of preclinical studies in both in vitro and in vivo models of Parkinson's disease have demonstrated that coenzyme Q10 can protect the nigrostriatal dopaminergic system. Some clinical trials have looked at the neuroprotective effects of coenzyme Q10 in patients with early and midstage Parkinson's disease.

OBJECTIVES

To assess the evidence from randomized controlled trials on the efficacy and safety of treatment with coenzyme Q10 compared to placebo in patients with early and midstage Parkinson's disease.

SEARCH METHODS

We searched the Cochrane Movment Disorders Group Trials Register, CENTRAL (The Cochrane Library 2009, Issue 4), MEDLINE (January 1966 to March 2011), and EMBASE (January 1985 to March 2011). We handsearched the references quoted in the identified trials, congress reports from the most important neurological association and movement disorder societies in Europe and America (March 2011), checked reference lists of relevant studies and contacted other researchers.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared coenzyme Q10 to placebo for patients who suffered early and midstage primary Parkinson's disease. Studies in which the method of randomization or concealment were unknown were included. Cross-over studies were excluded.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. All disagreements were resolved by consensus between authors and were explained. We attempted to contact the authors of studies for further details if any data were missing and to establish the characteristics of unpublished trials through correspondence with the trial coordinator or principal investigator. Adverse effects information was collected from the trials.

MAIN RESULTS

Four randomized, double-blind, placebo-controlled trials with a total of 452 patients met the inclusion criteria and were included in the review. In overall, there were improvements in activities of daily living (ADL) UPDRS (WMD -3.12, 95% CI -5.88 to -0.36) and Schwab and England (WMD 4.43, 95% CI 0.05 to 8.81) for coenzyme Q10 at 1200 mg/d for 16 months versus placebo.In safety outcomes, only the risk ratios (RR) of pharyngitis (RR 1.04, 95% CI 0.18 to 5.89) and diarrhea (RR 1.39, 95% CI 0.62 to 3.16) are mild elevated between coenzyme Q10 therapy and placebo and there were no differences in the number of withdrawals due to adverse effects (RR 0.61, 95% CI 0.23 to 1.62).

AUTHORS' CONCLUSIONS

Coenzyme Q10 therapy with 1200 mg/d for 16 months was well tolerated by patients with Parkinson's disease. The improvements in ADL UPDRS and Schwab and England were positive, but it need to be further confirmed by larger sample. For total and other subscores of UPDRS, the effects of coenzyme Q10 seemed to be less clear.

Retinal coenzyme Q in the bovine eye

Coenzyme Q plays an integral role in oxygen metabolism and management, and there is a positive correlation between low tissue coenzyme Q concentrations and the progression of many degenerative diseases. Retinal oxidative damage plays a role in the pathogenesis of many degenerative eye diseases; nevertheless, despite the retina's high rate of oxygen metabolism, there is little data relating to retinal coenzyme Q concentrations. In this study, we quantified coenzyme Q in the model bovine eye and determined whether it could function as a retinal lipid antioxidant. We found that the neural retina's ubiquinone concentration exceeded those of the vitreous humor, lens, choroid, and extraocular muscle, but it was lower than those measured in heart, kidney, liver, and brain tissues. Ubiquinol was found to be as effective as vitamin E as a retinal lipid antioxidant. The overall relatively low levels of ubiquinone found in the retina, coupled with the retina's need for lipid antioxidants and oxidative metabolism, suggests that retinal function might be sensitive to changes in ubiquinone concentrations.

New aspects of mitochondrial Uncoupling Proteins (UCPs) and their roles in tumorigenesis

Uncoupling proteins (UCPs) belong to a family of mitochondrial carrier proteins that are present in the mitochondrial inner membrane. UCP1 was first identified followed by its two homologs, UCP2 and UCP3. The physiological functions of UCP include lowering mitochondrial membrane potential and dissipating metabolic energy as heat. However, UCP can be dysregulated and may contribute to the pathogenesis of metabolic disorders and obesity. Recent studies suggest that UCP also plays a role in neurodegenerative diseases and atherosclerosis. In addition, the widely expressed UCP, UCP2, has been shown to be upregulated in a number of aggressive human cancers. One mechanism of UCP2 upregulation in these cancers is due to oxidative stress, and elevated UCP2 in turn reduces oxidative stress, which provides a growth advantage for these cancers. Nevertheless, new studies suggest UCP2 may interact with oncogenes and tumor suppressor genes, providing a potential new mechanism of how UCP2 contributes to cancer development. In this review, the evidence supporting the role of UCPs in diseases other than diabetes and obesity, the reports on how UCP is regulated in cancer cells, and how UCP may regulate p53 will be discussed.

Lanosterol induces mitochondrial uncoupling and protects dopaminergic neurons from cell death in a model for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder marked by the selective degeneration of dopaminergic neurons in the nigrostriatal pathway. Several lines of evidence indicate that mitochondrial dysfunction contributes to its etiology. Other studies have suggested that alterations in sterol homeostasis correlate with increased risk for PD. Whether these observations are functionally related is, however, unknown. In this study, we used a toxin-induced mouse model of PD and measured levels of nine sterol intermediates. We found that lanosterol is significantly (∼50%) and specifically reduced in the nigrostriatal regions of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mice, indicative of altered lanosterol metabolism during PD pathogenesis. Remarkably, exogenous addition of lanosterol rescued dopaminergic neurons from 1-methyl-4-phenylpyridinium (MPP+)-induced cell death in culture. Furthermore, we observed a marked redistribution of lanosterol synthase from the endoplasmic reticulum to mitochondria in dopaminergic neurons exposed to MPP+, suggesting that lanosterol might exert its survival effect by regulating mitochondrial function. Consistent with this model, we find that lanosterol induces mild depolarization of mitochondria and promotes autophagy. Collectively, our results highlight a novel sterol-based neuroprotective mechanism with direct relevance to PD.

BMSC and CoQ10 improve behavioural recovery and histological outcome in rat model of Parkinson's disease

OBJECTIVE

This study assessed the ability of a combination treatment of bone marrow stromal cell (BMSC) graft and oral coenzyme (CoQ10) in a rat model of Parkinson's disease (PD) as an appropriate substitute for current Parkinson treatments. The combination treatment was compared to sole treatments of BMSC and CoQ10.

MATERIALS AND METHODS

In this experimental study, there were six groups of male Wistar rats: control, sham, lesion, CoQ10, graft BMSC and graft BMSC plus CoQ10. Oral administration of CoQ10 began 1 week before the PD and continued during the entire treatment period. To simulate PD, we injected 6 hydroxydopamine (6OHDA) in rats. BMSC were labelled by 5-bromo-2'-deoxyuridine (Brdu) before transplantation. We assessed behaviour before PD, 2 weeks after PD and 8 weeks after cell transplantation. At the end of the second month of treatment, immunohistochemistry, histology and molecular studies were performed.

RESULTS

Behavioural assessment of the CoQ10 group and BMSC group indicated equal recovery in comparison with the lesion group (P<0.01), while the combined treatment of BMSC and CoQ10 showed considerably better recovery compared with the lesion group (P<0.001). There were no signs of gliosis and graft rejection. Immunohistochemistry analysis of Brdu indicated that cells were alive after 2 months of application in host tissue. Cell counts showed significantly greater numbers of neural cells in the combination treatment of BMSC and CoQ10 compared to the other groups. Tyrosine hydroxylase (TH) gene expression levels in the combined therapy group was significantly more than the other experimental groups (P<0.001).

CONCLUSION

The combined use of two neuroprotective treatments and cell replacement therapy can be effective in the treatment of PD, at least in experimental settings.