Preformed beta-amyloid fibrils are destabilized by coenzyme Q10 in vitro

Involvement of Coenzyme Q10 in Various Neurodegenerative and Psychiatric Diseases

Coenzyme Q10 (CoQ10), commonly known as ubiquinone, is a vitamin-like component generated in mitochondrial inner membranes. This molecule is detected broadly in different parts of the human body in various quantities. This molecule can be absorbed by the digestive system from various nutritional sources as supplements. CoQ10 exists in three states: in a of reduced form (ubiquinol), in a semiquinone radical form, and in oxidized ubiquinone form in different organs of the body, playing a crucial role in electron transportation and contributing to energy metabolism and oxygen utilization, especially in the musculoskeletal and nervous systems. Since the early 1980s, research about CoQ10 has become the interest for two reasons. First, CoQ10 deficiency has been found to have a link with cardiovascular, neurologic, and cancer disorders. Second, this molecule has an antioxidant and free-radical scavenger nature. Since then, several investigations have indicated that the drug may benefit patients with cardiovascular, neuromuscular, and neurodegenerative illnesses. CoQ10 may protect the neurological system from degeneration and degradation due to its antioxidant and energy-regulating activity in mitochondria. This agent has shown its efficacy in preventing and treating neurological diseases such as migraine, Parkinson's disease, Alzheimer's disease, Huntington's disease, amyotrophic lateral sclerosis, and Friedreich's ataxia. This study reviews the literature to highlight this agent's potential therapeutic effects in the mentioned neurological disorders.

Targeting mitochondria in the regulation of neurodegenerative diseases: A comprehensive review

Mitochondria are one of the essential cellular organelles. Apart from being considered as the powerhouse of the cell, mitochondria have been widely known to regulate redox reaction, inflammation, cell survival, cell death, metabolism, etc., and are implicated in the progression of numerous disease conditions including neurodegenerative diseases. Since brain is an energy-demanding organ, mitochondria and their functions are important for maintaining normal brain homeostasis. Alterations in mitochondrial gene expression, mutations, and epigenetic modification contribute to inflammation and neurodegeneration. Dysregulation of reactive oxygen species production by mitochondria and aggregation of proteins in neurons leads to alteration in mitochondria functions which further causes neuronal death and progression of neurodegeneration. Pharmacological studies have prioritized mitochondria as a possible drug target in the regulation of neurodegenerative diseases. Therefore, the present review article has been intended to provide a comprehensive understanding of mitochondrial role in the development and progression of neurodegenerative diseases mainly Alzheimer's, Parkinson's, multiple sclerosis, and amyotrophic lateral sclerosis followed by possible intervention and future treatment strategies to combat mitochondrial-mediated neurodegeneration.

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.

The Protective Effect of Ubiquinone against the Amyloid Peptide in Endothelial Cells Is Isoprenoid Chain Length-Dependent

Vascular brain pathology constitutes a common feature in neurodegenerative diseases that could underlie their development. Indeed, vascular dysfunction acts synergistically with neurodegenerative changes to exacerbate the cognitive impairment found in Alzheimer’s disease. Different injuries such as hypertension, high glucose, atherosclerosis associated with oxidized low-density lipoprotein or inflammation induce NADPH oxidase activation, overproduction of reactive oxygen species, and apoptosis in endothelial cells. Since it has been shown that pretreatment of cultured endothelial cells with the lipophilic antioxidant coenzyme Q10 (CoQ10) displays a protective effect against the deleterious injuries caused by different agents, this study explores the cytoprotective role of different CoQs homologues against Aβ_25–35-induced damage and demonstrates that only pretreatment with CoQ10 protects endothelial brain cells from Aβ_25–35-induced damage. Herein, we show that CoQ10 constitutes the most effective ubiquinone in preventing NADPH oxidase activity and reducing both reactive oxygen species generation and the increase in free cytosolic Ca²⁺ induced by Aβ_25–35, ultimately preventing apoptosis and necrosis. The specific cytoprotective effect of CoQ with a side chain of 10 isoprenoid units could be explained by the fact that CoQ10 is the only ubiquinone that significantly reduces the entry of Aβ_25–35 into the mitochondria.

Ubisol-Q10, a Nanomicellar and Water-Dispersible Formulation of Coenzyme-Q10 as a Potential Treatment for Alzheimer's and Parkinson's Disease

The world continues a desperate search for therapies that could bring hope and relief to millions suffering from progressive neurodegenerative diseases such as Alzheimer’s (AD) and Parkinson’s (PD). With oxidative stress thought to be a core stressor, interests have long been focused on applying redox therapies including coenzyme-Q₁₀. Therapeutic use has failed to show efficacy in human clinical trials due to poor bioavailability of this lipophilic compound. A nanomicellar, water-dispersible formulation of coenzyme-Q₁₀, Ubisol-Q₁₀, has been developed by combining coenzyme-Q₁₀ with an amphiphilic, self-emulsifying molecule of polyoxyethanyl α-tocopheryl sebacate (derivatized vitamin E). This discovery made possible, for the first time, a proper assessment of the true therapeutic value of coenzyme-Q₁₀. Micromolar concentrations of Ubisol-Q₁₀ show unprecedented neuroprotection against neurotoxin exposure in in vitro and in vivo models of neurodegeneration and was extremely effective when delivered either prior to, at the time of, and most significantly, post-neurotoxin exposure. These findings indicate a possible way forward for clinical development due to effective doses well within Federal Drug Administration guidelines. Ubisol-Q₁₀ is a potent mobilizer of astroglia, antioxidant, senescence preventer, autophagy activator, anti-inflammatory, and mitochondrial stabilizer. Here we summarize the work with oil-soluble coenzyme-Q₁₀, its limitations, and focus mainly on efficacy of water-soluble coenzyme-Q₁₀ in neurodegeneration.

Mitochondrial Dysfunction as a Driver of Cognitive Impairment in Alzheimer's Disease

Alzheimer’s disease (AD) is the most frequent cause of age-related neurodegeneration and cognitive impairment, and there are currently no broadly effective therapies. The underlying pathogenesis is complex, but a growing body of evidence implicates mitochondrial dysfunction as a common pathomechanism involved in many of the hallmark features of the AD brain, such as formation of amyloid-beta (Aβ) aggregates (amyloid plaques), neurofibrillary tangles, cholinergic system dysfunction, impaired synaptic transmission and plasticity, oxidative stress, and neuroinflammation, that lead to neurodegeneration and cognitive dysfunction. Indeed, mitochondrial dysfunction concomitant with progressive accumulation of mitochondrial Aβ is an early event in AD pathogenesis. Healthy mitochondria are critical for providing sufficient energy to maintain endogenous neuroprotective and reparative mechanisms, while disturbances in mitochondrial function, motility, fission, and fusion lead to neuronal malfunction and degeneration associated with excess free radical production and reduced intracellular calcium buffering. In addition, mitochondrial dysfunction can contribute to amyloid-β precursor protein (APP) expression and misprocessing to produce pathogenic fragments (e.g., Aβ1-40). Given this background, we present an overview of the importance of mitochondria for maintenance of neuronal function and how mitochondrial dysfunction acts as a driver of cognitive impairment in AD. Additionally, we provide a brief summary of possible treatments targeting mitochondrial dysfunction as therapeutic approaches for AD.

Coenzyme Q homeostasis in aging: Response to non-genetic interventions

Coenzyme Q (CoQ) is a key component for many essential metabolic and antioxidant activities in cells in mitochondria and cell membranes. Mitochondrial dysfunction is one of the hallmarks of aging and age-related diseases. Deprivation of CoQ during aging can be the cause or the consequence of this mitochondrial dysfunction. In any case, it seems clear that aging-associated CoQ deprivation accelerates mitochondrial dysfunction in these diseases. Non-genetic prolongevity interventions, including CoQ dietary supplementation, can increase CoQ levels in mitochondria and cell membranes improving mitochondrial activity and delaying cell and tissue deterioration by oxidative damage. In this review, we discuss the importance of CoQ deprivation in aging and age-related diseases and the effect of prolongevity interventions on CoQ levels and synthesis and CoQ-dependent antioxidant activities.

Changing Paradigm from one Target one Ligand Towards Multi-target Directed Ligand Design for Key Drug Targets of Alzheimer Disease: An Important Role of In Silico Methods in Multi-target Directed Ligands Design

Alzheimer disease (AD) is now considered as a multifactorial neurodegenerative disorder and rapidly increasing to an alarming situation and causing higher death rate. One target one ligand hypothesis does not provide complete solution of AD due to multifactorial nature of the disease and one target one drug fails to provide better treatment against AD. Moreo-ver, currently available treatments are limited and most of the upcoming treatments under clinical trials are based on modulat-ing single target. So, the current AD drug discovery research is shifting towards a new approach for a better solution that simultaneously modulates more than one targets in the neurodegenerative cascade. This can be achieved by network pharma-cology, multi-modal therapies, multifaceted, and/or the more recently proposed term “multi-targeted designed drugs”. Drug discovery project is a tedious, costly and long-term project. Moreover, multi-target AD drug discovery added extra challeng-es such as the good binding affinity of ligands for multiple targets, optimal ADME/T properties, no/less off-target side effect and crossing of the blood-brain barrier. These hurdles may be addressed by insilico methods for an efficient solution in less time and cost as computational methods successfully applied to single target drug discovery project. Here, we are summariz-ing some of the most prominent and computationally explored single targets against AD and further, we discussed a success-ful example of dual or multiple inhibitors for same targets. Moreover, we focused on ligand and structure-based computa-tional approach to design MTDL against AD. However, it is not an easy task to balance dual activity in a single molecule but computational approach such as virtual screening docking, QSAR, simulation and free energy is useful in future MTDLs drug discovery alone or in combination with a fragment-based method. However, rational and logical implementations of computational drug designing methods are capable of assisting AD drug discovery and play an important role in optimizing multi-target drug discovery.

Simultaneous activation of Nrf2 and elevation of antioxidant compounds for reducing oxidative stress and chronic inflammation in human Alzheimer's disease

Despite extensive research, neither the incidence nor the rate of progression of Alzheimer's disease (AD) has significantly changed. Some biochemical and genetic defects that initiate and promote AD include: (a) increased oxidative stress, (b) chronic inflammation (c) mitochondrial dysfunction, (d) Aß1-42 peptides generated from the amyloid precursor protein (APP), (e) proteasome inhibition, and (f) mutations in APP, presenilin-1 and presenilin-2 genes. Increased oxidative stress appears to precede other biochemical and genetic defects. Oxidative damage induces chronic inflammation. Therefore, reducing these defects simultaneously may reduce the development and progression of AD. Previous studies with individual antioxidants produced consistent benefits in animal models of AD; however, a similar approach produced inconsistent results in human AD. This review proposes a hypothesis that simultaneous elevation of the levels of antioxidant enzymes and antioxidant compounds is necessary for optimally reducing oxidative stress and chronic inflammation in human AD. Supplementation can enhance the levels of antioxidant compounds; but elevation of antioxidant enzymes requires activation of Nrf2. This review discusses activation and regulation of Nrf2. The need for multi- antioxidants that can affect multi-targets has been proposed without specific recommendations. This review proposes a micronutrient mixture that would simultaneously enhance the levels of antioxidant enzymes and antioxidant compounds in human AD.

Oxidative stress and Down syndrome. Do antioxidants play a role in therapy?

Oxidative stress is a phenomenon associated with imbalance between production of free radicals and reactive metabolites (e.g. superoxide and hydrogen peroxide) and the antioxidant defences. Oxidative stress in individuals with Down syndrome (DS) has been associated with trisomy of the 21st chromosome resulting in DS phenotype as well as with various morphological abnormalities, immune disorders, intellectual disability, premature aging and other biochemical abnormalities. Trisomy 21 in patients with DS results in increased activity of an important antioxidant enzyme Cu/Zn superoxide dismutase (SOD) which gene is located on the 21st chromosome along with other proteins such as transcription factor Ets-2, stress inducing factors (DSCR1) and precursor of beta-amyloid protein responsible for the formation of amyloid plaques in Alzheimer disease. Mentioned proteins are involved in the management of mitochondrial function, thereby promoting mitochondrial theory of aging also in people with DS. In defence against toxic effects of free radicals and their metabolites organism has built antioxidant defence systems. Their lack and reduced function increases oxidative stress resulting in disruption of the structure of important biomolecules, such as proteins, lipids and nucleic acids. This leads to their dysfunctions affecting pathophysiology of organs and the whole organism. This paper examines the impact of antioxidant interventions as well as positive effect of physical exercise on cognitive and learning disabilities of individuals with DS. Potential therapeutic targets on the molecular level (oxidative stress markers, gene for DYRK1A, neutrophic factor BDNF) after intervention of natural polyphenols are also discussed.

Two diseases, one approach: multitarget drug discovery in Alzheimer's and neglected tropical diseases

Multitarget drug discovery may represent a promising therapeutic approach to treat Alzheimer's and neglected tropical diseases.

In silico and in vitro characterization of anti-amyloidogenic activity of vitamin K3 analogues for Alzheimer's disease

BACKGROUND

Aggregation of amyloid-beta (Aβ) has been proposed as the main cause of Alzheimer's disease (AD). Vitamin K deficiency has been linked to the pathogenesis of AD. Therefore, 15 synthesized vitamin K3 (VK3) analogues were studied for their anti-amyloidogenic activity.

METHODS

Biological and spectroscopic assays were used to characterize the effect of VK3 analogues on amyloidogenic properties of Aβ, such as aggregation, free radical formation, and cell viability. Molecular dynamics simulation was used to calculate the binding affinity and mode of VK3 analogue binding to Aβ.

RESULTS

Both numerical and experimental results showed that several VK3 analogues, including VK3-6, VK3-8, VK3-9, VK3-10, and VK3-224 could effectively inhibit Aβ aggregation and conformational conversion. The calculated inhibition constants were in the μM range for VK3-10, VK3-6, and VK3-9 which was similar to the IC50 of curcumin. Cell viability assays indicated that VK3-9 could effectively reduce free radicals and had a protective effect on cytotoxicity induced by Aβ.

CONCLUSIONS

The results clearly demonstrated that VK3 analogues could effectively inhibit Aβ aggregation and protect cells against Aβ induced toxicity. Modified VK3 analogues can possibly be developed as effective anti-amyloidogenic drugs for the treatment of AD.

GENERAL SIGNIFICANCE

VK3 analogues effectively inhibit Aβ aggregation and are highly potent as anti-amyloidogenic drugs for therapeutic treatment of AD.

Discovery of Multi-Target Agents for Neurological Diseases via Ligand Design

The incidence of neurological disorders in the developed world is rising in concert with an increase in human life expectancy, due in large part to better nutrition and health care. Even as drug discovery efforts are refocused on these disorders, there has been a dearth in the introduction of new disease-modifying therapies to prevent or delay their onset, or reverse their progression. Mounting evidence points to complex and heterogeneous etiopathologies that underlie these diseases. Therefore, it is unlikely that disorders in this class will be mitigated by any single drug that acts exclusively on a single pathway or target. The rational design of novel drug entities with the ability to simultaneously address multiple drug targets of a complex pathophysiology has recently emerged as a new paradigm in drug discovery. Similarly to the concept of multi-target agents within the psychopharmacology field, ligand design has gained an increasing prominence within the medicinal chemistry community. In this chapter we discuss several examples of select chemical scaffolds (polyamines, alkylxanthines, and propargyl carbamates) wherein these concepts were applied to develop novel drug candidates for Alzheimer's disease and Parkinson's disease.

Coenzyme Q10 and cognition in atorvastatin treated dogs

Statins have been suggested to protect against Alzheimer's disease (AD). Recently, however, we reported that aged dogs that underwent chronic statin treatment exhibited cognitive deficits compared with age matched controls. In human studies, blood levels of Coenzyme Q10 (CoQ10) decrease with statin use. CoQ10 is important for proper mitochondrial function and is a powerful antioxidant, two important factors for cognitive health in aging. Thus, the current study tested the hypothesis that CoQ10 levels in the serum and/or parietal cortex are decreased in statin treated dogs and are associated with poorer cognition. Six aged beagles (>8 years) were administered 80 mg/day of atorvastatin for 14.5 months and compared with placebo-treated animals. As predicted, serum CoQ10 was significantly lower in statin-treated dogs. Parietal cortex CoQ10 was not different between the two groups. However, poorer cognition was correlated with lower parietal cortex CoQ10. This study in dogs suggests that serum CoQ10 is reduced with atorvastatin treatment. CoQ10 levels in brain may be linked to impaired cognition in response to atorvastatin, in agreement with previous reports that statins may have a negative impact on cognition in the elderly.

Natural products as a source of Alzheimer's drug leads

This review focuses on recent developments in the use of natural products as therapeutics for Alzheimer's disease. The compounds span a diverse array of structural classes and are organized according to their mechanism of action, with the focus primarily on the major hypotheses. Overall, the review discusses more than 180 compounds and summarizes 400 references.

Neurotherapeutic applications of nanoparticles in Alzheimer's disease

A rapid increase in incidence of neurodegenerative disorders has been observed with the aging of the population. Alzheimer's disease (AD) is the most common neurodegenerative disorder among the elderly. It is characterized by memory dysfunction, loss of lexical access, spatial and temporal disorientation and impairment of judgement clinically. Unfortunately, clinical development of drugs for the symptomatic and disease-modifying treatment of AD has resulted in both promise and disappointment. Indeed, a large number of drugs with differing targets and mechanisms of action were investigated with only a few of them being clinically available. The targeted drug delivery to the central nervous system (CNS), for the diagnosis and treatment of neurodegenerative disorders such as AD, is restricted due to the limitations posed by the blood-brain barrier (BBB) as well as due to opsonization by plasma proteins in the systemic circulation and peripheral side-effects. Over the last decade, nanoparticle-mediated drug delivery represents one promising strategy to successfully increase the CNS penetration of several therapeutic moieties. Different nanocarriers are being investigated to treat and diagnose AD by delivering at a constant rate a host of therapeutics over times extending up to days, weeks or even months. This review provides a concise incursion on the current pharmacotherapies for AD besides reviewing and discussing the literature on the different drug molecules that have been successfully encapsulated in nanoparticles (NPs). Some of them have been shown to cross the BBB and have been tested either for diagnosis or treatment of AD. Finally, the route of NPs administration and the future prospects will be discussed.

[Search for antiamyloidogenic compounds based on a nucleation-dependent polymerization model]

We have proposed that a nucleation-dependent polymerization model could explain the general mechanisms of amyloid fibril formation in vitro. Based on this model, we systematically demonstrated that several classes of organic compounds (e.g., wine-related polyphenols, non-steroidal anti-inflammatory drugs) not only inhibit the formation of Abeta amyloid fibrils from Abeta and their extension, but also destabilize Abeta amyloid fibrils dose-dependently in vitro. We found significant positive correlations of the effective concentrations (EC(50)) of these compounds ranging from 10 nM to 10 microM, for the formation and destabilization of Abeta amyloid fibrils. We next investigated the anti-amyloidogenic effects of five flavonoids on Abeta amyloid fibrils in vitro. Oxidized flavonoids generally inhibited fibril formation significantly more potently than fresh compounds. By surface plasmon resonance (SPR) analysis, distinct association and dissociation reactions of myricetin (Myr) to Abeta amyloid fibrils were observed, in contrast to the very weak binding to the Abeta monomer. A significant decrease in the rate of fibril extension was observed when>0.5 microM of Myr was injected into the SPR experimental system. These findings suggest that flavonoids, especially Myr exert an anti-amyloidogenic effect in vitro by preferentially and reversibly binding to the amyloid fibril structure of fibrils, rather than to Abeta monomers. This working model should prove useful not only for the rational development of preventive and therapeutics for Alzheimer's disease and other human amyloidosis, but also for understanding the basic mode of action of amyloid imaging compounds.

The inhibitory effect of pyrroloquinoline quinone on the amyloid formation and cytotoxicity of truncated alpha-synuclein

BACKGROUND

Parkinson's disease (PD) involves the selective damage of dopaminergic neuron cells resulting from the accumulation and fibril formation of alpha-synuclein. Recently, it has been shown that not only full-length alpha-synuclein, but also C-terminal truncated forms exist in the normal brain, as well as Lewy bodies, which are cytoplasmic inclusions in PD. It is known that truncated alpha-synuclein has a much higher ability to aggregate and fibrillate than full-length alpha-synuclein. Since the fibrils and precursor oligomers of alpha-synuclein are cytotoxic to the neuron, inhibitors that prevent the formation of oligomers and/or fibrils might open the way to a novel therapeutic approach to PD. However, no inhibitor for truncated alpha-synuclein has been reported yet.

RESULTS

In this study, we first characterized the aggregation and cytotoxicity of C-truncated alpha-synuclein119 and alpha-synuclein133 which have been found in both the normal and the pathogenic brain. Alpha-synuclein119 aggregated more rapidly and enhanced significantly the fibril formation of alpha-synuclein. Although both of alpha-synuclein119 and alpha-synuclein133 showed a high cytotoxicity, alpha-synuclein133 showed a similar aggregation with full-length alpha-synuclein and no acceleration effect. We showed that PQQ dramatically inhibits the fibril formation of C-terminal truncated alpha-synuclein110119, and 133 as well as the mixtures of full-length alpha-synuclein with these truncated variants. Moreover, PQQ decreases the cytotoxicity of truncated alpha-synuclein.

CONCLUSIONS

Our results demonstrate that PQQ inhibits the amyloid fibril formation and cytotoxicity of the C-truncated alpha-synuclein variants. We believe that PQQ is a strong candidate for a reagent compound in the treatment of PD.

Toward a rational design of multitarget-directed antioxidants: merging memoquin and lipoic acid molecular frameworks

Novel multitargeted antioxidants 3-6 were designed by combining the antioxidant features, namely, a benzoquinone fragment and a lipoyl function, of two multifunctional lead candidates. They were then evaluated to determine their profile against Alzheimer's disease. They showed antioxidant activity, improved following enzymatic reduction, in mitochondria and T67 cell line. They also displayed a balanced inhibitory profile against amyloid-beta aggregation and acetylcholinesterase, emerging as promising molecules for neuroprotectant lead discovery.

Phenolic compounds prevent Alzheimer's pathology through different effects on the amyloid-beta aggregation pathway

Inhibition of amyloid-beta (Abeta) aggregation is an attractive therapeutic strategy for Alzheimer's disease (AD). Certain phenolic compounds have been reported to have anti-Abeta aggregation effects in vitro. This study systematically investigated the effects of phenolic compounds on AD model transgenic mice (Tg2576). Mice were fed five phenolic compounds (curcumin, ferulic acid, myricetin, nordihydroguaiaretic acid (NDGA), and rosmarinic acid (RA)) for 10 months from the age of 5 months. Immunohistochemically, in both the NDGA- and RA-treated groups, Abeta deposition was significantly decreased in the brain (P < 0.05). In the RA-treated group, the level of Tris-buffered saline (TBS)-soluble Abeta monomers was increased (P < 0.01), whereas that of oligomers, as probed with the A11 antibody (A11-positive oligomers), was decreased (P < 0.001). However, in the NDGA-treated group, the abundance of A11-positive oligomers was increased (P < 0.05) without any change in the levels of TBS-soluble or TBS-insoluble Abeta. In the curcumin- and myricetin-treated groups, changes in the Abeta profile were similar to those in the RA-treated group, but Abeta plaque deposition was not significantly decreased. In the ferulic acid-treated group, there was no significant difference in the Abeta profile. These results showed that oral administration of phenolic compounds prevented the development of AD pathology by affecting different Abeta aggregation pathways in vivo. Clinical trials with these compounds are necessary to confirm the anti-AD effects and safety in humans.

Ellagic acid promotes Abeta42 fibrillization and inhibits Abeta42-induced neurotoxicity

Smaller, soluble oligomers of beta-amyloid (Abeta) play a critical role in the pathogenesis of Alzheimer's disease (AD). Selective inhibition of Abeta oligomer formation provides an optimum target for AD therapy. Some polyphenols have potent anti-amyloidogenic activities and protect against Abeta neurotoxicity. Here, we tested the effects of ellagic acid (EA), a polyphenolic compound, on Abeta42 aggregation and neurotoxicity in vitro. EA promoted Abeta fibril formation and significant oligomer loss, contrary to previous results that polyphenols inhibited Abeta aggregation. The results of transmission electron microscopy (TEM) and Western blot displayed more fibrils in Abeta42 samples co-incubated with EA in earlier phases of aggregation. Consistent with the hypothesis that plaque formation may represent a protective mechanism in which the body sequesters toxic Abeta aggregates to render them harmless, our MTT results showed that EA could significantly reduce Abeta42-induced neurotoxicity toward SH-SY5Y cells. Taken together, our results suggest that EA, an active ingredient in many fruits and nuts, may have therapeutic potential in AD.

Mitochondria: a therapeutic target in neurodegeneration

Mitochondrial dysfunction has long been associated with neurodegenerative disease. Therefore, mitochondrial protective agents represent a unique direction for the development of drug candidates that can modify the pathogenesis of neurodegeneration. This review discusses evidence showing that mitochondrial dysfunction has a central role in the pathogenesis of Alzheimer's, Parkinson's and Huntington's diseases and amyotrophic lateral sclerosis. We also debate the potential therapeutic efficacy of metabolic antioxidants, mitochondria-directed antioxidants and Szeto-Schiller (SS) peptides. Since these compounds preferentially target mitochondria, a major source of oxidative damage, they are promising therapeutic candidates for neurodegenerative diseases. Furthermore, we will briefly discuss the novel action of the antihistamine drug Dimebon on mitochondria.

Mitochondrial approaches for neuroprotection

A large body of evidence from postmortem brain tissue and genetic analysis in humans and biochemical and pathological studies in animal models (transgenic and toxin) of neurodegeneration suggest that mitochondrial dysfunction is a common pathological mechanism. Mitochondrial dysfunction from oxidative stress, mitochondrial DNA deletions, pathological mutations, altered mitochondrial morphology, and interaction of pathogenic proteins with mitochondria leads to neuronal demise. Therefore, therapeutic approaches targeting mitochondrial dysfunction and oxidative damage hold great promise in neurodegenerative diseases. This review discusses the potential therapeutic efficacy of creatine, coenzyme Q10, idebenone, synthetic triterpenoids, and mitochondrial targeted antioxidants (MitoQ) and peptides (SS-31) in in vitro studies and in animal models of Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and Alzheimer's disease. We have also reviewed the current status of clinical trials of creatine, coenzyme Q10, idebenone, and MitoQ in neurodegenerative disorders. Further, we discuss newly identified therapeutic targets, including peroxisome proliferator-activated receptor-gamma-coactivator and sirtuins, which provide promise for future therapeutic developments in neurodegenerative disorders.

Coenzyme Q10 effects in neurodegenerative disease

Coenzyme Q10 (CoQ10) is an essential cofactor in the mitochondrial respiratory chain, and as a dietary supplement it has recently gained attention for its potential role in the treatment of neurodegenerative disease. Evidence for mitochondrial dysfunction in neurodegenerative disorders derives from animal models, studies of mitochondria from patients, identification of genetic defects in patients with neurodegenerative disease, and measurements of markers of oxidative stress. Studies of in vitro models of neuronal toxicity and animal models of neurodegenerative disorders have demonstrated potential neuroprotective effects of CoQ10. With this data in mind, several clinical trials of CoQ10 have been performed in Parkinson's disease and atypical Parkinson's syndromes, Huntington's disease, Alzheimer disease, Friedreich's ataxia, and amyotrophic lateral sclerosis, with equivocal findings. CoQ10 is widely available in multiple formulations and is very well tolerated with minimal adverse effects, making it an attractive potential therapy. Phase III trials of high-dose CoQ10 in large sample sizes are needed to further ascertain the effects of CoQ10 in neurodegenerative diseases.

Memoquin: a multi-target-directed ligand as an innovative therapeutic opportunity for Alzheimer's disease

Alzheimer's disease is currently thought to be a complex, multifactorial syndrome, unlikely to arise from a single causal factor; instead, a number of related biological alterations are thought to contribute to its pathogenesis. This may explain why the currently available drugs, developed according to the classic drug discovery paradigm of "one-molecule-one-target," have turned out to be palliative. In light of this, drug combinations that can act at different levels of the neurotoxic cascade offer new avenues toward curing Alzheimer's and other neurodegenerative diseases. In parallel, a new strategy is emerging-that of developing a single chemical entity able to modulate multiple targets simultaneously. This has led to a new paradigm in medicinal chemistry, the "multi-target-directed ligand" design strategy, which has already been successfully exploited at both academic and industrial levels. As a case study, we report here on memoquin, a new molecule developed following this strategy. The in vitro and in vivo biological profile of memoquin demonstrates the suitability of the new strategy for obtaining innovative drug candidates for the treatment of neurodegenerative diseases.

Small molecule protein-protein interaction inhibitors as CNS therapeutic agents: current progress and future hurdles

Protein-protein interactions are a crucial element in cellular function. The wealth of information currently available on intracellular-signaling pathways has led many to appreciate the untapped pool of potential drug targets that reside downstream of the commonly targeted receptors. Over the last two decades, there has been significant interest in developing therapeutics and chemical probes that inhibit specific protein-protein interactions. Although it has been a challenge to develop small molecules that are capable of occluding the large, often relatively featureless protein-protein interaction interface, there are increasing numbers of examples of small molecules that function in this manner with reasonable potency. This article will highlight the current progress in the development of small molecule protein-protein interaction inhibitors that have applications in the treatment or study of central nervous system function and disease. In particular, we will focus upon recent work towards developing small molecule inhibitors of amyloid-beta and alpha-synuclein aggregation, inhibitors of critical components of G-protein-signaling pathways, and PDZ domain inhibitors.

Grape seed polyphenols and curcumin reduce genomic instability events in a transgenic mouse model for Alzheimer's disease

The study set out to determine (a) whether DNA damage is elevated in mice that carry mutations in the amyloid precursor protein (APP695swe) and presenilin 1 (PSEN1-dE9) that predispose to Alzheimer's disease (AD) relative to non-transgenic control mice, and (b) whether increasing the intake of dietary polyphenols from curcumin or grape seed extract could reduce genomic instability events in a transgenic mouse model for AD. DNA damage was measured using the micronucleus (MN) assay in both buccal mucosa and erythrocytes and an absolute telomere length assay for both buccal mucosa and olfactory bulb tissue. MN frequency tended to be higher in AD mice in both buccal mucosa (1.7-fold) and polychromatic erythrocytes (1.3-fold) relative to controls. Telomere length was significantly reduced by 91% (p=0.04) and non-significantly reduced by 50% in buccal mucosa and olfactory bulbs respectively in AD mice relative to controls. A significant 10-fold decrease in buccal MN frequency (p=0.01) was found for AD mice fed diets containing curcumin (CUR) or micro-encapsulated grape seed extract (MGSE) and a 7-fold decrease (p=0.02) for AD mice fed unencapsulated grape seed extract (GSE) compared to the AD group on control diet. Similarly, in polychromatic erythrocytes a significant reduction in MN frequency was found for the MGSE cohort (65.3%) (p<0.05), whereas the AD CUR and AD GSE groups were non-significantly reduced by 39.2 and 34.8% respectively compared to the AD Control. A non-significant 2-fold increase in buccal cell telomere length was evident for the CUR, GSE and MGSE groups compared to the AD control group. Olfactory bulb telomere length was found to be non-significantly 2-fold longer in mice fed on the CUR diet compared to controls. These results suggest potential protective effects of polyphenols against genomic instability events in different somatic tissues of a transgenic mouse model for AD.

TiO2 nanoparticles promote beta-amyloid fibrillation in vitro

Alzheimer's disease (AD) is the most common neurodegenerative disease in the world. The pathogenesis of AD is associated with beta-amyloid (Abeta) fibrillation. Nanoparticles have large surface area and can access the brain. But no investigation has been made to study the relationship between nanoparticles and AD. In our study, we observed Abeta fibril formation in the presence of six kinds of nanoparticles and found that TiO2 nanoparticles can promote Abeta fibrillation by shortening nucleation process, which is the key rate-determining step of fibrillation. Hereby the interaction between Abeta and nanoparticles may contribute to AD etiology.

Distinguishing Lewy body dementias from Alzheimer's disease

Lewy body dementia (LBD) is the second most common dementia after Alzheimer's disease (AD). LBD is characterized clinically by visual hallucinations, extrapyramidal symptoms, cognitive fluctuations and neuroleptic sensitivity. LBD and AD share many common features in pathology, genetics and biochemical alterations; however, correct clinical distinction between these disorders has prognostic and therapeutic implications. There are currently no definitive radiological or biological markers for LBD, but studies suggest that premorbid differences in cognitive domains and personality traits, differences in clinical presentation, and alterations in autonomic function and sleep may improve diagnosis. Cholinergic dysfunction plays a major role in both AD and LBD; however, dysfunction is greater in LBD. This may account for the more prominent hallucinations, and offers the possibility of a greater response to cholinesterase inhibitors in LBD. The treatment of LBD is symptomatic and is based on a limited number of clinical trials and extension of results from trials in AD. Current research is focused on the role of synuclein aggregation with possible roles for synuclein-derived peptides as aggregation inhibitors. Other approaches target amyloid, neuroinflammation, oxidative injury, proteolysis, lipid peroxidation and immunotherapies with variable results. Improved understanding of disease mechanisms may open new therapeutic avenues for LBD in the future.

Small molecule inhibitors of Abeta assembly

The Abeta peptide assembles into a variety of distinct types of structures in vitro and in the brain which have different biological consequences. Differential effects of inhibitory small molecules suggest that a sequential monomer - oligomer - fibril mechanism is overly simplistic and that soluble toxic oligomers and fibrils can be formed in common or separate pathways depending on the local environment. As a result, the effects of inhibitors are often assay-dependent because multiple pathways are operating. This review discusses strategies for teasing apart the intricate protein-protein interactions that result in Abeta assembly.

Vitamin A potently destabilizes preformed α-synuclein fibrils in vitro: Implications for Lewy body diseases

Alpha-synuclein (alphaS) is the major component of the filamentous inclusions that constitute defining characteristics of Lewy body diseases (LBD) and multiple system atrophy (MSA). Clinically, antioxidant vitamins, such as vitamin E and the vitamin-like substance coenzyme Q10, have been used in the treatment of LBD with some efficacy. Using fluorescence spectroscopy with thioflavin S, electron microscopy and atomic force microscopy, here we examined the effects of ten antioxidant vitamins and vitamin-like substances, vitamin A (retinol, retinal and retinoic acid), beta-carotene, vitamins B2, B6, C, E, coenzyme Q10 and alpha-lipoic acid, on the formation of alphaS fibrils (falphaS) and on preformed falphaS. Among them, vitamin A, beta-carotene and coenzyme Q10 dose-dependently inhibited the formation of falphaS. Moreover, they also dose-dependently destabilized preformed falphaS. With such potent anti-fibrillogenic as well as fibril-destabilizing activities, these compounds could be useful in the treatment and prevention of LBD and MSA.

Alpha-lipoic acid exhibits anti-amyloidogenicity for beta-amyloid fibrils in vitro

Inhibition of the formation of beta-amyloid fibrils (fAbeta), as well as the destabilization of preformed fAbeta in the CNS would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of alpha-lipoic acid (LA) and the metabolic product of LA, dihydrolipoic acid (DHLA), on the formation, extension, and destabilization of fAbeta at pH 7.5 at 37 degrees C in vitro. LA and DHLA dose-dependently inhibited fAbeta formation from amyloid beta-protein, as well as their extension. Moreover, they destabilized preformed fAbetas. LA and DHLA could be key molecules for the development of therapeutics for AD.