Inhibition of amyloid-beta aggregation and caspase-3 activation by the Ginkgo biloba extract EGb761

Prevention of sporadic Alzheimer's disease: lessons learned from clinical trials and future directions

Interventions that have even quite modest effects at the individual level could drastically reduce the future burden of dementia associated with Alzheimer's disease at the population level. In the past three decades, both pharmacological and lifestyle interventions have been studied for the prevention of cognitive decline or dementia in randomised controlled trials of individuals mostly aged older than 50-55 years with or without risk factors for Alzheimer's disease. Several trials testing the effects of physical activity, cognitive training, or antihypertensive interventions showed some evidence of efficacy on a primary cognitive endpoint. However, most of these trials had short follow-up periods, and further evidence is needed to confirm effectiveness and establish the optimum design or dose of interventions and ideal target populations. Important innovations in ongoing trials include the development of multidomain interventions, and the use of biomarker or genetic inclusion criteria. Challenges include the use of adaptive trial designs, the development of standardised, sensitive outcome measures, and the need for interventions that can be implemented in resource-poor settings.

Phytomedicines as potential inhibitors of β amyloid aggregation: significance to Alzheimer's disease

Throughout the history of drug development, plants have been an important source for the discovery of novel therapeutically active compounds for many diseases. The ethnopharmacological approach has provided several leads to identify potential new drugs from plant sources, including those for memory disorders. For the treatment of Alzheimer's disease the drug discovery focus shifted from cholinesterase inhibitors, to other targets primarily based on two key neuropathological hallmarks, namely the hyperphosphorylation of the tau protein resulting in the formation of neurofibrillary tangles (NFTs), and the increased formation and aggregation of amyloid-beta peptide (Aβ) derived from amyloid precursor protein (APP). The present article aims to provide a comprehensive literature survey of plants and their constituents that have been tested for Aβ aggregation, thus possibly relieving several features of Alzheimer's disease (AD).

Long-term treatment with Ginkgo biloba extract EGb 761 improves symptoms and pathology in a transgenic mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by extracellular deposits of amyloid β peptide (Aβ) and microglia-dominated neuroinflammation. The therapeutic options for AD are currently limited. In this study, we investigated the antiinflammatory effects and the underlying molecular mechanisms of Ginkgo biloba extract EGb 761 when administered to TgCRND8 AD mice, which overexpress human Alzheimer's amyloid precursor protein (APP) specifically in neurons. We gave APP-transgenic mice EGb 761 as a dietary supplement for 2 or 5months. Plasma concentrations of EGb 761 components in mice were in the same range as such concentrations in humans taking EGb 761 at the recommended dose (240mg daily). Treatment with EGb 761 for 5months significantly improved the cognitive function of the mice as measured by the Barnes Maze test. It also attenuated the loss of synaptic structure proteins, such as PSD-95, Munc18-1, and SNAP25. Treatment with EGb 761 for 5months inhibited microglial inflammatory activation in the brain. The effects of treatment with EGb 761 for 2months were weak and not statistically significant. Moreover, EGb 761 activated autophagy in microglia. Treatment with EGb 761 decreased Aβ-induced microglial secretion of TNF-α and IL-1β and activation of caspase-1, both of which were abolished by the inhibition of autophagy. Treatment with EGb 761 also reduced the concentrations of NLRP3 protein that colocalized with LC3-positive autophagosomes or autolysosomes in microglia. Additionally, long-term treatment with EGb 761 may reduce cerebral Aβ pathology by inhibiting β-secretase activity and Aβ aggregation. Therefore, long-term treatment with G. biloba extract EGb 761, a clinically available and well-tolerated herbal medication, ameliorates AD pathology by antiinflammatory and Aβ-directed mechanisms.

Neuroprotective effects of geniposide in SH-SY5Y cells and primary hippocampal neurons exposed to Aβ42

Our former studies have suggested that TongLuoJiuNao (TLJN) is clinically efficacious in the treatment of dementia and improving learning and memory in AD models. When Aβ aggregated with oligomer, it is known to be able to induce cellular toxicity as well as cognitive impairment. We tested the possibility that TLJN affects the formation of Aβ oligomers. In our experiment, TLJN improved cell viability, inhibited LDH release, and promoted the outgrowth of neurites of neurons treated with Aβ. Geniposide, the main component of TLJN, could increase the cell viability of SY5Y-APP695sw cells. The cytotoxicity of pretreated Aβ with geniposide was decreased in a dose-dependent manner. SDS-PAGE and Western blotting showed that geniposide and TLJN stimulated Aβ oligomer assembly. Compared with the control, more and longer fibrils of Aβ in the presence of geniposide were observed under electron microscope though the fibrils became less sensitive to thioflavin T staining. In sum, geniposide is able to protect neurons from Aβ-induced damage by remodeling Aβ.

Flavonoids in Ginkgo biloba fallen leaves induce apoptosis through modulation of p53 activation in melanoma cells

The aim of the present study was to examine the apoptotic effect of flavonoids in methanol extracts of Ginkgo biloba fallen leaves (MEGFL) on melanoma cells. Ginkgo biloba is a deciduous castle chaplain and its leaves include various types of flavonoids such as flavonol-O-glycosides. Ginkgo biloba is known to have therapeutic properties against a number of diseases such as cerebrovascular diseases, blood circulation disease and hypertension. In the present study MEGFL exhibited a higher cytotoxic effect on melanoma cells than Ginkgo biloba leaves (MEGL). It was also found that MEGFL induced apoptotic cell death which was characterized by DNA fragmentation. During the cell death process following treatment with MEGFL, the expression of a variety of death-associated proteins including p53, caspase-3, caspase-9, cytochrome c and Bax were analyzed in the cytosol of melanoma cells. MEGFL significantly increased the expression levels of caspase-3, caspase-9 and p53 in a dose-dependent manner. Our results indicate that MEGFL induced apoptotic cell death by increasing the expression of cell death-associated proteins in melanoma cells.

Effects of long-term feeding of the polyphenols resveratrol and kaempferol in obese mice

The effect of the intake of antioxidant polyphenols such as resveratrol and others on survival and different parameters of life quality has been a matter of debate in the last years. We have studied here the effects of the polyphenols resveratrol and kaempferol added to the diet in a murine model undergoing long-term hypercaloric diet. Using 50 mice for each condition, we have monitored weight, survival, biochemical parameters such as blood glucose, insulin, cholesterol, triglycerides and aspartate aminotransferase, neuromuscular coordination measured with the rotarod test and morphological aspect of stained sections of liver and heart histological samples. Our data show that mice fed since they are 3-months-old with hypercaloric diet supplemented with any of these polyphenols reduced their weight by about 5–7% with respect to the controls fed only with hypercaloric diet. We also observed that mice fed with any of the polyphenols had reduced levels of glucose, insulin and cholesterol, and better marks in the rotarod test, but only after 1 year of treatment, that is, during senescence. No effect was observed in the rest of the parameters studied. Furthermore, although treatment with hypercaloric diets induced large changes in the pattern of gene expression in liver, we found no significant changes in gene expression induced by the presence of any of the polyphenols. Thus, our data indicate that addition of resveratrol or kaempferol to mice food produces an initial decrease in weight in mice subjected to hypercaloric diet, but beneficial effects in other parameters such as blood glucose, insulin and cholesterol, and neuromuscular coordination, only appear after prolonged treatments.

Effects of secondary metabolite extract from Phomopsis occulta on β-amyloid aggregation

Inhibition of β-amyloid (Aβ) aggregation is an attractive therapeutic and preventive strategy for the discovery of disease-modifying agents in Alzheimer's disease (AD). Phomopsis occulta is a new, salt-tolerant fungus isolated from mangrove Pongamia pinnata (L.) Pierre. We report here the inhibitory effects of secondary metabolites from Ph. occulta on the aggregation of Aβ42. It was found that mycelia extracts (MEs) from Ph. occulta cultured with 0, 2, and 3 M NaCl exhibited inhibitory activity in an E. coli model of Aβ aggregation. A water-soluble fraction, ME0-W-F1, composed of mainly small peptides, was able to reduce aggregation of an Aβ42-EGFP fusion protein and an early onset familial mutation Aβ42E22G-mCherry fusion protein in transfected HEK293 cells. ME0-W-F1 also antagonized the cytotoxicity of Aβ42 in the neural cell line SH-SY5Y in dose-dependent manner. Moreover, SDS-PAGE and FT-IR analysis confirmed an inhibitory effect of ME0-W-F1 on the aggregation of Aβ42 in vitro. ME0-W-F1 blocked the conformational transition of Aβ42 from α-helix/random coil to β-sheet, and thereby inhibited formation of Aβ42 tetramers and high molecular weight oligomers. ME0-W-F1 and other water-soluble secondary metabolites from Ph. occulta therefore represent new candidate natural products against aggregation of Aβ42, and illustrate the potential of salt tolerant fungi from mangrove as resources for the treatment of AD and other diseases.

Systemic and cerebral exposure to and pharmacokinetics of flavonols and terpene lactones after dosing standardized Ginkgo biloba leaf extracts to rats via different routes of administration

BACKGROUND AND PURPOSE

Flavonols and terpene lactones are putatively responsible for the properties of Ginkgo biloba leaf extracts that relate to prevention and treatment of cardiovascular disease and cerebral insufficiency. Here, we characterized rat systemic and cerebral exposure to these ginkgo compounds after dosing, as well as the compounds' pharmacokinetics.

EXPERIMENTAL APPROACH

Rats received single or multiple doses of ShuXueNing injection (prepared from GBE50 for intravenous administration) or GBE50 (a standardized extract of G. biloba leaves for oral administration). Brain delivery of the ginkgo compounds was assessed with microdialysis. Various rat samples were analysed using liquid chromatography/mass spectrometry.

KEY RESULTS

Slow terminal elimination features of the flavonols counterbalanced the influence of poor oral bioavailability on their systemic exposure levels, which also resulted in significant accumulation of the compounds in plasma during the subchronic treatment with ShuXueNing injection and GBE50. Unlike the flavonols, the terpene lactones had poor enterohepatic circulation due to their rapid renal excretion and unknown metabolism. The flavonol glycosides occurred as major forms in plasma after dosing with ShuXueNing injection, while the flavonol aglycone conjugates were predominant in plasma after dosing with GBE50. Cerebral exposure was negligible for the flavonols and low for the terpene lactones.

CONCLUSION AND IMPLICATIONS

Unlike the significant systemic exposure levels, the levels of cerebral exposure to the flavonols and terpene lactones are low. The elimination kinetic differences between the two classes of ginkgo compounds influence their relative systemic exposure levels. The information gained is relevant to linking ginkgo administration to the medicinal effects.

Protective effects of Ginkgo biloba extract EGb 761 against noise trauma-induced hearing loss and tinnitus development

Noise-induced hearing loss (NIHL) and resulting comorbidities like subjective tinnitus are common diseases in modern societies. A substance shown to be effective against NIHL in an animal model is the Ginkgo biloba extract EGb 761. Further effects of the extract on the cellular and systemic levels of the nervous system make it a promising candidate not only for protection against NIHL but also for its secondary comorbidities like tinnitus. Following an earlier study we here tested the potential effectiveness of prophylactic EGb 761 treatment against NIHL and tinnitus development in the Mongolian gerbil. We monitored the effects of EGb 761 and noise trauma-induced changes on signal processing within the auditory system by means of behavioral and electrophysiological approaches. We found significantly reduced NIHL and tinnitus development upon EGb 761 application, compared to vehicle treated animals. These protective effects of EGb 761 were correlated with changes in auditory processing, both at peripheral and central levels. We propose a model with two main effects of EGb 761 on auditory processing, first, an increase of auditory brainstem activity leading to an increased thalamic input to the primary auditory cortex (AI) and second, an asymmetric effect on lateral inhibition in AI.

The Ginkgo biloba Extract EGb 761 Modulates Proteasome Activity and Polyglutamine Protein Aggregation

The standardized Ginkgo biloba extract EGb 761 has well-described antioxidative activities and effects on different cytoprotective signaling pathways. Consequently, a potential use of EGb 761 in neurodegenerative diseases has been proposed. A common characteristic feature of a variety of such disorders is the pathologic formation of protein aggregates, suggesting a crucial role for protein homeostasis. In this study, we show that EGb 761 increased the catalytic activity of the proteasome and enhanced protein degradation in cultured cells. We further investigated this effect in a cellular model of Huntington's disease (HD) by employing cells expressing pathologic variants of a polyglutamine protein (polyQ protein). We show that EGb 761 affected these cells by (i) increasing proteasome activity and (ii) inducing a more efficient degradation of aggregation-prone proteins. These results demonstrate a novel activity of EGb 761 on protein aggregates by enhancing proteasomal protein degradation, suggesting a therapeutic use in neurodegenerative disorders with a disturbed protein homeostasis.

Effects of Gingko biloba supplementation in Alzheimer's disease patients receiving cholinesterase inhibitors: data from the ICTUS study

Ginkgo biloba (Gb) is currently the most investigated and adopted herbal remedy for cognitive disorders and Alzheimer's disease (AD). Nevertheless, its efficacy in the prevention and treatment of dementia still remains controversial. Specifically, the added effects of Gb in subjects already receiving "conventional" anti-dementia treatments have been to date very scarcely investigated. We evaluated whether the use of Gb is associated with additional cognitive and functional benefit in AD patients already in treatment with cholinesterase inhibitors (ChEIs). Data are from mild to moderate AD patients under ChEI treatment recruited in the Impact of Cholinergic Treatment USe (ICTUS) study. Mixed model analyses were performed to measure six-monthly modifications in the Mini Mental State Examination (MMSE), the Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog) subscale score, and the Activities of Daily Living (ADL) scale over a follow-up of 1 year according to the additional Gb supplementation. A total of 828 subjects were considered for the present analyses. Significantly different modifications at the MMSE score over the 12-month follow-up were reported between patients on combined therapy compared to those only taking ChEIs. On the contrary, the modification of the ADAS-Cog score between the two groups did not show statistically significant differences, although similar trends were noticed. No significant modifications of the two adopted outcome measures were observed at the mid-term 6-month evaluation. The modifications over time of the ADL score did not show statistically significant differences between the two groups of interest. Our findings suggest that Gb may provide some added cognitive benefits in AD patients already under ChEIs treatment. The clinical meaningfulness of such effects remains to be confirmed and clarified.

Quantitative analysis of the flavonoid glycosides and terpene trilactones in the extract of Ginkgo biloba and evaluation of their inhibitory activity towards fibril formation of β-amyloid peptide

The standard extract of Ginkgobiloba leaves (EGb761) is used clinically in Europe for the symptomatic treatment of impaired cerebral function in primary degenerative dementia syndromes, and the results of numerous in vivo and in vitro studies have supported such clinical use. The abnormal production and aggregation of amyloid β peptide (Aβ) and the deposition of fibrils in the brain are regarded as key steps in the onset of Alzheimer’s Disease (AD), and the inhibition of Aβ aggregation and destabilization of the preformed fibrils represent viable approaches for the prevention and treatment of AD. Flavonoid glycosides and terpene trilactones (TTLs) are the two main components of EGb761 which represent 24 and 6% of the overall content, respectively. In our research, seven abundant flavonoid glycosides 1–7 were isolated from the extract of Ginkgobiloba leaves and characterized by spectroscopic analysis. Furthermore, an ultra-high performance liquid chromatography method was established for the simultaneous quantification of these seven flavonoids. The inhibitory activities of these flavonoids, as well as four TTLs, i.e., ginkgolides A, B, and C and bilobalide (compounds 8–11), were evaluated towards Aβ42 fibril formation using a thioflavin T fluorescence assay. It was found that three flavonoids 1, 3 and 4 exhibited moderate inhibitory activities, whereas the other four flavonoids 2, 5, 6 and 7, as well as the four terpene trilactones, showed poor activity. This is the first report of the inhibition of Aβ fibril formation of two characteristic acylated flavonoid glycosides 6, 7 in Ginkgo leaves, on the basis of which the structure-activity relationship of these flavonoids 1–7 was discussed.

The flavonoid derivative 2-(4' Benzyloxyphenyl)-3-hydroxy-chromen-4-one protects against Aβ42-induced neurodegeneration in transgenic Drosophila: insights from in silico and in vivo studies

In the pathogenesis of Alzheimer's disease (AD), it is well established that the self-association of Aβ peptides into amyloid fibrils and/or plaque like aggregates causes neurotoxicity. As there is no cure for AD till date, identification of specific compounds that either inhibit the formation of Aβ-fibrils or help in the dissolution of already formed amyloid plaques makes an appealing therapeutic and preventive strategy in the development of drugs. In the present study, four synthetic flavonoid derivatives (1, 2, 3 and 4) were examined for docking studies with Amyloid beta (PDB Code: 1IYT) and Amyloid fibril (PDB Code: 2BEG). Of these, compound 1 and 4 were found to be potential inhibitors, as supported by computational molecular docking studies with adequate pharmacokinetic properties. Compound 1 was further tested in vivo in transgenic AD model of Drosophila. The disease causing human Aβ42 peptide was expressed in the compound eye by driving UAS-Aβ42 with ey-GAL4, which caused severe degeneration in eye tissues ranging from loss of bristles, ommatidial holes to severe ommatidial disruption as revealed by digital camera imaging and scanning electron microscopy. When the Aβ42 expressing larvae were grown in medium containing Compound 1, ~70 % rescue of the rough eye phenotype was observed at 75 and 100 μM concentrations. This is further corroborated by significant reduction in amyloid plaques in eye imaginal disks of compound 1 treated larvae as revealed by immuno-confocal imaging studies. Further, rescue of locomotor deficit and improved life span in compound 1 treated Aβ flies also confirm the neuroprotective activity of this compound. Thus, our results support the neuroprotective efficacy of compound 1 in preventing Aβ42-induced neurotoxicity in vivo and identify it as a future therapeutic agent against AD.

Protective Effect of Standardized Extract of Ginkgo biloba against Cisplatin-Induced Nephrotoxicity

Cisplatin (CDDP) is a potent antitumor compound widely used with a notably side effect of nephrotoxicity inducing oxidative stress and apoptosis in kidneys. Standardized extract from the leaves of the Ginkgo biloba trees, labeled EGb761 (EGb), has been available on the market for its beneficial effects. The purpose of this study was to investigate the ability of EGb to prevent the nephrotoxic effect of CDDP and the mechanisms involved. Our results showed that EGb treatment restored the levels of creatinine, BUN, MDA, NO, SOD, CAT, GPx, and GSSG/GSH ratio in kidneys after CDDP injection. EGb also exhibited a tendency to decrease the elevated NF-κB translocation and caspase-3 protein levels in CDDP-treated kidneys. We further used a porcine kidney proximal tubular epithelial (LLC-PK1) cell line, finding that EGb accordingly inhibited ROS accumulation and iNOS increase induced by CDDP in vitro. EGb also attenuated IκB degradation and p65 NF-κB phosphorylation triggered by CDDP in LLC-PK1 cells. But EGb failed to influence CDDP-stimulated caspase cascade. These findings suggested that EGb's renoprotective effect might be mediated by not only its well-known antioxidant activity but also the anti-inflammatory activity.

The analog of Ginkgo biloba extract 761 is a protective factor of cognitive impairment induced by chronic fluorosis

Ginkgo biloba extract EGb761 is widely used to treat patients with learning and memory impairment in Alzheimer's disease and Parkinson's disease in China. However, it is not yet clear whether the analog of EGb761 (EGb) has a protective effect on the learning and memory damage induced by chronic fluorosis. In this study, 30 Wistar rats were randomly divided into three groups: a control group, a sodium fluoride (NaF) + EGb group, and a NaF group. The rats were administered 0.5 ml water containing NaF (100 mg/l) and EGb (120 mg/kg) per day via gavage. After 3 months, the rats' capacity for learning and memory was tested using a Y-maze. Damage to hippocampal neurons was evaluated by histological examination of the CA3 area. Superoxide dismutase (SOD) activity and the levels of glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) were measured. Furthermore, the expression levels of Bcl-2 and Bax and the levels of cleaved Caspase3 in the hippocampus were evaluated by RT-PCR and Western blotting. The results showed that EGb could improve learning and memory abilities, enhance the activities of SOD and GSH-Px, attenuate the level of MDA, upregulate the ratio of Bcl-2/Bax, and downregulate the level of cleaved Caspase3.

Plants traditionally used in age-related brain disorders (dementia): an ethanopharmacological survey

CONTEXT

Epidemiological studies have shown that despite mortality due to communicable diseases, poverty and human conflicts, the incidence of dementia increases in the developing world in tandem with the ageing population. Although some FDA approved drugs are available for the treatment of dementia, the outcomes are often unsatisfactory. In traditional practices of medicine, numerous plants have been used to treat cognitive disorders, including neurodegenerative diseases such as Alzheimer's disease (AD) and other memory-related disorders. In western medicine most of the drugs used for the treatment of neurodegenerative disorders are derived from plant sources.

OBJECTIVE

This article reviews plants and their active constituents that have been used for their reputed cognitive-enhancing and antidementia effects.

METHODS

A literature survey in Science Direct, Pubmed, and Google Scholar was performed to gather information regarding drug discovery from plants sources for the treatment of congnitive disorders and dementia.

RESULTS

More than forty herbal remedies were identified with cholinesterase inhibitory, anti-inflammatory, or antioxidant activities. Bioactive compounds include alkaloids, flavonoids, steroids, saponins, terpenoids, and essential oils. About eleven herbal plants with multipotent activity against AD are discussed.

CONCLUSION

Literature surveys show that most of the research has been conducted on herbal remedies effect on cholinesterase inhibitory and antioxidant activities. Studies regarding the effect of herbal drugs on β-secretase inhibitory activity and antiaggregation property are lacking. This review provides leads for identifying potential new drugs from plant sources for the treatment of neurodegenerative disorders.

Luteolin attenuates diabetes-associated cognitive decline in rats

Diabetes mellitus can cause dysfunction of the central nervous system called "diabetic encephalopathy". Although various oral drugs are used to treat diabetes, they do not prevent the development of diabetes-associated cognitive decline in rats, and novel strategies for the prevention and treatment are urgently needed. Luteolin, a flavonoid isolated from Cirsium japonicum, has antioxidant, anti-inflammatory and neuroprotective activities. However, no report is available on influence of luteolin on streptozotocin-induced memory impairment. Therefore, we tested its influence against cognitive dysfunction in streptozotocin-induced diabetic rats using Morris water maze test. Nissl's staining, choline esterase (ChE) activity as marker of cholinergic function and oxidative stress were assessed in the cerebral cortex and hippocampus to evaluate the neuropathological changes and the effects of luteolin on diabetic rats. The results showed that streptozotocin-induced diabetes produced obvious neuron damage and cognitive dysfunction coupling with markedly increased oxidative stress and ChE activity in the brain. In contrast, chronic treatment with luteolin (50 and 100mg/kg) improved neuronal injury and cognitive performance by attenuating oxidative stress and ChE activity in diabetic rats. In conclusion, the present study suggested that oral supplementation of luteolin might be a potential therapeutic strategy for the treatment and/or prevention of diabetic encephalopathy.

Evaluation of Ginkgo biloba extract as an activator of human glucocorticoid receptor

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba, which is one of the most frequently used herbal medicines, is commonly used in the management of several conditions, including memory impairment. Previously, it was reported to decrease the expression of peripheral benzodiazepine receptor and the biosynthesis of glucocorticoids, thereby regulating glucocorticoid levels. However, it is not known whether Ginkgo biloba extract regulates the function of the glucocorticoid receptor.

AIM OF THE STUDY

We determined whether Ginkgo biloba extract and several of its chemical constituents affect the activity of human glucocorticoid receptor (hGR).

MATERIALS AND METHODS

A hGR-dependent reporter gene assay was conducted in HepG2 human hepatocellular carcinoma cells and hGR target gene expression assays were performed in primary cultures of human hepatocytes.

RESULTS

Multiple lots and concentrations of the extract and several of its chemical constituents (ginkgolide A, ginkgolide B, ginkgolide C, ginkgolide J, and bilobalide) did not increase hGR activity, as assessed by a cell-based luciferase reporter gene assay. The extract did not influence the expression of hGR target genes, including tyrosine aminotransferase (hTAT), constitutive androstane receptor (hCAR), or pregnane X receptor (hPXR), in primary cultures of human hepatocytes. Moreover, hGR antagonism by mifepristone (also known as RU486) did not attenuate the extent of induction of hCAR- and hPXR-regulated target genes CYP2B6 and CYP3A4 by Ginkgo biloba extract.

CONCLUSION

Ginkgo biloba extract, ginkgolide A, ginkgolide B, ginkgolide C, ginkgolide J, and bilobalide are not activators of hGR. Furthermore, the extract does not influence the hGR-hCAR or the hGR-hPXR signaling pathway in primary cultures of human hepatocytes.

Ginkgo biloba extract and long-term cognitive decline: a 20-year follow-up population-based study

Background

Numerous studies have looked at the potential benefits of various nootropic drugs such as Ginkgo biloba extract (EGb761®; Tanakan®) and piracetam (Nootropyl®) on age-related cognitive decline often leading to inconclusive results due to small sample sizes or insufficient follow-up duration. The present study assesses the association between intake of EGb761® and cognitive function of elderly adults over a 20-year period.

Methods and Findings

The data were gathered from the prospective community-based cohort study ‘Paquid’. Within the study sample of 3612 non-demented participants aged 65 and over at baseline, three groups were compared: 589 subjects reporting use of EGb761® at at least one of the ten assessment visits, 149 subjects reporting use of piracetam at one of the assessment visits and 2874 subjects not reporting use of either EGb761® or piracetam. Decline on MMSE, verbal fluency and visual memory over the 20-year follow-up was analysed with a multivariate mixed linear effects model. A significant difference in MMSE decline over the 20-year follow-up was observed in the EGb761® and piracetam treatment groups compared to the ‘neither treatment’ group. These effects were in opposite directions: the EGb761® group declined less rapidly than the ‘neither treatment’ group, whereas the piracetam group declined more rapidly (β = −0.6). Regarding verbal fluency and visual memory, no difference was observed between the EGb761® group and the ‘neither treatment’ group (respectively, β = 0.21 and β = −0.03), whereas the piracetam group declined more rapidly (respectively, β = −1.40 and β = −0.44). When comparing the EGb761® and piracetam groups directly, a different decline was observed for the three tests (respectively β = −1.07, β = −1.61 and β = −0.41).

Conclusion

Cognitive decline in a non-demented elderly population was lower in subjects who reported using EGb761® than in those who did not. This effect may be a specific medication effect of EGb761®, since it was not observed for another nootropic medication, piracetam.

Pharmacological Treatment of Mild Cognitive Impairment as a Prodromal Syndrome of Alzheimer´s Disease

Mild cognitive impairment (MCI) is a syndrome which, depending on various neurobiological, psychological and social factors, carries a high risk of developing into dementia. As far as diagnostic uncertainty and the heterogeneous underlying pathophysiological mechanisms are concerned, only limited therapeutic options are currently available. Clinical trials involving a wide range of substances have failed to show efficacy on primary and secondary outcome parameters. Most results reflect not only a lack of effectiveness of drug therapy but also methodological constraints in true prodromal Alzheimer´s disease (AD) based on clinical criteria. Biomarkers may help to identify MCI as a prodromal phase of dementia, so it is important to use them to improve specificity of case selection in future studies. For MCI as a prodromal syndrome of AD, clinical trials with disease modifying drugs that target underlying pathological mechanisms such as amyloid-beta accumulation and neurofibrillary tangle formation may help develop effective treatment options in the future. Alternative pharmacological approaches are currently being evaluated in ongoing phase 1 and phase 2 studies. Nevertheless, a lack of approved pharmacotherapeutic options has led to specific interventions that focus on patient education and life-style related factors receiving increasing attention.

Keampferol-3-O-rhamnoside abrogates amyloid beta toxicity by modulating monomers and remodeling oligomers and fibrils to non-toxic aggregates

BACKGROUND

Aggregation of soluble, monomeric β- amyloid (Aβ) to oligomeric and then insoluble fibrillar Aβ is a key pathogenic feature in development of Alzheimer's disease (AD). Increasing evidence suggests that toxicity is linked to diffusible Aβ oligomers, rather than to insoluble fibrils. The use of naturally occurring small molecules for inhibition of Aβ aggregation has recently attracted significant interest for development of effective therapeutic strategies against the disease. A natural polyphenolic flavone, Kaempferol-3-O-rhamnoside (K-3-rh), was utilized to investigate its effects on aggregation and cytotoxic effects of Aβ42 peptide. Several biochemical techniques were used to determine the conformational changes and cytotoxic effect of the peptide in the presence and absence of K-3-rh.

RESULTS

K-3-rh showed a dose-dependent effect against Aβ42 mediated cytotoxicity. Anti-amyloidogenic properties of K-3-rh were found to be efficient in inhibiting fibrilogenesis and secondary structural transformation of the peptide. The consequence of these inhibitions was the accumulation of oligomeric structural species. The accumulated aggregates were smaller, soluble, non-β-sheet and non-toxic aggregates, compared to preformed toxic Aβ oligomers. K-3-rh was also found to have the remodeling properties of preformed soluble oligomers and fibrils. Both of these conformers were found to remodel into non-toxic aggregates. The results showed that K-3-rh interacts with different Aβ conformers, which affects fibril formation, oligomeric maturation and fibrillar stabilization.

CONCLUSION

K-3-rh is an efficient molecule to hinder the self assembly and to abrogate the cytotoxic effects of Aβ42 peptide. Hence, K-3-rh and small molecules with similar structure might be considered for therapeutic development against AD.

Ginkgolide B preconditioning on astrocytes promotes neuronal survival in ischemic injury via up-regulating erythropoietin secretion

Although ischemic preconditioning (IP) can provide powerful protection on brain against ischemic insult, it is rarely used in clinic to prevent the occurrence of ischemic stroke because of safety concerns. It is therefore necessary to seek the safer stimuli to initiate pharmacological preconditioning. Our previous work demonstrated that ginkgolide B (GB) could protect neurons against ischemia-induced apoptosis. Astrocytes are the most numerous cells in mammalian central nervous system and there is a close bi-directional communication between neurons and astrocytes in brain. Besides neurons, whether GB can exert the role of preconditioning on astrocytes through which to further improve neuronal survival under ischemic condition is not yet known. In the present study, primary cultured astrocytes were treated with GB for 24h or short-term ischemia (ischemia for 3h, as ischemic preconditioning/IP), and then cultured back to normoxia and normal medium for 24h to induce the preconditioning response. Astrocyte-conditioned medium (ACM) was then collected and used to incubate the cultured neurons for 24h before neurons were subjected to severe ischemia. Our results demonstrated that not only GB and IP increased astrocytic viability in ischemia, but also the conditioned medium from astrocytes treated with GB or IP increased cell viability and decreased the number of apoptosis of neurons in ischemia. We also found that GB and IP significantly stimulated astrocytes to express and secrete erythropoietin (EPO) into ACM, and the addition of anti-EPO antibody blocked the protective effect of GB or IP-treated astrocytes culture medium on neurons in ischemia. Further study of above protection revealed that ACM from astrocytes treated with GB or IP induced the inactivation of proapoptotic factor Bad by phosphorylation at serine 136 and 112 ((136)p-Bad and (112)p-Bad) in neurons. Together, our results suggest that GB is capable of preconditioning on astrocytes as IP and then protects neurons against ischemia-induced apoptosis, which is mediated by EPO.

Brain-derived neurotrophic factor levels and its Val66Met gene polymorphism predict tardive dyskinesia treatment response to Ginkgo biloba

BACKGROUND

Tardive dyskinesia (TD) has no well-accepted treatments or known pathophysiology, but low brain-derived neurotrophic factor (BDNF) may play an important role in its pathophysiology. Ginkgo biloba (EGb-761) is a potent antioxidant that has neuroprotective effects mediated through enhancing BDNF levels. We hypothesized that treatment with EGb-761 would increase serum BDNF levels and reduce TD, particularly among schizophrenia patients who have the BDNF valine 66 to methionine (Val66Met) genotype (Val/Val).

METHODS

Serum BDNF levels and genotyping for the BDNF gene Val66Met polymorphism were assessed in Chinese schizophrenic patients with (n = 368) and without (n = 563) TD as well as healthy control subjects (n = 546). About half of the TD patients (n = 157) then participated in a double-blind, randomized, placebo-control 12-week treatment with 240 mg per day of EGb-761. Serum BDNF levels were measured again at posttreatment. Clinical efficacy was determined using the Abnormal Involuntary Movement Scale (AIMS).

RESULTS

TD patients had lower BDNF levels than the non-TD patients and healthy controls. EGb-761 treatment improved symptoms of TD and increased BDNF levels compared with placebo treatment. Moreover, the improvement of AIMS total score correlated with the increase in BDNF levels. Furthermore, improvement in the AIMS score was greatest in those with the Val/Val allele and lowest with the Met/Met allele.

CONCLUSIONS

The BDNF system may be implicated in the pathophysiology of TD and its improvement with antioxidant treatment. Furthermore, patients with the genetic potential for greater BDNF release (Val/Val at 66) may obtain a greater reduction in TD from EGb-761 treatment.

Inhibitory effect of Ginkgo biloba extract on fatty liver: regulation of carnitine palmitoyltransferase 1a and fatty acid metabolism

OBJECTIVE

To investigate the potential effect of Ginkgo biloba extract (GBE) on the prevention and treatment of nonalcoholic fatty liver disease (NAFLD).

METHODS

Male Wistar rats were divided into 4 groups (the control group, GBE group, high-fat diet [HFD] group and HFD + GBE group). The human hepatocellular carcinoma cell line (HepG2) was treated with GBE and its flavonoid ingredients. The fatty acid composition of the rat liver was analyzed with gas chromatography/time-of-flight mass spectrometry (GC/TOFMS). Triglyceride contents of both the rat liver and HepG2 cells were measured by enzymatic colorimetric method. The expressions of fatty acid metabolism-related genes were analyzed with real-time reverse transcription-polymerase chain reaction (RT-PCR). The protein expression and enzymatic activity were subsequently measured.

RESULTS

In rat livers, GBE reduced the elevations of hepatic triglyceride contents caused by HFD and the increased hepatic fatty acids were differentially affected by GBE. Notably, the expression and total activity of the fatty acid β-oxidation rate-limiting enzyme, carnitine palmitoyltransferase 1a (CPT1A), were also promoted with GBE ingestion. In HepG2 cells, GBE and its ingredients, quercetin, kaempferol and isorhamnetin, could decrease the cellular triglyceride content and upregulate the expression and total activity of CPT1A, respectively.

CONCLUSIONS

The triglyceride-lowering effect of GBE on the HFD rat liver is closely associated with the increased expression and activity of CPT1A, and the flavonoid ingredients are the major contributors of GBE.

Nutraceutical interventions for promoting healthy aging in invertebrate models

Aging is a complex and inevitable biological process that is associated with numerous chronically debilitating health effects. Development of effective interventions for promoting healthy aging is an active but challenging area of research. Mechanistic studies in various model organisms, noticeably two invertebrates, Caenorhabditis elegans and Drosophila melanogaster, have identified many genes and pathways as well as dietary interventions that modulate lifespan and healthspan. These studies have shed light on some of the mechanisms involved in aging processes and provide valuable guidance for developing efficacious aging interventions. Nutraceuticals made from various plants contain a significant amount of phytochemicals with diverse biological activities. Phytochemicals can modulate many signaling pathways that exert numerous health benefits, such as reducing cancer incidence and inflammation, and promoting healthy aging. In this paper, we outline the current progress in aging intervention studies using nutraceuticals from an evolutionary perspective in invertebrate models.

Neurological disorders and therapeutics targeted to surmount the blood-brain barrier

We are now in an aging population, so neurological disorders, particularly the neurodegenerative diseases, are becoming more prevalent in society. As per the epidemiological studies, Europe alone suffers 35% of the burden, indicating an alarming rate of disease progression. Further, treatment for these disorders is a challenging area due to the presence of the tightly regulated blood-brain barrier and its unique ability to protect the brain from xenobiotics. Conventional therapeutics, although effective, remain critically below levels of optimum therapeutic efficacy. Hence, methods to overcome the blood-brain barrier are currently a focus of research. Nanotechnological applications are gaining paramount importance in addressing this question, and yielding some promising results. This review addresses the pathophysiology of the more common neurological disorders and novel drug candidates, along with targeted nanoparticle applications for brain delivery.

Herbal Extracts Combination (WNK) Prevents Decline in Spatial Learning and Memory in APP/PS1 Mice through Improvement of Hippocampal Aβ Plaque Formation, Histopathology, and Ultrastructure

To investigate the cognitive enhancement effect of WNK, an extracts combination of P. ginseng,  G. biloba, and C. sativus L. and possible mechanisms, 5-month-old APP/PS1 transgenic mice were used in this study. After 3 months of administration, all mice received Morris water maze (MWM) training and a probe test. Mouse brain sections were detected by immunohistochemistry, HE staining, and transmission electron microscopy. MWM results showed significant difference between transgenic mice and nontransgenic littermates (P < 0.05, P < 0.01). WNK-treated mice exhibited enhanced maze performance over the training progression, especially better spatial memory retention in probe test compared to transgenic mice (P < 0.05, P < 0.01) and better spatial learning and memory at the fourth day of MWM test compared to EGB761- (G. biloba extract-) treated ones (P < 0.05). Hippocampal Aβ plaque burden significantly differed between APP/PS1 and littermate mice (P < 0.001), while decreased Aβ plaque appeared in WNK- or EGB761-treated transgenic brains (P < 0.05). Neurodegenerative changes were evident from light microscopic and ultrastructural observations in transgenic brains, which were improved by WNK or EGB761 treatment. These data indicate WNK can reduce the decline in spatial cognition, which might be due to its effects on reducing Aβ plaque formation and ameliorating histopathology and ultrastructure in hippocampus of APP/PS1 mouse brain.

Ginkgo biloba extract (EGb 761) prevents the ischemic brain injury-induced decrease in parvalbumin expression

Ginkgo biloba extract (EGb 761) exerts a neuroprotective effect against ischemic brain injury through an anti-apoptotic mechanism. Parvalbumin is a calcium buffering protein that plays an important role in modulating intracellular calcium concentration and regulating apoptotic cell death. The aim of this study was to investigate whether EGb 761 affects parvalbumin expression in cerebral ischemic injury. Adult male Sprague-Dawley rats were treated with vehicle or EGb 761 (100 mg/kg) prior to middle cerebral artery occlusion (MCAO) and cerebral cortex tissues were collected 24 h after MCAO. A proteomic approach revealed a reduction in parvalbumin expression in the vehicle-treated animals, whereas EGb 761 pretreatment attenuates the ischemic injury-induced decrease in parvalbumin expression. RT-PCR and Western blot analyses clearly confirmed the fact that EGb 761 prevents the injury-induced decrease in parvalbumin. Moreover, the results of immunohistochemical staining showed that the number of parvalbumin-positive cells was lower in vehicle-treated animals than in sham-operated animals, and EGb 761 averted this decrease. Thus, these results suggest that the maintenance of parvalbumin expression is associated with the neuroprotective function of EGb 761 against neuronal damage induced by ischemia.

Gingko biloba Extract (EGb 761) Attenuates the Focal Cerebral Ischemic Injury-Induced Decrease in Astrocytic Phosphoprotein PEA-15 Levels

EGb 761 is an extract of Gingko biloba that is neuroprotective against focal cerebral ischemic injury. PEA-15 (phosphoprotein enriched in astrocytes 15) modulates cell proliferation and apoptosis. In this study, we investigated whether EGb 761 regulates the expression of PEA-15 and two phosphorylated forms of PEA-15 (Ser 104 and Ser 116) in middle cerebral artery occlusion (MCAO)-induced injury. Adult male rats were treated with vehicle or EGb 761 (100 mg/kg) prior to MCAO and cerebral cortices were collected 24 h after MCAO. A reduction in expression of PEA-15 and its phosphorylated forms induced by MCAO injury was detected using a proteomic approach. EGb 761 pretreatment prevented the ischemic injury-induced decrease in PEA-15 expression. Western blot analysis demonstrated that EGb 761 attenuates the injury-induced reduction in PEA-15, phospho-PEA-15 (Ser 104), phospho-PEA-15 (Ser 116). Phosphorylation of PEA-15 influences its anti-apoptotic function; a decrease in PEA-15 phosphorylation induces apoptotic cell death. The maintenance of PEA-15 phosphorylation by EGb 761 pretreatment during cerebral ischemic injury indicates that EGb 761 is a neuroprotective against cerebral ischemic injury.

Experimental inhibition of fibrillogenesis and neurotoxicity by amyloid-beta (Aβ) and other disease-related peptides/proteins by plant extracts and herbal compounds

Amyloid-β (Aβ) fibrillogenesis and associated cyto/neurotoxicity are major pathological events and hallmarks in diseases such as Alzheimer's disease (AD). The understanding of Aβ molecular pathogenesis is currently a pharmacological target for rational drug design and discovery based on reduction of Aβ generation, inhibition of Aβ fibrillogenesis and aggregation, enhancement of Aβ clearance and amelioration of associated cytotoxicity. Molecular mechanisms for other amyloidoses, such as transthyretin amyloidosis, AL-amyloidosis, as well as α-synuclein and prion protein are also pharmacological targets for current drug therapy, design and discovery. We report on natural herbal compounds and extracts that are capable binding to and inhibiting different targets associated with AD and other amyloid-associated diseases, providing a basis for future therapeutic strategies. Many herbal compounds, including curcumin, galantamine, quercetin and other polyphenols, are under active investigation and hold considerable potential for future prophylactic and therapeutic treatment against AD and other neurodegenerative diseases, as well as systemic amyloid diseases. A common emerging theme throughout many studies is the anti-oxidant and anti-inflammatory properties of the compounds or herbal extracts under investigation, within the context of the inhibition of cyto/neurotoxicity and anti-amyloid activity.

Neuronal and vascular oxidative stress in Alzheimer's disease

The brain is a highly metabolically active organ producing large amounts of reactive oxygen species (ROS). These ROS are kept in check by an elaborate network of antioxidants. Although ROS are necessary for signaling and synaptic plasticity, their uncontrolled levels cause oxidation of essential macromolecules such as membrane lipids, nucleic acids, enzymes and cytoskeletal proteins. Indeed, overproduction of ROS and/or failure of the antioxidant network lead to neuronal oxidative stress, a condition associated with not only aging but also Alzheimer's disease (AD). However, the specific source of excessive ROS production has not yet been identified. On one hand, amyloid beta (Aβ) has been extensively shown to act as an oxidant molecule. On the other hand, oxidative stress has been shown to precede and exacerbate Aβ pathology. This review will address the involvement of oxidative stress in the context of neuronal as well as vascular dysfunction associated with AD.

Antioxidant properties of natural polyphenols and their therapeutic potentials for Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease and most common cause of dementia. However, there is no known way to halt or cure the neurodegenerative disease. Oxidative stress is a cardinal hallmark of the disease and has been considered as therapeutic target for AD treatment. Several factors may contribute to oxidative stress in AD brains. First, mitochondrion is a key player that produces reactive oxygen species (ROS). Mitochondrial dysfunction found in AD patients may exaggerate generation of ROS and oxidative stress. Second, amyloid-beta peptide generates ROS in the presence of metal ions such as Fe(2+) and Cu(2+). Third, activated glial cells in AD brains may produce excessive amount of superoxide and nitric oxide through NADPH oxidase and inducible nitric oxide synthase, respectively. Increased ROS can cause damage to protein, lipid and nucleic acids. Numerous studies demonstrated that natural polyphenolic compounds protect against various neurotoxic insults in vitro and in vivo AD models. In these studies, dietary polyphenolic compounds exhibit neuroprotective effects through scavenging free radicals and increasing antioxidant capacity. Furthermore, they could facilitate the endogenous antioxidant system by stimulating transcription. Some epidemiological and clinical studies highlighted their therapeutic potential for AD treatment. In this review, we will briefly discuss causes of oxidative stress in AD brains, and describe antioxidant neuroprotective effects and therapeutic potential for AD of selected natural polyphenolic compounds.

The neuroprotective potential of flavonoids: a multiplicity of effects

Flavonoids exert a multiplicity of neuroprotective actions within the brain, including a potential to protect neurons against injury induced by neurotoxins, an ability to suppress neuroinflammation, and the potential to promote memory, learning and cognitive function. These effects appear to be underpinned by two common processes. Firstly, they interact with critical protein and lipid kinase signalling cascades in the brain leading to an inhibition of apoptosis triggered by neurotoxic species and to a promotion of neuronal survival and synaptic plasticity. Secondly, they induce beneficial effects on the vascular system leading to changes in cerebrovascular blood flow capable of causing angiogenesis, neurogenesis and changes in neuronal morphology. Through these mechanisms, the consumption of flavonoid-rich foods throughout life holds the potential to limit neurodegeneration and to prevent or reverse age-dependent loses in cognitive performance. The intense interest in the development of drugs capable of enhancing brain function means that flavonoids may represent important precursor molecules in the quest to develop of a new generation of brain enhancing drugs.

Natural substances and Alzheimer's disease: from preclinical studies to evidence based medicine

Over the last 10 years, the potential therapeutic effects of nutraceuticals to prevent or delay Alzheimer's disease were proposed. Among dietary antioxidants curcumin, Ginkgo biloba and carnitines were extensively studied for their neuroprotective effects. The rationale for this alternative therapeutic approach was based on several preclinical studies which suggested the neuroprotective effects for curcumin, Ginkgo biloba and acetyl-l-carnitine due to either a free radical scavenging activity or the inhibition of pro-inflammatory pathways or the potentiation of the cell stress response. However, although these are interesting premises, clinical studies were not able to demonstrate significant beneficial effects of curcumin, Ginkgo biloba and acetyl-l-carnitine in improving cognitive functions in Alzheimer's disease patients. The aim of this review is to summarize the main pharmacologic features of curcumin, Ginkgo biloba and carnitines as well as to underlie the main outcomes reached by clinical studies designed to demonstrate the efficacy of these natural substances in Alzheimer's disease patients. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.

Isoform-selective activation of human constitutive androstane receptor by Ginkgo biloba extract: functional analysis of the SV23, SV24, and SV25 splice variants

Naturally occurring splice variants of human constitutive androstane receptor (hCAR) exist, including hCAR-SV23 (insertion of amino acids SPTV), hCAR-SV24 (APYLT), and hCAR-SV25 (SPTV and APYLT). An extract of Ginkgo biloba was reported to activate hCAR-SV24 and the wild type (hCAR-WT). However, it is not known whether it selectively affects hCAR splice variants, how it activates hCAR isoforms, and which chemical is responsible for the effects of the extract. Therefore, we evaluated the impact of G. biloba extract on the functionality of hCAR-SV23, hCAR-SV24, hCAR-SV25, and hCAR-WT and compared it with that of phenobarbital, di-(2-ethylhexyl)phthalate (DEHP), 6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime (CITCO), and 1,4-bis-[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) in cell-based reporter gene assays. Among the hCAR splice variants investigated, only hCAR-SV23 was activated by G. biloba extract, and this required cotransfection of a retinoid X receptor α (RXRα) expression plasmid. The extract activated hCAR-SV23 to a lesser extent than hCAR-WT, but ginkgolide A, ginkgolide B, ginkgolide C, ginkgolide J, and bilobalide were not responsible for the effects of the extract. CITCO activated hCAR-SV23, hCAR-SV24, and hCAR-WT. By comparison, phenobarbital activated hCAR-WT, whereas DEHP activated hCAR-SV23, hCAR-SV24 (with exogenous RXRα supplementation), and hCAR-WT. TCPOBOP did not affect the activity of any of the isoforms. G. biloba extract and phenobarbital did not bind or recruit coactivators to the ligand-binding domains of hCAR-WT and hCAR-SV23, whereas positive results were obtained with the controls (CITCO for hCAR-WT and DEHP for hCAR-SV23). In conclusion, G. biloba extract activates hCAR in an isoform-selective manner, and hCAR-SV23, hCAR-SV24, and hCAR-WT have overlapping, but distinct, sets of ligands.

Current therapeutic options for Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease in the developed world. The increasing life expectancy in the last years has led to an increase in the prevalence of this age-related condition and has posed an important medical and social challenge for developed societies. The mainstays of current therapy for AD rely on the cholinergic hypothesis developed more than 20 years ago. These compounds, known as acetylcholinesterase inhibitors (AChEIs), inhibit the cholinesterases and aim at improving the brain synaptic availability of acetylcholine. These drugs have been approved for the treatment of AD based on pivotal clinical trials showing modest symptomatic benefit on cognitive, behavioral, and global measures. Memantine, an NMDA antagonist, has been recently included as a therapeutic option for AD. Memantine can be combined safely with AChEIs for an additional symptomatic benefit. During the last years our understanding of the mechanisms underlying the pathogenesis of AD has markedly expanded. Several putative neuroprotective drugs are thoroughly investigated and many of them have reached the clinical arena. It can be anticipated that some of these drugs will be able to slow/prevent the progression of this condition in the near future.