Oral administration of (-)catechin protects against ischemia-reperfusion-induced neuronal death in the gerbil

Dietary Intake of Flavonoids Associated with Sleep Problems: An Analysis of Data from the National Health and Nutrition Examination Survey, 2007-2010

Flavonoids possess the latent ability to protect against sleep disorders. We examined the correlation between daily flavonoid intake and sleep duration, and sleep disorders. We enrolled 8216 participants aged ≥ 20 from the National Health and Nutrition Examination Survey (NHANES, 2007-2010), carrying out a cross-sectional study. Flavonoid intake was collected by dietary intake interview recalls. Logistic regression was utilized to evaluate the association between flavonoid intake sleep duration, and sleep disorders. We used subgroup and interaction analysis to explore differences between subgroups. When adjusting covariates in model 2, anthocyanidins, flavan-3-ols, flavones, flavonols, and the sum of flavonoids were considerably related to insufficient sleep duration (odds ratio (OR) (95% confidence interval (CI)); 0.83 (0.72, 0.95); 0.91 (0.83, 0.98); 0.63 (0.41, 0.98); 0.78 (0.64, 0.94); 0.85 (0.76, 0.95), respectively); the converse association was observed between flavanones, and flavones and the risk of sleep disorders (OR (95% CI); 0.85 (0.77, 0.95); 0.61 (0.41, 0.90), respectively). In relation to insufficient sleep, there were statistically significant interactions between flavonoid consumption and race/ethnicity, and education level. In relation to insufficient sleep, there were statistically significant interactions between flavonoid consumption and working status. In this study, we found that certain flavonoids were linked to increased sleep duration and a lower risk of sleep problems. Our research indicated that flavonoids might be a preventive factor for sleep disorders.

A Review on Polyphenols in Salicornia ramosissima with Special Emphasis on Their Beneficial Effects on Brain Ischemia

There has been an increasing interest in the consumption of halophytes as a healthy food in the last few years. Salicornia ramosissima is a seasonal Mediterranean halophyte with an interesting profile of bioactive compounds, including more than 60 identified polyphenols with a broad range of biological activities. Accumulating evidence supports the role of dietary polyphenols in the prevention of cardiovascular diseases, such as stroke. Stroke is the second cause of death worldwide and it is estimated that a substantial proportion of stroke incidence and recurrence may be prevented by healthier dietary patterns. Here, we have grouped the phenolic acids and flavonoids identified in S. ramosissima and reviewed their potential protective effect on brain ischemia, which are mostly related to the reduction of oxidative stress and inflammation, the inhibition of cell death pathways and their role in the preservation of the vascular function. Despite the fact that most of these compounds have been reported to be neuroprotective through multiple mechanisms, human studies are still scarce. Given the safe profile of polyphenols identified in S. ramosissima, this halophyte plant could be considered as a source of bioactive compounds for the nutraceutical industry.

Novel Nutraceutical Compounds in Alzheimer Prevention

Alzheimer's disease (AD) incidence is increasing worldwide at an alarming rate. Considering this increase, prevention efforts, stemming from scientific research, health education, and public policies, are critical. Clinical studies evidenced that healthy lifestyles along with natural multitarget and disease-modifying agents have a preventative impact on AD or mitigate symptoms in diagnosed patients. The pathological alterations of AD start 30 years before symptoms, and it is essential to develop the capacity to detect those changes. In this regard, molecular biomarkers that detect early pathological manifestations are helpful. Based on markers data, early preventive interventions could reduce more than 40% of AD cases. Protective actions include exercise, shown to induce neurogenesis, cognitive stimulation, intellectual-social activity, and nutrition among others. Mediterranean diet, preprobiotics, and nutraceuticals containing bioactive molecules with antioxidant and anti-inflammatory properties are relevant. Antiprotein aggregation molecules whose mechanisms were described are important. Anti-inflammatory agents with anti-aggregation properties that help to control cognitive impairment, include quercetin, biocurcumin, rosemarinic acid, and Andean shilajit. Anthocyanidins, e.g., delphinidin, malvidin, and natural flavonoids, are also included. Quercetin and hydroxy-tyrosol are antiaging molecules and could have anti-AD properties. We emphasize the relevance of nutraceuticals as a main actor in the prevention and/or control of dementia and particularly AD.

Pharmacological Potentiality of Bioactive Flavonoid against Ketamine Induced Cell Death of PC 12 Cell Lines: An In Vitro Study

During the past few years, there has been exponential growth in the field of ethnopharmacology in the treatment of different human ailments, including neurological disorders. In our previous study, we isolated, characterized, and reported a novel bioactive compound with therapeutic efficacy in vivo, which was used in the current study. This study was designed to investigate the pharmacological effect and therapeutic mechanism of the natural plant compound 3-(3,4-dimethoxy phenyl)-1-(4-methoxy phenyl)prop-2-en-1-one against ketamine-induced toxicity in PC 12 cell lines. Cell death was induced in PC 12 cell lines by incubating with ketamine, and the protection offered by the compound at different concentrations was studied during pretreatment. The therapeutic efficacy was screened through MTT assay, LDH assay, DCF-DA assay, clonogenic assay, RT-PCR, and densitometric analysis. The bioactive compound caused a significant elevation in cell viability up to approximately 80%, down-regulation of cell damage, reduction in free radical damage caused by intracellular reactive oxygen species, and up-regulation of cell survival ability, which was dysregulated during ketamine induction. In addition, RT-PCR analysis of DOPA-related genes suggests that the compound exerted significant inhibition in the expression of these genes, which were overexpressed during ketamine induction. The current findings provide new insight into the neuroprotective mediation of bioactive factors as a prospective therapy for neurological disorders.

Effects of Daily Matcha and Caffeine Intake on Mild Acute Psychological Stress-Related Cognitive Function in Middle-Aged and Older Adults: A Randomized Placebo-Controlled Study

Matcha, a type of green tea, has a higher amino acid content than other types of tea. We previously examined the ability of matcha to improve cognitive function in older adults and determined that continuous matcha intake improves attention and executive function. This study aimed to compare the effects of matcha and caffeine and clarify the differences between these effects. The study was registered at the University Hospital Medical Information Network (UMIN000036578). The effect of single and continuous intake was compared, and the usefulness of continuous intake was evaluated under the stress condition. The Uchida-Kraepelin test (UKT) was used to induce mild acute stress, and the Cognitrax was used to evaluate cognitive function. A single dose of caffeine improved attentional function during or after stress loading. The reduced reaction time in the Cognitrax, observed following a single dose of matcha, was likely due to caffeine. The matcha group showed an increase in the amount of work after continuous intake, whereas the caffeine group only showed an increase in the amount of work for the UKT after a single dose. Ingesting matcha with caffeine improves both attention and work performance when suffering from psychological stress compared with caffeine alone.

Matcha consumption maintains attentional function following a mild acute psychological stress without affecting a feeling of fatigue: A randomized placebo-controlled study in young adults

Tea is a beverage commonly consumed worldwide. Matcha is a type of green tea produced by drying and grinding tea leaves (Camellia sinensis L.) into a fine powder. Matcha contains catechin, theanine, and caffeine, which affect cognitive function. Epidemiological studies conducted in Japan have shown that green tea consumption improves cognitive impairment. Previously, we found that daily matcha intake improves attention and executive function in middle-aged and older people. However, its effect on cognitive function in younger adults remains unclear. Moreover, it is unclear which cognitive functions are impaired by stress. This study aimed to clarify whether the administration of matcha improves the attentional function of young adults after mild acute stress and which cognitive function is improved. We included 42 participants aged 25 to 34 years who consumed 2 g of matcha daily for 2 weeks. The Uchida-Kraepelin test was used to induce mild acute psychological stress. Memory, attention, facial expression recognition, working memory, visual information, and motor function were evaluated. Reaction times on the Stroop test for attentional function were significantly lower in the matcha group than in the placebo group. Correct hits in the emotion perception test increased significantly for participants in the matcha group compared to those in the placebo group. We found no significant between-group differences in the other tests. In conclusion, after 2 weeks of matcha intake, the attentional function was maintained after mild acute psychological stress. Thus, matcha might improve cognitive function during or after stress conditions in young adults.

Enantiomeric Isoflavones with neuroprotective activities from the Fruits of Maclura tricuspidata

Seven pairs of enantiomeric isoflavones (1a/1b–7a/7b) were obtained from the ethyl acetate extract of the fruits of Maclura tricuspidata (syn. Cudrania tricuspidata), and successfully separated by chiral high-pressure liquid chromatography (HPLC). The structures and absolute configurations of the enantiomeric isoflavones were established on the basic of comprehensive spectroscopic analyses and quantum chemical calculation methods. Compounds 1, 1a, and 1b exhibited neuroprotective activities against oxygen-glucose deprivation/reoxygenation (ODG/R)-induced SH-SY5Y cells death with EC₅₀ values of 5.5 µM, 4.0 µM, and 10.0 µM, respectively. Furthermore, 1, 1a, and 1b inhibited OGD/R-induced reactive oxygen species generation in SH-5Y5Y cells with IC₅₀ values of 6.9 µM, 4.5 µM, and 9.5 µM, respectively.

Green tea and cocoa enhance cognition in Lymnaea

A flavonoid, (-)-epicatechi (Epi), enhances long-term memory (LTM) formation in Lymnaea and reverses memory obstruction caused by stress. Many foods contain substantial amounts of Epi, (e.g. green tea and cocoa). In humans eating such foods may directly or indirectly enhance cognition. We directly test whether operant conditioning training Lymnaea in these natural foods result in the same effects as training snails in pure Epi. We found that exposure to products containing high concentrations of Epi (e.g. green tea and cocoa) during training enhanced memory formation and could even reverse a learning and memory deficit brought about by stress. Epi can be photo-inactivated by exposure to ultraviolet light. We found that following photo-inactivation of Epi, memory enhancement did not occur. Photo-inactivation of foods containing Epi (e,g. green tea) blocked their ability to enhance LTM. Our data are thus consistent with the hypothesis that dietary sources of Epi can have positive benefits on cognitive ability and be able to reverse memory aversive states.

Beneficial roles of honey polyphenols against some human degenerative diseases: A review

Honey contains many active constituents and antioxidants such as polyphenols. Polyphenols are phytochemicals, a generic term for the several thousand plant-based molecules with antioxidant properties. Many in vitro studies in human cell cultures as well as many animal studies confirm the protective effect of polyphenols on a number of diseases such as cardiovascular diseases (CVD), diabetes, cancer, neurodegenerative diseases, pulmonary diseases, liver diseases and so on. Nevertheless, it is challenging to identify the specific biological mechanism underlying individual polyphenols and to determine how polyphenols impact human health. To date, several studies have attempted to elucidate the molecular pathway for specific polyphenols acting against particular diseases. In this review, we report on the various polyphenols present in different types of honey according to their classification, source, and specific functions and discuss several of the honey polyphenols with the most therapeutic potential to exert an effect on the various pathologies of some major diseases including CVD, diabetes, cancer, and neurodegenerative diseases.

Role of Bioflavonoid Quercetin on Expression of Urea Cycle Enzymes, Astrocytic and Inflammatory Markers in Hyperammonemic Rats

This study evaluates the role of quercetin on the expression of urea cycle enzymes, astrocytic, neuronal and inflammatory markers in hyperammonemic rats. Hyperammonemia (provoked by intraperitonial injections of (ammonium chloride-100 mg/kg b.w for 56 days), showed diminished expression of urea cycle enzymes [carbamyl phosphate synthetase-1 (CPS-1), ornithine transcarbamylase (OTC), argininosuccinate synthetase (ASS) and arginase (ARG)] in liver and decreased expression of neuronal and astrocytic markers-glutamine synthase (GS) and phosphate activated glutaminase (PAG) in brain and increased expression of brain inflammatory markers such as interleukin 6 (IL6), inducible nitric oxide synthase (iNOS) and nuclear transcription factor kappa B (NF-κB) (by western blot analysis) and exhibited downregulated expression of soluble guanylate cyclase (sGC), glial fibrillary acidic protein (GFAP) in brain and ASS in liver investigated (by RT-PCR). Oral treatment of quercetin (50 mg/kg b.w) to hyperammonemic rats (1) increased the expression of urea cycle enzymes (CPS-1, OTC, ASS and ARG), neuronal and astrocytic markers (GS and PAG) (2) decreased the expression of IL6, iNOS and NF-κB and (3) upregulated mRNA expression of SGC, GFAP and ASS. Our results specify that quercetin's antihyperammonemic effects could be through its, anti-inflammatory, neuroprotective and hepatoprotective effects.

Rosmarinic acid prevents against memory deficits in ischemic mice

Polyphenols have neuroprotective effects after brain ischemia. It has been demonstrated that rosmarinic acid (RA), a natural phenolic compound, possesses antioxidant and anti-inflammatory properties. To evaluate the effectiveness of RA against memory deficits induced by permanent middle cerebral artery occlusion (pMCAO) mice were treated with RA (0.1, 1, and 20mg/kg/day, i.p. before ischemia and during 5 days). Animals were evaluated for locomotor activity and working memory 72 h after pMCAO, and spatial and recognition memories 96 h after pMCAO. In addition, in another set of experiments brain infarction, neurological deficit score and myeloperoxidase (MPO) activity were evaluates 24h after the pMCAO. Finally, immunohistochemistry, and western blot, and ELISA assay were used to analyze glial fibrillary acidic protein (GFAP), and synaptophysin (SYP) expression, and BDNF level, respectively. The working, spatial, and recognition memory deficits were significantly improved with RA treatment (20mg/kg). RA reduced infarct size and neurological deficits caused by acute ischemia. The mechanism for RA neuroprotection involved, neuronal loss suppression, and increase of synaptophysin expression, and increase of BDNF. Furthermore, the increase of MPO activity and GFAP immunireactivity were prevented in MCAO group treated with RA. These results suggest that RA exerts memory protective effects probably due to synaptogenic activity and anti-inflammatory action.

(+)-Catechin Attenuates NF-κB Activation Through Regulation of Akt, MAPK, and AMPK Signaling Pathways in LPS-Induced BV-2 Microglial Cells

(+)-catechin is a flavanol that possesses various health and medicinal values, which include neuroprotection, anti-oxidation, antitumor and antihepatitis activities. This study investigated the modulatory effects of (+)-catechin on the lipopolysaccharides (LPS)-stimulated BV-2 cells. (+)-catechin attenuated LPS-induced inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and inhibited microglial NO and ROS production. Additionally, (+)-catechin suppressed the production of tumor necrosis factor-α (TNF-α) and interleukin (IL)-6, while augmenting IL-4. (+)-catechin attenuated LPS-induced nuclear factor-κB (NF-κB) p65 nuclear translocation via the inhibition of IκB-α phosphorylation. Moreover, (+)-catechin blocked the activation of Akt and its inhibition was shown to play a crucial role in LPS-induced inflammation in BV-2 microglial cells. (+)-catechin also attenuated the LPS-induced phosphorylation of extracellular signal-regulated kinase (ERK1/2), and p-38 mitogen activated protein kinases (p38 MAPK) and specific inhibitors of ERK1/2 (UO126) and p38 MAPK (SB202190) subsequently down-regulated the expression of the proinflammatory mediators iNOS and COX-2. Further mechanistic study revealed that (+)-catechin acted through the amelioration of the LPS-induced suppression of adenosine monophosphate-activated protein kinase (AMPK) activity. Taken together, our data indicate that (+)-catechin exhibits anti-inflammatory effects in BV-2 cells by suppressing the production of proinflammatory mediators and mitigation of NF-κB through Akt, ERK, p38 MAPK, and AMPK pathways.

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.

Flavonoid regulation of EAG1 channels

The voltage-gated, K⁺-selective ether á go-go 1 (EAG1) channel is expressed throughout the brain where it is thought to regulate neuronal excitability. Besides its normal physiological role in the brain, EAG1 is abnormally expressed in several cancer cell types and promotes tumor progression. Like all other channels in the KCNH family, EAG1 channels have a large intracellular carboxy-terminal region that shares structural similarity with cyclic nucleotide–binding homology domains (CNBHDs). EAG1 channels, however, are not regulated by the direct binding of cyclic nucleotides and have no known endogenous ligands. In a screen of biological metabolites, we have now identified four flavonoids as potentiators of EAG1 channels: fisetin, quercetin, luteolin, and kaempferol. These four flavonoids shifted the voltage dependence of activation toward more hyperpolarizing potentials and slowed channel deactivation. All four flavonoids regulated channel gating with half-maximal concentrations of 2–8 µM. The potentiation of gating did not require the amino-terminal or post-CNBHD regions of EAG1 channels. However, in fluorescence resonance energy transfer and anisotropy-based binding assays, flavonoids bound to the purified CNBHD of EAG1 channels. The CNBHD of KCNH channels contains an intrinsic ligand, a conserved stretch of residues that occupy the cyclic nucleotide–binding pocket. Mutations of the intrinsic ligand in EAG1 (Y699A) potentiated gating similar to flavonoids, and flavonoids did not further potentiate EAG1-Y699A channels. Furthermore, the Y699A mutant CNBHD bound to flavonoids with higher affinity than wild-type CNBHD. These results suggest that the flavonoids identified here potentiated EAG1 channels by binding to the CNBHD, possibly by displacing their intrinsic ligand. EAG1 channels should be considered as a possible target for the physiological effects of flavonoids.

Flavonoid regulation of HCN2 channels

The hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are pacemaker channels whose currents contribute to rhythmic activity in the heart and brain. HCN channels open in response to hyperpolarizing voltages, and the binding of cAMP to their cyclic nucleotide-binding domain (CNBD) facilitates channel opening. Here, we report that, like cAMP, the flavonoid fisetin potentiates HCN2 channel gating. Fisetin sped HCN2 activation and shifted the conductance-voltage relationship to more depolarizing potentials with a half-maximal effective concentration (EC50) of 1.8 μM. When applied together, fisetin and cAMP regulated HCN2 gating in a nonadditive fashion. Fisetin did not potentiate HCN2 channels lacking their CNBD, and two independent fluorescence-based binding assays reported that fisetin bound to the purified CNBD. These data suggest that the CNBD mediates the fisetin potentiation of HCN2 channels. Moreover, binding assays suggest that fisetin and cAMP partially compete for binding to the CNBD. NMR experiments demonstrated that fisetin binds within the cAMP-binding pocket, interacting with some of the same residues as cAMP. Together, these data indicate that fisetin is a partial agonist for HCN2 channels.

Anti-inflammatory effects of total isoflavones from Pueraria lobata on cerebral ischemia in rats

Puerariae radix, the dried root of Pueraria lobata Ohwi, is one of earliest and most important edible crude herbs used for various medical purposes in Oriental medicine. The aim of the present study was to determine the anti-inflammatory effects of Total Isoflavones from P. lobata (TIPL), which contains the unique isoflavone puerarin, in ischemia in vivo models. Oral administration of TIPL (100 mg/kg) reduced the brain infarct volume and attenuated ischemia-induced cyclooxygenase-2 (COX-2) up-regulation at 2 days after middle cerebral artery occlusion (MCAo) in rats. Moreover, TIPL reduced activation of glial fibrillary acid protein (GFAP) and CD11b antibody (OX-42) at 7 days after MCAo in hippocampal CA1 region. These results show that TIPL can protect the brain from ischemic damage after MCAo. Regarding the immunohistochemical study, the effects of TIPL may be attributable to its anti-inflammatory properties by the inhibition of COX-2 expression, astrocyte expression, and microglia.

Epigallocatechin gallate attenuates L-DOPA-induced apoptosis in rat PC12 cells

In this study, the protective effects of EGCG on L-3,4-dihydroxyphenylalanine (L-DOPA)-induced oxidative cell death in catecholaminergic PC12 cells, the in vitro model of Parkinson's disease, were investigated. Treatment with L-DOPA at concentrations higher than 150 µM caused cytotoxicity in PC12 cells, as determined using the 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry detection. The apoptotic ratio was similar in cells treated with 100 µM EGCG plus 150 µM L-DOPA (5.02%) and the control (0.96%) (P > 0.05), and was lower than that of cells treated with L-DOPA only (32.24%, P < 0.05). The generation level of ROS (% of control) in cells treated with EGCG plus L-DOPA was lower than that in cells treated with L-DOPA only (123.90% vs 272.32%, P < 0.05). The optical density in production of TBARS in cells treated with L-DOPA only was higher than that in the control (0.27 ± 0.05 vs 0.08 ± 0.04, P < 0.05), and in cells treated with EGCG only (0.14 ± 0.02, P < 0.05), and EGCG plus L-DOPA (0.13 ± 0.02, P < 0.05). The intracellular level of GSH in cells treated with EGCG plus L-DOPA was higher than that in cells treated with L-DOPA only (233.25 ± 16.44 vs 119.23 ± 10.25, P < 0.05). These results suggest that EGCG protects against L-DOPA-induced oxidative apoptosis in PC12 cells, and might be a potent neuroprotective agent.

A flavonol present in cocoa [(-)epicatechin] enhances snail memory

Dietary consumption of flavonoids (plant phytochemicals) may improve memory and neuro-cognitive performance, though the mechanism is poorly understood. Previous work has assessed cognitive effects in vertebrates; here we assess the suitability of Lymnaea stagnalis as an invertebrate model to elucidate the effects of flavonoids on cognition. (-)Epicatechin (epi) is a flavonoid present in cocoa, green tea and red wine. We studied its effects on basic snail behaviours (aerial respiration and locomotion), long-term memory (LTM) formation and memory extinction of operantly conditioned aerial respiratory behaviour. We found no significant effect of epi exposure (15 mg l(-1)) on either locomotion or aerial respiration. However, when snails were operantly conditioned in epi for a single 0.5 h training session, which typically results in memory lasting ~3 h, they formed LTM lasting at least 24 h. Snails exposed to epi also showed significantly increased resistance to extinction, consistent with the hypothesis that epi induces a more persistent LTM. Thus training in epi facilitates LTM formation and results in a more persistent and stronger memory. Previous work has indicated that memory-enhancing stressors (predator kairomones and KCl) act via sensory input from the osphradium and are dependent on a serotonergic (5-HT) signalling pathway. Here we found that the effects of epi on LTM were independent of osphradial input and 5-HT, demonstrating that an alternative mechanism of memory enhancement exists in L. stagnalis. Our data are consistent with the notion that dietary sources of epi can improve cognitive abilities, and that L. stagnalis is a suitable model with which to elucidate neuronal mechanisms.

Antioxidant therapy: still in search of the 'magic bullet'

The therapeutic potential of natural phenolic antioxidants in human diseases associated with oxidative damage has received great attention to date. Appraisal of literature evidences that, in general, antioxidant therapy has enjoyed relative successes in preclinical studies but little benefits in human intervention studies or clinical trials. In fact, despite the huge, largely untapped potential therapeutic benefit of natural phenolic antioxidants, such as vitamins, non-flavonoid and flavonoid compounds, they appear not to be suitable drug candidates. The problem may be related, among others, to their non-drug-likeness properties. Though controversial the results obtained so far confirm the importance of exploring phenolic natural systems as safe templates for the design of new antioxidants. To support the assumption an outlook of the lead structural optimization process to improve ADME properties was given by means of natural hydroxycinnamic acids as a case study. The optimization of drug physicochemical properties and the development of appropriate delivery antioxidant systems can provide in the next future a way out to attain effective therapeutic antioxidant agents.

Neuroprotective and anti-inflammatory effects of the flavonoid-enriched fraction AF4 in a mouse model of hypoxic-ischemic brain injury

We report here neuroprotective and anti-inflammatory effects of a flavonoid-enriched fraction isolated from the peel of Northern Spy apples (AF4) in a mouse of model of hypoxic-ischemic (HI) brain damage. Oral administration of AF4 (50 mg/kg, once daily for 3 days) prior to 50 min of HI completely prevented motor performance deficits assessed 14 days later that were associated with marked reductions in neuronal cell loss in the dorsal hippocampus and striatum. Pre-treatment with AF4 (5, 10, 25 or 50 mg/kg, p.o.; once daily for 3 days) produced a dose-dependent reduction in HI-induced hippocampal and striatal neuron cell loss, with 25 mg/kg being the lowest dose that achieved maximal neuroprotection. Comparison of the effects of 1, 3 or 7 doses of AF4 (25 mg/kg; p.o.) prior to HI revealed that at least 3 doses of AF4 were required before HI to reduce neuronal cell loss in both the dorsal hippocampus and striatum. Quantitative RT-PCR measurements revealed that the neuroprotective effects of AF4 (25 mg/kg; p.o.; once daily for 3 days) in the dorsal hippocampus were associated with a suppression of HI-induced increases in the expression of IL-1β, TNF-α and IL-6. AF4 pre-treatment enhanced mRNA levels for pro-survival proteins such as X-linked inhibitor of apoptosis and erythropoietin following HI in the dorsal hippocampus and striatum, respectively. Primary cultures of mouse cortical neurons incubated with AF4 (1 µg/ml), but not the same concentrations of either quercetin or quercetin-3-O-glucose or its metabolites, were resistant to cell death induced by oxygen glucose deprivation. These findings suggest that the inhibition of HI-induced brain injury produced by AF4 likely involves a transcriptional mechanism resulting from the co-operative actions of various phenolics in this fraction which not only reduce the expression of pro-inflammatory mediators but also enhance pro-survival gene signalling.

Methylparaben protects 6-hydroxydopamine-induced neurotoxicity in SH-SY5Y cells and improved behavioral impairments in mouse model of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder of unknown etiology. Considerable evidence suggests that free radical formation and oxidative stress might play an important role in the pathogenesis of PD. In the present investigation we evaluated the therapeutic potential of methylparaben (MP) a well known pharmaceutical preservative against 6-hydroxydopamine (6-OHDA) neurotoxicity in SH-SY5Y cells and in a mouse model of PD. At nanomolar concentrations MP (0.01, 0.1 and 1 nM) significantly attenuated the 6-OHDA- and hydrogen peroxide-induced cytotoxicity in SH-SY5Y cells. The reactive oxygen species generated by 6-OHDA in SH-SY5Y cells was also inhibited by MP in a concentration dependent fashion. Further, intranigral damage induced by stereotaxically injecting 6-OHDA in mouse brain was significantly attenuated by MP treatment. MP (1, 10 or 50 μg/kg, i.p.) prevented apomorphine-induced rotational behavior and significantly improved motor deficits in 6-OHDA-lesioned mice. The cognitive impairments as evaluated by passive avoidance and Y-maze task in mice were also attenuated by MP concentration dependently. Immunohistochemical analysis of substantia nigra in MP treated mice showed significantly higher number of surviving tyrosine hydroxylase positive cells. Furthermore, MP also suppressed the lipid peroxidation products in 6-OHDA-lesioned mouse brain tissues. Considering the results obtained, the marked neuroprotection exhibited by MP might be attributed to its potent antioxidant property. In conclusion, this study reports the neuroprotective properties of MP in experimental models of PD for the first time and can be developed as a potential therapeutic agent.

Bioassay-guided isolation of neuroprotective compounds from Loranthus parasiticus against H₂O₂-induced oxidative damage in NG108-15 cells

ETHNOPHARMACOLOGICAL RELEVANCE

A parasite plant, Loranthus parasiticus (Loranthaceae), which is generally known as benalu teh (in Malay), Sang Ji Sheng (in Chinese), and baso-kisei (in Japan) distributed in south and southwest part of China, has been used as a folk medicine for the treatment of schizophrenia in southwest China. Loranthus parasiticus has various uses in folk and traditional medicines for bone, brain, kidney, liver, expels wind-damp, and prevents miscarriage.

AIM OF THE STUDY

The current study was designed to evaluate the neuroprotective activity of Loranthus parasiticus against hydrogen peroxide (H(2)O(2))-induced oxidative damage in NG108-15 hybridoma cells, so as to present evidence for the traditional use of this parasite plant in the treatment of oxidative stress related neurodegenerative diseases.

MATERIALS AND METHODS

Dried and ground leaves of Loranthus parasiticus were extracted and fractionated into Loranthus parasiticus ethanol extract (LPEE), Loranthus parasiticus ethyl acetate fraction (LPEAF), and Loranthus parasiticus aqueous fraction (LPAF), which were subjected to neuroprotective activity assessment by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay. Bioassay-guided fractionation and isolation was performed subsequently to identify the most neuroactive compound. Mechanism studies underlying the present neuroprotection model of the isolated neuroactive compound was evaluated by employing 2,7-dichlorofluorescein diacetate (DCFH-DA) for intracellular reactive oxygen species (ROS) measurement, annexin V/propidium iodide (PI) for translocation of membrane phosphatidyleserine to identify cells undergo apoptosis, 5,5',6,6'-tetrachloro-1,1',3,3' tetraethylbenzimidazolylcarbocyanine iodide (JC-1) for mitochondrial membrane potential (MMP) detection, and PI for cell cycle events analysis.

RESULTS

Among those tested extract and fractions (LPEE, LPEAF, and LPAF) in our previous screening, LPAF significantly (P<0.01) yielded the highest neuroprotective activity with 78.00±1.85% cell viability in a dose dependent manner, supporting a neuroprotective role for LPAF in vitro. AC trimer and (+)-catechin have been isolated from LPAF successfully through bioassay-guided fractionation and isolation approach and (+)-catechin exhibited stronger neuroprotective activity as compared with AC trimer. (+)-Catechin increased cell viability and decreased the level of intracellular reactive oxygen species (ROS) in a dose-dependent manner against H(2)O(2)-induced oxidative stress in NG108-15 cells. Moreover, (+)-catechin reduced total annexin V positive cells (early and late apoptotic cells), attenuated the collapsed of MMP, and inhibited cell cycle arrested at sub-G(1) population following H(2)O(2) insult.

CONCLUSION

Collectively, the use of Loranthus parasiticus as folk medicine in the treatment of mental disorder was attributed to the presence of proanthocyanidins in this parasite plant. These findings support the traditional use of Loranthus parasiticus which is capable in managing neurological disorder where oxidative stress is implicated.

Effect of polyphenols on oxidative stress and mitochondrial dysfunction in neuronal death and brain edema in cerebral ischemia

Polyphenols are natural substances with variable phenolic structures and are elevated in vegetables, fruits, grains, bark, roots, tea, and wine. There are over 8000 polyphenolic structures identified in plants, but edible plants contain only several hundred polyphenolic structures. In addition to their well-known antioxidant effects, select polyphenols also have insulin-potentiating, anti-inflammatory, anti-carcinogenic, anti-viral, anti-ulcer, and anti-apoptotic properties. One important consequence of ischemia is neuronal death and oxidative stress plays a key role in neuronal viability. In addition, neuronal death may be initiated by the activation of mitochondria-associated cell death pathways. Another consequence of ischemia that is possibly mediated by oxidative stress and mitochondrial dysfunction is glial swelling, a component of cytotoxic brain edema. The purpose of this article is to review the current literature on the contribution of oxidative stress and mitochondrial dysfunction to neuronal death, cell swelling, and brain edema in ischemia. A review of currently known mechanisms underlying neuronal death and edema/cell swelling will be undertaken and the potential of dietary polyphenols to reduce such neural damage will be critically reviewed.

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.

Regulation of cell survival and death signals induced by oxidative stress

Oxidative stress stimulates two opposite signaling pathways leading to cell death and cell survival. Preferential selection of survival signals leads to the protection of cells against damage induced by reactive oxygen species, whereas preferential acceleration of death signals can be used to advantage in tumor therapy with oxidizing agents such as ionizing radiation and anticancer drugs. In vitro and in vivo experiments using cultured mammalian cells and experimental animals showed that ERK was included in survival signals and SAPK and p38 MAPK in death signals in oxidative stress. The activation of SAPK/JNK and subsequent expression of death receptor Fas on the cell surface caused the induction of cell death. The results mean that the acceleration of the activation of SAPK/JNK might lead to the enhancement of cell death by oxidizing agents like ionizing radiation and anticancer drugs. In fact, when cultured mammalian cells were exposed to ionizing radiation with 2-nitroimidazole derivatives having electrophilicity, the lethal effect of ionizing radiation was found to be enhanced together with the activation of SAPK/JNK and the enhancement of Fas expression. The activation of both survival and death signals was suppressed by the antioxidants N-acetylcystein and Trolox, suggesting that both signaling pathways are redox-regulated.

Similar potency of catechin and its enantiomers in alleviating 1-methyl-4-phenylpyridinium ion cytotoxicity in SH-SY5Y cells

OBJECTIVES

Previously, the flavonoid (±)-catechin was shown to exert potent neuroprotective action in the mouse 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's disease model. The purpose of this study was to investigate whether the different enantiomers of catechin ((+)-catechin, (-)-catechin and (±)-catechin, a 50:50 mixture of (+)-catechin and (-)-catechin) could protect SH-SY5Y cells against 1-methyl-4-phenylpyridinium ion (MPP(+) ) toxicity by decreasing the generation of oxygen free radicals. The inhibitive effect of (±)-catechin on JNK/c-Jun activation was investigated.

METHODS

The effects of (+)-catechin, (-)-catechin or (±)-catechin in protecting against MPP(+) toxicity were evaluated and compared in SH-SY5Y cells by testing the release of lactate dehydrogenase. The generation of reactive oxygen species (ROS) was measured by immunochemistry and the phosphorylation level of JNK/c-Jun was determined by Western blotting.

KEY FINDINGS

In SH-SY5Y cells, (+)-catechin, (-)-catechin or (±)-catechin reduced apoptosis induced by MPP(+) and decreased ROS generation caused by MPP(+) . Different enantiomers of catechin showed protective effects at similar potency. Moreover (±)-catechin decreased JNK/c-Jun phosphorylation which was increased by MPP(+).

CONCLUSIONS

  Catechin and its two enantiomers could protect SH-SY5Y cells against MPP(+) cytotoxicity at a similar potency. Antioxidative stress and inhibition of the JNK/c-Jun signalling pathway might have been involved in the neuroprotective mechanisms of catechin against MPP(+) cytotoxicity in SH-SY5Y cells.

Mechanisms underlying the protective effects of myricetin and quercetin following oxygen-glucose deprivation-induced cell swelling and the reduction in glutamate uptake in glial cells

The protective effects of the flavonoid polyphenols, myricetin and quercetin, were investigated on key features of ischemic injury in cultures including cell swelling and the reduction in glutamate uptake. C6 glial cells were exposed to oxygen-glucose deprivation (OGD) for 5 h and cell swelling was determined 90 min after the end of OGD. OGD-induced swelling was significantly blocked by both quercetin and myricetin although higher concentrations were required for quercetin. OGD-induced free radical production, a contributing factor in cell swelling, was significantly reduced by both myricetin and quercetin. However, depolarization of the inner mitochondrial membrane potential (ΔΨ(m)), the blockade of which generally reduces swelling, was significantly diminished by myricetin, but not quercetin. This indicated that quercetin could reduce swelling despite its inability to prevent depolarization of ΔΨ(m) possibly through other signaling pathways. Increased intracellular calcium ([Ca²+](i)) is an important characteristic of ischemic injury and is implicated in swelling. Both myricetin and quercetin attenuated the increase in [Ca²+](i). Further, a reduction in [Ca²+](i), through the use of nifedipine, nimodipine, verapamil, dantrolene, or BAPTA-AM, significantly reduced OGD-induced cell swelling indicating that one possible mechanism by which such flavonoids attenuate cell swelling may be through regulating [Ca²+](i). OGD-induced decrease in glutamate uptake was attenuated by myricetin, but not quercetin. Cyclosporin A, a blocker of the mitochondrial permeability transition (mPT) pore, but not FK506 (that does not block the mPT), attenuated the decline in glutamate uptake after OGD, indicating the involvement of the mPT in glutamate uptake. Our results indicated that while blockade of ΔΨ(m) may be sufficient to reduce swelling, it may not be a necessary factor, and that flavonoids reduce cell swelling by regulating [Ca²+](i). The differential effects of myricetin and quercetin on OGD-induced reduction on glutamate uptake may be due to their differential effects on mitochondria.

Neuroprotective properties of resveratrol and derivatives

Stilbenoid compounds consist of a family of resveratrol derivatives. They have demonstrated promising activities in vitro and in vivo that indicate they may be useful in the prevention of a wide range of pathologies, such as cardiovascular diseases and cancers, as well have anti-aging effects. More recently stilbenoid compounds have shown promise in the treatment and prevention of neurodegenerative disorders, such as Huntington's, Parkinson's, and Alzheimer's diseases. This paper primarily focuses on the impact of stilbenoids in Alzheimer's disease and more specifically on the inhibition of β-amyloid peptide aggregation.

Polyphenols and human health: prevention of disease and mechanisms of action

Polyphenols are found ubiquitously in plants and their regular consumption has been associated with a reduced risk of a number of chronic diseases, including cancer, cardiovascular disease (CVD) and neurodegenerative disorders. Rather than exerting direct antioxidant effects, the mechanisms by which polyphenols express these beneficial properties appear to involve their interaction with cellular signaling pathways and related machinery that mediate cell function under both normal and pathological conditions. We illustrate that their interactions with two such pathways, the MAP kinase (ERK, JNK, p38) and PI3 kinase/Akt signaling cascades, allow them to impact upon normal and abnormal cell function, thus influencing the cellular processes involved in the initiation and progression of cancer, CVD and neurodegeneration. For example, their ability to activate ERK in neurons leads to a promotion of neuronal survival and cognitive enhancements, both of which influence the progression of Alzheimer’s disease, whilst ERK activation by polyphenols in vascular endothelial cells influences nitric oxide production, blood pressure and ultimately CVD risk. The main focus of this review is to provide an overview of the role that polyphenols play in the prevention of cancer, cardiovascular disease and neurodegeneration. We present epidemiological data, human intervention study findings, as well as animal and in vitro studies in support of these actions and in each case we consider how their actions at the cellular level may underpin their physiological effects.

Effect of salvianolic acid B and paeonol on blood lipid metabolism and hemorrheology in myocardial ischemia rabbits induced by pituitruin

The purpose of this study was to determine the therapeutic effect of salvianolic acid b and paeonol on coronary disease. The ischemia myocardial animal model is induced by administering pituitrin (20 μg·kg⁻¹) intravenously via the abdominal vein. A combination of salvianolic acid b and paeonol (CSAP) (5, 10 and 15 mg/kg BW) was administrated to experimental rabbits. Biochemical indices were evaluated during six weeks of intervention. We found that the compound of salvianolic acid b and paeonol (5, 10 and 15 mg/kg BW) can markedly and dose-dependently reduce fibrinogen and malonaldehyde levels, increase the HDL level, improve blood viscosity and plasma viscosity in rabbits. In addition, the medicine can still reduce the ratio of NO/ET and the contents of lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) in a dose-dependent manner. This study demonstrates that compound of salvianolic acid b and paeonol (5, 10 and 15 mg/kg BW) can improve the blood hemorrheology, decrease oxidative injury and repair the function of blood vessel endothelium, and subsequently prevent the development of Coronary disease.

(-)-Epigallocatechin-3-gallate increases cell proliferation and neuroblasts in the subgranular zone of the dentate gyrus in adult mice

Neurogenesis is regulated by several factors such as age, stress and pharmacological agents. We observed the effects of (-)-epigallocatechin-3-gallate (EGCG), a major catechin of green tea, on neurogenesis in mice. The animals were orally administered EGCG for 4 weeks. Brain sections were stained using a marker for cell proliferation (Ki67 and BrdU) and neuroblasts (doublecortin, DCX). In all groups, Ki67, BrdU and DCX immunoreaction were observed in the subgranular zone of the dentate gyrus. Oral administration of EGCG significantly increased the number of Ki67-, BrdU- and DCX-immunoreactive cells as well as BrdU/DCX-colabled cells in the subgranular zone when compared to those in the vehicle-treated group. These results indicate that oral administration of EGCG can enhance cell proliferation and increase the number of neuroblasts in mice hippocampal dentate gyrus.

Dietary soy may not confound acute experimental stroke infarct volume outcomes in ovariectomized female rats

Oestrogen administration can alter experimental stroke outcomes. Soy as a source of phytoestrogens may therefore modulate responses in 'oestrogen-sensitive' stroke models, thus potentially confounding results. We evaluated the effects of dietary soy on acute infarct volumes in a pilot study using a rat focal stroke model. We hypothesized that ovariectomized (OVX) rats fed a soy-rich diet would have smaller acute infarct volumes than rats fed a soy-free diet. OVX rats were randomly assigned to a soy-free (n = 6) or a soy-rich (n = 6) diet for four weeks and weighed weekly. Following the dietary trial, rats underwent 2 h of middle cerebral artery occlusion (MCAO). Mean arterial blood pressure, rectal and temporalis muscle temperatures, arterial blood gases and blood glucose were recorded peri-ischaemia. Rats were euthanized 22 h following 2 h of MCAO. Brains were stained with 2,3,5-triphenyl tetrazolium chloride for acute infarct volume analysis. Uterine weight and histology were also evaluated as additional internal oestrogen-sensitive controls. Rats on the soy-free diet had greater gains in body weight (259 +/- 6% baseline body weight) than rats on the soy-rich diet (238 +/- 4% baseline body weight). No differences were seen in uterine weight and histology, peri-ischaemic physiological parameters and infarct volumes between the treatment groups. The results of this pilot study suggest that the dietary soy level tested may not alter acute infarct volumes in ischaemic female rat brain. More studies addressing the potential confounding effects of dietary soy in 'oestrogen-sensitive' stroke models are needed if investigators are to make informed choices regarding diets used in experimental stroke research.

Catechin induced longevity in C. elegans: from key regulator genes to disposable soma

The flavanol catechin is a ubiquitous metabolite within the plant kingdom. Several health benefits have previously been reported, however, to date, most attention has been devoted to gallated forms of catechin. This study utilized the nematode Caenorhabditis elegans to assess potential life expanding effects of non-gallated catechin. Longevity was observed at three different catechin concentrations, an effect that was neither linked to a specific temperature nor to the viability of the feeding bacteria. Taken all tests into account, hormesis, calorie restriction, as well as the presence of simple antioxidative or antibacterial effects could be excluded. Likewise, the insulin/IGF-1 like signaling pathway and the calmodulin kinase II pathway were not considered to play a major mechanic role. Moreover, stress resistance was enhanced without a marked alteration in reproductive behavior. In addition, lifespan tests with various stress and lifespan relevant mutant strains revealed that the life span extending phenotype was absent in mev-1, daf-2, akt-2 and nhr-8. Finally, catechin elicited a significant reduction in body length, a finding that is in line with the "Disposable Soma Theory". It is proposed that catechin modulates an energy-intensive stress response and repair system that results in reduced body length and an enhanced lifespan.

Green tea polyphenols attenuate glial swelling and mitochondrial dysfunction following oxygen-glucose deprivation in cultures

Astrocyte swelling is a major component of cytotoxic brain edema in ischemia. Oxidative stress and mitochondrial dysfunction have been hypothesized to contribute to such swelling in cultures. We investigated the protective effects of polyphenol-rich green tea extract (GTE) on key features of ischemic injury namely cell swelling, nitric oxide (NO) production, and depolarization of the inner mitochondrial membrane potential (Deltapsi(m)). C6 glial cultures were subjected to 5-h oxygen-glucose deprivation (OGD) and cell volume was determined using the 3-O-methyl-glucose method. At 90 min after the end of OGD, cell volume increased by > 33% and this increase was attenuated by GTE but not by the individual polyphenol components including catechin, epicatechin, or epigallocatechin gallate (EGCG). However, a combination of catechin, epicatechin and EGCG prevented swelling. OGD-induced increase in NO was further increased by GTE. OGD-induced decline in Deltapsi(m) was also attenuated by green tea extract, EGCG and a combination of catechin, epicatechin and EGCG but not by catechin or epicatechin alone. Our findings indicate a protective effect of GTE in cell swelling in ischemic injury and such protective effects may be mediated by its effect on the mitochondria. It appears that effects on cell swelling are mediated by the concerted action of more than one of the individual components of GTE.

Amyloid beta-protein assembly as a therapeutic target of Alzheimer's disease

Alzheimer's disease (AD), the most common neurodegenerative disorder in the aged, is characterized by the cerebral deposition of fibrils formed by the amyloid beta-protein (Abeta), a 40-42 amino acid peptide. The folding of Abeta into neurotoxic oligomeric, protofibrillar, and fibrillar assemblies is hypothesized to be the key pathologic event in AD. Abeta is formed through cleavage of the Abeta precursor protein by two endoproteinases, beta-secretase and gamma-secretase, that cleave the Abeta N-terminus and C-terminus, respectively. These facts support the relevance of therapeutic strategies targeting Abeta production, assembly, clearance, and neurotoxicity. Currently, no disease-modifying therapeutic agents are available for AD patients. Instead, existing therapeutics provide only modest symptomatic benefits for a limited time. We summarize here recent efforts to produce therapeutic drugs targeting Abeta assembly. A number of approaches are being used in these efforts, including immunological, nutraceutical, and more classical medicinal chemical (peptidic inhibitors, carbohydrate-containing compounds, polyamines, "drug-like" compounds, chaperones, metal chelators, and osmolytes), and many of these have progressed to phase III clinical trails. We also discuss briefly a number of less mature, but intriguing, strategies that have therapeutic potential. Although initial trials of some disease-modifying agents have failed, we argue that substantial cause for optimism exists.

Natural antioxidants protect neurons in Alzheimer's disease and Parkinson's disease

"Modern" medicine and pharmacology require an effective medical drug with a single compound for a specific disease. This seams very scientific but usually has unavoidable side effects. For example, the chemical therapy to cancer can totally damage the immunological ability of the patient leading to death early than non-treatment. On the other hand, natural antioxidant drugs not only can cure the disease but also can enhance the immunological ability of the patient leading to healthier though they usually have several compounds or a mixture. For the degenerative disease such as Alzheimer's disease (AD) and Parkinson's disease (PD), natural antioxidant drugs are suitable drugs, because the pathogenesis of these diseases is complex with many targets and pathways. These effects are more evidence when the clinic trial is for long term treatment. The author reviews the studies on the protecting effects of natural antioxidants on neurons in neurodegenerative diseases, especially summarized the results about protective effect of green tea polyphenols on neurons against apoptosis of cellular and animal PD models, and of genestine and nicotine on neurons against A beta-induced apoptosis of hippocampal neuronal and transgenic mouse AD models.