Long-term ginsenoside consumption prevents memory loss in aged SAMP8 mice by decreasing oxidative stress and up-regulating the plasticity-related proteins in hippocampus

A comprehensive review of the therapeutic and pharmacological effects of ginseng and ginsenosides in central nervous system

Ginseng is one of the most widely used herbal medicines in human. Central nervous system (CNS) diseases are most widely investigated diseases among all others in respect to the ginseng’s therapeutic effects. These include Alzheimer’s disease, Parkinson’s disease, cerebral ischemia, depression, and many other neurological disorders including neurodevelopmental disorders. Not only the various types of diseases but also the diverse array of target pathways or molecules ginseng exerts its effect on. These range, for example, from neuroprotection to the regulation of synaptic plasticity and from regulation of neuroinflammatory processes to the regulation of neurotransmitter release, too many to mention. In general, ginseng and even a single compound of ginsenoside produce its effects on multiple sites of action, which make it an ideal candidate to develop multi-target drugs. This is most important in CNS diseases where multiple of etiological and pathological targets working together to regulate the final pathophysiology of diseases. In this review, we tried to provide comprehensive information on the pharmacological and therapeutic effects of ginseng and ginsenosides on neurodegenerative and other neurological diseases. Side by side comparison of the therapeutic effects in various neurological disorders may widen our understanding of the therapeutic potential of ginseng in CNS diseases and the possibility to develop not only symptomatic drugs but also disease modifying reagents based on ginseng.

Postsynaptic density protein (PSD)-95 expression is markedly decreased in the hippocampal CA1 region after experimental ischemia-reperfusion injury

Synaptic plasticity is important for functional recovery after cerebral ischemic injury. In the present study, we investigated chronological change in the immunoreactivity of PSD-95, a kind of postsynaptic density protein, in the hippocampus proper (CA1-3 regions) after 5 min of transient cerebral ischemia in gerbils. PSD-95 immunoreactivity was observed in MAP-2-immunoreactive dendrites in the CA1-3 regions of the sham group. The PSD-95 immunoreactivity was shown as beaded structure in the MAP-2-immunoreactive dendrites. However, PSD-95 immunoreactivity began to be dramatically decreased in MAP-2-immunoreactive dendrites in the CA1 region, not CA2-3 region, at early time after ischemia-reperfusion. At 5 days after ischemia-reperfusion, MAP-2 immunoreactivity almost disappeared in the ischemic CA1 region, and PSD-95 immunoreactivity was much lower than that in the sham group. In brief, PSD-95 immunoreactivity in the CA1 dendrites was markedly decreased at early time after ischemia-reperfusion. We suggest that decreased PSD-95 immunoreactivity in the ischemic CA1 region may lead to a deficit of postsynaptic plasticity in the brain.

Chronic administration of anti-stroke herbal medicine TongLuoJiuNao reduces amyloidogenic processing of amyloid precursor protein in a mouse model of Alzheimer's disease

Composed of Ginsenoside Rg1 and Geniposide, the herbal medicine TongLuoJiuNao (TLJN) injection liquid has anti-inflammatory properties and can improve learning and memory in mice. Recently, TLJN has been used to treat the patients with cerebral ischemic stroke and vascular dementia, which significantly increase the risk of developing Alzheimer’s disease (AD) in the early human beings. Although beneficial effects of TLJN have been reported in the vascular-associated brain disorders, the roles of TLJN in AD brains are still not clear. In this study, we chronically administered TLJN in amyloid precursor protein (APP) Swedish mutant transgenic mice (APP23) from 6 months old of age, which is at the onset of Aβ plaques, to 12 months old. We found that TLJN significantly decreased Aβ production and deposition in the brain of APP23 mice. Furthermore, we observed that TLJN down-regulated the levels and activity of β-secretase 1 (BACE1) protein as well as the expression levels of γ-secretase complex components: PS1, nicastrin and anterior pharynx-defective 1 (APH1) but not presenilin enhancer 2 (PEN2). The results suggest an inhibitory effect of TLJN on amyloidogenic APP processing by down-regulating the cleavage enzymes BACE1 and γ-secretase.

Chotosan ameliorates cognitive and emotional deficits in an animal model of type 2 diabetes: possible involvement of cholinergic and VEGF/PDGF mechanisms in the brain

BACKGROUND

Diabetes is one of the risk factors for cognitive deficits such as Alzheimer's disease. To obtain a better understanding of the anti-dementia effect of chotosan (CTS), a Kampo formula, we investigated its effects on cognitive and emotional deficits of type 2 diabetic db/db mice and putative mechanism(s) underlying the effects.

METHODS

Seven-week-old db/db mice received daily administration of CTS (375 - 750 mg/kg, p.o.) and the reference drug tacrine (THA: 2.5 mg/kg, i.p.) during an experimental period of 7 weeks. From the age of 9-week-old, the animals underwent the novel object recognition test, the modified Y-maze test, and the water maze test to elucidate cognitive performance and the elevated plus maze test to elucidate anxiety-related behavior. After completing behavioral studies, Western blotting and immunohistochemical studies were conducted.

RESULTS

Compared with age-matched non-diabetic control strain (m/m) mice, db/db mice exhibited impaired cognitive performance and an increased level of anxiety. CTS ameliorated cognitive and emotional deficits of db/db mice, whereas THA improved only cognitive performance. The phosphorylated levels of Akt and PKCα in the hippocampus were significantly lower and higher, respectively, in db/db mice than in m/m mice. Expression levels of the hippocampal cholinergic marker proteins and the number of the septal cholinergic neurons were also reduced in db/db mice compared with those in m/m mice. Moreover, the db/db mice had significantly reduced levels of vasculogenesis/angiogenesis factors, vascular endothelial growth factor (VEGF), VEGF receptor type 2, platelet-derived growth factor-B, and PDGF receptor β, in the hippocampus. CTS and THA treatment reversed these neurochemical and histological alterations caused by diabetes.

CONCLUSION

These results suggest that CTS ameliorates diabetes-induced cognitive deficits by protecting central cholinergic and VEGF/PDGF systems via Akt signaling pathway and that CTS exhibits the anxiolytic effect via neuronal mechanism(s) independent of cholinergic or VEGF/PDGF systems in db/db mice.

Chronological changes in inflammatory cytokines immunoreactivities in the mouse hippocampus after systemic administration of high dosage of tetanus toxin

Tetanus toxin (TeT) is an exotoxin and has a capacity for neuronal binding and internalization. In the present study, we compared changes in the immunoreactivities and protein levels of interleukin (IL-) 2 as a pro-inflammatory cytokine and IL-4 as an anti-inflammatory cytokine in the hippocampus proper (HP) and dentate gyrus (DG) after systemic treatment of 10 or 100 ng/kg TeT into mice. In this study, we could not find any neuronal damage or loss in any subregions of the hippocampus after TeT treatment. In the control groups, strong IL-2 immunoreactivity was shown in the stratum pyramidal (SP) of the HP and in the granule cell layer (GCL) of the DG. At 6 h post-treatment, IL-2 immunoreactivity was hardly detected in the SP and GCL; however, strong IL-2 immunoreactivity was shown in the stratum oriens of the HP in both the groups. Thereafter, intermediate IL-2 immunoreactivity was shown in the SP and GCL. On the other hand, intermediate IL-4 immunoreactivity was detected in the SP and GCL of the control groups. At 6 h post-treatment, IL-4 immunoreactivity in the SP and GCL was apparently increased. Thereafter, IL-4 immunoreactivity was lower than that at 6 h post-treatment. In brief, IL-2 and 4 immunoreactivities were easily detected in SP and GCL in the controls and dramatically decreased and increased at 6 h post-treatment, respectively.

Promising therapeutics with natural bioactive compounds for improving learning and memory--a review of randomized trials

Cognitive disorders can be associated with brain trauma, neurodegenerative disease or as a part of physiological aging. Aging in humans is generally associated with deterioration of cognitive performance and, in particular, learning and memory. Different therapeutic approaches are available to treat cognitive impairment during physiological aging and neurodegenerative or psychiatric disorders. Traditional herbal medicine and numerous plants, either directly as supplements or indirectly in the form of food, improve brain functions including memory and attention. More than a hundred herbal medicinal plants have been traditionally used for learning and memory improvement, but only a few have been tested in randomized clinical trials. Here, we will enumerate those medicinal plants that show positive effects on various cognitive functions in learning and memory clinical trials. Moreover, besides natural products that show promising effects in clinical trials, we briefly discuss medicinal plants that have promising experimental data or initial clinical data and might have potential to reach a clinical trial in the near future.

Promotive effect of ginsenoside Rd on proliferation of neural stem cells in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Ginseng, the root of Panax ginseng C. A. MEYER (Araliaceae), is reputedly known for its nootropic and anti-aging functions and has been widely used to treat various diseases and enhance health for thousands of years in Asia. Recent studies revealed that ginsenoside, responsible for the pharmacological effects of ginseng, can prevent memory loss and improve spatial learning in mice, but underlying mechanisms are still largely unknown. Active neurogenesis in adult hippocampus is closely related to animals' learning and memory ability. The present study aimed to investigate the possible effects of ginsenoside Rd, one of the most effective ingredients in ginseng, on neurogenesis in vivo and in vitro.

MATERIALS AND METHODS

Adult rats and cultured neural stem cells were treated with ginsenoside Rd at different doses, and the changes in the proliferation and differentiation of neural stem cells were examined by immunohistochemistry and immunocytochemistry.

RESULTS

Ginsenoside Rd significantly increased the numbers of BrdU(+) and DCX(+) cells in the hippocampal dentate gyrus but did not affect the ratio of NeuN/BrdU double-labeled cells to the total number of BrdU(+) cells. For cultured neural stem cells, ginsenoside Rd promoted the size and number of neurospheres, increased the number of BrdU(+) and Ki67(+) cells but did not affect the differentiation of neural stem cells into neurons, astrocytes and oligodendrocytes.

CONCLUSIONS

These results indicate that ginsenoside Rd can enhance the proliferation but not affect the differentiation of neural stem cells in vivo and in vitro.

Participation of microRNA 124-CREB pathway: a parallel memory enhancing mechanism of standardised extract of Bacopa monniera (BESEB CDRI-08)

Bacosides, the effective component of standardised leaf extract of Bacopa monniera (BESEB CDRI-08) has been reported to have memory enhancing effect. Our previous reports suggested that BESEB CDRI-08 (BME) improves memory in postnatal rats by enhancing serotonin [5-hydroxytryptamine (5-HT)] metabolism, its transportation and subsequently activates 5-HT(3A) receptor during hippocampus-dependent learning. In this study, we examine whether the up-regulated 5-HT(3A) receptor activity by BME modulate microRNA 124-CREB pathway to enhance synaptic plasticity. Wistar rat pups received single dose of vehicle solution (0.5 % gum acacia + 0.9 % saline)/BME (80 mg/kg)/mCPBG (10 mg/kg)/BME + mCPBG during the postnatal days (PND) 15-29. On PND 30, individuals were trained at brightness discrimination task and 24 h later, they were tested on the task. The BME treated group exhibited significantly lower percentage of errors during retention than acquisition. In addition, pre-miR-124 expression in hippocampus was significantly down-regulated in the BME and mCPBG + BME treated groups combined with a significant increase in the plasticity related genes, cAMP response element-binding protein, its phosphorylation and postsynaptic density protein 95. Our results suggest that this may be one of the mechanisms of bacosides present in BME for the memory enhancement.

Age-dependent decline of motor neocortex but not hippocampal performance in heterozygous BDNF mice correlates with a decrease of cortical PSD-95 but an increase of hippocampal TrkB levels

Brain-derived neurotrophic factor (BDNF) is a key player in learning and memory processes. However, little is known about brain area-specific functions of this neurotrophin. Here we investigated whether BDNF could differently affect motor neocortical and hippocampal-related cognitive and plastic morphologic changes in young (12-week-old) and middle-aged (30-week-old) BDNF heterozygous (BDNF⁺/⁻) and wild type (wt) mice. We found that at 30 weeks of age, BDNF⁺/⁻ mice showed impaired performance in accelerating rotarod and grasping tests while preserved spatial learning in a T-maze and recognition memory in an object recognition task compared with wt mice suggesting a specific neocortical dysfunction. Accordingly, a significant reduction of synaptic markers (PSD-95 and GluR1) and corresponding puncta was observed in motor neocortex but not in hippocampus of BDNF⁺/⁻ mice. Interestingly, 30-week-old BDNF⁺/⁻ mice displayed increased TrkB levels in the hippocampus but not in the motor neocortex, which suggests specific hippocampal compensatory mechanisms as a consequence of BDNF decrease. In conclusion, our data indicates that BDNF could differentially regulate the neuronal micro-structures and cognition in a region-specific and in an age-dependent manner.

Treatment with ginseng total saponins reduces the secondary brain injury in rat after cortical impact

The present study was designed to investigate the neuroprotective effect of ginseng total saponins (GTSs) and its underlying mechanisms in a rat model of traumatic brain injury (TBI). Rats were injected with GTSs (20 mg/kg, i.p.) or vehicle for 14 days after TBI. Neurological functions were determined using beam balance and prehensile traction tests at 1-14 days after trauma. Brain samples were extracted at 1 day after trauma for determination of water content, Nissl staining, enzyme-linked immunosorbent assay, immunohistochemistry, terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick end labeling, and measurement of oxidative stress variables and inflammatory cytokines. Moreover, the dose response of the neuroprotective effect and time window of the efficacy of GTSs were also determined. We found that treatment of GTSs 1) improved the neurological function with an effective dosage of 5-80 mg/kg and an efficacy time window of 3-6 hr after TBI; 2) reduced brain water content and neuronal loss in the hippocampal CA3 area; 3) increased the activity of superoxide dismutase and decreased the activity of nitric oxide synthase and the amount of malondialdehyde and nitric oxide; 4) down-regulated interleukin-1β, interleukin-6, and tumor necrosis factor-α and upregulated interleukin-10 in the cortical area surrounding the injured core; and 5) inhibited the apoptotic cell death and expression of caspase-3 and bax and raised the expression of bcl-2. These findings suggest that administration of GTSs after TBI could reduce the secondary injury through inhibiting oxidative and nitrative stress, attenuating inflammatory response, and reducing apoptotic cell death.

Conditioned fear stress combined with single-prolonged stress: a new PTSD mouse model

There are still some defects in current single-prolonged stress (SPS) model and conditioned fear (CF) stress model of post-traumatic stress disorder (PTSD). The purpose of this study is to evaluate a novel mouse model of PTSD. Male KM mice suffered the double stresses-SPS and CF. After incubation time, the novel model exhibited the PTSD-like behaviors: sensitive fear and conditioned fear, low activities and defects in novel object recognition abilities. The apoptosis in the hippocampus was significantly increased, which was induced by the double stresses and further caused the synaptic structure damages in the hippocampus. The electron microscopy analysis further proved the synaptic losses and neuronal impairments in the hippocampus. Our results indicated this combined stresses mouse model was better than the SPS model and CF model. In addition, in order to further verify this model, paroxetine was administered after the double stresses. The results showed that paroxetine administration reduced PTSD-like behaviors, hippocampal apoptosis and structure damages. We conclude that this mouse model is novel and more predictably mimicked the clinical characteristics of PTSD, and this model can be further used for investigating the mechanisms of PTSD and screening effective therapeutics agents.

Protective effects of ginsenosides against Bisphenol A-induced cytotoxicity in 15P-1 Sertoli cells via extracellular signal-regulated kinase 1/2 signalling and antioxidant mechanisms

Numerous studies have demonstrated that Bisphenol A (BPA) can cause reproductive toxicity. Ginseng has wide range of pharmacological actions and, more importantly, has proven its worth with respect to reproductive function in several reports. We have suggested that ginsenosides, the main active components of ginseng, may protect against BPA-induced cell damage. Therefore, an in vitro culture model of 15P-1 Sertoli cells was employed to investigate whether ginsenosides have protective effects on BPA-stimulated 15P-1 Sertoli cells. The results revealed that ginsenosides (75 μg/ml) significantly inhibited BPA-induced decreases in cell viability and increases in apoptosis. Immunofluorescence staining showed that BPA exposure-induced collapse of vimentin intermediate filaments was prevented by the application of ginsenosides. Ginsenosides also inhibited extracellular signal-regulated kinase (ERK1/2) phosphorylation and BPA-induced alterations of Bcl-2 and Bax protein expression in 15P-1 Sertoli cells. Furthermore, the alterations of T-AOC, superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione and malondialdehyde levels in BPA-stimulated cells were partially prevented with pre-treatment with ginsenosides. Taken together, these results suggest that ginsenosides have protective effects against BPA-induced cell damage and that these effects are mediated by preventing ERK1/2 phosphorylation and through the enhancement of cellular antioxidant capacity. Ginsenosides may therefore be beneficial in the prevention of environmental BPA-induced, reproduction-related toxicity.

Gliosis in the mouse hippocampus without neuronal death after systemic administration of high dosage of tetanus toxin

Tetanus toxin (TeT), an exotoxin, has been studied to cause tetanus in mammalian brains, and it can block the release of some neurotransmitters and affect seizure propagation. In the present study, we investigated neuronal damage/death and glial changes in the mouse hippocampus after systemic administration (intraperitoneal injection) of TeT 10 and 100 ng/kg. In both the 10 and 100 ng/kg TeT-treated groups, no neuronal death occurred in any subregions of the mouse hippocampus until 24 h post-treatment; however, there were changes in glia in the hippocampus depending on time course and dosage. The morphology of GFAP-immunoreactive astrocytes and Iba-1-immunoreactive microglia was apparently changed in the 100 ng/kg TeT treated-group compared to the 10 ng/kg TeT treated-group. In the 100 ng/kg TeT treated-group, they were increased in size and their immunoreactivity was distinctively increased from 12 h post-treatment. We also found that their protein levels were increased in the hippocampus at 12 h post-treatment of 100 ng/kg TeT. In conclusion, these results indicate that the systemic administration of 100 ng/kg TeT induced a distinctive microglia changes in the mouse hippocampus without any neuronal death/damage.

Diabetes-induced central cholinergic neuronal loss and cognitive deficit are attenuated by tacrine and a Chinese herbal prescription, kangen-karyu: elucidation in type 2 diabetes db/db mice

We investigated the effect of kangen-karyu (KK), a Chinese herbal prescription, on cognitive deficits and central cholinergic systems of type 2 diabetic db/db mice. Seven-week-old db/db (Y-db/db) mice received daily administration of test drugs during an experimental period of 12 weeks. At 18 weeks of age (O-db/db), the animals underwent the water maze test. Compared with age-matched control strain mice (O-m/m), vehicle-treated O-db/db mice showed impaired learning and memory performance. KK (100 - 200 mg/kg per day) and the reference drug tacrine (THA: 2.5 mg/kg per day) ameliorated the performance of O-db/db mice without affecting their serum glucose level. O-db/db mice had lower levels of brain-derived neurotrophic factor (BDNF) mRNA and its protein in the brain than O-m/m mice. Expression levels of central cholinergic marker proteins in the hippocampus and the number of cholinergic cells in the medial septum and basal forebrain were also significantly lower in O-db/db than in O-m/m mice, whereas no significant differences in the expression levels of these factors and the cell number were found between Y-m/m and Y-db/db mice. KK and THA treatment significantly reversed the down-regulated levels of cholinergic markers, choline acetyltransferase-positive cell number, and BDNF expression in db/db mice. These findings suggest that KK as well as THA prevents diabetes-induced cognitive deficits by attenuating dysfunction of central cholinergic systems.

Multi-faced neuroprotective effects of Ginsenoside Rg1 in an Alzheimer mouse model

There has been no extensive characterization of the effects of Ginsenoside Rg1, a pharmacological active component purified from the nature product ginseng, in an Alzheimer's disease mouse model. The well-characterized transgenic Alzheimer disease (AD) mice over expressing amyloid precursor protein (APP)/Aβ (Tg mAPP) and nontransgenic (nonTg) littermates at age of 6 and 9 months were treated with Rg 1 for three months via intraperitoneal injection. Mice were then evaluated for changes in amyloid pathology, neuropathology and behavior. Tg mAPP treated with Rg1 showed a significant reduction of cerebral Aβ levels, reversal of certain neuropathological changes, and preservation of spatial learning and memory, as compared to vehicle-treated mice. Rg1 treatment inhibited activity of γ-secretase in both Tg mAPP mice and B103-APP cells, indicating the involvement of Rg1 in APP regulation pathway. Furthermore, administration of Rg1 enhanced PKA/CREB pathway activation in mAPP mice and in cultured cortical neurons exposed to Aβ or glutamate-mediated synaptic stress. Most importantly, the beneficial effects on attenuation of cerebral Aβ accumulation, improvement in neuropathological and behavioral changes can be extended to the aged mAPP mice, even to 12-13 months old mice that had extensive amyloid pathology and severe neuropathological and cognitive malfunction. These studies indicate that Rg1 has profound multi-faced and neuroprotective effects in an AD mouse model. Rg1 induces neuroprotection through ameliorating amyloid pathology, modulating APP process, improving cognition, and activating PKA/CREB signaling. These findings provide a new perspective for the treatment of AD and demonstrate potential for a new class of drugs for AD treatment.

Chotosan (Diaoteng San)-induced improvement of cognitive deficits in senescence-accelerated mouse (SAMP8) involves the amelioration of angiogenic/neurotrophic factors and neuroplasticity systems in the brain

Background

Chotosan (CTS, Diaoteng San), a Kampo medicine (ie Chinese medicine) formula, is reportedly effective in the treatment of patients with cerebral ischemic insults. This study aims to evaluate the therapeutic potential of CTS in cognitive deficits and investigates the effects and molecular mechanism(s) of CTS on learning and memory deficits and emotional abnormality in an animal aging model, namely 20-week-old senescence-accelerated prone mice (SAMP8), with and without a transient ischemic insult (T2VO).

Methods

Age-matched senescence-resistant inbred strain mice (SAMR1) were used as control. SAMP8 received T2VO (T2VO-SAMP8) or sham operation (sham-SAMP8) at day 0. These SAMP8 groups were administered CTS (750 mg/kg, p.o.) or water daily for three weeks from day 3.

Results

Compared with the control group, both sham-SAMP8 and T2VO-SAMP8 groups exhibited cognitive deficits in the object discrimination and water maze tests and emotional abnormality in the elevated plus maze test. T2VO significantly exacerbated spatial cognitive deficits of SAMP8 elucidated by the water maze test. CTS administration ameliorated the cognitive deficits and emotional abnormality of sham- and T2VO-SAMP8 groups. Western blotting and immunohistochemical studies revealed a marked decrease in the levels of phosphorylated forms of neuroplasticity-related proteins, N-methyl-D-aspartate receptor 1 (NMDAR1), Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), cyclic AMP responsive element binding protein (CREB) and brain-derived neurotrophic factor (BDNF) in the frontal cortices of sham-SAMP8 and T2VO-SAMP8. Moreover, these animal groups showed significantly reduced levels of vasculogenesis/angiogenesis factors, vascular endothelial growth factor (VEGF), VEGF receptor type 2 (VEGFR2), platelet-derived growth factor-A (PDGF-A) and PDGF receptor α (PDGFRα). CTS treatment reversed the expression levels of these factors down-regulated in the brains of sham- and T2VO-SAMP8.

Conclusion

Recovery of impaired neuroplasticity system and VEGF/PDGF systems may play a role in the ameliorative effects of CTS on cognitive dysfunction caused by aging and ischemic insult.

Caffeine induces beneficial changes in PKA signaling and JNK and ERK activities in the striatum and cortex of Alzheimer's transgenic mice

Caffeine intake has been associated with a lower incidence of Alzheimer's disease (AD) in humans. In AD mouse models, caffeine significantly decreases senile plaques and amyloid beta (Aβ) levels while also protecting against or reversing cognitive impairment. To understand the mechanism(s) underlying the protective effects of caffeine against AD pathology, we investigated the effects of a two-week treatment with caffeine (3mg/day) in transgenic (APPswe) mice and non-transgenic (NT) mice on signaling factors involved in neuronal plasticity and survival. We evaluated cAMP-dependent protein kinase A (PKA), phospho-cyclic AMP response-element binding protein (phospho-CREB), and the pro-apoptotic protein kinases extracellular signal-regulated kinase 1/2 (phospho-ERK) and phospho-c-Jun N-terminal kinase 1 (phospho-JNK) in the striatum and frontal cortex of caffeine-treated mice. In the striatum, APPswe control mice exhibited a significant decrease in phospho-CREB, as well as significant increases in phospho-JNK and phospho-ERK in comparison to NT mice. Caffeine treatment stimulated PKA activity, increased phospho-CREB levels, and decreased phospho-JNK and phospho-ERK expression in the striatum of APPswe mice, all of which are thought to be beneficial changes for brain function. Even caffeine-treated NT mice exhibited some of these changes in striatum. In the frontal cortex, caffeine did not significantly increase phospho-CREB and PKA activity, but significantly reduced phospho-JNK and phospho-ERK expression in both APPswe and NT mice. These results suggest that caffeine shifts the balance between neurodegeneration and neuronal survival toward the stimulation of pro-survival cascades and inhibition of pro-apoptotic pathways in the striatum and/or cortex, which may contribute to its beneficial effects against AD.

Ginsenoside Rd protects neurons against glutamate-induced excitotoxicity by inhibiting ca(2+) influx

Our previous studies have demonstrated that ginsenoside Rd (GSRd), one of the principal ingredients of Pana notoginseng, has neuroprotective effects against ischemic stroke. However, the possible mechanism(s) underlying the neuroprotection of GSRd is/are still largely unknown. In this study, we treated glutamate-injured cultured rat hippocampal neurons with different concentrations of GSRd, and then examined the changes in neuronal apoptosis and intracellular free Ca(2+) concentration. Our MTT assay showed that GSRd significantly increased the survival of neurons injured by glutamate in a dose-dependent manner. Consistently, TUNEL and Caspase-3 staining showed that GSRd attenuated glutamate-induced cell death. Furthermore, calcium imaging assay revealed that GSRd significantly attenuated the glutamate-induced increase of intracellular free Ca(2+) and also inhibited NMDA-triggered Ca(2+) influx. Thus, the present study demonstrates that GSRd protects the cultured hippocampal neurons against glutamate-induced excitotoxicity, and that this neuroprotective effect may result from the inhibitory effects of GSRd on Ca(2+) influx.

Ginsenosides from American ginseng: chemical and pharmacological diversity

Ginseng occupies a prominent position in the list of best-selling natural products in the world. Compared to the long history of use and widespread research on Asian ginseng, the study of American ginseng is relatively limited. In the past decade, some promising advances have been achieved in understanding the chemistry, pharmacology and structure-function relationship of American ginseng. To date, there is no systematic review of American ginseng. In this review, the different structures of the ginsenosides in American ginseng are described, including naturally occurring compounds and those resulting from steaming or biotransformation. Preclinical and clinical studies published in the past decade are also discussed. Highlighted are the chemical and pharmacological diversity and potential structural-activity relationship of ginsenosides. The goal is that this article is a useful reference to chemists and biologists researching American ginseng, and will open the door to agents in drug discovery.

Protective Action of Neurotrophic Factors and Estrogen against Oxidative Stress-Mediated Neurodegeneration

Oxidative stress is involved in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. Low levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are important for maintenance of neuronal function, though elevated levels lead to neuronal cell death. A complex series of events including excitotoxicity, Ca(2+) overload, and mitochondrial dysfunction contributes to oxidative stress-mediated neurodegeneration. As expected, many antioxidants like phytochemicals and vitamins are known to reduce oxidative toxicity. Additionally, growing evidence indicates that neurotrophic factors such as brain-derived neurotrophic factor (BDNF) and estrogens significantly prevent neuronal damage caused by oxidative stress. Here, we review and discuss recent studies addressing the protective mechanisms of neurotrophic factors and estrogen within this system.

Nutrigenetics and nutrigenomics: viewpoints on the current status and applications in nutrition research and practice

Nutrigenetics and nutrigenomics hold much promise for providing better nutritional advice to the public generally, genetic subgroups and individuals. Because nutrigenetics and nutrigenomics require a deep understanding of nutrition, genetics and biochemistry and ever new 'omic' technologies, it is often difficult, even for educated professionals, to appreciate their relevance to the practice of preventive approaches for optimising health, delaying onset of disease and diminishing its severity. This review discusses (i) the basic concepts, technical terms and technology involved in nutrigenetics and nutrigenomics; (ii) how this emerging knowledge can be applied to optimise health, prevent and treat diseases; (iii) how to read, understand and interpret nutrigenetic and nutrigenomic research results, and (iv) how this knowledge may potentially transform nutrition and dietetic practice, and the implications of such a transformation. This is in effect an up-to-date overview of the various aspects of nutrigenetics and nutrigenomics relevant to health practitioners who are seeking a better understanding of this new frontier in nutrition research and its potential application to dietetic practice.

Long-term ginsenoside administration prevents memory loss in aged female C57BL/6J mice by modulating the redox status and up-regulating the plasticity-related proteins in hippocampus

Memory impairment is considered to be one of the most prominent consequences of aging. Deterioration of memory begins in advance of old age in animals, including humans. The generation of reactive oxygen species (ROS) and/or free radicals-induced oxidative stress which is the major age-related changes, can lead to hippocampus damage and increase vulnerability to impaired learning and memory. Ginsenoside, the effective ingredient of ginseng, has been reported to have a neuron beneficial effect. In the present study, C57BL/6J mice aged 12 months were chronically treated with ginsenoside (three dose groups were given ginsenoside in drinking water for 8 months, the concentration of ginsenoside in drinking water was 0.028%, 0.056%, and 0.112% (w/v), respectively). Placebo-treated aged mice and young ones (4 months old) were used as controls. The efficacious effect of ginsenoside was manifested in the amelioration of memory impairment in aged mice by Morris water maze and step-down tests. Total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), and thiobarbituric acid reactive substances (TBARS) have been used as the biomarkers of oxidative stress. In ginsenoside treated groups, the activities of T-SOD and GSH-Px markedly increased, and the levels of TBARS and the content of protein carbonyl decreased significantly in serum and in hippocampus. The activation of lipofuscin formation, disruption or loss of cristae in mitochondria, the irregular nucleus and condensed chromatin laid against the nuclear membrane in pyramidal cells of hippocampal CA1 region, which are all related to oxidative stress, were also reduced after ginsenoside treatment. Processes of memory formation and functional plasticity are associated with postsynaptic density-95 (PSD-95), protein kinase Cγ subunit (PKCγ) and brain derived neurotrophic factor (BDNF). In the present study, we found that long-term ginsenoside treatment prevented age-related reductions of PSD-95, PKCγ, and BDNF in the hippocampus. These results demonstrated that long-term ginsenoside administration may prevent memory loss in aged C57BL/6J mice by modulating the redox status and up-regulating the plasticity-related proteins in hippocampus.

Implication of phosphatidylinositol-3 kinase/Akt/glycogen synthase kinase-3β pathway in ginsenoside Rb1's attenuation of beta-amyloid-induced neurotoxicity and tau phosphorylation

Ginseng has long been used to alleviate many ailments, particularly those associated with aging and memory deterioration. In the present study we aimed to investigate the neuroprotective effects of ginsenoside Rb1, against Aβ(1-42) toxicity in cultured cortical neurons and also the potential involvement of PI3K/Akt/GSK-3β signal pathway. Cortical neurons were pre-treated with ginsenoside Rb1 (20, 40, 100 μM) or LiCl (1, 5, 10 mM) for 24 h, and then were co-treated with 20 μM Aβ(1-42) for 12 h. In some experiments to evaluate the mechanism of Rb1 action, a PI3K inhibitor (LY294002 10 μM) was co-administered with Rb1 for the 24-h pretreatment. We revealed that Rb1 significantly attenuated Aβ(1-42)-induced neurotoxicity and tau hyperphosphorylation at multiple AD-related sites in a dose-dependent manner. Simultaneously, it increased the levels of phospho-Ser(473)-Akt and down-regulated GSK-3β activity by PI3K activation. The neuroprotective effects of Rb1 against Aβ(1-42)-induced neurotoxicity and tau hyperphosphorylation were blocked by LY294002 (10 μM), a PI3K inhibitor. In addition, Rb1 reversed the Aβ(1-42)-induced decrease in phosphorylation cyclic AMP response element binding (CREB) protein, which could also be blocked by the PI3K inhibitor. All these findings suggest that Rb1 may represent a potential treatment strategy for Alzheimer's disease.

Kangen-karyu improves memory deficit caused by aging through normalization of neuro-plasticity-related signaling system and VEGF system in the brain

AIM OF THE STUDY

Kangen-karyu (KK) is a traditional Chinese prescription consisting of six different herbs. This study was conducted to investigate the anti-dementia effect of KK on aging-induced cognitive deficits and the underlying mechanism using senescence-accelerated mice prone (SAMP8).

MATERIALS AND METHODS

Twenty-week old SAMP8 (older SAMP8) were used as an animal model of aging and age-matched senescence-resistant inbred strain (SAMR1) and 8-week-old SAMP8 (young SAMP8) were as controls. Older SAMP8 received daily administration of KK (100 mg/kg, p.o.) or water vehicle for 22 days.

RESULTS

Compared to the controls, older SAMP8 exhibited cognitive deficits in the object recognition and object location tests; however, KK improved the deficits caused by aging. Moreover, the older SAMP8 treated with vehicle exhibited reduced anxiety-like behavior in the elevated plus-maze test compared to SAMR1, but KK had no effect on emotional disorder of older SAMP8. The levels of biochemical factors related to neuro-plasticity and learning and memory; i.e., phosphorylated forms of N-methyl-D-aspartate receptor 1, Ca(2+)/calmodulin-dependent protein kinase II, and cyclic AMP-responsive element-binding protein, and brain-derived neurotrophic factor, were significantly decreased in older SAMP8 compared to those in the control animals. KK normalized the levels of these factors. Moreover, the mRNA and protein levels of vascular endothelial growth factor (VEGF) and its receptor type 2 in the cerebral cortices of older SAMP8 were down-regulated by aging, but these levels were reversed by KK.

CONCLUSIONS

These findings suggest that normalization of neuro-plasticity-related neuronal signaling and VEGF systems in the brain may be of the mechanisms underlying the ameliorative effects of KK on the cognitive deficits in older SAMP8.

Anti-aging herbal medicine--how and why can they be used in aging-associated neurodegenerative diseases?

Aging is a universal biological process that leads to progressive and deleterious changes in organisms. From ancient time, mankind has already interested in preventing and keeping ourselves young. Anti-aging study is certainly not a new research area. Nowadays, the meaning of anti-aging has been changed from simply prolonging lifespan to increasing health span, which emphasizes more on the quality of life. This is the concept of healthy aging and prevention of pathological aging, which is associated with diseases. Keeping our brain functions as in young age is an important task for neuroscientists to prevent aging-associated neurological disorders, such as Alzheimer's diseases (AD) and Parkinson's disease (PD). The causes of these diseases are not fully understood, but it is believed that these diseases are affected by multiple factors. Neurodegenerative diseases can be cross-linked with a number of aging-associated conditions. Based on this, a holistic approach in anti-aging research seems to be more reasonable. Herbal medicine has a long history in Asian countries. It is believed that many of the medicinal herbs have anti-aging properties. Recent studies have shown that some medicinal herbs are effective in intervention or prevention of aging-associated neurological disorders. In this review, we use wolfberry and ginseng as examples to elaborate the properties of anti-aging herbs. The characteristics of medicinal herbs, especially their applications in different disease stages (prevention and intervention) and multi-targets properties, allow them to be potential anti-aging intervention in prevention and treatment of the aging-associated neurological disorders.

Genome-wide gene expression profiling in GluR1 knockout mice: key role of the calcium signaling pathway in glutamatergically mediated hippocampal transmission

Alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors (AMPARs) convey fast synaptic transmission in the CNS and mediate various forms of hippocampal plasticity. Disruption of glutamate receptor type 1 (GluR1), a member of the AMPAR family, causes synaptic alterations and learning/memory deficits in mice. To gain mechanistic insight into the synaptic and behavioral changes associated with GluR1 deletion, hippocampal genome-wide expression profiling was conducted using groups of GluR1 knockout (KO) mice and their wild-type littermates. Regulation of 38 genes was found to be altered more than 30% (P < 0.01, n = 8), and seven of these genes were studied with additional quantitative experiments. A large portion of the altered genes encoded molecules involved in calcium signaling, including calcium channel components, calcium-binding proteins and calcium-calmodulin-dependent protein kinase II subunits. At the protein level, we further evaluated some genes in the calcium pathway that were altered in GluR1 KO mice. Protein levels of two key molecules in the calcium pathway - GluR, ionotropic, N-methyl-d-aspartate-1 and calcium/calmodulin-dependent protein kinase II alpha - showed similar changes to those observed in mRNA levels. These findings raise the possibility that calcium signaling and other plasticity molecules may contribute to the hippocampal plasticity and behavioral deficits observed in GluR1 KO mice.

Red mold rice promoted antioxidase activity against oxidative injury and improved the memory ability of zinc-deficient rats

Zn deficiency is a common disease leading to memory impairment with increasing age. This study evaluated the protection effects of red mold rice (RMR) administration and Zn supplementation against memory and learning ability impairments from oxidative stress caused by Zn deficiency. Rats (4 weeks old) were induced to be Zn deficiency by a Zn-deficient diet for 12 weeks. After that, rats were administered Zn, 1xRMR, 5xRMR, and various dosages of RMR plus Zn, respectively. Decreases of antioxidant enzyme activities in the hippocampus and cortex were observed, and the levels of Ca, Fe, and Mg were increased in the hippocampus and cortex of Zn-deficient rats, leading to memory and learning ability injury. However, the administration of RMR (1- or 5-fold dosage) and with or without Zn significantly improved the antioxidase and neural activity to maintain cortex and hippocampus functions. This study demonstrates that RMR is a possible functional food for the prevention or cure of neural injury associated with Zn deficiency.

Antidepressant effects of ginseng total saponins in the forced swimming test and chronic mild stress models of depression

Ginseng total saponins (GTS) are the major active components of Panax ginseng C.A. Meyer, which has been used as a popular tonic herb for 2000 years in Far East countries. In the present study, two classic animal models: the forced swimming test (FST) and the chronic mild stress (CMS) model were used to evaluate the antidepressant-like activities of GTS. It was observed that GTS at doses of 50 and 100 mg/kg significantly reduced the immobility time in the FST in mice after 7-day treatment. GTS also reversed the reduction in the sucrose preference index, decrease in locomotor activity as well as prolongation of latency of feeding in the novelty environment displayed by CMS rats. In addition, HPLC-ECD and immunohistochemical staining analysis indicated that the CMS-induced decrease in monoamine neurotransmitter concentration and brain-derived neurotrophic factor (BDNF) expression in the hippocampus were almost completely reversed by GTS. In conclusion, GTS exerts antidepressant-like effects in two highly specific and predictive animal models of depression. The activity of GTS in antidepression may be mediated partly through enhancing the monoamine neurotransmitter concentration and BDNF expression in the hippocampus.