Ginsenoside Rb1 promotes neurotransmitter release by modulating phosphorylation of synapsins through a cAMP-dependent protein kinase pathway

The anti-aging mechanism of ginsenosides with medicine and food homology

With the acceleration of global aging and the rise in living standards, the achievement of healthy aging is becoming an imperative issue globally. Ginseng, a medicinal plant that has a long history of dietary intake and remarkable medicinal value, has become a research hotspot in the field of food and medicine. Ginsenosides, especially protopanaxadiol-type saponins and protopanaxatriol-type saponins, are among the most important active ingredients in ginseng. Ginsenosides have been found to exhibit powerful and diverse pharmacological activities, such as antiaging, antitumor, antifatigue and immunity enhancement activities. Their effects in antiaging mainly include (1) promotion of metabolism and stem cell proliferation, (2) protection of skin and nerves, (3) modulation of intestinal flora, (4) maintenance of mitochondrial function, and (5) enhancement of telomerase activity. The underlying mechanisms are primarily associated with the intervention of the signaling pathways in apoptosis, inflammation and oxidative stress. In this review, the mechanism of action of ginsenosides in antiaging as well as the potential values of developing ginsenoside-based functional foods and antiaging drugs are discussed.

Protective Effects of Different Doses of Ginsenoside-Rb1 Experimental Cataract Model That in Chick Embryos

PURPOSE

There has been increased interest in phytochemical antioxidants to prevent protein damage and aggregate formation in cataract treatment. In this study, the protective effect of different doses of Rb1 (GRb1), one of the ginsenosides of Panax Ginseng, in the experimental cataract model formed in chick embryos was investigated.

METHODS

Five different experimental groups were formed with 100 SPF fertilized eggs: Control (0.9% NaCl to physiological saline), hydrocortisone hemisuccinate sodium (HC), low dose (HC + L-GRb1 (1 mg/kg)), medium dose (HC+). M-GRb1 (2.5 mg/kg)), and high dose (HC + H-GRb1 (5 mg/kg)). All solutions were given to air sack at 15 days of incubation. On the 17th day, the bulbous oculi of the chick embryos were dissected. Cataract formations of the lenses, glutathione (GSH), malondialdehyde (MDA), total antioxidant (TAS), total oxidant (TOS) levels, Caspase-3 H-score, and TUNEL index were determined. In addition, crystalline alpha A (CRYAA) gene expression was evaluated.

RESULTS

Cataracts were observed in the control, HC, HC + L-GRb1, HC + M-GRb1, and HC + H-GRb1 groups with a frequency of 0%, 100%, 75%, 56.25%, and 100%, respectively. There were statistically significant differences between the control and HC groups in terms of TAS, TOS, MDA, GSH, Caspase-3 H-score, and TUNEL index (p < .05). When the therapeutic effect of the GRb1 groups was evaluated, the HC group showed significant differences with the HC + L-GRb1 and HC + M-GRb1 groups in almost all parameters (p < .05), while there was no statistical difference with the HC + H-GRb1 group (p > .05). In addition, gene expression levels differed between the groups, although not statistically significant (p > .05).

CONCLUSION

1 mg/kg and 2.5 mg/kg GRb1 applications show therapeutic properties on the HC-induced cataract model. This effect is more pronounced at 2.5 mg/kg.

Identification of metabolites in plasma related to different biological activities of Panax ginseng and American ginseng

RATIONALE

Panax ginseng (PG) and American ginseng (AMG) are both medicinal plants of the Panax genus in the Acanthopanax family. Although PG and AMG have similar components of ginsenosides, there are many differences of their bioactivities. In this study, the biochemical mechanisms of different bioactivities of PG and AMG were explored by researching the differential metabolites in plasma after administration of each of PG and AMG.

METHODS

In order to explore the material basis of differential bioactivities, two groups of mice were administrated orally with PG and AMG, and the method of metabolomics was used to identify the differential metabolites in plasma. Then network pharmacology was used based on the differential metabolites. Afterward, the metabolite-target-pathway network of PG and AMG was constructed; thus the pathways related to different bioactivities were analyzed.

RESULTS

Through principal component analysis and orthogonal projections to latent structures discriminant analysis, there were 10 differential metabolites identified in the PG group and 8 differential metabolites identified in the AMG group. Based on network pharmacology, the differential metabolites were classified and related to differential bioactivities of PG and AMG. In the PG group, there were 6 metabolites related to aphrodisiac effect and exciting the nervous system, and 5 metabolites associated with raised blood pressure. In the AMG group, 5 metabolites were classified as having the effect of inhibiting the nervous system, and 6 metabolites were related to antihypertensive effect.

CONCLUSIONS

This study explored the material basis of the differential biological activities between PG and AMG, which is significant for the research of PG and AMG use and to promote human health.

Medicinal Herbs Used in Traditional Management of Breast Cancer: Mechanisms of Action

Background: Breast cancer is one of the principal causes of death among women and there is a pressing need to develop novel and effective anti-cancer agents. Natural plant products have shown promising results as anti-cancer agents. Their effectiveness is reported as decreased toxicity in usage, along with safety and less recurrent resistances compared with hormonal targeting anti-cancer agents. Methods: A literature search was conducted for all English-language literature published prior to June 2020. The search was conducted using electronic databases, including PubMed, Embase, Web of Science, and Cochrane Library. The search strategy included keywords such as breast cancer, herbs, anti-cancer biologically active components, clinical research, chemotherapy drugs amongst others. Results: The literature provides documented evidence of the chemo-preventative and chemotherapeutic properties of Ginseng, garlic (Allium sativum), Black cohosh (Actaea racemose), Tumeric (Curcuma longa), Camellia sinenis (green tea), Echinacea, Arctium (burdock), Flaxseed (Linum usitatissimum) and Black Cumin (Nigella sativa). Conclusions: The nine herbs displayed anti-cancer properties and their outcomes and mechanisms of action include inhibition of cell proliferation, angiogenesis and apoptosis as well as modulation of key intracellular pathways. However, more clinical trials and cohort human studies should be conducted to provide key evidence of their medical benefits.

Biotechnological Interventions for Ginsenosides Production

Ginsenosides are secondary metabolites that belong to the triterpenoid or saponin group. These occupy a unique place in the pharmaceutical sector, associated with the manufacturing of medicines and dietary supplements. These valuable secondary metabolites are predominantly used for the treatment of nervous and cardiac ailments. The conventional approaches for ginsenoside extraction are time-consuming and not feasible, and thus it has paved the way for the development of various biotechnological approaches, which would ameliorate the production and extraction process. This review delineates the biotechnological tools, such as conventional tissue culture, cell suspension culture, protoplast culture, polyploidy, in vitro mutagenesis, hairy root culture, that have been largely implemented for the enhanced production of ginsenosides. The use of bioreactors to scale up ginsenoside yield is also presented. The main aim of this review is to address the unexplored aspects and limitations of these biotechnological tools, so that a platform for the utilization of novel approaches can be established to further increase the production of ginsenosides in the near future.

Herbal Medicine of the 21st Century: A Focus on the Chemistry, Pharmacokinetics and Toxicity of Five Widely Advocated Phytotherapies

Widely advocated for their health benefits worldwide, herbal medicines (HMs) have evolved into a billion dollar generating industry. Much is known regarding their wellness inducing properties, prophylactic and therapeutic benefits for the relief of both minor to chronic ailment conditions given their long-standing use among various cultures worldwide. On the other hand, their equally meaningful chemistry, pharmacokinetic profile in humans, interaction and toxicity profile have been poorly researched and documented. Consequently, this review is an attempt to highlight the health benefits, pharmacokinetics, interaction, and toxicity profile of five globally famous HMs. A systematic literature search was conducted by browsing major scientific databases such as Bentham Science, SciFinder, ScienceDirect, PubMed, Google Scholar and EBSCO to include 196 articles. In general, ginsenosides, glycyrrhizin and curcumin demonstrate low bioavailability when orally administered. Ginkgo biloba L. induces both CYP3A4 and CYP2C9 and alters the AUC and Cmax of conventional medications including midazolam, tolbutamide, lopinavir and nifedipine. Ginsenosides Re stimulates CYP2C9, decreasing the anticoagulant activity of warfarin. Camellia sinensis (L.) Kuntze increases the bioavailability of buspirone and is rich in vitamin K thereby inhibiting the activity of anticoagulant agents. Glycyrrhiza glabra L. displaces serum bound cardiovascular drugs such as diltiazem, nifedipine and verapamil. Herbal medicine can directly affect hepatocytes leading to hepatoxicity based on both intrinsic and extrinsic factors. The potentiation of the activity of concurrently administered conventional agents is potentially lethal especially if the drugs bear dangerous side effects and have a low therapeutic window.

Ginsenoside Rb1 Promotes Motor Functional Recovery and Axonal Regeneration in Post-stroke Mice through cAMP/PKA/CREB Signaling Pathway

The central nervous system (CNS) has a poor self-repairing capability after injury because of the inhibition of axonal regeneration by many myelin-associated inhibitory factors. Therefore, ischemic stroke usually leads to disability. Previous studies reported that Ginsenoside Rb1 (GRb1) plays a role in neuronal protection in acute phase after ischemic stroke, but its efficacy in post-stroke and the underlying mechanism are not clear. Recent evidences demonstrated GRb1 promotes neurotransmitter release through the cAMP-depend protein kinase A (PKA) pathway, which is related to axonal regeneration. The present study aimed to determine whether GRb1 improves long-term motor functional recovery and promotes cortical axon regeneration in post-stroke. Adult male C57BL/6 mice were subjected to distal middle cerebral artery occlusion (dMCAO). GRb1 solution (5 mg/ml) or equal volume of normal saline was injected intraperitoneally for the first time at 24 h after surgery, and then daily injected until day 14. Day 3, 7, 14 and 28 after dMCAO were used as observation time points. Motor functional recovery was assessed with Rota-rod test and grid walking task. The expression of growth-associated protein 43 (GAP43) and biotinylated dextran amine (BDA) was measured to evaluate axonal regeneration. The levels of cyclic AMP (cAMP) and PKA were measured by Elisa, PKAc and phosphorylated cAMP response element protein (pCREB) were determined by western blot. Our results shown that GRb1 treatment improved motor function and increased the expression of GAP43 and BDA in ipsilesional and contralateral cortex. GRb1 significantly elevated cAMP and PKA, increased the protein expression of PKAc and pCREB. However, the effects of GRb1 were eliminated by H89 intervention (a PKA inhibitor). These results suggested that GRb1 improved functional recovery in post-stroke by stimulating axonal regeneration and brain repair. The underlying mechanism might be up-regulating the expression of cAMP/PKA/CREB pathway.

Ginsenoside Rb1 pretreatment reverses hippocampal changes in BDNF/TrkB mRNA and protein in rats subjected to acute immobilization stress

Purpose

Episodes of acute emotional or physical stress can have significant adverse effects on the hippocampus. Ginsenoside Rb1, the most predominant ginsenoside present in Panax species, has been reported to show a neuroprotective effect. The purpose of this study was to investigate the influence of ginsenoside Rb1 on plasma corticosterone (CORT) and adrenocorticotropic hormone (ACTH) levels and hippocampal brain-derived neurotrophic factor (BDNF) and tyrosine kinase B (TrkB) levels in rats subjected to acute immobilization stress.

Methods

Wistar rats were divided into controls treated with saline only (N), rats exposed to stress only (M), and rats pretreated with Rb1 (40 mg.kg (−1)) thirty minutes prior to stress exposure (R). In the model, animals were restrained in a plastic immobilizer for 2 h of acute immobilization stress at room temperature. ELISA was used to determine plasma levels of CORT and ACTH. The effect of Rb1 pretreatment on the expression of BDNF and TrkB was determined by immunofluorescence, real-time PCR, and Western blotting analysis.

Results

The R group showed significantly increased plasma CORT and ACTH levels compared to the N and M groups. Acute stress stimulation suppressed BDNF and TrkB protein and mRNA expression in the hippocampus; otherwise, Rb1 pretreatment reversed the decreases.

Conclusion

The results from this study demonstrate that Rb1 pretreatment reverses the decreases in hippocampal BDNF/TrkB and increases the plasma levels of CORT and ACTH, indicating a potential neuroprotective effect of Rb1 against acute stress.

Ginseng: A Qualitative Review of Benefits for Palliative Clinicians

Ginseng has been used for centuries to treat various diseases and has been commercially developed and cultivated in the past 300 years. Ginseng products may be fresh, dried (white), or dried and steamed (red). Extracts may be made using water or alcohol. There are over 50 different ginsenosides identified by chromatography. We did an informal systematic qualitative review that centered on fatigue, cancer, dementia, respiratory diseases, and heart failure, and we review 113 studies in 6 tables. There are multiple potential benefits to ginseng in cancer. Ginseng, in certain circumstances, has been shown to improve dementia, chronic obstructive pulmonary disease, and heart failure through randomized trials. Most trials had biases or unknown biases and so most evidence is of low quality. We review the gaps in the evidence and make some recommendations regarding future studies.

Major compounds of red ginseng oil attenuate Aβ25-35-induced neuronal apoptosis and inflammation by modulating MAPK/NF-κB pathway

β-Amyloid (Aβ)-induced neuronal toxicity in Alzheimer's disease (AD) is associated with complex mechanisms. Thus, a multi-target approach might be suitable for AD treatment. Following our previous study on the neuroprotective effects of red ginseng oil extract, its major compounds, including linoleic acid (LA), β-sitosterol (BS), and stigmasterol (SS), were examined to elucidate the mechanism of anti-apoptosis and anti-inflammation in Aβ25-35-stimulated PC12 cells. The results showed that the three compounds mitigated Aβ25-35 toxicity by regulating oxidative stress, apoptotic responses, and pro-inflammatory mediators. LA and SS strongly regulated intrinsic apoptosis markers, such as mitochondrial membrane potential, intracellular Ca2+, Bax/Bcl-2 ratio, and caspases-9, -3, and -8. However, BS blocked only the intrinsic apoptotic pathway, particularly by suppressing Ca2+ accumulation. Furthermore, all three compounds downregulated iNOS and phospho-nuclear factor-κB, but only LA and SS inhibited the expression of cyclooxygenase-2 and phospho-IκB. In assays to evaluate MAPK expression for confirming upstream signal pathways, BS decreased the phosphorylation of p38 and ERK, but not JNK, while SS markedly decreased the phosphorylation of all three MAPKs, and LA clearly decreased the phosphorylation of ERK and JNK, but not p38. These results indicate that LA, BS, and SS act as neuroprotectives against Aβ25-35-induced injury by distinct molecular mechanisms, indicating their preventive and/or therapeutic potential to treat AD.

Memory enhancing effects of BPN14770, an allosteric inhibitor of phosphodiesterase-4D, in wild-type and humanized mice

Inhibitors of phosphodiesterase-4 (PDE4) have beneficial effects on memory in preclinical and clinical studies. Development of these drugs has stalled due to dose-limiting side effects of nausea and emesis. While use of subtype-selective inhibitors (i.e., for PDE4A, B, or D) could overcome this issue, conservation of the catalytic region, to which classical inhibitors bind, limits this approach. The present study examined the effects of BPN14770, an allosteric inhibitor of PDE4D, which binds to a primate-specific, N-terminal region. In mice engineered to express PDE4D with this primate-specific sequence, BPN14770 was 100-fold more potent for improving memory than in wild-type mice; meanwhile, it exhibited low potency in a mouse surrogate model for emesis. BPN14770 also antagonized the amnesic effects of scopolamine, increased cAMP signaling in brain, and increased BDNF and markers of neuronal plasticity associated with memory. These data establish a relationship between PDE4D target engagement and effects on memory for BPN14770 and suggest clinical potential for PDE4D-selective inhibitors.

Pharmacological and medical applications of Panax ginseng and ginsenosides: a review for use in cardiovascular diseases

Panax ginseng, also called Asian or Korean ginseng, has long been traditionally used in Korea and China to treat various diseases. The major active ingredients of P. ginseng are ginsenosides, which have been shown to have a variety of therapeutic effects, including antioxidation, anti-inflammatory, vasorelaxation, antiallergic, antidiabetic, and anticancer. To date, approximately 40 ginsenoside components have been reported. Current research is concentrating on using a single ginseng compound, one of the ginsenosides, instead of the total ginseng compounds, to determine the mechanisms of ginseng and ginsenosides. Recent in vitro and in vivo results show that ginseng has beneficial effects on cardiac and vascular diseases through efficacy, including antioxidation, control of vasomotor function, modulation of ion channels and signal transduction, improvement of lipid profiles, adjustment of blood pressure, improvement in cardiac function, and reduction in platelet adhesion. This review aims to provide valuable information on the traditional uses of ginseng and ginsenosides, their therapeutic applications in animal models and humans, and the pharmacological action of ginseng and ginsenosides.

Inhibition of Autophagy is Involved in the Protective Effects of Ginsenoside Rb1 on Spinal Cord Injury

Spinal cord injury (SCI) is a devastating neurological disorder. Autophagy is induced and plays a crucial role in SCI. Ginsenoside Rb1 (Rb1), one of the major active components extracted from Panax Ginseng CA Meyer, has exhibited neuroprotective effects in various neurodegenerative diseases. However, it remains unknown whether autophagy is involved in the neuroprotection of Rb1 on SCI. In this study, we examined the regulation of autophagy following Rb1 treatment and its involvement in the Rb1-induced neuroprotection in SCI and in vitro injury model. Firstly, we found that Rb1 treatment decreased the loss of motor neurons and promoted function recovery in the SCI model. Furthermore, we found that Rb1 treatment inhibited autophagy in neurons, and suppressed neuronal apoptosis and autophagic cell death in the SCI model. Finally, in the in vitro injury model, Rb1 treatment increased the viability of PC12 cells and suppressed apoptosis by inhibiting excessive autophagy, whereas stimulation of autophagy by rapamycin abolished the anti-apoptosis effect of Rb1. Taken together, these findings suggest that the inhibition of autophagy is involved in the neuroprotective effects of Rb1 on SCI.

A Modified Chinese Herbal Decoction (Kai-Xin-San) Promotes NGF-Induced Neuronal Differentiation in PC12 Cells via Up-Regulating Trk A Signaling

Kai-Xin-San (KXS), a Chinese herbal decoction, has been applied to medical care of depression for thousands of years. It is composed of two functional paired-herbs: Ginseng Radix et Rhizoma (GR)-Polygalae Radix (PR) and Acori Tatarinowii Rhizoma (ATR)-Poria (PO). The compatibility of the paired-herbs has been frequently changed to meet the criteria of syndrome differentiation and treatment variation. Currently, a modified KXS (namely KXS₂₀₁₂) was prepared by optimizing the combinations of GR-PR and ATR-PO: the new herbal formula was shown to be very effective in animal studies. However, the cellular mechanism of KXS₂₀₁₂ against depression has not been fully investigated. Here, the study on KXS₂₀₁₂-induced neuronal differentiation in cultured PC12 cells was analyzed. In PC12 cultures, single application of KXS₂₀₁₂ showed no effect on the neuronal differentiation, but which showed robust effects in potentiating nerve growth factor (NGF)-induced neurite outgrowth and neurofilament expression. The potentiating effect of KXS₂₀₁₂ was mediated through NGF receptor, tropomyosin receptor kinase (Trk) A: because the receptor expression and activity was markedly up-regulated in the presence of KXS₂₀₁₂, and the potentiating effect was blocked by k252a, an inhibitor of Trk A. Our current results in cell cultures fully support the therapeutic efficacy of KXS₂₀₁₂ against depression.

Ginsenoside Rb1 ameliorates cisplatin-induced learning and memory impairments

Background

Ginsenoside Rb1 (Rb1), a dominant component from the extract of Panax ginseng root, exhibits neuroprotective functions in many neurological diseases. This study was intended to investigate whether Rb1 can attenuate cisplatin-induced memory impairments and explore the potential mechanisms.

Methods

Cisplatin was injected intraperitoneally with a dose of 5 mg/kg/wk, and Rb1 was administered in drinking water at the dose of 2 mg/kg/d to rats for 5 consecutive wk. The novel objects recognition task and Morris water maze were used to detect the memory of rats. Nissl staining was used to examine the neuron numbers in the hippocampus. The activities of superoxide dismutase, glutathione peroxidase, cholineacetyltransferase, acetylcholinesterase, and the levels of malondialdehyde, reactive oxygen species, acetylcholine, tumor necrosis factor-α, interleukin-1β, and interleukin-10 were measured by ELISA to assay the oxidative stress, cholinergic function, and neuroinflammation in the hippocampus.

Results

Rb1 administration effectively ameliorates the memory impairments caused by cisplatin in both novel objects recognition task and Morris water maze task. Rb1 also attenuates the neuronal loss induced by cisplatin in the different regions (CA1, CA3, and dentate gyrus) of the hippocampus. Meanwhile, Rb1 is able to rescue the cholinergic neuron function, inhibit the oxidative stress and neuroinflammation in cisplatin-induced rat brain.

Conclusion

Rb1 rescues the cisplatin-induced memory impairment via restoring the neuronal loss by reducing oxidative stress and neuroinflammation and recovering the cholinergic neuron functions.

Protective effects of ginseng on neurological disorders

Ginseng (Order: Apiales, Family: Araliaceae, Genus: Panax) has been used as a traditional herbal medicine for over 2000 years, and is recorded to have antianxiety, antidepressant and cognition enhancing properties. The protective effects of ginseng on neurological disorders are discussed in this review. Ginseng species and ginsenosides, and their intestinal metabolism and bioavailability are briefly introduced. This is followed by molecular mechanisms of effects of ginseng on the brain, including glutamatergic transmission, monoamine transmission, estrogen signaling, nitric oxide (NO) production, the Keap1/Nrf2 adaptive cellular stress pathway, neuronal survival, apoptosis, neural stem cells and neuroregeneration, microglia, astrocytes, oligodendrocytes and cerebral microvessels. The molecular mechanisms of the neuroprotective effects of ginseng in Alzheimer’s disease (AD) including β-amyloid (Aβ) formation, tau hyperphosphorylation and oxidative stress, major depression, stroke, Parkinson’s disease and multiple sclerosis are presented. It is hoped that this discussion will stimulate more studies on the use of ginseng in neurological disorders.

Neuroprotection by saponins

Saponins, an important group of bioactive plant natural products, are glycosides of triterpenoid or steroidal aglycones. Their diverse biological activities are ascribed to their different structures. Saponins have long been recognized as key ingredients in traditional Chinese medicine. Accumulated evidence suggests that saponins have significant neuroprotective effects on attenuation of central nervous system disorders, such as stroke, Alzheimer's disease, Parkinson's disease, and Huntington's disease. However, our understanding of the mechanisms underlying the observed effects remains incomplete. Based on recently reported data from basic and clinical studies, this review highlights the proposed mechanisms of their neuroprotective function including antioxidant, modulation of neurotransmitters, anti-apoptosis, anti-inflammation, attenuating Ca(2+) influx, modulating neurotrophic factors, inhibiting tau phosphorylation, and regeneration of neural networks.

Ginseng panaxoside Rb1 reduces body weight in diet-induced obese mice

Crude extracts from ginseng demonstrated anti-obesity properties. Ginsenoside Rb1 is the main component of ginseng, however, there are only few studies examining its effects in obesity. In the present study, we evaluated its potential anti-obesity effects in the murine model of diet-induced obesity. Seventy male C57BL/6 mice were randomly divided to consume for 12 weeks either chow diet (N = 8) or high-fat (HF) diet (N = 62). The latter mice were then divided into four groups: diet-induced obesity group (DIO; N = 10), obesity-resistant group (OR; N = 10), HF group (N = 5), and the group whose diet was changed from HF to normal diet (DC; N = 5). Intraperitoneal injections of Rb-1 were administered daily to mice in the DIO and OR groups for 3 weeks. Body weight and energy intake were monitored, and fasting blood glucose, lipids, neuropeptide Y, Y2 receptor, and peptide YY were quantified. Compared with HF group, weight gain and food intake of DIO mice with Rb-1 injection was significantly decreased (p < 0.05). Further, levels of blood glucose and some lipids were also decreased in DIO-Rb1 group compared with HF group. Furthermore, Rb1 was also found to modulate serum levels of PYY and NPY, and mRNA expression of NPY, Y2 receptor and PYY in tissue samples of DIO mice. Taken together, ginsenoside Rb1 may be useful in the treatment of obesity via modifying the serum content and mRNA expression of NPY, Y2 receptor and PYY.

Chemical and pharmacological studies of saponins with a focus on American ginseng

Asian ginseng (Panax ginseng) and American ginseng (Panax quinquefolius L.) are the two most recognized ginseng botanicals. It is believed that the ginseng saponins called ginsenosides are the major active constituents in both ginsengs. Although American ginseng is not as extensively studied as Asian ginseng, it is one of the best selling herbs in the U.S., and has garnered increasing attention from scientists in recent years. In this article, after a brief introduction of the distribution and cultivation of American ginseng, we discuss chemical analysis of saponins from these two ginsengs, i.e., their similarities and differences. Subsequently, we review pharmacological effects of the saponins, including the effects on the cardiovascular system, immune system, and central nervous system as well as the antidiabetes and anti-cancer effects. These investigations were mainly derived from American ginseng studies. We also discuss evidence suggesting that chemical modifications of ginseng saponins would be a valuable approach to develop novel compounds in drug discovery.

Traditional Korean East Asian medicines and herbal formulations for cognitive impairment

Hanbang, the Traditional Korean Medicine (TKM), is an inseparable component of Korean culture both within the country, and further afield. Korean traditional herbs have been used medicinally to treat sickness and injury for thousands of years. Oriental medicine reflects our ancestor’s wisdom and experience, and as the elderly population in Korea is rapidly increasing, so is the importance of their health problems. The proportion of the population who are over 65 years of age is expected to increase to 24.3% by 2031. Cognitive impairment is common with increasing age, and efforts are made to retain and restore the cognition ability of the elderly. Herbal materials have been considered for this purpose because of their low adverse effects and their cognitive-enhancing or anti-dementia activities. Herbal materials are reported to contain several active compounds that have effects on cognitive function. Here, we enumerate evidence linking TKMs which have shown benefits in memory improvements. Moreover, we have also listed Korean herbal formulations which have been the subject of scientific reports relating to memory improvement.

Ginsenoside rb1 reduces isoproterenol-induced cardiomyocytes apoptosis in vitro and in vivo

Cardiomyocytes apoptosis can lead to heart failure. Conventional and alternative drugs, such as Chinese herbal remedies, have been developed to target cardiomyoblast cells apoptosis. In this study, we investigated the effects of ginsenoside Rb1 (Rb1), an active compound, which is isolated from Notoginseng and Ginseng on isoproterenol-(ISO-) induced apoptosis in rat cardiomyocytes and its mechanism in vivo and in vitro. Rb1 reduced the ISO-induced apoptosis in rat cardiomyocytes and H9c2 cells. The effect of Rb1 was significantly suppressed by H89 (inhibitor for PKA), but not by C-1 (inhibitor for PKC). Based on in-cell blot analysis, the ISO-induced PKA and PKC expressions were decreased by Rb1, which was inhibited by H89, but not by C-1. The expressions of caspase-3 and caspase-9 were decreased after treatment with both ISO and Rb1, but with no change for caspase-8. Our results indicated that Rb1 reducing ISO-induced rat cardiomyocytes apoptosis may be involved in PKA and caspase-9 pathways.

Neuroprotective effects of ginsenoside Rb1 on high glucose-induced neurotoxicity in primary cultured rat hippocampal neurons

Ginsenoside Rb1 is one of the main active principles in traditional herb ginseng and has been reported to have a wide variety of neuroprotective effects. Endoplasmic reticulum (ER) stress has been implicated in neurodegenerative diseases, so the present study aimed to observe the effects of ginsenoside Rb1 on ER stress signaling pathways in high glucose-treated hippocampal neurons. The results from MTT, TUNEL labeling and Annexin V-FITC/PI/Hoechst assays showed that incubating neurons with 50 mM high glucose for 72h decreased cell viability and increased the number of apoptotic cells whereas treating neurons with 1 μM Rb1 for 72h protected the neurons against high glucose-induced cell damage. Further molecular mechanism study demonstrated that Rb1 suppressed the activation of ER stress-associated proteins including protein kinase RNA (PKR)-like ER kinase (PERK) and C/EBP homology protein (CHOP) and downregulation of Bcl-2 induced by high glucose. Moreover, Rb1 inhibited both the elevation of intracellular reactive oxygen species (ROS) and the disruption of mitochondrial membrane potential induced by high glucose. In addition, the high glucose-induced cell apoptosis, activation of ER stress, ROS accumulation and mitochondrial dysfunction can also be attenuated by the inhibitor of ER stress 4-phenylbutyric acid (4-PBA) and anti-oxidant N-acetylcysteine(NAC). In conclusion, these results suggest that Rb1 may protect neurons against high glucose-induced cell injury through inhibiting CHOP signaling pathway as well as oxidative stress and mitochondrial dysfunction.

Panax notoginsenoside Rb1 ameliorates Alzheimer's disease by upregulating brain-derived neurotrophic factor and downregulating Tau protein expression

Alzheimer's disease (AD) is a neurodegenerative disorder and the main cause of dementia. Panax notoginsenoside Rb1 (PNRb1), which is also known as (3β,12β)-20-[(6-O-β-D-glucopyranosyl-β-D-glucopyranosyl)oxy]-12-hydroxydammar-24-en-3-yl 2-O-β-D-glucopyranosyl-β-D-glucopyranoside and is the main active component of the plant Panax notoginseng, is effective in treating AD. However, the mechanisms of PNRb1 remain unknown. In the present study, rat brain tissue sections were pretreated with PNRb1 and then induced by okadaic acid to establish brain slice models of AD. The results of qPCR and immunoblot analyses demonstrated that PNRb1 suppressed the protein expression of phosphorylated Tau and upregulated the expression levels of brain-derived neurotrophic factor (BDNF). These results suggest that PNRb1 is able to upregulate the protein level of BDNF and downregulate Tau protein phosphorylation in AD.

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.

Wound-healing effect of ginsenoside Rd from leaves of Panax ginseng via cyclic AMP-dependent protein kinase pathway

Panax ginseng is considered as one of the most valuable medicinal herbs in traditional medicine, and ginsenoside Rd is one of the main active ingredients in P. ginseng leaf. Although there is significant number of evidences implicated on the beneficial effects of the ginsenosides with diverse associated mechanisms, reports on the skin regeneration by the ginsenoside Rd are not sufficient. Therefore, we examined the mitogenic and protective effects of the ginsenoside Rd in the keratinocyte progenitor cells (KPCs) and human dermal fibroblasts (HDFs). Furthermore, the signaling pathways involved in the activation of KPCs and HDFs were investigated, and wound-healing effect is evaluated in vivo through animal wound models. We found that the ginsenoside Rd significantly increased the proliferation and migration level of KPCs and HDFs in a dose-dependent manner. Additionally, the cell survival was significantly increased in H2O2 treated KPCs. Moreover, the ginsenoside Rd effectively induced collagen type 1 and down-regulated matrix metalloprotinase-1 (MMP-1) in a dose-dependent manner. All of these beneficial effects are associated with an induction of intracellular cAMP levels and phosphorylated cAMP response element-binding protein expression in nucleus, which both attenuated by adenine 9-β-d-arabinofuranoside, an adenylate cyclase inhibitor. Application of the ginsenoside Rd to an excision wound in mice showed an effective healing process. As skin regeneration is mainly associated with the activation of HDFs and KPCs, P. ginseng leaf, an alternative source of the ginsenoside Rd, can be used as a natural source for skin regeneration.

Aglycone of Rh4 inhibits melanin synthesis in B16 melanoma cells: possible involvement of the protein kinase A pathway

To our knowledge, there is no report that directly shows an inhibitory effect of ginsenoside on melanin synthesis in B16 melanoma cells. Hence, we investigated whether the aglycone of Rh(4) (A-Rh4) inhibits melanin synthesis in B16 melanoma cells, and determined the mechanism of melanin inhibition. We isolated 12 ginsenoside compounds from leaves of Panax ginseng and tested them in B16 melanoma cells. It significantly reduced melanin content and tyrosinase activity under alpha-melanocyte stimulating hormone- and forskolin-stimulated conditions. It significantly reduced the cyclic AMP (cAMP) level in B16 melanoma cells, and this might be responsible for the regulation down of MITF and tyrosinase. Phosphorylation of a downstream molecule, a cAMP response-element binding protein, was significantly decreased according to Western blotting and immunofluorescence assay. These data suggest that A-Rh4 has an anti-melanogenic effect via the protein kinase A pathway.

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.

Inhibitory effects of Ginsenoside Rb1 on apoptosis caused by HSV-1 in human glioma cells

To investigate the inhibitory effects of Ginsenoside Rb1 (GRb1) on apoptosis caused by Herpes Simplex Virus-1(HSV-1) in Human Glioma Cells (U251), U251 cells were infected by HSV-1 at a multiplicity of infection of 5 and GRb1, GRb1+HSV-1, HSV-1 and control groups. MTT and cell apoptosis assays were used to detect the inhibitory effects of GRb1 on the apoptosis of U251 cells that caused by HSV-1 infection for various concentrations of drug and virus treatments by MTT assay. We found that in the 400 μg/mL GRb1 and 400 μg/mL GRb1+HSV-1 groups, MTT values were higher than control group at all times (P<0. 05). Moreover, the apoptosis rate in the 400 μg/mL GRb1+HSV-1 group was lower than the HSV-1 group (P<0. 05). These results confirmed that, at appropriate concentrations, GRb1 could inhibit nerve cell apoptosis in HSV-1 infections.

Extracts of Rehmanniae radix, Ginseng radix and Scutellariae radix improve glucose-stimulated insulin secretion and beta-cell proliferation through IRS2 induction

Recent studies have revealed that beta-cell dysfunction is an important factor in developing type 2 diabetes. beta-cell dysfunction is related to impairment of the insulin/IGF-1 signaling cascade through insulin receptor substrate-2 (IRS2). The induction of IRS2 in beta-cells plays an important role in potentiating beta-cell function and mass. In this study, we investigated whether herbs used for treating diabetes in Chinese medicine-Galla rhois, Rehmanniae radix, Machilus bark, Ginseng radix, Polygonatum radix, and Scutellariae radix-improved IRS2 induction in rat islets, glucose-stimulated insulin secretion and beta-cell survival. R. radix, Ginseng radix and S. radix significantly enhanced glucose-stimulated insulin secretion compared to the control, i.e., by 49, 67 and 58%, respectively. These herbs induced the expression of IRS2, pancreas duodenum homeobox-1 (PDX-1), and glucokinase. The increased level of glucokinase could explain the enhancement of glucose-stimulated insulin secretion with these extracts. Increased PDX-1 expression was associated with beta-cell proliferation, which was consistent with the cell viability assay. In conclusion, R. radix, Ginseng radix and S. radix had an insulinotropic action similar to that of exendin-4.

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.

Beneficial estrogen-like effects of ginsenoside Rb1, an active component of Panax ginseng, on neural 5-HT disposition and behavioral tasks in ovariectomized mice

Decreased 5-hydroxytryptamine (5-HT) concentration in the brain has been linked to central nervous system dysfunctions, especially in menopausal women. Ginsenoside Rb1, a potential phytoestrogen, has been shown to improve central nervous system dysfunctions, comparable to the estrogen treatment. To investigate the estrogen-like effects of ginsenoside Rb1 on neural 5-HT disposition and behavioral tasks, we quantified the concentrations of 5-HT and other related endogenous substances in the frontal cortex and striatum of ovariectomized mice. The activities of tryptophan hydroxylase (TPH), aromatic amino acid decarboxylase (AAAD) and monoamine oxidase (MAO) were also measured to evaluate the synthesis and metabolism of neural 5-HT. Our work shows that both ginsenoside Rb1 and estradiol increased the neural 5-HT concentration. Ginsenoside Rb1 and estradiol administration resulted in elevated TPH and depressed MAO activities, indicating that modulating the synthesis and metabolism of neural 5-HT successfully elevated 5-HT concentration. Ginsenoside Rb1 and estradiol also improved object recognition and decreased immobility time in the forced swimming test. However, a pretreatment with clomiphene (an estrogen receptor antagonist) blocked the beneficial effects of ginsenoside Rb1 and estradiol, suggesting that the estrogen-like effects of ginsenoside Rb1 were estrogen receptor-dependent.

Ginsenoside Rb1 improves spatial learning and memory by regulation of cell genesis in the hippocampal subregions of rats

Ginsenoside Rb1 (Rb1) is known to improve learning and memory in hippocampus-dependent tasks. However, the cellular mechanism remains unknown. Cell genesis in hippocampus is involved in spatial learning and memory. In the present study, Rb1 was orally administrated to adult rats for 30days. The behavioral training tests indicated that Rb1 improved spatial cognitive performance of rats in Morris water maze (MWM). Furthermore, we investigated the effects of Rb1 on cell genesis in adult rats' hippocampus, using thymidine analog bromodeoxyuridine (BrdU) as a marker for dividing cells. It has been shown that hippocampal cell genesis can be influenced by several factors such as learning and exercise. In order to avoid the effects of the interfering factors, only the rats treated with Rb1 without training in MWM were used to investigate cell genesis in hippocampus. When BrdU was given to the rats 30days prior to being killed, it was shown that oral administration of Rb1 significantly increased cell survival in dentate gyrus and hippocampal subregion CA3. However, when BrdU was injected 2h prior to sacrifice, the results indicated that Rb1 had no significant influence on cell proliferation in the hippocampal subregions. Thus, an increase of cell survival in hippocampus stimulated by Rb1 may be one of the mechanisms by which ginseng facilitates spatial learning and memory. Our study also indicates that Rb1 may be developed as a therapeutic agent for patients with memory impairment.

Ginsenoside Rb1 promotes PC12 cell cycle kinetics through an adenylate cyclase-dependent protein kinase A pathway

Ginsenoside Rb1 (G-Rb1), a constituent of ginseng, bears various beneficial effects on neuroendocrine cells. Previous studies have indicated that G-Rb1 can enhance glutamate release in undifferentiated and differentiated PC12 cells via the protein kinase A (PKA)-dependent signaling pathway. We hypothesized that G-Rb1 stimulates rat adrenomedullary chromaffin cell line PC12 (PC12 cells) proliferation and mitosis by promoting the cell cycle at all regulatory points. This mechanism is partly mediated via the adenylate cyclase-dependent PKA signaling pathway. In the present study, we investigated the mechanism by which G-Rb1 promotes cell cycle kinetics from the PC12 cells. The cell cycle kinetics of these cells were determined using flow cytometric DNA analysis. Analysis of the PC12 cell cycle revealed that G-Rb1 may affect all phases of the cell cycle and accelerate cell cycle kinetics by stimulating G0G1 phase transiting to S and G2M phases. The cell cycle kinetics were decreased by coincubating with the adenylate cyclase inhibitor SQ22536. Compared with the G-Rb1-treated group, the PKA inhibitor H89 produced a marked decrease in the G-Rb1-stimulated cell cycle kinetics by inhibiting G0G1 phase from transiting to the S phase. These results support the position that G-Rb1 exerts a stimulatory effect on cell cycle kinetics to promote PC12 cell proliferation. The result also suggests that the division rate is mediated via the adenylate cyclase-dependent PKA signaling pathway.

Ginsenosides and their CNS targets

Ginsenosides are a special group of triterpenoid saponins attributed to medical effects of ginseng. Therefore, they have been research targets over the last three decades to explain ginseng actions and a wealth of literature has been presented reporting on ginsenosides' effects on the human body. Recently, there is increasing evidence on beneficial effects of ginsenosides to the central nervous system (CNS). Using a wide range of in vitro and in vivo models, researchers have attributed these effects to specific pharmacological actions of ginsenosides on cerebral metabolism, oxidative stress and radical formation, neurotransmitter imbalance and membrane stabilizing effects, and even antiapoptotic effects. Modulating these particular mechanisms by ginsenosides has thus been reported to exert either general stimulatory effects on the brain functions or protecting the CNS against various disease conditions. In this review, we try to address the recently reported ginsenosides' actions on different CNS targets particularly those supporting possible therapeutic efficacies in CNS disorders and neurodegenerative diseases.

Ginsenoside Rb1 regulates the expressions of brain-derived neurotrophic factor and caspase-3 and induces neurogenesis in rats with experimental cerebral ischemia

AIM OF THE STUDY

Recent studies have revealed that ginsenoside Rb1 (GRb1) is neuroprotective for cerebral ischemia. However, the mechanism underlying of this function is unclear. We assessed whether this neuroprotective effect of GRb1 was mediated by the levels of brain-derived neurotrophic factor (BDNF), by the levels of caspase-3 proteins and by induced neurogenesis in rats following transient cerebral ischemia or not.

MATERIALS AND METHODS

Cerebral ischemia was prepared by a 2 h occlusion of the middle cerebral artery and reperfusion, followed by infusion of GRb1 (40 mg/kg) and saline (GRb1 and ischemia groups, respectively). All rats were sacrificed at 3 and 12 h, 1, 2, 3, 5, and 10 days after reperfusion. Normal and sham-operated rats were used in control group. Modified Neurological Severity Scores (mNSS) test and hematoxylin and eosin staining were respectively performed to evaluate neurological function and histological feature. Immunohistochemistry was used to identify intrinsic neurogenesis by nestin antibody. Western blotting was used to detect BDNF and caspase-3 protein content.

RESULTS

GRb1 infusion after cerebral ischemia significantly promoted recoveries of neurological functions at 3 and 5 days after reperfusion compared to ischemic rats. The number of nestin-positive cells was apparently increased after GRb1 infusion compared to ischemia rats at given time. Moreover, BDNF was significantly increased in GRb1-treated rats compared to ischemia rats at different time points. In contrast, GRb1 infusion after the onset of reperfusion, caspase-3 at a given time was significantly reduced compared to ischemia rats, but still significantly increased compared to control rats.

CONCLUSIONS

Promotion of the neurogenesis and regulation of the expressions of BDNF and caspase-3 may be involved in GRb1-induced neuroprotection against cerebral ischemia.

Ginsenosides Rb1 and Rg1 promote proliferation and expression of neurotrophic factors in primary Schwann cell cultures

Ginsenoside Rb1 (GRb1) and ginsenoside Rg1 (GRg1), two major ingredients in ginseng root, have gained extensive attention because of its neuroprotective properties. Thus far, most of the studies on GRb1 and GRg1 have been focused on their neuroprotective effects on neurons. The potential beneficial effects of GRb1 and GRg1 on Schwann cells have not been investigated comprehensively. The present study was designed to examine the possible beneficial effect of GRb1 and GRg1 on proliferation and expression of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in Schwann cells. Schwann cells were incubated without or with GRb1 and GRg1 at different doses. The proliferation of Schwann cells was examined by cell counting. The expression and secretion of NGF and BDNF were examined by western blotting and ELISA. We found that both GRb1 and GRg1 were capable of increasing the proliferation of, and the expression and secretion of NGF and BDNF in Schwann cells. Further studies showed that both GRb1 and GRg1 were able to increase intracellular cyclic AMP (cAMP) level and protein kinase A (PKA) activity. Preincubation with 10 μM H89 (a PKA inhibitor) significantly inhibited the beneficial effects of GRb1 and GRg1 on Schwann cells. These findings indicate that the beneficial effects of GRb1 and GRg1 on proliferation and expression of NGF and BDNF occurs mainly through the PKA pathway in cultured Schwann cells.

Dammarane saponins from Gynostemma pentaphyllum

Dammarane-type saponins (1-7), together with five known compounds, were isolated from the aerial parts of Gynostemma pentaphyllum. Compounds 1-4, 6 and 7 induced the phosphorylation of ERK protein in primary rat cortical neurons, which indicates their potential neuroactivity. On the other hand, no induction of ERK phosphorylation was observed for HEK293 cells following treatment with saponins 1, 3, 4 and 7.

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.

Compound K, a metabolite of ginsenosides, facilitates spontaneous GABA release onto CA3 pyramidal neurons

Ginsenoside Rb1, a major ingredient of ginseng saponins, can affect various brain functions, including learning and memory. When ingested orally, ginsenoside Rb1 is not found in plasma as well as urine, but its metabolite compound K (ComK) reaches the systemic circulation in animals and human. Nevertheless, the pharmacological actions of ComK are still poorly known. In the present study, we investigated the effect of ComK on GABAergic spontaneous miniature inhibitory post-synaptic currents (mIPSCs) in acutely isolated rat hippocampal CA3 pyramidal neurons using a conventional whole-cell patch-clamp technique. While ComK significantly increased mIPSC frequency in a concentration-dependent manner, it had no effect on the current amplitude, suggesting that ComK acts pre-synaptically to increase the probability of spontaneous GABA release. ComK still increased mIPSC frequency even in a Ca(2+) -free external solution, suggesting that the ComK-induced increase spontaneous GABA release is not related to Ca(2+) influx from the extracellular space. However, the ComK-induced increase mIPSC frequency was significantly decreased after the blockade of either sarcoplasmic/endoplasmic reticulum Ca(2+) -ATPase or Ca(2+) release channels. These results strongly suggest that ComK enhances spontaneous GABA release by increasing intraterminal Ca(2+) concentration via Ca(2+) release from pre-synaptic Ca(2+) stores. The ComK-induced modulation of inhibitory transmission onto CA3 pyramidal neurons could have a broad impact on the excitability of CA3 pyramidal neurons and affect the physiological functions mediated by the hippocampus.

Ginsenoside Rg1 promotes glutamate release via a calcium/calmodulin-dependent protein kinase II-dependent signaling pathway

Ginseng is one of most extensively used traditional oriental medicines worldwide with beneficial efficacy on cognitive function disorders. Pharmacological researches on its active ingredient--ginsenoside Rg1 revealed that it can improve learning and memory potentially via modulating neurotransmission in the central nervous system, whereas the specific mechanism involved has not been elucidated yet. Our previous studies have indicated that ginsenoside Rb1 could enhance glutamate release via PKA-dependent signaling pathway whereas Rg1 could enhance glutamate release via PKA-independent signaling pathway. In this work we sought to determine the role of another key mediator in neurotransmitter release--calcium/calmodulin-dependent protein kinase II (CaMKII) in the mechanism of Rg1-enhanced glutamate release. Pre-treatment with CaMKII inhibitor KN93 blocked Rg1-induced glutamate release in primary hippocampal neurons. To investigate how CaMKII was involved in this process, the effect of Rg1 on CaMKII was further studied. Rg1 activated CaMKII and subsequently increased phosphorylation level of Synapsin I (Serine(603), a substrate site of CaMKII)--an abundant phosphoprotein essential for regulating neurotransmitter release, which could be blocked by pre-treatment with CaMKII inhibitor KN93. In conclusion, the present study suggests that Rg1 promotes glutamate release potentially via a CaMKII-dependent signaling pathway in which Synapsin I may potentially act as a downstream effector. Combined with our previous study on Rb1, these two studies altogether indicated that different ginsenosides may promote neurotransmitter release via differential signaling pathways.