Microglia Specific Drug Targeting Using Natural Products for the Regulation of Redox Imbalance in Neurodegeneration

Microglia, a type of innate immune cell of the brain, regulates neurogenesis, immunological surveillance, redox imbalance, cognitive and behavioral changes under normal and pathological conditions like Alzheimer's, Parkinson's, Multiple sclerosis and traumatic brain injury. Microglia produces a wide variety of cytokines to maintain homeostasis. It also participates in synaptic pruning and regulation of neurons overproduction by phagocytosis of neural precursor cells. The phenotypes of microglia are regulated by the local microenvironment of neurons and astrocytes via interaction with both soluble and membrane-bound mediators. In case of neuron degeneration as observed in acute or chronic neurodegenerative diseases, microglia gets released from the inhibitory effect of neurons and astrocytes, showing activated phenotype either of its dual function. Microglia shows neuroprotective effect by secreting growths factors to heal neurons and clears cell debris through phagocytosis in case of a moderate stimulus. But the same microglia starts releasing pro-inflammatory cytokines like TNF-α, IFN-γ, reactive oxygen species (ROS), and nitric oxide (NO), increasing neuroinflammation and redox imbalance in the brain under chronic signals. Therefore, pharmacological targeting of microglia would be a promising strategy in the regulation of neuroinflammation, redox imbalance and oxidative stress in neurodegenerative diseases. Some studies present potentials of natural products like curcumin, resveratrol, cannabidiol, ginsenosides, flavonoids and sulforaphane to suppress activation of microglia. These natural products have also been proposed as effective therapeutics to regulate the progression of neurodegenerative diseases. The present review article intends to explain the molecular mechanisms and functions of microglia and molecular dynamics of microglia specific genes and proteins like Iba1 and Tmem119 in neurodegeneration. The possible interventions by curcumin, resveratrol, cannabidiol, ginsenosides, flavonoids and sulforaphane on microglia specific protein Iba1 suggest possibility of natural products mediated regulation of microglia phenotypes and its functions to control redox imbalance and neuroinflammation in management of Alzheimer's, Parkinson's and Multiple Sclerosis for microglia-mediated therapeutics.

Ginseng ginsenoside pharmacology in the nervous system: involvement in the regulation of ion channels and receptors

Ginseng, the root of Panax ginseng C.A. Meyer, is one of the oldest traditional medicines and is thought to be a tonic. It has been claimed that ginseng may improve vitality and health. Recent studies have advanced ginseng pharmacology and shown that ginseng has various pharmacological effects in the nervous system. Ginsenosides, steroid glycosides extracted from ginseng, were one of the first class of biologically active plant glycosides identified. The diverse pharmacological effects of ginsenosides have been investigated through the regulation of various types of ion channels and receptors in neuronal cells and heterologous expression systems. Ginsenoside Rg3 regulates voltage-gated ion channels such as Ca(2+), K(+), and Na(+) channels, and ligand-gated ion channels such as GABAA, 5-HT3, nicotinic acetylcholine, and N-methyl-D-aspartate (NMDA) receptors through interactions with various sites including channel blocker binding sites, toxin-binding sites, channel gating regions, and allosteric channel regulator binding sites when the respective ion channels or receptors are stimulated with depolarization or ligand treatment. Treatment with ginsenoside Rg3 has been found to stabilize excitable cells by blocking influxes of cations such as Ca(2+) and Na(+), or by enhancing Cl(-) influx. The aim of this review is to present recent findings on the pharmacological functions of the ginsenosides through the interactions with ion channels and receptors. This review will detail the pharmacological applications of ginsenosides as neuroprotective drugs that target ion channels and ligand-gated ion channels.

Effects of Minor Ginsenosides, Ginsenoside Metabolites, and Ginsenoside Epimers on the Growth of Caenorhabditis elegans

In the previous report, we have demonstrated that ginsenoside Rc, one of major ginsenosides, is a major component for the restoration for normal growth of worms in cholesterol-deprived medium. In the present study, we further investigated the roles of minor ginsenosides, such as ginsenoside Rh₁ and Rh₂, ginsenoside metabolites such as compound K (CK), protopanaxadiol (PPD), and protopanaxatriol (PPT) and ginsenoside epimers such as 20(R)- and 20(S)-ginsenoside Rg₃ in cholesterol-deprived medium. We found that ginsenoside Rh₁ almost restored normal growth of worms in cholesterol-deprived medium in F1 generation. However, supplement of ginsenoside Rh₂ caused a suppression of worm growths in cholesterol-deprived medium. In addition, CK and PPD also slightly restored normal growth of worms in cholesterol-deprived medium but PPT not. In experiments using ginsenoside epimers, supplement of 20(S)- but not 20(R)-ginsenoside Rg₃ in cholesterol-deprived medium also almost restored worm growth. These results indicate that the absence or presence of carbohydrate component at backbone of ginsenoside, the number of carbohydrate attached at carbon-3, and the position of hydroxyl group at carbon-20 of ginsenoside might plays important roles in restoration of worm growth in cholesterol-deprived medium.

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 Rg3 activates human KCNQ1 K+ channel currents through interacting with the K318 and V319 residues: a role of KCNE1 subunit

The slowly activating delayed rectifier K(+) channels (I(Ks)) are one of the main pharmacological targets for development of drugs against cardiovascular diseases. Cardiac I(Ks) consists of KCNQ1 plus KCNE1 subunits. Ginsenoside, one of the active ingredient of Panax ginseng, enhances cardiac I(Ks) currents. However, little is known about the molecular mechanisms of how ginsenoside interacts with channel proteins to enhance cardiac I(Ks). In the present study, we investigated ginsenoside Rg(3) (Rg(3)) effects on human I(Ks) by co-expressing human KCNQ1 plus KCNE1 subunits in Xenopus oocytes. Rg(3) enhanced I(Ks) currents in concentration- and voltage-dependent manners. The EC(50) was 15.2+/-8.7 microM. However, in oocytes expressing KCNQ1 alone, Rg(3) inhibited the currents with concentration- and voltage-dependent manners. The IC(50) was 4.8+/-0.6 microM. Since Rg(3) acts opposite ways in oocytes expressing KCNQ1 alone or KCNQ1 plus KCNE1 subunits, we examined Rg(3) effects after co-expression of different ratios of KCNE1 and KCNQ1. The increase of KCNE1/KCNQ1 ratio converted I(Ks) inhibition to I(Ks) activations. One to ten ratio of KCNE1 and KCNQ1 subunit is required for Rg(3) activation of I(Ks). Mutations of K318 and V319 into K318Y and V319Y of KCNQ1 channel abolished Rg(3) effects on KCNQ1 or KCNQ1 plus KCNE1 channel currents. The docked modeling revealed that K318 residue plays a key role in stabilization between Rg(3) and KCNQ1 plus KCNE1 or KCNQ1 subunit. These results indicate that Rg(3)-induced activation of I(Ks) requires co-assembly of KCNQ1 and KCNE1 subunits and achieves this through interaction with residues K318 and V319 of KCNQ1 subunit.

Ginsenosides: are any of them candidates for drugs acting on the central nervous system?

The last two decades have shown a marked expansion in the number of publications regarding the effects of Panax ginseng. Ginsenosides, which are unique saponins isolated from Panax ginseng, are the pharmacologically active ingredients in ginseng, responsible for its effects on the central nervous system (CNS) and the peripheral nervous system. Recent studies have shown that ginsenosides regulate various types of ion channels, such as voltage-dependent and ligand-gated ion channels, in neuronal and heterologously expressed cells. Ginsenosides inhibit voltage-dependent Ca(2+), K(+), and Na(+) channel activities in a stereospecific manner. Ginsenosides also inhibit ligand-gated ion channels such as N-methyl-d-aspartate, some subtypes of nicotinic acetylcholine, and 5-hydroxytryptamine type 3 receptors. Competition and site-directed mutagenesis experiments revealed that ginsenosides interact with ligand-binding sites or channel pore sites and inhibit open states of ion channels. This review will introduce recent findings and advances on ginsenoside-induced regulation of ion channel activities in the CNS, and will further expand the possibilities that ginsenosides may be useful and potentially therapeutic choices in the treatment of neurodegenerative disorders.

Effects of ginsenosides, active ingredients of Panax ginseng, on development, growth, and life span of Caenorhabditis elegans

The backbone structure of ginsenosides, active ingredients of Panax ginseng, is similar with that of sterol, especially cholesterol. Caenorhabditis elegans (C. elegans) is one of free living nematodes and is well-established animal model for biochemical and genetic studies. C. elegans cannot synthesize de novo cholesterol, although cholesterol is essential requirement for its growth and development. In the present study, we investigated the effects of ginseng total saponins (GTS) on the average brood size, growth, development, worm size, and life span of C. elegans in cholesterol-deprived and -fed medium. Cholesterol deprivation caused damages on normal growth, reproduction, and life span of worms throughout F1 to F3 generations. GTS supplement to cholesterol-deprived medium restored the growth, reproduction, and life span of worms as much as cholesterol alone-fed medium. GTS co-supplement to cholesterol-fed medium not only promoted worm reproduction but also induced bigger worms and faster growth than cholesterol-fed medium. In study to identify which ginsenosides are responsible for life span restoring effects of GTS, we found that ginsenoside Rc supplement not only restored life span of worms grown in cholesterol-deprived medium but also prolonged life span of worms grown in cholesterol-fed medium. Worms grown in medium supplemented with ginsenoside Rb(1) or Rc to cholesterol-deprived medium exhibited strong filipin staining, in which filipin forms tight and specific complexes with 3beta-hydroxy sterols. These results show a possibility that ginsenosides could be utilized by C. elegans as a sterol substitute and further indicate that ginsenoside Rc is the component of Panax ginseng that prolongs the life span of C. elegans.

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

Ginseng, the root of Panax ginseng C.A. Meyer (Araliaceae), has been extensively used in traditional oriental medicine for the prevention and treatment of aging-related disorders for over 2000 years. Accumulating evidence suggests that ginsenosides such as Rg1 and Rb1, which are the pharmacologically active ingredients of ginseng, modulate neurotransmission. Synapsins are abundant phosphoproteins essential for regulating neurotransmitter release. All synapsins contain a short amino-terminal domain A that is highly conserved and phosphorylated by cAMP-dependent protein kinase (PKA), which plays a key role in regulating neurotransmitter release. In the present study, we demonstrated that both Rg1 and Rb1 increased neurotransmitter release in undifferentiated and differentiated PC12 cells. However, in the presence of the PKA inhibitor H89, Rg1, but not Rb1, still induced neurotransmitter release. Moreover, Rb1, but not Rg1, enhanced the phosphorylation of synapsins via PKA pathway. In summary, Rb1 promotes neurotransmitter release by increasing the phosphorylation of synapsins through the PKA pathway, whereas the similar effects observed with Rg1 are independent of the phosphorylation of synapsins.

Prevention of ginsenoside-induced desensitization of Ca2+-activated Cl- current by microinjection of inositol hexakisphosphate in Xenopus laevis oocytes: involvement of GRK2 and beta-arrestin I

We demonstrated that ginsenosides, the active ingredient of Panax ginseng, enhance endogenous Ca(2+)-activated Cl(-) currents via Galpha(q/11)-phospholipase C-beta3 pathway in Xenopus laevis oocytes. Moreover, prolonged treatment of ginsenosides induced Cl(-) channel desensitization. However, the molecular mechanisms involved in ginsenoside-induced Cl(-) channel desensitization have not yet been determined precisely. To provide answers to these questions, we investigated the changes in ginsenoside-induced Cl(-) channel desensitization after intraoocyte injection of inositol hexakisphosphate (InsP(6)), which is known to bind beta-arrestins and interfere with beta-arrestin-induced receptor down-regulation, and cRNAs coding beta-arrestin I/II and G-protein receptor kinase 2 (GRK2), which is known to phosphorylate G protein-coupled receptors and attenuate agonist stimulations. When control oocytes were stimulated with ginsenosides, the second, third, and fourth responses to ginsenosides were 69.6 +/- 4.1, 9.2 +/- 2.3, and 2.6 +/- 2.2% of the first responses, respectively. Preintraoocyte injection of InsP(6) before ginsenoside treatment restored ginsenoside effect to initial response levels in a concentration-, time-, and structurally specific manner, in that inositol hexasulfate had no effect. The EC(50) was 13.9 +/- 8.7 microM. Injection of cRNA coding beta-arrestin I but not beta-arrestin II blocked InsP(6) effect on prevention of ginsenoside-induced Cl(-) channel desensitization. Injection of cRNA coding GRK2 abolished ginsenoside effect enhancing Cl(-) current. However, the GRK2-caused loss of ginsenoside effect on Cl(-) current was prevented by coinjection of GRK2 with GRK2-K220R, a dominant-negative mutant of GRK. These results indicate that ginsenoside-induced Cl(-) channel desensitization is mediated via activation of GRK2 and beta-arrestin I.

Addressing use of herbal medicine in the primary care setting

PURPOSE

To critically evaluate existing approaches to the integration of allopathic and complementary and alternative medicine (CAM) and develop a middle ground approach to addressing use of herbal medicine and other forms of CAM in the primary care setting.

DATA SOURCES

Extensive review of scientific literature and Internet sources supported by legal, philosophical, and ethical arguments.

CONCLUSIONS

A review of medical literature indicates that a growing number of people perceive both allopathic and CAM to be valued aspects of health care. Whether we agree with this perception or not, ethical, legal, clinical, and social considerations dictate that we assist patients in their efforts to derive benefit from use of CAM while helping them to minimize risks. Yet the current approach to addressing CAM in primary care is "don't ask, don't tell," with approaches to filling this clinical void ranging from "just say no" to CAM use, to allopathic practitioners who also are CAM practitioners.

IMPLICATIONS FOR PRACTICE

It is possible to occupy the middle ground, neither rejecting nor embracing CAM, but recognizing its significant impact on health care. In order to do this safely, clinicians need to be informed about herbs and other CAM practices, document thoroughly the informed consent and decision-making process, and monitor patients carefully for adverse effects.

Potentiation of warfarin by dong quai

Dong quai is a Chinese herbal supplement touted for treatment of menstrual cramping, irregular menses, and menopausal symptoms. Phytochemical analyses found it to consist of natural coumarin derivatives, as well as constituents possessing antithrombotic, antiarrhythmic, phototoxic, and carcinogenic effects. A 46-year-old African-American woman with atrial fibrillation stabilized on warfarin experienced a greater than 2-fold elevation in prothrombin time and international normalized ratio after taking dong quai concurrently for 4 weeks. No identifiable cause was ascertained for the increase except dong quai. The patient's coagulation values returned to acceptable levels 1 month after discontinuing the herb. One animal study suggests a pharmacodynamic interaction between the product and warfarin, but the true mechanism remains unknown. Practitioners should be aware of the possibility of such an interaction and should inform patients of potential hazards of taking the two together.

Possible influences of ginseng on the pharmacokinetics and pharmacodynamics of warfarin in rats

We evaluated the significance of a reported clinical case of drug-drug interaction between ginseng and warfarin using a robust pharmacokinetic/pharmacodynamic approach in a rat model. The influence of ginseng on the pharmacokinetics and pharmacodynamics of oral warfarin after a single dose (2 mg kg(-1)) and at steady state (0.2 mg kg(-1) daily x 6 days) was studied in male Sprague-Dawley rats. Prothrombin time was employed as a pharmacodynamic index. Warfarin plasma concentration and vitamin K content in the ginseng extract were assessed by validated HPLC assays. The pharmacokinetics of warfarin after a single dose were not altered in the presence of ginseng; peak plasma concentration (control 7.8+/-0.5; ginseng 7.3+/-2.5 microg mL(-1)), time to peak (control 2.6+/-1.0; ginseng 3.1+/-1.1 h), elimination half-life (control 14.3+/-5.8; ginseng 10.6+/-3.1 h), and oral clearance (control 17.5+/-3.3; ginseng 20.2+/-5.5 mL h(-1)) were not significantly different (P>0.05). Similarly, alterations in the pharmacokinetics of warfarin were not detected under the multiple dosing paradigm. Under both dosing conditions, ginseng also showed no significant impact on the pharmacodynamics of warfarin as assessed by the area under the prothrombin time vs time curve (multiple dosing; control 3776+/-619, ginseng 3830+/-362 sh) and maximum prothrombin time (control 57.2+/-11.8, ginseng 63.3+/-9.1 s). Furthermore, the content of vitamin K was undetectable in the ginseng decoction. In conclusion, current data obtained in the rat showed no significant impact of ginseng on the pharmacokinetics/pharmacodynamics of warfarin when they are concomitantly administered.

Panax ginseng pharmacology: a nitric oxide link?

Panax ginseng is used in traditional Chinese medicine to enhance stamina and capacity to cope with fatigue and physical stress. Major active components are the ginsenosides, which are mainly triterpenoid dammarane derivatives. The mechanisms of ginseng actions remain unclear, although there is an extensive literature that deals with effects on the CNS (memory, learning, and behavior), neuroendocrine function, carbohydrate and lipid metabolism, immune function, and the cardiovascular system. Reports are often contradictory, perhaps because the ginsenoside content of ginseng root or root extracts can differ, depending on the method of extraction, subsequent treatment, or even the season of its collection. Therefore, use of standardized, authentic ginseng root both in research and by the public is to be advocated. Several recent studies have suggested that the antioxidant and organ-protective actions of ginseng are linked to enhanced nitric oxide (NO) synthesis in endothelium of lung, heart, and kidney and in the corpus cavernosum. Enhanced NO synthesis thus could contribute to ginseng-associated vasodilatation and perhaps also to an aphrodisiac action of the root. Ginseng is sold in the U.S. as a food additive and thus need not meet specific safety and efficacy requirements of the Food and Drug Administration. Currently, such sales amount to over $300 million annually. As public use of ginseng continues to grow, it is important for this industry and Federal regulatory authorities to encourage efforts to study the efficacy of ginseng in humans by means of appropriately designed double-blind clinical studies.