Ginsenosides stimulate endogenous production of nitric oxide in rat kidney

Inhibitory effects of ginsenoside-rb2 on nicotinic stimulation-evoked catecholamine secretion

The aim of the present study was to investigate whether ginsenoside-Rb2 (Rb2) can affect the secretion of catecholamines (CA) in the perfused model of the rat adrenal medulla. Rb2 (3~30 µM), perfused into an adrenal vein for 90 min, inhibited ACh (5.32 mM)-evoked CA secretory response in a dose- and time-dependent fashion. Rb2 (10 µM) also time-dependently inhibited the CA secretion evoked by DMPP (100 µM, a selective neuronal nicotinic receptor agonist) and high K(+) (56 mM, a direct membrane depolarizer). Rb2 itself did not affect basal CA secretion (data not shown). Also, in the presence of Rb2 (50 µg/mL), the secretory responses of CA evoked by veratridine (a selective Na(+) channel activator (50 µM), Bay-K-8644 (an L-type dihydropyridine Ca(2+) channel activator, 10 µM), and cyclopiazonic acid (a cytoplasmic Ca(2+)-ATPase inhibitor, 10 µM) were significantly reduced, respectively. Interestingly, in the simultaneous presence of Rb2 (10 µM) and L-NAME (an inhibitor of NO synthase, 30 µM), the inhibitory responses of Rb2 on ACh-evoked CA secretory response was considerably recovered to the extent of the corresponding control secretion compared with the inhibitory effect of Rb2-treatment alone. Practically, the level of NO released from adrenal medulla after the treatment of Rb2 (10 µM) was greatly elevated compared to the corresponding basal released level. Collectively, these results demonstrate that Rb2 inhibits the CA secretory responses evoked by nicotinic stimulation as well as by direct membrane-depolarization from the isolated perfused rat adrenal medulla. It seems that this inhibitory effect of Rb2 is mediated by inhibiting both the influx of Ca(2+) and Na(+) into the adrenomedullary chromaffin cells and also by suppressing the release of Ca(2+) from the cytoplasmic calcium store, at least partly through the increased NO production due to the activation of nitric oxide synthase, which is relevant to neuronal nicotinic receptor blockade.

Inhibitory Effects of Total Ginseng Saponin on Catecholamine Secretion from the Perfused Adrenal Medulla of SHRs

There seems to be some controversy about the effect of total ginseng saponin (TGS) on the secretion of catecholamines (CA) from the adrenal gland. Therefore, the present study aimed to determine whether TGS can affect the CA release in the perfused model of the adrenal medulla isolated from spontaneously hypertensive rats (SHRs). TGS (15-150 μg/mL), perfused into an adrenal vein for 90 min, inhibited the CA secretory responses evoked by acetylcholine (ACh, 5.32 mM) and high K⁺ (56 mM, a direct membrane depolarizer) in a dose- and time-dependent fashion. TGS (50 μg/mL) also time-dependently inhibited the CA secretion evoked by 1.1-dimethyl-4 -phenyl piperazinium iodide (DMPP; 100 μM, a selective neuronal nicotinic receptor agonist) and McN-A-343 (100 μM, a selective muscarinic M₁ receptor agonist). TGS itself did not affect basal CA secretion (data not shown). Also, in the presence of TGS (50 μg/mL), the secretory responses of CA evoked by veratridine (a selective Na⁺ channel activator (50 μM), Bay-K-8644 (an L-type dihydropyridine Ca²⁺ channel activator, 10 μM), and cyclopiazonic acid (a cytoplasmic Ca²⁺-ATPase inhibitor, 10 μM) were significantly reduced, respectively. Interestingly, in the simultaneous presence of TGS (50 μg/mL) and Nω-nitro-L-arginine methyl ester hydrochloride [an inhibitor of nitric oxide (NO) synthase, 30 μM], the inhibitory responses of TGS on the CA secretion evoked by ACh, high K⁺, DMPP, McN-A-343, Bay-K-8644, cyclopiazonic acid, and veratridine were considerably recovered to the extent of the corresponding control secretion compared with the inhibitory effect of TGS-treatment alone. Practically, the level of NO released from adrenal medulla after the treatment of TGS (150 μg/mL) was greatly elevated compared to the corresponding basal released level. Taken together, these results demonstrate that TGS inhibits the CA secretory responses evoked by stimulation of cholinergic (both muscarinic and nicotinic) receptors as well as by direct membrane-depolarization from the isolated perfused adrenal medulla of the SHRs. It seems that this inhibitory effect of TGS is mediated by inhibiting both the influx of Ca²⁺ and Na⁺ into the adrenomedullary chromaffin cells and also by suppressing the release of Ca²⁺ from the cytoplasmic calcium store, at least partly through the increased NO production due to the activation of nitric oxide synthase, which is relevant to neuronal nicotinic receptor blockade, without the enhancement effect on the CA release. Based on these effects, it is also thought that there are some species differences in the adrenomedullary CA secretion between the rabbit and SHR.

Inhibitory Effect of Ginsenoside Rg1 on Vascular Smooth Muscle Cell Proliferation Induced by PDGF-BB Is Involved in Nitric Oxide Formation

Ginsenoside Rg1 (Rg1) has been reported to suppress the proliferation of vascular smooth muscle cells (VSMCs). This study aimed to observe the role of nitric oxide (NO) in Rg1-antiproliferative effect. VSMCs from the thoracic aorta of SD rats were cultured by tissue explant method, and the effect of Rg1 (20 mg·L⁻¹, 60 mg·L⁻¹, and 180 mg·L⁻¹) on platelet-derived growth factor-BB (PDGF-BB)-induced proliferation was evaluated by MTT assay. The cell cycle was analyzed by flow cytometry. For probing the mechanisms, the content of NO in supernatant and cGMP level in VSMCs was measured by nitric oxide kit and cGMP radio-immunity kit, respectively; the expressions of protooncogene c-fos and endothelial NO synthase (eNOS) mRNA in the VSMCs were detected by real-time RT-PCR; the intracellular free calcium concentration ([Ca2⁺]_i) was detected with Fura-2/AM-loaded VSMCs. Comparing with that in normal group, Rg1 180 mg·L⁻¹ did not change the absorbance of MTT and cell percent of G₀/G₁, G₂/M, and S phase in normal cells (P > 0.05). Contrarily, PDGF-BB could increase the absorbance of MTT (P < 0.01) and the percent of the S phase cells but decrease the G₀/G₁ phase cell percent in the cell cycle, accompanied with an upregulating c-fos mRNA expression (P < 0.01), which was reversed by additions of Rg1(20 mg·L⁻¹, 60 mg·L⁻¹, and 180 mg·L⁻¹). Rg1 administration could also significantly increase the NO content in supernatant and the cGMP level in VSMCs, as well as the eNOS mRNA expression in the cells, in comparison of that in the group treated with PDGF-BB alone (P < 0.01). Furthermore, Rg1 caused a further increase in the elevated [Ca²⁺]_i induced by PDGF-BB. It was concluded that Rg1 could inhibit the VSMC proliferation induced by PDGF-BB through restricting the G₀/G₁ phase to S-phase progression in cell cycle. The mechanisms may be related to the upregulation of eNOS mRNA and the increase of the formation of NO and cGMP.

Role of nitric oxide in ginsenoside Rg(1)-induced protection against left ventricular hypertrophy produced by abdominal aorta coarctation in rats

Ginsenoside Rg(1) (Rg(1)), one of the active components of Panax ginseng, has been reported to promote endogenous nitric oxide (NO) production in some tissues, and to inhibit left ventricular (LV) hypertrophy in rats. This study aimed to investigate whether Rg(1)-induced inhibition of rat LV hypertrophy is mediated by NO-production. Rat LV hypertrophy was induced by abdominal aorta coarctation. Rg(1) 15 mg/kg/d, L-arginine 200 mg/kg/d, and the nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine-methyl ester (L-NAME) 100 mg/kg/d used with the same dose of L-arginine or Rg(1) were given starting from 1 d after surgery for 21 consecutive days. LV hypertrophy was evidenced by determining LV weight and mRNA expression of atrial natriuretic peptide, a marker of cardiac hypertrophic response, as well as by histopathology. Rg(1) and L-arginine administration significantly reduced the elevated LV hypertrophic parameters independent of LV systolic pressure changing, and ameliorated the histopathology of LV myocardium and LV diastolic function. All the beneficial effects of Rg(1) and L-arginine were abolished or blunted by L-NAME. Further to examine the role of NO in Rg(1) inhibition on LV hypertrophy, expression of endothelial NOS was determined at the transcript levels. In our experimental conditions endothelial NOS mRNA expression in LV tissue was lowered by abdominal aorta coarctation, and upregulated by Rg(1) administration. These results demonstrate that Rg(1)-induced protection against LV hypertrophy elicited by abdominal aorta coarctation in rats is mediated, at least in part, via endogenous NO production and release.

Total ginsenosides inhibit the right ventricular hypertrophy induced by monocrotaline in rats

Ginsenosides have been reported to release nitric oxide (NO) and decrease intracellular free Ca(2+) in cardiovascular system, which play important roles in antihypertrophic effect. This study investigated the potential inhibitory effect of total ginsenosides (TG) on right ventricular hypertrophy induced by monocrotaline (MCT, 60 mg/kg/d) and examined the possible antihypertrophic mechanism in male Sprague Dawley rats. MCT-intoxicated animals were treated with TG (20, 40, 60 mg/kg/d) for 18 d. TG treatment ameliorated MCT-induced elevations in right ventricular peak systolic pressure, right ventricular hypertrophy and the expression of atrial natriuretic peptide; N(G)-nitro-L-arginine-methyl ester (L-NAME), an NO synthase (NOS) inhibitor, had no influence on these inhibitory effects of TG 40 mg/kg/d, and TG at this dose had no any effect on the eNOS mRNA expression, suggesting the limited rule of NO in TG's effects. To further examine the mechanisms of the protection, the expression of calcineurin and its catalytic subunit CnA, as well as extracellular signal-regulated kinase-1 (ERK-1) and mitogen-activated protein kinase (MAPK) Phosphatase-1 (MKP-1) was examined. TG treatment significantly suppressed MCT-induced elevations of these signaling pathways in a dose-dependent manner. In summary, TG is effective in protecting against MCT-induced right ventricle hypertrophy, possibly through lowering pulmonary hypertension. Multiple molecular mechanisms appeared to be involved in this protection, such as the suppression of MCT-activated calcineurin and ERK signaling pathways.

Effect of sun ginseng methanol extract on lipopolysaccharide-induced liver injury in rats

Sun ginseng (SG) is heat-processed Panax ginseng C.A. Meyer steamed at 120 degrees C, which has ginsenoside-Rg(3), -Rk(1), and -Rg(5) as its main ginsenoside components. The effect of SG on lipopolysaccharide (LPS)-induced liver injury in rats was investigated in this study. Intravenous injection of LPS induced excessive nitric oxide (*NO) generation in serum and increased the hepatic mitochondrial thiobarbituric acid-reactive substance (TBA-RS) level. However, the elevated TBA-RS level was significantly lowered by 15 consecutive days of SG administrations. In addition, up-regulated hepatic inducible nitric oxide synthase and heme oxygenase 1 levels in LPS-treated control rats were significantly lowered and increased, respectively, by 100 mg/kg body weight/day of SG administration. These antioxidant effects were thought to be partially related to the deactivation of nuclear factor-kappaB by SG administration.

Effect of Panax ginseng extract (G115) on angiotensin-converting enzyme (ACE) activity and nitric oxide (NO) production

This study investigates the effects of the Panax ginseng (Araliaceae) extract G115 on angiotensin-converting enzyme (ACE) activity and nitric oxide (NO) in cultured human endothelial cells from umbilical veins (HUVEC) and bovine mesenteric arteries (BMA). In HUVEC, ACE activity was significantly reduced after 10 min incubation with aqueous extract of ginseng 5.0 and 10 mg/ml. This effect was additative with the inhibition of the traditional ACE inhibitor enalaprilat. No effect was seen on NO production from the cells. Angiotensin I-induced contraction of BMA was significantly attenuated by 0.1 and 0.5 mg/ml ginseng, while no endothelium-dependent or -independent relaxation was seen. In conclusion, extract of Panax ginseng (G115) inhibits ACE activity, but does not affect NO production in HUVEC and BMA.

Single doses of Panax ginseng (G115) reduce blood glucose levels and improve cognitive performance during sustained mental activity

Single doses of the traditional herbal treatment Panax ginseng have recently been shown to elicit cognitive improvements in healthy young volunteers. The mechanisms by which ginseng improves cognitive performance are not known. However, they may be related to the glycaemic properties of some Panax species. Using a double-blind, placebo-controlled, balanced crossover design, 30 healthy young adults completed a 10 min test battery at baseline, and then six times in immediate succession commencing 60 min after the day's treatment (placebo, 200mg G115 or 400mg G115). The 10 min battery comprised a Serial Threes subtraction task (2 min); a Serial Sevens task (2 min); a Rapid Visual Information Processing task (5 min); then a 'mental fatigue' visual analogue scale. Blood glucose was measured prior to each day's treatment, and before, during and after the post-dose completions of the battery. Both the 200mg and 400mg treatments led to significant reductions in blood glucose levels at all three post-treatment measurements (p 0.005 in all cases). The most notable behavioural effects were associated with 200mg of ginseng and included significantly improved Serial Sevens subtraction task performance and significantly reduced subjective mental fatigue throughout all (with the exception of one time point in each case) of the post-dose completions of the 10 min battery (p 0.05). Overall these data suggest that Panax ginseng can improve performance and subjective feelings of mental fatigue during sustained mental activity. This effect may be related to the acute gluco-regulatory properties of the extract.

Alternative therapies for male and female sexual dysfunction

Sexual dysfunction is prevalent in both men and women. Although new pharmaceutical agents have been identified for male erectile problems, sexual desire and orgasm disorders, individuals with sexual dysfunction often seek alternative therapies, including traditional Chinese medicine. This article reviews currently used alternative therapies, such as herbal medications, L-arginine, acupuncture, biofeedback and others. Potential herb-drug interactions are also presented.

Ginseng: potential for the enhancement of cognitive performance and mood

Ginseng has been used medicinally in the Far East for several millennia and is currently one of the most widely taken herbal products throughout the world. It has been attributed with a plethora of physiological effects that could potentially benefit cognitive performance or mood. Studies involving animals show that ginseng and its constituent ginsenosides can modulate indices of stress, fatigue, and learning. However, there is a lack of adequately controlled research showing behavioural effects following chronic administration to humans. Recent research has demonstrated that single doses of ginseng most notably engender cognitive benefits in terms of improved memory, but can also be associated with 'costs' in terms of attention task deficits following less mnemonically beneficial doses. A single dose of ginseng has also been shown to modulate cerebroelectrical (EEG) activity. It is suggested that ginseng would benefit from rigorous research further delineating its acute effects and exploring the relationship between acute effects and those seen during and following chronic administration regimens.

Stimulation of nitric oxide synthesis by the aqueous extract of Panax ginseng root in RAW 264.7 cells

1. In this study, we investigated the effect of Panax ginseng root aqueous extracts upon inducible nitric oxide synthesis in RAW 264.7 cells. Panax ginseng root extract has been used in the Asian world for centuries as a traditional herb to enhance physical strength and resistance and is becoming more and more popular in Europe and North America. 2. Incubation of murine macrophages (RAW 264.7 cells) with increasing amounts of aqueous extracts of Panax ginseng (0.05 - 0.8 microg microl(-1)) showed a dose dependent stimulation of inducible nitric oxide synthesis. 3. Polysaccharides isolated from Panax ginseng showed strong stimulation of inducible nitric oxide synthesis, whereas a triterpene-enriched fraction from an aqueous extract of Panax ginseng did not show any stimulation. 4. Inducible nitric oxide synthase protein expression was enhanced in a dose dependent manner as revealed by immunoblotting when cells were incubated with increasing amounts of Panax ginseng extract. This was associated with an incline in inducible nitric oxide synthase mRNA-levels as determined by semiquantitative polymerase chain reaction and electromobility shift assay studies indicated enhanced nuclear factor-kappaB DNA binding activity. 5. As nitric oxide plays an important role in immune function, Panax ginseng treatment could modulate several aspects of host defense mechanisms due to stimulation of the inducible nitric oxide synthase.

A double-blind placebo-controlled study of ArginMax, a nutritional supplement for enhancement of female sexual function

This study was open to women over the age of 21 years with an interest in improving their sexual function. Of the 77 participants, 34 received ArginMax and 43 received a placebo. ArginMax for Women is a proprietary nutritional supplement consisting of extracts of ginseng, ginkgo, and damiana, L-arginine, multivitamins, and minerals. After 4 weeks, 73.5% of the ArginMax group improved in satisfaction with their overall sex life, compared with 37.2% of the placebo group (p < 0.01). Notable improvements were also observed in sexual desire, reduction of vaginal dryness, frequency of sexual intercourse and orgasm, and clitoral sensation. No significant side effects were noted.

Ginsenoside potentiates NO-mediated neurogenic vasodilatation of monkey cerebral arteries

The aqueous extract of the Panax ginseng (GE) potentiated the relaxation induced by transmural electrical stimulation or nicotine in monkey cerebral arterial strips denuded of the endothelium and partially contracted with prostaglandin F(2 alpha). The response to electrical stimulation was abolished by tetrodotoxin, whereas that to nicotine was suppressed by hexamethonium. N(G)-nitro-L-arginine abolished both of the neurogenic relaxation. Atropine did not alter the potentiating effect of GE. Relaxations induced by exogenous NO were unaffected by GE. The enhancement by GE, of the neurogenic response, appears to be associated with increment in the synthesis or release of NO from the perivascular nerve. Blockade of muscarinic prejunctional inhibition, superoxide scavenging action and phosphodiesterase inhibition are not involved.

K(Ca) channel-opening activity of Ginkgo Biloba extracts and ginsenosides in cultured endothelial cells

1. Extracts of Ginkgo biloba (EGb) and ginsenosides (GS) have been reported to induce vasorelaxation. In the present study, the role of K+ channels in the action of EGb and GS to activate nitric oxide synthase (NOS) activity was investigated in cultured endothelial cells. 2. Nitric oxide synthase activity of cultured endothelial cells detected by the reduced nicotinamide adenine dinucleotide phosphate (NADPH) histochemistry method was significantly increased after treatment with 20 microg/mL EGb or 40 microg/mL GS plus 10 mmol/L L-arginine. The effect was completely abolished by the addition of 0.5 micromol/L Nomega-nitro-L-arginine, an inhibitor of NOS, to the incubation medium and partially inhibited by 10 micromol/L tetraethylammonium (TEA), an inhibitor of Ca2+-activated K+ (KCa) channels. 3. Application of EGb to the intracellular surface of excised inside-out patches activated K+ channels in a concentration-dependent manner in the concentration range 1-100 microg/mL. Channel activity was also activated by application of GS at concentrations ranging from 1 to 300 microg/mL. The modulation of channel activity was inhibited by 0.5 mmol/L TEA but not by 0.5 mmol/L glibenclamide, an inhibitor of ATP-sensitive K+ channels. 4. Thus, in cultured endothelial cells, the increase in NOS activity induced by EGb or GS depends on the activity of KCa channels. These compounds may regulate nitric oxide release by changing the cell membrane potential in vascular endothelial cells.

Ginsenoside Rg3 mediates endothelium-dependent relaxation in response to ginsenosides in rat aorta: role of K+ channels

The aim of the present study was to characterize the endothelium-dependent relaxation elicited by ginsenosides, a mixture of saponin extracted from Panax ginseng, in isolated rat aorta. Relaxations elicited by ginsenosides were mimicked by ginsenoside Rg1 and ginsenoside Rg1, two major ginsenosides of the protopanaxatriol group. Ginsenoside Rg3 was about 100-fold more potent than ginsenoside Rg1. The endothelium-dependent relaxation in response to ginsenoside Rg3 was associated with the formation of cycle GMP. These effects were abolished by N(G)-nitro-L-arginine and methylene blue. Relaxations in response to ginsenoside Rg3 were unaffected by atropine, diphenhydramine, [D-Pro2, D-Trp7,9]substance P, propranolol, nifedipine, verapamil and glibenclamide but were markedly reduced by tetraethylammonium. Tetraethylammonium modestly reduced the relaxation induced by sodium nitroprusside. These findings indicate that ginsenoside Rg3 is a major mediator of the endothelium-dependent nitric oxide-mediated relaxation in response to ginsenosides in isolated rat aorta, possibly via activation of tetraethylammonium-sensitive K+ channels.

Inhibition of stress-induced plasma corticosterone levels by ginsenosides in mice: involvement of nitric oxide

Ginseng total saponins (GTS) injected intracerebroventricularly (i.c.v.) at doses of 0.1-1 microg inhibited the i.c.v. injection stress-induced plasma corticosterone levels in mice. The inhibitory action of GTS was blocked by co-administered N(G)-nitro-L-arginine methyl ester (L-NAME; 1.5 microg, i.c.v.), an inhibitor of nitric oxide synthase (NOS). Of the ginsenosides Rb1, Rb2, Rc, Rd, Re, Rf, Rg1, 20(S)-Rg3 and 20(R)-Rg3 injected i.c.v. at doses of 0.01-1 microg, 20(S)-Rg3 and Rc significantly inhibited the i.c.v. injection stress-induced plasma corticosterone levels. The inhibitory actions of 20(S)-Rg3 and Rc were blocked by co-administered L-NAME (1.5 microg, i.c.v.). These results suggest that GTS, 20(S)-Rg3 and Rc may inhibit the i.c.v. injection stress-induced hypothalamo-pituitary-adrenal response by inducing NO production in the brain.

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.