Effect of ginseng saponins on a rat visceral hypersensitivity model

The 5-hydroxytryptamine3A (5-HT3) receptor is closely related with irritable bowel syndrome (IBS) in enteric nervous systems. We previously demonstrated that ginseng total saponins (GTS, also called ginsenosides), the active ingredients of Panax ginseng, inhibit the activity of 5-HT3A receptor channels expressed in Xenopus laevis oocytes. Here, we further investigated whether the in vitro inhibitory effect of ginsenosides on 5-HT3A receptor channel activity is coupled to in vivo attenuation of IBS. A rat model of IBS was induced by colorectal distention (CRD) and intracolonic infusion of 0.6% acetic acid (CRD-acetic acid), and visceral hypersensitivity was assessed by counting the contractions in the external oblique muscles of conscious rats during the 10 min distention period. We found that oral administration of GTS significantly and dose-dependently inhibited CRD-acetic acid-induced visceral hypersensitivity. The EC50 was 5.5+/-4.7 mg/kg (95% confidence intervals: 1.2-15.7) and the inhibitory effect of GTS against visceral hypersensitivity persisted for 4 h. When we compared the effects of protopanaxadiol (PD) ginsenosides and protopanaxatriol (PT) ginsenosides against CRD-acetic acid-induced visceral hypersensitivity, we found that PT but not PD ginsenosides significantly attenuated the CRD-acetic acid-induced visceral hypersensitivity. These results indicate that PT ginsenosides of Panax ginseng might be the main active components for the attenuation of experimentally CRD-acetic acid-induced visceral hypersensitivity, and may be clinically relevant for the future treatment of IBS.     

Selective down-regulation of c-jun gene expression by pentoxifylline and c-jun antisense interrupts platelet-derived growth factor signaling: pentoxifylline inhibits phosphorylation of c-Jun on serine 73

Platelet-derived growth factor (PDGF) signals through several pathways, including mitogen-activated protein (MAP) kinase, Jun kinase, and C kinase, and stimulates proliferation of fibroblasts. Pentoxifylline inhibits PDGF-driven proliferation of fibroblasts. We have reported that pentoxifylline did not inhibit binding of PDGF to its specific cell-surface receptors or PDGF receptor phosphorylation. In this study, we investigated the effect of PDGF on the expression of c-fos and c-jun, because c-fos and c-jun form activator protein-1 complexes that stimulate genes involved in proliferation. We determined whether pentoxifylline would alter the expression of c-fos and c-jun. Our results indicate that PDGF induced the expression of both c-fos and c-jun. Pentoxifylline effectively reduced c-jun gene expression, which had been up-regulated by PDGF, but did not alter c-fos gene expression. The lack of effect on c-fos supports other studies from this laboratory, which indicate that pentoxifylline did not inhibit PDGF activation of MAP kinase. Treatment of fibroblasts with a phosphothioate c-jun antisense oligodeoxynucleotide reduced the levels of c-Jun protein and blocked PDGF-stimulated proliferation, suggesting a critical role for c-jun in PDGF-mediated proliferation. Combination of pentoxifylline and c-jun antisense suggested that they were likely inhibiting PDGF-stimulated proliferation at a single site in the PDGF signaling pathway. These results suggest that pentoxifylline inhibits PDGF-stimulated proliferation by selectively decreasing c-jun expression. To further define the mechanism of action of pentoxifylline, we assessed the effect of pentoxifylline on c-Jun and phosphorylated c-Jun immunoreactivity in cells treated with PDGF and cells that were transfected with wild-type c-jun plasmid using immunocytochemistry and Western blot analyses, and our results indicate that pentoxifylline inhibited phosphorylation of c-Jun on serine 73.     

Expression of core binding factor alpha1 up-regulated by IGF-I, GM-CSF, and EGF through MAPK pathway in MC3T3-E1 and C2C12 cells

AIM: To study the regulating function and mechanism of insulin-like growth factor-I (IGF-I), granulocyte-macrophage colony-stimulating factor (GM-CSF), and epidermal growth factor (EGF) on murine core binding factor alpha1 (Cbfalpha1) gene expression. METHODS: Luciferase reporter gene method and RT-PCR technique were used to examine the effects of these growth factors on the promoter activity and mRNA expression of Cbfalpha1 gene in MC3T3-E1 and C2C12 cells. RESULTS: IGF-I (from 1 nmol/L to 1 micromol/L), GM-CSF (100 nmol/L), and EGF (1 micromol/L) increased the luciferase expression in MC3T3-E1 cells (P<0.05). And mitogen-activated protein kinase (MAPK) inhibitor, PD 98059 (10 micromol/L), completely blocked IGF-1, GM-CSF, and EGF-induced expression of Cbfa1 promoter activity (P<0.01). In C2C12 cells, IGF-I (from 1 nmol/L to 10 micromol/L), GM-CSF (100 nmol/L and 1 micromol/L), and EGF (100 nmol/L) enhanced the expression of luciferase reporter plasmid driven by mCbfalpha1 promoter (P<0.05). Addition of PD 98059 also blocked the stimulatory effects of these growth factors on Cbfalpha1 promoter activity (P<0.01). Moreover, Cbfalpha1 mRNA expression was significantly increased after treatment with IGF-I (1 nmol/L, 100 nmol/L), GM-CSF (100 nmol/L, 1 micromol/L), and EGF (1 micromol/L, 100 nmol/L) in MC3T3-E1 and C2C12 cells, respectively (P<0.05). These stimulatory effects of IGF-I, GM-CSF, and EGF on Cbfalpha1 mRNA expression were abolished by PD 98059. CONCLUSION: IGF-I, GM-CSF, and EGF could increase the promoter activity and the mRNA expression of murine Cbfalpha1 gene in MC3T3-E1 and C2C12 cells. These stimulatory effects might be mediated by activating the intracellular MAPK-dependent signaling pathway.     

Effect ofPanax ginseng on the development of morphine induced tolerance and dependence (VI). On the oral administration of ginseng ether fraction and saponins

The present study was undertaken to determine the inhibitory effects of orally adminstered ginseng saponins(GS), protopanaxadiol saponins(PD), protopanaxatriol saponins(PT) and ginseng ether fraction(GE) on the development of morphine induced tolerance and physical dependence in mice and also to determine the hepatic glutathione contents. GS, PD and PT inhibited significantly the development of morphine induced tolerance and physical dependence, but GE was effective only on the inhibition of the development of morphine induced physical dependence. GS, PD, PT and GE also inhibited the hepatic glutathione level decrease induced by morphine multiple injections.     

The immediate early genes,c-fos,c-jun and AP-1, are early markers of platinum analogue toxicity in human proximal tubular cell primary cultures

These studies tested the hypothesis that c-fos, c-jun and AP-1 are early markers of platinum analogue-induced proximal tubule nephrotoxicity in primary rat proximal tubule (RPT) and human proximal tubule (HPT) cell cultures. The order of platinum analogue toxicity was cisplatin > transplatin > carboplatin in RPT and HPT cultures. Following a 2-h platinum analogue treatment, c-fos protein expression correlated with toxicity. Maximal c-fos protein levels were observed at 8-h (RPT) and 4-h (HPT) post-platinum analogue treatment. c-jun and AP-1 protein levels were maximal 4-h and 8-h, respectively, post cisplatin treatment in HPT cultures. In contrast, c-jun and AP-1 protein were not detected in RPT cultures. c-fos and c-jun mRNA levels were maximal at 60 and 120-min in RPT cell cultures, respectively, whilst c-fos and c-jun mRNA levels were maximal at 120-min in HPT cultures. Differences between HPT and RPT responses to cisplatin reveal inter-species differences associated with induction of c-fos and c-jun mRNA and protein, which in turn form the functional AP-1 complex prior to the onset of cellular toxicity. These studies highlight the utility of HPT cultures as an in vitro model system, and the potential of c-fos and c-jun as early markers of nephrotoxicity to screen therapeutic lead compounds.     

Metabolism of ginsenoside Re by human intestinal microflora and its estrogenic effect

To understand the relationship between the metabolism and biological activity of ginsenoside Re, a main protopanaxatriol saponin in Panax ginseng C. A. MEYER, its metabolic pathway and estrogenic effect by human intestinal microflora were investigated. All human fecal specimens metabolized ginsenoside Re, mainly to ginsenoside Rh1 and ginsenoside F1, via ginsenoside Rg1, with protopanaxadiol as a minor component. Almost all isolated ginsenoside Re-metabolizing intestinal bacteria (GHIB) also metabolized ginsenoside Re, mainly to ginsenosides Rh1 and F1, via ginsenoside Rg1. Alpha-Rhamnosidase and beta-glucosidase, partially purified from the most potent GHIB, Bacteroides JY-6, hydrolyzed ginsenoside Re and ginsenoside Rg1, respectively; however, they did not hydrolyze ginsenosides Rh1 and F1. These findings suggest that the ginsenosides Rh1 and/or F1 may not be suitable substrates of intestinal bacteria, particularly Bacteroides JY-6. The estrogenic effects of ginsenoside Re and its main metabolites, ginsenosides Rg1 and Rh1, were also investigated. Ginsenoside Rh1 showed the greatest estrogenic effect in human breast carcinoma MCF-7 cells. Based on these findings, the estrogenic effect of ginsenoside Re may be expressed by intestinal microflora.     

Effects of the Ginsenosides Rg1 and Rb1 on Morphine-induced Hyperactivity and Reinforcement in Mice

Recent studies have demonstrated that ginseng saponin inhibits the hyperactivity and conditioned place-preference response induced by psychostimulants and opiates. This seems to occur by direct or indirect modulation of dopaminergic activity. However, it is not known which components of ginseng saponin are active. These experiments were conducted to determine the effects of the ginsenosides Rb₁ and Rg₁, major components of the protopanaxadiol and protopanaxatriol fractions of ginseng saponin, on morphine-induced hyperactivity and conditioned place-preference. Morphine-induced hyperactivity, but not apomorphine-induced climbing behaviour, was inhibited by both Rb₁ and Rg₁. These findings confirm the hypothesis that ginsenosides modulate catecholaminergic activity preferentially at pre-synaptic sites. Morphine-induced conditioned place-preference was inhibited by Rg₁, but not by Rb₁. It has previously been shown that at low doses Rb₁ and Rg₁ are equally effective at inhibition of catecholamine secretion at the pre-synaptic site, but that at high doses Rg₁ is a more effective inhibitor. This observation might explain our finding that morphine-induced conditioned place-preference was inhibited by Rg₁ only. Our findings suggest that Rg₁, a component of ginseng saponin with appropriate activity, might be a useful agent for prevention and treatment of the adverse effects of morphine.     

Differential effect of bovine serum albumin on ginsenoside metabolite-induced inhibition of α3β4 nicotinic acetylcholine receptor expressed in<Emphasis Type="Italic">Xenopus</Emphasis> oocytes

Ginsenosides, major active ingredients of Panax ginseng, that exhibit various pharmacological and physiological actions are transformed into compound K (CK) or M4 by intestinal microorganisms. CK is a metabolite derived from protopanaxadiol (PD) ginsenosides, whereas M4 is a metabolite derived from protopanaxatriol (PT) ginsenosides. Recent reports shows that ginsenosides might play a role as pro-drugs for these metabolites. In present study, we investigated the effect of bovine serum albumin (BSA), which is one of major binding proteins on various neurotransmitters, hormones, and other pharmacological agents, on ginsenoside Rg2-, CK-, or M4-induced regulation of alpha3beta4 nicotinic acetylcholine (ACh) receptor channel activity expressed in Xenopus oocytes. In the absence of BSA, treatment of ACh elicited inward peak current (I(ACh)) in oocytes expressing alpha3beta4 nicotinic ACh receptor. Co-treatment of ginsenoside Rg2, CK, or M4 with ACh inhibited I(ACh) in oocytes expressing (alpha3beta4 nicotinic ACh receptor with reversible and dose-dependent manner. In the presence of 1% BSA, treatment of ACh still elicited I(ACh) in oocytes expressing alpha3beta4 nicotinic ACh receptor and co-treatment of ginsenoside Rg2 or M4 but not CK with ACh inhibited I(ACh) in oocytes expressing alpha3beta4 nicotinic ACh receptor with reversible and dose-dependent manner. These results show that BSA interferes the action of CK rather than M4 on the inhibitory effect of I(ACh) in oocytes expressing alpha3beta4 nicotinic ACh receptor and further suggest that BSA exhibits a differential interaction on ginsenoside metabolites.     

柚皮苷对乳鼠成骨细胞增殖及c-fos、c-jun表达的影响

目的研究柚皮苷(naringin)对体外培养的小鼠成骨细胞增殖及c-fos和c-jun表达的影响。方法取第1代BALB/c小鼠颅盖骨成骨细胞,将柚皮苷以0.1、1、10μmol·L-1 3种浓度分别加入新生大鼠颅骨成骨细胞培养液中,MTT法观察各组对成骨细胞的增殖作用并绘制细胞生长曲线,用PNPP法测定成骨细胞内碱性磷酸酶(alkaliphos-phatase,ALP)活性,RT-PCR法检测成骨细胞c-fos和c-jun的转录水平。结果细胞生长曲线显示各组成骨细胞数量均随时间延长而增加,中、高浓度的柚皮苷能提高成骨细胞的ALP活性,促进c-fos mRNA表达(P<0.01),对成骨细胞c-jun mRNA表达增强作用不明显(P>0.05)。结论低浓度柚皮苷(0.1μmol·L-1)对骨更新作用不明显,而中、高浓度的柚皮苷(1、10μmol·L-1)能通过上调c-fos mRNA表达,促进成骨细胞的生成功能,增强骨更新。柚皮苷不是通过促进c-jun表达来促进成骨细胞增殖与分化的。     

Cloning of the pig PEPT2 (pPEPT2) and characterization of the effects of epidermal growth factor (EGF) on pPEPT2-mediated peptide uptake in the renal porcine cell line LLC-PK1

The renal di/tri-peptide transporter PEPT2 is situated in the distal parts of the proximal tubule, where it mediates reabsorption of peptides from the primary urine. The transporter has been thoroughly characterised with respect to substrate–affinity relationships, however little is known about its regulation. Previous studies from our group have shown that epidermal growth factor (EGF) down-regulates PepT2 in the rat proximal kidney tubule cell line SKPT0193 cl.2. The aim of the present work was to clone the pig PEPT2 (pPEPT2) and to study the effect of EGF on pPEPT2 expression in the porcine kidney cell line LLC-PK1. pPEPT2 from LLC-PK1 cells was PCR-cloned. The predicted protein consisted of 729 amino acids, had a molecular mass of 81.7 kDa and was 88% identical and 94% similar to hPEPT2, thus displaying a close similarity to the human orthologue. pPepT2 expressing LLC-PK1 cells were cultured in the absence and presence of EGF in the culture media. EGF induced an increase in uptake of ¹⁴C-glycylsarcosine ([¹⁴C]-Gly-Sar), accompanied by an increase in transcellular electrical resistance, total cell protein, alkaline phosphatase activity and cell density. The increase in uptake of [¹⁴C]-Gly-Sar was maximal when cells were cultured in the presence of EGF throughout the culture period of 10 days. The EGF-treatment did not induce significant changes in pPepT2 mRNA expression, as determined by real-time PCR. The effect of EGF thus appears to be an increase in the number of cells without a loss of differentiation, an effect which is quite different from earlier observations on the SKPT cell line.     

Epidermal growth factor-mediated activation of the map kinase cascade results in altered expression and function of ABCG2 (BCRP).

Epidermal growth factor (EGF) is a multifunctional growth factor known to play a major role in proliferation and differentiation processes. EGF-induced differentiation is a prerequisite for function of various cell types, among them cytotrophoblasts, a functionally important cellular fraction in human placenta. Stimulation of cytotrophoblasts with EGF results in formation of a multinuclear syncytium representing the feto-maternal interface, which protects the fetus against exogenous substances. It is well established that part of this protection system is based on ATP-binding cassette (ABC) transporters such as ABCG2 (breast cancer resistance protein, BCRP). However, little is known about regulation of transport proteins in the framework of EGF-mediated cellular differentiation. In the present work we show a significant increase of ABCG2 expression by EGF in cytotrophoblasts, BeWo, and MCF-7 cells on both mRNA and protein levels. This increase resulted in decreased sensitivity to the ABCG2 substrates mitoxantrone and topotecan. In each cell type, EGF increases expression of ABCG2 by activation of mitogen-activated protein kinase cascade via phosphorylation of extracellular regulated kinase (ERK)1/2 and c-jun NH-terminal kinase/stress-activated protein kinase (JNK/SAPK). Consequently, the increase of ABCG2 by EGF was abolished by pretreatment of cells with the tyrosine kinase inhibitor 4-(3-chloroanillino)-6,7-dimethoxyquinazoline (AG1478) or the mitogen-activated protein kinase kinase inhibitor 2'-amino-3'methoxyflavone (PD 98059), thereby reestablishing sensitivity toward mitoxantrone. Moreover, analysis of ABCG2 expression during placental development revealed a significant increase in preterm versus term placenta. Taken together, our data show regulation of ABCG2 expression by EGF. In view of EGF signal transduction as a target for drugs (e.g., gefitinib), which are in turn substrates and/or inhibitors of ABCG2, this regulation has therapeutic consequences.     

肿瘤坏死因子-α对原代大鼠肾近端小管上皮细胞Toll样受体2表达的调控及机制

目的探讨肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)对原代大鼠肾近端小管上皮细胞Toll样受体2(tolllike receptor2,TLR2)表达的调控以及核因子-κB(nuclearfactor-κB,NF-κB)在其中的作用。方法体外分离与培养原代大鼠肾近端小管上皮细胞,以TNF-α按不同时间给予刺激,Western blot检测TLR2,I-κBα,磷酸化I-κBα(pI-κBα),GAPDH蛋白水平。分别以TNF-α、NF-κB特异性抑制剂Bay11-7082处理25h、Bay11-7082预处理1h后加入TNF-α刺激24h,检测TLR2表达的变化。结果TNF-α刺激6~24h,TLR2高于基线水平;Bay11-7082处理组和Bay11-7082+TNF-α处理组的TLR2蛋白表达水平高于对照组。Bay11-7082+TNF-α处理组与单独TNF-α处理组TLR2蛋白表达水平无差异。TNF-α刺激后5~120min,pI-κBα蛋白水平升高。结论TNF-α促进原代大鼠肾近端小管上皮细胞TLR2蛋白表达,NF-κB对TLR2的表达可能起负调节作用。     

Reduction of electrically evoked neural activity by ginseng saponin in rat hippocampal slices

It is well established that ginseng saponin has positive influences on various neural diseases, but little is known about its electrophysiological effects in the central nervous system. In this study, we examined the electrophysiological effects of ginseng saponin in rat hippocampal slices. Total saponin from ginseng root reduced the slope of fEPSPs (field excitatory postsynaptic potentials) in the CA1 area in a dose-dependent manner (9.1 +/-5.4%, 48.4+/-12.1%, and 60.5+/-15.3% at 10, 50, and 100 microg/ml, respectively), which was reversed within 10 min of washout. Seven different ginsenosides resulted in varied degrees of fEPSPs reduction. The rank order of reduction was Rb1, Rg1 >Rg2, Rh1, Rc>Rd, Re within a range of 5-64% reduction. No difference in the suppressive action between protopanaxadiol (Rb1, Rc, Rd) and protopanaxatriol (Rg1, Rg2, Re, Rh1) saponins was shown; the slope of fEPSPs was reduced by 38% and 40% on average, respectively. The possible role of gamma-aminobutyric acid (GABA(A)) receptor in the suppressive action of ginseng saponins was tested using whole cell patch recording in acutely isolated hippocampal neurons. Ginsenosides did not induce chloride current nor modified GABA-induced current. Also, the suppressive effect of ginsenosides on fEPSPs was still observed in the presence of the GABA(A) receptor antagonist, bicuculline methiodide 50 microM. These results suggest that the suppressive effect is not attributable to regulation of GABA(A) receptor activation.     

Inhibition of EGF/EGFR activation with naphtho[1,2-b]furan-4,5-dione blocks migration and invasion of MDA-MB-231 cells

Naphtho[1,2-b]furan-4,5-dione (NFD), a bioactive component of Avicennia marina, has been demonstrated to display anti-cancer activity. Activation of epidermal growth factor receptor (EGFR)-induced signaling pathway has been correlated with cancer metastasis in various tumors, including breast carcinoma. We use EGF as a metastatic inducer of MDA-MB-231 cells to investigate the effect of NFD on cell migration and invasion. NFD suppressed EGF-mediated protein levels of c-Jun and c-Fos, and reduced MMP-9 expression and activity, concomitantly with a marked inhibition on cell migration and invasion without obvious cellular cytotoxicity. NFD abrogated EGF-induced phosphorylation of EGF receptor (EGFR) and phosphatidylinositol 3-kinase (PI3K)/Akt. The specific PI3K inhibitor, wortmannin, blocked significantly EGF-induced cell migration and invasion. Furthermore, the EGFR inhibitor AG1478 inhibited EGF-induced MMP-9 expression, cell migration and invasion, as well as the activation of PI3K/Akt, suggesting that PI3K/Akt activation occur downstream of EGFR activation. These findings suggest that NFD inhibited the EGF-induced invasion and migration of MDA-MB-231 cells via EGFR-dependent PI3K/Akt signaling, leading to the down-regulation of MMP-9 expression. These results provide a novel mechanism to explain the role of NFD as a potent anti-metastatic agent in MDA-MB-231 cells.     

Proliferative responses observed following vancomycin treatment in renal proximal tubule epithelial cells

Vancomycin (VAN) is a glycopeptide antibiotic used to treat gram-positive infections. Nephrotoxicity is a common side effect observed with vancomycin therapy. However, the mechanism of vancomycin-induced nephrotoxicity has not been fully characterized. In this study we examined the effect of vancomycin on cellular proliferation in renal proximal tubule cells. A dose- and time-dependent increase in cell number and total cellular protein was observed following vancomycin exposure. Vancomycin exposure also caused an increase in BrdU incorporation followed by the accumulation of renal proximal tubule cells in G₂/M phase of the cell cycle. These effects were inhibited by pretreatment with the mitogen-activated protein kinase inhibitor, PD098059, suggesting an association between the cell proliferative effect of VAN and the induction of the mitogen-activated protein kinase signaling pathway. Mitochondrial function in renal proximal tubule cells was assessed using oxygen consumption and ATP concentrations. We observed an increase in oxygen consumption and ATP concentrations following short-term exposure to vancomycin. Together, our data suggest that vancomycin treatment produces alterations in mitochondrial function that coincide with a cell proliferative response in renal proximal tubule epithelial cells.