Yuying Fan

Anti-fatigue activity of the water-soluble polysaccharides isolated from Panax ginseng C. A. Meyer

AIM OF THE STUDY Panax ginseng C. A. Meyer (ginseng) is a well-known Chinese herb often used in Asian countries for physical strength development. Ginseng polysaccharides are its active component and have a lot of pharmaceutical activities. However, anti-fatigue activity of ginseng polysaccharides has not yet been tested. The current study was designed to evaluate the anti-fatigue activity of ginseng polysaccharides (WGP) in an animal test for fatigue and compare the activities between the neutral (WGPN) and acidic (WGPA) portion in an attempt to determine whether the medicinal uses are supported by pharmacological effects. MATERIALS AND METHODS WGP, WGPN and WGPA were orally administrated to mice once daily for 15 days. Anti-fatigue activity was assessed using the forced swim test (FST) and serum biochemical parameters were determined by autoanalyzer and commercially available kits. RESULTS While all compounds were found to reduce immobility in the FST, the effect of WGPA was demonstrated in lower doses compared with WGP and WGPN. Moreover, the FST-induced reduction in glucose (GLU) and glutathione peroxidase (GPx) and increase in creatine phosphokinase (CK), lactic dehydrogenase (LDH) and malondialdehyde (MDA) levels, all indicators of fatigue, were inhibited by the corresponding doses of WGP, WGPN and WGPA. CONCLUSIONS Ginseng polysaccharides have anti-fatigue activity, also reflected in the effects on the physiological markers for fatigue. The acidic polysaccharide is more potent than the neutral polysaccharide.

Antitumor Activities and Immunomodulatory Effects of Ginseng Neutral Polysaccharides in Combination with 5-Fluorouracil

A neutral polysaccharide fraction (WGPN) prepared from Panax ginseng C.A. Meyer by hot water extraction and DEAE-cellulose chromatography was tested for its anticancer activity alone and in combination with 5-fluorouracil (5-FU) in Sarcoma-180 (S180) tumor-bearing mice by intragastric administration. WGPN alone inhibited S180 tumor growth in a bell-shaped dose-response curve, and the combination with 5-FU showed a synergistic effect. Studies of various immunological activities in S180-bearing mice revealed that WGPN stimulated the proliferation of lymphocytes, increased natural killer cell cytotoxicity, enhanced the phagocytosis and nitric oxide production by macrophages, and increased the level of tumor necrosis factor-alpha in serum. In combination with 5-FU, WGPN mitigated damage to the immune system caused by 5-FU in S180-bearing mice. These results suggest that WGPN might be a potential adjuvant for chemotherapeutic drugs.

Comparative studies of the antiproliferative effects of ginseng polysaccharides on HT-29 human colon cancer cells

Ginseng polysaccharide has anticancer activity. However, the structure–activity relationship and the activity mechanism are still unclear. Therefore, it is necessary to study the anticancer activity of structurally different ginseng polysaccharide fractions and their potential mechanisms. Ginseng polysaccharide fractions and their temperature-modified products were assayed for their effects on HT-29 cell proliferation by MTT assay, on cell cycle progression by flow cytometry, and on caspase-3 activation by western blot analysis. The HG-rich ginseng pectin inhibited cell proliferation and induced cell cycle arrest in the G2/M phase. The temperature-modified HG-rich pectin had dramatically increased antiproliferative effect and induced apoptosis accompanied by the activation of caspase-3. Starch-like glucan and arabinogalactan of ginseng exhibited no antiproliferative effects. Even after temperature modification, their inhibitory effects either remained unchanged or increased slightly. The HG-rich pectin exerts its antiproliferative effect via cell cycle arrest and the temperature modification markedly increased the antiproliferative effect.

The Two Endocytic Pathways Mediated by the Carbohydrate Recognition Domain and Regulated by the Collagen-like Domain of Galectin-3 in Vascular Endothelial Cells

Galectin-3 plays an important role in endothelial morphogenesis and angiogenesis. We investigated the endocytosis of galectin-3 in human vascular endothelial cells and showed that galectin-3 could associate with and internalized into the cells in a carbohydrate-dependent manner. Our work also revealed that galectin-3 was transported to the early/recycling endosomes and then partitioned into two routes – recycling back to the plasma membrane or targeting to the late endosomes/lysosomes. Various N- and C-terminal truncated forms of galectin-3 were constructed and compared with the full-length protein. These comparisons showed that the carbohydrate-recognition domain of galectin-3 was required for galectin-3 binding and endocytosis. The N-terminal half of the protein, which comprises the N-terminal leader domain and the collagen-like internal repeating domain, could not mediate binding and endocytosis alone. The collagen-like domain, although it was largely irrelevant to galectin-3 trafficking to the early/recycling endosomes, was required for targeting galectin-3 to the late endosomes/lysosomes. In contrast, the leader domain was irrelevant to both binding and intracellular trafficking. The data presented in this study correlate well with different cellular behaviors induced by the full-length and the truncated galectin-3 and provide an alternative way of understanding its angiogenic mechanisms.

In vivo antimalarial activities of glycoalkaloids isolated from Solanaceae plants

Context: Malaria is one of the most common and serious protozoan tropical diseases. Multi-drug resistance remains pervasive, necessitating the continuous development of new antimalarial agents. Objective: Many glycosides, such as triterpenoid saponins, were shown to have antimalarial activity against Plasmodium falciparum in vitro. This study was to elucidate the ability of five glycoalkaloids against Plasmodium yoelii and develop new antimalarial lead compounds. Materials and methods: Glycoalkaloids were isolated from three kinds of Solanaceae plants: chaconine and solanine were isolated from Solanum tuberosum L. sprouts, solamargine and solasonine from Solanum nigrum L. fruit, tomatine from Lycopersicon esculentum Mill. fruit. The five isolated glycoalkaloids were evaluated against Plasmodium yoelii 17XL in mice with 4-day parasitemia suppression test in different concentrations. Results: Chaconine showed a dose-dependent suppression of malaria infection, ED50, 4.49 mg/kg; therapeutic index (TI), ≈9. At a dose of 7.50 mg/kg, the parasitemia suppressions of chaconine, tomatine, solamargine, solasonine and solanine were 71.38, 65.25, 64.89, 57.47 and 41.30%, respectively. At 3.75 mg/kg, the parasitemia suppression of chaconine was 42.66%, but the derivative, chaconine-6-O-sulfate, appeared to show no antimalarial activity. Simultaneous administration of chaconine and solanine in 1:1 did not show any synergistic effects. Discussion and conclusion: The results showed that the glycoalkaloids with chacotriose (chaconine and solamargine) were more active than those with solatriose (solanine and solasonine). Chaconine was the most active among the five glycoalkaloids. We propose that the activity is dependent upon non-specific carbohydrate interactions. The 6-OH of chaconine is important for antimalarial activity.

Further analysis of the structure and immunological activity of an RG-I type pectin from Panax ginseng

In this paper, we further analysed the structure of a type I rhamnogalacturonan (RG-I) pectin (WGPA-2-RG) fractionated from ginseng polysaccharides. Methylation and periodate oxidation analyses showed that WGPA-2-RG has a backbone consisting of alternating rhamnose (Rha) and galacturonic acid (GalA) residues and side chains consisting of type II arabinogalactan (AG-II). Partial acidic hydrolysis for 6h completely removed arabinose (Ara), partial galactose (Gal), but little GalA and Rha. During partial hydrolysis, the molecular weight of WGPA-2-RG decreased smoothly, suggesting that the Ara and cleavable Gal residues exist on the surface of the molecule, while GalA and Rha residues exist in the core of the molecule. The bioactivity assay showed that the arabinogalactan side chains of WGPA-2-RG are essential structures for stimulating NO secretion and lymphocyte proliferation. However, removal of the Ara and Gal residues through hydrolysis did not appreciably affect the ability of WGPA-2-RG to enhance macrophage phagocytosis.

Anti-hyperglycemic and anti-oxidative activities of ginseng polysaccharides in STZ-induced diabetic mice

Neutral (WGPN) and acidic (WGPA) polysaccharides were fractionated from ginseng polysaccharide. WGPN and WGPA decreased fasting blood glucose by different manners of administration. Intra-gastric administration of WGPA showed a marked hypoglycemic effect, which may be related to its anti-oxidative activity. The results indicated that WGPA may have anti-diabetic potential.

Neuroprotective effects of ginseng pectin through the activation of ERK/MAPK and Akt survival signaling pathways.

In this study, we investigated the neuroprotective activities of ginseng pectin (GP) against hydrogen peroxide (H2O2)-induced neuronal toxicity in different neuronal cells. GP selectively attenuated H2O2-induced damage up to 26% in primary cortical neuron cells and human glioblastoma U87 cells. Following H2O2 exposure, DAPI staining and neuron-specific β-tubulin antibody probing indicated that GP maintained cell integrity and decreased nuclei condensation. Data from western blot analysis revealed that pre-treatment with GP increased the phosphorylation of both the extracellular signal-regulated kinases 1 and 2 (ERK1/2) and Akt in cortical neuron cells. However, the phosphorylation of ERK1/2 was increased, but that of Akt was decreased in U87 cells. These results suggest that the protective effects of GP against H2O2-induced apoptosis may be due to the activation of the phosphorylation of ERK1/2 and Akt; however, the mechanisms involved differ depending on the cell line. This neuroprotective property indicates that GP could serve as a potential therapeutic agent for neurodegenerative diseases.

A Becn1 mutation mediates hyperactive autophagic sequestration of amyloid oligomers and improved cognition in Alzheimer's disease

Impairment of the autophagy pathway has been observed during the pathogenesis of Alzheimer’s disease (AD), a neurodegenerative disorder characterized by abnormal deposition of extracellular and intracellular amyloid β (Aβ) peptides. Yet the role of autophagy in Aβ production and AD progression is complex. To study whether increased basal autophagy plays a beneficial role in Aβ clearance and cognitive improvement, we developed a novel genetic model to hyperactivate autophagy in vivo. We found that knock-in of a point mutation F121A in the essential autophagy gene Beclin 1/Becn1 in mice significantly reduces the interaction of BECN1 with its inhibitor BCL2, and thus leads to constitutively active autophagy even under non-autophagy-inducing conditions in multiple tissues, including brain. Becn1F121A-mediated autophagy hyperactivation significantly decreases amyloid accumulation, prevents cognitive decline, and restores survival in AD mouse models. Using an immunoisolation method, we found biochemically that Aβ oligomers are autophagic substrates and sequestered inside autophagosomes in the brain of autophagy-hyperactive AD mice. In addition to genetic activation of autophagy by Becn1 gain-of-function, we also found that ML246, a small-molecule autophagy inducer, as well as voluntary exercise, a physiological autophagy inducer, exert similar Becn1-dependent protective effects on Aβ removal and memory in AD mice. Taken together, these results demonstrate that genetically disrupting BECN1-BCL2 binding hyperactivates autophagy in vivo, which sequestrates amyloid oligomers and prevents AD progression. The study establishes new approaches to activate autophagy in the brain, and reveals the important function of Becn1-mediated autophagy hyperactivation in the prevention of AD.

Identification of natural products with neuronal and metabolic benefits through autophagy induction

ABSTRACT Autophagy is a housekeeping lysosomal degradation pathway important for cellular survival, homeostasis and function. Various disease models have shown that upregulation of autophagy may be beneficial to combat disease pathogenesis. However, despite several recently reported small-molecule screens for synthetic autophagy inducers, natural chemicals of diverse structures and functions have not been included in the synthetic libraries, and characterization of their roles in autophagy has been lacking. To discover novel autophagy-regulating compounds and study their therapeutic mechanisms, we used analytic chemistry approaches to isolate natural phytochemicals from a reservoir of medicinal plants used in traditional remedies. From this pilot plant metabolite library, we identified several novel autophagy-inducing phytochemicals, including Rg2. Rg2 is a steroid glycoside chemical that activates autophagy in an AMPK-ULK1-dependent and MTOR-independent manner. Induction of autophagy by Rg2 enhances the clearance of protein aggregates in a cell-based model, improves cognitive behaviors in a mouse model of Alzheimer disease, and prevents high-fat diet-induced insulin resistance. Thus, we discovered a series of autophagy-inducing phytochemicals from medicinal plants, and found that one of the compounds Rg2 mediates metabolic and neurotrophic effects dependent on activation of the autophagy pathway. These findings may help explain how medicinal plants exert the therapeutic functions against metabolic diseases.