Activation of human platelet phospholipases C and A2 by various oxygenated triterpenes

Biosynthesis of mushroom-derived type II ganoderic acids by engineered yeast

Type II ganoderic acids (GAs) produced by the traditional medicinal mushroom Ganoderma are a group of triterpenoids with superior biological activities. However, challenges in the genetic manipulation of the native producer, low level of accumulation in the farmed mushroom, the vulnerabilities of the farming-based supply chain, and the elusive biosynthetic pathway have hindered the efficient production of type II GAs. Here, we assemble the genome of type II GAs accumulating G. lucidum accession, screen cytochrome P450 enzymes (CYPs) identified from G. lucidum in baker's yeast, identify key missing CYPs involved in type II GAs biosynthesis, and investigate the catalytic reaction sequence of a promiscuous CYP. Then, we engineer baker's yeast for bioproduciton of GA-Y (3) and GA-Jb (4) and achieve their production at higher level than those from the farmed mushroom. Our findings facilitate the further deconvolution of the complex GA biosynthetic network and the development of microbial cell factories for producing GAs at commercial scale.

The interaction between self - assembling peptides and emodin and the controlled release of emodin from in-situ hydrogel

Ion-complementary self-assembling peptides have potential in delivering hydrophobic drugs. This study involved two self-assembling peptides, RADA16-I and RVDV16-I, of which RVDV16-I was a novel self-assembling peptide with different hydrophobic side chains designed from RADA16-I. The purpose of this study was to observe the interaction between different self-assembling peptides and emodin through fluorescence spectrophotometry, CD, SEM and AFM; to construct a preliminary suspension in-situ hydrogel delivery system for emodin with the self-assembling peptides; and to investigate the drug-loading and drug-releasing properties of the self-assembling peptides on emodin. The results showed that both peptides can interact with emodin and the interaction was dominated by hydrophobic interaction. The aqueous solutions of both self-assembling peptides can form relatively stable suspensions with emodin under mechanical stirring, and the suspension can form in-situ hydrogel under physiological condition. In vitro release of emodin from the hydrogels showed a manner of sustained release to some extent. Cell viability studies showed inherent proliferation inhibiting effects of emodin on tumor cells was maintained or enhanced through the in-situ hydrogels. The self-assembling peptides RADA16-I and RVDV16-I had showed promising drug-loading and drug-releasing performance for hydrophobic drugs. It is reasonable to exploit self-assembling peptides as drug carriers for their great potential to improve delivery of hydrophobic drugs.

Optimization of Culture Condition for Ganoderic Acid Production in Ganoderma lucidum Liquid Static Culture and Design of a Suitable Bioreactor

Ganoderma lucidum, a famous medicinal mushroom used worldwide, is a rich source of triterpenoids which, together with polysaccharides, are believed to be the main effective constituents of G. lucidum. With the increase of market demand, the wild resource is facing serious limitations, and the quality of cultivated fruiting bodies can be seriously affected by the availability of wood resources and by cultivation management practices. In the present study, we aimed to develop an alternative way to produce useful triterpenoids from G. lucidum. We cultured the strain using a two-stage liquid culture strategy and investigated the effects of nitrogen limitation, carbon supply, static culture volume and air supply in the static culture stage on the accumulation of five triterpenoids (GA-P, GA-Q, GA-T, GA-S, GA-R). Our results showed that, under optimized condition, the total yield of the five triterpenoids reached 963 mg/L (as determined by HPLC). Among the five triterpenoids, GA-T accounted for about 75% of the total yield. Besides, a bioreactor suitable for fungal liquid static culture with a 10 L extensible plastic bag shaped culture unit was designed and in which the maximum total yield of the five GAs reached 856.8 mg/L, and the GAs content reached 5.99%. Our results demonstrate the potential of industrial application of G. lucidum culture for the production of triterpenoids, especially GA-T. Air supply significantly improved the accumulation of triterpenoids, and this will provide important clues to understand why more triterpenoids are produced in the mycelia mat under static liquid culture conditions.

The mechanism of action of ursolic acid as insulin secretagogue and insulinomimetic is mediated by cross-talk between calcium and kinases to regulate glucose balance

BACKGROUND

The effect of in vivo treatment with ursolic acid (UA) on glycemia in hyperglycemic rats and its mechanism of action on muscle were studied.

METHODS

The UA effects on glycemia, glycogen, LDH, calcium and on insulin levels were evaluated after glucose tolerance curve. The β-cells were evaluated through the transmission electron microscopy. UA mechanism of action was studied on muscles through the glucose uptake with/without specific insulin signaling inhibitors. The nuclear effect of UA and the GLUT4 expression on muscle were studied using thymidine, GLUT4 immunocontent, immunofluorescence and RT-PCR.

RESULTS

UA presented a potent antihyperglycemic effect, increased insulin vesicle translocation, insulin secretion and augmented glycogen content. Also, UA stimulates the glucose uptake through the involvement of the classical insulin signaling related to the GLUT4 translocation to the plasma membrane as well as the GLUT4 synthesis. These were characterized by increasing the GLUT4 mRNA expression, the activation of DNA transcription, the expression of GLUT4 and its presence at plasma membrane. Also, the modulation of calcium, phospholipase C, protein kinase C and PKCaM II is mandatory for the full stimulatory effect of UA on glucose uptake. UA did not change the serum LDH and serum calcium balance.

CONCLUSIONS

The antihyperglycemic role of UA is mediated through insulin secretion and insulinomimetic effect on glucose uptake, synthesis and translocation of GLUT4 by a mechanism of cross-talk between calcium and protein kinases.

GENERAL SIGNIFICANCE

UA is a potential anti-diabetic agent with pharmacological properties for insulin resistance and diabetes therapy.

Ganoderic acid Mf and S induce mitochondria mediated apoptosis in human cervical carcinoma HeLa cells

In this work, the effects of a pair of positional isomer of ganoderic acids (GAs), namely ganoderic acid Mf (GA-Mf) and ganoderic acid S (GA-S) purified from the fermented mycelia of Ganoderma lucidum, on induction of cell apoptosis and the apoptotic pathway in HeLa cells were investigated. The results demonstrate that both isomers decreased cell population growth on various human carcinoma cell lines by MTT assay, while GA-Mf had better selectivity between normal and cancer cells. The flow cytometry analysis indicated that treatment of HeLa cells with GA-S caused cell cycle arrest in the S phase, while GA-Mf caused cell cycle arrest in the G1 phase. Compared with GA-S, GA-Mf had more potent increase in the number of early and late apoptotic cells. Treatment of HeLa cells with each isomer decreased the mitochondria membrane potential and caused the release of cytochrome c from mitochondria into the cytosol. In addition, stimulation of caspase-3 and caspase-9 activity was observed. The Bax/Bcl-2 ratio was also increased in GA-treated HeLa cells. The results demonstrated that both isomers GA-Mf and GA-S induced apoptosis of human HeLa cells through a mitochondria mediated pathway, but they had the different cell cycle arrest specificity. The findings will be helpful to the development of useful cancer chemopreventive compounds from G. lucidum.

Ganoderic acid X, a lanostanoid triterpene, inhibits topoisomerases and induces apoptosis of cancer cells

Lanostanoid triterpenes isolated from Ganoderma amboinense were found to inhibit the growth of numerous cancer cell lines, and some of them inhibited the activities of topoisomerases I and IIalpha in vitro. Among the bioactive isolates, one of the most potent triterpene was identified to be 3 alpha-hydroxy-15 alpha-acetoxy-lanosta-7,9(11),24-trien-26-oic acid, ganoderic acid X (GAX). Treatment of human hepatoma HuH-7 cells with GAX caused immediate inhibition of DNA synthesis as well as activation of ERK and JNK mitogen-activated protein kinases, and cell apoptosis. Molecular events of apoptosis including degradation of chromosomal DNA, decrease in the level of Bcl-xL, the disruption of mitochondrial membrane, cytosolic release of cytochrome c and activation of caspase-3 were elucidated. The ability of GAX to inhibit topoisomerases and to sensitize the cancer cells toward apoptosis fulfills the feature of a potential anticancer drug.

Natural products of the medicinal fungus Ganoderma lucidum: occurrence, biological activities, and pharmacological functions

Ganoderma lucidum, a fungus used in traditional Chinese medicine, produces polysaccharides and oxygenated triterpenoids with a very broad spectrum of biological activities and pharmacological functions. Among the Ganoderma triterpenoids, many pairs of C-3 alpha/beta stereoisomers and C-3/C-15 positional isomers have been identified. Biosynthetic study has indicated that the C-3alpha series of oxygenated triterpenoids is derived from the C-3beta series via an oxidation-reduction pathway. The interaction of Ganoderma triterpenoids with human platelets in the induction of aggregation and inhibition of agonist-induced aggregation and signal transduction has been elucidated. Reduction of cellular mevalonate content to a stage in which cholesterol synthesis is strongly inhibited and cell growth is marginally arrested sensitizes hepatoma cells to the oxygenated triterpenoids. A combination treatment of lovastatin and Ganoderma triterpenoids in animal studies has exhibited a potential anticancer effect.

Ginseng pharmacology: multiple constituents and multiple actions

Ginseng is a highly valued herb in the Far East and has gained popularity in the West during the last decade. There is extensive literature on the beneficial effects of ginseng and its constituents. The major active components of ginseng are ginsenosides, a diverse group of steroidal saponins, which demonstrate the ability to target a myriad of tissues, producing an array of pharmacological responses. However, many mechanisms of ginsenoside activity still remain unknown. Since ginsenosides and other constituents of ginseng produce effects that are different from one another, and a single ginsenoside initiates multiple actions in the same tissue, the overall pharmacology of ginseng is complex. The ability of ginsenosides to independently target multireceptor systems at the plasma membrane, as well as to activate intracellular steroid receptors, may explain some pharmacological effects. This commentary aims to review selected effects of ginseng and ginsenosides and describe their possible modes of action. Structural variability of ginsenosides, structural and functional relationship to steroids, and potential targets of action are discussed.

Predominant inhibition of ganodermic acid S on the thromboxane A2-dependent pathway in human platelets response to collagen

Ganodermic acid S (GAS), a membrane acting agent, exerts multiple effects on human platelet function (C.N. Wang et al. (1991) Biochem. J. 277, 189-197). The study reported how GAS affected the response of human gel-filtered platelets (GFP) to collagen. The agent inhibited cell aggregation by prolonging lag and shape change periods and decreasing the initial cell aggregation rate. However, the inhibitory efficiency was less than its inhibition on GFP response to U46619, a thromboxane (TX) A2 mimetic. In the agent-effect on biochemical events, GAS effectively inhibited Ca2+ mobilization, phosphorylation of myosin light chain, dense granule secretion and TXB2 generation. The inhibitions might originate from blocking Ca2+ mobilization of the TXA2-dependent pathway. GAS partially decreased the phosphorylation of most phosphotyrosine proteins from early activation to the integrin alphaIIbbeta3-regulated steps. The agent did not affect the phosphorylation of three proteins at the steps regulated by integrin alphaIIbbeta3. The results suggest that GAS inhibits the collagen response predominantly on the TXA2-dependent signaling, and the tyrosine kinase-dependent pathway in collagen response plays a major role in aggregation.