Astragaloside IV and cycloastragenol stimulate the phosphorylation of extracellular signal-regulated protein kinase in multiple cell types.

Two Chinese herb-derived small molecule telomerase activators, astragaloside IV (AG-IV) and cycloastragenol (CAG), have recently been shown to improve the proliferative response of CD8+ T lymphocytes from HIV-infected patients by upregulating telomerase activity. Here, we examined the signaling mechanism of AG-IV and CAG. Telomerase activity in human embryonic kidney HEK293 fibroblasts was increased upon treatment with increasing concentrations of AG-IV or CAG. Both compounds induced the phosphorylation of extracellular signal-regulated protein kinase (ERK) in a time- and dose-dependent manner in HEK293 cells and HEK-neo keratinocytes. AG-IV and CAG also stimulated ERK phosphorylation in other cell lines of lung, brain, mammary, endothelial, and hematopoietic origins. Use of selective inhibitors and dominant negative mutants revealed the involvement of c-Src, MEK (ERK kinase), and epidermal growth factor receptor in CAG-induced ERK phosphorylation. Our data indicate that AG-IV and CAG may exert their cellular effects through the activation of the Src/MEK/ERK pathway.

A new carotenoid glycoside from Rehmannia glutinosa.

A new carotenoid glycoside, namely neo-rehmannioside (1), together with five known compounds, 6-O-seco-hydroxyaeginetoyl ajugol (2), oxyrehmaionoside B (3), ajugol (4), geniposidic acid (5) and geniposide (6) was isolated from the 95% ethanol extract of dry roots of Rehmannia glutinosa. The structure of the new compound (1) was determined based on MS, IR, 1-D and 2-D NMR spectral data.

In vitro intestinal absorption and first-pass intestinal and hepatic metabolism of cycloastragenol, a potent small molecule telomerase activator.

Cycloastragenol (CAG) is the aglycone derivative of astragaloside IV which has recently been demonstrated to activate telomerase and represents a potential drug candidate for the treatment of degenerative diseases. In the present study, intestinal absorption and metabolism of CAG were examined using the Caco-2 model and liver microsomes, respectively. The results showed that CAG rapidly passes through the Caco-2 cell monolayer by passive diffusion. Four different glucuronide conjugates and two oxidized CAG metabolites were found in the apical and basolateral sides of Caco-2 monolayer, suggesting that first-pass intestinal metabolism of CAG might occur upon passage through the intestinal epithelium. CAG underwent extensive metabolism in rat and human liver microsomes with only 17.4% and 8.2%, respectively, of the starting amount of CAG remaining after 30 min of incubation. Monohydroxylation of the parent and oxidization of the hydroxylated CAG were found in the liver samples. The present study indicates that CAG is efficiently absorbed through intestinal epithelium. However, extensive first-pass hepatic metabolism would limit the oral bioavailability of this compound.

Dammarane saponins from Gynostemma pentaphyllum.

Dammarane-type saponins (1-7), together with five known compounds, were isolated from the aerial parts of Gynostemma pentaphyllum. Compounds 1-4, 6 and 7 induced the phosphorylation of ERK protein in primary rat cortical neurons, which indicates their potential neuroactivity. On the other hand, no induction of ERK phosphorylation was observed for HEK293 cells following treatment with saponins 1, 3, 4 and 7.

New secoiridoid glucosides from Ligustrum lucidum induce ERK and CREB phosphorylation in cultured cortical neurons.

Two new secoiridoid glucosides, namely iso-oleonuezhenide (1) and methyloleoside 7-ethyl ester (2), along with five known ones, oleonuezhenide (3), nuezhenide (4), oleuropein (5), G13 (6), and jaspolyside methyl ester (7), were isolated from the fruits of Ligustrum lucidum. Their structures were assigned based on 1H-NMR, 13C-NMR, and 2D-NMR analyses, in combination with HR-MS experiments and the comparison with literature data of related compounds, as well as on chemical experiments. We have examined the ability of these compounds to activate ERK and CREB in cultured cortical neurons. Our studies demonstrate that compound 1 induces ERK and CREB phosphorylation in primary cortical neurons in a dose- and temporal-dependent manner, suggesting its bioactivity on neurons.

Naturally occurring phenylethanoid glycosides: potential leads for new therapeutics.

Natural products have long been regarded as excellent sources for drug discovery given their structure diversity and wide variety of biological activities. Phenylethanoid glycosides are naturally occurring compounds of plant origin and are structurally characterized with a hydroxyphenylethyl moiety to which a glucopyranose is linked through a glycosidic bond. To date several hundred compounds of this type have been isolated from medicinal plants and further pharmacological studies in vitro or in vivo have shown that these compounds possess a broad array of biological activities including antibacterial, antitumor, antiviral, anti-inflammatory, neuro-protective, antioxidant, hepatoprotective, immunomodulatory, and tyrosinase inhibitory actions. Given their extensive activity profile, structure-activity relationships analyses of these compounds have been performed in a number of studies to reveal potential leads for future drug design. This article will summarize the major developments in phenylethanoid glycosides-based research in the past decade. The progresses made in phytochemistry and biological activity studies of these compounds will be reviewed. Particular attention will be given to the novel structures identified to date and the prominent therapeutic values associated with these molecules.

CKBM stimulates MAPKs but inhibits LPS-induced IFN-gamma in lymphocytes.

CKBM is an herbal formula composed of five Chinese medicinal herbs (Panax ginseng, Schisandra chinensis, Fructus crataegi, Ziziphus jujuba and Glycine max) supplemented with processed Saccharomyces cerevisiae. It has been demonstrated that CKBM is capable of triggering the release of IL-6 and TNFalpha from human peripheral blood mononuclear cells. In this report, T-lymphocytic Sup-T1 cells and B-lymphocytic Ramos cells were utilized as cellular models to investigate how CKBM regulates intracellular signaling as well as the production of cytokines. CKBM stimulated the three major subgroups of mitogen-activated protein kinase (i.e. ERK, JNK and p38) in Sup-T1 cells, but only triggered the activation of ERK and p38 in Ramos cells. The induction of mitogen-activated protein kinases (MAPK) activations varied with the duration of treatment, as well as with the dosage of CKBM. In terms of cytokine production, treatment of CKBM alone did not trigger the release of IL-1beta and IFNgamma, but it suppressed the LPS-induced IFNgamma production from both Sup-T1 cells and Ramos cells. In view of the therapeutic effects of traditional Chinese medicines in inflammatory and autoimmune disorders, the results suggest that CKBM may exhibit its immuno-modulatory effects by regulating intracellular signaling as well as cytokine production in different lymphocytic cell types.

The aqueous extract of Radix Glycyrrhizae stimulates mitogen-activated protein kinases and nuclear factor-kappaB in Jurkat T-cells and THP-1 monocytic cells.

Radix Glycyrrhizae (RG) is a medicinal herb extensively utilized in numerous Chinese medical formulae for coordinating the actions of various components in the recipes and strengthening the body functions. In this report, we demonstrate that the aqueous extract of Radix Glycyrrhizae is capable of stimulating the c-Jun N-terminal kinase and p38 subgroups of mitogen-activated protein kinases (MAPKs), and the nuclear factor-kappaB (NFkappaB) in Jurkat T-lymphocytes. The activation magnitudes of MAPKs and NFkappaB were dose-dependent (EC(50) approximately 1 mg/ml) and time-dependent (maximal around 15-30 minutes). Stimulations of MAPKs and NFkappaB were not associated with changes in intracellular Ca(2+) mobilization. Similar activation profiles of MAPK and NFkappaB were obtained from THP-1 monocytes treated with the extract. In terms of chemotactic activity, the SDF-induced chemotaxis of Jurkat cells and THP-1 cells were inhibited by RG extract at 1-10 mg/ml, while a lower RG concentration (0.1-0.3 mg/ml) potentiated the SDF-induced chemotaxis for the former, but not the latter cell type. Given the fact that MAPKs and NFkappaB are important signaling intermediates for lymphocyte activities, our results suggest that Radix Glycyrrhizae may contain active constituents capable of modulating immuno-responses through various intracellular signaling pathways.

Immuno-regulatory effects of CKBM on the activities of mitogen-activated protein kinases and the release of cytokines in THP-1 monocytic cells.

CKBM is an herbal formula composed of five Chinese medicinal herbs (Panax ginseng, Schisandra chinensis, Fructus crataegi, Ziziphus jujube and Glycine Max) supplemented with processed Saccharomyces cerevisiae. Previous studies have demonstrated that CKBM is capable of triggering the release of IL-6 and TNFalpha from human peripheral blood mononuclear cells, and its anti-tumorigenic activity has been demonstrated in nude mice with gastric cancer. In this report, we utilized the THP-1 monocytic cell line as a cellular model to investigate how CKBM regulates the intracellular signaling of monocytes and the subsequent release of the produced cytokines. In terms of mitogen-activated protein kinase (MAPK) cascades, CKBM (20%) had no significant effect on ERK, but was linked to an inhibitory effect on JNK and a stimulatory effect on p38 MAPK. The differential responsiveness of JNK and p38 was dependent on the duration of treatment, as well as on the dosage of CKBM. Treatment of CKBM alone induced the release of IL-10 and IFNgamma, but not IL-1beta, IL-4, IL-6 and TNFbeta, while increase of intracellular Ca2+ concentration by A23187 triggered the release of IL-10 only. Interestingly, A23187 synergized with the activities of CKBM-treated THP-1 cells in terms of IL-1beta and IFNgamma production, while the IL-10 production showed no synergistic relationship between CKBM and A23187. This A23187-induced synergism was associated with a dose-dependent character towards CKBM administration. In view of the intracellular Ca2+ elevation during monocyte activation, our results suggest that CKBM can serve as a promoting agent for modulating the functions of monocytes.

Carvacrol and eugenol differentially stimulate intracellular Ca2+ mobilization and mitogen-activated protein kinases in Jurkat T-cells and monocytic THP-1 cells.

Essential oils are a major active constituent found in many Chinese medicinal herbs. Here, we demonstrate that two components of essential oils, carvacrol and eugenol, dose-dependently trigger intracellular Ca2+ mobilization in Jurkat T-cells and THP-1 monocytic cells. Both carvacrol and eugenol are also capable of stimulating the active phosphorylation of the p38 subgroup of mitogen-activated protein kinases (MAPKs) in both cell types. However, carvacrol selectively activated the ERK subgroup in Jurkat T-cells, and stimulated the JNK subgroup in THP-1 monocytic cells. Eugenol treatment was not linked to ERK or JNK activation in either cell type. EC50 values for the induction of Ca2+ mobilization and MAPK activation were around 10 - 30 microM for both carvacrol and eugenol. Our results suggest that these essential oil components may act as effective agents to modulate the functions of immuno-responsive cells via different intracellular signaling pathways.