Zhi-Ling Yu

New Perspectives on How to Discover Drugs from Herbal Medicines: CAM's Outstanding Contribution to Modern Therapeutics

With tens of thousands of plant species on earth, we are endowed with an enormous wealth of medicinal remedies from Mother Nature. Natural products and their derivatives represent more than 50% of all the drugs in modern therapeutics. Because of the low success rate and huge capital investment need, the research and development of conventional drugs are very costly and difficult. Over the past few decades, researchers have focused on drug discovery from herbal medicines or botanical sources, an important group of complementary and alternative medicine (CAM) therapy. With a long history of herbal usage for the clinical management of a variety of diseases in indigenous cultures, the success rate of developing a new drug from herbal medicinal preparations should, in theory, be higher than that from chemical synthesis. While the endeavor for drug discovery from herbal medicines is “experience driven,” the search for a therapeutically useful synthetic drug, like “looking for a needle in a haystack,” is a daunting task. In this paper, we first illustrated various approaches of drug discovery from herbal medicines. Typical examples of successful drug discovery from botanical sources were given. In addition, problems in drug discovery from herbal medicines were described and possible solutions were proposed. The prospect of drug discovery from herbal medicines in the postgenomic era was made with the provision of future directions in this area of drug development.

Historical Perspective of Traditional Indigenous Medical Practices: The Current Renaissance and Conservation of Herbal Resources

In recent years, increasing numbers of people have been choosing herbal medicines or products to improve their health conditions, either alone or in combination with others. Herbs are staging a comeback and herbal “renaissance” occurs all over the world. According to the World Health Organization, 75% of the worlds populations are using herbs for basic healthcare needs. Since the dawn of mankind, in fact, the use of herbs/plants has offered an effective medicine for the treatment of illnesses. Moreover, many conventional/pharmaceutical drugs are derived directly from both nature and traditional remedies distributed around the world. Up to now, the practice of herbal medicine entails the use of more than 53,000 species, and a number of these are facing the threat of extinction due to overexploitation. This paper aims to provide a review of the history and status quo of Chinese, Indian, and Arabic herbal medicines in terms of their significant contribution to the health promotion in present-day over-populated and aging societies. Attention will be focused on the depletion of plant resources on earth in meeting the increasing demand for herbs.

Quercetin exerts anti-melanoma activities and inhibits STAT3 signaling

Melanoma is highly resistant to chemotherapy, and the mortality rate is increasing rapidly worldwide. STAT3 signaling has been implicated in the pathogenesis of melanoma and constitutive activated STAT3 has been validated can as a target for melanoma therapy. Quercetin, a noncarcinogenic dietary flavonoid with low toxicity, has been shown to exert anti-melanoma activity. However, the anti-melanoma mechanisms of quercetin are not fully understood. In this study, we sought to test the involvement of STAT3 signaling in the inhibitory effects of quercetin on melanoma cell growth, migration and invasion. Our results showed that exposure to quercetin resulted in inhibition of proliferation of melanoma cells, induction of cell apoptosis, and suppression of migratory and invasive properties. Mechanistic study indicated that quercetin inhibited the activation of STAT3 signaling by interfering with STAT3 phosphorylation, and reducing STAT3 nuclear localization. This inhibited STAT3 transcription activity and down-regulated STAT3 targeted genes Mcl-1, MMP-2, MMP-9 and VEGF, which are involved in cell growth, migration and invasion. Importantly, overexpression of constitutively active STAT3 partially rescued the growth inhibiting effects induced by quercetin. Furthermore, quercetin suppressed A375 tumor growth and STAT3 activities in xenografted mice model, and inhibited murine B16F10 cells lung metastasis in an animal model. Overall, these results indicate that the antitumor activity of quercetin is at least partially due to inhibition of STAT3 signaling in melanoma cells. Our findings provided new insight into the action of quercetin potently inhibits the STAT3 signaling pathway, suggesting it has a potential role in the prevention and treatment of melanoma.

Involvement of p38 MAPK signaling pathway in the anti-melanogenic effect of San-bai-tang, a Chinese herbal formula, in B16 cells

AIM OF THE STUDY San-bai-tang (SBT), a Chinese herbal formula, is traditionally used as a skin whitener in China. In our previous screening assays, SBT was identified as an effective tyrosinase inhibitor. In this study, we aim to investigate the anti-melanogenic effect and mechanisms of SBT in B16 cells. MATERIALS AND METHODS Cell viability was examined by the MTT assay. Cellular tyrosinase activity and melanin content were determined using spectrophotographic methods. Protein expression was analyzed by immunoblotting. RESULTS SBT inhibited tyrosinase activity with an IC(50) of 215.6 ± 10.3 μg/ml, and decreased cellular melanin content with an IC(50) of 254.8 ± 14.5 μg/ml at 48 h. MTT assay demonstrated that 48-h SBT (50-400 μg/ml) treatment did not show obvious cytotoxicity. Immunoblot analysis showed that SBT (100, 200 or 400 μg/ml) treatment for 48 h down-regulated the expression levels of phosphorylated-p38, MITF, tyrosinase, TRP-1 and TRP-2 in a dose-dependent manner. CONCLUSIONS SBT inhibited melanogenesis in B16 cells, and suppression of p38 MAPK signaling pathway contributed to the anti-melanogenic effect of SBT by down-regulating the expression of MITF and melanogenic enzymes. These novel findings demonstrated the anti-melanogenic effect and mechanisms of SBT, and provide pharmacological basis for the traditional use of SBT.

Schisandrin B from Schisandra chinensis reduces hepatic lipid contents in hypercholesterolaemic mice.

The effects of schisandrin B (Sch B) on liver and serum lipid contents were investigated in mice with experimentally‐induced hypercholesterolaemia. Hypercholesterolaemia was induced either by oral administration of a cholesterol/bile salts mixture (2/0.5 g kg−1) for four days or by feeding a high fat/cholesterol/bile salts (10/1/0.3%, w/w) diet for seven days. Daily co‐administration of Sch B (50–200 mg kg−1, i.g.) for four or six days, respectively, decreased hepatic total cholesterol (TC) and triglyceride (TG) levels (by up to 50% and 52%, respectively) in hypercholesterolaemic mice. Sch B treatment also increased hepatic indices (14–84%) in hypercholesterolaemic mice. The results indicated that Sch B treatment could decrease hepatic TC and TG levels, and increase liver weight, in mouse models of hypercholesterolaemia. Fenofibrate treatment (100 mg kg−1) produced effects similar to those of Sch B on the hepatic index and lipid levels of hypercholesterolaemic mice.

20(S)-Protopanaxadiol, a metabolite of ginsenosides, induced cell apoptosis through endoplasmic reticulum stress in human hepatocarcinoma HepG2 cells.

20(S)-Protopanaxadiol (PPD), a metabolite of ginsenosides, has been demonstrated to possess cytotoxic effects on several cancer cell lines. The molecular mechanism is, however, not well understood. In this study, we have shown that PPD inhibits cell growth and induces apoptosis in human hepatocarcinoma HepG2 cells. PPD-treated cells showed a massive cytoplasmic vacuolization and a dramatic change of endoplasmic reticulum (ER) morphology. The induction of ER stress is associated with the upregulation of ER stress-associated genes and proteins. PPD activates the unfolded protein response (UPR) through the phosphorylation of PERK and eIF2α, the splicing of XBP1 mRNA, and the cleavage of AFT6. PPD also induces the intrinsic and extrinsic apoptotic pathways. It activates DR5, caspase-8, -9, -3, and promotes the cleavage of PARP while it downregulates Bcl-2, Bcl-x(L) and mitochondrial membrane potential. Knockdown of one of the three UPR limbs by specific siRNAs did not affect PPD-induced apoptosis, which was however, significantly suppressed by the downregulation of CHOP. Western blot analysis showed that PPD-stimulated downregulation of Bcl-2 protein, increase of DR5 protein, activation of caspase-8 and cleavage of PARP were significantly inhibited in CHOP siRNA-transfected cells. Taken together, we have identified ER as a molecular target of PPD and our data support the hypothesis that PPD induces HepG2 cell apoptosis through the ER stress pathway.

1α,25-Dihydroxyvitamin D3 inhibits transcriptional potential of nuclear factor kappa B in breast cancer cells

1alpha,25-Dihydroxyvitamin D(3) (VD(3)), the biologically active form of vitamin D, may have either pro- or anti-inflammatory activities because of its diverse actions on nuclear factor kappa B (NF-kappaB). Previous studies indicated that VD(3) can either activate or inhibit NF-kappaB via Akt-induced I kappaB alpha phosphorylation and increase in I kappaB alpha synthesis respectively. At present, the relevant contribution of each mechanism has not been fully explored. We observed a VD(3)-mediated NF-kappaB inhibitory effect in vitamin D receptor (VDR)-positive MCF-7 breast cancer cells. We showed that VD(3) induced VDR-dependent I kappaB alpha expression but still able to lead on transient NF-kappaB p65 nuclear translocation through Akt-induced I kappaB alpha phosphorylation. Upon TNFalpha stimulation, VD(3) was not capable to inhibit I kappaB alpha degradation, p65 nuclear translocation and p65/p50-DNA binding. Here, we found that VD(3) strongly repressed p65 transactivation in MCF-7 cells using Gal4-p65 chimeras system. VDR was required for the VD(3)-mediated transrepression and mutations in VDR affected its suppressive ability. We also demonstrated that neither inhibition of p65 phosphorylation nor acetylation was responsible for the transrepression. In fact, we found that treatment of MCF-7 cells with histone deacetylase inhibitors abrogated VD(3)-induced p65 transrepression. In addition, knockdown of two nuclear corepressors HDAC3 and SMRT relieved p65 transactivation and particular TNFalpha-triggered gene expression. In conclusion, the reduction of gene activation by VD(3) in breast cancer cells was caused by the interference of the transactivation potential of NF-kappaB p65 subunit. Our studies provide a scientific background for rational use of vitamin D in the prevention and treatment of inflammatory diseases.

Proteomic identification of proteins involved in the anticancer activities of oridonin in HepG2 cells.

Oridonin is the main bioactive constituent of the Chinese medicinal herb Isodon rubescens and has been shown to have anti-neoplastic effects against a number of cancers in vitro and in vivo. Here we report the proteomic identification of proteins involved in the anticancer properties of oridonin in hepatocarcinoma HepG2 cells. Cell viability assay showed that oridonin dose-dependently inhibited cell growth with an IC(50) of 41.77μM. Treatment with oridonin at 44μM for 24h induced apoptosis and G2/M cell cycle arrest, which were associated with nine differentially expressed proteins identified by proteomic analysis. The proteomic expression patterns of Hsp70.1, Sti1 and hnRNP-E1 were confirmed by quantitative real-time PCR and/or immunoblotting. Eight of the nine identified proteins are shown, for the first time, to be involved in the anticancer activities of oridonin. Up-regulation of Hsp70.1, STRAP, TCTP, Sti1 and PPase, as well as the down-regulation of hnRNP-E1 could be responsible for the apoptotic and G2/M-arresting effects of oridonin observed in this study. Up-regulation of HP1 beta and GlyRS might contribute to inhibitory effects of oridonin on telomerase and tyrosine kinase, respectively. These findings shed new insights into the molecular mechanisms underlying the anticancer properties of oridonin in liver cancer cells.

Flavonoids, apigenin and icariin exert potent melanogenic activities in murine B16 melanoma cells

We aimed to screen for melanogenic agents among 35 botanical compounds. The compounds were first assessed with regard to their effects on tyrosinase activity in B16 cells. At 100 μM, 13 compounds showed tyrosinase activity-enhancing effects, ranging from 2.6 to 372.8% activation. Five of them showed more than 50% enhancement and were further tested for their EC(50) values. Compared with 8-Methoxypsoralen, an effective tyrosinase activator with an EC(50) of 7.26 μM, 3 compounds exhibited smaller EC(50) values (apigenin, 0.45 μM; hyperosid, 0.92 μM; and icariin, 1.01 μM for enhancing tyrosinase activity). The 3 compounds significantly increased cellular melanin contents without affecting cell proliferation. Compared with 8-Methoxypsoralen (EC(50), 35.94 μM for stimulating pigmentation), apigenin (EC(50), 17.46 μM) and icariin (EC(50), 32.77 μM) showed better melanogenic activity, while hyperosid (EC(50), 70.4 μM) was less potent. Western blot analysis demonstrated that the 3 compounds could differentially increase the expression levels of tyrosinase, and tyrosinase-related proteins 1 and 2. Together these data suggest that apigenin and icariin exert potent melanogenic activities through, at least in part, upregulating the protein expression levels of melanogenic enzymes in B16 cells. Thus, further investigations are merited to ascertain their potential application in treating hypopigmentation disorders.

Proteomic identification of differentially expressed proteins in curcumin-treated MCF-7 cells

Curcumin (CM), a well-known dietary pigment derived from Curcuma longa L., possess anticancer activities against a variety of tumors including human breast carcinoma. In combination with docetaxel, CM has been used in breast cancer management in the clinic. In order to explore the possible mechanism of anticancer activity of CM, in the present study, we aimed to identify proteins involved in the anticancer activity of CM in human breast cancer cell line MCF-7 using the two-dimensional electrophoresis (2-DE)-based proteomic analysis. MCF-7 cells were cultured at 37°C in an atmosphere of 5.0% CO(2). All the following experiments were repeated three times. Cell viability assay showed that after a 48-h incubation CM dose-dependently inhibited cell growth with an IC(50) value of 47.42 μM. Treatment of CM at 47.42 μM for 48 h induced apoptosis as determined by nuclear morphologic changes of Hoechst stained cells and flow cytometric analysis of Annexin V-FITC/PI stained cells. Proteomic analysis identified 12 differentially expressed proteins which contributed to multiple functional activities such as DNA transcription, mRNA splicing and translation, amino acid synthesis, protein synthesis, folding and degradation, lipid metabolism, glycolysis, and cell motility. Among them 7 proteins were up-regulated and 5 down-regulated. The up-regulated ones were verified by quantitative real-time PCR. The down-regulated proteins, TDP-43, SF2/ASF and eIF3i, as well as up-regulated ones, 3-PGDH, ERP29, and platelet-activating factor acetylhydrolase IB subunit beta positively contribute to the anticancer activity of CM in MCF-7 cells. These molecules are implicated in the bioactivities of CM for the first time. The findings of this study would shed new insights for systematically understanding the mechanisms of CM in breast cancer intervention.