The effects of genkwadaphnin and gnidilatidin on the growth of P-388, L-1210 leukemia and KB carcinoma cells in vitro

Metabolism, pharmacokinetics, and bioavailability of yuanhuacine in rat using LC-MS

Yuanhuacine is a Daphne-type diterpene ortho-ester and is one of the main active ingredients of genkwa flos. Anticancer activity of yuanhuacine has been well investigated in various tumor cells and animal models, but information on metabolism and pharmacokinetics is limited. The aims of the present study were to investigate the metabolic and pharmacokinetic profiles of yuanhuacine in rat. The metabolic profile of yuanhuacine was obtained from rat plasma, urine, and feces using ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. A total of seven metabolites were detected, and the proposed metabolic pathways involved oxidation and glucuronidation. A simple and sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry method was developed for the determination of yuanhuacine in rat plasma. The linear range of yuanhuacine was 1-1000 ng/ml (R²  = 0.998). The intra- and inter-precision (coefficient of variation %) of the assay was 3.86-6.18% and 2.65-5.75%, respectively, and the intra- and inter-accuracy (relative error %) was -3.83-4.77% and -3.03-5.11%, respectively. The extraction recovery, matrix effect, stability, and incurred sample reanalysis of yuanhuacine were within acceptable levels. The established method was validated and successfully applied to the preclinical pharmacokinetic study of yuanhuacine. The absolute oral bioavailability of yuanhuacine was calculated as 1.14%, and it reached the maximum plasma concentration of 28.21 ± 2.79 ng/ml in rat plasma at 2 h in the oral dosing group. The apparent volume of distribution of intravenous and intragastric administrations was 26.07 ± 6.45 and 21.83 ± 3.54 L/kg, respectively. The half-life of elimination of yuanhuacine was 9.64 ± 1.53 h in the intravenous dosing group.

Yuanhuacin and Related Anti-Inflammatory and Anticancer Daphnane Diterpenes from Genkwa Flos-An Overview

The dried flower buds of the plant Daphne genkwa Sieb. et Zucc. have been largely used in traditional Chinese medicine for the treatment of inflammatory diseases. Numerous diterpenoids have been isolated from the Genkwa Flos (yuanhua in Chinese), including a series of daphnane-type diterpene designated as yuanhuacin (YC, often improperly designated as yuanhuacine) and analogues with a patronymic name. The series includes ten daphnane-type diterpenes: yuanhuacin, yuanhuadin (YD), yuanhuafin (YF), yuanhuagin (YG), yuanhuahin (YH), yuanhuajin (YJ), yuanhualin (YL), yuanhuamin (YM), yuanhuapin (YP), and yuanhuatin (YT). They are distinct from the rare flavonoid yuanhuanin. The series comprises several anticancer agents, such as the lead compound YC, which has revealed potent activity in vitro and in vivo against models of lung and breast cancers. The main signaling pathways implicated in the antitumor effects have been delineated. Protein kinase C is a key factor of activity for YC, but in general the molecular targets at the origin of the activity of these compounds remain little defined. Promising anticancer effects have been reported with analogues YD and YT, whereas compounds YF and YP are considered more toxic. The pharmacological activity of each compound is presented, as well as the properties of Genkwa Flos extracts. The potential toxic effects associated with the use of these compounds are also underlined.

PRDM1, a Tumor-Suppressor Gene, is Induced by Genkwadaphnin in Human Colon Cancer SW620 Cells

Genkwadaphnin (GD-1) is isolated from the flower buds of Daphne genkwa Siebold et Zuccarini (Thymelaeaceae), and it has been used as a traditional Korean and Chinese medicine. In this study, the authors observe that GD-1 inhibits the growth of the colon cancer cell line, SW620, through the up-regulation of p21 expression in a PRDM1-dependent manner. After treatment with GD-1, the transcriptional repressor PRDM1 is prominently induced in SW620 cells. Furthermore, GD-1 induce the phosphorylation of PKD1 and MEK and subsequently provide PRDM1 enhancement, resulting in the suppression of c-Myc expression and the up-regulation of p21. PKD1 knockdown using siRNA abrogates PRDM1 expression by GD-1 and subsequently disrupts the regulation of c-Myc and p21 expression. Treating SW620 cells with GD-1 inhibits cell-cycle progression and is characterized by the down-regulation of c-Myc followed by the up-regulation of p21 expression. The up-regulation of p21 by GD-1 induces the growth arrest of the SW620 colon cancer cell line. Based on these data, the authors propose that GD-1 has tumor-suppressor activity that may contribute to the anti-tumor effects of PRDM1 in colon cancer.

Functional restoration of exhausted CD4(+) and CD8(+) T cells in chronic viral infection by vinegar-processed flos of Daphne genkwa

T-cell exhaustion has become an important issue in chronic infection because exhausted antigen-specific T cells show impaired abilities to eradicate persistently infected pathogens and produce effector cytokines, such as IFN-γ and TNF-α. Thus, strategies to either restore endogenous exhausted T cell responses or provide functional T cells are needed for therapeutics of chronic infection. Despite promising developments using antibodies and cell immunotherapy, there have been no reported attempts to restore exhausted T cells using treatment with materials derived from natural resources. Here, using a mouse model of chronic infection with lymphocytic choriomeningitis virus (LCMV), we found that vinegar-processed flowers (flos) of Daphne genkwa (vp-genkwa), which was composed mainly of four index components, restored exhausted CD4(+) and CD8(+) T cells significantly, as corroborated by evidence that vp-genkwa treatment enhanced functional LCMV-specific CD4(+) and CD8(+) T cells, both quantitatively and qualitatively. Furthermore, pretreatment with vp-genkwa prevented the generation of exhausted LCMV-specific CD8(+) T cells. Such restorations of exhausted LCMV-specific CD4(+) and CD8(+) T cells by vp-genkwa were closely associated with reduced viral burden in sera and tissues. More interestingly, vp-genkwa treatment induced down-regulation of negative molecules, such as PD-1 and Tim-3, in exhausted CD4(+) and CD8(+) T cells with more apparent down-regulation of Tim-3, suggesting that Tim-3 molecule may be a major target in restoring exhausted T cell responses. Collectively, these results provide valuable new insights into the use of vp-genkwa to develop a therapeutic strategy for chronic human diseases, such as hepatitis B and C virus, human immunodeficiency virus, and cancers.

The Chinese herb isolate yuanhuacine (YHL-14) induces G2/M arrest in human cancer cells by up-regulating p21 protein expression through an p53 protein-independent cascade

Yuanhuacine (YHL-14), the major component of daphnane diterpene ester isolated from the flower buds of Daphne genkwa, has been reported to have activity against cell proliferation in various cancer cell lines. Nevertheless, the potential mechanism has not been explored yet. Here we demonstrate that YHL-14 inhibits bladder and colon cancer cell growth through up-regulation of p21 expression in an Sp1-dependent manner. We found that YHL-14 treatment resulted in up-regulation of p21 expression and a significant G2/M phase arrest in T24T and HCT116 cells without affecting p53 protein expression and activation. Further studies indicate that p21 induction by YHL-14 occurs at the transcriptional level via up-regulation of Sp1 protein expression. Moreover, our results show that p38 is essential for YHL-14-mediated Sp1 protein stabilization, G2/M growth arrest induction, and anchorage-independent growth inhibition of cancer cells. Taken together, our studies demonstrate a novel mechanism of YHL-14 against cancer cell growth in bladder and colon cancer cell lines, which provides valuable information for the design and synthesis of other new conformation-constrained derivatives on the basis of the structure of YHL-14 for cancer therapy.

Guanosine supplementation reduces the antiproliferative and apoptotic effects of the IMPDH inhibitor gnidilatimonoein in K562 cells

IMPDH (inosine 5'-monophosphate dehydrogenase) is the rate-limiting enzyme in the de novo biosynthetic pathway of guanine nucleotides, which is usually up-regulated in human leukaemia cell lines. Our previous studies have classified gnidilatimonoein, isolated from Daphne mucronata, as an IMPDH inhibitor and a strong antiproliferative agent among several types of leukaemia cells. In the present study, we investigated the effects of gnidilatimonoein on intracellular GTP pool size and its link to differentiation and apoptosis of K562 cells. It was found that gnidilatimonoein inhibited cell proliferation and induced G0/G1 cell cycle arrest in K562 cells after 24 h exposure to a single dose of gnidilatimonoein (1.5 μM), while no significant effects were observed on unstimulated and phytohaemagglutinin-stimulated peripheral blood lymphocyte cells at the gnidilatimonoein dose (1.5 μM) used. Based on the morphological changes, Wright-Giemsa staining, benzidine assay and the expression of cell surface markers [GPIIb (glycoprotein IIb) and glycophorin A], as analysed by flow cytometry, we found that K562 cells had differentiated towards megakaryocytic lineage. In addition, gnidilatimonoein induced apoptosis among K562 cells based on Acridine Orange/ethidium bromide and annexin V/propidium iodide double-staining observations. These changes, which were abrogated by the addition of guanosine, became evident when the intracellular GTP level decreased to approx. 20-35% of the untreated control level. Based on these findings, it can be concluded that gnidilatimonoein induces differentiation and apoptosis in K562 cells through perturbation of GTP metabolism, as one of its routes of action.

Pharmacokinetics, tissue distribution, and metabolism of novel DNA topoisomerase I inhibitor yuanhuacine in rabbit

A liquid chromatography/tandem mass spectrometry method was developed and validated for the quantitative determination of yuanhuacine (YHC), a daphne diterpene ortho-ester anticancer agent, and identification of its metabolites. Pharmacokinetic behaviour, tissue distribution, and metabolism were investigated in rabbit. YHC plasma data best fitted to a two-compartment model and were characterized by an elimination half-life t(1/2)(beta) of 11.1 h following intravenous administration. Tissue distribution studies did not identify any tissues having a high affinity for YHC. The main metabolites are proposed to be M392I, M392II, and M390, resulting from the ortho-ester group and aromatic ester bond being cleaved off simultaneously during Phase I metabolism. This investigation contributes to an understanding of the metabolism of daphne diterpene ortho-esters.

Daphnane diterpene esters isolated from flower buds of Daphne genkwa induce apoptosis in human myelocytic HL-60 cells and suppress tumor growth in Lewis lung carcinoma (LLC)-inoculated mouse model

In this study, two daphnane diterpene esters isolated from the flower buds of Daphne genkwa, genkwadaphnin (1) and yuanhuacine (2), were assessed with regard to their apoptotic activity in human promyelocytic HL-60 cells. Both 1 and 2 were demonstrated to activate the apoptotic process, including DNA fragmentation, chromatin condensation, and sub-G1 hypodiploidy. In our immunoblotting analysis, treatment with compounds 1 and 2 resulted in the cleavage of procaspase-3 and poly(ADP-ribose)polymerase (PARP) into active forms, and the expression of Bcl-2 proteins was shifted toward apoptosis; the expression of the pro-apoptotic protein, Bax, was increased, and the expression of Bcl-2 and Bcl-XL, both anti-apoptotic proteins, were suppressed in a dose-dependent manner. The administration (ip) of the compounds to Lewis lung carcinoma (LLC)-inoculated mice evidenced a significant inhibition of tumor growth (volume), with reductions of 47.9% and 63.1% (1), and 24.2% and 45.8% (2) at concentrations of 0.1 mg/kg and 0.5 mg/kg, as compared with the control mice. These results indicate that compounds 1 and 2 are potent apoptotic constituents of Daphne genkwa, and might be potent as anti-tumoric agents.

Evaluation of Daphne genkwa diterpenes: fingerprint and quantitative analysis by high performance liquid chromatography

Daphne genkwa contains a novel class of anticancer diterpene esters that inhibit DNA topoisomerase I. Fingerprint and quantitative analysis by HPLC were performed in order to characterise and evaluate D. genkwa. A standard fingerprint of Daphne diterpene esters from the root extract was first established by HPLC-UV, and the major peaks in the fingerprint profile were preliminarily determined using HPLC-MS. The principal Daphne diterpene esters, yuanhuacine (1), yuanhuadine (2), yuanhuajine (3) and yuanhuagine (4), were isolated and identified using a combination of UV, IR, MS, 1H-NMR and 13C-NMR spectral data. Quantitative analysis indicated that 1 was the principal component in the root, and that 2 was the major component in the buds. The average extraction rates of 1 and 2 were 0.0151 and 0.0033% (n=10) from the root, respectively, and 0.0020 and 0.0078% (n=3) from the buds, respectively.

Preparation of yuanhuacine and relative daphne diterpene esters from Daphne genkwa and structure–activity relationship of potent inhibitory activity against DNA topoisomerase I

Two new daphne diterpene esters Yuanhuajine (2) and Yuanhuagine (4), together with three known daphne diterpene esters yuanhuacine (1), yuanhuadine (3), and yuanhuapine (5), were isolated and identified from Daphne genkwa, a traditional Chinese medicine. Their structures were elucidated by a combination of UV, IR, MS and NMR ((1)H NMR, (13)C NMR, HSQC, and HMBC) spectra. In order to explore the structure-activity relationship, three compounds 6, 7, and 8 were prepared as three derivatives of 1. Inhibitory activities against DNA topoisomerase I (topo I) were assessed for the compounds 1-8. These compounds, except for 8, exhibited potent inhibitory activities against DNA topo I at IC(50) levels of 11.1-53.4 microM and they are new type of topo I inhibitors bearing different structures compared with the known topo I inhibitors. The agarose-gel electrophoresis experiments showed that the orthoester group of daphne diterpene esters was necessary for the inhibitory activity against DNA topo I, and the inhibition against DNA topo I is probably one of the anti-tumor mechanisms of daphne diterpene esters.

3-Hydrogenkwadaphnin targets inosine 5'-monophosphate dehydrogenase and triggers post-G1 arrest apoptosis in human leukemia cell lines

3-Hydrogenkwadaphnin (3-HK) is a recently characterized daphnane-type compound isolated from Dendrostellera lessertii with high anti-tumor activity in animal models. Herein, we report on time- and dose-dependent effects of this compound on growth, differentiation, IMPDH inhibition, cell cycle and apoptosis of a panel of human leukemia cell lines (HL-60, K562 and Molt4). The drug decreased the growth of leukemia cells in less than 24 h of treatment. However, longer exposure times and/or higher concentrations were required to promote cell apoptosis. Cell cycle analysis revealed the accumulation of cells in their G1 phase as early as 12 h after drug exposure but sub-G1 population was recorded after 24 h. Occurrence of apoptosis was constantly accompanied by morphological (staining with DNA-binding dyes) and biochemical (DNA fragments) variations among drug-treated cells. Despite these observations, non-activated normal human PBL were insensitive to the drug action. In addition, treatment of PHA-activated PBL, K562, Molt4 and HL-60 cells with a single dose of the drug for 24 h led to the inhibition of IMPDH activity by almost 37, 38, 44 and 50%, respectively. In contrast, no difference in IMPDH activities were seen between normal PBL and the drug treated PBL cells. Restoration of the depleted GTP concentration by exogenous addition of guanosine (25-50 microM) reversed the drug effects on cell growth, DNA fragmentation and apoptosis. Furthermore, the drug effects were potentiated by exogenous addition of hypoxanthine to the drug-treated cells. Reduction of the drug potency on the non-proliferative (retinoic acid treated) HL-60 cells by almost 40%, compared to the proliferative cells, clearly shows type II IMPDH as one of the main targets of the drug. These results suggest that 3-HK may be a powerful candidate for treatment of leukemia.

The Cytotoxic and Anti-proliferative Effects of 3-Hydrogenkwadaphnin in K562 and Jurkat Cells Is Reduced by Guanosine

3-hydrogenwadaphnin (3-HK) is a new daphnane-type diterpene ester isolated from Dendrostellera lessertii with strong anti-tumoral activity in animal models and in cultures. Here, prolonged effects of this new agent on proliferation and viability of several different cancerous cell lines were evaluated. Using [(3)H]thymidine incorporation, it was found that the drug inhibited cell proliferation and induced G1/S cell cycle arrest in leukemic cells 24 h after a single dose treatment. The cell viability of Jurkat cells was also decreased by almost 10 %, 31 % and 40 % after a single dose treatment (7.5 nM) at 24, 48 and 72 h, respectively. The drug-treated cells were stained with acridine orange/ ethidium bromide to document the chromatin condensation and DNA fragmentation. These observations were further confirmed by detection of DNA laddering pattern in the agarose gel electrophoresis of the extracted DNA from the treated cells. Treatment of K562 cells with the drug at 7.5, 15 and 30 nM caused apoptosis in 25 %, 45 % and 65 % of the cells, respectively. Exogenous addition of 25-50 microM guanosine and/or deoxyguanosine to the cell culture of the drug-treated cells restored DNA synthesis, released cell arrest at G1/S checkpoint and decreased the apoptotic cell death caused by the drug. These observations were not made using adenosine. However, the drug effects on K562 cells were potentiated by hypoxanthine. Based on these observations, perturbation of GTP metabolism is considered as one of the main reasons for apoptotic cell death by 3-HK.