Yuna Pyee

Thalassospiramide G, a New γ-Amino-Acid-Bearing Peptide from the Marine Bacterium Thalassospira sp.

In the chemical investigation of marine unicellular bacteria, a new peptide, thalassospiramide G (1), along with thalassospiramides A and D (2–3), was discovered from a large culture of Thalassospira sp. The structure of thalassospiramide G, bearing γ-amino acids, such as 4-amino-5-hydroxy-penta-2-enoic acid (AHPEA), 4-amino-3,5-dihydroxy-pentanoic acid (ADPA), and unique 2-amino-1-(1H-indol-3-yl)ethanone (AIEN), was determined via extensive spectroscopic analysis. The absolute configuration of thalassospiramide D (3), including 4-amino-3-hydroxy-5-phenylpentanoic acid (AHPPA), was rigorously determined by 1H–1H coupling constant analysis and chemical derivatization. Thalassospiramides A and D (2–3) inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated mouse macrophage RAW 264.7 cells, with IC50 values of 16.4 and 4.8 μM, respectively.

Antitumor Activity of Spicatoside A by Modulation of Autophagy and Apoptosis in Human Colorectal Cancer Cells

The antitumor activity of spicatoside A (1), a steroidal saponin isolated from the tuber of Liriope platyphylla, and its underlying mechanisms were investigated in HCT116 human colorectal cancer cells. Compound 1 induced autophagy and apoptotic cell death and inhibited tumor growth in a nude mouse xenograft model implanted with HCT116 cells. Treatment with 1 for 24 h enhanced the formation of acidic vesicular organelles in the cytoplasm, indicating the induction of the onset of autophagy. This event was associated with the regulation of autophagic markers including microtubule-associated protein 1 light chain 3 (LC3)-II, p62, beclin 1, lysosomal-associated membrane protein 1 (LAMP 1), and cathepsin D by inhibiting the PI3K/Akt/mTOR signaling pathway, regulating mitogen-activated protein kinase (MAPK) signaling, and increasing p53 levels. However, a prolonged exposure to 1 resulted in apoptosis characterized by the accumulation of a sub-G1 cell population and an annexin V/propidium iodide (PI)-positive cell population. Apoptosis induced by 1 was associated with the regulation of apoptotic proteins including Bcl-2, Bax, and Bid, the release of cytochrome c into the cytosol, and the accumulation of cleaved poly-ADP-ribose polymerase (PARP). Further study revealed that cleavage of beclin 1 by caspases plays a critical role in the 1-mediated switch from autophagy to apoptosis. Taken together, these findings highlight the significance of 1 in the modulation of crosstalk between autophagy and apoptosis, as well as the potential use of 1 as a novel candidate in the treatment of human colorectal cancer cells.

25-Methoxyhispidol A, a novel triterpenoid of Poncirus trifoliata, inhibits cell growth via the modulation of EGFR/c-Src signaling pathway in MDA-MB-231 human breast cancer cells.

The fruit of Poncirus trifoliata (Rutaceae) has been used a medicinal food and traditional medicine. Recently we reported the isolation of 25-methoxyhispidol A (25-MHA) as a novel triterpenoid from the immature fruit of P. trifoliata with the potential growth inhibition of cancer cells. However, the molecular mechanisms on the anti-proliferative activity in cancer cells remain to be elucidated. In the present study, we investigated the anti-proliferative activity and mechanisms of actions mediated by 25-MHA in estrogen receptor (ER)-negative MDA-MB-231 human breast cancer cells. 25-MHA exhibited the growth inhibitory activity against MDA-MB-231 cells with the cell cycle arrest in the G0/G1 phase. The cell cycle arrest in the G0/G1 by 25-MHA was well correlated with the downregulation of cyclin D1, cyclin dependent kinase (CDK4), CDK2, cyclin A, phosphorylated retinoblastoma protein (pRb), and induction of cdk inhibitor p21(WAF1/Cip1) protein. 25-MHA also suppressed the activation of c-Src/epidermal growth factor receptor (EGFR)/Akt signaling, and consequently led to the inactivation of mTOR and its downstream signal molecules including 4E-binding protein (4E-BP) and p70 S6 kinase. These findings suggest that 25-MHA-mediated inhibitory activity of human breast cancer cell growth might be related with the cell cycle arrest and modulation of signal transduction pathways.

Suppression of inflammatory responses by handelin, a guaianolide dimer from Chrysanthemum boreale, via downregulation of NF-κB signaling and pro-inflammatory cytokine production.

The anti-inflammatory activity of handelin (1), a guaianolide dimer from Chrysanthemum boreale flowers, was evaluated in vivo, and the effects on mediators nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) and the nuclear factor-κB (NF-κB) and ERK/JNK signaling pathways were investigated in vitro. Compound 1 inhibited lipopolysaccharide (LPS)-induced production of NO and PGE2 in cultured mouse macrophage RAW 264.7 cells. The suppression of NO and PGE2 production by 1 was correlated with the downregulation of mRNA and protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Compound 1 also suppressed the induction of pro-inflammatory cytokines TNF-α and IL-1β in LPS-stimulated RAW 264.7 cells. To further clarify the transcriptional regulatory pathway in the expression of iNOS and COX-2 by 1, the role of NF-κB was determined in RAW 264.7 cells. Compound 1 inhibits the binding activity of NF-κB into the nuclear proteins. The transcriptional activity of NF-κB stimulated with LPS was also suppressed by 1, which coincided with the inhibition of IκB degradation. Compound 1 also suppressed the activation of mitogen-activated protein kinases, including ERK and JNK signaling. In addition, the LPS-stimulated upregulation of miRNA-155 expression was suppressed by 1. The oral administration of 1 inhibited acute inflammation in carrageenan-induced paw and 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ear edema models. The serum level of IL-1β was also inhibited by 1 in a carrageenan-induced paw edema model. These findings suggest that the suppression of NF-κB activation and pro-inflammatory cytokine production may be a plausible mechanism of action for the anti-inflammatory activity of handelin.

In vitro stability and in vivo anti-inflammatory efficacy of synthetic jasmonates

A chlorinated methyl jasmonate analog (J7) was elaborated as an in vitro anti-inflammatory lead. However, its in vitro efficacy profile was not reproduced in a subsequent in vivo evaluation, presumably due to its rapid enzymatic hydrolysis in a biological system. In an attempt to improve the metabolic stability of the lead J7 by replacement of its labile methyl ester with reasonable ester groups, several analogs resistant to enzymatic hydrolysis were synthesized. In vivo evaluation of the stability-improved analogs showed that these compounds displayed higher efficacy than the lead J7, suggesting that these new jasmonate analogs may serve as potential anti-inflammatory leads.

Suppression of inducible nitric oxide synthase expression by nyasol and broussonin A, two phenolic compounds from Anemarrhena asphodeloides, through NF-κB transcriptional regulation in vitro and in vivo.

Anemarrhena asphodeloides is widely used in traditional Chinese medicine, and is known to possess antidiabetic and anti‐inflammatory properties. Because inducible nitric oxide synthase (iNOS) plays an important role in inflammation, we investigated the inhibitory effects of two known phenolic compounds, nyasol (1) and broussonin A (2), from A. asphodeloides, on iNOS and its plausible mechanism of action. Compounds 1 and 2 exhibited inhibitory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)‐stimulated RAW 264.7 macrophage cells. Compounds 1 and 2 also suppressed the expressions of iNOS protein and mRNA. Moreover, compounds 1 and 2 suppressed the expression of inflammatory cytokines such as interleukin‐1β (IL‐1β) and interferon‐β (IFN‐β). They also inhibited the transcriptional activity of NF‐κB and degradation of IκB‐α, as well as the activation of Akt and ERK in LPS‐stimulated RAW 264.7 cells. In in vivo animal model, compounds 1 and 2 significantly inhibited TPA‐induced mouse ear edema. These results suggest that 1 and 2 suppress LPS‐stimulated iNOS expression at the transcriptional level through modulating NF‐κB and down‐regulation of the Akt and ERK signaling pathways. Taken together, these findings indicate that the suppressive effects of 1 and 2 on iNOS expression might provide one possible mechanism for their anti‐inflammatory activities.

Abstract 259: Antitumor activities of yuanhuadine, a daphnane diterpene from Daphne genkwa, via epidermal growth factor receptor signaling in non-small cell lung cancer cells

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL The growth inhibition and antitumor activities of yuanhuadine (1), a daphnane diterpenoid from the flowers of Daphne genkwa, were investigated in human lung cancer cells. Compound 1 exhibited a relatively selective growth inhibition against human lung cancer cells compared to other solid human cancer cell lines. The potent antiproliferative activity by 1 was associated with cell-cycle arrest and modulation of cell signaling pathways. Cell-cycle arrest in the G0/G1 and G2/M phase was induced by 1 in A549 human non-small cell lung cancer cells, and these events were correlated with the expression of checkpoint proteins including the up-regulation of p21, and down-regulation of cyclins, cyclin-dependent kinases 2 (CDK2) and 4 (CDK4), and c-Myc. Compound 1 also suppressed the expression of the Akt/mammalian target of rapamycin (mTOR) and its downstream effector molecules including p70 S6 kinase (p70S6K) and eukaryotic initiation factor 4E-binding protein 1 (4EBP1). The ligand-induced epidermal growth factor receptor (EGFR) and c-Met signalings were also inhibited by 1. The oral administration of 1 (0.5 mg/kg body weight, daily) for 14 days inhibited tumor growth in athymic xenograft nude mouse model bearing human lung A549 cells significantly, without any overt toxicity. Synergistic antiproliferative effects of compound 1 were also found in combination with the EGFR inhibitor gefitinib. Cell-cycle arrest and suppression of Akt/mTOR and EGFR signaling pathways might be plausible mechanisms of actions for the antiproliferative and antitumor activity of 1 in human non-small cell lung cancer cells Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 259. doi:1538-7445.AM2012-259

Abstract 3334: Antiangiogenic activity of honokiol through inhibition of vascular vessel formation in the mouse embryonic stem cell-derived endothelial cells

Embryonic stem (ES) cells, which are characterized by pluripotency and self-renewal, have recently been highlighted in several aspects of drug discovery. In particular, the potential of ES cells to differentiate into specific-cell types make them an extremely useful tool in the evaluation of the biological activity of test compounds. In the present study, we employed mouse embryonic stem (mES) cell-derived embryoid bodies (EBs) to evaluate the antiangiogenic activity of natural compounds. Honokiol, a major neolignan derived from the bark of Magnolia obovata Thunberg (Magnoliaceae), was capable of inhibiting differentiation and vascular vessel formation in mES cell models. EBs were formed using hanging drop cultures. The induction of vascular formation was carried out on gelatin-coated plates in EGM-2 medium. Cell proliferation was measured by MTT assay. RT-PCR, immunocytochemistry, and Western blotting were used to measure differentiation of EBs into endothelial cells and vessel formation. The growth inhibition of honokiol in EB-derived endothelial cells was found that honokiol is more sensitive in the differentiated cells (on day 8) compared to the undifferentiated EB-derived endothelial cells (on day 1) with the IC 50 values of 6.0 and 17.8 μM, respectively. Honokiol also dramatically decreased the expressions of an endothelial biomarker PECAM in the differentiated EB-derived endothelial cells (on day 11). Honokiol also suppressed the activation of p38 MAPK, Akt, ERK1/2 and SAPK/JNK in EB-derived endothelial cells. The antiangiogenic activity of honokiol is associated with the suppression of PECAM and the MAPK pathway in EB-derived endothelial cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3334. doi:1538-7445.AM2012-3334

Abstract 1974: Growth inhibition and antitumor activity of chikusetsusaponin IVa methyl ester, an oleanane-type triterpenoid from the root of Acyranthes japonica, in HCT 116 human colon cancer cells

Chikusetsusaponin IVa methyl ester (CSME) is an oleanane-type triterpenoid isolated from the root of Acyranthes japonica (Amaranthaceae). In the present study, the growth inhibition and antitumor activity of CSME were investigated in cultured human colon cancer cell HCT 116. CSME inhibited the proliferation of cancer cells with an IC 50 value of 22.4 μM. Flow cytometric analysis indicated that CSME markedly induced the accumulation of cells in the G0/G1 phase and the increase of cell population in sub-G1 phase. G0/G1 cell cycle arrest by CSME was associated with the down-regulation of the expression of cyclin D1, cyclin A, CDK4, CDK2, c-myc and Rb phosphorylation. The increase of sub-G1 peak by CSME was closely correlated with the induction of apoptosis, which was evidenced by the induction of cleaved poly-(ADP ribose) polymerase, activation of caspases, and suppression of Bid and Bcl-2 expression. Treatment of CSME (0.25, 1.0, or 3.0 mg/kg, i.p) also effectively suppressed tumor growth in the HCT 116 implanted xenograft nude mouse model without any overt toxicity. Taken together, these findings suggest that CSME might be a potential candidate for the development of cancer chemotherapeutic agents derived from natural products. (Acknowledgement; this study was supported by a grant Studies on the Identification of the Efficacy of Biologically Active Components from Oriental Herbal Medicines from the Korea Food and Drug Administration (2010)). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1974. doi:1538-7445.AM2012-1974