Bombyxamycins A and B, Cytotoxic Macrocyclic Lactams from an Intestinal Bacterium of the Silkworm Bombyx mori.

Bombyxamycins A and B (1 and 2) were discovered from a silkworm gut Streptomyces bacterium. Spectroscopic analysis and multiple-step chemical derivatization identified them as 26-membered cyclic lactams with polyene features. Bombyxamycin A showed significant antibacterial and antiproliferative effects. The bombyxamycin biosynthetic gene cluster was identified by genetic analysis. Gene deletion experiments confirmed that the cytochrome P450 BomK is responsible for the generation of 2, which unprecedentedly bears tetrahydrofuran in its macrocyclic ring.

Borrelidins C-E: New Antibacterial Macrolides from a Saltern-Derived Halophilic Nocardiopsis sp.

Chemical investigation of a halophilic actinomycete strain belonging to the genus Nocardiopsis inhabiting a hypersaline saltern led to the discovery of new 18-membered macrolides with nitrile functionality, borrelidins C-E (1-3), along with a previously reported borrelidin (4). The planar structures of borrelidins C-E, which are new members of the rare borrelidin class of antibiotics, were elucidated by NMR, mass, IR, and UV spectroscopic analyses. The configurations of borrelidines C-E were determined by the interpretation of ROESY NMR spectra, J-based configuration analysis, a modified Mosher's method, and CD spectroscopic analysis. Borrelidins C and D displayed inhibitory activity, particularly against the Gram-negative pathogen Salmonella enterica, and moderate cytotoxicity against the SNU638 and K562 carcinoma cell lines.

Anti-melanogenic activity of phytosphingosine via the modulation of the microphthalmia-associated transcription factor signaling pathway.

BACKGROUND: Microphthalmia-associated transcription factor (MITF) suppresses the expression of enzymes controlling the production of melanin. Phytosphingosine is a well-known cosmetic agent, but its anti-melanogenic activity and mechanism of action remain unclear. OBJECTIVE: This study was designed to investigate the effects of phytosphingosine on melanin synthesis and elucidate the plausible mechanism of actions in vitro and ex vivo systems. METHODS: Melanin content, cell viability, tyrosinase activity, p-CREB DNA binding activity, and the protein gene expression levels of the enzymes and proteins involved in melanogenesis were measured with the treatment of phytosphingosine. RESULTS: Phytosphingosine inhibits melanin synthesis in cultured melan-a cells and a reconstructed human skin model. One possible mechanism of the anti-melanogenic activity of phytosphingosine appears to be associated with the modulation of MITF, which suppresses the expression of tyrosinase, tyrosinase-related protein-1 (TRP-1), and TRP-2. Further analysis revealed that phytosphingosine suppressed paired box 3 and SRY-related HMG-box 10, critical transcription factors of MITF. Phytosphingosine also effectively downregulated the protein levels of ß-catenin and the phospho-cAMP response element binding protein, an upstream regulatory factor of MITF. These results are closely related to the suppression of MITF gene expression. In addition, treatment with phytosphingosine for over 12h, which is a relatively long period of time, did not directly suppress these MITF transcriptional factors. Instead, phytosphingosine induced ERK activation, which led to MITF phosphorylation, followed by its degradation. Therefore, the downregulation of MITF protein levels by phytosphingosine with a long time exposure is in part associated with MITF protein degradation through the MAPK kinase activation pathway. CONCLUSION: The modulation of MITF by phytosphingosine is closely related with the signaling pathways, such as the suppression of the MITF gene expression and the degradation of the MITF protein, depending on the duration of treatment time. These results suggest that phytosphingosine might serve as an effective melanogenesis inhibitor in melanocytes via the regulation of the MITF signaling pathways.

Effective Killing of Cancer Cells Through ROS-Mediated Mechanisms by AMRI-59 Targeting Peroxiredoxin I.

AIMS: The intrinsic increase of reactive oxygen species (ROS) production in cancer cells after malignant transformation frequently induces redox adaptation, leading to enhanced antioxidant capacity. Peroxiredoxin I (PrxI), an enzyme responsible for eliminating hydrogen peroxide, has been found to be elevated in many types of cancer cells. Since overexpression of PrxI promoted cancer cells' survival and resistance to chemotherapy and radiotherapy, PrxI has been proposed as a therapeutic target for anticancer drugs. In this study, we aimed to investigate the anticancer efficacy of a small molecule inhibitor of PrxI. RESULTS: By a high-throughput screening approach, we identified AMRI-59 as a potent inhibitor of PrxI. AMRI-59 increased cellular ROS, leading to the activation of both mitochondria- and apoptosis signal-regulated kinase-1-mediated signaling pathways, resulting in apoptosis of A549 human lung adenocarcinoma. AMRI-59 caused no significant changes in ROS level, proliferation, and apoptosis of PrxI-knockdown A549 cells by RNA interference. PrxI overexpression or N-acetylcysteine pretreatment abrogated AMRI-59-induced cytotoxicity in A549 cells. AMRI-59 rendered tumorigenic ovarian cells more susceptible to ROS-mediated death compared with nontumorigenic cells. Moreover, significant antitumor activity of AMRI-59 was observed in mouse tumor xenograft model implanted with A549 cells with no apparent acute toxicity. INNOVATION: This study offers preclinical proof-of-concept for AMRI-59, a lead small molecule inhibitor of PrxI, as an anticancer agent. CONCLUSIONS: Our results highlight a promising strategy for cancer therapy that preferentially eradicates cancer cells by targeting the PrxI-mediated redox-dependent survival pathways.

Differences in driving performance due to headway distances and gender: the application of jerk cost function.

Driving is directly controlled by the driver's movement. This study tried to compare differences in gender and headway distances between the DRIVING phase and the SUDDEN STOP phase by using subjects' movement during driving in the simulator. To quantify subjects' movement, the jerk cost function (JC) was used, and conventional vehicle control parameters such as the coefficient of variation of the mediolateral trajectory (MLCV) for lane keeping and the brake time (BT) were also used. As the headway distance increased, MLCV and JC decreased significantly in the DRIVING phase. In the SUDDEN STOP phase, BT was increased and, MLCV and JC were decreased. Differences between genders were detected for both MLCV (males < females) and JC (males > females). The results of this study demonstrate that JC may be used as a variable in evaluating driving performance as influenced by driving conditions and gender.

Suppression of MAPK Signaling and Reversal of mTOR-Dependent MDR1-Associated Multidrug Resistance by 21α-Methylmelianodiol in Lung Cancer Cells.

Lung cancer is the leading cause of cancer-related deaths worldwide and remains the most prevalent. Interplay between PI3K/AMPK/AKT and MAPK pathways is a crucial effector in lung cancer growth and progression. These signals transduction protein kinases serve as good therapeutic targets for non-small cell lung cancer (NSCLC) which comprises up to 90% of lung cancers. Here, we described whether 21α-Methylmelianodiol (21α-MMD), an active triterpenoid derivative of Poncirus trifoliate, can display anticancer properties by regulating these signals and modulate the occurrence of multidrug resistance in NSCLC cells. We found that 21α-MMD inhibited the growth and colony formation of lung cancer cells without affecting the normal lung cell phenotype. 21α-MMD also abrogated the metastatic activity of lung cancer cells through the inhibition of cell migration and invasion, and induced G0/G1 cell cycle arrest with increased intracellular ROS generation and loss of mitochondrial membrane integrity. 21α-MMD regulated the expressions of PI3K/AKT/AMPK and MAPK signaling which drove us to further evaluate its activity on multidrug resistance (MDR) in lung cancer cells by specifying on P-glycoprotein (P-gp)/MDR1-association. Employing the established paclitaxel-resistant A549 cells (A549-PacR), we further found that 21α-MMD induced a MDR reversal activity through the inhibition of P-gp/MDR1 expressions, function, and transcription with regained paclitaxel sensitivity which might dependently correlate to the regulation of PI3K/mTOR signaling pathway. Taken together, these findings demonstrate, for the first time, the mechanistic evaluation in vitro of 21α-MMD displaying growth-inhibiting potential with influence on MDR reversal in human lung cancer cells.

Efficient synthesis and biological activity of Psammaplin A and its analogues as antitumor agents.

We describe a new concise method for the synthesis of psammaplin A and its analogues, and antitumor activity of psammaplin A analogues. Psammaplin A was obtained with 41% yield in 5 steps from 3-bromo-4-hydroxybenzaldahyde and ethyl acetoacetate via Knoevenagel condensation and α-nitrosation as key steps. Twenty eight analogues of psammaplin A were prepared employing the new synthetic approach. Structure-activity relationship study against cytotoxicity reveal that the free oxime group and disulfide functional group were responsible for high cytotoxicity. Also the bromotyrosine component was relatively tolerable and hydrophobic aromatic groups preserved the cytotoxicity. The cytotoxicity of aromatic group is dependent on the size and spatial geometry. Among them, five compounds showed comparable cytotoxicity to psammaplin A. Compound 30 exhibited potential HDAC inhibitory activity and in vivo antitumor activity.

Salternamides A-D from a Halophilic Streptomyces sp. Actinobacterium.

Salternamides A-D (1-4), the first secondary metabolites discovered from saltern-derived actinomycetes, were isolated from a halophilic Streptomyces strain isolated from a saltern on Shinui Island in the Republic of Korea. The planar structures of the salternamides, which are new members of the manumycin family, were elucidated by a combination of spectroscopic analyses. The absolute configurations of the salternamides were determined by chemical and spectroscopic methods, including the modified Mosher's method, J-based configuration analysis, and circular dichroism spectroscopy. Salternamide A (1), which is the first chlorinated compound in the manumycin family, exhibited potent cytotoxicity against a human colon cancer cell line (HCT116) and a gastric cancer cell line (SNU638) with submicromolar IC50 values. Salternamides A and D were also determined to be weak Na(+)/K(+) ATPase inhibitors.

Pentacyclic antibiotics from a tidal mud flat-derived actinomycete.

The combination of investigating a unique source of chemically prolific bacterium with an LC/MS-based bacterial strain selection approach resulted in the discovery of two new secondary metabolites, buanmycin (1) and buanquinone (2), from the culture of a marine Streptomyces strain, which was isolated from a tidal mudflat in Buan, Republic of Korea. The carbon backbone of buanmycin (1), comprising 20 quaternary carbons out of 30 total carbons, was determined via (13)C-(13)C COSY NMR analysis after labeling 1 with (13)C by culturing the bacterium with (13)C-glucose. The complete structure of 1 was confidently elucidated, primarily based on 1D and 2D NMR spectroscopic and X-ray crystallographic analysis, as that of a new pentacyclic xanthone. The absolute configuration of the α-methyl serine unit in 1 was established by applying the advanced Marfey's method. The structure of buanquinone (2) was determined to be a new pentacyclic quinone based on NMR and MS spectroscopic data. Buanmycin exhibited potent cytotoxicity against colorectal carcinoma cells (HCT-116) and gastric carcinoma cells (SNU-638) with submicromolar IC50 values and strongly inhibited the pathogenic Gram-negative bacterium Salmonella enterica (MIC = 0.7 µM). In particular, buanmycin demonstrated inhibition of sortase A, which is a promising target for antibiotic discovery.

New benzoxazine secondary metabolites from an arctic actinomycete.

Two new secondary metabolites, arcticoside (1) and C-1027 chromophore-V (2), were isolated along with C-1027 chromophore-III and fijiolides A and B (3-5) from a culture of an Arctic marine actinomycete Streptomyces strain. The chemical structures of 1 and 2 were elucidated through NMR, mass, UV, and IR spectroscopy. The hexose moieties in 1 were determined to be d-glucose from a combination of acid hydrolysis, derivatization, and gas chromatographic analyses. Arcticoside (1) and C-1027 chromophore-V (2), which have a benzoxazine ring, inhibited Candida albicans isocitrate lyase. Chromophore-V (2) exhibited significant cytotoxicity against breast carcinoma MDA-MB231 cells and colorectal carcinoma cells (line HCT-116), with IC50 values of 0.9 and 2.7 µM, respectively.

Differences in gait pattern between the elderly and the young during level walking under low illumination.

The purpose of this study was to compare changes in the gait pattern between the elderly and young during level (i.e., even surface) walking under low illumination. Vision during walking plays a role in avoiding obstacles and uneven surfaces, as well as an important role in the proactive control of dynamic stability and route planning for level walking. Fourteen elderly and fourteen young male subjects walked on a 7 m walkway with two illumination conditions using self-selected walking speed: walking with normal (>300 lux) and low illumination (<10 lux). Walking speed, stance phase ratio, toe clearance on swing phase, and range of motion at the center of mass were used to compare the differences in gait pattern between two illumination conditions and ages. During walking with low illumination, walking speed and stance phase ratio of the young decreased, and toe clearance of the young increased. However, there was no difference in these variables due to low illumination in the elderly subjects. Despite level walking conditions, there were some differences in gait pattern between the young and the elderly due to illumination conditions. This implies that the young showed a more positive change of gait pattern, due to low illumination, than that of the elderly. In this respect, further study is necessary to identify differences between the young and the elderly, when they walk on an uneven or obstacle walkway with low illumination.

A new benzofuran glycoside and indole alkaloids from a sponge-associated rare actinomycete, Amycolatopsis sp.

Three new secondary metabolites, amycofuran (1), amycocyclopiazonic acid (2), and amycolactam (3), were isolated from the sponge-associated rare actinomycete Amycolatopsis sp. Based on combined spectroscopic analyses, the structures of 1-3 were determined to be a new benzofuran glycoside and new indole alkaloids related to cyclopiazonic acids, a class that has previously only been reported in fungi. The absolute configurations of 1 and 3 were deduced by ECD calculations, whereas that of 2 was determined using the modified Mosher method. Amycolactam (3) displayed significant cytotoxicity against the gastric cancer cell line SNU638 and the colon cancer cell line HCT116.

Separacenes A-D, novel polyene polyols from the marine actinomycete, Streptomyces sp.

Separacenes A-D (1-4), novel polyene polyols, were isolated from Streptomyces sp. collected from the southern area of Jeju Island, Korea. The chemical structures of 1-4 were established by NMR, mass, UV, and IR spectroscopy as well as the modified Mosher's method. Separacenes A-B (1-2), which share an identical planar structure but possess different relative configurations, bear tetraene units flanked by two diol moieties, whereas the stereoisomeric separacenes C-D (3-4) possess a triene moiety between two diol substructures. Separacenes A-D each contain a terminal olefinic methylene. Separacene A displayed inhibitory activity against Candida albicans isocitrate lyase and weak cytotoxicity against both the colon carcinoma cell line HCT-116 and the lung cancer cell line A549.

Antimetastatic effect of halichondramide, a trisoxazole macrolide from the marine sponge Chondrosia corticata, on human prostate cancer cells via modulation of epithelial-to-mesenchymal transition.

Halichondramide (HCA), a trisoxazole-containing macrolide isolated from the marine sponge Chondrosia corticata has been shown to exhibit cytotoxicity and antifungal activities. In our previous study, HCA was also found to exhibit antiproliferative activity against a variety of cancer cells. However, the precise mechanism of action of HCA in the antitumor activity remains to be elucidated. In the present study, we identified the antimetastatic activity of HCA in the highly metastatic PC3 human prostate cancer cells. HCA showed potent growth inhibitory activity of the PC3 cells with an IC50 value of 0.81 µM. Further analysis revealed that HCA suppressed the expression of a potential metastatic biomarker, phosphatase of regenerating liver-3 (PRL-3), in PC3 cells. The suppression of PRL-3 by HCA sequentially down-regulates the expression of phosphoinositide 3-kinase (PI3K) subunits p85 and p110. The antimetastatic effect of HCA was also correlated with the down-regulation of matrix metalloproteases (MMPs) and the modulation of cadherin switches N-cadherin and E-cadherin. In addition, HCA also effectively suppressed the migration and invasion of PC3 cells. These findings suggest that halichondramide might serve as a potential inhibitor of tumor cell metastasis with the modulation of PRL-3.

Wnt/ß-catenin signaling mediates the antitumor activity of magnolol in colorectal cancer cells.

Abnormal activation of the canonical Wnt/ß-catenin pathway and up-regulation of the ß-catenin/T-cell factor (TCF) response to transcriptional signaling play a critical role early in colorectal carcinogenesis. Therefore, Wnt/ß-catenin signaling is considered an attractive target for cancer chemotherapeutic or chemopreventive agents. Small molecules derived from the natural products were used in our cell-based reporter gene assay to identify potential inhibitors of Wnt/ß-catenin signaling. Magnolol, a neolignan from the cortex of Magnolia obovata, was identified as a promising candidate because it effectively inhibited ß-catenin/TCF reporter gene (TOPflash) activity. Magnolol also suppressed Wnt3a-induced ß-catenin translocation and subsequent target gene expression in human embryonic kidney 293 cells. To further investigate the precise mechanisms of action in the regulation of Wnt/ß-catenin signaling by magnolol, we performed Western blot analysis, real-time reverse transcriptase-polymerase chain reactions, and an electrophoretic mobility shift assay in human colon cancer cells with aberrantly activated Wnt/ß-catenin signaling. Magnolol inhibited the nuclear translocation of ß-catenin and significantly suppressed the binding of ß-catenin/TCF complexes onto their specific DNA-binding sites in the nucleus. These events led to the down-regulation of ß-catenin/TCF-targeted downstream genes such as c-myc, matrix metalloproteinase-7, and urokinase-type plasminogen activator in SW480 and HCT116 human colon cancer cells. In addition, magnolol inhibited the invasion and motility of tumor cells and exhibited antitumor activity in a xenograft nude mouse model bearing HCT116 cells. These findings suggest that the growth inhibition of magnolol against human colon cancer cells can be partly attributed to the regulation of the Wnt/ß-catenin signaling pathway.

Antimetastatic activity of pinosylvin, a natural stilbenoid, is associated with the suppression of matrix metalloproteinases.

Metastasis is a major cause of death in cancer patients. Our previous studies showed that pinosylvin, a naturally occurring trans-stilbenoid mainly found in Pinus species, exhibited a potential cancer chemopreventive activity and also inhibited the growth of various human cancer cell lines via the regulation of cell cycle progression. In this study, we further evaluated the potential antimetastatic activity of pinosylvin in in vitro and in vivo models. Pinosylvin suppressed the expression of matrix metalloproteinase (MMP)-2, MMP-9 and membrane type 1-MMP in cultured human fibrosarcoma HT1080 cells. We also found that pinosylvin inhibited the migration of HT1080 cells in colony dispersion and wound healing assay systems. In in vivo spontaneous pulmonary metastasis model employing intravenously injected CT26 mouse colon cancer cells in Balb/c mice, pinosylvin (10 mg/kg body weight, intraperitoneal administration) significantly inhibited the formation of tumor nodules and tumor weight in lung tissues. The analysis of tumor in lung tissues indicated that the antimetastatic effect of pinosylvin coincided with the down-regulation of MMP-9 and cyclooxygenase-2 expression, and phosphorylation of ERK1/2 and Akt. These data suggest that pinosylvin might be an effective inhibitor of tumor cell metastasis via modulation of MMPs.