Topological Complex Charge Conservation in Nontrivial Z2 × Z2 Domain Walls.

Localized topological modes such as solitons, Majorana Fermions, and skyrmions are attracting great interest as robust information carriers for future devices. Here, a novel conserved quantity for topological domain wall networks of a Z2 × Z2 order generated with spin-polarized current in Sr2VO3FeAs is discovered. Domain walls are mobilized by the scanning tunneling current, which also observes in atomic scale active dynamics of domain wall vertices including merge, bifurcation, pair creation, and annihilation. Within this dynamics, the product of the topological complex charges defined for domain wall vertices is conserved with a novel boundary-charge correspondence rule. These results may open an avenue toward topological electronics based on domain wall vertices in generic Z2 × Z2 systems.

Nematicidal activity of teleocidin B4 isolated from Streptomyces sp. against pine wood nematode, Bursaphelenchus xylophilus.

BACKGROUND: Pine wilt disease (PWD) is a plant disease that causes serious damage to pine trees. PWD occurs when the host plant is infected with pinewood nematode (PWN), Bursaphelenchus xylophilus. In this study, a compound with nematicidal activity was isolated from actinomycetes and its efficacy was investigated in vitro. RESULT: We screened and selected Streptomyces sp. 680560, which had nematicidal activity against B. xylophilus. Based on 16S rRNA sequence analysis, it showed 99.93% similarity with Streptomyces blastmyceticus NRRB-5480T . Furthermore, the active compound was isolated and identified as teleocidin B4. Teleocidin B4 at concentrations ranging from 6.25 to 100 µM had low nematicidal activity after 24 and 36 h against adult and stage juveniles (J2) of B. xylophilus, but after 48 h nematicidal activity exceeded 95%. The rate of inhibition of egg hatching for Teleocidin B4 6.25, 12.5, 25, 50, and 100 µM was confirmed to be dose-dependently inhibited after 48 h of treatment. Teleocidin B4 is not only toxic to hatched B. xylophilus, but also affects egg hatching. CONCLUSION: This study was carried out to isolate actinomycete metabolites from pine tree endophytes from various natural environments for control of PWD. A compound with nematicidal activity was isolated from a selected strain and its structure was identified as teleocidin B4. The nematicidal effect of the isolated active substance, teleocidin B4, was confirmed. This is the first report of the effect of teleocidin B4 on B. xylophilus, suggesting its possibility as a PWD control agent. © 2020 Society of Chemical Industry.

Anticancer effects of Poncirus fructus on hepatocellular carcinoma through regulation of apoptosis, migration, and invasion.

Poncirus fructus (PF) is a phytochemical compound extracted from the dry, immature fruits of Poncirus trifoliate. PF is traditionally used to treat gastrointestinal disorders, allergies, and inflammatory disease. In East Asia, PF is also known for its anticancer properties. There are numerous reports on the anticancer and anti­inflammatory effects of PF in a wide range of cancers and gastrointestinal diseases, respectively. However, the role of PF in inducing apoptosis and suppressing the invasiveness of hepatocellular carcinoma (HCC) remains unclear. This study investigated the ability of PF to induce apoptosis and inhibit the invasiveness and migratory ability of HCC cell lines (Hep3B and Huh7). Wound healing, Transwell migration and invasion, and colony­formation assays, as well as flow cytometry, were used to analyze cell proliferation, migration, invasion, and apoptosis. Epithelial­mesenchymal transition (EMT)­related and apoptotic proteins were assessed by western blotting. The mitochondrial membrane potential of the Hep3B and Huh7 cells was observed with tetramethylrhodamine ethyl ester. The reactive oxygen species (ROS) level was determined by dihydroethidium (DHE) staining. PF treatment significantly decreased the proliferation of Hep3B and Huh7 cells in a dose­dependent manner, reduced the mitochondrial membrane potential, increased ROS levels, decreased the protein levels of Bcl­2, and increased the protein levels of Bax and cleaved caspase­3 and 9, suggesting that PF mediated HCC apoptosis via a mitochondrial pathway. Our findings showed that PF prevented HCC cell migration and invasion by inhibiting the EMT process and downregulating MMP­2 and MMP­9 activities. The results suggest the potential anticancer effects of PF by inhibiting proliferation, inducing apoptosis, and reducing the invasion and migration of HCC cells.

Pseudogap and Weak Multifractality in 2D Disordered Mott Charge-Density-Wave Insulator.

We investigate electronic states of Se-substituted 1T-TaS2 by scanning tunneling microscopy/spectroscopy (STM/STS), where superconductivity emerges from the unique Mott-charge-density-wave (Mott-CDW) state. Spatially resolved STS measurements reveal that a pseudogap replaces the Mott gap with the CDW gaps intact. The pseudogap has little correlation with the unit-cell-to-unit-cell variation in the local Se concentration but appears globally. The correlation length of the local density of states (LDOS) is substantially enhanced at the Fermi energy and decays rapidly at high energies. Furthermore, the statistical analysis of LDOS indicates the weak multifractal behavior of the wave functions. These findings suggest a correlated metallic state induced by disorder and provide a new insight into the emerging superconductivity in two-dimensional materials.

Pancastatin A and B Have Selective Cytotoxicity on Glucose-Deprived PANC-1 Human Pancreatic Cancer Cells.

Glucose deprivation and hypoxia frequently occur in solid tumor cells, including pancreatic cancer cells. Glucose deprivation activates the unfolded protein response (UPR) and causes the upregulation of glucose-regulated protein 78 (GRP78). Induction of GRP78 has been shown to protect cancer cells. Therefore, shutting down of GRP78 expression may be a novel strategy in anticancer drug development. Based on this understanding, a screening system established for anticancer agents that exhibit selective cytotoxicity on pancreatic cancer cells under glucose-deprived conditions. To test this hypothesis, the new compounds isolated, pancastatin A (PST-A) and B (PSTB), from Ponciri Fructus. PST-A and B were identified as glabretal triterpenoid moieties by electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopic methods. PST-A and B suppressed the accumulation of the UPR hallmark gene, GRP78, during glucose deprivation. Furthermore, PST-A and B showed selective cytotoxicity on PANC-1 pancreatic cancer cells under glucose deprivation. Interestingly, PST-A and B had no effect on these cells under normal growth conditions. Our results suggest that PST-A and B act as novel therapeutic agents to induce selective cell death in glucose-deprived pancreatic cancer cells.

Arctigenin Inhibits Etoposide Resistance in HT-29 Colon Cancer Cells during Microenvironmental Stress.

Microenvironmental stress, which is naturally observed in solid tumors, has been implicated in anticancer drug resistance. This tumor-specific stress causes the degradation of topoisomerase IIα, rendering cells resistant to topoisomerase IIα-targeted anticancer agents. In addition, microenvironmental stress can induce the overexpression of 78kDa glucose regulated protein (GRP78), which can subsequently block the activation of apoptosis induced by treatment with anticancer agents. Therefore, inhibition of topoisomerase IIα degradation and reduction in GRP78 expression may be effective strategies for inhibiting anticancer drug resistance. In this study, we investigated the active compound arctigenin, which inhibited microenvironmental stress-induced etoposide resistance in HT-29 cells. Arctigenin was also highly toxic to etoposide-resistant HT-29 cells, with an IC50 value of 10 µM for colony formation. We further showed that arctigenin inhibited the degradation of topoisomerase IIα and reduced the expression of GRP78. Thus, these results suggest that arctigenin is a novel therapeutic agent that inhibits resistance to etoposide associated with microenvironmental stress conditions.

New Glabretal Triterpenes from the Immature Fruits of Poncirus trifoliata and Their Selective Cytotoxicity.

Two new glabretal triterpenes, pancastatins A (1) and B (2), were isolated from the immature fruits of Poncirus trifoliata. Their chemical structures were elucidated by spectroscopic analyses including one- and two-dimensional NMR and high-resolution electrospray ionization mass spectrometry. Compounds 1 and 2 exhibited selective cytotoxicity against PANC-1 pancreatic cancer cells under low-glucose stress conditions.

Compound C prevents the unfolded protein response during glucose deprivation through a mechanism independent of AMPK and BMP signaling.

Inhibiting the unfolded protein response (UPR) can be a therapeutic approach, especially for targeting the tumor microenvironment. Here, we show that compound C (also known as dorsomorphin), a small-molecule inhibitor of AMP-activated protein kinase (AMPK) and bone morphogenetic protein (BMP) signaling, inhibit the UPR-induced transcription program depending on the glucose deprivation conditions. We found that compound C prevented UPR marker glucose-regulated protein 78 (GRP78) accumulation and exerted enhanced cytotoxicity during glucose deprivation. Gene expression profiling, together with biochemical analysis, revealed that compound C had a unique mode of action to suppress the transcriptional activation of UPR-targeted genes, as compared with the classic UPR inhibitors versipelostatin and biguanides. Surprisingly, the UPR-inhibiting activity of compound C was not associated with either AMPK or BMP signaling inhibition. We further found that combination treatments of compound C and the classic UPR inhibitors resulted in synergistic cell death with UPR suppression during glucose deprivation. Our findings demonstrate that compound C could be a unique tool for developing a UPR-targeted antitumor therapy.

Neuroprotective effects of SG-168 against oxidative stress-induced apoptosis in PC12 cells.

Postmortem examinations of tissues of humans and rodents with a host of neurodegenerative conditions, including Alzheimer's and Parkinson's diseases, have identified oxidative damage in proteins, lipids, and DNA. The aim of this study was to better understand the cellular mechanisms of neuronal cell degeneration induced via oxidative stress and the protective roles of bioactive substance. In order to achieve this aim, we established a screening program to discover therapeutic agents that exhibit preferential neuroprotective activity in H(2)O(2)-treated PC12 cells. During the course of our screening program, we isolated an active compound, SG-168, from Dendrobium nobile Lindley and identified it as a neuroprotective agent. SG-168 was identified as a compound with an acetal skeleton, a prototypical compound, by electrospray ionization-mass spectrometry analysis and various nuclear magnetic resonance spectroscopic methods. The protective effect of SG-168 in PC12 cells with H(2)O(2)-induced oxidative damage was investigated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay. As expected, incubation with H(2)O(2) for 2 hours resulted in cell viability of 31.8% compared to the control, while pretreatment of SG-168 increased cell viability by 15-50% compared to the H(2)O(2)-stressed control cells. These results showed that SG-168 inhibits H(2)O(2)-induced apoptotic cell death. Interestingly, flow cytometric analysis showed that H(2)O(2)-treated PC12 cells incubated with SG-168 exhibited greatly suppressed apoptosis. In summation, the results of this study suggest that SG-168 has potential as a new antioxidant agent against neuronal diseases.

Arctigenin blocks the unfolded protein response and shows therapeutic antitumor activity.

Cancer cells in poorly vascularized solid tumors are constantly or intermittently exposed to stressful microenvironments, including glucose deprivation, hypoxia, and other forms of nutrient starvation. These tumor-specific conditions, especially glucose deprivation, activate a signaling pathway called the unfolded protein response (UPR), which enhances cell survival by induction of the stress proteins. We have established a screening method to discover anticancer agents that could preferentially inhibit tumor cell viability under glucose-deprived conditions. Here we identify arctigenin (ARC-G) as an active compound that shows selective cytotoxicity and inhibits the UPR during glucose deprivation. Indeed, ARC-G blocked expression of UPR target genes such as phosphorylated-PERK, ATF4, CHOP, and GRP78, which was accompanied by enhanced phosphorylation of eIF2 alpha during glucose deprivation. The UPR inhibition led to apoptosis involving a mitochondrial pathway by activation of caspase-9 and -3. Furthermore, ARC-G suppressed tumor growth of colon cancer HT-29 xenografts. Our results demonstrate that ARC-G can be served as a novel type of antitumor agent targeting the UPR in glucose-deprived solid tumors.

Selective cytotoxicity of Ponciri Fructus against glucose-deprived PANC-1 human pancreatic cancer cells via blocking activation of GRP78.

Pancreatic cancer cells are sometimes exposed to stressful microenvironments such as glucose deprivation, hypoxia, and starvation of other nutrients. These stresses, which are characteristic of poorly vascularized solid tumors, activate the unfolded protein response (UPR). The UPR is a stress-signaling pathway present in tumor cells that is associated with molecular chaperone GRP78. Induction of GRP78 has been found to increase cell survival and decrease apoptotic potential through genetic alterations. Thus GRP78 may represent a novel target in the development of anticancer drugs. Here we established a novel screening program to identify chaperone modulators that exhibit preferential cytotoxic activity in glucose-deprived pancreatic cancer cells. During the course of our screening, we isolated an active substance, Ponciri Fructus (PF), from an herbal medicine source and identified it as a down-regulator of GRP78. As expected, PF inhibited expression of the GRP78 protein under glucose-deprivation conditions in a dose-dependent manner. Furthermore, it induced selective cytotoxicity against glucose-deprived cancer cells; this effect was not observed under normal growth conditions. We also detected apoptotic bodies on Hoechst staining and attempted to determine whether PF-induced apoptosis involved caspase-3 activation. Our results suggest that the GRP78-inhibitory action of PF was dependent on strict hypoglycemic conditions and that it resulted in the selective death of glucose-deprived pancreatic cancer cells.

Chemical genomics identifies the unfolded protein response as a target for selective cancer cell killing during glucose deprivation.

Glucose deprivation, a cell condition that occurs in solid tumors, activates the unfolded protein response (UPR). A key feature of the UPR is the transcription program activation, which allows the cell to survive under stress conditions. Here, we show that the UPR transcription program is disrupted by the antidiabetic biguanides metformin, buformin, and phenformin depending on cellular glucose availability. These drugs inhibit production of the UPR transcription activators XBP1 and ATF4 and induce massive cell death during glucose deprivation as did the antitumor macrocyclic compound versipelostatin. Gene expression profiling shows remarkable similarity in the modes of action of biguanides and versipelostatin determined by the broad range of glucose deprivation-inducible genes. Importantly, during glucose deprivation, most of the biguanide suppression genes overlap with the genes induced by tunicamycin, a chemical UPR inducer. Gene expression profiling also identifies drug-driven signatures as a tool for discovering pharmacologic UPR modulators. Our findings show that disrupting the UPR during glucose deprivation could be an attractive approach for selective cancer cell killing and could provide a chemical genomic basis for developing UPR-targeting drugs against solid tumors.

Glycerol affects the acyl moieties of teicoplanin components produced by Actinoplanes teichomyceticus MSl2210.

Teicoplanin, a glycopeptide antibiotic, is composed of five main components, denoted T-A2-1 to T-A2-5. We investigated the use of glycerol as a carbon source affecting the teicoplanin components and its acyl moieties. As a result, we show the change of teicoplanin components, as well as an increase of total teicoplanin yields, caused by the addition of glycerol to the production medium. Analysis of the total cell lipids upon the addition of glycerol also showed a corresponding change in the proportion of teicoplanin, suggesting that glycerol strongly affects a change of teicoplanin branched acyl moieties.

Preventing the unfolded protein response via aberrant activation of 4E-binding protein 1 by versipelostatin.

We recently isolated a macrocyclic compound, versipelostatin (VST), that exerts in vivo antitumor activity. VST shows unique, selective cytotoxicity to glucose-deprived tumor cells by preventing the unfolded protein response (UPR). Here we show that eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), a negative regulator of eukaryotic initiation factor 4E-mediated protein translation, plays a role in the UPR-inhibitory action of VST. Indeed, 4E-BP1 is aberrantly activated by VST. This activation occurs specifically during glucose deprivation and results in profound translation repression and prevents induction of the typical UPR markers glucose-regulated protein (GRP) 78 and activating transcription factor (ATF) 4. Our overexpression and knockdown experiments showed that 4E-BP1 can regulate GRP78 and ATF4 expression. These mechanisms appear to be specific for VST. By contrast, rapamycin, which activates 4E-BP1 regardless of cellular glucose availability, has only marginal effects on the expression of GRP78 and ATF4. Our present findings demonstrate that aberrant 4E-BP1 activation can contribute to UPR preventing by VST, possibly through a mechanism that does not operate in rapamycin-treated cells.

Antioxidative and antigenotoxic activity of extracts from cosmos (Cosmos bipinnatus) flowers.

The Cosmos bipinnatus has been used in a traditional herbal remedy for various diseases such as jaundice, intermittent fever, and splenomegaly. The present study describes the preliminary evaluation of antioxidant activities and antigenotoxic effect of Cosmos bipinnatus flowers according to four different colors (white, pink, orange, and violet). The antioxidants properties were evaluated by determining TPC, DPPH RSA, ABTS RSA, and RP. The highest TPC of methanolic CFE (at concentration of 1 mg/ml) showed in violet colored CF (1,013 microM), and IC(50) of DPPH RSA, ABTS RSA, and RP were also the lowest in violet colored CFE with values of 0.61, 1.48, and 0.82 mg/ml, respectively. The antigenotoxic effect of the CFE on DNA damage induced by H(2)O(2) in human leukocytes was evaluated by Comet assay. Pretreatments with CFE produced significant reductions in oxidative DNA damage at the concentration of 500 microg/ml, except for violet colored CFE. The ED(50) value of white colored CFE has shown the highest inhibition (0.40 mg/ml) on H(2)O(2) induced DNA damage, followed by orange > pink > violet color. These results suggested that Cosmos bipinnatus has significant antioxidant activity and protective effect against oxidative DNA damage.

Protective effects of Paeonia lactiflora pall on hydrogen peroxide-induced apoptosis in PC12 cells.

This study was conducted to examine the antioxidative and neuroprotective effects of Paeonia lactiflora pall (PLE). Total phenolic content of PLE was 89.65 mg of gallic acid equivalent per gram of PLE. IC(50) values for reducing power, hydrogen peroxide scavenging activity, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were 297.57, 3.33, and 32.74 microg, respectively. The protective effect of PLE against H(2)O(2)-induced oxidative damage to PC12 cells was investigated by an 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) reduction assay and lactate dehydrogenase (LDH) release assay. After 2 h of cell exposure to 0.5 mM H(2)O(2), a marked reduction in cell survival was observed. However, this reduction was significantly prevented by 10-100 microg/ml of PLE. H(2)O(2) also induced severe apoptosis of the PC12 cells, which was indicated by a flow cytometric analysis. Interestingly, the H(2)O(2)-stressed PC12 cells that had been incubated with PLE had greatly suppressed apoptosis. The results suggest that PLE could be a candidate for a new antioxidant against neuronal diseases.

Methanolic extracts of Uncaria rhynchophylla induce cytotoxicity and apoptosis in HT-29 human colon carcinoma cells.

In this paper, we report the anticancer activities of Uncaria rhynchophylla extracts, a Rubiaceae plant native to China. Traditionally, Uncaria rhynchophylla has been used in the prevention and treatment of neurotoxicity. However, the cytotoxic activity of Uncaria rhynchophylla against human colon carcinoma cells has not, until now, been elucidated. We found that the methanolic extract of Uncaria rhynchophylla (URE) have cytotoxic effects on HT-29 cells. The URE showed highly cytotoxic effects via the MTT reduction assay, LDH release assay, and colony formation assay. As expected, URE inhibited the growth of HT-29 cells in a dose-dependent manner. In particular, the methanolic URE of the 500 microg/ml showed 15.8% inhibition against growth of HT-29 cells. It induced characteristic apoptotic effects in HT-29 cells, including chromatin condensation and sharking occurring 24 h when the cells were treated at a concentration of the 500 microg/ml. The activation of caspase-3 and the specific proteolytic cleavage of poly (ADP-ribose) polymerase were detected over the course of apoptosis induction. These results indicate that URE contains bioactive materials with strong activity, and is a potential chemotherapeutic agent candidate against HT-29 human colon carcinoma cells.

Functional analysis of a BarX homologue (SngA) as a pleiotropic regulator in Streptomyces natalensis.

The prior sequencing of the upstream region of the gamma-butyrolactone autoregulator receptor gene (sngR) in Streptomyces natalensis revealed the presence of a 972-bp gene encoding a BarX homologue (SngA), which acts as a pleiotropic regulator controlling secondary metabolism and morphological differentiation. In this study, we investigated the in vivo function of SngA in S. natalensis, by comparing the natamycin production, morphology, and transcription of genes related to natamycin biosynthesis in a wild-type strain and a sngA-deleted mutant. The disruption of sngA resulted in a decrease in natamycin production, and in the induction of pigment production that had not been previously observed from S. natalensis. On the other hand, the insertion of the intact sngA with its own promoter, into the wild-type strain, resulted in a 1.7-fold increase in natamycin production. Spore formation decreased in comparison to that of the wild-type strain when the sngA-deleted mutant was grown on YEME agar, MS medium, and ISP4 medium. All phenotypes were restored to the original wild-type phenotypes upon complementation with the intact sngA, suggesting that SngA has pleiotropic functions in controlling both morphological differentiation and secondary metabolite production.

Etoposide-resistant HT-29 human colon carcinoma cells during glucose deprivation are sensitive to piericidin A, a GRP78 down-regulator.

Glucose deprivation, a pathophysiological cell condition, causes up-regulation of GRP78 and induction of etoposide resistance in human cancer cells. The induction of drug resistance can be partly explained by the fact that GRP78 can block activation of caspase-7 induced by treatment with etoposide. Therefore, downregulating GRP78 expression may be a novel strategy anticancer drug development. Based on that premise, we established a screening program for anticancer agents that exhibit preferential cytotoxic activity for etoposide-resistant cancer cells under glucose-deprived conditions. We recently isolated an active compound, AR-054, from the culture broth of Streptomyces sp., which prevents stress-induced etoposide resistance in vitro. AR-054 was identified as piericidin A, a prototypical compound, by ESI-MS analysis and various NMR spectroscopic methods. Here, we showed that piericidin A suppressed the accumulation of GRP78 protein and was also highly toxic to etoposide-resistant HT-29 cells, with IC50 values for colony formation of 6.4 and 7.7 nM under 2-deoxyglucose supplemented and glucose-deprived conditions, respectively. Interestingly, piericidin A had no effect under normal growth conditions. Therefore, we suggest that piericidin A prevents up-regulation of GRP78, and exhibits cytotoxicity in glucose-deprived HT-29 cells that are resistant to etoposide.

Mithramycin inhibits etoposide resistance in glucose-deprived HT-29 human colon carcinoma cells.

Physiological cell conditions such as glucose deprivation and hypoxia play roles in the development of drug resistance in solid tumors. These tumor-specific conditions cause decreased expression of DNA topoisomerase IIalpha, rendering cells resistant to topo II target drugs such as etoposide. Thus, targeting tumor-specific conditions such as a low glucose environment may be a novel strategy in the development of anticancer drugs. On this basis, we established a novel screening program for anticancer agents with preferential cytotoxic activity in cancer cells under glucose-deprived conditions. We recently isolated an active compound, AA-98, from Streptomyces sp. AA030098 that can prevent stress-induced etoposide resistance in vitro. Furthermore, LC-MS and various NMR spectroscopic methods identified AA-98 as mithramycin, which belongs to the aureolic acid group of antitumor compounds. We found that mithramycin prevents the etoposide resistance that is induced by glucose deprivation. The etoposide-chemosensitive action of mithramycin was just dependent on strict low glucose conditions, and resulted in the selective cell death of etoposide-resistant HT-29 human colon cancer cells.