Eupatorin-Induced Cell Death in Human Leukemia Cells Is Dependent on Caspases and Activates the Mitogen-Activated Protein Kinase Pathway

Eupatorin is a naturally occurring flavone that inhibits cell proliferation in human tumor cells. Here we demonstrate that eupatorin arrests cells at the G₂-M phase of the cell cycle and induces apoptotic cell death involving activation of multiple caspases, mitochondrial release of cytochrome c and poly(ADP-ribose) polymerase cleavage in human leukemia cells. This flavonoid induced the phosphorylation of members of the mitogen-activated protein kinases and cell death was attenuated by inhibition of c-jun N-terminal kinases/stress activated protein kinases. Eupatorin-induced cell death is mediated by both the extrinsic and the intrinsic apoptotic pathways and through a mechanism dependent on reactive oxygen species generation.     

Solid-phase synthesis and investigation of benzofurans as selective estrogen receptor modulators

A library of benzofurans was prepared by solid-phase synthesis methods, and several analogues were identified as potent ligands for the estrogen receptors ER-alpha and ER-beta, with some compounds having selectivity for ER-alpha. Analogues designed to more closely mimic Raloxifene were less effective. Certain benzofurans were effective in a bone pit assay, but were characterized as agonists in a MCF-7 breast tumor cell proliferation assay.     

FGF21 mediates the lipid metabolism response to amino acid starvation

Lipogenic gene expression in liver is repressed in mice upon leucine deprivation. The hormone fibroblast growth factor 21 (FGF21), which is critical to the adaptive metabolic response to starvation, is also induced under amino acid deprivation. Upon leucine deprivation, we found that FGF21 is needed to repress expression of lipogenic genes in liver and white adipose tissue, and stimulate phosphorylation of hormone-sensitive lipase in white adipose tissue. The increased expression of Ucp1 in brown adipose tissue under these circumstances is also impaired in FGF21-deficient mice. Our results demonstrate the important role of FGF21 in the regulation of lipid metabolism during amino acid starvation.     

Characterization of the single-stranded DNA binding protein pV(VGJΦ) of VGJΦ phage from Vibrio cholerae

pV(VGJΦ), a single-stranded DNA binding protein of the vibriophage VGJΦ was subject to biochemical analysis. Here, we show that this protein has a general affinity for single-stranded DNA (ssDNA) as documented by Electrophoretic Mobility Shift Assay (EMSA). The apparent molecular weight of the monomer is about 12.7kDa as measured by HPLC-SEC. Moreover, isoelectrofocusing showed an isoelectric point for pV(VGJΦ) of 6.82 pH units. Size exclusion chromatography in 150mM NaCl, 50mM sodium phosphate buffer, pH 7.0 revealed a major protein species of 27.0kDa, suggesting homodimeric protein architecture. Furthermore, pV(VGJΦ) binds ssDNA at extreme temperatures and the complex was stable after extended incubation times. Upon frozen storage at -20°C for a year the protein retained its integrity, biological activity and oligomericity. On the other hand, bioinformatics analysis predicted that pV(VGJΦ) protein has a disordered C-terminal, which might be involved in its functional activity. All the aforementioned features make pV(VGJΦ) interesting for biotechnological applications.     

Human HMGCS2 regulates mitochondrial fatty acid oxidation and FGF21 expression in HepG2 cell line

HMGCS2 (hydroxymethylglutaryl CoA synthase 2), the gene that regulates ketone body production, is barely expressed in cultured cell lines. In this study, we restored HMGCS2 expression and activity in HepG2 cells, thus showing that the wild type enzyme can induce fatty acid β-oxidation (FAO) and ketogenesis, whereas a catalytically inactive mutant C166A did not generate either process. Peroxisome proliferator-activated receptor (PPAR) α expression also induces fatty acid β-oxidation and endogenous HMGCS2 expression. Interestingly, PPARα-mediated induction was abolished when HMGCS2 expression was down-regulated by RNAi. These results indicate that HMGCS2 expression is both sufficient and necessary to the control of fatty acid oxidation in these cells. Next, we examined the expression pattern of several PPARα target genes in this now "ketogenic" HepG2 cell line. FGF21 (fibroblast growth factor 21) expression was specifically induced by HMGCS2 activity or by the inclusion of the oxidized form of ketone bodies (acetoacetate) in the culture medium. This effect was blunted by SirT1 (sirtuin 1) RNAi, so we propose a SirT1-dependent mechanism for FGF21 induction by acetoacetate. These data suggest a novel feed-forward mechanism by which HMGCS2 could regulate adaptive metabolic responses during fasting. This mechanism could be physiologically relevant, because fasting-mediated induction of liver FGF21 was dependent on SirT1 activity in vivo.     

New insights into the structure-cytotoxicity relationship of spirostan saponins and related glycosides

A variety of spirostan saponins and related glycosides were synthesized and evaluated for their cytotoxicity against the human myeloid leukemia cell line (HL-60). A linear glycosylation strategy allowed for accessing a variety of functionalization patterns at both the spirostanic and the saccharide moieties, which provides new information regarding the structure-cytotoxicity relationship of this family of steroidal glycosides. Intriguing results were achieved with respect to hecogenyl and 5α-hydroxy-laxogenyl β-chacotriosides, turning out to be the former very cytotoxic and the latter no cytotoxic at all. Importantly, the partially pivaloylated β-d-glucosides of 5α-hydroxy-laxogenin were the most potent cytotoxic compounds among all tested glycosides. This comprises the first report on acylated spirostanyl glucosides displaying significant cytotoxicity, and therefore, it opens up new opportunities toward the development of saponin analogues as anticancer agents.     

No shallow talk: Cryptic strategy in the vocal communication of Blainville's beaked whales

Communicating animals must balance fitness benefits against the costs of signaling, such as increased predation risk. Cetaceans communicate mainly with sound and near‐surface vocalizations can place signalers at risk from shallow‐diving top‐predators with acute hearing such as killer whales. Beaked whales are deep divers living in small cohesive groups with little social defense from predation. Little if anything is known about their acoustic communication. Here, eight Blainville's beaked whales were studied with suction cup attached DTags to provide the first report on social communication as a function of diving behavior for any of the 21 ziphiid species. Tagged whales produced two previously unrecorded signals with apparent communicative functions: (1) fast series of ultrasonic frequency modulated clicks (rasps) were recorded from six individuals, and (2) harmonically rich short whistles with a mean fundamental frequency of 12 kHz were recorded from one whale at up to 900 m depth, the deepest whistles recorded from a marine mammal. Blainville's were silent 80% of the time, whenever shallower than 170 m depth and during the prolonged (19 min) silent ascents from vocal dives. This behavior limits the ability of shallow‐diving predators to track Blainville's acoustically and may provide a striking example of the evolutionary influence of the risk of predation on animal communication.     

Rapid identification of monospecific monoclonal antibodies using a human proteome microarray

To broaden the range of tools available for proteomic research, we generated a library of 16,368 unique full-length human ORFs that are expressible as N-terminal GST-His(6) fusion proteins. Following expression in yeast, these proteins were then individually purified and used to construct a human proteome microarray. To demonstrate the usefulness of this reagent, we developed a streamlined strategy for the production of monospecific monoclonal antibodies that used immunization with live human cells and microarray-based analysis of antibody specificity as its central components. We showed that microarray-based analysis of antibody specificity can be performed efficiently using a two-dimensional pooling strategy. We also demonstrated that our immunization and selection strategies result in a large fraction of monospecific monoclonal antibodies that are both immunoblot and immunoprecipitation grade. Our data indicate that the pipeline provides a robust platform for the generation of monoclonal antibodies of exceptional specificity.     

TLP01, an mshA mutant of Vibrio cholerae O139 as vaccine candidate against cholera

No commercially live vaccine against cholera caused by Vibrio cholerae O139 serogroup is available and it is currently needed. Virulent O139 strain CRC266 was genetically modified by firstly deleting multiple copies of the filamentous phage CTXφ, further tagging by insertion of the endoglucanase A coding gene from Clostridium thermocellum into the hemagglutinin/protease gene and finally deleting the mshA gene, just to improve the vaccine biosafety. One of the derived strains designated as TLP01 showed full attenuation and good colonizing capacity in the infant mouse cholera model, as well as highly immunogenic properties in the adult rabbit and rat models. Since TLP01 lacks MSHA fimbriae, it is refractory to infection with another filamentous phage VGJφ and therefore protected of acquiring CTXφ from a recombinant hybrid VGJφ/CTXφ. This strategy could reduce the possibilities of stable reversion to virulence out of the human gut. Furthermore, this vaccine strain was impaired to produce biofilms under certain culture conditions, which might have implications for the strain survival in natural settings contributing to vaccine biosafety as well. The above results has encouraged us to consider TLP01 as a live attenuated vaccine strain having an adequate performance in animal models, in terms of attenuation and immunogenicity, so that it fulfills the requirements to be evaluated in human volunteers.     

Endogenous ATP potentiates only vasopressin secretion from neurohypophysial terminals

Exogenous ATP induces inward currents and causes the release of arginine-vasopressin (AVP) from isolated neurohypophysial terminals (NHT); both effects are inhibited by the P2X2 and P2X3 antagonists, suramin and PPADS. Here we examined the role of endogenous ATP in the neurohypophysis. Stimulation of NHT caused the release of both AVP and ATP. ATP induced a potentiation in the stimulated release of AVP, but not of oxytocin (OT), which was blocked by the presence of suramin. In loose-patch clamp recordings, from intact neurohypophyses, suramin or PPADS produces an inhibition of action potential currents in a static bath, that can be mimicked by a hyperpolarization of the resting membrane potential (RMP). Correspondingly, in a static versus perfused bath there is a depolarization of the RMP of NHT, which was reduced by either suramin or PPADS. We measured an accumulation of ATP (3.7 +/- 0.7 microM) released from NHT in a static bath. Applications of either suramin or PPADS to a static bath decreased burst-stimulated capacitance increases in NHT. Finally, only vasopressin release from electrically stimulated intact neurohypophyses was reduced in the presence of Suramin or PPADS. These data suggest that there was sufficient accumulation of ATP released from the neurohypophysis during stimulations to depolarize its nerve terminals. This would occur via the opening of P2X2 and P2X3 receptors, inducing an influx of Ca2+. The subsequent elevation in [Ca2+](i) would further increase the stimulated release of only vasopressin from NHT terminals. Such purinergic feedback mechanisms could be physiologically important at most CNS synapses.