Hypoxia-Induced Changes in the Bioactivity of Cytotrophoblast-Derived Exosomes

Migration of extravillous trophoblasts (EVT) into decidua and myometrium is a critical process in the conversion of maternal spiral arterioles and establishing placenta perfusion. EVT migration is affected by cell-to-cell communication and oxygen tension. While the release of exosomes from placental cells has been identified as a significant pathway in materno-fetal communication, the role of placental-derived exosomes in placentation has yet to be established. The aim of this study was to establish the effect of oxygen tension on the release and bioactivity of cytotrophoblast (CT)-derived exosomes on EVT invasion and proliferation. CT were isolated from first trimester fetal tissue (n = 12) using a trypsin-deoxyribonuclease-dispase/Percoll method. CT were cultured under 8%, 3% or 1% O2 for 48 h. Exosomes from CT-conditioned media were isolated by differential and buoyant density centrifugation. The effect of oxygen tension on exosome release (µg exosomal protein/10⁶cells/48 h) and bioactivity were established. HTR-8/SVneo (EVT) were used as target cells to establish the effect (bioactivity) of exosomes on invasion and proliferation as assessed by real-time, live-cell imaging (Incucyte™). The release and bioactivity of CT-derived exosomes were inversely correlated with oxygen tension (p<0.001). Under low oxygen tensions (i.e. 1% O2), CT-derived exosomes promoted EVT invasion and proliferation. Proteomic analysis of exosomes identified oxygen-dependent changes in protein content. We propose that in response to changes in oxygen tension, CTs modify the bioactivity of exosomes, thereby, regulating EVT phenotype. Exosomal induction of EVT migration may represent a normal process of placentation and/or an adaptive response to placental hypoxia.     

Cloning, expression, and characterization of a lipolytic enzyme gene (lip8) from Pseudomonas aeruginosa LST-03

A lipolytic enzyme gene (lip8) was cloned from organic solvent-tolerant Pseudomonas aeruginosa LST-03 and sequenced. In the sequenced nucleotides, an open reading frame consisting of 1,173 nucleotides and encoding 391 amino acids was found. Lip8 is considered to belong to the family VIII of lipolytic enzymes whose serine in the consensus sequence of -Ser-Xaa-Xaa-Lys- acts as catalytic nucleophile. The gene was expressed in Escherichia coli and purified by a combination of ammonium sulfate fractionation and hydrophobic interaction and ion-exchange chromatographies to homogeneity on SDS-PAGE analysis. The optimum temperature and heat stability of Lip8 were not as high as those of Lip3 and LST-03 lipase, two other lipolytic enzymes from the same strain. Addition of glycerol to a solution containing Lip8 stabilized this enzyme. By measuring the activities against various triacylglycerols and fatty acid methyl esters having carbon chains of different lengths, Lip8 was categorized as an esterase which has higher activities against fatty acid methyl esters with short-chain fatty acids.     

Discovery of Power-Law Growth in the Self-Renewal of Heterogeneous Glioma Stem Cell Populations

Background

Accumulating evidence indicates that cancer stem cells (CSCs) drive tumorigenesis. This suggests that CSCs should make ideal therapeutic targets. However, because CSC populations in tumors appear heterogeneous, it remains unclear how CSCs might be effectively targeted. To investigate the mechanisms by which CSC populations maintain heterogeneity during self-renewal, we established a glioma sphere (GS) forming model, to generate a population in which glioma stem cells (GSCs) become enriched. We hypothesized, based on the clonal evolution concept, that with each passage in culture, heterogeneous clonal sublines of GSs are generated that progressively show increased proliferative ability.

Methodology/Principal Findings

To test this hypothesis, we determined whether, with each passage, glioma neurosphere culture generated from four different glioma cell lines become progressively proliferative (i.e., enriched in large spheres). Rather than monitoring self-renewal, we measured heterogeneity based on neurosphere clone sizes (#cells/clone). Log-log plots of distributions of clone sizes yielded a good fit (r>0.90) to a straight line (log(% total clones) = k*log(#cells/clone)) indicating that the system follows a power-law (y = x^k) with a specific degree exponent (k = −1.42). Repeated passaging of the total GS population showed that the same power-law was maintained over six passages (CV = −1.01 to −1.17). Surprisingly, passage of either isolated small or large subclones generated fully heterogeneous populations that retained the original power-law-dependent heterogeneity. The anti-GSC agent Temozolomide, which is well known as a standard therapy for glioblastoma multiforme (GBM), suppressed the self-renewal of clones, but it never disrupted the power-law behavior of a GS population.

Conclusions/Significance

Although the data above did not support the stated hypothesis, they did strongly suggest a novel mechanism that underlies CSC heterogeneity. They indicate that power-law growth governs the self-renewal of heterogeneous glioma stem cell populations. That the data always fit a power-law suggests that: (i) clone sizes follow continuous, non-random, and scale-free hierarchy; (ii) precise biologic rules that reflect self-organizing emergent behaviors govern the generation of neurospheres. That the power-law behavior and the original GS heterogeneity are maintained over multiple passages indicates that these rules are invariant. These self-organizing mechanisms very likely underlie tumor heterogeneity during tumor growth. Discovery of this power-law behavior provides a mechanism that could be targeted in the development of new, more effective, anti-cancer agents.     

The ferrous-oxy complex of human aromatase

In this communication, we document the self-assembly of heterologously expressed truncated human aromatase (CYP19) into nanometer scale phospholipids bilayers (Nanodiscs). The resulting P450 CYP19 preparation is stable and can tightly associate with the substrate androstenedione to form a nearly complete high-spin ferric protein. Ferrous CYP19 in Nanodiscs was mixed anaerobically in a rapid-scan stopped-flow with atmospheric dioxygen and the formation of the ferrous-oxy complex observed. First order decay of the oxy-complex to release superoxide and regenerate the ferric enzyme was monitored kinetically. Surprisingly, the ferrous-oxy complex of aromatase is more stable than that of hepatic CYP3A4, opening the path to precisely determine the biochemical and biophysical properties of the reaction cycle intermediates in this important human drug target.     

Tracking adenovirus genomes identifies morphologically distinct late DNA replication compartments

In adenoviral virions, the genome is organized into a chromatin‐like structure by viral basic core proteins. Consequently viral DNAs must be replicated, chromatinized and packed into progeny virions in infected cells. Although viral DNA replication centers can be visualized by virtue of viral and cellular factors, the spatiotemporal regulation of viral genomes during subsequent steps remains to be elucidated. In this study, we used imaging analyses to examine the fate of adenoviral genomes and to track newly replicated viral DNA as well as replication‐related factors. We show de novo formation of a subnuclear domain, which we termed Virus‐induced Post‐Replication (ViPR) body, that emerges concomitantly with or immediately after disintegration of initial replication centers. Using a nucleoside analogue, we show that viral genomes continue being synthesized in morphologically distinct replication compartments at the periphery of ViPR bodies and are then transported inward. In addition, we identified a nucleolar protein Mybbp1a as a molecular marker for ViPR bodies, which specifically associated with viral core protein VII. In conclusion, our work demonstrates the formation of previously uncharacterized viral DNA replication compartments specific for late phases of infection that produce progeny viral genomes accumulating in ViPR bodies.      

Remodeling of ER‐exit sites initiates a membrane supply pathway for autophagosome biogenesis

Autophagosomes are double‐membrane vesicles generated during autophagy. Biogenesis of the autophagosome requires membrane acquisition from intracellular compartments, the mechanisms of which are unclear. We previously found that a relocation of COPII machinery to the ER–Golgi intermediate compartment (ERGIC) generates ERGIC‐derived COPII vesicles which serve as a membrane precursor for the lipidation of LC3, a key membrane component of the autophagosome. Here we employed super‐resolution microscopy to show that starvation induces the enlargement of ER‐exit sites (ERES) positive for the COPII activator, SEC12, and the remodeled ERES patches along the ERGIC. A SEC12 binding protein, CTAGE5, is required for the enlargement of ERES, SEC12 relocation to the ERGIC, and modulates autophagosome biogenesis. Moreover, FIP200, a subunit of the ULK protein kinase complex, facilitates the starvation‐induced enlargement of ERES independent of the other subunits of this complex and associates via its C‐terminal domain with SEC12. Our data indicate a pathway wherein FIP200 and CTAGE5 facilitate starvation‐induced remodeling of the ERES, a prerequisite for the production of COPII vesicles budded from the ERGIC that contribute to autophagosome formation.     

Effects of combined β-adrenergic and cholinergic blockade on the initial ventilatory response to exercise in humans

To elucidate whether combined adrenergic and parasympathetic blockade would affect the ventilatory response to exercise, especially at the initial stage (phase I), six healthy subjects performed a brief and light voluntary bilateral leg extension exercise and passive movements under the conditions of control (before the blockade) and after intravenous administration of combined β-adrenergic (propranolol, 0.2 mg · kg⁻¹) and muscarinic (atropine, 0.04 mg · kg⁻¹) receptor antagonists. The movements were continued only within two breaths after the onset of the motion. Ventilation increased immediately and significantly (P<0.05) within the first breath at the onset of voluntary exercise in all conditions as compared with at rest. However, the magnitude of increase in mean ventilation within two breaths at the start of exercise as against the resting value (delta ventilation) was significantly less (P<0.05) after the combined blockades (2.5 l · min⁻¹) than in the control condition (3.7 l · min⁻¹). Passive movements showed a similar but smaller change as compared with voluntary exercise. The heart rate response to exercise was attenuated by the combined blockade while cardiac output showed a slight change at the onset of exercise. It is concluded that phase I should occur despite the inhibited activity of the β-adrenergic and the cholinergic systems; nevertheless, the response was attenuated by the combined blockade. These results suggest a possible role of the β-adrenergic and/or cholinergic systems in the rapid increase in ventilation that occurs at the start of exercise. Accepted: 2 March 1997     

Comparison of the anorexigenic activity of CRF family peptides

Corticotropin releasing factor (CRF) family peptides have an important role in the control of food intake. We investigated the effects of CRF family peptides on food intake and body weight gain in mice. Of the CRF family peptides, including CRF, urocortin1 (Ucn1), urocortin2 (Ucn2) and urocortin3 (Ucn3), peripherally administered Ucn1 was shown to have the most potent inhibitory effect on the food intake and body weight gain of both lean and high fat fed obese mice. In addition, repeated administration of Ucn1 lowered blood glucose and acylated ghrelin, and decreased the visceral fat weight of high fat fed obese mice.     

Self-propagating calciferous particles detected in a human cell line Kasumi-6 (JCRB 1024)

Summary Tiny particles were found in the medium in the presence of the human leukemia cell line Kasumi-6. The particles were separated from human cells by filtration and incubated in RPMI1640 supplemented with 10% fetal calf serum at 37 C. The particles increased in number very slowly in the liquid medium but did not reveal any biological activity. Transmission electron microscopy of the particles showed a spheroid or ovoid shape in ultrathin section. No specific polypeptides from the purified particles were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), except for bovine fetuin that adsorbed to the surface of the particles. X-ray diffractometry as well as Fourier transform infrared spectrometry suggested the particles consisted of hydroxyapatite. The mechanism of self-propagation of the hydroxyapatite particles in liquid medium is currently unknown. This type of particle has been overlooked for a long period because it is noncultivable. It will be necessary to examine its biological effects to the cultured cells.