bluuebunny/crossref_metadata_2025_split huggingface dataset:
An ERBB3/ERBB2 oncogenic unit plays a key role in NRG1 signaling and melanoma cell growth and survival
Authors: Zhang Keman , Wong Poki , Duan Jiaqi , Jacobs Barbara , Borden Ernest C. , Bedogni Barbara 
Published: March 2013

SummaryWe recently identified neuregulin‐1 (NRG1) as a novel target of Notch1 required in Notch‐dependent melanoma growth. ERBB3 and ERBB4, tyrosine kinase receptors specifically activated by NRG1, have been shown to be either elevated in melanoma cell lines and tumors or to be mutated in 20% of melanomas, respectively. While these data support key roles of NRG1 and its receptors in the pathogenesis of melanoma, whether ERBB3 and ERBB4 display redundant or exclusive functions is not known. Here, we show that ERBB3 and ERBB4 inhibition results in distinct outcomes. ERBB3 inhibition ablates the cellular responses to NRG1, results in AKT inactivation and leads to cell growth arrest and apoptotic cell death. In contrast, ERBB4 knockdown mildly affects cell growth, has no effects on cell survival and, importantly, does not alter the responses to NRG1. Finally, we identified ERBB2 as a key coreceptor in NRG1‐dependent ERBB3 signaling. ERBB2 forms a complex with ERBB3, and its inhibition recapitulates the phenotypes observed upon ERBB3 ablation. We propose that an NRG1‐ERBB3‐ERBB2 signaling unit operates in melanoma cells where it promotes growth and survival.
Kv3.1 channels stimulate adult neural precursor cell proliferation and neuronal differentiation
Authors: Yasuda Takahiro , Cuny Hartmut , Adams David J. 
Published: March 2013

Key points
In the adult mammalian brain, neural precursor cells (NPCs) play an important role in neuronal plasticity.
Although adult NPCs exhibit voltage‐gated, delayed rectifier K+ (KDR) channel currents, the KDR channel subtype dominantly expressed in adult NPCs and its functional role have not been defined.
Using gene knockdown targeting Kv3.1 K+ channels, we show Kv3.1 is a dominant KDR subtype expressed in adult NPCs.
Kv3.1 knockdown significantly decreased adult NPC proliferation and reduced differentiation into neuroblasts.
Our findings provide new insight into a mechanism of adult neurogenesis and suggest that selective activation of Kv3.1 in adult NPCs may be a new therapeutic approach to treating neurodegenerative diseases.
Abstract  Adult neural stem/precursor cells (NPCs) play a pivotal role in neuronal plasticity throughout life. Among ion channels identified in adult NPCs, voltage‐gated delayed rectifier K+ (KDR) channels are dominantly expressed. However, the KDR channel subtype and its physiological role are still undefined. We used real‐time quantitative RT‐PCR and gene knockdown techniques to identify a major functional KDR channel subtype in adult NPCs. Dominant mRNA expression of Kv3.1, a high voltage‐gated KDR channel, was quantitatively confirmed. Kv3.1 gene knockdown with specific small interfering RNAs (siRNA) for Kv3.1 significantly inhibited Kv3.1 mRNA expression by 63.9% (P < 0.001) and KDR channel currents by 52.2% (P < 0.001). This indicates that Kv3.1 is the subtype responsible for producing KDR channel outward currents. Resting membrane properties, such as resting membrane potential, of NPCs were not affected by Kv3.1 expression. Kv3.1 knockdown with 300 nm siRNA inhibited NPC growth (increase in cell numbers) by 52.9% (P < 0.01). This inhibition was attributed to decreased cell proliferation, not increased cell apoptosis. We also established a convenient in vitro imaging assay system to evaluate NPC differentiation using NPCs from doublecortin‐green fluorescent protein transgenic mice. Kv3.1 knockdown also significantly reduced neuronal differentiation by 31.4% (P < 0.01). We have demonstrated that Kv3.1 is a dominant functional KDR channel subtype expressed in adult NPCs and plays key roles in NPC proliferation and neuronal lineage commitment during differentiation.
Extracellular DNA Shields against Aminoglycosides in Pseudomonas aeruginosa Biofilms
Authors: Chiang Wen-Chi , Nilsson Martin , Jensen Peter Østrup , Høiby Niels , Nielsen Thomas E. , Givskov Michael , Tolker-Nielsen Tim 
Published: March 2013

ABSTRACT

Within recent years, it has been established that extracellular DNA is a key constituent of the matrix of microbial biofilms. In addition, it has recently been demonstrated that DNA binds positively charged antimicrobials such as aminoglycosides and antimicrobial peptides. In the present study, we provide evidence that extracellular DNA shields against aminoglycosides in
Pseudomonas aeruginosa
biofilms. We show that exogenously supplemented DNA integrates into
P. aeruginosa
biofilms and increases their tolerance toward aminoglycosides. We provide evidence that biofilms formed by a DNA release-deficient
P. aeruginosa
quorum-sensing mutant are more susceptible to aminoglycoside treatment than wild-type biofilms but become rescued from the detrimental action of aminoglycosides upon supplementation with exogenous DNA. Furthermore, we demonstrate that exposure to lysed polymorphonuclear leukocytes, which are thought to be a source of extracellular DNA at sites of infections, increases the tolerance of
P. aeruginosa
biofilms toward aminoglycosides. Although biofilm-associated aminoglycoside tolerance recently has been linked to extracellular DNA-mediated activation of the
pmr
genes, we demonstrate that the aminoglycoside tolerance mediated by the presence of extracellular DNA is not caused by activation of the
pmr
genes in our
P. aeruginosa
biofilms but rather by a protective shield effect of the extracellular DNA.
Quantifying Subpopulation Synergy for Antibiotic Combinations via Mechanism-Based Modeling and a Sequential Dosing Design
Authors: Landersdorfer Cornelia B. , Ly Neang S. , Xu Hongmei , Tsuji Brian T. , Bulitta Jürgen B. 
Published: March 2013

ABSTRACT

Quantitative modeling of combination therapy can describe the effects of each antibiotic against multiple bacterial populations. Our aim was to develop an efficient experimental and modeling strategy that evaluates different synergy mechanisms using a rapidly killing peptide antibiotic (nisin) combined with amikacin or linezolid as probe drugs. Serial viable counts over 48 h were obtained in time-kill experiments with all three antibiotics in monotherapy against a methicillin-resistant
Staphylococcus aureus
USA300 strain (inoculum, 10
8
CFU/ml). A sequential design (initial dosing of 8 or 32 mg/liter nisin, switched to amikacin or linezolid at 1.5 h) assessed the rate of killing by amikacin and linezolid against nisin-intermediate and nisin-resistant populations. Simultaneous combinations were additionally studied and all viable count profiles comodeled in S-ADAPT and NONMEM. A mechanism-based model with six populations (three for nisin times two for amikacin) yielded unbiased and precise (
r
= 0.99, slope = 1.00; S-ADAPT) individual fits. The second-order killing rate constants for nisin against the three populations were 5.67, 0.0664, and 0.00691 liter/(mg · h). For amikacin, the maximum killing rate constants were 10.1 h
−1
against its susceptible and 0.771 h
−1
against its less-susceptible populations, with 14.7 mg/liter amikacin causing half-maximal killing. After incorporating the effects of nisin and amikacin against each population, no additional synergy function was needed. Linezolid inhibited successful bacterial replication but did not efficiently kill populations less susceptible to nisin. Nisin plus amikacin achieved subpopulation synergy. The proposed sequential and simultaneous dosing design offers an efficient approach to quantitatively characterize antibiotic synergy over time and prospectively evaluate antibiotic combination dosing strategies.
Introduction of a Lysine Residue Promotes Aggregation of Temporin L in Lipopolysaccharides and Augmentation of Its Antiendotoxin Property
Authors: Srivastava Saurabh , Ghosh Jimut Kanti 
Published: March 2013

ABSTRACT

Temporin L (TempL) is a 13-residue frog antimicrobial peptide that shows moderate bactericidal activity and antiendotoxin properties in macrophages. We envisioned that, due to its very hydrophobic nature, the peptide might fail to show its desired biological properties. It was predicted by employing the available algorithms that the replacement of a glutamine by lysine at position 3 could appreciably reduce its aggregation propensity in an aqueous environment. In order to investigate the structural, functional, and biological consequences of replacement of glutamine by lysine at its third position, TempL and the corresponding analog, Q3K-TempL, was synthesized and characterized. Introduction of the lysine residue significantly promoted the self-assembly and oligomeric state of TempL in lipopolysaccharide (LPS). Q3K-TempL exhibited augmented binding to LPS and also dissociated LPS aggregates with greater efficacy than TempL. Further, Q3K-TempL inhibited the LPS-induced proinflammatory cytokines in rat primary macrophages
in vitro
and
in vivo
in BALB/c mice with greater efficacy than TempL. The results showed that a simple amino acid substitution in a short hydrophobic antimicrobial peptide, TempL, enhanced its antiendotoxin properties and illustrate a plausible correlation between its aggregation properties in LPS and LPS detoxification activity.
Identification and Evaluation of Novel Acetolactate Synthase Inhibitors as Antifungal Agents
Authors: Richie Daryl L. , Thompson Katherine V. , Studer Christian , Prindle Vivian C. , Aust Thomas , Riedl Ralph , Estoppey David , Tao Jianshi , Sexton Jessica A. , Zabawa Thomas , Drumm Joseph , Cotesta Simona , Eichenberger Jürg , Schuierer Sven , Hartmann Nicole , Movva N. Rao , Tallarico John A. , Ryder Neil S. , Hoepfner Dominic 
Published: March 2013

ABSTRACT

High-throughput phenotypic screening against the yeast
Saccharomyces cerevisiae
revealed a series of triazolopyrimidine-sulfonamide compounds with broad-spectrum antifungal activity, no significant cytotoxicity, and low protein binding. To elucidate the target of this series, we have applied a chemogenomic profiling approach using the
S. cerevisiae
deletion collection. All compounds of the series yielded highly similar profiles that suggested acetolactate synthase (Ilv2p, which catalyzes the first common step in branched-chain amino acid biosynthesis) as a possible target. The high correlation with profiles of known Ilv2p inhibitors like chlorimuron-ethyl provided further evidence for a similar mechanism of action. Genome-wide mutagenesis in
S. cerevisiae
identified 13 resistant clones with 3 different mutations in the catalytic subunit of acetolactate synthase that also conferred cross-resistance to established Ilv2p inhibitors. Mapping of the mutations into the published Ilv2p crystal structure outlined the chlorimuron-ethyl binding cavity, and it was possible to dock the triazolopyrimidine-sulfonamide compound into this pocket
in silico
. However, fungal growth inhibition could be bypassed through supplementation with exogenous branched-chain amino acids or by the addition of serum to the medium in all of the fungal organisms tested except for
Aspergillus fumigatus
. Thus, these data support the identification of the triazolopyrimidine-sulfonamide compounds as inhibitors of acetolactate synthase but suggest that targeting may be compromised due to the possibility of nutrient bypass
in vivo
.
Genetic Characterization of IncI2 Plasmids Carrying
bla
CTX-M-55
Spreading in both Pets and Food Animals in China
Authors: Lv Luchao , Partridge Sally R. , He Liangying , Zeng Zhenling , He Dandan , Ye Jiahui , Liu Jian-Hua 
Published: March 2013

ABSTRACT

pHN1122-1 carrying
bla
CTX-M-55
, from an
Escherichia coli
isolate from a dog, was completely sequenced. pHN1122-1 has an IncI2 replicon and typical IncI2-associated genetic modules, including
mok
/
hok-finO-yafA
/
B
,
nikABC
, and two transfer regions,
tra
and
pil
, as well as a shufflon.
bla
CTX-M-55
is found within a 3.084-kb IS
Ecp1
transposition unit that includes a fragment of IncA/C plasmid backbone. pHN1122-1 and closely related plasmids were identified in other
E. coli
isolates from animals in China.
Efficacy of Repeated Intravenous Injection of Peramivir against Influenza A (H1N1) 2009 Virus Infection in Immunosuppressed Mice
Authors: Kitano Mitsutaka , Kodama Makoto , Itoh Yasushi , Kanazu Takushi , Kobayashi Masanori , Yoshida Ryu , Sato Akihiko 
Published: March 2013

ABSTRACT

The efficacy of intravenous peramivir against influenza A (H1N1) 2009 virus infection was evaluated in mice in which the immune system was suppressed by cyclophosphamide (CP) treatment. The mortality rate of the vehicle control group was 100%, and the mice lost 20% of their body weight on average by day 13 postinfection (p.i.). Repeated administration of peramivir (40 mg/kg of body weight once a day, given intravenously for 20 days), starting at 1 h p.i., significantly reduced mortality, body weight loss, viral titers, and cytokine production in infected mice compared with results for administration of vehicle (
P
< 0.01). In addition, repeated administration of peramivir, starting at 24 h, 48 h, or 72 h p.i., also resulted in increases in survival rates and reduction of viral titers in the lungs (
P
< 0.01). The mean days to death (MDD) of the vehicle group was 14.5 days, while in the groups treated with peramivir starting at 24 h, 48 h, and 72 h p.i., the MDDs were >23.0, 20.9, and 21.8 days, respectively. In comparison, repeated administration of oseltamivir phosphate (5 mg/kg twice a day, given orally for 20 days), starting at 24 h, 48 h, and 72 h p.i., also significantly prevented body weight loss, whereas no significant differences in mortality rates and viral titers in the lungs were observed compared with results for the vehicle group. These data indicated that repeated administration of peramivir was effective in promoting the survival and reducing virus replication in immunosuppressed mice infected with influenza A (H1N1) 2009 virus.
Pharmacodynamic Evaluation of the Intracellular Activity of Antibiotics towards Pseudomonas aeruginosa PAO1 in a Model of THP-1 Human Monocytes
Authors: Buyck Julien M. , Tulkens Paul M. , Van Bambeke Françoise 
Published: March 2013

ABSTRACT

Pseudomonas aeruginosa
invades epithelial and phagocytic cells, which may play an important role in the persistence of infection. We have developed a 24-h model of THP-1 monocyte infection with
P. aeruginosa
PAO1 in which bacteria are seen multiplying in vacuoles by electron microscopy. The model has been used to quantitatively assess antibiotic activity against intracellular and extracellular bacteria by using a pharmacodynamic approach (concentration-dependent experiments over a wide range of extracellular concentrations to calculate bacteriostatic concentrations [
C
s
] and maximal relative efficacies [
E
max
]; Hill-Langmuir equation). Using 16 antipseudomonal antibiotics (three aminoglycosides, nine β-lactams, three fluoroquinolones, and colistin), dose-response curves were found to be undistinguishable for antibiotics of the same pharmacological class if data were expressed as a function of the corresponding MICs. Extracellularly, all of the antibiotics reached a bacteriostatic effect at their MIC, and their
E
max
exceeded the limit of detection (−4.5 log
10
CFU compared to the initial inoculum). Intracellularly,
C
s
values remained unchanged for β-lactams, fluoroquinolones, and colistin but were approximately 10 times higher for aminoglycosides, whereas
E
max
values were markedly reduced (less negative), reaching −3 log
10
CFU for fluoroquinolones and only −1 to −1.5 log
10
CFU for all other antibiotics. The decrease in intracellular aminoglycoside potency (higher
C
s
) can be ascribed to the acid pH to which bacteria are exposed in vacuoles. The decrease in the
E
max
may reflect a reversible alteration of bacterial responsiveness to antibiotics in the intracellular milieu. The model may prove useful for comparison of antipseudomonal antibiotics to reduce the risk of persistence or relapse of pseudomonal infections.
Role of Ficolin-A and Lectin Complement Pathway in the Innate Defense against Pathogenic Aspergillus Species
Authors: Bidula Stefan , Kenawy Hany , Ali Youssif M. , Sexton Darren , Schwaeble Wilhelm J. , Schelenz Silke 
Published: March 2013

ABSTRACTAspergillusspecies are saprophytic molds causing life-threatening invasive fungal infections in the immunocompromised host. Innate immune recognition, in particular, the mechanisms of opsonization and complement activation, has been reported to be an integral part of the defense against fungi. We have shown that the complement component ficolin-A significantly binds toAspergillusconidia and hyphae in a concentration-dependent manner and was inhibited byN-acetylglucosamine andN-acetylgalactosamine. Calcium-independent binding toAspergillus fumigatusandA. terreuswas observed, but binding toA. flavusandA. nigerwas calcium dependent. Ficolin-A binding to conidia was increased under low-pH conditions, and opsonization led to enhanced binding of conidia to A549 airway epithelial cells. In investigations of the lectin pathway of complement activation, ficolin-A-opsonized conidia did not lead to lectin pathway-specific C4 deposition. In contrast, the collectin mannose binding lectin C (MBL-C) but not MBL-A led to efficient lectin pathway activation onA. fumigatusin the absence of ficolin-A. In addition, ficolin-A opsonization led to a modulation of the proinflammatory cytokine interleukin-8. We conclude that ficolin-A may play an important role in the innate defense againstAspergillusby opsonizing conidia, immobilizing this fungus through enhanced adherence to epithelial cells and modulation of inflammation. However, it appears that other immune pattern recognition molecules, i.e., those of the collectin MBL-C, are involved in theAspergillus-lectin complement pathway activation rather than ficolin-A.
Study of the Response Regulator Rrp1 Reveals Its Regulatory Role in Chitobiose Utilization and Virulence of Borrelia burgdorferi
Authors: Sze Ching Wooen , Smith Alexis , Choi Young Hee , Yang Xiuli , Pal Utpal , Yu Aiming , Li Chunhao 
Published: March 2013

ABSTRACT

Life cycle alternation between arthropod and mammals forces the Lyme disease spirochete,
Borrelia burgdorferi
, to adapt to different host milieus by utilizing diverse carbohydrates. Glycerol and chitobiose are abundantly present in the
Ixodes
tick.
B. burgdorferi
can utilize glycerol as a carbohydrate source for glycolysis and chitobiose to produce
N
-acetylglucosamine (GlcNAc), a key component of the bacterial cell wall. A recent study reported that Rrp1, a response regulator that synthesizes cyclic diguanylate (c-di-GMP), governs glycerol utilization in
B. burgdorferi
. In this report, we found that the
rrp1
mutant had growth defects and formed membrane blebs that led to cell lysis when GlcNAc was replaced by chitobiose in the growth medium. The gene
chbC
encodes a key chitobiose transporter of
B. burgdorferi
. We found that the expression level of
chbC
was significantly repressed in the mutant and that constitutive expression of
chbC
in the mutant successfully rescued the growth defect, indicating a regulatory role of Rrp1 in chitobiose uptake. Immunoblotting and transcriptional studies revealed that Rrp1 is required for the activation of
bosR
and
rpoS
and that its impact on
chbC
is most likely mediated by the BosR-RpoS regulatory pathway. Tick-mouse infection studies showed that although the
rrp1
mutant failed to establish infection in mice via tick bite, exogenous supplementation of GlcNAc into unfed ticks partially rescued the infection. The finding reported here provides us with new insight into the regulatory role of Rrp1 in carbohydrate utilization and virulence of
B. burgdorferi
.
Predominant Role of Host Proteases in Myocardial Damage Associated with Infectious Endocarditis Induced by Enterococcus faecalis in a Rat Model
Authors: Augustin Pascal , Alsalih Ghada , Launey Yoann , Delbosc Sandrine , Louedec Liliane , Ollivier Véronique , Chau Françoise , Montravers Philippe , Duval Xavier , Michel Jean-Baptiste , Meilhac Olivier 
Published: March 2013

ABSTRACT

Infective endocarditis (IE) remains a life-threatening infectious disease with high morbidity and mortality. The objectives of the present study are to assess the host proteolytic activities of the vegetations and their cytotoxic potential in a rat model of experimental IE. Rats were infected with a strain of
Enterococcus faecalis
of particularly low virulence and weak protease expression. We tested the presence of proteases released by infiltrated leukocytes (matrix metalloproteinases and elastase) or produced
in situ
within the septic vegetation, such as those linked to the fibrinolytic system (plasmin and plasminogen activators). We also assessed the tissue damage induced by the infective thrombus
in vitro
and
ex vivo
. The model of IE was characterized by larger and more extensive vegetations in infected than in nonseptic rats and by an intense neutrophil infiltrate interfacing with the injured underlying tissue. Neutrophil extracellular DNA was shown to trap bacteria and to produce increased levels of cell-free DNA in plasma. Matrix metalloproteinase-9, elastase, and plasminogen activators were increased in septic versus nonseptic vegetations (as shown by zymography and immunohistology). Finally, proteolysis of the extracellular matrix and apoptosis were shown to be associated with host proteases. Bacteria exhibited no detectable proteolytic activity or direct cytotoxic effects. Bacterial membranes/dead bacteria were sufficient to induce leukocyte recruitment and activation that could promote vegetation formation and growth. Our results suggest that, despite the lack of bacterial proteases, the continuous attractant signals coming from bacterial colonies may lead to a chronic and deleterious aggression toward myocardial/valvular tissues by host proteases.
Expression and Function of Psoriasin (S100A7) and Koebnerisin (S100A15) in the Brain
Authors: Jansen Sandra , Podschun Rainer , Leib Stephen L. , Grötzinger Joachim , Oestern Stefanie , Michalek Matthias , Pufe Thomas , Brandenburg Lars-Ove 
Published: March 2013

ABSTRACT

The expression and function of psoriasin in the brain have been insufficiently characterized. Here, we show the induction of psoriasin expression in the central nervous system (CNS) after bacterial and viral stimulation. We used a pneumococcal meningitis
in vivo
model that revealed S100A15 expression in astrocytes and meningeal cells. These results were confirmed by a cell-based
in vivo
assay using primary rat glial and meningeal cell cultures. We investigated psoriasin expression in glial and meningeal cells using polyinosinic-polycytidylic acid, a synthetic analog of double-stranded RNA that mimics viral infection. Furthermore, previous results showed that antimicrobial peptides have not only bactericidal but also immunomodulatory functions. To test this statement, we used recombinant psoriasin as a stimulus. Glial and meningeal cells were treated with recombinant psoriasin at concentrations from 25 to 500 ng/ml. Treated microglia and meningeal cells showed phosphorylation of the extracellular signal-regulated kinase 1 (ERK1)/ERK2 (ERK1/2) signal transduction pathway. We demonstrated that this activation of ERK depends on RAGE, the receptor for advanced glycation end products. Furthermore, microglia cells treated with recombinant psoriasin change their phenotype to an enlarged shape. In conclusion, our results indicate an occurrence of psoriasin in the brain. An involvement of psoriasin as an antimicrobial protein that modulates the innate immune system after bacterial or viral stimulation is possible.