bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carboxymefloquine, the Major Metabolite of the Antimalarial Drug Mefloquine, Induces Drug-Metabolizing Enzyme and Transporter Expression by Activation of Pregnane X Receptor
Authors: Piedade Rita , Traub Stefanie , Bitter Andreas , Nüssler Andreas K. , Gil José P. , Schwab Matthias , Burk Oliver 
Published: October 2014

ABSTRACT

Malaria patients are frequently coinfected with HIV and mycobacteria causing tuberculosis, which increases the use of coadministered drugs and thereby enhances the risk of pharmacokinetic drug-drug interactions. Activation of the pregnane X receptor (PXR) by xenobiotics, which include many drugs, induces drug metabolism and transport, thereby resulting in possible attenuation or loss of the therapeutic responses to the drugs being coadministered. While several artemisinin-type antimalarial drugs have been shown to activate PXR, data on nonartemisinin-type antimalarials are still missing. Therefore, this study aimed to elucidate the potential of nonartemisinin antimalarial drugs and drug metabolites to activate PXR. We screened 16 clinically used antimalarial drugs and six major drug metabolites for binding to PXR using the two-hybrid PXR ligand binding domain assembly assay; this identified carboxymefloquine, the major and pharmacologically inactive metabolite of the antimalarial drug mefloquine, as a potential PXR ligand. Two-hybrid PXR-coactivator and -corepressor interaction assays and PXR-dependent promoter reporter gene assays confirmed carboxymefloquine to be a novel PXR agonist which specifically activated the human receptor. In the PXR-expressing intestinal LS174T cells and in primary human hepatocytes, carboxymefloquine induced the expression of drug-metabolizing enzymes and transporters on the mRNA and protein levels. The crucial role of PXR for the carboxymefloquine-dependent induction of gene expression was confirmed by small interfering RNA (siRNA)-mediated knockdown of the receptor. Thus, the clinical use of mefloquine may result in pharmacokinetic drug-drug interactions by means of its metabolite carboxymefloquine. Whether these
in vitro
findings are of
in vivo
relevance has to be addressed in future clinical drug-drug interaction studies.
Probing the Molecular Mechanism of Hypericin-Induced Parasite Death Provides Insight into the Role of Spermidine beyond Redox Metabolism in Leishmania donovani
Authors: Singh Shalini , Sarma Shyamali , Katiyar Shashank P. , Das Mousumi , Bhardwaj Ruchika , Sundar Durai , Dubey Vikash Kumar 
Published: October 2014

ABSTRACT

Hypericin, a natural compound from
Hypericum perforatum
(St. John's wort), has been identified as a specific inhibitor of
Leishmania donovani
spermidine synthase (LdSS) using integrated computational and biochemical approaches. Hypericin showed
in vitro
inhibition of recombinant LdSS enzyme activity. The
in vivo
estimation of spermidine levels in
Leishmania
promastigotes after hypericin treatment showed significant decreases in the spermidine pools of the parasites, indicating target specificity of the inhibitor molecule. The inhibitor, hypericin, showed significant antileishmanial activity, and the mode of death showed necrosis-like features. Further, decreased trypanothione levels and increased glutathione levels with elevated reactive oxygen species (ROS) levels were observed after hypericin treatment. Supplementation with trypanothione in the medium with hypericin treatment restored
in vivo
trypanothione levels and ROS levels but could not prevent necrosis-like death of the parasites. However, supplementation with spermidine in the medium with hypericin treatment restored
in vivo
spermidine levels and parasite death was prevented to a large extent. The data overall suggest that the parasite death due to spermidine starvation as a result of LdSS inhibition is not related to elevated levels of reactive oxygen species. This suggests the involvement of spermidine in processes other than redox metabolism in
Leishmania
parasites. Moreover, the work provides a novel scaffold, i.e., hypericin, as a potent antileishmanial molecule.
Effects of Shiga Toxin Type 2 on a Bioengineered Three-Dimensional Model of Human Renal Tissue
Authors: DesRochers Teresa M. , Kimmerling Erica Palma , Jandhyala Dakshina M. , El-Jouni Wassim , Zhou Jing , Thorpe Cheleste M. , Leong John M. , Kaplan David L. 
Published: October 2014

ABSTRACT

Shiga toxins (Stx) are a family of cytotoxic proteins that can cause hemolytic-uremic syndrome (HUS), a thrombotic microangiopathy, following infections by Shiga toxin-producing
Escherichia coli
(STEC). Renal failure is a key feature of HUS and a major cause of childhood renal failure worldwide. There are currently no specific therapies for STEC-associated HUS, and the mechanism of Stx-induced renal injury is not well understood primarily due to a lack of fully representative animal models and an inability to monitor disease progression on a molecular or cellular level in humans at early stages. Three-dimensional (3D) tissue models have been shown to be more
in vivo
-like in their phenotype and physiology than 2D cultures for numerous disease models, including cancer and polycystic kidney disease. It is unknown whether exposure of a 3D renal tissue model to Stx will yield a more
in vivo
-like response than 2D cell culture. In this study, we characterized Stx2-mediated cytotoxicity in a bioengineered 3D human renal tissue model previously shown to be a predictor of drug-induced nephrotoxicity and compared its response to Stx2 exposure in 2D cell culture. Our results demonstrate that although many mechanistic aspects of cytotoxicity were similar between 3D and 2D, treatment of the 3D tissues with Stx resulted in an elevated secretion of the kidney injury marker 1 (Kim-1) and the cytokine interleukin-8 compared to the 2D cell cultures. This study represents the first application of 3D tissues for the study of Stx-mediated kidney injury.
The Conserved Hypothetical Protein Rv0574c Is Required for Cell Wall Integrity, Stress Tolerance, and Virulence of Mycobacterium tuberculosis
Authors: Garg Rajni , Tripathi Deeksha , Kant Sashi , Chandra Harish , Bhatnagar Rakesh , Banerjee Nirupama 
Published: October 2014

ABSTRACT

The virulence of
Mycobacterium tuberculosis
is intimately related to its distinctive cell wall. The biological significance of poly-α-
l
-glutamine (PLG), a component in the cell wall of virulent mycobacteria, has not been explored adequately. The focus of this study is to investigate the role of a locus, Rv0574c, coding for a polyglutamate synthase-like protein, in the synthesis of poly-α-
l
-glutamine in the context of mycobacterial virulence. Evaluation of Rv0574c gene expression in
M. tuberculosis
demonstrated its growth-phase-linked induction with concomitant accumulation of poly-α-
l
-glutamine in the cell wall. Rv0574c was activated under conditions prevalent in the tubercular granuloma, e.g., hypoxia, nitric oxide, and CO
2
. For functional characterization, we produced a deletion mutant of the Rv0574c gene by allelic exchange. The mutant produced smaller amounts of poly-α-
l
-glutamine in the cell wall than did the wild-type bacterium. Additionally, the increased sensitivity of the mutant to antitubercular drugs, SDS, lysozyme, and mechanical stress was accompanied by a drastic reduction in the ability to form biofilm. Growth of the ΔRv0574c strain was normal under
in vitro
conditions but was retarded in THP-1 macrophages and in the lungs and spleen of BALB/c mice. This was in agreement with histopathology of the lungs showing slow growth and less severe pathology than that of the wild-type strain. In summary, this study demonstrates that the protein encoded by the Rv0574c locus, by virtue of modulating PLG content in the cell wall, helps in maintaining cellular integrity in a hostile host environment. Also, its involvement in protecting the pathogen from host-generated lethal factors contributes to the infectious biology of
M. tuberculosis
.
In VivoMechanisms Involved in Enhanced Protection Utilizing an Fc Receptor-Targeted Mucosal Vaccine Platform in a Bacterial Vaccine and Challenge Model
Authors: Bitsaktsis Constantine , Babadjanova Zulfia , Gosselin Edmund J. 
Published: October 2014

ABSTRACTTargeting antigens (Ag) to Fcγ receptors (FcγR) intranasally (i.n.) enhances immunogenicity and protection against intracellular and extracellular pathogens. Specifically, we have demonstrated that targeting fixed (inactivated)Francisella tularensis(iFT) organisms to FcR in mice i.n., with MAb-iFT immune complexes, enhancesF. tularensis-specific immune responses and protection againstF. tularensischallenge. Furthermore, traditional adjuvant is not required. In addition, we have demonstrated that the increased immunogenicity following the targeting of iFT to FcR is due, in part, to enhanced dendritic cell (DC) maturation, enhanced internalization, and processing and presentation of iFT by DCs, as well as neonatal FcR (FcRn)-enhanced trafficking of iFT from the nasal passage to the nasal mucosa-associated lymphoid tissue (NALT). Using this immunization and challenge model, we expanded on these studies to identify specificin vivoimmune responses impacted and enhanced by FcR targeting of iFT i.n. Specifically, the results of this study demonstrate for the first time that targeting iFT to FcR increases the frequency of activated DCs within the lungs of MAb-iFT-immunized mice subsequent toF. tularensisLVS challenge. In addition, the frequency and number of gamma interferon (IFN-γ)-secreting effector memory (EM) CD4+T cells elicited byF. tularensisinfection (postimmunization) is increased in an interleukin 12 (IL-12)-dependent manner. In summary, these studies build significantly upon previously published work utilizing this vaccine platform. We have identified a number of additional mechanisms by which this novel, adjuvant-independent, FcR-targeted mucosal vaccine approach enhances immunity and protection against infection, while further validating its potential as a universal vaccine platform against mucosal pathogens.
Oral Streptococci and Nitrite-Mediated Interference of Pseudomonas aeruginosa
Authors: Scoffield Jessica A. , Wu Hui 
Published: October 2014

ABSTRACT

The oral cavity harbors a diverse community of microbes that are physiologically unique. Oral microbes that exist in this polymicrobial environment can be pathogenic or beneficial to the host. Numerous oral microbes contribute to the formation of dental caries and periodontitis; however, there is little understanding of the role these microbes play in systemic infections. There is mounting evidence that suggests that oral commensal streptococci are cocolonized with
Pseudomonas aeruginosa
during cystic fibrosis pulmonary infections and that the presence of these oral streptococci contributes to improved lung function. The goal of this study was to examine the underlying mechanism by which
Streptococcus parasanguinis
antagonizes pathogenic
P. aeruginosa
. In this study, we discovered that oral commensal streptococci, including
Streptococcus parasanguinis
,
Streptococcus sanguinis
, and
Streptococcus gordonii
, inhibit the growth of
P. aeruginosa
and that this inhibition is mediated by the presence of nitrite and the production of hydrogen peroxide (H
2
O
2
) by oral streptococci. The requirement of both H
2
O
2
and nitrite for the inhibition of
P. aeruginosa
is due to the generation of reactive nitrogenous intermediates (RNI), including peroxynitrite. Transposon mutagenesis showed that a
P. aeruginosa
mutant defective in a putative ABC transporter permease is resistant to both streptococcus/nitrite- and peroxynitrite-mediated killing. Furthermore,
S. parasanguinis
protects
Drosophila melanogaster
from killing by
P. aeruginosa
in a nitrite-dependent manner. Our findings suggest that the combination of nitrite and H
2
O
2
may represent a unique anti-infection strategy by oral streptococci during polymicrobial infections.
CD4+T Cells Promote Antibody Production but Not Sustained Affinity Maturation during Borrelia burgdorferi Infection
Authors: Elsner Rebecca A. , Hastey Christine J. , Baumgarth Nicole 
Published: October 2014

ABSTRACTCD4 T cells are crucial for enhancing B cell-mediated immunity, supporting the induction of high-affinity, class-switched antibody responses, long-lived plasma cells, and memory B cells. Previous studies showed that the immune response toBorrelia burgdorferiappears to lack robust T-dependent B cell responses, as neither long-lived plasma cells nor memory B cells form for months after infection, and nonswitched IgM antibodies are produced continuously during this chronic disease. These data prompted us to evaluate the induction and functionality ofB. burgdorferiinfection-induced CD4 TFHcells. We report that CD4 T cells were effectively primed and TFHcells induced afterB. burgdorferiinfection. These CD4 T cells contributed to the control ofB. burgdorferiburden and supported the induction ofB. burgdorferi-specific IgG responses. However, while affinity maturation of antibodies against a prototypic T-dependentB. burgdorferiprotein, Arthritis-related protein (Arp), were initiated, these increases were reversed later, coinciding with the previously observed involution of germinal centers. The cessation of affinity maturation was not due to the appearance of inhibitory or exhausted CD4 T cells or a strong induction of regulatory T cells.In vitroT-B cocultures demonstrated that T cells isolated fromB. burgdorferi-infected but notB. burgdorferi-immunized mice supported the rapid differentiation of B cells into antibody-secreting plasma cells rather than continued proliferation, mirroring the induction of rapid short-lived instead of long-lived T-dependent antibody responsesin vivo. The data further suggest thatB. burgdorferiinfection drives the humoral response away from protective, high-affinity, and long-lived antibody responses and toward the rapid induction of strongly induced, short-lived antibodies of limited efficacy.
A Moraxella catarrhalis Two-Component Signal Transduction System Necessary for Growth in Liquid Media Affects Production of Two Lysozyme Inhibitors
Authors: Joslin Stephanie N. , Pybus Christine , Labandeira-Rey Maria , Evans Amanda S. , Attia Ahmed S. , Brautigam Chad A. , Hansen Eric J. 
Published: October 2014

ABSTRACT

There are a paucity of data concerning gene products that could contribute to the ability of
Moraxella catarrhalis
to colonize the human nasopharynx. Inactivation of a gene (
mesR
) encoding a predicted response regulator of a two-component signal transduction system in
M. catarrhalis
yielded a mutant unable to grow in liquid media. This
mesR
mutant also exhibited increased sensitivity to certain stressors, including polymyxin B, SDS, and hydrogen peroxide. Inactivation of the gene (
mesS
) encoding the predicted cognate sensor (histidine) kinase yielded a mutant with the same inability to grow in liquid media as the
mesR
mutant. DNA microarray and real-time reverse transcriptase PCR analyses indicated that several genes previously shown to be involved in the ability of
M. catarrhalis
to persist in the chinchilla nasopharynx were upregulated in the
mesR
mutant. Two other open reading frames upregulated in the
mesR
mutant were shown to encode small proteins (LipA and LipB) that had amino acid sequence homology to bacterial adhesins and structural homology to bacterial lysozyme inhibitors. Inactivation of both
lipA
and
lipB
did not affect the ability of
M. catarrhalis
O35E to attach to a human bronchial epithelial cell line
in vitro
. Purified recombinant LipA and LipB fusion proteins were each shown to inhibit human lysozyme activity
in vitro
and in saliva. A
lipA lipB
deletion mutant was more sensitive than the wild-type parent strain to killing by human lysozyme in the presence of human apolactoferrin. This is the first report of the production of lysozyme inhibitors by
M. catarrhalis
.
Mutational Analysis of the Shigella flexneri O-Antigen Polymerase Wzy: Identification of Wzz-Dependent Wzy Mutants
Authors: Nath Pratiti , Tran Elizabeth Ngoc Hoa , Morona Renato 
Published: October 2014

ABSTRACT

The O-antigen (Oag) component of lipopolysaccharide (LPS) is a major virulence determinant of
Shigella flexneri
and is synthesized by the O-antigen polymerase, Wzy
Sf
. Oag chain length is regulated by chromosomally encoded Wzz
Sf
and pHS-2 plasmid-encoded Wzz
pHS2
. To identify functionally important amino acid residues in Wzy
Sf
, random mutagenesis was performed on the

wzy
Sf

gene in a pWaldo-TEV-GFP plasmid, followed by screening with colicin E2. Analysis of the LPS conferred by mutated Wzy
Sf
proteins in the

wzy
Sf

-deficient (Δ
wzy
) strain identified 4 different mutant classes, with mutations found in periplasmic loop 1 (PL1), PL2, PL3, and PL6, transmembrane region 2 (TM2), TM4, TM5, TM7, TM8, and TM9, and cytoplasmic loop 1 (CL1) and CL5. The association of Wzy
Sf
and Wzz
Sf
was investigated by transforming these mutated

wzy
Sf

plasmids into a

wzy
Sf

- and

wzz
Sf

-deficient (Δ
wzy Δwzz
) strain. Comparison of the LPS profiles in the Δ
wzy
and Δ
wzy Δwzz
backgrounds identified Wzy
Sf
mutants whose polymerization activities were Wzz
Sf
dependent. Colicin E2 and bacteriophage Sf6c sensitivities were consistent with the LPS profiles. Analysis of the expression levels of the Wzy
Sf
-GFP mutants in the Δ
wzy
and Δ
wzy Δwzz
backgrounds identified a role for Wzz
Sf
in Wzy
Sf
stability. Hence, in addition to its role in regulating Oag modal chain length, Wzz
Sf
also affects Wzy
Sf
activity and stability.
Interaction of the C-Terminal Tail of FliF with FliG from the Na
+
-Driven Flagellar Motor of Vibrio alginolyticus
Authors: Ogawa Ryo , Abe-Yoshizumi Rei , Kishi Takaaki , Homma Michio , Kojima Seiji 
Published: October 2014

ABSTRACT

Rotation of the polar flagellum of
Vibrio alginolyticus
is driven by a Na
+
-type flagellar motor. FliG, one of the essential rotor proteins located at the upper rim of the C ring, binds to the membrane-embedded MS ring. The MS ring is composed of a single membrane protein, FliF, and serves as a foundation for flagellar assembly. Unexpectedly, about half of the
Vibrio
FliF protein produced at high levels in
Escherichia coli
was found in the soluble fraction. Soluble FliF purifies as an oligomer of ∼700 kDa, as judged by analytical size exclusion chromatography. By using fluorescence correlation spectroscopy, an interaction between a soluble FliF multimer and FliG was detected. This binding was weakened by a series of deletions at the C-terminal end of FliF and was nearly eliminated by a 24-residue deletion or a point mutation at a highly conserved tryptophan residue (W575). Mutations in FliF that caused a defect in FliF-FliG binding abolish flagellation and therefore confer a nonmotile phenotype. As data from
in vitro
binding assays using the soluble FliF multimer correlate with data from
in vivo
functional analyses, we conclude that the C-terminal region of the soluble form of FliF retains the ability to bind FliG. Our study confirms that the C-terminal tail of FliF provides the binding site for FliG and is thus required for flagellation in
Vibrio
, as reported for other species. This is the first report of detection of the FliF-FliG interaction in the Na
+
-driven flagellar motor, both
in vivo
and
in vitro
.
Clinic Type and Patient Characteristics Affecting Time to Resolution after an Abnormal Cancer-Screening Exam
Authors: Krok-Schoen Jessica L. , Kurta Michelle L. , Weier Rory C. , Young Greg S. , Carey Autumn B. , Tatum Cathy M. , Paskett Electra D. 
Published: October 2014

AbstractBackground: Research shows that multilevel factors influence healthcare delivery and patient outcomes. The study goal was to examine how clinic type [academic medical center (AMC) or federally qualified health center (FQHC)] and patient characteristics influence time to resolution (TTR) among individuals with an abnormal cancer-screening test enrolled in a patient navigation (PN) intervention.Methods: Data were obtained from the Ohio Patient Navigation Research Project, a group-randomized trial of 862 patients from 18 clinics in Columbus, Ohio. TTR of patient after an abnormal breast, cervical, or colorectal screening test and the clinics' patient and provider characteristics were obtained. Descriptive statistics and Cox shared frailty proportional hazards regression models of TTR were used.Results: The mean patient age was 44.8 years and 71% of patients were white. In models adjusted for study arm, FQHC patients had a 39% lower rate of resolution than AMC patients (P = 0.004). Patient factors of having a college education, private insurance, higher income, and being older were significantly associated with lower TTR. After adjustment for factors that substantially affected the effect of clinic type (patient insurance status, education level, and age), clinic type was not significantly associated with TTR.Conclusions: These results suggest that TTR among individuals participating in PN programs are influenced by multiple socioeconomic patient-level factors rather than clinic type. Consequently, PN interventions should be tailored to address socioeconomic status factors that influence TTR.Impact: These results provide clues regarding where to target PN interventions and the importance of recognizing predictors of TTR according to clinic type. Cancer Epidemiol Biomarkers Prev; 24(1); 162–8. ©2014 AACR.
Lung Cancer Detectability by Test, Histology, Stage, and Gender: Estimates from the NLST and the PLCO Trials
Authors: ten Haaf Kevin , van Rosmalen Joost , de Koning Harry J. 
Published: October 2014

Abstract
Background: Implementing optimal lung cancer screening programs requires knowledge of the natural history and detectability of lung cancer. This information can be derived from the results of clinical trials with the aid of microsimulation models.
Methods: Data from the Surveillance, Epidemiology, and End Results (SEER) program and individual-level data from the National Lung Screening Trial (NLST) and the Prostate, Lung, Colon, and Ovarian Cancer Screening trial (PLCO) were used to investigate the sensitivity (by histology and stage) of CT and chest radiography (CXR) and the mean preclinical sojourn time (MPST) of lung cancer (by gender, histology, and stage). The MISCAN-Lung model was used to reproduce the lung cancer incidence by method of detection (clinically or screen-detected), gender, histology, and stage in both trials and SEER, by calibrating CT and CXR sensitivity and natural history parameters.
Results: CT sensitivity ranges from 8.83% to 99.35% and CXR sensitivity from 2.51% to 97.31%, depending on histology and stage. CT sensitivity for stage IA is more than 3-fold higher compared with CXR, for all histologies. The total MPST estimates for lung cancer progressing through preclinical stages IA to IV range from 3.09 to 5.32 years for men and 3.35 to 6.01 years for women. The largest difference in total MPST between genders was estimated for adenocarcinoma.
Conclusions: We estimate longer MPSTs for lung cancer compared with previous research, suggesting a greater window of opportunity for lung cancer screening.
Impact: This study provides detailed insights into the natural history of lung cancer and CT screening effectiveness. Cancer Epidemiol Biomarkers Prev; 24(1); 154–61. ©2014 AACR.