bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isoniazid Mediates the
CYP2B6*6
Genotype-Dependent Interaction between Efavirenz and Antituberculosis Drug Therapy through Mechanism-Based Inactivation of CYP2A6
Authors: Court Michael H. , Almutairi Fawziah E. , Greenblatt David J. , Hazarika Suwagmani , Sheng Hongyan , Klein Kathrin , Zanger Ulrich M. , Bourgea Joanne , Patten Christopher J. , Kwara Awewura 
Published: May 2014

ABSTRACT

Efavirenz is commonly used to treat patients coinfected with human immunodeficiency virus and tuberculosis. Previous clinical studies have observed paradoxically elevated efavirenz plasma concentrations in patients with the
CYP2B6*6/*6
genotype (but not the
CYP2B6*1/*1
genotype) during coadministration with the commonly used four-drug antituberculosis therapy. This study sought to elucidate the mechanism underlying this genotype-dependent drug-drug interaction.
In vitro
studies were conducted to determine whether one or more of the antituberculosis drugs (rifampin, isoniazid, pyrazinamide, or ethambutol) potently inhibit efavirenz 8-hydroxylation by CYP2B6 or efavirenz 7-hydroxylation by CYP2A6, the main mechanisms of efavirenz clearance. Time- and concentration-dependent kinetics of inhibition by the antituberculosis drugs were determined using genotyped human liver microsomes (HLMs) and recombinant CYP2A6, CYP2B6.1, and CYP2B6.6 enzymes. Although none of the antituberculosis drugs evaluated at up to 10 times clinical plasma concentrations were found to inhibit efavirenz 8-hydroxylation by HLMs, both rifampin (apparent inhibition constant [

K
i

] = 368 μM) and pyrazinamide (

K
i

= 637 μM) showed relatively weak inhibition of efavirenz 7-hydroxylation. Importantly, isoniazid demonstrated potent time-dependent inhibition of efavirenz 7-hydroxylation in both HLMs (inhibitor concentration required for half-maximal inactivation [

K
I

] = 30 μM; maximal rate constant of inactivation [
k
inact
] = 0.023 min
−1
) and recombinant CYP2A6 (

K
I

= 15 μM;
k
inact
= 0.024 min
−1
) and also formed a metabolite intermediate complex consistent with mechanism-based inhibition. Selective inhibition of the CYP2B6.6 allozyme could not be demonstrated for any of the antituberculosis drugs using either recombinant enzymes or
CYP2B6*6
genotype HLMs. In conclusion, the results of this study identify isoniazid as the most likely perpetrator of this clinically important drug-drug interaction through mechanism-based inactivation of CYP2A6.
Hsp90 Inhibitors as New Leads To Target Parasitic Diarrheal Diseases
Authors: Debnath Anjan , Shahinas Dea , Bryant Clifford , Hirata Ken , Miyamoto Yukiko , Hwang Grace , Gut Jiri , Renslo Adam R. , Pillai Dylan R. , Eckmann Lars , Reed Sharon L. , McKerrow James H. 
Published: May 2014

ABSTRACT

Entamoeba histolytica
and
Giardia lamblia
are anaerobic protozoan parasites that cause amebiasis and giardiasis, two of the most common diarrheal diseases worldwide. Current therapy relies on metronidazole, but resistance has been reported and the drug has significant adverse effects. Therefore, it is critical to search for effective, better-tolerated antiamebic and antigiardial drugs. We synthesized several examples of a recently reported class of Hsp90 inhibitors and evaluated these compounds as potential leads for antiparasitic chemotherapy. Several of these inhibitors showed strong
in vitro
activity against both
E. histolytica
and
G. lamblia
trophozoites. The inhibitors were rescreened to discriminate between amebicidal and giardicidal activity and general cytotoxicity toward a mammalian cell line. No mammalian cytotoxicity was found at >100 μM for 48 h for any of the inhibitors. To understand the mechanism of action, a competitive binding assay was performed using the fluorescent ATP analogue bis-ANS (4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic acid dipotassium salt) and recombinant
E. histolytica
Hsp90 preincubated in both the presence and absence of Hsp90 inhibitors. There was significant reduction in fluorescence compared to the level in the control, suggesting that
E. histolytica
Hsp90 is a selective target. The
in vivo
efficacy and safety of one Hsp90 inhibitor in a mouse model of amebic colitis and giardiasis was demonstrated by significant inhibition of parasite growth at a single oral dose of 5 mg/kg of body weight/day for 7 days and 10 mg/kg/day for 3 days. Considering the results for
in vitro
activity and
in vivo
efficacy, Hsp90 inhibitors represent a promising therapeutic option for amebiasis and giardiasis.
Reclaiming the Efficacy of β-Lactam–β-Lactamase Inhibitor Combinations: Avibactam Restores the Susceptibility of CMY-2-Producing Escherichia coli to Ceftazidime
Authors: Papp-Wallace Krisztina M. , Winkler Marisa L. , Gatta Julian A. , Taracila Magdalena A. , Chilakala Sujatha , Xu Yan , Johnson J. Kristie , Bonomo Robert A. 
Published: May 2014

ABSTRACT

CMY-2 is a plasmid-encoded Ambler class C cephalosporinase that is widely disseminated in
Enterobacteriaceae
and is responsible for expanded-spectrum cephalosporin resistance. As a result of resistance to both ceftazidime and β-lactamase inhibitors in strains carrying
bla
CMY
, novel β-lactam–β-lactamase inhibitor combinations are sought to combat this significant threat to β-lactam therapy. Avibactam is a bridged diazabicyclo [3.2.1]octanone non-β-lactam β-lactamase inhibitor in clinical development that reversibly inactivates serine β-lactamases. To define the spectrum of activity of ceftazidime-avibactam, we tested the susceptibilities of
Escherichia coli
clinical isolates that carry
bla
CMY-2
or
bla
CMY-69
and investigated the inactivation kinetics of CMY-2. Our analysis showed that CMY-2-containing clinical isolates of
E. coli
were highly susceptible to ceftazidime-avibactam (MIC
90
, ≤0.5 mg/liter); in comparison, ceftazidime had a MIC
90
of >128 mg/liter. More importantly, avibactam was an extremely potent inhibitor of CMY-2 β-lactamase, as demonstrated by a second-order onset of acylation rate constant (
k
2
/
K
) of (4.9 ± 0.5) × 10
4
M
−1
s
−1
and the off-rate constant (
k
off
) of (3.7 ± 0.4) ×10
−4
s
−1
. Analysis of the reaction of avibactam with CMY-2 using mass spectrometry to capture reaction intermediates revealed that the CMY-2–avibactam acyl-enzyme complex was stable for as long as 24 h. Molecular modeling studies raise the hypothesis that a series of successive hydrogen-bonding interactions occur as avibactam proceeds through the reaction coordinate with CMY-2 (e.g., T316, G317, S318, T319, S343, N346, and R349). Our findings support the microbiological and biochemical efficacy of ceftazidime-avibactam against
E. coli
containing plasmid-borne CMY-2 and CMY-69.
Antiherpesvirus Activities of Two Novel 4′-Thiothymidine Derivatives, KAY-2-41 and KAH-39-149, Are Dependent on Viral and Cellular Thymidine Kinases
Authors: Coen Natacha , Duraffour Sophie , Haraguchi Kazuhiro , Balzarini Jan , van den Oord Joost J. , Snoeck Robert , Andrei Graciela 
Published: May 2014

ABSTRACT

The emergence of drug-resistant herpesviruses represents a significant problem in clinical practice, primarily in immunocompromised patients. Furthermore, effective antiviral therapies against gammaherpesvirus-associated diseases are lacking. Here, we present two thiothymidine derivatives, KAY-2-41 and KAH-39-149, with different spectra of antiviral activity from those of the reference antiherpetic drugs, showing inhibitory activities against herpes simplex virus, varicella-zoster virus (VZV), and particularly against Epstein-Barr virus, with high selectivity
in vitro
. While KAY-2-41- and KAH-39-149-resistant herpesviruses were found to harbor mutations in the viral thymidine kinase (TK), these mutations conferred only low levels of resistance to these drugs but high levels to other TK-dependent drugs. Also, antiviral assays in HeLa TK-deficient cells showed a lack of KAY-2-41 and KAH-39-149 activities against herpes simplex virus 1 (HSV-1) and HSV-2 TK-deficient mutants. Furthermore, enzymatic TK assays showed the ability of HSV-1 TK, VZV TK, and cellular TK1 and TK2 to recognize and phosphorylate KAY-2-41 and KAH-39-149. These results demonstrate that the compounds depend on both viral and host TKs to exert antiviral activity. Additionally, the antiviral efficacy of KAH-39-149 proved to be superior to that of KAY-2-41 in a mouse model of gammaherpesvirus infection, highlighting the potential of this class of antiviral agents for further development as selective therapeutics against Epstein-Barr virus.
Structural Analysis of Base Substitutions in Thermus thermophilus 16S rRNA Conferring Streptomycin Resistance
Authors: Demirci Hasan , Murphy Frank V. , Murphy Eileen L. , Connetti Jacqueline L. , Dahlberg Albert E. , Jogl Gerwald , Gregory Steven T. 
Published: May 2014

ABSTRACT

Streptomycin is a bactericidal antibiotic that induces translational errors. It binds to the 30S ribosomal subunit, interacting with ribosomal protein S12 and with 16S rRNA through contacts with the phosphodiester backbone. To explore the structural basis for streptomycin resistance, we determined the X-ray crystal structures of 30S ribosomal subunits from six streptomycin-resistant mutants of
Thermus thermophilus
both in the apo form and in complex with streptomycin. Base substitutions at highly conserved residues in the central pseudoknot of 16S rRNA produce novel hydrogen-bonding and base-stacking interactions. These rearrangements in secondary structure produce only minor adjustments in the three-dimensional fold of the pseudoknot. These results illustrate how antibiotic resistance can occur as a result of small changes in binding site conformation.
Clinical Outcomes of Hospital-Acquired Infection with Acinetobacter nosocomialis and Acinetobacter pittii
Authors: Chusri Sarunyou , Chongsuvivatwong Virasakdi , Rivera Jesabel I. , Silpapojakul Kachornsakdi , Singkhamanan Kamonnut , McNeil Edward , Doi Yohei 
Published: May 2014

ABSTRACT

The role of
Acinetobacter nosocomialis
and
Acinetobacter pittii
, which belong to the
A. calcoaceticus
-
A. baumannii
complex, in hospital-acquired infections is increasingly recognized. Here we describe a retrospective cohort study of hospital-acquired
A. calcoaceticus
-
A. baumannii
complex infections at a university hospital in Thailand. A total of 222 unique cases were identified between January 2010 and December 2011. The genomospecies of the
A. calcoaceticus
-
A. baumannii
complex isolates were classified as follows:
A. baumannii
, 197 (89%);
A. nosocomialis
, 18 (8%); and
A. pittii
, 7 (3%). All
A. nosocomialis
and
A. pittii
isolates were susceptible to imipenem and meropenem. The patients infected with
A. nosocomialis
and
A. pittii
had lower 30-day mortality than those infected with carbapenem-susceptible
A. baumannii
(
P
= 0.025) and carbapenem-resistant
A. baumannii
(
P
= 0.013). The factors influencing 30-day mortality were infection with non-
baumannii A. calcoaceticus
-
A. baumannii
complex (hazard ratio [HR], 0.12; 95% confidence interval [CI], 0.03 to 0.51;
P
= 0.004), infection with carbapenem-resistant
A. baumannii
(HR, 1.57; 95% CI, 0.89 to 2.79;
P
= 0.105), appropriate empirical antimicrobial therapy (HR, 0.38; 95% CI, 0.23 to 0.61;
P
< 0.001), and higher acute physiology and chronic health evaluation II (APACHE II) score (HR, 1.15; 95% CI, 1.10 to 1.19;
P
< 0.001). In
Galleria mellonella
assays, the survival rates were significantly higher for the larvae infected with
A. nosocomialis
or
A. pittii
than for those infected with either carbapenem-susceptible
A. baumannii
or carbapenem-resistant
A. baumannii
, but no differences in survival rates were observed between carbapenem-susceptible
A. baumannii
and carbapenem-resistant
A. baumannii
. These findings suggest intrinsic differences in virulence between non-
baumannii A. calcoaceticus
-
A. baumannii
complex species and
A. baumannii
but not between carbapenem-susceptible and resistant
A. baumannii
.
Phase-Variable Expression of
lptA
Modulates the Resistance of Neisseria gonorrhoeae to Cationic Antimicrobial Peptides
Authors: Kandler Justin L. , Joseph Sandeep J. , Balthazar Jacqueline T. , Dhulipala Vijaya , Read Timothy D. , Jerse Ann E. , Shafer William M. 
Published: May 2014

ABSTRACT

Phosphoethanolamine (PEA) decoration of lipid A produced by
Neisseria gonorrhoeae
has been linked to bacterial resistance to cationic antimicrobial peptides/proteins (CAMPs) and
in vivo
fitness during experimental infection. We now report that the
lptA
gene, which encodes the PEA transferase responsible for this decoration, is in an operon and that high-frequency mutation in a polynucleotide repeat within
lptA
can influence gonococcal resistance to CAMPs.
Association of Heme Oxygenase 1 with the Restoration of Liver Function after Damage in Murine Malaria by Plasmodium yoelii
Authors: Dey Sumanta , Mazumder Somnath , Siddiqui Asim Azhar , Iqbal M. Shameel , Banerjee Chinmoy , Sarkar Souvik , De Rudranil , Goyal Manish , Bindu Samik , Bandyopadhyay Uday 
Published: May 2014

ABSTRACT

The liver efficiently restores function after damage induced during malarial infection once the parasites are cleared from the blood. However, the molecular events leading to the restoration of liver function after malaria are still obscure. To study this, we developed a suitable model wherein mice infected with
Plasmodium yoelii
(45% parasitemia) were treated with the antimalarial α/β-arteether to clear parasites from the blood and, subsequently, restoration of liver function was monitored. Liver function tests clearly indicated that complete recovery of liver function occurred after 25 days of parasite clearance. Analyses of proinflammatory gene expression and neutrophil infiltration further indicated that hepatic inflammation, which was induced immediately after parasite clearance from the blood, was gradually reduced. Moreover, the inflammation in the liver after parasite clearance was found to be correlated positively with oxidative stress and hepatocyte apoptosis. We investigated the role of heme oxygenase 1 (HO-1) in the restoration of liver function after malaria because HO-1 normally renders protection against inflammation, oxidative stress, and apoptosis under various pathological conditions. The expression and activity of HO-1 were found to be increased significantly after parasite clearance. We even found that chemical silencing of HO-1 by use of zinc protoporphyrin enhanced inflammation, oxidative stress, hepatocyte apoptosis, and liver injury. In contrast, stimulation of HO-1 by cobalt protoporphyrin alleviated liver inflammation and reduced oxidative stress, hepatocyte apoptosis, and associated tissue injury. Therefore, we propose that selective induction of HO-1 in the liver would be beneficial for the restoration of liver function after parasite clearance.
Surface Structure Characterization of Aspergillus fumigatus Conidia Mutated in the Melanin Synthesis Pathway and Their Human Cellular Immune Response
Authors: Bayry Jagadeesh , Beaussart Audrey , Dufrêne Yves F. , Sharma Meenu , Bansal Kushagra , Kniemeyer Olaf , Aimanianda Vishukumar , Brakhage Axel A. , Kaveri Srini V. , Kwon-Chung Kyung J. , Latgé Jean-Paul , Beauvais Anne 
Published: May 2014

ABSTRACT

In
Aspergillus fumigatus
, the conidial surface contains dihydroxynaphthalene (DHN)-melanin. Six-clustered gene products have been identified that mediate sequential catalysis of DHN-melanin biosynthesis. Melanin thus produced is known to be a virulence factor, protecting the fungus from the host defense mechanisms. In the present study, individual deletion of the genes involved in the initial three steps of melanin biosynthesis resulted in an altered conidial surface with masked surface rodlet layer, leaky cell wall allowing the deposition of proteins on the cell surface and exposing the otherwise-masked cell wall polysaccharides at the surface. Melanin as such was immunologically inert; however, deletion mutant conidia with modified surfaces could activate human dendritic cells and the subsequent cytokine production in contrast to the wild-type conidia. Cell surface defects were rectified in the conidia mutated in downstream melanin biosynthetic pathway, and maximum immune inertness was observed upon synthesis of vermelone onward. These observations suggest that although melanin as such is an immunologically inert material, it confers virulence by facilitating proper formation of the
A. fumigatus
conidial surface.
Role of the Aryl Hydrocarbon Receptor in the Immune Response Profile and Development of Pathology during Plasmodium berghei Anka Infection
Authors: Brant Fatima , Miranda Aline S. , Esper Lisia , Rodrigues David Henrique , Kangussu Lucas Miranda , Bonaventura Daniella , Soriani Frederico Marianetti , Pinho Vanessa , Souza Danielle G. , Rachid Milene Alvarenga , Weiss Louis M. , Tanowitz Herbert B. , Teixeira Mauro Martins , Teixeira Antônio Lucio , Machado Fabiana Simão 
Published: May 2014

ABSTRACT

Infection with
Plasmodium falciparum
may result in severe disease affecting various organs, including liver, spleen, and brain, resulting in high morbidity and mortality.
Plasmodium berghei
Anka infection of mice recapitulates many features of severe human malaria. The aryl hydrocarbon receptor (AhR) is an intracellular receptor activated by ligands important in the modulation of the inflammatory response. We found that AhR-knockout (KO) mice infected with
P. berghei
Anka displayed increased parasitemia, earlier mortality, enhanced leukocyte-endothelial cell interactions in the brain microvasculature, and increased inflammation in brain (interleukin-17 [IL-17] and IL-6) and liver (gamma interferon [IFN-γ] and tumor necrosis factor alpha [TNF-α]) compared to infected wild-type (WT) mice. Infected AhR-KO mice also displayed a reduction in cytokines required for host resistance, including TNF-α, IL-1β, and IFN-γ, in the brain and spleen. Infection of AhR-KO mice resulted in an increase in T regulatory cells and transforming growth factor β, IL-6, and IL-17 in the brain. AhR modulated the basal expression of SOCS3 in spleen and brain, and
P. berghei
Anka infection resulted in enhanced expression of SOCS3 in brain, which was absent in infected AhR-KO mice. These data suggest that AhR-mediated control of SOCS3 expression is probably involved in the phenotype seen in infected AhR-KO mice. This is, to our knowledge, the first demonstration of a role for AhR in the pathogenesis of malaria.
Deficiency of Lymph Node-Resident Dendritic Cells (DCs) and Dysregulation of DC Chemoattractants in a Malnourished Mouse Model of Leishmania donovani Infection
Authors: Ibrahim Marwa K. , Barnes Jeffrey L. , Osorio E. Yaneth , Anstead Gregory M. , Jimenez Fabio , Osterholzer John J. , Travi Bruno L. , Ahuja Seema S. , White A. Clinton , Melby Peter C. 
Published: May 2014

ABSTRACT

Malnutrition is thought to contribute to more than one-third of all childhood deaths via increased susceptibility to infection. Malnutrition is a significant risk factor for the development of visceral leishmaniasis, which results from skin inoculation of the intracellular protozoan
Leishmania donovani
. We previously established a murine model of childhood malnutrition and found that malnutrition decreased the lymph node barrier function and increased the early dissemination of
L. donovani
. In the present study, we found reduced numbers of resident dendritic cells (conventional and monocyte derived) but not migratory dermal dendritic cells in the skin-draining lymph nodes of
L. donovani
-infected malnourished mice. Expression of chemokines and their receptors involved in trafficking of dendritic cells and their progenitors to the lymph nodes was dysregulated. C-C chemokine receptor type 2 (CCR2) and its ligands (CCL2 and CCL7) were reduced in the lymph nodes of infected malnourished mice, as were CCR2-bearing monocytes/macrophages and monocyte-derived dendritic cells. However, CCR7 and its ligands (CCL19 and CCL21) were increased in the lymph node and CCR7 was increased in lymph node macrophages and dendritic cells. CCR2-deficient mice recapitulated the profound reduction in the number of resident (but not migratory dermal) dendritic cells in the lymph node but showed no alteration in the expression of CCL19 and CCL21. Collectively, these results suggest that the malnutrition-related reduction in the lymph node barrier to dissemination of
L. donovani
is related to insufficient numbers of lymph node-resident but not migratory dermal dendritic cells. This is likely driven by the altered activity of the CCR2 and CCR7 chemoattractant pathways.
Role of Tumor Suppressor TSC1 in Regulating Antigen-Specific Primary and Memory CD8 T Cell Responses to Bacterial Infection
Authors: Krishna Sruti , Yang Jialong , Wang Hongxia , Qiu Yurong , Zhong Xiao-Ping 
Published: May 2014

ABSTRACT

The serine/threonine kinase mammalian/mechanistic target of rapamycin (mTOR) integrates various environmental cues such as the presence of antigen, inflammation, and nutrients to regulate T cell growth, metabolism, and function. The tuberous sclerosis 1 (TSC1)/TSC2 complex negatively regulates the activity of an mTOR-containing multiprotein complex called mTOR complex 1. Recent studies have revealed an essential cell-intrinsic role for TSC1 in T cell survival, quiescence, and mitochondrial homeostasis. Given the emerging role of mTOR activity in the regulation of the quantity and quality of CD8 T cell responses, in this study, we examine the role of its suppressor, TSC1, in the regulation of antigen-specific primary and memory CD8 T cell responses to bacterial infection. Using an established model system of transgenic CD8 cell adoptive transfer and challenge with
Listeria monocytogenes
expressing a cognate antigen, we found that TSC1 deficiency impairs antigen-specific CD8 T cell responses, resulting in weak expansion, exaggerated contraction, and poor memory generation. Poor expansion of TSC1-deficient cells was associated with defects in survival and proliferation
in vivo
, while enhanced contraction was correlated with an increased ratio of short-lived effectors to memory precursors in the effector cell population. This perturbation of effector-memory differentiation was concomitant with decreased expression of eomesodermin among activated TSC1 knockout cells. Upon competitive adoptive transfer with wild-type counterparts and antigen rechallenge, TSC1-deficient memory cells showed moderate defects in expansion but not cytokine production. Taken together, these findings provide direct evidence of a CD8 T cell-intrinsic role for TSC1 in the regulation of antigen-specific primary and memory responses.