bluuebunny/crossref_metadata_2025_split huggingface dataset:
HilE Interacts with HilD and Negatively Regulates
hilA
Transcription and Expression of the
Salmonella enterica
Serovar Typhimurium Invasive Phenotype
Authors: Baxter M. Aaron , Fahlen Thomas F. , Wilson Rebecca L. , Jones Bradley D. 
Published: February 2003

ABSTRACT

The ability of
Salmonella enterica
serovar Typhimurium to traverse the intestinal mucosa of a host is an important step in its ability to initiate gastrointestinal disease. The majority of the genes required for this invasive characteristic are encoded on
Salmonella
pathogenicity island 1 (SPI1), and their expression is controlled by the transcriptional activator HilA, a member of the OmpR/ToxR family of proteins. A variety of genes (
hilC
,
hilD
,
fis
,
sirA
/
barA
,
csrAB
,
phoB
,
fadD
,
envZ
/
ompR
,
fliZ
,
hilE
,
ams
,
lon
,
pag
, and
hha
) have been identified that exert positive or negative effects on
hilA
expression, although the mechanisms by which these gene products function remain relatively unclear. Recent work indicates that the small DNA-binding protein, Hha, has a significant role in repressing
hilA
transcription and the invasive phenotype, particularly in response to osmolarity signals. We have characterized the
Salmonella
-specific gene,
hilE
, and found that it plays an important regulatory role in
hilA
transcription and invasion gene expression. Mutation of
hilE
causes derepression of
hilA
transcription, and overexpression of
hilE
superrepresses
hilA
expression and the invasive phenotype. Bacterial two-hybrid experiments indicate that the HilE protein interacts with HilD, suggesting a possible mechanism for HilE negative regulation of
hilA
gene expression and the
Salmonella
invasive phenotype. Finally, we have found that the
hilE
gene resides on a region of the serovar Typhimurium chromosome that has many characteristics of a pathogenicity island.
EnterohemorrhagicEscherichia coliO157:H7 Disrupts Stat1-Mediated Gamma Interferon Signal Transduction in Epithelial Cells
Authors: Ceponis Peter J. M. , McKay Derek M. , Ching Joyce C. Y. , Pereira Perpetual , Sherman Philip M. 
Published: February 2003

ABSTRACTEnterohemorrhagicEscherichia coli(EHEC) O157:H7 is a clinically important bacterial enteropathogen that manipulates a variety of host cell signal transduction cascades to establish infection. However, the effect of EHEC O157:H7 on Jak/Stat signaling is unknown. To define the effect of EHEC infection on epithelial gamma interferon (IFN-γ)-Stat1 signaling, human T84 and HEp-2 epithelial cells were infected with EHEC O157:H7 and then stimulated with recombinant human IFN-γ. Cells were also infected with different EHEC strains, heat-killed EHEC, enteropathogenicE. coli(EPEC) O127:H6, and the commensal strainE. coliHB101. Nuclear and whole-cell protein extracts were prepared and were assayed by an electrophoretic mobility shift assay (EMSA) and by Western blotting, respectively. Cells were also processed for immunofluorescence to detect the subcellular localization of Stat1. The EMSA revealed inducible, but not constitutive, Stat1 activation upon IFN-γ treatment of both cell lines. The EMSA also showed that 6 h of EHEC O157:H7 infection, but not 30 min of EHEC O157:H7 infection, prevented subsequent Stat1 DNA binding induced by IFN-γ, whereas infection with EPEC did not. Immunoblotting showed that infection with EHEC, but not infection with EPEC, eliminated IFN-γ-induced Stat1 tyrosine phosphorylation in both dose- and time-dependent fashions and disrupted inducible protein expression of the Stat1-dependent gene interferon regulatory factor 1. Immunofluorescence revealed that EHEC infection did not prevent nuclear accumulation of Stat1 after IFN-γ treatment. Also, Stat1 tyrosine phosphorylation was suppressed by different EHEC isolates, including intimin-, type III secretion- and plasmid-deficient strains, but not by HB101 and heat-killed EHEC. These findings indicate the novel disruption of host cell signaling caused by EHEC infection but not by EPEC infection.
Shiga Toxin 1 Triggers a Ribotoxic Stress Response Leading to p38 and JNK Activation and Induction of Apoptosis in Intestinal Epithelial Cells
Authors: Smith Wendy E. , Kane Anne V. , Campbell Sausan T. , Acheson David W. K. , Cochran Brent H. , Thorpe Cheleste M. 
Published: February 2003

ABSTRACT

Shiga toxins made by Shiga toxin-producing
Escherichia coli
(STEC) are associated with hemolytic uremic syndrome. Shiga toxins (Stxs) may access the host systemic circulation by absorption across the intestinal epithelium. The effects of Stxs on this cell layer are not completely understood, although animal models of STEC infection suggest that, in the gut, Stxs may participate in both immune activation and apoptosis. Stxs have one enzymatically active A subunit associated with five identical B subunits. The A subunit inactivates ribosomes by cleaving a specific adenine from the 28S rRNA. We have previously shown that Stxs can induce multiple C-X-C chemokines in intestinal epithelial cells in vitro, including interleukin-8 (IL-8), and that Stx-induced IL-8 expression is linked to induction of c-Jun mRNA and p38 mitogen-activated protein (MAP) kinase pathway activity. We now report Stx1 induction of both primary response genes
c-jun
and c-
fos
and activation of the stress-activated protein kinases, JNK/SAPK and p38, in the intestinal epithelial cell line HCT-8. By 1 h of exposure to Stx1, mRNAs for
c-jun
and c-
fos
are induced, and both JNK and p38 are activated; activation of both kinases persisted up to 24 h. Stx1 enzymatic activity was required for kinase activation; a catalytically defective mutant toxin did not activate either. Stx1 treatment of HCT-8 cells resulted in cell death that was associated with caspase 3 cleavage and internucleosomal DNA fragmentation; this cytotoxicity also required Stx1 enzymatic activity. Blocking Stx1-induced p38 and JNK activation with the inhibitor SB202190 prevented cell death and diminished Stx1-associated caspase 3 cleavage. In summary, these data link the Stx1-induced ribotoxic stress response with both chemokine expression and apoptosis in the intestinal epithelial cell line HCT-8 and suggest that blocking host cell MAP kinases may prevent these Stx-associated events.
MutantEscherichia coliHeat-Labile Toxin B Subunit That Separates Toxoid-Mediated Signaling and Immunomodulatory Action from Trafficking and Delivery Functions
Authors: Fraser Sylvia A. , de Haan Lolke , Hearn Arron R. , Bone Heather K. , Salmond Robert J. , Rivett A. Jennifer , Williams Neil A. , Hirst Timothy R. 
Published: February 2003

ABSTRACTThe homopentameric B-subunit components ofEscherichia coliheat-labile enterotoxin (EtxB) and cholera toxin (CtxB) possess the capacity to enter mammalian cells and to activate cell-signaling events in leukocytes that modulate immune cell function. Both properties have been attributed to the ability of the B subunits to bind to GM1-ganglioside receptors, a ubiquitous glycosphingolipid found in the plasma membrane. Here we describe the properties of EtxB(H57S), a mutant B subunit with a His→Ser substitution at position 57. The mutant was found to be severely defective in inducing leukocyte signaling, as shown by failure to (i) trigger caspase 3-mediated CD8+-T-cell apoptosis, (ii) activate nuclear translocation of NF-κB in Jurkat T cells, (iii) induce a potent anti-B-subunit response in mice, or (iv) serve as a mucosal adjuvant. However, its GM1 binding, cellular uptake, and delivery functions remained intact. This was further validated by the finding that EtxB(H57S) was as effective as EtxB in delivering a conjugated model class I epitope into the major histocompatibility complex class I pathway of a dendritic cell line. These observations imply that GM1 binding alone is not sufficient to trigger the signaling events responsible for the potent immunomodulatory properties of EtxB. Moreover, they demonstrate that its signaling properties play no role in EtxB uptake and trafficking. Thus, EtxB(H57S) represents a novel tool for evaluating the complex cellular interactions and signaling events occurring after receptor interaction, as well as offering an alternative means of delivering attached peptides in the absence of the potent immunomodulatory signals induced by wild-type B subunits.
Cell Adhesion and Ca
2+
Signaling Activity in Stably Transfected
Trypanosoma cruzi
Epimastigotes Expressing the Metacyclic Stage-Specific Surface Molecule gp82
Authors: Manque Patricio M. , Neira Ivan , Atayde Vanessa D. , Cordero Esteban , Ferreira Alice T. , da Silveira José Franco , Ramirez Marcel , Yoshida Nobuko 
Published: February 2003

ABSTRACT

Metacyclic trypomastigotes of
Trypanosoma cruzi
express a developmentally regulated 82-kDa surface glycoprotein (gp82) that has been implicated in host cell invasion. gp82-mediated interaction of metacyclic forms with target cells induces in both cells activation of the signal transduction pathways, leading to intracellular Ca
2+
mobilization, which is required for parasite internalization. Noninfective epimastigotes do not express detectable levels of gp82 and are unable to induce a Ca
2+
response. We stably transfected epimastigotes with a
T. cruzi
expression vector carrying the metacyclic stage gp82 cDNA. These transfectants produced a functional gp82, which bound to and triggered a Ca
2+
response in HeLa cells, in the same manner as the metacyclic trypomastigote gp82. Such properties were not found in epimastigotes transfected with the plasmid vector alone. Epimastigotes expressing gp82 on the surface adhered to HeLa cells but were not internalized. Treatment of gp82-expressing epimastigotes with forskolin, an activator of adenylyl cyclase that increases the metacyclic trypomastigote entry into target cells, did not promote parasite internalization. P175, an intracellular tyrosine phosphorylated protein, which appears to play a role in gp82-dependent signaling cascade in metacyclic forms, was undetectable in epimastigotes, either transfected or not with pTEX-gp82. Overall, our results indicate that gp82 is required but not sufficient for target cell invasion.
Interleukin-6-Deficient Mice Are Highly Susceptible toGiardia lambliaInfection but Exhibit Normal Intestinal Immunoglobulin A Responses against the Parasite
Authors: Bienz Marianne , Dai Wen Juan , Welle Monika , Gottstein Bruno , Müller Norbert 
Published: February 2003

ABSTRACTIn the present study, interleukin-6 (IL-6)-deficient mice were infected withGiardia lambliaclone GS/M-83-H7. Murine IL-6 deficiency did not affect the synthesis of parasite-specific intestinal immunoglobulin A. However, in contrast to wild-type mice, IL-6-deficient animals were not able to control the acute phase of parasite infection. Reverse transcription-PCR-based quantitation of cytokine mRNA levels in peripheral lymph node cells exhibited a short-term up-regulation of IL-4 expression in IL-6-deficient mice that seemed to be associated with failure in controlling the parasite population. This observation suggests a further elucidation of IL-4-dependent, Th2-type regulatory processes regarding their potential to influence the course ofG. lambliainfection in the experimental murine host.
Nonhuman Primate Model for
Listeria monocytogenes
-Induced Stillbirths
Authors: Smith Mary Alice , Takeuchi Kazue , Brackett Robert E. , McClure Harold M. , Raybourne Richard B. , Williams Kristina M. , Babu Uma S. , Ware Glenn O. , Broderson J. Roger , Doyle Michael P. 
Published: February 2003

ABSTRACT

Listeria monocytogenes
, isolated from outbreaks in either human or nonhuman primate populations, was administered orally at doses ranging from 10
6
to 10
10
CFU. Four of 10 treated animals delivered stillborn infants.
L. monocytogenes
was isolated from fetal tissue, and the pathology was consistent with
L. monocytogenes
infection as the cause of pregnancy loss. For all pregnancies resulting in stillbirths,
L. monocytogenes
was isolated from maternal feces, indicating that
L. monocytogenes
had survived and had probably colonized the gastrointestinal tract. Antibodies and antigen-specific lymphocyte proliferation against
Listeria
increased in animals that had stillbirths.
Bacterial [Cu,Zn]-Cofactored Superoxide Dismutase Protects Opsonized, EncapsulatedNeisseria meningitidisfrom Phagocytosis by Human Monocytes/Macrophages
Authors: Dunn Kate L. R. , Farrant Jayne L. , Langford Paul R. , Kroll J. Simon 
Published: February 2003

ABSTRACTSuperoxide dismutase cofactored by copper and zinc ([Cu,Zn]-SOD) contributes to the protection of opsonized serogroup BNeisseria meningitidisagainst phagocytosis by human monocytes/macrophages, withsodCmutant organisms being endocytosed in significantly higher numbers than are wild-type organisms. The influence of [Cu,Zn]-SOD was found to be exerted at the stage of phagocytosis, rather than at earlier (modulating surface association) or later (intracellular killing) stages.
Extensive Association Analysis Between Polymorphisms of PON Gene Cluster With Coronary Heart Disease in Chinese Han Population
Authors: Wang Xiaoling , Fan Zhongjie , Huang Jianfeng , Su Shaoyong , Yu Quanjun , Zhao Jiangong , Hui Rutai , Yao Zhijian , Shen Yan , Qiang Boqin , Gu Dongfeng 
Published: February 2003

Objective—An extensive association analysis of PON gene cluster (PONs) with coronary heart disease (CHD) was performed in Chinese Han population.Methods and Results—Thirty polymorphisms of PON1, PON2, and PON3 gene were identified by direct sequencing of genomic DNA derived from 48 randomly selected patients. Twelve polymorphisms were additionally investigated for association with CHD in 474 male patients and 475 controls. Univariate analyses showed the cases had significantly higher frequencies of PON1 192Q allele, 160R allele, −162A allele, and PON2 311C allele than were seen in the controls. Logistic regression analyses revealed only the PON1 R160G and −162G/A polymorphisms remained significantly associated with CHD (P=0.0054 andP=0.0002). Haplotype analyses for various polymorphism combinations additionally confirmed the results of individual polymorphism analyses. Only the frequencies of haplotypes containing −162A allele were significantly higher, whereas only the frequencies of haplotypes containing 160G allele were significantly lower in cases than in controls in various polymorphism combinations.Conclusions—This extensive association study has identified the PON1 −162G/A and R160G polymorphisms to be independently associated with CHD in Chinese Han population and warrants additional study to elucidate the biological mechanism.
Disparity of MCP-1 mRNA and Protein Expressions Between the Carotid Artery and the Aorta in WHHL Rabbits
Authors: Tanaka Eriko , Shimokawa Hiroaki , Kamiuneten Hitoshi , Eto Yasuhiro , Matsumoto Yasuharu , Morishige Kunio , Koike George , Yoshinaga Masaru , Egashira Kensuke , Tokunaga Osamu , Shiomi Masashi , Takeshita Akira 
Published: February 2003

Objective—This study was designed to examine why in WHHL rabbits, muscular arteries, such as the carotid artery, are relatively resistant to atherosclerosis compared with the aorta, with a special reference to monocyte chemoattractant protein (MCP)-1.Methods and Results—MCP-1 mRNA expression was quantitated by Northern blot analysis, and its protein expression was quantitated by immunostaining and ELISA at the age of 1, 3, 6, and 12 months (n=5 to 6 each). In the aorta, atherosclerotic lesions were progressively developed with aging, and MCP-1 was highly expressed in endothelial cells and infiltrating macrophages. By contrast, in the carotid artery, atherosclerotic lesions and MCP-1 immunoreactivity were not evident throughout the experimental period. Unexpectedly, however, the extent of MCP-1 mRNA expression was comparable between the aorta and the carotid artery throughout the experimental period. Endothelial cells in primary culture from the aorta and the carotid artery expressed the same extent of MCP-1 mRNA on stimulation by oxidized LDL. There was no abnormality in primary structure of MCP-1 cDNA in WHHL.Conclusions—These results suggest that in WHHL, the atherosclerosis process, including MCP-1 protein expression, may be reduced in the carotid artery (and possibly in other muscular arteries), accounting in part for the regional resistance to atherosclerosis.
Lysophosphatidic Acid Induction of Tissue Factor Expression in Aortic Smooth Muscle Cells
Authors: Cui Mei-Zhen , Zhao Guojun , Winokur Allison L. , Laag Essam , Bydash Jason R. , Penn Marc S. , Chisolm Guy M. , Xu Xuemin 
Published: February 2003

Objective—Tissue factor (TF), the initiator of the coagulation cascade, is expressed by cells in atherosclerotic lesions. Lysophosphatidic acid (LPA) is a component of oxidized lipoproteins and an agent released by activated platelets. The present study investigated whether and how TF expression is regulated by LPA.Methods and Results—Northern blotting, Western blotting, and TF activity assays demonstrated that LPA markedly induced TF mRNA, protein, and activity in vascular smooth muscle cells. LPA-induced TF expression is primarily controlled at the transcriptional level. Phosphorylation of mitogen-activated protein kinase kinase (MEK) and extracellular signaling–regulated kinases (ERK1/2) was rapidly and markedly induced by LPA. MEK inhibitors U0126 and PD98059 blocked both ERK activation and the increase in TF mRNA. In contrast, the specific p38 MAP kinase inhibitor SB203580 had no effect on LPA-induced TF mRNA increase. The Gαi protein inhibitor, pertussis toxin, abolished LPA-induced phosphorylation of MEKs and ERKs, as well as the induction of TF mRNA.Conclusions—Our data demonstrate that a Gαi protein and activation of MEKs and ERKs mediate LPA-induced TF expression. Our data suggest that elevated LPA could be a thrombogenic risk factor by upregulating TF expression. These results may have important implications in vascular remodeling and vascular diseases.
Depression of phenytoin metabolic capacity by 5-fluorouracil and doxifluridine in rats
Authors: Konishi Hiroki , Yoshimoto Takashi , Morita Kunihiko , Minouchi Tokuzo , Sato Takashi , Yamaji Akira 
Published: February 2003

Abstract
It has been found in clinical practice that the serum level of phenytoin, of which metabolism is mediated by hepatic CYP2C enzymes, was markedly elevated by co-administration of 5-fluorouracil (5-FU) and doxifluridine (5′-deoxy-5-fluorouridine; 5′-DFUR), a prodrug of 5-FU, but the detailed mechanisms are unclear. A study using rats was undertaken to examine the effects of 5-FU and 5′-DFUR on phenytoin metabolism in hepatic microsomes and phenytoin pharmacokinetics in-vivo. Neither 5-FU nor 5′-DFUR exhibited direct inhibitory effects on hepatic microsomal phenytoin p-hydroxylation, a major metabolic route catalysed by CYP2C in rats, as in humans. 5-FU and 5′-DFUR were injected intraperitoneally into male rats as single doses (1.68 mmol kg−1) and repeated doses (0.24 mmol kg−1 for 7 days). Control rats received vehicle alone. A significant reduction in the activity of phenytoin p-hydroxylation was observed 4 days after the last administration irrespective of the agents and their treatment regimens, although the activity was unchanged on Day 1. Pharmacokinetic analysis of phenytoin revealed that the elimination rate constant and the total clearance was decreased by 70–75 % in both the 5′-DFUR-treated and 5-FU-treated rats, indicating that the decrease in the metabolic capacity of phenytoin was responsible for the change in phenytoin disposition in-vivo. On the other hand, 5-FU significantly depressed the total P450 content, NADPH cytochrome c reductase activity and activities of progesterone hydroxylations. However, the depressive effects of 5′-DFUR were not very potent relative to those of 5-FU, which can be explained by the fact that 5-FU is derived from 5′-DFUR to only a small extent. According to a recent report, phenytoin p-hydroxylation and progesterone 2α-/21-hydroxylations share common CYP2C enzymes as their catalysts. Because there was a difference in the modulation profiles between phenytoin p-hydroxylation and progesterone 2α-/21-hydroxylations after exposure to 5′-DFUR, 5′-DFUR might modulate phenytoin metabolism without loss of catalytic ability for other substrates, unlike 5-FU. The present study suggested that the down-regulation of hepatic CYP2C enzymes occurs by 5-FU exposure even at a low level, and provided a fundamental explanation for the drug interaction encountered in clinical practice.
Anti- and pro-oxidant activity of rutin and quercetin derivatives
Authors: Kessler Marc , Ubeaud Geneviève , Jung Louis 
Published: February 2003

Abstract
Some semi-synthetic flavonoids, particularly derivatives of rutin, are used as therapeutic agents in the treatment of diseases involving free radicals. Here, for the first time, a complete study has been made of the relationship between the structure of such molecules and their superoxide, hydroxyl and peroxyl radical scavenging activity. The molecules chosen for this study were rutin, its aglycone (quercetin), and their methyl ethyl and hydroxyl-ethyl derivatives. Our results are consistent with the general agreement on the structural requirements for free radical scavenging activity. Moreover, we have shown that alkylation of the hydroxyl in position 7 enhanced the scavenging, and also that in a Fenton reaction system, some quercetin derivatives with free catechol moiety or free hydroxyl in position 3 (or both) were pro-oxidant, through superoxide radical and hydrogen peroxide production. Although the structural features needed for pro-oxidant activity are not entirely clear, it appears that to avoid pro-oxidant behaviour, the hydroxyl group in position 3 should be blocked to prevent its auto-oxidation. Thus, flavonoids cannot only be considered purely as antioxidants, since under certain reaction conditions they can also display pro-oxidant activity. This unexpected behaviour could explain, in part, the observed toxicity of some flavonoids in-vivo.
Synthesis and biochemical evaluation of some novel benzoic acid based esters as potential inhibitors of oestrone sulphatase
Authors: Owen Caroline , James Karen , Sampson Luther , Ahmed Sabbir 
Published: February 2003

Abstract
Oestrone sulphatase is an important target in the fight against hormone-dependent breast cancer. In an effort to investigate the reported definitive pharmacophore for oestrone sulphatase and continue our search for potent inhibitors of this enzyme, we have undertaken extensive synthesis, biochemical evaluation and physicochemical property determination of a range of benzoic acid based esters. Here, we report the initial results of our study into a series of straight chain alkyl esters of 4-sulphonylbenzoic acid. Using these compounds, we have investigated the involvement of two physicochemical properties, namely logP and pKa. The results of this study show that there was a strong correlation between the inhibitory activity and the logP of the parent compound. Within the series of compounds studied, hydrophobicity appears to be a more important factor than pKa in determining the overall inhibitory activity. In a previous report, we showed that pKa plays an important role in stabilizing the phenoxide ion resulting from the hydrolysis of the sulphamate group. Here, we propose that although pKa is an important factor in determining the overall inhibitory activity when a wide range of compounds are considered, both hydrophobicity and pKa need to be considered in the design of potential inhibitors of oestrone sulphatase.