A pneumococcal MerR-like regulator and S-nitrosoglutathione reductase are required for systemic virulence

Copyright © 2007 by the Infectious Diseases Society of America. All rights reserved.A transcriptional regulator, NmlR(sp), has been identified in Streptococcus pneumoniae that is required for defense against nitric oxide (NO) stress. The nmlR(sp) gene is cotranscribed with adhC, which encodes an alcohol dehydrogenase that is able to reduce S-nitrosoglutathione (GSNO) with NADH as reductant. nmlR(sp) and adhC mutants exhibited a reduced level of NADH-GSNO oxidoreductase activity and were more susceptible to killing by NO than were wild-type cells. Comparison of the virulence of wild-type and mutant strains by use of a mouse model system showed that NmlR(sp) and AdhC do not play a key role in the adherence of pneumococci to the nasopharynx in vivo. An intraperitoneal challenge experiment revealed that both NmlR(sp) and AdhC were required for survival in blood. These data identify novel components of a NO defense system in pneumococci that are required for systemic infection.Uwe H. Stroeher, Robert S. Kidd, Sian L. Stafford, Michael P. Jennings, James C. Paton and Alastair G. McEwa

Differential activation of inflammatory pathways in A549 type II pneumocytes by Streptococcus pneumoniae strains with different adherence properties

BACKGROUND: Adherence of Streptococcus pneumoniae bacteria to lung cells is a first step in the progression from asymptomatic carriage to pneumonia. Adherence abilities vary widely among S. pneumoniae patient isolates. In this study, the binding properties of S. pneumoniae isolates and the effects of binding on activation of the Nuclear Factor-Kappa-B (NFκB) pathway and cytokine secretion by type II pneumocytes were measured. METHODS: Mechanisms of high- and low-binding S. pneumoniae adherence to A549 cells were investigated by blocking putative receptors on bacteria and host cells with antibody and by eluting choline-binding proteins off of bacterial surfaces. NFκB activation was measured by western blot and immunocytochemistry and cytokine secretion was detected by a protein array. RESULTS: This study shows that S. pneumoniae isolates from pneumonia patients (n = 298) can vary by as much as 1000-fold in their ability to bind to human lung epithelial cells. This difference resulted in differential activation of the NFκB pathway. High-, but not low-binding S. pneumoniae used Choline-binding protein A (CbpA) to bind to complement component C3 on epithelial cell surfaces. Interleukin-8 (IL-8) was the only cytokine secreted by cells treated with either low- or high-binding S. pneumoniae. CONCLUSION: These results indicate that S. pneumoniae clinical isolates are not homogeneous in their interaction with host epithelial cells. The differential activation of host cells by high- and low-binding S. pneumoniae strains could have implications for the treatment of pneumococcal pneumonia and for vaccine development

The Pore-Forming Toxin Listeriolysin O Mediates a Novel Entry Pathway of L. monocytogenes into Human Hepatocytes

Intracellular pathogens have evolved diverse strategies to invade and survive within host cells. Among the most studied facultative intracellular pathogens, Listeria monocytogenes is known to express two invasins-InlA and InlB-that induce bacterial internalization into nonphagocytic cells. The pore-forming toxin listeriolysin O (LLO) facilitates bacterial escape from the internalization vesicle into the cytoplasm, where bacteria divide and undergo cell-to-cell spreading via actin-based motility. In the present study we demonstrate that in addition to InlA and InlB, LLO is required for efficient internalization of L. monocytogenes into human hepatocytes (HepG2). Surprisingly, LLO is an invasion factor sufficient to induce the internalization of noninvasive Listeria innocua or polystyrene beads into host cells in a dose-dependent fashion and at the concentrations produced by L. monocytogenes. To elucidate the mechanisms underlying LLO-induced bacterial entry, we constructed novel LLO derivatives locked at different stages of the toxin assembly on host membranes. We found that LLO-induced bacterial or bead entry only occurs upon LLO pore formation. Scanning electron and fluorescence microscopy studies show that LLO-coated beads stimulate the formation of membrane extensions that ingest the beads into an early endosomal compartment. This LLO-induced internalization pathway is dynamin-and F-actin-dependent, and clathrin-independent. Interestingly, further linking pore formation to bacteria/bead uptake, LLO induces F-actin polymerization in a tyrosine kinase-and pore-dependent fashion. In conclusion, we demonstrate for the first time that a bacterial pathogen perforates the host cell plasma membrane as a strategy to activate the endocytic machinery and gain entry into the host cell

Extracellular matrix formation enhances the ability of streptococcus pneumoniae to cause invasive disease

Extent: 17p.During infection, pneumococci exist mainly in sessile biofilms rather than in planktonic form, except during sepsis. However, relatively little is known about how biofilms contribute to pneumococcal pathogenesis. Here, we carried out a biofilm assay on opaque and transparent variants of a clinical serotype 19F strain WCH159. After 4 days incubation, scanning electron microscopy revealed that opaque biofilm bacteria produced an extracellular matrix, whereas the transparent variant did not. The opaque biofilm-derived bacteria translocated from the nasopharynx to the lungs and brain of mice, and showed 100- fold greater in vitro adherence to A549 cells than transparent bacteria. Microarray analysis of planktonic and sessile bacteria from transparent and opaque variants showed differential gene expression in two operons: the lic operon, which is involved in choline uptake, and in the two-component system, ciaRH. Mutants of these genes did not form an extracellular matrix, could not translocate from the nasopharynx to the lungs or the brain, and adhered poorly to A549 cells. We conclude that only the opaque phenotype is able to form extracellular matrix, and that the lic operon and ciaRH contribute to this process. We propose that during infection, extracellular matrix formation enhances the ability of pneumococci to cause invasive disease.Claudia Trappetti, Abiodun D. Ogunniyi, Marco R. Oggioni and James C. Pato

Serum iron levels and the risk of Parkinson disease: a Mendelian randomization study

BACKGROUND: Although levels of iron are known to be increased in the brains of patients with Parkinson disease (PD), epidemiological evidence on a possible effect of iron blood levels on PD risk is inconclusive, with effects reported in opposite directions. Epidemiological studies suffer from problems of confounding and reverse causation, and mendelian randomization (MR) represents an alternative approach to provide unconfounded estimates of the effects of biomarkers on disease. We performed a MR study where genes known to modify iron levels were used as instruments to estimate the effect of iron on PD risk, based on estimates of the genetic effects on both iron and PD obtained from the largest sample meta-analyzed to date. METHODS AND FINDINGS: We used as instrumental variables three genetic variants influencing iron levels, HFE rs1800562, HFE rs1799945, and TMPRSS6 rs855791. Estimates of their effect on serum iron were based on a recent genome-wide meta-analysis of 21,567 individuals, while estimates of their effect on PD risk were obtained through meta-analysis of genome-wide and candidate gene studies with 20,809 PD cases and 88,892 controls. Separate MR estimates of the effect of iron on PD were obtained for each variant and pooled by meta-analysis. We investigated heterogeneity across the three estimates as an indication of possible pleiotropy and found no evidence of it. The combined MR estimate showed a statistically significant protective effect of iron, with a relative risk reduction for PD of 3% (95% CI 1%-6%; p = 0.001) per 10 microg/dl increase in serum iron. CONCLUSIONS: Our study suggests that increased iron levels are causally associated with a decreased risk of developing PD. Further studies are needed to understand the pathophysiological mechanism of action of serum iron on PD risk before recommendations can be mad

Molecular Evolution Patterns in Metastatic Lymph Nodes Reflect the Differential Treatment Response of Advanced Primary Lung Cancer

Tumor heterogeneity influences the clinical outcome of patients with cancer, and the diagnostic method to measure the tumor heterogeneity needs to be developed. We analyzed genomic features on pairs of primary and multiple metastatic lymph nodes from six patients with lung cancer using whole-exome sequencing and RNA sequencing. Although somatic single-nucleotide variants were shared in primary lung cancer and metastases, tumor evolution predicted by the pattern of genomic alterations was matched to anatomic location of the tumors. Four of six cases exhibited a branched clonal evolution pattern. Lymph nodes with acquired somatic variants demonstrated resistance to the cancer treatment. In this study, we demonstrated that multiple biopsies and sequencing strategies for different tumor regions are required for a comprehensive understanding of the landscape of genetic alteration and for guiding targeted therapy in advanced primary lung cancer. Cancer Res; 76(22); 6568-76. ©2016 AACR

The Effect of Estrogen Usage on Eccentric Exercise-Induced Damage in Rat Testes

BACKGROUND: Recent years, lots of scientific studies are focused on the possible mechanism of inflammatory response and oxidative stress which are the mechanism related with tissue damage and exercise fatigue. It is well-known that free oxygen radicals may be induced under invitro conditions as well as oxidative stress by exhaustive physical exercise. OBJECTIVES: The aim of this study was to investigate the effects of anabolic steroids in conjunction with exercise in the process of spermatogenesis in the testes, using histological and stereological methods. MATERIALS AND METHODS: Thirty-six male Sprague Dawley rats were divided to six groups, including the control group, the eccentric exercise administered group, the estrogen applied group, the estrogen applied and dissected one hour after eccentric exercise group, the no estrogen applied and dissected 48 hours after eccentric exercise group and the estrogen applied and dissected 48 hours after eccentric exercise group. Eccentric exercise was performed on a motorized rodent treadmill and the estrogen applied groups received daily physiological doses by subcutaneous injections. Testicular tissues were examined using specific histopathological, immunohistochemical and stereological methods. Sections of the testes tissue were stained using the TUNEL method to identify apoptotic cells. Apoptosis was calculated as the percentage of positive cells, using stereological analysis. A statistical analysis of the data was carried out with one-way analysis of variance (ANOVA) for the data obtained from stereological analysis. RESULTS: Conventional light microscopic results revealed that testes tissues of the eccentric exercise administered group and the estrogen supplemented group exhibited slight impairment. In groups that were both eccentrically exercised and estrogen supplemented, more deterioration was detected in testes tissues. Likewise, immunohistochemistry findings were also more prominent in the eccentrically exercised and estrogen supplemented groups. CONCLUSIONS: The findings suggest that estrogen supplementation increases damage in testicular tissue due to eccentric exercise

Pneumococcal 6-phosphogluconate-dehydrogenase, a putative adhesin, induces protective immune response in mice

For most bacteria, adherence to human cells is achieved by bacterial lectins binding to mammalian surface glyconjugates. 6-Phosphogluconate dehydrogenase (6PGD) was identified by us as one of Streptococcus pneumoniae cell wall lectin proteins, which elicits an age-dependent immune response in humans. This study assesses the role of 6PGD in S. pneumoniae pathogenesis as an adhesin and its ability to elicit a protective immune response in mice. Recombinant 6PGD (r6PGD) was cloned from S. pneumoniae serotype 3 (strain WU2). r6PGD interference in adhesion of three genetically unrelated unencapsulated pneumococcal strains (3·8, 14·8 and R6) and two genetically unrelated encapsulated pneumococcal strains (WU2 and D39) to A549 type II lung carcinoma cell was tested. BALB/c mice were immunized with r6PGD and boosted after 3 weeks. Immunized mice were challenged intranasally with a lethal dose of S. pneumoniae. r6PGD inhibited 90% and 80% of pneumococcal adhesion to the A549 cells of three unencapsulated S. pneumoniae strains and two encapsulated S. pneumoniae strains, respectively, in a concentration-dependent manner (P< 0·05). Antibodies to r6PGD produced in mice significantly inhibited bacterial adhesion to A549 cell (P< 0·05). Immunization of mice with r6PGD protected 60% (P< 0·001) of mice for 5 days and 40% (P< 0·05) of the mice for 21 days following intranasal lethal challenge. We have identified 6PGD as a surface-located immunogenic lectin protein capable of acting as an adhesin. 6PGD importance to bacterial pathogenesis was demonstrated by the ability of r6PGD to elicit a protective immune response in mice