Examinando por Autor "Morales, Eduardo H."

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    Participation of the Salmonella OmpD porin in the infection of RAW264.7 macrophages and BALB/c mice
    (Public Library of Science, 2014) Ipinza, Francisco; Collao, Bernardo; Monsalva, Debbie; Bustamante, Victor H.; Luraschi, Roberto; Alegría-Arcos, Melissa; Almonacid, Daniel E.; Aguayo, Daniel; Calderón, Iván L.; Gil, Fernando; Santiviago, Carlos A.; Morales, Eduardo H.; Calva, Edmundo; Saavedra, Claudia P.
    Salmonella Typhimurium is the etiological agent of gastroenteritis in humans and enteric fever in mice. Inside these hosts, Salmonella must overcome hostile conditions to develop a successful infection, a process in which the levels of porins may be critical. Herein, the role of the Salmonella Typhimurium porin OmpD in the infection process was assessed for adherence, invasion and proliferation in RAW264.7 mouse macrophages and in BALB/c mice. In cultured macrophages, a ΔompD strain exhibited increased invasion and proliferation phenotypes as compared to its parental strain. In contrast, overexpression of ompD caused a reduction in bacterial proliferation but did not affect adherence or invasion. In the murine model, the ΔompD strain showed increased ability to survive and replicate in target organs of infection. The ompD transcript levels showed a down-regulation when Salmonella resided within cultured macrophages and when it colonized target organs in infected mice. Additionally, cultured macrophages infected with the ΔompD strain produced lower levels of reactive oxygen species, suggesting that down-regulation of ompD could favor replication of Salmonella inside macrophages and the subsequent systemic dissemination, by limiting the reactive oxygen species response of the host. © 2014 Ipinza et al.
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    The small RNA RyhB homologs from Salmonella typhimurium participate in the response to S-nitrosoglutathione-induced stress
    (Academic Press Inc., 2014-07) Calderón, Paulina F.; Morales, Eduardo H.; Acuña, Lillian G.; Fuentes, Danitza N.; Gil, Fernando; Porwollik, S.; McClelland, Michael; Saavedra, Claudia P.; Calderón, Iván L.
    Typically, the expression of sRNAs is activated in response to environmental stimuli in order to regulate gene expression through post-transcriptional mechanisms. In the present work we show that the Salmo nella typhimurium paralogous sRNAs RyhB-1 and RyhB-2 are induced in response to the nitrosating agent S-nitrosoglutathione (GSNO). Inactivation of these sRNAs decreased S. typhimurium resistance to GSNO and increased the levels of nitrosylated proteins. These results prompted us to evaluate a possible role of these sRNAs in nitrosative stress resistance. RNA profiling was used as a screen to identify novel RyhB-1 and RyhB-2 regulated targets. A subset of genes was filtered based on their potential role in the response to nitrosative stress and their expression was analyzed by quantitative RT-PCR in wild type, single and double mutant strains (DryhB1, DryhB2 and DryhB1 DryhB2) treated with GSNO. In response to GSNO RyhB-1 and RyhB-2 negatively regulate the expression of the genes cyoABC (cytochrome bo oxi dase), cydB (cytochrome bd oxidase), cybC (cytochrome b-562), and positively regulate the nirBCD operon (nitrite reductase system). Together, these results suggest that RyhB-1 and RyhB-2 finely tune the expres sion of genes coding for cytochrome oxidases and the nitrate reductase system, allowing the cell to cope with GSNO-induced stress. 2014 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).
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    Ítem
    The transcription factor SlyA from Salmonella Typhimurium regulates genes in response to hydrogen peroxide and sodium hypochlorite
    (Elsevier Masson SAS, 2018-07) Cabezas, Carolina E.; Briones, Alan C.; Aguirre, Camila; Pardo-Esté, Coral; Castro-Severyn, Juan; Salinas, César R.; Baquedano, María S.; Hidalgo, Alejandro A.; Fuentes, Juan A.; Morales, Eduardo H.; Meneses, Claudio A.; Castro-Nallar, Eduardo; Saavedra, Claudia Paz
    Salmonella Typhimurium is an intracellular pathogen that is capable of generating systemic fever in a murine model. Over the course of the infection, Salmonella faces different kinds of stressors, including harmful reactive oxygen species (ROS). Various defence mechanisms enable Salmonella to successfully complete the infective process in the presence of such stressors. The transcriptional factor SlyA is involved in the oxidative stress response and invasion of murine macrophages. We evaluated the role of SlyA in response to H2O2 and NaOCl and found an increase of slyA expression upon exposure to these toxics. However, the SlyA target genes and the molecular mechanisms by which they influence the infective process are unknown. We hypothesised that SlyA regulates the expression of genes required for ROS resistance, metabolism, or virulence under oxidative stress conditions. Transcriptional profiling in wild type and ΔslyA strains confirmed that SlyA regulates the expression of several genes involved in virulence [sopD (STM14_3550), sopE2 (STM14_2244), hilA (STM14_3475)] and central metabolism [kgtP (STM14_3252), fruK (STM14_2722), glpA (STM14_2819)] in response to H2O2 and NaOCl. These findings were corroborated by functional assay and transcriptional fusion assays using GFP. DNA-protein interaction assays showed that SlyA regulates these genes through direct interaction with their promoter regions. © 2018 The Author(s)