			Home About us Contact

Oxidative Response (oxidative + response)

Distribution by Scientific Domains

Medical Sciences	80%

Selected Abstracts

Adaptive tolerance to oxidative stress and the induction of antioxidant enzymatic activities in Candida albicans are independent of the Hog1 and Cap1-mediated pathways

FEMS YEAST RESEARCH, Issue 6 2010
Pilar Gónzalez-Párraga
Abstract In the pathogenic yeast Candida albicans, the MAP-kinase Hog1 mediates an essential protective role against oxidative stress, a feature shared with the transcription factor Cap1. We analysed the adaptive oxidative response of strains with both elements altered. Pretreatment with gentle doses of oxidants or thermal upshifts (28,37 and 37,42 °C) improved survival in the face of high concentrations of oxidants (50 mM H2O2 or 40 mM menadione), pointing to a functional cross-protective mechanism in the mutants. The oxidative challenge promoted a marked intracellular synthesis of trehalose, although hog1 (but not cap1) cells always displayed high basal trehalose levels. Hydrogen peroxide (H2O2) induced mRNA expression of the trehalose biosynthetic genes (TPS1 and TPS2) in the tested strains. Furthermore, oxidative stress also triggered a differential activation of various antioxidant activities, whose intensity was greater after HOG1 and CAP1 deletion. The pattern of activity was dependent on the oxidant dosage applied: low concentrations of H2O2 (0.5,5 mM) clearly induced catalase and glutathione reductase (GR), whereas drastic H2O2 exposure (50 mM) increased Mn-superoxide dismutase (SOD) isozyme-mediated SOD activity. These results firmly support the existence in C. albicans of both Hog1- and Cap1-independent mechanisms against oxidative stress. [source]

Effect of reactive oxygen intermediaries on the viability and infectivity of Mycobacterium lepraemurium

INTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 3 2007
Kendy Wek-Rodriguez
Summary Murine leprosy is a natural disease of the mouse, the most popular model animal used in biomedical research; the disease is caused by Mycobacterium lepraemurium (MLM), a successful parasite of macrophages. The aim of the study was to test the hypothesis that MLM survives within macrophages because it highly resists the toxic effects of the reactive oxygen intermediaries produced by these cells in response to infection by the microorganism. MLM cells were incubated in the presence of horseradish peroxidase (HRPO),H2O2,halide for several periods of time. The peroxidative effect of this system was investigated by assessing the changes occurred in (a) lipid composition; (b) viability; and (c) infectivity of the microorganism. Changes in the lipid composition of peroxidated- vs. intact-MLM were analysed by thin layer chromatography. The effect of the peroxidative system on the viability and infectivity of MLM was measured by the alamar blue reduction assay and by its ability to produce an infection in the mouse, respectively. Peroxidation of MLM produced drastic changes in the lipid envelope of the microorganism, killed the bacteria and abolished their ability to produce an in vivo infection in the mouse. In vitro, MLM is highly susceptible to the noxious effects of the HRPO,H2O2,halide system. Although the lipid envelope of MLM might protect the microorganism from the peroxidative substances produced at ,physiological' concentrations in vivo, the success of MLM as a parasite of macrophages might rather obey for other reasons. The ability of MLM to enter macrophages without triggering these cells' oxidative response and the lack of granular MPO in mature macrophages might better explain its success as an intracellular parasite of these cells. [source]

Intracellular oxidative response of human monocytes and granulocytes to different strains of Aspergillus fumigatus

MYCOSES, Issue 2 2006
Alexandrine Pastor
Summary Aspergillus fumigatus is one of the most prevalent airborne fungal pathogens, causing severe and often fatal infections. Its fungal virulence factors have not been clearly identified. Reactive oxygen species produced by phagocytic cells are potent fungicides for A. fumigatus. The aim of this study was to examine the influence of conidia pigmentation, fungal development stage and genotype strain on human leucocytes oxidative response. Various A. fumigatus strains were used and the oxidative response was analysed by flow cytometry. A significant difference was observed between live- and killed-conidia. A pigmentless strain gave an important intracellular oxidative response compared with pigmented strains. But no difference was observed between strains isolated from patients with invasive aspergillosis (IA) and bronchial colonisation. The modification of healthy phagocytes' oxidative response caused by A. fumigatus components is not sufficient to explain the virulence of fungus and to predict an evolution of patients with IA. [source]