Home About us Contact
|
Home About us Contact | ||
|
|
||
Reactive Nitrogen Intermediates (reactive + nitrogen_intermediate)
Selected AbstractsDetrimental role of endogenous nitric oxide in host defence against Sporothrix schenckiiIMMUNOLOGY, Issue 4 2008Karla Simone S. Fernandes Summary We earlier demonstrated that nitric oxide (NO) is a fungicidal molecule against Sporothrix schenckii in vitro. In the present study we used mice deficient in inducible nitric oxide synthase (iNOS,/,) and C57BL/6 wild-type (WT) mice treated with N,-nitro-arginine (Nitro-Arg-treated mice), an NOS inhibitor, both defective in the production of reactive nitrogen intermediates, to investigate the role of endogenous NO during systemic sporotrichosis. When inoculated with yeast cells of S. schenckii, WT mice presented T-cell suppression and high tissue fungal dissemination, succumbing to infection. Furthermore, susceptibility of mice seems to be related to apoptosis and high interleukin-10 and tumour necrosis factor-, production by spleen cells. In addition, fungicidal activity and NO production by interferon-, (IFN-,) and lipopolysaccharide-activated macrophages from WT mice were abolished after fungal infection. Strikingly, iNOS,/, and Nitro-Arg-treated mice presented fungal resistance, controlling fungal load in tissues and restoring T-cell activity, as well as producing high amounts of IFN-, Interestingly, macrophages from these groups of mice presented fungicidal activity after in vitro stimulation with higher doses of IFN-,. Herein, these results suggest that although NO was an essential mediator to the in vitro killing of S. schenckii by macrophages, the activation of NO system in vivo contributes to the immunosuppression and cytokine balance during early phases of infection with S. schenckii. [source] Characterization of a Mycobacterium tuberculosis proteasomal ATPase homologueMOLECULAR MICROBIOLOGY, Issue 2 2005K. Heran Darwin Summary A screen for Mycobacterium tuberculosis (Mtb) mutants sensitive to reactive nitrogen intermediates identified transposon insertions in the presumptive proteasomal ATPase gene mpa (mycobacterium proteasome ATPase; Rv2115c). mpa mutants are attenuated in both wild type and nitric oxide synthase 2 deficient mice. In this work, we show that attenuation of mpa mutants is severe, and that Mpa is an ATPase associated with various cellular activities (AAA) ATPase that forms hexameric rings resembling the eukaryotic complex p97/valosin-containing protein (VCP). Point mutations in the conserved Walker box ATPase motifs of Mpa greatly reduced or abolished ATPase activity in vitro and abrogated protection of Mtb against acidified nitrite. A mutant Mpa protein missing only its last two amino acids retained ATPase activity, yet failed to protect Mtb against nitrite. The corresponding strain was attenuated in mice. Thus, Mpa is an ATPase whose enzymatic activity is necessary but not sufficient to protect against reactive nitrogen intermediates. [source] Antibody-dependent cell-mediated cytotoxicity to newly excysted juvenile Fasciola hepatica in vitro is mediated by reactive nitrogen intermediatesPARASITE IMMUNOLOGY, Issue 9 2001D. Piedrafita Passive intraperitoneal transfer of sera from Fasciola hepatica- infected sheep, cattle or rats can protect naive rats from F. hepatica infection, suggesting a parasite killing mechanism within the peritoneal cavity that is dependent on the presence of parasite-specific antibody. We investigated antibody-dependent cell-mediated cytotoxicity by resident peritoneal lavage cell populations, containing large numbers of monocytes/macrophages, as a potential host resistance mechanism by which juvenile flukes could be killed within the peritoneal cavity of naive rats. Comparative studies were conducted using cell populations containing large numbers of monocytes/macrophages from sheep. The results demonstrate that monocyte/macrophage-rich lavage cell populations from rat and sheep differ substantially in their ability to generate nitric oxide . Only resident rat peritoneal lavage cells were able to mediate antibody-dependent cell-mediated cytotoxicity against newly excysted juvenile liver fluke. The mechanism of cytotoxicity was dependent on, and directly proportional to, the production of nitric oxide and required attachment of effector cells to the newly excysted juvenile liver fluke tegument, which occurred following the addition of sera from F. hepatica -infected animals. This is the first report demonstrating a mechanism of cell-mediated cytotoxicity to newly excysted juvenile liver fluke. [source] Free radical generation during the activation of hemolymph prepared from the homopteran Dactylopius coccusARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 1 2007F. García-Gil De Muñoz Abstract Superoxide anion (O,2) and nitric oxide (NO) generation in Dactylopius coccus hemolymph obtained by perfusion and activated with zymosan was studied. Activated hemolymph reduced 3-[4,5 dimethylthiazolil-2]-2,5-diphenyl tetrazolium bromide. This reduction was prevented by superoxide dismutase (SOD) indicating O,2 generation. This activity was dependent on temperature, and hemolymph incubated at 75°C lost its activity. Chromatocytes incubated with zymosan released their content and produced O,2. Activated hemolymph also produced NO and this activity was prevented in the presence of NG-nitro-L-arginine methyl ester, suggesting that nitric oxide synthase (NOS) might be present in D. coccus hemolymph. The probable source of O,2 in the D. coccus hemolymph is the anthraquinone oxidation, since commercial carminic dye produced O,2 during its oxidation by Agaricus bisporus tyrosinase. Gram+ Micrococcus luteus exposed to activated hemolymph were killed in vitro, and addition of NG-nitro-L-arginine methyl ester and D-Mannitol (a hydroxyl radical scavenger) prevented their killing. The cytotoxic effect produced by the activated hemolymph was not observed with the Gram, bacteria Serratia marcescens. These results suggest that D. coccus activated hemolymph generates reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI) that may limit M. luteus growth. Arch. Insect Biochem. Physiol. 65:20,28, 2007. © 2007 Wiley-Liss, Inc. [source] | ||||||||||