Abstract Aims: Present study explores importance of inducible nitric oxide synthase (iNOS) and its interaction with Rac2 in reactive oxygen species (ROS)/reactive nitrogen species (RNS) generation, protein-nitration and in microbial killing by neutrophils. Results: The iNOS transcript and protein were constitutively present in human as well as in mice neutrophils. iNOS protein was found in cytosol, granules containing elastase and gelatinase, and in other subcellular organelles in resting human neutrophils. After phagocytosis of bovine serum albumin (BSA) coated beads, both human and mice neutrophils showed significant elevation in superoxide radicals, nitric oxide (NO), ROS/RNS and consequent BSA nitration. These responses were significantly reduced in presence of iNOS, NADPH oxidase (NOX), myeloperoxidase or Rac inhibitors, as well as in iNOS, Nox2 and Rac2 silenced human or iNOS-knockout mice neutrophils. Complex formed on interaction of iNOS with Rac2 coprecipitated with anti-Rac2, predominantly in cytosol in resting human neutrophils, while iNOS-Rac2 complex translocated to phagosomes after phagocytosis. This was accompanied by generation of superoxide radicals, NO, ROS/RNS and consequent BSA-nitration. Importance of Rac2 in iNOS mediated NO formation and microbial killing was confirmed by pretreatment of mice with Rac inhibitor, NSC23766 that significantly abrogated NO release and microbial killing in vivo. Innovation: Present study highlights previously undefined role of Rac2-iNOS interaction, in translocation of iNOS to phagosomal compartment and consequent NO, superoxide radicals, ROS/RNS generation, BSA nitration and microbial killing. Conclusions: Altogether results obtained demonstrate the role of iNOS in NO and ROS/RNS generation, after phagocytosis of coated latex beads by human polymorphonuclear neutrophils. These studies imply functional importance of iNOS and its interaction with Rac2 in pathogen killing by the neutrophils. Antioxid. Redox Signal. 00, 000-000.
Glutathione is considered the main regulator of redox balance in the cellular milieu due to its capacity for detoxifying deleterious molecules. The oxidative stress induced as a result of a variety of stimuli promotes protein oxidation, usually at cysteine residues, leading to changes in their activity. Mild oxidative stress, which may take place in physiological conditions, induces the reversible oxidation of cysteines to sulfenic acid form, while pathological conditions are associated with higher rates of reactive oxygen species production, inducing the irreversible oxidation of cysteines. Among these, neurodegenerative disorders, cardiovascular diseases and diabetes have been proposed to be pathogenetically linked to this state. In diabetes-associated vascular complications, lower levels of glutathione and increased oxidative stress have been reported. S-glutathionylation has been proposed as a posttranslational modification able to protect proteins from over-oxidizing environments. S-glutathionylation has been identified in proteins involved in diabetic models both in vitro and in vivo. In all of them, S-glutathionylation represents a mechanism that regulates the response to diabetic conditions, and has been described to occur in erythrocytes and neutrophils from diabetic patients. However, additional studies are necessary to discern whether this modification represents a biomarker for the early onset of diabetic vascular complications.
Neutrophils expel extracellular traps (NETs) to entrap and exterminate the invaded micro-organisms. Acute/chronic inflammatory disorders are often observed with aberrantly enhanced NETs formation and high nitric oxide (NO) availability. Recent study from this laboratory demonstrated release of NETs from human neutrophils following treatment with SNP or SNAP. This study is an extension of our previous finding to explore the extracellular bacterial killing, source of DNA in the expelled NETs, their ability to induce proinflammatory cytokines release from platelets/THP-1 cells, and assessment of NO-mediated free radical formation by using a consistent NO donor, DETA-NONOate. NO-mediated NETs exhibited extracellular bacterial killing as determined by colony forming units. NO-mediated NETs formation was due to the activation of NADPH oxidase and myeloperoxidase. NO- or PMA-mediated NETs were positive for both nuclear and mitochondrial DNA as well as proteolytic enzymes. Incubation of NETs with human platelets enhanced the release of IL-1? and IL-8, while with THP-1 cells, release of IL-1?, IL-8, and TNF? was observed. This study demonstrates that NO by augmenting enzymatic free radical generation release NETs to promote extracellular bacterial killing. These NETs were made up of mitochondrial and nuclear DNA and potentiated release of proinflammatory cytokines.
A 50% enhancement in the conversion efficiency (4.9-7.37%) is realized in dye-sensitized solar cells using hydrothermally synthesized TiO(2)-multiwalled carbon nanotube (MWCNT) nanocomposites as compared to hydrothermally synthesized TiO(2) without MWCNT and Degussa P25. Several characterizations have been employed to reveal the nature of the modification imparted to the MWCNTs under hydrothermal processing conditions and the resulting TiO(2)-MWCNT conjugation through -COOH groups. Efficient charge transfer in the nanocomposite and efficient electron transport by MWCNT (significantly higher incident-photon-to-current conversion efficiency) are suggested to be the possible reasons for the enhancement.
Neutrophils (PMNs) and cytokines have a critical role to play in host defense and systemic inflammatory response syndrome (SIRS). Neutrophil extracellular traps (NETs) have been shown to extracellularly kill pathogens, and inflammatory potential of NETs has been shown. Microbial killing inside the phagosomes or by NETs is mediated by reactive oxygen and nitrogen species (ROS/RNS). The present study was undertaken to assess circulating NETs contents and frequency of NETs generation by isolated PMNs from SIRS patients. These patients displayed significant augmentation in the circulating myeloperoxidase (MPO) activity and DNA content, while PMA stimulated PMNs from these patients, generated more free radicals and NETs. Plasma obtained from SIRS patients, if added to the PMNs isolated from healthy subjects, enhanced NETs release and free radical formation. Expressions of inflammatory cytokines (IL-1?, TNF? and IL-8) in the PMNs as well as their circulating levels were significantly augmented in SIRS subjects. Treatment of neutrophils from healthy subjects with TNF?, IL-1?, or IL-8 enhanced free radicals generation and NETs formation, which was mediated through the activation of NADPH oxidase and MPO. Pre-incubation of plasma from SIRS with TNF?, IL-1?, or IL-8 antibodies reduced the NETs release. Role of IL-1?, TNF? and IL-8 thus seems to be involved in the enhanced release of NETs in SIRS subjects.
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