title: INF-γ Enhances Nox2 Activity by Upregulating phox Proteins When Applied to Differentiating PLB-985 Cells but Does Not Induce Nox2 Activity by Itself.
abstract: BACKGROUND
  The cytokine and drug interferon-γ enhances superoxide anion production by the antimicrobicidal Nox2 enzyme of neutrophils. Because mature neutrophils have a short lifespan, we hypothesized that the effects of interferon-γ on these cells might be mediated by its prolonged exposure to differentiating neutrophil precursors in the bone marrow rather than its brief exposure to mature circulating neutrophils. Effects of INF-Γ on NOX2 activity: To address this possibility we exposed the myeloid PLB-985 cell line to interferon-γ for 3 days in the presence of dimethyl sulfoxide which induces terminal differentiation of these cells. Interferon-γ was found to enhance superoxide production by Nox2 in a concentration dependent manner. In contrast, application of interferon-γ alone for 3 days failed to induce detectible Nox2 activity. Additionally, application of interferon-γ for 3 hours to pre-differentiated PLB-985 cells, which models studies using isolated neutrophils, was much less effective at enhancing superoxide anion production. Effects of INF-Γ on phox protein levels: Addition of interferon-γ during differentiation was found to upregulate the Nox2 proteins gp91phox and p47phox in concert with elevated transcription of their genes. The p22phox protein was upregulated in the absence of increased transcription presumably reflecting stabilization resulting from binding to the elevated gp91phox. Thus, increased levels of gp91phox, p47phox and p22phox likely account for the interferon-γ mediated enhancement of dimethyl sulfoxide-induced Nox2 activity. In contrast, although interferon-γ alone also increased various phox proteins and their mRNAs, the pattern was very different to that seen with interferon-γ plus dimethyl sulfoxide. In particular, p47phox was not induced thus explaining the inability of interferon -γ alone to enhance Nox2 activity. Short application of interferon-γ to already differentiated cells failed to increase any phox proteins.
  
  
  CONCLUSIONS
  Our findings indicate that interferon-γ has complex effects on phox protein expression and that these are different in cells undergoing terminal differentiation. Understanding these changes may indicate additional therapeutic uses for this cytokine in human disorders.
authors: Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, United States of America.
authors: Michael A
authors: MA
authors: Ellison
authors: Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, United States of America.
authors: Gail
authors: G
authors: Thurman
authors: Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, United States of America.
authors: Christy M
authors: CM
authors: Gearheart
authors: Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, United States of America.
authors: Ryan H
authors: RH
authors: Seewald
authors: Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, United States of America.
authors: Christopher C
authors: CC
authors: Porter
authors: Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, United States of America; Department of Pediatrics, University of Colorado Denver, The Anschutz Medical Campus, Aurora, Colorado, United States of America; Department of Pathology, University of Colorado Denver, The Anschutz Medical Campus, Aurora, Colorado, United States of America; The Center for Cancer and Blood Disorders, Transfusion Services, Children's Hospital Colorado, Aurora, Colorado, United States of America; Hematology/Oncology and Bone Marrow Transplantation Laboratories, Aurora, Colorado, United States of America.
authors: Daniel R
authors: DR
authors: Ambruso
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D002460:Cell Line; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: C573415:IFNG protein, human; D008562:Membrane Glycoproteins; D007371:Interferon-gamma; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C086986:CYBA protein, human; C060505:neutrophil cytosolic factor 1