bims-noxint Biomed News
on NADPH oxidases in tumorigenesis
Issue of 2019‒06‒16
three papers selected by
Laia Caja Puigsubira
Uppsala University

  1. Oxid Med Cell Longev. 2019 ;2019 3264858
    Helfinger V, Palfi K, Weigert A, Schröder K.
      The family of NADPH oxidases represents an important source of reactive oxygen species (ROS) within the cell. Nox4 is a special member of this family as it constitutively produces H2O2 and its loss promotes inflammation. A major cellular component of inflammation is the macrophage population, which can be divided into several subpopulations depending on their phenotype, with proinflammatory M(LPS+IFNγ) and wound-healing M(IL4+IL13) macrophages being extremes of the functional spectrum. Whether Nox4 is expressed in macrophages is discussed controversially. Here, we show that macrophages besides a high level of Nox2 indeed express Nox4. As Nox4 contributes to differentiation of many cells, we hypothesize that Nox4 plays a role in determining the polarization and the phenotype of macrophages. In bone marrow-derived monocytes, ex vivo treatment with LPS/IFNγ or IL4/IL13 results in polarization of the cells into M(LPS+IFNγ) or M(IL4+IL13) macrophages, respectively. In this ex vivo setting, Nox4 deficiency reduces M(IL4+IL13) polarization and forces M(LPS+IFNγ). Nox4-/- M(LPS+IFNγ)-polarized macrophages express more Nox2 and produce more superoxide anions than wild type M(LPS+IFNγ)-polarized macrophages. Mechanistically, Nox4 deficiency reduces STAT6 activation and promotes NFκB activity, with the latter being responsible for the higher level of Nox2 in Nox4-deficient M(LPS+IFNγ)-polarized macrophages. According to those findings, in vivo, in a murine inflammation-driven fibrosarcoma model, Nox4 deficiency forces the expression of proinflammatory genes and cytokines, accompanied by an increase in the number of proinflammatory Ly6C+ macrophages in the tumors. Collectively, the data obtained in this study suggest an anti-inflammatory role for Nox4 in macrophages. Nox4 deficiency results in less M(IL4+IL13) polarization and suppression of NFκB activity in monocytes.
  2. Exp Eye Res. 2019 Jun 09. pii: S0014-4835(19)30181-2. [Epub ahead of print] 107692
    Das S, Wikström P, Walum E, Lovicu FJ.
      Many of the small molecule-based inhibitors of NADPH oxidase activity are largely inadequate to substantiate broad claims, often exhibiting a lack of Nox-isoform-specificity, and sometimes only acting as scavengers of reactive oxygen species (ROS). In the present study, we use a newly developed highly selective Nox4 inhibitor, GLX7013114, to modulate TGFβ-induced lens epithelial to mesenchymal transition (EMT). Rat lens epithelial explants were pre-treated with 0.3  μM of GLX7013114, and then treated with 200 pg/ml of TGF-β2 to induce lens EMT. ROS production was visualized microscopically using the superoxide fluorogenic probe, dihydroethidium (DHE). The EMT process was documented using phase-contrast microscopy, and molecular EMT markers were immunolabeled. qPCR was also performed to observe changes in EMT-associated genes. TGFβ-induced ROS was evident at 8 h of culture and its intensity was found to be significantly reduced when GLX7013114 was applied, comparable to ROS levels measured in untreated explants. Using phase-contrast microscopy to follow TGFβ-induced EMT over 5 days in the presence of the inhibitor, lens epithelial cells in explants became myofibroblastic by day 2 and underwent progressive apoptosis to reveal a bare lens capsule by day 5. Explants treated with TGFβ and GLX7013114 had some increased cell survival; however, these differences were not significant. For the first time, Nox4 inhibition by GLX7013114 was shown to reduce the TGFβ-induced gene expression of α-smooth muscle actin (SMA), collagen 1a and fibronectin. GLX7013114, given that it appears to block aspects of TGFβ-induced EMT, including ROS production, may be a new useful Nox4-selective inhibitor for further studies.
  3. Biochim Biophys Acta Biomembr. 2019 Jun 11. pii: S0005-2736(19)30137-3. [Epub ahead of print]
    Merla C, Liberti M, Consales C, Denzi A, Apollonio F, Marino C, Benassi B.
      BACKGROUND: Molecular mechanisms of interaction between cells and extremely low frequency magnetic fields (ELF-MFs) still represent a matter of scientific debate. In this paper, to identify the possible primary source of oxidative stress induced by ELF-MF in SH-SY5Y human neuroblastoma cells, we estimated the induced electric field and current density at the cell level.METHODS: We followed a computational multiscale approach, estimating the local electric field and current density from the whole sample down to the single cell level. The procedure takes into account morphological modeling of SH-SY5Y cells, arranged in different topologies. Experimental validation has been carried out: neuroblastoma cells have been treated with Diphenyleneiodonium (DPI) -an inhibitor of the plasma membrane enzyme NADPH oxidase (Nox)- administered 24 h before exposure to 50 Hz (1 mT) MF.
    RESULTS: Macroscopic and microscopic dosimetric evaluations suggest that increased current densities are induced at the plasma membrane/extra-cellular medium interface; identifying the plasma membrane as the main site of the ELF-neuroblastoma cell interaction. The in vitro results provide an experimental proof that plasma membrane Nox exerts a key role in the redox imbalance elicited by ELF, as DPI treatment reverts the generation of reactive oxygen species induced by ELF exposure.
    GENERAL SIGNIFICANCE: Microscopic current densities induced at the plasma membrane are likely to play an active physical role in eliciting ELF effects related to redox imbalance. Multiscale computational dosimetry, supported by an in vitro approach for validation, is proposed as the innovative and rigorous paradigm to unveil mechanisms underlying the complex ELF-MF interactions.
    Keywords:  Extremely low frequency-magnetic field; Induced current density; Nox; Oxidative stress; Plasma membrane