bims-noxint Biomed News
on NADPH oxidases in tumorigenesis
Issue of 2021‒03‒14
five papers selected by
Laia Caja Puigsubira
Uppsala University

  1. Free Radic Biol Med. 2021 Mar 09. pii: S0891-5849(21)00126-X. [Epub ahead of print]
      Gas plasma is a partially ionized gas increasingly recognized for targeting cancer. Several hypotheses attempt to explain the link between plasma treatment and cytotoxicity in cancer cells, all focusing on cellular membranes that are the first to be exposed to plasma-generated reactive oxygen species (ROS). One proposes high levels of aquaporins, membrane transporters of water and hydrogen peroxide, to mark tumor cell line sensitivity to plasma treatment. A second focuses on membrane-expression of redox-related enzymes such as NADPH oxidases (NOX) that may modify or amplify the effects of plasma-derived ROS, fueling plasma-induced cancer cell death. Another hypothesis is that the decreased cholesterol content of tumor cell membranes sensitizes these to plasma-mediated oxidation and subsequently, cytotoxicity. Screening 33 surface molecules in 36 tumor cell lines in correlation to their sensitivity to plasma treatment, the expression of aquaporins or NOX members could not explain the sensitivity but were rather associated with treatment resistance. Correlation with transporter or enzyme activity was not tested. Analysis of cholesterol content confirmed the proposed positive correlation with treatment resistance. Strikingly, the strongest correlation was found for baseline metabolic activity (Spearman r = 0.76). Altogether, these data suggest tumor cell metabolism as a novel testable hypothesis to explain cancer cell resistance to gas plasma treatment for further elucidating this innovative field's chances and limitations in oncology.
    Keywords:  NADPH oxidase; aquaporin; catalase; cholesterol; flow cytometry; heat-shock protein; kINPen; plasma medicine; reactive oxygen species
  2. Nat Commun. 2021 03 08. 12(1): 1508
      LC3-associated phagocytosis (LAP) contributes to a wide range of cellular processes and notably to immunity. The stabilization of phagosomes by the macroautophagy machinery in human macrophages can maintain antigen presentation on MHC class II molecules. However, the molecular mechanisms involved in the formation and maturation of the resulting LAPosomes are not completely understood. Here, we show that reactive oxygen species (ROS) produced by NADPH oxidase 2 (NOX2) stabilize LAPosomes by inhibiting LC3 deconjugation from the LAPosome cytosolic surface. NOX2 residing in the LAPosome membrane generates ROS to cause oxidative inactivation of the protease ATG4B, which otherwise releases LC3B from LAPosomes. An oxidation-insensitive ATG4B mutant compromises LAP and thereby impedes sustained MHC class II presentation of exogenous Candida albicans antigens. Redox regulation of ATG4B is thereby an important mechanism for maintaining LC3 decoration of LAPosomes to support antigen processing for MHC class II presentation.
  3. Arterioscler Thromb Vasc Biol. 2021 Mar 11. ATVBAHA120315773
      OBJECTIVE: Despite the importance of reactive oxygen species (ROS) and NOX (nicotinamide adenine dinucleotide phosphate [NADPH] oxidase) 2 in platelet activation and in vivo thrombosis, it is unclear how ROS and NOX2 play a role in platelet activation and why NOX2 deficiencies in humans and mice do not affect hemostasis. Outside-in signaling of integrin αIIbβ3 mediates platelet response to shear stress, secondary platelet activation, and thrombus expansion and is critical to thrombosis but dispensable for hemostasis. We studied the mechanisms of platelet ROS generation, ROS-mediated platelet response, and the role of ROS in integrin αIIbβ3 outside-in signaling. Approach and Results: ROS generation in activated platelets was low and slow without shear but was robust under shear. Shear-enhanced ROS generation and activation of p47phox, an important regulatory subunit of NOX2, were diminished by the integrin antagonist integrilin or β3 knockout, and by Gα13 knockout or blocking the Gα13-β3 interaction. Resting platelets spreading on integrin ligand fibrinogen also Gα13-dependently stimulated ROS generation and p47phox activation. Hence, Gα13-mediated outside-in signaling induces NOX2 activation and ROS generation which is greatly enhanced by shear. Outside-in NOX2 activation requires Src, phosphoinositide 3-kinase and Akt downstream of Gα13. Importantly, NOX2-knockout platelets showed defective ROS generation, reduced platelet spreading without shear, and reduced platelet adhesion and thrombus volume on collagen and VWF (von Willibrand factor) under shear, whereas ROS inhibition diminished activation of tyrosine kinase Syk.CONCLUSIONS: Outside-in signaling activates the mainly NOX2-mediated ROS generation, which mediates Syk-dependent secondary platelet activation, adhesion, and thrombosis with minimal effect on hemostasis.
    Keywords:  fibrinogen; glycoprotein; integrin; reactive oxygen species; thrombosis
  4. Ann Hepatol. 2021 Mar 03. pii: S1665-2681(21)00038-7. [Epub ahead of print] 100339
      INTRODUCTION AND OBJECTIVES: It is well-known that signaling mediated by the hepatocyte growth factor (HGF) and its receptor c-Met in the liver is involved in the control of cellular redox status and oxidative stress, particularly through its ability to induce hepatoprotective gene expression by activating survival pathways in hepatocytes. It has been reported that HGF can regulate the expression of some members of the NADPH oxidase family in liver cells, particularly the catalytic subunits and p22phox. In the present work we were focused to characterize the mechanism of regulation of p22phox by HGF and its receptor c-Met in primary mouse hepatocytes as a key determinant for cellular redox regulation.MATERIALS AND METHODS: Primary mouse hepatocytes were treated with HGF (50 ng/ml) for different times. cyba expression (gene encoding p22phox) or protein content were addressed by real time RT-PCR, Western blot or immunofluorescence. Protein interactions were explored by immunoprecipitation and FRET analysis.
    RESULTS: Our results provided mechanistic information supporting the transcriptional repression ofcyba induced by HGF in a mechanism dependent of NF-κB activity. We identified a post-translational regulation mechanism directed by p22phox degradation by proteasome 26S, and a second mechanism mediated by p22phox sequestration by c-Met in plasma membrane.
    CONCLUSION: Our data clearly show that HGF/c-Met exerts regulation of the NADPH oxidase by a wide-range of molecular mechanisms. NADPH oxidase-derived reactive oxygen species regulated by HGF/c-Met represents one of the main mechanisms of signal transduction elicited by this growth factor.
    Keywords:  HGF; NADPH oxidase; c-Met; hepatocytes; p22(phox)
  5. Free Radic Biol Med. 2021 Mar 05. pii: S0891-5849(21)00121-0. [Epub ahead of print]
      The neural stem cells (NSCs) are essential for normal brain development and homeostasis. The cell state (i.e. quiescent versus activated) and fate (i.e. the cell lineage of choice upon differentiation) of NSCs are tightly controlled by various redox and epigenetic regulatory mechanisms. There is an increasing appreciation that redox and epigenetic regulations are intimately linked, but how this redox-epigenetics crosstalk affects NSC activity remains poorly understood. Another unresolved topic is whether the NSCs actually contribute to brain ageing and neurodegenerative diseases. In this review, we aim to 1) distill concepts that underlie redox and epigenetic regulation of NSC state and fate; 2) provide examples of the redox-epigenetics crosstalk in NSC biology; and 3) highlight potential redox- and epigenetic-based therapeutic opportunities to rescue NSC dysfunctions in ageing and neurodegenerative diseases.
    Keywords:  Alzheimer’s disease; ageing; epigenetics; metabolism; neural stem cells; reactive oxygen species; redox