Iron-dependent trafficking of 5-lipoxygenase and impact on human macrophage activation

Beatrice Dufrusine, Andrea Di Francesco, Sergio Oddi, Lucia Scipioni, Clotilde Beatrice Angelucci, Claudio D'Addario, Mauro Serafini, Ann Kathrin Häfner, Dieter Steinhilber, Mauro Maccarrone, Enrico Dainese

Research output: Contribution to journalArticle

Abstract

5-lipoxygenase (5-LOX) is a non-heme iron-containing dioxygenase expressed in immune cells that catalyzes the two initial steps in the biosynthesis of leukotrienes. It is well known that 5-LOX activation in innate immunity cells is related to different iron-associated proinflammatory disorders, including cancer, neurodegenerative diseases, and atherosclerosis. However, the molecular and cellular mechanism(s) underlying the interplay between iron and 5-LOX activation are largely unexplored. In this study, we investigated whether iron (in the form of Fe3+ and hemin) might modulate 5-LOX influencing its membrane binding, subcellular distribution, and functional activity. We proved by fluorescence resonance energy transfer approach that metal removal from the recombinant human 5-LOX, not only altered the catalytic activity of the enzyme, but also impaired its membrane-binding. To ascertain whether iron can modulate the subcellular distribution of 5-LOX in immune cells, we exposed THP-1 macrophages and human primary macrophages to exogenous iron. Cells exposed to increasing amounts of Fe3+ showed a redistribution (ranging from ~45 to 75%) of the cytosolic 5-LOX to the nuclear fraction. Accordingly, confocal microscopy revealed that acute exposure to extracellular Fe3+, as well as hemin, caused an overt increase in the nuclear fluorescence of 5-LOX, accompanied by a co-localization with the 5-LOX activating protein (FLAP) both in THP-1 macrophages and human macrophages. The functional relevance of iron overloading was demonstrated by a marked induction of the expression of interleukin-6 in iron-treated macrophages. Importantly, pre-treatment of cells with the iron-chelating agent deferoxamine completely abolished the hemin-dependent translocation of 5-LOX to the nuclear fraction, and significantly reverted its effect on interleukin-6 overexpression. These results suggest that exogenous iron modulates the biological activity of 5-LOX in macrophages by increasing its ability to bind to nuclear membranes, further supporting a role for iron in inflammation-based diseases where its homeostasis is altered and suggesting further evidence of risks related to iron overload.

Original languageEnglish
Article number1347
JournalFrontiers in Immunology
Volume10
Issue numberJUN
DOIs
Publication statusPublished - Jan 1 2019

Keywords

  • 5-lipoxygenase
  • Enzyme activation
  • Iron
  • Macrophage activation
  • Macrophages
  • Nuclear translocation

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology

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    Dufrusine, B., Francesco, A. D., Oddi, S., Scipioni, L., Angelucci, C. B., D'Addario, C., Serafini, M., Häfner, A. K., Steinhilber, D., Maccarrone, M., & Dainese, E. (2019). Iron-dependent trafficking of 5-lipoxygenase and impact on human macrophage activation. Frontiers in Immunology, 10(JUN), [1347]. https://doi.org/10.3389/fimmu.2019.01347