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OP0056 12/15-lipoxygenase mediates GC-induced anti-inflammatory mechanisms in monocytes
  1. Y. Fleischer1,
  2. K. Barczyk1,
  3. L. Klotz2,
  4. H. Wiendl2,
  5. J. Roth1
  1. 1Institute of Immunology
  2. 2Department of Neurology-Inflammatory Disorders of the Nervous System and Neurooncology, University Hospital Münster, Münster, Germany

Abstract

Background Glucocorticoids (GC) are used for the treatment of many chronic inflammatory diseases. We have previously shown that GC treatment does not simply suppress monocyte functions but rather induces a distinct anti-inflammatory phenotype1. Treatment of inflammatory monocytes with GC leads to re-programming of these cells towards a specific population involved in resolution of inflammation. Gene expression analysis has shown that 12/15-lipoxygenase (12/15-LOX) is one of the most up-regulated genes in GC- and LPS/GC-treated monocytes. Lipoxygenases are known to generate lipid mediators that contribute to the resolution of inflammation2.

Objectives The aim of our studies was to determine lipoxygenase-dependent and independent effects in GC-treated monocytes. Identification of specific GC-induced signaling pathways may elicit molecular targets for novel therapeutic strategies.

Methods Bone marrow–derived monocytes were isolated from wild type (wt) and 12/15-LOX knock-out mice and stimulated with GC and LPS. Gene and protein expression was analyzed using quantitative RT-PCR, Western Blot, Flow Cytometry, ELISA and CBA technology. Functional assays were performed to analyze monocyte migration and oxidative burst.

Results No significant differences in production of pro-inflammatory cytokines were observed between monocytes isolated from wt and 12/15-LOX knock-out mice. Although GC treatment reduced adhesion in monocytes of both mice strains, decrease in adhesion was much more pronounced in cells lacking 12/15-LOX. Migration was enhanced in GC- and LPS/GC-treated monocytes isolated either from wt or 12/15-LOX knock-out mice. Analysis of cell survival revealed that the rate of apoptotic cells was reduced in monocytes treated with GC but also LPS/GC with no significant variations between the two mouse strains. Treatment of resting monocytes with GC reduced the production of ROS only in monocytes from wild type but not from 12/15-LOX knock-out mice whereas GC treatment of pro-inflammatory (LPS-stimulated) monocytes reduced production of ROS in wt as well as 12/15-LOX knock-out mice. GC treatment led to increased phagocytosis of carboxylate-modified latex beads (used as model for phagocytosis of apoptotic cells). However, this effect was much weaker in GC-treated monocytes isolated from 12/15-LOX knock-out mice. In contrast, phagocytosis of latex beads mimicking foreign particles was not significantly altered in monocytes isolated from wild type and 12/15-LOX knock-out mice.

Conclusions GC-treatment induced anti-inflammatory and pro-resolving properties in resting and activated monocytes. Many of GC-induced mechanisms like decreased adhesion, enhanced migration or phagocytosis are 12/15-LOX independent. However, inhibitions of ROS production as well as enhancement of anti-inflammatory phagocytosis of apoptotic cells by GC-treatment are at least partially mediated by 12/15-LOX. Specific targeting of these mechanisms may be a promising strategy to block undesirable inflammation with fewer side effects.

  • [1] Barczyk, K. et al. Blood 116, 446-455 (2010).

  • [2] Conrad, D.J. Clinical Reviews in Allergy & Immunology 17, 71-89 (1999).

Disclosure of Interest None Declared

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