An unrestrained proinflammatory M1 macrophage population induced by iron impairs wound healing in humans and mice
Anca Sindrilaru, … , Cord Sunderkötter, Karin Scharffetter-Kochanek
Anca Sindrilaru, … , Cord Sunderkötter, Karin Scharffetter-Kochanek
Published February 7, 2011
Citation Information: J Clin Invest. 2011;121(3):985-997. https://doi.org/10.1172/JCI44490.
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Research Article Inflammation

An unrestrained proinflammatory M1 macrophage population induced by iron impairs wound healing in humans and mice

Abstract

Uncontrolled macrophage activation is now considered to be a critical event in the pathogenesis of chronic inflammatory diseases such as atherosclerosis, multiple sclerosis, and chronic venous leg ulcers. However, it is still unclear which environmental cues induce persistent activation of macrophages in vivo and how macrophage-derived effector molecules maintain chronic inflammation and affect resident fibroblasts essential for tissue homeostasis and repair. We used a complementary approach studying human subjects with chronic venous leg ulcers, a model disease for macrophage-driven chronic inflammation, while establishing a mouse model closely reflecting its pathogenesis. Here, we have shown that iron overloading of macrophages — as was found to occur in human chronic venous leg ulcers and the mouse model — induced a macrophage population in situ with an unrestrained proinflammatory M1 activation state. Via enhanced TNF-α and hydroxyl radical release, this macrophage population perpetuated inflammation and induced a p16INK4a-dependent senescence program in resident fibroblasts, eventually leading to impaired wound healing. This study provides insight into the role of what we believe to be a previously undescribed iron-induced macrophage population in vivo. Targeting this population may hold promise for the development of novel therapies for chronic inflammatory diseases such as chronic venous leg ulcers.

Authors

Anca Sindrilaru, Thorsten Peters, Stefan Wieschalka, Corina Baican, Adrian Baican, Henriette Peter, Adelheid Hainzl, Susanne Schatz, Yu Qi, Andrea Schlecht, Johannes M. Weiss, Meinhard Wlaschek, Cord Sunderkötter, Karin Scharffetter-Kochanek

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Figure 4

The iron-induced macrophage population with unrestrained proinflammatory M1 phenotype releases toxic amounts of OH• and ONOO• in situ.

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The iron-induced macrophage population with unrestrained proinflammatory...
(A) Representative photomicrographs of skin cryosections derived from wound margins of AWs 2 days after wounding and CVUs. Oxidative burst was detected in cryosections incubated with DHR, a ROS-sensitive dye; thus, ROS concentrations correlated with green fluorescence. Shown are coincubations of cryosections with DHR and SOD, which scavenges O2–•, with the H2O2 scavenger Cat, and with the OH• scavenger DMSO. Nuclei were stained with DAPI. Scale bars: 150 μm. (B and C) Representative photomicrographs of paraffin-embedded skin sections from AWs 3 days after wounding and CVUs stained with (B) an antibody against 8OHdG and (C) an antibody against 3-NT. Dashed lines indicate the junction between epidermis and dermis. Scale bars: 150 μm; 50 μm (insets). Quantification of positive cells per 10 high-power fields, assessed for 10 different sections of 5 different AW and CVU samples, is shown as mean ± SD ratios of positive to total cells. (B) The brown-colored precipitate is indicative of oxidative DNA damage in CVUs (inset, arrows), but not AWs. (C) Increased protein nitration was observed in CVUs, but not AWs. (D) Nitroblot analysis of wound lysates with an antibody against 3-NT from PBS-treated mice and from iron-loaded mice and iron-loaded mice treated with DFX, etanercept, or clodronate equilibrated to actin. Positive bands indicate increased levels of protein nitration in iron-loaded wounds compared with reduced levels in iron-dextran–loaded mice treated with DFX, etanercept, or clodronate.