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 p16 INK4a -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.

We have found that panel A in Figure 5 (subpanel Old + C) is mistakenly a duplication of panel H in Figure 4 (subpanel Old + FL). According to our inspection of the original data sets, this is due to a mistake during the assembly of the panels. We show here the amended correct images for Figure 5, panel A (Old + C).The change does not affect the original conclusions presented. We apologize for this mistake. All authors approve of this correction. Old + Thr

Summary A rare eosinophilic dermatosis, Wells syndrome, also referred to as eosinophilic cellulitis, is characterized by great clinical variability. Typical findings include infiltrated erythematous plaques arising on the extremities. Lesions initially resemble erysipelas/cellulitis, however, they do not improve with antibiotic treatment. Eosinophilic cellulitis is a diagnosis of exclusion that may only be made over the course of the disease, taking into account clinical and characteristic histological findings (flame figures). Although multiple potential triggers have been proposed, the exact etiology remains unresolved. Involvement of abnormal Th2 cells, IL‐5, and activated eosinophilic granulocytes suggest a nonspecific hypersensitivity response to exogenous or endogenous stimuli. Corticosteroids may have a beneficial effect on the chronic, recurrent course frequently observed. The disease is often self‐limiting, healing without sequelae. Given that transitions to hematological and oncological disorders have been observed, patients should be closely followed up.

Psoriasis vulgaris is a common chronic inflammatory skin disease involving cytokines and an activated cellular immune system. At variance to skin from patients with atopic dermatitis or from healthy subjects, human psoriatic skin lesions exhibit strong activation of transcription factor NF-κB that is mainly confined to dermal macrophages, whereas only a few dendritic cells but no CD3+ lymphocytes show activated NF-κB. Since NF-κB signaling is required for the induction and/or function of many cytokines and aberrant cytokine expression has been proposed as an underlying cause of psoriasis, we investigated whether NF-κB targeting would affect the course of the disease in the CD18 hypomorphic (CD18hypo) mouse model of psoriasis. When mice with severe psoriasiform lesions were treated systemically or locally with the IκB kinase inhibitor acetyl-11-keto-β-boswellic acid (AKβBA), NF-κB signaling and the subsequent NF-κB-dependent cytokine production as shown by the TNF-α production of macrophages were profoundly suppressed. Additionally, application of the compound counteracted the intradermal MCP-1, IL-12, and IL-23 expression in previously lesional skin areas, led to resolution of the abundant immune cell infiltrates, and significantly reduced the increased proliferation of the keratinocytes. Overall, the AKβBA treatment was accompanied by a profound improvement of the psoriasis disease activity score in the CD18hypo mice with reconstitution of a nearly normal phenotype within the chosen observation period. Our data demonstrate that NF-κB signaling is pivotal for the pathogenesis in the CD18hypo mouse model of psoriasis. Therefore, targeting NF-κB might provide an effective strategy for the treatment of psoriasis.

No abstract