Stephan Seeliger

Loss of S100A9 (MRP14) Results in Reduced Interleukin-8-Induced CD11b Surface Expression, a Polarized Microfilament System, and Diminished Responsiveness to Chemoattractants In Vitro

ABSTRACT The S100A9 (MRP14) protein is abundantly expressed in myeloid cells and has been associated with various inflammatory diseases. The S100A9-deficient mice described here were viable, fertile, and generally of healthy appearance. The myelopoietic potential of the S100A9-null bone marrow was normal. S100A8, the heterodimerization partner of S100A9 was not detectable in peripheral blood cells, suggesting that even a deficiency in both S100A8 and S100A9 proteins was compatible with viable and mature neutrophils. Surprisingly, the invasion of S100A9-deficient leukocytes into the peritoneum and into the skin in vivo was indistinguishable from that in wild-type mice. However, stimulation of S100A9-deficient neutrophils with interleukin-8 in vitro failed to provoke an up-regulation of CD11b. Migration upon a chemotactic stimulus through an endothelial monolayer was markedly diminished in S100A9-deficient neutrophils. Attenuated chemokinesis of the S100A9-deficient neutrophils was observed by using a three-dimensional collagen matrix migration assay. The altered migratory behavior was associated with a microfilament system that was highly polarized in unstimulated S100A9-deficient neutrophils. Our data suggest that loss of the calcium-binding S100A9 protein reduces the responsiveness of the neutrophils upon chemoattractant stimuli at least in vitro. Alternative pathways for neutrophil emigration may be responsible for the lack of any effect in the two in vivo models we have investigated so far.

Proinflammatory role of proteinase-activated receptor-2 in humans and mice during cutaneous inflammation in vivo

Proteinase‐activated receptor‐2 belongs to a new subfamily of G‐protein‐coupled receptors. Its precise role during inflammation and the underlying mechanisms is still unclear. Our study establishes that PAR‐2 plays a direct proinflammatory role during cutaneous inflammation in mice and humans in vivo. In a model of experimentally induced allergic (ACD) and toxic (ICD) contact dermatitis (CD) we show that ear swelling responses, plasma extravasation, and leucocyte adherence were significantly attenuated in PAR‐2 null mutant (PAR‐2−7−) mice compared with wild‐type (PAR‐2+/+) mice, especially at early stages. The proinflammatory effects by PAR‐2 activation were significantly diminished using nitric oxide‐synthase inhibitors, while NF‐kappaB and neuropeptides appear to play a minor role in these mechanisms. PAR‐2‐mediated up‐regulation of E‐selectin and cell adhesion molecule ICAM‐1;enhanced plasma extravasation was observed in humans and mice and of interleukin‐6 in mice in vivo. Thus, PAR‐2 may be a beneficial therapeutic target for the treatment of inflammatory skin diseases.— Seeliger, S., Derian, C. K., Vergnolle, N., Bunnett, N. W., Nawroth, R., Schmelz, M., von der Weid, P.‐Y., Buddenkotte, J., Sunderko¨tter, C., Metze, D., Andrade‐ Gordon, P., Harms, E., Vestweber, D., Luger, T. A., Steinhoff, M. Proinflammatory role of proteinase‐activated receptor‐2 in humans and mice during cutaneous inflammation in vivo. FASEB J. 17, 1871–1885 (2003)

Glucocorticoids induce an activated, anti-inflammatory monocyte subset in mice that resembles myeloid-derived suppressor cells

Glucocorticoids (GC) are still the most widely used immunosuppressive agents in clinical medicine. Surprisingly, little is known about the mechanisms of GC action on monocytes, although these cells exert pro‐ and anti‐inflammatory effects. We have shown recently that GC induce a specific monocyte phenotype with anti‐inflammatory properties in humans. We now investigated whether this also applies for the murine system and how this subset would relate to recently defined murine subtypes. After treatment with dexamethasone for 48 h, monocytes up‐regulated scavenger receptor CD163 and Gr‐1, down‐regulated CX3CR1, and shared with human GC‐treated monocytes functional features such as low adhesiveness but high migratory capacity. They specifically up‐regulated anti‐inflammatory IL‐10, but not TGF‐β, and in contrast to their human counterparts, they down‐regulated IL‐6. Although GC‐induced monocytes down‐regulated CX3CR1, a distinctive marker for classical/proinflammatory human and murine monocytes (CX3CR1loCCR2+Ly6Chi), they differed from this physiologically occurring subset, as they remained Ly6Cmed and unactivated (CD62 ligand++). In addition to their immunosuppressive effects, they were CD11b+Gr‐1+ and expressed the IL‐4Rα chain (CD124), a recently described, signature molecule of tumor‐induced myeloid‐derived suppressor cells (MDSC). We therefore generated murine MDSC in B16 melanoma‐bearing mice and indeed found parallel up‐regulation of CD11b+Gr‐1+ and CD124 on GC‐induced monocytes and MDSC. These data allow us to speculate that the GC‐induced subtype shares with inflammatory monocytes the ability to migrate quickly into inflamed tissue, where they, however, exert anti‐inflammatory effects and that similarities between GC‐induced monocytes and MDSC may be involved in progression of some tumors observed in patients chronically treated with GC.

Neurovascular and Neuroimmune Aspects in the Pathophysiology of Rosacea

Rosacea is a common skin disease with a high impact on quality of life. Characterized by erythema, edema, burning pain, immune infiltration, and facial skin fibrosis, rosacea has all the characteristics of neurogenic inflammation, a condition induced by sensory nerves via antidromically released neuromediators. To investigate the hypothesis of a central role of neural interactions in the pathophysiology, we analyzed molecular and morphological characteristics in the different subtypes of rosacea by immunohistochemistry, double immunofluorescence, morphometry, real-time PCR, and gene array analysis, and compared the findings with those for lupus erythematosus or healthy skin. Our results showed significantly dilated blood and lymphatic vessels. Signs of angiogenesis were only evident in phymatous rosacea. The number of mast cells and fibroblasts was increased in rosacea, already in subtypes in which fibrosis is not clinically apparent, indicating early activation. Sensory nerves were closely associated with blood vessels and mast cells, and were increased in erythematous rosacea. Gene array studies and qRT-PCR confirmed upregulation of genes involved in vasoregulation and neurogenic inflammation. Thus, dysregulation of mediators and receptors implicated in neurovascular and neuroimmune communication may be crucial at early stages of rosacea. Drugs that function on neurovascular and/or neuroimmune communication may be beneficial for the treatment of rosacea.

Tumor immune escape by the loss of homeostatic chemokine expression

The novel keratinocyte-specific chemokine CCL27 plays a critical role in the organization of skin-associated immune responses by regulating T cell homing under homeostatic and inflammatory conditions. Here we demonstrate that human keratinocyte-derived skin tumors may evade T cell-mediated antitumor immune responses by down-regulating the expression of CCL27 through the activation of epidermal growth factor receptor (EGFR)–Ras–MAPK-signaling pathways. Compared with healthy skin, CCL27 mRNA and protein expression was progressively lost in transformed keratinocytes of actinic keratoses and basal and squamous cell carcinomas. In vivo, precancerous skin lesions as well as cutaneous carcinomas showed significantly elevated levels of phosphorylated ERK compared with normal skin, suggesting the activation of EGFR–Ras signaling pathways in keratinocyte-derived malignancies. In vitro, exogenous stimulation of the EGFR–Ras signaling pathway through EGF or transfection of the dominant-active form of the Ras oncogene (H-RasV12) suppressed whereas an EGFR tyrosine kinase inhibitor increased CCL27 mRNA and protein production in keratinocytes. In mice, neutralization of CCL27 led to decreased leukocyte recruitment to cutaneous tumor sites and significantly enhanced primary tumor growth. Collectively, our data identify a mechanism of skin tumors to evade host antitumor immune responses.

Expression of S100A12 (EN-RAGE) in cystic fibrosis

Background: Chronic airway inflammation and recurrent infections are a core phenomenon in cystic fibrosis (CF). Diagnosing acute infectious exacerbations is difficult in the presence of chronic inflammatory processes. S100A12 exhibits proinflammatory functions via interaction with the multiligand receptor for advanced glycation end products. Blocking this interaction inhibits inflammatory processes in mice. Methods: The expression of S100A12 in lung specimens of patients with end stage lung disease of CF was investigated, and S100A12 levels in the serum of patients with acute infectious exacerbations of CF were measured. Results: Immunohistochemical studies of CF lung biopsy specimens revealed a significant expression of S100A12 by infiltrating neutrophils. High S100A12 levels were found in the sputum of patients with CF, and serum levels of S100A12 during acute infectious exacerbations were significantly increased compared with healthy controls (median 225 ng/ml v 46 ng/ml). After treatment with intravenous antibiotics the mean S100A12 level decreased significantly. There was also a significant difference between S100A12 levels in patients with acute infectious exacerbations and 18 outpatients without exacerbations (median 225 ng/ml v 105 ng/ml). Conclusions: S100A12 is extensively expressed at local sites of inflammation in CF. It is a serum marker for acute infectious exacerbations. High local expression of S100A12 suggests that this protein has a proinflammatory role during airway inflammation and may serve as a novel target for anti-inflammatory treatments.

Distribution and expression of non-neuronal transient receptor potential (TRPV) ion channels in rosacea.

Rosacea is a frequent chronic inflammatory skin disease of unknown etiology. Because early rosacea reveals all characteristics of neurogenic inflammation, a central role of sensory nerves in its pathophysiology has been discussed. Neuroinflammatory mediators and their receptors involved in rosacea are poorly defined. Good candidates may be transient receptor potential (TRP) ion channels of vanilloid type (TRPV), which can be activated by many trigger factors of rosacea. Interestingly, TRPV2, TRPV3, and TRPV4 are expressed by both neuronal and non-neuronal cells. Here, we analyzed the expression and distribution of TRPV receptors in the various subtypes of rosacea on non-neuronal cells using immunohistochemistry, morphometry, double immunoflourescence, and quantitative real-time PCR (qRT-PCR) as compared with healthy skin and lupus erythematosus. Our results show that dermal immunolabeling of TRPV2 and TRPV3 and gene expression of TRPV1 is significantly increased in erythematotelangiectatic rosacea (ETR). Papulopustular rosacea (PPR) displayed an enhanced immunoreactivity for TRPV2, TRPV4, and also of TRPV2 gene expression. In phymatous rosacea (PhR)-affected skin, dermal immunostaining of TRPV3 and TRPV4 and gene expression of TRPV1 and TRPV3 was enhanced, whereas epidermal TRPV2 staining was decreased. Thus, dysregulation of TRPV channels also expressed by non-neuronal cells may be critically involved in the initiation and/or development of rosacea. TRP ion channels may be targets for the treatment of rosacea.

β2 integrins are required for skin homing of primed T cells but not for priming naive T cells

Beta2 integrins are of critical importance for leukocyte extravasation through vascular endothelia and for T cell activation. To elucidate the role of beta2 integrins in T cell-mediated immune responses, allergic contact dermatitis (ACD), irritant dermatitis, and delayed-type hypersensitivity (DTH) were assessed in mice lacking the beta2 integrin subunit, CD18. ACD and DTH responses, but not edema formation, were severely suppressed in CD18(-/-) mice. Extravasation of CD18(-/-) T cells into eczematous skin lesions was greatly impaired, whereas migration of Langerhans cell precursors and dendritic cells was normal in CD18(-/-) mice. CD18(-/-)lymph nodes (LNs) contained an abnormal population of CD3(-)CD44(high) lymphocytes and showed evidence of widespread T cell activation. T cells from regional LNs of sensitized CD18(-/-) mice proliferated in response to hapten challenge, and subcutaneous injection of sensitized syngeneic LN cells directly into ears of hapten-challenged naive recipients restored the defective ACD in CD18(-/-) mice, suggesting that CD18 is not required for priming of naive T cells but is indispensable for T cell extravasation. Thus, a dysfunction of T cells, in addition to granulocytes, may contribute to the pathophysiology of leukocyte adhesion deficiency type I, which arises from mutations in the human CD18 gene.

Expression of Calcium-Binding Proteins MRP8 and MRP14 in Inflammatory Muscle Diseases

The pathophysiological role of infiltrating macrophages and their subtypes in idiopathic inflammatory myopathies such as dermatomyositis, polymyositis, and inclusion body myositis is not fully clear. Monocytes exhibit various phenotypes with different functional properties such as release of pro- or anti-inflammatory mediators. Expression of myeloid-related proteins MRP8 and MRP14, two calcium-binding S100-proteins, characterizes a proinflammatory subtype of macrophages. We immunohistochemically investigated expression of MRP8 and MRP14 in muscle biopsies of 33 patients with dermatomyositis, polymyositis, and inclusion body myositis. We found a clear association of expression of MRP8 and MRP14 by infiltrating macrophages with degeneration of myofibers. Because MRP8 and MRP14 are secreted by activated macrophages we investigated if these proteins would have direct extracellular effects on myocytes. We found that the purified MRP8/MRP14 complex inhibited proliferation and differentiation of C2C12 myoblasts and that it induced apoptosis via activation of caspase-3 in a time- and dose-dependent manner. These results indicate that in the course of inflammatory myopathies, activated macrophages can promote destruction and impair regeneration of myocytes via secretion of MRP8/MRP14.

Different pathways leading to cutaneous leukocytoclastic vasculitis in mice.

Abstract: To investigate the pathomechanisms of leukocytoclastic vasculitis (LcV) we compared mouse models of LcV with non‐vasculitic irritant contact dermatitis (ICD). Criteria for LcV as met by the immune complex‐mediated Arthus reaction (Art‐r) were also fulfilled by the localized Shwartzman reaction (Shw‐r) and by cutaneous Loxoscelism (Lox) (injection of venom from Loxosceles reclusa containing sphingomyelinase D). After depletion of PMN (by γ‐irradiation) vessel damage could not be elicited in these models, distinguishing them from models of direct endothelial insult (necrotizing ICD). Depletion of complement could only delay, but not inhibit the Art‐r, and did not change ICD, Lox or the Shw‐r. The Shw‐r exclusively revealed a sustained local expression of vascular adhesion molecules for 24 h in the preparatory phase (LPS s.c.), not observed in the Art‐r, in Lox or ICD. Subsequent challenge with LPS i.p. was associated with upregulation of Mac‐1 and ICAM‐1 on PMN, but not of VLA‐4 or LFA‐1 (FACS analysis). Cytokines which were able to replace LPS in priming for LcV in the Shw‐r (TNF‐α and IL‐1β) also induced sustained expression of adhesion molecules, whereas IL‐12 and IFN‐γ did neither. Neutralizing IL‐12 or IFN‐γ also inhibited neither LcV nor sustained expression of adhesion molecules, whereas anti‐TNF‐α inhibited both. Anti‐TNF‐α had no marked inhibitory effects in the Art‐r, in Lox or ICD. Combined (but not separate) neutralization of both E‐selectin and VCAM‐1 by antibodies suppressed LcV independent from reducing influx of PMN, proving that their sustained expression is decisive for the Shw‐r and interferes with normal diapedesis. Since Loxosceles venom is known to dysregulate diapedesis and degranulation of PMN in vitro, since adherent immune complexes activate PMN at the vessel wall, and since adhesion molecules are dysregulated in the Shw‐r, we suggest that LcV develops when activation of PMN coincides with vascular alterations which interfere with normal diapedesis.