Eosinophil-specific deletion of IκBα in mice reveals a critical role of NF-κB-induced Bcl-xL for inhibition of apoptosis.

Eosinophils are associated with type 2 immune responses to allergens and helminths. They release various proinflammatory mediators and toxic proteins on activation and are therefore considered proinflammatory effector cells. Eosinophilia is promoted by the cytokines interleukin (IL)-3, IL-5, and granulocyte macrophage-colony-stimulating factor (GM-CSF) and can result from enhanced de novo production or reduced apoptosis. In this study, we show that only IL-5 induces differentiation of eosinophils from bone marrow precursors, whereas IL-5, GM-CSF, and to a lesser extent IL-3 promote survival of mature eosinophils. The receptors for these cytokines use the common ß chain, which serves as the main signaling unit linked to signal transducer and activator of transcription 5, p38 mitogen-activated protein kinase, and nuclear factor (NF)-κB pathways. Inhibition of NF-κB induced apoptosis of in vitro cultured eosinophils. Selective deletion of IκBα in vivo resulted in enhanced expression of Bcl-xL and reduced apoptosis during helminth infection. Retroviral overexpression of Bcl-xL promoted survival, whereas pharmacologic inhibition of Bcl-xL in murine or human eosinophils induced rapid apoptosis. These results suggest that therapeutic strategies targeting Bcl-xL in eosinophils could improve health conditions in allergic inflammatory diseases.

Primary cutaneous follicle center lymphoma with diffuse CD30 expression: a report of 4 cases of a rare variant.

BACKGROUND: CD30 is expressed in aggressive and Epstein-Barr virus-associated forms of B-cell non-Hodgkin lymphomas, but is rarely expressed by the majority of tumor cells in primary cutaneous B-cell lymphomas (CBCLs). The expression of CD30 in CBCLs may be at risk for misinterpretation as an unequivocal indicator of a highly aggressive form of the disease. OBJECTIVE: We report 4 cases of low malignant primary cutaneous follicle center lymphoma (PCFCL) with diffuse and strong expression of CD30 by the majority of neoplastic cells. RESULTS: The patients included 3 men and 1 woman with tumors on the scalp (3 patients) and chest wall (1 patient). The histologic examinations revealed a mixed, diffuse, and follicular growth pattern with CD20(+), bcl-6(+), and bcl-2(-) tumor cells. Seventy percent to 90% of the tumor cells expressed CD30. Clonal rearrangement of immunoglobulin heavy chain genes was found in 1 of 4 cases. None of the 3 cases yielded positivity for Epstein-Barr virus RNA. LIMITATIONS: The study is limited by the small number of patients. CONCLUSIONS: This rare variant of CD30(+) PCFCL needs be distinguished from CD30(+) aggressive B-cell lymphomas. CD30 in this variant of CBCLs may serve as a therapeutic target for anti-CD30 antibody-based strategies.

Intestinal tumorigenesis initiated by dedifferentiation and acquisition of stem-cell-like properties.

Cell-type plasticity within a tumor has recently been suggested to cause a bidirectional conversion between tumor-initiating stem cells and nonstem cells triggered by an inflammatory stroma. NF-κB represents a key transcription factor within the inflammatory tumor microenvironment. However, NF-κB's function in tumor-initiating cells has not been examined yet. Using a genetic model of intestinal epithelial cell (IEC)-restricted constitutive Wnt-activation, which comprises the most common event in the initiation of colon cancer, we demonstrate that NF-κB modulates Wnt signaling and show that IEC-specific ablation of RelA/p65 retards crypt stem cell expansion. In contrast, elevated NF-κB signaling enhances Wnt activation and induces dedifferentiation of nonstem cells that acquire tumor-initiating capacity. Thus, our data support the concept of bidirectional conversion and highlight the importance of inflammatory signaling for dedifferentiation and generation of tumor-initiating cells in vivo.

Fumarates improve psoriasis and multiple sclerosis by inducing type II dendritic cells.

Fumarates improve multiple sclerosis (MS) and psoriasis, two diseases in which both IL-12 and IL-23 promote pathogenic T helper (Th) cell differentiation. However, both diseases show opposing responses to most established therapies. First, we show in humans that fumarate treatment induces IL-4-producing Th2 cells in vivo and generates type II dendritic cells (DCs) that produce IL-10 instead of IL-12 and IL-23. In mice, fumarates also generate type II DCs that induce IL-4-producing Th2 cells in vitro and in vivo and protect mice from experimental autoimmune encephalomyelitis. Type II DCs result from fumarate-induced glutathione (GSH) depletion, followed by increased hemoxygenase-1 (HO-1) expression and impaired STAT1 phosphorylation. Induced HO-1 is cleaved, whereupon the N-terminal fragment of HO-1 translocates into the nucleus and interacts with AP-1 and NF-κB sites of the IL-23p19 promoter. This interaction prevents IL-23p19 transcription without affecting IL-12p35, whereas STAT1 inactivation prevents IL-12p35 transcription without affecting IL-23p19. As a consequence, GSH depletion by small molecules such as fumarates induces type II DCs in mice and in humans that ameliorate inflammatory autoimmune diseases. This therapeutic approach improves Th1- and Th17-mediated autoimmune diseases such as psoriasis and MS by interfering with IL-12 and IL-23 production.

Myeloid IκBα deficiency promotes atherogenesis by enhancing leukocyte recruitment to the plaques.

Activation of the transcription factor NF-κB appears to be involved in different stages of atherogenesis. In this paper we investigate the role of NF-κB inhibitor IκBα in atherosclerosis. Myeloid-specific deletion of IκBα results in larger and more advanced lesions in LDL-R-deficient mice without affecting the compositional phenotype of the plaques or systemic inflammatory markers in the plasma. We show that IκBα-deleted macrophages display enhanced adhesion to an in vitro endothelial cell layer, coinciding with an increased expression of the chemokine CCL5. Also, in vivo we found that IκBα(del) mice had more leukocytes adhering to the luminal side of the endothelial cell layers that cover the atherosclerotic plaques. Moreover, we introduce ER-MP58 in this paper as a new immunohistochemical tool for quantifying newly recruited myeloid cells in the atherosclerotic lesion. This staining confirms that in IκBα(del) mice more leukocytes are attracted to the plaques. In conclusion, we show that IκBα deletion in myeloid cells promotes atherogenesis, probably through an induced leukocyte recruitment to plaques.

What is really in control of skin immunity: lymphocytes, dendritic cells, or keratinocytes? facts and controversies.

The pathophysiology of atopic dermatitis is still under discussion. Although it is widely accepted that environmental factors and a genetic predisposition are essential, the role of the innate and adaptive immune system and the functional cascade of the cells involved is still unclear. A concept that integrates all immune cells as equally essential has allure. In addition, barrier abnormalities due to mutations of the gene coding for filaggrin and down-regulation of antimicrobial peptides, such as LL-37 and beta-defensins 2 and 3, were very recently found to be relevant for the pathogenesis of atopic dermatitis.

Complementary therapy for atopic dermatitis and other allergic skin diseases: facts and controversies.

The term complementary or alternative medicine encompasses numerous diverse therapeutic concepts, ranging from as herbal medicine, diet with essential fatty acids, and probiotics, to acupuncture. The main focus of these treatment methods is inflammatory skin disease, in particular atopic dermatitis. Although integrative medicine enjoys increasing popularity, particularly in industrialized countries, clinical studies that meet the double-blind, placebo-controlled standard are rare or nonexistent. The aim of this contribution is to provide the various concepts of integrative medicine.

The potential role of c-Jun activation in patients with cutaneous lichen planus.

c-Jun, a component of the activating protein-1 transcription factor family, has been known to play an important role in the control of cell proliferation. It is also suspected to be a critical mediator of tumor promotion. However, investigations of c-Jun activation patterns in inflammatory and inflammatory transforming skin diseases have not been described so far. In this work, we show the c-Jun activation pattern in skin samples of patients with cutaneous lichen planus (LP), squamous cell carcinoma (SCC), psoriasis and normal skin using an immunohistochemical approach and Western blot analysis. In addition, we studied the c-Jun activation pattern in histological samples of three patients in whom LP transformed to SCC. We show that c-Jun is rarely activated in normal skin and psoriasis in contrast to LP and SCC. Our results suggest that c-Jun activation in human skin is involved in (1) proliferation and (2) could potentially participate in the transformation of LP from an inflammatory to a carcinogenic state. Nevertheless, JNK1/2, an important c-Jun activating kinase, was not found to be differentially regulated in LP and SCC compared with normal skin.

IkappaBalpha is required for marginal zone B cell lineage development.

Inactivation of members of the nuclear factor-kappaB (NF-kappaB) family results in the decrease or defect of marginal zone B (MZB) cells. It is not known which inhibitors of the NF-kappaB family (IkappaB) are required for MZB cell development. Here, we show that mice with B cell-specific inactivation of the main NF-kappaB inhibitor IkappaBalpha have a marked decrease of MZB cells and their presumed precursors. They exhibited increased mortality rates after blood-borne bacterial infection, indicating the importance of MZB cells for bacterial clearance. In contrast, response to T cell-dependent and -independent antigens resulted only in minor changes in immunoglobulin production. Our data demonstrate the importance of the intact NF-kappaB/IkappaBalpha pathway for proper MZB cell development.

Role of NF-kappaB/RelA and MAPK pathways in keratinocytes in response to sulfur mustard.

Sulfur mustard (SM) is a strong vesicant that has been used as a chemical warfare agent. To understand the molecular mechanisms that underlie the inflammatory skin reaction in response to SM, we analyzed the activation pattern of the NF-kappaB and mitogen-activated protein kinase (MAPK) pathways. Keratinocytes responded with an induction of the canonical NF-kappaB pathway, including activation of IkappaB kinase 2, followed by phosphorylation and degradation of IkappaBalpha and of the transactivating subunit RelA at Ser536. The biphasic NF-kappaB response was strictly dependent on the transactivating subunit RelA, as demonstrated by keratinocytes lacking RelA. Parallel to NF-kappaB activation, we observed an induction of the Raf-1/MEK1/2/ERK1/2/MSK1 and MKK3/6/p38/MSK1 pathways. Although mitogen and stress-activated kinase 1 has been described as a RelA kinase with Ser276 as its target, this site remained unphosphorylated in response to SM. A further MAPK pathway induced by SM was the MKK4/7/JNK1/2 pathway, which resulted in phosphorylation of the transcription factor activating transcription factor-2, but not c-Jun. Our results indicate that SM induces a complex cellular response in keratinocytes, with the activation of three MAPK pathways and the NF-kappaB pathway.

Crosstalk between keratinocytes and adaptive immune cells in an IkappaBalpha protein-mediated inflammatory disease of the skin.

Inflammatory diseases at epithelial borders develop from aberrant interactions between resident cells of the tissue and invading immunocytes. Here, we unraveled basic functions of epithelial cells and immune cells and the sequence of their interactions in an inflammatory skin disease. Ubiquitous deficiency of the IkappaBalpha protein (Ikba(Delta)(/Delta)) as well as concomitant deletion of Ikba specifically in keratinocytes and T cells (Ikba(K5Delta/K5Delta lckDelta/lckDelta)) resulted in an inflammatory skin phenotype that involved the epithelial compartment and depended on the presence of lymphocytes as well as tumor necrosis factor and lymphotoxin signaling. In contrast, mice with selective ablation of Ikba in keratinocytes or lymphocytes showed inflammation limited to the dermal compartment or a normal skin phenotype, respectively. Targeted deletion of RelA from epidermal keratinocytes completely rescued the inflammatory skin phenotype of Ikba(Delta)(/Delta) mice. This finding emphasizes the important role of aberrant NF-kappaB activation in both keratinocytes and lymphocytes in the development of the observed inflammatory skin changes.

Pathogenic role for skin macrophages in a mouse model of keratinocyte-induced psoriasis-like skin inflammation.

Psoriasis is a common skin disease, the pathogenesis of which has not yet been resolved. In mice, epidermis-specific deletion of inhibitor of NF-kappaB (IkappaB) kinase 2 (IKK2) results in a skin phenotype that mimics human psoriasis in several aspects. Like psoriasis, this skin disease shows pronounced improvement when mice are treated with a TNF-neutralizing agent. We have found previously that this phenotype does not depend on the presence of alphabeta T lymphocytes. In order to evaluate contributions of other immune cell populations to the skin disease, we selectively eliminated macrophages and granulocytes from the skin of mice with epidermis-specific deletion of IKK2 (K14-Cre-IKK2fl/fl mice). Elimination of skin macrophages by subcutaneous injection of clodronate liposomes was accompanied by inhibition of granulocyte migration into the skin and resulted in a dramatic attenuation of psoriasis-like skin changes. The hyperproliferative, inflammatory skin disease in K14-Cre-IKK2fl/fl mice was a direct consequence of the presence of macrophages in the skin, as targeted deletion of CD18, which prevented accumulation of granulocytes but not macrophages, did not lead to major changes in the phenotype. Targeted deletion of the receptor for IFN-gamma revealed that the pathogenesis of the skin disease does not depend on classical IFN-gamma-mediated macrophage activation. Our results demonstrate that in mice epidermal keratinocytes can initiate a hyperproliferative, inflammatory, IFN-gamma-independent, psoriasis-like skin disease whose development requires essential contributions from skin macrophages but not from granulocytes or alphabeta T lymphocytes.

Stroma-mediated dysregulation of myelopoiesis in mice lacking I kappa B alpha.

Hematopoiesis occurs in the liver and the bone marrow (BM) during murine development. Newborn mice with a ubiquitous deletion of I kappa B alpha develop a severe hematological disorder characterized by an increase of granulocyte/erythroid/monocyte/macrophage colony-forming units (CFU-GEMM) and hypergranulopoiesis. Here, we report that this particular myeloproliferative disturbance is mediated by continuously deregulated perinatal expression of Jagged1 in I kappa B alpha-deficient hepatocytes. The result is a permanent activation of Notch1 in neutrophils. In contrast, in mice with a conditional deletion of I kappa B alpha only in the myeloid lineage (ikba(flox/flox) x LysM-Cre) and in fetal liver cell chimeras (ikba(FL delta/FL delta)), a cell-autonomous induction of the myeloproliferative disease was not observed. Coculture of I kappa B alpha-deficient hepatocytes with wild-type (wt) BM cells induced a Jagged1-dependent increase in CFUs. In summary, we show that cell-fate decisions leading to a premalignant hematopoietic disorder can be initiated by nonhematopoietic cells with inactive I kappa B alpha.

Induction of nuclear factor- kappa B and c-Jun/activator protein-1 via toll-like receptor 2 in macrophages by antimycotic-treated Candida albicans.

We examined the role of Toll-like receptors (TLRs) by using TLR2-deficient (TLR2(-/-)), TLR4-defective (TLR4(d/d)), and double-knockout murine macrophages and human embryonic kidney (HEK) 293 cells transfected with human TLR2 or TLR4 expression plasmids after stimulation with different preparations of the human pathogenic fungus Candida albicans. Compared with wild-type macrophages, TLR2(-/-) and TLR4(d/d) macrophages had impaired recognition of viable C. albicans, whereas antimycotic (AM)-treated C. albicans solely used TLR2 in a TLR4- and interferon- gamma -independent manner. In human HEK293 cells, AM-treated C. albicans elicited mainly TLR2-dependent activation. The differences in responsiveness to viable C. albicans, compared with C. albicans treated with cytoplasmic membrane-interacting AMs, suggest specific recognition of different pathogen-associated patterns by TLRs in innate antifungal responses. Our analyses of signal transduction after stimulation of wild-type macrophages with AM-treated C. albicans demonstrated involvement of the transcription factors nuclear factor- kappa B and c-Jun/activator protein-1 and of the mitogen-activated protein kinases p38, extracellular-related kinase, and c-Jun NH(2)-terminal kinase.

Toll-like receptors and innate antifungal responses.

The mammalian Toll-like receptors (TLRs) are homologues of Drosophila Toll and constitute a novel protein family involved in the mediation of innate immunity and the activation of adaptive immunity. Analysis of infection with human pathogenic fungi Candida albicans and Aspergillus fumigatus implicated TLR2 and TLR4 in elicitation of immune responses. Cryptococcus neoformans is recognized by a process that uses TLR4. C. albicans induces immunostimulation through causative agents, such as mannan or its structural derivatives (e.g. phospholipomannan), which are recognized by the immune system as pathogen-associated molecular patterns and are located in the cell wall of fungi. Secreted aspartic proteinases represent a key virulence factor that contributes to the ability of C. albicans to cause mucosal and disseminated infections, and might be a further potential stimulator of TLRs. Simultaneous activation of other pattern recognition receptors collaborating with TLRs illustrates the cooperation of various chains within ligand-specific receptor complexes for the recognition of fungal pathogens and their cell wall components.

[Graft-versus-host disease: a dermatologic view of an interdisciplinary problem]. / Graft-versus-Host-Disease: Ein interdisziplinäres Problem aus der Sicht des Dermatologen.

Graft-versus-host disease (GVHD) is a frequent complication following hematopoietic stem cell transplantation. Acute and chronic GVHD are identified based on the onset of clinical symptoms and signs. Whereas acute GVHD is relatively uniform in its appearance, chronic GVHD is characterized by a broad spectrum of clinical manifestations. The aim of this review is to introduce the reader to the pathophysiologic processes underlying GVHD, to demonstrate its manifestations in the skin and to review current therapeutic options.