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Chemerin expression marks early psoriatic skin lesions and correlates with plasmacytoid dendritic cell recruitment

Psoriasis is a type I interferon-driven T cell–mediated disease characterized by the recruitment of plasmacytoid dendritic cells (pDC) into the skin. The molecules involved in pDC accumulation in psoriasis lesions are unknown. Chemerin is the only inflammatory chemotactic factor that is directly active on human blood pDC in vitro. The aim of this study was to evaluate the role of the chemerin/ChemR23 axis in the recruitment of pDC in psoriasis skin. Prepsoriatic skin adjacent to active lesions and early lesions were characterized by a strong expression of chemerin in the dermis and by the presence of CD15+ neutrophils and CD123+/BDCA-2+/ChemR23+ pDC. Conversely, skin from chronic plaques showed low chemerin expression, segregation of neutrophils to epidermal microabscesses, and few pDC in the dermis. Chemerin expression was localized mainly in fibroblasts, mast cells, and endothelial cells. Fibroblasts cultured from skin of psoriatic lesions expressed higher levels of chemerin messenger RNA and protein than fibroblasts from uninvolved psoriatic skin or healthy donors and promoted pDC migration in vitro in a chemerin-dependent manner. Therefore, chemerin expression specifically marks the early phases of evolving skin psoriatic lesions and is temporally strictly associated with pDC. These results support a role for the chemerin/ChemR23 axis in the early phases of psoriasis development.

Human CD25+ Regulatory T Cells Maintain Immune Tolerance to Nickel in Healthy, Nonallergic Individuals

We investigated the capacity of CD25+ T regulatory cells (Treg) to modulate T cell responses to nickel, a common cause of allergic contact dermatitis. CD4+ T cells isolated from the peripheral blood of six healthy, nonallergic individuals showed a limited capacity to proliferate in response to nickel in vitro, but responsiveness was strongly augmented (mean increment ± SD, 240 ± 60%) when cells were depleted of CD25+ Treg. Although CD25+ Treg were anergic to nickel, a small percentage up-regulated membrane CTLA-4 upon nickel exposure. CD25+ Treg strongly and dose-dependently inhibited nickel-specific activation of CD25− T lymphocytes in coculture experiments in a cytokine-independent, but cell-to-cell contact-dependent, manner. Approximately 30% of circulating CD25+ Treg expressed the cutaneous lymphocyte-associated Ag (CLA), and CLA+CD25+ Treg were more efficient than CLA−CD25+ cells in suppressing nickel responsiveness of CD25− T cells. The site of a negative patch test in response to nickel showed an infiltrate of CD4+CLA+ cells and CD25+ cells, which accounted for ∼20% of the total T cells isolated from the tissue. Skin-derived T cells suppressed nickel-specific responses of peripheral blood CD25− T cells. In addition, 60 ± 14% of peripheral blood CD25+ Treg expressed the chemokine receptor CCR7 and strongly inhibited naive T cell activation in response to nickel. Finally, CD25+ T cells isolated from peripheral blood of nickel-allergic patients showed a limited or absent capacity to suppress metal-specific CD4+ and CD8+ T cell responses. The results indicates that in healthy individuals CD25+ Treg can control the activation of both naive and effector nickel-specific T cells.

CD56brightCD16(-) NK cells accumulate in psoriatic skin in response to CXCL10 and CCL5 and exacerbate skin inflammation.

Psoriasis is an immune‐mediated skin disease characterized by lymphocytic infiltration and altered keratinocyte differentiation. Using immunohistochemical techniques we found that the cellular infiltrate in acute psoriatic plaques includes 5–8% CD3–CD56+ natural killer (NK) cells, mostly localized in the mid and papillary dermis. NK lymphocytes isolated from punch biopsy specimens of psoriatic plaques showed a CD56brightCD16–CD158b– phenotype, failed to express the skin homing cutaneous lymphocyte‐associated antigen and released abundant IFN‐γ upon stimulation. Supernatants from psoriatic NK cells induced MHC class II and ICAM‐1 expression and release of CXCL10 and CCL5 by cultured psoriatic keratinocytes. Skin NK cells expressed high levels of the chemokines receptors CXCR3 and CCR5, intermediate amounts of CXCR1, CCR6 and CCR8, and low levels of CCR1, CCR2, CCR4, CCR7 and CX3CR1. In addition, they promptly migrated in vitro toward CXCL10, CCL5, supernatants of IFN‐γ‐activated psoriatic keratinocytes and, to a lower extent, CCL20 and CCL4. In contrast, they failed to migrate toward CXCL8, CCL1, CCL2, CCL3, CCL17, CCL19 and CX3CL1. Taken together, our results implicate NK lymphocytes as newly identified protagonists in the pathogenesis of psoriasis. Their distinctive homing properties should be taken into account in the design of specific therapy aimed at blocking pathogenic cell accumulation in the skin.

IL-4 and IL-13 Negatively Regulate TNF-α- and IFN-γ-Induced β-Defensin Expression through STAT-6, Suppressor of Cytokine Signaling (SOCS)-1, and SOCS-3

Human β-defensins (HBDs) are a major class of antimicrobial peptides that play an important role in the innate immune response, however, the induction and regulation of these antimicrobial peptides is not well understood. We demonstrate here that stimulation of keratinocytes with TNF-α/IFN-γ induces HBD-2 and HBD-3 by activating STAT-1 and NF-κB signaling. We further demonstrate that IL-4 and IL-13 activate STAT-6 and induce the suppressors of cytokine signaling (SOCS)-1 and -3. This interferes with STAT-1 and NF-κB signaling, thereby inhibiting TNF-α/IFN-γ-mediated induction of HBD-2 and HBD-3. These data suggest that targeting the STAT-1-signaling pathway or suppressor of cytokine signaling expression enhances β-defensin expression and represents a new therapeutic strategy for reduction of infection in human diseases associated with β-defensin deficiency.

The role of chemokines in allergic contact dermatitis

Abstract. Chemokines are important mediators of immune-mediated skin diseases. Allergic contact dermatitis (ACD) is the most thoroughly investigated T cell-mediated disorder because of the ability to easily reproduce the lesions in humans and the availability of an excellent mouse model. Migration of dendritic cells from the skin to lymph nodes is absolutely required for induction of hapten sensitization, and depends upon expression of CCR7 by mature dendritic cells and SLC in the lymph nodes. During expression of ACD, recruitment of T lymphocytes is driven by chemokines exposed on the surface of endothelial cells or released by activated resident skin cells such as mast cells, fibroblasts and keratinocytes. Chemokines are produced in a coordinated and sequential manner, with IL-8 and RANTES induced by TNF-α during early stages, and MCP-1, IP-10, Mig, I-TAC, I-309 and MDC induced by IFN-γ during later stages. Infiltrating monocytes, dendritic cells and T cells are additional sources of chemokines for further leukocyte accumulation. Distinct T cell subsets express different chemokine receptors, with type 2 cells mostly attracted by eotaxin, MDC, TARC and I-309, and type 1 cells sensitive to IP-10, Mig, I-TAC, RANTES and MIP-1β. MCP-1 is effective on both subsets. T regulatory cells, which inhibit dendritic cell function and are probably involved in the termination of ACD, are sensitive to MCP-1, MIPs and TARC, but express high levels of CCR8 and are more specifically attracted by I-309. Targeting chemokines and chemokine receptors may offer new opportunities for therapeutic interventions in ACD and other chronic inflammatory skin diseases.

Lipophilic antioxidants in human sebum and aging.

Skin surface lipids (SSL), a very complex mixture of sebum mixed to small amounts of epidermal lipids, mantle the human epidermis, thus representing the outermost protection of the body against exogenous oxidative insults. The present work is a systematic and quantitative analysis of upper-chest SSL and their content in antioxidants in 100 healthy volunteers, divided into five age groups using TLC, HPLC, and GC-MS methods. Further, the effect of exposing SSL in vitro to increasing doses of UV irradiation was examined. Straight monounsaturated and diunsaturated as well as branched monounsaturated fatty acids of triglycerides and pooled fractions were found to be higher at maturity than in childhood and in advancing age. Diunsaturated fatty acids were below 3% of the total and constituted exclusively of C18:2 j 5,8 , C20:2 j 7,10 , C18:2 j 9,12 . Squalene, vitamin E (vit. E) and Coenzyme Q 10 (CoQ 10 ) were found to increase from childhood to maturity to decrease again significantly in old age. Vitamin E and CoQ 10 were the only known lipophilic antioxidants present in SSL. In spite of their low levels they were found to synergically inhibit the UV induced depletion of squalene, cholesterol and of unsaturated fatty acids of SSL. In fact, exposure of SSL to increasing amounts of UV irradiation led preferentially to lowering of the levels of vit. E and CoQ 10 . Four minimal erythema dose (MED) (5.6 J/cm 2 ) were able to deplete 84% vit. E and 70% ubiquinone, and only 13% squalene. Diunsaturated and monounsaturated fatty acids as well as cholesterol were unaffected even following 10 MED UV exposures, which produced a 26% loss of squalene. The same UV dose when applied in the absence of vit. E and CoQ 10 produced a 90% decrease of squalene.

IL-4 Enhances Keratinocyte Expression of CXCR3 Agonistic Chemokines

IFN-induced protein of 10 kDa (IP-10), monokine induced by IFN-γ (Mig), and IFN-inducible T-cell α-chemoattractant (I-TAC) belong to the non-glutamate-leucine-arginine motif CXC chemokine family and act solely through the CXCR3 receptor for potent attraction of T lymphocytes. In this study, we evaluated the capacity of the T cell-derived cytokines IL-4, IL-10, and IL-17 to modulate IP-10, Mig, and I-TAC in cultured human keratinocytes and CXCR3 expression in T cells from allergic contact dermatitis (ACD). IL-4, but not IL-10 or IL-17, significantly up-regulated IFN-γ- or TNF-α-induced IP-10, Mig, and I-TAC mRNA accumulation in keratinocytes and increased the levels of IP-10 and Mig in keratinocyte supernatants. Immunohistochemistry of skin affected by ACD revealed that >70% of infiltrating cells were reactive for CXCR3 and that CXCR3 staining colocalized in CD4+ and CD8+ T cells. Nickel-specific CD4+ and CD8+ T cell lines established from ACD skin produced IFN-γ and IL-4 and expressed moderate to high levels of CXCR3. Finally, CXCR3 agonistic chemokines released by stimulated keratinocytes triggered calcium mobilization in skin-derived nickel-specific CD4+ T cells and promoted their migration, with supernatant from keratinocyte cultures stimulated with IFN-γ and IL-4 attracting more efficaciously than supernatant from keratinocytes activated with IFN-γ alone. In conclusion, IL-4 exerts a proinflammatory function on keratinocytes by potentiating IFN-γ and TNF-α induction of IP-10, Mig, and I-TAC, which in turn may determine a prominent recruitment of CXCR3+ T lymphocytes at inflammatory reaction sites.

Eotaxins and CCR3 Receptor in Inflammatory and Allergic Skin Diseases: Therapeutical Implications

Cell migration is mediated by a group of chemotactic cytokines called chemokines: low molecular weight molecules that have been shown as important leukocyte chemical attractants to sites of inflammation and infection. Eotaxin-1, also called CCL11, was first described in 1994, as a highly specific eosinophils chemokine. Many cell types including lymphocytes, macrophages, bronchial smooth muscle cells, endothelial cells and eosinophils, are able to produce this chemokine, predominantly after cytokine stimulation, however little is known about its expression in human skin in vivo. Eotaxin-1 also regulates the chemiotaxis and, in some conditions, activation of basophils, mast cells and T lymphocytes. Chemokine receptors are named from their ligand families, thus the CC chemokine eotaxin-1 binds to the CCR3 receptor which is expressed on eosinophis, mast cells, Th2 type lymphocytes and even on keratinocytes. It seems that eotaxin-1 is one of the most important cytokines involved in tissue inflammation playing a central role in the pathogenesis of allergic airway diseases (asthma and rhinitis), in inflammatory bowel disease and gastrointestinal allergic hypersensitivity and recently it has been proposed as a therapeutical target for these conditions. Our group has studied the role of eotaxin-1 in the pathogenesis of two skin conditions: dermatitis herpetiformis and AIDS-associated eosinophilic folliculitis, demonstrating that this chemokine, together with Th2 type cytokines (IL-13 and IL-4) is important in cell recruitment, inflammation and tissue damage; moreover eotaxin has proven to paly an important role in other skin conditions such as, bullous pemphigoid, pemphigoid gestationis, atopic dermatitis and allergic drug reactions Recent advances in the understanding of eotaxin-1-mediated mechanisms of chemotaxis in allergic and inflammatory conditions may predict that therapeutic antagonism is achievable. This paper will focus on the role that eotaxin and its receptor play in the pathogenetical mechanism in a number of dermatologic diseases, some of which, like atopic dermatitis, may benefit from the introduction of novel and more selective therapeutic options.

Therapy with rituximab for autoimmune pemphigus: Results from a single-center observational study on 42 cases with long-term follow-up

BACKGROUND Rituximab induces depletion of B cells and has shown efficacy in antibody-mediated autoimmune disorders. In studies on small series of patients with pemphigus, rituximab administration results in significant improvement. However, differences in inclusion criteria, treatment protocols, and follow-up make it difficult to derive uniform conclusions. OBJECTIVES We sought to test the efficacy and tolerability of rituximab as adjuvant therapy to corticosteroids in the treatment of pemphigus. METHODS In all, 42 patients with pemphigus were treated with rituximab and followed up for up to 5 years. No additional immunosuppressive agents were used. Steroids were rapidly tapered. Outcomes were the proportion of patients who achieved a complete response on or off therapy, the rate of discontinuation of corticosteroid within 6 months, length of remission, time to relapses, and occurrence of adverse events. RESULTS In all, 36 of 42 patients (86%; 95% confidence interval 75%-96%) achieved a complete response on or off therapy and discontinued steroids within 6 months from induction therapy. Six patients had a complete response off therapy with an additional infusion of rituximab 6 months after initial treatment. Twenty patients experienced a total of 34 relapses; the time to relapse was 8 to 64 months. Every relapse was treated with rituximab (500 mg) without corticosteroids, which induced a new complete response. No serious adverse events were observed. LIMITATIONS Lack of a control group is a limitation. CONCLUSIONS Rituximab therapy induces prolonged clinical remission in patients with pemphigus. Coadministration of other immunosuppressive agents is not necessary. Relapses can be managed with additional infusions administered on demand.

Nitric Oxide Donors Suppress Chemokine Production by Keratinocytes in Vitro and in Vivo

Nitric oxide (NO) is involved in the modulation of inflammatory responses. In psoriatic skin, NO is highly produced by epidermal keratinocytes in response to interferon-gamma and tumor necrosis factor-alpha. In this study, we investigated whether the NO donors, S-nitrosoglutathione (GS-NO) and NOR-1, could regulate chemokine production by human keratinocytes activated with interferon-gamma and tumor necrosis factor-alpha. In addition, we studied the effects of the topical application of a GS-NO ointment on chemokine expression in lesional psoriatic skin. NO donors diminished in a dose-dependent manner and at both mRNA and protein levels the IP-10, RANTES, and MCP-1 expression in keratinocytes cultured from healthy patients and psoriatic patients. In contrast, constitutive and induced interleukin-8 production was unchanged. GS-NO-treated psoriatic skin showed reduction of IP-10, RANTES, and MCP-1, but not interleukin-8 expression by keratinocytes. Moreover, the number of CD14(+) and CD3(+) cells infiltrating the epidermis and papillary dermis diminished significantly. NO donors also down-regulated ICAM-1 protein expression without affecting mRNA accumulation in vitro, and suppressed keratinocyte ICAM-1 in vivo. Finally, NO donors inhibited nuclear factor-kappa B and STAT-1, but not AP-1 activities in transiently transfected keratinocytes. These results define NO donors as negative regulators of chemokine production by keratinocytes.