Blockade of costimulatory molecules B7-1 (CD80) and B7-2 (CD86) down-regulates induction of contact sensitivity by haptenated epidermal cells

Black Raspberries and Protocatechuic Acid Mitigate DNFB-Induced Contact Hypersensitivity by Down-Regulating Dendritic Cell Activation and Inhibiting Mediators of Effector Responses

Contact hypersensitivity (CHS) is the most common occupational dermatological disease. Dendritic cells (DCs) mediate the sensitization stage of CHS, while T-cells facilitate the effector mechanisms that drive CHS. Black raspberry (Rubus occidentalis, BRB) and BRB phytochemicals possess immunomodulatory properties, but their dietary effects on CHS are unknown. We examined the effects of diets containing BRB and protocatechuic acid (PCA, a constituent of BRB and an anthocyanin metabolite produced largely by gut microbes), on CHS, using a model induced by 2,4-dinitrofluorobenze (DNFB). Mice were fed control diet or diets supplemented with BRB or PCA. In vitro bone-marrow derived DCs and RAW264.7 macrophages were treated with BRB extract and PCA. Mice fed BRB or PCA supplemented diets displayed decreased DNFB-induced ear swelling, marked by decreased splenic DC accumulation. BRB extract diminished DC maturation associated with reduced Cd80 expression and Interleukin (IL)-12 secretion, and PCA reduced IL-12. Dietary supplementation with BRB and PCA induced differential decreases in IL-12-driven CHS mediators, including Interferon (IFN)-γ and IL-17 production by T-cells. BRB extracts and PCA directly attenuated CHS-promoting macrophage activity mediated by nitric oxide and IL-12. Our results demonstrate that BRB and PCA mitigate CHS pathology, providing a rationale for CHS alleviation via dietary supplementation with BRB or BRB derived anthocyanins.

A nucleic acid-based medication for allergic skin diseases

Among allergic skin diseases, atopic dermatitis is the most difficult to cure. In the majority of patients, atopic dermatitis can be easily controlled by treatment based on three therapeutic approaches: avoidance of precipitating factors, skin care, and medication. In some adult patients, however, severe atopic dermatitis is refractory to treatment, and no fundamental effective treatment modality has yet been established for such cases. Chronic contact dermatitis without an identified causative hapten is also considered an allergic skin disease that is difficult to cure. Topical nucleic acid-based medications are currently being applied clinically, and an ointment containing nuclear factor-κB decoy oligodeoxynucleotides (hereafter referred to as Decoy) has reached clinical trials. In addition, synthetic double-stranded DNA with high affinity for signal transducers and activators of transcription 6 (STAT6) introduced in vivo as a decoy cis element to bind the transcriptional factor and block the activated gene that contributes to the onset and progression of atopic dermatitis functions as an effective therapeutic agent. We also introduce another STAT1 decoy treatment, cytosine-phosphate-guanine-ODN or STAT6 small interfering RNA therapy, for allergic skin diseases.

Topical application of siRNA targeting cutaneous dendritic cells in allergic skin disease

RNA interference is a promising method for silencing specific genes and has great potential for therapeutic applications. However, the major hurdle for therapeutic application is the limited stability of double-strand RNA (dsRNA) and the absence of a reliable delivery method to target cells. Skin appears to be a favorable target for small interfering RNA (siRNA) therapy. Dendritic cells (DCs) exist in the skin and mucosae on the front lines of defense; these cells capture antigens and play a crucial role in inducing immunity and tolerance.In our recent work, we have shown a successful treatment using CD86 siRNA targeting cutaneous DCs. A costimulatory molecule, CD86, is induced on DCs in situ after antigen uptake, and CD86-expressing DCs migrate to the regional lymph nodes to present antigens to T cells. Topical application of cream-emulsified CD86 siRNA ameliorated the clinical manifestations in murine contact hypersensitivity (CH) and atopic dermatitis (AD)-like disease. Our method may be advantageous for the treatment of allergic skin diseases.

Characterization of the Sensitizing Potential of Chemicals by In Vitro Analysis of Dendritic Cell Activation and Skin Penetration

Development of in vitro models to identify sensitizing chemicals receives public interest since animal testing should be avoided whenever possible. In this article we analyze two essential properties of sensitizing chemicals: skin penetration and dendritic cell (DC) activation. Activation of immature DC derived from peripheral blood monocytes was evaluated by flow cytometric analysis of CD86 positive cells and quantitative measurement of interleukin-1beta and aquaporin P3 gene expression. The sensitizer 2,4,6-trinitrobenzenesulfonic acid induced a concentration-dependent response for all parameters, whereas the irritant sodium lauryl sulfate did not. When two related aromatic amines, p-toluylenediamine (PTD) and hydroxyethyl-p-phenylenediamine (HE-PPD) were tested, both induced substantial DC activation indicating their potential sensitizing properties. These findings contrasted with in vivo results: in murine local lymph node assays (LLNA) PTD, but not HE-PPD, was sensitizing using acetone/aqua/olive oil as vehicle. Skin penetration measurement revealed that this was due to bioavailability differences. On retesting HE-PPD in the LLNA using the penetration enhancer dimethylsulfoxide as vehicle, it induced a specific response. We conclude that in vitro analysis of DC activation capability of the two selected chemicals demonstrates that prediction of skin sensitization potential is possible provided that skin penetration data indicate sufficient bioavailability of the test compound.

Biological response modifiers and their potential use in the treatment of inflammatory skin diseases

In recent years, a more detailed understanding of the pathogenesis of several inflammatory skin diseases, combined with the developments within biotechnology, has made it possible to design more selective response modifiers. Biological response modifiers hold the potential for greater effectiveness and fewer side-effects than the current systemic therapies now used for severe psoriasis, contact dermatitis and atopic dermatitis. In the pathogenesis of inflammatory skin diseases, the immune system plays a pivotal role, and this is where biological response modifiers such as monoclonal antibodies, recombinant cytokines, or fusion proteins may be effective. Several biological response modifiers have already shown positive results in phase II/III clinical trials in skin diseases, and many new biological response modifiers are in progress.

IL-2-IgG2b fusion protein suppresses murine contact hypersensitivity in vivo

Interleukin-15 shares several functional properties with interleukin-2, and signals through the beta and gamma chain of the interleukin-2 receptor as well as through its own high affinity alpha chain. In agreement with the concept that interleukin-2 plays a key role in type IV immune responses, we have recently shown that an IL-2-IgG2b fusion protein potently suppresses Th1-type delayed type hypersensitivity reaction and Th2-type allergic sensitization in mice. We have now compared the in vivo effects of IL-2-IgG2b fusion protein with those of IL-15-IgG2b fusion protein in a murine model of Th1-type contact hypersensitivity reaction. Daily systemic injections of IL-2-IgG2b fusion protein during the sensitization phase or application of IL-2-IgG2b fusion protein just 2 h before and 10 h after antigen challenge significantly inhibited the contact hypersensitivity ear swelling response, and this without any overt signs of associated toxicity. Even local injection of IL-2-IgG2b fusion protein into the earlobe around the time of antigen challenge inhibited the ear swelling reaction significantly. In contrast, neither systemic nor local injection of the IL-15-IgG2b fusion protein modulated the contact hypersensitivity reaction significantly. IL-2-IgG2b but not IL-15-IgG2b fusion protein reduced migration of antigen-presenting cells from the skin to local lymph nodes, inhibited the expression of CD80 and CD86, and induced a significant higher number of CD4+CD25+ T cells. Therefore, the IL-2-IgGb fusion protein offers a powerful tool for suppressing and/or preventing T-cell-mediated hypersensitivity reaction in vivo.

Enhanced contact hypersensitivity in human monocyte chemoattractant protein-1 transgenic mouse

Monocyte chemoattractant protein (MCP)-1 is a chemotactic cytokine for monocytes, memoryT cells and dendritic cells (DC). However, the precise role of MCP-1 in a variety of immunological responses remains unclear. In the present study, we analyzed contact hypersensitivity (CHS) using human MCP-1 transgenic mice (hMCP-1Tgm) that constitutively produce high levels of hMCP-1 in the sera. Following 2,4-dinitrofluorobenzene (DNFB) sensitization, enhancement of CHS was demonstrated in Tgm as compared with that in non-Tgm. Anti-hMCP-1 antibodies significantly inhibited the CHS in Tgm. A prominent accumulation of B7-1+I-Ad+ Langerhans' cells (LC) bearing haptens was detected in draining lymph nodes (DLN) of Tgm 24 h after DNFB or fluorescein isothiocyanate (FITC) sensitization. Similar results were obtained with BALB/c mice administrated recombinant (r) hMCP-1. Langerhans' cells (LC) in the epidermal sheets of Tgm increased in size and expressed high levels of I-Ad and B7-1 12 h after FITC application compared with those of non-Tgm. After 18 h, the number of LC in the epidermis was reduced in Tgm. It was also shown that the B7-1 expression on LC of BALB/c mice was augmented after culture with rhMCP-1. These findings demonstrate that MCP-1 not only accelerates LC migration from epidermis into the DLN after sensitization with haptens but also up-regulates the I-Ad and B7-1 expressions, which results in the enhanced T cell activation and CHS.

Signal transducer and activator of transcription 6 is essential in the induction of contact hypersensitivity

Contact hypersensitivity (CHS) is thought to be mainly associated with the activation of T helper type 1 (Th1) cells. However, there is also evidence that Th2 cells or Th2 cytokines play a role in the development of CHS. To analyze the functional contribution of Th2 cytokines interleukin (IL)-4 and IL-13, signal transducer and activator of transcription 6 (STAT6)-deficient (STAT6(-/)-) and wild-type (wt) control C57BL/6 mice were contact sensitized with 5% 2,4,6-trinitrochlorobenzene (TNCB), 0.5% 2,4-dinitrofluorobenzene, or 5% 4-ethoxyl methylene-2-phenyl-2-oxazolin-5-one, and any skin reactions were examined. Ear swelling was significantly reduced with a delayed peak response in STAT6(-/)- mice compared with wt mice.A histological analysis revealed that the infiltration of both eosinophils and neutrophils in the skin challenged after 24 h in STAT6(-/)- mice decreased substantially compared with that in wt mice. The expression of Th2 cytokines (IL-4, IL-5) in TNCB-challenged skin tissues and the supernatants from T cells stimulated by 2,4,6-trinitrobenzene sulfonate-modified spleen cells, as well as the immunoglobulin (Ig)E and IgG1 response after challenge, were also profoundly reduced in STAT6(-/)- mice, whereas the expression of interferon gamma was the same in STAT6(-/)- and wt mice after challenge. Furthermore, adoptive transfer experiments revealed that STAT6(-/)- mice induced CHS after injection of lymph node cells obtained from sensitized wt mice. Our data suggest that the STAT6 signal plays a critical role in the induction phase of CHS.

Formation of antigenic quinolone photoadducts on Langerhans cells initiates photoallergy to systemically administered quinolone in mice

Quinolone antibacterial agents are well known to cause photoallergy as a side-effect. Murine photoallergy to fluoroquinolones is a T cell-mediated immune response, evoked either by systemic fluoroquinolone and subsequent exposure of skin to ultraviolet A light or by subcutaneous injection of fluoroquinolone-photomodified epidermal cells. In this photosensitivity, epidermal Langerhans cells may be photomodified initially with the drug and thus present photohaptenic moieties to sensitize and restimulate T cells. Although we have shown that Langerhans cells photocoupled in vitro with fluoroquinolones are capable of stimulating sensitized T cells, it remains unclear whether systemically given fluoroquinolone photomodifies Langerhans cells upon ultraviolet A irradiation of the skin and the Langerhans cells become photohapten-bearing, T cell-stimulatory cells. In a murine model of fleroxacin photoallergy induced by intraperitoneal injection of the drugs plus ultraviolet A irradiation of skin, we found that Langerhans cells as well as keratinocytes are photoderivatized with fleroxacin as demonstrated with a fluoroquinolone-specific monoclonal antibody. Langerhans-cell-enriched epidermal cells prepared from mice treated with fleroxacin and ultraviolet A induced proliferation of sensitized T cells, indicating that photomodified Langerhans cells are functional. There was an optimal range of ultraviolet A dose to quantitatively and qualitatively form fleroxacin-photomodified Langerhans cells, as excess ultraviolet A rather reduced the photoantigen-presenting capacity of Langerhans cells presumably because of drug phototoxicity. Our study suggests that Langerhans cells serve as photoantigen-presenting cells in drug photoallergy.

Quinolone photoallergy: photosensitivity dermatitis induced by systemic administration of photohaptenic drugs

Quinolone antibacterial agents are well known to elicit photosensitivity as a side effect. The photoallergenicity of fluoroquinolones, the representative quinolone derivatives, is mainly derived from their photohaptenic moiety. When epidermal cells are irradiated with ultraviolet A light in the presence of fluoroquinolones, quinolone photoadducts are formed in the treated cells. This photomodification is thought to be an initial step for sensitization and elicitation of this photoallergy, and quinolone-photoderivatized Langerhans cells are capable of stimulating immune T cells in mice. In the murine model, fluoroquinolone photoallergy is mediated by Th1 cells bearing T cell receptor Vbeta 13. There is a broad photoantigenic cross-reactivity among fluoroquinolones in recognition by T cells and immunoglobulins. Therefore, it is most likely that fluoroquinolones carry the same photoantigenic epitope, which is recognized by Vbetal3+ T cells, leading to fluoroquinolone photosensitivity and cross-reactivity.

Cross-Reactivity in Murine Fluoroquinolone Photoallergy: Exclusive Usage of TCR Vβ13 by Immune T Cells That Recognize Fluoroquinolone-Photomodified Cells

Fluoroquinolone antibacterial agents are well known to elicit photosensitivity as an adverse effect, and their cross-reactivity has been clinically documented. The photoallergenicity of fluoroquinolones is mainly derived from their photohaptenic moiety, and photomodification of skin epidermal cells with fluoroquinolones is thought to be an initial step for this photoallergy. Here we have explored, both in vivo and in vitro, T cell responses to fluoroquinolone-photomodified cells, focusing on their photoantigenic cross-reactivity. Cells were derivatized with fluoroquinolones under exposure to UV-A, and fluoroquinolone photoadducts were detected in photomodified cells by immunostaining, flow cytometry, and cell ELISA using fluoroquinolone-specific mAb. T cell-mediated hypersensitivity induced and elicited by s.c. injection of fluoroquinolone-photomodified epidermal cells was cross-reactive among six fluoroquinolones. In addition, lymph node cells from mice sensitized with fluoroquinolone-photomodified cells proliferated well in vitro not only to Langerhans cell-enriched epidermal cells photoderivatized with corresponding fluoroquinolone, but also to those photomodified with any of five other fluoroquinolones, supporting their cross-reactivity. In three fluoroquinolones tested, Th1 populations that expanded after in vitro photoantigenic stimulation of immune lymph node cells expressed the same Vβ13 of TCR. The sensitivity could be transferred by the i.v. administration of this Vβ13+ T cell line into naive recipients, in which a high percentage of Vβ13+ cells infiltrated at the challenge site. These findings suggest that these fluoroquinolones carry the same photoantigenic epitope, which is recognized by Vβ13+ T cells, leading to fluoroquinolone photosensitivity and cross-reactivity.