Model Of Allergic Contact Dermatitis Research Articles

Effects of cilomilast on dendritic cell function in contact sensitivity and dendritic cell migration through skin

The phosphodiesterase 4 inhibitor cilomilast demonstrated strong inhibitory effects in a model of allergic contact dermatitis. In this study, we examined whether this inhibitory effect is at least partly due to modulation of dendritic cell function. Bone marrow-derived dendritic cells were pulsed with the sensitizer toluene-2,4-diisocyanate and administered subcutaneously to nonsensitized mice. Five days later, the mice were challenged with a low dose of toluene-2,4-diisocyanate onto the ears. In contrast to sham-treated mice, mice obtaining toluene-2,4-diisocyanate pulsed dendritic cells showed a significant increase in ear swelling. This swelling was not influenced when the dendritic cells were pre-incubated with cilomilast. When cilomilast was administered systemically simultaneously to the application of toluene-2,4-diisocyanate pulsed cells, there was an impaired allergic reaction provoked 5 days later. Additionally, a topical treatment with cilomilast resulted in a significant inhibition of skin dendritic cell migration. These results indicate that the antigen-presenting function of dendritic cells is not influenced by cilomilast but the dendritic cell T cell interaction and dendritic cell migration is modulated.

Afferent and Efferent Phases of Allergic Contact Dermatitis (ACD) Can Be Induced After a Single Skin Contact with Haptens: Evidence Using a Mouse Model of Primary ACD

Allergic contact dermatitis is a T cell-mediated delayed type hypersensitivity reaction that occurs upon hapten challenge in sensitized individuals. The inflammatory response in classical allergic contact dermatitis requires both a sensitization phase and an elicitation phase responsible for the recruitment and activation of specific T cells at the site of hapten skin challenge. Conversely, previously unsensitized patients may develop a "primary allergic contact dermatitis" after the first skin contact with potent contact sensitizers leading to a skin inflammation with all the features of classical allergic contact dermatitis. In this study we used an experimental murine model, referred to as contact hypersensitivity, to study the pathophysiology of primary allergic contact dermatitis and its relationship to classical allergic contact dermatitis. We show that one epicutaneous application of a nonirritant dose of hapten (2,4-dini-trofluorobenzene, fluorescein isothiocyanate) was sufficient to induce an optimal allergic contact dermatitis reaction at the site of primary contact with the hapten without subsequent challenge. As in classical allergic contact dermatitis, the skin inflammation in primary allergic contact dermatitis was mediated by interferon-gamma producing, CD8+ effector T cells that were induced in the draining lymph nodes at day 5 postsensitization and downregulated by CD4+ T cells. Reverse transcription-polymerase chain reaction analysis revealed that the primary allergic contact dermatitis reaction was mediated by a recruitment of CD8+ T cells at the sensitization skin site at day 6 postsensitization. Analysis of the fate of the hapten fluorescein isothiocyanate applied once on the skin revealed its persistence in the epidermis for up to 14 d after skin painting. These results suggest that the development of primary allergic contact dermatitis (i.e., without secondary challenge) is associated with persistence of the hapten in the skin, which allows the recruitment and activation of CD8+ T cells at the site of the single hapten application.

Liver X Receptor Activators Display Anti-Inflammatory Activity in Irritant and Allergic Contact Dermatitis Models: Liver-X-Receptor-Specific Inhibition of Inflammation and Primary Cytokine Production

Activators of liver X receptors (LXR) stimulate epidermal differentiation and development, but inhibit keratinocyte proliferation. In this study, the anti-inflammatory effects of two oxysterols, 22(R)-hydroxy-cholesterol (22ROH) and 25-hydroxycholesterol (25OH), and a nonsterol activator of LXR, GW3965, were examined utilizing models of irritant and allergic contact dermatitis. Irritant dermatitis was induced by applying phorbol 12-myristate-13-acetate (TPA) to the surface of the ears of CD1 mice, followed by treatment with 22ROH, 25OH, GW3965, or vehicle alone. Whereas TPA treatment alone induced an approximately 2-fold increase in ear weight and thickness, 22ROH, 25OH, or GW3965 markedly suppressed the increase (greater than 50% decrease), and to an extent comparable to that observed with 0.05% clobetasol treatment. Histology also revealed a marked decrease in TPA-induced cutaneous inflammation in oxysterol-treated animals. As topical treatment with cholesterol did not reduce the TPA-induced inflammation, and the nonsterol LXR activator (GW3965) inhibited inflammation, the anti-inflammatory effects of oxysterols cannot be ascribed to a nonspecific sterol effect. In addition, 22ROH did not reduce inflammation in LXRbeta-/- or LXRalphabeta-/- animals, indicating that LXRbeta is required for this anti-inflammatory effect. 22ROH also caused a partial reduction in ear thickness in LXRalpha-/- animals, however (approximately 50% of that observed in wild-type mice), suggesting that this receptor also mediates the anti-inflammatory effects of oxysterols. Both ear thickness and weight increased (approximately 1.5-fold) in the oxazolone-induced allergic dermatitis model, and 22ROH and GW3965 reduced inflammation by approximately 50% and approximately 30%, respectively. Finally, immunohistochemistry demonstrated an inhibition in the production of the pro-inflammatory cytokines interleukin-1alpha and tumor necrosis factor alpha in the oxysterol-treated sites from both TPA- and oxazolone-treated animals. These studies demonstrate that activators of LXR display potent anti-inflammatory activity in both irritant and allergic contact models of dermatitis, requiring the participation of both LXRalpha and LXRbeta. LXR activators could provide a new class of therapeutic agents for the treatment of cutaneous inflammatory disorders.

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Beyond our pages

Topical Peroxisome Proliferator Activated Receptor-α Activators Reduce Inflammation in Irritant and Allergic Contact Dermatitis Models

Activators of peroxisome proliferator activated receptor-alpha, a nuclear hormone receptor that heterodimerizes with retinoid X receptor, stimulate epidermal differentiation and inhibit proliferation. Here we determined the anti-inflammatory effects of peroxisome proliferator activated receptor-alpha agonists in models of irritant and allergic contact dermatitis produced in mouse ears by topical treatment with 12-O-tetradecanoylphorbol-13-acetate and oxazalone, respectively. As expected, 12-O-tetradecanoylphorbol-13-acetate treatment resulted in a marked increase in the thickness and weight of the ears and provoked an inflammatory cell infiltrate in the dermis. Topical treatment with three different peroxisome proliferator activated receptor-alpha agonists, clofibrate, WY 14643, or linoleic acid, 45 min and 4 h after 12-O-tetradecanoylphorbol-13-acetate application, resulted in a marked decrease in ear thickness and weight and a reduction in the number of inflammatory cells in the dermis. The reduction in inflammation by these peroxisome proliferator activated receptor-alpha agonists was of similar magnitude to that seen with a potent topical glucocorticoid, clobetasol. In contrast, stearic acid, a free fatty acid that does not activate peroxisome proliferator activated receptor-alpha, had no effect on the 12-O-tetradecanoylphorbol-13-acetate-induced inflammation. Moreover, clofibrate did not significantly alter ear thickness following 12-O-tetradecanoylphorbol-13-acetate treatment in peroxisome proliferator activated receptor-alpha-/- mice, indicating that the anti-inflammatory effect is mediated by peroxisome proliferator activated receptor-alpha. As tumor necrosis factor-alpha and interleukin-1alpha are major mediators of cutaneous inflammation we next used immunohistochemistry to determine whether the peroxisome proliferator activated receptor-alpha agonists reduce the levels of these cytokines in 12-O-tetradecanoylphorbol-13-acetate-treated skin. 12-O-tetradecanoylphorbol-13-acetate treatment resulted in an increase in tumor necrosis factor and interleukin-1alpha staining in the epidermis that was reduced by clofibrate treatment. Finally, clofibrate treatment also reduced ear thickness and weight in oxazalone-induced allergic dermatitis, a change that was accompanied by a reduction in inflammatory cells in the dermis and a decrease in tumor necrosis factor-alpha and interleukin-1alpha levels in the oxazalone-treated epidermis. These studies demonstrate that topically applied peroxisome proliferator activated receptor-alpha agonists possess receptor mediated, anti-inflammatory activity in both irritant and allergic contact dermatitis animal models. The anti-inflammatory properties of peroxisome proliferator activated receptor-alpha agonists, coupled with their anti-proliferative and pro-differentiating effects, suggest that they could be beneficial for the treatment of a variety of cutaneous diseases.

Pimecrolimus (Elidel, SDZ ASM 981)--preclinical pharmacologic profile and skin selectivity.

The ascomycin macrolactam derivative pimecrolimus (Elidel, SDZ ASM 981; Novartis Pharma AG, Basel Switzerland) is a cell-selective inhibitor of inflammatory cytokines specifically developed for the treatment of inflammatory skin diseases, such as atopic dermatitis, allergic contact dermatitis, irritant contact dermatitis, and plaque-type psoriasis. It inhibits the production of inflammatory cytokines in T cells and mast cells and prevents the release of preformed inflammatory mediators from mast cells. Topically administered pimecrolimus is as effective as the high-potency corticosteroid clobetasol-17-propionate in a pig model of allergic contact dermatitis (ACD). Unlike clobetasol, however, it does not cause skin atrophy. Given orally, pimecrolimus is as potent or superior to tacrolimus (FK 506) in treating ACD in mice and rats. Pimecrolimus also effectively reduces skin inflammation and pruritus in hypomagnesemic hairless rats, a model that mimics acute signs of atopic dermatitis. Pimecrolimus shows only a low potential to impair systemic immune responses when compared with tacrolimus as shown in rats in (1) the localized graft-versus-host reaction, (2) the antibody formation to sheep red blood cells, and (3) kidney transplantation. Pimecrolimus permeates through pig skin in vitro at a 10-times lower rate than tacrolimus, indicating a lower potential for percutaneous absorption in vivo. The data suggest that pimecrolimus combines high anti-inflammatory activity in the skin with a low potential to impair systemic immune reactions.

Anti-inflammatory planar chiral [2.2]paracyclophaneacetic acid enantiomers.

To elucidate if the planar chiral paracyclophane moiety conveys pharmacological activity to arylacetic acid analogs in two animal models. Female NMRI mice (6 mice/group); female Wistar rats (8 rats/group); thrombocytes from human blood. The enantiomers of [2.2]paracyclophaneacetic acid were applied locally (10(-7) and 10(-6) mol/ear) and orally (10-100 mg/kg). (a) Phorbol myristyl acetate model of acute inflammation of the inner auricle. (b) Oxazolone model of allergic contact dermatitis. (c) Carrageenan model of acute inflammation. (d) Inhibition of cyclooxygenase-1 and 12-lipoxygenase (in vitro). (a) PMA model: pR-(-)-[2.2]paracyclophaneacetic acid (10(-6) mmol/ear): 58% inhibition after 24 h (p < 0.05). (b) Oxazolone model: pR-(-)-[2.2]paracyclophaneacetic acid (10(-6) mmol/ear): 42% inhibition after 24 h (p < 0.05). (c) Carrageenan model: pR-(-)-[2.2]paracyclophaneacetic acid (10 mg/kg): 31.4% inhibition (paw volume 0.48 +/- 0.13 ml). (d) Cyclooxygenase-1 and 12-lipoxygenase: no inhibition at concentrations up to 10 microM. The easily accessible [2.2]paracyclophane moiety should find its use in medicinal chemistry as it is a pharmacophoric substituent with the interesting feature of planar chirality.

Chemical carcinogenicity: can it be predicted from knowledge of mutagenicity and allergic contact dermatitis?

We investigated the suggestion [R.E. Albert, Environ. Health Perspect. 105 (1997) 940–948.] that results of mutagenicity testing in Salmonella combined with allergic contact dermatitis (ACD) testing in humans would be predictive of carcinogenicity in rodents. Using the cancer bioassay results of the US National Toxicology Program (NTP), Salmonella mutagenicity tests and a highly predictive structure–activity relational model of ACD, we conclude that the combination is not more predictive than the results of the Salmonella mutagenicity assay alone.

A novel anti-inflammatory drug, SDZ ASM 981, for the treatment of skin diseases: in vitro pharmacology.

SDZ ASM 981, a novel ascomycin macrolactam derivative, has high anti-inflammatory activity in animal models of allergic contact dermatitis and shows clinical efficacy in atopic dermatitis, allergic contact dermatitis and psoriasis, after topical application. Here we report on the in vitro activities of this promising new drug. SDZ ASM 981 inhibits the proliferation of human T cells after antigen-specific or non-specific stimulation. It downregulates the production of Th1 [interleukin (IL)-2, interferon-gamma] and Th2 (IL-4, IL-10) type cytokines after antigen-specific stimulation of a human T-helper cell clone isolated from the skin of an atopic dermatitis patient. SDZ ASM 981 inhibits the phorbol myristate acetate/phytohaemagglutinin-stimulated transcription of a reporter gene coupled to the human IL-2 promoter in the human T-cell line Jurkat and the IgE/antigen-mediated transcription of a reporter gene coupled to the human tumour necrosis factor (TNF)-alpha promoter in the murine mast-cell line CPII. It does not, however, affect the human TNF-alpha promoter controlled transcription of a reporter gene in a murine dendritic cell line (DC18 RGA) after stimulation via the FcgammaRIII receptor. SDZ ASM 981 also prevents the release of preformed pro-inflammatory mediators from mast cells, as shown in the murine cell line CPII after stimulation with IgE/antigen. In summary, these results demonstrate that SDZ ASM 981 is a specific inhibitor of the production of pro-inflammatory cytokines from T cells and mast cells in vitro.

Relationship between allergic contact dermatitis and electrophilicity.

To evaluate the role of electrophilicity in the induction of allergic contact dermatitis (ACD) in humans, we compared the structure-activity relationship (SAR) model of ACD with those of electrophilic and nonelectrophilic subsets of chemicals in the ACD database. For these analyses, electrophilicity was defined as the potential of a chemical to induce mutations in Salmonella. It was found that electrophilicity accounted for approximately 30-40% of ACD-inducing ability, and the remainder was associated with nonelectrophilic structures. The identification of these moieties opens the possibility for studying their role in ACD.

Ascomycins in dermatology.

Ascomycin derivatives represent a novel class of anti-inflammatory macrolactams that are under development for the treatment of skin diseases. The main biological effect of ascomycins is a blockage of the synthesis of both Th1- and Th2-type cytokines in target cells. SDZ ASM 981 is the most advanced ascomycin derivative under development. It has high antiinflammatory activity in animal models of allergic contact dermatitis and does not induce skin atrophy. Topical application of SDZ ASM 981 has been shown to be effective in atopic dermatitis (AD) and allergic contact dermatitis. Clinical studies using semi-occlusive conditions have also shown effectiveness in psoriasis. SDZ ASM 981 holds promise in overcoming the drawbacks of topical corticosteroids and studies are ongoing to further investigate its efficacy and safety in the treatment of inflammatory skin diseases.

A novel anti-inflammatory drug, SDZ ASM 981, for the topical and oral treatment of skin diseases: in vivo pharmacology.

There is a need for safe and effective therapies for inflammatory skin diseases. Current topical and systemic treatment of psoriasis is effective but suffers from side-effects or is inconvenient. The therapeutic armamentarium for atopic dermatitis is very limited and far from satisfactory. In vivo preclinical data are presented for SDZ ASM 981, a novel ascomycin macrolactam derivative with high anti-inflammatory activity. Anti-inflammatory activity was observed in mouse, rat and pig models of allergic contact dermatitis. In the pig model, topical SDZ ASM 981 was as effective as the ultrapotent corticosteroid clobetasol-17-propionate, and when compared with a series of commercial topical corticosteroid preparations, 0.1% SDZ ASM 981 had equivalent efficacy to clobetasol-17-propionate (0.05%), the most potent product on the market. Unlike the corticosteroid, however, SDZ ASM 981 did not cause skin atrophy in pigs. SDZ ASM 981 potently inhibited allergic contact dermatitis in mice and rats when given systemically, and oral treatment was more effective than cyclosporin A in rats. Furthermore, SDZ ASM 981 has a low potential for affecting systemic immune responses, as demonstrated in rat models of localized graft vs. host reaction and allogeneic kidney transplantation. Preclinical results suggest that SDZ ASM 981 has the potential to be a well-tolerated and effective drug for topical as well as oral treatment of inflammatory skin diseases.

A murine in vitro model of allergic contact dermatitis to sesquiterpene alpha-methylene-gamma-butyrolactones.

The use of a lymphocyte transformation test (LTT) to provide evidence of allergic contact dermatitis was investigated. The haptens studied were alantolactone and isoalantolactone, two moderate allergens from Inula helenium L., a decorative and medicinal plant. Only alantolactone showed a significant response in vivo and in vitro in mice sensitized epicutaneously, without using Freund's complete adjuvant. Isoalantolactone did not show any sensitizing capacity in the murine model studied. The comparison of in vitro lymphocyte proliferation and in vivo allergenic capacity showed a good correlation and clearly demonstrates that, of the two sesquiterpene lactones, alantolactone is the better sensitizer.

Anti-Inflammatory Effects of Macrophilin-lnteracting Drugs in Animal Models of Irritant and Allergic Contact Dermatitis.

The macrolide antibiotics, FK 506 and rapamycin, have been reported to be potent immunosuppressive drugs. Both FK506 and rapamycin bind to the immunophilin macrophilin-12. Rapamycin, however, acts on T cells by a different mode of action which does not affect the transcription of lymphokines. The anti-inflammatory effects of FK 506 and rapamycin have been tested in mouse models of irritant dermatitis after topical application, and in allergic contact dermatitis after topical or oral application, using mice and domestic pigs. In irritant dermatitis, both FK 506 and rapamycin exerted significant, but moderate topical activity at concentrations of 0.4-3.6%. In allergic contact dermatitis, topical FK 506 proved to be highly active at concentrations of 0.01-0.1% and even superior to corticosteroids. In contrast, rapamycin was inactive. After oral treatment of mice, FK506 was significantly active (2 × 30mg/kg/ day) while rapamycin was inactive up to the highest dose tested (2 × 90 mg/kg/ day). These results indicate that, despite the chemical similarity of FK 506 and rapamycin and their common intracellular receptor, there are different fundamental pharmacological properties of FK 506 and rapamycin, which may reflect their different modes of action.

Sensitizing capacity of three methyl alkanesulphonates: a murine in vivo and in vitro model of allergic contact dermatitis

A murine model for in vivo and in vitro studies of contact sensitization to methyl alkanesulphonate derivatives has been developed. Contact sensitivity was quantified in vivo by measuring the ear thickness increase, and the influence of the alkyl chain length (hexyl, dodecyl, hexadecyl) was investigated. Long chain methyl alkanesulphonates (dodecyl and hexadecyl) are strong sensitizers, while the shorter alkyl chain, methyl hexanesulphonate, is a weak sensitizer. In vitro lymphocyte blastogenesis was measured by the 3H-thymidine uptake and exhibited a stimulation index between 2 and 8. The results nicely parallelled the in vivo sensitization measurements, except for methyl dodecanesulphonate. This could be explained by the cytotoxic activity of this compound, the most toxic of the three methyl alkanesulphonates tested. Thus, murine sensitization to methyl alkanesulphonates provides a good model system for preliminary investigations of delayed type hypersensitivity mechanisms.

Local Murine Recombinant Gamma Interferon Enhances the Acquisition of Allergic Contact Dermatitis in the Mouse

Using the model of allergic contact dermatitis in mice, we have demonstrated that local administration of recombinant (r) murine gamma interferon (gamma-rIFN) to the sensitization site substantially enhances the acquisition of delayed-type hypersensitivity. Single doses of gamma-rIFN from 500 to 2,000 U immunopotentiate successfully, with a suggestion of a better response at the higher doses. The immunoadjuvant effect is lost when the injections of gamma-rIFN are at a site distant from the sensitization site. Kinetic studies imply that gamma-rIFN is most effective when given at the time of sensitization, but significant immunopotentiation can be seen when gamma-rIFN is given several days before or after sensitization.

Cyclosporine and Murine Allergic Contact Dermatitis

Cyclosporine is a new antilymphocytic, immunosuppressive agent currently being used primarily in experimental and human organ transplantation. The current study evaluated the effect of systemically administered cyclosporine on a cutaneous T-cell-mediated disorder by using the murine model of allergic contact dermatitis to dinitrofluorobenzene. Cyclosporine was found to significantly inhibit the ear swelling response, whether the drug was given during the early sensitization period or at the time of antigenic challenge to fully sensitized mice. This suppressive effect was reversible when mice were rechallenged with dinitrofluorobenzene 96 hours after the first challenge. Cyclosporine was not effective if given to sensitized animals as late as six hours after challenge. Lastly, the observed inhibition of the ear swelling response to cyclosporine closely paralleled a diminished degree of inflammation seen histopathologically.