Suppressive effect of topically applied CX-659S, a novel diaminouracil derivative, on the contact hypersensitivity reaction in various animal models

Scratching behavior does not necessarily correlate with epidermal nerve fiber sprouting or inflammatory cell infiltration

BACKGROUND

Increased sprouting of epidermal nerve fibers of lesional skin are thought to be associated with persistent pruritus in chronic inflammatory dermatitis such as atopic dermatitis as supported by a murine study using tacrolimus (or FK506: FK) which was shown to inhibit both epidermal sprouting of nerves and scratching behavior or by immunohistochemical observations of lesional skin in the patients with atopic dermatitis or prurigo, etc.

OBJECTIVES

To examine a mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1/2 (MEK1/2) inhibitor (CX-659S: CX) for a possible anti-pruritic property in vivo since some MEK1/2 inhibitors have been reported to inhibit neurite growth in vitro.

METHODS

CX, FK and corticosteroids (betamethasone valerate: BV) were topically applied on inflamed skin in a mouse model of chronic dermatitis using repetitive hapten painting to examine anti-pruritic property and anti-inflammatory effects. Scratching behaviors were assessed using MicroAct automatic measuring system, and epidermal sprouting of nerves and skin inflammation was assessed histologically.

RESULTS

FK significantly decrease scratching behavior, but CX and BV failed to do so despite of their ability to significantly inhibit epidermal nerve fiber sprouting and skin inflammation, respectively. In addition, CX+BV mixture synergistically inhibited epidermal nerve fiber sprouting and skin inflammation even more potently than FK without decreasing scratching behavior.

CONCLUSIONS

These findings suggest that the scratching behavior does not necessarily correlate with epidermal nerve fiber sprouting or inflammatory cell infiltration.

Use of contact hypersensitivity in immunotoxicity testing

The histopathological examination of lymphoid organs together with a T-dependent antibody (TDAR) assay are the primary components of preclinical immunotoxicity assessment. Additional testing including measurement of cellular immunity may be considered. Besides ex vivo lymphocyte proliferation assays, either delayed or contact hypersensitivity models can be used. Contact hypersensitivity testing is typically performed either in mice or in guinea pigs and is directly derived from classical models used for the detection of contact sensitizing chemicals. Whatever the selected model, it is comprised of a sensitizing phase where the animals are applied a strong contact sensitizer topically, then a rest phase, and finally an eliciting phase where sensitized animals are challenged topically with the same contact sensitizer.In mice, the ear-swelling test is the reference procedure in which mice are sensitized to the ear or shaved abdominal skin and then challenged on the ear. Ear swelling usually measured from ear thickness reflects a cell-mediated immune response. In guinea pigs, a strong sensitizer is applied on the shaved skin of the abdomen or the interscapular area. The sensitized animals are challenged on another area of the shaved abdomen, and the cell-mediated response is assessed semiquantitatively from the magnitude of induced erythema inconsistently associated with edema. Treatment or exposure with immunosuppressive chemicals can result in a significantly decreased ear swelling or skin reaction. Contact hypersensitivity models are seldom used nowadays in preclinical immunotoxicity testing, most likely because of the lack of standardization and extensive validation as well as their use being restricted to mice or guinea pigs.

[Recent development of new drugs for the treatment of allergic diseases]

Due to the prevalence of allergic diseases such as bronchial asthma, allergic rhinoconjunctivitis and dermallergosis, efforts at the discovery of novel and effective medications for prevention and treatment of these conditions have been reinforced. Recently, it has been recognized that these allergic diseases are a chronic inflammatory disorder of the lower and upper airways and skin. In this article, we reviewed the recent development of the following new antiallergic therapies: anti-Th2 cytokine antibodies, decoy receptors, receptor antibodies, anti-IgE antibodies, anti-cell adhesion molecules antibodies, antisense oligonucleotides, keratinocyte modulators, inhibitors of phosphodiesterase 4, tachykinin receptor antagonists, and anti-histaminic drugs. Most of these new agents are aimed to inhibit various components of allergic inflammation. The future use of allergic disease therapies hold great promise and excitement.

Structure and activity relationships of novel uracil derivatives as topical anti-inflammatory agents

In order to create novel, topical anti-inflammatory compounds exhibiting more potent activities than lead compound CX-659S (1), we designed and synthesized various derivatives of 1 focusing on the uracil N(1)- and N(3)-substituents, and evaluated their anti-inflammatory activities via inhibition of the picryl chloride-induced contact hypersensitivity reaction (CHR) in mice. In the course of our structure and activity relationship study, we found that compounds 6k, 6q, and 6r inhibited by approximately 50% the CHR, at 0.1 mg/ear. These activities were essentially equipotent with that of Tacrolimus, a strong immunosuppressant.

CX-659S, a diaminouracil derivative, indirectly inhibits the function of Langerhans cells by blocking the MEK1/2-Erk1/2 pathway in keratinocytes

Keratinocytes are an important component of the skin immune system, and keratinocyte-derived cytokines control the function of Langerhans cells. We previously showed that CX-659S, a novel diaminouracil derivative, had an inhibitory effect on hapten-induced contact hypersensitivity reaction in mice. In this study, we investigated the mechanism by which CX-659S elicits its inhibitory effect. CX-659S inhibited the expressions of CD80 and CD86, but not that of CD54, on Langerhans cells in epidermal cell suspensions. Exogenous granulocyte-macrophage colony-stimulating factor restored the CX-659S-induced inhibition of CD80 and CD86 expressions of Langerhans cells. The production of interleukin-2 from allogeneic T cells was also inhibited when the cells were stimulated with CX-659S-treated epidermal cells, and this inhibition was suppressed by the addition of granulocyte-macrophage colony-stimulating factor during CX-659S treatment. As CX-659S significantly inhibited production of granulocyte-macrophage colony-stimulating factor from keratinocytes, CX-659S was thought to indirectly affect Langerhans cells by inhibiting the function of keratinocytes. These effects of CX-659S were preceded by blockade of the phosphorylation of extracellular-signal-regulated kinase 1/2 and their direct activators, mitogen-activated protein kinase/extracellular-signal-regulated kinase 1/2 (MEK1/2), but not p38 mitogen-activated protein kinase or inhibitory nuclear factor kappaBalpha, in keratinocytes. Furthermore, a specific MEK1/2 inhibitor, U0126, mimicked the effect of CX-659S. CX-659S, a keratinocyte-response modifier, would be an effective therapeutic compound to inhibit contact hypersensitivity reaction, its action mechanism being different from those of other immunosuppressive agents such as glucocorticosteroids or cyclosporine A.

Inhibitory activity of CX-659S, a novel diaminouracil derivative, against the rebound phenomenon following withdrawal of corticosteroid therapy for chronic contact hypersensitivity responses

BACKGROUND

CX-659S, a newly discovered anti-inflammatory compound, exerts inhibitory effects on chronic contact hypersensitivity responses (CHRs) induced by repeated application with picryl chloride (PC), which is known to mimic many, if not all, events occurring within lesional skin of patients with atopic dermatitis (AD). CX-659S suppresses the expression of mRNA for interleukin (IL)-4 and IL-10 but not that for IFN-gamma, and inhibits serum IgE production in a chronic CHR model. Although topical corticosteroids have been widely utilized in steroid-responsive dermatoses such as AD, their chronic use may be associated with significant side effects. In addition, a rebound phenomenon often occurs after discontinuation of prolonged use of topical corticosteroids, with enhanced production of IgE and Th2 cell cytokines. The purpose of this study was to assess whether CX- 659S inhibits the rebound phenomenon after discontinuation of chronic treatment with prednisolone in a chronic CHR model in mice.

METHODS

The efficacy of CX-659S as a sequential therapeutic agent after discontinuation of chronic treatment with prednisolone was tested on PC-treated ears of BALB/c mice with chronic CHR. Effects were quantified by measurements of ear thickness, serum IgE and cytokine mRNA expression.

RESULTS

The rebound phenomenon was confirmed after discontinuation of chronic treatment with prednisolone in chronic CHR in mice, i.e. by evidence of flare thickening of the ear, enhanced expression of mRNA for IL-4 and IL-10 and increased serum IgE. Sequentially applied CX-659S suppressed these rebound phenomena with a good cosmetic result.

CONCLUSIONS

CX-659S is the first promising compound with inhibitory activity on the rebound phenomenon following withdrawal of corticosteroid therapy without immunosuppression.

A resorcylic acid lactone, 5Z-7-oxozeaenol, prevents inflammation by inhibiting the catalytic activity of TAK1 MAPK kinase kinase

TAK1, a member of the mitogen-activated kinase kinase kinase (MAPKKK) family, participates in proinflammatory cellular signaling pathways by activating JNK/p38 MAPKs and NF-kappaB. To identify drugs that prevent inflammation, we screened inhibitors of TAK1 catalytic activity. We identified a natural resorcylic lactone of fungal origin, 5Z-7-oxozeaenol, as a highly potent inhibitor of TAK1. This compound did not effectively inhibit the catalytic activities of the MEKK1 or ASK1 MAPKKKs, suggesting that 5Z-7-oxozeaenol is a selective inhibitor of TAK1. In cell culture, 5Z-7-oxozeaenol blocked interleukin-1-induced activation of TAK1, JNK/p38 MAPK, IkappaB kinases, and NF-kappaB, resulting in inhibition of cyclooxgenase-2 production. Furthermore, in vivo 5Z-7-oxozeaenol was able to inhibit picryl chloride-induced ear swelling. Thus, 5Z-7-oxozeaenol blocks proinflammatory signaling by selectively inhibiting TAK1 MAPKKK.

Inhibitory activities of novel pyrimidine derivatives on the contact hypersensitivity reaction

In order to obtain novel topically applied anti-inflammatory compounds containing an inexpensive anti-oxidative moiety without chirality, we synthesized compound 2c derivatives having a di-tert-butylphenol moiety, and evaluated by topical administration their anti-inflammatory potentials on picryl chloride-(PC) induced contact hypersensitivity reaction (CHR) in mice. In the course of our structure-activity relationship (SAR) studies on the pyrimidine or the anti-oxidative moiety and the linker between them, the most potent compounds (10, 11) were obtained by the insertion of a C2 unit in compound 2c. The potencies of these compounds were 2-fold greater than that of 1. Compounds 10 and 11 were considered to be useful lead compounds having inexpensive anti-oxidative moieties without chirality.

The combined effect of topical CX-659S, a novel diaminouracil derivative, with topical corticosteroid on the three types of allergic responses in mice or guinea pigs

CX-659S ((S)-6-amino-5-(6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxamido)-3-methyl-1-phenyl-2,4(1H,3H)-pyrimidinedione), a newly discovered anti-inflammatory compound, exerts inhibitory effects against picryl chloride-, oxazolone-, and dinitrochlorobenzene-induced acute contact hypersensitivity responses (CHRs) characterized by Th1-type reactions. Furthermore, this compound suppressed chronic CHRs characterized by Th2-type reactions, which is well known to mimic many, if not all, events occurring within the lesional skin of patients with atopic dermatitis (AD). The present study was conducted to determine the combined effect of topical CX-659S with topical corticosteroid on immediate type (ITR), late type (LTR), and delayed type hypersensitivity (DTHR) allergic reactions that are involved in AD. An ineffective dose of CX-659S (0.03 mg/ear) combined with betamethasone valerate (BV) significantly potentiated inhibitory activity of BV alone (0.1 micro g/ear and 0.3Shizuokag/ear) on both the ITR and the LTR in mice with the ovalbumin (OVA)-induced biphasic cutaneous reaction. Furthermore, the combined effect of CX-659S with BV was also observed on dinitrochlorobenzene (DNCB)-induced DTHR in guinea pigs. These results indicate that CX-659S has a combined effect with corticosteroids on every ITR, LTR, and DTHR. Proper treatment with corticosteroids for a safe and effective treatment of AD is needed. Thus, the combination therapy of topical CX-659S with topical corticosteroid would be one of the potential approaches for devising a proper treatment with corticosteroids.

Synthesis and activity of a metabolite of (S)-6-amino-5-(6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxamido)-3-methyl-1-phenyl-2,4-(1H,3H)-pyrimidinedione (CX-659S)

CX-659S (1) [(S)-6-amino-5-(6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxamido)-3-methyl-1-phenyl-2,4-(1H,3H)-pyrimidinedione], has been developed as a new type anti-inflammatory agent for the treatment of dermatitis. The structure of a major metabolite of CX-659S was determined as (S)-6-amino-5-[2-hydroxy-2-methyl-4-(2,4,5-trimethyl-3,6-dioxo-1,4-cyclohexadienyl)butanamide]-3-methyl-1-phenyl-2,4-(1H,3H)-pyrimidinedione (2) by direct comparison with the synthesized authentic compound. The anti-inflammatory activity of 2 was equipotent with that of 1 on the contact hypersensitivity reaction (CHR) induced by picryl chloride (PC) in mice, suggesting that compound 2 contributes, at least in part, to the anti-inflammatory activity of CX-659S.

Protective and curative effects of topically applied CX-659S, a novel diaminouracil derivative, on chronic picryl chloride-induced contact hypersensitivity responses

BACKGROUND

CX-659S, a newly discovered anti-inflammatory compound, exerts inhibitory effects against acute contact hypersensitivity responses (CHRs) induced by picryl chloride (PC), oxazolone and dinitrochlorobenzene. The murine model of chronic CHR induced by repeated application of PC is known to mimic many, if not all, events occurring within the lesional skin of patients with atopic dermatitis (AD).

OBJECTIVES

To investigate the ability of CX-659S to inhibit PC-induced chronic CHR in mice.

METHODS

The protective and curative effects of CX-659S were tested on PC-treated ears of BALB/c mice, and were compared with those of prednisolone. Effects were quantified by measurements of ear thickness, serum IgE and cytokine mRNA expression.

RESULTS

Both protectively applied and curatively applied CX-659S significantly inhibited increases in ear thickness and total serum IgE. Inhibition was dose-dependent. Although protectively applied prednisolone showed similar activities to CX-659S against chronic CHR, curatively applied prednisolone did not affect the serum IgE level despite inhibiting increases in ear thickness and inflammatory cell infiltration. Consistent with these results, CX-659S reduced mRNA expression of interleukin (IL)-4 and IL-10 but not of interferon (IFN)-gamma, whereas prednisolone inhibited not only mRNA expression of IL-4 and IL-10 but also that of IFN-gamma in the ear lesion. In contrast to prednisolone, CX-659S did not show any side-effect such as atrophy, alopecia or telangiectasia.

CONCLUSIONS

CX-659S is the first promising compound having inhibitory activities against chronic CHR accompanied by a diminishing effect on elevated serum IgE, without any other side-effect. Therefore, CX-659S may be a promising candidate for management of patients with recurring AD who require long-term therapy.

CX-659S: a novel diaminouracil derivative that has antioxidative and acute anti-inflammatory activities

We investigated the antioxidative activities and the effects on acute inflammation in mice of a novel diaminouracil derivative, CX-659S ((S)-6-amino-5-(6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxamido)-3-methyl-1-phenyl-2,4(1H,3H)-pyrimidinedione). CX-659S showed potent scavenging activities against the hydroxyl radical and peroxynitrite and inhibited lipid peroxidation in rat brain homogenates in vitro. Topically applied CX-659S dose-dependently inhibited arachidonic acid- and 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ear edema in mice. Consistent with its antioxidative properties in vitro, CX-659S dramatically attenuated the accumulation of lipid peroxides in the mouse ear elicited by repeated application of TPA. Previously, we reported the effectiveness of CX-659S against contact hypersensitivity reactions in both mouse and guinea pig models. These present results further suggest the therapeutic potential of CX-659S for acute skin inflammation that may involve oxidative tissue damage.