PGD2 plays roles in allergic inflammation via specific receptors, the PGD receptor designated DP and CRTH2 (chemoattractant receptor homologous molecule expressed on Th2 cells). We generated mutant mice carrying a targeted disruption of the CRTH2 gene to investigate the functional roles of CRTH2 in cutaneous inflammatory responses. CRTH2-deficent mice were fertile and grew normally. Ear-swelling responses induced by hapten-specific IgE were less pronounced in mutant mice, giving 35–55% of the responses of normal mice. Similar results were seen in mice treated with a hemopoietic PGD synthase inhibitor, HQL-79, or a CRTH2 antagonist, ramatroban. The reduction in cutaneous responses was associated with decreased infiltration of lymphocytes, eosinophils, and basophils and decreased production of macrophage-derived chemokine and RANTES at inflammatory sites. In models of chronic contact hypersensitivity induced by repeated hapten application, CRTH2 deficiency resulted in a reduction by approximately half of skin responses and low levels (63% of control) of serum IgE production, although in vivo migration of Langerhans cells and dendritic cells to regional lymph nodes was not impaired in CRTH2-deficient mice. In contrast, delayed-type hypersensitivity to SRBC and irritation dermatitis in mutant mice were the same as in wild-type mice. These findings indicate that the PGD2-CRTH2 system plays a significant role in chronic allergic skin inflammation. CRTH2 may represent a novel therapeutic target for treatment of human allergic disorders, including atopic dermatitis.

SUMMARYWe previously reported the establishment of a mouse model system of contact hypersensitivity (CHS) to paraphenylemediamine (PPD). In order to analyse the functional contribution of Th2 cytokines, IL-4 and IL-5, in PPD induced CHS, STAT6 deficient (STAT6 -/-) and wild-type control (WT) mice (C57BL/ 6) were immunized by the topical application of a PPD solution, and then the subsequent skin reactions were examined. Ear swelling was significantly reduced with a delayed peak response in STAT6 -/-mice as compared with that of WT mice. A histological analysis showed the infiltration of both eosinophils and neutrophils in the skin of STAT6 -/-mice challenged 24 h previously to significantly decrease in comparison with that in the WT mice. The expression of Th2 cytokines (IL-4, IL-5) by ELISA in the PPDchallenged skin tissue specimens as well as the IgE and IgG1 response after challenge were also profoundly reduced in the STAT6 -/-mice. The adoptive transfer of the serum obtained from sensitized WT mice for the putative IgE transfer induced a peak response at 3 h and 24 h after challenge. To further investigate the role of mast cells in the induction of PPD-CHS, mast cell deficient W/W v mice were sensitized with PPD and then were challenged. Maximal ear swelling was detected from 12 to 24 h and another small peak response was observed at 1 h in + / + mice, whereas only a small peak response at 24 h was detected in W/W v mice. These data indicate that not only Th2 cytokines and IgE but also mast cells play an essential role in the induction of PPD-CHS.

Signal transducers and activators of transcription 6 (STAT6) play a crucial role in the transactivation of IL-4 and IL-13, which might be involved in the pathogenesis of atopic dermatitis (AD). We herein reported that the IgE-mediated late-phase reaction significantly decreased in STAT6-deficient (STAT6 À/À ) mice in AD model mice induced by intravenous injection of monoclonal anti-dinitrophenyl (DNP)-IgE antibody and subsequent skin testing with dinitrofluorobenzene. We therefore hypothesized that synthetic double-stranded DNA with a high affinity for STAT6 could be introduced in vivo as decoy cis elements to bind the transcriptional factor and block the gene activation contributing to the onset and progression of AD, thus providing effective therapy for AD. Treatment by the transfection of STAT6 decoy oligodeoxynucleotides (ODNs), but not scramble decoy ODN after sensitization by anti-DNP-IgE antibody, had a significant inhibitory effect on not only STAT6 binding to nuclei but also on the late-phase response. A histological analysis revealed that both edema and the infiltration of neutrophils and eosinophils significantly decreased in STAT6 decoy ODN-transfected mice. To examine the mechanism of the in vivo effect of STAT6 decoy ODN, we employed an in vitro mast cells culture system. After IgE receptor engagement, mast cells transfected by STAT6 decoy ODN exhibited normal histamine release, but their cytokine release (TNF-a, IL-6) markedly decreased. We herein report the first successful in vivo transfer of STAT6 decoy ODN to reduce the late-phase reaction, thereby providing a new therapeutic strategy for AD.

We herein demonstrate that STAT6 plays an important role in the induction of not only acute contact hypersensitivity (CHS), but also chronic CHS in a mouse model using STAT6-deficient (STAT6 À/À ) mice. We, therefore, determine whether synthetic double-stranded DNA with a high affinity for STAT6 can be introduced in vivo as a decoy cis element to bind the transcriptional factor and block the induction of not only acute CHS but also chronic CHS. Treatment by the transfection of STAT6 decoy oligodeoxynucleotides (ODN), after the induction of 2,4,6-trinitrochlorobenzene or other haptens had a significant inhibitory effect on the induction of both acute CHS and chronic CHS. We thus examined the mechanism of the in vivo effect of the transfection of STAT6 decoy ODN in both acute and chronic CHS. In the histological analysis, the infiltration of eosinophils and degranulated mast cells, and the production of IL-4, IL-6 and eotaxin, but not IFN-g in the extracts from challenged skin significantly decreased by the transfection of STAT6 decoy ODN. We herein report the first successful in vivo transfer of STAT6 decoy ODN to inhibit acute and chronic CHS, thus providing a new therapeutic strategy not only for the treatment of CHS but also for atopic dermatitis.

Cutaneous fibrous histiocytomas are usually regarded as superficial lesions and commonly known as dermatofibromas; however, unusual cases histologically showing fibrohistiocytic proliferation extending into the deeper dermis or subcutaneous tissues are occasionally experienced. Some authors propose this type as benign fibrous histiocytoma of the skin, distinct from dermatofibroma. We describe herein a case of systemic lupus erythematosus (SLE) who developed multiple nodules on the face, trunk and extremities. The nodule on the forehead did not present a typical clinical appearance of dermatofibroma, and histopathological examination showed fibrohistiocytic proliferation with a storiform pattern extending into the deep dermis and subcutaneous tissues. By contrast, histology of the nodule on the abdomen showed fibrohistiocytic proliferation confined to the dermis and compatible with dermatofibroma. Although multiple dermatofibromas are occasionally seen in patients with SLE, benign fibrous histiocytoma of the skin showing deeper invasion than dermatofibroma is rarely associated with SLE.