Ken Igawa

11β-Hydroxysteroid Dehydrogenase-1 Is a Novel Regulator of Skin Homeostasis and a Candidate Target for Promoting Tissue Repair

11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) catalyzes the interconversion of cortisone and cortisol within the endoplasmic reticulum. 11β-HSD1 is expressed widely, most notably in the liver, adipose tissue, and central nervous system. It has been studied intensely over the last 10 years because its activity is reported to be increased in visceral adipose tissue of obese people. Epidermal keratinocytes and dermal fibroblasts also express 11β-HSD1. However, the function of the enzymatic activity 11β-HSD1 in skin is not known. We found that 11β-HSD1 was expressed in human and murine epidermis, and this expression increased as keratinocytes differentiate. The expression of 11β-HSD1 by normal human epidermal keratinocytes (NHEKs) was increased by starvation or calcium-induced differentiation in vitro. A selective inhibitor of 11β-HSD1 promoted proliferation of NHEKs and normal human dermal fibroblasts, but did not alter the differentiation of NHEKs. Topical application of selective 11β-HSD1 inhibitor to the dorsal skin of hairless mice caused proliferation of keratinocytes. Taken together, these data suggest that 11β-HSD1 is involved in tissue remodeling of the skin. This hypothesis was further supported by the observation that topical application of the selective 11β-HSD1 inhibitor enhanced cutaneous wound healing in C57BL/6 mice and ob/ob mice. Collectively, we conclude that 11β-HSD1 is negatively regulating the proliferation of keratinocytes and fibroblasts, and cutaneous wound healing. Hence, 11β-HSD1 might maintain skin homeostasis by regulating the proliferation of keratinocytes and dermal fibroblasts. Thus 11β-HSD1 is a novel candidate target for the design of skin disease treatments.

Dendritic Cells Express Hematopoietic Prostaglandin D Synthase and Function as a Source of Prostaglandin D2 in the Skin

Prostaglandin D2 (PGD2), an arachidonic acid metabolite, has been implicated in allergic responses. A major source of PGD2 in the skin is mast cells that express hematopoietic PGD synthase (H-PGDS). In this study, we show the expression of H-PGDS in human dendritic cells (DCs) and the regulatory mechanisms by which DCs produce PGD2. We detected H-PGDS in epidermal Langerhans cells, dermal DCs, plasmacytoid DCs, and myeloid DCs. Monocyte-derived DCs rapidly secreted PGD2 when stimulated with the calcium ionophore A23187. More importantly, pretreatment of monocyte-derived DCs with PMA (phorbol 12-myrisate 13-acetate) synergistically enhanced the rapid PGD2 secretion induced by A23187, whereas PMA alone did not induce PGD2 secretion. Lipopolysaccharide (LPS) reduced H-PGDS expression, but interferon-gamma followed by LPS induced significant PGD2 production in a delayed time course at 6 hours. This effect was associated with inhibition of LPS-induced H-PGDS reduction. Interestingly, an irritant compound, SDS, also induced a rapid PGD2 release. PGD2 synergistically enhanced CCL22/macrophage-derived chemokine synthesis in interferon-gamma-treated human keratinocytes. In addition, bone marrow-derived DCs from wild-type mice stimulated lymph node cells to produce higher amounts of interleukin-17 than did DCs from mice lacking the H-PGDS gene. Thus, DCs could be an important source of skin PGD2 and may mediate or regulate skin inflammation by releasing PGD2 in response to various stimuli, contributing to the innate and/or acquired immune responses.

γδ T cells assist αβ T cells in the adoptive transfer of contact hypersensitivity to para-phenylenediamine

Para‐phenylenediamine (PPD) is known to be a common sensitizer of allergic contact dermatitis and contact urticaria. To clarify the mechanism of contact hypersensitivity (CHS) to PPD, we established a mouse model of PPD‐induced CHS. BALB/c mice were immunized for 3 consecutive days by painting topically a 2·5% PPD solution on their shaved abdominal skin. On days 5, 7 or 9 after the initial application, the mice were challenged by applications of a 2·5% PPD solution. Maximal ear swelling was determined at 24 h but another statistically significant and smaller ear swelling was observed 1 h after challenge with PPD in a hapten‐specific manner. Adoptive cell transfer experiments demonstrated that the ear swelling of the adoptive cell transferred mice displayed an early response at 6 h and a late response from 12 h to 24 h when the recipient mice were challenged immediately after transfer. Both MoAbs and complement treatment of the transferred cells demonstrated that the phenotype of the early response cells which elicited a response at 6 h after challenge was Thy1+, B220+, αβ TCR, γδ TCR, CD3, CD4, CD5+ and CD8. The in vitro treatment of effector cells with MoAbs against not only αβ TCR but also γδ TCR, together with complement, was found to diminish substantially the late response, elicited 12–24 h after challenge. γδ T cells reconstituted the ability of αβ T cells to transfer 24 h CHS responsiveness. The phenotype of the γδ T cells that assist CHS effector αβ T cells was CD3+, CD4 and CD8+ and these regulatory γδ T cells were neither Ag‐specific nor MHC‐restricted. Furthermore, γδ T cells from normal spleen could also assist αβ T cells in adoptive transfer of the 24 h CHS response in a non‐MHC‐restricted manner. RT‐PCR demonstrated that αβ T cells strongly expressed mRNA IFN‐γ, whereas γδ T cells expressed not only IFN‐γ but also IL‐4 and IL‐10. These data indicate that not only early response cells and αβ T cells but also Th2 type γδ T cells may play an important role in the elicitation of CHS to PPD.

Th2 cytokines, IgE and mast cells play a crucial role in the induction of para-phenylenediamine-induced contact hypersensitivity in mice

We 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 PPD‐challenged 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/Wv 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/Wv 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.

Anti-Oxidative Therapy with Oral Dapsone Improved HCV Antibody Positive Annular Elastolytic Giant Cell Granuloma

A 72‐year‐old fisherman who was positive for the HCV antibody developed an annular, erythematous, infiltrated lesions on sun‐exposed areas. The lesions were diagnosed as annular elastolytic giant cell granuloma both clinically and histologically. Topical corticosteroid and cryotherapy with liquid nitrogen for several months failed to improve the lesions. We then started dapsone, a known anti‐oxidant, at 50 mg/day. A month later, the margins of the erythematous lesions faded, and the infiltration gradually decreased. No recurrence has been observed for one year after the start of the therapy. Anti‐oxidative therapy appears to be effective for annular elastolytic giant cell granuloma and could be an alternate therapy for refractory granulomatous disease.

Regulatory mechanisms of galectin‐9 and eotaxin‐3 synthesis in epidermal keratinocytes: possible involvement of galectin‐9 in dermal eosinophilia of Th1‐polarized skin inflammation

Background:  Skin eosinophilia is a common feature of allergic skin diseases, but it is unclear how epidermal and dermal eosinophil infiltration is controlled. To investigate regulation of localization of eosinophils in skin, we examined the regulatory mechanisms of expression of eosinophil‐specific chemoattractants in dermal fibroblasts and epidermal keratinocytes.

Gene silencing of STAT6 with siRNA ameliorates contact hypersensitivity and allergic rhinitis

To cite this article: Hosoya K, Satoh T, Yamamoto Y, Saeki K, Igawa K, Okano M, Moriya T, Imamura O, Nemoto Y, Yokozeki H. Gene silencing of STAT6 with siRNA ameliorates contact hypersensitivity and allergic rhinitis. Allergy 2011; 66: 124–131.

Impaired expression of Tim-3 on Th17 and Th1 cells in psoriasis.

Psoriasis is a chronic skin disease mediated by Th17 and/or Th1 cells. Tim-3 is a cell surface molecule preferentially expressed on Th17 and Th1 cells. The interaction of Tim-3 with Tim-3 ligand inhibits cytokine production. To assess whether T cells in psoriasis have functional abnormalities, expression of cell surface Tim-3 on blood T cells producing interleukin-17 (Th17/Tc17 cells) or interferon-γ (Th1/Tc1 cells) was examined by flow cytometry. Psoriasis patients had higher numbers of Th17 and Tc17 cells, as well as Th1 and Tc1 cells, than healthy donors. However, Th17, Th1 and Tc1 cells in psoriasis did not efficiently express Tim-3 upon activation, compared with those from atopic dermatitis and healthy donors. Tim-3- cells showed more potent cytokine production than Tim-3+ cells. Impaired Tim-3 expression allows Th17, Th1 and Tc1 cells to escape from Tim-3-mediated negative regulatory systems and may contribute to the pathogenesis of psoriasis.

Necrobiosis Lipoidica‐like Skin Lesions in Systemic Sarcoidosis

A 62‐year‐old woman with systemic sarcoidosis developed erythematous plaques on her lower legs. Clinically, two kinds of skin lesions were distinguished; one type formed brownish‐red plaques with induration suggesting plaque‐type skin sarcoid, and the other formed purplish erythematous plaques with atrophic centers resembling necrobiosis lipoidica. In spite of this clinical appearance, a biopsy specimen from one of the latter lesions revealed typical skin sarcoid histology composed of discrete non‐caseating granulomas, while that from one of the other lesions showed necrobiotic changes of collagen bundles surrounded by epitheloid histiocytes and foreign‐body giant cells. Because cutaneous involvement of sarcoidosis may mimic necrobiosis lipoidica clinically and/or histologically, we diagnosed her skin lesions as necrobiosis‐like skin sarcoid.

Involvement of UV-irradiation in pemphigus foliaceus.

Ultraviolet (UV) light has been implicated in inducing acantholysis in the uninvolved skin of pemphigus patients. This report presents the case of a 55‐year‐old man with pemphigus foliaceus in whom skin lesions were induced and exacerbated by UV‐irradiation.