Kazuya Tokime

Human Mast Cell Chymase Cleaves Pro-IL-18 and Generates a Novel and Biologically Active IL-18 Fragment

Increased release of IL-18 in the skin causes atopic dermatitis (AD)-like skin lesions, suggesting a role of IL-18 in the pathogenesis of AD. Caspase-1 is a well-known activator of IL-18, but caspase-1 knockout mice still have biologically active IL-18. Normal human keratinocyte constitutively produces pro-IL-18, but it is unable to activate it, suggesting the existence of an alternative pathway for IL-18 in the skin. Dermal accumulation of mast cells is commonly observed in AD patients and in experimental mouse models of AD. Connective tissue mast cells contain high amounts of chymase and tryptase in their cytoplasmic granules. In the present study, we demonstrated that activation of IL-18 is a novel function of human mast cell chymase. Human mast cell chymase rapidly cleaves recombinant pro-IL-18 at 56-phenylalanine and produces a biologically active IL-18 fragment that is smaller than any other reported IL-18-derived species. The human mast cell chymase and the novel IL-18-derived active peptide may be novel therapeutic targets in AD- and IL-18-associated diseases

Granzyme B is a novel interleukin-18 converting enzyme

BACKGROUND Granzyme B (GrB) is recognized to induce apoptosis; however, little is known about its possible role in other biological events. IL-18, a potent inflammatory cytokine, is produced as an inactive precursor (proIL-18). Several cells, including monocytes/macrophage lineage and non-hematopoietic cells such as keratinocytes, produce proIL-18. ProIL-18 requires appropriate processing to become active. Caspase-1 is the authentic IL-18 processing enzyme and is essential for IL-18 release from monocyte/macrophage lineage cells. However, caspase-1 is absent in non-hematopoietic cells, suggesting that there is another candidate to cleave proIL-18 except for caspase-1. OBJECTIVE GrB can invade and be active in cytoplasm of non-hematopoietic cells via perforin, therefore we investigated whether GrB converts proIL-18 into the biologically active form. METHODS Recombinant proIL-18 (rproIL-18) was produced and purified for protease reaction with GrB; this incubate was evaluated by immunoblotting. Biological activity of the proteolytic fragment cleaved by GrB was determined by IFN-gamma assay using KG-1 cells. IFN-gamma induction was also analyzed between extracts from GrB(+)/caspase-1(-) human CD8+ T cells and proIL-18 from normal human keratinocytes (NHK). RESULTS The proteolytic fragment that GrB cleaved proIL-18 had the same sequence and biological activity compared with mature IL-18 cleaved by caspase-1. Culture extracts from CD8+ T cells was able to cleave proIL-18 into authentic mature IL-18. IFN-gamma induction was also detected in NHK treated with CD8+ T cells. CONCLUSION GrB is a potent IL-18 converting enzyme and suggest that GrB secreted by CTLs and/or NK cells may initiate IL-18 release from target cells, leading to the development of inflammation.

IL-4/IL-13 antagonist DNA vaccination successfully suppresses Th2 type chronic dermatitis

Background  Atopic dermatitis (AD) is a chronic disease with a Th2‐type‐cytokine dominant profile. Several cytokines and related peptides have been used for the treatment of AD but they were ineffective because of their limited biological half‐life. We have recently developed a highly efficient mouse dominant negative interleukin (IL)‐4/IL‐13 antagonist (IL‐4DM), which blocks both IL‐4 and IL‐13 signal transductions.

Topical suplatast tosilate (IPD) ameliorates Th2 cytokine-mediated dermatitis in caspase-1 transgenic mice by downregulating interleukin-4 and interleukin-5

Background  Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by elevated serum levels of IgE. AD is associated with Th2 cytokines including interleukin (IL)‐4, IL‐5, IL‐13 and IL‐10. Systemic administration of suplatast tosilate (IPD) is currently used to treat Th2 cytokine‐mediated AD.

Enhanced production and secretion of glial cell line-derived neurotrophic factor and nerve growth factor from the skin in atopic dermatitis mouse model

Role of neurotrophic factors including nerve growth factor (NGF) in the mechanism of overgrowth and hypersensitivity of sensory nerve in atopic dermatitis (AD) has been proposed. Glial cell line-derived neurotrophic factor (GDNF) is a member of neurotrophic factors of the nervous systems; however, the role of GDNF in dermatitis is unknown. IL-18 promotes Th2 type allergic condition in skin and various organs in the absence of IL-12. In this report, we evaluated the expression of GDNF in AD and its association with NGF and IL-18. Mice expressing skin-specific IL-18 (KIL18Tg) or caspase-1, an IL-18 converting enzyme, (KCASP1Tg) were used as AD models; GDNF expression was examined by RT-PCR, enzyme immunoassay, and immunohistochemistry. The mRNA expressions of GDNF and NGF were detected in the epidermis and they were increased in the skin of KIL18Tg and KCASP1Tg mice. GDNF protein production in the skin was also elevated in both transgenic mice and mostly expressed at the basal layer of the epidermis as assessed by immunohistochemistry. Furthermore, the number of nerve fibers was increased in KCASP1Tg, suggesting increased cutaneous innervation. The present results suggest that in addition to NGF, elevated production and secretion of GDNF in the skin associated with overproduction of IL-18 may also be a potent causative factor of itching in AD.

A Case of Acute Graft‐versus‐Host Disease Following Autologous Peripheral Blood Stem Cell Transplantation

A 42–year‐old woman developed severe erythema with exfoliative scaling on the bilateral palms and soles and erosive dermatitis on the axillae and groin eight days after an autologous peripheral blood stem cell transplantation for the treatment of non‐Hodgkins lymphoma. She also developed exanthema; however she did not show intestinal, hepatic, or renal involvement. The skin biopsy revealed characteristic apoptotic cell death of the epidermis with eosinophilic necrosis, and she was diagnosed with acute graft‐versus‐host disease (GVHD). The cutaneous lesions responded to topical corticosteroid treatments and improved within a month without systemic immunosuppressing therapies. The cutaneous GVH reaction did not recur. However, she was treated with an intermittent thrombocyte transfusion because of persistent thrombocytopenia. On day 130, she developed intestinal pneumonia and died due to respiratory dysfunction. Unlike an allo‐bone marrow graft, GVHD after an autologous stem cell transplantation is not common. Even for an autologous transplantation, GVH may develop with less characteristic clinical manifestations.

Epidermal cyst with pilomatricoma (follicular hybrid cyst): Immunohistochemical study with epithelial keratins and filaggrin

Dear Editor, We reported a case with a follicular hybrid cyst: an epidermal cyst with pilomatricoma and studied immunohistochemically focusing epithelial keratins and filaggrin expression. Epidermal cyst (EC) is a common subcutaneous epithelial tumor. Histopathologically, EC is considered to be derived from the follicular infundibulum, and is also referred to as an infundibular cyst. However, EC is rarely complicated with pilomatricoma-like changes with basophilic cells and shadow cells in Gardner’s syndrome. The histogenesis of pilomatricoma is considered to be derived from the hair matrix and hair cortex because of the presence of hairspecific keratins. Concerning the coexistence of various cystic lesions (epidermal cysts, trichilemmal cysts) and pilomatricoma, Requena et al. have proposed the concept of a follicular hybrid cyst, which includes any types of cyst arising from the various parts of the pilosebaceous unit. Keratin is found as intermediate-sized filaments and is a differentiation marker of epithelial tumor. Filaggrin, filament aggregating protein, is a major component of keratohyaline granules and is a marker of terminal differentiation. To determine the origin and differentiation of the tumor, we report a case of epidermal cyst with pilomatricoma (follicular hybrid cyst) in which we have made an immunohistochemical study of epithelial keratins and filaggrin. A 20-year-old man presented with subcutaneous nodules on the right side of his neck. He had a 5-year history of subcutaneous nodules on the right side of the neck. On physical examination, there was a dome-shaped, pale whitish colored, hard subcutaneous nodule, 30 mm · 20 mm in diameter, with a