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

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We report two cases of eccrine porocarcinoma (EPC), one of intrepidermal EPC (IEEPC) and one of intradermal invasive EPC (IDEPC) in an immunohistochemical study of cytokeratins (CK) using nine different anti-keratin antibodies against CK1, 7, 8, 10, 14, 16, 17, 18 and 19. IEEPC expressed terminal differentiated CK1 and CK10. In contrast, IDEPC expressed simple-epithelial keratins such as CK7, 8, 18 and 19. Keratin expression of IEEPC preserves the immunophenotypes of normal epidermis. IDEPC, however, expresses poorly differentiated keratin. These results suggest that the keratin profiles of EPC are correlated with the invasive degree and reflect the clinical prognosis of EPC.

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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.

This study shows that topical therapy with IPD inhibits the expression of IL-4 and IL-5 and ameliorates skin manifestations in an AD mouse model, suggesting the potential usefulness of topical IPD for the treatment of AD.

These data showed that the simultaneous suppression of IL-4/IL-13 signals successfully controlled Th2-type chronic dermatitis. IL-4DM DNA treatment is a potent therapy for AD and related diseases.

Abstract. Primary cutaneous apocrine carcinoma (PCAC) is a rare neoplasm of skin appendages. To determine the differentiation of apocrine carcinoma, we studied the expression of epithelial keratins and filaggrin immunohistochemically using 10 anti-keratin antibodies againt keratin (K) 1,7,8,10,14,15,16,17,18,19 and the anti-filaggrin antibody. PCAC demonstrated strong positivity for K7, K8, K18 and K19. These keratins are distributed in secretory cells of normal apocrine glands. The tumor cells were negative for K14 and K17. The two keratins exist in myoepithelial cells in normal apocrine glands. Results suggest that PCAC shows differentiation into secretory cells of apocrine glands, although it does not differentiate into myoepithelial cells. K14 is also known as undifferentiated keratin, whereas K17 is considered to be a hyperproliferative keratin. Absence of the expression of K14 and K17 may reflect an indolent clinical course of PCAC.