小宮根 真弓

IL-36γ is highly expressed in psoriatic skin lesions and promotes neutrophil infiltration through the induction of neutrophil chemotactic chemokines. While IL-36γ has been established to play an important role in the pathogenesis of psoriasis, its localization in the psoriatic epidermis has not been fully elucidated, and the difference in its expression patterns among other inflammatory skin diseases remains unclear. We investigated IL-36γ localization using immunohistochemistry in skin specimens from patients with psoriasis vulgaris (n = 36), generalized pustular psoriasis (n = 11), pyoderma gangrenosum (n = 6), palmoplantar pustulosis (n = 6), tumor necrosis factor inhibitor-induced paradoxical reaction (n = 3), pustular drug eruption (n = 5), atopic dermatitis (n = 11), tinea infection (n = 3), and mycosis fungoides (n = 9), as well as uninvolved skin adjacent to benign tumors (n = 4). Staining scores were assessed based on intensity and distribution, and nuclear positivity was compared among diseases. IL-36γ was strongly expressed in the upper epidermis of psoriasis vulgaris and generalized pustular psoriasis, with staining scores significantly higher than those in atopic dermatitis and adjacent normal skin. Expression in pyoderma gangrenosum, palmoplantar pustulosis, paradoxical reaction, and pustular drug eruption was comparable to psoriasis vulgaris. Nuclear staining of IL-36γ was frequent in psoriasis vulgaris (33/36, 92%) and generalized pustular psoriasis (11/11, 100%), but absent in pyoderma gangrenosum. The difference in nuclear positivity between psoriasis and pyoderma gangrenosum was statistically significant. These findings confirm that IL-36γ is highly expressed in psoriatic lesions but is not specific to psoriasis, as it is also upregulated in other inflammatory skin diseases. Nuclear staining was observed in psoriasis but not in pyoderma gangrenosum, suggesting a potential disease-specific localization pattern. The biological significance and mechanism of nuclear localization remain unclear, as the IL-36γ molecule lacks a nuclear localization signal. Our findings highlight that the localization of IL-36γ differs among inflammatory skin diseases, suggesting that it may reflect pathogenic differences and warrant further investigation.

Systemic therapies are required to control disease severity of patients with psoriasis vulgaris (PsO) and psoriatic arthritis (PsA) experiencing refractory skin lesions that persisted despite systemic therapies. Various oral medications and biologics are currently available in Japan. The aim of this study was to evaluate the treatment outcomes of refractory regions of PsO and PsA treated with systemic therapy. A total of 77 patients who received oral medications and biologics between 1 January 2010 and 31 March 2019 at the Jichi Medical University Hospital were enrolled. The PsO group included 39 men and 11 women, whereas the PsA group included 20 men and 7 women. Oral medications included etretinate (7 PsO patients and 3 PsA patients), cyclosporine (39 PsO patients and 20 PsA patients), apremilast (7 PsO patients), and methotrexate (5 PsA patients), including 4 patients treated with etretinate and cyclosporine combination (3 PsO patients and 1 PsA patient). The biologics included infliximab (5 PsO patients and 8 PsA patients), adalimumab (11 PsO patients and 11 PsA patients), ustekinumab (21 PsO patients and 6 PsA patients), guselkumab (5 PsO patients), secukinumab (2 PsO patients and 1 PsA patient), ixekizumab (5 PsO patients and 1 PsA patient), and brodalumab (1 PsO patient). The most common biologic-resistant regions were the lower extremities, followed by the upper extremities and back in patients with PsO, and the scalp, followed by the lower extremities and abdomen in patients with PsA. Despite the introduction of biologics, no significant differences were observed in the efficacy on the face, neck, palm, and buttocks in patients with PsO and the face, sole, and buttocks in patients with PsA compared to oral medications. These findings will provide useful information regarding biologic-resistant psoriatic regions in the Japanese patients.

Ceramide deficiency in the stratum corneum (SC) is a key etiological factor in atopic dermatitis (AD). To clarify the direct role of SC ceramide depletion in impairing SC barrier and water-holding functions and in initiating AD-like skin symptoms and disease-specific molecular alterations, we generated Tg mice overexpressing a mutant form of acid ceramidase (aCDase) under the control of the involucrin promoter, resulting in targeted expression in the upper epidermis. By 3 weeks of age, Tg mice developed noninflammatory, scaly skin characterized by severely compromised barrier integrity and water-holding capacity, along with significantly elevated epidermal aCDase activity and markedly reduced ceramide levels in the SC. Compared to WT controls, Tg mice also exhibited increased epidermal innervation and reduced intraepidermal semaphorin 3a protein levels. Additionally, Tg skin showed substantial changes in the expression of AD-associated biomarkers involved in barrier impairment, pruritus, and Th2 polarization. These included increased levels of Il10, Il17a, S100a7, S100a8, and S100a9 and decreased levels of Cxcl10, Ifng, Il2, Il13, Il33, Sema3a, and Tlr9. Repeated topical application of mite antigens induced allergic responses in Tg mice, but not in WT mice. These responses were characterized by prominent eosinophil infiltration in the dermis and significantly elevated serum IgE levels. Allergen-challenged ear skin from Tg mice also demonstrated significantly increased expression of inflammatory mediators related to AD, including Ccl17, Ccl22, Ccl26, Ccl27, Il3, Il13, Il22, and Il33. These findings establish Tg mice as a pathophysiologically relevant model of AD, presenting key features such as xerotic, pruritic skin, impaired barrier and water-retention functions, and Th2-dominant allergic inflammation. This model provides important insights into ceramide-dependent mechanisms in AD pathogenesis and offers a useful platform for therapeutic development. © 2026 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.