Kazuko Mizuno1, Shin Morizane2, Tetsuya Takiguchi3, Keiji Iwatsuki1. 1. Department of Dermatology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan. 2. Department of Dermatology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan. Electronic address: zanemori@cc.okayama-u.ac.jp. 3. Department of Dermatology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan; Department of Plastic and Reconstructive Surgery, Hamamatsu University School of Medicine, Hamamatsu, Japan.
Abstract
BACKGROUND: Thymic stromal lymphopoietin (TSLP) initiates the Th2-type allergic inflammation, and is thought to play an important role in the pathogenesis of atopic dermatitis (AD). TNF-α is a key cytokine which is involved in the pathophysiology of various inflammatory diseases, and the expression level is elevated in the sera and skin of patients with AD. In addition, TNF-α has been reported to induce TSLP expression in epidermal keratinocytes. Topical glucocorticoids and calcineurin inhibitors are safe and effective agents for AD, but the effects of these agents on TNF-α-induced TSLP expression are not fully understood. OBJECTIVE: To investigate whether the glucocorticosteroid dexamethasone and the calcineurin inhibitor tacrolimus could affect TSLP expression induced by TNF-α in lesional keratinocytes of AD. METHODS: The effects of topical dexamethasone and tacrolimus on TSLP expression were evaluated in an AD mouse model induced by repeated 2,4,6-trinitro-1-chlorobenzene application. Co-immunostaining for TSLP and TNF-α was performed using skin samples from AD patients and the mouse model. Normal human epidermal keratinocytes (NHEKs) were cultured with dexamethasone or tacrolimus in the presence of TNF-α to analyze TSLP expression. RESULTS: Topical application of dexamethasone but not tacrolimus repressed TSLP expression in the mouse model. TSLP and TNF-α showed similar distribution pattern in epidermal keratinocytes of AD lesions and the mouse model. TSLP expression was induced by TNF-α via NF-κB in a dose-dependent and an autocrine and/or paracrine manner in NHEKs, which was significantly suppressed by dexamethasone but not by tacrolimus. Similarly to TSLP expression, IL-6, TNF-α, IL-8, and IL-36γ expression induced by TNF-α were significantly suppressed by dexamethasone but not by tacrolimus in NHEKs. CONCLUSION: Dexamethasone but not tacrolimus suppresses the TSLP expression induced by TNF-α in lesional keratinocytes of AD model. Our observations uncover the unreported functional difference between topical glucocorticosteroids and calcineurin inhibitors in cutaneous inflammatory diseases.
BACKGROUND:Thymic stromal lymphopoietin (TSLP) initiates the Th2-type allergic inflammation, and is thought to play an important role in the pathogenesis of atopic dermatitis (AD). TNF-α is a key cytokine which is involved in the pathophysiology of various inflammatory diseases, and the expression level is elevated in the sera and skin of patients with AD. In addition, TNF-α has been reported to induce TSLP expression in epidermal keratinocytes. Topical glucocorticoids and calcineurin inhibitors are safe and effective agents for AD, but the effects of these agents on TNF-α-induced TSLP expression are not fully understood. OBJECTIVE: To investigate whether the glucocorticosteroiddexamethasone and the calcineurin inhibitortacrolimus could affect TSLP expression induced by TNF-α in lesional keratinocytes of AD. METHODS: The effects of topical dexamethasone and tacrolimus on TSLP expression were evaluated in an ADmouse model induced by repeated 2,4,6-trinitro-1-chlorobenzene application. Co-immunostaining for TSLP and TNF-α was performed using skin samples from ADpatients and the mouse model. Normal human epidermal keratinocytes (NHEKs) were cultured with dexamethasone or tacrolimus in the presence of TNF-α to analyze TSLP expression. RESULTS: Topical application of dexamethasone but not tacrolimus repressed TSLP expression in the mouse model. TSLP and TNF-α showed similar distribution pattern in epidermal keratinocytes of AD lesions and the mouse model. TSLP expression was induced by TNF-α via NF-κB in a dose-dependent and an autocrine and/or paracrine manner in NHEKs, which was significantly suppressed by dexamethasone but not by tacrolimus. Similarly to TSLP expression, IL-6, TNF-α, IL-8, and IL-36γ expression induced by TNF-α were significantly suppressed by dexamethasone but not by tacrolimus in NHEKs. CONCLUSION:Dexamethasone but not tacrolimus suppresses the TSLP expression induced by TNF-α in lesional keratinocytes of AD model. Our observations uncover the unreported functional difference between topical glucocorticosteroids and calcineurin inhibitors in cutaneous inflammatory diseases.