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RIPK1 Downregulation in Keratinocyte Enhances TRAIL Signaling in Psoriasis

Nao Saito, Masaru Honma, Takashi Shibuya, Shin Iinuma, Satomi Igawa, Mari Kishibe, Akemi Ishida-Yamamoto

J Dermatol Sci. 2018 Jul;91(1):79-86.

PMID: 29661487

Abstract:

Background:
Psoriasis, a common inflammatory skin disorder characterized by scaly erythema and plaques, is induced by dysregulation of dendritic cell- and T cell-mediated immune reaction. Receptor-interacting protein kinase 1 (RIPK1) regulates inflammatory signaling in response to stimuli such as TNF-α, TRAIL, and TLRs, resulting in apoptosis, necroptosis and NF-κB activation. However, the physiological relevance in human epidermis remains elusive.
Objective:
In this study, we examined whether RIPK1 is involved in the pathogenesis of psoriasis vulgaris.
Methods:
Skin samples of eight patients with psoriasis vulgaris were investigated by western blotting and immunohistochemistry. The functions of RIPK1 in keratinocytes were examined by RT-PCR and ELISA in vitro. TRAIL-neutralization-experiment was employed in an imiquimod-induced murine psoriasis model.
Results:
In lesional psoriatic epidermis, RIPK1-expression was decreased compared with that in normal epidermis. Cytokines involved in the pathomechanism of psoriasis, such as IL-1β, IL-17A, IL-22 and TRAIL, reduced RIPK1-expression in normal human epidermal keratinocytes (HEK) in vitro. In addition, RIPK1-knockdown enhanced TRAIL-mediated expression of psoriasis-relating cytokines, such as IL-1β, IL-6, IL-8, TNF-α, in HEK. Numerous TRAIL-positive cells were detected in the dermis of lesional psoriatic skin, and TRAIL receptors were expressed in psoriatic epidermis and HEK in conventional cultures. Moreover, TRAIL-neutralization in an imiquimod-induced murine psoriasis model remarkably improved skin phenotypes, such as ear thickness, and TNF-α expression in lesional skin.
Conclusions:
These results lead us to conclude that RIPK1-downregulation in keratinocytes increases their susceptibility to TRAIL stimulation, and plays a role in the pathogenesis of psoriasis vulgaris.

Chemicals Related in the Paper:

Catalog Number Product Name Structure CAS Number Price
IAR42412946 TRAIL murine TRAIL murine Price
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