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Nutrition and Psoriasis
Open AccessArticle

Indoleamine 2,3-Dioxygenase 2 Deficiency Exacerbates Imiquimod-Induced Psoriasis-Like Skin Inflammation

1
Department of Dermatology, Gifu University Graduate School of Medicine, 1-1 Yanagito, Gifu 501-1194, Japan
2
Department of Disease Control and Prevention, Fujita Health University Graduate School of Health Sciences, 1-98 Dengakugakubo, Kutsukake, Toyoake, Aichi 470-1192, Japan
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2020, 21(15), 5515; https://doi.org/10.3390/ijms21155515
Received: 16 July 2020 / Revised: 28 July 2020 / Accepted: 31 July 2020 / Published: 1 August 2020
(This article belongs to the Special Issue Psoriasis: Pathogenesis, Comorbidities, and Therapy Updated)
Indoleamine 2,3-dioxygenase 1 (IDO1) is an enzyme known to suppress immune responses, and several reports have showed that it is associated with psoriasis. IDO2 is an isoform of IDO1, recently identified as a catalytic enzyme in the tryptophan-kynurenine pathway, which is expressed in dendritic cells and monocytes. The expression of IDO2 in immune cells suggests that IDO2 may contribute to immune functions. However, the role of IDO2 in the pathogenesis of psoriasis remains unclear. In this study, to elucidate the role of IDO2 in psoriasis, we assessed imiquimod (IMQ)-induced psoriasis-like dermatitis in IDO2 knockout (KO) mice. Skin inflammation, evaluated by scoring erythema, scaling, and ear thickness, was significantly worse in the IDO2 KO mice than in the wild-type (WT) mice. The mRNA expression levels of TNF-α, IL-23p19, and IL-17A, key cytokines involved in the development of psoriasis, were also increased in the IDO2 KO mice. Furthermore, immunohistochemistry revealed that the number of Ki67-positive cells in the epidermis and CD4-, CD8-, and IL-17-positive lymphocytes infiltrating the dermis were significantly increased in the IDO2 KO mice. These results suggest that IDO2 might decrease IL-17 expression, thereby resulting in the suppression of skin inflammation in IMQ-induced psoriasis-like dermatitis. View Full-Text
Keywords: psoriasis; IDO2; IDO1; tryptophan; kynurenine; IMQ; skin; inflammation; IL-17 psoriasis; IDO2; IDO1; tryptophan; kynurenine; IMQ; skin; inflammation; IL-17
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Fujii, K.; Yamamoto, Y.; Mizutani, Y.; Saito, K.; Seishima, M. Indoleamine 2,3-Dioxygenase 2 Deficiency Exacerbates Imiquimod-Induced Psoriasis-Like Skin Inflammation. Int. J. Mol. Sci. 2020, 21, 5515.

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