The severity of imiquimod-induced mouse skin inflammation is independent of endogenous IL-38 expression

PLoS One. 2018 Mar 19;13(3):e0194667. doi: 10.1371/journal.pone.0194667. eCollection 2018.

Abstract

The IL-1 cytokine family includes eleven members, among which Il-36α, β and γ, IL-36Ra and IL-38. The IL-36 cytokines are involved in the pathogenesis of psoriasis. IL-38 is also expressed in the skin and was previously proposed to act as an IL-36 antagonist. In this study, we thus examined expression and function of Il-38 in a mouse model of imiquimod (IMQ)-induced skin inflammation. Il-38 mRNA was detected in the epidermis and in primary mouse keratinocytes, but not in dermal fibroblasts. At the peak of IMQ-induced inflammation, skin Il-38 mRNA levels were reduced, whereas Il-36ra mRNA expression increased. The severity of IMQ-induced skin inflammation, as assessed by recording ear thickness and histological changes, was similar in Il-38 KO and WT littermate control mice, while, in contrast, Il-36ra-deficient mice displayed more severe skin pathology than their WT littermates. Il-38-deficiency had no impact on IMQ-induced expression of proinflammatory mediators in the skin in vivo, on the basal expression of various cytokines or chemokines by cultured primary keratinocytes and dermal fibroblasts in vitro, or on the response of these cells to Il-36β. Finally, after cessation of topical IMQ application, the resolution of skin inflammation was also not altered in Il-38 KO mice. In conclusion, Il-38-deficiency did not impact the development or resolution of IMQ-induced skin inflammation. Our observations further suggest that endogenous Il-38 does not exert Il-36 inhibitory activity in this model, or in cultured skin cells. A potential anti-inflammatory function of Il-38 in mouse skin thus still remains to be demonstrated.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminoquinolines*
  • Animals
  • Cells, Cultured
  • Dermatitis / genetics*
  • Dermatitis / metabolism
  • Dermatitis / pathology
  • Disease Models, Animal
  • Drug Eruptions / genetics*
  • Drug Eruptions / metabolism
  • Drug Eruptions / pathology
  • Female
  • Imiquimod
  • Inflammation / chemically induced*
  • Inflammation / genetics
  • Inflammation / pathology
  • Interleukin-1 / genetics*
  • Interleukin-1 / metabolism
  • Interleukins / genetics*
  • Interleukins / metabolism
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Severity of Illness Index
  • Skin / metabolism*
  • Skin / pathology

Substances

  • Aminoquinolines
  • Il1f10 protein, mouse
  • Interleukin-1
  • Interleukins
  • Imiquimod

Grants and funding

This work was supported by the Rheumasearch Foundation (http://www.rheumasearch.ch) and the Institute of Arthritis Research (https://www.iar-suisse.ch/home.html). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.