title: Epidermal keratinocytes sense dsRNA via the NLRP3 inflammasome, mediating interleukin (IL)-1β and IL-18 release.
abstract: Skin epidermis, in addition to its barrier function, is able to actively sense harmful pathogens using pattern recognition receptors. In immune cells, the nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing 3 (NLRP3) inflammasome can mediate innate immunity against viral infection via a mechanism involving viral dsRNA recognition. Epidermal keratinocytes express NLRP3 inflammasome, which can sense contact sensitizers and mite allergens, leading to pro-interleukin (IL)-1β and pro-IL-18 cleavage into their active forms. Skin often faces viral infection. However, it is unknown whether viral dsRNA can be detected by the keratinocyte NLRP3 inflammasome. We transfected polyinosinic:polycytidylic acid (poly I:C), a synthetic viral dsRNA analogue, into cultured primary human keratinocytes at the aid of Lipofectamine 2000, and found that transfected poly I:C activated caspase-1 and induced caspase-1-dependent release of IL-1β and IL-18, which were suppressed on transfection with NLRP3 siRNA. The activation of keratinocyte NLRP3 inflammasome by transfected poly I:C was dependent on dsRNA-induced protein kinase (PKR) activation, and priming with type I interferons upregulated NLRP3 inflammasome activation through promoting PKR activation in poly I:C-transfected keratinocytes. In conclusion, the NLRP3 inflammasome can act as a sensor of dsRNA in epidermal keratinocytes, which may be important in both skin innate immune defense against viral infection and skin inflammation.
authors.affiliation: Department of Dermatology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan.
authors.forename: Xiuju
authors.identifier: 0000-0002-1487-7466
authors.initials: X
authors.lastname: Dai
authors.affiliation: Department of Dermatology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan.
authors.forename: Mikiko
authors.initials: M
authors.lastname: Tohyama
authors.affiliation: Department of Dermatology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan.
authors.forename: Masamoto
authors.initials: M
authors.lastname: Murakami
authors.affiliation: Department of Dermatology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Sayama
mesh_terms: D020170:Caspase 1 / Q000378:metabolism; D002478:Cells, Cultured; D004279:DNA, Viral / Q000276:immunology*; D000078404:Epidermal Cells; D004817:Epidermis / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007231:Infant, Newborn; D058847:Inflammasomes / Q000276:immunology*; D007370:Interferon Type I / Q000276:immunology; D020382:Interleukin-18 / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D015603:Keratinocytes / Q000276:immunology* / Q000378:metabolism; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein / Q000235:genetics / Q000276:immunology*; D011070:Poly I-C / Q000235:genetics / Q000276:immunology; D061251:Primary Cell Culture; D012330:RNA, Double-Stranded / Q000276:immunology*; D034741:RNA, Small Interfering / Q000235:genetics; D051192:Receptors, Pattern Recognition / Q000276:immunology; D014162:Transfection; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: D004279:DNA, Viral; D058847:Inflammasomes; D007370:Interferon Type I; D020382:Interleukin-18; D053583:Interleukin-1beta; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D012330:RNA, Double-Stranded; D034741:RNA, Small Interfering; D051192:Receptors, Pattern Recognition; D019892:eIF-2 Kinase; D020170:Caspase 1; D011070:Poly I-C
keywords: 
  PKR
  ; IFN-α; IFN-β; caspase-1; poly I:C