title: Notch down-regulation in regenerated epidermis contributes to enhanced expression of interleukin-36α and suppression of keratinocyte differentiation during wound healing.
abstract: BACKGROUND
  Notch signaling controls a number of cellular processes, including cell fate decisions, proliferation, differentiation, and survival/apoptosis, in multiple tissues. In the epidermis, Notch1 functions as a molecular switch that controls the transition of cells from an undifferentiated state into a differentiated state.
  
  
  OBJECTIVE
  To clarify the functions of Notch in the regenerated epidermis during wound healing.
  
  
  METHODS
  Wounds on mouse skin were immunostained. To investigate the functions of Notch, Notch was inhibited in primary keratinocytes by treatment with a γ-secretase inhibitor and by small interfering RNA-mediated knockdown, and was activated by a recombinant adenovirus approach.
  
  
  RESULTS
  Notch1 and Notch2 were down-regulated in the regenerated epidermis during wound healing. To clarify the significance of this down-regulation, we examined its effect on expression of the interleukin (IL)-1 family of proinflammatory cytokines because wounds are exposed to pathogens from the outside world. Among the IL-1 family, IL-36α expression was induced by Notch inhibition. This was consistent with the decreased IL-36α expression in Notch-overexpressing keratinocytes. Notch down-regulation in the regenerated epidermis may reinforce defense against stress from the outside world by inducing IL-36α expression. Next, we examined the effects of Notch down-regulation on keratinocyte growth and differentiation. Notch down-regulation did not alter keratinocyte proliferation. On the other hand, Notch1 down-regulation suppressed induction of spinous layer-specific keratins (keratin1 and keratin10) in keratinocytes, which was consistent with the decreased expression of these keratins in the regenerated epidermis. The reduced levels of these keratins would increase cellular flexibility.
  
  
  CONCLUSIONS
  Notch down-regulation in the epidermis appears to contribute to tissue regeneration during wound healing.
authors.affiliation: Department of Dermatology, Shinshu University School of Medicine, Matsumoto, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Takazawa
authors.affiliation: Department of Dermatology, Shinshu University School of Medicine, Matsumoto, Japan.
authors.forename: Eisaku
authors.initials: E
authors.lastname: Ogawa
authors.affiliation: Tohoku Medical Megabank Organization, Tohoku University, Sendai, Japan.
authors.forename: Rumiko
authors.initials: R
authors.lastname: Saito
authors.affiliation: Department of Dermatology, Shinshu University School of Medicine, Matsumoto, Japan.
authors.forename: Ryuhei
authors.initials: R
authors.lastname: Uchiyama
authors.affiliation: Department of Project Programs, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
authors.forename: Shuntaro
authors.initials: S
authors.lastname: Ikawa
authors.affiliation: Department of Dermatology, Shinshu University School of Medicine, Matsumoto, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Uhara
authors.affiliation: Department of Dermatology, Shinshu University School of Medicine, Matsumoto, Japan. Electronic address: rokuyama@shinshu-u.ac.jp.
authors.forename: Ryuhei
authors.initials: R
authors.lastname: Okuyama
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors; D000818:Animals; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D004151:Dipeptides / Q000494:pharmacology; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004817:Epidermis / Q000378:metabolism*; D005260:Female; D055785:Gene Knockdown Techniques; D007375:Interleukin-1 / Q000235:genetics / Q000378:metabolism*; D053556:Keratin-1 / Q000378:metabolism; D053550:Keratin-10 / Q000378:metabolism; D015603:Keratinocytes / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000378:metabolism; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D051883:Receptor, Notch2 / Q000235:genetics / Q000378:metabolism*; D012038:Regeneration; D015398:Signal Transduction / Q000187:drug effects; D014945:Wound Healing / Q000187:drug effects / Q000502:physiology*
chemical_list: D004151:Dipeptides; D004791:Enzyme Inhibitors; D007375:Interleukin-1; D053556:Keratin-1; C419410:N-(N-(3,5-difluorophenacetyl)alanyl)phenylglycine tert-butyl ester; C497762:Notch1 protein, mouse; C497765:Notch2 protein, mouse; D012333:RNA, Messenger; D051881:Receptor, Notch1; D051883:Receptor, Notch2; C543716:interleukin 1F6, mouse; D053550:Keratin-10; D053829:Amyloid Precursor Protein Secretases
keywords: Cytokine; Keratin; Keratinocyte; Notch pathway; Wound healing