title: Indigo naturalis upregulates claudin-1 expression in human keratinocytes and psoriatic lesions.
abstract: BACKGROUND
  Indigo naturalis is used in traditional Chinese medicine to treat various dermatoses. Our previous clinical studies showed that indigo naturalis is an effective treatment for psoriasis. Herein, the capabilities of indigo naturalis extract and its derivatives to increase claudin-1 expression and tight junction (TJ) function in human keratinocytes and psoriatic lesions were further studied.
  
  
  METHODS
  Claudin-1 expression in psoriatic plaques with or without indigo naturalis treatment was analyzed by immunohistochemical methods. In primary human keratinocytes, the expression of claudin-1 was analyzed by fluorescent immunostaining, a real-time RT-PCR, and Western blot analysis. The effect of indigo naturalis on TJs was evaluated by measuring the transepithelial electrical resistance (TEER) and paracellular tracer flux.
  
  
  RESULTS
  The indigo naturalis extract upregulated mRNA and protein expressions of claudin-1 and function of TJs in primary human keratinocytes in concentration-dependent manners. Its main components, indirubin, indigo, and tryptanthrin, exerted synergistic effects on upregulating TJ functions in primary human keratinocytes. In addition, indigo naturalis increased the activity of protein kinase C (PKC), and a known potent PKC inhibitor, Ro318220, attenuated the indigo naturalis-induced claudin-1 expression. Significantly, restoration of claudin-1 was observed in healed psoriatic lesions after indigo naturalis treatment.
  
  
  CONCLUSIONS
  Indigo naturalis upregulates claudin-1 expression and restores TJ function in keratinocytes. Our data also suggest that indirubin, indigo, and tryptanthrin have a synergistic effect on TJ function.
authors.affiliation: Department of Traditional Chinese Medicine, Chang Gung Memorial Hospital, Keelung 204, Taiwan.
authors.forename: Yin-Ku
authors.initials: YK
authors.lastname: Lin
authors.forename: Hsiao-Wen
authors.initials: HW
authors.lastname: Chen
authors.forename: Yann-Lii
authors.initials: YL
authors.lastname: Leu
authors.forename: Yueh-Lung
authors.initials: YL
authors.lastname: Yang
authors.forename: Yu
authors.initials: Y
authors.lastname: Fang
authors.forename: Jong-Hwei
authors.initials: JH
authors.lastname: Su Pang
authors.forename: Tsong-Long
authors.initials: TL
authors.lastname: Hwang
mesh_terms: D027901:Acanthaceae; D000328:Adult; D002478:Cells, Cultured; D062445:Claudin-1 / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D010936:Plant Extracts / Q000494:pharmacology*; D011565:Psoriasis / Q000378:metabolism; D012867:Skin / Q000187:drug effects; D019108:Tight Junctions / Q000187:drug effects; D015854:Up-Regulation
chemical_list: D062445:Claudin-1; D010936:Plant Extracts