title: Tight junction components occludin, ZO-1, and claudin-1, -4 and -5 in active and healing psoriasis.
abstract: BACKGROUND
  Cells of the granular layer are interconnected by tight junctions (TJs) in normal epidermis. The structural proteins of epidermal TJs include occludin, ZO-1, and claudin-1 and -4.
  
  
  OBJECTIVE
  Our aim was to correlate the expression of TJ components with keratinocyte differentiation using psoriasis as a model of premature keratinization.
  
  
  METHODS
  The distribution of TJ proteins was evaluated in the skin of nine patients with psoriasis. Punch biopsies were taken from perilesional skin, from active psoriasis plaques, and from healed, previously lesional locations. The punch biopsies were analysed using indirect immunolabelling for ZO-1, occludin and claudin-1, -4 and -5. In addition, epidermal samples were analysed by reverse transcription-polymerase chain reaction for claudin-1, -4 and -5 mRNAs.
  
  
  RESULTS
  Claudin-5 was localized to the granular cell layers of normal control skin as well as perilesional and lesional psoriatic epidermis. This was unexpected, as previous studies have not detected claudin-5 in the epidermis. Occludin and ZO-1 were expressed in the granular cell layer in psoriatic perilesional epidermis. In the psoriasis plaques, ZO-1 and occludin were detected in a wider zone extending from the granular layer to the middle spinous cell layers. In healed psoriasis plaques, the expression of occludin and ZO-1 resumed a normal-looking profile, being restricted to the upper epidermis only. Claudin-1 and -4 did not show marked changes in psoriasis compared with normal skin.
  
  
  CONCLUSIONS
  The results demonstrate claudin-5 in normal epidermis and psoriatic skin, and abnormal distribution of occludin and ZO-1 in psoriasis plaques. Clinical healing of aberrant keratinization is associated with restoration of the normal distribution of occludin, ZO-1 and also involucrin.
authors.affiliation: Department of Dermatology, University of Turku, PL 52, Turku, Finland. sirkku.peltonen@tyks.fi
authors.forename: S
authors.initials: S
authors.lastname: Peltonen
authors.forename: J
authors.initials: J
authors.lastname: Riehokainen
authors.forename: K
authors.initials: K
authors.lastname: Pummi
authors.forename: J
authors.initials: J
authors.lastname: Peltonen
mesh_terms: D000328:Adult; D000368:Aged; D001706:Biopsy; D062445:Claudin-1; D062506:Claudin-4; D062507:Claudin-5; D004817:Epidermis / Q000378:metabolism; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008875:Middle Aged; D062793:Occludin; D010750:Phosphoproteins / Q000378:metabolism; D011565:Psoriasis / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D019108:Tight Junctions / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein
chemical_list: C568108:CLDN1 protein, human; C568157:CLDN4 protein, human; C107466:CLDN5 protein, human; D062445:Claudin-1; D062506:Claudin-4; D062507:Claudin-5; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D010750:Phosphoproteins; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein