title: The in vitro effect of hydroxychloroquine on skin morphology and transglutaminase.
abstract: BACKGROUND
  Antimalarials are some of the most notorious drugs which may induce psoriasis, with 25% of all reported cases being associated with them. Antimalarials do not induce psoriasis de novo, but trigger subclinical psoriasis. In a previous report, we suggested that antimalarials exert their effect by interfering with the epidermal transglutaminase (TGase) activity.
  
  
  OBJECTIVE
  To verify this hypothesis by examining the effect of hydroxychloroquine sulfate (HCQS) on cultured human skin and on TGase activity in vitro.
  
  
  METHODS
  Skin samples from normal donors were cultured in the presence of HCQS for 4 days, and then processed for microscopic examination. TGase activity was assayed in the presence of HCQS and compared with blanks.
  
  
  RESULTS
  Significant changes in epidermal morphology were seen in all explants cultured in the presence of HCQS at all concentrations employed. Areas of enhanced and irregular keratinization were observed in the upper epidermis, while a loss of cell polarity, with keratinocyte crowding and disarray, was seen in the lower epidermis. In addition, we observed intraepidermal splitting at different levels and dermo-epidermal detachments. HCQS showed a concentration-dependent inhibition of TGase activity.
  
  
  CONCLUSIONS
  We suggest that HCQS causes an initial break in the barrier function of the epidermis by inhibiting TGase activity; this is followed by a physiologic response of the epidermis aimed at barrier restoration. This rather nonspecific stimulus to epidermal proliferation is probably sufficient to trigger psoriasis in predisposed individuals or aggravate it in psoriatic patients.
authors.affiliation: Macabbi Health Care Outpatient Clinic, Faculty of Medicine, Tel-Aviv University, Israel.
authors.forename: R
authors.initials: R
authors.lastname: Wolf
authors.forename: A
authors.initials: A
authors.lastname: Lo Schiavo
authors.forename: M L
authors.initials: ML
authors.lastname: Lombardi
authors.forename: C
authors.initials: C
authors.lastname: Esposito
authors.forename: V
authors.initials: V
authors.lastname: Ruocco
mesh_terms: D000962:Antimalarials / Q000009:adverse effects*; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006886:Hydroxychloroquine / Q000009:adverse effects*; D008962:Models, Theoretical; D012016:Reference Values; D012867:Skin / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D011503:Transglutaminases / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000962:Antimalarials; D006886:Hydroxychloroquine; D011503:Transglutaminases