title: Antioxidants protect keratinocytes against M. ulcerans mycolactone cytotoxicity.
abstract: BACKGROUND
  Mycobacterium ulcerans is the causative agent of necrotizing skin ulcerations in distinctive geographical areas. M. ulcerans produces a macrolide toxin, mycolactone, which has been identified as an important virulence factor in ulcer formation. Mycolactone is cytotoxic to fibroblasts and adipocytes in vitro and has modulating activity on immune cell functions. The effect of mycolactone on keratinocytes has not been reported previously and the mechanism of mycolactone toxicity is presently unknown. Many other macrolide substances have cytotoxic and immunosuppressive activities and mediate some of their effects via production of reactive oxygen species (ROS). We have studied the effect of mycolactone in vitro on human keratinocytes--key cells in wound healing--and tested the hypothesis that the cytotoxic effect of mycolactone is mediated by ROS.
  
  
  RESULTS
  The effect of mycolactone on primary skin keratinocyte growth and cell numbers was investigated in serum free growth medium in the presence of different antioxidants. A concentration and time dependent reduction in keratinocyte cell numbers was observed after exposure to mycolactone. Several different antioxidants inhibited this effect partly. The ROS inhibiting substance deferoxamine, which acts via chelation of Fe(2+), completely prevented mycolactone mediated cytotoxicity.
  
  
  CONCLUSIONS
  This study demonstrates that mycolactone mediated cytotoxicity can be inhibited by deferoxamine, suggesting a role of iron and ROS in mycolactone induced cytotoxicity of keratinocytes. The data provide a basis for the understanding of Buruli ulcer pathology and the development of improved therapies for this disease.
authors.affiliation: Molecular Dermatology, Department of Medicine, Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden. alvar.gronberg@ki.se
authors.forename: Alvar
authors.initials: A
authors.lastname: Grönberg
authors.forename: Louise
authors.initials: L
authors.lastname: Zettergren
authors.forename: Kerstin
authors.initials: K
authors.lastname: Bergh
authors.forename: Mona
authors.initials: M
authors.lastname: Ståhle
authors.forename: Johan
authors.initials: J
authors.lastname: Heilborn
authors.forename: Kristian
authors.initials: K
authors.lastname: Angeby
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Small
authors.forename: Hannah
authors.initials: H
authors.lastname: Akuffo
authors.forename: Sven
authors.initials: S
authors.lastname: Britton
mesh_terms: D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt / Q000494:pharmacology; D000328:Adult; D000975:Antioxidants / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000302:isolation & purification / Q000494:pharmacology*; D002374:Catalase / Q000494:pharmacology; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002839:Chromans / Q000494:pharmacology; D003676:Deferoxamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018942:Macrolides; D019911:Mycobacterium ulcerans / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D017262:Siderophores / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000975:Antioxidants; D001427:Bacterial Toxins; D002839:Chromans; D018942:Macrolides; D016877:Oxidants; D017382:Reactive Oxygen Species; D017262:Siderophores; C117218:mycolactone; D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; D006861:Hydrogen Peroxide; D002374:Catalase; D003676:Deferoxamine; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid