Low catalase levels in the epidermis of patients with vitiligo.
Suction blister roofs taken from the involved and uninvolved epidermis of patients with vitiligo showed a consistent reduction in levels of catalase compared to normal healthy controls of matched photo-skin types (Fitzpatrick classification). A decrease in catalase activity is expected to increase the concentration of hydrogen peroxide in the epidermis of these patients. Hydrogen peroxide functions as a reversible inhibitor of human tyrosinase with a KI of 8 X 10(-6) M. Also, hydrogen peroxide undergoes photochemical reduction yielding highly reactive hydroxyl radicals (OH.) and hydroxyl ions (OH-) mainly by the Haber-Weiss reaction. Hydroxyl radicals are capable of bleaching constitutional melanin and cause membrane lysis through lipid peroxidation reactions. Hydroxyl ions increase the pH in the epidermis, and as a consequence glutathione reductase activity is increased in patients with vitiligo compared to controls. Based on these new results, together with the previously reported calcium transport defect, a new hypothesis has been formulated for the pathogenesis of vitiligo.
Schallreuter
K U
KU
Department of Dermatology, University of Hamburg, Germany.
Wood
J M
JM
Berger
J
J
D002374:Catalase / Q000032:analysis*; D005980:Glutathione Reductase / Q000032:analysis; D006801:Humans; D012867:Skin / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D013880:Thioredoxin-Disulfide Reductase / Q000032:analysis; D014820:Vitiligo / Q000201:enzymology*
D002374:Catalase; D005980:Glutathione Reductase; D013880:Thioredoxin-Disulfide Reductase