Increased melanogenesis is a risk factor for oxidative DNA damage--study on cultured melanocytes and atypical nevus cells.
Melanin synthesis is an oxygen-dependent process that acts as a potential source of reactive oxygen species (ROS) inside pigment-forming cells. The synthesis of the lighter variant of melanin, pheomelanin, consumes cysteine and this may limit the capacity of the cellular antioxidative defense. We show that tyrosine-induced melanogenesis in cultured normal human melanocytes (NHM) is accompanied by increased production of ROS and decreased concentration of intracellular glutathione. Clinical atypical (dysplastic) nevi (DN) regularly contain more melanin than do normal melanocytes (MC). We also show that in these cultured DN cells three out of four exhibit elevated synthesis of pheomelanin and this is accompanied by their early senescence. By using various redox-sensitive molecular probes, we demonstrate that cultured DN cells produce significantly more ROS than do normal MC from the same donor. Our experiments employing single-cell gel electrophoresis (comet assay) usually reveal higher fragmentation of DNA in DN cells than in normal MC. Even if in some cases the normal alkaline comet assay shows no differences in DNA fragmentation between DN cells and normal MC, the use of the comet assay with formamidopyrimidine DNA glycosylase can disclose that the DNA of the cultured DN cells harbor more oxidative damage than the DNA of normal MC from the same person.
Smit
Nico P M
NP
Department of Clinical Chemistry, Leiden University Medical Center, Leiden, The Netherlands. n.p.m.smit@lumc.nl
van Nieuwpoort
Frans A
FA
Marrot
Laurent
L
Out
Coby
C
Poorthuis
Ben
B
van Pelt
Hans
H
Meunier
Jean-Roch
JR
Pavel
Stan
S
D002478:Cells, Cultured; D004249:DNA Damage; D004416:Dysplastic Nevus Syndrome / Q000473:pathology*; D006801:Humans; D008543:Melanins / Q000096:biosynthesis*; D008544:Melanocytes / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D018384:Oxidative Stress / Q000528:radiation effects; D010858:Pigmentation; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012307:Risk Factors; D012867:Skin / Q000166:cytology; D014466:Ultraviolet Rays / Q000009:adverse effects*
D008543:Melanins; D017382:Reactive Oxygen Species