Dopamine-induced apoptosis in human melanocytes involves generation of reactive oxygen species.
BACKGROUND
Previous studies have shown that significant increases in urinary and plasma levels of several monoamines and their metabolites characterize the onset of vitiligo and its progression. Recently, both epidermal keratinocytes and melanocytes were found to have the capacity for the biosynthesis of several catecholamines and serotonin. Some monoamines and their metabolites can induce apoptosis and cytotoxicity in neural cells. However, no previous report has investigated the potential role of these monoamines in inducing apoptosis or cytotoxicity in melanocytes.


OBJECTIVE
To study the effects of dopamine (DA), norepinephrine (NE), epinephrine (EP), and serotonin (5-HT) on melanocyte cytotoxicity and apoptosis.


METHODS
Primary cultures of normal human melanocytes established from the foreskins of normal individuals were treated with different concentrations of DA, NE, EP and 5-HT for 5 and 7 days. Cell viability was measured by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Melanocyte apoptosis was evaluated by morphological examination and flow cytometric analysis. We also measured the generation of reactive oxygen species (ROS) after DA treatment.


RESULTS
Among the four monoamines used in this study, only DA had an effect, dose-dependently decreasing the melanocyte viability at concentrations ranging from 0.01 to 100 micromol L(-1) (0.1 and 1 micromol L(-1), P < 0.05; 10 micromol L(-1), P < 0.01). In addition, DA-induced melanocyte apoptosis was evidenced by the increased percentage of sub-G1 cells from 7.71 +/- 0.28% (control) to 12.22 +/- 1.05% (0.1 micromol L(-1) DA) (P < 0.005), and treatment with the antioxidant N-acetylcysteine (NAC) reversed this apoptotic effect. DA treatment led to the generation of ROS, which could be prevented by pretreatment with NAC.


CONCLUSIONS
DA can induce melanocyte apoptosis, which might be related to the generation of ROS. This novel effect might play an important role in the development or progression of vitiligo, which is currently viewed as a disease process closely related to melanocyte apoptosis.
Chu
C-Y
CY
Department of Dermatology, National Taiwan University Hospital and National Taiwan University College of Medicine, 7 Chung-Shan South Road, Taipei 100, Taiwan.
Liu
Y-L
YL
Chiu
H-C
HC
Jee
S-H
SH
D000111:Acetylcysteine / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D008297:Male; D008544:Melanocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology
D018492:Dopamine Antagonists; D017382:Reactive Oxygen Species; D012701:Serotonin; D004298:Dopamine; D000111:Acetylcysteine; D009638:Norepinephrine; D004837:Epinephrine