Ceramide inhibits cell proliferation through Akt/PKB inactivation and decreases melanin synthesis in Mel-Ab cells.
Ceramide is a bioactive sphingolipid that mediates a variety of cell functions. However, the effects of ceramide on cell growth and the melanogenesis of melanocytes are not known. In the present study, we investigated the actions of cell-permeable ceramide and its possible role in the signaling pathway of a spontaneously immortalized mouse melanocyte cell line, Mel-Ab. Our results show that C2-ceramide inhibits DNA synthesis in Mel-Ab cells and G361 human melanoma cells in a dose-dependent manner. Cell cycle analysis confirmed the inhibition of DNA synthesis by a reduction in the S phase. To investigate the ceramide signaling pathway, we studied whether C2-ceramide is able to influence extracellular signal-regulated kinase (ERK) and/or Akt/protein kinase B (PKB) activation. We demonstrated that phosphorylated Akt/PKB is decreased by C2-ceramide, whereas phosphorylated ERK was only slightly affected. Therefore, the C2-ceramide-induced inactivation of Akt/PKB may be closely related to the reduced cell proliferation of Mel-Ab cells. Furthermore, we assessed the effects of C2-ceramide on the pigmentation of Mel-Ab cells. The results obtained showed that the melanin content of cells was significantly reduced by C2-ceramide at concentrations in the range of 1-10 microM, and that the pigmentation-inhibiting effect of C2-ceramide is much greater than that of kojic acid at 1-100 microM. In addition, we found that the activity of tyrosinase is reduced by C2-ceramide treatment. Our results demonstrate that C2-ceramide reduces the pigmentation of Mel-Ab cells by inhibiting tyrosinase activity.
Kim
D S
DS
Department of Dermatology and Artificial Organ, Seoul National University College of Medicine, Chongno-Gu, Korea.
Kim
S Y
SY
Moon
S J
SJ
Chung
J H
JH
Kim
K H
KH
Cho
K H
KH
Park
K C
KC
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008543:Melanins / Q000096:biosynthesis*; D008544:Melanocytes / Q000187:drug effects / Q000378:metabolism*; D008545:Melanoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D014442:Monophenol Monooxygenase / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D008543:Melanins; C064769:N-acetylsphingosine; D011518:Proto-Oncogene Proteins; D014442:Monophenol Monooxygenase; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D013110:Sphingosine