ABSTRACT
Geniposide is an iridoid glycoside isolated from the fruit of Gardenia jasminoides Ellis used as a Chinese traditional medicine for treatment of generalized vitiligo. Stem cell factor from keratinocyte recognizes and activates its receptor c-kit carried by melanocyte to potent enhance melanocytic melanogenesis that can be suppressed by norepinephrine. This study addresses the action and mechanism of geniposide enhancing melanogenesis in norepinephrine-exposed normal human epidermal melanocyte. Flow cytometry results from this study exhibited the augmentation effect of geniposide on production of c-kit receptor by norepinephrine-exposed normal human epidermal melanocyte. However, geniposide did not affect the production of stem cell factor by norepinephrine-exposed normal human epidermal keratinocyte assessed by cellular enzyme-linked immunosorbent assay (ELISA). ELISA indicated that at the presence of stem cell factor, geniposide was capable of elevating the level of extracellular signal-regulated kinase 1/2 phosphorylation within norepinephrine-exposed normal human epidermal melanocyte, which is known to be involved in stem cell factor/c-kit downstream signalling. And inhibition of c-kit with inhibitory antibody K44.2 completely blocked the increase in geniposide-stimulated extracellular signal-regulated kinase 1/2 phosphorylation. In addition, spectrophotometry demonstrated the enhancement effect of geniposide on melanogenesis (tyrosinase activity and melanin production) in norepinephrine-exposed normal human epidermal melanocyte at the presence of stem cell factor, which was blocked by c-kit inhibitory antibody K44.2. Data from this study suggest that geniposide can enhance melanogenesis by stem cell factor/c-kit signalling in which the expression of c-kit receptor is augmented in norepinephrine-exposed normal human epidermal melanocyte.
Subject(s)
Epidermal Cells , Iridoids/pharmacology , Melanins/metabolism , Melanocytes/drug effects , Norepinephrine/pharmacology , Proto-Oncogene Proteins c-kit/physiology , Stem Cell Factor/physiology , Cell Line , Enzyme-Linked Immunosorbent Assay , Extracellular Signal-Regulated MAP Kinases/metabolism , Flow Cytometry , Humans , Keratinocytes/drug effects , Keratinocytes/metabolism , Melanocytes/metabolism , Oxidoreductases/physiology , Phosphorylation , Proto-Oncogene Proteins c-kit/biosynthesis , Signal Transduction , Stem Cell Factor/antagonists & inhibitorsABSTRACT
OBJECTIVE: In order to investigate the pharmacological properties of Ginkgo biloba extract (GBE) on improving blood circulation, the regulating action of GBE and quercetin (a main flavonoid ingredient in GBE) on thrombomodulin (TM) expression and tissue-type plasminogen activator (t-PA) secretion was studied. METHODS: Using flow cytometer and gel image system respectively, we evaluated the TM expression and the t-PA secretion by human umbilical vein endothelial cells (HUVECs) in vitro. RESULTS: The increase of TM expression on HUVECs surface was induced by GBE rather than quercetin in a dose- and time-dependent manner. Both GBE and quercetin increased the t-PA release significantly. CONCLUSION: The effect of GBE on improving blood circulation may be partly attributed to its promoting TM expression and t-PA secretion by endothelial cells, and quercetin participated in the effect of GBE on t-PA secretion. However, the action of GBE on increasing TM expression needs further study.