diphenylhexatriene and Melanoma

Herbal remedies containing root extracts of Panax ginseng are commonly used for complementary or alternative therapies. Ginsenosides, the major components of root extracts, are responsible for ginseng's pharmacological and biological effects; however, their mechanisms of action are unclear. We examined whether membrane cholesterol was involved in the mechanism of action of ginsenoside Rh2 in cultured cells. In B16 melanoma cells, Rh2 (18.5 µM) induced dendrite formation within 2 h. Depletion of cholesterol by pretreatment with 10 mM methyl-β-cyclodextrin suppressed this effect of Rh2. Rh2 did not change the cellular cholesterol content and the immunofluorescence staining pattern of the lipid-raft-associated molecules, ganglioside GM3, Caveolin-1, Flotillin-1, and Flotillin-2, for up to 3 or 6 h. However, within 2 min of addition, Rh2 changed the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) but not of 1-[4-(trimethylammonio)phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH). DPH is more sensitive than TMA-DPH to changes in the physical properties of membrane lipid bilayers regulated by cholesterol. These results suggest that Rh2 affects the physical properties of cholesterol-regulated membrane lipid bilayers and could lead to changes in cellular functions.

Topics: Adaptor Proteins, Signal Transducing; Animals; Cell Line, Tumor; Cholesterol; Dendrites; Diphenylhexatriene; Fluorescence Polarization Immunoassay; Gangliosides; Ginsenosides; Melanoma; Membrane Microdomains; Mice

We have shown that the ginsenosides Rh1 and Rh2, which are plant glycosides with a dammarane skeleton resembling a steroid skeleton as an aglycone, control the phenotypic expression of mouse B16 melanoma cells in different ways. The effects of Rh1 and Rh2 on the cell surface were studied to clarify the relationship between the control of phenotypic expression and modification of the cell surface in B16 melanoma cells. Rh2, which has the capacity to inhibit the growth of and to stimulate melanogenesis in B16 melanoma cells, causes flattening of the cells cultured in a collagen gel, leading to organized, nonoverlapping monolayers. Cell-to-cell adhesiveness and cell-to-substrate adhesiveness were markedly increased in the B16 melanoma cells treated with Rh2. In Rh2-treated cells, the binding of peanut agglutinin on the cell surface was also increased, whereas no marked changes were observed in the binding of concanavalin A or wheat germ agglutinin. In contrast, Rh1, which showed no effect on cell growth, but did stimulate melanogenesis, did not cause morphological changes of the cells and exerted no effect on cell adhesiveness or cell surface lectin binding. 1,6-Diphenyl-1,3,5-hexatriene polarization values markedly decreased in cells treated with either Rh1 or Rh2. Rh2 was found to be incorporated in the lipid fraction of the B16 melanoma cell membrane. In contrast, Rh1 was not detected in the lipid fraction of B16 melanoma cells. However, novel lipid components were found.

Topics: Agglutination; Animals; Cell Adhesion; Cell Differentiation; Cell Membrane; Diphenylhexatriene; Ginsenosides; Lectins; Melanoma; Membrane Fluidity; Membrane Lipids; Mice; Phenotype; Saponins; Surface Properties

The fluorescence polarization of diphenylhexatriene (DPH) and trimethylammonium diphenylhexatriene (TMA-DPH) was measured when these markers were imbedded in cells of the human melanoma cell lines IGR37, IGR39, IGR3 and IGR4, as well as in cells of the mouse melanoma cell lines B16F1 and B16 F10. These measurements were performed on cell cultures which were grown on quartz plates as well as on cell suspensions. Considerable differences are found between the polarization values of the human cell lines that are related to their different origins. Differences for the plated cells are considerably greater than those for the suspensions. No differences in the polarization values were found for the two mouse melanoma lines. It is concluded that differences in lipid structural order can be found between cell types endowed with different metastasizing capabilities.

Topics: Animals; Cell Line; Diphenylhexatriene; Fluorescence Polarization; Humans; Lipids; Melanoma; Mice; Neoplasm Metastasis