Effects of Glycyrrhizin on C6 Glioma Cells, with Special Reference to Cell Proliferation and Cell-Specific Proteins

The effects of glycyrrhizin (GL) on cell proliferation, cell viability, and expression of cell-associated proteins, such as glial fibrillary acidic protein (GFAP), vimentin and S-100 protein, were estimated using an ethylnitrosourea (ENU)-elicited rat glioma cell line (C6). Graded concentrations of GL, 1.0, 1.5 and 2.0 mg/ml, were added individully to C6 cultures every 24 h and examined up to 72 hour. Cell viability was determined using a propidium iodide (PI) exclusion method. Cell cycle analyses were performed on the DNA histrogram using flow cytometry. We also investigated changes in the expression of proteins by the FITC/PI double-staining technique using flow cytometry. Cell proliferation was retarded and the number of the dead cells was increased dose-dependently by GL treatment. In cells treated with 1.0 or 1.5 mg/ml GL, cell-cycle alterations indicating an increase of the G0/G1 phase and a decrease of the S and G2M phases from the first day, were similar to those in the control group. In cells treated with 2.0 mg/ml GL, the fraction of G0/G1-phase cells did not increase, probably because the excessive dose of GL had an intense cytotoxic effect, resulting in paucity of cells in culture. These results suggest that cells were eventually lost from all phases of the cell cycle, in a dose-dependent manner and that the main effect of GL on cell proliferation was direct cytotoxicity. Maximum exposure to GL caused increased expression of each cell-specific protein, especially GFAP. However, no obvious clarification of the phenotypic alteration induced by GL treatment was obtained.

Glycyrrhizin

C6 glioma cell

Cell proliferation

Specific protein