The Impact Of Peroxisome Proliferator Activated Receptor-γ (PPAR-γ) Agonists Rosiglitazone On Glioma Cells And The Underlying Mechanism

Objective:Cytological experiments and molecular biology methods were applied to investgate the impact of peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, rosiglitazone, on human glioma cell proliferation, apoptosis, cell cycle and cell invasiveness. To observe the mechanism of invasiveness alterations under application of rosiglitazone to glioma cell, the changes of expression of the adhesion factors (ICAM-1and VCAM-1and E-selectin) was obsvered in the gene and protein level. Expression of TGF-β signaling pathway and its downstream key proteins and genes in human glioma cell were observed. The changes of TGF-β signaling pathway can clarify the molecular mechanisms of PPAR-γ agonists affect glioma cell proliferation, apoptosis, cell cycle and invasiveness.Materials and Methods:1) MTT in different dose of rosiglitazone and in different time to investagate the inhibition of cells proliferation of U87cells and U251.2) Annexin V-FITC and PI assay were applied to obsver the effect on rosiglitazone human glioma U87cells and U251cell apoptosis and cell cycle.3) Invasiveness of glioma cells were studied by the Transwell method. Alteration of adhesion factors (ICAM-1and VCAM-1and E-selectin) expression in the U87cells and U251were dected by Western blot and RT-PCR.4) The effect of rosiglitazone on the TGF-beta pathway and its downstream key molecule in the U87cells and U251cells were investgated by Western blot. ELISA assay were used to examine the secretion of TGF-P in human glioma cells. The expression of Smad3/Smad4were dected the by immunofluorescence.Results:1) Varying degrees of proliftive inhibition were obsvered after using rosiglitazone24h,48h and72h, in U87and U251cells, this inhibition in a dose-dependent way.2) Under the influence of the rosiglitazone, the proportion of cells in G1phase of U87and U251cells increased significantly, while the S and G2/M phase cells was significantly reduced. Using rosiglitazone in higher concentration increased the proportion of apoptotic cells.3) With increasing doses of rosiglitazone, the invassivess of U87and U251glioma cell decreased significantly. Glioma in the natural evolution process of the brain tissue often in a hypoxic state, under the hypoxic condition glioma cell adhesion molecule (ICAM-1, VCAM-1and E-selectin), upregulation of PPAR-gamma activator can significantly inhibit glioma cell adhesion molecule expression.4) Under the rosiglitazone effect, the TGF-β and TGF-βR2expression and TGF-3secretion decreased. And the inhibition of rosiglitazone showed a significant dose-dependent way. Smad3phosphorylation levels decreased significantly too. Smad3/Smad4complexes, P-21and C-myc expression was also decreased under the rosiglitazone effect.Conclusions:1) PPAR-gamma agonist rosiglitazone can significantly inhibit the proliferation of glioma cells. This inhibition is dose and time dependent.2) PPAR-gamma activator rosiglitazone significantly inhibited the invasiveness of glioma U87and U251cells. Adhesion molecules (ICAM-1, VCAM-1and E-selectin) of Glioma cells declined under PPAR-gamma activator rosiglitazone. which was associated with glioma cell invasion decreasing.3) The TGF-β/Smad3signaling pathway was important in rosiglitazone inhibiting glioma cell proliferation, invasion and metastasis which can be the basis for the clinical application of rosiglitazone in the treatment of glioma.