Dexamethasone inhibits apoptosis in C6 glioma cells through increased expression of Bcl-XL.

The glucocorticoid dexamethasone (Dex) has been reported to modulate a number of signaling pathways and physiological processes, including apoptosis. This study was carried out to investigate the cytoprotective mechanism of Dex in C6 glioma cells. Pre-treatment of cells with Dex inhibited apoptosis induced by staurosporine, etoposide and thapsigargin. Apoptosis inhibition correlated with blockade of mitochondrial cytochrome c release, abolition of caspase-3 activity along with inhibition of caspase-9 and PARP cleavage. Dex-mediated cytoprotection coincided with the induction of the anti-apoptotic protein, Bcl-X(L). The specific glucocorticoid receptor antagonist, RU486, reversed the anti-apoptotic effect of Dex and prevented Bcl-X(L) induction. Here, we show for the first time that knockdown of Bcl-X(L) expression with siRNA reversed the protective effects of the glucocorticoid in glioma cells. We conclude that Dex-mediated inhibition of apoptosis in C6 glioma cells is through induction of Bcl-X(L).