Neurosteroid-growth factor cross-talk induces up and down regulation of GFAP and vimentin expression in serum free astrocyte cultures.

In this research we aimed to investigate the interactions between growth factors (GFs) and dexamethasone (DEX) on cytoskeletal proteins GFAP and vimentin (VIM) expression under the following experimental condition: 24h pretreatment with bFGF, subsequent 72h switching in serum-free medium (SFM) and final addition of GFs, only one or more in the last 24h, after a prolonged (60h) DEX treatment. Western blot analysis data showed a marked GFAP expression in cultures submitted to our experimental condition comparing results to untreated or treated controls. In particular, the maximum level of GFAP expression is observed when EGF or INS or both together are added in a prolonged 60h DEX treatment. This finding well correlates with differentiative role played by glucocorticoids interacting with the "competence" factor bFGF and demonstrates as increased GFAP expression mostly depends on maturation, rather than proliferating status of astroglial cells in culture. VIM expression was instead significantly reduced after GFs addition in the last 24h of 60h DEX treatment, respect to control DEX-pretreated ones. Comparing the data to untreated controls, VIM expression was significantly enhanced after GFs addition. Collectively, our findings evidence an interactive effect between GFs and DEX in astroglial cultures, co-pretreated with DEX and bFGF, regulating cytoskeletal network under stressfull conditions.