Treatment of Adenosine Activates Mitogen-activated Protein Kinases via Activation of Transcriptional Factor, Elk-1, in Rat Ovarian Surface Epithelial Cells.

Abstract

Extracellular adenosine has been suggested to play a role in cellular proliferation and intracellular calcium concentrations (Ca2+) in ovarian cells. To investigate the role of adenosine in rat ovarian folliculogenesis or steroidogenesis, we examined the expression of the adenosine receptors and effect of adenosine on growth stimulation in rat ovarian surface epithelial (OSE) cells. Rat OSE cells were isolated and cultured in DMEM media with 10% FBS. Our results indicated that adenosine mRNA was expressed and adenosine exerted a growth-stimulatory effect in rat OSE cells. To investigate the mechanism of the growth-stimulatory effect, the activation of mitogen-activated protein kinases (MAPKs) by adenosine was examined. Treatment with adenosine resulted in MAPK activation in these cells, whereas the stimulatory effect of adenosine in the cellular proliferation and MAPK activation was completely abolished in the presence of PD98059 (a MAPK/ERK Kinase, MEK inhibitor) and staurosporin (a Protein Kinase C, PKC inhibitor), suggesting that the growth stimulatory effect of adenosine may be mediated via PKC-dependent MAPK activation in rat OSE cells. In a time-dependent study, adenosine significantly increased MAPK activity at 5-20 min and the activated MAPK declined to control level after 20 min in these cells. Similarly, treatment with adenosine significantly induced MAPK activation after 5 min and sustained for 60 min in these OSE cells. In addition, treatment with adenosine resulted in substantial phosphorylation of Elk-1, confirming that adenosine action is mediated by activation of MAPK. In conclusion, we demonstrated that adenosine receptor was expressed and adenosine induced a growth-stimulation in rat OSE cells. Furthermore, the treatment with adenosine resulted in the activation of MAPK cascade and phosphorylation of Elk-1 in these cells. Taken together, these results suggest that the MAPK cascade may be involved in the growth stimulation in response to adenosine in rat OSE cells.[This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2010-0003093).] (poster)