Erythropoietin modulates intracellular calcium in a human neuroblastoma cell line

1. Recent investigations have shown that the glycoprotein erythropoietin (Epo) and its specific receptor (EpoR) are present in the mammalian brain including human, monkey and mouse. These findings suggest a local action of Epo in the nervous system. The aim of this study was to elucidate a possible functional interaction of Epo with neuronal cells. 2. To examine the influence of externally applied Epo on Ca²⁺ homeostasis the human neuroblastoma cell line SK-N-MC was chosen as a suitable in vitro model for undifferentiated neuronal cells. 3. Expression of the EpoR in SK-N-MC cells was detected by reverse transcription-PCR, Western blot and immunofluorescence analysis. 4. Patch-clamp studies of SK-N-MC cells confirmed the expression of T-type Ca²⁺ channels, whose peak macroscopic current was increased by the addition of recombinant human Epo (rhEpo) to the bathing medium. 5. Confocal laser scanning microscopy analysis of SK-N-MC cells confirmed a transient increase in intracellular free [Ca²⁺] in response to externally applied rhEpo. 6. The transient response to Epo was dependent on external Ca²⁺ and remained even after depletion of internal Ca²⁺ stores by caffeine or thapsigargin. However, after depletion the response to Epo was absent when cells were superfused with the T-type Ca²⁺ channel blocker flunarizine. 7. This study demonstrates that Epo can interact with neuronal cells by affecting Ca²⁺ homeostasis through an increase in Ca²⁺ influx via plasma membrane T-type voltage-dependent Ca²⁺ channels.