Erythropoietin modulates intracellular calcium in a human neuroblastoma cell line

Abstract

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.