Interferon-α-induced serotonin uptake in Jurkat T cells via mitogen-activated protein kinase and transcriptional regulation of the serotonin transporter

Interferon (IFN)-α upregulates serotonin (5-HT) uptake and serotonin transporter (5-HTT) messenger ribonucleic acid (mRNA) expression in immune cells, which implies the mechanism underlying IFN-α-induced depression. However, the signal transduction of this effect remains unclear. We investigated whether the effects of IFN-α on the functions of 5-HTT were related to mitogen-activated protein kinase (MAPK). By performing Western blotting, real-time reverse transcriptase-polymerase chain reaction and [ ³H]5-HT labelling, we examined MAPK phosphorylation, 5-HTT mRNA expression and 5-HT uptake in Jurkat T cells. The cells had been cultured for different time periods (1) with IFN-α alone and (2) preincubated with either MAPK inhibitors or with the selective serotonin reuptake inhibitor, fluoxetine, and subsequently cultured along with IFN-α. The levels of MAPK phosphorylation, 5-HTT mRNA expression and 5-HT uptake all increased in the IFN-α-treated cells but were blocked in those that were pretreated with MAPK inhibitors and fluoxetine. These results appear to clarify the association of depression with IFN-α-induced 5-HT uptake that reduces the 5-HT levels and IFN-α-regulated transcription of 5-HTT; further, the results suggest the involvement of MAPK in this process.