Effects of Erythropoietin on Neuronal Activity

Abstract

Abstract:Recently, erythropoietin (EPO) receptors and synthesis of EPO have been identified in the brain. To clarify the effects of EPO on neuronal cells, we investigated the effects of EPO on Ca 2ϩ uptake, intracellular Ca 2ϩ concentration, membrane potential, cell survival, release and biosynthesis of dopamine, and nitric oxide (NO) production in differentiated PC12 cells, which possess EPO receptors. EPO (10 Ϫ12 -10 Ϫ10 M) increased 45 Ca 2ϩ uptake and intracellular Ca 2ϩ concentration in PC12 cells in a dose-related manner; these increases were inhibited by nicardipine (1 M) or anti-EPO antibody (1:100 dilution). EPO induced membrane depolarization in PC12 cells. After a 5-day culture without serum and nerve growth factor (NGF), viable cell number decreased to 50% of that of the control cells cultured with serum and NGF. EPO (10 Ϫ13 -10 Ϫ10 M) increased the number of viable cells cultured without serum and NGF; this increase was blunted by nicardipine or anti-EPO antibody. Incubation with EPO (10 Ϫ13 -10 Ϫ10 M) stimulated mitogen-activated protein kinase activity in PC12 cells. EPO (10 Ϫ13 -10 Ϫ10 M) increased dopamine release from PC12 cells and tyrosine hydroxylase activity; these increases were sensitive to nicardipine or anti-EPO antibody. Following a 4-h incubation with EPO (10 Ϫ14 -10 Ϫ10 M), NO production was increased, which was blunted by nicardipine and anti-EPO antibody. In contrast, maximal NO synthase activity was not changed by EPO. These results suggest that EPO stimulates neuronal function and viability via activation of Ca 2ϩ channels. Key Words: Erythropoietin-PC12 cells-Ca 2ϩ channels-Cell survivalDopamine release -Nitric oxide.

Asialoerythropoietin is a nonerythropoietic cytokine with broad neuroprotective activity in vivo

“…PC-12 cells were differentiated in the presence of nerve growth factor (NGF) and cell death was triggered by NGF withdrawal. EPO variants were used in this assay as described (32) and were present 24 h before and during the withdrawal period. For viability assessment the reduction of thiozole salts was used.…”

Neuroprotection by erythropoietin administration after experimental traumatic brain injury

“…Processes occurring in the early stage after TBI, such as release of glutamate, lactate, potassium, calcium, free oxygen radicals, histamine, and kinins by injured cells, seem to be more relevant in the pathophysiological mechanisms underlying brain damage following TBI (Unterberg et al, 2004). In this regard, EPO administration has been associated with protection from glutamate toxicity by activation of calcium channels (Sakanaka et al, 1998), production of antioxidant enzymes in neurons (Koshimura et al, 1999), and reduction of the NO toxicity in neurons (Calapai et al, 2000;Sakanaka et al, 1998).…”

Neuroprotective effects and intracellular signaling pathways of erythropoietin in a rat model of multiple sclerosis

“…In previous studies on hematopoietic progenitors as well as in a study on neuronal cell cultures, an Epo-induced activation of the MEK/MAPK pathway has been demonstrated. 43,[51][52][53] To investigate the functional significance of this part of the Epoinduced signal transduction in vivo, we treated rats with a combination of Epo and PD 98059, a selective and cellpermeable inhibitor of the single upstream kinase MEK. 54 Under this combined treatment, RGC counts were only moderately decreased when compared to Epo monotherapy, indicating that phosphorylation of MAPKs has a smaller impact on Epo-induced RGC survival than activation of PI3-K/ Akt.…”