Beneficial effects of carbamylated erythropoietin against oxygen-glucose deprivation/reperfusion-induced astrocyte swelling: proposed molecular mechanisms of action.

Carbamylated erythropoietin (C-EPO), one of the erythropoietin derivatives, retains strong anti-edema and neuroprotective properties while lacking the hematopoietic complications of erythropoietin. This study investigated the intracellular and molecular mechanisms underlying the anti-edema property of C-EPO. An in vitro model of astrocyte swelling was created by 5h of oxygen-glucose deprivation and subsequent reperfusion (OGD/Rep). Astrocyte cultures were then treated with C-EPO or left as control cells. Here we show that increases in astrocyte volume, morphological cell swelling, and changes in ultrastructure after OGD/Rep were significantly mitigated by treatment with C-EPO (10 ng/ml). The decreases in AQP-4 phosphorylation after OGD/Rep were remarkably recovered by C-EPO treatment. The OGD/Rep-induced upregulations of AQP-4 mRNA and protein were also prevented by C-EPO treatment. Additional treatment with phorbol myristate acetate, an activator of protein kinase C (PKC), enhanced C-EPO-mediated neuroprotective effects, while that of H-7, an inhibitor of PKC, blocked these protections. Our findings establish that C-EPO effectively mitigates astrocyte swelling induced by ischemia and reperfusion-like injury. The modulation of AQP-4 phosphorylation and expression via the PKC pathway is participated in the neuroprotective effects of C-EPO.