Aims: To compare the neuroprotection of erythropoietin (EPO) and EPO fusion protein containing transduction
domain derived from HIV TAT (EPO-TAT) against ischemic brain injury, inclusive of the side effect, and explore the
mechanism underlying the role of EPO-TAT in a transient focal cerebral ischemia model in rats.
Methods: Transient focal ischemia was induced by middle cerebral artery occlusion (MCAO) in rats. Rats were treated,
respectively, with following regimens: saline, 1000 U/kg EPO, 5000 U/kg EPO, 1000 U/kg EPO-TAT, 1000 U/kg EPOTAT
+ 5 µl of 10 mM LY294002 (or/plus 5 µl of 5 mM PD98059). Neurological deficit scores, infarct volume, and
hematologic side effect were assessed at 72 hours after MCAO. Apoptotic cells were determined with TUNEL staining.
The expression and localization of phosphorylated AKT (pAKT) and phosphorylated ERK (pERK) were detected with
Western blot, immunohistochemistry, and immunofluorescence, respectively.
Results: 1000 U/kg EPO-TAT exhibited a comparable neuroprotection to 5000 U/kg EPO, as evidenced by a comparable
attenuation in neurological deficit, infarct volume, and number of apoptotic cells in the rat ischemic cortex after MCAO.
The pAKT and pERK levels were significantly elevated solely in neurons of rodents receiving EPO or EPO-TAT
treatments, suggesting the concurrent activation of these two pathways. Specific inhibition of either AKT or ERK
pathway partially abolished EPO-TAT protection, but exhibited no influence on the activation status of its counterpart,
suggesting no cross-modulation between these two protective pathways.
Conclusion: Our study indicates that EPO-TAT at 1000 U/kg displays neuroprotection with no detectable side effects. The
mechanism for neuroprotection may be attributable to the simultaneous activation of the AKT and ERK pathways, which
preserve neuronal cell viability and attenuate behavioral deficits.