Elsevier

Brain Research

Volume 1254, 13 February 2009, Pages 120-127
Brain Research

Research Report
Continuous intraventricular infusion of erythropoietin exerts neuroprotective/rescue effects upon Parkinson's disease model of rats with enhanced neurogenesis

https://doi.org/10.1016/j.brainres.2008.11.094Get rights and content

Abstract

Parkinson's disease (PD) is characterized by degeneration of nigrostriatal dopaminergic neuronal systems. Several therapeutic tools for PD include medication using l-DOPA and surgeries such as deep brain stimulation are established. However, the therapies are considered as symptomatic therapy, but not basic remedy for PD and a new regenerative therapy would be desired to explore. In this study, the neuroprotective/rescue effects of erythropoietin (EPO), a well known hematopoietic hormone, on dopaminergic neurons were explored with neurogeneic potencies of EPO. EPO (100 IU/day) was continuously administered with micro-osmotic pump for a week to PD model of rats induced by intrastriatal 6-hydroxydopamine (6-OHDA) injection with subsequent behavioral and immunohistochemical investigations. The number of amphetamine-induced rotations of EPO-treated rats significantly decreased, compared to the control rats. The preservation of dopaminergic neurons of EPO-treated rats were confirmed by tyrosine hydroxylase staining and Fluoro-Gold staining. The number of bromodeoxyuridine (BrdU)/polysialic acid-neural cell adhesion molecule (PSA-NCAM) double positive cells in the subventricular zone of EPO-treated rats significantly increased with migratory potencies to the damaged striatum, compared to the control rats. Furthermore, TUNEL staining and phosphorylated Akt staining revealed that the neuroprotective/rescue effects of EPO might be mediated by anti-apoptotic effects through the increase of phosphorylated Akt. These results suggest that continuous low dose infusion of EPO exerts neuroprotective/rescue effects with neurogeneic potentials. EPO might be a strong tool for PD therapy, although the further experiments should be added.

Introduction

Parkinson's disease (PD) is a neurodegenerative disease with clinical symptoms such as bradykinesia, rigidity, tremor and abnormal postural reflexes (Sethi, 2002). The medication using l-DOPA is established as an effective therapy, although long term administration of l-DOPA causes side effects including on–off phenomena, wearing-off phenomena, or drug-induced dyskinesia. Surgeries such as deep brain stimulation and thalamotomy are also established with a certain achievement. However the therapeutic tools for PD above described are all symptomatic, but not essential and regenerative. As hopeful therapeutic tools for PD, transplantation of fetal nigral cell or infusion of glial cell line-derived neurotrophic factor (GDNF) was developed. However, nigral cell transplantation just achieved partial effectiveness and GDNF therapy did not show any significant behavioral amelioration in several randomized controlled trials (Lang et al., 2006, Freed et al., 2001). Therefore, it is important to develop new therapies.

Erythropoietin (EPO) is a well-known hematopoietic hormone produced in the kidney. EPO is used for renal anemia and proven safe. Recent studies revealed various potentials of EPO other than hematopoiesis. Neuroprotective effects of EPO have been demonstrated in a variety of animal models of hypoxic/ischemic CNS disorders (Maurer et al., 2008). Neuroprotective effects of EPO were proved using preclinical models of CNS diseases including focal and global ischemia, neurotrauma, autoimmune encephalitis, kainate-induced seizures, subarachnoid hemorrhage and spinal cord injury. Furthermore, EPO is used for patients with cerebral infarct and effectiveness was demonstrated recently (Ehrenreich et al., 2002). The mechanisms of EPO-induced neuroprotection include prevention of glutamate-induced toxicity, inhibition of apoptosis, anti-inflammatory effects, anti-oxidant effects, and stimulation of angiogenesis (Montero et al., 2007, Zhang et al., 2006, Liu et al., 2005). In our study, we would like to clarify if EPO exerts neuroprotective/rescue and neurogeneic effects on 6-hydroxydopamine (6-OHDA)-treated dopaminergic neurons in vivo.

Section snippets

Intraventricular EPO infusion did not demonstrate significant hematopoietic effects

The low dose (100 IU/day) of EPO-treated rats slightly increased without significant differences in hematocrit (47 ± 3.5%) and hemoglobin (15.7 ± 0.7 g/dl), compared with the control (43 ± 4.1% and 14.1 ± 0.6; p = 0.11 and 0.08, respectively). All rats in the both groups were healthy and had no differences in the spontaneous behavior.

EPO reduced the number of amphetamine-induced rotation

There were no significant changes in the spontaneous behavior between EPO-treated and the control rats (data not shown). In the control rats, the number of

Discussion

In this study, continuous infusion of low dose of EPO exerted neuroprotective/rescue effects on Parkinson's disease model of rats behaviorally and immunohistochemically. The neuroprotective/rescue effects were at least partially mediated through anti-apoptotic effects via the increase of phosphorylated Akt and neurogeneic effects in the subventricular zone.

Conclusions

Continuous infusion of low dose of EPO exerted neuroprotective/rescue effects in reversing behavioral deficits associated with PD and prevented apoptosis of the dopaminergic neurons through the PI3K pathway. Additionally, EPO might enhance intrinsic neurogenesis and migration towards damaged striatum. Recent pharmacological development enabled us to take advantages of EPO without hematopoietic side effects (Lapchak, 2008, Villa et al., 2007, Leist et al., 2004). Consequently, EPO might be a

Experimental protocol

Neurotoxin, 6-hydroxydopamine (6-OHDA) was injected into the right striatum of female Sprague–Dawley rats. Thirty minutes later, rats were divided into 2 groups, that is, EPO-treated rats and the control rats. Because our preliminary study using single administration of EPO did not show any neuroprotective effects on PD model of rats, continuous administration of EPO was designed. In EPO-treated rats, EPO (100 IU/day) dissolved in rat serum albumin was continuously infused into the right

Acknowledgments

This work was supported in part by Grants-in-Aid for Scientific Research and by the grant from the Project for realization of regenerative medicine from the Ministry of Education, Culture, Sports, Science, and Technology, Japan.

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