Counteracting neuroinflammation in experimental Parkinson’s disease favors recovery of function : effects of Er-NPCs administration

Parkinson’s disease (PD) is the second most common neurodegenerative disease, presenting with midbrain dopaminergic neuronal degeneration. A growing number of studies suggest that microglial activation plays a role in PD. Indeed, inflammation-derived oxidative stress and cytokine-dependent toxicity may contribute to nigrostriatal pathway degeneration and exacerbate the progression of the disease in patients with idiopathic PD. Cell therapies have long been considered a feasible regenerative approach to compensate for the loss of specific cell populations such as the one that occurs in PD. We recently demonstrated that Erythropoietin-releasing Neural Precursors (Er-NPCs) administered to MPTP intoxicated animals survive after transplantation in the recipient damaged brain, differentiate and rescue degenerating striatal dopaminergic neurons. Here we aimed to investigate the potential anti-inflammatory actions of Er-NPCs infused in an MPTP experimental model of PD. The degeneration was obtained by the intraperitoneal administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (36 mg/kg) in C57BL/6 male mice. 2.5x105 GFP-labeled Er-NPCs were administered by stereotaxic injection unilaterally in the left striatum. Functional recovery was assessed by two independent behavioral tests. Neuroinflammation was investigated measuring the mRNAs levels of pro-inflammatory and anti-inflammatory cytokines and immunohistochemistry studies were performed to evaluate markers of inflammation and the potential rescue of endogenous TH positive projections in the recipient striatum. Our results show that animals grafted with Er-NPCs determined a remarkable improvement of behavior measured by means of horizontal, vertical and olfactory tests beginning the third day after transplantation. By means of immunofluorescence staining, we found that the majority of transplanted Er-NPCs were vital and promote the recovery of dopaminergic markers such as DAT and TH. Furthermore, Er-NPCs administration promoted a rapid anti-inflammatory effect that was already evident 24h after transplant with a decrease of pro-inflammatory and increase of anti-inflammatory cytokines mRNA expression levels. This effect was maintained during the complete observational period, two weeks post-transplant. We also show that Er-NPCs transplant reduces the macrophage infiltration, directly counteracting the M1 pro-inflammatory response of primary murine activated microglia, with the decrease of CD68 and CD86 markers, and inducing M2 pro-regeneration traits, as indicated by the increase of CD206 expression. Moreover, we also show that Er-NPCs-derived Erythropoietin (EPO) mediates this activity, since the co-injection of precursors with an anti-EPO antibody neutralizes the anti-inflammatory effect of the Er-NPCs treatment. This study shows the anti-inflammatory actions exerted by Er-NPCs and we suggest that these cells may represent good candidates for cellular therapy to counteract neuroinflammation in neurodegenerative disorders.