Objective/Rationale:Neurotrophic factors have been explored as a novel treatment for Parkinson’s disease. Toxic effect of α-synucleinopathies, one of the hallmarks in PD pathophysiology, occurs in endoplasmic reticulum (ER) and α-synuclein accumulation leads to ER stress and contributes to neurodegeneration. Recent data about the mechanism of CDNF indicate that its neuroprotective effects are mediated by mechanisms involved in ER stress. This proposal studies the effectiveness of human CDNF protein in pre-clinical models of α-synuclein-induced dopamine neurondegeneration.
The neuroprotective effectiveness of intrastriatally delivered CDNF protein against neurodegeneration of nigral dopamine neurons in α-synucleipathies induced by α-synuclein expressing viral vectors will be studied. First, we will compare four different preparations of adeno-associated virus (AAV)-vectors expressing α-synuclein in their ability to induce neurodegeneration in substantia nigra. Amphetamine-induced rotation and cylinder test, as well tyrosine hydroxylase immunohistochemistry from striatum and substantia nigra, will be performed. CDNF protein or vehicle (PBS buffer solution) will be injected unilaterally at the dose of 10 μg into the striatum. The dose has been chosen based on previous studies. AAV-6 vector carrying human α-synuclein cDNA will be injected just above pre-clinical model substantia nigra one day later. Similar outcome measures as stated above will be used in the neuroprotection experiment.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
Our results show that CDNF is a potent treatment candidate to stop the progression of PD. Our main goal is to take CDNF to the clinic for the treatment of PD. To reach that goal this study will further clarify the pharmacodynamic action of CDNF in another pre-clinical model of PD. This study will further enable to predict the efficacy of CDNF in human PD patients.
Neurotrophic factors GDNF and NRTN are in clinical trials for PD, but current results show their modest clinical benefit. One reason for this is poor diffusion of GDNF and NRTN in the brain. GDNF has no neuropoetective effecsts in α-synuclein overexpressing rat models of PD. CDNF diffuses significantly better in brain and is involved in protein folding and regulation of ER stress. We postulate that CDNF can assist α-synuclein folding and protect neurons against α-synucleopathies.
The aim of the project was to study further what is the optimal site of delivery for novel neurotrophic factor CDNF and clarify the its mode of action in vivo and in vitro. We found that CDNF can protect and rescue dopamine neurons in rat pre-clinical model of Parkinson’s disease (PD) when delivered either to the striatum (STR), or to the substantia nigra (SN) or simultaneously to both sites. Experiments carried out at different doses of CDNF clearly show that simultaneous delivery of CDNF to SN and STR is more efficient than delivery to a single site. However, the difference is not dramatic and therefore either delivery of CDNF protein to the STR or simultaneous delivery to two sites is recommended.
We have earlier found that CDNF and the related protein, MANF have a unique structure. Now we found that CDNF has a unique mode of action that dramatically differs from the mechanism of action of other neurotrophic factors. CDNF mainly acts inside the cells in the endoplasmic reticulum (ER) where it interacts with key molecules of unfolded protein response pathways and rescues neurons from ER stress-induced cell death. CDNF can also act extracellularly, but CDNF in the culture medium cannot protect naïve dopamine neurons from cell death. Surprisingly, dopamine neurons become CDNF-responsive only after ER stress or injury. This is a conceptually important finding demonstrating that CDNF acts only on ER stressed or injured neurons and has no effects on healthy naïve neurons.