Depertment of pharmacology and clinical neuroscience

Telomere length (TL) is regarded as a marker of cellular aging due to the gradual shortening by each cell division, but is influenced by a number of factors including oxidative stress and inflammation. Parkinson's disease and atypical forms of parkinsonism occur mainly in the elderly, with oxidative stress and inflammation in afflicted cells. In this study the relationship between blood TL and prognosis of 168 patients with idiopathic parkinsonism (136 Parkinson's disease [PD], 17 Progressive Supranuclear Palsy [PSP], and 15 Multiple System Atrophy [MSA]) and 30 controls was investigated. TL and motor and cognitive performance were assessed at baseline (diagnosis) and repeatedly up to three to five years follow up. No difference in TL between controls and patients was shown at baseline, nor any significant difference in TL stability or attrition during follow up. Interestingly, a significant relationship between TL at diagnosis and cognitive phenotype at follow up in PD and ...

Adeno-associated virus (AAV) vectors are used to deliver potentially therapeutic genes in clinical trials in Parkinson's disease (PD). Pre-existing immunity to AAV and a local neuroinflammatory response might negatively affect the efficacy of such AAV-mediated gene delivery. We pre-immunized rats with wild-type AAV-2. Three months later, we created PD-like lesions by intrastriatal injections of 6-hydroxydopamine (6-OHDA) in 50% of the animals. One month later, we injected AAV2 vector expressing enhanced green fluorescent protein (eGFP) in the striatum. Using immunohistochemistry, we assessed eGFP expression, microglia activation and CD8 T cell infiltration. We also measured AAV-2 specific neutralizing antibody titers in the serum. The number of striatal cells transduced with AAV2 vector expressing eGFP was reduced by 71% in rats pre-immunized with wild-type AAV2 compared to non-immunized animals. We detected elevated numbers of OX6(+) activated microglia in the striatum and circulating AAV2-specific neutralizing antibodies in pre-immunized rats. We also observed that the intrastriatal 6-OHDA injection promoted CD8(+) T cell infiltration and enhanced microglia activation. Nevertheless, the 6-OHDA lesion did not alter AAV2-mediated expression of eGFP in either pre-immunized or non-immunized rats. Our findings indicate that intracerebral AAV2-based gene therapy is compromised in rats with pre-existing immunity to AAV2. By contrast, a local neuroinflammatory response, caused by intrastriatal a 6-OHDA injection, does not affect viral vector-mediated transgene expression. Our results emphasize the importance of monitoring circulating AAV-specific neutralizing antibodies in patients undergoing intracerebral gene therapy using AAV vectors.

Current research on Parkinson's disease (PD) pathogenesis requires relevant animal models that mimic the gradual and progressive development of neuronal dysfunction and degeneration that characterizes the disease. Polymorphisms in engrailed 1 (En1), a homeobox transcription factor that is crucial for both the development and survival of mesencephalic dopaminergic neurons, are associated with sporadic PD. This suggests that En1 mutant mice might be a promising candidate PD model. Indeed, a mouse that lacks one En1 allele exhibits decreased mitochondrial complex I activity and progressive midbrain dopamine neuron degeneration in adulthood, both features associated with PD. We aimed to further characterize the disease-like phenotype of these En1(+/-) mice with a focus on early neurodegenerative changes that can be utilized to score efficacy of future disease modifying studies. We observed early terminal defects in the dopaminergic nigrostriatal pathway in En1(+/-) mice. Several weeks before a significant loss of dopaminergic neurons in the substantia nigra could be detected, we found that striatal terminals expressing high levels of dopaminergic neuron markers TH, VMAT2, and DAT were dystrophic and swollen. Using transmission electron microscopy, we identified electron dense bodies consistent with abnormal autophagic vacuoles in these terminal swellings. In line with these findings, we detected an up-regulation of the mTOR pathway, concurrent with a downregulation of the autophagic marker LC3B, in ventral midbrain and nigral dopaminergic neurons of the En1(+/-) mice. This supports the notion that autophagic protein degradation is reduced in the absence of one En1 allele. We imaged the nigrostriatal pathway using the CLARITY technique and observed many fragmented axons in the medial forebrain bundle of the En1(+/-) mice, consistent with axonal maintenance failure. Using in vivo electrochemistry, we found that nigrostriatal terminals in the dorsal striatum were severely deficient in dopamine release and reuptake. Our findings support a progressive retrograde degeneration of En1(+/-) nigrostriatal neurons, akin to what is suggested to occur in PD. We suggest that using the En1(+/-) mice as a model will provide further key insights into PD pathogenesis, and propose that axon terminal integrity and function can be utilized to estimate dopaminergic neuron health and efficacy of experimental PD therapies.

Early in differentiation, all neural cells have a rostral character. Only later do posteriorly positioned neural cells acquire characteristics of caudal forebrain, midbrain and hindbrain cells. Caudalization of neural tissue in the chick embryo apparently involves the convergent actions of (i) fibroblast growth factor (FGF) signaling and (ii) signaling from the caudal paraxial mesoderm, or 'PMC activity', which has not yet been defined molecularly. Here we report evidence that Wnt signaling underlies PMC activity, and show that Wnt signals act directly and in a graded manner on anterior neural cells to induce their progressive differentiation into caudal forebrain, midbrain and hindbrain cells.