Stefan Lorenzl

Dipeptide repeat protein pathology in C9ORF72 mutation cases: clinico-pathological correlations

Hexanucleotide repeat expansion in C9ORF72 is the most common genetic cause of frontotemporal dementia and motor neuron disease. Recently, unconventional non-ATG translation of the expanded hexanucleotide repeat, resulting in the production and aggregation of dipeptide repeat (DPR) proteins (poly-GA, -GR and GP), was identified as a potential pathomechanism of C9ORF72 mutations. Besides accumulation of DPR proteins, the second neuropathological hallmark lesion in C9ORF72 mutation cases is the accumulation of TDP-43. In this study, we characterized novel monoclonal antibodies against poly-GA and performed a detailed analysis of the neuroanatomical distribution of DPR and TDP-43 pathology in a cohort of 35 cases with the C9ORF72 mutation that included a broad spectrum of clinical phenotypes. We found the pattern of DPR pathology to be highly consistent among cases regardless of the phenotype with high DPR load in the cerebellum, all neocortical regions (frontal, motor cortex and occipital) and hippocampus, moderate pathology in subcortical areas and minimal pathology in lower motor neurons. No correlation between DPR pathology and the degree of neurodegeneration was observed, while a good association between TDP-43 pathology with clinical phenotype and degeneration in key anatomical regions was present. Our data confirm that the presence of DPR pathology is intimately related to C9ORF72 mutations. The observed dissociation between DPR inclusion body load and neurodegeneration might suggest inclusion body formation as a potentially protective response to cope with soluble toxic DPR species. Moreover, our data imply that alterations due to the C9ORF72 mutation resulting in TDP-43 accumulation and dysmetabolism as secondary downstream effects likely play a central role in the neurodegenerative process in C9ORF72 pathogenesis.

Davunetide in patients with progressive supranuclear palsy: a randomised, double-blind, placebo-controlled phase 2/3 trial

BACKGROUND In preclinical studies, davunetide promoted microtubule stability and reduced tau phosphorylation. Because progressive supranuclear palsy (PSP) is linked to tau pathology, davunetide could be a treatment for PSP. We assessed the safety and efficacy of davunetide in patients with PSP. METHODS In a double-blind, parallel group, phase 2/3 trial, participants were randomly assigned with permuted blocks in a 1:1 ratio to davunetide (30 mg twice daily, intranasally) or placebo for 52 weeks at 48 centres in Australia, Canada, France, Germany, the UK, and the USA. Participants met the modified Neuroprotection and Natural History in Parkinson Plus Syndrome study criteria for PSP. Primary endpoints were the change from baseline in PSP Rating Scale (PSPRS) and Schwab and England Activities of Daily Living (SEADL) scale at up to 52 weeks. All participants and study personnel were masked to treatment assignment. Analysis was by intention to treat. The trial is registered with Clinicaltrials.gov, number NCT01110720. FINDINGS 313 participants were randomly assigned to davunetide (n=157) or to placebo (n=156), and 241 (77%) completed the study (118 and 156 in the davunetide and placebo groups, respectively). There were no differences in the davunetide and placebo groups in the baseline PSPRS and SEADL. The davunetide and placebo groups did not differ in the change from baseline in PSPRS (median 11·8 [95% CI 10·5 to 13·0] vs 11·8 [10·5 to 13·0], respectively, p=0·41) or SEADL (-0·20 [-0·20 to -0·17] vs -0·20 [-0·22 to -0·17], respectively, p=0·92). 54 serious adverse events were reported in each of the treatment groups, including 11 deaths in the davunetide group and ten in the placebo group. The frequency of nasal adverse events was greater in the davunetide group than in the placebo group (epistaxis 18 [12%] of 156 vs 13 [8%] of 156, rhinorrhoea 15 [10%] vs eight [5%], and nasal discomfort 15 [10%] vs one [<1%]). INTERPRETATION Davunetide is not an effective treatment for PSP. Clinical trials of disease-modifying treatment are feasible in patients with PSP and should be pursued with other promising tau-directed treatments. FUNDING Allon Therapeutics.

Clinical diagnosis of progressive supranuclear palsy: The movement disorder society criteria.

Background: PSP is a neuropathologically defined disease entity. Clinical diagnostic criteria, published in 1996 by the National Institute of Neurological Disorders and Stroke/Society for PSP, have excellent specificity, but their sensitivity is limited for variant PSP syndromes with presentations other than Richardsons syndrome.

Homocysteine, folate and vitamin B12 in neuropsychiatric diseases: review and treatment recommendations

In Europe, neuropsychiatric diseases currently make up approximately a third of the total burden of disease. In 2004, 27% of the overall population was affected by at least one of the most frequent neuropsychiatric diseases such as Alzheimer’s dementia, Parkinson’s disease, stroke or depression. The annual costs of care exceed those of cancer, cardiovascular conditions and diabetes. In order to delay the onset or course of neurodegenerative diseases, the available potential should be utilized. As well as improving quality of life of patients and relatives, this may reduce the great financial burden caused by neurodegenerative disorders. However, the availability of established drugs or therapeutic agents is very limited. This paper reviews the state of current knowledge as to how homocysteine metabolism is relevant for neurodegenerative and other neuropsychiatric diseases, with particular emphasis on the evidence for prophylactic and therapeutic strategies. In the European countries, many people do not take the recommended daily minimum amount of folate and vitamin B12. Deficiency of these vitamins and secondary changes in the concentrations of associated metabolites, such as methylmalonic acid and homocysteine, may contribute to the onset and progression of neuropsychiatric diseases. This paper reviews the evidence regarding whether substitution of folate and vitamin B12 is beneficial, for example, in cerebrovascular disease, dementia and depression.

Antioxidants attenuate microvascular changes in the early phase of experimental pneumococcal meningitis in rats.

Background and Purpose: We tested in a rat meningitis model 1) whether pneumococcal cell wall components are capable of producing changes in regional cerebral blood flow, brain water content, and intracranial pressure similar to those we have already observed after intracisternal inoculation of live pneumococci and 2) whether antioxidants would modulate these alterations in the early phase of meningitis. Methods: Regional cerebral blood flow as measured by laser Doppler flowmetry and intracranial pressure were monitored continuously for 4 hours after intracisternal challenge. Brain edema formation was assessed by brain water content determinations. We investigated the following groups: rats challenged intracisternally with the whole intact pneumococcal cell wall (n=7) or the pneumococcal cell wall hydrolyzed by the Ml-muramidase (n=7); rats injected intracisternally with phosphate-buffered saline (n=6); rats pretreated intravenously with superoxide dismutase conjugated with polyethylene glycol (10,000 units/kg) and injected intracisternally with cell wall components (n=5) or phosphate-buffered saline (n=6); rats injected intracisternally with phosphate-buffered saline and pretreated intravenously with polyethylene glycol (10% solution, 1.2 ml/kg, n=S) or continuously treated with intravenous free superoxide dismutase (22,000 units/kg per hour, n=6); and rats continuously treated intravenously with deferoxamine mesylate (10 mg/kg per hour) and injected intracisternally with cell wall components (n=6) or phosphate-buffered saline (n=7). Results: Both pneumococcal cell wall preparations produced a significant increase in regional cerebral blood flow, intracranial pressure, and brain water content Conjugated superoxide dismutase as well as deferoxamine prevented the increase in intracranial pressure and brain water content In addition, the increase in regional cerebral blood flow as observed in untreated, cell wall-challenged rats (baseline, 100%; 183.1 ± 123% after 4 hours, mean±SEM) was significantly attenuated by administration of both conjugated superoxide dismutase (136.6±14.1%) and deferoxamine (149.8±8J%) (p<0.05). Polyethylene glycol-conjugated superoxide dismutase alone produced an increase in regional cerebral blood flow (L25.6±8.7% after 4 hours). We found that polyethylene glycol per se accounts for this action. Conclusions: These data show that pneumococcal cell wall components containing teichoic acid produce changes in regional cerebral blood flow, intracranial pressure, and brain water content and that oxygen radicals contribute to these pathophysiological alterations in the early phase of experimental pneumococcal meningitis.

Increased α-synuclein aggregation following limited cleavage by certain matrix metalloproteinases

Recent evidence indicates that protein aggregation and in particular the formation of toxic protein oligomers is a key mechanism in synucleinopathies such as Parkinsons disease (PD). Post mortem brain tissue studies as well as animal studies furthermore suggest that matrix metalloproteinases (MMPs) are also involved in the pathogenesis of PD. We used confocal single molecule spectroscopy to characterize the influence of MMPs and other proteases on the aggregation of alpha-synuclein. These studies were complemented by the characterization of alpha-synuclein fragment patterns generated by these proteases using gel electrophoresis and mass spectrometry. Limited digestion by MMP-1 and MMP-3, but not by MMP-9, increased the tendency of alpha-synuclein to aggregate. Proteinase K and Trypsin did not increase the level of de novo aggregation of alpha-synuclein. SDS-PAGE as well as MALDI-ToF analysis of limitedly digested alpha-synuclein demonstrate that all proteases generate different fragments of alpha-synuclein. We provide mass spectrometry data of proteolytic alpha-synuclein fragments and propose specific cleavage sites for MMP-1 and MMP-9 in alpha-synuclein. We furthermore found four additional cleavage sites of MMP-3 that had not been described previously. In order to increase aggregation of alpha-synuclein, specific cleavage between the highly charged C-terminal domain and the aggregation-prone NAC domain of alpha-synuclein seems to be crucial. Our findings obtained in vitro in a well-characterized model of pathological alpha-synuclein aggregation indicate that MMP-1 and MMP-3 may also influence pathogenesis of PD in vivo by generation of specific aggregation-enhancing alpha-synuclein fragments resulting from limited proteolysis.

A consensus review on the development of palliative care for patients with chronic and progressive neurological disease

The European Association of Palliative Care Taskforce, in collaboration with the Scientific Panel on Palliative Care in Neurology of the European Federation of Neurological Societies (now the European Academy of Neurology), aimed to undertake a review of the literature to establish an evidence‐based consensus for palliative and end of life care for patients with progressive neurological disease, and their families.

Postural imbalance and falls in PSP correlate with functional pathology of the thalamus

Objective: To determine how postural imbalance and falls are related to regional cerebral glucose metabolism (PET) and functional activation of the cerebral postural network (fMRI) in patients with progressive supranuclear palsy (PSP). Methods: Sixteen patients with PSP, who had self-monitored their frequency of falls, underwent a standardized clinical assessment, posturographic measurement of balance during modified sensory input, and a resting [18F]FDG-PET. In addition, patients performed an fMRI paradigm using mental imagery of standing. Results were compared to healthy controls (n = 16). Results: The frequency of falls/month in patients (range 1–40) correlated with total PSP rating score (r = 0.90). Total sway path in PSP significantly correlated with frequency of falls, especially during modulated sensory input (eyes open: r = 0.62, eyes closed: r = 0.67, eyes open/head extended: r = 0.84, eyes open/foam-padded platform: r = 0.87). Higher sway path values and frequency of falls were associated with decreased regional glucose metabolism (rCGM) in the thalamus (sway path: r = −0.80, falls: r = −0.64) and increased rCGM in the precentral gyrus (sway path: r = 0.79, falls: r = 0.64). Mental imagery of standing during fMRI revealed a reduced activation of the mesencephalic brainstem tegmentum and the thalamus in patients with postural imbalance and falls. Conclusions: The new and clinically relevant finding of this study is that imbalance and falls in PSP are closely associated with thalamic dysfunction. Deficits in thalamic postural control get most evident when balance is assessed during modified sensory input. The results are consistent with the hypothesis that reduced thalamic activation via the ascending brainstem projections may cause postural imbalance in PSP.

Functional disturbance of the locomotor network in progressive supranuclear palsy

Objective: To determine pathologic regulations and potential compensatory mechanisms in the supraspinal locomotor network of patients with progressive supranuclear palsy (PSP) by investigation of brain activation during walking and correlation to gait performance. Methods: Twelve patients with PSP were scanned with [18F]-FDG-PET during walking and at rest as has been described earlier. Results were compared to age-matched healthy controls (n = 12). Results: The major results were as follows. 1) At rest, the regional cerebral glucose metabolism (rCGM) in the supraspinal locomotor centers, i.e., the prefrontal cortex, the subthalamic nucleus, and the pedunculopontine/cuneiform nucleus complex, was reduced in PSP. 2) Severity of gait impairment, measured by gait velocity, step length, and progressive supranuclear palsy rating scales/gait, correlated with decrease of rCGM in the prefrontal cortex and subthalamic nucleus. 3) Accordingly, during walking functional activation of the prefrontal cortex, the subthalamic nucleus, the pedunculopontine/cuneiform nucleus complex, and the thalamus was reduced in patients with PSP compared to controls. 4) The precentral gyrus and the vermal cerebellum were activated more strongly during locomotion in PSP. Conclusions: Gait impairment in PSP is especially associated with dysfunction of the indirect, modulatory prefrontal–subthalamic–pedunculopontine loop of locomotor control. The direct, stereotyped locomotor loop from the primary motor cortex to the spinal cord with rhythmic cerebellar drive shows increased activity in PSP. The latter can be interpreted as an attempt of compensation, but may also contribute to a stereotyped gait pattern in PSP.

Critical appraisal of the role of davunetide in the treatment of progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a rare neurodegenerative disease characterized by the accumulation of tau protein aggregates in the basal ganglia, brainstem and cerebral cortex leading to rapid disease progression and death. The neurofibrillary tangles that define the neuropathology of PSP are comprised of aggregated 4R tau and show a well-defined distribution. Classically, PSP is diagnosed by symptoms that include progressive gait disturbance, early falls, vertical ophthalmoparesis, akinetic-rigid features, prominent bulbar dysfunction and fronto-subcortical dementia. There are currently no effective therapies for the treatment of this rapidly degenerating and debilitating disease. Davunetide is a novel neuroprotective peptide that is thought to impact neuronal integrity and cell survival through the stabilization of microtubules. Preclinical activity in models of tauopathy has been translated to clinical studies, demonstrating pharmacologic activity that has supported further development. Davunetide’s efficacy and tolerability are being tested in a placebo-controlled study in PSP patients, making it the most advanced drug candidate in this indication. This review examines the disease characteristics of PSP, the rationale for treating PSP with davunetide and assesses some of the challenges of clinical trials in this patient population.