Neurology Publications and Presentations

Neuroprotective effects of statins: evidence from preclinical and clinical studies

Marc Fisher et al. — Tue, 12 Feb 2013 19:29:33 PST

OPINION STATEMENT: The benefits of statins for both primary and secondary prevention of ischemic stroke are clearly established. Evidence is accumulating that statin withdrawal after ischemic stroke may lead to worse outcome and that initiation of statins after ischemic stroke may reduce mortality and improve outcome. Current treatment guidelines recommend starting statins before discharge in patients with stroke related to atherosclerosis or who have elevated cholesterol. The primary treatment question then is not if to start statins in most ischemic stroke patients, but when. Our recommendation would be start a statin as soon as the patient passes a dysphagia screen and can safely take oral medication. Based on the results of the Heart Protection Study and the SPARCL trial, either simvastatin 40 mg or atorvastatin 80 mg are appropriate alternatives. Clinical trials are needed to demonstrate unequivocal efficacy of improved outcome and to determine if lower doses may have this effect. Additionally, improved outcome needs to be established in cardioembolic stroke patients before routine use of statins in this stroke subtype can be recommended.

International, multicenter randomized preclinical trials in translational stroke research: it's time to act

Ulrich Dirnagl et al. — Tue, 12 Feb 2013 19:29:32 PST

Translational stroke research is in a crisis, and pharmaceutical companies continue to exit the field. Many reasons for the apparently insurmountable barrier between the bench and bedside in stroke drug development have been identified. It is time to act now to bridge the gap between preclinical and clinical studies of purported new therapies. We strongly believe that it is too early to abandon translational stroke research.

Endovascular acute ischemic stroke therapy: applying basic science to clinical decisions

Marc Fisher — Tue, 12 Feb 2013 19:29:31 PST

Excerpt: The interface between basic science and clinical medicine is a key to an enhanced understanding of disease pathophysiology and for developing novel therapies. The term translational research is applied to this interface and provides a framework for the interaction between basic scientists and clinicians. Ischemic stroke is a medical disorder for which translational research is particularly important, because of rapidly developing advances in understanding the cellular consequences of focal brain ischemia, the contributions of the neurovascular unit to disease pathophysiology, and the role of blood vessel abnormalities. These and other factors contribute to the development and evolution of ischemic brain injury when a thrombus impairs blood flow to a brain region. Reperfusion of these ischemic brain regions with thrombolytic drugs such as tissue plasminogen activator (tPA) or by deploying a mechanical device to remove the occluding thrombus is a logical approach to ischemic stroke therapy, because each method restores the availability of oxygen and glucose-rich blood flow that potentiate salvage of ischemic tissue destined for infarction.

Identifying and utilizing the ischemic penumbra

Marc Fisher et al. — Tue, 12 Feb 2013 19:29:30 PST

The penumbral concept is defined as different areas within the ischemic region evolve into irreversible brain injury over time and that this evolution is most critically linked to the severity of the decline in cerebral blood flow (CBF). The ischemic penumbra was initially defined as a region of reduced CBF with absent spontaneous or induced electrical potentials that still maintained ionic homeostasis and transmembrane electrical potentials. The reduction of CBF levels to between 10 and 15 mL/100 g/min and approximately 25 mL/100 g/min are likely to identify penumbral tissue, and the ischemic core of irreversible ischemic tissue has a CBF value below the lower threshold. The role of identifying this critically deprived brain tissue from CBF in triaging patients for endovascular ischemic therapy is evolving. In this review we focus on the basic science of the penumbral concept and identification using various imaging modalities (PET, MRI, and CT) in animal models and human studies. Another article in this supplement addresses the clinical implication and the current understanding and application of this concept into clinical practice of endovascular ischemic stroke therapy.

A call for transparent reporting to optimize the predictive value of preclinical research

Story C. Landis et al. — Tue, 12 Feb 2013 19:29:29 PST

The US National Institute of Neurological Disorders and Stroke convened major stakeholders in June 2012 to discuss how to improve the methodological reporting of animal studies in grant applications and publications. The main workshop recommendation is that at a minimum studies should report on sample-size estimation, whether and how animals were randomized, whether investigators were blind to the treatment, and the handling of data. We recognize that achieving a meaningful improvement in the quality of reporting will require a concerted effort by investigators, reviewers, funding agencies and journal editors. Requiring better reporting of animal studies will raise awareness of the importance of rigorous study design to accelerate scientific progress.

RNA-binding proteins in neurological disease

Fen-Biao Gao et al. — Thu, 13 Sep 2012 07:49:19 PDT

Homologous Recombination Mediates Functional Recovery of Dysferlin Deficiency following AAV5 Gene Transfer

William E. Grose et al. — Thu, 13 Sep 2012 07:49:18 PDT

The dysferlinopathies comprise a group of untreatable muscle disorders including limb girdle muscular dystrophy type 2B, Miyoshi myopathy, distal anterior compartment syndrome, and rigid spine syndrome. As with other forms of muscular dystrophy, adeno-associated virus (AAV) gene transfer is a particularly auspicious treatment strategy, however the size of the DYSF cDNA (6.5 kb) negates packaging into traditional AAV serotypes known to express well in muscle (i.e. rAAV1, 2, 6, 8, 9). Potential advantages of a full cDNA versus a mini-gene include: maintaining structural-functional protein domains, evading protein misfolding, and avoiding novel epitopes that could be immunogenic. AAV5 has demonstrated unique plasticity with regards to packaging capacity and recombination of virions containing homologous regions of cDNA inserts has been implicated in the generation of full-length transcripts. Herein we show for the first time in vivo that homologous recombination following AAV5.DYSF gene transfer leads to the production of full length transcript and protein. Moreover, gene transfer of full-length dysferlin protein in dysferlin deficient mice resulted in expression levels sufficient to correct functional deficits in the diaphragm and importantly in skeletal muscle membrane repair. Intravascular regional gene transfer through the femoral artery produced high levels of transduction and enabled targeting of specific muscle groups affected by the dysferlinopathies setting the stage for potential translation to clinical trials. We provide proof of principle that AAV5 mediated delivery of dysferlin is a highly promising strategy for treatment of dysferlinopathies and has far-reaching implications for the therapeutic delivery of other large genes.

Association of UBQLN1 mutation with Brown-Vialetto-Van Laere syndrome but not typical ALS

Paloma Gonzalez-Perez et al. — Thu, 13 Sep 2012 07:49:17 PDT

Genetic variants in UBQLN1 gene have been linked to neurodegeneration and mutations in UBQLN2 have recently been identified as a rare cause of amyotrophic lateral sclerosis (ALS). OBJECTIVE: To test if genetic variants in UBQLN1 are involved in ALS. METHODS: 102 and 94 unrelated patients with familial and sporadic forms of ALS were screened for UBQLN1 gene mutations. Single nucleotide variants were further screened in a larger set of sporadic ALS (SALS) patients and unrelated control subjects using high-throughput Taqman genotyping; variants were further assessed for novelty using the 1000Genomes and NHLBI databases. In vitro studies tested the effect of UBQLN1 variants on the ubiquitin-proteasome system (UPS). RESULTS: Only two UBQLN1 coding variants were detected in the familial and sporadic ALS DNA set; one, the missense mutation p.E54D, was identified in a single patient with atypical motor neuron disease consistent with Brown-Vialetto-Van Laere syndrome (BVVLS), for whom c20orf54 mutations had been excluded. Functional studies revealed that UBQLN1(E54D) protein forms cytosolic aggregates that contain mislocalized TDP-43 and impairs degradation of ubiquitinated proteins through the proteasome. CONCLUSIONS: Genetic variants in UBQLN1 are not commonly associated with ALS. A novel UBQLN1 mutation (E45D) detected in a patient with BVVLS altered nuclear TDP-43 localization in vitro, suggesting that UPS dysfunction may also underlie the pathogenesis of this condition.

Suberoylanilide hydroxamic acid (vorinostat) up-regulates progranulin transcription: rational therapeutic approach to frontotemporal dementia

Basar Cenik et al. — Thu, 13 Sep 2012 06:19:39 PDT

Progranulin (GRN) haploinsufficiency is a frequent cause of familial frontotemporal dementia, a currently untreatable progressive neurodegenerative disease. By chemical library screening, we identified suberoylanilide hydroxamic acid (SAHA), a Food and Drug Administration-approved histone deacetylase inhibitor, as an enhancer of GRN expression. SAHA dose-dependently increased GRN mRNA and protein levels in cultured cells and restored near-normal GRN expression in haploinsufficient cells from human subjects. Although elevation of secreted progranulin levels through a post-transcriptional mechanism has recently been reported, this is, to the best of our knowledge, the first report of a small molecule enhancer of progranulin transcription. SAHA has demonstrated therapeutic potential in other neurodegenerative diseases and thus holds promise as a first generation drug for the prevention and treatment of frontotemporal dementia.

MicroRNA-9: functional evolution of a conserved small regulatory RNA

Yeliz Yuva-Aydemir et al. — Thu, 13 Sep 2012 06:19:38 PDT

The functional significance of microRNA-9 (miR-9) during evolution is evidenced by its conservation at the nucleotide level from flies to humans but not its diverse expression patterns. Recent studies in several model systems reveal that miR-9 can regulate neurogenesis through its actions in neural or non-neural cell lineages. In vertebrates, miR-9 exerts diverse cell-autonomous effects on the proliferation, migration, and differentiation of neural progenitor cells by modulating different mRNA targets. In some developmental contexts, miR-9 suppresses apoptosis and is misregulated in several types of cancer cells, influencing proliferation or metastasis formation. Moreover, downregulation of miR-9 in postmitotic neurons is also implicated in some neurodegenerative diseases. Thus, miR-9 is emerging as an important regulator in development and disease through its ability to modulate different targets in a manner dependent on the developmental stage and the cellular context.

Midbody accumulation through evasion of autophagy contributes to cellular reprogramming and tumorigenicity

Tse-Chun Kuo et al. — Thu, 13 Sep 2012 06:19:37 PDT

The midbody is a singular organelle formed between daughter cells during cytokinesis and required for their final separation. Midbodies persist in cells long after division as midbody derivatives (MB(d)s), but their fate is unclear. Here we show that MB(d)s are inherited asymmetrically by the daughter cell with the older centrosome. They selectively accumulate in stem cells, induced pluripotent stem cells and potential cancer 'stem cells' in vivo and in vitro. MB(d) loss accompanies stem-cell differentiation, and involves autophagic degradation mediated by binding of the autophagic receptor NBR1 to the midbody protein CEP55. Differentiating cells and normal dividing cells do not accumulate MB(d)s and possess high autophagic activity. Stem cells and cancer cells accumulate MB(d)s by evading autophagosome encapsulation and exhibit low autophagic activity. MB(d) enrichment enhances reprogramming to induced pluripotent stem cells and increases the in vitro tumorigenicity of cancer cells. These results indicate unexpected roles for MB(d)s in stem cells and cancer 'stem cells'.

FXR1P but not FMRP regulates the levels of mammalian brain-specific microRNA-9 and microRNA-124

Xia-Lian Xu et al. — Thu, 13 Sep 2012 06:19:36 PDT

Mammalian brain-specific miR-9 and miR-124 have been implicated in several aspects of neuronal development and function. However, it is not known how their expression levels are regulated in vivo. We found that the levels of miR-9 and miR-124 are regulated by FXR1P but not by the loss of FXR2P or FMRP in vivo, a mouse model of fragile X syndrome. Surprisingly, the levels of miR-9 and miR-124 are elevated in fmr1/fxr2 double-knock-out mice, in part reflecting posttranscriptional upregulation of FXR1P. Indeed, FXR1P is required for efficient processing of pre-miR-9 and pre-miR-124 in vitro and forms a complex with Dicer and pre-miRNAs. These findings reveal differential roles of FMRP family proteins in controlling the expression levels of brain-specific miRNAs.

Neurophysiological defects and neuronal gene deregulation in Drosophila mir-124 mutants

Kailiang Sun et al. — Thu, 13 Sep 2012 06:19:35 PDT

miR-124 is conserved in sequence and neuronal expression across the animal kingdom and is predicted to have hundreds of mRNA targets. Diverse defects in neural development and function were reported from miR-124 antisense studies in vertebrates, but a nematode knockout of mir-124 surprisingly lacked detectable phenotypes. To provide genetic insight from Drosophila, we deleted its single mir-124 locus and found that it is dispensable for gross aspects of neural specification and differentiation. On the other hand, we detected a variety of mutant phenotypes that were rescuable by a mir-124 genomic transgene, including short lifespan, increased dendrite variation, impaired larval locomotion, and aberrant synaptic release at the NMJ. These phenotypes reflect extensive requirements of miR-124 even under optimal culture conditions. Comparison of the transcriptomes of cells from wild-type and mir-124 mutant animals, purified on the basis of mir-124 promoter activity, revealed broad upregulation of direct miR-124 targets. However, in contrast to the proposed mutual exclusion model for miR-124 function, its functional targets were relatively highly expressed in miR-124-expressing cells and were not enriched in genes annotated with epidermal expression. A notable aspect of the direct miR-124 network was coordinate targeting of five positive components in the retrograde BMP signaling pathway, whose activation in neurons increases synaptic release at the NMJ, similar to mir-124 mutants. Derepression of the direct miR-124 target network also had many secondary effects, including over-activity of other post-transcriptional repressors and a net incomplete transition from a neuroblast to a neuronal gene expression signature. Altogether, these studies demonstrate complex consequences of miR-124 loss on neural gene expression and neurophysiology.

Neuronal Functions of ESCRTs

Jin-A Lee et al. — Thu, 13 Sep 2012 06:19:34 PDT

The endosomal sorting complexes required for transport (ESCRTs) regulate protein trafficking from endosomes to lysosomes. Recent studies have shown that ESCRTs are involved in various cellular processes, including membrane scission, microRNA function, viral budding, and the autophagy pathway in many tissues, including the nervous system. Indeed, dysfunctional ESCRTs are associated with neurodegeneration. However, it remains largely elusive how ESCRTs act in post-mitotic neurons, a highly specialized cell type that requires dynamic changes in neuronal structures and signaling for proper function. This review focuses on our current understandings of the functions of ESCRTs in neuronal morphology, synaptic plasticity, and neurodegenerative diseases.

Cause or Effect: Misregulation of microRNA Pathways in Neurodegeneration

Eduardo Gascon et al. — Thu, 13 Sep 2012 06:19:33 PDT

During normal aging or neurodegenerative diseases, neuronal survival and function depend on protein homeostasis, which is regulated by multiple mechanisms, including the microRNA (miRNA) pathway. In different cells types, the absence of Dicer, a key miRNA processing enzyme, leads to neurodegeneration through cell-autonomous and non-cell-autonomous mechanisms. Loss of certain miRNAs also causes neurodegeneration in some model organisms. On the other hand, miRNA expression is misregulated in patients with different neurodegenerative diseases. Thus, the miRNA pathway appears to be essential in the pathogenesis of several age-dependent neurodegenerative conditions; however, our understanding of the underlying mechanism remains rudimentary. The precise causal relationships between specific miRNAs and neurodegeneration in humans need to be further investigated.

Visualization of clot lysis in a rat embolic stroke model: application to comparative lytic efficacy

Ronn P. Walvick et al. — Tue, 29 May 2012 14:56:49 PDT

BACKGROUND AND PURPOSE: The purpose of this study was to develop a novel MRI method for imaging clot lysis in a rat embolic stroke model and to compare tissue plasminogen activator (tPA)-based clot lysis with and without recombinant Annexin-2 (rA2).

METHODS: In experiment 1 we used in vitro optimization of clot visualization using multiple MRI contrast agents in concentrations ranging from 5 to 50 muL in 250 muL blood. In experiment 2, we used in vivo characterization of the time course of clot lysis using the clot developed in the previous experiment. Diffusion, perfusion, angiography, and T1-weighted MRI for clot imaging were conducted before and during treatment with vehicle (n=6), tPA (n=8), or rA2 plus tPA (n=8) at multiple time points. Brains were removed for ex vivo clot localization.

RESULTS: Clots created with 25 muL Magnevist were the most stable and provided the highest contrast-to-noise ratio. In the vehicle group, clot length as assessed by T1-weighted imaging correlated with histology (r=0.93). Clot length and cerebral blood flow-derived ischemic lesion volume were significantly smaller than vehicle at 15 minutes after treatment initiation in the rA2 plus tPA group, whereas in the tPA group no significant reduction from vehicle was observed until 30 minutes after treatment initiation. The rA2 plus tPA group had a significantly shorter clot length than the tPA group at 60 and 90 minutes after treatment initiation and significantly smaller cerebral blood flow deficit than the tPA group at 90 minutes after treatment initiation.

CONCLUSIONS: We introduce a novel MRI-based clot imaging method for in vivo monitoring of clot lysis. Lytic efficacy of tPA was enhanced by rA2.

Partial aortic occlusion for cerebral perfusion augmentation: safety and efficacy of NeuroFlo in Acute Ischemic Stroke trial

Ashfaq Shuaib et al. — Tue, 29 May 2012 14:56:36 PDT

BACKGROUND AND PURPOSE: Fewer than 5% of patients with acute ischemic stroke are currently treated, and there is need for additional treatment options. A novel catheter treatment (NeuroFlo) that increases cerebral blood flow was tested to 14 hours.

METHODS: The Safety and Efficacy of NeuroFlo in Acute Ischemic Stroke trial is a randomized trial of the safety and efficacy of NeuroFlo treatment in improving neurological outcome versus standard medical management. The primary safety end point was the incidence of serious adverse events through 90 days. The primary efficacy end point on a modified intent-to-treat population was a global disability end point at 90 days. Secondary end points included mortality, intracranial hemorrhage, modified Rankin scale score outcome of 0 to 2, and modified Rankin scale shift analysis.

RESULTS: Between October 2005 and January 2010, 515 patients were enrolled at 68 centers in 9 countries. The primary efficacy end point did not reach statistical significance (OR, 1.17; CI, 0.81-1.67; P=0.407). The primary safety end point did not show a difference in serious adverse events (P=0.923). Ninety-day mortality was 11.3% (26/230) in treatment and 16.3% (42/257) in control (P=0.087). Post hoc analyses showed that patients presenting within 5 hours (OR, 3.33; CI, 1.31-8.48), with NIHSS score 8 to 14 (OR, 1.80; CI, 0.99-3.30), or older than age 70 years (OR, 2.02; CI, 1.02-4.03) had better modified Rankin scale score outcomes of 0 to 2; additionally, there were fewer stroke-related deaths in treatment compared to control groups (7.4% = 17/230; 14.4% = 37/257).

CONCLUSIONS: The trial met its primary safety end point but not its primary efficacy end point. Signals of treatment effect were suggested on all-cause mortality, in patients presenting early, older than age 70 years, or with moderate strokes, but these require confirmation.

CLINICAL TRIAL REGISTRATION INFORMATION: URL: http://clinicaltrials.gov. Unique identifier: NCT00119717.

Terutroban versus aspirin in patients with cerebral ischaemic events (PERFORM): a randomised, double-blind, parallel-group trial

Marie-Germaine Bousser et al. — Tue, 29 May 2012 14:56:23 PDT

BACKGROUND: Patients with ischaemic stroke or transient ischaemic attack (TIA) are at high risk of recurrent stroke or other cardiovascular events. We compared the selective thromboxane-prostaglandin receptor antagonist terutroban with aspirin in the prevention of cerebral and cardiovascular ischaemic events in patients with a recent non-cardioembolic cerebral ischaemic event.

METHODS: This randomised, double-blind, parallel-group trial was undertaken in 802 centres in 46 countries. Patients who had an ischaemic stroke in the previous 3 months or a TIA in the previous 8 days were randomly allocated with a central interactive response system to 30 mg per day terutroban or 100 mg per day aspirin. Patients and investigators were masked to treatment allocation. The primary efficacy endpoint was a composite of fatal or non-fatal ischaemic stroke, fatal or non-fatal myocardial infarction, or other vascular death (excluding haemorrhagic death). We planned a sequential statistical analysis of non-inferiority (margin 1.05) followed by analysis of superiority. Analysis was by intention to treat. The study was stopped prematurely for futility on the basis of the recommendation of the Data Monitoring Committee. This study is registered, number ISRCTN66157730.

FINDINGS: 9562 patients were assigned to terutroban (9556 analysed) and 9558 to aspirin (9544 analysed); mean follow-up was 28.3 months (SD 7.7). The primary endpoint occurred in 1091 (11%) patients receiving terutroban and 1062 (11%) receiving aspirin (hazard ratio [HR] 1.02, 95% CI 0.94-1.12). There was no evidence of a difference between terutroban and aspirin for the secondary or tertiary endpoints. We recorded some increase in minor bleedings with terutroban compared with aspirin (1147 [12%] vs 1045 [11%]; HR 1.11, 95% CI 1.02-1.21), but no significant differences in other safety endpoints.

INTERPRETATION: The trial did not meet the predefined criteria for non-inferiority, but showed similar rates of the primary endpoint with terutroban and aspirin, without safety advantages for terutroban. In a worldwide perspective, aspirin remains the gold standard antiplatelet drug for secondary stroke prevention in view of its efficacy, tolerance, and cost.

FUNDING: Servier, France.

Neuroprotection by freezing ischemic penumbra evolution without cerebral blood flow augmentation with a postsynaptic density-95 protein inhibitor

Bernt T. Bratane et al. — Tue, 29 May 2012 14:56:09 PDT

BACKGROUND AND PURPOSE: The purpose of this study was to determine whether neuroprotection is feasible without cerebral blood flow augmentation in experimental permanent middle cerebral artery occlusion.

METHODS: Rats were subjected to permanent middle cerebral artery occlusion by the suture occlusion method and were treated 1 hour thereafter with a single 5-minute intravenous infusion of the postsynaptic density-95 protein inhibitor Tat-NR2B9c (7.5 mg/kg) or saline (n=8/group). Arterial spin-labeled perfusion-weighted MRI and diffusion weighted MRI were obtained with a 4.7-T Bruker system at 30, 45, 70, 90, 120, 150, and 180 minutes postmiddle cerebral artery occlusion to determine cerebral blood flow and apparent diffusion coefficient maps, respectively. At 24 hours, animals were neurologically scored (0 to 5), euthanized, and the brains stained with 2-3-5-triphenyl tetrazolium chloride to ascertain infarct volumes corrected for edema. Additionally, the effects of Tat-NR2B9c on adenosine 5'-triphosphate levels were measured in vitro in neurons subjected to oxygen-glucose deprivation.

RESULTS: Final infarct volume was decreased by 30.3% in the Tat-NR2B9c-treated animals compared with controls (P=0.028). There was a significant improvement in 24 hours neurological scores in the Tat-NR2B9c group compared with controls, 1.8+/-0.5 and 2.8+/-1.0, respectively (P=0.021). Relative to controls, Tat-NR2B9c significantly attenuated diffusion-weighted imaging lesion growth and preserved the diffusion-weighted imaging/perfusion-weighted imaging mismatch (ischemic penumbra) without affecting cerebral blood flow in the ischemic core or penumbra. Tat-NR2B9c treatment of primary neuronal cultures resulted in 26% increase in cell viability and 34% greater adenosine 5'-triphosphate levels after oxygen-glucose deprivation.

CONCLUSIONS: Preservation of adenosine 5'-triphosphate levels in vitro and neuroprotection in permanent middle cerebral artery occlusion in rats is achievable without cerebral blood flow augmentation using a postsynaptic density-95 protein inhibitor.

Improving the accuracy of perfusion imaging in acute ischemic stroke

Gregory W. Albers et al. — Tue, 29 May 2012 14:55:56 PDT