Subcortical functional connectivity and its association with walking performance following deployment related mild TBI

Introduction

The relation between traumatic brain injury (TBI), its acute and chronic symptoms, and the potential for remote neurodegenerative disease is a priority for military research. Structural and functional connectivity (FC) of the basal ganglia, involved in motor tasks such as walking, are altered in some samples of Service Members and Veterans with TBI, but any behavioral implications are unclear and could further depend on the context in which the TBI occurred.

Methods

In this study, FC from caudate and pallidum seeds was measured in Service Members and Veterans with a history of mild TBI that occurred during combat deployment, Service Members and Veterans whose mild TBI occurred outside of deployment, and Service Members and Veterans who had no lifetime history of TBI.

Results

FC patterns differed for the two contextual types of mild TBI. Service Members and Veterans with deployment-related mild TBI demonstrated increased FC between the right caudate and lateral occipital regions relative to both the non-deployment mild TBI and TBI-negative groups. When evaluating the association between FC from the caudate and gait, the non-deployment mild TBI group showed a significant positive relationship between walking time and FC with the frontal pole, implicated in navigational planning, whereas the deployment-related mild TBI group trended towards a greater negative association between walking time and FC within the occipital lobes, associated with visuo-spatial processing during navigation.

Discussion

These findings have implications for elucidating subtle motor disruption in Service Members and Veterans with deployment-related mild TBI. Possible implications for future walking performance are discussed.

Codon-optimized TDP-43 mediates neurodegeneration in a Drosophila model of ALS/FTLD

Transactive response DNA binding protein-43 (TDP-43) is known to mediate neurodegeneration associated with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). The exact mechanism by which TDP-43 exerts toxicity in the brains, spinal cord, and lower motor neurons of affected patients remains unclear. In a novel Drosophila melanogaster model, we report gain-of-function phenotypes due to misexpression of insect codon-optimized version of human wild-type TDP-43 (CO-TDP-43) using both the binary GAL4/UAS system and direct promoter fusion constructs. The CO-TDP-43 model showed robust tissue specific phenotypes in the adult eye, wing, and bristles in the notum. Compared to non-codon optimized transgenic flies, the CO-TDP-43 flies produced increased amount of high molecular weight protein, exhibited pathogenic phenotypes, and showed cytoplasmic aggregation with both nuclear and cytoplasmic expression of TDP-43. Further characterization of the adult retina showed a disruption in the morphology and function of the photoreceptor neurons with the presence of acidic vacuoles that are characteristic of autophagy. Based on our observations, we propose that TDP-43 has the propensity to form toxic protein aggregates via a gain-of-function mechanism, and such toxic overload leads to activation of protein degradation pathways such as autophagy. The novel codon optimized TDP-43 model is an excellent resource that could be used in genetic screens to identify and better understand the exact disease mechanism of TDP-43 proteinopathies and find potential therapeutic targets.

A pilot study of olfactory function in veterans with a history of deployment-related mild traumatic brain injury

Olfactory impairment in military populations is highly prevalent and often attributed to the long-term effects of mild traumatic brain injury (mTBI) and chronic psychiatric disorders. The main goal of this investigation was to examine olfactory function in a cohort of combat veterans using a quantitative smell test.Participants underwent a neurological examination, completed performance validity testing (PVT), provided deployment history, and their medical records were reviewed.Participants were 38 veterans with a deployment-related mTBI who passed the PVT and did not have ongoing substance misuse issues. Olfactory examination revealed normosmia in 20 participants and various degrees of deficit in 18. The groups did not differ in demographics, post-injury interval, or current clinical (non-psychiatric) conditions. Participants with hyposmia frequently reported being exposed to a higher number of blasts and being positioned closer to the nearest primary blast, and more often endorsed a period of loss of consciousness after the most serious mTBI. In addition, they more often reported tympanic membrane perforation, extracranial injuries, and histories of both blast and blunt force mTBI. Comorbid diagnoses of posttraumatic stress disorder, depression, chronic headaches, and pain were more common among them as well.Several blast exposure and injury-related characteristics increase the likelihood of long-term olfactory impartments, comorbid psychiatric conditions, and chronic pain among veterans with history of deployment-related mTBI. Notably, none of the participants with hyposmia had a clinical diagnosis of olfactory dysfunction or were receiving service-connected disability for loss of sense of smell at the time of their assessment.

Use of EpiAlveolar Lung Model to Predict Fibrotic Potential of Multiwalled Carbon Nanotubes

Expansion in production and commercial use of nanomaterials increases the potential human exposure during the lifecycle of these materials (production, use, and disposal). Inhalation is a primary route of exposure to nanomaterials; therefore it is critical to assess their potential respiratory hazard. Herein, we developed a three-dimensional alveolar model (EpiAlveolar) consisting of human primary alveolar epithelial cells, fibroblasts, and endothelial cells, with or without macrophages for predicting long-term responses to aerosols. Following thorough characterization of the model, proinflammatory and profibrotic responses based on the adverse outcome pathway concept for lung fibrosis were assessed upon repeated subchronic exposures (up to 21 days) to two types of multiwalled carbon nanotubes (MWCNTs) and silica quartz particles. We simulate occupational exposure doses for the MWCNTs (1-30 μg/cm²) using an air-liquid interface exposure device (VITROCELL Cloud) with repeated exposures over 3 weeks. Specific key events leading to lung fibrosis, such as barrier integrity and release of proinflammatory and profibrotic markers, show the responsiveness of the model. Nanocyl induced, in general, a less pronounced reaction than Mitsui-7, and the cultures with human monocyte-derived macrophages (MDMs) showed the proinflammatory response at later time points than those without MDMs. In conclusion, we present a robust alveolar model to predict inflammatory and fibrotic responses upon exposure to MWCNTs.

Use of EpiAlveolar Lung Model to Predict Fibrotic Potential of Multiwalled Carbon Nanotubes

Expansion in production and commercial use of nanomaterials increases the potential human exposure during the lifecycle of these materials (production, use, and disposal). Inhalation is a primary route of exposure to nanomaterials; therefore it is critical to assess their potential respiratory hazard. Herein, we developed a three-dimensional alveolar model (EpiAlveolar) consisting of human primary alveolar epithelial cells, fibroblasts, and endothelial cells, with or without macrophages for predicting long-term responses to aerosols. Following thorough characterization of the model, proinflammatory and profibrotic responses based on the adverse outcome pathway concept for lung fibrosis were assessed upon repeated subchronic exposures (up to 21 days) to two types of multiwalled carbon nanotubes (MWCNTs) and silica quartz particles. We simulate occupational exposure doses for the MWCNTs (1-30 μg/cm²) using an air-liquid interface exposure device (VITROCELL Cloud) with repeated exposures over 3 weeks. Specific key events leading to lung fibrosis, such as barrier integrity and release of proinflammatory and profibrotic markers, show the responsiveness of the model. Nanocyl induced, in general, a less pronounced reaction than Mitsui-7, and the cultures with human monocyte-derived macrophages (MDMs) showed the proinflammatory response at later time points than those without MDMs. In conclusion, we present a robust alveolar model to predict inflammatory and fibrotic responses upon exposure to MWCNTs.

Revisiting the intersection of amyloid, pathologically modified tau and iron in Alzheimer's disease from a ferroptosis perspective

The complexity of Alzheimer's disease (AD) complicates the search for effective treatments. While the key roles of pathologically modified proteins has occupied a central role in hypotheses of the pathophysiology, less attention has been paid to the potential role for transition metals overload, subsequent oxidative stress, and tissue injury. The association of transition metals, the major focus heretofore iron and amyloid, the same can now be said for the likely pathogenic microtubular associated tau (MAPT). This review discusses the interplay between iron, pathologically modified tau and oxidative stress, and connects many related discoveries. Basic principles of the transition to pathological MAPT are discussed. Iron, its homeostatic mechanisms, the recently described phenomenon of ferroptosis and purported, although still controversial roles in AD are reviewed as well as considerations to overcome existing hurdles of iron-targeted therapeutic avenues that have been attempted in AD. We summarize the involvement of multiple pathological pathways at different disease stages of disease progression that supports the potential for a combinatorial treatment strategy targeting multiple factors.

Feasibility study: Effect of hand resistance exercise on handwriting in Parkinson's disease and essential tremor

STUDY DESIGN

A single group, repeated measures design was used.

INTRODUCTION

Tremor can lead to impaired hand function in patients with Parkinson's disease (PD) and essential tremor (ET). Difficulty with handwriting is a common complaint in these patients suffering from hand tremors. The effect of hand resistance exercise on handwriting is unknown.

PURPOSE OF THE STUDY

To explore the influence of 6 weeks of home-based hand resistance exercise on handwriting in individuals with PD and ET.

METHODS

Nine individuals with PD and 9 with ET participated in the study. The average age was 65.3 (6.0) years with an average disease duration of 7.8 years. Participants were instructed to perform a home-based, hand and arm resistance exercise program 3 times a week for 6 weeks. Samples of the area of handwriting and maximal grip strength were measured at baseline and after 6 weeks of exercise. The area of the handwriting sample and maximal grip strength measured before and after 6 weeks were compared.

RESULTS

Mean grip strength of the participants with PD improved after 6 weeks of hand resistance exercise (P = .031), but grip strength did not change in ET (P = .091). The size of the handwriting samples (words and sentences) did not change after exercise in either participants with PD or ET.

DISCUSSION

Micrographia in patients with PD and macrographia in patients with ET represent complex fine motor skills. More research is needed to understand what therapies could be effective in modifying the size and quality of handwriting.

CONCLUSIONS

The purpose of this feasibility study was to explore the influence of home-based wrist resistance exercise on handwriting in individuals with PD and ET. Despite small gains in grip strength, the size of the handwriting samples (words and sentences) did not change for patients with PD or ET following a 6-week home-based hand resistance exercise program.

Insulin-Mediated Changes in Tau Hyperphosphorylation and Autophagy in a Drosophila Model of Tauopathy and Neuroblastoma Cells

Almost 50 million people in the world are affected by dementia; the most prevalent form of which is Alzheimer’s disease (AD). Although aging is considered to be the main risk factor for AD, growing evidence from epidemiological studies suggests that type 2 diabetes mellitus (T2DM) increases the risk of dementia including AD. Defective brain insulin signaling has been suggested as an early event in AD and other tauopathies but the mechanisms that link these diseases are largely unknown. Tau hyperphosphorylation is a hallmark of neurofibrillary pathology and insulin resistance increases the number of neuritic plaques particularly in AD. Utilizing a combination of our Drosophila models of tauopathy (expressing the 2N4R-Tau) and neuroblastoma cells, we have attempted to decipher the pathways downstream of the insulin signaling cascade that lead to tau hyperphosphorylation, aggregation and autophagic defects. Using cell-based, genetic, and biochemical approaches we have demonstrated that tau phosphorylation at AT8 and PHF1 residues is enhanced in an insulin-resistant environment. We also show that insulin-induced changes in total and phospho-tau are mediated by the crosstalk of AKT, glycogen synthase kinase-3β, and extracellular regulating kinase located downstream of the insulin receptor pathway. Finally, we demonstrate a significant change in the levels of the key proteins in the mammalian target of rapamycin/autophagy pathway, implying an increased impairment of aggregated protein clearance in our transgenic Drosophila models and cultured neuroblastoma cells.

Prevalidation of an Acute Inhalation Toxicity Test Using the EpiAirway In Vitro Human Airway Model

Introduction: Knowledge of acute inhalation toxicity potential is important for establishing safe use of chemicals and consumer products. Inhalation toxicity testing and classification procedures currently accepted within worldwide government regulatory systems rely primarily on tests conducted in animals. The goal of the current work was to develop and prevalidate a nonanimal (in vitro) test for determining acute inhalation toxicity using the EpiAirway™ in vitro human airway model as a potential alternative for currently accepted animal tests.

Materials and Methods: The in vitro test method exposes EpiAirway tissues to test chemicals for 3 hours, followed by measurement of tissue viability as the test endpoint. Fifty-nine chemicals covering a broad range of toxicity classes, chemical structures, and physical properties were evaluated. The in vitro toxicity data were utilized to establish a prediction model to classify the chemicals into categories corresponding to the currently accepted Globally Harmonized System (GHS) and the Environmental Protection Agency (EPA) system.

Results: The EpiAirway prediction model identified in vivo rat-based GHS Acute Inhalation Toxicity Category 1–2 and EPA Acute Inhalation Toxicity Category I–II chemicals with 100% sensitivity and specificity of 43.1% and 50.0%, for GHS and EPA acute inhalation toxicity systems, respectively. The sensitivity and specificity of the EpiAirway prediction model for identifying GHS specific target organ toxicity-single exposure (STOT-SE) Category 1 human toxicants were 75.0% and 56.5%, respectively. Corrosivity and electrophilic and oxidative reactivity appear to be the predominant mechanisms of toxicity for the most highly toxic chemicals.

Conclusions: These results indicate that the EpiAirway test is a promising alternative to the currently accepted animal tests for acute inhalation toxicity.

SCA31 Flies Perform in a Balancing Act between RAN Translation and RNA-Binding Proteins

In this issue of Neuron, Ishiguro et al. (2017) explore the toxicity of RAN translation in spinocerebellar ataxia 31. Using a Drosophila model, the authors demonstrate that TDP-43 and other RNA-binding proteins act as chaperones to regulate the formation of toxic RNA aggregates.

Molecular Impact of Electronic Cigarette Aerosol Exposure in Human Bronchial Epithelium

Little evidence is available regarding the physiological effects of exposure to electronic cigarette (ECIG) aerosol. We sought to determine the molecular impact of ECIG aerosol exposure in human bronchial epithelial cells (HBECs). Gene-expression profiling was conducted in primary grown at air liquid interface and exposed to 1 of 4 different ECIG aerosols, traditional tobacco cigarette (TCIG) smoke, or clean air. Findings were validated experimentally with quantitative polymerase chain reaction and a reactive oxygen species immunoassay. Using gene set enrichment analysis, signatures of in vitro ECIG exposure were compared with those generated from bronchial epithelial brushings of current TCIG smokers and former TCIG smokers currently using ECIGs. We found 546 genes differentially expressed across the ECIG, TCIG, and air-exposed groups of HBECs (ANOVA; FDR q < .05; fold change > 1.5). A subset of these changes were shared between TCIG- and ECIG-exposed HBECs. ECIG exposure induced genes involved in oxidative and xenobiotic stress pathways and increased a marker of reactive oxygen species production in a dose-dependent manner. ECIG exposure decreased expression of genes involved in cilia assembly and movement. Furthermore, gene-expression differences observed in vitro were concordant with differences observed in airway epithelium collected from ECIG users (q < .01). In summary, our data suggest that ECIG aerosol can induce gene-expression changes in bronchial airway epithelium in vitro, some of which are shared with TCIG smoke. These changes were generally less pronounced than the effects of TCIG exposure and were more pronounced in ECIG products containing nicotine than those without nicotine. Our data further suggest that the gene-expression alterations seen with the in vitro exposure system reflects the physiological effects experienced in vivo by ECIG users.

Treadmill exercise tests in persons with Parkinson's disease: responses and disease severity

BACKGROUND AND AIMS

There is a paucity of information on cardiovascular responses with regard to the disease stage of Parkinson's disease (PD) when using an exercise test. Our purpose was to examine whether cardiovascular responses to the treadmill exercise test differed among persons with PD who have different disease severity.

METHODS

Forty-five subjects with PD were studied (34 men and 11 women). The subjects underwent a treadmill exercise test using a modified Bruce protocol. Resting heart rate (HR), resting blood pressure (BP), maximal HR, maximal BP, exercise duration, maximum percentage HR and METs achieved after the treadmill exercise test were studied.

RESULTS

Seventeen subjects were in Hoehn and Yahr Staging Scale (HY) 2, 16 were in HY 2.5, and 12 were in HY 3. HR increased significantly in all three stages. Systolic BP increased significantly in the HY 2 and 2.5, but not the HY 3. Diastolic BP did not change in any stage. Resting HR was lower in the HY 2 compared to the HY 3 and resting systolic BP was higher in HY 2 compared to the HY 2.5. The three HY stages were not different in exercise duration, HR and BP responses, maximum percentage HR achieved, and METs achieved. Fatigue was a primary reason to discontinue the test. There were no fall incidents in any of the tests.

CONCLUSIONS

Cardiovascular responses to the treadmill exercise test did not vary with disease severity. Treadmill exercise tests were safe to perform in persons with PD.

Uncoupling neuronal death and dysfunction in Drosophila models of neurodegenerative disease

Common neurodegenerative proteinopathies, such as Alzheimer's disease (AD) and Parkinson's disease (PD), are characterized by the misfolding and aggregation of toxic protein species, including the amyloid beta (Aß) peptide, microtubule-associated protein Tau (Tau), and alpha-synuclein (αSyn) protein. These factors also show toxicity in Drosophila; however, potential limitations of prior studies include poor discrimination between effects on the adult versus developing nervous system and neuronal versus glial cell types. In addition, variable expression paradigms and outcomes hinder systematic comparison of toxicity profiles. Using standardized conditions and medium-throughput assays, we express human Tau, Aß or αSyn selectively in neurons of the adult Drosophila retina and monitor age-dependent changes in both structure and function, based on tissue histology and recordings of the electroretinogram (ERG), respectively. We find that each protein causes a unique profile of neurodegenerative pathology, demonstrating distinct and separable impacts on neuronal death and dysfunction. Strikingly, expression of Tau leads to progressive loss of ERG responses whereas retinal architecture and neuronal numbers are largely preserved. By contrast, Aß induces modest, age-dependent neuronal loss without degrading the retinal ERG. αSyn expression, using a codon-optimized transgene, is characterized by marked retinal vacuolar change, progressive photoreceptor cell death, and delayed-onset but modest ERG changes. Lastly, to address potential mechanisms, we perform transmission electron microscopy (TEM) to reveal potential degenerative changes at the ultrastructural level. Surprisingly, Tau and αSyn each cause prominent but distinct synaptotoxic profiles, including disorganization or enlargement of photoreceptor terminals, respectively. Our findings highlight variable and dynamic properties of neurodegeneration triggered by these disease-relevant proteins in vivo, and suggest that Drosophila may be useful for revealing determinants of neuronal dysfunction that precede cell loss, including synaptic changes, in the adult nervous system.

Glucose variability and inner retinal sensory neuropathy in persons with type 1 diabetes mellitus

PurposeTo quantify early neuroretinal alterations in patients with type 1 diabetes mellitus (T1DM) and to assess whether glycemic variability contributes to alterations in neuroretinal structure or function.MethodsThirty patients with T1DM and 51 controls underwent comprehensive ophthalmic examination and assessment of retinal function or structure with frequency doubling perimetry (FDP), contrast sensitivity, dark adaptation, fundus photography, and optical coherence tomography (OCT). Diabetic participants wore a subcutaneous continuous glucose monitor for 5 days, from which makers of glycemic variability including the low blood glucose index (LGBI) and area under the curve (AUC) for hypoglycemia were derived.ResultsSixteen patients had no diabetic retinopathy (DR), and 14 had mild or moderate DR. Log contrast sensitivity for the DM group was significantly reduced (mean±SD=1.63±0.06) compared with controls (1.77±0.13, P<0.001). OCT analysis revealed that the inner temporal inner nuclear layer (INL) was thinner in patients with T1DM (34.9±2.8 μm) compared with controls (36.5±2.9 μm) (P=0.023), although this effect lost statistical significance after application of the Bonferroni correction for multiple comparisons. Both markers of glycemic variability, the AUC for hypoglycemia (R=-0.458, P=0.006) and LGBI (R=-0.473, P=0.004), were negatively correlated with inner temporal INL thickness.ConclusionsPatients with T1DM and no to moderate DR exhibit alterations in inner retinal structure and function. Increased glycemic variability correlates with retinal thinning on OCT imaging, suggesting that fluctuations in blood glucose may contribute to neurodegeneration.

Pathological interface between oligomeric alpha-synuclein and tau in synucleinopathies

BACKGROUND

Aberrant accumulation of α-synuclein constitutes inclusion bodies that are considered a characteristic feature of a group of neurological disorders described as synucleinopathies. Often, multiple disease-causing proteins overlap within a given disease pathology. An emerging body of research focuses on the oligomeric populations of various pathogenic proteins, considering them as the culprits causing neuronal damage and degeneration. To this end, the use of conformation-specific antibodies has proven to be an effective tool. Previous work from our laboratory and others has shown that oligomeric entities of α-synuclein and tau accumulate in their respective diseases, but their interrelationship at this higher order has yet to be shown in synucleinopathies.

METHODS

Here, we used two novel conformation-specific antibodies, F8H7 and Syn33, which recognize α-synuclein oligomers and were developed in our laboratory. We investigated brain tissue from five of each Parkinson's disease and dementia with Lewy bodies patients by performing biophysical and biochemical assays using these antibodies, in addition to the previously characterized anti-tau oligomer antibody T22.

RESULTS

We demonstrate that in addition to the deposition of oligomeric α-synuclein, tau oligomers accumulate in these diseased brains compared with control brains. Moreover, we observed that oligomers of tau and α-synuclein exist in the same aggregates, forming hybrid oligomers in these patients' brains.

CONCLUSIONS

In addition to the deposition of tau oligomers, our results also provide compelling evidence of co-occurrence of α-synuclein and tau into their most toxic forms, i.e., oligomers suggesting that these species interact and influence each other's aggregation via an interface in synucleinopathies.

Comprehensive evaluation of poly(I:C) induced inflammatory response in an airway epithelial model

Respiratory viruses invade the upper airway of the lung, triggering a potent immune response that often exacerbates preexisting conditions such as asthma and COPD. Poly(I:C) is a synthetic analog of viral dsRNA that induces the characteristic inflammatory response associated with viral infection, such as loss of epithelial integrity, and increased production of mucus and inflammatory cytokines. Here, we explore the mechanistic responses to poly(I:C) in a well-defined primary normal human bronchial epithelial (NHBE) model that recapitulates in vivo functions and responses. We developed functional and quantifiable methods to evaluate the physiology of our model in both healthy and inflamed states. Through gene and protein expression, we validated the differentiation state and population of essential cell subtypes (i.e., ciliated, goblet, club, and basal cells) as compared to the human lung. Assays for total mucus production, cytokine secretion, and barrier function were used to evaluate in vitro physiology and response to viral insult. Cells were treated apically with poly(I:C) and evaluated 48 h after induction. Results revealed a dose-dependent increase in goblet cell differentiation, as well as, an increase in mucus production relative to controls. There was also a dose-dependent increase in secretion of IL-6, IL-8, TNF-α, and RANTES. Epithelial barrier function, as measured by TEER, was maintained at 1501 ± 355 Ω*cm² postdifferentiation, but dropped significantly when challenged with poly(I:C). This study provides first steps toward a well-characterized model with defined functional methods for understanding dsRNA stimulated inflammatory responses in a physiologically relevant manner.

Learn to forget: regulation of age-related memory impairment by neuronal-glial crosstalk

Dementia is among the most feared complications of aging in the U.S. In this issue of Neuron, Yamazaki et al. (2014) present a tour de force mechanistic analysis of a "hit" from a proteomic screen carried out using a Drosophila mutation that affects memory.

Amyloid-β oligomers as a template for secondary amyloidosis in Alzheimer's disease

Alzheimer's disease is a complex disease characterized by overlapping phenotypes with different neurodegenerative disorders. Oligomers are considered the most toxic species in amyloid pathologies. We examined human AD brain samples using an anti-oligomer antibody generated in our laboratory and detected potential hybrid oligomers composed of amyloid-β, prion protein, α-synuclein, and TDP-43 phosphorylated at serines 409 and 410. These data and in vitro results suggest that Aβ oligomer seeds act as a template for the aggregation of other proteins and generate an overlapping phenotype with other neuronal disorders. Furthermore, these results could explain why anti-amyloid-β therapy has been unsuccessful.

Evidence for autophagic gridlock in aging and neurodegeneration

Autophagy is essential to neuronal homeostasis, and its impairment is implicated in the development of neurodegenerative pathology. However, the underlying mechanisms and consequences of this phenomenon remain a matter of conjecture. We show that misexpression of human tau in Drosophila induces accumulation of autophagic intermediates with a preponderance of large vacuoles, which we term giant autophagic bodies (GABs), which are reminiscent of dysfunctional autophagic entities. Lowering basal autophagy reduces GABs, whereas increasing autophagy decreases mature autolysosomes. Induction of autophagy is also associated with rescue of the tauopathy phenotype, suggesting that formation of GABs may be a compensatory mechanism rather than a trigger of neurodegeneration. Last, we show that the peculiar Biondi bodies observed in the choroid epithelium of both elderly and Alzheimer's disease human brains express immunoreactive markers similar to those of GABs. Collectively, these data indicate that autophagic gridlock contributes to the development of pathology in aging and neurodegeneration.

Hemichorea in a patient with diabetic ketoacidosis

BACKGROUND

Chorea is a common presenting feature of metabolic disorders, including nonketotic hyperglycemia in patients with type 2 diabetes mellitus, but rarely has been reported in diabetic ketoacidosis, hypothyroidism and vitamin B12 deficiency.

METHODS

Review the literature for reported cases of chorea as a presenting manifestation in metabolic disorders.

RESULTS

We report a case of hemichorea in a patient with type 2 diabetes mellitus complicated by diabetic ketoacidosis. The patient had a two day history of right sided hemichorea and decreased level of consciousness. Initial laboratory studies revealed hyperglycemia, ketosis and an anion gap metabolic acidosis consistent with diabetic ketoacidosis. Once treatment was started the choreiform movements significantly improved over three weeks.

CONCLUSION

Although DKA has been rarely reported as a trigger for chorea, it should be in the differential diagnosis of a patient presenting with an acute chorea. Given the reversible nature of this disease, early recognition and treatment are imperative.

Interactions between Tau and α-synuclein augment neurotoxicity in a Drosophila model of Parkinson's disease

Clinical and pathological studies have suggested considerable overlap between tauopathies and synucleinopathies. Several genome-wide association studies have identified alpha-Synuclein (SNCA) and Tau (MAPT) polymorphisms as common risk factors for sporadic Parkinson's disease (PD). However, the mechanisms by which subtle variations in the expression of wild-type SNCA and MAPT influence risk for PD and the underlying cellular events that effect neurotoxicity remain unclear. To examine causes of neurotoxicity associated with the α-Syn/Tau interaction, we used the fruit fly as a model. We utilized misexpression paradigms in three different tissues to probe the α-Syn/Tau interaction: the retina, dopaminergic neurons and the larval neuromuscular junction. Misexpression of Tau and α-Syn enhanced a rough eye phenotype and loss of dopaminergic neurons in fly tauopathy and synucleinopathy models, respectively. Our findings suggest that interactions between α-Syn and Tau at the cellular level cause disruption of cytoskeletal organization, axonal transport defects and aberrant synaptic organization that contribute to neuronal dysfunction and death associated with sporadic PD. α-Syn did not alter levels of Tau phosphorylated at the AT8 epitope. However, α-Syn and Tau colocalized in ubiquitin-positive aggregates in eye imaginal discs. The presence of Tau also led to an increase in urea soluble α-Syn. Our findings have important implications in understanding the cellular and molecular mechanisms underlying α-Syn/Tau-mediated synaptic dysfunction, which likely arise in the early asymptomatic phase of sporadic PD.

TDP-43 Phosphorylation by casein kinase Iε promotes oligomerization and enhances toxicity in vivo

Dominant mutations in transactive response DNA-binding protein-43 (TDP-43) cause amyotrophic lateral sclerosis. TDP-43 inclusions occur in neurons, glia and muscle in this disease and in sporadic and inherited forms of frontotemporal lobar degeneration. Cytoplasmic localization, cleavage, aggregation and phosphorylation of TDP-43 at the Ser409/410 epitope have been associated with disease pathogenesis. TDP-43 aggregation is not a common feature of mouse models of TDP-43 proteinopathy, and TDP-43 is generally not thought to acquire an amyloid conformation or form fibrils. A number of putative TDP-43 kinases have been identified, but whether any of these functions to regulate TDP-43 phosphorylation or toxicity in vivo is not known. Here, we demonstrate that human TDP-43(Q331K) undergoes cytoplasmic localization and aggregates when misexpressed in Drosophila when compared with wild-type and M337V forms. Coexpression of Q331K with doubletime (DBT), the fly homolog of casein kinase Iε (CKIε), enhances toxicity. There is at best modest basal phosphorylation of misexpressed human TDP-43 in Drosophila, but coexpression with DBT increases Ser409/410 phosphorylation of all TDP-43 isoforms tested. Phosphorylation of TDP-43 in the fly is specific for DBT, as it is not observed using the validated tau kinases GSK-3β, PAR-1/MARK2 or CDK5. Coexpression of DBT with TDP-43(Q331K) enhances the formation of high-molecular weight oligomeric species coincident with enhanced toxicity, and treatment of recombinant oligomeric TDP-43 with rat CKI strongly enhances its toxicity in mammalian cell culture. These data identify CKIε as a potent TDP-43 kinase in vivo and implicate oligomeric species as the toxic entities in TDP-43 proteinopathies.

Disruption of glycerol metabolism by RNAi targeting of genes encoding glycerol kinase results in a range of phenotype severity in Drosophila

In Drosophila, RNAi targeting of either dGyk or dGK can result in two alternative phenotypes: adult glycerol hypersensitivity or larval lethality. Here we compare these two phenotypes at the level of glycerol kinase (GK) phosphorylation activity, dGyk and dGK-RNA expression, and glycerol levels. We found both phenotypes exhibit reduced but similar levels of GK phosphorylation activity. Reduced RNA expression levels of dGyk and dGK corresponded with RNAi progeny that developed into glycerol hypersensitive adult flies. However, quantification of dGyk/dGK expression levels for the larval lethality phenotype revealed unexpected levels possibly due to a compensatory mechanism between dGyk and dGK or RNAi inhibition. The enzymatic role of glycerol kinase converts glycerol to glycerol 3-phosphate. As expected, elevated glycerol levels were observed in larvae that went on to develop into glycerol hypersensitive adults. Interestingly, larvae that died before eclosion revealed extremely low glycerol levels. Further characterization identified a wing phenotype that is enhanced by a dGpdh null mutation, indicating disrupted glycerol metabolism underlies the wing phenotype. In humans, glycerol kinase deficiency (GKD) exhibits a wide range of phenotypic variation with no obvious genotype-phenotype correlations. Additionally, disease severity often does not correlate with GK phosphorylation activity. It is intriguing that both human GKD patients and our GKD Drosophila model show a range of phenotype severity. Additionally, the lack of correlation between GK phosphorylation and dGyk/dGK-RNA expression with phenotypic severity suggests further study including understanding the alternative functions of the GK protein, could provide insights into the complex pathogenic mechanism observed in human GKD patients.

Rapid accumulation of endogenous tau oligomers in a rat model of traumatic brain injury: possible link between traumatic brain injury and sporadic tauopathies

Traumatic brain injury (TBI) is a serious problem that affects millions of people in the United States alone. Multiple concussions or even a single moderate to severe TBI can also predispose individuals to develop a pathologically distinct form of tauopathy-related dementia at an early age. No effective treatments are currently available for TBI or TBI-related dementia; moreover, only recently has insight been gained regarding the mechanisms behind their connection. Here, we used antibodies to detect oligomeric and phosphorylated Tau proteins in a non-transgenic rodent model of parasagittal fluid percussion injury. Oligomeric and phosphorylated Tau proteins were detected 4 and 24 h and 2 weeks post-TBI in injured, but not sham control rats. These findings suggest that diagnostic tools and therapeutics that target only toxic forms of Tau may provide earlier detection and safe, more effective treatments for tauopathies associated with repetitive neurotrauma.

Novel technologies and an overall strategy to allow hazard assessment and risk prediction of chemicals, cosmetics, and drugs with animal-free methods

Several alternative methods to replace animal experiments have been accepted by legal bodies. An even larger number of tests are under development or already in use for non-regulatory applications or for the generation of information stored in proprietary knowledge bases. The next step for the use of the different in vitro methods is their combination into integrated testing strategies (ITS) to get closer to the overall goal of predictive "in vitro-based risk evaluation processes." We introduce here a conceptual framework as the basis for future ITS and their use for risk evaluation without animal experiments. The framework allows incorporation of both individual tests and already integrated approaches. Illustrative examples for elements to be incorporated are drawn from the session "Innovative technologies" at the 8th World Congress on Alternatives and Animal Use in the Life Sciences, held in Montreal, 2011. For instance, LUHMES cells (conditionally immortalized human neurons) were presented as an example for a 2D cell system. The novel 3D platform developed by InSphero was chosen as an example for the design and use of scaffold-free, organotypic microtissues. The identification of critical pathways of toxicity (PoT) may be facilitated by approaches exemplified by the MatTek 3D model for human epithelial tissues with engineered toxicological reporter functions. The important role of in silico methods and of modeling based on various pre-existing data is demonstrated by Altamira's comprehensive approach to predicting a molecule's potential for skin irritancy. A final example demonstrates how natural variation in human genetics may be overcome using data analytic (pattern recognition) techniques borrowed from computer science and statistics. The overall hazard and risk assessment strategy integrating these different examples has been compiled in a graphical work flow.

The downward spiral of tau and autolysosomes: a new hypothesis in neurodegeneration

A growing body of research has connected autophagy to neurodegenerative diseases such as Alzheimer disease (AD). In autopsied AD brain, large multivesicular bodies accumulate in neurons. Knockout mice deficient for key autophagy genes demonstrate age-dependent neurodegeneration. Most neurodegenerative diseases are characterized by accumulation of insoluble protein species; the type of protein and the location of aggregates within the nervous system help to define the type of disorder. It has been hypothesized that the inability to degrade such aggregates is a major causative factor in neuronal dysfunction and eventual neuronal death. As neurons are postmitotic and thus cannot regenerate themselves, mechanisms of protein clearance have received much attention in the field. The function of the ubiquitin-proteasome system (UPS) is impaired in models of neurodegeneration, and overexpression of chaperone proteins, such as those in the HSP70 family, leads to beneficial effects in many models of proteinopathies. Recently, studies of the effects of autophagy as a clearance mechanism have uncovered compelling evidence that inducing autophagy can alleviate many pathogenic and behavioral symptoms in animal and cellular models of neurodegeneration.

Abstract 3173: Identification of miR-4423 as a primate-specific microRNA highly expressed in airway epithelium and associated with lung cancer

Smoking is a significant risk factor for lung cancer, the leading cause of cancer-related deaths worldwide. Our group has previously shown that epithelial gene expression is altered throughout the airway of smokers and that some of these changes are regulated by microRNAs. Moreover, we have previously identified gene expression differences in cytologically normal bronchial airway epithelial cells between smokers with and without lung cancer that can serve as an early diagnostic biomarker for lung cancer. Here, we use next-generation sequencing of small RNAs to identify novel microRNAs expressed in airway epithelium and associated with lung cancer. We identify miR-4423 as a primate-specific microRNA highly expressed in the airway epithelium. In vitro, the expression of miR-4423 increases as Normal Human Bronchial Epithelial cells are differentiated into mucociliary epithelium at an Air Liquid Interface, while its mRNA targets decrease in expression. Furthermore, the expression of miR-4423 is reduced in lung tumors and in the cytologically normal bronchial airway epithelium of smokers with lung cancer. In gain-of-function experiments, ectopic expression of miR-4423 in lung cancer cell lines resulted in reduced colony formation in soft agar. Taken together, these data support the power of next-generation sequencing in identifying novel cell type- specific transcripts and provides evidence that this newly characterized microRNA may play a role in promoting the differentiation and/or maintenance of airway epithelium, and can reduce anchorage-independent lung cancer cell growth.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3173. doi:1538-7445.AM2012-3173

Guidelines for the use and interpretation of assays for monitoring autophagy

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.

Identification of oligomers at early stages of tau aggregation in Alzheimer's disease

Neurofibrillary tangles (NFTs) are a pathological hallmark of Alzheimer's disease (AD); however, the relationship between NFTs and disease progression remains controversial. Analyses of tau animal models suggest that phenotypes coincide with accumulation of soluble aggregated tau species but not the accumulation of NFTs. The pathological role of prefilamentous tau aggregates, e.g., tau oligomeric intermediates, is poorly understood, in part because of methodological challenges. Here, we engineered a novel tau oligomer-specific antibody, T22, and used it to elucidate the temporal course and biochemical features of oligomers during NFT development in AD brain. We found that tau oligomers in human AD brain samples were 4-fold higher than those in the controls. We also revealed the role of oligomeric tau conformers in pretangles, neuritic plaques, and neuropil threads in the frontal cortex tissue from AD brains; this analysis uncovers a consistent code that governs tau oligomerization with regard to degree of neuronal cytopathology. These data are the first to characterize the role of tau oligomers in the natural history of NFTs, and they highlight the suitability of tau oligomers as therapeutic targets in AD and related tauopathies.

Formation of immunoglobulin light chain amyloid oligomers in primary cutaneous nodular amyloidosis

BACKGROUND

Primary cutaneous nodular amyloidosis (PCNA) is thought to be a plasma cell dyscrasia. The amyloid deposits are found in the dermis and subcutis, and they contain clonal immunoglobulin light chains, produced by a local proliferation of plasma cells. New insights into amyloid diseases have revealed that the pathology is due more to the presence of small, misfolded protein species termed oligomers than to the deposition of fibrillar material.

OBJECTIVES

To demonstrate the presence of amyloid oligomers in PCNA and to provide evidence that cutaneous amyloid diseases share a common pathogenic pathway similar to other amyloid diseases.

METHODS

Immunohistochemical staining with conformation-specific and sequence-specific antibodies was used to localize different amyloid species of light chain immunoglobulins in a case of PCNA. Additionally, in vitro characterization of immunoglobulin oligomers and fibrils was performed to determine, through toxicity studies in a human keratinocyte cell line, which amyloidogenic form of the immunoglobulin is toxic in PCNA.

RESULTS

Amyloid oligomers were identified in PCNA. Oligomers were mainly formed by lambda light chain immunoglobulins, and kappa light chain oligomers were detected in lesser amounts. Amyloid species were detected intra- and extracellularly. In addition, amyloid oligomers and fibrils, derived from unknown protein sources, were detected. This finding suggests that immunoglobulin amyloids can act as seeds capable of inducing the aggregation of heterogeneous proteins in the skin. Furthermore, cytotoxicity studies demonstrated that immunoglobulin oligomers, but not monomers or fibrils, are toxic to human keratinocytes.

CONCLUSIONS

These data indicate that PCNA has common pathways with other amyloid diseases with respect to protein misfolding and pathogenesis. Immunoglobulin oligomers may prove to be targets for the treatment of PCNA.

Functional genomic screen and network analysis reveal novel modifiers of tauopathy dissociated from tau phosphorylation

A functional genetic screen using loss-of-function and gain-of-function alleles was performed to identify modifiers of tau-induced neurotoxicity using the 2N/4R (full-length) isoform of wild-type human tau expressed in the fly retina. We previously reported eye pigment mutations, which create dysfunctional lysosomes, as potent modifiers; here, we report 37 additional genes identified from ∼1900 genes screened, including the kinases shaggy/GSK-3beta, par-1/MARK, CamKI and Mekk1. Tau acts synergistically with Mekk1 and p38 to down-regulate extracellular regulated kinase activity, with a corresponding decrease in AT8 immunoreactivity (pS202/T205), suggesting that tau can participate in signaling pathways to regulate its own kinases. Modifiers showed poor correlation with tau phosphorylation (using the AT8, 12E8 and AT270 epitopes); moreover, tested suppressors of wild-type tau were equally effective in suppressing toxicity of a phosphorylation-resistant S11A tau construct, demonstrating that changes in tau phosphorylation state are not required to suppress or enhance its toxicity. Genes related to autophagy, the cell cycle, RNA-associated proteins and chromatin-binding proteins constitute a large percentage of identified modifiers. Other functional categories identified include mitochondrial proteins, lipid trafficking, Golgi proteins, kinesins and dynein and the Hsp70/Hsp90-organizing protein (Hop). Network analysis uncovered several other genes highly associated with the functional modifiers, including genes related to the PI3K, Notch, BMP/TGF-β and Hedgehog pathways, and nuclear trafficking. Activity of GSK-3β is strongly upregulated due to TDP-43 expression, and reduced GSK-3β dosage is also a common suppressor of Aβ42 and TDP-43 toxicity. These findings suggest therapeutic targets other than mitigation of tau phosphorylation.

Retinal function in relation to improved glycaemic control in type 1 diabetes

AIMS/HYPOTHESIS

To study long-term changes in retinal function in response to sustained glycaemia reduction in participants with type 1 diabetes.

METHODS

Prospective study using objective measures of retinal function in 17 participants with type 1 diabetes mellitus and minimal to moderate retinopathy who switched from conventional subcutaneous injection to continuous subcutaneous infusion of insulin (CSII).

RESULTS

Glycated haemoglobin HbA(1c) gradually decreased from 9.1% at baseline before CSII to 7.4% after 1 year on CSII. Glycaemia was markedly reduced within 1 week after initiation of CSII and remained stable thereafter. Dark adaptation and retinal electroretinographic function at 1, 4 and 16 weeks after initiation of CSII were comparable with baseline values, whereas a significant improvement in rod photoreceptor dark adaptation and dark-adapted b-wave amplitudes were seen after 52 weeks (time to rod-cone break -25% [p < 0.0001], time to a standardised rod intercept -13% [p < 0.0001], dark-adapted rod b-wave full-field amplitude +15% [p = 0.0125], standard combined rod-cone b-wave amplitude +8% [p = 0.049]). No detectable change was observed in cone adaptation, electroretinographic cone function or retinopathy.

CONCLUSIONS/INTERPRETATION

After initiation of CSII, the retinal visual pathway of the rods improved with a delay of more than 4 months, over a time scale comparable with the duration of the diabetic retinopathy early worsening response to sustained glycaemia reduction. This indicates that glycaemia has a long-term effect on the disposition of functional capacity in the retinal visual pathway of rod photoreceptors, the cells that appear to be driving the development of diabetic retinopathy.

Tau oligomers impair memory and induce synaptic and mitochondrial dysfunction in wild-type mice

Background

The correlation between neurofibrillary tangles of tau and disease progression in the brains of Alzheimer's disease (AD) patients remains an area of contention. Innovative data are emerging from biochemical, cell-based and transgenic mouse studies that suggest that tau oligomers, a pre-filament form of tau, may be the most toxic and pathologically significant tau aggregate.

Results

Here we report that oligomers of recombinant full-length human tau protein are neurotoxic in vivo after subcortical stereotaxic injection into mice. Tau oligomers impaired memory consolidation, whereas tau fibrils and monomers did not. Additionally, tau oligomers induced synaptic dysfunction by reducing the levels of synaptic vesicle-associated proteins synaptophysin and septin-11. Tau oligomers produced mitochondrial dysfunction by decreasing the levels of NADH-ubiquinone oxidoreductase (electron transport chain complex I), and activated caspase-9, which is related to the apoptotic mitochondrial pathway.

Conclusions

This study identifies tau oligomers as an acutely toxic tau species in vivo, and suggests that tau oligomers induce neurodegeneration by affecting mitochondrial and synaptic function, both of which are early hallmarks in AD and other tauopathies. These results open new avenues for neuroprotective intervention strategies of tauopathies by targeting tau oligomers.

Alzheimers disease: review of emerging treatment role for intravenous immunoglobulins

Alzheimer’s disease (AD) is the most common neurodegenerative disorder. Currently available therapies are symptomatic but do not alter underlying disease progression. Immunotherapeutic approaches such as anti Aβ peptide active vaccination trials have had limited success to date. Intravenous immunoblobulin (IVIg) is widely used in immune-mediated neurological disorders such myasthenia gravis and Guillain-Barre syndrome. These preparations have been obtained from the pooled plasma of healthy human donors and contain natural anti-amyloid antibodies and are well tolerated. A small pilot study of passive immunotherapy using IVIg has suggested cognitive improvement. A multicenter phase III trial is ongoing and will determine whether or not this treatment can ameliorate cognitive deficits in mild-to-moderate AD. Here, we briefly review the pathogenic role of amyloid and tau in AD, as well as immunotherapeutic efforts to date. We also summarize what is known about naturally occurring anti-Aβ and tau antibodies in IVIg with a view toward explaining potential mechanisms underlying their therapeutic effects.

Pathogenic VCP/TER94 alleles are dominant actives and contribute to neurodegeneration by altering cellular ATP level in a Drosophila IBMPFD model

Inclusion body myopathy with Paget's disease of bone and frontotemporal dementia (IBMPFD) is caused by mutations in Valosin-containing protein (VCP), a hexameric AAA ATPase that participates in a variety of cellular processes such as protein degradation, organelle biogenesis, and cell-cycle regulation. To understand how VCP mutations cause IBMPFD, we have established a Drosophila model by overexpressing TER94 (the sole Drosophila VCP ortholog) carrying mutations analogous to those implicated in IBMPFD. Expression of these TER94 mutants in muscle and nervous systems causes tissue degeneration, recapitulating the pathogenic phenotypes in IBMPFD patients. TER94-induced neurodegenerative defects are enhanced by elevated expression of wild-type TER94, suggesting that the pathogenic alleles are dominant active mutations. This conclusion is further supported by the observation that TER94-induced neurodegenerative defects require the formation of hexamer complex, a prerequisite for a functional AAA ATPase. Surprisingly, while disruptions of the ubiquitin-proteasome system (UPS) and the ER-associated degradation (ERAD) have been implicated as causes for VCP-induced tissue degeneration, these processes are not significantly affected in our fly model. Instead, the neurodegenerative defect of TER94 mutants seems sensitive to the level of cellular ATP. We show that increasing cellular ATP by independent mechanisms could suppress the phenotypes of TER94 mutants. Conversely, decreasing cellular ATP would enhance the TER94 mutant phenotypes. Taken together, our analyses have defined the nature of IBMPFD-causing VCP mutations and made an unexpected link between cellular ATP level and IBMPFD pathogenesis.

Demise of the flies: why Drosophila models still matter

Over the past decade, Drosophila melanogaster has emerged as a widely used model for human disease via targeted misexpression of human disease-associated proteins. The chief advantage of creating such models is that once a suitable phenotype has been obtained, the genetic toolkit of fly genetics can be used to dissect underlying disease pathways. Although some critics of this approach have argued that it has not generated many novel insights, we would argue that fly models of human neurodegenerative disorders have provided valuable information when viewed within the context of other models and systems of analysis. Here, we will provide a brief overview of some Drosophila models of neurodegenerative disorders with a special focus on our own work.

Preparation and characterization of neurotoxic tau oligomers

Tau aggregation is a pathological hallmark of Alzheimer's disease, Parkinson's disease, and many other neurodegenerative disorders known as tauopathies. Tau aggregates take on many forms, and their formation is a multistage process with intermediate stages. Recently, tau oligomers have emerged as the pathogenic species in tauopathies and a possible mediator of amyloid-β toxicity in Alzheimer's disease. Here, we use a novel, physiologically relevant method (oligomer cross-seeding) to prepare homogeneous populations of tau oligomers and characterize these oligomers in vitro. We show that both Aβ and α-synuclein oligomers induce tau aggregation and the formation of β-sheet-rich neurotoxic tau oligomers.