Familial amyloid precursor protein mutants cause caspase-6-dependent but amyloid β-peptide-independent neuronal degeneration in primary human neuron cultures.

Although familial Alzheimer disease (AD)-associated autosomal dominant mutants have been extensively studied, little is known about the underlying molecular mechanisms of neurodegeneration induced by these mutants in AD. Wild-type, Swedish or London amyloid precursor protein (APP) transfection in primary human neurons induced neuritic beading, in which several co-expressed proteins, such as enhanced green fluorescent protein, red fluorescent protein (RFP)-tau and RFP-ubiquitin, accumulated. APP-induced neuritic beading was dependent on caspase-6 (Casp6), because it was inhibited with 5 μM z-VEID-fmk or with dominant-negative Casp6. Neuritic beading was independent from APP-mediated amyloid β-peptide (Aβ) production, because the APPM596V (APPMV) mutant, which cannot generate Aβ, still induced Casp6-dependent neuritic beading. However, the beaded neurons underwent Casp6- and Aβ-dependent cell death. These results indicate that overexpression of wild-type or mutant APP causes Casp6-dependent but Aβ-independent neuritic degeneration in human neurons. Because Casp6 is activated early in AD and is involved in axonal degeneration, these results suggest that the inhibition of Casp6 may represent an efficient early intervention against familial forms of AD. Furthermore, these results indicate that removing Aβ without inhibiting Casp6 may have little effect in preventing the progressive dementia associated with sporadic or familial AD

Hepcidin and ferritin levels as markers of immune cell activation during septic shock, severe COVID-19 and sterile inflammation

IntroductionMajor clinically relevant inflammatory events such as septic shock and severe COVID-19 trigger dynamic changes in the host immune system, presenting promising candidates for new biomarkers to improve precision diagnostics and patient stratification. Hepcidin, a master regulator of iron metabolism, has been intensively studied in many pathologies associated with immune system activation, however these data have never been compared to other clinical settings. Thus, we aimed to reveal the dynamics of iron regulation in various clinical settings and to determine the suitability of hepcidin and/or ferritin levels as biomarkers of inflammatory disease severity.CohortsTo investigate the overall predictive ability of hepcidin and ferritin, we enrolled the patients suffering with three different diagnoses – in detail 40 patients with COVID-19, 29 patients in septic shock and eight orthopedic patients who were compared to nine healthy donors and all cohorts to each other.ResultsWe showed that increased hepcidin levels reflect overall immune cell activation driven by intrinsic stimuli, without requiring direct involvement of infection vectors. Contrary to hepcidin, ferritin levels were more strongly boosted by pathogen-induced inflammation – in septic shock more than four-fold and in COVID-19 six-fold in comparison to sterile inflammation. We also defined the predictive capacity of hepcidin-to-ferritin ratio with AUC=0.79 and P = 0.03.DiscussionOur findings confirm that hepcidin is a potent marker of septic shock and other acute inflammation-associated pathologies and demonstrate the utility of the hepcidin-to-ferritin ratio as a predictor of mortality in septic shock, but not in COVID-19

Updated clinical diagnostic criteria for sporadic Creutzfeldt-Jakob disease

Several molecular subtypes of sporadic Creutzfeldt-Jakob disease have been identified and electroencephalogram and cerebrospinal fluid biomarkers have been reported to support clinical diagnosis but with variable utility according to subtype. In recent years, a series of publications have demonstrated a potentially important role for magnetic resonance imaging in the pre-mortem diagnosis of sporadic Creutzfeldt-Jakob disease. Magnetic resonance imaging signal alterations correlate with distinct sporadic Creutzfeldt-Jakob disease molecular subtypes and thus might contribute to the earlier identification of the whole spectrum of sporadic Creutzfeldt-Jakob disease cases. This multi-centre international study aimed to provide a rationale for the amendment of the clinical diagnostic criteria for sporadic Creutzfeldt-Jakob disease. Patients with sporadic Creutzfeldt-Jakob disease and fluid attenuated inversion recovery or diffusion-weight imaging were recruited from 12 countries. Patients referred as ‘suspected sporadic Creutzfeldt-Jakob disease' but with an alternative diagnosis after thorough follow up, were analysed as controls. All magnetic resonance imaging scans were assessed for signal changes according to a standard protocol encompassing seven cortical regions, basal ganglia, thalamus and cerebellum. Magnetic resonance imaging scans were evaluated in 436 sporadic Creutzfeldt-Jakob disease patients and 141 controls. The pattern of high signal intensity with the best sensitivity and specificity in the differential diagnosis of sporadic Creutzfeldt-Jakob disease was identified. The optimum diagnostic accuracy in the differential diagnosis of rapid progressive dementia was obtained when either at least two cortical regions (temporal, parietal or occipital) or both caudate nucleus and putamen displayed a high signal in fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging. Based on our analyses, magnetic resonance imaging was positive in 83% of cases. In all definite cases, the amended criteria would cover the vast majority of suspected cases, being positive in 98%. Cerebral cortical signal increase and high signal in caudate nucleus and putamen on fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging are useful in the diagnosis of sporadic Creutzfeldt-Jakob disease. We propose an amendment to the clinical diagnostic criteria for sporadic Creutzfeldt-Jakob disease to include findings from magnetic resonance imaging scan

Herpes Simplex Virus Dances with Amyloid Precursor Protein while Exiting the Cell

Herpes simplex type 1 (HSV1) replicates in epithelial cells and secondarily enters local sensory neuronal processes, traveling retrograde to the neuronal nucleus to enter latency. Upon reawakening newly synthesized viral particles travel anterograde back to the epithelial cells of the lip, causing the recurrent cold sore. HSV1 co-purifies with amyloid precursor protein (APP), a cellular transmembrane glycoprotein and receptor for anterograde transport machinery that when proteolyzed produces A-beta, the major component of senile plaques. Here we focus on transport inside epithelial cells of newly synthesized virus during its transit to the cell surface. We hypothesize that HSV1 recruits cellular APP during transport. We explore this with quantitative immuno-fluorescence, immuno-gold electron-microscopy and live cell confocal imaging. After synchronous infection most nascent VP26-GFP-labeled viral particles in the cytoplasm co-localize with APP (72.8+/−6.7%) and travel together with APP inside living cells (81.1+/−28.9%). This interaction has functional consequences: HSV1 infection decreases the average velocity of APP particles (from 1.1+/−0.2 to 0.3+/−0.1 µm/s) and results in APP mal-distribution in infected cells, while interplay with APP-particles increases the frequency (from 10% to 81% motile) and velocity (from 0.3+/−0.1 to 0.4+/−0.1 µm/s) of VP26-GFP transport. In cells infected with HSV1 lacking the viral Fc receptor, gE, an envelope glycoprotein also involved in viral axonal transport, APP-capsid interactions are preserved while the distribution and dynamics of dual-label particles differ from wild-type by both immuno-fluorescence and live imaging. Knock-down of APP with siRNA eliminates APP staining, confirming specificity. Our results indicate that most intracellular HSV1 particles undergo frequent dynamic interplay with APP in a manner that facilitates viral transport and interferes with normal APP transport and distribution. Such dynamic interactions between APP and HSV1 suggest a mechanistic basis for the observed clinical relationship between HSV1 seropositivity and risk of Alzheimer's disease

Updated clinical diagnostic criteria for sporadic Creutzfeldt-Jakob disease

Several molecular subtypes of sporadic Creutzfeldt–Jakob disease have been identified and electroencephalogram and cerebrospinal fluid biomarkers have been reported to support clinical diagnosis but with variable utility according to subtype. In recent years, a series of publications have demonstrated a potentially important role for magnetic resonance imaging in the pre-mortem diagnosis of sporadic Creutzfeldt–Jakob disease. Magnetic resonance imaging signal alterations correlate with distinct sporadic Creutzfeldt–Jakob disease molecular subtypes and thus might contribute to the earlier identification of the whole spectrum of sporadic Creutzfeldt–Jakob disease cases. This multi-centre international study aimed to provide a rationale for the amendment of the clinical diagnostic criteria for sporadic Creutzfeldt–Jakob disease. Patients with sporadic Creutzfeldt–Jakob disease and fluid attenuated inversion recovery or diffusion-weight imaging were recruited from 12 countries. Patients referred as ‘suspected sporadic Creutzfeldt–Jakob disease’ but with an alternative diagnosis after thorough follow up, were analysed as controls. All magnetic resonance imaging scans were assessed for signal changes according to a standard protocol encompassing seven cortical regions, basal ganglia, thalamus and cerebellum. Magnetic resonance imaging scans were evaluated in 436 sporadic Creutzfeldt–Jakob disease patients and 141 controls. The pattern of high signal intensity with the best sensitivity and specificity in the differential diagnosis of sporadic Creutzfeldt–Jakob disease was identified. The optimum diagnostic accuracy in the differential diagnosis of rapid progressive dementia was obtained when either at least two cortical regions (temporal, parietal or occipital) or both caudate nucleus and putamen displayed a high signal in fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging. Based on our analyses, magnetic resonance imaging was positive in 83% of cases. In all definite cases, the amended criteria would cover the vast majority of suspected cases, being positive in 98%. Cerebral cortical signal increase and high signal in caudate nucleus and putamen on fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging are useful in the diagnosis of sporadic Creutzfeldt–Jakob disease. We propose an amendment to the clinical diagnostic criteria for sporadic Creutzfeldt–Jakob disease to include findings from magnetic resonance imaging scans

Calcium signals can freely cross the nuclear envelope in hippocampal neurons: somatic calcium increases generate nuclear calcium transients

<p>Abstract</p> <p>Background</p> <p>In hippocampal neurons, nuclear calcium signaling is important for learning- and neuronal survival-associated gene expression. However, it is unknown whether calcium signals generated by neuronal activity at the cell membrane and propagated to the soma can unrestrictedly cross the nuclear envelope to invade the nucleus. The nuclear envelope, which allows ion transit via the nuclear pore complex, may represent a barrier for calcium and has been suggested to insulate the nucleus from activity-induced cytoplasmic calcium transients in some cell types.</p> <p>Results</p> <p>Using laser-assisted uncaging of caged calcium compounds in defined sub-cellular domains, we show here that the nuclear compartment border does not represent a barrier for calcium signals in hippocampal neurons. Although passive diffusion of molecules between the cytosol and the nucleoplasm may be modulated through changes in conformational state of the nuclear pore complex, we found no evidence for a gating mechanism for calcium movement across the nuclear border.</p> <p>Conclusion</p> <p>Thus, the nuclear envelope does not spatially restrict calcium transients to the somatic cytosol but allows calcium signals to freely enter the cell nucleus to trigger genomic events.</p

Transient Focal Cerebral Ischemia/Reperfusion Induces Early and Chronic Axonal Changes in Rats: Its Importance for the Risk of Alzheimer's Disease

The dementia of Alzheimer's type and brain ischemia are known to increase at comparable rates with age. Recent advances suggest that cerebral ischemia may contribute to the pathogenesis of Alzheimer's disease (AD), however, the neuropathological relationship between these two disorders is largely unclear. It has been demonstrated that axonopathy, mainly manifesting as impairment of axonal transport and swelling of the axon and varicosity, is a prominent feature in AD and may play an important role in the neuropathological mechanisms in AD. In this study, we investigated the early and chronic changes of the axons of neurons in the different brain areas (cortex, hippocampus and striatum) using in vivo tracing technique and grading analysis method in a rat model of transient focal cerebral ischemia/reperfusion (middle cerebral artery occlusion, MCAO). In addition, the relationship between the changes of axons and the expression of β-amyloid 42 (Aβ42) and hyperphosphorylated Tau, which have been considered as the key neuropathological processes of AD, was analyzed by combining tracing technique with immunohistochemistry or western blotting. Subsequently, we found that transient cerebral ischemia/reperfusion produced obvious swelling of the axons and varicosities, from 6 hours after transient cerebral ischemia/reperfusion even up to 4 weeks. We could not observe Aβ plaques or overexpression of Aβ42 in the ischemic brain areas, however, the site-specific hyperphosphorylated Tau could be detected in the ischemic cortex. These results suggest that transient cerebral ischemia/reperfusion induce early and chronic axonal changes, which may be an important mechanism affecting the clinical outcome and possibly contributing to the development of AD after stroke

Mitochondrial Superoxide Contributes to Blood Flow and Axonal Transport Deficits in the Tg2576 Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by the progressive decline in cognitive functions and the deposition of aggregated amyloid beta (Abeta) into senile plaques and the protein tau into tangles. In addition, a general state of oxidation has long been known to be a major hallmark of the disease. What is not known however, are the mechanisms by which oxidative stress contributes to the pathology of AD.In the current study, we used a mouse model of AD and genetically boosted its ability to quench free radicals of specific mitochondrial origin. We found that such manipulation conferred to the AD mice protection against vascular as well as neuronal deficits that typically affect them. We also found that the vascular deficits are improved via antioxidant modulation of the endothelial nitric oxide synthase, an enzyme primarily responsible for the production of nitric oxide, while neuronal deficits are improved via modulation of the phosphorylation status of the protein tau, which is a neuronal cytoskeletal stabilizer.These findings directly link free radicals of specific mitochondrial origin to AD-associated vascular and neuronal pathology

Early B-cell Factor gene association with multiple sclerosis in the Spanish population

BACKGROUND: The etiology of multiple sclerosis (MS) is at present not fully elucidated, although it is considered to result from the interaction of environmental and genetic susceptibility factors. In this work we aimed at testing the Early B-cell Factor (EBF1) gene as a functional and positional candidate risk factor for this neurological disease. Axonal damage is a hallmark for multiple sclerosis clinical disability and EBF plays an evolutionarily conserved role in the expression of proteins essential for axonal pathfinding. Failure of B-cell differentiation was found in EBF-deficient mice and involvement of B-lymphocytes in MS has been suggested from their presence in cerebrospinal fluid and lesions of patients. METHODS: The role of the EBF1 gene in multiple sclerosis susceptibility was analyzed by performing a case-control study with 356 multiple sclerosis patients and 540 ethnically matched controls comparing the EBF1 polymorphism rs1368297 and the microsatellite D5S2038. RESULTS: Significant association of an EBF1-intronic polymorphism (rs1368297, A vs. T: p = 0.02; OR = 1.26 and AA vs. [TA+TT]: p = 0.02; OR = 1.39) was discovered. This association was even stronger after stratification for the well-established risk factor of multiple sclerosis in the Major Histocompatibility Complex, DRB1*1501 (AA vs. [TA+TT]: p = 0.005; OR = 1.78). A trend for association in the case-control study of another EBF1 marker, the allele 5 of the very informative microsatellite D5S2038, was corroborated by Transmission Disequilibrium Test of 53 trios (p = 0.03). CONCLUSION: Our data support EBF1 gene association with MS pathogenesis in the Spanish white population. Two genetic markers within the EBF1 gene have been found associated with this neurological disease, indicative either of their causative role or that of some other polymorphism in linkage disequilibrium with them

Kinesin Light Chain 1 Suppression Impairs Human Embryonic Stem Cell Neural Differentiation and Amyloid Precursor Protein Metabolism

The etiology of sporadic Alzheimer disease (AD) is largely unknown, although evidence implicates the pathological hallmark molecules amyloid beta (Aβ) and phosphorylated Tau. Work in animal models suggests that altered axonal transport caused by Kinesin-1 dysfunction perturbs levels of both Aβ and phosphorylated Tau in neural tissues, but the relevance of Kinesin-1 dependent functions to the human disease is unknown. To begin to address this issue, we generated human embryonic stem cells (hESC) expressing reduced levels of the kinesin light chain 1 (KLC1) Kinesin-1 subunit to use as a source of human neural cultures. Despite reduction of KLC1, undifferentiated hESC exhibited apparently normal colony morphology and pluripotency marker expression. Differentiated neural cultures derived from KLC1-suppressed hESC contained neural rosettes but further differentiation revealed obvious morphological changes along with reduced levels of microtubule-associated neural proteins, including Tau and less secreted Aβ, supporting the previously established connection between KLC1, Tau and Aβ. Intriguingly, KLC1-suppressed neural precursors (NPs), isolated using a cell surface marker signature known to identify cells that give rise to neurons and glia, unlike control cells, failed to proliferate. We suggest that KLC1 is required for normal human neural differentiation, ensuring proper metabolism of AD-associated molecules APP and Tau and for proliferation of NPs. Because impaired APP metabolism is linked to AD, this human cell culture model system will not only be a useful tool for understanding the role of KLC1 in regulating the production, transport and turnover of APP and Tau in neurons, but also in defining the essential function(s) of KLC1 in NPs and their progeny. This knowledge should have important implications for human neurodevelopmental and neurodegenerative diseases