Julio C. Rojas

ApoE4 markedly exacerbates tau-mediated neurodegeneration in a mouse model of tauopathy

APOE4 is the strongest genetic risk factor for late-onset Alzheimer disease. ApoE4 increases brain amyloid-β pathology relative to other ApoE isoforms. However, whether APOE independently influences tau pathology, the other major proteinopathy of Alzheimer disease and other tauopathies, or tau-mediated neurodegeneration, is not clear. By generating P301S tau transgenic mice on either a human ApoE knock-in (KI) or ApoE knockout (KO) background, here we show that P301S/E4 mice have significantly higher tau levels in the brain and a greater extent of somatodendritic tau redistribution by three months of age compared with P301S/E2, P301S/E3, and P301S/EKO mice. By nine months of age, P301S mice with different ApoE genotypes display distinct phosphorylated tau protein (p-tau) staining patterns. P301S/E4 mice develop markedly more brain atrophy and neuroinflammation than P301S/E2 and P301S/E3 mice, whereas P301S/EKO mice are largely protected from these changes. In vitro, E4-expressing microglia exhibit higher innate immune reactivity after lipopolysaccharide treatment. Co-culturing P301S tau-expressing neurons with E4-expressing mixed glia results in a significantly higher level of tumour-necrosis factor-α (TNF-α) secretion and markedly reduced neuronal viability compared with neuron/E2 and neuron/E3 co-cultures. Neurons co-cultured with EKO glia showed the greatest viability with the lowest level of secreted TNF-α. Treatment of P301S neurons with recombinant ApoE (E2, E3, E4) also leads to some neuronal damage and death compared with the absence of ApoE, with ApoE4 exacerbating the effect. In individuals with a sporadic primary tauopathy, the presence of an ε4 allele is associated with more severe regional neurodegeneration. In individuals who are positive for amyloid-β pathology with symptomatic Alzheimer disease who usually have tau pathology, ε4-carriers demonstrate greater rates of disease progression. Our results demonstrate that ApoE affects tau pathogenesis, neuroinflammation, and tau-mediated neurodegeneration independently of amyloid-β pathology. ApoE4 exerts a ‘toxic’ gain of function whereas the absence of ApoE is protective.

Plasma neurofilament light chain predicts progression in progressive supranuclear palsy

Blood‐based biomarkers for neurodegenerative conditions could improve diagnosis and treatment development. Neurofilament light chain (NfL), a marker of axonal injury, is elevated in cerebrospinal fluid (CSF) of patients with progressive supranuclear palsy (PSP). The goal of this study was to determine the diagnostic and prognostic value of plasma NfL in patients with PSP.

Mitochondrial respiration as a target for neuroprotection and cognitive enhancement

This paper focuses on brain mitochondrial respiration as a therapeutic target for neuroprotection and cognitive enhancement. We propose that improving brain mitochondrial respiration is an important future direction in research and treatment of Alzheimers disease (AD) and other conditions associated with cognitive impairment and neurodegeneration. The central thesis is that supporting and improving brain mitochondrial respiration constitutes a promising neurotherapeutic principle, with potential applications in AD as well as in a wide variety of neuropsychological conditions. We propose three different interventional approaches to improve brain mitochondrial respiration based on (a) pharmacology, (b) photobiomodulation and (c) nutrition interventions, and provide detailed examples for each type of intervention. First, low-dose USP methylene blue is described as a pharmacological intervention that can successfully increase mitochondrial respiration and result in memory enhancement and neuroprotection. Second, transcranial low-level light/laser therapy with near-infrared light is used to illustrate a photobiomodulation intervention with similar neurometabolic mechanisms of action as low-dose methylene blue. Finally, a nutrition intervention to improve mitochondrial respiration is proposed by increasing ketone bodies in the diet. The evidence discussed for each intervention supports a fundamental neurotherapeutic strategy based on improving oxidative energy metabolism while at the same time reducing the pro-oxidant tendencies of the nervous system. Targeting brain mitochondrial respiration with these three types of interventions is proposed as part of a holistic neurotherapeutic approach to improve brain energy metabolism and antioxidant defenses. This strategy represents a promising new bioenergetics direction for treatment of AD and other neuropsychological disorders featuring cognitive impairment and neurodegeneration.

Pearls & Oy-sters: Acute ischemic stroke caused by atypical thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is an episodic microangiopathic coagulopathy characterized by profound thrombocytopenia and hemolytic anemia. Neurovascular complications, including stroke and TIA, occur commonly upon initial TTP presentation, and the underlying etiology of such neurologic manifestations is usually hinted by the concomitant hematologic abnormalities.

Factors contributing to delay in diagnosis of Guillain‐Barré syndrome and impact on clinical outcome

Heterogeneity of presenting symptoms makes the initial clinical diagnosis of Guillain‐Barré syndrome (GBS) challenging.

Neurodegenerative disease in 2015: Targeting tauopathies for therapeutic translation.

Tau protein abnormalities are key pathogenic features of Alzheimer disease and other neurodegenerative diseases. In 2015, new studies of the less common tauopathies, including progressive supranuclear palsy, chronic traumatic encephalopathy and frontotemporal lobar degeneration, have identified in vivo biomarkers and mechanisms that initiate tau pathology.

CSF neurofilament light chain and phosphorylated tau 181 predict disease progression in PSP

Objective To determine the ability of CSF biomarkers to predict disease progression in progressive supranuclear palsy (PSP). Methods We compared the ability of baseline CSF β-amyloid1–42, tau, phosphorylated tau 181 (p-tau), and neurofilament light chain (NfL) concentrations, measured by INNO-BIA AlzBio3 or ELISA, to predict 52-week changes in clinical (PSP Rating Scale [PSPRS] and Schwab and England Activities of Daily Living [SEADL]), neuropsychological, and regional brain volumes on MRI using linear mixed effects models controlled for age, sex, and baseline disease severity, and Fisher F density curves to compare effect sizes in 50 patients with PSP. Similar analyses were done using plasma NfL measured by single molecule arrays in 141 patients. Results Higher CSF NfL concentration predicted more rapid decline (biomarker × time interaction) over 52 weeks in PSPRS (p = 0.004, false discovery rate–corrected) and SEADL (p = 0.008), whereas lower baseline CSF p-tau predicted faster decline on PSPRS (p = 0.004). Higher CSF tau concentrations predicted faster decline by SEADL (p = 0.004). The CSF NfL/p-tau ratio was superior for predicting change in PSPRS, compared to p-tau (p = 0.003) or NfL (p = 0.001) alone. Higher NfL concentrations in CSF or blood were associated with greater superior cerebellar peduncle atrophy (fixed effect, p ≤ 0.029 and 0.008, respectively). Conclusions Both CSF p-tau and NfL correlate with disease severity and rate of disease progression in PSP. The inverse correlation of p-tau with disease severity suggests a potentially different mechanism of tau pathology in PSP as compared to Alzheimer disease.

Distinct Lysosomal Network Protein Profiles in Parkinsonian Syndrome Cerebrospinal Fluid

Background: Clinical diagnosis of parkinsonian syndromes like Parkinson’s disease (PD), corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) is hampered by overlapping symptomatology and lack of diagnostic biomarkers, and definitive diagnosis is only possible post-mortem. Objective: Since impaired protein degradation plays an important role in many neurodegenerative disorders, we hypothesized that profiles of select lysosomal network proteins in cerebrospinal fluid could be differentially expressed in these parkinsonian syndromes. Methods: Cerebrospinal fluid samples were collected from PD patients (n = 18), clinically diagnosed 4-repeat tauopathy patients; corticobasal syndrome (CBS) (n = 3) and PSP (n = 8); and pathologically diagnosed PSP (n = 8) and CBD patients (n = 7). Each patient set was compared to its appropriate control group consisting of age and gender matched individuals. Select lysosomal network protein levels were detected via Western blotting. Factor analysis was used to test the diagnostic sensitivity, specificity and accuracy of the select lysosomal network protein expression profiles. Results: PD, CBD and PSP were markedly different in their cerebrospinal fluid lysosomal network protein profiles. Lysosomal-associated membrane proteins 1 and 2 were significantly decreased in PD; early endosomal antigen 1 was decreased and lysozyme increased in PSP; and lysosomal-associated membrane proteins 1 and 2, microtubule-associated protein 1 light chain 3 and lysozyme were increased in CBD. A panel of lysosomal-associated membrane protein 2, lysozyme and microtubule-associated protein 1 light chain discriminated between controls, PD and 4-repeat tauopathies. Conclusions: This study offers proof of concept that select lysosomal network proteins are differentially expressed in cerebrospinal fluid of Parkinson’s disease, corticobasal syndrome and progressive supranuclear palsy. Lysosomal network protein analysis could be further developed as a diagnostic fluid biomarker in parkinsonian syndromes.

Tau Secretion and Propagation Is Regulated by p300/CBP via Autophagy-Lysosomal Pathway in Tauopathy

The trans-neuronal propagation of tau has been implicated in the progression of tau-mediated neurodegeneration. Tau secretion from neurons is the first step in tau transmission, but little is known about the cellular mechanism. Here, we report that p300/CBP, the lysine acetyltransferase that acetylates tau and regulates its homeostasis and toxicity, serves as a key regulator of tau secretion by inhibiting the autophagy-lysosomal pathway (ALP). Increased p300/CBP activity was associated with impaired function of this pathway in a tau transgenic mouse model. p300/CBP hyperactivation increased tau secretion by blocking autophagic flux. Conversely, inhibiting p300/CBP genetically or pharmacologically promoted autophagic flux, and reduced tau accumulation, tau secretion, and tau propagation in fibril-induced tau spreading models in vitro and in vivo. Our findings show that p300/CBP-induced impairment in the ALP underlies excessive unconventional secretion and pathogenic spread of tau.

Multiproteinopathy, neurodegeneration and old age: a case study

ABSTRACT A complex spectrum of mixed brain pathologies is common in older people. This clinical pathologic conference case study illustrates the challenges of formulating clinicopathologic correlations in late-onset neurodegenerative diseases featuring cognitive-behavioral syndromes with underlying multiple proteinopathy. Studies on the co-existence and interactions of Alzheimer’s disease (AD) with neurodegenerative non-AD pathologies in the aging brain are needed to understand the pathogenesis of neurodegeneration and to support the development of diagnostic biomarkers and therapies.