In vivo rate-determining steps of tau seed accumulation in Alzheimer's disease

Both the replication of protein aggregates and their spreading throughout the brain are implicated in the progression of Alzheimer’s disease (AD). However, the rates of these processes are unknown and the identity of the rate-determining process in humans has therefore remained elusive. By bringing together chemical kinetics with measurements of tau seeds and aggregates across brain regions, we can quantify their replication rate in human brains. Notably, we obtain comparable rates in several different datasets, with five different methods of tau quantification, from postmortem seed amplification assays to tau PET studies in living individuals. Our results suggest that from Braak stage III onward, local replication, rather than spreading between brain regions, is the main process controlling the overall rate of accumulation of tau in neocortical regions. The number of seeds doubles only every ∼5 years. Thus, limiting local replication likely constitutes the most promising strategy to control tau accumulation during AD

Targeted Retreatment of Incompletely Recovered Chronic Obstructive Pulmonary Disease Exacerbations with Ciprofloxacin. A Double-Blind, Randomized, Placebo-controlled, Multicenter, Phase III Clinical Trial

RATIONALE: COPD exacerbations are prone to non-recovery but there are no data about the effectiveness of retreatment on these prolonged events. We examined whether further therapy with ciprofloxacin for incompletely resolved COPD exacerbations prolonged the time until the next event. METHODS: This multi-centre randomised double-blind placebo-controlled trial studied retreatment with oral ciprofloxacin 500mg or matched placebo twice daily for 7 days in patients with GOLD stage II - IV COPD with persistent symptoms and/or serum C-reactive protein (CRP) ≥8mg/L initiated 14 (+/- 3) days after an index COPD exacerbation. The primary outcome was the time to the next exacerbation within a 90-day period. RESULTS: Of 826 patients screened at 4 centres, 144 eligible participants with incomplete recovery were randomised to receive ciprofloxacin (n=72) or placebo (n=72). 57% of patients in the ciprofloxacin group had experienced 1 or more exacerbations, compared to 53% in the placebo group. The median time to the next exacerbation was 32.5 days (IQR 13-50) in the placebo arm and 34 days (IQR 17-62) in the ciprofloxacin arm, which was not significantly different (adjusted hazard ratio = 1.07, 95% CI 0.68-1.68; p=0.76). No significant differences were seen in quality of life scores or lung function between treatment groups. CONCLUSION: In patients with persistent symptoms and/or raised CRP 14 days following a COPD exacerbation, an additional course of ciprofloxacin resulted in no additional benefit compared to placebo. This suggests that non-recovered exacerbations are not driven by ongoing bacterial infection and may potentially be targeted with anti-inflammatory therapy

[18F]AV-1451 PET in behavioral variant frontotemporal dementia due to MAPT mutation

The validation of tau radioligands could improve the diagnosis of frontotemporal lobar degeneration and the assessment of disease-modifying therapies. Here, we demonstrate that binding of the tau radioligand [18F]AV-1451 was significantly abnormal in both magnitude and distribution in a patient with familial frontotemporal dementia due to a MAPT 10 + 16C>T gene mutation, recapitulating the pattern of neuropathology seen in her father. Given the genetic diagnosis and the non-Alzheimer's pathology, these findings suggest that [18F]AV-1451 might be a useful biomarker in primary tauopathies. Largerscale in vivo and post-mortem studies will be needed to assess the technique's specificity.TEC is supported by the Association of British Neurologists and the Patrick Berthoud Charitable Trust. JRH, JK, and SF are supported by funding to Forefront, a collaborative research group dedicated to the study of frontotemporal dementia and motor neuron disease, from the National Health and Medical research Council of Australia program grant (1037746). JBR is supported by the Wellcome Trust (103838). The Cambridge Brain Bank, JPC, WRBJ, MGS, and LP are supported by the Cambridge Biomedical Research Centre. MGS is supported by the UK MRC.This is the final version of the article. It first appeared from Wiley via https://doi.org/10.1002/acn3.36

Identification of β-Secretase (BACE1) Substrates Using Quantitative Proteomics

β-site APP cleaving enzyme 1 (BACE1) is a transmembrane aspartyl protease with a lumenal active site that sheds the ectodomains of membrane proteins through juxtamembrane proteolysis. BACE1 has been studied principally for its role in Alzheimer's disease as the β-secretase responsible for generating the amyloid-β protein. Emerging evidence from mouse models has identified the importance of BACE1 in myelination and cognitive performance. However, the substrates that BACE1 processes to regulate these functions are unknown, and to date only a few β-secretase substrates have been identified through candidate-based studies. Using an unbiased approach to substrate identification, we performed quantitative proteomic analysis of two human epithelial cell lines stably expressing BACE1 and identified 68 putative β-secretase substrates, a number of which we validated in a cell culture system. The vast majority were of type I transmembrane topology, although one was type II and three were GPI-linked proteins. Intriguingly, a preponderance of these proteins are involved in contact-dependent intercellular communication or serve as receptors and have recognized roles in the nervous system and other organs. No consistent sequence motif predicting BACE1 cleavage was identified in substrates versus non-substrates. These findings expand our understanding of the proteins and cellular processes that BACE1 may regulate, and suggest possible mechanisms of toxicity arising from chronic BACE1 inhibition

Therapeutic opportunities within the DNA damage response

The DNA damage response (DDR) is essential for maintaining the genomic integrity of the cell, and its disruption is one of the hallmarks of cancer. Classically, defects in the DDR have been exploited therapeutically in the treatment of cancer with radiation therapies or genotoxic chemotherapies. More recently, protein components of the DDR systems have been identified as promising avenues for targeted cancer therapeutics. Here, we present an in-depth analysis of the function, role in cancer and therapeutic potential of 450 expert-curated human DDR genes. We discuss the DDR drugs that have been approved by the US Food and Drug Administration (FDA) or that are under clinical investigation. We examine large-scale genomic and expression data for 15 cancers to identify deregulated components of the DDR, and we apply systematic computational analysis to identify DDR proteins that are amenable to modulation by small molecules, highlighting potential novel therapeutic targets

DNA base damage recognition and processing

In living cells DNA base lesions are formed continuously as a consequence of normal metabolism and are also generated by a number of external factors. Simple base damages are repaired by base excision repair that is initiated by a damage specific DNA glycosylase, which removes the damaged base creating an abasic site (apurinic/apyrimidinic, AP site). AP endonuclease cleaves the phosphodiester bond 5′ to the AP site and then DNA polymerase β adds the first nucleotide to the 3′-end of the incised AP site and at the same time removes the 5′-sugar phosphate residue. DNA ligase completes the repair by sealing the DNA ends. These processes are directed and co-ordinated by multiple protein-protein interactions. This review focuses primarily on mammalian base excision repair, and in particular addresses the enzymology of the repair process and co-ordination of repair reactions. © 2005 Springer-Verlag Berlin Heidelberg

[18F]AV-1451 PET in behavioural variant frontotemporal dementia due to MAPT mutation

The validation of tau radioligands could improve the diagnosis of frontotemporal lobar degeneration and the assessment of disease-modifying therapies. Here, we demonstrate that binding of the tau radioligand [18F]AV-1451 was significantly abnormal in both magnitude and distribution in a patient with familial frontotemporal dementia due to a MAPT 10 + 16C>T gene mutation, recapitulating the pattern of neuropathology seen in her father. Given the genetic diagnosis and the non-Alzheimer's pathology, these findings suggest that [18F]AV-1451 might be a useful biomarker in primary tauopathies. Largerscale in vivo and post-mortem studies will be needed to assess the technique's specificity.NHMRC RGMS ID P0291957