The cure for your infection, may be the thing that eventually kills you; amyloids which build up plaque in the brain associated with Alzheimer’s Disease. The brains reactive inflammation to the plaque may cause the onset of Alzheimer’s.

RESEARCH ARTICLEALZHEIMER’S DISEASE

Amyloid-β peptide protects against microbial infection in mouse and worm models of Alzheimer’s disease
Vol. 8, Issue 340, pp. 340ra72
DOI: 10.1126/scitranslmed.aaf1059

Rehabilitation of a β-amyloid bad boy

A protein called Aβ is thought to cause neuronal death in Alzheimer’s disease (AD). Aβ forms insoluble aggregates in the brains of patients with AD, which are a hallmark of the disease. Aβ and its propensity for aggregation are widely viewed as intrinsically abnormal. However, in new work, Kumar et al. show that Aβ is a natural antibiotic that protects the brain from infection. Most surprisingly, Aβ aggregates trap and imprison bacterial pathogens. It remains unclear whether Aβ is fighting a real or falsely perceived infection in AD. However, in any case, these findings identify inflammatory pathways as potential new drug targets for treating AD.

Abstract

The amyloid-β peptide (Aβ) is a key protein in Alzheimer’s disease (AD) pathology. We previously reported in vitro evidence suggesting that Aβ is an antimicrobial peptide. We present in vivo data showing that Aβ expression protects against fungal and bacterial infections in mouse, nematode, and cell culture models of AD. We show that Aβ oligomerization, a behavior traditionally viewed as intrinsically pathological, may be necessary for the antimicrobial activities of the peptide. Collectively, our data are consistent with a model in which soluble Aβ oligomers first bind to microbial cell wall carbohydrates via a heparin-binding domain.  Consistent with our model, SalmonellaTyphimurium bacterial infection of the brains of mice resulted in rapid seeding and accelerated β-amyloid deposition, which (entrap invading bacteria). Our findings raise the intriguing possibility that β-amyloid may play a protective role in innate immunity and infectious or sterile inflammatory stimuli may drive amyloidosis. These data suggest a dual protective/damaging role for Aβ, as has been described for other antimicrobial peptides.

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