Low dose aspirin may help cells in the brain to clear away a toxic protein molecule at the core of Alzheimer's, early research suggests.
Scientists showed the common pain killer stimulated cellular machinery that acts as a waste disposal system to keep the brain "clean".
Genetically engineered mice given the drug had reduced levels of a key hallmark of Alzheimer's in their brains, sticky clumps of beta amyloid peptide.
Impaired clearance of the protein building block from the brain is thought to be one of the main causes of the disease.
A US team led by Professor Kalipada Pahan, from Rush University Medical Center in Chicago, found low-dose aspirin stimulated the formation of lysosomes - tiny sacs in cells filled with digestive enzymes that help break down and clear away unwanted or harmful material.
The scientists wrote in the journal JNeurosci: "Stimulation of lysosomal biogenesis and reduction of amyloid plaque pathology by low-dose aspirin holds promising therapeutic potential for treatment of AD (Alzheimer's disease)."
However British experts urged caution.
Professor Tara Spires-Jones, deputy director of the Centre for Discovery Brain Sciences at the University of Edinburgh, said: "While this work is scientifically interesting, it is at very early stages.
"The amyloid reducing effects of aspirin were shown in cells in a dish and in a single mouse model of Alzheimer's disease with relatively few mice per group.
"Further, the study did not show whether aspirin helped the brain function in this disease model. More work will need to be done in order to know whether low-dose aspirin could help prevent or treat Alzheimer's."
Rob Howard, Professor of Old Age Psychiatry at University College London, added: "Clinical trials of aspirin have already been performed in patients with Alzheimer's disease.
"The drug had no beneficial effects on outcome measures and was associated with an increased risk of gastrointestinal haemorrhage."
The American researchers pointed out the mechanism appeared to be dependent on a protein called PPAR-alpha, levels of which fell significantly with age.
This might explain why trials looking at the effects of aspirin on elderly Alzheimer's patients had produced disappointing results, they said.
Dr Sara Imarisio, from Alzheimer's Research UK, said: "Aspirin is a commonly taken medicine for a number of health conditions, but there has been little research to examine potential benefits for Alzheimer's disease.
"This early-stage research suggests aspirin may help improve how the brain removes amyloid, a protein known to build up in Alzheimer's. The study reveals important insights into the mechanisms through which aspirin may impact brain health, however this is a small study in mice so it's too early to draw conclusions about whether aspirin could be used to treat Alzheimer's in people."
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