Enzyme can destroy Alzheimer's plaques

Oct. 24, 2006 at 9:48 PM

ST. LOUIS, Oct. 24 (UPI) -- A natural brain enzyme called matrix metalloproteinase 9 (MMP-9) can break down the brain plaques linked to Alzheimer's, say U.S. researchers. Previously identified enzymes could only degrade small plaques, leading scientists to believe the plaques were so tightly bound the fibrils were indestructible.

Researcher Jin-Moo Lee led the research, which was performed at the Washington University School of Medicine in St. Louis, Mo.

The team noted that MMP-9, which was already associated with cancer metastases, vascular disease, arthritis, and other pathologies, was secreted from brain support cells called astrocytes and was active in the spaces outside of cells. Since the amyloid beta (Abeta) plaques typical of Alzheimer's form outside the cells, they decided to see if MMP-9 had an effect on them.

The researchers created mice that couldn't produce MMP-9 and found that Abeta built up in the spaces between their neurons, proving that the enzyme played a role in clearing Abeta from these locations. They had already found that astrocytes close to amyloid plaques increased their MMP-9 production, and hypothesized that MMP-9 and other brain enzymes were responsible for the previously unexplained phenomena of Alzheimer's plaques not growing beyond a certain size.

The team is planning to test whether increasing MMP-9 levels can delay the onset of Alzheimer's, and hope the enzyme can be used in new treatments for the disease.

A report on the research appears in the October 25 issue of the Journal of Neuroscience.

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