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The vasoactivity of A beta peptides
1Department of Psychiatry, Roskamp Laboratories, University of South Florida, Tampa 33613, USA.
Annals of the New York Academy of Sciences
|November 5, 1997
Summary
Amyloid beta (A beta) peptides enhance blood vessel constriction in rats, suggesting a role in Alzheimer's disease (AD) neurodegeneration. This vasoconstriction may be linked to reduced nitric oxide and increased free radicals.
Area of Science:
- Neuroscience
- Cardiovascular Research
- Biochemistry
Background:
- Alzheimer's disease (AD) is a neurodegenerative disorder characterized by amyloid beta (A beta) peptide accumulation.
- A beta peptide's role in cerebrovascular dysfunction and its direct impact on blood vessel constriction remain incompletely understood.
- Previous studies focused on A beta cytotoxicity in cell cultures, often requiring prolonged incubation times.
Purpose of the Study:
- To investigate the immediate effects of freshly solubilized A beta peptides on isolated rat aorta vasoconstriction.
- To explore the potential mechanism of A beta-induced vasoconstriction, particularly its relation to nitric oxide and superoxide radicals.
- To differentiate the vasoactive properties of different A beta peptide forms from their cytotoxic effects.
Main Methods:
- Isolated rat aorta preparations were used to measure vasoconstriction responses.
- A beta peptides (A beta 1-40, A beta 1-42, A beta 25-35) were applied at varying concentrations (100 nM - 5 microM).
- Vasoconstrictors phenylephrine and endothelin were used to assess A beta peptide's modulatory effects.
- Superoxide dismutase (SOD) was employed to investigate the role of the nitric oxide/superoxide balance.
Main Results:
- Freshly solubilized A beta peptides (100 nM-1 microM) significantly enhanced vasoconstriction induced by phenylephrine and endothelin.
- These effects were immediate and occurred at concentrations lower than those causing endothelial cell toxicity in vitro.
- Superoxide dismutase (SOD) pre-treatment reduced the A beta-mediated enhancement of vasoconstriction, indicating involvement of the nitric oxide/superoxide ratio.
- A beta 1-40 and A beta 1-42 enhanced vasoconstriction, whereas A beta 25-35 did not, suggesting distinct mechanisms from cytotoxicity.
Conclusions:
- A beta peptides can directly induce or enhance vasoconstriction in isolated rat aorta, independent of aggregation-dependent cytotoxicity.
- The mechanism appears partly mediated by an altered nitric oxide/superoxide balance, favoring vasoconstriction.
- These findings suggest that A beta peptides interacting with cerebrovasculature could contribute to reduced blood flow and neurodegeneration in Alzheimer's disease.