Effects of docosahexaenoic acid on in vitro amyloid beta peptide 25–35 fibrillation

Amyloid beta peptide(25-35) (Abeta(25-35)) encompasses one of the neurotoxic domains of full length Abeta(1-40/42), the major proteinaceous component of amyloid deposits in Alzheimer's disease (AD). We investigated the effect of docosahexaenoic acid (DHA, 22:6, n-3), an essential brain polyunsaturated fatty acid, on the in vitro fibrillation of Abeta(25-35) and found that it significantly reduced the degree of fibrillation, as shown by a decrease in the intensity of both the thioflavin T and green fluorescence in confocal microscopy. Transmission electron microscopy revealed that DHA-incubated samples were virtually devoid of structured fibrils but had an amorphous-like consistency, whereas the controls contained structured fibers of various widths and lengths. The in vitro fibrillation of Abeta(25-35) appeared to be pH-dependent, with the strongest effect…