Mechanisms of the Effects of Crocin on Aggregation and Deposition of Aβ1–40 Fibrils in Alzheimer’s Disease

Abstract

Alzheimer’s disease (AD) is among the most important health-care problems in the world. The two pathological hallmarks of AD are extracellular neuritic amyloid plaques and intracellular neurofibrillary tangles. The aggregation of Aβ and β-sheet formation are considered to be the critical events which render these peptides neurotoxic. AD is affecting a large percentage of the elderly around the world. Many studies have been done on drugs to cure or at least slow Alzheimer’s disease. Most drugs produced for this disease aim at compensating for the performance of specific cell groups affected by the disease or restoring the function of these cells.This study examined the interaction of crocin, the main pigment of saffron, with the amyloid-β peptides 1 + 40 (Aβ 40) to determine the effects on peptide conformation and fibril formation using fluorescence spectroscopy, CD spectroscopy and electron microscopy. ThT data demonstrated the appearance of well-defined amyloid fibrils indicating an enhanced nucleation of Aβ40. Incubation of pre-formed Aβ40 fibrils with crocin resulted in extensive lateral aggregation and precipitation of the fibrils. Consistent with this, electron microscopy data indicated that crocin decreased the number of fibrils formed and significantly reduced the average fibril length of Aβ40 as assessed by low levels of thioflavin T binding data. The mechanism by which, crocin prevented fibril formation was demonstrated by ANS binding assay and CD spectroscopy. In summary, crocin interacts with Aβ peptides and prevents amyloid formation. This means that it has the potential to be an important therapeutic drug against AD.