Abstract
Aβ is the main constituent of the amyloid plaque found in the brains of patients with Alzheimer’s disease. There are two common isoforms of Aβ: the more common form, Aβ40, and the less common but more amyloidogenic form, Aβ42. Crocin is a carotenoid from the stigma of the saffron flower and it has many medicinal properties, including antioxidant effects. In this study, we examined the potential of crocin as a drug candidate against Aβ42 amyloid formation. The thioflavin T-binding assay and electron microscopy were used to examine the effects of crocin on the extension and disruption of Aβ42 amyloids. To further investigate the relationship between crocin and Aβ42 structure, we analyzed peptide conformation using the ANS-binding assay and circular dichroism (CD) spectroscopy. An increase in the thioflavin T fluorescence intensity upon incubation revealed amyloid formation in Aβ42. It was found that crocin has the ability to prevent amyloid formation by decreasing the fluorescence intensity. Electron microscopy data also indicated that crocin decreased the amyloid fibril content of Aβ. The ANS-binding assay showed that crocin decreased the hydrophobic area in incubated Aβ42. CD spectroscopy results also showed that the peptide undergoes a structural change to α-helical and β-turn. Our study shows that the anti-amyloidogenic effect of crocin may be exerted not only by the inhibition of Aβ amyloid formation but also by the disruption of amyloid aggregates. Therefore, crocin could be essential in the search for therapies inhibiting aggregation or disrupting aggregation.
Highlights
Alzheimer’s disease (AD) is categorized as an advanced disorder involving brain nerve cell destruction
The results show that hydrophobic surface exposure of Aβ42 decreased in the presence of crocin, and this implies interaction between crocin and the protein and the formation of a complex between them
The inhibitory effects of crocin clearly indicate that it could be used as a pharmacological agent to inhibit or retard amyloid fibril formation in Alzheimer’s disease
Summary
Alzheimer’s disease (AD) is categorized as an advanced disorder involving brain nerve cell destruction It is considered the most common kind of mental agitation or paranoia for which no valid diagnostic test has been found and is one of the major causes of death in the world [1,2,3]. Unlike intracellular neurofibrillary tangles, aging plaques can accumulate in extracellular positions These plaques arise due to the accumulation of Aβ peptides that consist of 40 or 42 amino acids (Aβ40 and Aβ42) and are formed by sequential cleavage of the amyloid precursor protein (APP), which is a membrane protein containing 695-770 amino acids [5, 8]. High concentrations of soluble aggregates of Aβ act as a poison and can lead to cell apoptosis This state can induce oxidative stress that is regarded as an important factor in the onset of AD. This is due to an imbalance between free radicals and a shortage of their cleaner or a malfunction in the system that should
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