Copper-mediated formation of hydrogen peroxide from the amylin peptide: a novel mechanism for degeneration of islet cells in type-2 diabetes mellitus?

Amyloid deposits derived from the amylin peptide accumulate within pancreatic islet beta-cells in most cases of type-2 diabetes mellitus (T2Dm). Human amylin 'oligomers' are toxic to these cells. Using two different experimental techniques, we found that H(2)O(2) was generated during the aggregation of human amylin into amyloid fibrils.

A spectroscopic study of some of the peptidyl radicals formed following hydroxyl radical attack on beta-amyloid and alpha-synuclein.

There is clear evidence implicating oxidative stress in the pathology of many neurodegenerative diseases. Reactive oxygen species (ROS) are the primary mediators of oxidative stress, and hydrogen peroxide, a key ROS, is generated during aggregation of the amyloid proteins associated with some of these diseases. Hydrogen peroxide is catalytically converted to the aggressive hydroxyl radical in the presence of Fe(II) and Cu(I), which renders amyloidogenic proteins such as beta-amyloid and alpha-synuclein (implicated in Alzheimer's disease (AD) and Parkinson's disease (PD), respectively) vulnerable to self-inflicted hydroxyl radical attack.

Hydrogen peroxide is generated during the very early stages of aggregation of the amyloid peptides implicated in Alzheimer disease and familial British dementia.

Alzheimer disease and familial British dementia are neurodegenerative diseases that are characterized by the presence of numerous amyloid plaques in the brain. These lesions contain fibrillar deposits of the beta-amyloid peptide (Abeta) and the British dementia peptide (ABri), respectively. Both peptides are toxic to cells in culture, and there is increasing evidence that early "soluble oligomers" are the toxic entity rather than mature amyloid fibrils.

Both the D-(+) and L-(-) enantiomers of nicotine inhibit Abeta aggregation and cytotoxicity.

The underlying cause of Alzheimer's disease is thought to be the aggregation of monomeric beta-amyloid (Abeta), through a series of toxic oligomers, which forms the mature amyloid fibrils that accumulate at the center of senile plaques. It has been reported that L-(-)-nicotine prevents Abeta aggregation and toxicity, and inhibits senile plaque formation. Previous NMR studies have suggested that this could be due to the specific binding of L-(-)-nicotine to histidine residues (His6, His13, and His14) in the peptide.

Quinacrine acts as an antioxidant and reduces the toxicity of the prion peptide PrP106-126.

The accumulation of protein aggregates in the brain is a central feature of several different neurodegenerative diseases. We have recently shown that Abeta and alpha-synuclein, associated with Alzheimer's disease, Parkinson's disease and related disorders, can both induce the formation of hydroxyl radicals following incubation in solution, upon addition of Fe(II). PrP106-126, a model peptide for the study of prion protein-mediated cell death, shares the same property.

Generation of hydrogen peroxide from mutant forms of the prion protein fragment PrP121-231.

By means of electron spin resonance spectroscopy, in conjunction with the spin trapping technique, we have shown previously that Abeta and alpha-synuclein (aggregating proteins that accumulate in the brain in Alzheimer's disease, Parkinson's disease, and related disorders) both induce the formation of hydroxyl radicals following incubation in solution, upon addition of Fe(II). These hydroxyl radicals are apparently formed from hydrogen peroxide, via Fenton's reaction. An N-terminally truncated fragment of the mouse prion protein (termed PrP121-231) is toxic to cerebellar cells in culture, and certain human mutations, responsible for inherited prion disease, enhance this toxicity.

Copper-dependent generation of hydrogen peroxide from the toxic prion protein fragment PrP106-126.

Oligomeric forms of many of the aggregating proteins associated with neurodegenerative diseases are toxic to cultured cells. We have shown recently that Abeta and alpha-synuclein can both induce the formation of hydroxyl radicals following incubation in solution, upon the addition of Fe(II). Thus, they appear to generate hydrogen peroxide, which is converted to hydroxyl radicals via the Fenton reaction.

Formation of hydrogen peroxide and hydroxyl radicals from A(beta) and alpha-synuclein as a possible mechanism of cell death in Alzheimer's disease and Parkinson's disease.

The formation of extracellular or intracellular deposits of amyloid-like protein fibrils is a prominent pathological feature of many different neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). In AD, the beta-amyloid peptide (A(beta)) accumulates mainly extracellularly at the center of senile plaques, whereas, in PD, the alpha-synuclein protein accumulates within neurons inside the Lewy bodies and Lewy neurites. We have shown recently that solutions of A(beta) 1-40, A(beta) 1-42, A(beta) 25-35, alpha-synuclein and non-A(beta) component (NAC; residues 61-95 of alpha-synuclein) all liberate hydroxyl radicals upon incubation in vitro followed by the addition of small amounts of Fe(II).