The relationship between the aggregational state of the amyloid-beta peptides and free radical generation by the peptides.
In the present study, we investigated whether or not the amyloid-beta protein (Abeta) peptide itself spontaneously generates free radicals using electron spin resonance (ESR) spectroscopy while also monitoring the aggregational state of Abeta and Abeta-induced cytotoxicity. The present results demonstrated a four-line spectrum in the presence of both Abeta40 and Abeta42 with Ntert-butyl-alpha-phenylnitrone (PBN), but not in the presence of PBN alone in phosphate-buffered saline (PBS). The fact that the four-line spectrum obtained for the Abeta/PBN in PBS was completely abolished in the presence of the iron-chelating agent Desferal demonstrated the observed four-line spectrum to be iron-dependent. The present study also revealed that either Abeta40 or Abeta42 with PBN in phosphate buffer (PB) did not produce any definite four-line spectrum. Both a thioflavine-T (Th-T) fluorometric assay and circular dichroism (CD) spectroscopy showed the amyloid fibril formation of Abeta in PBS to be much higher than that of Abeta in PB. Moreover, Abeta-induced cytotoxicity assays showed Abeta incubated in PBS to be more cytotoxic than that incubated in PB. These results thus suggest that Abeta-associated free radical generation is strongly influenced by the aggregational state of the peptides.
Monji
A
A
Department of Neuropsychiatry, Graduate School of Medical Sciences, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan. amonji@hf.rim.or.jp
Utsumi
H
H
Ueda
T
T
Imoto
T
T
Yoshida
I
I
Hashioka
S
S
Tashiro
K
K
Tashiro
N
N
D000544:Alzheimer Disease / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism* / Q000633:toxicity; D000818:Animals; D052160:Benzothiazoles; D002470:Cell Survival / Q000187:drug effects; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D005456:Fluorescent Dyes; D005609:Free Radicals / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D016716:PC12 Cells; D051381:Rats; D013844:Thiazoles
D016229:Amyloid beta-Peptides; D052160:Benzothiazoles; D005456:Fluorescent Dyes; D005609:Free Radicals; D013844:Thiazoles; C009462:thioflavin T