Reduced D-aspartic acid (D-Asp) levels were found in human brain samples from Alzheimer’s disease (AD) patients compared to healthy controls (D’Aniello et al., 1998).
Repeated treatment with D-Asp in a long-lasting model of neuropathic pain in mice (i.e. the spared nerve injury, characterized by increased form of insoluble amyloid-β peptide 1-42, Aβ, in hippocampus and cognitive impairment) reduced abnormal behaviors, normalized the Aβ levels, and increased steroids level in prefrontal cortex and hippocampus (D’aniello et al., 2017).
Human amyloid-β peptide 1-42 (Aβ) was subjected to a radical reaction using ascorbic acid and CuCl2. At 24 h the percentage of D-Asp increased to 6.69 ± 0.09%, which was comparable with the reported D-Asp concentration of purified core amyloids of Alzheimer’s disease patients (Tambo et al., 2013). This racemization was significantly inhibited by radical scavengers. The racemization of Asp by a radical reaction is much faster than that by an ionic reaction. L-alanine was also racemized during the same reaction (Tambo et al, 2013).
D’Aniello A., Lee J.M., Petrucelli L., Di Fiore M.M. Regional decreases of free D-aspartate levels in Alzheimer’s disease. Neurosci. Lett. (1998) 250(2), 131-134.
D’Aniello A., Luongo L., Romano R., Iannotta M., Marabese I., Boccella S., Belardo C., de Novellis V., Arra C., Barbieri A., D’Aniello B., Scandurra A., Magliozzi L., Fisher G., Guida F., Maione S. D-Aspartic acid ameliorates painful and neuropsychiatric changes and reduces β-amyloid Aβ1-42 peptide in a long lasting model of neuropathic pain. Neurosci. Lett. (2017) 651, 151-158.
Tambo K., Yamaguchi T., Kobayashi K., Terauchi E., Ichi I., Kojo S. Racemization of the aspartic acid residue of amyloid- β peptide by a radical reaction. Biosci. Biotechnol. Biochem. (2013) 77, 416-418.
Shosuke Kojo, Nara Women’s University
Loredano Pollegioni, University of Insubria