%0 Journal Article
%T Reciprocal modulation of A¦Â42 aggregation by copper and homocysteine
%A Salla Keskitalo
%A Melinda Farkas
%A Michael Hanenberg
%A Anita Szodorai
%A Alexander Semmler
%A Michael Weller
%A Roger M. Nitsch
%J Frontiers in Aging Neuroscience
%D 2014
%I Frontiers Media
%R 10.3389/fnagi.2014.00237
%X Hyperhomocysteinemia is a risk factor for Alzheimer¡¯s disease (AD). Both homocysteine (Hcy) and amyloid ¦Â (A¦Â), which accumulates in the brain of AD patients, bind copper. Aim of this study was to test the hypothesis that the association of Hcy and AD results from a molecular interaction between Hcy and A¦Â that is mediated by copper. We established a microtiter plate format thioflavin T aggregation assay to monitor A¦Â42 fibrillization. Copper (5 ¦ÌM) completely prevented A¦Â42 (5 ¦ÌM) fibrillization. Homocysteine in the absence of copper did not impact A¦Â42 fibrillization, but physiological concentrations of Hcy (10¨C100 ¦ÌM) attenuated the inhibitory effect of copper on A¦Â42 fibril formation. These results were qualitatively confirmed by electron microscopy, which did not reveal morphological differences. To compare the toxicity of fibrillar and non-fibrillar A¦Â42 exposed to copper or Hcy, rat primary cortical neurons were treated in vitro with 5 ¦ÌM A¦Â42 for 72 h. After incubation with 5 ¦ÌM A¦Â42 that had been aggregating in the absence of Hcy or copper, cell viability was reduced to 40%. Incubation with 5 ¦ÌM A¦Â42, in which fibril formation had been prevented or reverted by the addition of 5 ¦ÌM copper, resulted in cell viability of approximately 25%. Accordingly, viability was reduced to 25% after incubation with 5 ¦ÌM monomeric, i.e., non-fibrillized, A¦Â42. The addition of Hcy plus copper to 5 ¦ÌM A¦Â42 yielded 50% viability. In conclusion, copper prevents and reverts A¦Â fibril formation leading rather to formation of lower order oligomers or amorphous aggregates, and Hcy reduces these effects. Such mechanisms may explain the association of hyperhomocysteinemia and AD, leading to novel therapeutic strategies in the prevention and treatment of this disease.
%K homocysteine
%K Alzheimer¡¯s disease
%K copper
%K A¦Â
%K cytotoxicity
%K primary neurons
%U http://www.frontiersin.org/Journal/10.3389/fnagi.2014.00237/abstract