Astrocytic urea cycle detoxifies Aβ-derived ammonia while impairing memory in Alzheimers Disease

Ju, Y. H.; Bhalla, M.; Hyeon, S. J.; Oh, J. E.; Yoo, S.; Chae, U.; Kwon, J.; Koh, W.; Lim, J.; Park, Y. M.; Lee, J.; Cho, I. J.; Lee, H.; Ryu, H.; Lee, C. J. J.

doi:10.1101/2021.10.15.464517

bioRxiv · 10.1101/2021.10.15.464517

Astrocytic urea cycle detoxifies Aβ-derived ammonia while impairing memory in Alzheimers Disease

Ju, Y. H.·Bhalla, M.·Hyeon, S. J.·Oh, J. E.·Yoo, S.·Chae, U.·Kwon, J.·Koh, W.·Lim, J.·Park, Y. M.·Lee, J.·Cho, I. J.·Lee, H.·Ryu, H.·Lee, C. J. J.

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Abstract

Alzheimers disease (AD) is one of the foremost neurodegenerative diseases, characterized by beta-amyloid (A{beta}) plaques and significant progressive memory loss. In AD, astrocytes are known to take up and clear A{beta} plaques. However, how A{beta} induces pathogenesis and memory impairment in AD remains elusive. We report that normal astrocytes show non-cyclic urea metabolism, whereas A{beta}-treated astrocytes show switched-on urea cycle with upregulated enzymes and accumulated entering-metabolite aspartate, starting-substrate ammonia, end-product urea, and side-product putrescine. Gene-silencing of astrocytic ornithine decarboxylase-1 (ODC1), facilitating ornithine-to-putrescine conversion, boosts urea cycle and eliminates aberrant putrescine and its toxic by-products ammonia, H2O2, and GABA to recover from reactive astrogliosis and memory impairment in AD model. Our findings implicate that astrocytic urea cycle exerts opposing roles of beneficial A{beta} detoxification and detrimental memory impairment in AD. We propose ODC1-inhibition as a promising therapeutic strategy for AD to facilitate removal of toxic molecules and prevent memory loss.

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Ju, Y. H., Bhalla, M., Hyeon, S. J., Oh, J. E., Yoo, S., Chae, U., Kwon, J., Koh, W., Lim, J., Park, Y. M., Lee, J., Cho, I. J., Lee, H., Ryu, H., Lee, C. J. J.. 2021-10-16. Astrocytic urea cycle detoxifies Aβ-derived ammonia while impairing memory in Alzheimers Disease. https://doi.org/10.1101/2021.10.15.464517

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