Editorial on, “Amyloid-beta clearance in Alzheimer's disease”
Robert A. Marr- Department of Neuroscience, Rosalind Franklin University of Medicine and Science/Chicago Medical School, North Chicago, IL, USA
Alzheimer's disease (AD) is the most common form of dementia and is exacting a tremendous economic and personal toll on nations as well as families throughout the world and this toll will continue to grow over the passing decades. This crisis is compounded by the lack of effective treatments for this disease and the widespread failure of a multitude of therapeutic clinical trials targeting many identified disease pathways including amyloid-beta (Aβ), tau, inflammation, oxidative stress and more (reviewed in Schneider et al., 2014). Regardless of these failures, all of these disease pathways are likely key players in disease pathogenesis and improved therapeutics as well as better clinical study design may yet prove effective. Because reduced clearance of Aβ has been clinically linked to AD (Mawuenyega et al., 2010), it is likely important to disease pathogenesis. This research topic focuses on aspects of Aβ clearance in AD and its therapeutic relevance.
The research topic on Aβ clearance in AD in Frontiers in Aging Neuroscience has produced a highly informative collection of reviews, mini-reviews, opinions, hypothesis and theory articles, as well as original research articles that cover key aspects related to Aβ clearance. These aspects include proteolytic degradation, low-density lipoprotein (LDL) receptor related clearance, cellular signaling pathways related to clearance, and transport/phagocytosis.
With regards to proteases, Marr and Hafez produced a mini-review that provides a concise rationale for the amyloid hypothesis of AD and updates recent finding related to the neprilysin-2 (NEP2) enzyme and its potential role in AD (Marr and Hafez, 2014). The other articles concerning proteases present new angles of looking at this topic. Malcolm Leissring contributed an opinion specifically on the critical role of clearance of intracellular Aβ in disease pathogenesis; while Miners et al. gave us a review focused on a dual role for these enzymes in both Aβ clearance and cerebral perfusion as well as how these process may interact (Leissring, 2014; Miners et al., 2014). Nalivaeva et al. produced a comprehensive review of key Aβ-degrading enzymes focusing on the epigenetic regulation of their expression. This review also discusses transthyretin (TTR), an Aβ binding protein involved in its transport/clearance (Nalivaeva et al., 2014). Related to this, the original article contributed by Philibert et al. includes the characterization of TTR binding to Aβ and its ability to prevent oligomerization. This original article also characterizes the direct Aβ degrading activity of thimet oligopeptidase (EC 3.4.24.15) (Philibert et al., 2014).
On the subtopic of LDL receptors, Kanekiyo and Bu provided a review on the role of LDL receptor-related protein 1 (LRP1) in Aβ endocytosis and signal transduction in relation to AD pathogenesis (Kanekiyo and Bu, 2014). Also regarding endocytosis (and LDL receptors), Zhao et al. contributed an original article on the effects of aging and apolipoprotein E status on glial uptake of lentiviral-expressed Aβ, showing that apoE4 results in less efficient microglial clearance of Aβ (Zhao et al., 2014). Following on the subtopic of glial uptake, Bhattacharjee et al. produced an opinion focusing on miRNA-34a as a regulator of the phagocytosis sensor-receptor, TREM2, and its potential role in AD (Bhattacharjee et al., 2014). Zolezzi et al. provided a comprehensive review of AD pathogenesis and Aβ regulation focusing on the PPAR signaling pathway; while Hernandez-Rapp et al. wrote a mini review on PrPc signaling and its effects on Aβ clearance (Hernandez-Rapp et al., 2014; Zolezzi et al., 2014).
These articles also discuss the therapeutic implications of their topics. Related to this, Spencer and Masliah provided a review on the state of immunotherapy for AD and future perspectives on this type of Aβ clearance-related therapeutic approach (Spencer and Masliah, 2014). Finally, Qiu and Zhu produced a hypothesis and theory article on the relevance of amylin to AD therapy (Qiu and Zhu, 2014). Therefore, this compilation of articles is highly relevant to the study and development of AD therapies.
Conflict of Interest Statement
The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Acknowledgment
I would like to thank Dr. Eliezer Masliah who acted as co-editor on the topic.
References
Bhattacharjee, S., Zhao, Y., and Lukiw, W. J. (2014). Deficits in the miRNA-34a-regulated endogenous TREM2 phagocytosis sensor-receptor in Alzheimer's disease (AD); an update. Front. Aging Neurosci. 6:116. doi: 10.3389/fnagi.2014.00116
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Hernandez-Rapp, J., Martin-Lanneree, S., Hirsch, T. Z., Launay, J. M., and Mouillet-Richard, S. (2014). Hijacking PrP(c)-dependent signal transduction: when prions impair Abeta clearance. Front. Aging Neurosci. 6:25. doi: 10.3389/fnagi.2014.00025
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Kanekiyo, T., and Bu, G. (2014). The low-density lipoprotein receptor-related protein 1 and amyloid-beta clearance in Alzheimer's disease. Front. Aging Neurosci. 6:93. doi: 10.3389/fnagi.2014.00093
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Leissring, M. A. (2014). Abeta degradation-the inside story. Front. Aging Neurosci. 6:229. doi: 10.3389/fnagi.2014.00229
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Marr, R. A., and Hafez, D. M. (2014). Amyloid-beta and Alzheimer's disease: the role of neprilysin-2 in amyloid-beta clearance. Front. Aging Neurosci. 6:187. doi: 10.3389/fnagi.2014.00187
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Mawuenyega, K. G., Sigurdson, W., Ovod, V., Munsell, L., Kasten, T., Morris, J. C., et al. (2010). Decreased clearance of CNS beta-amyloid in Alzheimer's disease. Science 330, 1774. doi: 10.1126/science.1197623
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Miners, J. S., Palmer, J. C., Tayler, H., Palmer, L. E., Ashby, E., Kehoe, P. G., et al. (2014). Abeta degradation or cerebral perfusion? Divergent effects of multifunctional enzymes. Front. Aging Neurosci. 6:238. doi: 10.3389/fnagi.2014.00238
Nalivaeva, N. N., Belyaev, N. D., Kerridge, C., and Turner, A. J. (2014). Amyloid-clearing proteins and their epigenetic regulation as a therapeutic target in Alzheimer's disease. Front. Aging Neurosci. 6:235. doi: 10.3389/fnagi.2014.00235
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Philibert, K. D., Marr, R. A., Norstrom, E. M., and Glucksman, M. J. (2014). Identification and characterization of Aβ peptide interactors in Alzheimer's disease by structural approaches. Front. Aging Neurosci. 6:265. doi: 10.3389/fnagi.2014.00265
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Qiu, W. Q., and Zhu, H. (2014). Amylin and its analogs: a friend or foe for the treatment of Alzheimer's disease? Front. Aging Neurosci. 6:186. doi: 10.3389/fnagi.2014.00186
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Schneider, L. S., Mangialasche, F., Andreasen, N., Feldman, H., Giacobini, E., Jones, R., et al. (2014). Clinical trials and late-stage drug development for Alzheimer's disease: an appraisal from 1984 to 2014. J. Intern. Med. 275, 251–283. doi: 10.1111/joim.12191
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Spencer, B., and Masliah, E. (2014). Immunotherapy for Alzheimer's disease: past, present and future. Front. Aging Neurosci. 6:114. doi: 10.3389/fnagi.2014.00114
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Zhao, W., Zhang, J., Davis, E. G., and Rebeck, G. W. (2014). Aging reduces glial uptake and promotes extracellular accumulation of Abeta from a lentiviral vector. Front. Aging Neurosci. 6:210. doi: 10.3389/fnagi.2014.00210
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Zolezzi, J. M., Bastias-Candia, S., Santos, M. J., and Inestrosa, N. C. (2014). Alzheimer's disease: relevant molecular and physiopathological events affecting amyloid-beta brain balance and the putative role of PPARs. Front. Aging Neurosci. 6:176. doi: 10.3389/fnagi.2014.00176
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text | Google Scholar
Keywords: Alzheimer's disease, amyloid-beta, clearance, proteases, LDL receptors, signal transduction
Citation: Marr RA (2014) Editorial on, “Amyloid-beta clearance in Alzheimer's disease”. Front. Aging Neurosci. 6:310. doi: 10.3389/fnagi.2014.00310
Received: 21 October 2014; Accepted: 22 October 2014;
Published online: 20 November 2014.
Edited and reviewed by: Rodrigo Orlando Kuljiš, Zdrav Mozak Limitada, Chile
Copyright © 2014 Marr. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: robert.marr@rosalindfranklin.edu