| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
|
FJ
EXPRESS SUMMARY ARTICLE The Full-length version of this article is also available, published online January 21, 2005 as doi:10.1096/fj.04-2582fje. |
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
,1
,,2
* Departments of Surgery, Pathology, and Neurology, College of Physicians and Surgeons, Columbia University, New York, New York, USA;
Department of Analytical Chemistry, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, Kobe, Japan;
Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, Columbia University, New York, New York, USA;
Department of Anatomy and Cell Biology, SUNY, Health Science Center at Brooklyn, Brooklyn, New York, USA;
|| Dean’s Office, Medical College of Georgia, Augusta, Georgia, USA; and
Nathan Kline Institute, New York University, School of Medicine, New York, New York, USA
2Correspondence: Departments of Pathology and Surgery, College of Physicians & Surgeons of Columbia University, 650 West 168th St., Black Building, Room 17-07, New York, NY 10032, USA. E-mail: sdy1{at}columbia.edu
SPECIFIC AIMS
Amyloid-ß alcohol dehydrogenase (ABAD) is a member of the short chain dehydrogenase reductase family present in mitochondria and binds amyloid-ß peptide (Aß). We have hypothesized that ABAD-Aß complex induces oxidant stress and mitochondrial dysfunction. An earlier study in double transgenic mice overexpressing mutant amyloid precursor protein (the latter generating an Aß-rich environment) and ABAD (Tg mAPP/ABAD) demonstrated enhanced generation of oxidants in the brain and accelerated impairment of spatial learning/memory. In this report we analyze cortical neurons from Tg mAPP/ABAD and assess mitochondrial function.
Our specific aims were to 1) analyze mitochondrial dysfunction in cultured cortical neurons and in the brains of Tg mAPP/ABAD mice; 2) assess whether such mitochondrial dysfunction triggers programmed cell death in neurons from Tg mAPP/ABAD mice; and 3) analyze electrophysiologic properties of hippocampal slices to determine whether mitochondrial dysfunction can be correlated with impaired synaptic function.
PRINCIPAL FINDINGS
1. Cortical neurons cultured from Tg mAPP/ABAD mice displayed spontaneous release of hydrogen peroxide and superoxide detectable at the first time point studied (2–3 days in culture) compared with neurons from Tg mAPP, Tg ABAD, and nonTg littermates
The source of these reactive oxygen species (ROS) appeared to be mitochondria based on inhibition by the uncoupling agent FCCP. Although inhibitors of mitochondrial respiratory complexes I and II were without effect on generation of ROS, myxothiazol, an inhibitor of complex III, blocked elaboration of free radicals. Together with the observation that KCN, an inhibitor of complex IV, enhanced generation of ROS, we hypothesize that Tg mAPP/ABAD neurons display leakage of radicals at the level of complex III.
2. Consistent with evidence of mitochondrial dysfunction, Tg mAPP/ABAD neurons displayed decreased inner mitochondrial membrane potential, ATP levels, and activity of respiratory chain complex IV (cytochrome c oxidase or COX) by day 4 in culture compared with neurons from Tg mAPP, Tg ABAD, and nonTg littermates
In contrast, activity of complexes I, II, and III was comparable in neurons from Tg mAPP/ABAD mice and the other genotypes.
3. By day 5–6 in culture, Tg mAPP/ABAD neurons first demonstrated increased caspase-3-like activity
This was not observed in neurons from Tg mAPP, Tg ABAD, or nonTg littermates. From day 6 in culture onward, Tg mAPP/ABAD neurons displayed DNA fragmentation and release of LDH into culture supernatants consistent with cell death. Studies with a range of inhibitors indicated that the pathway leading to cell death in Tg mAPP/ABAD neurons involved ROS (based on inhibition in the presence of vitamin E or N-acetylcysteine), the mitochondrial permeability transition pore (based on inhibition by cyclosporine A or bongkrekate/aristolochic acid), and activated caspase-3 (based on inhibition with DMQD-CHO). In contrast, KCN enhanced caspase-3 activation, DNA fragmentation, and LDH release in Tg mAPP/ABAD neurons.
4. Consistent with these in vitro data, abnormalities of mitochondrial function were observed in Tg mAPP/ABAD mice
At 4 months of age there was a selective decrease in complex IV activity in mitochondria from the cerebral cortex of Tg mAPP/ABAD mice compared with the other genotypes (activity of complexes I, II, and III was comparable among the different groups). At 9 months of age, ATP levels were prominently reduced in brains of Tg mAPP/ABAD mice compared with other groups. Metabolic studies showed diminished utilization of 13C-labeled glucose by brains of Tg mAPP/ABAD mice.
5. In the setting of such abnormalities of mitochondrial function, analysis of hippocampal slices from Tg mAPP/ABAD mice displayed diminished long-term potentiation (LTP) compared with other genotypes
CONCLUSIONS AND SIGNIFICANCE
Our results provide a link between ABAD and mitochondrial dysfunction in an Aß-rich environment. Mitochondrial dysfunction in Tg mAPP/ABAD mice is associated with impaired activity of respiratory chain complex IV, potentially promoting leakage of ROS at the level of complex III, as well as decreased inner membrane potential and ATP levels. Generation of ROS and potential opening of the membrane permeability transition pore trigger an apoptotic pathway in neurons cultured from Tg mAPP/ABAD mice. This pathway involves activation of caspase-3-like activity, DNA fragmentation, and ultimately loss of cell viability. At the level of global neuronal dysfunction, abnormalities in behavioral and electrophysiologic properties are exaggerated in Tg mAPP/ABAD mice.
We previously showed that ABAD and Aß form a complex in the mitochondrial matrix. The latter observation suggests the possibility that this complex may acquire pathogenic properties ("gain of function") actively perturbs mitochondrial properties (see Fig. 1
). However, it is certainly possible that Aß at the level of the cytosol/endoplasmic reticulum, or even at the cell membrane, affects mitochondrial properties in a manner exaggerating negative effects of ABAD. Nonetheless, our results indicate that ABAD can serve as an important cofactor for mitochondrial dysfunction in an Aß-rich environment.
|
These results suggest a means to link the long-known association of Alzheimer’s disease with mitochondrial dysfunction according to a specific molecular pathway—interaction of ABAD with Aß within mitochondria. Interception of ABAD interaction with Aß may be a potential therapeutic pathway for Alzheimer disease.
FOOTNOTES
1 These authors contributed equally to this work. 
To read the full text of this article, go to http://www.fasebj.org/cgi/doi/10.1096/fj.04-2582fje; doi: 10.1096/fj.04-2582fje
This article has been cited by other articles:
|
|
 |
|
  Y. He, K. W. Leung, Y.-H. Zhang, S. Duan, X.-F. Zhong, R.-Z. Jiang, Z. Peng, J. Tombran-Tink, and J. Ge Mitochondrial Complex I Defect Induces ROS Release and Degeneration in Trabecular Meshwork Cells of POAG Patients: Protection by Antioxidants Invest. Ophthalmol. Vis. Sci., April 1, 2008; 49(4): 1447 - 1458. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Origlia, M. Righi, S. Capsoni, A. Cattaneo, F. Fang, D. M. Stern, J. X. Chen, A. M. Schmidt, O. Arancio, S. D. Yan, et al. Receptor for Advanced Glycation End Product-Dependent Activation of p38 Mitogen-Activated Protein Kinase Contributes to Amyloid-{beta}-Mediated Cortical Synaptic Dysfunction J. Neurosci., March 26, 2008; 28(13): 3521 - 3530. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Ren, H. W. Xu, F. Davey, M. Taylor, J. Aiton, P. Coote, F. Fang, J. Yao, D. Chen, J. X. Chen, et al. Endophilin I Expression Is Increased in the Brains of Alzheimer Disease Patients J. Biol. Chem., February 29, 2008; 283(9): 5685 - 5691. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Kroemer, L. Galluzzi, and C. Brenner Mitochondrial Membrane Permeabilization in Cell Death Physiol Rev, January 1, 2007; 87(1): 99 - 163. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Zhu, Y. Lai, P. B. Shelat, C. Hu, G. Y. Sun, and J. C-M. Lee Phospholipases A2 Mediate Amyloid-beta Peptide-Induced Mitochondrial Dysfunction J. Neurosci., October 25, 2006; 26(43): 11111 - 11119. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Prabhakaran, L. Li, E. M. Mills, J. L. Borowitz, and G. E. Isom Up-Regulation of Uncoupling Protein 2 by Cyanide Is Linked with Cytotoxicity in Mesencephalic Cells J. Pharmacol. Exp. Ther., September 1, 2005; 314(3): 1338 - 1345. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
m, inner mitochondrial membrane potential; ROS, reactive oxygen species.