WWW.JNEUROSCI.ORG
-
The Journal of Neuroscience
QUICK SEARCH:   [advanced]


     
-


HOME  |   SEARCH  |   ARCHIVE  |   SUBSCRIBE  |   CONTACT  |   HELP
The Journal of Neuroscience, February 7, 2007, 27(6):1247-1254; doi:10.1523/JNEUROSCI.5320-06.2007

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Submit an eLetter
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Related articles in J. Neurosci.
Right arrow Similar articles in this journal
Right arrow Similar articles in Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Web of Science (16)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Xie, Z.
Right arrow Articles by Tanzi, R. E.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Xie, Z.
Right arrow Articles by Tanzi, R. E.
Right arrowPubmed/NCBI databases
*Compound via MeSH
*Substance via MeSH
Hazardous Substances DB
*CLIOQUINOL
*COPPER, ELEMENTAL
*ZINC COMPOUNDS
*ZINC, ELEMENTAL

 Previous Article  |  Next Article 

Neurobiology of Disease
The Inhalation Anesthetic Isoflurane Induces a Vicious Cycle of Apoptosis and Amyloid ß-Protein Accumulation

Zhongcong Xie,1,2 Yuanlin Dong,1,2 Uta Maeda,1,2 Robert D. Moir,1 Weiming Xia,3 Deborah J. Culley,4 Gregory Crosby,4 and Rudolph E. Tanzi1

1Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, and Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129-2060, 2Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, and 3Center for Neurologic Diseases and 4Department of Anesthesia, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
The anesthetic isoflurane has been reported to induce apoptosis and increase Aß generation and aggregation. However, the molecular mechanism underlying these effects remains unknown. We therefore set out to assess whether the effects of isoflurane on apoptosis are linked to amyloid ß-protein (Aß) generation and aggregation. For this purpose, we assessed the effects of isoflurane on ß-site amyloid ß precursor protein (APP)-cleaving enzyme (BACE) and {gamma}-secretase, the proteases responsible for Aß generation. We also tested the effects of inhibitors of Aß aggregation (iAß5, a ß-sheet breaker peptide; clioquinol, a copper–zinc chelator) on the ability of isoflurane to induce apoptosis. All of these studies were performed on naive human H4 neuroglioma cells as well as those overexpressing APP (H4-APP cells). Isoflurane increased the levels of BACE and {gamma}-secretase and secreted Aß in the H4-APP cells. Isoflurane-induced Aß generation could be blocked by the broad-based caspase inhibitor Z-VAD. The Aß aggregation inhibitors, iAß5 and clioquinol, selectively attenuated caspase-3 activation induced by isoflurane. However, isoflurane was able to induce caspase-3 activation in the absence of any detectable alterations of Aß generation in naive H4 cells. Finally, Aß potentiated the isoflurane-induced caspase-3 activation in naive H4 cells. Collectively, these findings suggest that isoflurane can induce apoptosis, which, in turn, increases BACE and {gamma}-secretase levels and Aß secretion. Isoflurane also promotes Aß aggregation. Accumulation of aggregated Aß in the media can then promote apoptosis. The result is a vicious cycle of isoflurane-induced apoptosis, Aß generation and aggregation, and additional rounds of apoptosis, leading to cell death.

Key words: Alzheimer's disease; APP; Aß; apoptosis; anesthesia; isoflurane


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Alzheimer's disease (AD), the most common form of age-related dementia, is a rapidly growing health problem. Amyloid ß-protein (Aß) production and/or accumulation are major pathological hallmarks of AD (Glenner and Wong, 1984Go) (for review, see Tanzi and Bertram, 2005Go). Aß is produced via serial proteolysis of the amyloid ß precursor protein (APP) by aspartyl protease ß-site APP-cleaving enzyme (BACE) or ß-secretase and {gamma}-secretase. BACE cleaves APP to generate a 99-residue membrane-associated C-terminal fragment (CTF) (APP-C99). APP-C99 is further cleaved by {gamma}-secretase to release 4 kDa Aß and AICD (ß-amyloid precursor protein intracellular domain) (Gu et al., 2001Go; Sastre et al., 2001Go; Yu et al., 2001Go). Presenilin (PS) and {gamma}-secretase cofractionate as a detergent-sensitive, high-molecular-weight complex (Li et al., 2000Go) that includes at least three other proteins, nicastrin/anterior pharynx defective protein 2 (APH-2), APH-1, and presenilin enhancer protein 2 (PEN-2), all of which are necessary and sufficient for {gamma}-secretase activity (Yu et al., 2000Go; Francis et al., 2002Go; Steiner et al., 2002Go). Increasing evidence suggests a role for caspase activation and apoptotic cell death in AD, as well as in a large number of other neurodegenerative disorders, such as Huntington's disease, amyotrophic lateral sclerosis, and spinocerebellar ataxia (Holtzman and Deshmukh, 1997Go; Lunkes et al., 1998Go; Namura et al., 1998Go). Aß has been shown to cause caspase activation and apoptosis, which can in turn potentiate Aß generation (LeBlanc, 1995Go; Guo et al., 1997Go; Galli et al., 1998Go; Gervais et al., 1999Go; LeBlanc et al., 1999Go; Pillot et al., 1999Go; Sponne et al., 2003Go; Tesco et al., 2003Go; Sodhi et al., 2004Go; Kriem et al., 2005Go; Florent et al., 2006Go). Finally, fibrillar aggregates of Aß and oligomeric species of Aß are more neurotoxic (Pike et al., 1993Go; Lorenzo and Yankner, 1994Go; Lambert et al., 1998Go; Grace et al., 2002Go; Walsh et al., 2002Go; Wang et al., 2002Go; Kayed et al., 2003Go; Kim et al., 2003Go; De Felice et al., 2004Go).

Perioperative factors, including hypoxia (Kokmen et al., 1996Go; Jendroska et al., 1997Go; Nagy et al., 1997Go; Snowdon et al., 1997Go; Kalaria, 2000Go), hypocapnia (Xie et al., 2004Go), and anesthetics (Eckenhoff et al., 2004Go; Xie et al., 2006aGo), have been reported to potentially contribute to AD neuropathogenesis. These perioperative factors may also cause postoperative cognitive dysfunction, a dementia associated with surgery and anesthesia, by trigging AD neuropathogenesis. Treatment with a commonly used inhalation anesthetic isoflurane (1.2–2.5% for 6 h) has been shown to enhance Aß aggregation and cytotoxicity in pheochromocytoma cells (Eckenhoff et al., 2004Go). We recently showed that a clinically relevant concentration (2%) of isoflurane can induce apoptosis, alter APP processing, and increase production of Aß in H4 human neuroglioma cells (Xie et al., 2006aGo).

Given these observations, we set out to determine the relationship between isoflurane-induced apoptosis and Aß generation/aggregation. More specifically, we addressed the hypothesis that isoflurane induces a vicious cycle of apoptosis, Aß generation, Aß aggregation, and additional rounds of apoptosis and Aß production.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Cell lines. We used H4 human neuroglioma cells (naive H4 cells) and H4 human neuroglioma cells stably transfected to express full-length (FL) APP (H4-APP cells) in the experiments. All cell lines were cultured in DMEM (high glucose) containing 9% heat-inactivated fetal calf serum, 100 U/ml penicillin, 100 µg/ml streptomycin, and 2 mM L-glutamine. Stably transfected H4 cells were additionally supplemented with 200 µg/ml G418.

Cell treatment. The cells were treated with 21% O2, 5% CO2, and 2% isoflurane as described by Xie et al. (2006a)Go. In the interaction studies, the cells were treated with Z-VAD (100 µM), Aß (2.5, 5, and 7.5 µM), iAß5 (1.5 µg/µl), and clioquinol (1 µM) 1 h before the treatment with 2% isoflurane or 100 nM staurosporine (STS). Control conditions included 5% CO2 plus 21% O2, which did not affect caspase-3 activation, cell viability, APP processing, and Aß generation (data not shown).

Cell lysis and protein amount quantification. Cell pellets were detergent extracted on ice using immunoprecipitation buffer (10 mM Tris-HCl, pH 7.4, 150 mM NaCl, 2 mM EDTA, and 0.5% Nonidet P-40) plus protease inhibitors (1 µg/ml aprotinin, 1 µg/ml leupeptin, and 1 µg/ml pepstatin A). The lysates were collected, centrifuged at 12,000 rpm for 10 min, and quantified for total proteins by the BCA protein assay kit (Pierce, Iselin, NJ).

Western blot analysis. The cells were harvested at the end of the experiments and were subjected to Western blot analyses as described by Xie et al. (2005a)Go. Antibodies A8717 (1:2000; Sigma, St. Louis, MO) and anti-ß-actin (1:5000; Sigma) were used to visualize APP-FL (110 kDa), APP-CTFs (10–12 kDa), and ß-actin (42 kDa), respectively. A caspase-3 antibody (1:1000 dilution; Cell Signaling Technology, Beverly, MA) was used to recognize the caspase-3 fragment (17–20 kDa) resulting from cleavage at aspartate position 175 and caspase-3 FL (35–40 kDa). Rabbit polyclonal anti-BACE-1 antibody ab2077 (1:1000; Abcam, Cambridge, MA) was used to detect the protein levels of BACE (65 kDa). Antibody anti-nicastrin (1:1000; Calbiochem, La Jolla, CA) was used to detect nicastrin levels. The quantitation of Western blots was performed as described by Xie et al. (2005a)Go. Briefly, the intensity of signals was analyzed by using an NIH Image program (NIH Image 1.62). We quantified the Western blots using two steps. First, we used the levels of ß-actin to normalize (e.g., determining the ratio of APP-FL amount to ß-actin amount) the levels of APP-FL, APP-CTFs, FL-caspase-3, caspase-3 fragment, BACE, and nicastrin to control for the loading differences in total protein amounts. Second, we presented the changes in the levels of APP-FL, APP-CTFs, FL-caspase-3, caspase-3 fragment, and nicastrin in the cells treated with isoflurane, Z-VAD, iAß5, clioquinol, and Aß as the percentage of those in the cells treated with controls. In this study, 100% caspase-3 activation, APP-FL, APP-CTFs, BACE, and nicastrin refer to control levels for the purpose of comparison with experimental conditions.

Quantitation of Aß using sandwich ELISA assay. Secreted Aß was measured with a sandwich ELISA assay by using an Aß measurement kit (Invitrogen, Carlsbad, CA) and by the Aß ELISA Core Facility at the Center for Neurological Diseases, Brigham and Women's Hospital, Harvard Medical School (Boston, MA), as described by Xie et al. (2005b)Go. Specifically, 96-well plates were coated with mouse monoclonal antibodies specific to Aß40 (ß-amyloid [1-40] cleavage site-specific antibody) or Aß42 (ß-amyloid [1-42] cleavage site-specific antibody). After blocking with Block Ace, wells were incubated overnight at 4°C with test samples of conditioned cell culture media, and then an anti-Aß ({alpha}-Aß-HR1) conjugated to horseradish peroxidase was added. Plates were then developed with tetramethylbenzidine reagent, and well absorbance was measured at 450 nm. Aß levels in test samples were determined by comparison with the signal from unconditioned media spiked with known quantities of Aß40 and Aß42.

Cell viability study. The cell viability was determined by using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT; Sigma). The experiments were performed according to the manufacturer's protocol. Briefly, we added 150 µl of MTT solution to each well, containing 1.5 ml of cell culture media, of a six-well plate. We then returned the cell culture to the incubator for 2 h. Finally, we removed the cell culture fluid and added 1.5 ml of isopropanol into the wells. We spectrophotometrically measured the absorbance at a wavelength of 570 nm. We present the changes in the absorbance, as a measure of cell viability, in the cells treated with isoflurane as the percentage of those in the cells treated with control conditions.

Statistics. Given the presence of background caspase-3 activation and cell death in cells cultured in serum-free media, we did not use absolute values to describe changes in caspase-3 activation and cell viability. Instead, changes in caspase-3 activation and cell viability were presented as a percentage of those of the control group. One-hundred percent caspase-3 activation or cell viability refers to control levels for purposes of comparison with experimental conditions. Data were expressed as mean ± SD. The number of samples varied from three to 10, and the samples were normally distributed. We used a two-tailed t test to compare the difference between the experimental groups. p values <0.05 and 0.01 were considered statistically significant.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Isoflurane can induce caspase-3 activation in naive H4 cells
We previously reported that isoflurane can induce apoptosis and potentiate Aß levels in the conditioned media of H4-APP cells (Xie et al., 2006aGo). To test whether isoflurane can induce apoptosis in cells with low (barely detectable) basal levels of secreted Aß, naive H4 human neuroglioma cells were treated with 2% isoflurane for 6 h. Because caspase-3 activation is one of the final steps of cellular apoptosis (Thornberry, 1998Go), we assessed the effects of isoflurane on caspase-3 activation by quantitative Western blot analyses. Isoflurane treatment led to caspase-3 activation (Fig. 1A,B), as evidenced by increased ratios of cleaved (activated) caspase-3 fragment (17–19 kDa) to FL caspase-3 (35–40 kDa). Quantitation of the Western blots, based on the ratio of caspase-3 fragment to FL caspase-3, revealed that the 2% isoflurane treatment (Fig. 1B, black bar) led to a 240% increase in caspase-3 activation compared with control cells (Fig. 1B, white bar, **p < 0.01). Treatment with 2% isoflurane (Fig. 1C, black bar) also decreased cell viability by 17% compared with the control cells (Fig. 1C, white bar, *p < 0.05). APP immunoblotting revealed no significant differences in the levels of APP-CTFs and APP-FL between 2% isoflurane-treated (Fig. 1D, lanes 3, 4; E,F, black bar) and control (Fig. 1D, lanes 1, 2; E,F, white bar) naive H4 cells. Treatment with 2% isoflurane (black bar) did not increase levels of Aß40 (27 vs 30 pg/ml) or Aß42 (7 vs 9 pg/ml) compared with the control cells (white bar) (Fig. 1G). These results suggest that the isoflurane can induce apoptosis independently of changes in APP processing and Aß generation in naive H4 cells. Collectively, these findings suggest that isoflurane can induce apoptosis/caspase activation in the absence of any significant alterations in APP processing and Aß generation.


Figure 1
View larger version (15K):
[in this window]
[in a new window]

  		Figure 1. Treatment with 2% isoflurane induces caspase-3 activation and decreases cell viability without detectable changes in APP processing and Aß generation in naive H4 cells. A, The 2% isoflurane treatment (lanes 1–3) induces caspase-3 cleavage (activation) compared with control conditions (lanes 4–6) in naive H4 cells. There is no significant difference in the amounts of ß-actin between the control- or 2% isoflurane-treated naive H4 cells. B, Caspase-3 activation assessed by quantifying the ratio of caspase-3 fragment to caspase-3-FL in the Western blots. Quantification of the Western blot shows that the 2% isoflurane treatment (black bar) increases caspase-3 activation compared with control conditions (white bar), normalized to ß-actin levels. C, Treatment with 2% isoflurane (black bar) decreases cell viability compared with control conditions (white bar) in naive H4 cells. D, Treatment with 2% isoflurane (lanes 3, 4) does not alter the levels of APP-FL and APP-CTFs compared with control conditions (lanes 1, 2). There is no significant difference in the amounts of ß-actin in the control- or 2% isoflurane-treated naive H4 cells. E, Quantification of the Western blot shows that the 2% isoflurane treatment (black bar) does not alter the protein levels of APP-FL compared with control conditions (white bar) in H4 naive cells, normalized to ß-actin levels. F, Quantification of the Western blot shows that the 2% isoflurane treatment (black bar) does not alter the protein levels of APP-CTFs compared with control conditions (white bar) in H4 naive cells, normalized to ß-actin levels. G, Treatment with 2% isoflurane (black bar) does not increase the generation of Aß40 and Aß42 compared with control conditions (white bar). Data are means ± SD; n = 9–10 for each experimental group. t test was used to compare the difference between control condition and the 2% isoflurane treatment condition (*p < 0.05; **p < 0.01).

 
Isoflurane-induced alterations in APP processing and Aß generation can be attenuated by the caspase inhibitor Z-VAD in H4-APP cells
We reported previously that isoflurane can alter APP processing and increase Aß generation in H4-APP cells (Xie et al., 2006aGo). We next asked whether these effects are dependent on caspase activation. For this purpose, we incubated H4-APP cells with Z-VAD (100 µM), a caspase inhibitor, for 1 h, followed by treatment with 2% isoflurane for 6 h. Isoflurane induced caspase-3 activation, which was blocked by treatment with Z-VAD (Fig. 2A). Quantification of the Western blots, based on the ratio of caspase-3 fragment to FL caspase-3, revealed that treatment with 2% isoflurane induced caspase-3 activation by 350% over that of control cells (Fig. 2B, **p < 0.01). Treatment with isoflurane and Z-VAD reduced caspase-3 activation from 350 to 151% (Fig. 2B, ##p < 0.01). Treatment with Z-VAD also attenuated isoflurane-induced alterations in APP processing and Aß generation. As can be seen in Figure 2C, APP immunoblotting revealed that isoflurane treatment (lanes 5, 6) decreased protein levels of APP-FL and APP-CTFs, compared with the control cells (lanes 1, 2). Z-VAD (lanes 7, 8) suppressed these decreases in levels of APP-FL and APP-CTFs induced by isoflurane, whereas Z-VAD treatment alone (lanes 3, 4) did not alter APP-FL and APP-CTF protein levels (Fig. 2C). Quantification of the Western blots showed that treatment with isoflurane (black bar) led to a 35% reduction in levels of APP-FL (Fig. 2D) and 51% reduction in levels of APP-CTFs (Fig. 2E). Treatment with isoflurane plus Z-VAD (striped bar) resulted in only a 10% decrease in protein levels of APP-FL (Fig. 2D) and a 12% decrease in protein levels of APP-CTFs (Fig. 2E). Isoflurane treatments, but not Z-VAD treatment, significantly increased Aß levels in the conditioned media, whereas treatment with isoflurane plus Z-VAD (striped bar) led to smaller increases in Aß levels (157%) versus treatment with isoflurane alone (black bar; 204%) (Fig. 2F) compared with control conditions (white bar). These results indicate that isoflurane-induced alterations in APP processing and Aß generation are dependent on the ability of isoflurane to induce caspase-3 activation and apoptosis.


Figure 2
View larger version (46K):
[in this window]
[in a new window]

  		Figure 2. The caspase inhibitor Z-VAD inhibits the caspase-3 activation and the increases in Aß generation induced by 2% isoflurane in H4-APP cells. A, Treatment with 2% isoflurane (lanes 5, 6) induces caspase-3 cleavage (activation) compared with control conditions (lanes 1, 2) or Z-VAD (100 µM) treatment (lanes 3, 4). The Z-VAD treatment inhibits the caspase-3 cleavage induced by 2% isoflurane (lane 7, 8). There is no significant difference in the amounts of ß-actin in the H4-APP cells with the above treatments. B, Quantitation of the Western blot shows that the 2% isoflurane treatment (black bar) increases caspase-3 activation compared with control conditions (white bar) or the Z-VAD (100 µM) treatment (gray bar), normalized to ß-actin levels. The isoflurane-induced caspase-3 activation is inhibited by the Z-VAD treatment (striped bar). C, Z-VAD inhibits the isoflurane-induced changes in APP processing in H4-APP cells. Treatment with 2% isoflurane (lanes 5, 6) decreases the protein levels of APP-FL and APP-CTFs compared with control conditions (lanes 1, 2) or Z-VAD (100 µM) treatment (lanes 3, 4). The Z-VAD treatment (lanes 7, 8) inhibits the isoflurane-induced decreases in the protein levels of APP-FL and APP-CTFs. There is no significant difference in the amounts of ß-actin in the H4-APP cells with all of the above treatments. D, Quantification of the Western blot shows that 2% isoflurane treatment (black bar) decreases the protein levels of APP-FL compared with the control condition (white bar) or Z-VAD treatment (gray bar), normalized to ß-actin levels. The isoflurane-induced decrease in the protein levels of APP-FL is inhibited by the Z-VAD treatment (striped bar). E, Quantification of the Western blot also shows that 2% isoflurane treatment (black bar) decreases the protein levels of APP-CTFs compared with the control condition (white bar) or Z-VAD treatment (gray bar), normalized to ß-actin levels. The isoflurane-induced decrease in the protein levels of APP-CTFs is also inhibited by the Z-VAD treatment (striped bar). F, Z-VAD inhibits the isoflurane-induced increases in Aß generation. Treatment with 2% isoflurane (black bar) increases the levels of Aß40 compared with the control condition (white bar). Z-VAD treatment alone (gray bar) does not change the levels of Aß40; however, Z-VAD treatment inhibits the isoflurane-induced increases in the levels of Aß40. Data are means ± SD; n = 6 for each experimental group. t test is used to compare the difference between control conditions and 2% isoflurane treatment (*p < 0.05; **p < 0.01) and the difference between 2% isoflurane plus DMSO treatment and 2% isoflurane plus Z-VAD treatment (#p < 0.05; ##p < 0.01).

 
Isoflurane enhances levels of BACE and {gamma}-secretase in H4-APP cells
Given that 2% isoflurane can induce apoptosis and increase Aß generation, we next asked whether isoflurane can increase the levels of the amyloidogenic secretases, BACE and {gamma}-secretase, in H4-APP cells. Treatment with 2% isoflurane for 6 h increased caspase-3 activation and simultaneously increased the levels of BACE. The level of APP-FL was also decreased by isoflurane-induced caspase activation (Fig. 3A,B). Next, we assessed the effects of isoflurane on the levels of nicastrin, a {gamma}-secretase complex component, in H4-APP cells. Treatment with 2% isoflurane increased protein levels of mature (121%) and immature (156%) nicastrin compared with the control cells (Fig. 3C,D).


Figure 3
View larger version (25K):
[in this window]
[in a new window]

  		Figure 3. Isoflurane increases levels of BACE and nicastrin in H4-APP cells. A, Treatment with 2% isoflurane (lane 1) induces caspase-3 cleavage (17 kDa; activation), increases the level of BACE (65 kDa), and decreases the APP-FL level (110 kDa) compared with the control condition (lane 2). There is no significant difference in the amounts of ß-actin between the control condition- or 2% isoflurane-treated H4-APP cells. B, Quantification of the Western blot shows that 2% isoflurane treatment (black bar) induces caspase-3 activation, increases BACE levels, and decreases APP-FL levels, normalized to ß-actin levels. C, Treatment with 2% isoflurane (lanes 4–6) increases the levels of immature and mature nicastrin compared with the control condition (lanes 1–3). There is no significant difference in the amounts of ß-actin between the control- or 2% isoflurane-treated H4-APP cells. D, Quantification of the Western blot shows that 2% isoflurane treatment (black bar) increases the levels of both immature and mature nicastrin, normalized to ß-actin levels. Data are means ± SD; n = 3 for each experimental group. t test was used to compare the difference between control condition and 2% isoflurane treatment (*p < 0.05; **p < 0.01).

 
Aß aggregation inhibitors, iAß5 and clioquinol, attenuate isoflurane-induced caspase-3 activation
Isoflurane has previously been shown to enhance Aß aggregation (Eckenhoff et al., 2004Go). Thus, we next tested whether Aß aggregation can potentiate the effects of isoflurane on caspase-3 activation and apoptosis. For this purpose, we set out to assess the effects of two known Aß aggregation inhibitors, the ß-sheet breaker peptide iAß5 (Soto et al., 1998Go) and the metal protein attenuation compound (MPAC), clioquinol (Cherny et al., 2001Go), on isoflurane-induced caspase-3 activation. H4-APP cells were incubated with iAß5 (1.5 µg/µl) or clioquinol (1 µM) for 1 h, followed by treatment with 2% isoflurane or 100 nM STS for 6 h. Treatment with 2% isoflurane alone induced caspase-3 activation in H4-APP cells (Fig. 4A,B). iAß5 plus 2% isoflurane treatment reduced caspase-3 activation relative to the treatment with isoflurane alone (170 vs 247%) (Fig. 4A,B). In contrast, iAß5 treatment did not attenuate STS-induced caspase-3 activation in H4-APP cells. iAß5 alone did not induce caspase-3 activation; treatment with either STS or STS plus iAß5 led to similar increases in caspase-3 activation (1200 vs 1250%) (Fig. 4C,D). These results suggest that iAß5 selectively attenuates isoflurane-induced, but not STS-induced, caspase-3 activation.


Figure 4
View larger version (40K):
[in this window]
[in a new window]

  		Figure 4. iAß5 and clioquinol specifically attenuate isoflurane-induced caspase-3 activation in H4-APP cells. A, iAß5 plus 2% isoflurane treatment (lane 2) results in a lower degree of caspase-3 cleavage than 2% isoflurane treatment alone (lane 1). There is no significant difference in the amounts of ß-actin between the 2% isoflurane- and iAß5 plus 2% isoflurane-treated H4-APP cells. B, Quantification of the Western blot, based on the ratio of caspase-3 fragment to caspase-3 FL, shows that iAß5 treatment (black bar) reduces the isoflurane-induced caspase-3 activation (white bar), normalized to ß-actin levels. C, STS treatment (lane 3), but not iAß5 treatment (lane 2), causes caspase-3 activation compared with control condition (lane 1) in H4-APP cells. iAß5 plus STS treatment (lane 4) leads to a degree of caspase-3 activation similar to STS treatment alone (lane 3). There is no significant difference in the amounts of ß-actin in the control-, iAß5-, STS-, or iAß5 plus STS-treated H4-APP cells. D, Quantification of the Western blot shows that iAß5 (striped bar) does not reduce the STS-induced (black bar) caspase-3 activation, normalized to ß-actin levels. E, Two percent isoflurane (lane 3) or STS (lane 5) treatment causes caspase-3 activation compared with control condition (lane 1) or clioquinol treatment (lane 2) in H4-APP cells. Clioquinol plus 2% isoflurane treatment (lane 4) leads to a lower degree of caspase-3 activation than 2% isoflurane treatment alone (lane 3). Clioquinol plus STS treatment (lane 6) leads to a degree of caspase-3 activation similar to STS treatment alone (lane 5). There is no significant difference in the amounts of ß-actin in all of the above treatments in H4-APP cells. F, Quantification of the Western blot shows that clioquinol reduces the isoflurane-induced (gray bar vs black bar), but not STS-induced (dotted bar vs striped bar), caspase-3 activation, normalized to ß-actin levels. Data are means ± SD; n = 3 for each experimental group. t test was used to compare the difference of caspase-3 activation between control condition and STS or 2% isoflurane treatment (*p < 0.05; **p < 0.01) and between saline treatment and iAß5 or clioquinol treatment (#p < 0.05).

 
We next tested the ability of clioquinol to attenuate isoflurane-induced caspase activation in the H4-APP cells. Treatment with clioquinol alone did not increase caspase-3 cleavage (Fig. 4E,F). Both 2% isoflurane and STS induced caspase-3 activation. Treatment with 2% isoflurane plus clioquinol reduced caspase-3 activation relative to treatment with 2% isoflurane alone (174 vs 257%) (Fig. 4E,F). In contrast, treatment with STS alone or STS plus clioquinol led to similar increases in caspase-3 activation (487 vs 501%) (Fig. 4E,F). Thus, both Aß aggregation inhibitors, iAß5 and clioquinol, selectively attenuated isoflurane-induced, but not STS-induced, caspase-3 activation. These findings suggest that Aß aggregation can potentiate the ability of isoflurane to induce caspase-3 activation.

Exogenously added Aß can potentiate isoflurane-induced caspase-3 activation
Given that that Aß aggregation potentiates isoflurane-induced caspase-3 activation, we next asked whether exogenously added Aß can potentiate isoflurane-induced caspase activation. Naive H4 cells were incubated with Aß (2.5, 5, and 7.5 µM both Aß40 and Aß42) for 1 h, followed by treatment with 2% isoflurane for 6 h. Both 2% isoflurane and Aß alone induced caspase-3 activation in naive H4 cells (Fig. 5A,B). However, treatment with Aß plus 2% isoflurane resulted in a greater degree of caspase-3 cleavage than either treatment alone, in a dose-dependent manner (469, 403, 612, and 1223%) (Fig. 5A,B). These results suggest that exogenously added Aß can potentiate the isoflurane-induced caspase-3 activation in naive H4 cells.


Figure 5
View larger version (37K):
[in this window]
[in a new window]

  		Figure 5. Aß potentiates the isoflurane-induced caspase-3 activation in H4 naive cells. A, Treatments with 2% isoflurane (lanes 3, 7, 11) cause caspase-3 cleavage (activation) compared with control conditions (lanes 1, 5, 9) in H4 naive cells. Aß plus 2% isoflurane treatment (lanes 4, 8, 12) leads to a greater degree of caspase-3 cleavage than 2% isoflurane treatment alone (lanes 3, 7, 11) in a dose-dependent manner. Aß treatments alone (lanes 2, 6, 10) also cause caspase-3 activation compared with saline treatments (lanes 1, 5, 9) in a dose-dependent manner. There is no significant difference in the amounts of ß-actin between the control- or 2% isoflurane-treated H4-APP cells. B, Quantification of the Western blot shows that Aß [0 (white bar), 2.5 (gray bar), 5 (black bar), and 7.5 µM (striped bar)] induces caspase-3 activation and potentiates the isoflurane-induced caspase-3 activation in a dose-dependent manner, normalized to ß-actin levels. Data are means ± SD; n = 3 for each experimental group. t test was used to compare the difference of caspase-3 activation between saline and Aß treatment in 2% isoflurane-treated cells (*p < 0.05; **p < 0.01) and in cells with the control condition (#p < 0.05; ##p < 0.01).

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
We have shown previously that the commonly used inhalation anesthetic isoflurane can induce cellular apoptosis and increase Aß generation in H4-APP cells (Xie et al., 2006aGo). Here, we set out to assess whether the effects of isoflurane on apoptosis are linked to Aß generation and aggregation. First, we found that isoflurane can induce caspase-3 activation in naive H4 cells without significantly affecting APP processing and Aß generation (Fig. 1). This indicates that isoflurane-induced apoptosis can occur independently of alterations in APP processing and Aß generation. However, it is still possible that isoflurane may lead to undetectable changes in APP processing and Aß generation in naive H4 cells.

Next, we examined whether isoflurane-induced alterations in APP processing and Aß generation are dependent on isoflurane-induced apoptosis. Using the broad caspase activation inhibitor, Z-VAD, we were able to show that inhibition of isoflurane-induced caspase-3 activation was coupled to inhibition of the effects of isoflurane on APP processing and Aß generation (Fig. 2). These findings revealed that the isoflurane-induced alterations in APP processing and Aß generation are largely dependent on the ability of isoflurane to induce apoptosis. Collectively, these findings suggest that isoflurane can induce caspase-3 activation and apoptosis, which, in turn, alter APP processing and increase Aß generation. In contrast, isoflurane was able to induce apoptosis in the absence of any detectable effects on APP processing and Aß generation.

In exploring the mechanism by which isoflurane increases Aß generation, we tested the effects of isoflurane on the amyloidogenic secretases, BACE and {gamma}-secretase. We showed that treatment of H4-APP cells with 2% isoflurane for 6 h was able to enhance protein levels of the BACE and {gamma}-secretase complex component nicastrin (Fig. 3). These findings suggest that isoflurane-induced apoptosis is linked to increases in the levels of BACE and nicastrin, leading to elevated BACE and {gamma}-secretase activity, as evidenced by enhanced levels of Aß. In contrast, treatment with 2% isoflurane for 6 h did not alter the protein levels of the three other components of {gamma}-secretase, PS-1, PEN-2, and APH-1 (data not shown). It is possible that longer treatment time may be required to affect the levels of the other components of the {gamma}-secretase complex.

Isoflurane has previously been shown to enhance Aß aggregation and potentiate the cytotoxicity of Aß (Eckenhoff et al., 2004Go). It has been reported that oligomeric and fibrillar species of Aß are more neurotoxic (Pike et al., 1993Go; Lorenzo and Yankner, 1994Go; Lambert et al., 1998Go; Grace et al., 2002Go; Walsh et al., 2002Go; Wang et al., 2002Go; Kayed et al., 2003Go; Kim et al., 2003Go; De Felice et al., 2004Go). We have shown previously that an amyloid fibril-binding dye, Congo red, which has been reported to inhibit Aß fibrillar aggregation and to prevent neurotoxicity (Lorenzo and Yankner, 1994Go), can attenuate 2% isoflurane-induced apoptosis. Thus, Aß aggregation induced by isoflurane may be able to further potentiate the proapoptotic effects of isoflurane (Xie et al., 2006bGo). To further explore this effect with more specific Aß aggregation inhibitors, we tested the ability of iAß5, a ß-sheet breaker peptide (Soto et al., 1998Go), and clioquinol, an MPAC (Cherny et al., 2001Go), to attenuate isoflurane-induced apoptosis. We found that both compounds were able to attenuate the 2% isoflurane-induced apoptosis. The effects were also specific for isoflurane, because neither compound attenuated STS-induced apoptosis. Given that both iAß5 and clioquinol have been reported to inhibit Aß aggregation (Soto et al., 1998Go; Cherny et al., 2001Go), these findings suggest that isoflurane-induced apoptosis can be potentiated by Aß aggregation. Finally, testing for the possibility of a vicious cycle of isoflurane-induced apoptosis and Aß accumulation, we found that exogenously added Aß potentiated isoflurane-induced caspase-3 activation in a dose-dependent manner in naive H4 cells. These findings suggest that the increased Aß generation induced by isoflurane can further potentiate the isoflurane-induced apoptosis, leading to a vicious cycle.

Collectively, our studies defined the molecular pathways by which isoflurane induces apoptosis, alters APP processing, increases Aß levels, and enhances Aß aggregation. As can be seen in Figure 6, our studies illustrate that isoflurane can induce caspase activation and apoptosis, which then increase the activities of BACE and {gamma}-secretase. The enhanced BACE and {gamma}-secretase will be able to facilitate the APP processing to increase Aß generation/accumulation. Finally, the increased Aß generation/accumulation will potentiate the isoflurane-induced caspase activation and apoptosis.


Figure 6
View larger version (14K):
[in this window]
[in a new window]

  		Figure 6. Hypothetical pathway by which isoflurane induces a vicious cycle of apoptosis and Aß generation and aggregation. Isoflurane induces caspase-3 activation/apoptosis. Caspase activation, in turn, increases the activities of both BACE and {gamma}-secretase, which serve to increase Aß generation/accumulation. Isoflurane also enhances Aß aggregation, which further induces caspase-3 activation and apoptosis. Elevated Aß generation/accumulation and Aß aggregation then further induce apoptosis, leading to a vicious cycle of isoflurane-induced apoptosis and Aß generation/accumulation and aggregation.

 
Alternatively, isoflurane may induce the cycle of apoptosis and Aß generation/accumulation by first promoting Aß aggregation, especially because isoflurane has previously been reported to induce Aß aggregation (Eckenhoff et al., 2004Go). Moreover, in the present study, we found that iAß5 and clioquinol, effective inhibitors of Aß aggregation, specifically attenuated isoflurane-induced apoptosis. Collectively, our studies have shown that isoflurane can induce a vicious cycle of apoptosis and Aß generation/accumulation and aggregation, followed by additional rounds of apoptosis, ultimately leading to cell death. These findings suggest that patients with elevated Aß levels could be more vulnerable to isoflurane-induced cytotoxicity.

It is possible that the elevated Aß levels are also associated with postoperative cognitive dysfunction, a subtle form of dementia after surgery and anesthesia (Xie and Tanzi, 2006Go). Additional investigation will be necessary to determine whether occurrences of postoperative cognitive dysfunction are linked to elevated Aß levels in the human brain, CSF, and plasma.

Isoflurane induces apoptosis, which, in turn, increases BACE levels in both naive H4 cells and H4-APP cells. However, the effects on APP processing and Aß generation are only detectable in H4-APP cells that contain sufficient levels of APP.

The molecular mechanism by which isoflurane induces apoptosis remains unclear and is an important topic for future studies. Previous studies have shown that isoflurane can induce calcium release from endoplasmic reticulum (ER) in cerebrocortical and hippocampal neurons (Kindler et al., 1999Go). Wei et al. (2005)Go reported that dantrolene, a selective ryanodine receptor antagonist that inhibits calcium release from ER, can suppress isoflurane-induced cytotoxicity. These findings suggest that isoflurane may induce cellular apoptosis by facilitating calcium release from ER. Aß has also been shown to elevate basal intracellular calcium levels and facilitate calcium overload after activation of glutamate receptors (Mattson et al., 1992Go; Mark et al., 1995Go) (for review, see Mattson and Chan, 2003Go). Furthermore, dantrolene has also been shown to inhibit Aß-induced cytotoxicity (Guo et al., 1997Go). Thus, these findings suggest that isoflurane can induce apoptosis by facilitating calcium release from ER to elevate intracellular calcium levels. Aggregated Aß may then potentiate isoflurane-induced apoptosis by further enhancing the intracellular calcium concentration. Future studies will be necessary to assess whether the effects of isoflurane and Aß on cell death are mediated by cellular calcium homeostasis (Yoo et al., 2000Go).

Although our findings and the results from other studies suggest that isoflurane may affect AD neuropathogenesis, these experiments were performed only in cultured cells. The determination of the in vivo relevance of isoflurane on AD neuropathogenesis will be necessary before we can conclude that the inhalation anesthetic isoflurane facilitates or exacerbates AD neuropathogenesis in humans.

In conclusion, we found that isoflurane can induce both apoptosis and changes in APP processing, leading to increased generation of Aß. Increased levels of Aß generation and subsequent aggregation induced by isoflurane can further potentiate isoflurane-induced apoptosis, forming a vicious cycle of apoptosis and Aß generation/accumulation and aggregation. These studies should facilitate future strategies for delivering safer anesthesia care to patients, especially senior patients, who are particularly susceptible to the incidence of postoperative cognitive dysfunction and risk for AD.


   Footnotes
 
Received Dec. 8, 2006; revised Dec. 27, 2006; accepted Dec. 30, 2006.

This work was supported by National Institutes of Health (NIH) Grants R01AG 014713 and R01MH 60009 (R.E.T.); NIH Grants K12AG 000294, K08 NS048140, and P60 AG008812 and the American Geriatrics Society Jahnigen Award (Z.X.); NIH Grant K08GM077057 (D.J.C.); and NIH Grant R01AG20253 (G.C.). The cost of anesthetic isoflurane and salary support of Yuanlin Dong and Uta Maeda were generously provided by the Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School (Boston, MA).

Correspondence should be addressed to Dr. Rudolph E. Tanzi, Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, and Department of Neurology, Massachusetts General Hospital and Harvard Medical School, 114 16th Street, C3009, Charlestown, MA 02129-4404. Email: tanzi{at}helix.mgh.harvard.edu

Copyright © 2007 Society for Neuroscience 0270-6474/07/271247-08$15.00/0


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

Cherny RA, Atwood CS, Xilinas ME, Gray DN, Jones WD, McLean CA, Barnham KJ, Volitakis I, Fraser FW, Kim Y, Huang X, Goldstein LE, Moir RD, Lim JT, Beyreuther K, Zheng H, Tanzi RE, Masters CL, Bush AI (2001) Treatment with a copper-zinc chelator markedly and rapidly inhibits beta-amyloid accumulation in Alzheimer's disease transgenic mice. Neuron 30:665–676.[CrossRef][Web of Science][Medline]

De Felice FG, Vieira MN, Saraiva LM, Figueroa-Villar JD, Garcia-Abreu J, Liu R, Chang L, Klein WL, Ferreira ST (2004) Targeting the neurotoxic species in Alzheimer's disease: inhibitors of Abeta oligomerization. FASEB J 18:1366–1372.[Abstract/Free Full Text]

Eckenhoff RG, Johansson JS, Wei H, Carnini A, Kang B, Wei W, Pidikiti R, Keller JM, Eckenhoff MF (2004) Inhaled anesthetic enhancement of amyloid-beta oligomerization and cytotoxicity. Anesthesiology 101:703–709.[CrossRef][Web of Science][Medline]

Florent S, Malaplate-Armand C, Youssef I, Kriem B, Koziel V, Escanye MC, Fifre A, Sponne I, Leininger-Muller B, Olivier JL, Pillot T, Oster T (2006) Docosahexaenoic acid prevents neuronal apoptosis induced by soluble amyloid-beta oligomers. J Neurochem 96:385–395.[CrossRef][Web of Science][Medline]

Francis R, McGrath G, Zhang J, Ruddy DA, Sym M, Apfeld J, Nicoll M, Maxwell M, Hai B, Ellis MC, Parks AL, Xu W, Li J, Gurney M, Myers RL, Himes CS, Hiebsch R, Ruble C, Nye JS, Curtis D (2002) aph-1 and pen-2 are required for Notch pathway signaling, gamma-secretase cleavage of betaAPP, and presenilin protein accumulation. Dev Cell 3:85–97.[CrossRef][Web of Science][Medline]

Galli C, Piccini A, Ciotti MT, Castellani L, Calissano P, Zaccheo D, Tabaton M (1998) Increased amyloidogenic secretion in cerebellar granule cells undergoing apoptosis. Proc Natl Acad Sci USA 95:1247–1252.[Abstract/Free Full Text]

Gervais FG, Xu D, Robertson GS, Vaillancourt JP, Zhu Y, Huang J, LeBlanc A, Smith D, Rigby M, Shearman MS, Clarke EE, Zheng H, Van Der Ploeg LH, Ruffolo SC, Thornberry NA, Xanthoudakis S, Zamboni RJ, Roy S, Nicholson DW (1999) Involvement of caspases in proteolytic cleavage of Alzheimer's amyloid-beta precursor protein and amyloidogenic A beta peptide formation. Cell 97:395–406.[CrossRef][Web of Science][Medline]

Glenner GG, Wong CW (1984) Alzheimer's disease and Down's syndrome: sharing of a unique cerebrovascular amyloid fibril protein. Biochem Biophys Res Commun 122:1131–1135.[CrossRef][Web of Science][Medline]

Grace EA, Rabiner CA, Busciglio J (2002) Characterization of neuronal dystrophy induced by fibrillar amyloid beta: implications for Alzheimer's disease. Neuroscience 114:265–273.[CrossRef][Web of Science][Medline]

Gu Y, Misonou H, Sato T, Dohmae N, Takio K, Ihara Y (2001) Distinct intramembrane cleavage of the beta-amyloid precursor protein family resembling gamma-secretase-like cleavage of Notch. J Biol Chem 276:35235–35238.[Abstract/Free Full Text]

Guo Q, Sopher BL, Furukawa K, Pham DG, Robinson N, Martin GM, Mattson MP (1997) Alzheimer's presenilin mutation sensitizes neural cells to apoptosis induced by trophic factor withdrawal and amyloid ß-peptide: involvement of calcium and oxyradicals. J Neurosci 17:4212–4222.[Abstract/Free Full Text]

Holtzman DM, Deshmukh M (1997) Caspases: a treatment target for neurodegenerative disease? Nat Med 3:954–955.[CrossRef][Web of Science][Medline]

Jendroska K, Hoffmann OM, Patt S (1997) Amyloid beta peptide and precursor protein (APP) in mild and severe brain ischemia. Ann NY Acad Sci 826:401–405.[Medline]

Kalaria RN (2000) The role of cerebral ischemia in Alzheimer's disease. Neurobiol Aging 21:321–330.[CrossRef][Web of Science][Medline]

Kayed R, Head E, Thompson JL, McIntire TM, Milton SC, Cotman CW, Glabe CG (2003) Common structure of soluble amyloid oligomers implies common mechanism of pathogenesis. Science 300:486–489.[Abstract/Free Full Text]

Kim HJ, Chae SC, Lee DK, Chromy B, Lee SC, Park YC, Klein WL, Krafft GA, Hong ST (2003) Selective neuronal degeneration induced by soluble oligomeric amyloid beta protein. FASEB J 17:118–120.[Abstract/Free Full Text]

Kindler CH, Eilers H, Donohoe P, Ozer S, Bickler PE (1999) Volatile anesthetics increase intracellular calcium in cerebrocortical and hippocampal neurons. Anesthesiology 90:1137–1145.[CrossRef][Web of Science][Medline]

Kokmen E, Whisnant JP, O'Fallon WM, Chu CP, Beard CM (1996) Dementia after ischemic stroke: a population-based study in Rochester, Minnesota (1960–1984). Neurology 46:154–159.[Abstract/Free Full Text]

Kriem B, Sponne I, Fifre A, Malaplate-Armand C, Lozac'h-Pillot K, Koziel V, Yen-Potin FT, Bihain B, Oster T, Olivier JL, Pillot T (2005) Cytosolic phospholipase A2 mediates neuronal apoptosis induced by soluble oligomers of the amyloid-beta peptide. FASEB J 19:85–87.[Abstract/Free Full Text]

Lambert MP, Barlow AK, Chromy BA, Edwards C, Freed R, Liosatos M, Morgan TE, Rozovsky I, Trommer B, Viola KL, Wals P, Zhang C, Finch CE, Krafft GA, Klein WL (1998) Diffusible, nonfibrillar ligands derived from Abeta1–42 are potent central nervous system neurotoxins. Proc Natl Acad Sci USA 95:6448–6453.[Abstract/Free Full Text]

LeBlanc A (1995) Increased production of 4 kDa amyloid ß peptide in serum deprived human primary neuron cultures: possible involvement of apoptosis. J Neurosci 15:7837–7846.[Abstract]

LeBlanc A, Liu H, Goodyer C, Bergeron C, Hammond J (1999) Caspase-6 role in apoptosis of human neurons, amyloidogenesis, and Alzheimer's disease. J Biol Chem 274:23426–23436.[Abstract/Free Full Text]

Li YM, Lai MT, Xu M, Huang Q, DiMuzio-Mower J, Sardana MK, Shi XP, Yin KC, Shafer JA, Gardell SJ (2000) Presenilin 1 is linked with gamma-secretase activity in the detergent solubilized state. Proc Natl Acad Sci USA 97:6138–6143.[Abstract/Free Full Text]

Lorenzo A, Yankner BA (1994) Beta-amyloid neurotoxicity requires fibril formation and is inhibited by Congo red. Proc Natl Acad Sci USA 91:12243–12247.[Abstract/Free Full Text]

Lunkes A, Trottier Y, Mandel JL (1998) Pathological mechanisms in Huntington's disease and other polyglutamine expansion diseases. Essays Biochem 33:149–163.[Web of Science][Medline]

Mark RJ, Hensley K, Butterfield DA, Mattson MP (1995) Amyloid ß-peptide impairs ion-motive ATPase activities: evidence for a role in loss of neuronal Ca2+ homeostasis and cell death. J Neurosci 15:6239–6249.[Abstract]

Mattson MP, Chan SL (2003) Neuronal and glial calcium signaling in Alzheimer's disease. Cell Calcium 34:385–397.[CrossRef][Web of Science][Medline]

Mattson MP, Cheng B, Davis D, Bryant K, Lieberburg I, Rydel RE (1992) ß-Amyloid peptides destabilize calcium homeostasis and render human cortical neurons vulnerable to excitotoxicity. J Neurosci 12:376–389.[Abstract]

Nagy Z, Esiri MM, Jobst KA, Morris JH, King EM, McDonald B, Joachim C, Litchfield S, Barnetson L, Smith AD (1997) The effects of additional pathology on the cognitive deficit in Alzheimer disease. J Neuropathol Exp Neurol 56:165–170.[Web of Science][Medline]

Namura S, Zhu J, Fink K, Endres M, Srinivasan A, Tomaselli KJ, Yuan J, Moskowitz MA (1998) Activation and cleavage of caspase-3 in apoptosis induced by experimental cerebral ischemia. J Neurosci 18:3659–3668.[Abstract/Free Full Text]

Pike CJ, Burdick D, Walencewicz AJ, Glabe CG, Cotman CW (1993) Neurodegeneration induced by ß-amyloid peptides in vitro: the role of peptide assembly state. J Neurosci 13:1676–1687.[Abstract]

Pillot T, Drouet B, Queille S, Labeur C, Vandekerchkhove J, Rosseneu M, Pincon-Raymond M, Chambaz J (1999) The nonfibrillar amyloid beta-peptide induces apoptotic neuronal cell death: involvement of its C-terminal fusogenic domain. J Neurochem 73:1626–1634.[CrossRef][Web of Science][Medline]

Sastre M, Steiner H, Fuchs K, Capell A, Multhaup G, Condron MM, Teplow DB, Haass C (2001) Presenilin-dependent gamma-secretase processing of beta-amyloid precursor protein at a site corresponding to the S3 cleavage of Notch. EMBO Rep 2:835–841.[CrossRef][Web of Science][Medline]

Snowdon DA, Greiner LH, Mortimer JA, Riley KP, Greiner PA, Markesbery WR (1997) Brain infarction and the clinical expression of Alzheimer disease. The Nun Study. JAMA 277:813–817.[Abstract/Free Full Text]

Sodhi CP, Rampalli S, Perez RG, Koo EH, Quinn B, Gottardi-Littell NR (2004) The endocytotic pathway is required for increased A beta 42 secretion during apoptosis. Brain Res Mol Brain Res 128:201–211.[Medline]

Soto C, Sigurdsson EM, Morelli L, Kumar RA, Castano EM, Frangione B (1998) Beta-sheet breaker peptides inhibit fibrillogenesis in a rat brain model of amyloidosis: implications for Alzheimer's therapy. Nat Med 4:822–826.[CrossRef][Web of Science][Medline]

Sponne I, Fifre A, Drouet B, Klein C, Koziel V, Pincon-Raymond M, Olivier JL, Chambaz J, Pillot T (2003) Apoptotic neuronal cell death induced by the non-fibrillar amyloid-beta peptide proceeds through an early reactive oxygen species-dependent cytoskeleton perturbation. J Biol Chem 278:3437–3445.[Abstract/Free Full Text]

Steiner H, Winkler E, Edbauer D, Prokop S, Basset G, Yamasaki A, Kostka M, Haass C (2002) PEN-2 is an integral component of the gamma-secretase complex required for coordinated expression of presenilin and nicastrin. J Biol Chem 277:39062–39065.[Abstract/Free Full Text]

Tanzi RE, Bertram L (2005) Twenty years of the Alzheimer's disease amyloid hypothesis: a genetic perspective. Cell 120:545–555.[CrossRef][Web of Science][Medline]

Tesco G, Koh YH, Tanzi RE (2003) Caspase activation increases beta-amyloid generation independently of caspase cleavage of the beta-amyloid precursor protein (APP). J Biol Chem 278:46074–46080.[Abstract/Free Full Text]

Thornberry NA (1998) Caspases: key mediators of apoptosis. Chem Biol 5:R97–R103.[CrossRef][Web of Science][Medline]

Walsh DM, Klyubin I, Fadeeva JV, Rowan MJ, Selkoe DJ (2002) Amyloid-beta oligomers: their production, toxicity and therapeutic inhibition. Biochem Soc Trans 30:552–557.[CrossRef][Web of Science][Medline]

Wang HW, Pasternak JF, Kuo H, Ristic H, Lambert MP, Chromy B, Viola KL, Klein WL, Stine WB, Krafft GA, Trommer BL (2002) Soluble oligomers of beta amyloid (1–42) inhibit long-term potentiation but not long-term depression in rat dentate gyrus. Brain Res 924:133–140.[CrossRef][Web of Science][Medline]

Wei H, Kang B, Wei W, Liang G, Meng QC, Li Y, Eckenhoff RG (2005) Isoflurane and sevoflurane affect cell survival and BCL-2/BAX ratio differently. Brain Res 1037:139–147.[CrossRef][Web of Science][Medline]

Xie Z, Tanzi RE (2006) Alzheimer's disease and post-operative cognitive dysfunction. Exp Gerontol 41:346–359.[CrossRef][Web of Science][Medline]

Xie Z, Moir RD, Romano DM, Tesco G, Kovacs DM, Tanzi RE (2004) Hypocapnia induces caspase-3 activation and increases abeta production. Neurodegener Dis 1:29–37.[CrossRef][Medline]

Xie Z, Romano DM, Tanzi RE (2005a) Effects of RNAi-mediated silencing of PEN-2, APH-1a, and nicastrin on wild-type vs FAD mutant forms of presenilin 1. J Mol Neurosci 25:67–77.[CrossRef][Web of Science][Medline]

Xie Z, Romano DM, Tanzi RE (2005b) RNA interference-mediated silencing of X11alpha and X11beta attenuates amyloid beta-protein levels via differential effects on beta-amyloid precursor protein processing. J Biol Chem 280:15413–15421.[Abstract/Free Full Text]

Xie Z, Dong Y, Maeda U, Alfille P, Culley DJ, Crosby G, Tanzi RE (2006a) The common inhalation anesthetic isoflurane induces apoptosis and increases amyloid beta protein levels. Anesthesiology 104:988–994.[CrossRef][Web of Science][Medline]

Xie Z, Dong Y, Maeda U, Moir R, Inouye SK, Culley DJ, Crosby G, Tanzi RE (2006b) Isoflurane-induced apoptosis: a potential pathogenic link between delirium and dementia. J Gerontol A Biol Sci Med Sci 61A:1300–1306.[Abstract/Free Full Text]

Yoo AS, Cheng I, Chung S, Grenfell TZ, Lee H, Pack-Chung E, Handler M, Shen J, Xia W, Tesco G, Saunders AJ, Ding K, Frosch MP, Tanzi RE, Kim TW (2000) Presenilin-mediated modulation of capacitative calcium entry. Neuron 27:561–572.[CrossRef][Web of Science][Medline]

Yu C, Kim SH, Ikeuchi T, Xu H, Gasparini L, Wang R, Sisodia SS (2001) Characterization of a presenilin-mediated amyloid precursor protein carboxyl-terminal fragment gamma. Evidence for distinct mechanisms involved in gamma-secretase processing of the APP and Notch1 transmembrane domains. J Biol Chem 276:43756–43760.[Abstract/Free Full Text]

Yu G, Nishimura M, Arawaka S, Levitan D, Zhang L, Tandon A, Song YQ, Rogaeva E, Chen F, Kawarai T, Supala A, Levesque L, Yu H, Yang DS, Holmes E, Milman P, Liang Y, Zhang DM, Xu DH, Sato C, et al (2000) Nicastrin modulates presenilin-mediated notch/glp-1 signal transduction and betaAPP processing. Nature 407:48–54.[CrossRef][Medline]

Related articles in J. Neurosci.:

This Week in The Journal

J. Neurosci. 2007 27: i. [Full Text]  



This article has been cited by other articles:


Home page
 Arch NeurolHome page
Y. Dong, G. Zhang, B. Zhang, R. D. Moir, W. Xia, E. R. Marcantonio, D. J. Culley, G. Crosby, R. E. Tanzi, and Z. Xie
The Common Inhalational Anesthetic Sevoflurane Induces Apoptosis and Increases {beta}-Amyloid Protein Levels
Arch Neurol, May 1, 2009; 66(5): 620 - 631.
[Abstract] [Full Text] [PDF]

Home page
 Proc. Natl. Acad. Sci. USAHome page
C. A. Butts, J. Xi, G. Brannigan, A. A. Saad, S. P. Venkatachalan, R. A. Pearce, M. L. Klein, R. G. Eckenhoff, and I. J. Dmochowski
Identification of a fluorescent general anesthetic, 1-aminoanthracene
PNAS, April 21, 2009; 106(16): 6501 - 6506.
[Abstract] [Full Text] [PDF]

Home page
 J. Biol. Chem.Home page
C. Shen, Y. Chen, H. Liu, K. Zhang, T. Zhang, A. Lin, and N. Jing
Hydrogen Peroxide Promotes A{beta} Production through JNK-dependent Activation of {gamma}-Secretase
J. Biol. Chem., June 20, 2008; 283(25): 17721 - 17730.
[Abstract] [Full Text] [PDF]

Home page
 J. Biol. Chem.Home page
B. Zhang, Y. Dong, G. Zhang, R. D. Moir, W. Xia, Y. Yue, M. Tian, D. J. Culley, G. Crosby, R. E. Tanzi, et al.
The Inhalation Anesthetic Desflurane Induces Caspase Activation and Increases Amyloid {beta}-Protein Levels under Hypoxic Conditions
J. Biol. Chem., May 2, 2008; 283(18): 11866 - 11875.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurosci.Home page
G. Zhang, Y. Dong, B. Zhang, F. Ichinose, X. Wu, D. J. Culley, G. Crosby, R. E. Tanzi, and Z. Xie
Isoflurane-Induced Caspase-3 Activation Is Dependent on Cytosolic Calcium and Can Be Attenuated by Memantine
J. Neurosci., April 23, 2008; 28(17): 4551 - 4560.
[Abstract] [Full Text] [PDF]

Home page
 Anesth. Analg.Home page
G. Liang, Q. Wang, Y. Li, B. Kang, M. F. Eckenhoff, R. G. Eckenhoff, and H. Wei
A Presenilin-1 Mutation Renders Neurons Vulnerable to Isoflurane Toxicity
Anesth. Analg., February 1, 2008; 106(2): 492 - 500.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Submit an eLetter
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Related articles in J. Neurosci.
Right arrow Similar articles in this journal
Right arrow Similar articles in Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Web of Science (16)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Xie, Z.
Right arrow Articles by Tanzi, R. E.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Xie, Z.
Right arrow Articles by Tanzi, R. E.
Right arrowPubmed/NCBI databases
*Compound via MeSH
*Substance via MeSH
Hazardous Substances DB
*CLIOQUINOL
*COPPER, ELEMENTAL
*ZINC COMPOUNDS
*ZINC, ELEMENTAL

 -
-

Home  |   Search  |   Archive  |   Subscribe  |   Contact  |   Help
-
Copyright 2009 by Society for Neuroscience ONLINE ISSN: 1529-2401
-