d JOURNAL OF NEUROCHEMISTRY| 2008 | 104 | 1387–1393

doi: 10.1111/j.1471-4159.2007.05127.x

Interleukin-1b up-regulates TACE to enhance a-cleavage of APP
in neurons: resulting decrease in Ab production
Yuriko Tachida,*,1 Kazuhiro Nakagawa,*,1 Takashi Saito, ,1 Takaomi C. Saido, Takashi Honda,à
Yuko Saito,§ Shigeo Murayama,§ Tamao Endo,¶ Gaku Sakaguchi,** Akira Kato,**Shinobu Kitazume* and Yasuhiro Hashimoto*, ,1*Glyco-chain Functions Laboratory, Supra-biomolecular System Group, Frontier Research System, The Institute of Physical andChemical Research (RIKEN), Saitama, Japan, and CREST, Japan Science and Technology Agency, Saitama, Japan
Laboratory for Proteolytic Neuroscience, RIKEN Brain Science Institute, Saitama, JapanàAnatomy and Neuroscience, Division of Human Life Science, School of Nursing, Fukushima Medical University, Fukushima, Japan§Department of Neuropathology, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan¶The Glycobiology Research Group, Tokyo Metropolitan Institute of Gerontology, Foundation for Research on Aging and Promotionof Human Welfare, Tokyo, Japan**Pain and Neurology, Discovery Research Laboratories, Shionogi Co. Ltd., Shiga, Japan
Department of Biochemistry, School of Medicine, Fukushima Medical University, Fukushima, Japan

Abstract
The proinflammatory cytokine interleukin (IL)-1b is up-regulated in microglial cells surrounding amyloid plaques, leading
to the hypothesis that IL-1b is a risk factor for Alzheimer’s
disease. However, we unexpectedly found that IL-1b significantly enhanced a-cleavage, indicated by increases in sAPPa
and C83, but reduced b-cleavage, indicated by decreases insAPPb and Ab40/42, in human neuroblastoma SK-N-SH cells.
IL-1b did not significantly alter the mRNA levels of BACE1,
ADAM-9, and ADAM-10, but up-regulated that of TACE by
threefold. The proform and mature form of TACE protein werealso significantly up-regulated. A TACE inhibitor (TAPI-2)
concomitantly reversed the IL-1b-dependent increase insAPPa and decrease in sAPPb, suggesting that APP con-sumption in the a-cleavage pathway reduced its consumption
in the b-cleavage pathway. IL-1Ra, a physiological antagonist
for the IL-1 receptor, reversed the effects of IL-1b, suggestingthat the IL-1b-dependent up-regulation of a-cleavage ismediated by the IL-1 receptor. IL-1b also induced this concomitant increase in a-cleavage and decrease in b-cleavage
in mouse primary cultured neurons. Taken together we conclude that IL-1b is an anti-amyloidogenic factor, and thatenhancement of its signaling or inhibition of IL-1Ra activity
could represent potential therapeutic strategies against Alzheimer’s disease.
Keywords: Alzheimer’s disease, Ab, IL-1Ra, IL-1b, sAPPa,TACE.
J. Neurochem. (2008) 104, 1387–1393.

Deposition of amyloid-b peptide (Ab) in the brain is ahallmark of the pathogenesis of Alzheimer’s disease (AD)(Selkoe 2001). Ab (39–43 amino acids in length) is a
proteolytic product derived from amyloid precursor protein(APP). b-secretase (beta-site APP-cleaving enzyme: BACE1)
cleaves APP to produce a soluble NH2-terminal fragment(sAPPb) and a membrane-bound 12-kDa COOH-terminal
fragment (C99). C99 is further cleaved by c-secretase,resulting in the production of a pathogenic Ab peptide (DeAddress correspondence and reprint requests to Yasuhiro Hashimoto,
Glyco-chain Functions Laboratory, Supra-biomolecular System Group,
Frontier Research System, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama
351-0198, Japan. E-mail: yasua@riken.jp
1
These authors contributed equally to this study.
Abbreviations used: Ab, amyloid-b peptide; ADAM, a-disintegrin-andmetalloprotease; AD, Alzheimer’s disease; APP, amyloid precursor protein; APPwt, wild-type APP; APPswe, Swedish mutant of APP; BACE,
beta-site APP-cleaving enzyme; FL, full-length; GAPDH, glyceraldehyde
3-phosphate dehydrogenase; IL, interleukin; IL-1Ra, interleukin-1
receptor antagonist; N, N-terminal side; PS1, presenilin 1; sAPP, soluble
extracellular fragment of APP; sAPPa, soluble extracellular fragment of
APP generated by a-secretase; sAPPb, soluble extracellular fragment of
APP generated by b-secretase; TACE, tumor necrosis factor (TNF)a-converting enzyme; TAPI-2, TNF-a-protease inhibitor-2.

Received July 22, 2007; revised manuscript received September 27,
2007; accepted October 12, 2007.

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1388 | Y. Tachida et al.

Strooper et al. 1998; Wolfe et al. 1999). As an alternative
processing pathway, a-secretase cleaves within the Ab
sequence to produce a soluble NH2-terminal fragment(sAPPa) and a membrane-bound 10-kDa COOH-terminal
fragment (C83) (Buxbaum et al. 1998; Lammich et al.
1999). C83 is also cleaved by c-secretase to produce thenon-pathogenic p3 peptide. A-disintegrin-and-metalloprotease (ADAM) family proteases, such as tumor necrosis
factor (TNF)-a-converting enzyme (TACE/ADAM-17),
ADAM-9, and ADAM-10, have been shown to possess asecretase activity (Allinson et al. 2003; Kojro and Fahrenholz 2005). Not only does the action of a-secretase preclude
the formation of the intact Ab peptide, but the large
ectodomain of APP released from the cell surface (sAPPa)
has neuroprotective and memory-enhancing effects (Furukawa et al., 1996, Meziane et al., 1998; Mattson et al., 1999).
Thus, a-cleavage is important for the neuroprotective
pathway of APP metabolism.
Interleukin (IL)-1 has been found to play important rolesin the development of inﬂammatory responses in the brain
against acute injury, infection and chronic neurodegenerative
diseases, including AD (Rothwell and Luheshi 2000; Allanand Rothwell 2001). IL-1 is secreted by macrophages/
microglial cells upon their activation (Dinarello 1996), andtriggers both cytokine cascades and self-defense mechanisms. For example, IL-1 acts on hypothalamic sites andraises the body temperature, which is beneﬁcial for hostdefense mechanisms.
IL-1 receptor antagonist (IL-1Ra) is a naturally occurringinﬂammatory inhibitor that competes with IL-1b by binding
to the IL-1 receptor. Although IL-1Ra binds to the receptor,
it does not generate any intracellular signaling (Arend
1993; Arend et al. 1998). Indeed, lipopolysaccharide
injection into human volunteers increases the plasma
concentration of IL-1b (up to 80 pg/mL), followed by the
production of a large excess of IL-1Ra (up to 6400 pg/mL)(Arend et al. 1990; Granowitz et al. 1991), Thus, IL-1Ra
appears to be an important regulator of inﬂammatory
responses.
In the AD brain, IL-1 expression is up-regulated around
amyloid plaques (Mrak and Grifﬁn 2001). In the present
study, we examined the effects of IL-1b on a-cleavageof APP in neuroblastoma cells and primary cultured neurons.

Materials and methods
Materials
The materials and antibodies used in this study were as follows:
anti-APP (6E10) monoclonal antibody (Signet Laboratories, Dedham, MA, USA); anti-TACE polyclonal antibody and antiglyceraldehyde 3-phosphate dehydrogenase monoclonal antibody(Chemicon International, Temecula, CA, USA); anti-sAPPb antibody (IBL, Fujioka, Japan); recombinant murine IL-1b and humanIL-1b, IL-6, and IL-1Ra (PeproTech EC, London, England);TNF-a-protease inhibitor-2 (TAPI-2; Peptides International, Osaka,
Japan). An anti-APP (C15) antibody against endogenous membranebound (intact) APP was a generous gift from Dr. Kei Maruyama(Saitama Medical University, Saitama, Japan). An anti-sAPPa
antibody against a VRHQK peptide was prepared as described
previously (Saido et al. 1995).
ELISAs for amyloid peptides
The following ELISA kits were used: human amyloid-b (1–40)(FL), human amyloid-b (1–42) (N) and mouse/rat amyloid-b (1–40)(N) assay kits (IBL); human/rat b-amyloid (42) ELISA kit Wako,
high-sensitivity (Wako, Tokyo, Japan).
Cell culture
Human neuroblastoma SK-N-SH cells were cultured in Dulbecco’s
modiﬁed Eagle’s medium supplemented with 10% fetal bovine
serum, 100 U/mL penicillin and 100 lg/mL streptomycin sulfate.
SH-SY5Y cells, a subline of SK-N-SH cells, were also used.
Cortical neurons were isolated from C57BL/6CrSlc mice aspreviously described (Hama et al. 2001). Brieﬂy, cerebral cortices
were dissected from the brains of embryos at the developmental
stage of 16–18 days. After removal of the meninges, the brains
were minced in 0.25% trypsin (Difco, Sparks, MD, USA) and
0.05% Dnase I (Roche Diagnostics, Mannheim, Germany).
Cortical neurons were ﬁltered through a Cell Strainer (Falcon,
Oxford, UK) and seeded into 12-well plates (NUNC, Roskilde,
Denmark) coated with 100 mg/mL of poly-L-lysine (Sigma, St.
Louis, MO, USA) at a density of 4 · 105 cells/well. Subsequently,
the neurons were cultured in Neurobasal medium (Gibco-Invitrogen, Burlington, ON, USA) supplemented with 2% B27(Gibco-Invitrogen), 0.5 mmol/L glutamine (Gibco-Invitrogen) andpenicillin/streptomycin (Gibco-Invitrogen) at 37C under a humidiﬁed 95% air/5% CO2 atmosphere. The cells were cultured in thepresence or absence of IL-1b. The effects of TAPI-2 were
examined at ﬁnal concentrations of 2 and 10 lmol/L. After 18 h ofculture, the culture media were collected for analysis of the levelsof secreted sAPPa and sAPPb. During this experimental period,
the cell viability was 92–95%, as evaluated by Trypan blue dye
exclusion analysis. The cells were harvested for analysis of cellular
TACE, intact (membrane-bound) APP and GAPDH. Total RNA
fractions from the harvested cells were subjected to real-time PCR
analysis.
Western blot analysis
We analyzed the protein levels of TACE, intact APP and GAPDH bywestern blot analysis. SK-N-SH cells or primary cultured neurons
were lysed with radio-immunoprecipitation assay buffer (50 mmol/
L Tris–HCl pH 8.0, 150 mmol/L NaCl, 0.5% deoxycholate, 1%
NP40, 0.1% SDS) containing a protease inhibitor cocktail, and thencentrifuged at 17 000 g for 10 min. The protein concentrations of
the resulting supernatants were determined by a protein assay using
the bicinchonic acid reagent (Pierce, Rockford, IL, USA). The
sAPPa and sAPPb secreted into the culture medium wereprecipitated with heparin-agarose at 4C overnight, and thensubjected to sodium dodecyl sulfate–polyacrylamide gel electrophoresis (4–20% gradient gel). After transfer of the separated
proteins to a nitrocellulose membrane, the membrane was incubated 2007 The Authors
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Interleukin-1b up-regulates TACE | 1389

with a primary antibody, followed by incubation with an appropriate
secondary antibody, namely horseradish peroxidase-conjugated goatanti-mouse or anti-rabbit IgG. Binding of each antibody to its
antigen was detected using a chemiluminescent substrate (Pierce),
and the signals were quantiﬁed using a Luminoimage Analyzer
LAS-1000 PLUS (Fuji Film, Tokyo, Japan).
Quantitative real-time PCR analysis
We analyzed the mRNA levels of TACE, ADAM-9, and ADAM-10
by quantitative real-time PCR. Aliquots (2 lg) of total RNA werereverse-transcribed with random hexamers using a Super Script III
RT Kit (Invitrogen, Carlsbad, CA, USA) according to the
manufacturer’s protocol. The obtained cDNAs were ampliﬁed with
900 nmol/L forward primer, 900 nmol/L reverse primer, 250 nmol/
L ﬂuorogenic probe and 25 lL of Universal PCR Master Mix(Applied Biosystems, Foster City, CA, USA) in a total volume of
20 lL using an ABI PRISM 7900HT sequence detection system(Applied Biosystems). The PCR conditions were 1 cycle at 50C for
2 min and 1 cycle at 95C for 10 min, followed by 40 cycles of95C for 15 s and 50C for 1 min. All the primers and probes werepurchased from Applied Biosystems. Regarding the primers andprobes for human TACE, ADAM-9, ADAM-10, BACE1, and
GAPDH, we used Assays-on-Demand Gene Expression Products,
and added the cDNAs to TaqMan Universal PCR Master Mix,
which contained all the reagents required for PCR. The probes for
TACE, ADAM-9, ADAM-10 and BACE1 were labeled with theﬂuorescent reporter dye 6-carboxy-ﬂuorescein. The probes for
GAPDH were labeled with VIC at their 5¢ ends and the quencher
dye TAMRA at their 3¢ ends. The expression levels of the target
genes were measured in duplicate and normalized to the corresponding GAPDH expression levels.

(a)

(b)

Results
Effects of IL-1b on a-cleavage and TACE expression byhuman neuroblastoma SK-N-SH cells
We analyzed the effects of the proinﬂammatory cytokine IL1b on the secretion of sAPPa by neuroblastoma SK-N-SH
cells. Addition of IL-1b (1 ng/mL) to the culture medium
signiﬁcantly enhanced sAPPa secretion and C83 accumulation by threefold, whereas addition of IL-6 had no effect(Fig. 1a–c). IL-1b treatment increased the levels of both theproform and mature form of TACE protein by twofold(Fig. 1d and e). The levels of the cell-associated form of
intact APP were not increased by the addition of thesecytokines. The dose effects of IL-1b on the enhancement ofsAPPa secretion were examined in the range of 0.1–50 ng/
mL. The effect was linear for 0.1–1 ng/mL and then reacheda plateau (data not shown). Therefore, we used 1 ng/mL of
IL-1b as the standard assay condition in the following
experiments.
Effect of IL-1b on the mRNA levels of TACE, ADAM-9, and
ADAM-10
We examined the mRNA levels of possible a-secretases,
such as TACE/ADAM-17, ADAM-9, and ADAM-10, in SKN-SH cells. Quantitative real-time PCR revealed that IL-1b
treatment up-regulated the mRNA level of TACE by
threefold (Fig. 2a) but did not affect the levels of ADAM-9
and ADAM-10 (107% and 100% of the control levels,

(d)

(c)

Fig. 1 IL-1b up-regulates TACE to enhance sAPPa production inhuman neuroblastoma SK-N-SH cells. (a) SK-N-SH cells were incubated with or without IL-6 (10 ng/mL) or IL-1b (1 ng/mL) in OPTI-MEM(serum-free media) for 18 h. Proteins secreted into the conditioned
media were subjected to western blot analysis using the 6E10 antibody to detect sAPPa. Cellular protein extracts were subjected towestern blot analysis using the C15 antibody to detect the cell-associated forms of intact APP and C83. GAPDH was detected with a(e)specific antibody and used as a loading control. (b) Signal ratios ofsAPPa to intact APP are shown as the mean ± SEM (n = 9) of three
independent experiments (*p < 0.001). (c) Signal ratios of C83 to intact APP are shown as the mean ± SEM (n = 5) of three independent
experiments (*p < 0.05). (d) Cellular extracts were subjected to western blot analysis to detect TACE and GAPDH. (e) Signal ratios of
TACE to GAPDH are shown as the mean ± SEM (n = 4) of three
independent experiments (*p < 0.05).

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1390 | Y. Tachida et al.

Fig. 2 IL-1b up-regulates mRNA of TACE.
The mRNA levels of TACE (a), ADAM-9 (b)and ADAM-10 (c) were determined byreal-time PCR, and normalized by thecorresponding GAPDH mRNA level. Data
represent the mean ± SEM (n = 3) of three
independent experiments (*p < 0.01).

respectively) (Fig. 2b and c), suggesting that IL-1b enhancessAPPa production by up-regulating TACE transcription.
TAPI-2 reverses the IL-1b-dependent increase ina-cleavage
We examined the effect of TAPI-2, a TACE inhibitor, on the
IL-1b-dependent increase in a-cleavage in SK-N-SH cells.
The increases in sAPPa and C83 were reversed by theaddition of 2 or 10 lmol/L TAPI-2 (Fig. 3), suggesting that
TACE activity is required for the IL-1b-induced increase ina-cleavage. Furthermore, TAPI-1 was also effective forreversing the increase in a-cleavage.
Effects of IL-1Ra on the increases in TACE and sAPPa
IL-1Ra is a physiological antagonist of IL-1b that competes
with IL-1b by binding to the IL-1b receptor, thereby
preventing harmful inﬂammatory responses. We examinedthe effect of IL-1Ra on the IL-1b-induced increase in acleavage. Addition of IL-1Ra reversed the IL1b-dependent
increases in sAPPa, C83, and TACE protein (Fig. 4),
suggesting that the effects of IL-1b are mediated by the IL1b receptor. IL-1Ra addition alone slightly decreased thesAPPa secretion and TACE protein level, but the decreases
were not signiﬁcant.
Effects of inflammatory cytokines on b-cleavage of APP in
human neuroblastoma cells
Amyloid precursor protein is processed by two distinct
cleavage pathways, namely the a- and b-cleavage pathways.
We analyzed the effects of IL-1b on b-cleavage of APP in
SK-N-SH cells. Treatment with IL-1b (1 ng/mL) signiﬁcantly reduced the secretion of sAPPb (Fig. 5a and b). WhenTAPI-2 was added together with IL-1b, the reduced secretionof sAPPb was reversed to the control level (Fig. 5c and d),suggesting that the decrease in b-cleavage is due to upregulation of TACE activity. We examined the BACE1mRNA levels after IL-1b treatment. Quantitative real-time
PCR analysis revealed that BACE1 mRNA was slightly
decreased by IL-1b treatment, but the decrease was not
signiﬁcant (Fig. 5e). These results suggest that the decrease
in sAPPb secretion is not due to down-regulation of BACE1,
but possibly due to increased consumption of APP, thecommon substrate for both cleavage pathways. In otherwords, the decrease in sAPPb secretion may be a secondary

(a)

(b)

(c)

Fig. 3 Effect of TACE inhibition by TAPI-2 on the effect of IL-1b. (a),Proteins secreted into the conditioned media were subjected to western blot analysis using the 6E10 antibody to detect sAPPa. Cellular
protein extracts were subjected to western blot analysis using the C15
antibody to detect the cell-associated forms of intact APP and C83.
GAPDH was detected with a specific antibody and used as a loading
control. (b) Signal ratios of sAPPa to intact APP are shown as themean ± SEM (n = 6) of three independent experiments (*p < 0.005;**p < 0.01). (c) Signal ratios of C83 to intact APP are shown as themean ± SEM (n = 5) of three independent experiments (*p < 0.01;**p < 0.05).

effect of the increase in a-cleavage. We also tried to estimate
the amounts of Ab peptides in the culture medium of SK-NSH cells, but the levels of endogenous Ab peptides in themedium were too low to be detected. Therefore, we used SHSY5Y cells (a subline of SK-N-SH cells) stably overexpressing wild-type APP (APPwt; SH-SY5Y-APPwt cells).
Following addition of IL-1b (1 ng/mL) to the culture
medium, we detected a signiﬁcant decrease in Ab40
secretion and a slight decrease in Ab42 secretion by SHSY5Y-APPwt cells (Fig. 5f), suggesting that IL-1b is aneuroprotective cytokine that reduces Ab production by upregulating a-cleavage of APP.
Effects of IL-1b on APP cleavage in mouse primary neurons
We analyzed the effects of IL-1b on APP metabolism inmouse primary cultured neurons. IL-1b treatment signiﬁcantly increased the TACE mRNA level and sAPPa secretion

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Interleukin-1b up-regulates TACE | 1391

(a)

(d)

(c)

(b)

Fig. 4 Effects of IL-1Ra on sAPPa secretion and TACE protein levels.
(a) SK-N-SH cells were treated with IL-1b (1 ng/mL) in the presence orabsence of IL-1Ra for 18 h. Proteins secreted into the conditioned
media were subjected to western blot analysis using the 6E10 antibody to detect sAPPa. Cellular protein extracts were subjected towestern blot analysis using the C15 antibody to detect the cell-associated form of intact APP. (b) Signal ratios of sAPPa to intact APP are

(a)

(b)

(c)

(e)

shown as the mean ± SEM (n = 5) of three independent experiments(*p < 0.05; **p < 0.05). (c) Signal ratios of C83 to intact APP are
shown as the mean ± SEM (n = 4) of three independent experiments(*p < 0.05; **p < 0.05). (d) Cellular protein extracts were subjected towestern blot analysis to detect TACE and GAPDH. (e) Signal ratios of
TACE to GAPDH are shown as the mean ± SEM (n = 6) of three
independent experiments (*p < 0.05; **p < 0.05).

(e)

(d)

Fig. 5 Effects of IL-6 or IL-1b on the BACE1 mRNA level andsecretion of sAPPb and Ab by human neuroblastoma cells. (a) Proteins secreted into the conditioned media were subjected to western
blot analysis to detect sAPPb. Cellular extracts were subjected towestern blot analysis using the C15 antibody to detect the cell-associated form of intact APP. (b) Signal ratios of sAPPb to intact APP are
shown as the mean ± SEM (n = 7) of three independent experiments(*p < 0.001). (c) TAPI-2 was added together with IL-1b. sAPPa in the
media was subjected to western blot analysis using the sAPPb antibody. Cellular protein extracts were subjected to western blot analysis(f)using the C15 antibody to detect intact APP. GAPDH was detectedwith a specific antibody and as a loading control. (d) Signal ratios ofsAPPb to intact APP are shown as the mean ± SEM (n = 5) of three
independent experiments (*p < 0.05; **p < 0.05). (e) Quantitative realtime PCR was carried out to detect the BACE1 mRNA levels. (f) SHSY5Y-APPwt cells over-expressing wild-type APP were treated with
IL-1b, and conditioned media were analyzed by ELISA to detect the Ab
levels. Data are shown as the percent change relative to the control
level, and represent the mean ± SEM (n = 4) of three independent
experiments (*p < 0.05; **p < 0.01).

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Journal Compilation  2007 International Society for Neurochemistry, J. Neurochem. (2008) 104, 1387–1393

TACE mRNA

*

1.5
1

0.5
0

cont

+IL-1β

+I

100

sAPPα

100

intact APP

37

GAPDH

(c)
2

(d) 2
sAPPα

*

1.5
1
0.5
0

cont

+IL-1β% reduction of AβTACE / GAPDH ratio(a)2sAPPα / intact APP ratio

co
nt

(b)

L1β

1392 | Y. Tachida et al.

0
–2
–4
–6
–8
–10
–12
–14
–16
–18
–20

+ IL-1β1ng/mL 10ng/mL
Aβ40 Aβ42

Aβ40 Aβ42

**

*
**

Fig. 6 IL-1b up-regulates the TACE mRNA and protein levels inmouse primary cultured neurons, and the effect of IL-1b on Ab
secretion in mouse primary cultured neurons. (a) Mouse primaryneurons were treated with IL-1b (50 ng/mL) for 18 h, and the TACEmRNA levels were determined by quantitative real-time PCR. All values were normalized by the corresponding GAPDH mRNA level. Data
represent the mean ± SEM (n = 3) of three independent experiments(*p < 0.05). (b) Proteins secreted into the conditioned media were
subjected to western blot analysis to detect sAPPa. Cellular extracts

were subjected to western blot analysis using the C15 antibody todetect the cell-associated form of intact APP. (c) Signal ratios ofsAPPa to intact APP are shown as the mean ± SEM (n = 6) of three
independent experiments (*p < 0.05). (d) Conditioned media wereanalyzed by ELISA to detect the Ab levels. Data are shown as thepercentage change relative to the control level, and represent themean ± SEM (n = 6) of three independent experiments (*p < 0.05;**p < 0.01).

(Fig. 6a–c). The level of the cell-associated form of intact
APP was not increased by the addition of this cytokine. In
addition, IL-1b treatment signiﬁcantly reduced the secretionof Ab40 and Ab42 at a ﬁnal concentration of 50 ng/mL andthat of Ab40 at a ﬁnal concentration of 1 ng/mL (Fig. 6d),again suggesting that IL-1b could be protective against thepathogenesis of AD.

present ﬁndings, IL-1 appears to be a neuroprotective
cytokine for neuronal cells.
IL-1b is secreted by microglia, which phagocytose Ab
peptides around plaques. A recent study on a transgenic(APPswe/PS1) mouse model of AD revealed that many of the
microglia near plaques are recruited from the bone marrow andhave the ability to eliminate amyloid deposits by phagocytosis(Simard et al. 2006). These authors also reported that microglia responded to exogenous as well as endogenous Ab andsubsequently expressed mRNAs for IL-1b, monocyte chemoattractant protein-1 and TLR2. Moreover, these responses
appeared to be non-typical innate immunity, since up-regulation of TNF-a was not involved in the recruitment andphagocytosis. Microglia recruitment and up-regulation of
IL1b expression gradually increased with age (4–9 months) inthe transgenic mouse model, suggesting that up-regulation of
IL-1b persists throughout the long-term pathogenic processes.
Very recently, Shaftel et al. reported that over-expressionof IL1b attenuated plaque formation in an APPswe/PS1
transgenic mouse model, indicating that IL1b is neuroprotective against the pathogenesis of AD (Shaftel et al. 2007).
Although the involvement of TACE up-regulation was not
examined in their transgenic mouse model, our results
suggest that TACE up-regulation could be a downstream
event of the neuroprotective IL1b signaling. It is notable that
only a 30% increase in TACE mRNA signiﬁcantly reducedsAPPb and Ab production in mouse primary cultured

Discussion
In the present study, we have demonstrated that IL-1b upregulates TACE expression to enhance a-cleavage of APP inneuroblastoma cells and primary cultured neurons, resulting
in increased sAPPa production but decreased sAPPb and Ab
production.
Up-regulation of TACE activity is a downstream event of
IL-1 receptor signaling. Ma et al. reported that short-term IL1b treatment of neuroglioma U251 cells activated intracellular c-Jun N-terminal kinase (JNK) and mitogen-activatedprotein kinases to up-regulate a-secretase activity (Ma et al.
2005). Bandyopadhyay et al. extensively investigated theeffects of IL-1a on a-cleavage of APP in astrocytic cells andfound that it up-regulated ADAM-10 and ADAM-17 (TACE)
to increase a-cleavage through the activation of mitogenactivated protein kinases, p38 kinase and PI3 kinase, leading
to a concomitant decrease in the Ab level (Bandyopadhyay
et al. 2006). Taking their observations together with our 2007 The Authors
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Interleukin-1b up-regulates TACE | 1393

neurons in the present study, indicating that even subtle
enhancement of TACE could be sufﬁcient to reduce bcleavage of APP. Indeed, Skovronsky et al. reported thepresence of TACE protein in neurons surrounding plaques in
the AD brain (Skovronsky et al. 2001), supporting ourassumption that enhancement of TACE would be a beneﬁcial
response induced by IL-1b. In conclusion, IL-1b upregulates TACE in neurons to ameliorate AD plaquepathology. Thus, enhancement of IL-1b and depletion of
IL-1Ra could represent new therapeutic targets for treatmentof AD.

Acknowledgments
This work was supported by the New Energy and Industrial
Technology Development Organization (NEDO) of Japan. Yasuhiro
Hashimoto was the recipient of a grant from the Ministry of Health,
Labor and Welfare of Japan (No. 2006-Nanchi-Ippan-017).

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 2007 The Authors
Journal Compilation  2007 International Society for Neurochemistry, J. Neurochem. (2008) 104, 1387–1393