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The Journal of Neuroscience, June 15, 1999, 19(12):5054-5065
Interleukin-1 Immunoreactivity and Microglia Are Enhanced in
the Rat Hippocampus by Focal Kainate Application: Functional Evidence
for Enhancement of Electrographic Seizures
Annamaria
Vezzani 1,
Mirko
Conti 1,
Ada
De
Luigi 2,
Teresa
Ravizza 1,
Daniela
Moneta 1,
Francesco
Marchesi 1, and
Maria Grazia
De
Simoni 2
1 Laboratory of Experimental Neurology and
2 Laboratory of Inflammation and Nervous System Diseases,
Department of Neuroscience, Istituto di Ricerche Farmacologiche
"Mario Negri," 20157 Milan, Italy
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ABSTRACT |
Using immunocytochemistry and ELISA, we investigated the production
of interleukin (IL)-1 in the rat hippocampus after focal application
of kainic acid inducing electroencephalographic (EEG) seizures and CA3
neuronal cell loss. Next, we studied whether EEG seizures per se
induced IL-1 and microglia changes in the hippocampus using
bicuculline as a nonexcitotoxic convulsant agent. Finally, to address
the functional role of this cytokine, we measured the effect of human
recombinant (hr)IL-1 on seizure activity as one marker of the
response to kainate.
Three and 24 hr after unilateral intrahippocampal application of 0.19 nmol of kainate, IL-1 immunoreactivity was enhanced in glia in the
injected and the contralateral hippocampi. At 24 hr, IL-1
concentration increased by 16-fold (p < 0.01) in the injected hippocampus. Reactive microglia was enhanced with
a pattern similar to IL-1 immunoreactivity. Intrahippocampal
application of 0.77 nmol of bicuculline methiodide, which induces
EEG seizures but not cell loss, enhanced IL-1 immunoreactivity
and microglia, although to a less extent and for a shorter time
compared with kainate. One nanogram of (hr)IL-1 intrahippocampally
injected 10 min before kainate enhanced by 226% the time spent in
seizures (p < 0.01). This effect was
blocked by coinjection of 1 µg (hr)IL-1 receptor antagonist or 0.1 ng of 3-((+)-2-carboxypiperazin-4-yl)-propyl-1-phosphonate, selective
antagonists of IL-1 and NMDA receptors, respectively.
Thus, convulsant and/or excitotoxic stimuli increase the production of
IL-1 in microglia-like cells in the hippocampus. In addition,
exogenous application of IL-1 prolongs kainate-induced hippocampal
EEG seizures by enhancing glutamatergic neurotransmission.
Key words:
bicuculline; cytokines; EEG; epilepsy; interleukin
(IL)-1Ra; inflammation; neurodegeneration
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INTRODUCTION |
The proinflammatory cytokines
constitute a group of polypeptide hormones, which were first identified
as soluble mediators within the immune system (Schobitz et al., 1994 ).
Recently, cytokines and their receptors have been located in many other
tissues, including the peripheral and central nervous systems (Hopkins
and Rothwell, 1995). Receptors for interleukin (IL)-1 have been
found in rodent brain at particularly high density in the hippocampus,
where they are presumably located on dendrites of granule cells (Takao
et al., 1990; Ban et al., 1991; Nishiyori et al., 1997). Both neurons and glia have been shown to produce IL-1, thus indicating a local source of synthesis in CNS (Benveniste, 1992; Bartfai and Schultzberg, 1993; Hopkins and Rothwell, 1995).
The presence of cytokines in CNS has raised many questions about their
function and mechanisms of action. Besides their well known central
actions including effects on the hypothalamo-pituitary-adrenal axis, fever responses, somnogenic effects, and modification of the
peripheral immune response (Schobitz et al., 1994; Hopkins and
Rothwell, 1995), some cytokines have been recently shown to affect many
neurotransmitters, including noradrenaline, serotonin, GABA, and
acetylcholine (Rothwell and Hopkins, 1995; De Simoni and Imeri, 1998),
and the expression of various neuropeptides and neurotrophic factors in
several brain regions (Scarborough et al., 1989; Spranger et
al., 1990; Lapchak et al., 1993). In particular, electrophysiological
findings have shown that relatively low concentrations of IL-1,
IL-6, and tumor necrosis factor- (TNF-) inhibit long-term
potentiation (Katsuki et al., 1990; Bellinger et al., 1993; Cunningham
et al., 1996), affect excitatory synaptic transmission (Coogan and
O'Connor, 1997; D'Arcangelo et al., 1997; Zeise et al., 1997),
and modify ionic conductances, particularly Cl and
Ca2+ currents (Miller et al., 1991;
Plata-Salamàn and ffrench-Mullen, 1992).
The involvement of cytokines in neuronal network excitability was
recently suggested by the evidence that convulsant drugs increase mRNA
levels of IL-1, IL-6, and TNF- as well as of type 2-IL-1 receptor
and IL-1 receptor antagonist (Ra) in rat forebrain within hours of
seizure induction (Minami et al., 1990, 1991; Nishiyori et al., 1997;
Eriksson et al., 1998). In particular, in situ hybridization
analysis of IL-1 and IL-1Ra mRNAs after systemic injection of kainic
acid in rats has shown that these transcripts were significantly
induced in microglial cells in the hippocampus as well as in other
areas of the limbic system (Yabuuchi et al., 1993; Eriksson et al.,
1998). Interestingly, autoradiographic analysis of the binding of
radiolabeled IL-1 to rodent brain has revealed a high density of type I
receptors in neurons of the dentate gyrus (Takao et al., 1990; Ban et
al., 1991), thus suggesting that IL-1 is synthesized in glia and
then secreted in the extracellular space for interacting with its
specific receptors. In this regard, a larger release of inflammatory
cytokines has been described in hippocampal slices of epileptic rats
(de Bock et al., 1996).
Evidence in humans also indicates that IL-1 is produced in higher
amounts in epilepsy, because IL-1-immunoreactive microglia is
enhanced in surgically resected temporal lobe tissue (Sheng et al.,
1994).
Although the synthesis of cytokines appears to be tightly regulated at
the transcriptional level (Schobitz et al., 1994), the data available
so far in experimental models of seizures merely analyzed IL-1 mRNA
expression, thus not providing direct evidence that this cytokine is
indeed produced in higher amount in brain tissue.
In this study, we investigated (1) whether IL-1 production is
enhanced in the hippocampus after focal application of kainate inducing
both electroencephalographic (EEG) seizures and neuronal cell loss; (2)
whether IL-1 production was enhanced in the hippocampus by seizures
per se using bicuculline methiodide as a nonexcitotoxic convulsant
agent; (3) the cell types involved in this effect compared with the
pattern of activated microglial cells, because they have been described
as a major source of IL-1 in CNS (Giulian et al., 1986); and (4) the
effect of intrahippocampal application of (hr)IL-1 on
kainate-induced seizures; (5) finally, we probed the hypothesis that
glutamate was involved in the effect of (hr)IL-1 on kainate-induced seizures.
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MATERIALS AND METHODS |
Experimental animals. Male Sprague Dawley rats
(250-280 gm) were purchased from Charles River (Calco, Italy), and
they were housed at a constant temperature (23°C) and relative
humidity (60%) with free access to food and water and a fixed 12 hr
light/dark cycle.
Procedures involving animals and their care were conducted in
conformity with the institutional guidelines that are in compliance with national (4DL N116, GU, suppl 40, 18-2-1992) and
international laws and policies (Europen Community Council Directive
86/609, OJ L 358, 1, December 12, 1987; National Institutes of
Health Guide for the Care and Use of Laboratory Animals, US
National Reasearch Council, 1996).
Placement of cannula and electrodes for EEG recordings. Rats
were surgically implanted with cannula and electrodes under stereotaxic guidance as described in detail (Vezzani et al., 1986). Briefly, rats
were deeply anesthetized using Equithesin (1% phenobarbital and 4%
chloral hydrate; 3 ml/kg, i.p). Two screw electrodes were placed
bilaterally over the parietal cortex, along with a ground lead
positioned over the nasal sinus. Bipolar nichrome wire insulated electrodes (60 µm) were implanted bilaterally into the dentate gyrus
of the dorsal hippocampus (septal pole), and a cannula (22 gauge) was
unilaterally positioned on top of the dura and glued to one of the
depth electrodes for the intrahippocampal infusion of drugs. The
coordinates from bregma for implantation of the electrodes were (in
mm): anteroposterior  3.5; lateral, 2.4; and 3 below dura with the
nose bar set at 2.5 (Paxinos and Watson, 1986). The electrodes were
connected to a multipin socket (March Electronics, Bohemia, NY) and,
together with the injection cannula, were secured to the skull by
acrylic dental cement. The experiments were performed 7 d after
surgery when the animals did not show any sign of pain or discomfort.
EEG recordings and intrahippocampal injection of drugs. The
procedures for recording the EEG and intracerebral injection of drugs
have been previously described (Vezzani et al., 1986). Briefly, the
animals were allowed to acclimatize in a Plexiglas cage (25 × 25 × 60 cm) for a minimum of 10 min before the recording to enable them to adapt to the new environment. The rats were then connected to the lead socket, and a 15-30 min baseline recording was
made to establish an adequate control period. EEG recordings (four-channel EEG polygraph, BP8; Battaglia Rangoni, Bologna, Italy)
were made continuously during drug injection and up to 180 min after
drug infusion. All the injections were made to unanesthetized rats
using a needle (28 gauge) protruding 3 mm below the cannula.
Analysis of the EEG. Seizures were induced in rats by
intrahippocampal application of nanomole amounts of kainic acid, a
glutamate analog acting on kainate-type glutamate receptors (Watkins,
1978), or bicuculline methiodide, a GABA-A receptor antagonist (Curtis et al., 1970), and they were measured by EEG analysis. Kainate-induced seizures have been previously shown to provide a sensitive measure of
the anticonvulsant activity of drugs, and they are reportedly associated with neuronal cell loss restricted to the CA3 pyramidal cells in the injected hippocampus (Vezzani et al., 1991; Gariboldi et
al., 1998). EEG seizures induced by relatively low doses of bicuculline
(<1 nmol) are not associated with nerve cell loss, thus representing a
nonlesional model of seizure activity (Turski et al., 1985).
The EEG recording of each rat was analyzed visually to detect any
activity different from baseline. Seizures were defined by the
occurrence of discrete episodes consisting of the simultaneous occurrence of at least two of the following alterations in all four
leads of recordings: high-frequency and/or multispike complexes and/or
high-voltage synchronized spike or wave activity. These episodes were
typically observed in the first 120 min after kainate injection (Fig.
1b,c). Synchronous spiking was
often observed when seizures subsided (Fig. 1d). Seizure
episodes after bicuculline were not discrete but in continuity with
synchronous spiking (Fig. 1f,g). Epileptic-like activity was
restricted to the first 90 min after bicuculline injection.
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Figure 1.
Sections of the EEG tracing from a rat injected
unilaterally in the dorsal hippocampus with 0.19 nmol of kainic acid
(a-d) or 0.77 nmol of bicuculline methiodide
(e-g). a, e, Baseline recordings;
b, c, typical seizures; d, spiking
activity; f, g, seizure activity in continuity with
synchronous spiking. RCTX, LCTX, Right and left cortex,
respectively; RHP, LHP, right and left hippocampus,
respectively. Calibration, 100 µV. Arrowheads in
c and d delimit the duration of discrete
seizure episodes. Time elapsed from the injection of convulsant drugs
is indicated.
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The quantitative parameters chosen to quantify seizure activity after
kainate were the latency to the first seizure (onset), the total number
of seizures occurring in the 3 hr of recording, and the total time
spent in seizures, which was determined by adding together the duration
of all ictal episodes during the EEG recording period.
In pharmacological experiments, the EEG tracings from rats receiving
the various drugs and those receiving kainic acid alone were compared
visually. Shortly after administration, kainic acid induced stereotyped
behaviors such as sniffing and gnawing. "Wet dog shakes" were often
observed shortly after kainate and during seizures. These behaviors
were not significantly affected by the treatments.
Because ictal events and spiking activity were in continuity in rats
treated with bicuculline (Fig. 1f,g), we included both epileptic events when reckoning the total time in seizures (69.6 ± 12 min; n = 6). The onset time to the first
epileptic event after bicuculline was 2.6 ± 0.4 min. Jumping and
contralateral circling were induced in rats within the first 10 min
after injection. Circling and wet dog shakes were often observed
during EEG epileptic-like activity.
Schedule of treatment. Kainic acid (0.19 nmol in 0.5 µl)
or bicuculline methiodide (0.77 nmol in 0.5 µl) (Sigma, St. Louis, MO) were dissolved in PBS (0.1 M, pH 7.4) or 12%
polyethylene glycol (PEG 300; Bracco, Milan, Italy) in PBS,
respectively. These were the lowest doses causing EEG seizures in 100%
of the animals.
When assessing the effect of drugs on kainate-induced seizures, rats
used as controls were injected with 0.5 µl of heat-inactivated (hr)IL-1 (1 ng; human recombinant IL-1 kindly provided by Dr. Diana Boraschi, Dompé, L'Aquila, Italy; bioactivity in murine thymocyte stimulation assay, ~3 × 107 U/mg)
10 min before kainic acid [0.04 µg (0.19 nmol) in 0.5 µl of PBS].
Seizure activity (see Fig. 8, Table 1) did not significantly differ
from that measured in rats injected with 0.5 µl of PBS before
kainate. This excludes endotoxin contamination or unspecific effects on
seizure activity attributable to the injection of a large molecule in
the hippocampus. (hr)IL-1 was injected at doses ranging from 1 pg to
1 ng in 0.5 µl at the same site as kainic acid 10 min before the
convulsant. (hr)IL-1Ra (1 µg; human recombinant IL-1Ra kindly
provided by Dr. Diana Boraschi; inhibitory activity in murine thymocyte
proliferation assay, 1.7 × 106 U/mg), a
naturally occurring antagonist of type I and type II IL-1 receptors
(Eisenberg et al., 1990), was injected alone or together with IL-1
in 0.5 µl 10 min before kainate.
(3-((+)-2-carboxypiperazin-4-yl)-propyl-1-phosphonate) [(R)-CPP; 0.1 ng], a selective competitive
antagonist of NMDA receptors (Davies et al., 1986), was injected
alone or co-injected with 1 ng (hr)IL-1 in 0.5 µl 10 min before
kainate. All drugs were injected over 1 min using a Hamilton syringe,
and an additional minute elapsed before removal of the needle to avoid
backflow of the drug through the cannula.
After the experiment, all rats treated with kainate and/or the various
drugs were killed by decapitation, and their brains were extracted from
the skull, rapidly frozen on dry ice, and sectioned using a cryostat
(40 µm) for visual inspection of the traces of the electrodes and the
track of the injection needle. Rats treated with bicuculline were
transcardially perfused as described below. The rats with the
electrodes and/or the injection needle out of the hippocampus were
excluded from this study.
Tissue preparation for immunocytochemistry. To assess the
changes in the pattern of IL-1 immunoreactivity and for detecting microglia in the hippocampus, rats were injected with kainate or
bicuculline methiodide, and their EEG was recorded for 3 hr as
described above (n = 5-8).
For these experiments, kainate was injected in a group of rats
different from that used for pharmacological studies. Controls (n = 3 each group) were rats implanted with the
electrodes and injected with 0.5 µl of vehicle. The rats and their
respective controls were killed 3 and 24 hr after injection.
Rats were deeply anesthetized with Equithesin and perfused via the
ascending aorta with 250 ml PBS, 0.1 M, pH 7.4, followed by
500 ml of chilled paraformaldehyde (4%) in PBS as previously described
(Schwarzer et al., 1996). After carefully removing the brains from the
skull, they were post-fixed in the same fixative as above for 90 min at
4°C and then transferred to 20% sucrose in PBS at 4°C for 24 hr
for cryoprotection. The brains were then rapidly frozen by
immersion in isopentane at 70°C for 3 min before being sealed into
vials and stored at 70°C until use.
Immunocytochemistry. Serial cryostat sections (40 µm) were
cut horizontally from all brains. The first and second sections of each
series of five were collected for staining of IL-1, and adjacent
sections were used for detection of Griffonia simplicifolia B4-isolectin (GSA I-B4) staining as a specific marker of microglia (Streit, 1990).
Briefly, free-floating sections were rinsed for 5 min in 0.4% Triton
X-100 in 50 mM Tris-HCl-buffered saline (TBS) at 4°C followed by 15 min in 20% methanol and 0.6%
H2O2 in Triton X-100-TBS. The slices were then
incubated at 4°C for 90 min in 10% fetal calf serum (FCS) diluted in
0.4% Triton X-100-TBS. The primary antisera were diluted in 0.4%
Triton X-100-TBS containing 4% FCS, and slices were incubated at 4°C
for 72 hr with the primary polyclonal antibody against rat IL-1
(1:500; from Dr. S. Poole, National Institute for Biological Standards
and Control, Potters Bar, Hertsfordshire, UK). This antibody
recognizes both the pro-IL-1 and the mature proteins as assessed by
Western blot (S. Pool, personal communication), and its
cross-reactivity and specificity have been previously characterized in
detail (Bristow et al., 1991; Garabedian et al., 1995). After three 5 min washes in TBS, immunoreactivity was tested by the
avidin-biotin-peroxidase technique (Vectastain ABC kit; Vector
Laboratories, Burlingame, CA). The sections were then reacted by
incubation with 0.4 mM 3'-3'-diaminobenzidine (DAB; Sigma, Munich, Germany) in 50 mM Tris-HCl-buffered saline, pH 7.4, and 0.01% H2O2. After DAB incubation, three 5 min washes were done with TBS, and then the slices were mounted onto
gelatin-coated slides and dried overnight at room temperature. They
were dehydrated and coverslipped the next day.
Control slices were prepared using the primary antisera preadsorbed
with (hr)IL-1 (1 µM, 24 hr, 4°C) and by incubating the slices without the primary antisera.
For assessing microglia, the method described by Streit (1990) was
followed. Briefly the sections were immersed in PBS, pH 7.4, for 10 min. Slices were then incubated overnight at 4°C with GSA I-B4
isolectin coupled to HRP (10 µg/ml, Sigma) in PBS containing 0.1%
Triton X-100, 0.1 mM CaCl2, 0.1 mM MgCl2, and 0.1 mM
MnCl2. After the overnight incubation, the slices were
washed three times for 5 min in PBS before a reaction with DAB, which
allows the lectin binding sites to be visualized.
Sections were taken at comparable anteroposterior and mediolateral
levels in controls and epileptic rats. Nissl staining was performed
with cresyl violet (Paxinos and Watson, 1986) in representative sections of controls and epileptic rats and in a distinct group of rats
(n = 3-4) killed 1 week after convulsant injection to assess neurodegeneration.
ELISA. To quantify the increase in IL-1 depicted by
immunocytochemistry, different groups of rats were intrahippocampally injected with 0.19 nmol of kainate (n = 5) or 0.77 nmol
of bicuculline methiodide (n = 8) as previously described.
Twenty four hours after injection, the rats and their controls
(implanted with electrodes but injected with 0.5 µl of vehicle; n = 6-8) were killed by decapitation, and their
hippocampi were rapidly dissected out at 4°C and frozen on dry ice.
Brain tissue was weighted and homogenized in ice-cold PBS (5 gm/ml)
using a Potter homogenizer (1000 rpm, 10 strokes). The homogenates were centrifuged for 10 min (5000 rpm, 4°C). One hundred microliters of
the supernatant were taken in duplicate to measure IL-1.
IL-1 was measured in the hippocampus by a two-site ELISA using an
antibody selective against rat IL-1 (the same used for immunocytochemistry) as previously described (De Luigi et al., 1998).
Absorbance was read at 405 nm. The detection limit was 3.9 pg/ml.
Statistical analysis of data. Data are the means ± SE
(n = number of animals). The effects of treatments were
analyzed by one-way or two-way ANOVA followed by Tukey's test for
unconfounded means or by Student's t test.
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RESULTS |
Seizure-enhanced immunoreactivity of IL-1 in the rat
hippocampus: comparison with activated microglia
Figures 2 and 3 depict the pattern
of IL-1 immunoreactivity in various areas of the injected dorsal
hippocampus 3 hr after kainic acid. IL-1 staining in control
sections (from rats receiving 0.5 µl of PBS) was diffused and barely
detectable in glia-like cells throughout the dentate gyrus (Fig.
2A), CA1 (Fig.
3A), and CA3 (Fig.
3E) areas. Scattered, faintly stained neurons were observed in control sections of CA3 area (Fig. 3E) and in the granule
cell layer (Fig. 4A).
Seizures enhanced IL-1 immunoreactivity in all regions. Strongly
immunoreactive glia-like cells were observed in the granule cells layer
and in the hilus (Fig. 2C,E) as well as interposed between
pyramidal neurons in CA1 (Fig. 3C) and CA3 (Fig.
3G) areas.
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Figure 2.
Photomicrographs showing IL-1 immunoreactivity
(A, C, E) and B4-isolectin-positive microglia (B,
D, F) in coronal sections of the rat dorsal hippocampus
3 hr after a local injection of PBS saline (A, B) or
0.19 nmol of kainic acid (C-F). E,
F, Higher magnifications of pictures respectively depicted in
C and D. IL-1 immunoreactivity was
markedly increased in glia-like cells located in the granule cell layer
and in the molecular layer (ml) of the dentate
gyrus (arrowheads). These cells have a darkly stained
cell body and branched processes, and some of them have an ameboid
shape resembling microglia phenotype (E).
Scattered cells with neuronal appearance were also observed (E,
arrow). B4-isolectin-positive microglia was also increased in
the same regions (D, F). Note that microglia
cells and their processes were interposed between granule cells
(gc) and CA3 pyramidal neurons in the hilus
(h). Scale bars: A-D, 500 µm;
E, F, 200 µm.
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Figure 3.
High-magnification photomicrographs showing
IL-1 immunoreactivity (A, C, E, G) and
B4-isolectin-positive microglia (B, D, F, H) in
coronal sections of the CA1 (A-D) and CA3
(E-H) areas of the rat dorsal hippocampus 3 hr
after a local injection of PBS (A, B, E, F) or
0.19 nmol of kainic acid (C, D, G, H).
IL-1-positive neurons were lightly stained in CA3 pyramidal layer
and stratum oriens (so) and lucidum
(sl) in control sections (E,
arrows). IL-1 immunoreactivity and B4-isolectin
positive-microglia (round-shaped cells as well as cells with ramified
processes) were enhanced in pyramidal layer (CA1, CA3),
stratum oriens and radiatum (sr) of CA1 and CA3 areas,
and stratum lucidum CA3 (C, D, G, H, arrowheads).
f, Fissura hippocampi. Scale bar, 200 µm.
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Figure 4.
High-magnification photomicrographs showing
IL-1 immunoreactivity (A, C) and
B4-isolectin-positive microglia (B, D) in coronal
sections of the rat dorsal hippocampus 24 hr after a local injection of
PBS (A, B) or 0.19 nmol of kainic acid (C,
D). Note the diffuse pattern of enhanced IL-1
immunoreactivity in glia-like cells (C) and the
widespread staining of B4-isolectin-positive microglia
(D). Scattered IL-1 immunoreactive neurons
were also observed (A, C, arrows). gc,
Granule cells; f, fissura hippocampi;
CA1, CA1 pyramidal layer; slm, Stratum
lacunosum moleculare. Scale bar, 200 µm.
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Activated microglia as defined by an ameboid shape and lectin-positive
staining was similarly increased in adjacent sections (Figs.
2D,F, 3D,H). A few round-shaped,
darkly stained cells resembling phagocytic cells were observed in the
dentate gyrus and CA3 area (Figs. 2F,
3H).
Figure 4 depicts the patterns of IL-1 staining (Fig.
4A,C) and that of activated microglia (Fig.
4B,D) 24 hr after kainic acid in the injected
hippocampus. IL-1-immunoreactive cells and microglia staining were
enhanced in the various hippocampal areas with a more diffuse pattern
compared with the clusters of heavily stained IL-1-positive cells
and microglia found 3 hr after seizures.
Similar changes were found in the temporal pole of the injected
hippocampus. A small increase in IL-1 and microglia staining restricted to stratum radiatum CA3 was observed in the contralateral hippocampus at both time points (results not shown).
Nissl staining of coronal sections from rats killed 1 week after
kainate-induced seizures showed the typical pyramidal cell loss
restricted to CA3 area as previously reported (Vezzani et al., 1991)
(Fig. 5).
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Figure 5.
Nissl staining of coronal sections of the dorsal
hippocampus of a representative rat 1 week after the injection of PBS
(A) or 0.19 nmol of kainic acid
(B). Note the loss of CA3 neurons (B,
arrows) that was restricted to the injected dorsal hippocampus.
Scale bar, 200 µm.
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Rats were injected intrahippocampally with a previously described
nonlesional convulsant dose of bicuculline methiodide (Turski et al.,
1985) to investigate whether seizures per se, in the absence of cell
injury, induced IL-1 and microglia in the hippocampus. Nissl
staining performed in coronal brain sections of rats killed 1 week
after bicuculline-induced seizures (n = 4) confirmed
the lack of neurodegeneration. Thus, the injected and contralateral hippocampi did not differ from vehicle-injected rats as assessed by
light microscopic analysis (results not shown).
Figures 6 and
7 show the pattern of IL-1
immunoreactivity and activated microglia in the dentate gyrus (Fig.
6A-D) and hippocampus proper (Fig.
7A-H) 3 hr after bicuculline injection. IL-1
immunoreactivity was enhanced in all hippocampal subfields compared
with vehicle-injected rats, although to a less extent in CA1 and CA3
areas than in kainate-treated rats. Thus, few strongly immunoreactive
glial cells were present in CA1 after bicuculline (compare Figs.
7C, 3C). Darkly stained IL-1-positive cells
were absent in CA3, whereas a diffused pattern of faintly stained cells
was observed there (compare Figs. 7G, 3G). The
changes detected after bicuculline were more pronounced in the injected
hippocampus, although they also occurred in the contralateral site and
in the temporal poles as observed after kainate injection (results not
shown). Twenty four hours after bicuculline-induced seizures, IL-1
immunoreactivity was very similar to that in vehicle-injected rats, as
confirmed by measuring its tissue concentration by ELISA (see
below).
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Figure 6.
Photomicrographs showing IL-1 immunoreactivity
(A, C) and B4-isolectin-positive microglia (B,
D) in coronal sections of the rat dorsal hippocampus 3 hr after
a local injection of 12.5% PEG (A, B) or 0.77 nmol of
bicuculline methiodide (C, D). IL-1 immunoreactivity
was markedly increased in glia-like cells located in the granule cell
layer and in the molecular layer (ml) of the
dentate gyrus (arrowheads). These cells have a darkly
stained cell body and branched processes. Some of these cells were in
close proximity to granule cells (gc) and
interposed between CA3c neurons in the hilus (h;
C, arrowheads). B4-isolectin-positive microglia was
increased in the same regions (D). Scale bar, 200 µm.
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Figure 7.
High-magnification photomicrographs showing
IL-1 immunoreactivity (A, C, E, G) and
B4-isolectin-positive microglia (B, D, F, H) in
coronal sections of the CA1 (A-D) and CA3
(E-H) areas of the rat dorsal hippocampus 3 hr
after a local injection of 12.5% PEG (A, B, E,
F) or 0.77 nmol of bicuculline methiodide in PEG
(C, D, G, H). IL-1 immunoreactivity was
enhanced in darkly stained cells with ramified processes in stratum
radiatum (sr) of CA1 pyramidal layer (C,
arrowheads). A diffuse pattern of lightly stained cells was
observed in CA3 (G, arrowheads). B4-isolectin-positive
microglia was enhanced in stratum radiatum (sr) CA1
(D, arrowheads) and in stratum lucidum
(sl) CA3 (H, arrowheads).
Microglia processes were interposed between pyramidal cells in CA3.
f, Fissura hippocampi; so, stratum
oriens. Scale bar, 200 µm.
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The pattern of activated microglia after bicuculline was similar to
that observed after kainate, although cells were less intensively
stained in all hippocampal subfields (Figs. 6B,D
7B,D,F,H).
ELISA
Using ELISA, an average 16-fold increase in IL-1 concentration
was measured in the injected hippocampus 24 hr after kainic acid
compared with PBS-injected rats [pg/mg wet weight tissue: PBS,
1.55 ± 0.15 (n = 6); kainate, 24.2 ± 8.4*
(n = 5); *p < 0.01 by Student's
t test]. In accordance with the immunocytochemical evidence, a small increase (30%) was also measured in the hippocampus contralateral to the injected site (2.64 ± 1.0 pg/mg), although this effect was not statistically significant.
Twenty four hours after bicuculline, no significant differences were
found in the injected [pg/mg wet weight tissue: PEG, 1.8 ± 0.5 (n = 8); bicuculline, 2.9 ± 1.2] or
contralateral hippocampus (bicuculline, 1.24 ± 0.3 pg/mg).
Effect of IL-1 and/or IL-1Ra on kainic acid-induced
EEG seizures
Figure 8 shows the effect of 0.1 and
1.0 ng of (hr)IL-1 and/or 1.0 µg of IL-1Ra on EEG seizure activity
induced by 0.19 nmol of kainic acid in rats. The intrahippocampal
injection of 0.1 ng of (hr)IL1- 10 min before kainate was
ineffective on seizure parameters, whereas 1.0 ng of (hr)IL-1
increased by 2.3-fold on average the time spent in kainate seizures
(p < 0.01, one-way ANOVA followed by Tukey's
test), and this effect was similar to that observed after 10 ng of
(hr)IL-1 (data not shown). Interictal activity consisting of
high-frequency spiking synchronized in both hippocampi was observed in
the second hour of EEG recording after (hr)IL-1 plus kainic acid.
(hr)IL-1 did not significantly modify the time to onset of seizures
(10.8 ± 1.4 min; n = 21) and the number of
seizures (15.0 ± 1.0). Heat-inactivated (hr)IL-1 up to 1 ng
did not modify seizures (n = 10).
View larger version (28K):
[in this window]
[in a new window]
|
Figure 8.
Bar graph showing the effect of IL-1 and/or
IL-1Ra on the time spent in EEG seizures in rats treated with kainic
acid. Control (n = 21) represents rats receiving
0.5 µl of PBS 10 min before 0.19 nmol in 0.5 µl of kainic acid.
(hr)IL-1 (n = 10) was heat-inactivated by
boiling the solution for 15 min. Drugs were unilaterally injected in
the hippocampus in 0.5 µl alone (n = 7-11) or in
combination (n = 9) 10 min before kainic acid.
Seizure activity was recorded in freely moving rats for 3 hr from drug
injection. aF(1,51) = 8.6;
p < 0.01 by two-way ANOVA followed by Tukey's
test for uncounfounded means; *p < 0.01 versus
control; °p < 0.01 versus heat-inactivated
IL-1.
|
|
To assess whether the effect of IL-1 on seizures was
receptor-mediated, we injected the animals with 1 µg of (hr)IL-1Ra
(Eisenberg et al., 1990). It has been previously reported that doses of
IL-1Ra 102- to 103-fold higher
than those of IL-1 are needed to block the functional effects of
this cytokine (Arend et al., 1990). This likely depends on the fact
that only a few IL-1 receptors need to be stimulated to trigger a
biological response; thus high levels of IL-1Ra are necessary for
blocking unoccupied receptors (Rothwell, 1991). (hr)IL-1Ra per se
(n = 8) did not affect the baseline EEG pattern but
when co-injected with 1 ng of (hr)IL-1 blocked the proconvulsant effect of this cytokine (n = 8). Thus, the 2.3-fold
increase in the total time in seizures induced by 1.0 ng of (hr)IL-1
was abolished in the presence of the antagonist
(F(1,51) = 8.6; p < 0.01, two-way ANOVA) (Fig. 6). Heat-inactivated (hr)IL-1Ra did not modify the
effect of 1 ng of (hr)IL-1 on kainate seizures (data not shown).
Effect of (R)-CPP on the proconvulsant effect
of IL-1
Table 1 shows the effect of
(R)-CPP on the proconvulsant action of (hr)IL-1 on
kainate seizures (n = 7). (R)-CPP at
0.1 ng, a dose previously shown to block NMDA-induced behavioral
seizures in rodents (Davies et al., 1986), co-administered with
1 ng of IL-1 abolished the twofold increase induced by this cytokine in the total time spent in kainate seizures (n = 9;
F(1,30) = 7.6; p < 0.01 by
two-way ANOVA) without having an effect per se (n = 8).
The onset time to seizures and the total number of seizures measured in
rats treated with kainic acid (n = 26) were not
significantly modified by 1 ng of (hr)IL-1 (n = 8)
and/or 0.1 ng of (R)-CPP. Selective blockade of NMDA
receptors by (R)-CPP did not affect EEG seizures
induced by kainic acid per se, as previously reported (Lason et al.,
1988; Clifford et al., 1990).
View this table:
[in this window]
[in a new window]
|
Table 1.
Effect of (R)-CPP on the IL-1-induced
potentiation of seizure activity caused by 0.19 nmol of kainic acid
injected in the rat hippocampus
|
|
| |
DISCUSSION |
In the present study, we provide direct evidence that focal
intrahippocampal application of kainic acid in rats inducing EEG seizures and CA3 neuronal damage is associated with a rapid increase in
the levels of IL-1 in the hippocampus presumably in activated microglia cells.
The early induction of IL-1 induced by kainate injection is in
accordance with the rapid upregulation of its mRNA after
seizure-producing agents (Minami et al., 1990, 1991; Yabuuchi et al.,
1993) and with previous evidence showing that the mature form of
IL-1 increases as early as 4 hr after intracerebral injection of
NMDA in newborn rats (Hagan et al., 1996).
The finding that IL-1 immunoreactivity is enhanced in glial cells
resembling activated microglia agrees with the evidence that IL-1
mRNA expression induced by systemic kainic acid is localized in glial
cells not expressing glial fibrillary acidic protein, a selective
marker of astrocytes (Yabuuchi et al., 1993). In addition, recent
studies by Andersson et al. (1991) and Taniwaki et al. (1996) have
shown that kainate administration activates microglia in brain
structures involved in the propagation pathways of hippocampal seizures
and closely associated with seizure-induced neuronal damage.
Using bicuculline as a nonlesional model of seizures, we found that
both IL-1 and microglia were enhanced in the hippocampus. These
changes were induced to a lesser extent and for a shorter duration than
after kainate, although the time spent in EEG epileptic activity after
bicuculline was longer.
These findings show that direct stimulation of the kainate-type of
glutamate receptors is not a prerequisite for increasing IL-1 in
glia and that seizure activity per se is sufficient to trigger this
effect. Thus, we found no histological evidence of neuronal cells loss
in the hippocampus after the relatively low convulsant dose of
bicuculline we have used (also see Turski et al., 1985).
The contribution of neuronal cell injury in CA3 pyramidal layer to the
enhanced cytokine response to kainate cannot be solved in the present
study. However, various evidence suggests that degenerating neurons
represent a strong signal for IL-1 induction (Rothwell, 1991), and
microglial cells are known to be rapidly activated in response to even
minor pathological changes in CNS (Kreutzberg, 1996).
The widespread pattern of increased IL-1 immunoreactivity observed
after focal injection of kainate may depend on different factors or by
their concerted action: i.e., it is known that IL-1 induces its own
synthesis (Dinarello et al., 1987), and this positive feedback loop may
contribute to enhance and extend the IL-1 response; mild inflammatory
or edemic responses may occur in distant sites because of their direct
connections to the injured hippocampus and may trigger IL-1
production; the propagation of epileptic activity from its site of
onset to synaptically connected tissue (i.e., the contralateral site
and the temporal pole of the hippocampus) may trigger IL-1
production per se, as suggested by our findings after bicuculline seizures.
The mechanisms by which seizure activity per se may induce IL-1 in
the resident glial cells are unknown. Protein extravasation in the
brain parenchima caused by blood-brain barrier breakdown during
seizures (Nitsch et al., 1986) and/or ionic changes induced by seizures
in the extracellular environment and in glial cells (Barres, 1991) may
prime glia to synthesize higher amounts of cytokines.
In an attempt to address the functional role of this inflammatory
cytokine in seizures, we found that exogenously applied (hr)IL-1
enhanced EEG seizure activity induced by kainic acid in a
dose-dependent and receptor-mediated manner. EEG seizures induced by
focal kainate injection were not associated with behavioral convulsions, and the increase in focal EEG seizure duration induced by
IL-1 had no impact on rat behavior.
The action of IL-1 involves an increase in or facilitation of
glutamatergic function through the NMDA receptors, because the
enhancing effect on seizures was blocked by a selective NMDA receptor
antagonist. Blockade of IL-1 effect by IL-1Ra or
(R)-CPP excludes that this cytokine affects seizures
by merely delaying kainic acid elimination from the tissue.
The lack of effect of IL-1 on the onset time to seizures may be
related to its inability to interfere with the mechanisms involved in
seizure induction (Westbrook and Lothman, 1983), although it is
specifically effective on the events that are crucial for seizure
maintenance. In this respect, the evidence that IL-1 increases
extracellular glutamate availability (Ye and Sontheimer, 1996;
Mascarucci et al., 1998) and interacts with NMDA receptor function (as
shown by our pharmacological findings) is consistent with its effect of
prolonging the time spent in seizures. Thus, both synaptic and
intrinsic conductance properties of neurons are known to be involved in
sustaining synchronized afterdischarges in the hippocampus
(Traub et al., 1993). The specific effect of IL-1 on the duration of
seizures conforms our previous evidence showing that the onset, number,
and duration of EEG seizures can be independently affected by drugs
(Vezzani et al., 1986, 1991; Gariboldi et al., 1998).
These results are apparently at variance with the electrophysiological
evidence showing that IL-1 has inhibitory effects on long-term
potentiation (Katsuki et al., 1990; Bellinger et al., 1993; Cunningham
et al., 1996; Coogan and O'Connor, 1997), and it augments the
GABA-mediated increase in chloride permeability in cortical
synaptoneurosomes (Miller et al., 1991). However, in vitro
and in vivo evidence suggests that the effects of
IL-1 on neurons depend on several factors, including the functional state of the neurons (healthy or injured), the timing of cytokine release, the duration of tissue exposure, and the concentration of the
cytokine (Rothwell and Hopkins, 1995). In particular, relatively low
amounts of IL-1 (picomolar or low nanomolar range) inhibit neuronal
activity and support neuronal survival (Rothwell, 1991; Morganti-Kossmann et al., 1992), whereas concentrations of IL-1 similar to those used in the present study or higher have deleterious effects on neuron viability (Rothwell, 1991; Morganti-Kossmann et al.,
1992). Interestingly, the functional effects of IL-1 also depend on
the brain region examined. Thus, the ability of this cytokine to modify
excitotoxic brain damage in rats differs between striatum and cortex
(Lawrence et al., 1998), and even relatively low doses of IL-1 (0.5 nM) consistently decrease synaptic inhibition by ~30% in
CA3 pyramidal cells (Zeise et al., 1997).
With regard to the mechanism involved in the facilitation of
glutamatergic neurotransmission that appears to mediate the enhancing effect of IL-1 on kainate-induced EEG seizures, it remains to be
established whether this is secondary to an altered pattern of neuronal
damage (i.e., kainate seizures may be prolonged by IL-1 promoting
damage, which results in higher glutamate release). In this respect,
exogenously applied IL-1 exacerbates excitotoxic neuronal damage and
edema induced by ischemia (Yamasaki et al., 1995; Loddick and Rothwell,
1996) as well as the neurodegeneration induced in the cortex by
activation of the NMDA and AMPA subtypes of glutamate receptors
(Lawrence et al., 1998).
IL-1, however, may increase glutamate neurotransmission also by
mechanisms independent of neuronal cell injury. Thus, IL-1 markedly
attenuates astrocytic glutamate uptake (Ye and Sontheimer, 1996). This
effect may enhance the extracellular glutamate concentration and may
synergize with the increased glutamate release induced by kainate
(Ferkany and Coyle, 1983; Young et al., 1988). IL-1 may also
directly enhance NMDA receptor function, because IL-1 receptors are
associated with signal transduction pathways (i.e., activation of
Ser-Thr protein kinase (PK), PKA, and PKC and generation of nitric
oxide), which are known to affect the response of NMDA receptors to
endogenous ligands (Hewett et al., 1994; Hollman and Heinemann, 1994;
Schobitz et al., 1994).
Finally, the effect of IL-1 may involve other cytokines as well.
Thus, IL-1 induces the synthesis of IL-6 and TNF- in astrocytes and
microglia (Bartfai and Schultzberg, 1993; Schobitz et al., 1994), and
many actions of IL-1 in CNS are mediated by these cytokines (Rothwell,
1991). IL-6 and TNF-, in turn, have been reported to affect synaptic
transmission (Tancredi et al., 1992; Schobitz et al., 1994; Li et al.,
1997), and mice overexpressing IL-6 and TNF in glia develop both
seizures and neurodegeneration (Campbell et al., 1993; Akassoglou et
al., 1997).
The local administration of 0.1-1 µM (hr)IL-1 in the
rat hippocampus has been shown to increase the body temperature after 2-4 hr of continuous infusion. This increase was 2°C on average above physiological values (Linthorst et al., 1994) and was likely mediated by the hypothalamus, because there are reciprocal connections between the hippocampus and various hypothalamic areas (Amaral and
Witter, 1995). However, it is unlikely that the increase in body
temperature plays a role in the effect of IL-1, because values as
high as 42°C are needed to enhance EEG seizure activity induced by
kainic acid in rats (Liu et al., 1993).
IL-1Ra alone did not affect kainic acid-induced seizures after its
focal application in the hippocampus. Doses of >1 µg could not be
tested in our model because of the limit of solubility of this molecule
in the small volume required by intrahippocampal administration. We
have recent evidence, however, that repeated intraventricular injection
of 0.1 µg of IL-1Ra significantly reduced EEG seizures caused by
intrahippocampal kainate (our unpublished data).
Intraventricular injection of IL-1Ra may block more effectively the
action of endogenously produced IL-1 because of the
widespread pattern of induction of IL-1 not solely restricted to the
site of intrahippocampal IL-1Ra injection. These findings support a functional role of IL-1 endogenously produced after kainate.
IL-1 is known to upregulate the expression of neurotrophic factors such
as nerve growth factor and brain-derived neurotrophic factor (Spranger
et al., 1990; Lapchak et al., 1993) and neuropeptides such as
somatostatin (Scarborough et al., 1989) that are significantly involved in seizure modulation (Schwarzer et al., 1996; Scharfman, 1997). These events, however, require a time window not compatible with
the early action of IL-1 in our models of acute seizures. They may
represent long-term effects of this cytokine and possibly play a
functional role in the chronic changes in neurotransmission induced in
brain tissue by an acute epileptic event (M. G. De Simoni, C. Perego, T. Ravizza, D. Moneta, M. Conti, S. Garattini, and A. Vezzani, unpublished results).
Thus, convulsant and/or excitotoxic stimuli increase the production of
IL-1 in microglia-like cells in the hippocampus. In addition, our
pharmacological findings indicate that IL-1 enhances focal
electrographic seizures induced by kainate through an increase in
glutamatergic neurotransmission. Increased production of IL-1 has been
shown in human temporal lobe epilepsy (Sheng et al., 1994), thus
suggesting that this cytokine may play a role in the neuropathology of
the epileptic tissue.
| |
FOOTNOTES |
Received July 31, 1998; revised Feb. 25, 1999; accepted March 22, 1999.
This work was supported by Telethon Grant E.573. Rat IL-1 ELISA
reagents and rat IL-1 antibody were kindly provided by Dr. S. Poole.
(hr)IL-1 and (hr)IL-1Ra were kindly provided by Dr. Diana
Boraschi. We are grateful to Dr. R. Samanin for kindly revising this manuscript and to Andrea Borroni and Carlo Perego for their contribution to part of this study.
Correspondence should be addressed to Dr. Annamaria Vezzani, Laboratory
of Experimental Neurology, Istituto di Ricerche Farmacologiche "Mario
Negri," Via Eritrea 62, 20157 Milan, Italy.
| |
REFERENCES |
-
Akassoglou K,
Probert L,
Kontogeorgos G,
Kollias G
(1997)
Astrocyte-specific but not neuron-specific transmembrane TNF triggers inflammation and degeneration in the central nervous system of transgenic mice.
J Immunol
158:438-445[Abstract].
-
Amaral DG,
Witter MP
(1995)
Hippocampal formation.
In: Hippocampus (Paxinos G,
ed), pp 443-493. San Diego: Academic.
-
Andersson PB,
Perry VH,
Gordon S
(1991)
The kinetics and morphological characteristics of the macrophage-microglial response to kainic acid-induced neuronal degeneration.
Neuroscience
42:201-214[Web of Science][Medline].
-
Arend WP,
Welgus HG,
Thompson RC,
Eisenberg SP
(1990)
Biological properties of recombinant human monocyte-derived interleukin-1 receptor antagonist.
J Clin Invest
85:580-583.
-
Ban E,
Milon G,
Fillion G,
Haour F
(1991)
Receptors for interleukin-1 ( and ) in mouse brain: mapping and neuronal localization in hippocampus.
Neuroscience
43:21-30[Web of Science][Medline].
-
Barres BA
(1991)
New roles for glia.
J Neurosci
11:3685-3694[Web of Science][Medline].
-
Bartfai T,
Schultzberg M
(1993)
Cytokines in neuronal cell types.
Neurochem Int
22:435-444[Web of Science][Medline].
-
Bellinger FP,
Madamba S,
Siggins GR
(1993)
Interleukin 1 inhibits synaptic strength and long-term potentiation in the rat CA1 hippocampus.
Brain Res
628:227-234[Web of Science][Medline].
-
Benveniste EN
(1992)
Inflammatory cytokines within the central nervous system: sources, function and mechanism of action.
Am J Physiol
263:C1-C16[Abstract/Free Full Text].
-
Bristow AF,
Mosley K,
Poole S
(1991)
Interleukin-1 production in vivo and in vitro in rats and mice measured using specific immunoradiometric assays.
J Mol Endocrinol
7:1-7[Abstract/Free Full Text].
-
Campbell IL,
Abraham CR,
Masliah E,
Kemper P,
Inglis JD,
Oldstone MBA,
Mucke L
(1993)
Neurological disease induced in transgenic mice by cerebral overexpression of interleukin 6.
Proc Natl Acad Sci USA
90:10061-10065[Abstract/Free Full Text].
-
Clifford DB,
Olney JW,
Benz AM,
Fuller TA,
Zorumski CF
(1990)
Ketamine, phencyclidine and MK-801 protect against kainic acid-induced seizure-related brain damage.
Epilepsia
31:382-390[Web of Science][Medline].
-
Coogan A,
O'Connor JJ
(1997)
Inhibition of NMDA receptor-mediated synaptic transmission in the rat dentate gyrus in vitro by IL-1.
NeuroReport
8:2107-2110[Web of Science][Medline].
-
Cunningham AJ,
Murray CA,
O'Neill LAJ,
Lynch MA,
O'Connor JJ
(1996)
Interleukin-1 (IL-1) and tumor necrosis factor (TNF) inhibit long-term potentiation in the rat dentate gyrus in vitro.
Neurosci Lett
203:17-20[Web of Science][Medline].
-
Curtis DR,
Duggan AW,
Felix D,
Johnston GA
(1970)
GABA, bicuculline and central inhibition.
Nature
226:1222-1224[Medline].
-
D'Arcangelo G,
Dodt H,
Zieglgansberger W
(1997)
Reduction of excitation by interleukin-1 in rat neocortical slices visualized using infrared-darkfield video microscopy.
NeuroReport
8:2079-2083[Web of Science][Medline].
-
Davies J,
Evans RH,
Herrling PL,
Jones AW,
Olverman HJ,
Pook P,
Watkins JC
(1986)
CPP, a new potent NMDA antagonist. Depression of central neuron responses, affinity for (3H)D-AP5 binding sites on brain membranes and anticonvulsant activity.
Brain Res
382:169-173[Web of Science][Medline].
-
de Bock F,
Dornand J,
Rondouin G
(1996)
Release of TNF in the rat hippocampus following epileptic seizures and excitotoxic neuronal damage.
NeuroReport
7:1125-1129[Web of Science][Medline].
-
De Luigi A,
Terreni L,
Sironi M,
De Simoni MG
(1998)
The sympathetic nervous system tonically inhibits peripheral IL-1 and IL-6 induction by central lipopolysaccharide.
Neuroscience
83:1245-1250[Web of Science][Medline].
-
De Simoni MG,
Imeri L
(1998)
Cytokine-neurotrasmitter interactions in the brain.
Biol Signals
7:33-44[Web of Science][Medline].
-
Dinarello CA,
Ikejima T,
Warner SJ,
Orencole SF,
Lonnemann G,
Cannon JG,
Libby P
(1987)
Interleukin-1. I. Induction of circulating interleukin-1 in rabbits in vivo and in human mononuclear cells in vitro.
J Immunol
139:1902-1906[Abstract].
-
Eisenberg SP,
Evans RJ,
Arend WP,
Verber E,
Brewer MT,
Hannun CH,
Thompson RC
(1990)
Primary structure and functional expression from complementary DNA of a human interleukin-1 receptor antagonist.
Nature
343:341-346[Medline].
-
Eriksson C,
Winblad B,
Schltzberg M
(1998)
Kainic acid induced expression of interleukin-1 receptor antagonist mRNA in the rat brain.
Mol Brain Res
58:195-208[Medline].
-
Ferkany J,
Coyle JT
(1983)
Kainic acid selectively stimulates the release of endogenous excitatory acidic amino acids.
J Pharmacol Exp Ther
225:399-406[Abstract/Free Full Text].
-
Garabedian BS,
Poole S,
Allchorne A,
Winter J,
Woolf C
(1995)
Contribution of interleukin-1 to the inflammation-induced increase in nerve growth factor levels and inflammatory hyperalgesia.
Br J Pharmacol
115:1265-1275[Web of Science][Medline].
-
Gariboldi M,
Conti M,
Cavaleri D,
Samanin R,
Vezzani A
(1998)
Anticonvulsant properties of BIBP 3226, a non-peptide selective antagonist at neuropeptide Y Y-1 receptors.
Eur J Neurosci
10:757-759[Web of Science][Medline].
-
Giulian D,
Baker TJ,
Shih LC,
Lachman LB
(1986)
Interleukin-1 in the central nervous system is produced by ameboid microglia.
J Exp Med
164:594-604[Abstract/Free Full Text].
-
Hagan P,
Poole S,
Bristow AF,
Tilders F,
Siverstein FS
(1996)
Intracerebral NMDA injection stimulates production of interleukin-1 in perinatal rat brain.
J Neurochem
67:2215-2218[Web of Science][Medline].
-
Hewett SJ,
Csernansky CA,
Choi DW
(1994)
Selective potentiation of NMDA-induced neuronal injury following induction of astrocytic iNOS.
Neuron
13:487-494[Web of Science][Medline].
-
Hollmann M,
Heinemann S
(1994)
Cloned glutamate receptors.
In: Annual review of neuroscience (Cowan MW,
Shooter EM,
Stevens CF,
Thompson RF,
eds), pp 31-108. Palo Alto, CA: Annal Reviews.
-
Hopkins SJ,
Rothwell NJ
(1995)
Cytokine and the nervous system I: expression and recognition.
Trends Neurosci
18:83-88[Web of Science][Medline].
-
Katsuki H,
Nakai S,
Hirai Y,
Akaji K,
Kiso Y,
Satoh M
(1990)
Interleukin-1 inhibits long-term potentiation in the CA3 region of mouse hippocampal slices.
Eur J Pharmacol
181:323-326[Web of Science][Medline].
-
Kreutzberg GW
(1996)
Microglia: a sensor for pathological events in the CNS.
Trends Neurosci
19:312-318[Web of Science][Medline].
-
Lapchak PA,
Araujo DM,
Hefti F
(1993)
Systemic interleukin-1 decreases brain-derived neurotrophic factor messenger RNA expression in the rat hippocampal formation.
Neuroscience
53:297-301[Web of Science][Medline].
-
Lason W,
Simpson JN,
McGinty JF
(1988)
Effects of D-()-aminophosphonovalerate on behavioral and histological changes induced by systemic kainic acid.
Neurosci Lett
87:23-28[Web of Science][Medline].
-
Lawrence CB,
Allan SM,
Rothwell NJ
(1998)
Interleukin-1 and the interleukin-1 receptor antagonist act in the striatum to modify excitotoxic brain damage in the rat.
Eur J Neurosci
10:1188-1195[Web of Science][Medline].
-
Li A-J,
Katafuchi T,
Oda S,
Hori T,
Oomura Y
(1997)
Interleukin-6 inhibits long-term potentiation in rat hippocampal slices.
Brain Res
748:30-38[Web of Science][Medline].
-
Linthorst ACE,
Flachskam C,
Holsboer F,
Reul JMHM
(1994)
Local administration of recombinant human interleukin-1 in the rat hippocampus increases serotonergic neurotransmission, hypothalamic-pituitary-adrenocortical axis activity, and body temperature.
Endocrinology
135:520-532[Abstract].
-
Liu Z,
Gatt A,
Mikati M,
Holmes GL
(1993)
Effect of temperature on kainic acid-induced seizures.
Brain Res
631:51-58[Web of Science][Medline].
-
Loddick SA,
Rothwell NJ
(1996)
Neuroprotective effects of human recombinant interleukin-1 receptor antagonist in focal cerebral ischaemia in the rat.
J Cereb Blood Flow Metab
16:932-940[Web of Science][Medline].
-
Mascarucci P,
Perego C,
Terrazzino S,
De Simoni MG
(1998)
Glutamate release in the nucleus tractus solitarius induced by peripheral lipopolysaccharide and interleukin-1.
Neuroscience
86:1285-1290[Web of Science][Medline].
-
Miller LG,
Galpern WR,
Dunlap K,
Dinarello CA,
Turner TJ
(1991)
Interleukin-1 augments
 -aminobutyric acid receptor function in brain.
Mol Pharmacol
39:105-108[Abstract]. -
Minami M,
Kuraishi Y,
Yamaguchi T,
Nakai S,
Hirai Y,
Satoh M
(1990)
Convulsants induce interleukin-1 messenger RNA in rat brain.
Biochem Biophys Res Commun
171:823-827.
-
Minami M,
Kuraishi Y,
Satoh M
(1991)
Effects of kainic acid on messenger RNA levels of IL-1, IL-6, TNF, and Lif in the rat brain.
Biochem Biophys Res Commun
176:593-598[Web of Science][Medline].
-
Morganti-Kossmann MC,
Kossmann T,
Wahl SM
(1992)
Cytokines and neuropathology.
Trends Pharmacol Sci
131:286-290.
-
Nishiyori A,
Minami M,
Takami S,
Satoh M
(1997)
Type 2 interleukin-1 receptor mRNA is induced by kainic acid in the rat brain.
Mol Brain Res
50:237-245[Medline].
-
Nitsch C,
Goping G,
Klatzo I
(1986)
Pathophysiological aspects of blood-brain barrier permeability in epilectic seizures.
Adv Exp Med Biol
203:175-189[Medline].
-
Paxinos G,
Watson C
(1986)
In: The rat stereotaxic atlas. New York: Academic.
-
Plata-Salamàn CR,
ffrench-Mullen JMH
(1992)
Interleukin-1 depresses calcium currents in CA1 hippocampal neurons at pathophysiological concentrations.
Brain Res Bull
29:221-223[Web of Science][Medline].
-
Rothwell NJ
(1991)
Functions and mechanism of interleukin-1 in the brain.
Trends Pharmacol Sci
12:430-436[Medline].
-
Rothwell NJ,
Hopkins SJ
(1995)
Cytokines and the nervous system II: actions and mechanisms of action.
Trends Neurosci
18:130-136[Web of Science][Medline].
-
Scarborough DE,
Lee SL,
Dinarello CA,
Reichlin S
(1989)
Interleukin1 stimulates somatostatin biosynthesis in primary cultures of fetal rat brain.
Endocrinology
124:549-551[Abstract/Free Full Text].
-
Scharfman HE
(1997)
Hyperexcitability in combined entorhinal/hippocampal slices of adult rat after exposure to brain-derived neurotrophic factor.
J Neurophysiol
78:1082-1095[Abstract/Free Full Text].
-
Schobitz B,
De Kloet ER,
Holsboer F
(1994)
Gene expression and function of interleukin 6 and tumor necrosis factor in the brain.
Prog Neurobiol
44:397-342[Web of Science][Medline].
-
Schwarzer C,
Sperk G,
Samanin R,
Rizzi M,
Gariboldi M,
Vezzani A
(1996)
Neuropeptides-immunoreactivity and their mRNA expression in kindling: functional implications for limbic epileptogenesis.
Brain Res Rev
22:27-50[Medline].
-
Sheng JG,
Boop FA,
Mrak RE,
Griffin WST
(1994)
Increased neuronal -amyloid precursor protein expression in human temporal lobe epilepsy: association with interleukin-1 immunoreactivity.
J Neurochem
63:1872-1879[Web of Science][Medline].
-
Spranger M,
Lindholm D,
Bandtlow C,
Heumann R,
Gnahn H,
Naher-Noè M,
Thoenen H
(1990)
Regulation of Nerve growth factor (NGF) synthesis in the rat central nervous system: comparison between the effects of interleukin-1 and various growth factors in astrocyte cultures and in vivo.
Eur J Neurosci
2:69-76[Web of Science][Medline].
-
Streit WJ
(1990)
An improved staining method for rat microglial cells using the lectin from Griffonia simplicifolia (GSA I-B4).
J Histochem Cytochem
38:1683-1686[Abstract].
-
Takao T,
Tracey DE,
Mitchell WM,
de Souza EB
(1990)
Interleukin-1 receptors in mouse brain: characterization and neuronal localization.
Endocrinology
127:3070-3078[Abstract/Free Full Text].
-
Tancredi V,
D'Arcangelo G,
Grassi F,
Tarroni P,
Palmieri G,
Santoni A,
Eusebi F
(1992)
Tumor necrosis factor alters synaptic transmission in rat hippocampal slices.
Neurosci Lett
146:176-178[Web of Science][Medline].
-
Taniwaki Y,
Kato M,
Araki T,
Kobayashi T
(1996)
Microglial activation by epilectic activities through the propagation pathway of kainic acid induced hippocampal seizures in the rat.
Neurosci Lett
217:29-32[Web of Science][Medline].
-
Traub RD,
Miles R,
Jefferys JG
(1993)
Synaptic and intrinsic conductances shape picrotoxin-induced synchronized after-discharges in the guinea-pig hippocampal slice.
J Physiol (Lond)
461:525-547[Abstract/Free Full Text].
-
Turski WA,
Cavalheiro EA,
Calderazzo-Filho LS,
Kleinrok Z,
Czuczwar SJ,
Turski L
(1985)
Injections of picrotoxin and bicuculline into the amygdaloid complex of the rat: an electroencephalographic, behavioral and morphological analysis.
Neuroscience
14:37-53[Web of Science][Medline].
-
Vezzani A,
Wu HQ,
Tullii M,
Samanin R
(1986)
Anticonvulsant drugs effective against human temporal lobe epilepsy prevent seizures but not neurotoxicity induced in rats by quinolinic acid: electroencephalographic, behavioral and histological assessments.
J Pharmacol Exp Ther
239:256-262[Abstract/Free Full Text].
-
Vezzani A,
Serafini R,
Stasi MA,
Vigano' G,
Rizzi M,
Samanin R
(1991)
A peptidase-resistant cyclic octapeptide analogue of somatostatin (SMS 201-995) modulates seizures induced by quinolinic and kainic acids differently in the rat hippocampus.
Neuropharmacology
30:345-352[Web of Science][Medline].
-
Watkins JC
(1978)
Excitatory amino acids.
In: Kainic acid as a tool in neurobiology (McGeer EG,
Olney JW,
McGeer PL,
eds), pp 37-69. New York: Raven.
-
Westbrook GL,
Lothman EW
(1983)
Cellular and synaptic basis of kainic acid-induced hippocampal epileptiform activity.
Brain Res
273:97-109[Web of Science][Medline].
-
Yabuuchi K,
Minami M,
Katsumata S,
Satoh M
(1993)
In situ hybridization study of interleukin-1 mRNA induced by kainic acid in the rat brain.
Mol Brain Res
20:153-161[Medline].
-
Yamasaki Y,
Matsuura N,
Shozuhara H,
Onodera H,
Itojama Y,
Kogure K
(1995)
Interleukin-1 as a pathogenetic mediator of ischemic bain damage in rats.
Stroke
26:676-681[Abstract/Free Full Text].
-
Ye Z,
Sontheimer H
(1996)
Cytokine modulation of glial glutamate uptake: a possible involvement of nitric oxide.
NeuroReport
7:2181-2185[Web of Science][Medline].
-
Young AMG,
Crowder JM,
Bradford HF
(1988)
Potentiation by kainate of excitatory amino acid release in striatum: complementary in vivo and in vitro experiments.
J Neurochem
50:337-345[Web of Science][Medline].
-
Zeise ML,
Espinoza J,
Morales P,
Nalli A
(1997)
Interleukin-1 does not increase synaptic inhibition in hippocampal CA3 pyramidal and dentate gyrus granule cells of the rat in vitro.
Brain Res
768:341-344[Web of Science][Medline].
Copyright © 1999 Society for Neuroscience 0270-6474/99/19125054-12$05.00/0
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|
|
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|
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|
|
|
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|
|
|
|
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|
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|
|
|
|
|
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|
|
|
|
|
|
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|
|
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|
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|
|
|
|
|
|
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|
|
|
|
|
|
|
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|
|
|
|
|
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|
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ABSTRACT
INTRODUCTION
