Pediatric State of the Art Symposium
How might febrile status epilepticus lead to TLE? Predisposing factors and mechanisms
Tallie Z. Baram MD, PhD
Prof. Pediatrics, Anatomy / Neurobiology,
Neurology, Physiology/Biophysics
D. Shepard Prof., Neurological Sciences
University of California-Irvine
American Epilepsy Society | Annual Meeting
Disclosure and Thanks
The speaker’s research is supported by NIH grants R37 NS35439; RO1 NS78279 The speaker has no current financial relationships with entities producing, marketing, re-selling, or distributing health care goods or services consumed by, or used on, patients Thanks: Pediatric Content Committee, AES Members of lab ,collaborators and critics. NIH
American Epilepsy Society | Annual Meeting 2012
Learning Objectives
American Epilepsy Society | Annual Meeting 2012
What can we learn from animal models about:
a. The relationship between FSE and TLE Is FSE a marker of, or a contributor to, TLE?
b. Mechanisms of epileptogenesis that follows FSE
c. Biomarkers that predict TLE –Dr McNamara
Temporal Lobe Epilepsy (TLE):
‘Risk factors’:
•Trauma
•Long febrile seizures (FS) / FSE
•Brain infection
30-77% of patients with TLE have a history of early life
seizures, particularly prolonged FS or FSE.
FEBSTAT is prospectively demonstrating consequences
of FSE.
e.g., French, 1993; Cendes 1993, Shinnar 2008, 2012
What is the nature of the relationship
between FSE and TLE?
“Cause”
TLE
Febrile seizures
Febrile status epilepticus TLE
“Cause” TLE Febrile Status epilepticus
All of these scenarios may coexist.
In individual patients, the relative contribution of
*Genetics,
* Other pre-existing pathology
* The FSE itself
may vary.
If FSE contributes directly to the process that
results in TLE
Then, we have an accessible, tractable chance
at intervening after the FSE…
Issues in Human Research
•We cannot induce febrile seizures…
• We cannot control or even recognize all the genetic & acquired
factors that complicate things…
Animal Models
• Standardized and controlled
• Rapid prospective studies
• Mechanisms and intervention
• ‘Controllable’ predisposing factors
Fever cannot be produced in infant rats
Immature rodent model of prolonged (complex) FS
Age appropriate*
Physiological temps
>98% seizure induction
EEG validated
Controlled seizure duration
Little mortality, morbidity
*Age of hippocampal development, Avishai-Eliner, TiNS, 2002
40.3oC
41.2oC
Dubé et al, Ann Neurol, 2005; TiNS 2007; Vezzani & Baram, Nat Rev Neurol, 2011
Fever-related inflammatory mediators contribute
to the generation of experimental febrile seizures
*
IL-1 RI -/- C57BL
n = 26 n = 22
39
40
41
42
43
44 S
eiz
ure
thre
sh
old
(°C
)
IL-1 RI -/- : mice genetically
deficient in IL-1 receptors
C57BL : wild type mice
IL-1 in the Mechanisms of FS generation
Infectious Pyrogens (LPS) Heat source (hairdryer)
Peripheral IL-1 release
Fever Hyperthermia
IL-1 release and action in hippocampus
Seizures
In children In rodent model
Normothermic controls, HT seizures and HT controls.
Animals allowed to mature into young adults
Do Prolonged ‘FS’ Cause ‘TLE’?
Dube et al., Ann Neurol, 2000, Brain 2006, J Neurosci, 2010
• Frank limbic (Temporal Lobe) Epilepsy in 35% of FS rats
• Very mild, short seizures
• Interictal EEG abnormalities in most rats
• Hyper-excitable hippocampus in all
Dubé et al, Brain 2006
Prolonged FS in an animal model may be epileptogenic
Normothermic control
Hyperthermic control
Prolonged FS
100
80
60
40
20
0 Normal EEG
Seizures Interictal
events
(8) (5) (15)
(2) (0) (0) (0) (0)
(6)
% o
f ra
ts
Long febrile seizures, or Febrile Status Epilepticus?
The duration of the febrile seizure governs
severity of the resulting epilepsy
Dube et al, J Neurosci, 2010
20 min 40-60 min 20 min 40-60 min
(~2min 30sec)
FS10
Example of spontaneous seizure provoked
by ‘Febrile Status’
* Onset in hippocampus with rapid propagation to cortex
*
2 sec
Learning Objectives
American Epilepsy Society | Annual Meeting 2012
What can we learn from animal models about:
a. The relationship between FSE and TLE
FSE is a contributor to TLE b. Mechanisms of epileptogenesis that follows FSE
c. Biomarkers that predict TLE
Learning Objectives
American Epilepsy Society | Annual Meeting 2012
What can we learn from animal models about:
a. the relationship between FSE and TLE
FSE: A marker of, or a contributor to, TLE
b. Mechanisms of epileptogenesis that follows FSE
c. Biomarkers that predict TLE
FSE TLE
Cell death
How does FSE promote TLE?
Experimental
febrile seizures
Hyperthermia
no seizures
Toth et al, J Neurosci, 1998
No discernible cell death. Injury to hippocampal neurons
in the distribution of human MTS
Apoptotic neuron
What is the basis of the altered limbic circuit in
TLE that follows FSE?
Altered networks
Loss of neurons
Altered neurons
Altered molecules
Dubé et al, Ann Neurol, 2005; TiNS 2007; Vezzani & Baram, Nat Rev Neurol, 2011
*
IL-1 RI -/- C57BL
n = 26 n = 22
39
40
41
42
43
44 S
eiz
ure
thre
sh
old
(°C
)
IL-1 RI -/- : mice genetically
deficient in IL-1 receptors
C57BL : wild type mice
The generation of the febrile seizures themselves involves
inflammatory mediators, specifically interleukin-1β
Inflammatory molecules?
Inflammation: a contributor to FSE-related epilepsy?
Vezzani, French, Bartfai, Baram , Nature Rev Neurol, 2011;
In addition to its release, Il-1β synthesis is induced
by long FS: Levels are augmented at 24 hrs
Dube et al., J Neurosci, 2010
Hippocampal IL1β levels distinguish rats with
spontaneous seizures after febrile status epilepticus
But is this a consequence of the spontaneous seizures?
Dube et al., J Neurosci, 2010
FSE “anti inflammation” (Dexamethasone) Epilepsy
Does inflammation directly contribute to FSE-related TLE?
Two intervention trials:
FSE “anti interleukin” Epilepsy
Kate Patterson
What is the basis of the altered limbic circuit in
TLE that follows FSE?
Altered networks
Loss of neurons
Altered neurons
Altered molecules
How are ‘epileptic neurons’ generated?
Through altered / mutated genes
Through altered expression of genes
Seizures reduce expression of an ion channel, HCN1,
changing neuronal channel phenotype in hippocampus
Chen, Nat Med 2001; Brewster, J Neurosci, 2002;
HCN2 HCN1 HCN2 HCN1
Seizures
HCN1 HCN1
HCN1 HCN2
Control HT-activity KA-activity HT & PB0.0
0.1
0.2
*
*C
i/gm
Dysregulation of HCN channels expression and function
seems to be common in animal models of epilepsy Chen, Baram, Soltesz, Nature Med, 2001
Brewster…Baram J Neurosci. 2002
Ludwig …Biel, EMBO J. 2003
Shah…Johnston, Neuron 2004
Budde….Pape. J Neurosci. 2005
Kamal… de Graan, Ramakers, Eur J Neurosci, 2006
Kuisle…Baram, Luthi, J Physiol. 2006
Schridde, Strauss… van Luijtelaar 2006
Shin & Chetkovich, JBC, 2007
Jung…Poolos, J Neurosci. 2007
Zhang…Sanchez, Epilepsia, 2007
Powell… O’Brien, Epilepsia. 2008
Dugladze...Gloveli, PNAS 2008
Van Gaase...deGraan , 2008
Marcelin...Bernard, Neurobiol Dis. 2008
Santoro… Siegelbaum, Neuron, 2009
Lewis...Baram, Chetkovich , J Neurosci, 2009
Huang…Shah, J Neurosci, 2009
Chung…Chetkovich Neurobiol Dis, 2009
Santoro…Blumenfeld, Epilepsia 2010.
Jung…Poolos, J Neurosci. 2010 , 2011
Hablitz, Epilepsia 2010,
Tu et al., Brain Pathology, 2011
Noam et al., Curr Opin Neurobiol, 2011
Albertson.. Hablitz J Neurophysiol, 2011
Kanyshkova et al., Neurobiol Dis 2012
Kase & Imoto, J Neurophysiol, 2012
HCN1 HCN2
In addition to animal models, enduring changes in HCN1
expression found in resected tissue from patients with TLE
Autopsy no HS severe HS
Bender et al., J Neurosci, 2003
Altered HCN1 / Ih in TLE hippocampus Bender et al., J Neurosci 2003
Stegen et al., Cerebral Cortex, 2011
Surges et al., BBRC, 2012
HCN channel mutations in patients Dibbens, Ann Neurol, 2010
DiFrancesco, J Neurosci, 2011
The mechanisms that regulate persistent
HCN1 channel repression after seizures might be
informative about epileptogenesis
They might provide a ‘hook’ into large-scale gene-
network changes that contribute to the epileptogenic
process
McClelland, Ann Neurol 2011
HCN1 gene structure with
NRSF Binding Element
The hcn1 gene has a conserved binding site for
the transcriptional repressor NRSF (REST1)
McClelland, Ann Neurol, 2011
The canonic role of NRSF is to regulate neuronal genes
Many seizures that promote epilepsy, including “FSE”
induce expression of NRSF
NRSF targets hundreds of neuronal genes
Roopra & Dingledine, 2001; Johnson et al, Science, 2007
Is NRSF binding to the chromatin important?
If so, then blocking it should prevent gene repression and epilepsy…
Blocking interaction of NRSF with the chromatin
attenuates epileptogenesis in the adult brain
McClelland et al., Ann Neurol, 2011
NRSF represses hundreds of genes via an epigenetic process
Slide Unavailable
Ion channels, accessory subunits or receptors
HCN1 BAI2 KCNC1 (Kv3.1)
LRP11 SCN3B GLRA2 Glycine rec
KCNC2 (Kv3.2) SLC12A5 (KCC2) NTRK3 Trk3
KCNIP2 (Kv interacting) GRIN2A (NMDA rec)
Calcium-mediated cellular cascades
CADPS HPCA MYO5B
CALB1 CABP7 CAMKV
Phosphoenzymes
PRKCG (protein kinase C) PRKCB1 (protein kinase C)
GNAO1 NELL1
Others
KLF9 ICA1 NXPH1
STMN2 STMN3
OLFM3 OLFM1
The repressed genes that were rescued by interference with
NRSF binding are crucial for normal neuronal function,
and often implicated in epilepsy
Slide Unavailable
Epileptogenesis following FSE may also involve
Large-scale epigenetic regulation of important
neuronal genes.
Interference with ‘master-regulators’ such as NRSF
might abort such epileptogenesis.
McClelland, Ann Neurol 2011
Learning Objectives
American Epilepsy Society | Annual Meeting 2012
What can we learn from animal models about:
a. the relationship between FSE and TLE
FSE: A marker of, or a contributor to, TLE
b. Mechanisms of epileptogenesis that follows FSE
c. Biomarkers that predict TLE
Acute MRI signal in amygdala predicts ‘FSE’-induced ‘TLE’
M. Choy
Slide Unavailable
Summary
American Epilepsy Society | Annual Meeting 2012
a. We can learn from animal models about the relationship
between FSE and TLE…
FSE is a likely contributor to TLE even in a predisposed brain
b. Mechanisms of epileptogenesis that follows FSE may
involve inflammatory and epigenetic processes
c. Novel MR Imaging findings may help predict children at
risk for FSE-related TLE.
Acknowledgments
Celine Dubé, PhD Ivan Soltesz, PhD
Shawn McClelland, PhD Christophe Bernard, PhD
Mankin Choy, PhD Wytse Wadman, PhD
Amy Brewster, PhD D Chetkovich MD PhD
Yoav Noam, PhD Gary Mathern, MD
Cristina Richichi, PhD Heinz Beck, MD, PhD
Adrienne Andres Rainer Surges, MD
Kate Patterson, BA Annamaria Vezzani, PhD
Qinqin Zha, PhD Teresa Ravizza, PhD
Kang Chen, MD (c Soltesz) Chuck Ribak, PhD
Roland Bender, PhD Andre Obenaus, PhD
Zsolt Toth, MD Albert Becker, MD, PhD
NIH grants: R37 NS35439, NS28912;
T32 NS04450
EFA, AES, Milken foundation.
Is increased Hippocampal T2 after FS
a Biomarker for eventual TLE?
Lewis & Shinnar
2004; at 1 week Low resolution
CA1 involved in Rat
Dube, Ann Neurol, 2004
MRI at one month post seizures (24 min); 7 Tesla
Dube et al., Exp Neurol, 2009
Controls Febrile seizures
Suitable imaging sequences enable visualization of the
predictive changes on clinically-relevant scanners
11.7T 4.7T 11.7T 4.7T
