Rodent models of infantile spasms and the hunt for new treatments

Transcription

1 Rodent models of infantile spasms and the hunt for new treatments Morris H. Scantlebury M.D. Assistant Professor, Departments of Pediatrics and Clinical Neurosciences, University of Calgary, Canada.

2 Treatments Vigabatrin- effective 20-30% of the time. Much higher in patients with TS. ACTH/prednisolone- Effective 60-70% of the time Treatments are refractory 30-50% of the time Both treatments associated with considerable toxic side-effects!

3 Outcome Infantile Spasms Persistent psychomotor disabilities despite treatment Emergence of other seizure types High mortality of ~ 30% (50% are diseaserelated )

4 WE NEED SAFER AND BETTER TREATMENTS FOR INFANTILE SPASMS

5 ANIMAL MODELS OF INFANTILE SPASMS

6 Animal models of epilepsy: What are the considerations to model? There are many, many experimental models of epilepsy involving both invivo and in-vitro preparations There are several things to consider when evaluating or developing a model of epilepsy Species Syndrome Developmental specificity Sex differences Etiology Methods of induction Anatomical targets (Where to direct the inciting insult, where should be the damage Genetic background Predisposing factors Reason for using the model (high throughput for screening drugs or to study mechanisms) Comorbidities (depression, autism, learning and memory deficits) COST!!!!!!!

7 SPECIES DIFFERENCES DeFelipe J, Frontier in neuroanatomy 2011

8 HUMAN MOUSE DeFelipe J, Frontier in neuroanatomy 2011

9 DeFelipe J, Frontier in Neuroanatomy 2011

10 Which epilepsy syndrome to model? * * * * * * * * * * * * Blumke et al, Epilepsia 2011

11 Chronic TTX Infusion (right hippocampus) Model of Infantile Spasms Model of sodium channel dysfunction Lee et al, Epilepsia 2008

12 HFO increase at time of seizure

13 Vigabatrin suppresses spasms and late HFO of ictal onset Interictal HFOs were also suppressed

14 ECOG, 636 spasms in 11patients contacts Placement guided by EEG, MRI, PET Recorded HFO correlated with EMG with spasms Augmentation of HFO preceded the onset of spasms seen mainly in Rolandic cortex Post-surgical outcomes better if maximal HFO resected

15 Down s syndrome based model of IS Model of infantile spasms created by exposing Down s mice to a GABA B agonist such as baclofen or GHB. Note these mice overexpress (g-coupled inward rectifying potassium channels) specifically GIRK 2 channels GIRK 2 KO Down s mice are resistant to GIRK channel agonist-induced spasms- thus there is a specific molecular target for developing treatments of IS Cortez MA et al 2009, Joshi K et al 2016

16 WT Ts65Dn Ts65Dn + GBL- interictal Ts65Dn + GBL- ictal Cortez MA et al 2009, Joshi K et al 2016

17 Ultra slow oscillations common around time of spasms The USO are due to GIRK channel over activity

18 NMDA-Induced Motor Seizures Following Prenatal Betamethasone Baseline After NMDA After NMDA Velisek et al, Ann Neurol 2007

19 Effects of ACTH on Latency to NMDA-evoked Events Model of NMDA induced spasms in the stressed brain sensitive to ACTH Naïve Rats Prenatal Exposure to Betamethasone Velisek et al, Ann Neurol 2007

20 Upregulation of MC4 receptors in the hypothalamus in rats with spasms- if blocked pharmacologically then ACTH is no longer effective Immunohistochemistry Western blot Inching closer to knowing the exact mechanism and site of action of ACTH

21 Development of the triple-hit model of infantile spasms based on our best understanding of the mechanisms Hypothesized that spasms occur in patients with both abnormal cortical and brainstem function and/or abnormal communication between the two structures as can occur due to white matter injury Abnormal serotonerigic mechanisms would potentiate the spasms

22 Multiple-hit model: Robust model that allows for the rapid screening of drugs for IS Age : P9, Flexion spasm Age : P9, Extension spasm DOXORUBICIN: TO INDUCE CORTICAL AND BRAINSTEM INJURY LIPOPOLYSACCHARIDE: TO INDUCE INFLAMMATORY CASCADES AND WHITE MATTER INJURY PCPA: TO REDUCE SEROTONIN LEVELS Scantlebury MH et al: Neurobiol Dis 2010

23 Scantlebury MH et al: Neurobiol Dis 2010

24 Scantlebury MH et al: Neurobiol Dis 2010

25 Autistic features and learning deficits Scantlebury MH et al: Neurobiol Dis 2010

26 Spasms refractory to ACTH Paritaly Responsive to Vigabatrin Scantlebury MH, et al: Neurobiol Dis 2010

27 Carisbamate, but not phenytoin, suppresses spasms acutely Ono et al 2010

28 Rapamycin suppresses spasms and improves cognitive outcome Raffo et al 2010

29 Briggs et al Epilepsia 2014

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31 Body weight (g) 24 ND/Saline KD/Saline 22 ND/Treatment KD/Treatment * * # * * Postnatal age Treatment: p<0.001 Age: p<0.001 Treatment vs Age: p<0.001 *,#: significant differences from ND/Saline P4 P5 P6 P7 P8 P9 P10 P11 P12 * # # * # * Surface Righting Open Field Negative Geotaxis Age: p=0.001; Treatment x Age: p=0.01 Saline/ND Saline/KD Treatment/ND Treatment/KD Treatment: p=0.006; Age: p<0.001; Treatment x Age: p= Treatment: p=0.006; Age: p<0.001; Treatment x Age: p<0.001 Latency (sec) Latency (sec) Latency (sec) P5 P6 P7 P9 P10 P11 P12 Postnatal age 0 P5 P6 P7 P9 P10 P11 P12 Postnatal age P5 P6 P7 P9 P10 P11 P12 Postnatal age Scantlebury lab 2017 unpublished

32 E2 treatment prevent spasms and long-term seizures, restores GABAergic INs Not observed in model of NMDA induced spasms Arrested decent of the testes and changes in sexspecific behaviors a side effect Pedro R. Olivetti et al., Sci Transl Med 2014; Chachua T et al, Epilepsia 2016

33 MODLES Method Age Seizure type Ictal EEG Inter Ictal EEG Treatments Acquired CRH ** i.c.v. injections of CRH P5-16 Limbic like seizures( Chewing) Swimming, Leg clonus, Tonic limb posturing NMDA ** i.p. injections of NMDA P12-18 Tail twisting, spasms Semi rhythmic sharp wave and increased beta activity Suppression of activity or serrated waves which is runs of slow waves with superimposed fast activity - Effective: Phenytoin, alpha helical CRH Ineffective: ACTH - Effective: Vigabatrin (P12), VPA (P18), B6, (P12 and P18) Ineffective: VPA (P12), ACTH Betamethasone- NMDA ** TTX ** i.p. injections of NMDA in pups prenatally exposed to betamethasone Infusion of TTX into cortex and hippocampus P15 Tail twisting, spasms Suppression of activity or serrated waves which is runs of slow waves with superimposed fast activity P21-adults spasms High amplitude slow wave transient followed by attenuation with superimposed fast activity Multi-focal spikes and sharp wave discharges - Effective:ACTH None tested Genetic Down s * i.c.v injection of GHB to the Ts(1716)65Dn mouse P7 to adults spasms Bursts of epileptiform activity followed by attenuation Generalized voltage attenuation Effective: ACTH 1-24, CGP , ethosuxamide, valproate, Vigabatrin (partially) Ineffecttive: ACTH 1-39, Serotonin, baclofen, (latter two exacerbate the seizures) ARX * Conditional knock-out Adults spasms spike wave discharge followed by voltage attenuation on the EEG ARX (GCG)10+7 * Triplet repeat knock in expansion P7-11 spasms sharp transient followed by attenuation of the background activity Reduced delta and beta activity High amplitude spike slow wave discharges None tested Estradiol

34 IS lies along a spectrum of the DEEDs EIEE IS LGS

35 Comparison of the clinical feature of the epileptic encephalopathies Clinical features EIEE EME IS LGS Age at onset 75% < 1 month 96% < 1 month 90% 3-12 months 1-7 years Incidence/10,000 live births Rare (unknown) Rare (unknown) Seizure Types Tonic spasms* Partial motor Erratic focal motor Hemiconvulsions Generalized tonic Erratic/fragmentary myoclonus * Tonic Tonic spasms (rare) Simple focal Spasms (flexor, extensor, mixed flexor/extensor) * Focal Drop attacks Tonic (80-90%)* Atypical absence Atonic Drop attacks Non-convulsive status Ictal EEG Burst Suppresion Attenuation No clear correlate Electrodecremental (attenuation +/- with overriding fast activity) Paroxysmal fast Attenuation Slow spike wave discharges Combination Inter Ictal EEG Burst Suppresion Burst Suppresion Hypsarrhythmia Slow spike wave discharges Prognosis Poor Poor Etiology dependent Poor Treatment Non- effective Zonisamide, Vigabatrin in single case reports Non-effective. Pyridoxine in those due to pyridoxine deficiency ACTH, Vigabatrin in some patients Often intractable. Polytherapy often applied.

36 EIEE EME IS

37 LGS

38 Etiologies of the catastrophic epilepsies Etiology EIEE EME IS Structural abnormalities, Rare acquired or genetic Inborn errors of metabolism /mitochondrial disorders Other chromosomal abnormalities Cerebral dysgenesis Aicardi syndrome Hemimegalencephaly Lissencephaly Porencephaly Hydrocephalus Subacute Diffuse Encephalopathy Many genetic causes emerging Non-ketotic hyperglycinemia, Propionic aciduria, Methyl melonic academia, d-glyceric academia, Sulphite defficiency xantnine deficiency Menke s disease, Molybdenum co-factor deficiency Zellweger s syndrome, Pyridoxine dependency HIE, birth trauma Stroke, Hemorrhage Meningitis, encephalitis, congenital infections Focal cortical dysplasia Tuberous sclerosis Aicardi syndrome Periventricular nodular heterotopia Subcortical band heterotopia Polymicrogyria Hemimegencephaly Lissencephaly Pachygyria Microdysgenesis Holoprosencephaly Tay Sach s (phenylketonuria) dihydropteridine reductase deficiency Histidinemia Pyridoxine dependency Urea cycle disorders Alpers syndrome Leighs syndrome (cytochrome c oxidase deficiency) Down s syndrome (Trisomy 21) ARX

39 .therefore the knowledge gained from understanding one model may be applicable across the spectrum of etiologies of the epileptic encephalopathies.

40 Conclusion There is major recent advances in the understanding of the epileptic encephalopathies that would lead to new, safe and effective etiology specific treatments which are urgently needed clinically

41 Thanks Past and present Lab members: Dr. Morris Scantlebury Dr. Karlene Barrett Ms Anamika Choudhary Mr Lucas Scott Ms Keelin Rivard Collaborators: Dr. Richard Wilson Dr. Quentin Pittman Dr. Arijit Roy Funding: ACHRI start-up funds ACHRI postdoctoral fellowship (Karlene) ACRI-BDB theme group bridge funding CSMREP CIHR Project scheme