Examining the role of astrogliosis and JNK signaling in post-traumatic epilepsy

Objective Post-traumatic epilepsy is a devastating complication of traumatic brain injury that has no targeted pharmacological therapy. Previous literature has explored the role of the c-Jun N-terminal kinase (JNK) pathway in epilepsy and the creation of epileptogenic foci by reactive astrogliosis; however, the relationship between reactive astrogliosis and the c-Jun N-terminal kinase signaling pathway in the development of post-traumatic epilepsy has not been thoroughly examined. Methods Four experimental groups, consisting of c57/b16 male mice, were examined: (1) control, (2) traumatic brain injury of graded severity (mild, moderate, severe), (3) sub-convulsive kainic acid alone without traumatic brain injury (15 mg/kg i.p.), and (4) sub-convulsive kainic acid administered 72 h after moderate traumatic brain injury. Modified Racine scale from 1 to 72 h and total beam breaks at 72 h were used to assess seizure activity. Immunohistochemistry and western blot were utilized to examine astrogliosis (GFAP), microglia activation (IBA-1), and phosphorylated JNK in prefrontal cortex samples collected from the contracoup side at 72 h post-injury. Results Astrogliosis, measured by GFAP, was increased after traumatic brain injury and increased commensurately based on the degree of injury. Mice with traumatic brain injury demonstrated a four-fold increase in phosphorylated JNK: p < 0.001. Sub-convulsive kainic acid administration did not increase seizure activity nor phosphorylation of JNK in mice without traumatic brain injury; however, sub-convulsive kainic acid administration in mice with moderate traumatic brain injury did increase phosphorylated JNK. Seizure activity was worse in mice, with traumatic brain injury, administered kainic acid than mice administered kainic acid. Conclusions Reactive astrocytes may have dysfunctional glutamate regulation causing an increase in phosphorylated JNK after kainic acid administration. Future studies exploring the effects of JNK inhibition on post-traumatic epilepsy are recommended.

IL4 Reduces Epileptogenesis Susceptibility Acutely After TBI: The Role of Macrophage/Microglia Polarization

Traumatic brain injury (TBI) is responsible for 5% of all epilepsy cases, which are known as post-traumatic epilepsy. Macrophage/microglia are key players in TBI pathogenesis. They are activated after TBI, transform to inflammatory phenotype (M1) and trigger neuroinflammation, which provokes epileptogenesis. Interleukin-4 (IL-4) is a well-known polarizer of macrophage/microglia to the anti-inflammatory phenotype (M2). We tested the effect of IL-4 on the rate of epileptogenesis, brain expression of inflammatory and anti-inflammatory cytokines, and the lesion size in traumatic rats. Trauma was exerted to temporo-parietal cortex of rats by Controlled Cortical Impact. Thereafter, rats received a single dose (100ng/rat) of IL-4 through intracerebroventricular injection. After 24h, pentylenetetrazole (PTZ) kindling started and development of generalized seizures was recorded. Level of TNF-α, TGF-β, IL-10, and arginase-1 (Arg-1) was measured in the brain by immunoblotting at 6h, 12h, 24h, 48h, and 5 days after TBI. The lesion size and cell survival were determined by staining. Traumatic rats were kindled by 5±1 PTZ injections (significantly less than 11±2 injections of control and sham-operated rats, p<0.001). IL-4 did not change kindling rate in sham-operated rats but inhibited acceleration of kindling rate in traumatic rats (13±1 PTZ injections, p<0.001). IL-4 decreased post-TBI overexpression of TNF-α (6h, p<0.001) whereas upregulated post-TBI expression of TGF-β (48h, p<0.001), IL-10 (24h, p<0.05; 48h, p<0.01), and Arg-1 (24h, p<0.001). IL-4 decreased lesion volume and number of dead neurons. IL-4 suppresses TBI-induced acceleration of epileptogenesis in rats by directing macrophage/microglia to the anti-inflammatory M2 phenotype and inhibition of neuronal death.

Incidence of post-traumatic epilepsy following paediatric traumatic brain injury: protocol for systematic review and meta-analysis

IntroductionPost-traumatic epilepsy (PTE) is a recognised complication of traumatic brain injury (TBI), and is associated with higher rates of mortality and morbidity when compared with patients with TBI who do not develop PTE. The majority of the literature on PTE has focused on adult populations, and consequently there is a paucity of information regarding paediatric cohorts. Additionally, there is considerable heterogeneity surrounding the reported incidence of PTE following childhood TBI in the current literature. The primary aim of our study is to summarise reported PTE incidences in paediatric populations to derive an accurate estimate of the global incidence of PTE following childhood TBI. Our secondary aim is to explore risk factors that increase the likelihood of developing PTE.Methods and analysisA systematic literature search of Embase (1947–2021), PubMed (1996–2021) and Web of Science (1900–2021) will be conducted. Publications in English that report the incidence of PTE in populations under 18 years of age will be included. Publications that evaluate fewer than 10 patients, report an alternative cause of epilepsy, or in which a paediatric cohort is not discernable, will be excluded. Independent investigators will identify the relevant publications, and discrepancies will be adjudicated by a third independent investigator. Data extracted will include incidence of PTE, time intervals between TBI and PTE, seizure characteristics, injury characteristics, patient demographics and clinical data. Data extraction will be performed by two independent investigators and cross-checked by a third investigator. A descriptive analysis of PTE incidence will be conducted and a weighted mean will be calculated. If sufficient data are available, stratified meta-analysis of subgroups will also be conducted.Ethics and disseminationEthics approval was not required for this study. We intend to publish our findings in a high-quality peer-reviewed journal on completion.PROSPERO registration numberCRD42021245802.

Selected Molecular Targets for Antiepileptogenesis

The term epileptogenesis defines the usually durable process of converting normal brain into an epileptic one. The resistance of a significant proportion of patients with epilepsy to the available pharmacotherapy prompted the concept of a causative treatment option consisting in stopping or modifying the progress of epileptogenesis. Most antiepileptic drugs possess only a weak or no antiepileptogenic potential at all, but a few of them appear promising in this regard; these include, for example, eslicarbazepine (a sodium and T-type channel blocker), lamotrigine (a sodium channel blocker and glutamate antagonist) or levetiracetam (a ligand of synaptic vehicle protein SV2A). Among the approved non-antiepileptic drugs, antiepileptogenic potential seems to reside in losartan (a blocker of angiotensin II type 1 receptors), biperiden (an antiparkinsonian drug), nonsteroidal anti-inflammatory drugs, antioxidative drugs and minocycline (a second-generation tetracycline with anti-inflammatory and antioxidant properties). Among other possible antiepileptogenic compounds, antisense nucleotides have been considered, among these an antagomir targeting microRNA-134. The drugs and agents mentioned above have been evaluated in post-status epilepticus models of epileptogenesis, so their preventive efficacy must be verified. Limited clinical data indicate that biperiden in patients with brain injuries is well-tolerated and seems to reduce the incidence of post-traumatic epilepsy. Exceptionally, in this regard, our own original data presented here point to c-Fos as an early seizure duration, but not seizure intensity-related, marker of early epileptogenesis. Further research of reliable markers of early epileptogenesis is definitely needed to improve the process of designing adequate antiepileptogenic therapies.