Second-line immunotherapy in new onset refractory status epilepticus

Several pieces of evidence suggest immune dysregulation could trigger the onset and modulate sequelae of new onset refractory status epilepticus (NORSE), including its subtype with prior fever known as febrile infection-related epilepsy syndrome (FIRES). Consensus-driven recommendations have been established to guide the initiation of first- and second-line immunotherapies in these patients. Here, we review the literature to date on second-line immunotherapy for NORSE/FIRES, presenting results from 28 case reports and series describing the use of anakinra, tocilizumab, or intrathecal dexamethasone in 75 patients with NORSE. Among them, 52 patients were managed with anakinra, 21 with tocilizumab, and eight with intrathecal dexamethasone. Most had elevated serum or cerebrospinal fluid cytokine levels at treatment initiation. Treatments were predominantly initiated during the acute phase of the disease (92%) and resulted, within the first 2 weeks, in seizure control for up to 73% of patients with anakinra, 70% with tocilizumab, and 50% with intrathecal dexamethasone. Cytokine levels decreased after treatment for most patients. Anakinra and intrathecal dexamethasone were mainly initiated in children with FIRES, whereas tocilizumab was more frequently prescribed for adults, with or without a prior febrile infection. There was no clear correlation between the response to treatment and the time to initiate the treatment. Most patients experienced long-term disability and drug-resistant post-NORSE epilepsy. Initiation of second-line immunotherapies during status epilepticus (SE) had no clear effect on the emergence of post-NORSE epilepsy or long-term functional outcomes. In a small number of cases, the initiation of anakinra or tocilizumab several years after SE onset resulted in a reduction of seizure frequency for 67% of patients. These data highlight the potential utility of anakinra, tocilizumab, and intrathecal dexamethasone in patients with NORSE. There continues to be interest in the utilization of early cytokine measurements to guide treatment selection and response. Prospective studies are necessary to understand the role of early immunomodulation and its associations with epilepsy and functional outcomes.

Levetiracetam Suppresses the Infiltration of Neutrophils and Monocytes and Downregulates Many Inflammatory Cytokines during Epileptogenesis in Pilocarpine-Induced Status Epilepticus Mice

Acute brain inflammation after status epilepticus (SE) is involved in blood-brain barrier (BBB) dysfunction and brain edema, which cause the development of post-SE symptomatic epilepsy. Using pilocarpine-induced SE mice, we previously reported that treatment with levetiracetam (LEV) after SE suppresses increased expression levels of proinflammatory mediators during epileptogenesis and prevents the development of spontaneous recurrent seizures. However, it remains unclear how LEV suppresses neuroinflammation after SE. In this study, we demonstrated that LEV suppressed the infiltration of CD11b+CD45high cells into the brain after SE. CD11b+CD45high cells appeared in the hippocampus between 1 and 4 days after SE and contained Ly6G+Ly6C+ and Ly6G-Ly6C+ cells. Ly6G+Ly6C+ cells expressed higher levels of proinflammatory cytokines such as IL-1β and TNFα suggesting that these cells were inflammatory neutrophils. Depletion of peripheral Ly6G+Ly6C+ cells prior to SE by anti-Ly6G antibody (NIMP-R14) treatment completely suppressed the infiltration of Ly6G+Ly6C+ cells into the brain. Proteome analysis revealed the downregulation of a variety of inflammatory cytokines, which exhibited increased expression in the post-SE hippocampus. These results suggest that Ly6G+Ly6C+ neutrophils are involved in the induction of acute brain inflammation after SE. The proteome expression profile of the hippocampus treated with LEV after SE was similar to that after NIMP-R14 treatment. Therefore, LEV may prevent acute brain inflammation after SE by suppressing inflammatory neutrophil infiltration.

Glial responses during epileptogenesis in Mus musculus point to potential therapeutic targets

The Mesio-Temporal Lobe Epilepsy syndrome is the most common form of intractable epilepsy. It is characterized by recurrence of focal seizures and is often associated with hippocampal sclerosis and drug resistance. We aimed to characterize the molecular changes occurring during the initial stages of epileptogenesis in search of new therapeutic targets for Mesio-Temporal Lobe Epilepsy. We used a mouse model obtained by intra-hippocampal microinjection of kainate and performed hippocampal whole genome expression analysis at 6h, 12h and 24h post-injection, followed by multilevel bioinformatics analysis. We report significant changes in immune and inflammatory responses, neuronal network reorganization processes and glial functions, predominantly initiated during status epilepticus at 12h and persistent after the end of status epilepticus at 24h post-kainate. Upstream regulator analysis highlighted Cyba, Cybb and Vim as central regulators of multiple overexpressed genes implicated in glial responses at 24h. In silico microRNA analysis indicated that miR-9, miR-19b, miR-129, and miR-223 may regulate the expression of glial-associated genes at 24h. Our data support the hypothesis that glial-mediated inflammatory response holds a key role during epileptogenesis, and that microglial cells may participate in the initial process of epileptogenesis through increased ROS production via the NOX complex.

Effect of thymectomy on refractory autoimmune status epilepticus

Refractory status epilepticus (RSE) is an increasingly recognized manifestation of autoimmune encephalitis, which can occur either as a paraneoplastic or non-paraneoplastic disorder. The effect of tumor removal in paraneoplastic status epilepticus has never been explored systematically, although early tumor treatment is usually recommended. In this study, we report clinical, pathological and EEG findings of a patient who developed RSE as one of multiple paraneoplastic manifestations of thymoma and the effect of thymectomy on seizure outcome. To our knowledge, this is the first report of successful treatment of RSE with tumor removal in paraneoplastic encephalitis.

Mycophenolate mofetil prevents the delayed T cell response after pilocarpine-induced status epilepticus in mice

Growing clinical and laboratory evidence corroborates a role for the immune system in the pathophysiology of epilepsy. In order to delineate the immune response following pilocarpine-induced status epilepticus (SE) in the mouse, we monitored the kinetics of leukocyte presence in the hippocampus over the period of four weeks. SE was induced following a ramping protocol of pilocarpine injection into 4–5 weeks old C57BL/6 mice. Brains were removed at days 1–4, 14 or 28 after SE, and the hippocampi were analyzed via flow cytometry, via quantitative reverse transcriptase PCR (qRT-PCR) and via immunohistochemistry. Epileptogenesis was confirmed by Timm staining of mossy fiber sprouting in the inner molecular layer of the dentate gyrus. The flow cytometry data revealed a biphasic immune response following pilocarpine-induced SE with a transient increase in activated CD11b⁺ and F4/80⁺ macrophages within the first four days replaced by an increase in CD3⁺ T-lymphocytes around day 28. This delayed T cell response was confirmed via qRT-PCR and via immunohistochemistry. In addition, qRT-PCR data could show that the delayed T cell response was associated with an increased CD8/CD4 ratio indicating a cytotoxic T cell response after SE. Intriguingly, early intervention with mycophenolate mofetil administration on days 0–3 after SE prevented this delayed T cell response. These results show an orchestrated immunological sequela and provide evidence that the delayed T cell response is sensitive to early immunomodulatory intervention.

[Autoimmune encephalitis presenting with drug-resistant status epilepticus]

Autoimmune encephalitis is characterized by formation of antibodies against cell surface proteins. Antibodies against the gamma-aminobuturic acidB (GABAB) receptor lead to limbic encephalitis, drug-resistant seizures, confusion, cognitive impairment and changed behaviour. Some patients present with status epilepticus. GABAB encephalitis is associated with small-cell lung cancer or neuroendocrine lung tumour. This is a case report of a patient having status epilepticus due to GABAB encephalitis. In cases which are presumed to be autoimmune it is important that treatment starts immediately instead of awaiting antibody confirmation.

[Febrile infection-related status epilepticus in a child after a common infection]

A 13-year-old boy developed seizures and intractable status epilepticus a week after having had a sore throat. Ketogenic diet possibly had some effect. Antibodies to calmodulin dependent protein kinase II were found and could possibly suggest an immunologic aetiology.

Status epilepticus: immunologic and inflammatory mechanisms

Status epilepticus (SE) can be difficult to treat, particularly if refractory, and lead to significant morbidity and mortality. Prolonged seizures are also a risk factor for the subsequent diagnosis of epilepsy. Activation of the immune system and inflammation are areas of recent interest in the field of epilepsy, and there is growing evidence that these may be involved in the pathogenesis of ongoing SE and subsequent epileptogenesis. We review the current data on this topic in both animal models and human disease. We conclude that there is evidence suggesting a role for immunologic and inflammatory mechanisms in SE. Further research, especially human studies, is necessary to determine whether targeting the immune system would improve control of SE and prevent sequelae such as epileptogenesis.

Primary antiphospholipid syndrome manifesting as partial status epilepticus

Primary antiphospholipid syndrome (APS) is an autoimmune disease defined by vascular thrombosis, pregnancy complications, and persistent antiphospholipid antibodies. Neurological manifestations include stroke, seizures, and chorea among others. Seizures are often precipitated by an acute ischemic event, but occasionally, structural abnormalities are absent. We present a 61-year-old man who developed partial seizures that progressed into partial status epilepticus. His seizures were intractable and required aggressive treatment with multiple anti-epileptic medications. He was diagnosed with primary APS and treated with anticoagulation. Head imaging did not reveal any acute ischemic events. This case demonstrates that primary APS may present as a refractory status epilepticus unrelated to acute cerebral ischemia.

Peripheral immune challenge with dsRNA enhances kainic acid-induced status epilepticus

Clinical evidence implicates peripheral inflammatory diseases as comorbid factors in epilepsy. The present study was designed to determine the effect of the acute phase of antiviral response on seizure susceptibility. Young adult mice were intraperitoneally injected with 12 mg/kg of a viral mimic, polyinosinic:polycytidylic acid (PIC). After 48 h, seizures were induced by subcutaneous injection of kainic acid (KA). PIC-pretreatment profoundly enhances vulnerability to excitotoxic insult as evidenced by increased seizure intensity and extended duration of status epilepticus. These results support the notion that peripheral viral infections may alter brain function resulting in enhanced predilection to seizures.

P2X7 receptor regulates leukocyte infiltrations in rat frontoparietal cortex following status epilepticus

BACKGROUND

In the present study, we investigated the roles of P2X7 receptor in recruitment and infiltration of neutrophil during epileptogenesis in rat epilepsy models.

METHODS

Status epilepticus (SE) was induced by pilocarpine in rats that were intracerebroventricularly infused with either saline, 2',3'-O-(4-benzoylbenzoyl)-adenosine 5'-triphosphate (BzATP), adenosine 5'-triphosphate-2',3'-dialdehyde (OxATP), or IL-1Ra (interleukin 1 receptor antagonist) prior to SE induction. Thereafter, we performed immunohistochemical studies for myeloperoxidase (MPO), CD68, interleukin-1β (IL-1β), monocyte chemotactic protein-1 (MCP-1) and macrophage inflammatory protein-2 (MIP-2).

RESULTS

In saline-infused animals, neutrophils and monocytes were observed in frontoparietal cortex (FPC) at 1 day and 2 days after SE, respectively. In BzATP-infused animals, infiltrations of neutrophils and monocytes into the FPC were detected at 12 hr and 1 day after SE, respectively. In OxATP-infused animals, neutrophils and monocytes infiltrated into the FPC at 1 day and 2 days after SE, respectively. However, the numbers of both classes of leukocytes were significantly lower than those observed in the saline-infused group. In piriform cortex (PC), massive leukocyte infiltration was detected in layers III/IV of saline-infused animals at 1-4 days after induction of SE. BzATP or OxATP infusion did not affect neutrophil infiltration in the PC. In addition, P2X7 receptor-mediated MCP-1 (released from microglia)/MIP-2 (released from astrocytes) regulation was related to SE-induced leukocyte infiltration in an IL-1β-independent manner.

CONCLUSIONS

Our findings suggest that selective regulation of P2X7 receptor-mediated neutrophil infiltration may provide new therapeutic approaches to SE or epilepsy.

A patient with rubella encephalitis and status epilepticus

Rubella is an important childhood disease that was historically widespread but is now very infrequent. It is an acute viral infection ordinarily characterized by mild constitutional symptoms. Complications are relatively uncommon in childhood. Encephalitis similar to that seen with measles occurs in about 1 in 6,000 cases. The severity is highly variable, and there is an overall mortality rate of 20%. Symptoms in survivors usually resolve within 1-3 week without neurologic sequelae. An 8.5-year-old boy presented with rubella encephalitis and status epilepticus. Five days before admission the patient had erythematous maculopapular rash on the face, spreading to the trunk and extremities. On the admission day, he had a generalized tonic-clonic seizure with loss of consciousness. Microscopic and cytologic examinations of cerebrospinal fluid showed nonspecific. Electro-encephalography (EEG) showed diffuse slowing. An enzyme linked immunosorbent assay (ELISA) revealed that rubella IgM antibody titer was positive in serum and in cerebrospinal fluid. One day later, the patient became conscious with normal physical condition. As a conclusion, it is possible to prevent the complications of rubella infection, especially the congenital rubella syndrome and encephalitis with a rapid and efficient vaccination program.

[Three patients with a paraneoplastic neurological syndrome: the significance of paraneoplastic antibodies]

Establishing the presence of paraneoplastic antibodies is important in identifying an often severe neurological syndrome as paraneoplastic and hence directing the search for an underlying neoplasm. A paraneoplastic neurological syndrome was diagnosed in 3 patients. The first was a 64-year-old woman in whom paraneoplastic encephalomyelitis was diagnosed. The diagnosis was strongly supported by a high titre of serum anti-Hu antibodies, despite three negative biopsies from a mediastinal mass. The patient died of a non-convulsive status epilepticus; autopsy revealed not only paraneoplastic encephalomyelitis but also small-cell lung cancer. The second patient was a 55-year-old woman with metastatic breast cancer. After a three-year period of progressive neurological deterioration, a high titre of anti-CV2/CRMP5 antibodies was detected, on the basis of which the clinical syndrome was diagnosed as paraneoplastic. She received immunotherapy and her condition stabilised. The third patient, a 41-year-old man, presented with severe limbic encephalitis. Biopsy from a paraaortic mass was positive for undifferentiated carcinoma. The patient had a high titre ofanti-Ma2 antibodies and was subsequently tested positive for serum alpha-foetoprotein (AFP) and beta-human-chorionic gonadotrophin (bta-HCG). During chemotherapy for a non seminoma testicular cancer, the limbic encephalitis improved both clinically and radiologically, but the patient died as a result of the toxicity of the treatment.

Complement activation in experimental and human temporal lobe epilepsy

We investigated the involvement of the complement cascade during epileptogenesis in a rat model of temporal lobe epilepsy (TLE), and in the chronic epileptic phase in both experimental as well as human TLE. Previous rat gene expression analysis using microarrays indicated prominent activation of the classical complement pathway which peaked at 1 week after SE in CA3 and entorhinal cortex. Increased expression of C1q, C3 and C4 was confirmed in CA3 tissue using quantitative PCR at 1 day, 1 week and 3-4 months after status epilepticus (SE). Upregulation of C1q and C3d protein expression was confirmed mainly to be present in microglia and in a few hippocampal neurons. In human TLE with hippocampal sclerosis, astroglial, microglial and neuronal (5/8 cases) expression of C1q, C3c and C3d was observed particularly within regions where neuronal cell loss occurs. The membrane attack protein complex (C5b-C9) was predominantly detected in activated microglial cells. The persistence of complement activation could contribute to a sustained inflammatory response and could destabilize neuronal networks involved.

EFA6A-like antibodies in paraneoplastic encephalitis associated with immature ovarian teratoma: a case report

We describe a 19-year-old patient with paraneoplastic encephalitis associated with immature ovarian teratoma (OT), who presented with psychiatric symptoms, prolonged disturbance of consciousness, refractory status epilepticus, central hypoventilation, and various abnormal involuntary movements. Immunological characterization of the patient's serum and cerebrospinal fluid (CSF) demonstrated the presence of an autoantibody that colocalized with EFA6A, a brain-specific protein involved in the regulation of dendritic development of hippocampal neurons. Despite the severity of the symptoms, the patient showed significant neurological improvement following removal of the tumor and chemotherapy. This case suggests that physicians should rule out an OT in young women with encephalitis who present with the subacute-onset of psychiatric symptoms. Antibodies that colocalize with EFA6A are a valuable marker for early diagnosis of a potentially reversible paraneoplastic encephalitis associated with OT.

Inflammation and neurogenesis in temporal lobe epilepsy

The aim of the present review is to discuss the evidence supporting the hypothesis that inflammation and neurogenesis play an important role in temporal lobe epilepsy (TLE) and to examine whether possible strategies that involve the pharmacological manipulation of inflammation/neurogenesis can lead to the development of novel approaches for the treatment of epilepsy. Since it is not yet clear whether the neuron-glia response obtained in this pathology is a secondary effect of an aggressive inflammation or if it is somehow related to the cause of the epileptic condition, with the present review we guide the readers through the complex and ambiguous crosstalk between neuroimmunology and epilepsy.

Inflammatory response and glia activation in developing rat hippocampus after status epilepticus

PURPOSE

We investigated the activation of microglia and astrocytes, induction of cytokines, and hippocampal neuronal damage, 4 and 24 h after kainic acid-induced status epilepticus (SE) in postnatal day (PN) 9, 15, and 21 rats.

METHODS

Limbic seizures were induced by systemic injection of kainic acid. Glia activation and neuronal cell loss were studied by using immunocytochemistry and Western blot. Cytokine expression was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) followed by Southern blot quantification.

RESULTS

After SE onset, hippocampal glia activation, cytokine expression, and neuronal damage are all age-dependent phenomena. In the hippocampus, neuronal injury occurs only when cytokines are induced in glia, and cytokine synthesis precedes the appearance of degenerating neurons. Neuronal injury is more pronounced when interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) are produced in addition to IL-1beta.

CONCLUSIONS

This study shows that cytokine induction in rat brain after sustained seizures is age dependent, and it is associated with the appearance of cell injury.

Effect of topiramate on the kainate-induced status epilepticus, lipid peroxidation and immunoreactivity of rats

Topiramate, a new anticonvulsant, has been reported to possess neuroprotective effects in both in vivo and in vitro experiments. In the present study, the effect of topiramate (40 and 80 mg/kg ip) on the fully developed kainate-induced status epilepticus was evaluated in the rat. Injection of kainate (15 mg/kg ip) evoked recurrent limbic seizures which lasted several hours. Topiramate injected 1.5 h after kainate administration had no effect on the seizures and mortality of the animals. Biochemical study revealed that at 80 mg/kg ip, topiramate significantly attenuated the kainate-induced lipid peroxidation in the piriform cortex and showed similar tendency in the frontal cortex. Besides the central nervous system, the kainate-induced seizures evoked significant changes in immunoreactivity, such as reduction in thymus weight and the proliferative activity of splenocytes, and the splenocyte-increased production of interleukin-10, but not interferon-gamma. Topiramate did not affect the kainate-induced reduction in thymus weight, but attenuated changes in the proliferative activity of splenocytes. It is concluded that topiramate, when given during the fully developed kainate-induced status epilepticus in rats, has no effect on seizures, but attenuates lipid peroxidation in piriform cortex and prevents certain changes in immunoactivity.

Glia activation and cytokine increase in rat hippocampus by kainic acid-induced status epilepticus during postnatal development

In adult rats, status epilepticus (SE) induces cytokine production by glia especially when seizures are associated with neuronal injury. This suggests that cytokines may play a role in seizure-induced neuronal damage. As SE-induced injury is age-specific, we used rats of different ages (with distinct susceptibilities to seizure-induced neuronal injury) to elucidate the role of cytokines in this process. Thus, we investigated the activation of microglia and astrocytes, induction of cytokines, and hippocampal neuronal injury 4 and 24 h following kainic acid-induced SE in postnatal day (PN) 9, 15, and 21 rats. At PN9, there was little activation of microglia and astrocytes at any time point studied. Interleukin-1beta (IL), tumor necrosis factor-alpha (TNF), and IL-6 or the naturally occurring IL-1 receptor antagonist (Ra) mRNA expression did not increase. No evidence of cell injury has been detected. At PN15, immunostaining of microglia and astrocytes was enhanced, but only IL-1beta mRNA expression was increased. These changes were observed 4 h after SE. Scattered injured neurons in CA3 and subiculum, but not in any other region, were present 24 h following SE. At PN21, immunostaining of microglia and astrocytes and the mRNA expression of all cytokines studied was significantly increased already 4 h after SE. At 24 h, many injured neurons were present in CA1 and CA3 regions and in 40% of rats in other forebrain areas. These data show that (i) the pattern of glia activation and cytokine gene transcription induced by SE is age-dependent and (ii) neuronal injury in the hippocampus occurs only when cytokines are induced and their synthesis precedes the appearance of neuronal damage. Thus, cytokine expression in immature brain is associated specifically with cell injury rather than with seizures per se, suggesting that proinflammatory cytokines may contribute to the occurence of SE-induced hippocampal damage.

[Intrathecal glutamate receptor antibodies in a patient with elderly-onset refractory epilepsy]

Antibodies against a glutamate receptor in the central nervous system are reported to be an important autoimmune factor in infantile or childhood refractory epilepsy and in adult-onset paraneoplasstic cerebellar ataxia. We here reported a patient with glutamate receptor antibodies-positive elderly-onset intractable epilepsy and advanced-stage stomach cancer. A 77-year-old man with a history of resected bladder cancer suddenly developed an attack of epilepsia partialis continua in the right arm, followed by a generalized epileptic status. The ictal EEG showed spikes in the left parietal region with diffuse slow wave backgrounds. The brain MRI demonstrated a focal high signal intensity in the left postcentral gyrus on the T2-weighted and FLAIR images. The SPECT showed a high uptake in the focal area corresponding to the MRI lesion, suggesting a seizure focus. The routine analysis in the CSF was normal, but the glutamate receptor antibodies (IgG, IgM and C-terminal) were all positive. The status epilepticus was refractory to anticonvalsants, and the barbiturate anesthesia was introduced. Subsequently, the epilepsy has been fairly controlled by valproic acid and phenobarbital. The post ictal MRI demonstrated a focal atrophy in the left postcentral gyrus. The systemic evaluations revealed an advanced-stage stomach cancer. The glutamate receptor antibodies may play a role in late-onset refractory epilepsy, and may be an autoimmune factor in paraneoplstic neurologic syndrome presenting with epilepsy.

Status epilepticus due to human parvovirus B19 encephalitis in an immunocompetent adult

Human parvovirus (HPV) B19 is a rare cause of encephalitis in children and immunocompromised adults. The authors describe a case of an otherwise healthy woman who developed encephalitis complicated by prolonged status epilepticus. Human parvovirus B19 infection was suggested by a prodromal, malar rash and established by the presence of specific IgM and IgG antibodies in the patient's serum. This is the first reported case of HPV B19 encephalitis in an immunocompetent adult.

Inflammatory cytokines and related genes are induced in the rat hippocampus by limbic status epilepticus

Limbic status epilepticus was induced in rats by unilateral 60-min electrical stimulation of the CA3 region of the ventral hippocampus. As assessed by RT-PCR followed by Southern blot analysis, transcripts of interleukin-1beta, interleukin-6, interleukin-1 receptor antagonist and inducible nitric oxide synthase were significantly increased 2 h after status epilepticus in the stimulated hippocampus. Induction was maximal at 6 h for interleukin-1beta (445%), interleukin-6 (405%) and tumour necrosis factor-alpha (264%) and at 24 h for interleukin-1 receptor antagonist (494%) and inducible nitric oxide synthase (432%). In rats with spontaneous seizures (60 days after status epilepticus), interleukin-1beta mRNA was still higher than controls (241%). Immunocytochemical staining of interleukin-1beta, interleukin-6 and tumour necrosis factor-alpha was enhanced in glia with a time-course similar to that of the respective transcripts. Sixty days after status epilepticus, interleukin-1beta immunoreactivity was increased exclusively in neurons in one third of the animals. Multiple intracerebroventricular injections of interleukin-1 receptor antagonist (0.5 microg/3 microL) significantly decreased the severity of behavioural convulsions during electrical stimulation and selectively reduced tumour necrosis factor-alpha content in the hippocampus measured 18 h after status epilepticus. Thus, the induction of spontaneously recurring seizures in rats involves the activation of inflammatory cytokines and related pro- and anti-inflammatory genes in the hippocampus. These changes may play an active role in hyperexcitability of the epileptic tissue.

Status epilepticus with neuron-reactive serum antibodies: response to plasma exchange

The authors report a patient with partial and secondarily generalized status epilepticus who required 70 days of general anesthesia for seizure control. Although antiepileptic medications failed to control the seizures, they resolved with plasma exchange. The patient's serum reacted with rat cerebral cortex, hippocampus, and cerebellum, but not with cells expressing the glutamate receptor GluR3. These findings suggest an immune response against neuronal antigens other than GluR3.

Differential regulation of cytokine expression following pilocarpine-induced seizure

While the pathological changes that occur in the brain following seizure have been well characterized, the molecular mechanisms underlying these events are poorly understood. Cell death, reactive gliosis, and axonal sprouting are among the best studied alterations in the epileptic brain. Previous work in both the peripheral and the central nervous systems suggests that cytokines are capable of affecting each of these processes. To better understand the role of cytokines in seizures and their sequelae, we have characterized cytokine expression in an animal model of epilepsy. Using pilocarpine to chemically induce seizures, and RNase protection assays to assess mRNA levels, we have quantified changes in expression of several members of the neuropoietic cytokine family following a single, prolonged seizure. Levels of oncostatin M (OSM), leukemia inhibitory factor (LIF), cardiotrophin-1, and ciliary neurotrophic factor were all increased in the hippocampus after seizure, though to differing extents and with markedly different time courses. Cells expressing the most dramatically up-regulated cytokines, LIF and OSM, were identified by combined in situ hybridization and immunohistochemistry. The majority of LIF(+) cells in the hippocampus were glial fibrillary acidic protein(+) astrocytes, while the majority of OSM(+) cells had the morphology of interneurons and were occasionally colabeled with neurofilament markers. Both the time course and the localization of cytokine up-regulation following seizure suggest possible roles for these intercellular signaling molecules in epilepsy.

Transient suppression of a secondary humoral response in rats is evoked by lithium-pilocarpine-induced limbic seizures

Several experiments were designed to evaluate a secondary humoral response following limbic seizures. After baseline antigen binding capacity (ABC) had been determined for the primary response, a second subcutaneous injection of the antigen (human serum albumin) was accompanied by an injection of either lithium (3 mEq/kg)-pilocarpine (30 mg/kg) or one of two comparator treatments: metrazol (30 mg/kg) or cyclophosphamide (50 mg/kg); other rats served as drug controls. Only the groups that received the lithium-pilocarpine (status epilepticus) or cyclophosphamide (no seizure) displayed significant immunosuppression after 5 but not 10 days. The results support the hypothesis that seizure activity within the amygdaloid-hippocampal complex modulates immunocompetence through corticotropin mechanisms.