Tamas Bartfai

The role of inflammation in epilepsy

Epilepsy is the third most common chronic brain disorder, and is characterized by an enduring predisposition to generate seizures. Despite progress in pharmacological and surgical treatments of epilepsy, relatively little is known about the processes leading to the generation of individual seizures, and about the mechanisms whereby a healthy brain is rendered epileptic. These gaps in our knowledge hamper the development of better preventive treatments and cures for the ≈30% of epilepsy cases that prove resistant to current therapies. Here, we focus on the rapidly growing body of evidence that supports the involvement of inflammatory mediators—released by brain cells and peripheral immune cells—in both the origin of individual seizures and the epileptogenic process. We first describe aspects of brain inflammation and immunity, before exploring the evidence from clinical and experimental studies for a relationship between inflammation and epilepsy. Subsequently, we discuss how seizures cause inflammation, and whether such inflammation, in turn, influences the occurrence and severity of seizures, and seizure-related neuronal death. Further insight into the complex role of inflammation in the generation and exacerbation of epilepsy should yield new molecular targets for the design of antiepileptic drugs, which might not only inhibit the symptoms of this disorder, but also prevent or abrogate disease pathogenesis.

Interleukin-1β Enhances NMDA Receptor-Mediated Intracellular Calcium Increase through Activation of the Src Family of Kinases

Interleukin (IL)-1β is a proinflammatory cytokine implicated in various pathophysiological conditions of the CNS involving NMDA receptor activation. Circumstantial evidence suggests that IL-1β and NMDA receptors can functionally interact. Using primary cultures of rat hippocampal neurons, we investigated whether IL-1β affects NMDA receptor function(s) by studying (1) NMDA receptor-induced [Ca2+]i increase and (2) NMDA-mediated neurotoxicity. IL1β (0.01-0.1 ng/ml) dose-dependently enhances NMDA-induced [Ca2+]i increases with a maximal effect of ∼45%. This effect occurred only when neurons were pretreated with IL-1β, whereas it was absent if IL-1β and NMDA were applied simultaneously, and it was abolished by IL-1 receptor antagonist (50 ng/ml). Facilitation of NMDA-induced [Ca2+]i increase by IL-1β was prevented by both lavendustin (LAV) A (500 nm) and 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) (1 μm), suggesting an involvement of tyrosine kinases. Increased tyrosine phosphorylation of NMDA receptor subunits 2A and 2B and coimmunoprecipitation of activated Src tyrosine kinase with these subunits was observed after exposure of hippocampal neurons to 0.05 ng/ml IL-1β. Finally, 0.05 ng/ml IL-1β increased by ∼30% neuronal cell death induced by NMDA, and this effect was blocked by both lavendustin A and PP2. These data suggest that IL-1β increases NMDA receptor function through activation of tyrosine kinases and subsequent NR2A/B subunit phosphorylation. These effects may contribute to glutamate-mediated neurodegeneration.

Targeted pharmacological depletion of serum amyloid P component for treatment of human amyloidosis.

The normal plasma protein serum amyloid P component (SAP) binds to fibrils in all types of amyloid deposits, and contributes to the pathogenesis of amyloidosis. In order to intervene in this process we have developed a drug, R-1-[6-[R-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid, that is a competitive inhibitor of SAP binding to amyloid fibrils. This palindromic compound also crosslinks and dimerizes SAP molecules, leading to their very rapid clearance by the liver, and thus produces a marked depletion of circulating human SAP. This mechanism of drug action potently removes SAP from human amyloid deposits in the tissues and may provide a new therapeutic approach to both systemic amyloidosis and diseases associated with local amyloid, including Alzheimers disease and type 2 diabetes.

Cytokines and fever.

Cytokines are highly inducible, secreted proteins mediating intercellular communication in the nervous and immune system. Fever is the multiphasic response of elevation and decline of the body core temperature regulated by central thermoregulatory mechanisms localized in the preoptic area of the hypothalamus. The discovery that several proinflammatory cytokines act as endogenous pyrogens and that other cytokines can act as antipyretic agents provided a link between the immune and the central nervous systems and stimulated the study of the central actions of cytokines. The proinflammatory cytokines interleukin 1 (IL-1), interleukin 6 (IL-6) and the tumor necrosis factor alpha (TNF) as well as the antiinflammatory cytokines interleukin 1 receptor antagonist (IL-1ra) and interleukin 10 (IL-10) have been most investigated for their pyrogenic or antipyretic action. The experimental evidence demonstrating the role of these secreted proteins in modulating the fever response is as follows: 1) association between cytokine levels in serum and CSF and fever; 2) finding of the presence of cytokine receptors on various cell types in the brain and demonstration of the effects of pharmacological application of cytokines and of their neutralizing antibodies on the fever response; 3) fever studies on cytokine- and cytokine receptor- transgenic models. Studies on the peripheral and the central action of cytokines demonstrated that peripheral cytokines can communicate with the brain in several ways including stimulation of afferent neuronal pathways and induction of the synthesis of a non cytokine pyrogen, i.e. PGE2, in endothelial cells in the periphery and in the brain. Cytokines synthesized in the periphery may act by crossing the blood brain barrier and acting directly via neuronal cytokine receptors. The mechanisms that ultimately mediate the central action of cytokines and of LPS on the temperature-sensitive neurons in the preoptic hypothalamic region involved in thermoregulation, directly or via second mediators, remain to be fully elucidated.

Interleukin-1β Contributes to the Generation of Experimental Febrile Seizures

Fever can provoke “febrile” seizures (FS). Because complex FS may promote development of temporal lobe epilepsy, understanding their mechanisms is clinically important. Using an immature rodent model and transgenic technology, we examined the role of interleukin‐1β, (IL‐1β), a pyrogenic, proinflammatory cytokine, in FS. IL‐1β receptor–deficient mice were resistant to experimental FS. This resistance appeared independent of genetic background and was attributed to lack of IL‐1β signaling, because exogenous cytokine reduced seizure threshold in wild‐type but not receptor‐deficient mice independent of strain. In addition, high IL‐1β doses induced seizures only in IL‐1β receptor–expressing mice. These data indicate that IL‐1β signaling contributes critically to fever‐induced hyperexcitability underlying FS, constituting a potential target for their prevention. Ann Neurol 2005;57:152–155

Coexistence of peptides with classical neurotransmitters

In the present article the fact is emphasized that neuropeptides often are located in the same neurons as classical transmitters such as acetylcholine, 5-hydroxy-tryptamine, catecholamines, γ-aminobutyric acid (GABA) etc. This raises the possibility that neurons produce, store and release more than the one messenger molecule. The exact functional role of such coesisting peptides is often difficult to evaluate, especially in the central nervous system. In the periphery some studies indicate apparently meaningful interactions of different types with the classical transmitter, but other types of actions including trophic effects have been observed. More recently it has been shown that some neurons contain more than one classical transmitter, e.g. 5-HT plus GABA, further underlining the view that transfer of information across synapses may be more compex than perhaps hitherto assumed.

A Specific Role for NR2A-Containing NMDA Receptors in the Maintenance of Parvalbumin and GAD67 Immunoreactivity in Cultured Interneurons

Several lines of evidence suggest that a hypoglutamatergic condition may induce a phenotypic loss of cortical parvalbumin (PV)-positive GABAergic interneurons, such as that observed in brain tissue of schizophrenic subjects. However, it is not known whether the loss of PV interneurons is a consequence of the hypoglutamatergic condition or a secondary aspect of the disease. We characterized the signaling and subunit expression of NMDA receptors in cultured cortical PV interneurons and determined whether a hypoglutamatergic condition, created by direct application of sublethal concentrations of ketamine or subunit-selective NMDA receptor antagonists, can affect the expression of the GABAergic markers as observed in vivo. Real-time PCR performed on mRNA isolated from single neurons showed that PV interneurons present a fivefold higher NR2A/NR2B ratio than pyramidal neurons. Brief, nontoxic, exposure to NMDA led to an increase in ERK1/2 (extracellular signal-regulated kinase 1/2) and cAMP response element-binding protein phosphorylation in PV interneurons, and this increase was blocked by the NR2A-selective antagonist NVP-AAM077. Application of the nonselective NMDA receptor antagonist ketamine, at sublethal concentrations, induced a time and dose-dependent decrease in parvalbumin and GAD67 immunoreactivity specifically in PV interneurons. These effects were reversible and were also observed with the NR2A-selective antagonist, whereas the NR2B-selective antagonist Ro-25-6981 only partially reduced GAD67 immunoreactivity. Coexposure to the calcium channel opener BayK, or the group I metabotropic glutamate receptor agonist DHPG [(RS)-3,5-dihydroxyphenylglycine] attenuated the decrease in GAD67 and parvalbumin induced by the NMDA receptor antagonists. These results suggest that the activity of NR2A-containing NMDA receptors play a pivotal role in the maintenance of the GABAergic function of PV interneurons.

Galanin and galanin antagonists: molecular and biochemical perspectives

The neuropeptide galanin potently inhibits insulin release, hippocampal acetylcholine release and firing of locus coeruleus cells, and stimulates feeding and release of growth hormone. Galanin regulates K+ channels, adenylyl cyclase and phospholipase C by acting at Gi/Go protein-coupled high-affinity receptors. Galanin receptor agonists such as the N-terminal fragment galanin1-16 act synergistically with morphine in the somatosensory system and have potential analgetic application. Galanin antagonists may be useful therapeutic agents in endocrinology, neurology and psychiatry. The enhancing effect of such agents on hippocampal cholinergic function would be useful in treatment of Alzheimers disease. Recent synthesis of a series of high-affinity galanin antagonists, reviewed, along with galanins actions, by Tamas Bartfai and colleagues, opens the possibility of examining the functions of endogenous galanin and test the pharmacological usefulness of antagonism of galanin function in the endocrine, somatosensory and central nervous systems.

A blood based 12-miRNA signature of Alzheimer disease patients.

BackgroundAlzheimer disease (AD) is the most common form of dementia but the identification of reliable, early and non-invasive biomarkers remains a major challenge. We present a novel miRNA-based signature for detecting AD from blood samples.ResultsWe apply next-generation sequencing to miRNAs from blood samples of 48 AD patients and 22 unaffected controls, yielding a total of 140 unique mature miRNAs with significantly changed expression levels. Of these, 82 have higher and 58 have lower abundance in AD patient samples. We selected a panel of 12 miRNAs for an RT-qPCR analysis on a larger cohort of 202 samples, comprising not only AD patients and healthy controls but also patients with other CNS illnesses. These included mild cognitive impairment, which is assumed to represent a transitional period before the development of AD, as well as multiple sclerosis, Parkinson disease, major depression, bipolar disorder and schizophrenia. miRNA target enrichment analysis of the selected 12 miRNAs indicates an involvement of miRNAs in nervous system development, neuron projection, neuron projection development and neuron projection morphogenesis. Using this 12-miRNA signature, we differentiate between AD and controls with an accuracy of 93%, a specificity of 95% and a sensitivity of 92%. The differentiation of AD from other neurological diseases is possible with accuracies between 74% and 78%. The differentiation of the other CNS disorders from controls yields even higher accuracies.ConclusionsThe data indicate that deregulated miRNAs in blood might be used as biomarkers in the diagnosis of AD or other neurological diseases.

Ca2+ Signaling via the Neuronal Calcium Sensor-1 Regulates Associative Learning and Memory in C. elegans

On a radial temperature gradient, C. elegans worms migrate, after conditioning with food, toward their cultivation temperature and move along this isotherm. This experience-dependent behavior is called isothermal tracking (IT). Here we show that the neuron-specific calcium sensor-1 (NCS-1) is essential for optimal IT. ncs-1 knockout animals show major defects in IT behavior, although their chemotactic, locomotor, and thermal avoidance behaviors are normal. The knockout phenotype can be rescued by reintroducing wild-type NCS-1 into the AIY interneuron, a key component of the thermotaxis network. A loss-of-function form of NCS-1 incapable of binding calcium does not restore IT, whereas NCS-1 overexpression enhances IT performance levels, accelerates learning (faster acquisition), and produces a memory with slower extinction. Thus, proper calcium signaling via NCS-1 defines a novel pathway essential for associative learning and memory.