Adherence to anti-seizure medications in the Swedish Prospective Regional Epilepsy Database and Biobank for Individualized Clinical Treatment (PREDICT)

The aim of this study was to describe the extent of, and risk factors for, non-adherence to anti-seizure medications (ASMs) in adult people with epilepsy (PWE) in Sweden. A cross-sectional multi-centre study was performed of PWEs in western Sweden, with data from medical records, and a questionnaire filled in by the participants including self-reports on how often ASM doses had been forgotten during the past year. Participants were categorized into adherent if they forgot at 0-1 occasion, and non-adherent if they forgot at 2-10 or >10 occasions. Demographic and clinical factors were compared by Chi2- or Fisher's test and a logistic regression model was used to find risk factors for non-adherence. In the cohort of 416 PWE aged median 43, IQR 29-62 years, 398 patients were prescribed ASM treatment at inclusion, and 39 % (n = 154) were in the non-adherent group. Significant factors in the multivariable analysis were: younger age, seizure freedom the past year, valproate treatment and experiencing side effects. The rate of self-reported non-adherence was high, illustrating a need for continuous focus on fundamental aspects of epilepsy care. The identified risk factors could enable quality improvement projects and patient education to be directed to those at risk of non-adherence.

Cerebrospinal fluid markers of neuronal and glial cell damage in patients with autoimmune neurologic syndromes with and without underlying malignancies

Autoimmune neurologic syndromes can be paraneoplastic (associated with malignancies and/or onconeural antibodies), or non-paraneoplastic. Their clinical presentation is often similar. As prognosis is related to malignancy treatment, better biomarkers are needed to identify patients with malignancy. We investigated cerebrospinal fluid (CSF) markers of neuronal (neurofilament light chain, NFL and total tau protein, T-tau) and glial (glial fibrillary acidic protein) damage. CSF-NFL and T-tau were increased in both paraneoplastic and non-paraneoplastic autoimmune syndromes. Patients with manifest malignancies were older, had less epilepsy, more focal central and peripheral neurological signs and symptoms, and worse long-term outcome, than those without malignancy. CSF-NFL-levels predicted long-term outcome but were not diagnostic for malignancy, after age adjustment.

Cerebrospinal fluid markers of neuronal and glial cell damage to monitor disease activity and predict long-term outcome in patients with autoimmune encephalitis

BACKGROUND AND PURPOSE

Clinical symptoms and long-term outcome of autoimmune encephalitis are variable. Diagnosis requires multiple investigations, and treatment strategies must be individually tailored. Better biomarkers are needed for diagnosis, to monitor disease activity and to predict long-term outcome. The value of cerebrospinal fluid (CSF) markers of neuronal [neurofilament light chain protein (NFL), and total tau protein (T-tau)] and glial cell [glial fibrillary acidic protein (GFAP)] damage in patients with autoimmune encephalitis was investigated.

METHODS

Demographic, clinical, magnetic resonance imaging, CSF and antibody-related data of 25 patients hospitalized for autoimmune encephalitis and followed for 1 year were retrospectively collected. Correlations between these data and consecutive CSF levels of NFL, T-tau and GFAP were investigated. Disability, assessed by the modified Rankin scale, was used for evaluation of disease activity and long-term outcome.

RESULTS

The acute stage of autoimmune encephalitis was accompanied by high CSF levels of NFL and T-tau, whereas normal or significantly lower levels were observed after clinical improvement 1 year later. NFL and T-tau reacted in a similar way but at different speeds, with T-tau reacting faster. CSF levels of GFAP were initially moderately increased but did not change significantly later on. Final outcome (disability at 1 year) directly correlated with CSF-NFL and CSF-GFAP levels at all time-points and with CSF-T-tau at 3 ± 1 months. This correlation remained significant after age adjustment for CSF-NFL and T-tau but not for GFAP.

CONCLUSION

In autoimmune encephalitis, CSF levels of neuronal and glial cell damage markers appear to reflect disease activity and long-term disability.

Deletion of the adenosine A1 receptor gene does not alter neuronal damage following ischaemia in vivo or in vitro

Extracellular adenosine is dramatically increased during cerebral ischaemia and is considered to be neuroprotective due to its inhibitory effect on synaptic transmission mediated by the adenosine A1 receptor (A1R). We investigated the importance of the A1R in a mouse model of global ischaemia and in a murine hippocampal slice culture model of in vitro ischaemia, using mice with the A1R gene deleted. In brains from mice lacking the A1R, damage induced by global ischaemia was similar to that in wild-type animals. In contrast, treatment with a selective A1R antagonist [8-cyclo-pentyl theophylline (8-CPT)], administered before the ischaemic insult in naive wild-type mice, exacerbated the neuronal damage following global ischaemia. Although the inhibitory action of adenosine on excitatory neurotransmission in hippocampal slices was lost in A1R knockout mice, there was no difference in damage between slices from wild-type and knockout mice after in vitro ischaemia. The results suggest that some effects of the A1R are compensated for in knockout animals.

Glucose but not lactate in combination with acidosis aggravates ischemic neuronal death in vitro

BACKGROUND AND PURPOSE

Hyperglycemia aggravates brain damage in clinical stroke and in experimental in vivo models of cerebral ischemia. Elevated preischemic glucose levels, lactate production, and intracerebral acidosis correlate with increased brain damage. We have developed a murine hippocampal slice culture model of in vitro ischemia (IVI), suitable for studies of the mechanisms of neuronal death. In this model we investigated the individual contribution of glucose, pH, lactate, and combinations thereof as well as ionotropic glutamate receptor activation to the development of hyperglycemic ischemic cell death.

METHODS

Murine organotypic hippocampal slice cultures were exposed to IVI in a medium with an ionic composition similar to that of the extracellular fluid in the brain during ischemia in vivo. Cell death was assessed by propidium iodide uptake. Ionotropic glutamate receptor blockade was accomplished by D-2-amino-5-phosphonopentanoic acid (D-APV) or 2,3-dihydro-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX).

RESULTS

The combination of high glucose levels and acidosis (pH 6.8), but not acidosis per se or the combination of lactate and acidosis during IVI, exacerbated damage. Cell death after hyperglycemic IVI was not diminished by blockade of ionotropic glutamate receptors.

CONCLUSIONS

Aggravation of brain damage by hyperglycemia in vivo can be reproduced in hippocampal slice cultures in vitro. Our results demonstrate that glucose per se, but not lactate, in combination with acidosis mediates the detrimental hyperglycemic effect through a mechanism independent of ionotropic glutamate receptors.

Mouse hippocampal organotypic tissue cultures exposed to in vitro "ischemia" show selective and delayed CA1 damage that is aggravated by glucose

Oxygen and glucose deprivation (OGD) in cell cultures is generally studied in a medium, such as artificial cerebrospinal fluid (CSF), with an ion composition similar to that of the extracellular fluid of the normal brain (2 to 4 mmol/L K+, 2 to 3 mmol/L Ca2+; pH 7.4). Because the distribution of ions across cell membranes dramatically shifts during ischemia, the authors exposed mouse organotypic hippocampal tissue cultures to OGD in a medium, an ischemic cerebrospinal fluid, with an ion composition similar to the extracellular fluid of the brain during ischemia (70 mmol/L K+, 0.3 mmol/L Ca2+; pH 6.8). In ischemic CSF, OGD induced a selective and delayed cell death in the CA1 region, as assessed by propidium iodide uptake. Cell death was glutamate receptor dependent since blockade of the N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors mitigated cell damage. Hyperglycemia aggravates ischemic brain damage whereas glucose in artificial CSF prevents oxygen deprivation-induced damage. The authors demonstrate that glucose in ischemic CSF significantly exacerbates cell damage after oxygen deprivation. This new model of "ischemia" can be useful in future studies of the mechanisms and treatment of ischemic cell death, including studies using genetically modified mice.

Increased synaptic inhibition in dentate gyrus of mice with reduced levels of endogenous brain-derived neurotrophic factor

The aim of this study was to explore the role of endogenous neurotrophins for inhibitory synaptic transmission in the dentate gyrus of adult mice. Heterozygous knockout (+/-) mice or neurotrophin scavenging proteins were used to reduce the levels of endogenous brain-derived neurotrophic factor and neurotrophin-3. Patch-clamp recordings from dentate granule cells in brain slices showed that the frequency, but not the kinetics or amplitude, of miniature inhibitory postsynaptic currents was modulated in brain-derived neurotrophic factor +/- compared to wild-type (+/+) mice. Furthermore, paired-pulse depression of evoked inhibitory synaptic responses was increased in brain-derived neurotrophic factor +/- mice. Similar results were obtained in brain slices from brain-derived neurotrophic factor +/+ mice incubated with tyrosine receptor kinase B-immunoglobulin G, which scavenges endogenous brain-derived neurotrophic factor. The increased inhibitory synaptic activity in brain-derived neurotrophic factor +/- mice was accompanied by decreased excitability of the granule cells. No differences in the frequency, amplitude or kinetics of miniature inhibitory postsynaptic currents were seen between neurotrophin-3 +/- and +/+ mice. From these results we suggest that endogenous brain-derived neurotrophic factor, but not neurotrophin-3, has acute modulatory effects on synaptic inhibition onto dentate granule cells. The site of action seems to be located presynaptically, i.e. brain-derived neurotrophic factor regulates the properties of inhibitory interneurons, leading to increased excitability of dentate granule cells. We propose that through this mechanism, brain-derived neurotrophic factor can change the gating/filtering properties of the dentate gyrus for incoming information from the entorhinal cortex to hippocampus. This will have consequences for the recruitment of hippocampal neural circuitries both under physiological and pathological conditions, such as epileptogenesis.

Development and persistence of kindling epilepsy are impaired in mice lacking glial cell line-derived neurotrophic factor family receptor alpha 2

Seizure activity regulates gene expression for glial cell line-derived neurotrophic factor (GDNF) and neurturin (NRTN), and their receptor components, the transmembrane c-Ret tyrosine kinase and the glycosylphosphatidylinositol-anchored GDNF family receptor (GFR) alpha 1 and alpha 2 in limbic structures. We demonstrate here that epileptogenesis, as assessed in the hippocampal kindling model, is markedly suppressed in mice lacking GFR alpha 2. Moreover, at 6 to 8 wk after having reached the epileptic state, the hyperexcitability is lower in GFR alpha 2 knock-out mice as compared with wild-type mice. These results provide evidence that signaling through GFR alpha 2 is involved in mechanisms regulating the development and persistence of kindling epilepsy. Our data suggest that GDNF and NRTN may modulate seizure susceptibility by altering the function of hilar neuropeptide Y-containing interneurons and entorhinal cortical afferents at dentate granule cell synapses.

LTP of AMPA and NMDA receptor-mediated signals: evidence for presynaptic expression and extrasynaptic glutamate spill-over

We have addressed the expression of long-term potentiation (LTP) in hippocampal CA1 by comparing AMPA and NMDA receptor-(AMPAR- and NMDAR-) mediated postsynaptic signals. We find that potentiation of NMDAR-mediated signals accompanies LTP of AMPAR-mediated signals, and is associated with a change in variability implying an increase in quantal content. Further, tetanic LTP of NMDAR-mediated signals can be elicited when LTP of AMPAR-mediated signals is prevented. We propose that LTP is mainly expressed presynaptically, and that, while AMPARs respond only to glutamate from immediately apposed terminals, NMDARs also sense glutamate released from terminals presynaptic to neighboring cells. We also find that tetanic LTP increases the rate of depression of NMDAR-mediated signals by the use-dependent blocker MK-801, implying an increase in the glutamate release probability. These findings argue for a presynaptic contribution to LTP and for extrasynaptic spill-over of glutamate onto NMDARs.

Ionotropic glutamate receptors. Their possible role in the expression of hippocampal synaptic plasticity

In the brain, most fast excitatory synaptic transmission is mediated through L-glutamate acting on postsynaptic ionotropic glutamate receptors. These receptors are of two kinds--the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/kainate (non-NMDA) and the N-methyl-D-aspartate (NMDA) receptors, which are thought to be colocalized onto the same postsynaptic elements. This excitatory transmission can be modulated both upward and downward, long-term potentiation (LTP) and long-term depression (LTD), respectively. Whether the expression of LTP/LTD is pre-or postsynaptically located (or both) remains an enigma. This article will focus on what postsynaptic modifications of the ionotropic glutamate receptors may possibly underly long-term potentiation/depression. It will discuss the character of LTP/ LTD with respect to the temporal characteristics and to the type of changes that appears in the non-NMDA and NMDA receptor-mediated synaptic currents, and what constraints these findings put on the possible expression mechanism(s) for LTP/LTD. It will be submitted that if a modification of the glutamate receptors does underly LTP/LTD, an increase/ decrease in the number of functional receptors is the most plausible alternative. This change in receptor number will have to include a coordinated change of both the non-NMDA and the NMDA receptors.