Characterization of the intrahippocampal kainic acid model in female mice with a special focus on seizure suppression by antiseizure medications

Despite special challenges in the medical treatment of women with epilepsy, in particular preclinical animal studies were focused on males for decades and females have only recently moved into the focus of scientific interest. The intrahippocampal kainic acid (IHKA) mouse model of temporal lobe epilepsy (TLE) is one of the most studied models in males reproducing electroencephalographic (EEG) and histopathological features of human TLE. Hippocampal paroxysmal discharges (HPDs) were described as drug resistant focal seizures in males. Here, we investigated the IHKA model in female mice, in particular drug-resistance of HPDs and the influence of antiseizure medications (ASMs) on the power spectrum. After injecting kainic acid (KA) unilaterally into the hippocampus of female mice, we monitored the development of epileptiform activity by local field potential (LFP) recordings. Subsequently, we evaluated the effect of the commonly prescribed ASMs lamotrigine (LTG), oxcarbazepine (OXC) and levetiracetam (LEV), as well as the benzodiazepine diazepam (DZP) with a focus on HPDs and power spectral analysis and assessed neuropathological alterations of the hippocampus. In the IHKA model, female mice replicated key features of human TLE as previously described in males. Importantly, HPDs in female mice did not respond to commonly prescribed ASMs in line with the drug-resistance in males, thus representing a suitable model of drug-resistant seizures. Intriguingly, we observed an increased occurrence of generalized seizures after LTG. Power spectral analysis revealed a pronounced increase in the delta frequency range after the higher dose of 30 mg/kg LTG. DZP abolished HPDs and caused a marked reduction over a wide frequency range (delta, theta, and alpha) of the power spectrum. By characterizing the IHKA model of TLE in female mice we address an important gap in basic research. Considering the special challenges complicating the therapeutic management of epilepsy in women, inclusion of females in preclinical studies is imperative. A well-characterized female model is a prerequisite for the development of novel therapeutic strategies tailored to sex-specific needs and for studies on the effect of epilepsy and ASMs during pregnancy.

Dimethyl sulfoxide's impact on epileptiform activity in a mouse model of chronic temporal lobe epilepsy

In the quest for novel treatments for patients with drug-resistant seizures, poor water solubility of potential drug candidates is a frequent obstacle. Literature indicated that the highly efficient solvent dimethyl sulfoxide (DMSO) may have a confounding influence in epilepsy research, reporting both pro- and antiepileptic effects. In this study, we aim to clarify the effects of DMSO on epileptiform activity in one of the most frequently studied models of chronic epilepsy, the intrahippocampal kainic acid (IHKA) mouse model, and in a model of acute seizures. We show that 100 % DMSO (in a volume of 1.5 µl/g corresponding to 1651 mg/kg) causes a significant short-term anti-seizure effect in epileptic IHKA mice of both sexes, but does not affect the threshold of acute seizures induced by pentylenetetrazol (PTZ). These findings highlight that the choice of solvent and appropriate vehicle control is crucial to minimize undesirable misleading effects and that drug candidates exclusively soluble in 100 % DMSO need to be modified for better solubility already at initial testing.

Disruptor: Computational identification of oncogenic mutants disrupting protein-protein and protein-DNA interactions

We report an Osprey-based computational protocol to prospectively identify oncogenic mutations that act via disruption of molecular interactions. It is applicable to analyse both protein-protein and protein-DNA interfaces and it is validated on a dataset of clinically relevant mutations. In addition, it is used to predict previously uncharacterised patient mutations in CDK6 and p16 genes, which are experimentally confirmed to impair complex formation.

In vivo CRISPRa decreases seizures and rescues cognitive deficits in a rodent model of epilepsy

Epilepsy is a major health burden, calling for new mechanistic insights and therapies. CRISPR-mediated gene editing shows promise to cure genetic pathologies, although hitherto it has mostly been applied ex vivo. Its translational potential for treating non-genetic pathologies is still unexplored. Furthermore, neurological diseases represent an important challenge for the application of CRISPR, because of the need in many cases to manipulate gene function of neurons in situ. A variant of CRISPR, CRISPRa, offers the possibility to modulate the expression of endogenous genes by directly targeting their promoters. We asked if this strategy can effectively treat acquired focal epilepsy, focusing on ion channels because their manipulation is known be effective in changing network hyperactivity and hypersynchronziation. We applied a doxycycline-inducible CRISPRa technology to increase the expression of the potassium channel gene Kcna1 (encoding K_v1.1) in mouse hippocampal excitatory neurons. CRISPRa-mediated K_v1.1 upregulation led to a substantial decrease in neuronal excitability. Continuous video-EEG telemetry showed that AAV9-mediated delivery of CRISPRa, upon doxycycline administration, decreased spontaneous generalized tonic-clonic seizures in a model of temporal lobe epilepsy, and rescued cognitive impairment and transcriptomic alterations associated with chronic epilepsy. The focal treatment minimizes concerns about off-target effects in other organs and brain areas. This study provides the proof-of-principle for a translational CRISPR-based approach to treat neurological diseases characterized by abnormal circuit excitability.

Gating defects of disease-causing de novo mutations in Cav1.3 Ca2+ channels

Recently, we and others identified somatic and germline de novo gain-of-function mutations in CACNA1D, the gene encoding the α1-subunit of voltage-gated Ca_v1.3 Ca²⁺-channels. While somatic mutations identified in aldosterone producing adenomas (APAs) underlie treatment-resistant hypertension, germline CACNA1D mutations are associated with a neurodevelopmental disorder characterized by a wide symptomatic spectrum, including autism spectrum disorder. The number of newly identified CACNA1D missense mutations is constantly growing, but their pathogenic potential is difficult to predict in silico, making functional studies indispensable to assess their contribution to disease risk.

Here we report the functional characterization of previously identified CACNA1D APA mutations F747L and M1354I using whole-cell patch-clamp electrophysiology upon recombinant expression in tsA-201 cells. We also investigated if alternative splicing of Ca_v1.3 affects the aberrant gating of the previously characterized APA mutation R990H and two mutations associated with autism spectrum disorder (A479G and G407R). Splice-variant dependent gating changes are of particular interest for germline mutations, since the relative expression of Ca_v1.3 splice variants differs across different tissues and within brain regions and might therefore result in tissue-specific phenotypes. Our data revealed a complex gain-of-function phenotype for APA mutation F747L confirming its pathogenic role. Furthermore, we found splice-variant dependent gating changes in R990H, A749G and G407R. M1354I did not change channel function of Ca_v1.3 splice variants and should therefore be considered a rare non-pathogenic variant until further proof for its pathogenicity is obtained. Our new findings together with previously published data allow classification of pathogenic CACNA1D mutations into four categories based on prototypical functional changes.

Combination antioxidant therapy prevents epileptogenesis and modifies chronic epilepsy

Many epilepsies are acquired conditions following an insult to the brain such as a prolonged seizure, traumatic brain injury or stroke. The generation of reactive oxygen species (ROS) and induction of oxidative stress are common sequelae of such brain insults and have been shown to contribute to neuronal death and the development of epilepsy. Here, we show that combination therapy targeting the generation of ROS through NADPH oxidase inhibition and the endogenous antioxidant system through nuclear factor erythroid 2-related factor 2 (Nrf2) activation prevents excessive ROS accumulation, mitochondrial depolarisation and neuronal death during in vitro seizure-like activity. Moreover, this combination therapy prevented the development of spontaneous seizures in 40% of animals following status epilepticus (70% of animals were seizure free after 8 weeks) and modified the severity of epilepsy when given to chronic epileptic animals.

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Combination antioxidant therapy during seizure activity is neuroprotective.

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Antioxidant therapy can prevent the development of epilepsy.

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Chronic epilepsy can be modified by antioxidant therapy.

AMPA receptor GluA2 subunit defects are a cause of neurodevelopmental disorders

AMPA receptors (AMPARs) are tetrameric ligand-gated channels made up of combinations of GluA1-4 subunits encoded by GRIA1-4 genes. GluA2 has an especially important role because, following post-transcriptional editing at the Q607 site, it renders heteromultimeric AMPARs Ca2+-impermeable, with a linear relationship between current and trans-membrane voltage. Here, we report heterozygous de novo GRIA2 mutations in 28 unrelated patients with intellectual disability (ID) and neurodevelopmental abnormalities including autism spectrum disorder (ASD), Rett syndrome-like features, and seizures or developmental epileptic encephalopathy (DEE). In functional expression studies, mutations lead to a decrease in agonist-evoked current mediated by mutant subunits compared to wild-type channels. When GluA2 subunits are co-expressed with GluA1, most GRIA2 mutations cause a decreased current amplitude and some also affect voltage rectification. Our results show that de-novo variants in GRIA2 can cause neurodevelopmental disorders, complementing evidence that other genetic causes of ID, ASD and DEE also disrupt glutamatergic synaptic transmission.

Designer receptor technology for the treatment of epilepsy

Epilepsy remains refractory to medical treatment in ~30% of patients despite decades of new drug development. Neurosurgery to remove or disconnect the seizure focus is often curative but frequently contraindicated by risks of irreversible impairment to brain function. Novel therapies are therefore required that better balance seizure suppression against the risks of side effects. Among experimental gene therapies, chemogenetics has the major advantage that the action on the epileptogenic zone can be modulated on demand. Two broad approaches are to use a designer G-protein-coupled receptor or a modified ligand gated ion channel, targeted to specific neurons in the epileptogenic zone using viral vectors and cell-type selective promoters. The receptor can be activated on demand by either an exogenous compound or by pathological levels of extracellular glutamate that occur in epileptogenic tissue. We review the principal designer receptor technologies and their modes of action. We compare the drawbacks and benefits of each designer receptor with particular focus on the drug activators and the potential for clinical translation in epilepsy.

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Inhibitory designer receptors (DRs) allow on-demand suppression of seizures upon activation by exogenous drugs or endogenous neurotransmitters.

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DRs include modified G-protein coupled receptors, chimaeric ligand-gated ion channels, and mutated non-mammalian channels.

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Identification of drug activators of DRs that are already approved for use in humans significantly accelerates clinical translation.

Epilepsy Gene Therapy Using an Engineered Potassium Channel

Refractory focal epilepsy is a devastating disease for which there is frequently no effective treatment. Gene therapy represents a promising alternative, but treating epilepsy in this way involves irreversible changes to brain tissue, so vector design must be carefully optimized to guarantee safety without compromising efficacy. We set out to develop an epilepsy gene therapy vector optimized for clinical translation. The gene encoding the voltage-gated potassium channel Kv1.1, KCNA1, was codon optimized for human expression and mutated to accelerate the recovery of the channels from inactivation. For improved safety, this engineered potassium channel (EKC) gene was packaged into a nonintegrating lentiviral vector under the control of a cell type-specific CAMK2A promoter. In a blinded, randomized, placebo-controlled preclinical trial, the EKC lentivector robustly reduced seizure frequency in a male rat model of focal neocortical epilepsy characterized by discrete spontaneous seizures. When packaged into an adeno-associated viral vector (AAV2/9), the EKC gene was also effective at suppressing seizures in a male rat model of temporal lobe epilepsy. This demonstration of efficacy in a clinically relevant setting, combined with the improved safety conferred by cell type-specific expression and integration-deficient delivery, identify EKC gene therapy as being ready for clinical translation in the treatment of refractory focal epilepsy.SIGNIFICANCE STATEMENT Pharmacoresistant epilepsy affects up to 0.3% of the population. Although epilepsy surgery can be effective, it is limited by risks to normal brain function. We have developed a gene therapy that builds on a mechanistic understanding of altered neuronal and circuit excitability in cortical epilepsy. The potassium channel gene KCNA1 was mutated to bypass post-transcriptional editing and was packaged in a nonintegrating lentivector to reduce the risk of insertional mutagenesis. A randomized, blinded preclinical study demonstrated therapeutic effectiveness in a rodent model of focal neocortical epilepsy. Adeno-associated viral delivery of the channel to both hippocampi was also effective in a model of temporal lobe epilepsy. These results support clinical translation to address a major unmet need.

Olanzapine: A potent agonist at the hM4D(Gi) DREADD amenable to clinical translation of chemogenetics

Designer receptors exclusively activated by designer drugs (DREADDs) derived from muscarinic receptors not only are a powerful tool to test causality in basic neuroscience but also are potentially amenable to clinical translation. A major obstacle, however, is that the widely used agonist clozapine N-oxide undergoes conversion to clozapine, which penetrates the blood-brain barrier but has an unfavorable side effect profile. Perlapine has been reported to activate DREADDs at nanomolar concentrations but is not approved for use in humans by the Food and Drug Administration or the European Medicines Agency, limiting its translational potential. Here, we report that the atypical antipsychotic drug olanzapine, widely available in various formulations, is a potent agonist of the human M4 muscarinic receptor-based DREADD, facilitating clinical translation of chemogenetics to treat central nervous system diseases.

KCC2 overexpression prevents the paradoxical seizure-promoting action of somatic inhibition

Although cortical interneurons are apparently well-placed to suppress seizures, several recent reports have highlighted a paradoxical role of perisomatic-targeting parvalbumin-positive (PV+) interneurons in ictogenesis. Here, we use an acute in vivo model of focal cortical seizures in awake behaving mice, together with closed-loop optogenetic manipulation of PV+ interneurons, to investigate their function during seizures. We show that photo-depolarization of PV+ interneurons rapidly switches from an anti-ictal to a pro-ictal effect within a few seconds of seizure initiation. The pro-ictal effect of delayed photostimulation of PV+ interneurons was not shared with dendrite-targeting somatostatin-positive (SOM+) interneurons. We also show that this switch can be prevented by overexpression of the neuronal potassium-chloride co-transporter KCC2 in principal cortical neurons. These results suggest that strategies aimed at improving the ability of principal neurons to maintain a trans-membrane chloride gradient in the face of excessive network activity can prevent interneurons from contributing to seizure perpetuation.

Semiology, clustering, periodicity and natural history of seizures in an experimental occipital cortical epilepsy model

Focal neocortical epilepsy is a common form of epilepsy and there is a need to develop animal models that allow the evaluation of novel therapeutic strategies to treat this type of epilepsy. Tetanus toxin (TeNT) injection into the rat visual cortex induces focal neocortical epilepsy without preceding status epilepticus. The latency to first seizure ranged from 3 to 7 days. Seizure duration was bimodal, with both short (approximately 30 s) and long-lasting (>100 s) seizures occurring in the same animals. Seizures were accompanied by non-motor features such as behavioural arrest, or motor seizures with or without evolution to generalized tonic-clonic seizures. Seizures were more common during the sleep phase of a light-dark cycle. Seizure occurrence was not random, and tended to cluster with significantly higher probability of recurrence within 24 h of a previous seizure. Across animals, the number of seizures in the first week could be used to predict the number of seizures in the following 3 weeks. The TeNT model of occipital cortical epilepsy is a model of acquired focal neocortical epilepsy that is well-suited for preclinical evaluation of novel anti-epileptic strategies. We provide here a detailed analysis of the epilepsy phenotypes, seizure activity, electrographic features and the semiology. In addition, we provide a predictive framework that can be used to reduce variation and consequently animal use in preclinical studies of potential treatments.

Mechanisms Responsible for ω-Pore Currents in Cav Calcium Channel Voltage-Sensing Domains

Mutations of positively charged amino acids in the S4 transmembrane segment of a voltage-gated ion channel form ion-conducting pathways through the voltage-sensing domain, named ω-current. Here, we used structure modeling and MD simulations to predict pathogenic ω-currents in Ca_V1.1 and Ca_V1.3 Ca²⁺ channels bearing several S4 charge mutations. Our modeling predicts that mutations of Ca_V1.1-R1 (R528H/G, R897S) or Ca_V1.1-R2 (R900S, R1239H) linked to hypokalemic periodic paralysis type 1 and of Ca_V1.3-R3 (R990H) identified in aldosterone-producing adenomas conducts ω-currents in resting state, but not during voltage-sensing domain activation. The mechanism responsible for the ω-current and its amplitude depend on the number of charges in S4, the position of the mutated S4 charge and countercharges, and the nature of the replacing amino acid. Functional characterization validates the modeling prediction showing that Ca_V1.3-R990H channels conduct ω-currents at hyperpolarizing potentials, but not upon membrane depolarization compared with wild-type channels.

Omalizumab effectively protects against early and late allergic responses in asthma after 4 weeks

BACKGROUND

Omalizumab is licensed for therapy in severe allergic asthma with an effect demonstrated after 8 weeks or longer treatment. As new applications for omalizumab demand precise knowledge of the onset of effects, the objective of this study was to determine the time course of the early (EAR) and late allergic reaction (LAR).

MATERIALS AND METHODS

Ten patients (IgE>300 IU/mL and <700 IU/mL) with a significant response to allergen challenge were treated with omalizumab according to the approved dosing table. Bronchial allergen provocations (BAP) were repeated at weeks 1, 2, 4, and 8.

RESULTS

EAR was significantly reduced after 4 weeks (ΔFEV1 28% vs 11%; P<.001), eNO (86 vs 53 ppb; P<.05) and basophil activation after 2 weeks (CD63 expression 79% vs 32%, P<.05) and LAR already after 1 week (ΔFEV1 26% vs 13%, P<.05).

CONCLUSION

These results demonstrate the onset of protective effects earlier than previously determined, potentially improving seasonal utilization and combination with immunotherapy.

Cell-type-specific tuning of Cav1.3 Ca(2+)-channels by a C-terminal automodulatory domain

Cav1.3 L-type Ca(2+)-channel function is regulated by a C-terminal automodulatory domain (CTM). It affects channel binding of calmodulin and thereby tunes channel activity by interfering with Ca(2+)- and voltage-dependent gating. Alternative splicing generates short C-terminal channel variants lacking the CTM resulting in enhanced Ca(2+)-dependent inactivation and stronger voltage-sensitivity upon heterologous expression. However, the role of this modulatory domain for channel function in its native environment is unkown. To determine its functional significance in vivo, we interrupted the CTM with a hemagglutinin tag in mutant mice (Cav1.3DCRD(HA/HA)). Using these mice we provide biochemical evidence for the existence of long (CTM-containing) and short (CTM-deficient) Cav1.3 α1-subunits in brain. The long (HA-labeled) Cav1.3 isoform was present in all ribbon synapses of cochlear inner hair cells. CTM-elimination impaired Ca(2+)-dependent inactivation of Ca(2+)-currents in hair cells but increased it in chromaffin cells, resulting in hyperpolarized resting potentials and reduced pacemaking. CTM disruption did not affect hearing thresholds. We show that the modulatory function of the CTM is affected by its native environment in different cells and thus occurs in a cell-type specific manner in vivo. It stabilizes gating properties of Cav1.3 channels required for normal electrical excitability.

A Polybasic Plasma Membrane Binding Motif in the I-II Linker Stabilizes Voltage-gated CaV1.2 Calcium Channel Function

L-type voltage-gated Ca(2+) channels (LTCCs) regulate many physiological functions like muscle contraction, hormone secretion, gene expression, and neuronal excitability. Their activity is strictly controlled by various molecular mechanisms. The pore-forming α1-subunit comprises four repeated domains (I-IV), each connected via an intracellular linker. Here we identified a polybasic plasma membrane binding motif, consisting of four arginines, within the I-II linker of all LTCCs. The primary structure of this motif is similar to polybasic clusters known to interact with polyphosphoinositides identified in other ion channels. We used de novo molecular modeling to predict the conformation of this polybasic motif, immunofluorescence microscopy and live cell imaging to investigate the interaction with the plasma membrane, and electrophysiology to study its role for Cav1.2 channel function. According to our models, this polybasic motif of the I-II linker forms a straight α-helix, with the positive charges facing the lipid phosphates of the inner leaflet of the plasma membrane. Membrane binding of the I-II linker could be reversed after phospholipase C activation, causing polyphosphoinositide breakdown, and was accelerated by elevated intracellular Ca(2+) levels. This indicates the involvement of negatively charged phospholipids in the plasma membrane targeting of the linker. Neutralization of four arginine residues eliminated plasma membrane binding. Patch clamp recordings revealed facilitated opening of Cav1.2 channels containing these mutations, weaker inhibition by phospholipase C activation, and reduced expression of channels (as quantified by ON-gating charge) at the plasma membrane. Our data provide new evidence for a membrane binding motif within the I-II linker of LTCC α1-subunits essential for stabilizing normal Ca(2+) channel function.

CACNA1D de novo mutations in autism spectrum disorders activate Cav1.3 L-type calcium channels

BACKGROUND

Cav1.3 voltage-gated L-type calcium channels (LTCCs) are part of postsynaptic neuronal signaling networks. They play a key role in brain function, including fear memory and emotional and drug-taking behaviors. A whole-exome sequencing study identified a de novo mutation, p.A749G, in Cav1.3 α1-subunits (CACNA1D), the second main LTCC in the brain, as 1 of 62 high risk-conferring mutations in a cohort of patients with autism and intellectual disability. We screened all published genetic information available from whole-exome sequencing studies and identified a second de novo CACNA1D mutation, p.G407R. Both mutations are present only in the probands and not in their unaffected parents or siblings.

METHODS

We functionally expressed both mutations in tsA-201 cells to study their functional consequences using whole-cell patch-clamp.

RESULTS

The mutations p.A749G and p.G407R caused dramatic changes in channel gating by shifting (~15 mV) the voltage dependence for steady-state activation and inactivation to more negative voltages (p.A749G) or by pronounced slowing of current inactivation during depolarizing stimuli (p.G407R). In both cases, these changes are compatible with a gain-of-function phenotype.

CONCLUSIONS

Our data, together with the discovery that Cav1.3 gain-of-function causes primary aldosteronism with seizures, neurologic abnormalities, and intellectual disability, suggest that Cav1.3 gain-of-function mutations confer a major part of the risk for autism in the two probands and may even cause the disease. Our findings have immediate clinical relevance because blockers of LTCCs are available for therapeutic attempts in affected individuals. Patients should also be explored for other symptoms likely resulting from Cav1.3 hyperactivity, in particular, primary aldosteronism.

[Does coxitis fugax predispose for later Perthes' disease?--first results of an insurance data-based study]

INTRODUCTION

For decades, it has been a matter of debate whether coxitis fugax (CF) may trigger the onset of Perthes' disease (PD). However, the low incidence of both conditions limits the validity of clinical studies. As a novel approach, an analysis of patient data provided by a private health insurance (PHI) was performed. After calculation of the frequencies of CF and PD possible correlations were statistically assessed. We hypothesised that CF predisposes to the development of PD.

MATERIALS

A retrospective database analysis was conducted based on insurance data of patients aged between 1 and 14 years covering an observation period of 7 years. Cases of CF and PD were detected by a search algorithm based on the International Classification System of Diseases (ICD) encoding the ICD codes M12.85 to CF and M91.1 to PD, respectively. Cases where CF was followed by PD were separately assessed for plausibility considering the clinical course and the length of the symptom-free interval. Statistical analysis was performed by using the chi-square test with a significance level set at 5 %.

RESULTS

Among a cohort of 407,875 children 960 cases of CF were detected. Of these, 876 (91.3 %) had one single event of CF whereas 84 (8.7 %) children had two or more episodes. The average incidence of CF was 0.24 % per year. The frequency of PD was calculated to be 15.7 cases per 100, 000 children per year. In eleven cases (all male) CF was found to be followed by PD, however, after checking for plausibility only three cases remained. Statistical analysis revealed that the incidence of PD in male children with a previous CF episode was 21-times higher compared to children without CF (p < 0.0001).

DISCUSSION

The results of the hitherto largest study including more than 400 ,000 children showed a significantly higher rate of PD in male children with previous CF compared to boys without CF. However, different patterns of age distribution and the observation that multiple CF episodes do not trigger the development of PD contradict the assumption of a possible correlation between these two diseases. In two of the three cases where CF was followed by PD a so-called "late onset PD" was evident suggesting a misdiagnosed PD at initial presentation. The chosen study design using patient data provided by a PHI allows the acquisition and evaluation of large numbers of cases which may help to elucidate possible correlations between different medical conditions. To unambiguously answer the hypothesis of this study, the inclusion of additional insurance data is necessary.

C-terminal modulatory domain controls coupling of voltage-sensing to pore opening in Cav1.3 L-type Ca(2+) channels

Activity of voltage-gated Ca_v1.3 L-type Ca²⁺ channels is required for proper hearing as well as sinoatrial node and brain function. This critically depends on their negative activation voltage range, which is further fine-tuned by alternative splicing. Shorter variants miss a C-terminal regulatory domain (CTM), which allows them to activate at even more negative potentials than C-terminally long-splice variants. It is at present unclear whether this is due to an increased voltage sensitivity of the Ca_v1.3 voltage-sensing domain, or an enhanced coupling of voltage-sensor conformational changes to the subsequent opening of the activation gate. We studied the voltage-dependence of voltage-sensor charge movement (Q_ON-V) and of current activation (I_Ca-V) of the long (Ca_v1.3_L) and a short Ca_v1.3 splice variant (Ca_v1.3_42A) expressed in tsA-201 cells using whole cell patch-clamp. Charge movement (Q_ON) of Ca_v1.3_L displayed a much steeper voltage-dependence and a more negative half-maximal activation voltage than Ca_v1.2 and Ca_v3.1. However, a significantly higher fraction of the total charge had to move for activation of Ca_v1.3 half-maximal conductance (Ca_v1.3: 68%; Ca_v1.2: 52%; Ca_v3.1: 22%). This indicated a weaker coupling of Ca_v1.3 voltage-sensor charge movement to pore opening. However, the coupling efficiency was strengthened in the absence of the CTM in Ca_v1.3_42A, thereby shifting I_Ca-V by 7.2 mV to potentials that were more negative without changing Q_ON-V. We independently show that the presence of intracellular organic cations (such as n-methyl-D-glucamine) induces a pronounced negative shift of Q_ON-V and a more negative activation of I_Ca-V of all three channels. These findings illustrate that the voltage sensors of Ca_v1.3 channels respond more sensitively to depolarization than those of Ca_v1.2 or Ca_v3.1. Weak coupling of voltage sensing to pore opening is enhanced in the absence of the CTM, allowing short Ca_v1.3_42A splice variants to activate at lower voltages without affecting Q_ON-V.

Somatic mutations in ATP1A1 and CACNA1D underlie a common subtype of adrenal hypertension

At least 5% of individuals with hypertension have adrenal aldosterone-producing adenomas (APAs). Gain-of-function mutations in KCNJ5 and apparent loss-of-function mutations in ATP1A1 and ATP2A3 were reported to occur in APAs. We find that KCNJ5 mutations are common in APAs resembling cortisol-secreting cells of the adrenal zona fasciculata but are absent in a subset of APAs resembling the aldosterone-secreting cells of the adrenal zona glomerulosa. We performed exome sequencing of ten zona glomerulosa-like APAs and identified nine with somatic mutations in either ATP1A1, encoding the Na(+)/K(+) ATPase α1 subunit, or CACNA1D, encoding Cav1.3. The ATP1A1 mutations all caused inward leak currents under physiological conditions, and the CACNA1D mutations induced a shift of voltage-dependent gating to more negative voltages, suppressed inactivation or increased currents. Many APAs with these mutations were <1 cm in diameter and had been overlooked on conventional adrenal imaging. Recognition of the distinct genotype and phenotype for this subset of APAs could facilitate diagnosis.

Structural determinants of CaV1.3 L-type calcium channel gating

A C-terminal modulatory domain (CTM) tightly regulates the biophysical properties of Ca(v)1.3 L-type Ca(2+) channels, in particular the voltage dependence of activation (V(0.5)) and Ca(2+) dependent inactivation (CDI). A functional CTM is present in the long C-terminus of human and mouse Ca(v)1.3 (Ca(v)1.3(L)), but not in a rat long cDNA clone isolated from superior cervical ganglia neurons (rCa(v)1.3(scg)). We therefore addressed the question if this represents a species-difference and compared the biophysical properties of rCa(v)1.3(scg) with a rat cDNA isolated from rat pancreas (rCa(v)1.3(L)). When expressed in tsA-201 cells under identical experimental conditions rCa(v)1.3(L) exhibited Ca(2+) current properties indistinguishable from human and mouse Ca(v)1.3(L), compatible with the presence of a functional CTM. In contrast, rCa(v)1.3(scg) showed gating properties similar to human short splice variants lacking a CTM. rCa(v)1.3(scg) differs from rCa(v)1.3(L) at three single amino acid (aa) positions, one alternative spliced exon (exon31), and a N-terminal polymethionine stretch with two additional lysines. Two aa (S244, A2075) in rCa(v)1.3(scg) explained most of the functional differences to rCa(v)1.3(L). Their mutation to the corresponding residues in rCa(v)1.3(L) (G244, V2075) revealed that both contributed to the more negative V 0.5, but caused opposite effects on CDI. A2075 (located within a region forming the CTM) additionally permitted higher channel open probability. The cooperative action in the double-mutant restored gating properties similar to rCa(v)1.3(L). We found no evidence for transcripts containing one of the single rCa(v)1.3(scg) mutations in rat superior cervical ganglion preparations. However, the rCa(v)1.3(scg) variant provided interesting insight into the structural machinery involved in Ca(v)1.3 gating.

The coumarin scopoletin potentiates acetylcholine release from synaptosomes, amplifies hippocampal long-term potentiation and ameliorates anticholinergic- and age-impaired memory

In a previous study the simple, naturally derived coumarin scopoletin (SCT) was identified as an inhibitor of acetylcholinesterase (AChE), using a pharmacophore-based virtual screening approach. In this study the potential of SCT as procholinergic and cognition-enhancing therapeutic was investigated in a more detailed way, using different experimental approaches like measuring newly synthesized acetylcholine (ACh) in synaptosomes, long-term potentiation (LTP) experiments in hippocampal slices, and behavior studies. SCT enhanced the K⁺-stimulated release of ACh from rat frontal cortex synaptosomes, showing a bell-shaped dose effect curve (E_max: 4 μM). This effect was blocked by the nicotinic ACh receptor (nAChR) antagonists mecamylamine (MEC) and dihydro-β-erythroidine (DHE). The nAChR agonist (and AChE inhibitor) galantamine induced a similar increase in ACh release (E_max: 1 μM). SCT potentiated LTP in hippocampal slices of rat brain. The high-frequency stimulation (HFS)-induced, N-methyl-D-aspartate (NMDA) receptor dependent LTP of field excitatory postsynaptic potentials at CA3-CA1 synapses was greatly enhanced by pre-HFS application of SCT (4 μM for 4 min). This effect was mimicked by nicotine (2 μM) and abolished by MEC, suggesting an effect on nAChRs. SCT did not restore the total inhibition of LTP by NMDA receptor antagonist d, l-2-amino-5-phosphonopentanoic acid (AP-5). SCT (2 μg, i.c.v.) increased T-maze alternation and ameliorated novel object recognition of mice with scopolamine-induced cholinergic deficit. It also reduced age-associated deficits in object memory of 15–18-month-old mice (2 mg/kg sc). Our findings suggest that SCT possesses memory-improving properties, which are based on its direct nAChR agonistic activity. Therefore, SCT might be able to rescue impaired cholinergic functions by enhancing nAChR-mediated release of neurotransmitters and promoting neural plasticity in hippocampus.

Effect of n-3 polyunsaturated fatty acids in asthma after low-dose allergen challenge

BACKGROUND

We investigated the anti-inflammatory potential of n-3 polyunsaturated fatty acids (PUFA) on specific bronchial inflammation. Allergic asthmatics were challenged using a low-dose allergen provocation model.

METHODS

Our parallel double-blinded study randomly assigned 23 house dust mite-allergic asthmatics (aged 22-29 years; 13 females, 10 males) to dietary supplementation with either an n-3 PUFA-enriched fat blend (0.69 g/day) or placebo for 5 weeks. After 3 weeks, the patients were challenged daily with low doses of mite allergen for 2 weeks. Primary outcome parameters were effects on lung function (forced expiratory volume in 1 s, FEV(1)) and exhaled nitric oxide (eNO) as a marker of bronchial inflammation.

RESULTS

Even before the bronchial challenge, eNO was significantly lower in the n-3 PUFA group (p=0.014). Levels of eNO increased during allergen exposure in both groups, but differences in means were significantly lower in the n-3 PUFA group (p=0.022). During the low-dose allergen challenge, there were no differences between the groups with regard to symptoms, FEV(1) or the allergen dose required to induce deterioration of lung function (PD(20)). Numbers of sputum eosinophils did not differ significantly, while serum eosinophils (10.1+/-0.1.84 vs. 5.79+/-0.69%) as well as changes in eosinophilic cationic protein (20.5+/-9.93 vs. -1.68+/-4.36 ng/ml) and in vitro cysteinyl leukotriene release (2,889+/-872 vs. 1,120+/-173 ng/ml) were significantly lower in the n-3 PUFA group (p<0.05 each).

CONCLUSION

Our results provide evidence that dietary supplementation with n-3 PUFA is able to reduce bronchial inflammation even after low-dose allergen challenge.

Compressibility of the nitridosilicate SrYb[Si4N7] and the oxonitridoaluminosilicates MYb[Si4-xAlxOxN7-x] (x = 2; M = Sr, Ba)

The compressibilities of the nitridosilicate SrYb[Si(4)N(7)] and the oxonitridoaluminosilicates MYb[Si(4-x)Al(x)O(x)N(7-x)] (x = 2; M = Sr, Ba) were investigated by in situ high-pressure X-ray powder diffraction. Pressures up to 42 GPa were generated using the diamond-anvil cell technique. The title compounds are structurally stable to the highest pressure obtained. A fit of a third-order Birch-Murnaghan equation-of-state to the p-V data results in V(0) = 302.91 (6) A(3), B(0) = 176 (2) GPa and B' = 4.4 (2) for SrYb[Si(4)N(7)]; V(0) = 310.4 (1) A(3), B(0) = 161 (2) GPa and B' = 4.6 (2) for SrYb[Si(4-x)Al(x)O(x)N(7-x)]; and V(0) = 317.3 (5) A(3), B(0) = 168 (2) GPa and B' = 4.7 (2) for BaYb[Si(4-x)Al(x)O(x)N(7-x)]. While the linear compressibilities of the a and c axes of BaYb[Si(4-x)Al(x)O(x)N(7-x)] are very similar up to 30 GPa, distinct differences were observed for SrYb[Si(4)N(7)] and SrYb[Si(4-x)Al(x)O(x)N(7-x)], with the c axis being the most compressible axis. In all of the investigated compounds the bulk compressibility is dominated by the compression behaviour of the tetrahedral network, while the size of the substituted cation plays a minor role.

[Radiation therapy in two cats with pituitary tumors]

Two cats with large pituitary neoplasms (adenoma and adenocarcinoma) were treated with fractionated radiation therapy. Total doses of 40 Gy, respectively 36 Gy, were applied in 10 fractions of 4 Gy, and 3.6 Gy respectively. Side effects were minimal and transient. Anesthesia was well tolerated. Improvement of clinical signs could be observed during radiation therapy in both cats. One cat had a complete, the other a partial tumor response. One cat (suspicion of adenoma) was euthanized 1 3/4 years after therapy due to unrelated disease. No tumor was found on histopathology, however a small focal necrosis of brain tissue in the irradiated field was observed. The second animal with a pituitary adenocarcinoma was euthanized because of tumor recurrence 1 1/2 years after therapy. Radiation therapy was effective, despite the low total doses of radiation applied.