POS0035 GENE REGULATION IN T-CELLS FROM PsA PATIENTS DIFFERS BETWEEN PERIPHERAL BLOOD AND THE INFLAMED JOINTS: IMPLICATIONS FOR THE INTERPRETATION OF GWAS SIGNALS

Background

Genome-wide association studies (GWAS) have identified variants that are associated with complex diseases such as Psoriatic Arthritis (PsA). The majority of these variants do not affect the coding sequence of proteins but rather regulatory elements which are highly cell type and state specific, and can affect distally located genes via chromatin interaction mechanisms.

We and others have previously analysed GWAS loci for multiple conditions (including PsA and Rheumatoid Arthrtitis) in cell lines using functional genomics techniques, providing putative mechanisms to many loci with previously unknown function [1].

However, multiple studies have identified large differences in gene regulatory mechanisms between cell lines and primary cells, which could significantly alter the proposed mechanisms. Differences between between samples from healthy volunteers and patients, in particular from the affected tissue, have although not been exhaustively investigated.

Objectives

To assess the impact of using primary cells derived from PsA patients compared to healthy volunteers in functional genomics studies.

Methods

CD4+ and CD8+ T cells were isolated from peripherial blood from 10 healthy controls and 48 PsA patients and from 6 PsA synovial fluid samples.

We performed RNA-seq and ATAC-seq on these two cell types to analyse the global patterns of gene expression and chromatin activity.

Results

We find subtle differences between PsA patients and healthy controls in cells isolated from blood. RNA-seq analysis identified only a handful of differentially expressed genes whilst ATAC-seq analysis identified only 28 differential loci.

On the other hand, T cells isolated from synovial fluid showed significant differences compared to T cells isolated from patient’s blood. Interestingly, we find that CD4+ T cells show substantially more differentially expressed genes compared to CD8+ T cells (1168 vs 346 Log2FoldChange > 1, FDR < 0.01). Genes overexpressed in synovial CD4+ T cells are more strongly enriched for immune pathways such as cytokine signaling and T cell proliferation compared to synovial CD8+ T cells

We also find that synovial CD4+ T cells highly overexpress MHC class II genes (Figure 1).

Figure 1.

Normalized counts of the alpha chains of MHC class 2 genes in CD4+ and CD8+ T cells purified from blood from healthy subjects and patients and synovial fluid.

Conclusion

This preliminary analysis suggests that T cells isolated from peripherial blood do not seem to differ significantly between PsA patients and healthy controls. In contrast, cells isolated from synovial fluid are highly specialized and activated. Moreover, these cells do not resemble canonically activated T cells which means that this state can not be easily emulated in vitro.

This study indicates the importance of not only studying GWAS loci in relevant primary cells from patients, but also that attention needs to be given to cells isolated from the affected site.

References

[1]Shi C, Ray-Jones H, Ding J, et al (2021) Chromatin Looping Links Target Genes with Genetic Risk Loci for Dermatological Traits. J Invest Dermatol 141:1975–1984. https://doi.org/10.1016/J.JID.2021.01.015

Acknowledgements

This work was funded by the Wellcome Trust (award references 207491/Z/17/Z and 215207/Z/19/Z), the Versus Arthritis (award reference 21754), the NIHR Manchester Biomedical Research Centre, and the Medical Research Council (award reference MR/N00017X/1).

Disclosure of Interests

None declared

An Analysis of Pharmacogenomic-Guided Pathways and Their Effect on Medication Changes and Hospital Admissions: A Systematic Review and Meta-Analysis

Ninety-five percent of the population are estimated to carry at least one genetic variant that is discordant with at least one medication. Pharmacogenomic (PGx) testing has the potential to identify patients with genetic variants that puts them at risk of adverse drug reactions and sub-optimal therapy. Predicting a patient's response to medications could support the safe management of medications and reduce hospitalization. These benefits can only be realized if prescribing clinicians make the medication changes prompted by PGx test results. This review examines the current evidence on the impact PGx testing has on hospital admissions and whether it prompts medication changes. A systematic search was performed in three databases (Medline, CINAHL and EMBASE) to search all the relevant studies published up to the year 2020, comparing hospitalization rates and medication changes amongst PGx tested patients with patients receiving treatment-as-usual (TAU). Data extracted from full texts were narratively synthesized using a process model developed from the included studies, to derive themes associated to a suggested workflow for PGx-guided care and its expected benefit for medications optimization and hospitalization. A meta-analysis was undertaken on all the studies that report the number of PGx tested patients that had medication change(s) and the number of PGx tested patients that were hospitalized, compared to participants that received TAU. The search strategy identified 5 hospitalization themed studies and 5 medication change themed studies for analysis. The meta-analysis showed that medication changes occurred significantly more frequently in the PGx tested arm across 4 of 5 studies. Meta-analysis showed that all-cause hospitalization occurred significantly less frequently in the PGx tested arm than the TAU. The results show proof of concept for the use of PGx in prescribing that produces patient benefit. However, the review also highlights the opportunities and evidence gaps that are important when considering the introduction of PGx into health systems; namely patient involvement in PGx prescribing decisions, thus a better understanding of the perspective of patients and prescribers. We highlight the opportunities and evidence gaps that are important when considering the introduction of PGx into health systems.

An exploration of the impact of SARS-CoV-2 (COVID-19) restrictions on marginalised groups in the UK

Background

To contain the spread of COVID-19 within the UK over the past year, there have been a series of local and national lockdowns. These restrictions are likely to have impacted upon the health and well-being of marginalised groups who rely on now closed social and community support services to stay healthy. An understanding of the experiences of marginalised people is important; therefore, this study aimed to explore the impact of the COVID-19 restrictions on the health and well-being of marginalised groups in the UK.

Methods

In summer 2020, a rapid telephone survey was conducted by trained, trusted volunteers with 76 participants who were from marginalised groups. As part of this survey, 64 participants consented to describe their experience of lockdown. These case studies were thematically analysed to identify patterns of meaning.

Results

Findings indicate that lockdown led to the deterioration of health of participants, impacted adversely on their socio-economic positions and affected access to food and essential supplies. In addition, government public health messaging was considered confusing and inadequate.

Conclusions

This study highlights the need for pathways into services which support marginalised groups to remain accessible during periods of restrictions and essential supplies and food to be mapped and protected for marginalised individuals within our local communities.

Patient Perspectives on Factors Affecting Direct Oral Anticoagulant Use for Stroke Prevention in Atrial Fibrillation

INTRODUCTION

Oral anticoagulant therapy choices for patients with atrial fibrillation (AF) expanded in the last decade with the introduction of direct oral anticoagulants (DOAC). However, the implementation of DOACs was slow and varied across different health economies in England. There is limited evidence on the patient role in the uptake of new medicines, including DOACs, apart from considering their demographic and clinical characteristics. Hence, this study aimed to address the gap by exploring the view of patients with AF on factors affecting DOAC use.

METHODS

A qualitative study using semi-structured interviews was conducted in three health economies in the North of England. Adult patients (>18 years) diagnosed with non-valvular AF, prescribed an oral anticoagulant (vitamin K antagonist or DOAC), and able to give written consent were recruited. Data were collected between August 2018 and April 2019. Audio recorded interviews were transcribed verbatim and analyzed using the framework method.

RESULTS

Four themes with eleven subthemes discussed identified factors affecting the use of DOACs. They were linked to limited healthcare financial and workforce resources, patient involvement in decision-making, patient knowledge about DOACs, safety concerns about oral anticoagulants, and oral anticoagulant therapy impact on patients' daily lives. Lack of a) opportunities to voice patient preferences and b) information on available therapy options resulted in some patients experiencing difficulties with the prescribed therapy. This was reported to cause negative impact on their daily lives, adherence, and overall satisfaction with the therapy.

CONCLUSION

Greater patient involvement in decision-making could prevent and resolve difficulties encountered by some patients and potentially improve outcomes plus increase the uptake of DOACs.

Patients’ perspectives on factors affecting their involvement in decision-making on oral anticoagulant therapy for stroke prevention in non-valvular atrial fibrillation

Introduction

Acknowledging patients’ preferences and addressing their concerns is thought to improve patients’ satisfaction with consultations, resulting in improved adherence and health benefits [1]. Adherence to oral anticoagulant (OA) therapy in non-valvular atrial fibrillation (NVAF) is crucial to prevent AF-related strokes. Previous research on anticoagulation in NVAF indicated that decision-making was dominated by prescribers, but patients offered several therapy options reported being involved [2]. Identifying the patient’s perspective on factors affecting their involvement could help to deliver more patient-centred care in the management of AF.

Aim

To explore patients’ perspectives and experiences concerning factors affecting their involvement in decision-making about OA therapy for stroke prevention in NVAF.

Methods

Semi-structured face-to-face interviews were conducted with patients in three health economies in the North of England between August 2018 and April 2019. An interview topic guide based on narrative review findings [2] was developed and refined by a Patient and Public Involvement (PPI) group to ensure clarity. Theoretical sampling was used to recruit adults (&gt;18 years) diagnosed with NVAF, prescribed OA (vitamin K antagonist or direct oral anticoagulant (DOAC)), and able to give written consent. Up to 30 potential participants were approached by a member of their direct care team (nurse or pharmacist) in secondary and primary care anticoagulation or arrhythmia clinics. PPI members recruited patients from a local patient support group. Data collection continued until data saturation was achieved. Audio recorded interviews were transcribed verbatim and analysed using the Framework method.

Results

A total of 21 patient with median (IQR) age of 73 years (65–78 years) were interviewed. Eleven patients took DOACs. The median (IQR) time of taking OA was 3 years (4 weeks-7 years), warfarin 7 years (3–9 years) and DOAC 1 year (4 weeks-4 years). Interviews lasted between 15 and 48 minutes (average 27 minutes). Three themes were identified during analysis (Figure 1). Patients described therapy decisions being made by just the clinician, jointly with the clinician, and in few cases by the patient alone. The lack of involvement resulted from patients perceiving that there was only a choice between accepting and refusing the therapy, and clinician’s role was to make decisions. Limited consultation times, lack of continuous relationship with a clinician and knowledge about OAs options discouraged patients from being involved and some patients reported difficulties with the prescribed therapy. Patients that were involved considered safety of therapy options and impact on daily life.

Conclusions

Limited consultation time, patient’s perception of clinician’s role, quality of patient-clinician relationship, and patients’ awareness of therapy options were main factors influencing the level of patient involvement in the decision-making. Support from both organisation and clinicians (e.g., longer consultations, availability of different therapy options) is needed to facilitate greater patient involvement, which could prevent difficulties encountered by some patients. The main strength of this study was recruitment of participants from three health economies differing in anticoagulation service provision models, which enabled greater insight into potential barriers. However, the sample was lacking ethnic diversity and could have potential of recall bias.

References

1. Shay LA and Lafata JE. (2015). Where is the evidence? A systematic review of shared decision making and patient outcomes. Medical Decision Making. 35 (1): 114–131.

2. Medlinskiene K, Petty D, Richardson S and Stirling K. (2018) Are patients with non-valvular atrial fibrillation involved in decision-making about oral anticoagulants? A literature review. International Journal of Pharmacy Practice. 26 (Suppl. 1): 42–43.

Riluzole-Triazole Hybrids as Novel Chemical Probes for Neuroprotection in Amyotrophic Lateral Sclerosis

Despite intense attention from biomedical and chemical researchers, there are few approved treatments for amyotrophic lateral sclerosis (ALS), with only riluzole (Rilutek) and edaravone (Radicava) currently available to patients. Moreover, the mechanistic basis of the activity of these drugs is currently not well-defined, limiting the ability to design new medicines for ALS. This Letter describes the synthesis of triazole-containing riluzole analogues, and their testing in a novel neuroprotective assay. Seven compounds were identified as having neuroprotective activity, with two compounds having similar activity to riluzole.

Sonic hedgehog signalling mediates astrocyte crosstalk with neurons to confer neuroprotection

Sonic hedgehog (SHH) is a glycoprotein associated with development that is also expressed in the adult CNS and released after brain injury. Since the SHH receptors patched homolog‐1 and Smoothened are highly expressed on astrocytes, we hypothesized that SHH regulates astrocyte function. Primary mouse cortical astrocytes derived from embryonic Swiss mouse cortices, were treated with two chemically distinct agonists of the SHH pathway, which caused astrocytes to elongate and proliferate. These changes are accompanied by decreases in the major astrocyte glutamate transporter‐1 and the astrocyte intermediate filament protein glial fibrillary acidic protein. Multisite electrophysiological recordings revealed that the SHH agonist, smoothened agonist suppressed neuronal firing in astrocyte‐neuron co‐cultures and this was abolished by the astrocyte metabolic inhibitor ethylfluoroacetate, revealing that SHH stimulation of metabolically active astrocytes influences neuronal firing. Using three‐dimensional co‐culture, MAP2 western blotting and immunohistochemistry, we show that SHH‐stimulated astrocytes protect neurons from kainate‐induced cell death. Altogether the results show that SHH regulation of astrocyte function represents an endogenous neuroprotective mechanism.

A systematic review of feeding practices among postoperative patients: is practice in-line with evidenced-based guidelines?

BACKGROUND

Early oral feeding after surgery is best practice among adult, noncritically ill patients. Evidenced-based guidelines (EBG) recommend commencing liquid and solid feeding within 24 h of surgery to improve patient (e.g. reduced morbidity) and hospital (e.g. reduced length of stay) outcomes. Whether these EBG are adhered to in usual clinical practice remains unknown. The present study aimed to identify the time to commencement of first oral feed (liquid or solid) and first solid feed among postoperative, noncritically ill, adult patients.

METHODS

MEDLINE, CINAHL, SCOPUS and Web of Science databases were searched from inception to June 2016 for observational studies reporting liquid and/or solid feeding practices among postoperative patients. Studies reporting a mean/median time to first feed or first solid feed within 24 h of surgery or where ≥75% of patients were feeding by postoperative day one were considered in-line with EBG.

RESULTS

Of 5826 articles retrieved, 29 studies were included. Only 40% and 22% of studies reported time to first feed and time to first solid feed in-line with EBG, respectively. Clear and free liquids were the first diet types commenced in 86% of studies. When solids were commenced, 44% of studies reported using various therapeutic diet types (e.g. light) prior to the commencement of a regular diet. Patients who underwent gastrointestinal procedures appeared more likely to experience delayed postoperative feeding.

CONCLUSIONS

Our findings demonstrate a gap between postoperative feeding evidence and its practical application. This information provides a strong rationale for interventions targeting improved nutritional care following surgery.

Neuronal influences are necessary to produce mitochondrial co-localization with glutamate transporters in astrocytes

Recent evidence suggests that the predominant astrocyte glutamate transporter, GLT-1/ Excitatory Amino Acid Transporter 2 (EAAT2) is associated with mitochondria. We used primary cultures of mouse astrocytes to assess co-localization of GLT-1 with mitochondria, and tested whether the interaction was dependent on neurons, actin polymerization or the kinesin adaptor, TRAK2. Mouse primary astrocytes were transfected with constructs expressing V5-tagged GLT-1, pDsRed1-Mito with and without dominant negative TRAK2. Astrocytes were visualized using confocal microscopy and co-localization was quantified using Volocity software. Image analysis of confocal z-stacks revealed no co-localization between mitochondria and GLT-1 in pure astrocyte cultures. Co-culture of astrocytes with primary mouse cortical neurons revealed more mitochondria in processes and a positive correlation between mitochondria and GLT-1. This co-localization was not further enhanced after neuronal depolarization induced by 1 h treatment with 15 mM K⁺. In pure astrocytes, a rho kinase inhibitor, Y27632 caused the distribution of mitochondria to astrocyte processes without enhancing GLT-1/mitochondrial co-localization, however, in co-cultures, Y27632 abolished mitochondrial:GLT-1 co-localization. Disrupting potential mitochondrial: kinesin interactions using dominant negative TRAK2 did not alter GLT-1 distribution or GLT-1: mitochondrial co-localization. We conclude that the association between GLT-1 and mitochondria is modest, is driven by synaptic activity and dependent on polymerized actin filaments.Mitochondria have limited co-localization with the glutamate transporter GLT-1 in primary astrocytes in culture. Few mitochondria are in the fine processes where GLT-1 is abundant. It is necessary to culture astrocytes with neurones to drive a significant level of co-localization, but co-localization is not further altered by depolarization, manipulating sodium ion gradients or Na/K ATPase activity.

Immunoablation of cells expressing the NG2 chondroitin sulphate proteoglycan

Expression of the transmembrane NG2 chondroitin sulphate proteoglycan (CSPG) defines a distinct population of NG2-glia. NG2-glia serve as a regenerative pool of oligodendrocyte progenitor cells in the adult central nervous system (CNS), which is important for demyelinating diseases such as multiple sclerosis, and are a major component of the glial scar that inhibits axon regeneration after CNS injury. In addition, NG2-glia form unique neuron-glial synapses with unresolved functions. However, to date it has proven difficult to study the importance of NG2-glia in any of these functions using conventional transgenic NG2 'knockout' mice. To overcome this, we aimed to determine whether NG2-glia can be targeted using an immunotoxin approach. We demonstrate that incubation in primary anti-NG2 antibody in combination with secondary saporin-conjugated antibody selectively kills NG2-expressing cells in vitro. In addition, we provide evidence that the same protocol induces the loss of NG2-glia without affecting astrocyte or neuronal numbers in cerebellar brain slices from postnatal mice. This study shows that targeting the NG2 CSPG with immunotoxins is an effective and selective means for killing NG2-glia, which has important implications for studying the functions of these enigmatic cells both in the normal CNS, and in demyelination and degeneration.

SUMO-1 conjugation blocks beta-amyloid-induced astrocyte reactivity

Astrocyte reactivity is implicated in the neuronal loss underlying Alzheimer's disease. Curcumin has been shown to reduce astrocyte reactivity, though the exact pathways underlying these effects are incompletely understood. Here we investigated the role of the small ubiquitin-like modifier (SUMO) conjugation in mediating this effect of curcumin. In beta-amyloid (Aβ)-treated astrocytes, morphological changes and increased glial fibrillary acidic protein (GFAP) confirmed reactivity, which was accompanied by c-jun N-terminal kinase activation. Moreover, the levels of SUMO-1 conjugated proteins, as well as the conjugating enzyme, Ubc9, were decreased, with concomitant treatment with curcumin preventing these effects. Increasing SUMOylation in astrocytes, by over-expression of constitutively active SUMO-1, but not its inactive mutant, abrogated Aβ-induced increase in GFAP, suggesting astrocytes require SUMO-1 conjugation to remain non-reactive.

Dietary levels of pure flavonoids improve spatial memory performance and increase hippocampal brain-derived neurotrophic factor

Evidence suggests that flavonoid-rich foods are capable of inducing improvements in memory and cognition in animals and humans. However, there is a lack of clarity concerning whether flavonoids are the causal agents in inducing such behavioral responses. Here we show that supplementation with pure anthocyanins or pure flavanols for 6 weeks, at levels similar to that found in blueberry (2% w/w), results in an enhancement of spatial memory in 18 month old rats. Pure flavanols and pure anthocyanins were observed to induce significant improvements in spatial working memory (p = 0.002 and p = 0.006 respectively), to a similar extent to that following blueberry supplementation (p = 0.002). These behavioral changes were paralleled by increases in hippocampal brain-derived neurotrophic factor (R = 0.46, p<0.01), suggesting a common mechanism for the enhancement of memory. However, unlike protein levels of BDNF, the regional enhancement of BDNF mRNA expression in the hippocampus appeared to be predominantly enhanced by anthocyanins. Our data support the claim that flavonoids are likely causal agents in mediating the cognitive effects of flavonoid-rich foods.

Neuroprotective effects of phenolic antioxidant tBHQ associate with inhibition of FoxO3a nuclear translocation and activity

The Forkhead transcription factor, FoxO3a induces genomic death responses in neurones following translocation from the cytosol to the nucleus. Nuclear translocation of FoxO3a is triggered by trophic factor withdrawal, oxidative stress and the stimulation of extrasynaptic NMDA receptors. Receptor activation of phosphatidylinositol 3-kinase (PI3K)–Akt signalling pathways retains FoxO3a in the cytoplasm, thereby inhibiting the transcriptional activation of death-promoting genes. We hypothesized that phenolic antioxidants such as tert-Butylhydroquinone (tBHQ), which is known to stimulate PI3K–Akt signalling, would inhibit FoxO3a translocation and activity. Treatment of cultured cortical neurones with NMDA increased the nuclear localization of FoxO3a, reduced the phosphorylation of FoxO3a, increased caspase activity and up-regulated Fas ligand expression. In contrast the phenolic antioxidant, tBHQ, caused retention of FoxO3a in the cytosol coincident with enhanced PI3K- dependent phosphorylation of FoxO3a. tBHQ-induced nuclear exclusion of FoxO3a was associated with reduced FoxO-mediated transcriptional activity. Exposure of neurones to tBHQ inhibited NMDA-induced nuclear translocation of FoxO3a, prevented NMDA-induced up-regulation of FoxO-mediated transcriptional activity, blocked caspase activation and protected neurones from NMDA-induced excitotoxic death. Collectively, these data suggest that phenolic antioxidants such as tBHQ oppose stress-induced activation of FoxO3a and therefore have potential neuroprotective utility in neurodegeneration.

Riluzole neuroprotection in a Parkinson's disease model involves suppression of reactive astrocytosis but not GLT-1 regulation

Background

Riluzole is a neuroprotective drug used in the treatment of motor neurone disease. Recent evidence suggests that riluzole can up-regulate the expression and activity of the astrocyte glutamate transporter, GLT-1. Given that regulation of glutamate transport is predicted to be neuroprotective in Parkinson's disease, we tested the effect of riluzole in parkinsonian rats which had received a unilateral 6-hydroxydopamine injection into the median forebrain bundle.

Results

Rats were treated with intraperitoneal riluzole (4 mg/kg or 8 mg/kg), 1 hour before the lesion then once daily for seven days. Riluzole produced a modest but significant attenuation of dopamine neurone degeneration, assessed by suppression of amphetamine-induced rotations, preservation of tyrosine hydroxylase positive neuronal cell bodies in the substantia nigra pars compacta and attenuation of striatal tyrosine hydroxylase protein loss. Seven days after 6-hydroxydopamine lesion, reactive astrocytosis was observed in the striatum, as determined by increases in expression of glial fibrillary acidic protein, however the glutamate transporter, GLT-1, which is also expressed in astrocytes was not regulated by the lesion.

Conclusions

The results confirm that riluzole is a neuroprotective agent in a rodent model of parkinson's disease. Riluzole administration did not regulate GLT-1 levels but significantly reduced GFAP levels, in the lesioned striatum. Riluzole suppression of reactive astrocytosis is an intriguing finding which might contribute to the neuroprotective effects of this drug.

Riluzole elevates GLT-1 activity and levels in striatal astrocytes

Drugs which upregulate astrocyte glutamate transport may be useful neuroprotective compounds by preventing excitotoxicity. We set up a new system to identify potential neuroprotective drugs which act through GLT-1. Primary mouse striatal astrocytes grown in the presence of the growth-factor supplement G5 express high levels of the functional glutamate transporter, GLT-1 (also known as EAAT2) as assessed by Western blotting and ³H-glutamate uptake assay, and levels decline following growth factor withdrawal. The GLT-1 transcriptional enhancer dexamethasone (0.1 or 1 μM) was able to prevent loss of GLT-1 levels and activity following growth factor withdrawal. In contrast, ceftriaxone, a compound previously reported to enhance GLT-1 expression, failed to regulate GLT-1 in this system. The neuroprotective compound riluzole (100 μM) upregulated GLT-1 levels and activity, through a mechanism that was not dependent on blockade of voltage-sensitive ion channels, since zonasimide (1 mM) did not regulate GLT-1. Finally, CDP-choline (10 μM-1 mM), a compound which promotes association of GLT-1/EAAT2 with lipid rafts was unable to prevent GLT-1 loss under these conditions. This observation extends the known pharmacological actions of riluzole, and suggests that this compound may exert its neuroprotective effects through an astrocyte-dependent mechanism.

A paediatric palliative care programme in development: trends in referral and location of death

PURPOSE

To describe the formation of a paediatric palliative care programme providing care in hospital, at home or in hospice, ensuring continuity of care where the child and family desire.

STUDY DESIGN

Descriptive analysis was performed on referral source, diagnosis and reason for discharge for patients referred to the Palliative Care Team at the Children's Hospital of Eastern Ontario in Ottawa, Ontario, Canada from 1999 to 2007.

RESULTS

341 children were referred. 24% had a neurological condition, 21% had genetic disorders or congenital anomalies, 20% had cancer, 18% had metabolic or neurodegenerative conditions and 17% had another diagnosis. The major sources of referral included paediatricians, neonatologists, oncologists and intensivists. 55% of the children have died. 58% of these died in hospital, 27% at home and 15% in hospice. Of the remaining 152 children, 7% were discharged from the programme after clinical improvement, 4% were moved to another geographic location or an adult centre, 2% were not eligible, 1% declined services and 4% were lost to follow-up. The remaining 90 children continue to be followed-up. In the hospitalised patients who died, the annual referral rate increased from 20% to >50%.

IMPLICATIONS

Referral to the palliative care team has increased over time in all diagnostic categories and from all sources. Most children died in hospital; however, a significant number of families chose end-of-life care at home or in a hospice.

NG2 cells differentiate into astrocytes in cerebellar slices

NG2-glia are an abundant population of glial cells that have been considered by many to be oligodendrocyte progenitor cells (OPCs). However, growing evidence suggests that NG2-glia may also be capable of differentiating into astrocytes and neurons under certain conditions. Here, we have examined NG2-glia in cerebellar slices, using transgenic mice in which the astroglial marker glial specific protein (GFAP) drives expression of the reporter gene enhanced green fluorescent protein (EGFP). Immunolabelling for NG2 shows that NG2-glia and GFAP-EGFP astroglia are separate populations in most areas of the brain, although a substantial population of NG2-glia in the pons also express the GFAP-EGFP reporter. In the cerebellum, NG2-glia did not express EGFP, either at postnatal day (P)12 or P29-30. We developed an organotypic culture of P12 cerebellar slices that maintain cytoarchitectural integrity of Purkinje neurons and Bergmann glia. In these cultures, BrdU labelling indicates that the majority of NG2-glia enter the cell cycle within 2 days in vitro (DIV), suggesting that NG2-glia undergo a 'reactive' response in cerebellar cultures. After 2 DIV NG2-glia began to express the astroglial reporter EGFP and in some cases the respective GFAP protein. However, NG2-glia did not acquire phenotypic markers of neural stem cells or neurons. The results suggest that NG2-glia are not lineage restricted OPCs and are a potential source of astrocytes in the cerebellum.

The four major N- and C-terminal splice variants of the excitatory amino acid transporter GLT-1 form cell surface homomeric and heteromeric assemblies

The L-glutamate transporter GLT-1 is an abundant central nervous system (CNS) membrane protein of the excitatory amino acid transporter (EAAT) family that controls extracellular L-glutamate levels and is important in limiting excitotoxic neuronal death. Using reverse transcription-polymerase chain reaction, we have determined that four mRNAs encoding GLT-1 exist in mouse brain, with the potential to encode four GLT-1 isoforms that differ in their N and C termini. We expressed all four isoforms (termed MAST-KREK, MPK-KREK, MAST-DIETCI, and MPK-DIETCI according to amino acid sequence) in a range of cell lines and primary astrocytes and show that each isoform can reach the cell surface. In transfected human embryonic kidney (HEK) 293 or COS-7 cells, all four isoforms support high-affinity sodium-dependent L-glutamate uptake with identical pharmacological and kinetic properties. Inserting a viral epitope (tagged with V5, hemagglutinin, or FLAG) into the second extracellular domain of each isoform allowed coimmunoprecipitation and time-resolved Förster resonance energy transfer (tr-FRET) studies using transfected HEK-293 cells. Here we show for the first time that each of the four isoforms is able to combine to form homomeric and heteromeric assemblies, each of which is expressed at the cell surface of primary astrocytes. After activation of protein kinase C by phorbol ester, V5-tagged GLT-1 is rapidly removed from the cell surface of HEK-293 cells and degraded. This study provides direct biochemical evidence for oligomeric assembly of GLT-1 and reports the development of novel tools to provide insight into the trafficking of GLT-1.

Dietary flavonoid (-)epicatechin stimulates phosphatidylinositol 3-kinase-dependent anti-oxidant response element activity and up-regulates glutathione in cortical astrocytes

Flavonoids are plant-derived polyphenolic compounds with neuroprotective properties. Recent work suggests that, in addition to acting as hydrogen donors, they activate protective signalling pathways. The anti-oxidant response element (ARE) promotes the expression of protective proteins including those required for glutathione synthesis (xCT cystine antiporter, gamma-glutamylcysteine synthetase and glutathione synthase). The use of a luciferase reporter (ARE-luc) assay showed that the dietary flavan-3-ol (-)epicatechin activates this pathway in primary cortical astrocytes but not neurones. We also examined the distribution of NF-E2-related factor-2 (Nrf2), a key transcription factor in ARE-mediated gene expression. We found, using immunocytochemistry, that Nrf2 accumulated in the nuclei of astrocytes following exposure to tert-butylhydroquinone (100 microM) and (-)epicatechin (100 nM). (-)Epicatechin signalling via Nrf2 was inhibited by wortmannin implicating a phosphatidylinositol 3-kinase-dependent pathway. Finally, (-)epicatechin increased glutathione levels in astrocytes consistent with an up-regulation of ARE-mediated gene expression. Together, this suggests that flavonoids may be cytoprotective by increasing anti-oxidant gene expression.

Neuroprotective effects of hesperetin in mouse primary neurones are independent of CREB activation

Dietary flavonoids, including the citrus flavanone hesperetin, may have stimulatory effects on cytoprotective intracellular signalling pathways. In primary mouse cortical neurone cultures, but not SH-SY5Y human neuroblastoma cells or human primary dermal fibroblasts (Promocells), hesperetin (100-300nM, 15min) caused significant increases in the level of ERK1/2 phosphorylation, but did not increase CREB phosphorylation. Administration of hesperetin for 18h did not alter gene expression driven by the cyclic AMP response element (CRE), assessed using a luciferase reporter system, but 300nM hesperetin partially reversed staurosporine-induced cell death in primary neurones. Our data show that hesperetin is a neuroprotective compound at concentrations where antioxidant effects are unlikely to predominate. The effects of hesperetin are cell-type dependent and, unlike the flavanol (-)epicatechin, neuroprotection in vitro is not associated with enhanced CREB phosphorylation or CRE-mediated gene expression.

(-)Epicatechin stimulates ERK-dependent cyclic AMP response element activity and up-regulates GluR2 in cortical neurons

Emerging evidence suggests that the cellular actions of flavonoids relate not simply to their antioxidant potential but also to the modulation of protein kinase signalling pathways. We investigated in primary cortical neurons, the ability of the flavan-3-ol, (-)epicatechin, and its human metabolites at physiologically relevant concentrations, to stimulate phosphorylation of the transcription factor cAMP-response element binding protein (CREB), a regulator of neuronal viability and synaptic plasticity. (-)Epicatechin at 100-300 nmol/L stimulated a rapid, extracellular signal-regulated kinase (ERK)- and PI3K-dependent, increase in CREB phosphorylation. At micromolar concentrations, stimulation was no longer apparent and at the highest concentration tested (30 mumol/L) (-)epicatechin was inhibitory. (-)Epicatechin also stimulated ERK and Akt phosphorylation with similar bell-shaped concentration-response characteristics. The human metabolite 3'-O-methyl-(-)epicatechin was as effective as (-)epicatechin at stimulating ERK phosphorylation, but (-)epicatechin glucuronide was inactive. (-)Epicatechin and 3'-O-methyl-(-)epicatechin treatments (100 nmol/L) increased CRE-luciferase activity in cortical neurons in a partially ERK-dependent manner, suggesting the potential to increase CREB-mediated gene expression. mRNA levels of the glutamate receptor subunit GluR2 increased by 60%, measured 18 h after a 15 min exposure to (-)epicatechin and this translated into an increase in GluR2 protein. Thus, (-)epicatechin has the potential to increase CREB-regulated gene expression and increase GluR2 levels and thus modulate neurotransmission, plasticity and synaptogenesis.

Statistical mechanics of learning multiple orthogonal signals: asymptotic theory and fluctuation effects

The learning of signal directions in high-dimensional data through orthogonal decomposition or principal component analysis (PCA) has many important applications in physics and engineering disciplines, e.g., wireless communication, information theory, and econophysics. The accuracy of the orthogonal decomposition can be studied using mean-field theory. Previous analysis of data produced from a model with a single signal direction has predicted a retarded learning phase transition below which learning is not possible, i.e., if the signal is too weak or the data set is too small then it is impossible to learn anything about the signal direction or magnitude. In this contribution we show that the result can be generalized to the case where there are multiple signal directions. Each nondegenerate signal is associated with a retarded learning transition. However, fluctuations around the mean-field solution lead to large finite size effects unless the signal strengths are very well separated. We evaluate the one-loop contribution to the mean-field theory, which shows that signal directions are indistinguishable from one another if their corresponding population eigenvalues are separated by O(N(-tau)) with exponent tau>1/3, where N is the data dimension. Numerical simulations are consistent with the analysis and show that finite size effects can persist even for very large data sets.

Chronic hypoxia in the human neuroblastoma SH-SY5Y causes reduced expression of the putative alpha-secretases, ADAM10 and TACE, without altering their mRNA levels

Alzheimer's disease is more frequent following an ischemic or hypoxic episode, with levels of beta-amyloid peptides elevated in brains from patients. Similar increases are found after experimental ischemia in animals. It is possible that increased beta-amyloid deposition arises from alterations in amyloid precursor protein (APP) metabolism, indeed, we have shown that exposing cells of neuronal origin to chronic hypoxia decreased the secretion of soluble APP (sAPPalpha) derived by action of alpha-secretase on APP, coinciding with a decrease in protein levels of ADAM10, a disintegrin metalloprotease which is thought to be the major alpha-secretase. In the current study, we extended those observations to determine whether the expression of ADAM10 and another putative alpha-secretase, TACE, as well as the beta-secretase, BACE1 were regulated by chronic hypoxia at the level of protein and mRNA. Using Western blotting and RT-PCR, we demonstrate that after 48 h chronic hypoxia, such that sAPPalpha secretion is decreased by over 50%, protein levels of ADAM10 and TACE and by approximately 60% and 40% respectively with no significant decrease in BACE1 levels. In contrast, no change in the expression of the mRNA for these proteins could be detected. Thus, we conclude that under CH the level of the putative alpha-secretases, ADAM10 and TACE are regulated by post-translational mechanisms, most probably proteolysis, rather than at the level of transcription.

Serotonin transporter expression is not sufficient to confer cytotoxicity to 3,4-methylenedioxymethamphetamine (MDMA) in vitro

There is much evidence from animal studies that the recreational drug MDMA is a selective toxin which damages serotonin nerve terminals and axons. These in vivo studies show that an interaction between MDMA and the serotonin transporter protein (SERT) is the .rst step in toxicity. To further our understanding of the biochemical processes of MDMA toxicity we wished to use an in vitro model for toxicity. We produced two COS-7 cell lines with different levels of expression of recombinant rat SERT, as determined by 5-HT uptake assays, and compared them to human SERT expressing JAR cells and to untransfected COS-7 cells which do not express SERT. Cultured cells were exposed to MDMA (0.1 microM-1 mM) for 24 or 48 h at 37 degrees C before assessing cytotoxicity by LDH release and MTT turnover. Only at the highest concentration used, 1 mM, was MDMA cytotoxic, and this toxicity was found in all cell lines. Cytotoxicity caused by 48 h exposure to 1 mM MDMA at 37 degrees C was not related to the level of SERT expression, not blocked by the SERT-blocking drugs paroxetine or fluoxetine and not enhanced, in JAR cells, by forskolin preincubation that increased 5-HT uptake capacity by 50%. We conclude that SERT expression is not sufficient to confer MDMA toxicity to cell lines. Therefore SERT-expressing cell lines do not offer a simple model system to elucidate the mechanisms underlying MDMA toxicity.

Induction of aquaporin 1 but not aquaporin 4 messenger RNA in rat primary brain microvessel endothelial cells in culture

Aquaporins (AQPs) are a family of proteins that mediate water transport across cells, but the extent to which they are involved in water transport across endothelial cells of the blood-brain barrier is not clear. Expression of AQP1 and AQP4 in rat brain microvessel endothelial cells was investigated in order to determine whether these isoforms were present and, in particular, to examine the hypothesis that brain endothelial expression of AQPs is dynamic and regulated by astrocytic influences. Reverse-transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemistry showed that AQP1 mRNA and protein are present at very low levels in primary rat brain microvessel endothelial cells, and are up-regulated in passaged cells. Upon passage, endothelial cell expression of mdr1a mRNA is decreased, indicating loss of blood-brain barrier phenotype. In passage 4 endothelial cells, AQP1 mRNA levels are reduced by coculture above rat astrocytes, demonstrating that astrocytic influences are important in maintaining the low levels of AQP1 characteristic of the blood-brain barrier endothelium. Reverse-transcriptase-PCR revealed very low levels of AQP1 mRNA present in the RBE4 rat brain microvessel endothelial cell line, with no expression detected in primary cultures of rat astrocytes or in the C6 rat glioma cell line. In contrast, AQP4 mRNA is strongly expressed in astrocytes, but no expression is found in primary or passaged brain microvessel endothelial cells, or in RBE4 or C6 cells. Our results support the concept that expression of AQP1, which is seen in many non-brain endothelia, is suppressed in the specialized endothelium of the blood-brain barrier.

Technology evaluation: colostrinin, ReGen

ReGen Therapeutics is developing Colostrinin, a polypeptide complex derived from ovine colostrums, for the potential treatment of Alzheimer's disease. The compound is currently undergoing phase II clinical trials.

Rat brain serotonin neurones that express neuronal nitric oxide synthase have increased sensitivity to the substituted amphetamine serotonin toxins 3,4-methylenedioxymethamphetamine and p-chloroamphetamine

Substituted amphetamines such as p-chloroamphetamine and the abused drug methylenedioxymethamphetamine cause selective destruction of serotonin axons in rats, by unknown mechanisms. Since some serotonin neurones also express neuronal nitric oxide synthase, which has been implicated in neurotoxicity, the present study was undertaken to determine whether nitric oxide synthase expressing serotonin neurones are selectively vulnerable to methylenedioxymethamphetamine or p-chloroamphetamine. Using double-labeling immunocytochemistry and double in situ hybridization for nitric oxide synthase and the serotonin transporter, it was confirmed that about two thirds of serotonergic cell bodies in the dorsal raphé nucleus expressed nitric oxide synthase, however few if any serotonin transporter immunoreactive axons in striatum expressed nitric oxide synthase at detectable levels. Methylenedioxymethamphetamine (30 mg/kg) or p-chloroamphetamine (2 x 10 mg/kg) was administered to Sprague-Dawley rats, and 7 days after drug administration there were modest decreases in the levels of serotonin transporter protein in frontal cortex, and striatum using Western blotting, even though axonal loss could be clearly seen by immunostaining. p-Chloroamphetamine or methylenedioxymethamphetamine administration did not alter the level of nitric oxide synthase in striatum or frontal cortex, determined by Western blotting. Analysis of serotonin neuronal cell bodies 7 days after p-chloroamphetamine treatment, revealed a net down-regulation of serotonin transporter mRNA levels, and a profound change in expression of nitric oxide synthase, with 33% of serotonin transporter mRNA positive cells containing nitric oxide synthase mRNA, compared with 65% in control animals. Altogether these results support the hypothesis that serotonin neurones which express nitric oxide synthase are most vulnerable to substituted amphetamine toxicity, supporting the concept that the selective vulnerability of serotonin neurones has a molecular basis.

Expression of SOD1 G93A or wild-type SOD1 in primary cultures of astrocytes down-regulates the glutamate transporter GLT-1: lack of involvement of oxidative stress

Glutamate excitotoxicity is implicated in the aetiology of amyotrophic lateral sclerosis (ALS) with impairment of glutamate transport into astrocytes a possible cause of glutamate-induced injury to motor neurons. It is possible that mutations of Cu/Zn superoxide dismutase (SOD1), responsible for about 20% of familial ALS, down-regulates glutamate transporters via oxidative stress. We transfected primary mouse astrocytes to investigate the effect of the FALS-linked mutant hSOD1(G93A) and wild-type SOD1 (hSOD1wt) on the glutamate uptake system. Using western blotting, immunocytochemistry and RT-PCR it was shown that expression of either hSOD1(G93A) or hSOD1wt in astrocytes produced down-regulation of the levels of a glutamate transporter GLT-1, without alterations in its mRNA level. hSOD1(G93A) or hSOD1wt expression caused a decrease of the monomeric form of GLT-1 without increasing oxidative multimers of GLT-1. The effects were selective to GLT-1, since another glutamate transporter GLAST protein and mRNA levels were not altered. Reflecting the decrease in GLT-1 protein, [3H]d-aspartate uptake was reduced in cultures expressing hSOD1(G93A) or hSOD1wt. The hSOD1-induced decline in GLT-1 protein and [3H]d-aspartate uptake was not blocked by the antioxidant Trolox nor potentiated by antioxidant depletion using catalase and glutathione peroxidase inhibitors. Measurement of 2',7'-dichlorofluorescein (DCF)-induced fluorescence revealed that expression of hSOD1(G93A) or hSOD1wt in astrocytes does not lead to detectable increase of intracellular reactive oxygen species. This study suggests that levels of GLT-1 protein in astrocytes are reduced rapidly by overexpression of hSOD1, and is due to a property shared between the wild-type and G93A mutant form, but does not involve the production of intracellular oxidative stress.

Principal-component-analysis eigenvalue spectra from data with symmetry-breaking structure

Principal component analysis (PCA) is a ubiquitous method of multivariate statistics that focuses on the eigenvalues lambda and eigenvectors of the sample covariance matrix of a data set. We consider p, N-dimensional data vectors xi drawn from a distribution with covariance matrix C. We use the replica method to evaluate the expected eigenvalue distribution rho(lambda) as N--> infinity with p=alphaN for some fixed alpha. In contrast to existing studies we consider the case where C contains a number of symmetry-breaking directions, so that the sample data set contains some definite structure. Explicitly we set C=sigma2I+sigma(2)Sigma(S)(m=1)A(m)B(m)B(T)(m), with A(m)>0 for all m. We find that the bulk of the eigenvalues are distributed as for the case when the elements of xi are independent and identically distributed. With increasing alpha a series of phase transitions are observed, at alpha=A(-2)(m), m=1,2,..., S, each time a single delta function, delta(lambda-lambda(u)(A(m))), separates from the upper edge of the bulk distribution, where lambda(u)(A)=sigma(2)[1+A][1+(alphaA)(-1)]. We confirm the results of the replica analysis by studying the Stieltjes transform of rho(lambda). This suggests that the results obtained from the replica analysis are universal, irrespective of the distribution from which xi is drawn, provided the fourth moment of each element of xi exists.

Soya phytoestrogens change cortical and hippocampal expression of BDNF mRNA in male rats

Adult male hooded Lister rats were either fed a diet containing 150 microg/g soya phytoestrogens or a soya-free diet for 18 days. This concentration of phytoestrogens should have been sufficient to occupy the oestrogen-beta, but not the oestrogen-alpha, receptors. Using in situ hybridisation, significant reductions were found in brain-derived neurotrophic factor (BDNF) mRNA expression in the CA3 and CA4 region of the hippocampus and in the cerebral cortex in the rats fed the diet containing phytoestrogens, compared with those on the soya-free diet. No changes in glutamic acid decarboxylase-67 or glial fibrillary acidic protein mRNA were found. This suggests a role for oestrogen-beta receptors in regulating BDNF mRNA expression.

The 'glial' glutamate transporter, EAAT2 (Glt-1) accounts for high affinity glutamate uptake into adult rodent nerve endings

The excitatory amino acid transporters (EAAT) removes neurotransmitters glutamate and aspartate from the synaptic cleft. Most CNS glutamate uptake is mediated by EAAT2 into glia, though nerve terminals show evidence for uptake, through an unknown transporter. Reverse-transcriptase PCR identified the expression of EAAT1, EAAT2, EAAT3 and EAAT4 mRNAs in primary cultures of mouse cortical or striatal neurones. We have used synaptosomes and glial plasmalemmal vesicles (GPV) from adult mouse and rat CNS to identify the nerve terminal transporter. Western blotting showed detectable levels of the transporters EAAT1 (GLAST) and EAAT2 (Glt-1) in both synaptosomes and GPVs. Uptake of [3H]D-aspartate or [3H]L-glutamate into these preparations revealed sodium-dependent uptake in GPV and synaptosomes which was inhibited by a range of EAAT blockers: dihydrokainate, serine-o-sulfate, l-trans-2,4-pyrrolidine dicarboxylate (PDC) (+/-)-threo-3-methylglutamate and (2S,4R )-4-methylglutamate. The IC50 values found for these compounds suggested functional expression of the 'glial, transporter, EAAT2 in nerve terminals. Additionally blockade of the majority EAAT2 uptake sites with 100 micro m dihydrokainate, failed to unmask any functional non-EAAT2 uptake sites. The data presented in this study indicate that EAAT2 is the predominant nerve terminal glutamate transporter in the adult rodent CNS.

Bayesian phylogenetics using an RNA substitution model applied to early mammalian evolution

We study the phylogeny of the placental mammals using molecular data from all mitochondrial tRNAs and rRNAs of 54 species. We use probabilistic substitution models specific to evolution in base paired regions of RNA. A number of these models have been implemented in a new phylogenetic inference software package for carrying out maximum likelihood and Bayesian phylogenetic inferences. We describe our Bayesian phylogenetic method which uses a Markov chain Monte Carlo algorithm to provide samples from the posterior distribution of tree topologies. Our results show support for four primary mammalian clades, in agreement with recent studies of much larger data sets mainly comprising nuclear DNA. We discuss some issues arising when using Bayesian techniques on RNA sequence data.

Transgenic SOD1 G93A mice develop reduced GLT-1 in spinal cord without alterations in cerebrospinal fluid glutamate levels

Glutamate-induced excitotoxicity is suggested to play a central role in the development of amyotrophic lateral sclerosis (ALS), although it is still unclear whether it represents a primary cause in the cascade leading to motor neurone death. We used western blotting, immunocytochemistry and in situ hybridization to examine the expression of GLT-1 in transgenic mice carrying a mutated (G93A) human copper-zinc superoxide dismutase (TgSOD1 G93A), which closely mimic the features of ALS. We observed a progressive decrease in the immunoreactivity of the glial glutamate transporter (GLT-1) in the ventral, but not in the dorsal, horn of lumbar spinal cord. This effect was specifically found in 14- and 18-week-old mice that had motor function impairment, motor neurone loss and reactive astrocytosis. No changes in GLT-1 were observed at 8 weeks of age, before the appearance of clinical symptoms. Decreases in GLT-1 were accompanied by increased glial fibrillary acidic protein (GFAP) levels and no change in the levels of GLAST, another glial glutamate transporter. The glutamate concentration in the cerebrospinal fluid (CSF) of TgSOD1 G93A mice was not modified at any of the time points examined, compared with age-matched controls. These findings indicate that the loss of GLT-1 protein in ALS mice selectively occurs in the areas affected by neurodegeneration and reactive astrocytosis and it is not associated with increases of glutamate levels in CSF. The lack of changes in GLT-1 at the presymptomatic stage suggests that glial glutamate transporter reduction is not a primary event leading to motor neurone loss.

Cumulant dynamics of a population under multiplicative selection, mutation, and drift

We revisit the classical population genetics model of a population evolving under multiplicative selection, mutation, and drift. The number of beneficial alleles in a multilocus system can be considered a trait under exponential selection. Equations of motion are derived for the cumulants of the trait distribution in the diffusion limit and under the assumption of linkage equilibrium. Because of the additive nature of cumulants, this reduces to the problem of determining equations of motion for the expected allele distribution cumulants at each locus. The cumulant equations form an infinite dimensional linear system and in an authored appendix Adam Prügel-Bennett provides a closed form expression for these equations. We derive approximate solutions which are shown to describe the dynamics well for a broad range of parameters. In particular, we introduce two approximate analytical solutions: (1) Perturbation theory is used to solve the dynamics for weak selection and arbitrary mutation rate. The resulting expansion for the system's eigenvalues reduces to the known diffusion theory results for the limiting cases with either mutation or selection absent. (2) For low mutation rates we observe a separation of time-scales between the slowest mode and the rest which allows us to develop an approximate analytical solution for the dominant slow mode. The solution is consistent with the perturbation theory result and provides a good approximation for much stronger selection intensities.

Expression of amyloid precursor protein, tau and presenilin RNAs in rat hippocampus following deafferentation lesions

In this study, entorhinal cortex lesions and/or medial septal area cholinergic lesions were used in the rat to mimic some of the principal and earliest affects in Alzheimer's disease, namely hippocampal deafferentation. We wished to test the hypothesis that deafferentation lesions cause changes in the regulation of three proteins that are known to be important in Alzheimer's disease pathology, namely amyloid precursor protein, presenilin and tau. Expression of amyloid precursor protein mRNA was increased in several subfields of hippocampus when examined 1 week after entorhinal cortex lesion, but was reduced, compared to sham operated controls, after medial septal area cholinergic lesions. Cholinergic lesions were combined with entorhinal cortex lesions and produced no change in APP mRNA levels compared to controls. No significant changes were observed in the parietal cortex after entorhinal cortex or cholinergic lesions either alone or in combination. Tau mRNA level in hippocampus was unchanged after lesions. Presenilin-1 mRNA was expressed in the hippocampus at very low levels, and appeared to be increased following entorhinal cortex lesion. Our results support the hypothesis that amyloid precursor protein expression in hippocampal neurons is differentially affected by glutamatergic and cholinergic afferent input, and that presenilin-1, but not tau, may be subject to the same type of control in vivo.

Elevated levels of group-III metabotropic glutamate receptors in the inferior colliculus of genetically epilepsy-prone rats following intracollicular administration of L-serine-O-phosphate

The selective group-III metabotropic glutamate receptor agonist, L-serine-O-phosphate (L-SOP), when injected bilaterally into the inferior colliculus of the sound sensitive genetically epilepsy-prone (GEP) rats produces a short proconvulsant excitation followed by a long phase of protection against sound-induced seizures lasting for 2-4 days. We have studied this prolonged suppression of audiogenic seizures using pharmacological and molecular biological approaches including semiquantitative RT-PCR and western blotting. The intracerebroventricular injection of the protein synthesis inhibitor cycloheximide (120 microg) 30 min beforehand significantly reduces the proconvulsant seizure activity and the prolonged anticonvulsant effect of intracollicular L-SOP (500 nmol/side). The sensitive semiquantitative RT-PCR revealed a significant up-regulation in mGlu(4) and mGlu(7) mRNA levels in the inferior colliculus at 2 days (maximum suppression of audiogenic seizures) after intracollicular L-SOP injection compared with the non-injected, 2-day post-vehicle treated and 7-day (return to expressing audiogenic seizures) post-drug or vehicle-treated groups. No significant changes were observed in mGlu(6) or mGlu(8) mRNA expression levels in drug-treated compared with control groups. Examination of mGlu(4a) and mGlu(7a) protein levels using western blotting showed a significant increase in mGlu(7a) but no significant change in mGlu(4a) protein levels 2 days after L-SOP treatment compared with the control groups (non-injected and 2-day vehicle-injected group). These results suggest that up-regulation of mGlu(7) receptors is involved in the prolonged anticonvulsant effect of L-SOP against sound-induced seizures in GEP rats. The potential use of mGlu(7) agonists as novel anti-epileptic agents merits investigation.

Nicotine regulates 5-HT(1A) receptor gene expression in the cerebral cortex and dorsal hippocampus

The 5-HT(1A) receptor has previously been shown to be important in mediating the behavioural effects of nicotine. It is possible that nicotine administration might regulate the levels of 5-HT receptors in limbic and cortical regions, and such regulations may underlie adaptive responses to nicotine in the central nervous system. The effects of acute and chronic systemic (--)-nicotine administration on 5-HT(1A) receptor gene expression were measured by in situ hybridization, in the rat cerebral cortex, dorsal hippocampus and lateral septum. In the cortex, acute nicotine (0.5 mg/kg i.p.) significantly increased the expression of 5-HT(1A) receptor mRNA 2 h and 24 h after injection. Similarly, acute nicotine significantly increased 5-HT(1A) receptor mRNA in the dentate gyrus (DG), CA3 and CA1 regions of the dorsal hippocampus 2 h and 24 h after injection. Acute nicotine was without effect in the lateral septum. Chronic nicotine (0.5 mg/kg i.p; twice daily for 7 days) significantly decreased 5-HT(1A) receptor mRNA in the cortex 2 h after the final injection, but was without effect at 24 h or 72 h. Chronic nicotine caused no changes in 5-HT(1A) mRNA in the lateral septum or dorsal hippocampus. These data demonstrate that nicotine regulates 5-HT(1A) receptor gene expression in the cortex and hippocampus. The rapid regulation of expression of 5-HT(1A) receptor mRNA leads to the hypothesis that nicotine-induced 5-HT release may alter the postsynaptic sensitivity to 5-HT.

Is there nicotinic modulation of nerve growth factor? Implications for cholinergic therapies in Alzheimer's disease

Studies on the neurobiology of nerve growth factor (NGF) reveal a diverse range of actions. Through alterations in gene expression, NGF is important in maintaining and regulating the phenotype of neurons that express the high-affinity receptor, trkA. Nerve growth factor also has a rapid action, revealed by its role in pain signaling in bladder and in skin. In the central nervous system (CNS), NGF has an intimate relationship with the cholinergic system. It promotes cholinergic neuron survival after experimental injury but also maintains and regulates the phenotype of uninjured cholinergic neurons. In addition to these effects mediated by gene expression, NGF has a rapid neurotransmitter-like action to regulate cholinergic neurotransmission and neuronal excitability. Consistent with its actions on the cholinergic system, NGF can enhance function in animals with cholinergic lesions and has been proposed to be useful in humans with Alzheimer's disease (AD); however, the problems of CNS delivery and of side effects (particularly pain) limit the clinical efficacy of NGF. Drug treatment strategies to enhance production of NGF in the CNS may be useful in the treatment of AD. Nicotine is one such agent, which, when administered directly to the hippocampus in rats, produces long-lasting elevation of NGF production.

Acute nicotine decreases, and chronic nicotine increases the expression of brain-derived neurotrophic factor mRNA in rat hippocampus

Acute nicotine administration (0.5 mg/kg i.p.) significantly decreased BDNF mRNA levels in dentate gyrus, CA3 and CA1 subfields of the rat hippocampus 2 h and 24 h after administration. However, with 7 days nicotine treatment, tolerance developed to the inhibitory effect of nicotine on BDNF mRNA expression and there was a significant increase in BDNF expression 2 h after the final injection in the CA1 region. These data suggests that changes in expression of hippocampal BDNF may be involved in the behavioural effects of nicotine observed after acute and chronic treatment.

Hippocampal neurotrophin and trk receptor mRNA levels are altered by local administration of nicotine, carbachol and pilocarpine

Cholinergic receptor agonists nicotine (nicotinic), carbachol (nicotinic/muscarinic) and pilocarpine (muscarinic) were administered into the hippocampus and mRNA levels of neurotrophins and their receptors determined using in situ hybridisation. Drug doses were carefully chosen to avoid the potentially confounding effects of seizure and cell death. Nicotine caused a long-lasting increase in nerve growth factor (NGF) mRNA in all subfields of the hippocampus. The increase was evident from 24 h up to 72 h after drug administration. This increase was dependent on excitatory amino acid neurotransmission as it was blocked by administration of an AMPA or NMDA receptor antagonist. In contrast, carbachol and pilocarpine produced a transient increase in NGF mRNA levels present 4-8 h after drug administration. Pilocarpine caused a transient increase in hippocampal brain-derived neurotrophic factor (BDNF) levels, with carbachol and nicotine showing the same trend. Nicotine and carbachol caused transient decreases in NT-3 mRNA levels in dentate gyrus and CA2 with pilocarpine showing a similar trend. Increases in mRNA encoding full-length trkB were seen 8 h after nicotine, with nicotine also causing elevations in a mRNA encoding a truncated isoform (trkB.T2). TrkC mRNA was not altered by any of the conditions used. The study suggests that muscarinic and nicotinic receptor activation in the hippocampus causes transient changes in all of the neurotrophins, but that NGF levels are selectively up-regulated by nicotinic receptor stimulation. The reciprocal interaction between NGF and ascending cholinergic systems may be a component of the cognitive enhancing effects of nicotine.