Milestone review: GABA, from chemistry, conformations, ionotropic receptors, modulators, epilepsy, flavonoids, and stress to neuro-nutraceuticals

Arising out of a PhD project more than 50 years ago to synthesise analogues of the neurotransmitter GABA, a series of new chemical entities were found to have selective actions on ionotropic GABA receptors. Several of these neurochemicals are now commercially available. A new subtype of these receptors was discovered that could be a target for the treatment of myopia, the facilitation of learning and memory, and the improvement of post-stroke motor recovery. The development of these new chemical entities over many years demonstrates the importance of neurochemicals with which to investigate selective aspects of GABA receptors and illustrates the significance of collaboration between chemists and biologists in neurochemistry. Vital were the improvements in synthetic organic chemistry and the use of functional human receptors expressed in oocytes. Current interest in ionotropic GABA receptors includes the clinical development of subtype-specific agents and the role of gain-of-function receptor variants in epilepsy. Dietary flavonoids were found to cross the blood-brain barrier to influence brain function. Natural and synthetic flavonoids had a range of effects on GABA receptors, ranging from positive, silent, and negative allosteric modulators, to even second-order modulation of first-order modulators. Flavonoids have been called "a new family of benzodiazepines." Like benzodiazepines, flavonoids reduce stress. Stress produces changes in GABA receptors in the brain that may be because of changes in endogenous modulators, such as neurosteroids and corticosteroids. GABA also occurs naturally in the diet leading to studies of the effects of oral GABA on brain function. This finding has resulted in studies of GABA and related neurochemicals as neuro-nutraceuticals. GABA systems in the gut microbiome are essential to such studies. The actions of oral GABA and of GABA-enriched beverages and foodstuffs are now an area of considerable scientific and commercial interest. GABA is a deceptively simple chemical that can take up many shapes, which may underlie its complex functions. The need for new chemical entities with selective actions for further studies highlights the need for continuing collaboration between chemists and biologists.

The Concise Guide to PHARMACOLOGY 2023/24: Transporters

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and over 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (https://www.guidetopharmacology.org/), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.16182. Transporters are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein-coupled receptors, ion channels, nuclear hormone receptors, catalytic receptors and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Neuro-nutraceuticals: Natural products nourish the brain but be aware of contrary effects

In this Special Issue on "Nutraceuticals: Molecular and Functional Insights into how Natural Products Nourish the Brain", the editors bring together contributions from experts in nutraceutical research to provide a contemporary overview of how select chemically identified molecules from natural products can beneficially affect brain function at the molecular level. Other contributions address the holistic benefit of herbal medicines and their multi-targeted actions, which improve brain function in diverse cellular and animal models of brain injury. Not only are new targets for nutraceuticals reported, but their benefits on neurobehavioural problems are elucidated in conditions as diverse as obesity and menopause. Inflammation in neuropathologies, including Alzheimer's disease (AD), remains a huge focus and diverse nutraceuticals demonstrate therapeutic applicability via glial-mediated actions. While contrary actions should be borne in mind in the search for novel neurotherapeutics, the great promise offered by herbal medicines and their newly identified active principles offers unique options for the management of diverse neurological and psychiatric conditions.

Amyotrophic Lateral Sclerosis and Autophagy: Dysfunction and Therapeutic Targeting

Over the past 20 years, there has been a drastically increased understanding of the genetic basis of Amyotrophic Lateral Sclerosis. Despite the identification of more than 40 different ALS-causing mutations, the accumulation of neurotoxic misfolded proteins, inclusions, and aggregates within motor neurons is the main pathological hallmark in all cases of ALS. These protein aggregates are proposed to disrupt cellular processes and ultimately result in neurodegeneration. One of the main reasons implicated in the accumulation of protein aggregates may be defective autophagy, a highly conserved intracellular “clearance” system delivering misfolded proteins, aggregates, and damaged organelles to lysosomes for degradation. Autophagy is one of the primary stress response mechanisms activated in highly sensitive and specialised neurons following insult to ensure their survival. The upregulation of autophagy through pharmacological autophagy-inducing agents has largely been shown to reduce intracellular protein aggregate levels and disease phenotypes in different in vitro and in vivo models of neurodegenerative diseases. In this review, we explore the intriguing interface between ALS and autophagy, provide a most comprehensive summary of autophagy-targeted drugs that have been examined or are being developed as potential treatments for ALS to date, and discuss potential therapeutic strategies for targeting autophagy in ALS.

Mutant TDP-43 Expression Triggers TDP-43 Pathology and Cell Autonomous Effects on Primary Astrocytes: Implications for Non-cell Autonomous Pathology in ALS

Motor neuron degeneration in amyotrophic lateral sclerosis (ALS) caused by mutations in superoxide dismutase 1 (SOD1) is partly non-cell autonomous, involving cellular dysfunction of astrocytes. Whether non-cell autonomous effects occur in other forms of ALS, such as TAR DNA binding protein 43 (TDP-43)-related disease, remains unclear. Here, we characterised the impact of mutant TDP-43 expression on primary astrocytes derived from transgenic TDP-43A315T mice. Mutant TDP-43 astrocytes revealed evidence for TDP-43 pathology, shown by cytoplasmic TDP-43 inclusions and accumulation in insoluble cell fractions which was exacerbated by proteasomal inhibition. L-glutamate uptake, measured using an [3H]D-aspartate assay, was impaired in mutant TDP-43 astrocytes, while ATP accumulation was abnormal, suggesting mutant TDP-43 induced astrocytic dysfunction. Astrocyte activation coupled with spinal and cortical motor neuron loss in transgenic TDP-43A315T mice could imply non-cell autonomous effects of astrocytes in vivo. These data demonstrate mutant TDP-43-mediated cell autonomous effects on astrocytes that may contribute to motor neuron pathology in ALS.

Autophagy in neurodegeneration: New insights underpinning therapy for neurological diseases

In autophagy long-lived proteins, protein aggregates or damaged organelles are engulfed by vesicles called autophagosomes prior to lysosomal degradation. Autophagy dysfunction is a hallmark of several neurodegenerative diseases in which misfolded proteins or dysfunctional mitochondria accumulate. Excessive autophagy can also exacerbate brain injury under certain conditions. In this review, we provide specific examples to illustrate the critical role played by autophagy in pathological conditions affecting the brain and discuss potential therapeutic implications. We show how a singular type of autophagy-dependent cell death termed autosis has attracted attention as a promising target for improving outcomes in perinatal asphyxia and hypoxic-ischaemic injury to the immature brain. We provide evidence that autophagy inhibition may be protective against radiotherapy-induced damage to the young brain. We describe a specialized form of macroautophagy of therapeutic relevance for motoneuron and neuromuscular diseases, known as chaperone-assisted selective autophagy, in which heat shock protein B8 is used to deliver aberrant proteins to autophagosomes. We summarize studies pinpointing mitophagy mediated by the serine/threonine kinase PINK1 and the ubiquitin-protein ligase Parkin as a mechanism potentially relevant to Parkinson's disease, despite debate over the physiological conditions in which it is activated in organisms. Finally, with the example of the autophagy-inducing agent rilmenidine and its discrepant effects in cell culture and mouse models of motor neuron disorders, we illustrate the importance of considering aspects such a disease stage and aggressiveness, type of insult and load of damaged or toxic cellular components, when choosing the appropriate drug, timepoint and duration of treatment.

LRRK2 impairs PINK1/Parkin-dependent mitophagy via its kinase activity: pathologic insights into Parkinson's disease

Mutations of LRRK2, encoding leucine-rich repeat kinase 2 (LRRK2), are the leading cause of autosomal dominant Parkinson's disease (PD). The most frequent of these mutations, G2019S substitution, increases kinase activity, but it remains unclear how it causes PD. Recent studies suggest that LRRK2 modulates mitochondrial homeostasis. Mitochondrial dysfunction plays a key role in the pathogenesis of autosomal recessive PD forms linked to PARK2 and PINK1, encoding the cytosolic E3 ubiquitin-protein ligase Parkin and the mitochondrial kinase PINK1, which jointly regulate mitophagy. We explored the role of LRRK2 and its kinase activity in PINK1/Parkin-dependent mitophagy. LRRK2 increased mitochondrial aggregation and attenuated mitochondrial clearance in cells coexpressing Parkin and exposed to the protonophore carbonylcyanide m-chlorophenylhydrazone. Förster resonance energy transfer imaging microscopy showed that LRRK2 impaired the interactions between Parkin and Drp1 and their mitochondrial targets early in mitophagy. The inhibition of LRRK2 kinase activity by a 'kinase-dead' LRRK2 mutation or with a pharmacological inhibitor (LRRK2-IN-1) restored these interactions. The monitoring of mitophagy in human primary fibroblasts with the novel dual-fluorescence mtRosella reporter and a new hypothermic shock paradigm revealed similar defects in PD patients with the G2019S LRRK2 substitution or PARK2 mutations relative to healthy subjects. This defect was restored by LRRK2-IN-1 treatment in LRRK2 patients only. Our results suggest that PD forms due to LRRK2 and PARK2 mutations involve pathogenic mechanisms converging on PINK1/Parkin-dependent mitophagy.

SLC1 family of amino acid transporters (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

The SLC1 family of sodium dependent transporters includes the plasma membrane located glutamate transporters and the neutral amino acid transporters ASCT1 and ASCT2 [1, 49, 36, 37, 7].

The origins and early history of neurochemistry and its societies

At the 2017 joint meeting of the International Society for Neurochemistry (ISN) and the European Society for Neurochemistry, 150 years of neurochemistry - the 50th anniversary of ISN, 40 years of European Society for Neurochemistry, and 60 years of the Journal of Neurochemistry (JNC) - was celebrated with a historical symposium that explored the foundations of neurochemical societies, key international figures in the discipline of neurochemistry, and the pre-eminent role of the JNC. The foundations of neurochemistry were laid in Europe, notably France and Germany, in the late 18th and early 19th centuries. Neurochemists in the United Kingdom made globally relevant contributions before and after the Second World War, and Swedish contributions were especially prominent in the 1950s and 1960s. As neurochemistry is a truly international branch of neuroscience, the important contributions of neurochemists in the Americas and the Asia-Pacific were also recognized, as were the seminal roles of the American, Asia-Pacific, and Japanese Societies of Neurochemistry. Although ISN was only formed in 1967, earlier international meetings in Europe and the Americas reflected the growing recognition of the importance of chemistry and biochemistry for understanding and responding to the pathophysiology of clinical conditions and diseases of the central and peripheral nervous systems. JNC was first published in 1956, but the ISN only assumed complete ownership of the journal under tempestuous circumstances in 1970. The ISN-JNC interface and the sterling work of the JNC Editors has meant that the income generated by the journal has allowed the ISN Council to implement diverse programs for supporting neurochemistry internationally, including sustaining regional neurochemical societies, and supporting neurochemists in the developing world and schools of neurochemistry.

Inhibition of bioenergetics provides novel insights into recruitment of PINK1-dependent neuronal mitophagy

Contributions of damaged mitochondria to neuropathologies have stimulated interest in mitophagy. We investigated triggers of neuronal mitophagy by disruption of mitochondrial energy metabolism in primary neurons. Mitophagy was examined in cultured murine cerebellar granule cells after inhibition of mitochondrial respiratory chain by drugs rotenone, 3-nitropropionic acid, antimycin A, and potassium cyanide, targeting complexes I, II, III, and IV, respectively. Inhibitor concentrations producing slow cellular demise were determined from analyses of cellular viability, morphology of neuritic damage, plasma membrane permeability, and oxidative phosphorylation. Live cell imaging of dissipation of mitochondrial membrane potential (ΔΨ_m ) by drugs targeting mitochondrial complexes was referenced to complete depolarization by carbonyl cyanide m-chlorophenyl hydrazone. While inhibition of complexes I, III and IV effected rapid dissipation of ΔΨ_m , inhibition of complex II using 3-nitropropionic acid led to minimal depolarization of mitochondria. Nonetheless, all respiratory chain inhibitors triggered mitophagy as indicated by increased aggregation of mitochondrially localized PINK1. Mitophagy was further analyzed using a dual fluorescent protein biosensor reporting mitochondrial relocation to acidic lysosomal environment. Significant acidification of mitochondria was observed in neurons treated with rotenone or 3-nitropropionic acid, revealing mitophagy at distal processes. Neurons treated with antimycin A or cyanide failed to show mitochondrial acidification. Minor dissipation of ΔΨ_m by 3-nitropropionic acid coupled with vigorous triggering of mitophagy suggested depolarization of mitochondria is not a necessary condition to trigger mitophagy. Moreover, weak elicitation of mitophagy by antimycin A, subsequent to loss of ΔΨ_m , suggested that mitochondrial depolarization is not a sufficient condition for triggering robust neuronal mitophagy. Our findings provide new insight into complexities of mitophagic clearance of neuronal mitochondria.

Mitochondria in the nervous system: From health to disease, part II

In Part II of this Special Issue on "Mitochondria in the Nervous System: From Health to Disease", the editors bring together more reviews and original articles from researchers in the field of mitochondrial metabolism in the healthy and diseased nervous system. Subjects span from basic mitochondrial physiology to papers on mitochondrial dynamics and to those altered states of the nervous system that can be considered "mitopathologies". Finally, a few papers approach aspects of mitochondrial biology linked to the feasibility and validity of a mitochondrial therapy.

Rilmenidine promotes MTOR-independent autophagy in the mutant SOD1 mouse model of amyotrophic lateral sclerosis without slowing disease progression

Macroautophagy/autophagy is the main intracellular catabolic pathway in neurons that eliminates misfolded proteins, aggregates and damaged organelles associated with ageing and neurodegeneration. Autophagy is regulated by both MTOR-dependent and -independent pathways. There is increasing evidence that autophagy is compromised in neurodegenerative disorders, which may contribute to cytoplasmic sequestration of aggregation-prone and toxic proteins in neurons. Genetic or pharmacological modulation of autophagy to promote clearance of misfolded proteins may be a promising therapeutic avenue for these disorders. Here, we demonstrate robust autophagy induction in motor neuronal cells expressing SOD1 or TARDBP/TDP-43 mutants linked to amyotrophic lateral sclerosis (ALS). Treatment of these cells with rilmenidine, an anti-hypertensive agent and imidazoline-1 receptor agonist that induces autophagy, promoted autophagic clearance of mutant SOD1 and efficient mitophagy. Rilmenidine administration to mutant SOD1G93A mice upregulated autophagy and mitophagy in spinal cord, leading to reduced soluble mutant SOD1 levels. Importantly, rilmenidine increased autophagosome abundance in motor neurons of SOD1G93A mice, suggesting a direct action on target cells. Despite robust induction of autophagy in vivo, rilmenidine worsened motor neuron degeneration and symptom progression in SOD1G93A mice. These effects were associated with increased accumulation and aggregation of insoluble and misfolded SOD1 species outside the autophagy pathway, and severe mitochondrial depletion in motor neurons of rilmenidine-treated mice. These findings suggest that rilmenidine treatment may drive disease progression and neurodegeneration in this mouse model due to excessive mitophagy, implying that alternative strategies to beneficially stimulate autophagy are warranted in ALS.

Mitochondria in the nervous system: From health to disease, Part I

In Part I of this Special Issue on "Mitochondria in the Nervous System: From Health to Disease", the editors bring together contributions from experts in brain mitochondrial research to provide an up-to-date overview of mitochondrial functioning in physiology and pathology. The issue provides cutting edge reviews on classical areas of mitochondrial biology that include energy substrate utilization, calcium handling, mitochondria-endoplasmic reticulum communication, and cell death regulation. Additional reviews and original research articles touch upon key mitochondrial defects seen across multiple neurodegenerative conditions, including fragmentation, loss of respiratory capacity, calcium overload, elevated reactive oxygen species generation, perturbed NAD⁺ metabolism, altered protein acetylation, and compromised mitophagy. Emerging links between the genetics of neurodegenerative disorders and disruption in mitochondrial function are discussed, and a new mouse model of Complex I deficiency is described. Finally, novel ways to rescue mitochondrial structure and function in acute and chronic brain injury are explored.

Glutathione monoethyl ester prevents TDP-43 pathology in motor neuronal NSC-34 cells

Oxidative stress is recognised as central in a range of neurological diseases including Amyotrophic lateral sclerosis (ALS), a disease characterised by fast progressing death of motor neurons in the brain and spinal cord. Cellular pathology includes cytosolic protein aggregates in motor neurons and glia of which potentially cytotoxic hyper-phosphorylated fragments of the Transactive response DNA Binding Protein 43 kDa (TDP-43) constitute a major component. This is closely associated with an additional loss of nuclear TDP-43 expression indicating a "loss of function" mechanism, accelerating motor neuron (MN) loss. Furthermore, mutations in TDP-43 cause familial ALS and ALS-like disease in animal models. In this study, we investigated the role of glutathione (GSH) in modulating oxidative stress responses in TDP-43 pathology in motor neuron NSC-34 cells. Results demonstrate that depletion of GSH produces pathology similar to that of mutant TDP-43, including occurrence of cytosolic aggregates, TDP-43 phosphorylation and nuclear clearing of endogenous TDP-43. We also demonstrate that introduction of mutant TDP-43^A315T and silencing of endogenous TDP-43, but not overexpression of wild-type TDP-43, result in similar pathology, including depletion of intracellular GSH, possibly resulting from a decreased expression of a regulatory subunit of ɣ-glutamylcysteine ligase (GCLM), a rate limiting enzyme in GSH synthesis. Importantly, treatment of mutant cells with GSH monoethyl ester (GSHe) that directly increases intracellular GSH and bypasses the need for GSH synthesis, protected against mutant-induced TDP-43 pathology, including reducing aggregate formation, nuclear clearance, reactive oxygen species (ROS) production and cell death. Our data strongly suggest that oxidative stress is central to TDP-43 pathology and may result from a loss of function affecting GSH synthesis and that treatments directly aimed at restoring cellular GSH content may be beneficial in preventing cell death in TDP-43-mediated ALS.

Galactose-functionalised PCL nanofibre scaffolds to attenuate inflammatory action of astrocytes in vitro and in vivo

Astrocytes represent an attractive therapeutic target for the treatment of traumatic brain injury in the glial scar, which inhibits functional repair and recovery if persistent. Many biomaterial systems have been investigated for neural tissue engineering applications, including electrospun nanofibres, which are a favourable biomaterial as they can mimic the fibrous architecture of the extracellular matrix, and are conveniently modified to present biologically relevant cues to aid in regeneration. Here, we synthesised a novel galactose-presenting polymer, poly(l-lysine)-lactobionic acid (PLL-LBA), for use in layer-by-layer (LbL) functionalisation of poly(ε-caprolactone) (PCL) nanofibres, to covalently attach galactose moieties to the nanofibre scaffold surface. We have assessed the use of this novel biomaterial system in vitro and in vivo, and have shown, for the first time, the ability of galactose to maintain an attenuated inflammatory profile of astrocytes in culture, and to increase the survival of neurons after traumatic injury, as compared to control PCL nanofibres. This study highlights the importance of galactose in controlling the astrocytic response, and provides a promising biomaterial system to deliver the essential morphological and biological cues to achieve functional repair after traumatic brain injury.

MDMA-induced neurotoxicity of serotonin neurons involves autophagy and rilmenidine is protective against its pathobiology

Toxicity of 3,4-methylenedioxymethamphetamine (MDMA) towards biogenic amine neurons is well documented and in primate brain predominantly affects serotonin (5-HT) neurons. MDMA induces damage of 5-HT axons and nerve fibres and intracytoplasmic inclusions. Whilst its pathobiology involves mitochondrially-mediated oxidative stress, we hypothesised MDMA possessed the capacity to activate autophagy, a proteostatic mechanism for degradation of cellular debris. We established a culture of ventral pons from embryonic murine brain enriched in 5-HT neurons to explore mechanisms of MDMA neurotoxicity and recruitment of autophagy, and evaluated possible neuroprotective actions of the clinically approved agent rilmenidine. MDMA (100 μM-1 mM) reduced cell viability, like rapamycin (RM) and hydrogen peroxide (H₂O₂), in a concentration- and time-dependent manner. Immunocytochemistry revealed dieback of 5-HT arbour: MDMA-induced injury was slower than for RM and H₂O₂, neuritic blebbing occurred at 48 and 72 h and Hoechst labelling revealed nuclear fragmentation with 100 μM MDMA. MDMA effected concentration-dependent inhibition of [³H]5-HT uptake with 500 μM MDMA totally blocking transport. Western immunoblotting for microtubule associated protein light chain 3 (LC3) revealed autophagosome formation after treatment with MDMA. Confocal analyses and immunocytochemistry for 5-HT, Hoechst and LC3 confirmed MDMA induced autophagy with abundant LC3-positive puncta within 5-HT neurons. Rilmenidine (1 μM) protected against MDMA-induced injury and image analysis showed full preservation of 5-HT arbours. MDMA had no effect on GABA neurons, indicating specificity of action at 5-HT neurons. MDMA-induced neurotoxicity involves autophagy induction in 5-HT neurons, and rilmenidine via beneficial actions against toxic intracellular events represents a potential treatment for its pathobiology in sustained usage.

Inflammation: maladies, models, mechanisms and molecules

The continued focus of attention on the diversity of mechanisms underpinning inflammation has improved our understanding of the potential to target specific pathways in the inflammatory network to achieve meaningful therapeutic gains. In this themed issue of the British Journal of Pharmacology our scope was deliberately broad, ranging across both acute and chronic disease in various organs. Pro- and anti-inflammatory mechanisms receive attention as does the phenotype of macrophages. Whilst the manifestations of neuro-inflammation are less obvious than those in peripheral tissues, central innate and adaptive immunity in brain and the M1/M2 phenotypes of microglia are topics of special interest. The contributions to the inflammatory milieu of cytokines, chemokines and associated signalling cascades are considered. Overall, the coverage herein advances the basic science underpinning our understanding of inflammation and emphasizes its importance in different pathologies.

Synaptic signalling and its interface with neuropathologies: snapshots from the past, present and future

This 'Past to Future' Review as part of the 60th anniversary year of the Journal of Neurochemistry focuses on synaptic transmission and associated signalling, and seeks to identify seminal progress in neurochemistry over the last 10 years which has advanced our understanding of neuronal communication in brain. The approach adopted analyses neurotransmitters on a case by case basis (i.e. amino acids, monoamines, acetylcholine, neuropeptides, ATP/purines and gasotransmitters) to highlight novel findings that have changed the way we view each type of transmitter, to explore commonalities and interactions, and to note how new insights have changed the way we view the biology of degenerative, psychiatric and behavioural conditions. Across all transmitter systems there was remarkable growth in the identification of targets likely to provide therapeutic benefit and which undoubtedly was driven by the elucidation of circuit function and new vistas of synaptic signalling. There has been an increasing trend to relate signalling to disease, notably for Alzheimer's and Parkinson's disease and related conditions, and which has occurred for each transmitter family. Forebrain circuitry and tonic excitatory control have been the centre of great attention yielding novel findings that will impact upon cognitive, emotional and addictive behaviours. Other impressive insights focus on gasotransmitters integrating activity as volume transmitters. Exciting developments in how serotonin, cholinergic, l-glutamate, galanin and adenosine receptors and their associated signalling can be beneficially targeted should underpin the development of new therapies. Clearly integrated, multifaceted neurochemistry has changed the way we view synaptic signalling and its relevance to pathobiology. Highlighted are important advances in synaptic signalling over the last decade in the Journal of Neurochemistry. Across all transmitter systems elucidation of circuit function, and notably molecular insights, have underpinned remarkable growth in the identification of targets likely to provide therapeutic benefit in neuropathologies. Another commonality was wide interest in forebrain circuitry and its tonic excitatory control. Increasingly observations relate to signalling in disease and behavioural conditions. This article is part of the 60th Anniversary special issue.

Evidence for the recruitment of autophagic vesicles in human brain after stroke

Autophagy is a homeostatic process for recycling proteins and organelles that is increasingly being proposed as a therapeutic target for acute and chronic neurodegenerative diseases, including stroke. Confirmation that autophagy is present in the human brain after stroke is imperative before prospective therapies can begin the translational process into clinical trials. Our current study using human post-mortem tissue observed an increase in staining in microtubule-associated protein 1 light chain 3 (LC3), sequestosome 1 (SQSTM1; also known as p62) and the increased appearance of autophagic vesicles after stroke. These data confirm that alterations in autophagy take place in the human brain after stroke and suggest that targeting autophagic processes after stroke may have clinical significance.

Modulating Astrocyte Transition after Stroke to Promote Brain Rescue and Functional Recovery: Emerging Targets Include Rho Kinase

Stroke is a common and serious condition, with few therapies. Whilst previous focus has been directed towards biochemical events within neurons, none have successfully prevented the progression of injury that occurs in the acute phase. New targeted treatments that promote recovery after stroke might be a better strategy and are desperately needed for the majority of stroke survivors. Cells comprising the neurovascular unit, including blood vessels and astrocytes, present an alternative target for supporting brain rescue and recovery in the late phase of stroke, since alteration in the unit also occurs in regions outside of the lesion. One of the major changes in the unit involves extensive morphological transition of astrocytes resulting in altered energy metabolism, decreased glutamate reuptake and recycling, and retraction of astrocyte end feed from both blood vessels and neurons. Whilst globally inhibiting transitional change in astrocytes after stroke is reported to result in further damage and functional loss, we discuss the available evidence to suggest that the transitional activation of astrocytes after stroke can be modulated for improved outcomes. In particular, we review the role of Rho-kinase (ROCK) in reactive gliosis and show that inhibiting ROCK after stroke results in reduced scar formation and improved functional recovery.

Lactacystin-induced apoptosis of cultured mouse cortical neurons is associated with accumulation of PTEN in the detergent-resistant membrane fraction

The tumor suppressor function of PTEN is attributed to its phospholipid phosphatase activity that dephosphorylates the plasma membrane phosphatidylinositol-(3,4,5)-triphosphate [PtdIns(3,4,5)P3]. Implicit in this notion is that PTEN needs to be targeted to the plasma membrane to dephosphorylate PtdIns(3,4,5)P3. However, the recruitment of PTEN to the plasma membrane is not fully understood. Here, we demonstrate PTEN accumulation in the detergent-insoluble fraction of neuronal cells in response to treatment by the proteasome inhibitor lactacystin. First, lactacystin induces apoptosis and the activation of caspase-3 in cultured cortical neurons. Second, PTEN undergoes proteolysis to form a truncated 50-kDa form that lacks parts of its C-terminal tail. Third, the truncated PTEN is stably associated with the detergent-insoluble fraction in which the plasma membrane marker protein flotillin-1 resides. Taken together, our results suggest that truncation and accumulation of PTEN to the detergent-insoluble membrane fraction are two events associated with the apoptotic signals of the proteasome inhibitor in cortical neurons.

Comparative Microarray Analysis Identifies Commonalities in Neuronal Injury: Evidence for Oxidative Stress, Dysfunction of Calcium Signalling, and Inhibition of Autophagy-Lysosomal Pathway

Mitochondrial dysfunction, ubiquitin-proteasomal system impairment and excitotoxicity occur during the injury and death of neurons in neurodegenerative conditions. The aim of this work was to elucidate the cellular mechanisms that are universally altered by these conditions. Through overlapping expression profiles of rotenone-, lactacystin- and N-methyl-D-aspartate-treated cortical neurons, we have identified three affected biological processes that are commonly affected; oxidative stress, dysfunction of calcium signalling and inhibition of the autophagic-lysosomal pathway. These data provides many opportunities for therapeutic intervention in neurodegenerative conditions, where mitochondrial dysfunction, proteasomal inhibition and excitotoxicity are evident.

Neuro-nutraceuticals: The path to brain health via nourishment is not so distant

In this Special Issue on "Nutraceuticals: Molecular and Functional Insights into how Natural Products Nourish the Brain", the editors bring together contributions from experts in nutraceutical research to provide a contemporary overview of how select chemically identified molecules can beneficially affect brain function at the molecular level. Other contributions address key emergent issues such as bioavailability, formulation, blood brain permeability, neuronal health and inflammation that impact upon how nutraceuticals ultimately leverage the brain to function better. Whilst nutraceutical is used as marketing term, it has no regulatory definition, and there is a continuing need for licensing authorities to ensure that adequate guidelines exist pertinent to the safety to guide consumers internationally. In terms of the benefit of nutraceuticals is it clear that some naturally occurring molecules can be advantageous to both the young and aged brain, and that they have actions that ultimately can be directed to aid either in the improvement of cognition or in the management of debilitating neurodegenerative and neuropsychiatric conditions.

Astrocyte and microglial control of glutamatergic signalling: a primer on understanding the disruptive role of chronic stress

It is now well established that chronic stress can induce significant structural remodelling of astrocytes and microglia. Until recently, however, the full significance of these morphological disturbances has remained unclear. Clues to the significance of astroglial re-organisation following stress are beginning to emerge from a compelling literature describing how astrocytes contribute to glutamatergic neurotransmission. The present review briefly summarises these two fields of research, identifies points of overlap and, in doing so, pin-points future research directions for stress neurobiology. Ultimately, understanding how chronic stress can disrupt the interactions of astrocytes and microglia with neurones has the potential in the future to improve the development of therapeutics designed to treat stress-related illnesses such as depression.

Transcriptomic analysis and 3D bioengineering of astrocytes indicate ROCK inhibition produces cytotrophic astrogliosis

Astrocytes provide trophic, structural and metabolic support to neurons, and are considered genuine targets in regenerative neurobiology, as their phenotype arbitrates brain integrity during injury. Inhibitors of Rho kinase (ROCK) cause stellation of cultured 2D astrocytes, increased L-glutamate transport, augmented G-actin, and elevated expression of BDNF and anti-oxidant genes. Here we further explored the signposts of a cytotrophic, “healthy” phenotype by data-mining of our astrocytic transcriptome in the presence of Fasudil. Gene expression profiles of motor and autophagic cellular cascades and inflammatory/angiogenic responses were all inhibited, favoring adoption of an anti-migratory phenotype. Like ROCK inhibition, tissue engineered bioscaffolds can influence the extracellular matrix. We built upon our evidence that astrocytes maintained on 3D poly-ε-caprolactone (PCL) electrospun scaffolds adopt a cytotrophic phenotype similar to that produced by Fasudil. Using these procedures, employing mature 3D cultured astrocytes, Fasudil (100 μM) or Y27632 (30 μM) added for the last 72 h of culture altered arborization, which featured numerous additional minor processes as shown by GFAP and AHNAK immunolabelling. Both ROCK inhibitors decreased F-actin, but increased G-actin labeling, indicative of disassembly of actin stress fibers. ROCK inhibitors provide additional beneficial effects for bioengineered 3D astrocytes, including enlargement of the overall arbor. Potentially, the combined strategy of bio-compatible scaffolds with ROCK inhibition offers unique advantages for the management of glial scarring. Overall these data emphasize that manipulation of the astrocyte phenotype to achieve a “healthy biology” offers new hope for the management of inflammation in neuropathologies.

Silent information regulator 1 modulator resveratrol increases brain lactate production and inhibits mitochondrial metabolism, whereas SRT1720 increases oxidative metabolism

Silent information regulators (SIRTs) have been shown to deacetylate a range of metabolic enzymes, including those in glycolysis and the Krebs cycle, and thus alter their activity. SIRTs require NAD(+) for their activity, linking cellular energy status to enzyme activity. To examine the impact of SIRT1 modulation on oxidative metabolism, this study tests the effect of ligands that are either SIRT-activating compounds (resveratrol and SRT1720) or SIRT inhibitors (EX527) on the metabolism of (13)C-enriched substrates by guinea pig brain cortical tissue slices with (13)C and (1)H nuclear magnetic resonance spectroscopy. Resveratrol increased lactate labeling but decreased incorporation of (13)C into Krebs cycle intermediates, consistent with effects on AMPK and inhibition of the F0/F1-ATPase. By testing with resveratrol that was directly applied to astrocytes with a Seahorse analyzer, increased glycolytic shift and increased mitochondrial proton leak resulting from interactions of resveratrol with the mitochondrial electron transport chain were revealed. SRT1720, by contrast, stimulated incorporation of (13)C into Krebs cycle intermediates and reduced incorporation into lactate, although the inhibitor EX527 paradoxically also increased Krebs cycle (13)C incorporation. In summary, the various SIRT1 modulators show distinct acute effects on oxidative metabolism. The strong effects of resveratrol on the mitochondrial respiratory chain and on glycolysis suggest that caution should be used in attempts to increase bioavailability of this compound in the CNS.

Mitochondrial pharmacology: energy, injury and beyond

While the mitochondrion has long fascinated biologists and the sheer diversity of druggable targets has made it attractive for potential drug development, there has been little success translatable to the clinic. Given the diversity of inborn errors of metabolism and mitochondrial diseases, mitochondrially mediated oxidative stress (myopathies, reperfusion injury, Parkinson's disease, ageing) and the consequences of disturbed energetics (circulatory shock, diabetes, cancer), the potential for meaningful gain with novel drugs targeting mitochondrial mechanisms is huge both in terms of patient quality of life and health care costs. In this themed issue of the British Journal of Pharmacology, we highlight the key directions of the contemporary advances in the field of mitochondrial biology, emerging drug targets and new molecules which are close to clinical application. Authors' contributions are diverse both in terms of species and organs in which the mitochondrially related studies are performed, and from the perspectives of mechanisms under study. Defined roles of mitochondria in disease are updated and previously unknown contributions to disease are described in terms of the interface between basic science and pathological relevance.

The Concise Guide to PHARMACOLOGY 2013/14: overview

The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties from the IUPHAR database. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. This compilation of the major pharmacological targets is divided into seven areas of focus: G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors & Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and GRAC and provides a permanent, citable, point-in-time record that will survive database updates.

3D Electrospun scaffolds promote a cytotrophic phenotype of cultured primary astrocytes

Astrocytes are a target for regenerative neurobiology because in brain injury their phenotype arbitrates brain integrity, neuronal death and subsequent repair and reconstruction. We explored the ability of 3D scaffolds to direct astrocytes into phenotypes with the potential to support neuronal survival. Poly-ε-caprolactone scaffolds were electrospun with random and aligned fibre orientations on which murine astrocytes were sub-cultured and analysed at 4 and 12 DIV. Astrocytes survived, proliferated and migrated into scaffolds adopting 3D morphologies, mimicking in vivo stellated phenotypes. Cells on random poly-ε-caprolactone scaffolds grew as circular colonies extending processes deep within sub-micron fibres, whereas astrocytes on aligned scaffolds exhibited rectangular colonies with processes following not only the direction of fibre alignment but also penetrating the scaffold. Cell viability was maintained over 12 DIV, and cytochemistry for F-/G-actin showed fewer stress fibres on bioscaffolds relative to 2D astrocytes. Reduced cytoskeletal stress was confirmed by the decreased expression of glial fibrillary acidic protein. PCR demonstrated up-regulation of genes (excitatory amino acid transporter 2, brain-derived neurotrophic factor and anti-oxidant) reflecting healthy biologies of mature astrocytes in our extended culture protocol. This study illustrates the therapeutic potential of bioengineering strategies using 3D electrospun scaffolds which direct astrocytes into phenotypes supporting brain repair. Astrocytes exist in phenotypes with pro-survival and destructive components, and their biology can be modulated by changing phenotype. Our findings demonstrate murine astrocytes adopt a healthy phenotype when cultured in 3D. Astrocytes proliferate and extend into poly-ε-caprolactone scaffolds displaying 3D stellated morphologies with reduced GFAP expression and actin stress fibres, plus a cytotrophic gene profile. Bioengineered 3D scaffolds have potential to direct inflammation to aid regenerative neurobiology.

Gene profiling identifies commonalities in neuronal pathways in excitotoxicity: evidence favouring cell cycle re-activation in concert with oxidative stress

Excitotoxicity, induced by the aberrant rise in cytosolic Ca(2+) level, is a major neuropathological process in numerous neurodegenerative disorders. It is triggered when extracellular glutamate (Glu) concentration reaches neuropathological levels resulting in dysregulation and hyper-activation of ionotropic glutamate receptor subtype (iGluRs). Even though all three members of the iGluRs, namely N-methyl-d-aspartate (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPAR) and kainate (KAR) receptors are implicated in excitotoxicity, their individual contributions to downstream signaling transduction have not been explored. In this study, we report a comprehensive description of the recruitment of cellular processes in neurons upon iGluR activation during excitotoxicity through temporal (5h, 15h, and 24h) global gene profiling of AMPA, KA, NMDA, and Glu excitotoxic models. DNA microarray analyses of mouse primary cortical neurons treated with these four pharmacological agonists are further validated via real-time PCR. Bi-model analyses against Glu model demonstrate that NMDARs and KARs play a more pivotal role in Glu-mediated excitotoxicity, with a higher degree of global gene profiling overlaps, as compared to that of AMPARs. Comparison of global transcriptomic profiles reveals aberrant calcium ion binding and homeostasis, organellar (lysosomal and endoplasmic reticulum) stress, oxidative stress, cell cycle re-entry and activation of cell death processes as the main pathways that are significantly modulated across all excitotoxicity models. Singular profile analyses demonstrate substantial transcriptional regulation of numerous cell cycle proteins. For the first time, we show that iGluR activation forms the basis of cell cycle re-activation, and together with oxidative stress fulfill the "two-hit" hypothesis that accelerates neurodegeneration.

Transitory phases of autophagic death and programmed necrosis during superoxide-induced neuronal cell death

Neurons can undergo a diverse range of death responses under oxidative stress, encompassing apoptosis (caspase-dependent, programmed cell death) to various forms of caspase-independent death, including necrosis. We recently showed that primary murine cortical neurons exposed acutely to hydrogen peroxide undergo caspase-independent death, both autophagic cell death and programmed necrosis. To determine how oxidative stress induced by superoxide affects the route to cellular demise, we exposed primary cortical neurons to extended superoxide insult (provided by exogenous xanthine and xanthine oxidase in the presence of catalase). Under these conditions, over 24h, the nitroblue tetrazolium-reducing activity (indicative of superoxide) rose significantly during the first 4 to 8h and then declined to background levels. As with hydrogen peroxide, this superoxide insult failed to activate downstream caspases (-3, -7, and -9). Substantial depolarization of mitochondria occurred after 1h, and nuclear morphology changes characteristic of oxidative stress became maximal after 2h. However, death indicated by plasma membrane permeabilization (cellular uptake of propidium iodide) approached maximal levels only after 4h, at which time substantial redistribution to the cytosol of death-associated mitochondrial intermembrane space proteins, notably endonuclease G, had occurred. Applying established criteria for autophagic death (knockdown of Atg7) or programmed necrosis (knockdown of endonuclease G), cells treated with the relevant siRNA showed significant blockade of each type of cell death, 4h after onset of the superoxide flux. Yet at later times, siRNA-mediated knockdown failed to prevent death, monitored by cellular uptake of propidium iodide. We conclude that superoxide initially invokes a diverse programmed caspase-independent death response, involving transient manifestation in parallel of autophagic death and programmed necrosis. Ultimately most neurons become overwhelmed by the consequences of severe oxidative stress and die. This study reveals the multiple phases of neuronal cell death modalities under extended oxidative stress.

l-2,4-Diaminobutyric acid and the GABA system

The effects of l-2,4-diaminobutyric acid (DABA) on GABA levels and on the activity of GABA metabolizing enzymes have been studied in a number of rat brain regions after both acute and chronic administration. Kinetic studies indicated that DABA was a non-linear, non-competitive inhibitor of GABA transaminase activity. The DABA-induced elevation of GABA levels paralleled the inhibition of GABA transaminase activity. DABA was a more effective inhibitor of GABA transaminase in vivo than in vitro, and this inhibition probably produced the elevation of GABA levels. The neurotoxicity of DABA appears to produce a use in GABA replacement therapy.

Multifaceted role of nitric oxide in an in vitro mouse neuronal injury model: transcriptomic profiling defines the temporal recruitment of death signalling cascades

Nitric oxide is implicated in the pathogenesis of various neuropathologies characterized by oxidative stress. Although nitric oxide has been reported to be involved in the exacerbation of oxidative stress observed in several neuropathologies, existent data fail to provide a holistic description of how nitrergic pathobiology elicits neuronal injury. Here we provide a comprehensive description of mechanisms contributing to nitric oxide induced neuronal injury by global transcriptomic profiling. Microarray analyses were undertaken on RNA from murine primary cortical neurons treated with the nitric oxide generator DETA-NONOate (NOC-18, 0.5 mM) for 8–24 hrs. Biological pathway analysis focused upon 3672 gene probes which demonstrated at least a ±1.5-fold expression in a minimum of one out of three time-points and passed statistical analysis (one-way anova, P < 0.05). Numerous enriched processes potentially determining nitric oxide mediated neuronal injury were identified from the transcriptomic profile: cell death, developmental growth and survival, cell cycle, calcium ion homeostasis, endoplasmic reticulum stress, oxidative stress, mitochondrial homeostasis, ubiquitin-mediated proteolysis, and GSH and nitric oxide metabolism. Our detailed time-course study of nitric oxide induced neuronal injury allowed us to provide the first time a holistic description of the temporal sequence of cellular events contributing to nitrergic injury. These data form a foundation for the development of screening platforms and define targets for intervention in nitric oxide neuropathologies where nitric oxide mediated injury is causative.

Transcriptomic profiling of astrocytes treated with the Rho kinase inhibitor fasudil reveals cytoskeletal and pro-survival responses

Inhibitors of Rho kinase (ROCK) have potential for management of neurological disorders by inhibition of glial scarring. Since astrocytes play key roles in brain physiology and pathology, we determined changes in the astrocytic transcriptome produced by the ROCK inhibitor Fasudil to obtain mechanistic insights into its beneficial action during brain injury. Cultured murine astrocytes were treated with Fasudil (100 µM) and morphological analyses revealed rapid stellation by 1 h and time-dependent (2-24 h) dissipation of F-actin-labelled stress fibres. Microarray analyses were performed on RNA and the time-course of global gene profiling (2, 6, 12 and 24 h) provided a comprehensive description of transcriptomic changes. Hierarchical clustering of differentially expressed genes and analysis for over-represented gene ontology groups using the DAVID database focused attention on Fasudil-induced changes to major biological processes regulating cellular shape and motility (actin cytoskeleton, axon guidance, transforming growth factor-β (TGFβ) signalling and tight junctions). Bioinformatic analyses of transcriptomic changes revealed how these biological processes contributed to changes in astrocytic motility and cytoskeletal reorganisation. Here genes associated with extracellular matrix were also involved, but unexpected was a subset of alterations (EAAT2, BDNF, anti-oxidant species, metabolic and signalling genes) indicative of adoption by astrocytes of a pro-survival phenotype. Expression profiles of key changes with Fasudil and another ROCK inhibitor Y27632 were validated by real-time PCR. Although effects of ROCK inhibition have been considered to be primarily cytoskeletal via reduction of glial scarring, we demonstrate additional advantageous actions likely to contribute to their ameliorative actions in brain injury.

Combined excitotoxic-oxidative stress and the concept of non-cell autonomous pathology of ALS: insights into motoneuron axonopathy and astrogliosis

Non-cell autonomous pathology is widely accepted to determine the demise of motoneurons (MNs) in amyotrophic lateral sclerosis (ALS) with astrocytes, GFAP and glutamate transport suggested to play roles in reactive astrogliosis. Previously we described actions of excitotoxicity and oxidative stress to produce differential injury of motoneurons and astrocytes, respectively, and our goal here was to define patterns of MN injury and astrogliosis during a combined excitotoxic-oxidative injury since such a paradigm more closely models disease pathology. Using an in vitro neuronal-glial culture of embryonic mouse spinal cord, we demonstrate that glutamate transport activity was maintained or increased initially, despite a loss of cellular viability, induced by exposure to combinations of excitotoxic [(S)-5-fluorowillardiine (FW)] and oxidative [3-morpholinosydnonimine (SIN-1)] insults over 48 h. Under these conditions, injury was slow in time course and apoptotic-like as shown by the patterns of annexin V and propidium iodide (PI) labelling. Immunocytochemistry for SMI-32 revealed that injury produced time- and insult-dependent reductions in the size of MN arbours, axonal dieback and appreciable neuritic blebbing. These changes were preceded by early hypertrophy of GFAP-positive astrocytes, and followed by more delayed stellation and eventual gliotoxicity. Alterations to EAAT2 immunolabelling were similar to those found for GFAP being initially maintained and then eventually reduced at 48 h. Image analysis of immunocytochemical data confirmed the differential time-dependent changes found with SMI-32, GFAP and EAAT2. Axonopathy and blebbing of MNs was frequently associated with areas of low GFAP immunoreactivity. The exact profile of changes to MNs and astrocytes was context-dependent and sensitive to subtle changes in the mix of excitotoxic-oxidative insults. Overall our findings are consistent with the concepts that the nature, extent and time-course of astrogliosis are insult-dependent, and that discrete pro-survival and destructive components of astrogliosis are likely to determine the precise profile of MN injury in non-cell autonomous pathology of ALS.

Autophagic activity in cortical neurons under acute oxidative stress directly contributes to cell death

Primary neurons undergo insult-dependent programmed cell death. We examined autophagy as a process contributing to cell death in cortical neurons after treatment with either hydrogen peroxide (H(2)O(2)) or staurosporine. Although caspase-9 activation and cleavage of procaspase-3 were significant following staurosporine treatment, neither was observed following H(2)O(2) treatment, indicating a non-apoptotic death. Autophagic activity increased rapidly with H(2)O(2), but slowly with staurosporine, as quantified by processing of endogenous LC3. Autophagic induction by both stressors increased the abundance of fluorescent puncta formed by GFP-LC3, which could be blocked by 3-methyladenine. Significantly, such inhibition of autophagy blocked cell death induced by H(2)O(2) but not staurosporine. Suppression of Atg7 inhibited cell death by H(2)O(2), but not staurosporine, whereas suppression of Beclin 1 prevented cell death by both treatments, suggesting it has a complex role regulating both apoptosis and autophagy. We conclude that autophagic mechanisms are activated in an insult-dependent manner and that H(2)O(2) induces autophagic cell death.

The Rho kinase inhibitor Fasudil up-regulates astrocytic glutamate transport subsequent to actin remodelling in murine cultured astrocytes

BACKGROUND AND PURPOSE

Glutamate transporters play a major role in maintaining brain homeostasis and the astrocytic transporters, EAAT1 and EAAT2, are functionally dominant. Astrocytic excitatory amino acid transporters (EAATs) play important roles in various neuropathologies wherein astrocytes undergo cytoskeletal changes. Astrocytic plasticity is well documented, but the interface between EAAT function, actin and the astrocytic cytoskeleton is poorly understood. Because Rho kinase (ROCK) is a key determinant of actin polymerization, we investigated the effects of ROCK inhibitors on EAAT activity and astrocytic morphology.

EXPERIMENTAL APPROACH

The functional activity of glutamate transport was determined in murine cultured astrocytes after exposure to the ROCK inhibitors Fasudil (HA-1077) and Y27632 using biochemical, molecular and morphological approaches. Cytochemical analyses assessed changes in astrocytic morphology, F-/G-actin, and localizations of EAAT1/2.

RESULTS

Fasudil and Y27632 increased [(3)H]-D-aspartate (D-Asp) uptake into astrocytes, and the action of Fasudil was time-dependent and concentration-related. The rapid stellation of astrocytes (glial fibrillary acidic protein immunocytochemistry) induced by Fasudil was accompanied by reduced phalloidin staining of F-actin and increased V(max) for [(3)H]-D-Asp uptake. Immunoblotting after biotinylation demonstrated that Fasudil increased the expression of EAAT1 and EAAT2 on the cell surface. Immunocytochemistry indicated that Fasudil induced prominent labelling of astrocytic processes by EAAT1/2.

CONCLUSION AND IMPLICATIONS

These data show for the first time that ROCK plays a major role in determining the cell surface expression of EAAT1/2, providing new evidence for an association between transporter function and astrocytic phenotype. ROCK inhibitors, via the actin cytoskeleton, effect a consequent elevation of glutamate transporter function - this activity profile may contribute to their beneficial actions in neuropathologies.

Preconditioning protects against oxidative injury involving hypoxia-inducible factor-1 and vascular endothelial growth factor in cultured astrocytes

Tolerance to brain injury involves hypoxia-inducible factor-1 (HIF-1) and its target genes as the key pathway mediating a cascade of events including cell survival, energetics, and angiogenesis. In this study, we established the treatment paradigms for an in vitro model of tolerance to oxidative injury in primary astrocytic cultures and further examined the roles for the HIF-1 signalling cascade. Isolated murine astrocytes were preconditioned with sub-toxic concentrations of HIF-1 inducers and subsequently exposed to a H(2)O(2) insult, where changes in cell viability and protein expression were determined. Preconditioning with non-damaging concentrations of desferrioxamine (DFO) and ethyl-3,4-dihydroxybenzoate (EDHB) significantly improved cellular viability after H(2)O(2) injury treatment. Time course studies revealed that DFO and EDHB treatments alone induced sequential activation of HIF-1 signal transduction where nuclear HIF-1alpha protein accumulation was detected as early as 2h, followed by downstream upregulation of intracellular and released VEGF from 4h and 8h onwards, respectively. The protective effects of DFO and EDHB preconditioning against H(2)O(2) injury were abolished by co-treatment with cycloheximide, an inhibitor of protein synthesis. Importantly, when the anti-HIF-1 compound, 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) was used, the cytoprotection and VEGF accumulation produced by DFO and EDHB preconditioning were diminished. These results indicate the essential role of the HIF-1 pathway in our model of tolerance against oxidative injury in cultured astrocytes, and suggest roles for astrocytic HIF-1 expression and VEGF release which may influence the function of surrounding cells and vasculature during oxidative stress-related brain diseases.

Transportable and non-transportable inhibitors of L-glutamate uptake produce astrocytic stellation and increase EAAT2 cell surface expression

Astrocytic excitatory amino acid transporters (EAATs) regulate excitatory transmission and limit excitotoxicity. Evidence for a functional interface between EAATs and glial fibrillary acidic protein (GFAP) relevant to astrocytic morphology led to investigations of actions of transportable (D-Aspartate (D-Asp) and (2S,3S,4R)-2-(carboxycyclopropyl)glycine (L-CCG-III)) and non-transportable (DL-threo-beta-benzyloxyaspartate (DL-TBOA)) inhibitors of Glu uptake in murine astrocytes. D-Asp (1 mM), L-CCG-III (0.5 mM) and DL-TBOA (0.5 mM) produced time-dependent (24-72 h) reductions in (3)[H]D-Asp uptake (approximately 30-70%) with little or no gliotoxicity. All drugs induced a profound change in phenotype from cobblestone to stellate morphology and image analysis revealed increases in the intensity of GFAP immunolabelling for L-CCG-III and DL-TBOA. Cytochemistry indicated localized changes in F-actin distribution. Cell surface expression of EAAT2, but not EAAT1, was elevated at 72 h. Blockade of Glu uptake by both types of EAAT inhibitor exerts longer-term effects on astrocytic morphology and a compensatory homeostatic rise in EAAT2 abundance.

Proliferation deficits and gene expression dysregulation in Down's syndrome (Ts1Cje) neural progenitor cells cultured from neurospheres

Down's syndrome neurophenotypes are characterized by mental retardation and a decreased brain volume. To identify whether deficits in proliferation could be responsible for this phenotype, neural progenitor cells were isolated from the developing E14 neocortex of Down's syndrome partial trisomy Ts1Cje mice and euploid (WT) littermates and grown as neurospheres. Ts1Cje neural progenitors proliferated at a slower rate, because of a longer cell cycle, and a greater number of cells were positive for glial fibrillary acidic protein. An increase in cell death was also noted. Gene expression profiles of neural progenitor cells from Ts1Cje and WT showed that 54% of triploid genes had expression ratios (Ts1Cje/WT) significantly greater than the expected diploid gene ratio of 1.0. Some diploid genes associated with proliferation, differentiation, and glial function were dysregulated. Interestingly, proliferation and gene expression dysregulation detected in the Ts1Cje mice did not require overexpression of the chromosome 21 genes amyloid precursor protein (App) and soluble superoxide dismutase 1 (Sod1).

Oxidative stress triggers neuronal caspase-independent death: endonuclease G involvement in programmed cell death-type III

To characterize neuronal death, primary cortical neurons (C57/Black 6 J mice) were exposed to hydrogen peroxide (H2O2) and staurosporine. Both caused cell shrinkage, nuclear condensation, DNA fragmentation and loss of plasma membrane integrity. Neither treatment induced caspase-7 activity, but caspase-3 was activated by staurosporine but not H2O2. Each treatment caused redistribution from mitochondria of both endonuclease G (Endo G) and cytochrome c. Neurons knocked down for Endo G expression using siRNA showed reduction in both nuclear condensation and DNA fragmentation after treatment with H2O2, but not staurosporine. Endo G suppression protected cells against H2O2-induced cell death, while staurosporine-induced death was merely delayed. We conclude that staurosporine induces apoptosis in these neurons, but severe oxidative stress leads to Endo G-dependent death, in the absence of caspase activation (programmed cell death-type III). Therefore, oxidative stress triggers in neurons a form of necrosis that is a systematic cellular response subject to molecular regulation.

GABAergic striatal neurons exhibit caspase-independent, mitochondrially mediated programmed cell death

GABAergic striatal neurons are compromised in basal ganglia pathologies and we analysed how insult nature determined their patterns of injury and recruitment of the intrinsic mitochondrial pathway during programmed cell death (PCD). Stressors affecting targets implicated in striatal neurodegeneration [3-morpholinylsydnoneimine (SIN-1), 3-nitropropionic acid (3-NP), NMDA, 3,5-dihydroxyphenylglycine (DHPG), and staurosporine (STS)] were compared in cultured GABAergic neurons from murine striatum by analyzing the progression of injury and its correlation with mitochondrial involvement, the redistribution of intermembrane space (IMS) proteins, and patterns of protease activation. Stressors produced PCD exhibiting slow-onset kinetics with time-dependent annexin-V labeling and eventual DNA fragmentation. IMS proteins including cytochrome c were differentially distributed, although stressors except STS produced early redistribution of apoptosis-inducing factor and Omi, suggestive of early recruitment of both caspase-dependent and caspase-independent signaling. In general, Bax mobilization to mitochondria appeared to promote IMS protein redistribution. Caspase 3 activation was prominent after STS, whereas NMDA and SIN-1 produced mainly calpain activation, and 3-NP and DHPG elicited a mixed profile of protease activation. PCD and redistribution of IMS proteins in striatal GABAergic neurons were canonical and insult-dependent, reflecting differential interplay between the caspase cascade and alternate cell death pathways.