Neuron-restrictive silencer factor/repressor element 1-silencing transcription factor (NRSF/REST) controls spatial K buffering in primary cortical astrocytes.

Neuron-restrictive silencer factor/repressor element 1 (RE1)-silencing transcription factor (NRSF/REST) is a transcriptional repressor of a large cluster of neural genes containing RE1 motifs in their promoter region. NRSF/REST is ubiquitously expressed in non-neuronal cells, including astrocytes, while it is down-regulated during neuronal differentiation. While neuronal NRSF/REST homeostatically regulates intrinsic excitability and synaptic transmission, the role of the high NRSF/REST expression levels in the homeostatic functions of astrocytes is poorly understood.

Dynamic expression of homeostatic ion channels in differentiated cortical astrocytes in vitro.

The capacity of astrocytes to adapt their biochemical and functional features upon physiological and pathological stimuli is a fundamental property at the basis of their ability to regulate the homeostasis of the central nervous system (CNS). It is well known that in primary cultured astrocytes, the expression of plasma membrane ion channels and transporters involved in homeostatic tasks does not closely reflect the pattern observed in vivo. The individuation of culture conditions that promote the expression of the ion channel array found in vivo is crucial when aiming at investigating the mechanisms underlying their dynamics upon various physiological and pathological stimuli.

A developmental stage- and Kidins220-dependent switch in astrocyte responsiveness to brain-derived neurotrophic factor.

Astroglial cells are key to maintain nervous system homeostasis. Neurotrophins are known for their pleiotropic effects on neuronal physiology but also exert complex functions to glial cells. Here, we investigated (i) the signaling competence of mouse embryonic and postnatal primary cortical astrocytes exposed to brain-derived neurotrophic factor (BDNF) and, (ii) the role of kinase D-interacting substrate of 220 kDa (Kidins220), a transmembrane scaffold protein that mediates neurotrophin signaling in neurons.

Kidins220/ARMS controls astrocyte calcium signaling and neuron-astrocyte communication.

Through their ability to modulate synaptic transmission, glial cells are key regulators of neuronal circuit formation and activity. Kidins220/ARMS (kinase-D interacting substrate of 220 kDa/ankyrin repeat-rich membrane spanning) is one of the key effectors of the neurotrophin pathways in neurons where it is required for differentiation, survival, and plasticity. However, its role in glial cells remains largely unknown.

An Increase in Membrane Cholesterol by Graphene Oxide Disrupts Calcium Homeostasis in Primary Astrocytes.

The use of graphene nanomaterials (GNMs) for biomedical applications targeted to the central nervous system is exponentially increasing, although precise information on their effects on brain cells is lacking. In this work, the molecular changes induced in cortical astrocytes by few-layer graphene (FLG) and graphene oxide (GO) flakes are addressed. The results show that exposure to FLG/GO does not affect cell viability or proliferation.

Graphene Oxide Upregulates the Homeostatic Functions of Primary Astrocytes and Modulates Astrocyte-to-Neuron Communication.

Graphene-based materials are the focus of intense research efforts to devise novel theranostic strategies for targeting the central nervous system. In this work, we have investigated the consequences of long-term exposure of primary rat astrocytes to pristine graphene (GR) and graphene oxide (GO) flakes. We demonstrate that GR/GO interfere with a variety of intracellular processes as a result of their internalization through the endolysosomal pathway.

Direct conversion of fibroblasts into functional astrocytes by defined transcription factors.

Direct cell reprogramming enables direct conversion of fibroblasts into functional neurons and oligodendrocytes using a minimal set of cell-lineage-specific transcription factors. This approach is rapid and simple, generating the cell types of interest in one step. However, it remains unknown whether this technology can be applied to convert fibroblasts into astrocytes, the third neural lineage.

Intracellular Na(+) inhibits volume-regulated anion channel in rat cortical astrocytes.

Accumulating evidence indicates that increased intracellular Na(+) concentration ([Na(+) ]i ) in astroglial cells is associated with the development of brain edema under ischemic conditions, but the underlying mechanisms are still elusive. Here, we report that in primary cultured rat cortical astrocytes, elevations of [Na(+) ]i reflecting those achieved during ischemia cause a marked decrease in hypotonicity-evoked current mediated by volume-regulated anion channel (VRAC). Pharmacological manipulations revealed that VRAC inhibition was not due to the reverse mode of the plasma membrane sodium/calcium exchanger.

Megalencephalic leukoencephalopathy with subcortical cysts protein 1 regulates glial surface localization of GLIALCAM from fish to humans.

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a leukodystrophy characterized by myelin vacuolization and caused by mutations in MLC1 or GLIALCAM. Patients with recessive mutations in either MLC1 or GLIALCAM show the same clinical phenotype. It has been shown that GLIALCAM is necessary for the correct targeting of MLC1 to the membrane at cell junctions, but its own localization was independent of MLC1 in vitro.

Photostimulation of whole-cell conductance in primary rat neocortical astrocytes mediated by organic semiconducting thin films.

Astroglial ion channels are fundamental molecular targets in the study of brain physiology and pathophysiology. Novel tools and devices intended for stimulation and control of astrocytes ion channel activity are therefore highly desirable. The study of the interactions between astrocytes and biomaterials is also essential to control and minimize reactive astrogliosis, in view of the development of implantable functional devices.

The increased activity of TRPV4 channel in the astrocytes of the adult rat hippocampus after cerebral hypoxia/ischemia.

The polymodal transient receptor potential vanilloid 4 (TRPV4) channel, a member of the TRP channel family, is a calcium-permeable cationic channel that is gated by various stimuli such as cell swelling, low pH and high temperature. Therefore, TRPV4-mediated calcium entry may be involved in neuronal and glia pathophysiology associated with various disorders of the central nervous system, such as ischemia. The TRPV4 channel has been recently found in adult rat cortical and hippocampal astrocytes; however, its role in astrocyte pathophysiology is still not defined.

An aquaporin-4/transient receptor potential vanilloid 4 (AQP4/TRPV4) complex is essential for cell-volume control in astrocytes.

Regulatory volume decrease (RVD) is a key mechanism for volume control that serves to prevent detrimental swelling in response to hypo-osmotic stress. The molecular basis of RVD is not understood. Here we show that a complex containing aquaporin-4 (AQP4) and transient receptor potential vanilloid 4 (TRPV4) is essential for RVD in astrocytes.

A silk platform that enables electrophysiology and targeted drug delivery in brain astroglial cells.

Astroglial cell survival and ion channel activity are relevant molecular targets for the mechanistic study of neural cell interactions with biomaterials and/or electronic interfaces. Astrogliosis is the most typical reaction to in vivo brain implants and needs to be avoided by developing biomaterials that preserve astroglial cell physiological function. This cellular phenomenon is characterized by a proliferative state and altered expression of astroglial potassium (K(+)) channels.

Evidence for two conductive pathways in P2X receptor: differences in modulation and selectivity.

The P2X(7) receptor (P2X(7)R) is an ATP-gated cation channel whose biophysical properties remain to be unravelled unequivocally. Its activity is modulated by divalent cations and organic messengers such as arachidonic acid (AA). In this study, we analysed the differential modulation of magnesium (Mg(2+)) and AA on P2X(7)R by measuring whole-cell currents and intracellular Ca(2+) ([Ca(2+)](i)) and Na(+) ([Na(+)](i)) dynamics in HEK293 cells stably expressing full-length P2X(7)R and in cells endowed with the P2X(7)R variant lacking the entire C-terminus tail (trP2X(7)R), which is thought to control the pore activation.

Carbenoxolone inhibits volume-regulated anion conductance in cultured rat cortical astroglia.

Accumulating evidence indicate that the gap-junction inhibitor carbenoxolone (CBX) regulates neuronal synchronization, depresses epileptiform activity and has a neuroprotective action. These CBX effects do not depend solely on its ability to inhibit gap junction channels formed by connexins (Cx), but the underlying mechanisms remain to be elucidated. Here we addressed the questions whether CBX modulates volume-regulated anion channels (VRAC) involved in the regulatory volume decrease and regulates the associated release of excitatory amino acids in cultured rat cortical astrocytes.

Differential crosstalk between P2X7 and arachidonic acid in activation of mitogen-activated protein kinases.

Accumulating evidence indicates that astroglial syncytium plays key role in normal and pathological brain functions. Astrocytes both in vitro and in situ respond to extracellular adenine-based nucleotides via the activation of P2 receptors. Massive release of ATP from neurons and glial cells occurs as a result of pathological conditions of the brain leading to neuroinflammation and involving P2X7 receptors.

Functional down-regulation of volume-regulated anion channels in AQP4 knockdown cultured rat cortical astrocytes.

In the brain, the astroglial syncytium is crucially involved in the regulation of water homeostasis. Accumulating evidence indicates that a dysregulation of the astrocytic processes controlling water homeostasis has a pathogenetic role in several brain injuries. Here, we have analysed by RNA interference technology the functional interactions occurring between the most abundant water channel in the brain, aquaporin-4 (AQP4), and the swelling-activated Cl(-) current expressed by cultured rat cortical astrocytes.

Design and characterization of a noncompetitive antagonist of the transient receptor potential vanilloid subunit 1 channel with in vivo analgesic and anti-inflammatory activity.

Unlabelled: Vanilloid receptor subunit 1 (TRPV1) is an integrator of physical and chemical stimuli in the peripheral nervous system. This receptor plays a key role in the pathophysiology of inflammatory pain. Thus, the identification of receptor antagonists with analgesic and anti-inflammatory activity in vivo is an important goal of current neuropharmacology.

Guanosine promotes the up-regulation of inward rectifier potassium current mediated by Kir4.1 in cultured rat cortical astrocytes.

Guanosine (Guo) is an endogenous neuroprotective molecule of the CNS, which has various acute and long-term effects on both neurones and astroglial cells. Whether Guo also modulates the activity/expression of ion channels involved in homeostatic control of extracellular potassium by the astrocytic syncytium is still unknown. Here we provide electrophysiological evidence that chronic exposure (48 h) to Guo (500 microm) promotes the functional expression of an inward rectifier K+ (Kir) conductance in primary cultured rat cortical astrocytes.

Potentiation of native and recombinant P2X7-mediated calcium signaling by arachidonic acid in cultured cortical astrocytes and human embryonic kidney 293 cells.

In the brain, arachidonic acid (AA) plays a critical role in the modulation of a broad spectrum of biological responses, including those underlying neuroinflammation. By using microfluorometry, we investigated the action of extracellular AA in the modulation of the purinoceptor P2X7-mediated elevation of [Ca(2+)](i) in cultured neocortical type-1 astrocytes and P2X7-, P2X2-transfected human embryonic kidney (HEK) 293 cells. We report that in cultured astrocytes, AA-induced [Ca(2+)](i) elevation is coupled to depletion of intracellular Ca(2+) stores and to a sustained noncapacitative Ca(2+) entry.

Molecular compatibility of the channel gate and the N terminus of S5 segment for voltage-gated channel activity.

Voltage-gated ion channels are modular proteins designed by the structural linkage of a voltage sensor and a pore domain. The functional coupling of these two protein modules is a subject of intense research. A major focus has been directed to decipher the role of the S4-S5 linker and the C-end of the inner pore helix in channel gating.

Differential modulation of ATP-induced calcium signalling by A1 and A2 adenosine receptors in cultured cortical astrocytes.

1. Despite the accumulating evidence that under various pathological conditions the extracellular elevation of adenine-based nucleotides and nucleosides plays a key role in the control of astroglial reactivity, how these signalling molecules interact in the regulation of astrocyte function is still largely elusive. 2.

Pathological glial reactions in neurodegenerative disorders: prospects for future therapeutics.

Pathological activation of the immune-competent glial cells is an obligatory event in neurodegenerative diseases. The secondary recruitment of astrocytes, resulting from an upgraded microglial activation, represents a critical point. Reactive astrocytes have to give up physiologically important functions (control of extracellular homeostasis and of synaptic transmission) and build a synergistic alliance with microglia in promoting oxidative, excitotoxic and beta-amyloid-induced neuronal damage.