CACHD1 is an α2δ-like protein that modulates CaV3 voltage-gated calcium channel activity

The putative cache (Ca2+ channel and chemotaxis receptor) domain containing 1 (CACHD1) protein has predicted structural similarities to members of the alpha2delta voltage-gated Ca2+ channel (VGCC) auxiliary subunit family. CACHD1 mRNA and protein were highly expressed in the male mammalian CNS, in particular in the thalamus, hippocampus and cerebellum, with a broadly similar tissue distribution to CaV3 subunits, in particular, CaV3.1. In expression studies, CACHD1 increased cell-surface localization of CaV3.1 and these proteins were in close proximity at the cell surface consistent with the formation of CACHD1-CaV3.1 complexes. In functional electrophysiological studies, co-expression of human CACHD1 with CaV3.1, CaV3.2 and CaV3.3 caused a significant increase in peak current density and corresponding increases in maximal conductance. By contrast, alpha2delta-1 had no effect on peak current density or maximal conductance in either CaV3.1, CaV3.2 or CaV3.3. Comparison of CACHD1-mediated increases in CaV3.1 current density and gating currents revealed an increase in channel open probability. In hippocampal neurons from male and female E19 rats, CACHD1 overexpression increased CaV3-mediated action potential (AP) firing frequency and neuronal excitability. These data suggest that CACHD1 is structurally an alpha2delta-like protein that functionally modulates CaV3 voltage-gated calcium channel activity

Exogenous alpha-Synuclein decreases raft partitioning of Cav2.2 channels inducing dopamine release

alpha-Synuclein is thought to regulate neurotransmitter release through multiple interactions with presynaptic proteins, cytoskeletal elements, ion channels, and synaptic vesicles membrane. alpha-Synuclein is abundant in the presynaptic compartment, and its release from neurons and glia has been described as responsible for spreading of alpha-synuclein-derived pathology. alpha-Synuclein-dependent dysregulation of neurotransmitter release might occur via its action on surface-exposed calcium channels. Here, we provide electrophysiological and biochemical evidence to show that alpha-synuclein, applied to rat neurons in culture or striatal slices, selectively activates Cav2.2 channels, and said activation correlates with increased neurotransmitter release. Furthermore, in vivo perfusion of alpha-synuclein into the striatum also leads to acute dopamine release. We further demonstrate that alpha-synuclein reduces the amount of plasma membrane cholesterol and alters the partitioning of Cav2.2 channels, which move from raft to cholesterol-poor areas of the plasma membrane. We provide evidence for a novel mechanism through which alpha-synuclein acts from the extracellular milieu to modulate neurotransmitter release and propose a unifying hypothesis for the mechanism of alpha-synuclein action on multiple targets: the reorganization of plasma membrane microdomains

Nonpsychotropic plant cannabinoids, cannabidivarin (CBDV) and cannabidiol (CBD), activate and desensitize transient receptor potential vanilloid 1 (TRPV1) channels in vitro: potential for the treatment of neuronal hyperexcitability

Epilepsy is the most common neurological disorder, with over 50 million people worldwide affected. Recent evidence suggests that the transient receptor potential cation channel subfamily V member 1 (TRPV1) may contribute to the onset and progression of some forms of epilepsy. Since the two nonpsychotropic cannabinoids cannabidivarin (CBDV) and cannabidiol (CBD) exert anticonvulsant activity in vivo and produce TRPV1-mediated intracellular calcium elevation in vitro, we evaluated the effects of these two compounds on TRPV1 channel activation and desensitization and in an in vitro model of epileptiform activity. Patch clamp analysis in transfected HEK293 cells demonstrated that CBD and CBDV dose-dependently activate and rapidly desensitize TRPV1, as well as TRP channels of subfamily V type 2 (TRPV2) and subfamily A type 1 (TRPA1). TRPV1 and TRPV2 transcripts were shown to be expressed in rat hippocampal tissue. When tested on epileptiform neuronal spike activity in hippocampal brain slices exposed to a Mg2+-free solution using multielectrode arrays (MEAs), CBDV reduced both epileptiform burst amplitude and duration. The prototypical TRPV1 agonist, capsaicin, produced similar, although not identical effects. Capsaicin, but not CBDV, effects on burst amplitude were reversed by IRTX, a selective TRPV1 antagonist. These data suggest that CBDV antiepileptiform effects in the Mg2+-free model are not uniquely mediated via activation of TRPV1. However, TRPV1 was strongly phosphorylated (and hence likely sensitized) in Mg2+-free solution-treated hippocampal tissue, and both capsaicin and CBDV caused TRPV1 dephosphorylation, consistent with TRPV1 desensitization. We propose that CBDV effects on TRP channels should be studied further in different in vitro and in vivo models of epilepsy

Ion channels

Ion channels are protein molecules that span across the cell membrane allowing the passage of ions from one side of the membrane to the other. They have an aqueous pore, which becomes accessible to ions after a conformational change in the protein structure that causes the ion channel to open. Ion channels are selective meaning that they only allow certain ions to pass through them, and they play critical roles in controlling neuronal excitability. Ion channels are divided into those that are opened by changes in membrane potential, voltage-gated ion channels, and ion channels that are opened by the binding of a ligand, such as a hormone or a neurotransmitter, ligand-gated ion channels. In this chapter we introduce both voltage-gated and ligand-gated ion channels that are abundantly expressed within the central nervous system and the peripheral nervous system. Here, we discuss their roles in neurological disorders and introduce some common clinically used drugs that target ion channels as a means of treatment

Nonpsychotropic Plant Cannabinoids, Cannabidivarin (CBDV) and Cannabidiol (CBD), Activate and Desensitize Transient Receptor Potential Vanilloid 1 (TRPV1) Channels in Vitro: Potential for the Treatment of Neuronal Hyperexcitability

Epilepsy is the most common neurological disorder, with over 50 million people worldwide affected. Recent evidence suggests that the transient receptor potential cation channel subfamily V member 1 (TRPV1) may contribute to the onset and progression of some forms of epilepsy. Since the two nonpsychotropic cannabinoids cannabidivarin (CBDV) and cannabidiol (CBD) exert anticonvulsant activity in vivo and produce TRPV1-mediated intracellular calcium elevation in vitro, we evaluated the effects of these two compounds on TRPV1 channel activation and desensitization and in an in vitro model of epileptiform activity. Patch clamp analysis in transfected HEK293 cells demonstrated that CBD and CBDV dose-dependently activate and rapidly desensitize TRPV1, as well as TRP channels of subfamily V type 2 (TRPV2) and subfamily A type 1 (TRPA1). TRPV1 and TRPV2 transcripts were shown to be expressed in rat hippocampal tissue. When tested on epileptiform neuronal spike activity in hippocampal brain slices exposed to a Mg²⁺-free solution using multielectrode arrays (MEAs), CBDV reduced both epileptiform burst amplitude and duration. The prototypical TRPV1 agonist, capsaicin, produced similar, although not identical effects. Capsaicin, but not CBDV, effects on burst amplitude were reversed by IRTX, a selective TRPV1 antagonist. These data suggest that CBDV antiepileptiform effects in the Mg²⁺-free model are not uniquely mediated via activation of TRPV1. However, TRPV1 was strongly phosphorylated (and hence likely sensitized) in Mg²⁺-free solution-treated hippocampal tissue, and both capsaicin and CBDV caused TRPV1 dephosphorylation, consistent with TRPV1 desensitization. We propose that CBDV effects on TRP channels should be studied further in different in vitro and in vivo models of epilepsy

Impact of the New MELD-based Allocation System on Waiting List and Post-Transplant Survival - A Cohort Analysis Using the French National CRISTAL Database

International audienceConcerns related to equity and efficacy of our previous center-based allocation system have led us to introduce a patient-based allocation system called the "Liver Score" that incorporates the MELD score. The main objective of this study was to compare waitlist and post-transplant survivals before and after implementation of the "Liver Score" using the French transplant registry (period before: 2004-2006 and period after: 2007-2012). Patients transplanted during the second period were sicker and had a higher MELD. One-year waitlist survival (74% versus 76%; p=0.8) and one-year post-transplant survival (86.3% vs 85.7%; p=0.5) were similar between the 2 periods. Cirrhotic recipients with MELD>35 had lower one-year post-transplant survival compared to those with MELD35, patients presenting 2 or 3 risk factors (dialysis, intubation or infection) had a lower 1-year survival compared to those with none of these risk factors (61.2% vs 92%; p35 should be completed to allow safe transplantation. This article is protected by copyright. All rights reserved

Patients with acute liver failure listed for superurgent liver transplantation in France: Reevaluation of the clichy-villejuif criteria

International audienceIn France, decisions regarding superurgent (SU) liver transplantation (LT) for patients with acute liver failure (ALF) are principally based on the Clichy-Villejuif (CV) criteria. The aims of the present study were to study the outcomes of patients registered for SU LT and the factors that were predictive of spontaneous improvement and to determine the usefulness of the CV criteria. All patients listed in France for SU LT between 1997 and 2010 who were 15 years old or older with ALF were included. In all, 808 patients were listed for SU transplantation: 22% with paracetamol-induced ALF and 78% with non–paracetamol-induced ALF. Of these 808 patients, 112 improved spontaneously, 587 underwent LT, and 109 died or left the waiting list because of a worsening condition. The 1-year survival rate according to an intention-to-treat analysis and the survival after LT were 66.3% [interquartile range (IQR), 62.7%-69.7%] and 74.2% (IQR, 70.5%-77.6%), respectively. The factors that were predictive of a spontaneous recovery with ALF-related paracetamol hepatotoxicity were as follows: hepatic encephalopathy grade 0, 1, or 2 [odds ratio (OR), 4.8; 95% confidence interval (CI), 1.99-11.6]; creatinine clearance ≥ 60 mL/minute/1.73 m2 (OR, 4.77; 95% CI, 1.96-11.63), a bilirubin level \textless 200 µmol/L (OR, 21.64; 95% CI, 1.76-265.7); and a factor V level \textgreater 20% (OR, 5.79; 95% CI, 1.66-20.29). For ALF-related nonparacetamol hepatotoxicity, the factor that was predictive of a spontaneous recovery was a bilirubin level \textless 200 µmol/L (OR, 10.38; 95% CI, 4.71-22.86). The sensitivity, specificity, and positive and negative predictive values for the CV criteria were 75%, 56%, 50%, and 79%, respectively, for ALF due to paracetamol and 69%, 50%, 64%, and 55%, respectively, for ALF not related to paracetamol. The performance of current criteria for SU transplantation could be improved if paracetamol-induced ALF and non–paracetamol-induced ALF were split and 2 other items were included in this model: the bilirubin level and creatinine clearance. Liver Transpl 21:512-523, 2015. © 2015 AASLD