title: Monocyte Chemoattractant Protein-1 upregulates GABA-induced current: evidence of modified GABAA subunit composition in cortical neurons from the G93A mouse model of Amyotrophic Lateral Sclerosis.
abstract: Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disorder that affects upper and lower motor neurons. Previous evidence has indicated that excitotoxic cell death in ALS may remarkably depend on Cl(-) ion influx through the GABA(A) receptors. In this study we have analysed the effect of Monocyte Chemoattractant Protein-1 (MCP-1), a chemokine expressed to a higher level in ALS patients, on GABAA receptors in cultured cortical neurons from a genetic model of ALS (G93A) and compared with wild type SOD1 (SOD1) and their corresponding non transgenic littermates (Control). By performing electrophysiological experiments we have observed that, in cortical neurons MCP-1 (2-150 ng/ml) induced an enhancement of GABA-evoked currents that was significantly higher in G93A neurons compared to controls. The effect of MCP-1 was not dependent on the activation of its receptor CCR2, while it was blocked by flumazenil, the antagonist of benzodiazepine sites. Analysis of GABAA receptor subunit composition has indicated an altered subunit expression level in G93A cortical neurons compared to controls. Instead, in cultured spinal neurons MCP-1 induced a significant reduction of GABA-evoked currents, also through the benzodiazepine sites, indicating a region-specific mechanism of action. However, no differences were observed in the current reduction between the three neuronal populations. These findings provide the first evidence that MCP-1, acting on benzodiazepine sites, can modulate the GABA-evoked currents, depending on the subunit composition of GABA(A) receptor. In cortical neurons MCP-1 upmodulates the GABA-evoked current and this effect is exacerbated in the mutated neurons. It is reasonable to assume that the higher Cl(-) influx through GABA(A) receptors in the presence of MCP-1 in mutated cortical neurons may induce an excitotoxicity acceleration. Agents able to block the MCP-1 production may then prove useful for ALS treatment.
authors.affiliation: IRCCS Fondazione S. Lucia, Via del Fosso di Fiorano, 64, 00143 Rome, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Caioli
authors.forename: Massimo
authors.initials: M
authors.lastname: Pieri
authors.forename: Alessia
authors.initials: A
authors.lastname: Antonini
authors.forename: Angelo
authors.initials: A
authors.lastname: Guglielmotti
authors.forename: Cinzia
authors.initials: C
authors.lastname: Severini
authors.forename: Cristina
authors.initials: C
authors.lastname: Zona
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology; D018932:Chemokine CCL2 / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005260:Female; D005442:Flumazenil / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists / Q000494:pharmacology; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D021122:Protein Subunits / Q000378:metabolism; D011963:Receptors, GABA-A / Q000378:metabolism*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D058787:GABA-A Receptor Antagonists; D021122:Protein Subunits; D011963:Receptors, GABA-A; D005442:Flumazenil; D005680:gamma-Aminobutyric Acid
keywords: ALS; Electrophysiology; GABA receptor modulator; GABA-induced current; Immunosystem; Neurodegeneration