title: Involvement of the intracellular ion channel CLIC1 in microglia-mediated beta-amyloid-induced neurotoxicity.
abstract: It is widely believed that the inflammatory events mediated by microglial activation contribute to several neurodegenerative processes. Alzheimer's disease, for example, is characterized by an accumulation of beta-amyloid protein (Abeta) in neuritic plaques that are infiltrated by reactive microglia and astrocytes. Although Abeta and its fragment 25-35 exert a direct toxic effect on neurons, they also activate microglia. Microglial activation is accompanied by morphological changes, cell proliferation, and release of various cytokines and growth factors. A number of scientific reports suggest that the increased proliferation of microglial cells is dependent on ionic membrane currents and in particular on chloride conductances. An unusual chloride ion channel known to be associated with macrophage activation is the chloride intracellular channel-1 (CLIC1). Here we show that Abeta stimulation of neonatal rat microglia specifically leads to the increase in CLIC1 protein and to the functional expression of CLIC1 chloride conductance, both barely detectable on the plasma membrane of quiescent cells. CLIC1 protein expression in microglia increases after 24 hr of incubation with Abeta, simultaneously with the production of reactive nitrogen intermediates and of tumor necrosis factor-alpha (TNF-alpha). We demonstrate that reducing CLIC1 chloride conductance by a specific blocker [IAA-94 (R(+)-[(6,7-dichloro-2-cyclopentyl-2,3-dihydro-2-methyl-1-oxo-1H-inden-5yl)-oxy] acetic acid)] prevents neuronal apoptosis in neurons cocultured with Abeta-treated microglia. Furthermore, we show that small interfering RNAs used to knock down CLIC1 expression prevent TNF-alpha release induced by Abeta stimulation. These results provide a direct link between Abeta-induced microglial activation and CLIC1 functional expression.
authors.affiliation: Dipartimenti di Biologia Cellulare e dello Sviluppo, Universita La Sapienza, 00185 Rome, Italy.
authors.forename: Gaia
authors.initials: G
authors.lastname: Novarino
authors.forename: Cinzia
authors.initials: C
authors.lastname: Fabrizi
authors.forename: Raffaella
authors.initials: R
authors.lastname: Tonini
authors.forename: Michela A
authors.initials: MA
authors.lastname: Denti
authors.forename: Fiorella
authors.initials: F
authors.lastname: Malchiodi-Albedi
authors.forename: Giuliana M
authors.initials: GM
authors.lastname: Lauro
authors.forename: Benedetto
authors.initials: B
authors.lastname: Sacchetti
authors.forename: Silvia
authors.initials: S
authors.lastname: Paradisi
authors.forename: Arnaldo
authors.initials: A
authors.lastname: Ferroni
authors.forename: Paul M
authors.initials: PM
authors.lastname: Curmi
authors.forename: Samuel N
authors.initials: SN
authors.lastname: Breit
authors.forename: Michele
authors.initials: M
authors.lastname: Mazzanti
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects; D018118:Chloride Channels / Q000378:metabolism*; D015870:Gene Expression; D006016:Glycolates / Q000494:pharmacology*; D006801:Humans; D008264:Macrophages / Q000378:metabolism; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; C501966:CLIC1 protein, human; D018118:Chloride Channels; D006016:Glycolates; D018696:Neuroprotective Agents; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; C015765:MK 473