title: Differential Kv1.3, KCa3.1, and Kir2.1 expression in "classically" and "alternatively" activated microglia.
abstract: Microglia are highly plastic cells that can assume different phenotypes in response to microenvironmental signals. Lipopolysaccharide (LPS) and interferon-γ (IFN-γ) promote differentiation into classically activated M1-like microglia, which produce high levels of pro-inflammatory cytokines and nitric oxide and are thought to contribute to neurological damage in ischemic stroke and Alzheimer's disease. IL-4 in contrast induces a phenotype associated with anti-inflammatory effects and tissue repair. We here investigated whether these microglia subsets vary in their K+channel expression by differentiating neonatal mouse microglia into M(LPS) and M(IL-4) microglia and studying their K+channel expression by whole-cell patch-clamp, quantitative PCR and immunohistochemistry. We identified three major types of K+channels based on their biophysical and pharmacological fingerprints: a use-dependent, outwardly rectifying current sensitive to the KV1.3 blockers PAP-1 and ShK-186, an inwardly rectifying Ba2+-sensitive Kir2.1 current, and a Ca2+-activated, TRAM-34-sensitive KCa3.1 current. Both KV1.3 and KCa3.1 blockers inhibited pro-inflammatory cytokine production and iNOS and COX2 expression demonstrating that KV1.3 and KCa3.1 play important roles in microglia activation. Following differentiation with LPS or a combination of LPS and IFN-γ microglia exhibited high KV1.3 current densities (∼50 pA/pF at 40 mV) and virtually no KCa3.1 and Kircurrents, while microglia differentiated with IL-4 exhibited large Kir2.1 currents (∼ 10 pA/pF at -120 mV). KCa3.1 currents were generally low but moderately increased following stimulation with IFN-γ or ATP (∼10 pS/pF). This differential K+channel expression pattern suggests that KV1.3 and KCa3.1 inhibitors could be used to inhibit detrimental neuroinflammatory microglia functions. GLIA 2016;65:106-121.
authors.affiliation: Department of Pharmacology, University of California, Davis, California.
authors.forename: Hai M
authors.initials: HM
authors.lastname: Nguyen
authors.affiliation: Department of Pharmacology, University of California, Davis, California.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Grössinger
authors.affiliation: Department of Pathology and Laboratory Medicine, University of California Davis Medical Center, Sacramento, California.|M.I.N.D. Institute, University of California Davis Medical Center, Davis, Sacramento, California.
authors.forename: Makoto
authors.initials: M
authors.lastname: Horiuchi
authors.affiliation: Department of Pathology and Laboratory Medicine, University of California Davis Medical Center, Sacramento, California.
authors.forename: Kyle W
authors.initials: KW
authors.lastname: Davis
authors.affiliation: Department of Pathology and Laboratory Medicine, University of California Davis Medical Center, Sacramento, California.|M.I.N.D. Institute, University of California Davis Medical Center, Davis, Sacramento, California.
authors.forename: Lee-Way
authors.initials: LW
authors.lastname: Jin
authors.affiliation: Department of Pathology and Laboratory Medicine, University of California Davis Medical Center, Sacramento, California.|M.I.N.D. Institute, University of California Davis Medical Center, Davis, Sacramento, California.
authors.forename: Izumi
authors.initials: I
authors.lastname: Maezawa
authors.affiliation: Department of Pharmacology, University of California, Davis, California.
authors.forename: Heike
authors.initials: H
authors.lastname: Wulff
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D007371:Interferon-gamma / Q000378:metabolism; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D051664:Kv1.3 Potassium Channel / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation; D008564:Membrane Potentials; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*
chemical_list: D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496925:Kcnn4 protein, mouse; C489461:Kir2.1 channel; D051664:Kv1.3 Potassium Channel; D008070:Lipopolysaccharides; D024661:Potassium Channels, Inwardly Rectifying; D007371:Interferon-gamma
keywords: KCa3.1; Kir2.1; Kv1.3; PAP-1; TRAM-34; microglia; potassium channel