title: Neuroinflammation leads to region-dependent alterations in astrocyte gap junction communication and hemichannel activity.
abstract: Inflammation attenuates gap junction (GJ) communication in cultured astrocytes. Here we used a well-characterized model of experimental brain abscess as a tool to query effects of the CNS inflammatory milieu on astrocyte GJ communication and electrophysiological properties. Whole-cell patch-clamp recordings were performed on green fluorescent protein (GFP)-positive astrocytes in acute brain slices from glial fibrillary acidic protein-GFP mice at 3 or 7 d after Staphylococcus aureus infection in the striatum. Astrocyte GJ communication was significantly attenuated in regions immediately surrounding the abscess margins and progressively increased to levels typical of uninfected brain with increasing distance from the abscess proper. Conversely, astrocytes bordering the abscess demonstrated hemichannel activity as evident by enhanced ethidium bromide (EtBr) uptake that could be blocked by several pharmacological inhibitors, including the connexin 43 (Cx43) mimetic peptide Gap26, carbenoxolone, the pannexin1 (Panx1) mimetic peptide (10)Panx1, and probenecid. However, hemichannel opening was transient with astrocytic EtBr uptake observed near the abscess at day 3 but not day 7 after infection. The region-dependent pattern of hemichannel activity at day 3 directly correlated with increases in Cx43, Cx30, Panx1, and glutamate transporter expression (glial L-glutamate transporter and L-glutamate/L-aspartate transporter) along the abscess margins. Changes in astrocyte resting membrane potential and input conductance correlated with the observed changes in GJ communication and hemichannel activity. Collectively, these findings indicate that astrocyte coupling and electrical properties are most dramatically affected near the primary inflammatory site and reveal an opposing relationship between the open states of GJ channels versus hemichannels during acute infection. This relationship may extend to other CNS diseases typified with an inflammatory component.
authors.affiliation: Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA.
authors.forename: Nikolay
authors.initials: N
authors.lastname: Karpuk
authors.forename: Maria
authors.initials: M
authors.lastname: Burkovetskaya
authors.forename: Teresa
authors.initials: T
authors.lastname: Fritz
authors.forename: Amanda
authors.initials: A
authors.lastname: Angle
authors.forename: Tammy
authors.initials: T
authors.lastname: Kielian
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000473:pathology / Q000502:physiology*; D001922:Brain Abscess / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D002450:Cell Communication; D000075302:Connexin 30; D018031:Connexin 43 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D017630:Connexins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D003342:Corpus Striatum / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D004660:Encephalitis / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D027341:Excitatory Amino Acid Transporter 1 / Q000096:biosynthesis; D027342:Excitatory Amino Acid Transporter 2 / Q000096:biosynthesis; D017629:Gap Junctions / Q000502:physiology*; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D008564:Membrane Potentials; D051379:Mice; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D018408:Patch-Clamp Techniques; D011401:Promoter Regions, Genetic; D013203:Staphylococcal Infections / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D013211:Staphylococcus aureus
chemical_list: D000075302:Connexin 30; D018031:Connexin 43; D017630:Connexins; D027341:Excitatory Amino Acid Transporter 1; D027342:Excitatory Amino Acid Transporter 2; C100629:Gjb6 protein, mouse; D005904:Glial Fibrillary Acidic Protein; D009419:Nerve Tissue Proteins; C503631:Panx1 protein, mouse; C493393:Slc1a3 protein, mouse; D049452:Green Fluorescent Proteins