title: Bradykinin-induced astrocyte-neuron signalling: glutamate release is mediated by ROS-activated volume-sensitive outwardly rectifying anion channels.
abstract: Glial cells release gliotransmitters which signal to adjacent neurons and glial cells. Previous studies showed that in response to stimulation with bradykinin, glutamate is released from rat astrocytes and causes NMDA receptor-mediated elevation of intracellular Ca(2+) in adjacent neurons. Here, we investigate how bradykinin-induced glutamate release from mouse astrocytes signals to neighbouring neurons in co-cultures. Astrocyte-to-neuron signalling and bradykinin-induced glutamate release from mouse astrocytes were both inhibited by the anion channel blocker 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and phloretin. Glutamate release was also sensitive to 4-(2-Butyl-6,7-dichlor-2-cyclopentylindan-1-on-5-yl) oxybutyric acid (DCPIB), a specific blocker of the volume-sensitive outwardly rectifying anion channel (VSOR). Astrocytes, but not neurons, responded to bradykinin with activation of whole-cell Cl- currents. Although astrocytes stimulated with bradykinin did not undergo cell swelling, the bradykinin-activated current exhibited properties typical of VSOR: outward rectification, inhibition by osmotic shrinkage, sensitivity to DIDS, phloretin and DCPIB, dependence on intracellular ATP, and permeability to glutamate. Bradykinin increased intracellular reactive oxygen species (ROS) in mouse astrocytes. Pretreatment of mouse astrocytes with either a ROS scavenger or an NAD(P)H oxidase inhibitor blocked bradykinin-induced activation of VSOR, glutamate release and astrocyte-to-neuron signalling. By contrast, pretreatment with BAPTA-AM or tetanus neurotoxin A failed to suppress bradykinin-induced glutamate release. Thus, VSOR activated by ROS in mouse astrocytes in response to stimulation with bradykinin, serves as the pathway for glutamate release to mediate astrocyte-to-neuron signalling. Since bradykinin is an initial mediator of inflammation, VSOR might play a role in glia-neuron communication in the brain during inflammation.
authors.affiliation: Department of Cell Physiology, National Institute for Physiological Sciences, 38 Nishigonaka, Myodaiji-cho, Okazaki, Aichi 444-8585, Japan.
authors.forename: Hong-Tao
authors.initials: HT
authors.lastname: Liu
authors.forename: Tenpei
authors.initials: T
authors.lastname: Akita
authors.forename: Takahiro
authors.initials: T
authors.lastname: Shimizu
authors.forename: Ravshan Z
authors.initials: RZ
authors.lastname: Sabirov
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Okada
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001920:Bradykinin / Q000494:pharmacology*; D065168:Bradykinin Receptor Antagonists; D020013:Calcium Signaling / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects / Q000502:physiology; D002540:Cerebral Cortex / Q000166:cytology; D018920:Coculture Techniques; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism*; D006982:Hypertonic Solutions / Q000494:pharmacology; D007038:Hypotonic Solutions / Q000494:pharmacology; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D008959:Models, Neurological; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D019899:Paracrine Communication / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010693:Phloretin / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors
chemical_list: D065168:Bradykinin Receptor Antagonists; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D007473:Ion Channels; D017382:Reactive Oxygen Species; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D009247:NADH, NADPH Oxidoreductases; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D010693:Phloretin; D001920:Bradykinin