title: Inhibition of the Ca²⁺-dependent K⁺ channel, KCNN4/KCa3.1, improves tissue protection and locomotor recovery after spinal cord injury.
abstract: Spinal cord injury (SCI) triggers inflammatory responses that involve neutrophils, macrophages/microglia and astrocytes and molecules that potentially cause secondary tissue damage and functional impairment. Here, we assessed the contribution of the calcium-dependent K⁺ channel KCNN4 (KCa3.1, IK1, SK4) to secondary damage after moderate contusion lesions in the lower thoracic spinal cord of adult mice. Changes in KCNN4 mRNA levels (RT-PCR), KCa3.1 protein expression (Western blots), and cellular expression (immunofluorescence) in the mouse spinal cord were monitored between 1 and 28 d after SCI. KCNN4 mRNA and KCa3.1 protein rapidly increased after SCI; double labeling identified astrocytes as the main cellular source accounting for this upregulation. Locomotor function after SCI, evaluated for 28 d in an open-field test using the Basso Mouse Scale, was improved in a dose-dependent manner by treating mice with a selective inhibitor of KCa3.1 channels, TRAM-34 (triarylmethane-34). Improved locomotor function was accompanied by reduced tissue loss at 28 d and increased neuron and axon sparing. The rescue of tissue by TRAM-34 treatment was preceded by reduced expression of the proinflammatory mediators, tumor necrosis factor-α and interleukin-1β in spinal cord tissue at 12 h after injury, and reduced expression of inducible nitric oxide synthase at 7 d after SCI. In astrocytes in vitro, TRAM-34 inhibited Ca²⁺ signaling in response to metabotropic purinergic receptor stimulation. These results suggest that blocking the KCa3.1 channel could be a potential therapeutic approach for treating secondary damage after spinal cord injury.
authors.affiliation: Centre for Research in Neuroscience, The Research Institute of the McGill University Health Center, Montreal, Québec H3G1A4, Canada.
authors.forename: Delphine
authors.initials: D
authors.lastname: Bouhy
authors.forename: Nader
authors.initials: N
authors.lastname: Ghasemlou
authors.forename: Starlee
authors.initials: S
authors.lastname: Lively
authors.forename: Adriana
authors.initials: A
authors.lastname: Redensek
authors.forename: Khizr I
authors.initials: KI
authors.lastname: Rathore
authors.forename: Lyanne C
authors.initials: LC
authors.lastname: Schlichter
authors.forename: Samuel
authors.initials: S
authors.lastname: David
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D039481:CD11b Antigen / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000235:genetics / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000627:therapeutic use; D011720:Pyrazoles / Q000627:therapeutic use; D012333:RNA, Messenger / Q000378:metabolism; D013119:Spinal Cord Injuries / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology*; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*; D014544:Uridine Triphosphate / Q000494:pharmacology
chemical_list: D039481:CD11b Antigen; D016207:Cytokines; D004791:Enzyme Inhibitors; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496925:Kcnn4 protein, mouse; D009419:Nerve Tissue Proteins; D026902:Potassium Channel Blockers; D011720:Pyrazoles; D012333:RNA, Messenger; C411671:TRAM 34; D019284:Thapsigargin; D052247:Nitric Oxide Synthase Type II; D002118:Calcium; D014544:Uridine Triphosphate
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