title: Targeted inhibition of KCa3.1 attenuates TGF-β-induced reactive astrogliosis through the Smad2/3 signaling pathway.
abstract: Reactive astrogliosis, characterized by cellular hypertrophy and various alterations in gene expression and proliferative phenotypes, is considered to contribute to brain injuries and diseases as diverse as trauma, neurodegeneration, and ischemia. KCa3.1 (intermediate-conductance calcium-activated potassium channel), a potassium channel protein, has been reported to be up-regulated in reactive astrocytes after spinal cord injury in vivo. However, little is known regarding the exact role of KCa3.1 in reactive astrogliosis. To elucidate the role of KCa3.1 in regulating reactive astrogliosis, we investigated the effects of either blocking or knockout of KCa3.1 channels on the production of astrogliosis and astrocytic proliferation in response to transforming growth factor (TGF)-β in primary cultures of mouse astrocytes. We found that TGF-β increased KCa3.1 protein expression in astrocytes, with a concomitant marked increase in the expression of reactive astrogliosis, including glial fibrillary acidic protein and chondroitin sulfate proteoglycans. These changes were significantly attenuated by the KCa3.1 inhibitor 1-((2-chlorophenyl) (diphenyl)methyl)-1H-pyrazole (TRAM-34). Similarly, the increase in glial fibrillary acidic protein and chondroitin sulfate proteoglycans in response to TGF-β was attenuated in KCa3.1(-/-) astrocytes. TRAM-34 also suppressed astrocytic proliferation. In addition, the TGF-β-induced phosphorylation of Smad2 and Smad3 proteins was reduced with either inhibition of KCa3.1 with TRAM-34 or in KCa3.1(-/-) astrocytes. These findings highlight a novel role for the KCa3.1 channel in reactive astrogliosis phenotypic modulation and provide a potential target for therapeutic intervention for brain injuries. Reactive astrogliosis is characterized by the expression of glial fibrillary acidic protein and chondroitin sulfate proteoglycans. We demonstrate that either pharmacological blockade or knockout of KCa3.1 channels reduces reactive gliosis in cultured astrocytes caused by TGF-β, and also reduces TGF-β-induced phosphorylation of Smad2/3.
authors.affiliation: Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China.|Developmental Neurobiology Section, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Yu
authors.affiliation: Developmental Neurobiology Section, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Panpan
authors.initials: P
authors.lastname: Yu
authors.affiliation: Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Hongzhuan
authors.initials: H
authors.lastname: Chen
authors.affiliation: Developmental Neurobiology Section, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Herbert M
authors.initials: HM
authors.lastname: Geller
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D018390:Gene Targeting / Q000379:methods; D005911:Gliosis / Q000378:metabolism*; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors* / Q000172:deficiency* / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011720:Pyrazoles / Q000008:administration & dosage; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D051899:Smad2 Protein / Q000502:physiology*; D051900:Smad3 Protein / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000502:physiology*
chemical_list: D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496925:Kcnn4 protein, mouse; D011720:Pyrazoles; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; C411671:TRAM 34; D016212:Transforming Growth Factor beta
keywords: GFAP; astrocyte; chondroitin sulfate proteoglycans; culture; mouse