title: Phosphoinositide 3-Kinase γ Restrains Neurotoxic Effects of Microglia After Focal Brain Ischemia.
abstract: Phosphoinositide 3-kinase γ (PI3Kγ) is linked to neuroinflammation and phagocytosis. This study was conducted to elucidate conjectural differences of lipid kinase-dependent and kinase-independent functions of PI3Kγ in the evolvement of brain damage induced by focal cerebral ischemia/reperfusion. Therefore, PI3Kγ wild-type, knockout, and kinase-dead mice were subjected to middle cerebral artery occlusion followed by reperfusion. Tissue damage and cellular composition were assessed by immunohistochemical stainings. In addition, microglial cells derived from respective mouse genotypes were used for analysis of PI3Kγ effects on phagocytic activity, matrix metalloproteinase-9 release, and cAMP content under conditions of oxygen/glucose deprivation and recovery. Brain infarction was more pronounced in PI3Kγ-knockout mice compared to wild-type and kinase-dead mice 48 h after reperfusion. Immunohistochemical analyses revealed a reduced amount of galectin-3/MAC-2-positive microglial cells indicating that activated phagocytosis was reduced in ischemic brains of knockout mice. Cell culture studies disclosed enhanced metalloproteinase-9 secretion in supernatants derived from microglia of PI3Kγ-deficient mice after 2-h oxygen/glucose deprivation and 48-h recovery. Furthermore, PI3Kγ-deficient microglial cells showed a failed phagocytic activation throughout the observed recovery period. Lastly, PI3Kγ-deficient microglia exhibited strongly increased cAMP levels in comparison with wild-type microglia or cells expressing kinase-dead PI3Kγ after oxygen/glucose deprivation and recovery. Our data suggest PI3Kγ kinase activity-independent control of cAMP phosphodiesterase as a crucial mediator of microglial cAMP regulation, MMP-9 expression, and phagocytic activity following focal brain ischemia/recirculation. The suppressive effect of PI3Kγ on cAMP levels appears critical for the restriction of ischemia-induced immune cell functions and in turn tissue damage.
authors.affiliation: Institute of Molecular Cell Biology, Center for Molecular Biomedicine, Jena University Hospital, Friedrich Schiller University, Hans-Knöll-Strasse 2, D-07745, Jena, Germany.
authors.forename: Caroline
authors.initials: C
authors.lastname: Schmidt
authors.affiliation: Department of Neurology, Jena University Hospital, Jena, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Frahm
authors.affiliation: Institute of Molecular Cell Biology, Center for Molecular Biomedicine, Jena University Hospital, Friedrich Schiller University, Hans-Knöll-Strasse 2, D-07745, Jena, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Schneble
authors.affiliation: Institute of Molecular Cell Biology, Center for Molecular Biomedicine, Jena University Hospital, Friedrich Schiller University, Hans-Knöll-Strasse 2, D-07745, Jena, Germany.
authors.forename: Jörg P
authors.initials: JP
authors.lastname: Müller
authors.affiliation: Institute of Pathology, HELIOS Klinikum, Erfurt, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Brodhun
authors.affiliation: Department of Genetics, Biology, Biochemistry and Molecular Biotechnology Center, University of Torino, Torino, Italy.
authors.forename: Irene
authors.initials: I
authors.lastname: Franco
authors.affiliation: Department of Neurology, Jena University Hospital, Jena, Germany.
authors.forename: Otto W
authors.initials: OW
authors.lastname: Witte
authors.affiliation: Department of Genetics, Biology, Biochemistry and Molecular Biotechnology Center, University of Torino, Torino, Italy.
authors.forename: Emilio
authors.initials: E
authors.lastname: Hirsch
authors.affiliation: Institute of Molecular Cell Biology, Center for Molecular Biomedicine, Jena University Hospital, Friedrich Schiller University, Hans-Knöll-Strasse 2, D-07745, Jena, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Wetzker
authors.affiliation: Institute of Molecular Cell Biology, Center for Molecular Biomedicine, Jena University Hospital, Friedrich Schiller University, Hans-Knöll-Strasse 2, D-07745, Jena, Germany. reinhard.bauer@med.uni-jena.de.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Bauer
mesh_terms: D000818:Animals; D020520:Brain Infarction / Q000473:pathology; D002545:Brain Ischemia / Q000150:complications / Q000201:enzymology* / Q000473:pathology*; D002452:Cell Count; D002478:Cells, Cultured; D058544:Class Ib Phosphatidylinositol 3-Kinase / Q000172:deficiency / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D005947:Glucose / Q000172:deficiency; D020244:Infarction, Middle Cerebral Artery / Q000150:complications / Q000473:pathology; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017628:Microglia / Q000187:drug effects / Q000201:enzymology*; D008954:Models, Biological; D009498:Neurotoxins / Q000633:toxicity*; D009504:Neutrophils / Q000378:metabolism; D010100:Oxygen; D010587:Phagocytosis; D013997:Time Factors
chemical_list: D009498:Neurotoxins; D000242:Cyclic AMP; D058544:Class Ib Phosphatidylinositol 3-Kinase; C546764:Pik3cg protein, mouse; D020780:Matrix Metalloproteinase 9; D005947:Glucose; D010100:Oxygen
keywords: MCAO; Microglial cells; Neuroinflammation; PI3Kγ