title: The Akt signaling pathway contributes to postconditioning's protection against stroke; the protection is associated with the MAPK and PKC pathways.
abstract: We previously reported that ischemic postconditioning with a series of mechanical interruptions of reperfusion reduced infarct volume 2 days after focal ischemia in rats. Here, we extend this data by examining long-term protection and exploring underlying mechanisms involving the Akt, mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) signaling pathways. Post-conditioning reduced infarct and improved behavioral function assessed 30 days after stroke. Additionally, postconditioning increased levels of phosphorylated Akt (Ser473) as measured by western blot and Akt activity as measured by an in vitro kinase assay. Inhibiting Akt activity by a phosphoinositide 3-kinase inhibitor, LY294002, enlarged infarct in postconditioned rats. Postconditioning did not affect protein levels of phosphorylated-phosphatase and tensin homologue deleted on chromosome 10 or -phosphoinositide-dependent protein kinase-1 (molecules upstream of Akt) but did inhibit an increase in phosphorylated-glycogen synthase kinase 3beta, an Akt effector. In addition, postconditioning blocked beta-catenin phosphorylation subsequent to glycogen synthase kinase, but had no effect on total or non-phosphorylated active beta-catenin protein levels. Furthermore, postconditioning inhibited increases in the amount of phosphorylated-c-Jun N-terminal kinase and extracellular signal-regulated kinase 1/2 in the MAPK pathway. Finally, postconditioning blocked death-promoting deltaPKC cleavage and attenuated reduction in phosphorylation of survival-promoting epsilonPKC. In conclusion, our data suggest that postconditioning provides long-term protection against stroke in rats. Additionally, we found that Akt activity contributes to postconditioning's protection; furthermore, increases in epsilonPKC activity, a survival-promoting pathway, and reductions in MAPK and deltaPKC activity; two putative death-promoting pathways correlate with postconditioning's protection.
authors.affiliation: Department of Neurosurgery, Stanford University, Palo Alto, California 94305-5327, USA.
authors.forename: Xuwen
authors.initials: X
authors.lastname: Gao
authors.forename: Hanfeng
authors.initials: H
authors.lastname: Zhang
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Takahashi
authors.forename: Jason
authors.initials: J
authors.lastname: Hsieh
authors.forename: Janette
authors.initials: J
authors.lastname: Liao
authors.forename: Gary K
authors.initials: GK
authors.lastname: Steinberg
authors.forename: Heng
authors.initials: H
authors.lastname: Zhao
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology / Q000503:physiopathology; D002545:Brain Ischemia / Q000201:enzymology* / Q000503:physiopathology; D016923:Cell Death / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D019610:Cytoprotection / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D019194:Ischemic Preconditioning; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000378:metabolism*; D051745:Protein Kinase C-delta / Q000378:metabolism; D051744:Protein Kinase C-epsilon / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020521:Stroke / Q000201:enzymology* / Q000503:physiopathology
chemical_list: D004791:Enzyme Inhibitors; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D051057:Proto-Oncogene Proteins c-akt; C000605508:Gsk3b protein, rat