title: Regulating RISK: a role for JAK-STAT signaling in postconditioning?
abstract: Postconditioning (POC), a novel strategy of cardioprotection against ischemia-reperfusion injury, is clinically attractive because of its therapeutic application at the predictable onset of reperfusion. POC activates several intracellular kinase signaling pathways, including phosphatidylinositol 3-kinase (PI3K)-Akt (RISK). The regulation of POC-induced survival kinase signaling, however, has not been fully characterized. JAK-STAT activation is integral to cardiac ischemic tolerance and may provide upstream regulation of RISK. We hypothesized that POC requires the activation of both JAK-STAT and RISK signaling. Langendorff-perfused mouse hearts were subjected to 30 min of global ischemia and 40 min of reperfusion, with or without POC immediately after ischemia. A separate group of POC hearts was treated with AG 490, a JAK2 inhibitor, Stattic, a specific STAT3 inhibitor, or LY-294002, a PI3K inhibitor, at the onset of reperfusion. Cardiomyocyte-specific STAT3 knockout (KO) hearts were also subjected to non-POC or POC protocols. Myocardial performance (+dP/dt(max), mmHg/s) was assessed throughout each perfusion protocol. Phosphorylated (p-) STAT3 and Akt expression was analyzed by Western immunoblotting. POC enhanced myocardial functional recovery and increased expression of p-STAT3 and p-Akt. JAK-STAT inhibition abrogated POC-induced functional protection. STAT3 inhibition decreased expression of both p-STAT3 and p-Akt. PI3K inhibition also attenuated POC-induced cardioprotection and reduced p-Akt expression but had no effect on STAT3 phosphorylation. Interestingly, STAT3 KO hearts undergoing POC exhibited improved ischemic tolerance compared with KO non-POC hearts. POC induces myocardial functional protection by activating the RISK pathway. JAK-STAT signaling, however, is insufficient for effective POC without PI3K-Akt activation.
authors: Department of Surgery, University of Cincinnati, Cincinnati, Ohio 45267, USA. goodmamd@email.uc.edu
authors: Michael D
authors: MD
authors: Goodman
authors: Sheryl E
authors: SE
authors: Koch
authors: Geraldine A
authors: GA
authors: Fuller-Bicer
authors: Karyn L
authors: KL
authors: Butler
mesh_terms: D000818:Animals; D002867:Chromones / Q000494:pharmacology; D003499:Cyclic S-Oxides / Q000494:pharmacology; D053612:Janus Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009025:Morpholines / Q000494:pharmacology; D009200:Myocardial Contraction; D015428:Myocardial Reperfusion Injury / Q000201:enzymology / Q000503:physiopathology / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D020127:Recovery of Function; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D020032:Tyrphostins / Q000494:pharmacology; D016277:Ventricular Function, Left
chemical_list: D002867:Chromones; D003499:Cyclic S-Oxides; D053612:Janus Kinases; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D050796:STAT3 Transcription Factor; D020032:Tyrphostins; C494087:Stat3 protein, mouse; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; C517409:stattic; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one