title: Pioglitazone limits myocardial infarct size, activates Akt, and upregulates cPLA2 and COX-2 in a PPAR-γ-independent manner.
abstract: Pioglitazone (PIO), a PPAR-γ agonist, limits myocardial infarct size by activating Akt and upregulating cytosolic phospholipase A(2) (cPLA(2)) and cyclooxygenase (COX)-2. However, PIO has several PPAR-γ-independent effects. We assessed whether PIO limits myocardial infarct size in PPAR-γ-knockout mice, attenuates hypoxia-reoxygenation injury and upregulates P-Akt, cPLA(2), and COX-2 expression in PPAR-γ-knockout cardiomyocytes. Cardiac-specific inducible PPAR-γ knockout mice were generated by crossing αMHC-Cre mice to PPAR-γ(loxp/loxp) mice. PPAR-γ deletion was achieved after 7 days of intraperitoneal tamoxifen (20 mg/kg/day) administration. Mice received PIO (10 mg/kg/day), or vehicle, for 3 days and underwent coronary occlusion (30 min) followed by reperfusion (4 h). We assessed the area at risk by blue dye and infarct size by TTC. Cultured adult cardiomyocytes of PPAR-γ(loxp/loxp/cre) mice without or with pretreatment with tamoxifen were incubated with or without PIO and subjected to 2 h hypoxia/2 h reoxygenation. Cardiac-specific PPAR-γ knockout significantly increased infarct size. PIO reduced infarct size by 51% in PPAR-γ knockout mice and by 55% in mice with intact PPAR-γ. Deleting the PPAR-γ gene increased cell death in vitro. PIO reduced cell death in cells with and without intact PPAR-γ. PIO similarly increased myocardial Ser-473 P-Akt, cPLA(2), and COX-2 levels after hypoxia/reoxygenation in cells with and without intact PPAR-γ. PIO limited infarct size in mice in a PPAR-γ-independent manner. PIO activated Akt, increased the expression of cPLA(2) and COX-2, and protected adult cardiomyocytes against the effects of hypoxia/reoxygenation independent of PPAR-γ activation.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, 77555, USA.
authors.forename: Yochai
authors.initials: Y
authors.lastname: Birnbaum
authors.forename: Bo
authors.initials: B
authors.lastname: Long
authors.forename: Jinqiao
authors.initials: J
authors.lastname: Qian
authors.forename: Jose R
authors.initials: JR
authors.lastname: Perez-Polo
authors.forename: Yumei
authors.initials: Y
authors.lastname: Ye
mesh_terms: D000818:Animals; D051546:Cyclooxygenase 2 / Q000096:biosynthesis*; D004789:Enzyme Activation / Q000187:drug effects; D015870:Gene Expression; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D015151:Immunoblotting; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D009203:Myocardial Infarction / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000517:prevention & control; D032383:Myocytes, Cardiac / Q000378:metabolism; D047495:PPAR gamma / Q000378:metabolism; D054510:Phospholipases A2, Cytosolic / Q000096:biosynthesis*; D000077205:Pioglitazone; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D045162:Thiazolidinediones / Q000494:pharmacology*; D015854:Up-Regulation
chemical_list: D007004:Hypoglycemic Agents; D047495:PPAR gamma; D045162:Thiazolidinediones; D051546:Cyclooxygenase 2; D051057:Proto-Oncogene Proteins c-akt; D054510:Phospholipases A2, Cytosolic; D000077205:Pioglitazone