Myocardial ischemia is associated with increased production of cyclic adenosine monophosphate (cAMP), with potentially deleterious effects. We hypothesized that the ischemia-induced activation of cAMP-dependent protein kinase A (PKA), could beneficially be inhibited by a PKA-inhibitor N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinoline-sulfonamide (H-89). H-89 when given to isolated perfused rat hearts before 30 minutes of global ischemia-reperfusion improved postischemic function and decreased infarct size. In another series, H-89 administered prior to preconditioning by 10 minutes of transient global ischemia decreased PKA activity (measured at the end of the preconditioning protocol) and augmented postischemic mechanical recovery. H-89 given for 5 minutes before the 10 minutes of transient ischemia further decreased infarct size from 13.4 +/- 1.0% (preconditioning alone) to 7.0 +/- 0.93 (P < 0.01). In a third series, forskolin (0.3 muM, 5 minutes, 10 minutes washout prior to ischemia) increased PKA activity and reduced infarct size. Prior H-89 decreased PKA activity after 5 minutes of forskolin and further reduced infarct size versus forskolin alone. In conclusion, three procedures increased postischemic recovery and reduced infarct size: H-89; preconditioning by transient ischemia; or forskolin as a preconditioning-mimetic. PKA-inhibition by H-89 further decreased infarct size beyond preconditioning or forskolin. Despite the reservation that H-89 could be non-selective in its actions, we propose H-89 as a candidate cardioprotective agent.
"This finding is somewhat contradictory to previous studies. In isolated rat hearts, H-89 (2 μmol/L) improved postischemic function and decreased infarct size when injected 3 min before 30 min of global ischemia-reperfusion and further reduced the infarct size when administered 3 min prior to ischemic or forskolin (a cAMP-elevating agents) preconditioning33. However, when delivered at 1.35 μg/kg per minute in dogs or at 10 μmol/L in isolated rat hearts approximately 30 min before preconditioning, H-89 completely blunted the infarct-limitation effect of preconditioning12,34. Therefore, the partial inhibition of H-89 on SIM cardioprotection in our study most likely occurred because H-89 was delivered later than SIM, and the contradiction between these studies might be explained by the differences in H-89 dosage, experimental protocols, and animal species. "
[Show abstract][Hide abstract] ABSTRACT: The cholesterol-lowering drugs statins could enhance the activities of endothelial nitric oxide synthase (eNOS) and protect myocardium during ischemia and reperfusion. The aim of this study was to examine whether protein kinase A (PKA) was involved in statin-mediated eNOS phosphorylation and cardioprotection.
6-Month-old Chinese minipigs (20-30 kg) underwent a 1.5-h occlusion and 3-h reperfusion of the left anterior descending coronary artery (LAD). In the sham group, the LAD was encircled by a suture but not occluded. Hemodynamic and cardiac function was monitored using a polygraph. Plasma activity of creatine kinase and the tissue activities of PKA and NOS were measured spectrophotometrically. p-CREB, eNOS and p-eNOS levels were detected using Western blotting. Sizes of the area at risk, the area of no-reflow and the area of necrosis were measured morphologically.
Pretreatment of the animals with simvastatin (SIM, 2 mg/kg, po) before reperfusion significantly decreased the plasma activity of creatine kinase, an index of myocardial necrosis, and reduced the no-reflow size (from 50.4%±2.4% to 36.1%±2.1%, P<0.01) and the infarct size (from 79.0%±2.7% to 64.1%±4.5%, P<0.01). SIM significantly increased the activities of PKA and constitutive NOS, and increased Ser(133) p-CREB protein, Ser(1179) p-eNOS, and Ser(635) p-eNOS in ischemic myocardium. Intravenous infusion of the PKA inhibitor H-89 (1 μg·kg(-1)·min(-1)) partially abrogated the SIM-induced cardioprotection and eNOS phosphorylation. In contrast, intravenous infusion of the eNOS inhibitor L-NNA (10 mg·kg(-1)) completely abrogated the SIM-induced cardioprotection and eNOS phosphorylation during ischemia and reperfusion, but did not affect the activity of PKA.
Pretreatment with a single dose of SIM 2.5 h before reperfusion attenuates myocardial no-reflow and infarction through increasing eNOS phosphorylation at Ser(1179) and Ser(635) that was partially mediated via the PKA signaling pathway.
[Show abstract][Hide abstract] ABSTRACT: Despite nearly twenty years of research into the field of ischemic preconditioning, the actual mechanism of protection remains unclear. However, much progress has been made in elucidating the signal transduction pathways that convey the extracellular signal initiated by the preconditioning stimulus to the intracellular targets of cardioprotection, with many of these pathways involving the activation of a diverse array of survival protein kinase cascades. The powerful protective benefits of ischemic preconditioning have not yet been realised in the clinical arena, not least because of the prerequisite for any preconditioning intervention to be applied prior to the onset of index ischemia, which in the case of an acute myocardial infarction is difficult to institute. In this regard, the newly described phenomenon of ischemic postconditioning, which comprises a cardioprotective intervention that can be applied at the time of myocardial reperfusion, offers a far more attractive and amenable approach to myocardial protection. Interestingly, certain survival protein kinase cascades recruited at the time of myocardial reperfusion appear to be shared by both ischemic preconditioning and postconditioning, thereby offering a potentially common target of cardioprotection. The often disputed roles these different protein kinases play in mediating the cardioprotective effects of ischemic preconditioning and postconditioning are reviewed in this article, and include protein kinases C, G, and A, members of the MAPK family (Erk1/2, p38, JNK and BMK1), the PI3K-Akt cascade, and the JAK-STAT pathway.
Cardiovascular Research 06/2006; 70(2):240-53. DOI:10.1016/j.cardiores.2006.01.017 · 5.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Resveratrol (3,4',5-trihydroxy-trans-stilbene), a naturally occurring polyphenolic compound found abundantly in grape skins and red wines, has been found to pharmacologically precondition the heart against ischemia reperfusion injury through the potentiation of a survival signal involving cAMP response element-binding protein-dependent phosphatidylinositol 3-kinase-Akt-BclII pathway. The present study was designed to determine whether, similar to ischemic preconditioning, resveratrol uses mitogen-activated protein kinases (MAPKs) as upstream signaling targets. The isolated rat hearts were preperfused for 15 min with Krebs-Henseleit bicarbonate buffer in the absence (control) or presence of extracellular signal-regulated kinase (ERK) 1/2 inhibitor 2'-amino-3'-methoxyflavone (PD98059), p38 MAPK inhibitor 4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)-1H-imidazole (SB-202190), mitogen- and stress-activated protein kinase 1 (MSK-1) inhibitor N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline (H89), protein kinase A inhibitor (9S,10S,12R)-2,3,9,10,11,12-hexahydro-10hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3fg: 3',2',1'-kl]-pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid hexyl ester (KT5720), resveratrol only, resveratrol plus PD98059, resveratrol plus SB-202190, resveratrol plus H89, or resveratrol plus KT5720. Consistent with previous reports, resveratrol provided cardioprotection as evidenced by its ability to improve postischemic ventricular function, reduction of myocardial infarct size, and cardiomyocyte apoptosis. The cardioprotection afforded by resveratrol was partially abolished with PD98059 or SB-202190, suggesting that ERK1/2 and p38 MAPK play roles in resveratrol-mediated preconditioning. An MSK-1 inhibitor, H89, abolished resveratrol-mediated preconditioning, indicating MSK-1 to be the downstream target molecule for both ERK1/2 and p38 MAPK. KT5720 had no effect on resveratrol-mediated cardioprotection. Corroborating these results, Western blot analysis revealed phosphorylation of ERK1/2, p38 MAPK, MAPK-activated protein (MAPKAP) kinase 2, and MSK-1 with resveratrol and inhibition of phosphorylation with corresponding inhibitors. These results showed for the first time that resveratrol triggers an MAPK signaling pathway involving ERK1/2 and p38 MAPK, the former using MSK-1 as the downstream target and the latter, using both MAPKAP kinase 2 and MSK-1 as downstream targets.
Journal of Pharmacology and Experimental Therapeutics 07/2006; 317(3):980-8. DOI:10.1124/jpet.105.095133 · 3.97 Impact Factor
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