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  • American Physiological Society  (7)
  • 1
    Online Resource
    Online Resource
    Protective role of gap junctions in preconditioning against myocardial infarction
    American Physiological Society ; 2004
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 286, No. 1 ( 2004-01), p. H214-H221
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 286, No. 1 ( 2004-01), p. H214-H221
    Abstract: The aim of the present study was to examine the hypothesis that acceleration of gap junction (GJ) closure during ischemia contributes to anti-infarct tolerance afforded by preconditioning (PC). First, the effects of PC on GJ communication during ischemia were assessed. Isolated buffer-perfused rabbit hearts were subjected to 5-min global ischemia with or without PC with two cycles of 5-min ischemia/5-min reperfusion or a GJ blocker (2 mM heptanol), and then the tissue excised from the ischemic region was incubated in anoxic buffer containing lucifer yellow (LY; 2.5 mg/ml), a tracer of GJ permeability, for 20 min at 37°C. PC and heptanol significantly reduced the area to which LY was transported in the ischemic myocardium by 39% and by 54%, respectively. In the second series of experiments, three GJ blockers (heptanol, 18β-glycyrrhetinic acid, and 2,3-butanedione monoxime) infused after the onset of ischemia reduced infarct size after 30-min ischemia/2-h reperfusion to an extent equivalent to that in the case of PC. In the third series of experiments, Western blotting for connexin43 (Cx43) showed that PC shortened the time to the onset of ischemia-induced Cx43 dephosphorylation but reduced the extent of Cx43 dephosphorylation during a 30-min period of ischemia. Calphostin C, a protein kinase C (PKC) inhibitor, abolished preservation of phosphorylated Cx43 but not the early onset of Cx43 dephosphorylation after ischemia in the preconditioned myocardium. These results suggest that PC-induced reduction of GJ permeability during ischemia, presumably by PKC-mediated Cx43 phosphorylation, contributes to infarct size limitation.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.00441.2003
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2004
    detail.hit.zdb_id: 1477308-9
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    δ-Opioid receptor activation before ischemia reduces gap junction permeability in ischemic myocardium by PKC-ε-mediated phosphorylation of connexin 43
    American Physiological Society ; 2007
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 293, No. 3 ( 2007-09), p. H1425-H1431
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 293, No. 3 ( 2007-09), p. H1425-H1431
    Abstract: The aim of this study was to examine the hypothesis that δ-opioid receptor activation before ischemia suppresses gap junction (GJ) permeability by PKC-mediated connexin 43 (Cx43) modulation, which contributes to infarct size limitation afforded by the δ-opioid receptor activation. A δ-opioid receptor agonist, [d-Ala 2 ,d-Leu 5 ]-enkephalin acetate (DADLE, 300 nM), was used in place of preconditioning (PC) ischemia to trigger PC mechanisms in rat hearts. GJ permeability during ischemia, which was assessed by Lucifer yellow, was reduced by DADLE to 47% of the control level, and this effect of DADLE was almost abolished by a PKC-ε inhibitor [PKC-ε translocation inhibitory peptide (PKC-ε-TIP)] but was not affected by a PKC-δ inhibitor (rottlerin). After DADLE infusion, PKC-ε, but not PKC-δ, was coimmunoprecipitated with Cx43, and the level of phosphorylation of Cx43 at a PKC-dependent site (Ser 368 ) was significantly elevated during ischemia. DADLE reduced infarct size after 35 min of ischemia followed by 2 h of reperfusion by 69%, and PKC-ε-TIP and rottlerin eliminated 48% and 63%, respectively, of the infarct size-limiting effect of DADLE. Infusion of a GJ blocker, heptanol, before reperfusion reduced infarct size by 36%, and this protection was not enhanced by preischemic infusion of rottlerin + DADLE, which allows PKC-ε activation by DADLE. These results suggest that phosphorylation of Cx43 by PKC-ε plays a crucial role in δ-opioid-induced suppression of GJ permeability in ischemic myocardium and that this modulation of the GJ is possibly an adjunct mechanism of infarct size limitation afforded by preischemic δ-opioid receptor activation.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.01115.2006
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2007
    detail.hit.zdb_id: 1477308-9
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Ser9 phosphorylation of mitochondrial GSK-3β is a primary mechanism of cardiomyocyte protection by erythropoietin against oxidant-induced apoptosis
    American Physiological Society ; 2008
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 295, No. 5 ( 2008-11), p. H2079-H2086
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 295, No. 5 ( 2008-11), p. H2079-H2086
    Abstract: The aim of this study was to determine the role of GSK-3β in cardiomyocyte protection afforded by erythropoietin (EPO) against oxidant stress-induced apoptosis. Treatment with EPO (10 units/ml) induced Ser473 phosphorylation of Akt and Ser9 phosphorylation of GSK-3β and significantly reduced the proportion of apoptotic H9c2 cardiomyocytes after exposure to H 2 O 2 from 38.3 ± 2.7% to 26.0 ± 2.9%. This protection was not detected in cells transfected with constitutively active GSK-3β (S9A), which lacks Ser9 for inhibitory phosphorylation. The antiapoptotic effect of EPO was mimicked completely by GSK-3β knockdown using small interfering RNA and partly by the transfection with kinase-deficient GSK-3β (K85R). The level of colocalization of intracellular GSK-3β with mitochondria assessed by enhanced green fluorescent protein-tagged GSK-3β or immunocytochemistry was not altered by EPO treatment. However, EPO increased the level of Ser9-phospho-GSK-3β colocalized with mitochondria by 50% in a phosphatidylinositol 3-kinase-dependent manner. Mitochondrial translocation of Bcl-2-associated X protein (BAX) after exposure to H 2 O 2 was inhibited by EPO pretreatment and by GSK-3β knockdown. These results suggest that the suppression of GSK-3β activity by Akt-mediated Ser9 phosphorylation in the mitochondria affords cardiomyocytes tolerance against oxidant-induced apoptosis, possibly by inhibiting the access of BAX to the mitochondria.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.00092.2008
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2008
    detail.hit.zdb_id: 1477308-9
    SSG: 12
    Location Call Number Limitation Availability
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  • 4
    Online Resource
    Online Resource
    Roles of Cx43-associated protein kinases in suppression of gap junction-mediated chemical coupling by ischemic preconditioning
    American Physiological Society ; 2009
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 296, No. 2 ( 2009-02), p. H396-H403
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 296, No. 2 ( 2009-02), p. H396-H403
    Abstract: Ischemic preconditioning (PC) suppresses chemical coupling of cardiomyocytes via gap junctions (GJs) during ischemia, which is an adjunct mechanism of protection. The aim of this study was to characterize roles of protein kinases in PC-induced GJ modulation. In isolated rat hearts, ventricular tissues were sampled before and after ischemia with or without PC, and intercalated disc-rich fractions were separated for immunoprecipitation and immunoblotting. Levels of protein kinase C (PKC)-ε, p38mitogen-activated protein kinase (MAPK)-α, and Src coimmunoprecipitated with connexin-43 (Cx43) were increased after ischemia, whereas p38MAPKβ was not detected in the Cx43 immunoprecipitates. PC did not modify the level of Cx43-Src complex after ischemia. However, PC enhanced Cx43-PKCε complex formation, which was abolished by PKCε translocation inhibitory peptide (TIP). In contrast, PC reduced Cx43-p38MAPKα complex level and p38MAPK activity in the Cx43 immunoprecipitates after ischemia. The effect of PC on Cx43-p38MAPKα interaction was mimicked by SB-203580, a p38MAPK inhibitor. PC reduced permeability of GJs to Lucifer yellow in the myocardium at 25 min after ischemia, and this effect was abolished by PKCε-TIP. SB-203580 increased the GJ permeability at 15 min after ischemia compared with that in untreated controls, but the difference became insignificant 25 min after ischemia. In conclusion, PC has distinct effects on interaction of GJ Cx43 with PKCε, p38MAPKα, and Src during ischemia. Suppression of GJ permeability during ischemia by PC is primarily achieved by enhanced interaction of Cx43 with PKCε, which overwhelms the counterbalancing effect of reduced Cx43-p38MAPKα interaction.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.00448.2008
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2009
    detail.hit.zdb_id: 1477308-9
    SSG: 12
    Location Call Number Limitation Availability
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  • 5
    Online Resource
    Online Resource
    Ecto-5′-nucleotidase is not required for ischemic preconditioning in rabbit myocardium in situ
    American Physiological Society ; 1998
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 275, No. 4 ( 1998-10-01), p. H1329-H1337
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 275, No. 4 ( 1998-10-01), p. H1329-H1337
    Abstract: This study tested the hypothesis that cardiac ecto-5′-nucleotidase (ecto-5′-NT) activity during ischemic preconditioning (PC) contributes to augmented tolerance against ischemia, thereby reducing infarct size in the rabbit heart in situ. The effects of α,β-methylene-adenosine diphosphate (AOPCP), a selective inhibitor of ecto-5′-NT, on cardiovascular responses to AMP were measured to establish in vivo activities of the enzyme and its inhibitor. Left atrial infusion of AOPCP (0.75 mg ⋅ kg −1 ⋅ min −1 ) raised AOPCP plasma levels to 138 μM; under these conditions negative chronotropic and inotropic effects of AMP were blocked, demonstrating essentially full inhibition of ecto-5′-NT in the heart in situ. This AOPCP-blocked heart in situ model was used to examine the proposed contribution of ecto-5′-NT in ischemic PC. Myocardial infarction caused by 30-min ischemia was followed by 3-h reperfusion. Infarct size (IS) was measured and expressed as a percentage of the size of the area at risk (%IS/AR). In untreated controls, %IS/AR was 38.1 ± 3.8%; PC (5-min ischemia, 5-min reperfusion) markedly reduced %IS/AR to 10.0 ± 2.0%. Essentially identical IS reductions by PC were observed in AOPCP-blocked animals (%IS/AR = 13.8 ± 2.2 and 13.3 ± 1.8% in rabbits receiving AOPCP at 0.75 and 1.50 mg ⋅ kg −1 ⋅ min −1 , respectively); here plasma AOPCP levels were established before and during PC but not during the subsequent prolonged ischemia. As expected, AOPCP also did not affect %IS/AR in non-PC controls (%IS/AR = 35.5 ± 3.7%). In contrast but as predicted, adenosine-receptor blockade by 8-phenyltheophylline (10 mg/kg iv) substantially attenuated IS reduction by PC in both AOPCP-blocked and control hearts (%IS/AR = 25.2 ± 4.3 and 21.8 ± 2.2%, respectively; P 〈 0.05 vs. PC alone). The results demonstrate that cardiac ecto-5′-NT is not required for ischemic PC against infarction in the rabbit.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.1998.275.4.H1329
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1998
    detail.hit.zdb_id: 1477308-9
    SSG: 12
    Location Call Number Limitation Availability
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  • 6
    Online Resource
    Online Resource
    Erythropoietin affords additional cardioprotection to preconditioned hearts by enhanced phosphorylation of glycogen synthase kinase-3β
    American Physiological Society ; 2006
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 291, No. 2 ( 2006-08), p. H748-H755
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 291, No. 2 ( 2006-08), p. H748-H755
    Abstract: The aim of this study was to determine whether erythropoietin (EPO) affords additional cardioprotection to the preconditioned myocardium by enhanced phosphorylation of Akt, STAT3, or glycogen synthase kinase-3β (GSK-3β). Preconditioning (PC) with 5-min ischemia/5-min reperfusion and EPO (5,000 U/kg iv) reduced infarct size (as % of area at risk, %IS/AR) after 20-min ischemia in rat hearts in situ from 56.5 ± 1.8% to 25.2 ± 2.1% and to 36.2 ± 2.8%, respectively. PC-induced protection was significantly inhibited by a protein kinase C inhibitor, chelerythrine (5 mg/kg), and slightly blunted by a phosphatidylinositol-3-kinase inhibitor, wortmannin (15 μg/kg). The opposite pattern of inhibition was observed for EPO-induced protection. The combination of PC and EPO further reduced %IS/AR to 8.9 ± 1.9%, and this protection was inhibited by chelerythrine and wortmannin. The additive effects of PC and EPO on infarct size were mirrored by their effects on the level of phosphorylated GSK-3β at 5 min after reperfusion but not their effects on the level of phospho-Akt or phospho-STAT3. To mimic phosphorylation-induced inhibition of GSK-3β activity, SB-216763 (SB), a GSK-3β inhibitor, was administered before ischemia or 5 min before reperfusion. Infarct size was significantly reduced by preischemic injection (%IS/AR = 40.4 ± 2.2% by 0.6 mg/kg SB and 34.0 ± 1.8% by 1.2 mg/kg SB) and also by prereperfusion injection (%IS/AR = 32.0 ± 2.0% by 1.2 mg/kg SB). These results suggest that EPO and PC afford additive infarct size-limiting effects by additive phosphorylation of GSK-3β at the time of reperfusion by Akt-dependent and -independent mechanisms.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.00837.2005
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2006
    detail.hit.zdb_id: 1477308-9
    SSG: 12
    Location Call Number Limitation Availability
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  • 7
    Online Resource
    Online Resource
    Opening of mitochondrial K ATP channel occurs downstream of PKC-ε activation in the mechanism of preconditioning
    American Physiological Society ; 2002
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 283, No. 1 ( 2002-07-01), p. H440-H447
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 283, No. 1 ( 2002-07-01), p. H440-H447
    Abstract: We examined whether the mitochondrial ATP-sensitive K channel (K ATP ) is an effector downstream of protein kinase C-ε (PKC-ε) in the mechanism of preconditioning (PC) in isolated rabbit hearts. PC with two cycles of 5-min ischemia/5-min reperfusion before 30-min global ischemia reduced infarction from 50.3 ± 6.8% of the left ventricle to 20.3 ± 3.7%. PC significantly increased PKC-ε protein in the particulate fraction from 51 ± 4% of the total to 60 ± 4%, whereas no translocation was observed for PKC-δ and PKC-α. In mitochondria separated from the other particulate fractions, PC increased the PKC-ε level by 50%. Infusion of 5-hydroxydecanoate (5-HD), a mitochondrial K ATP blocker, after PC abolished the cardioprotection of PC, whereas PKC-ε translocation by PC was not interfered with 5-HD. Diazoxide, a mitochondrial K ATP opener, infused 10 min before ischemia limited infarct size to 5.2 ± 1.4%, but this agent neither translocated PKC-ε by itself nor accelerated PKC-ε translocation after ischemia. Together with the results of earlier studies showing mitochondrial K ATP opening by PKC, the present results suggest that mitochondrial K ATP -mediated cardioprotection occurs subsequent to PKC-ε activation by PC.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.00434.2001
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2002
    detail.hit.zdb_id: 1477308-9
    SSG: 12
    Location Call Number Limitation Availability
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