Persistence of gap junction communication during myocardial ischemia

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.

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“…However, recent studies (19,27) have shown that chemical coupling via the gap junction is main- Fig. 6.…”

Section: Physical Interaction Of Cx43 With Protein Kinases During Myomentioning

confidence: 99%

Roles of Cx43-associated protein kinases in suppression of gap junction-mediated chemical coupling by ischemic preconditioning

Naitoh¹,

Yano²,

Miura³

et al. 2009

American Journal of Physiology-Heart and Circulatory Physiology

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“…Assessment of GJIC activity in heart sections was performed using the method described by Ruiz-Meana et al 25 with a modification. Briefly, after 30 min of LAD occlusion and EB infusion, a thick transverse section was excised between the LAD ligature and the apex.…”

Section: Dye Transfer Assay In Heart Sectionsmentioning

confidence: 99%

Ischemia Enhances Translocation of Connexin43 and Gap Junction Intercellular Communication, Thereby Propagating Contraction Band Necrosis After Reperfusion

Shintani-Ishida

Unuma

Yoshida

2009

Circ J

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“…To confirm that the concentrations of 0.5 mM heptanol and, importantly, 6 M Gap 27 administered in protocol 2 inhibited gap junctions/hemichannels in normoxic myocardium (i.e., the conditions under which D-myo-IP 3 was administered and initiated protection), we assessed the intercellular transfer and tissue penetration of Lucifer yellow, a gap junction-permeable (but membrane-impermeable) fluorescent tracer dye (Ruiz-Meana et al, 2001;Miura et al, 2004), in nine additional hearts. After stabilization, hearts received a 5-min infusion of heptanol or Gap 27 as described for protocol 2 or buffer alone (n ϭ 3/group).…”

Section: Protocol 3: Confirmation Of Gap Junction Inhibitionmentioning

confidence: 99%

“…The hearts were then rapidly removed from the apparatus and cut into five transverse slices. We used previously published methods (Ruiz-Meana et al, 2001;Miura et al, 2004) with minor modifications to introduce the dye into the myocardial slices and quantify fluorescence. Specifically, in the three slices obtained from the mid-myocardial region (apex and base discarded), shallow incisions were made on the epicardial surface at a uniform calibrated depth of 1 mm, thereby disrupting sarcolemmal membranes and allowing initial uptake of the membrane-impermeable dye.…”

Section: Protocol 3: Confirmation Of Gap Junction Inhibitionmentioning

confidence: 99%

Pretreatment with d-myo-Inositol Trisphosphate Reduces Infarct Size in Rabbit Hearts: Role of Inositol Trisphosphate Receptors and Gap Junctions in Triggering Protection

Przyklenk

Maynard

Darling

et al. 2005

J Pharmacol Exp Ther

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Pretreatment with D-myo-inositol-1,4,5-trisphosphate hexasodium (D-myo-IP 3 ), the sodium salt of the second messenger inositol 1,4,5-trisphosphate (IP 3 ), is cardioprotective and triggers a reduction of infarct size comparable in magnitude to that obtained with ischemic preconditioning. However, this observation is enigmatic; whereas IP 3 signaling is conventionally initiated by receptor binding, IP 3 receptors are typically considered to be intracellular, and D-myo-IP 3 is membrane-impermeable. We propose that this paradox is explained by the presence of poorly characterized external IP 3 receptors and hypothesize that: 1) infarct size reduction with D-myo-IP 3 is receptor-mediated; and 2) communication via gap junctions and/or hemichannels is required to initiate this protection. To investigate the role of receptor binding, isolated buffer-perfused rabbit hearts underwent 30 min of coronary occlusion (CO) and 2 h of reflow. Prior to CO, hearts received no treatment (controls), D-myo-IP 3 , L-myo-IP 3 (enantiomer not recognized by the IP 3 receptor), D-myo-IP 3 ϩ the IP 3 receptor inhibitor xestospongin C (XeC), or XeC alone. Infarct size, assessed by tetrazolium staining, was reduced with D-myo-IP 3 treatment, whereas hearts that received L-myo-IP 3 or D-myo-IP 3 ϩ XeC showed no protection. To evaluate the contribution of gap junctions/hemichannels, additional control and D-myo-IP 3 -treated cohorts received a 5-min infusion of heptanol or Gap 27, two structurally distinct gap junction inhibitors, administered at doses confirmed to attenuate intercellular transmission of a gap junction-permeable fluorescent dye. There was no infarct-sparing effect of D-myo-IP 3 in inhibitor-treated hearts. These data support the concepts that infarct size reduction with D-myo-IP 3 is triggered by receptor binding and that communication via gap junctions/hemichannels is involved in initiating this protection.Inositol 1,4,5-trisphosphate (IP 3 ) is a ubiquitous second messenger generated in parallel with diacylglycerol in response to activation of G-protein-coupled receptors. Previous studies from our group have shown that prophylactic administration of D-myo-IP 3 hexasodium, the sodium salt of IP 3 , renders the heart resistant to a subsequent sustained ischemic insult and triggers a reduction of infarct size that is comparable in magnitude to the cardioprotection achieved with ischemic preconditioning (Gysembergh et al., 1999). However, this observation is enigmatic; i.e., whereas IP 3 (and presumably D-myo-IP 3 ) signaling is conventionally initiated by receptor binding, IP 3 receptors have historically been considered to be intracellular (specifically located on the endoplasmic reticulum or in the perinuclear region), and D-myo-IP 3 is well known to be membrane-impermeable (Berridge, 1993(Berridge, , 2002Taylor and Broad, 1998;Wilcox et al., 1998;Gysembergh et al., 1999;Ibarra et al., 2004;Vermassen et al., 2004).One potential explanation for this apparent paradox is that reduction of infarct size triggered by exog...

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Persistence of gap junction communication during myocardial ischemia

Cited by 62 publications

References 45 publications

Roles of Cx43-associated protein kinases in suppression of gap junction-mediated chemical coupling by ischemic preconditioning

Roles of Cx43-associated protein kinases in suppression of gap junction-mediated chemical coupling by ischemic preconditioning

Ischemia Enhances Translocation of Connexin43 and Gap Junction Intercellular Communication, Thereby Propagating Contraction Band Necrosis After Reperfusion

Pretreatment with d-myo-Inositol Trisphosphate Reduces Infarct Size in Rabbit Hearts: Role of Inositol Trisphosphate Receptors and Gap Junctions in Triggering Protection

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